Drop impact mitigation structure

Abstract

To provide a drop impact mitigation structure in a space-saving and simple shape, having an impact mitigation effect even when dropped in an inclined state.SOLUTION: A drop mitigation structure mitigating impact acting on a component 110 by drop of a collision object 100 accommodating the component 110 inside is provided with a projection 1 projecting outward of the collision object 100 from a bottom surface 101 of the collision object 100. The projection 1 is placed at a position deviated from a center 103 of gravity of the bottom surface 101.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a drop impact mitigation structure. Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2014-210572 (Patent Document 1) discloses an impact mitigation system that converts mechanical energy of a main device upon collision into potential energy of a shock absorbing spring, and then converts the energy back into mechanical energy of a slave device. Prior Art Literature Patent Literature

[0003] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2014-210572 Summary of the Invention Problem to be Solved by the Invention

[0004] The system described in the above document has a reduced impact mitigation effect when a collision occurs in an inclined state.

[0005] The present disclosure proposes a drop impact mitigation structure that has an impact mitigation effect even when dropped in an inclined state, is space-saving, and has a simple shape. Means for Solving the Problem

[0006] According to the present disclosure, there is proposed a drop impact mitigation structure that mitigates impact applied to a component caused by collision when a container accommodating the component therein falls. The drop impact mitigation structure includes a projection protruding outward from the container from a bottom surface of the container. The projection is arranged at a position offset from the center of gravity of the bottom surface. Effect of the Invention

[0007] According to the present disclosure, it is possible to realize a drop impact mitigation structure that has an impact mitigation effect even when dropped in an inclined state, is space-saving, and has a simple shape. [Brief explanation of the drawing]

[0008] [Figure 1] This is a side view of an object that is subject to a fall impact mitigation structure. [Figure 2] This is a perspective view of a stepped pin. [Figure 3] This is a cross-sectional view showing the stepped pin attached to the object it will collide with. [Figure 4] This is a bottom view of the impact and fall damage mitigation structure. [Figure 5] This is a side view showing the behavior of the colliding object as it falls. [Figure 6] This is a side view showing the collision object placed on a flat surface. [Figure 7] This graph shows the effectiveness of the drop impact mitigation structure. [Modes for carrying out the invention]

[0009] The embodiments will be described below with reference to the figures. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions of them will not be repeated. It is intended from the outset that any configuration may be extracted from the embodiments and combined in any way.

[0010] Figure 1 is a side view of the impact object 100 to which the impact mitigation structure is applied. The impact object 100 has a cylindrical outer shape. The impact object 100 has a bottom surface 101. The bottom surface 101 is one end face of the outer surface of the cylindrical impact object 100. The bottom surface 101 has a planar shape. The bottom surface 101 has a center of gravity 103. The bottom surface 101 may be a perfect circle, in which case the center of gravity 103 is at the center of that perfect circle. If the bottom surface 101 is elliptical, the center of gravity 103 is at the intersection of the major axis and minor axis of the ellipse. In this case, the impact object 100 becomes an elliptical cylinder. If the bottom surface 101 is rectangular, the center of gravity 103 is at the intersection of the diagonals. Furthermore, even if the bottom surface 101 is polygonal, its center of gravity 103 can be determined. In these cases, the impact object 100 becomes a rectangular tubular prism. Furthermore, the collision object 100 may be a truncated cone, a truncated pyramid, or any combination of shapes.

[0011] The centroid line L is a straight line passing through the centroid 103 and perpendicular to the base 101. The centroid line L passes through the centroid of the colliding object 100. The centroid line L extends in the axial direction of the cylindrical colliding object 100. The centroid line L is the central axis of the cylindrical colliding object 100.

[0012] The impact object 100 contains components 110 inside. The impact object 100 corresponds to an example of a container that contains components 110 inside. Components 110 are articles with low impact resistance, such as precision instruments. Components 110 have a low-strength part 111. The low-strength part 111 is a part of component 110 that is more susceptible to damage than other parts of component 110. The low-strength part 111 is particularly susceptible to damage from impacts in the direction along the center of gravity line L (referred to as the axial direction in this specification).

[0013] When the impact object 100 falls and hits a surface such as the ground, an impact load is generated on the impact object 100. This applies an impact acceleration to the internal components 110 of the impact object 100. If the axial component of this impact acceleration is large, the components 110 may be damaged. In particular, it is necessary to mitigate the axial impact applied to the components 110 (low-strength part 111) when the impact object 100 falls with its bottom surface 101 facing downwards. Therefore, the impact object 100 of this embodiment has a fall impact mitigation structure to mitigate the axial impact acceleration applied to the components 110 when the impact object 100 falls.

[0014] Specifically, countermeasures are taken on the bottom surface 101 of the outer surface of the impact object 100, which is close to the low-strength portion 111. A projection 1 is provided on the bottom surface 101. The projection 1 protrudes outward from the bottom surface 101 of the impact object 100. The projection 1 is provided so as to protrude from the bottom surface 101 of the outer surface of the impact object 100, which is close to the low-strength portion 111.

[0015] A stepped pin 10, which is constructed separately from the impact object 100, is attached to the impact object 100 to form a projection 1. Figure 2 is a perspective view of the stepped pin 10. The stepped pin 10 has a stepped shape. The stepped pin 10 has an intermediate portion 20, an impact portion 30, and a mounting portion 40. The intermediate portion 20 has a larger outer diameter than the impact portion 30 and the mounting portion 40.

[0016] Figure 3 is a cross-sectional view showing the stepped pin 10 attached to the impact object 100. The bottom surface 101 of the impact object 100 has a recess 102 formed in which a part of the bottom surface 101 is recessed. The mounting portion 40 of the stepped pin 10 is attached to the recess 102. The depth to which the recess 102 is recessed from the bottom surface 101 is greater than the length to which the mounting portion 40 protrudes from the intermediate portion 20. The mounting portion 40 is, for example, press-fitted into the recess 102. The stepped pin 10 is attached to the impact object 100 by housing the mounting portion 40 within the recess 102 and fixing it within the recess 102.

[0017] Of the stepped pin 10, the mounting portion 40 is housed in the collision object 100. Of the stepped pin 10, the intermediate portion 20 and the collision portion 30 protrude from the bottom surface 101 and constitute the projection 1. The intermediate portion 20 corresponds to an example of the "base portion" of the projection 1. The collision portion 30 corresponds to an example of the "tip portion" of the projection 1.

[0018] The intermediate portion 20 has higher rigidity than the mounting portion 40 and the collision portion 30 by increasing its diameter. The intermediate portion 20 has a contact surface 21. Since the diameter of the intermediate portion 20 is larger than that of the mounting portion 40, the contact surface 21 has a flange-like shape that projects radially outward with respect to the mounting portion 40. In a state where the stepped pin 10 is attached to the collision object 100, the contact surface 21 is in surface contact with the bottom surface 101 of the collision object 100. By increasing the diameter of the intermediate portion 20 to increase the contact area between the contact surface 21 and the bottom surface 101, detachment of the stepped pin 10 from the collision object 100 caused by bending deformation of the mounting portion 40 when the collision object 100 falls and the stepped pin 10 collides with a collision surface is suppressed.

[0019] The collision portion 30 has an outer diameter smaller than that of the intermediate portion 20. By reducing the diameter of the collision portion 30, the rigidity of the collision portion 30 is made lower than that of the intermediate portion 20. By making the collision portion 30 have low rigidity, when the collision object 100 falls and the stepped pin 10 comes into contact with the collision surface, the effect of mitigating impact by deforming the collision portion 30 is achieved.

[0020] By reducing the diameter of the collision portion 30, the effect of mitigating impact by reducing the collision area where the collision portion 30 contacts the collision surface at the time of collision is achieved. Assuming that the stress wave σ generated by impact is defined with colliding body material density ρ, colliding body stress propagation velocity C, and collision velocity V, σ=ρCV. Assuming that the load F generated by impact is defined with the collision area S between the colliding body and the collision surface, F=σS. Assuming that the impact acceleration a at the time of collision is defined with the mass m of the colliding body, a=F / m. From these relational expressions, a=(ρCVS) / m, and the impact acceleration a is proportional to the collision area S. Therefore, the impact acceleration can be reduced by reducing the collision area.

[0021] The impact portion 30 has a spherical portion 31 at its tip. The spherical portion 31 has a spherical shape. The radius of curvature of the spherical portion 31 is greater than or equal to the radius of the impact portion 30. It is more preferable to make the radius of curvature of the spherical portion 31 the same as the radius of the impact portion 30. By making the tip of the impact portion 30 spherical, when the impacting object 100 falls in an inclined position and the stepped pin 10 hits the impact surface in an inclined position, the consistency of the shape of the impact portion 30 that contacts the impact surface can be improved. The uniformity of the impact mitigation effect with respect to the position of the stepped pin 10 can be improved.

[0022] The diameter of the mounting portion 40 may be larger than the diameter of the impact portion 30. The length of the mounting portion 40 protruding from the intermediate portion 20 may be larger than the length of the impact portion 30 protruding from the intermediate portion 20. The length of the projection 1 protruding from the bottom surface 101 when the stepped pin 10 is attached to the impact object 100 may be twice or more the length of the mounting portion 40 protruding from the intermediate portion 20.

[0023] Figure 4 is a bottom view of the impact object 100 and the stepped pin 10. The stepped pin 10, which constitutes the projection 1, is positioned offset from the center of gravity 103 of the bottom surface 101. The stepped pin 10 is preferably positioned as far as the amount of offset from the center of gravity 103 is within the range in which the stepped pin 10 can be attached to the impact object 100. For example, the shortest distance between the periphery of the intermediate portion 20 and the center of gravity 103 may be greater than the diameter of the intermediate portion 20. The shortest distance between the periphery of the intermediate portion 20 and the periphery of the bottom surface 101 may be smaller than the diameter of the intermediate portion 20.

[0024] Figure 5 is a side view showing the behavior of the impacting object 100 during its fall. The impact surface P is, for example, a floor or the ground. The downward-pointing white arrows shown in Figure 5 indicate the direction of the impacting object 100's fall toward the impact surface P. The upward-pointing arrows from the protrusion 1 indicate the kinetic energy of the rebound in the upward direction. In the absence of the protrusion 1, if the bottom surface 101 falls toward the impact surface P with an angle of 0° between the bottom surface 101 and the impact surface P, all of the mechanical energy of the impacting object 100 at the time of impact will be used as kinetic energy for the rebound in the upward direction. Therefore, the axial impact applied to the internal components 110 of the impacting object 100 will be large.

[0025] The curved arrows shown in Figure 5 indicate the rotation of the collision part 30 around the point of contact with the collision surface P. Since the collision object 100 is provided with a projection 1, when the projection 1 collides with the collision surface P, the mechanical energy of the collision object 100 is used for rotational kinetic energy in addition to the kinetic energy for upward rebound. The larger the ratio of rotational kinetic energy to impact energy, the less upward rebound is reduced, thereby reducing the axial impact applied to the internal components 110 of the collision object 100. The further the projection 1 is moved from the center of gravity 103, the larger the ratio of rotational kinetic energy can be. By positioning the projection 1 as far away from the center of gravity 103 as possible, the effect of mitigating axial impact can be fully realized.

[0026] Figure 6 is a side view showing the impact object 100 placed on a flat surface. The impact surface P shown in Figure 6 has a flat shape. The impact surface P corresponds to an example of a "flat surface". The impact object 100 shown in Figure 6 is placed gently on the impact surface P. The bottom surface 101 is facing the impact surface P. The tip of the projection 1, i.e., the spherical part 31 at the tip of the impact part 30, and a part of the periphery of the bottom surface 101 are in contact with the impact surface P.

[0027] A portion of the periphery of the base surface 101 that contacts the impact surface P is a portion of the periphery opposite to the tip of the projection 1, with the center of gravity 103 in between. Of the periphery of the base surface 101, the portion furthest from the projection 1 contacts the impact surface P. The portion of the periphery of the base surface 101 that contacts the impact surface P, the center of gravity 103, and the tip of the projection 1 lie on the same plane.

[0028] With the tip of the projection 1 and a part of the periphery of the bottom surface 101 in contact with the impact surface P, the bottom surface 101 is inclined with respect to the impact surface P. The impact angle θ shown in Figure 6 is defined as the angle between the bottom surface 101 and the impact surface P when the impact object 100 is placed on a flat impact surface P with the bottom surface 101 facing the impact surface P.

[0029] Figure 7 is a graph showing the effect of the fall impact mitigation structure. In the graph shown in Figure 7, the horizontal axis represents the impact angle θ (unit: deg), and the vertical axis, maximum acceleration, represents the maximum axial impact acceleration applied to the internal components 110 of the impact object 100 when it collides with the impact surface P. In Figure 7, the maximum axial acceleration when the impact object 100 collides with the impact surface P at different impact angles θ, with and without the fall impact mitigation structure, is plotted, and approximation lines of these plots are drawn. The solid line in Figure 7 is the graph when the fall impact mitigation structure is provided. The dashed line in Figure 7 is the graph when the fall impact mitigation structure is not provided.

[0030] As shown by the dashed line in Figure 7, without a fall impact mitigation structure, the maximum axial acceleration increases sharply as the impact angle θ approaches 0°. When the impact angle θ is large, that is, when the colliding object 100 falls at an angle relative to the impact surface P, the maximum axial acceleration decreases. In the range where the impact angle θ is 20° or greater, the maximum axial acceleration remains almost constant. If the impact angle θ is 20° or greater, the maximum axial acceleration is small even without impact mitigation.

[0031] Therefore, as shown in Figure 6, the amount of projection 1 protruding from the bottom surface 101 is adjusted so that, when the tip of the projection 1 and a part of the periphery of the bottom surface 101 of the impact object 100 are in contact with the impact surface P, the bottom surface 101 and the impact surface P form an angle of 20° or more. This adjustment ensures that, in the range where the angle between the bottom surface 101 and the impact surface P when the impact object 100 falls is less than 20°, the projection 1 makes contact with the impact surface P before the impact object 100. As a result, as explained with reference to Figure 5, a portion of the mechanical energy of the impact object 100 is used as rotational kinetic energy. Consequently, the axial impact applied to the component 110 is reduced.

[0032] As shown by the solid line in Figure 7, by providing the drop impact mitigation structure, the maximum axial acceleration applied to component 110 is significantly reduced compared to the case without the drop impact mitigation structure, in the range where the impact angle θ is less than 20°. Furthermore, by providing the drop impact mitigation structure, the maximum acceleration can be kept almost constant regardless of the impact angle θ during the fall.

[0033] Although some of the above description overlaps with the above, the characteristic configuration and effects of this embodiment are summarized as follows.

[0034] As shown in Figures 1,4-6, the projection 1 that protrudes outward from the bottom surface 101 of the impacting object 100 is positioned offset from the center of gravity 103 of the bottom surface 101. By positioning the projection 1 offset from the center of gravity 103, a portion of the mechanical energy of the impacting object 100 during its fall is used as rotational kinetic energy. This reduces the kinetic energy of the upward rebound. Therefore, the axial impact applied to the internal components 110 of the impacting object 100 can be reduced, thereby suppressing damage to the components 110.

[0035] The impact of a fall can be mitigated by a simple configuration in which a protrusion 1 is provided on the object 100, thus enabling the realization of a space-saving and simple-shaped fall impact mitigation structure. As shown in Figure 7, by providing the fall impact mitigation structure, the impact of a fall can be mitigated regardless of the impact angle θ at the time of fall, and the impact mitigation effect can be obtained even when the object 100 falls at an angle.

[0036] As shown in Figures 1-6, the impact portion 30, which forms the tip of the projection 1, has less rigidity than the intermediate portion 20, which forms the base of the projection 1. By making the tip of the projection 1 less rigid, when the projection 1 collides with the impact surface P, the deformation of the tip of the projection 1 reduces the impact acceleration. Therefore, the axial impact applied to the internal components 110 of the impact object 100 can be reduced, thereby suppressing damage to the components 110.

[0037] As shown in Figures 1-6, the impact portion 30, which forms the tip of the projection 1, may have a smaller diameter than the intermediate portion 20, which forms the base of the projection 1. A projection 1 having such a shape is easy to manufacture. Therefore, a projection 1 with less rigidity at the tip than at the base can be reliably provided on the impact object 100.

[0038] As shown in Figures 1 to 6, the impact portion 30 that forms the tip of the projection 1 may have a spherical portion 31. If the impact portion 30 is not spherical, the shape of the impact portion 30 that impacts the impact surface P will not be constant depending on the impact angle θ. As a result, the variation in maximum acceleration will increase. By making the impact portion 30 spherical, the variation in maximum acceleration can be reduced, and the axial impact applied to the component 110 can be reliably reduced regardless of the impact angle θ.

[0039] As shown in Figures 1-6, the stepped pin 10 is constructed separately from the impact object 100, and the projection 1 may be formed by attaching the stepped pin 10 to the impact object 100. In this way, the stepped pin 10 can be retrofitted to an existing impact object 100, and the axial impact applied to the internal components 110 of the existing impact object 100 can be easily mitigated. The stepped pin 10 can be attached to an impact object 100 of any specifications, and the impact impact mitigation structure can be applied to that impact object 100.

[0040] As shown in Figures 2 and 3, a recess 102 is formed in the bottom surface 101 of the impact object 100, and the stepped pin 10 may have a mounting portion 40 that is attached to the recess 102. In this way, the separate stepped pin 10 can be easily attached to the impact object 100, for example by press-fitting the mounting portion 40 into the recess 102.

[0041] As shown in Figures 2 and 3, the intermediate portion 20 of the stepped pin 10, which forms the base of the projection 1, has a larger diameter than the mounting portion 40 and may make surface contact with the bottom surface 101 of the object 100. By making the intermediate portion 20 highly rigid, the overall rigidity of the stepped pin 10 can be ensured. By making the contact surface 21 of the intermediate portion 20 and the bottom surface 101 make surface contact, it is possible to suppress displacement of the stepped pin 10 relative to the object 100, such as the stepped pin 10 coming out of the object 100 when the stepped pin 10 collides with the object P.

[0042] As shown in Figure 6, when the object 100 is placed on a flat impact surface P with its bottom surface 101 facing the impact surface P, the tip of the projection 1 contacts the impact surface P, and the impact angle θ between the bottom surface 101 of the object 100 and the impact surface P may be 20° or more. By determining the amount of protrusion of the projection 1 from the bottom surface 101 in this way, as shown in Figure 7, the maximum acceleration can be reliably reduced by providing the impact mitigation structure in the range where the impact angle θ is less than 20°, in which the maximum acceleration increases rapidly without the impact mitigation structure.

[0043] In the explanation so far, we have described an example in which the stepped pin 10 is attached to the impact object 100 to form the projection 1, but the projection 1 may also be formed as a structure integral with the impact object 100. Even if the projection 1 and the impact object 100 are integral, the effect of mitigating the axial impact applied to the component 110 can be similarly obtained by positioning the projection 1 at a position offset from the center of gravity 103 of the bottom surface 101 and making the tip of the projection 1 less rigid than the base of the projection 1. When the projection 1 and the impact object 100 are integral, the projection 1 will not come off the impact object 100, so it is not necessarily required to make the diameter of the base of the projection 1 larger than the diameter of the tip in order to prevent the projection 1 from coming off.

[0044] The tip of projection 1 does not necessarily have to be spherical. If the tip of projection 1 has a shape other than a sphere, as described above, the maximum acceleration will vary depending on the impact angle θ. However, if the upper limit of this variation is smaller than the maximum acceptable acceleration, projection 1 may have a non-spherical tip.

[0045] The impact portion 30 at the tip of the projection 1 does not necessarily have to be smaller in diameter than the intermediate portion 20 at the base of the projection 1. For example, by using different materials to form the intermediate portion 20 and the impact portion 30, and forming the impact portion 30 with a less rigid material than the intermediate portion 20, it is possible to achieve a configuration in which the rigidity of the tip of the projection 1 is smaller than that of the base.

[0046] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the claims rather than the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended. [Industrial applicability]

[0047] This disclosure is not limited to, but may be applied, for example, to a fuse attached to a projectile. The fuse houses a power generation mechanism. The power generation mechanism generates electricity for detonation after impact while the projectile is in flight. The power generation mechanism starts generating electricity in response to the impact applied when the projectile is fired. It is necessary to mitigate the axial impact applied to the power generation mechanism so that it does not start generating electricity due to the impact of dropping the fuse before it is assembled to the projectile. By applying a drop impact mitigation structure according to this disclosure to the fuse, the axial impact applied to the power generation mechanism when the fuse is dropped can be mitigated. Therefore, it is possible to suppress the power generation mechanism from starting to generate electricity when the fuse is dropped. [Explanation of Symbols]

[0048] 1 projection, 10 stepped pin, 20 intermediate section, 21 contact surface, 30 impact section, 31 spherical section, 40 mounting section, 100 impact object, 101 bottom surface, 102 recess, 103 center of gravity, 110 component, 111 low-strength section, L center of gravity line, P impact surface.

Claims

1. A drop impact mitigation structure that reduces the impact applied to components by a collision caused by the fall of a housing that contains components inside, The container is provided with a projection that extends outward from the bottom surface of the container, The aforementioned protrusion is positioned at a location offset from the center of gravity of the base surface. The stepped pin, which is configured separately from the housing, is attached to the housing to form the projection. The bottom surface has a recess formed in which a part of the bottom surface is indented. The stepped pin has a mounting portion that is attached to the recess and an intermediate portion that forms the base of the projection. The aforementioned intermediate portion has a larger diameter than the aforementioned mounting portion and is in surface contact with the aforementioned bottom surface. A drop impact mitigation structure wherein, when the housing is placed on a flat surface with its bottom surface facing the flat surface, the projection contacts the flat surface, and the bottom surface and the flat surface form an angle of 20° or more.

2. The drop impact mitigation structure according to claim 1, wherein the tip of the projection has less rigidity than the base of the projection.

3. The drop impact mitigation structure according to claim 2, wherein the tip portion has a smaller diameter than the base portion.

4. The drop impact mitigation structure according to any one of claims 1 to 3, wherein the tip of the projection has a spherical shape.

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