Shock absorbing structure

There is provided a shock absorbing structure that can improve shock absorption performance by stabilizing the compressive deformation of a shock absorbing member in an axial direction. High-strength portions controlling deformation and low-strength portions controlling deformation are alternately disposed. Accordingly, when a shock is applied to a front side member from the front side of a vehicle, the front side member can be deformed in the shape of a bellows. Further, the respective low-strength portions, which are disposed closer to a rear end side in a longitudinal direction, have higher strength. Therefore, the front side member can be sequentially deformed from a front end side.

TECHNICAL FIELD

The present invention relates to a shock absorbing structure that absorbs a shock.

BACKGROUND ART

A shock absorbing structure where a plurality of beads are formed at the corners of a front side member is known as a shock absorbing structure in the related art (for example, see Patent Document 1). This shock absorbing structure includes reinforcing wall portions between the plurality of beads of the front side member. Since the shock absorbing structure has this configuration, the shock absorbing structure can absorb a shock at the time of a collision.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

Here, the above-mentioned shock absorbing structure has required the stabilization of the compressive deformation of a shock absorbing member such as a front side member in an axial direction and has further required the improvement of shock absorption performance.

The invention has been made to solve these problems. An object of the invention is to provide a shock absorbing structure that can improve shock absorption performance by stabilizing the compressive deformation of a shock absorbing member in an axial direction.

Solution to Problem

A shock absorbing structure according to the invention includes a shock absorbing member that extends from one end side toward the other end side, a plurality of first deformation controlling portions that are formed at the shock absorbing member and controls the deformation of the shock absorbing member by adjusting strength, and a plurality of second deformation controlling portions that are formed at the shock absorbing member and controls the deformation of the shock absorbing member by adjusting strength. The plurality of first deformation controlling portions are disposed at a predetermined interval in a longitudinal direction of the shock absorbing member. The plurality of second deformation controlling portions are disposed at a predetermined interval in the longitudinal direction. At least one of the plurality of first deformation controlling portions are disposed between a pair of the second deformation controlling portions. The plurality of first deformation controlling portions include a set of first deformation controlling portions formed so that the first deformation controlling portions disposed closer to the other end side in the longitudinal direction have higher strength.

According to the shock absorbing structure of the invention, at least one of the first deformation controlling portions is disposed between the pair of the second deformation controlling portions. That is, the first and second deformation controlling portions are disposed at least alternately. For example, deformation is facilitated by the reduction of the strength of the first deformation controlling portions, and deformation becomes difficult by the increase of the strength of the second deformation controlling portions. In this case, when a shock is applied to the shock absorbing member in the longitudinal direction, the shock absorbing member can be deformed in the shape of a bellows. Further, the first deformation controlling portions, which are disposed closer to the other end side in the longitudinal direction, have higher strength. Accordingly, the shock absorbing member can be sequentially deformed from one end side. According to the above description, the compressive deformation of the shock absorbing member in an axial direction is stabilized, so that shock absorption performance is improved.

In the shock absorbing structure according to the invention, first strength adjusting portions, which adjust strength, may be formed at the first deformation controlling portions so as to extend in a direction crossing the longitudinal direction and second strength adjusting portions, which adjust strength, may be formed at the second deformation controlling portions so as to extend in the longitudinal direction. Since the first strength adjusting portions such as beads are formed so as to extend in the direction crossing the longitudinal direction, it is possible to effectively reduce the strength of the first deformation controlling portions. Meanwhile, since the second strength adjusting portions such as beads are formed so as to extend in the longitudinal direction, it is possible to effectively increase the strength of the second deformation controlling portions. Accordingly, the compressive deformation of the shock absorbing member in the axial direction is stabilized, so that shock absorption performance is improved.

In the shock absorbing structure according to the invention, first strength adjusting portions, which adjust strength, may be formed at the first deformation controlling portions; second strength adjusting portions, which adjust strength, may be formed at the second deformation controlling portions; a first effective cross-sectional length may be determined by the length of portions of a plurality of sides of a cross-sectional shape of the first deformation controlling portion except for the first strength adjusting portions; a second effective cross-sectional length may be determined by the length of portions of a plurality of sides of a cross-sectional shape of the second deformation controlling portion except for the second strength adjusting portions; the first effective cross-sectional length and the second effective cross-sectional length may be set so as to be different from each other; and the first deformation controlling portions include a set of first deformation controlling portions formed so that the first deformation controlling portions disposed closer to the other end side in the longitudinal direction have a larger first effective cross-sectional length. The first effective cross-sectional length and the second effective cross-sectional length are set so as to be different from each other. Accordingly, the strength of the first deformation controlling portions can be different from the strength of the second deformation controlling portions. Further, the first deformation controlling portions include first deformation controlling portions formed so that the first deformation controlling portions disposed closer to the other end side in the longitudinal direction have a larger first effective cross-sectional length. Accordingly, the shock absorbing member can be sequentially deformed from one end side. According to the above description, the compressive deformation of the shock absorbing member in the axial direction is stabilized, so that shock absorption performance is improved.

In the shock absorbing structure according to the invention, beads may be formed at the first deformation controlling portions, so that first strength adjusting portions adjusting strength are formed. Further, beads may be formed at the second deformation controlling portions, so that second strength adjusting portions adjusting strength are formed. Accordingly, the strength of the first deformation control and the strength of the second deformation controlling portions are easily adjusted.

In the shock absorbing structure according to the invention, the first deformation controlling portions may have strength lower than the strength of deformation uncontrolling portions of the shock absorbing member except for the first and second deformation controlling portions. Accordingly, when a shock is applied from one end side of the shock absorbing member, stress at the first deformation controlling portions is locally increased. The first deformation controlling portions are subjected to plastic buckling and out-of-plane deformation. Accordingly, when a shock is applied in the longitudinal direction of the shock absorbing member, the shock absorbing member can be deformed in the shape of a bellows.

In the shock absorbing structure according to the invention, the second deformation controlling portions may have strength higher than the strength of the deformation uncontrolling portions and the first deformation controlling portions may be disposed at positions that are adjacent to the second deformation controlling portions in the longitudinal direction. The first deformation controlling portions having low strength are disposed so as to be adjacent to the second deformation controlling portions having high strength. Accordingly, portions where strength changes suddenly are formed at the shock absorbing member. Therefore, when a shock is applied in the longitudinal direction of the shock absorbing member, the shock absorbing member can be deformed in the shape of a bellows at the portions where strength changes suddenly. According to the above description, the compressive deformation of the shock absorbing member in the axial direction is stabilized, so that shock absorption performance is improved.

In the shock absorbing structure according to the invention, the shock absorbing member may be formed by welding a plurality of members and welded portions between the members may be formed at the second deformation controlling portions. The welded portions can increase the strength of the second deformation controlling portions. Accordingly, it is possible to further stabilize the compressive deformation of the shock absorbing member in the axial direction.

A shock absorbing structure according to the invention includes a shock absorbing member that extends from one end side toward the other end side, a plurality of first deformation controlling portions that are formed at the shock absorbing member and controls the deformation of the shock absorbing member, and a plurality of second deformation controlling portions that are formed at the shock absorbing member and controls the deformation of the shock absorbing member. The plurality of first deformation controlling portions are disposed at a predetermined interval in a longitudinal direction of the shock absorbing member. The plurality of second deformation controlling portions are disposed at a predetermined interval in the longitudinal direction. At least one of the first deformation controlling portions is disposed between a pair of the second deformation controlling portions. First strength adjusting portions, which control the deformation of the shock absorbing member, are formed at the first deformation controlling portions so as to extend in a direction crossing the longitudinal direction. Second strength adjusting portions, which control the deformation of the shock absorbing member, are formed at the second deformation controlling portions so as to extend in the longitudinal direction.

In the shock absorbing structure according to the invention, at least one of the first deformation controlling portions is disposed between the pair of the second deformation controlling portions. That is, the first and second deformation controlling portions are disposed at least alternately. For example, deformation is facilitated by the reduction of the strength of the first deformation controlling portions, and deformation becomes difficult by the increase of the strength of the second deformation controlling portions. In this case, when a shock is applied to the shock absorbing member in the longitudinal direction, the shock absorbing member can be deformed in the shape of a bellows. In particular, the first strength adjusting portions such as beads extend in a direction crossing the longitudinal direction. Accordingly, the first strength adjusting portions can effectively reduce the strength of the first deformation controlling portions. Meanwhile, the second strength adjusting portions such as beads extend in the longitudinal direction. Therefore, the second strength adjusting portions can effectively increase the strength of the second deformation controlling portions. According to the above description, the compressive deformation of the shock absorbing member in the axial direction is stabilized, so that shock absorption performance is improved.

A shock absorbing structure according to the invention includes a shock absorbing member that extends from one end side toward the other end side, a plurality of first deformation controlling portions that are formed at the shock absorbing member and controls the deformation of the shock absorbing member, and a plurality of second deformation controlling portions that are formed at the shock absorbing member and controls the deformation of the shock absorbing member. The plurality of second deformation controlling portions are disposed at a predetermined interval in a longitudinal direction of the shock absorbing member. The second deformation controlling portions have strength higher than the strength of deformation uncontrolling portions of the shock absorbing member except for the first and second deformation controlling portions. The first deformation controlling portions are disposed so as to be adjacent to the second deformation controlling portions in the longitudinal direction of the shock absorbing member and have strength lower than the strength of the deformation uncontrolling portions.

In the shock absorbing structure according to the invention, the first deformation controlling portions having low strength are disposed so as to be adjacent to the second deformation controlling portions having high strength. Accordingly, portions where strength changes suddenly are formed at the shock absorbing member. Therefore, when a shock is applied in the longitudinal direction of the shock absorbing member, the shock absorbing member can be deformed in the shape of a bellows at the portions where strength changes suddenly. According to the above description, the compressive deformation of the shock absorbing member in the axial direction is stabilized, so that shock absorption performance is improved.

Advantageous Effects of Invention

According to the invention, it is possible to improve shock absorption performance by stabilizing the compressive deformation of a shock absorbing member in an axial direction.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of a shock absorbing structure according to the invention will be described in detail below with reference to the drawings.

First Embodiment

FIG. 1is a perspective view of a shock absorbing structure100according to a first embodiment of the invention. The shock absorbing structure100is a vehicle body structure that is provided at the front portion of a vehicle. The shock absorbing structure100has a function of absorbing a shock that is applied to the shock absorbing structure100from the front face of a vehicle body. The shock absorbing structure100is adapted so that the strength of the front end side portion of a front side member (shock absorbing member)2is adjusted. Meanwhile, inFIG. 1, a positive direction of an X axis represents the outside of a vehicle, a positive direction of a Y axis represents the front side of the vehicle, and a positive direction of a Z axis represents the upper side of the vehicle.

The front side member2is a hollow member that extends from a front end (one end)2atoward a rear end (the other end)2b. The front side member2has a function of absorbing a shock that is applied to the front side member2from the front face of the vehicle. The front side member2includes a front side member outer3that is disposed outside of the vehicle, and a front side member inner4that is disposed inside the vehicle. The front side member outer3is a flat plate-like member that extends in a longitudinal direction.

The front side member inner4is a member that is formed by bending a flat plate extending in the longitudinal direction. The front side member inner4includes a pair of flange portions6and7, an upper surface portion8, a lower surface portion9, a side surface portion11, an inclined surface portion12, and an inclined surface portion13. The pair of flange portions6and7is joined to the front side member outer3. The upper surface portion8extends horizontally from the upper flange portion6toward the inside of the vehicle. The lower surface portion9extends horizontally from the lower flange portion7toward the inside of the vehicle. The side surface portion11extends vertically inside the vehicle. The inclined surface portion12connects the side surface portion11to the upper surface portion8. The inclined surface portion13connects the side surface portion11to the lower surface portion9.

The thickness of the front side member inner4is set to a value larger than Tminthat is obtained by the following expression (1). Since the thickness of the front side member inner4is set to a value larger than Tmin, the front side member inner4is apt to cause stable plastic buckling deformation. Further, the front side member inner4can avoid the disturbance of deformation caused by an unstable elastic collapse phenomenon. Meanwhile, E denotes Young's modulus of a material, γ denotes Poisson's ratio, σydenotes yield strength, and bmaxdenotes the maximum side length of a cross-section. The maximum side length means the length of the longest side of the cross-sectional shape of the front side member inner4. In this embodiment, the length of the cross-sectional shape of the side surface portion11of the front side member inner4(that is, the width of the side surface portion11in a vertical direction) is the maximum side length.

A reinforcing member14is mounted on the inner portion of the front end portion of the front side member inner4, so that the front end portion of the front side member inner4is reinforced. Further, a welded portion21, which connects the flange portion6to the front side member outer3, is formed at the front end portion of the front side member inner4. Furthermore, a welded portion21, which connects the flange portion7to the front side member outer3, is formed at the front end portion of the front side member inner4. Accordingly, the front end portion of the front side member inner4can function as a first high-strength portion31of which the strength against buckling in the longitudinal direction is increased. The first high-strength portion31has strength higher than the strength of deformation uncontrolling portions30of which the strength is not adjusted. The first high-strength portion31has a function of controlling the deformation of the front side member2by suppressing the deformation of the front side member2. The width of the first high-strength portion31in the longitudinal direction of the vehicle is set to about 10 to 20 mm. Meanwhile, the deformation uncontrolling portions30are portions of the front side member2except for the first high-strength portion31, a second high-strength portion32, a third high-strength portion33, a fourth high-strength portion34, a first low-strength portion36, a second low-strength portion37, and a third low-strength portion38. InFIG. 1, the second high-strength portion32, the third high-strength portion33, and the fourth high-strength portion34are shown in a pale pear-skin pattern. The first low-strength portion36, the second low-strength portion37, and the third low-strength portion38are shown in a dark pear-skin pattern.

The second high-strength portion32is formed at the front side member inner4in the rear of the first high-strength portion31by a distance of L (mm). L is obtained by the following expression (2). The second high-strength portion32has strength higher than the strength of the deformation uncontrolling portions30. The second high-strength portion32has a function of controlling the deformation of the front side member2by suppressing the deformation of the front side member2. The second high-strength portion32is set over the flange portion6, the upper surface portion8, the inclined surface portion12, the side surface portion11, the inclined surface portion13, the lower surface portion9, and the flange portion7in the vertical direction of the vehicle. The width of the second high-strength portion32in the longitudinal direction of the vehicle is set to 10 mm or less.
[Expression 2]
30≦L≦0.7×bmax(2)

Specifically, second strength adjusting portions41, which increase strength, are formed at the second high-strength portion32. The second strength adjusting portions41are formed of a plurality of beads that extend in the longitudinal direction of the front side member2. Each of the beads, which form the second strength adjusting portions41, has a length within the width of the second high-strength portion32. The second strength adjusting portions41are formed of a bead that is formed at the inclined surface portion12of the second high-strength portion32, a bead that is formed at the inclined surface portion13of the second high-strength portion32, and two beads that are formed at the side surface portion11of the second high-strength portion32. These beads are recessed inwardly and extend in the longitudinal direction. A welded portion22, which is connected to the front side member outer3, is formed at the flange portion6of the second high-strength portion32. A welded portion22, which is connected to the front side member outer3, is formed at the flange portion7of the second high-strength portion32.

The third high-strength portion33is formed at the front side member inner4in the rear of the second high-strength portion32by a distance of L (mm). The third high-strength portion33has strength higher than the strength of the deformation uncontrolling portions30. The third high-strength portion33has a function of controlling the deformation of the front side member2by suppressing the deformation of the front side member2. The third high-strength portion33is set over the flange portion6, the upper surface portion8, the inclined surface portion12, the side surface portion11, the inclined surface portion13, the lower surface portion9, and the flange portion7in the vertical direction of the vehicle. The width of the third high-strength portion33in the longitudinal direction of the vehicle is set to 10 mm or less.

Specifically, second strength adjusting portions42, which increase strength, are formed at the third high-strength portion33. The second strength adjusting portions42are formed of a plurality of beads that extend in the longitudinal direction of the front side member2. Each of the beads, which form the second strength adjusting portions42, has a length within the width of the third high-strength portion33. The second strength adjusting portions42are formed of a bead that is formed at the inclined surface portion12of the second high-strength portion32, a bead that is formed at the inclined surface portion13of the second high-strength portion32, and two beads that are formed at the side surface portion11of the second high-strength portion32. These beads are recessed inwardly and extend in the longitudinal direction. A welded portion23, which is connected to the front side member outer3, is formed at the flange portion6of the third high-strength portion33. A welded portion23, which is connected to the front side member outer3, is formed at the flange portion7of the third high-strength portion33.

The fourth high-strength portion34is formed at the front side member inner4in the rear of the third high-strength portion33by a distance of L (mm). The fourth high-strength portion34has strength higher than the strength of the deformation uncontrolling portions30. The fourth high-strength portion34has a function of controlling the deformation of the front side member2by suppressing the deformation of the front side member2. The fourth high-strength portion34is set over the flange portion6, the upper surface portion8, the inclined surface portion12, the side surface portion11, the inclined surface portion13, the lower surface portion9, and the flange portion7in the vertical direction of the vehicle. The width of the fourth high-strength portion34in the longitudinal direction of the vehicle is set to 10 mm or less.

Specifically, second strength adjusting portions43, which increase strength, are formed at the fourth high-strength portion34. The second strength adjusting portions43are formed of a plurality of beads that extend in the longitudinal direction of the front side member2. Each of the beads, which form the second strength adjusting portions43, has a length within the width of the fourth high-strength portion34. The second strength adjusting portions43are formed of a bead that is formed at the inclined surface portion12of the second high-strength portion32, a bead that is formed at the inclined surface portion13of the second high-strength portion32, and two beads that are formed at the side surface portion11of the second high-strength portion32. These beads are recessed inwardly and extend in the longitudinal direction. A welded portion24, which is connected to the front side member outer3, is formed at the flange portion6of the fourth high-strength portion34. A welded portion24, which is connected to the front side member outer3, is formed at the flange portion7of the fourth high-strength portion34.

The first low-strength portion36is formed at the front side member inner4at the middle position between the first and second high-strength portions31and32. The first low-strength portion36has low strength against a shock in the longitudinal direction of the vehicle, as compared to the deformation uncontrolling portions30. The first low-strength portion36has a function of controlling the deformation of the front side member2by allowing the front side member2to be easily deformed. Since the first low-strength portion36has a shape where stress concentration easily occurs at the time of a collision, the first low-strength portion36functions as a portion that corresponds to the peak of deformation. The first low-strength portion36is set over the flange portion6, the upper surface portion8, the inclined surface portion12, the side surface portion11, the inclined surface portion13, the lower surface portion9, and the flange portion7in the vertical direction of the vehicle.

Specifically, first strength adjusting portions44, which reduce strength, are formed at the first low-strength portion36. The first strength adjusting portions44are formed of a plurality of beads that extend in a direction orthogonal to the longitudinal direction of the front side member2. The first strength adjusting portions44are formed of beads that are formed at the corner between the upper surface portion8and the inclined surface portion12of the first low-strength portion36, the corner between the lower surface portion9and the inclined surface portion13of the first low-strength portion36, the corner between the inclined surface portion12and the side surface portion11of the first low-strength portion36, and the corner between the inclined surface portion13and the side surface portion11of the first low-strength portion36. These beads are recessed inwardly and extend in the direction orthogonal to the longitudinal direction.

The second low-strength portion37is formed at the front side member inner4at the middle position between the second and third high-strength portions32and33. The second low-strength portion37has strength lower than the strength of the deformation uncontrolling portions30. The second low-strength portion37has strength higher than the strength of the first low-strength portion36. The second low-strength portion37has a function of controlling the deformation of the front side member2by allowing the front side member2to be easily deformed. Since the second low-strength portion37has a shape where stress concentration easily occurs at the time of a collision, the second low-strength portion37functions as a portion that corresponds to the peak of deformation. The second low-strength portion37is set over the flange portion6, the upper surface portion8, the inclined surface portion12, the side surface portion11, the inclined surface portion13, the lower surface portion9, and the flange portion7in the vertical direction of the vehicle.

Specifically, first strength adjusting portions45, which reduce strength, are formed at the second low-strength portion37. The first strength adjusting portions45are formed of a plurality of beads that extend in a direction orthogonal to the longitudinal direction of the front side member2. The first strength adjusting portions45are formed of beads that are shorter than the first strength adjusting portions44. The first strength adjusting portions45are formed of beads that are formed at the corner between the upper surface portion8and the inclined surface portion12of the first low-strength portion36, the corner between the lower surface portion9and the inclined surface portion13of the first low-strength portion36, the corner between the inclined surface portion12and the side surface portion11of the first low-strength portion36, and the corner between the inclined surface portion13and the side surface portion11of the first low-strength portion36. These beads are recessed inwardly and extend in the direction orthogonal to the longitudinal direction.

The third low-strength portion38is formed at the front side member inner4at the middle position between the third and fourth high-strength portions33and34. The third low-strength portion38has strength lower than the strength of the deformation uncontrolling portions30. The third low-strength portion38has strength higher than the strength of the second low-strength portion37. The third low-strength portion38has a function of controlling the deformation of the front side member2by allowing the front side member2to be easily deformed. Since the third low-strength portion38has a shape where stress concentration easily occurs at the time of a collision, the third low-strength portion38functions as a portion that corresponds to the peak of deformation. The third low-strength portion38is set over the flange portion6, the upper surface portion8, the inclined surface portion12, the side surface portion11, the inclined surface portion13, the lower surface portion9, and the flange portion7in the vertical direction of the vehicle.

Specifically, first strength adjusting portions46, which reduce strength, are formed at the third low-strength portion38. The first strength adjusting portions46are formed of a plurality of beads that extend in a direction orthogonal to the longitudinal direction of the front side member2. The first strength adjusting portions46are formed of beads that are shorter than the first strength adjusting portions45. The first strength adjusting portions46are formed of beads that are formed at the corner between the upper surface portion8and the inclined surface portion12of the first low-strength portion36, the corner between the lower surface portion9and the inclined surface portion13of the first low-strength portion36, the corner between the inclined surface portion12and the side surface portion11of the first low-strength portion36, and the corner between the inclined surface portion13and the side surface portion11of the first low-strength portion36. These beads are recessed inwardly and extend in the direction orthogonal to the longitudinal direction.

According to the above description, the respective low-strength portions36,37, and38, which are disposed closer to the rear end2bside in the longitudinal direction, sequentially have higher strength. That is, the strength of the low-strength portion closer to the front end2ais lower, and the strength of the low-strength portion closer to the rear end2bis higher. Meanwhile, the middle positions of the upper surface portion8, the lower surface portion9, the side surface portion11, the inclined surface portion12, and the inclined surface portion13in the cross-section of each of the low-strength portions36,37, and38serve as the starting point of plastic buckling. Accordingly, it is preferable that beads be not formed at the above-mentioned positions. A relationship where the strength of the low-strength portion having the highest strength is lower than that of the low-strength portion having the lowest strength is satisfied.

FIG. 2is a cross-sectional view taken along a line II-II shown inFIG. 1.FIG. 2shows the cross-sectional shape of the first low-strength portion36. The cross-sectional shape of the first low-strength portion36includes a plurality of sides. Specifically, the cross-sectional shape of the first low-strength portion36includes sides that correspond to the flange portion6, the flange portion7, the upper surface portion8, the lower surface portion9, the side surface portion11, the inclined surface portion12, the inclined surface portion13, the first strength adjusting portions44, and the front side member outer3. The effective cross-sectional length SC1of the first low-strength portion36is defined as the length that is obtained by subtracting the length of the sides corresponding to the first strength adjusting portions44from the sum of the lengths of the sides forming the cross-sectional shape. Specifically, the effective cross-sectional length SC1is determined by the length of the dashed-dotted lines shown inFIG. 2. Meanwhile, inFIG. 2, a dashed-dotted line is drawn at the middle position in the thickness of the cross-sectional shape. The length of the side of the cross-sectional shape is determined on the basis of the above-mentioned position. However, the length of the side of the cross-sectional shape may be determined on the basis of the position on the outer periphery or the inner periphery of the cross-sectional shape.

The effective cross-sectional length SC2of the second low-strength portion37and the effective cross-sectional length SC3of the third low-strength portion38are determined by the same method as the method in the case of the effective cross-sectional length SC1of the first low-strength portion36. The first strength adjusting portions45of the second low-strength portion37are shorter than the first strength adjusting portions44of the first low-strength portion36, and the first strength adjusting portions46of the third low-strength portion38are shorter than the first strength adjusting portions45of the second low-strength portion37. Accordingly, a relationship of SC1<SC2<SC3is satisfied among the effective cross-sectional lengths SC1, SC2, and SC3. That is, the low-strength portions36,37, and38, which are disposed closer to the rear end2bside in the longitudinal direction, have a larger effective cross-sectional length.

FIG. 3is a cross-sectional view taken along a line III-III shown inFIG. 1.FIG. 3shows the cross-sectional shape of the second high-strength portion32. The cross-sectional shape of the second high-strength portion32includes a plurality of sides. Specifically, the cross-sectional shape of the second high-strength portion32includes sides that correspond to the flange portion6, the flange portion7, the upper surface portion8, the lower surface portion9, the side surface portion11, the inclined surface portion12, the inclined surface portion13, the second strength adjusting portions41, and the front side member outer3. The effective cross-sectional length SN of the second high-strength portion32is defined as the length that is obtained by subtracting the length of the sides corresponding to the second strength adjusting portions41from the sum of the lengths of the sides forming the cross-sectional shape. Specifically, the effective cross-sectional length SN is determined by the length of the dashed-dotted lines shown inFIG. 3. Meanwhile, inFIG. 3, a dashed-dotted line is drawn at the middle position in the thickness of the cross-sectional shape. The length of the side of the cross-sectional shape is determined on the basis of the above-mentioned position. However, the length of the cross-sectional shape may be determined on the basis of the position on the outer periphery or the inner periphery of the cross-sectional shape. Each of the effective cross-sectional lengths of the third and fourth high-strength portions33and34becomes SN. Each of the effective cross-sectional lengths SN of the high-strength portions32,33, and34is set to be larger than any one of the effective cross-sectional lengths SC1, SC2, and SC3.

Next, the operation and effect of the shock absorbing structure100according to the first embodiment will be described.

When a shock is applied to the front side member2from the front side of a vehicle, stress at each of the low-strength portions36,37, and38is locally increased. Each of the low-strength portions36,37, and38is subjected to out-of-plane deformation. The out-of-plane deformation of each of the low-strength portions36,37, and38proceeds in the longitudinal direction of the vehicle, but is received by each of the high-strength portions31,32,33, and34having high strength. Accordingly, the front side member2is deformed in the shape of a bellows in a mode where each of the high-strength portions31,32,33, and34corresponds to a half wavelength. That is, when a shock is applied to the front side member2in the longitudinal direction of the vehicle, the front side member2is deformed in the shape of a bellows so that each of the low-strength portions36,37, and38corresponds to an antinode and each of the high-strength portions31,32,33, and34corresponds to a node. Further, the respective low-strength portions36,37, and38, which are disposed closer to the rear end2bside, have higher strength. Accordingly, the deformation of the front side member2sequentially occurs from the front end2aside. According to the above description, the compressive deformation of the front side member2in an axial direction is stabilized, so that shock absorption performance is improved.

According to the above description, the respective high-strength portions31,32,33, and34and the respective low-strength portions36,37, and38are alternately disposed in the shock absorbing structure100according to the first embodiment. Accordingly, when a shock is applied to the front side member2in the longitudinal direction of the vehicle, the front side member2can be deformed in the shape of a bellows. Further, the respective low-strength portions36,37, and38, which are disposed closer to the rear end2bside in the longitudinal direction, have higher strength. Therefore, the front side member2can be sequentially deformed from the front end2aside. According to the above description, the compressive deformation of the front side member2in an axial direction is stabilized, so that shock absorption performance is improved.

Furthermore, in the shock absorbing structure100according to the first embodiment, the first strength adjusting portions44,45, and46such as beads extend in the direction orthogonal to the longitudinal direction. Accordingly, the first strength adjusting portions44,45, and46can effectively reduce the strengths of the respective low-strength portions36,37, and38. Meanwhile, the second strength adjusting portions41,42, and43such as beads extend in the longitudinal direction. Accordingly, the second strength adjusting portions41,42, and43can effectively increase the strengths of the respective high-strength portions31,32,33, and34. Therefore, the compressive deformation of the front side member2in an axial direction is stabilized, so that shock absorption performance is improved.

Moreover, in the shock absorbing structure100according to the first embodiment, the effective cross-sectional lengths of the respective low-strength portions36,37, and38and the effective cross-sectional lengths of the respective high-strength portions31,32,33, and34are different from each other. Accordingly, the strengths of the respective low-strength portions36,37, and38and the respective high-strength portions31,32,33, and34are different from each other. Further, the respective low-strength portions36,37, and38, which are disposed closer to the rear end2bside in the longitudinal direction, have a larger effective cross-sectional length. Therefore, the front side member2can be sequentially deformed from the front end2aside. According to the above description, the compressive deformation of the front side member2in an axial direction is stabilized, so that shock absorption performance is improved.

Furthermore, in the shock absorbing structure100according to the first embodiment, each of the low-strength portions36,37, and38has strength lower than the strength of the deformation uncontrolling portions30. Accordingly, when a shock is applied to the front side member2from the front side of a vehicle, stress at each of the low-strength portions36,37, and38is locally increased. Each of the low-strength portions36,37, and38is subjected to plastic buckling and out-of-plane deformation. Accordingly, when a shock is applied to the front side member2from the front side of a vehicle, the front side member2can be deformed in the shape of a bellows.

Moreover, in the shock absorbing structure100according to the first embodiment, the welded portions21to24are formed at the high-strength portions31,32,33, and34, respectively. The welded portions21to24can increase the strengths of the high-strength portions31,32,33, and34, respectively. Accordingly, it is possible to further stabilize the compressive deformation of the front side member2in the axial direction.

Second Embodiment

Next, a shock absorbing structure200according to a second embodiment of the invention will be described with reference toFIG. 4.FIG. 4is a perspective view of the shock absorbing structure200according to the second embodiment of the invention. InFIG. 4, a front side member inner4is shown by an imaginary line and only a front side member outer53is shown by a solid line. The shock absorbing structure200according to the second embodiment is mainly different from the shock absorbing structure100according to the first embodiment in that beads are formed even at the front side member outer53.

As shown inFIG. 4, a front side member52of the shock absorbing structure200includes the front side member inner4and the front side member outer53. The front side member outer53includes flange portions54and55, a side surface portion56, and inclined surface portions57and58. Further, beads, which extend in the longitudinal direction of a vehicle, are formed at the corner between the side surface portion56and the inclined surface portion57and the corner between the side surface portion56and the inclined surface portion58.

The strength of a position of the front side member outer53, which corresponds to a first high-strength portion31of a front side member inner4as seen in a vehicle width direction, is made high. That is, second strength adjusting portions61are formed at the position. The second strength adjusting portions61are formed of reinforcing beads that are formed at the side surface portion56and the inclined surface portions57and58. These beads are recessed inwardly and extend in the longitudinal direction. Likewise, second strength adjusting portions, which are formed of reinforcing beads, are formed at positions corresponding to the respective high-strength portions32,33, and34on the side that is closer to the rear end than the position.

The strength of a position of the front side member outer53, which corresponds to a first low-strength portion36of the front side member inner4as seen in the vehicle width direction, is made low. That is, first strength adjusting portions62are formed at the position. The first strength adjusting portions62are formed of deformation facilitating beads that are formed at the corner between the side surface portion56and the inclined surface portion57and the corner between the side surface portion56and the inclined surface portion58. These beads are recessed inwardly and extend in a direction orthogonal to the longitudinal direction. Likewise, first strength adjusting portions, which are formed of deformation facilitating beads, are formed at positions corresponding to the respective low-strength portions37and38on the side that is closer to the rear end than the position.

According to the above description, in the shock absorbing structure200according to the second embodiment, the strength of each of the low-strength portions36,37, and38is further reduced. Further, the strength of each of the high-strength portions31,32,33, and34is further increased.

Third Embodiment

Next, a shock absorbing structure300according to a third embodiment of the invention will be described with reference toFIG. 5.FIG. 5is a perspective view of the shock absorbing structure300according to the third embodiment of the invention. The shock absorbing structure300according to the third embodiment is mainly different from the shock absorbing structure100according to the first embodiment in that bulkheads70are provided at the respective high-strength portions32,33, and34.

As shown inFIG. 5, beads, which extend in the longitudinal direction, are not formed at the respective high-strength portions32,33, and34. The bulkheads70are disposed in a front side member2at the respective high-strength portions32,33, and34. Accordingly, the strength of each of the high-strength portions32,33, and34is increased. Therefore, when a shock is applied to the front side member2from the front side of a vehicle, the deformation of each of the high-strength portions32,33, and34is suppressed.

Fourth Embodiment

Next, a shock absorbing structure400according to a fourth embodiment of the invention will be described with reference toFIG. 6.FIG. 6is a perspective view of the shock absorbing structure400according to the fourth embodiment of the invention. The shock absorbing structure400according to the fourth embodiment is mainly different from the shock absorbing structure100according to the first embodiment in that each of low-strength portions86,87, and88is formed by heat treatment.

As shown inFIG. 6, each of the low-strength portions86,87, and88is subjected to heat treatment or the like. Accordingly, the strength of each of the low-strength portions86,87, and88is made lower than the strength of deformation uncontrolling portions30. The strength of the second low-strength portion87is higher than the strength of the first low-strength portion86, and the strength of the third low-strength portion88is higher than the strength of the second low-strength portion87. According to the shock absorbing structure400of the fourth embodiment, it is possible to reduce the strength of each of the low-strength portions86,87, and88without forming beads. Meanwhile, the strength of each of the high-strength portions may be increased by heat treatment or the like.

Fifth Embodiment

Next, a shock absorbing structure500according to a fifth embodiment of the invention will be described with reference toFIG. 7.FIG. 7is a perspective view of the shock absorbing structure500according to the fifth embodiment of the invention. The shock absorbing structure500according to the fifth embodiment is mainly different from the shock absorbing structure400according to the fourth embodiment in that low-strength portions are formed at positions adjacent to high-strength portions.

As shown inFIG. 7, each of high-strength portions91,92, and93is subjected to heat treatment. Accordingly, the strength of each of high-strength portions91,92, and93is made significantly higher than the strength of deformation uncontrolling portions30. First and second low-strength portions94and95are formed at positions that are adjacent to both ends of the second high-strength portion91in the longitudinal direction of a vehicle. Third and fourth low-strength portions96and97are formed at positions that are adjacent to both ends of the third high-strength portion92in the longitudinal direction of the vehicle. Fifth and sixth low-strength portions98and99are formed at positions that are adjacent to both ends of the fourth high-strength portion93in the longitudinal direction of the vehicle. Accordingly, the first low-strength portion94is disposed between a first high-strength portion31and the second high-strength portion91. The second and third low-strength portions95and96are disposed between second and third high-strength portions91and92. The fourth and fifth low-strength portions97and98are disposed between the third and fourth high-strength portions92and93.

The strength of each of the low-strength portions94to99is made lower than the strength of deformation uncontrolling portions30by heat treatment or the like. The difference between the strength of the third high-strength portion92and the strength of each of the low-strength portions96and97is made smaller than the difference between the strength of the second high-strength portion91and the strength of each of the low-strength portions94and95. Further, the difference between the strength of the fourth high-strength portion93and the strength of each of the low-strength portions98and99is made smaller than the difference between the strength of the third high-strength portion92and the strength of each of the low-strength portions96and97. That is, the difference between the strengths of the high-strength portion and the low-strength portion, which are disposed closer to the rear end, is smaller. For example, when the strengths of the respective high-strength portions91to93are equal to each other, the respective low-strength portions94to99, which are disposed closer to the rear end, have higher strength. Meanwhile, low-strength portions and high-strength portions are formed even at the front side member outer3like in the front side member inner4.

According to the above description, in the shock absorbing structure500according to the fifth embodiment, the low-strength portions94to99are disposed so as to be adjacent to the high-strength portions31,91,92, and93, respectively. Accordingly, portions where strength changes suddenly are formed at a front side member2. Therefore, when a shock is applied to the front side member2from the front side of a vehicle, the front side member2can be deformed in the shape of a bellows at the portions where strength changes suddenly. According to the above description, the compressive deformation of the front side member2in an axial direction is stabilized, so that shock absorption performance is improved.

The invention is not limited to the above-mentioned embodiments.

For example, in the above-mentioned embodiments, the strength of the low-strength portion has been reduced by beads. However, the strength of the low-strength portion may be reduced by long holes.

Further, the shape of the front side member is not limited to the above-mentioned embodiments. Furthermore, the number of the low-strength portions and the number of the high-strength portions are not limited to the above-mentioned embodiments. Moreover, in the above-mentioned embodiments, the low-strength portions, which are disposed closer to the other end in the longitudinal direction, had higher strength. However, this relationship may be satisfied at a part of the plurality of low-strength portions according to a position where deformation is intended to be controlled. For example, on the front side of a low-strength portion that has low strength and is disposed close to the front end, a low-strength portion of which the strength is higher than the strength of the low-strength portion may be disposed. Alternatively, a plurality of sets of patterns, which are formed so that low-strength portions disposed closer to the other end in the longitudinal direction have higher strength, may be formed in the longitudinal direction of the front side member.

INDUSTRIAL APPLICABILITY

The invention may be used to improve the shock absorption of a vehicle.