Buffer brake

Abstract

The present invention relates to a cushion brake interposed between two members which are relatively displaced in the axial direction, the cushion brake comprising an elastic body which is compressed in the axial direction by the two members and expands outward in the radial direction when the distance between the two members is reduced. A second member that suppresses expansion of the elastic body is attached to the outer peripheral portion of the elastic body in a partial region in the axial direction, and when the elastic body is compressed in the axial direction by the two members, the second member expands while receiving resistance caused by the second member. The expanded elastic body is in contact with a side wall of one of the two members, and the second member has an elasticity that expands radially outward when pressed against the elastic body that expands radially outward, and a rigidity that is higher than the elastic body and is in contact with the side wall earlier than the elastic body.

Description

[0001] This application is a divisional application of the invention patent application with application date of November 27, 2018, application number 201880074303.4, and invention name “Buffer Brake”. Technical Field

[0002] The present invention relates to a buffer brake that stops the displacement of a movable member, the relative displacement between members, and the like while exerting a buffering effect. Background Art

[0003] The buffer brake is used as a rack end brake at the end of a steering rack provided in a vehicle steering device, for example. Figure 6 As shown, the rack end brake compressively deforms an elastic body 82 made of a rubber material between the rack housing 51 and the rack 61 , which are axially opposed to each other and relatively displaced in the axial direction.

[0004] The cushion brake 81 cushions the impact caused when the rack 61 collides with the rack housing 51 when the steering wheel is suddenly twisted to full lock in a steering rack assisted by hydraulic pressure, electric power, or the like.

[0005] The buffering brake 81 buffers the impact by absorbing the kinetic energy caused by the weight and speed of the movable body (rack 61) by utilizing the displacement and reaction force of the buffer brake 81 (elastic body 82). Figure 7 As shown in the curve, the absorbable energy is determined by the size of the area S shown in the curve graph composed of the displacement of the buffer brake 81 and the reaction force.

[0006] Therefore, in order to increase the absorbable energy, the area S is generally increased by increasing the displacement of the cushion brake 81 or increasing the reaction force (rigidity = spring constant).

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 8-133102 Summary of the Invention

[0010] Technical problem to be solved by the invention

[0011] The above technology has room for improvement in the following aspects.

[0012] Regarding the buffer brake 81, due to the typical properties of elastic materials, a corresponding strain is required to achieve high reaction forces, such as those in the nonlinear region. In this regard, in the above-described structure, the brake size must be increased to meet the required functionality. However, due to design constraints related to the surrounding components, increasing the size is not easy.

[0013] As a solution to the above problem, there is an idea to fill the gap c between the counterpart member (housing 51 ) and the brake 81 with the elastic body 82 deformed by the input, thereby obtaining a high reaction force.

[0014] However, in this method, the reaction force increases rapidly when the elastic body 82 is filled, so that energy cannot be absorbed efficiently. As a result, the absorbable energy cannot be increased.

[0015] An object of the present invention is to provide a cushion brake capable of increasing absorbable energy.

[0016] Technical means for solving technical problems

[0017] The buffer brake of the present invention includes: an elastomer, which is arranged between two components that are relatively displaced in the axial direction, and is compressed in the axial direction by the two components and expands radially outward when the interval between the two components is reduced; and a second component, which is installed on the outer periphery of the elastomer in a part of the axial direction of the elastomer and suppresses the expansion of the elastomer in the part. The elastomer expands while being subjected to resistance caused by the second component, thereby contacting the side wall of one of the two components.

[0018] Effects of the Invention

[0019] According to the present invention, resistance due to the second member can be generated during the expansion of the elastic body, thereby increasing the energy that can be absorbed. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a cross-sectional view of a main part of the cushion brake according to the first embodiment.

[0021] Figure 2 It is a cross-sectional view of the main parts showing the operating state of the buffer brake.

[0022] Figure 3 Graph showing the relationship between the displacement and the reaction force in the cushion brake.

[0023] Figure 4 It is a cross-sectional view of a main part of a cushion brake according to a second embodiment.

[0024] Figure 5 Graph showing the relationship between the displacement and the reaction force in the cushion brake.

[0025] Figure 6 This is a cross-sectional view of the main parts of the cushion brake described in the background art.

[0026] Figure 7 Graph showing the relationship between the displacement and the reaction force in the cushion brake. DETAILED DESCRIPTION

[0027] The buffer brake 11 of this embodiment is an example of a rack end brake of a steering rack provided in a steering device of a vehicle. Figure 1 or Figure 4 As shown, the buffer brake 11 is interposed between a rack housing 51 and a rack 61 , which are two members that are axially opposed to each other and relatively displaced in the axial direction.

[0028] The rack housing 51 has a flat end face 52 at right angles to the axis. A step 53 is provided on the outer circumference of the end face 52, and a side wall 54 is provided on the inner circumference of the step 53. The rack 61 has an end face 62 axially opposed to the end face 52 of the rack housing 51. A step 63 is provided on the inner circumference of the end face 62, and a side wall 64 is provided on the outer circumference of the step 63. Thus, an annular assembly space 71 is defined, surrounded on all four sides by the end face 52 and side wall 54 of the rack housing 51, and the end face 62 and side wall 64 of the rack 61. The cushion brake 11 is formed in an annular shape as a whole and is assembled within the assembly space 71.

[0029] [First embodiment]

[0030] based on Figures 1 to 3 The first embodiment will be described.

[0031] like Figure 1 As shown, the damping brake 11 includes an elastic body 21 compressed in the axial direction between an end surface 52 of a rack housing 51 and an end surface 62 of a rack 61 .

[0032] The elastic body 21 is formed into a ring shape by a predetermined rubber material, and a metal mounting ring 31 having an L-shaped cross section is bonded (vulcanized) to the end and inner peripheral surface of one axial side (the upper side in the figure, the rack 61 side). Figure 2 As shown, when the rack 61 moves toward the rack housing 51 (in the direction of arrow D) and the distance between the end faces 52 and 62 decreases, the elastic body 21 is axially compressed by the rack housing 51 and the rack 61 and expands radially outward.

[0033] During implementation, a metal mounting ring (not shown) may be bonded to the end portion of the elastic body 21 on the other axial side (the lower side in the figure, on the rack housing 51 side).

[0034] The buffer brake 11 includes a second member 41 that is attached to a portion of the outer peripheral portion of the elastic body 21 in the axial direction and that restricts expansion of the elastic body 21 in the portion in the axial direction. That is, the second member 41 is attached to the outer peripheral portion of the elastic body 21 in a portion of the axial direction of the elastic body 21, thereby suppressing expansion of the elastic body 21 in the portion.

[0035] The second component 41 is a rigid ring body that does not contact the side wall 54 when the elastic body 21, which has expanded radially outward, contacts the side wall 54. One example of the ring body is made of metal, while another example is made of resin. The ring body has a shape in which the dimension perpendicular to the axis is larger than the dimension in the axial direction, and is assembled into an annular mounting groove 24 provided in the elastic body 21. The mounting groove 24 is a groove pre-formed on the outer peripheral surface of the elastic body 21.

[0036] The mounting groove 24 is formed at a position that divides the elastic body 21 into the portion 22 of length L1 and the portion 23 of length L2. Therefore, the ring body constituting the second component 41 is mounted at a position that divides the elastic body 21 into the portion 22 of length L1, which is longer in the axial direction, and the portion 23 of length L2, which is shorter in the axial direction. Needless to say, the axial length is not an absolute length, but rather a relative relationship between the portions 22 and 23. Based on this structure, the ring body has a shape like an interleaf that is sandwiched between the portion of the elastic body 21 of length L1, which is longer in the axial direction, and the portion of the elastic body of length L2, which is shorter in the axial direction.

[0037] As another embodiment, a cutout portion or the like may be provided at one location on the circumference of the annular second member 41 to facilitate assembly into the mounting groove 24. Alternatively, the second member 41 may be embedded in the elastomer 21 by insert molding during vulcanization molding of the elastomer 21 using a mold. The second member 41 may be referred to as a resistance member or an elastomer fastening member, depending on its function and the like.

[0038] The outer diameter of the second member 41 is formed to be larger than the outer diameter of the elastic body 21. Thus, the second member 41 protrudes radially outward from the outer peripheral surface of the elastic body 21.

[0039] The outer diameter of the second member 41 is smaller than the inner diameter of the side wall 54 of the rack housing 51. This creates a radial gap c1 between the second member 41 and the side wall 54. However, since the second member 41 does not expand, a configuration in which the outer diameter of the second member 41 and the inner diameter of the side wall 54 are equal and the second member 41 and the side wall 54 are in contact with each other can also be employed.

[0040] The outer diameter of the elastic body 21 is formed to be smaller than the inner diameter of the side wall 54 of the rack housing 51 , thereby forming a radial gap c2 between the elastic body 21 and the side wall 54 .

[0041] In the cushion brake 11 of this embodiment, when the rack 61 displaces toward the rack housing 51 (arrow D) and the gap between the end faces 52, 62 decreases, the elastic body 21 is compressed axially between the rack housing 51 and the rack 61, and accordingly expands radially outward. The second member 41 is attached to a portion of the outer circumference of the elastic body 21 in the axial direction, thereby acting as a resistance element to the expansion of the elastic body 21. As a result, the radially outward expansion of the elastic body 21 is limited in a portion of the axial direction.

[0042] As described above, the elastic body 21 is divided into the portion 22 having a length L1 that is longer in the axial direction and the portion 23 having a length L2 that is shorter in the axial direction. The elastic body 21 expands in each of the two portions 22 and 23 .

[0043] If the portion 22 with the longer axial length L1 is compared with the portion 23 with the shorter axial length L2, the portion 22 with the longer axial length L1 has a larger surface area than the portion 23 with the longer axial length L2 and expands more radially outward. Figure 2 As shown, the portion 22 of length L1 first contacts the side wall 54. Therefore, a situation can be achieved in which the portion 22 of length L1 expands and contacts the side wall 54, while the portion 23 of length L2 expands but does not yet contact the side wall 54.

[0044] Therefore, if Figure 3 As shown in the graph, the rise (increase) of the reaction force after contact becomes slower, so the displacement amount until the allowable reaction force is reached increases, thereby enabling efficient energy absorption and increasing the absorbable energy.

[0045] exist Figure 3 In the graph of FIG, the comparative example shows a conventional buffer brake having no second member 41. In this comparative example, the displacement is small because the reaction force increases rapidly after contact. Point E shows the moment when the elastic body 21 contacts the side wall 54.

[0046] [Second embodiment]

[0047] based on Figure 4 and Figure 5 The second embodiment will be described. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0048] like Figure 4As shown, the cushion brake 11 includes an elastic body 21 compressed in the axial direction between the end surface 52 of the rack housing 51 and the end surface 62 of the rack 61 .

[0049] The elastic body 21 is formed into an annular shape from a predetermined rubber material. A metal mounting ring 31 with an L-shaped cross section is bonded (vulcanization bonded) to the end and inner circumference of one axial side (the upper side in the figure, on the rack 61 side). When the rack 61 moves toward the rack housing 51 and the distance between the end surfaces 52 and 62 decreases, the elastic body 21 is axially compressed by the rack housing 51 and rack 61, causing it to expand radially outward.

[0050] During implementation, a metal mounting ring (not shown) may be bonded to the end portion of the elastic body 21 on the other axial side (the lower side in the figure, on the rack housing 51 side).

[0051] The buffer brake 11 includes a second member 41 that is attached to a portion of the outer periphery of the elastic body 21 in the axial direction and that restricts expansion of the elastic body 21 in the portion in the axial direction. Specifically, the second member 41 is attached to the outer periphery of the elastic body 21 in a portion of the axial direction of the elastic body 21, thereby suppressing expansion of the elastic body 21 in the portion.

[0052] The second member 41 is a ring body having elasticity and rigidity. The elasticity refers to the elasticity that causes it to expand radially outward when pressed against the elastic body 21, which expands radially outward. The rigidity refers to the rigidity that is higher than that of the elastic body 21, so that it contacts the side wall 54 earlier than the elastic body 21. The ring body having such characteristics is formed from a different material from the elastic body 21, thereby having a higher rigidity than the elastic body 21. As an example, the second member 41 is formed from polyurethane.

[0053] As another embodiment, to facilitate assembly into the mounting groove 24, a cutout portion or the like may be provided at one location on the circumference of the ring body constituting the second component 41. Alternatively, the ring body may be divided into two parts along the circumference, creating a bifurcated structure. The second component 41 may be referred to as either a resistance component or an elastic fastening component, depending on its function.

[0054] The outer diameter of the second member 41 is formed to be larger than the outer diameter of the elastic body 21. Thus, the second member 41 protrudes radially outward from the outer peripheral surface of the elastic body 21.

[0055] The outer diameter of the second member 41 is formed to be smaller than the inner diameter of the side wall portion 54 of the rack housing 51 . Thus, a radial gap c1 is formed between the second member 41 and the side wall portion 54 .

[0056] The outer diameter of the elastic body 21 is formed smaller than the inner diameter of the side wall portion 54 of the rack housing 51 , thereby forming a radial gap c2 between the elastic body 21 and the side wall portion 54 .

[0057] In the cushion brake 11 of this embodiment, when the rack 61 displaces toward the rack housing 51 and the gap between the end faces 52, 62 decreases, the elastic body 21 is compressed axially between the rack housing 51 and the rack 61, and accordingly expands radially outward. The second member 41 is attached to a portion of the outer circumference of the elastic body 21 in the axial direction, thereby acting as a resistance element to this expansion. As a result, radially outward expansion of the elastic body 21 is restricted in the axial portion.

[0058] As the elastic body 21 continues to expand under the load associated with the displacement of the rack 61, the pressure generated by this expansion presses the second member 41 radially outward, causing the second member 41 to expand radially outward (deform in diameter) and come into contact with the side wall 54. Since a large load is required to expand the second member 41 radially outward and come into contact with the side wall 54, the rigidity of the entire buffer brake 11 is increased, generating a larger reaction force than when the elastic body 21 is used alone.

[0059] Thereafter, when the rack 61 moves toward the rack housing 51 while the second member 41 is in contact with the side wall 54, the second member 41 slides relative to the side wall 54, generating sliding resistance between the second member 41 and the side wall 54. This sliding resistance also increases rigidity, thereby generating a greater reaction force.

[0060] like Figure 5 As shown in the graph, according to the buffer brake 11 of this embodiment, the reaction force starts to rise rapidly (increase) early at the moment (point F) when the second member 41 contacts the side wall 54. This allows for efficient energy absorption, thereby increasing the amount of energy that can be absorbed.

[0061] Figure 5 The graph of the comparative example shows the characteristics of a buffer brake without the second member 41. In this comparative example, the reaction force begins to rise sharply (increase) at the moment (point E) when the elastic body 21 contacts the side wall 54. Therefore, efficient energy absorption cannot be achieved, and the absorbable energy cannot be increased.

[0062] Description of Reference Numerals

[0063] 11 Buffer brake

[0064] 21 Elastomer

[0065] 22 The part with longer axial length

[0066] 23 The shorter axial length part

[0067] 24 assembly slots

[0068] 31 Mounting ring

[0069] 41 Second Part

[0070] 51 rack housing

[0071] 52, 62 end faces

[0072] 53, 63 step difference

[0073] 54, 64 sidewalls

[0074] 61 rack

[0075] 71 assembly space

[0076] c1, c2 radial clearance

Claims

1. A buffer brake, wherein: comprising an elastic body and a second component, The elastic body is provided between two components that are relatively displaced in the axial direction, and is compressed in the axial direction by the two components and expands radially outward when the interval between the two components is reduced. The second member is attached to the outer peripheral portion of the elastic body in a portion of the axial direction of the elastic body and suppresses expansion of the elastic body in the portion. The elastic body expands while receiving resistance from the second member, thereby coming into contact with a side wall of one of the two members. The second component has the following elasticity and rigidity: The elastic member has elasticity that allows the elastic member to expand radially outward when pressed against the elastic member that expands radially outward, and has higher rigidity than the elastic member so as to come into contact with the side wall earlier than the elastic member.

2. The buffer brake according to claim 1, wherein The second member is assembled into an annular mounting groove provided in the elastic body.

3. The buffer brake according to claim 1, wherein: The second component is a ring.

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