friction damper

Abstract

This design enables the creation of a friction damper that easily achieves the required damping characteristics without the need for parts replacement. [Solution] The friction damper 100 comprises a cylinder 1, a sliding body 2 that reciprocates axially L inside the cylinder 1, and a rod 5 that reciprocates axially L together with the sliding body 2. The sliding body 2 comprises a sliding member 3 having a sliding surface 31A that contacts the inner circumferential surface 11 of the cylinder 1, and an adjustment mechanism 4 that changes the radial position R of the sliding surface 31A. The adjustment mechanism 4 comprises a support member 41 positioned radially inward R2 relative to the sliding member 3, and a relative movement mechanism 42 that moves the sliding member 3 and the support member 41 relative to each other axially L. A first inclined surface 3A inclined with respect to the axial direction L is formed on the inner circumferential surface of the sliding member 3, and a second inclined surface 4A is formed on the outer circumferential surface of the support member 41 that is opposite to and parallel to the first inclined surface 3A.

Description

Technical Field

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[0001] The present invention relates to a friction damper including a cylinder and a sliding body that reciprocates inside the cylinder while sliding on the inner peripheral surface of the cylinder.

Background Art

[0002] Techniques related to friction dampers are disclosed in, for example, Patent Document 1. Hereinafter, in the description of this background art, the reference numerals and names in Patent Document 1 are cited in parentheses.

[0003] Patent Document 1 discloses a friction damper (D1) including a cylindrical cylinder (outer shell 1) and a sliding body (piston portion 2b) that reciprocates axially inside the cylinder (D1) while sliding on a sliding surface (friction member 3) disposed inside the cylinder (outer shell 1) (room R).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The damping characteristics of the friction damper (D1) disclosed in Patent Document 1 are determined by the material and dimensions of the components constituting the sliding surface (friction member 3). Therefore, when the required damping characteristics cannot be obtained with the components constituting the sliding surface (friction member 3), it may be necessary to replace the components constituting the sliding surface (friction member 3) with those having different materials and dimensions.

[0006] Therefore, it is desired to realize a friction damper that can easily obtain the required damping characteristics without component replacement.

Means for Solving the Problems

[0007] The friction damper relating to this disclosure comprises a cylindrical cylinder and A sliding body that moves back and forth within the cylinder in the axial direction while sliding against the inner circumferential surface of the cylinder, with the direction along the axis of the cylinder as the axial direction, A rod connected to the sliding body and moving back and forth in the axial direction together with the sliding body, A friction damper equipped with, The direction perpendicular to the axis of the cylinder is defined as the radial direction, and the direction around the axis of the cylinder is defined as the circumferential direction. The sliding body is, A sliding member having a sliding surface that contacts the inner circumferential surface of the cylinder, An adjustment mechanism for changing the radial position of the sliding surface, Equipped with, The adjustment mechanism is, A support member positioned radially inward relative to the sliding member, A relative movement mechanism that moves the sliding member and the support member relative to each other in the axial direction, Equipped with, The sliding member comprises at least one of an elastic structure having elasticity in the circumferential direction and a segmented structure divided in the circumferential direction. A first inclined surface is formed on the inner circumferential surface of the sliding member, which is inclined with respect to the axial direction. A second inclined surface is formed on the outer circumferential surface of the support member, which is opposite to and parallel to the first inclined surface.

[0008] With this configuration, the adjustment mechanism changes the radial position of the sliding surface, thereby adjusting the contact pressure between the inner surface of the cylinder and the sliding surface of the sliding member. This allows for adjustment of the damping characteristics without replacing the components that make up the sliding surface. Furthermore, as the first and second inclined surfaces move relative to each other in the axial direction, the first inclined surface is pushed radially outward, causing the sliding surface to move radially outward. In this way, the adjustment mechanism can adjust the contact pressure between the inner surface of the cylinder and the sliding surface of the sliding member, allowing for highly accurate adjustment of the radial position of the sliding surface and making it easier to obtain the desired damping characteristics. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram showing the axial cross-section of Embodiment 1. [Figure 2] Radial cross-sectional view of the II-II section shown in Figure 1. [Figure 3] A schematic diagram showing the radial cross-section of Embodiment 2. [Figure 4] A schematic diagram showing the axial cross-section of Embodiment 3. [Figure 5] A schematic diagram showing the axial cross-section of Embodiment 4. [Figure 6] A schematic diagram showing the axial cross-section of Embodiment 5. [Figure 7] A schematic diagram showing the axial cross-section of Embodiment 6. [Figure 8] A diagram showing an example of the use of the damper in the embodiment. [Modes for carrying out the invention]

[0010] 〔overview〕 An overview of the friction damper 100 according to this embodiment will be described with reference to Figures 1 and 8. The friction damper 100 dampens vibrations transmitted to various mechanical elements. As shown in Figure 8, the friction damper 100 of this embodiment is used in conjunction with an elastically deformable spring element K to dampen vibrations transmitted from a load W to a structure S to an external force input. In particular, the friction damper 100 of this embodiment is preferably used as a suspension to dampen vibrations transmitted to the vehicle body, which is the structure S, by external forces input from the wheels, which are the load W. In addition, the friction damper 100 of this embodiment is preferably mounted on a hybrid vehicle, electric vehicle, or other automobile.

[0011] As shown in Fig. 1, the friction damper 100 includes a cylindrical cylinder 1, a sliding body 2 disposed inside the cylinder 1, and a rod 5 connected to the sliding body 2. Hereinafter, the details of the cylinder 1, the sliding body 2, and the rod 5 will be described. For convenience of explanation, in this specification, the direction along the axis X of the cylinder 1 is referred to as the axial direction L. Also, the direction orthogonal to the axis X of the cylinder 1 is referred to as the radial direction R. In the radial direction R, the side closer to the axis X of the cylinder 1 is referred to as the inner radial side R2, and the side farther from the axis X of the cylinder 1 is referred to as the outer radial side R1. And the direction of orbiting around the axis X of the cylinder 1 is referred to as the circumferential direction C.

[0012] The cylinder 1 has an inner peripheral surface (hereinafter referred to as the sliding surface 11) that surrounds its interior from the outer radial side R1. One end of the cylinder 1 in the axial direction L is closed, and an opening through which the rod 5 is inserted is provided at the other end in the axial direction L. The opening is provided along the axis X of the cylinder 1. A sleeve 12 through which the rod 5, the details of which will be described later, can slide in the axial direction L is inserted into the opening illustrated in Fig. 1. The sleeve 12 restricts the movement of the rod 5 in the radial direction R and guides the movement of the rod 5 so as to move along the axial direction L of the rod 5.

[0013] By receiving a force along the axial direction L, the sliding body 2 reciprocates in the axial direction L inside the cylinder 1 while sliding with respect to the sliding surface 11. When the sliding body 2 slides with respect to the sliding surface 11, a frictional force is generated between the sliding surface 11 and the sliding body 2. This frictional force serves as a resistance to the reciprocating movement of the sliding body 2. In this embodiment, the sliding body 2 contacts the sliding surface 11 over the entire circumference of its outer peripheral surface. Therefore, the frictional force generated between the sliding surface 11 and the sliding body 2 is not likely to be concentrated and increased at a specific part in the circumferential direction C. Thus, the sliding body 2 can move stably along the axial direction L.

[0014] The rod 5 reciprocates in the axial direction L together with the slider 2. The rod 5 is a rod-shaped member extending along the axial direction L. In the present embodiment, the rod 5 is arranged from the inside to the outside of the cylinder 1 along the axial direction L. The tip end portion 51, which is one end portion of the rod 5 in the axial direction L, is arranged inside the cylinder 1. The slider 2 is connected to the tip end portion 51. In the example shown in FIG. 1, a male thread 53 is provided on the tip end portion 51. Specifically, a male thread 53 having a stepped portion 54 is formed along the axial direction L on the tip end portion 51 illustrated in FIG. 1. The slider 2 is fixed to the male thread 53. On the other hand, the base end portion (not shown), which is the other end portion of the rod 5 in the axial direction L, is arranged outside the cylinder 1. For example, the aforementioned load portion W and the structure S are connected to the base end portion.

[0015] In the present embodiment, the intermediate portion between the tip end portion 51 and the base end portion of the rod 5 is inserted into the aforementioned sleeve 12. The intermediate portion of the rod 5 includes a portion arranged inside the cylinder 1 and a protruding portion 52 protruding outward in the axial direction L with respect to the cylinder 1. The protruding amount of the protruding portion 52 with respect to the cylinder 1 changes as the rod 5 relatively moves in the axial direction L with respect to the cylinder 1.

[0016] Hereinafter, the details of the friction damper 100 of Embodiments 1 to 6 will be described. The internal configurations of the friction dampers 100 of Embodiments 1 to 6 are different from each other. For convenience of explanation, in this specification, when explaining the configuration arranged inside the cylinder 1, one side and the other side in the axial direction L are defined based on the protruding portion 52. The side of the protruding portion 52 in the axial direction L with respect to the configuration arranged inside the cylinder 1 is referred to as the axial outer side L1. Conversely, the opposite side of the axial outer side L1 is referred to as the axial inner side L2.

[0017] 〔Embodiment 1〕 The friction damper 100 according to Embodiment 1 will be described with reference to Figures 1 and 2. The friction damper 100 of this embodiment comprises a sliding member 3 having a sliding surface 31A that contacts a sliding surface 11, and an adjustment mechanism 4 that adjusts the contact pressure between the sliding surface 11 and the sliding surface 31A. When a frictional force is generated between the sliding surface 11 and the sliding member 2, the aforementioned frictional force is generated between the sliding surface 11 and the sliding surface 31A. The frictional force generated between the sliding surface 11 and the sliding surface 31A changes as the adjustment mechanism 4 increases or decreases the contact pressure between the sliding surface 11 and the sliding surface 31A. Specifically, the frictional force increases with increasing contact pressure and decreases with decreasing contact pressure.

[0018] In this embodiment, the sliding member 3 comprises a sliding portion 31 that forms a sliding surface 31A, and a holding portion 32 that holds the sliding portion 31. The holding portion 32 is connected to the tip portion 51 of the rod 5 so as to be positioned where the sliding surface 31A contacts the surface to be slid 11. The sliding portion 31 illustrated in Figures 1 and 2 extends in the circumferential direction C and is formed continuously around the entire circumference in the circumferential direction C. In this embodiment, the holding portion 32 is supported by an adjustment mechanism 4, which will be described in detail later. The holding portion 32 illustrated in Figures 1 and 2 is a cylindrical member that extends along the axial direction L when viewed from the axial direction L. The sliding portion 31 is fixed to the outer circumferential surface of the holding portion 32. As a result, the sliding portion 31 is positioned between the surface to be slid 11 and the outer circumferential surface of the holding portion 32. Therefore, as the position of the outer circumferential surface of the holding portion 32 moves radially outward R1, the contact pressure between the surface to be slid 11 and the sliding surface 31A increases.

[0019] The sliding member 3 comprises at least one of an elastic structure having elasticity in the circumferential direction C, and a segmented structure divided in the circumferential direction C. With this configuration, the sliding member 3 can be expanded radially outward R1. As the sliding member 3 expands radially outward R1, the sliding surface 31A moves radially R. In this embodiment, the sliding member 3 comprises an elastic structure. The elastic structure illustrated in Figure 2 is formed by the shape of the holding portion 32. The holding portion 32 shown in Figure 2 includes a thin-walled portion 33 whose thickness in the radial direction R when viewed from the axial direction L is relatively thinner than that of adjacent portions in the circumferential direction C. When a force is applied to the holding portion 32 from the radially inward R2, it deforms to expand radially outward R1 starting from the thin-walled portion 33.

[0020] Preferably, the thin-walled portion 33 is provided over the entire axial L region of the holding portion 32 and is evenly distributed at multiple locations (four locations in this example) along the circumferential C direction. With this configuration, the holding portion 32 can be extended radially outward R1 without bias in the circumferential C direction and the axial L direction. Therefore, the contact pressure between the sliding surface 11 and the sliding surface 31A is less likely to become unevenly large at specific locations in the circumferential C direction and the axial L direction. Furthermore, the thin-walled portion 33 illustrated in Figure 2 is formed to continuously connect the outer circumferential surface of the holding portion 32 in the circumferential C direction. In detail, the thin-walled portion 33 is the part that is arranged radially outward R1 with respect to a groove formed on the inner circumferential surface of the holding portion 32 along the axial L direction. With this configuration, the holding portion 32 can hold the sliding portion 31 over the entire circumference of the circumferential C direction.

[0021] In this embodiment, the holding portion 32 supports a sheet-like sliding portion 31 having a sliding surface 31A coated with friction material from the radially inner side R2. Preferably, the friction material has viscoelastic properties. Specifically, the friction material exhibits viscous properties when the sliding surface 31A is stationary relative to the sliding surface 11, and exhibits elastic properties due to the relative movement of the sliding surface 31A in the axial direction L relative to the sliding surface 11. With this configuration, the difference between static friction force and kinetic friction force between the sliding surface 11 and the sliding surface 31A can be reduced. That is, with this configuration, the static friction force between the sliding surface 31A and the sliding surface 11 when the sliding surface 31A is stationary relative to the sliding surface 11 is kept low. On the other hand, the kinetic friction force between the sliding surface 11 and the sliding surface 31A when the sliding surface 31A is moving relative to the sliding surface 11 is increased. As a result, the damping characteristics of the friction damper 100 become smoother when the rod 5 switches from a state where it is stationary relative to the cylinder 1 to a state where it is moving relative to the cylinder 1.

[0022] The adjustment mechanism 4 changes the position of the sliding surface 31A in the radial direction R. As the position of the sliding surface 31A in the radial direction R changes, the contact pressure of the sliding surface 31A with respect to the sliding surface 11 changes. In this embodiment, the adjustment mechanism 4 changes the position of the sliding surface 31A in the radial direction R by combining a diameter expansion structure and a relative movement structure. The diameter expansion structure expands the sliding part 31 radially outward R1 by changing the position in which the adjustment mechanism 4 holds the sliding part 31. The relative movement structure changes the position in which the adjustment mechanism 4 holds the sliding part 31 by moving the adjustment mechanism 4 and the sliding part 31 relative to each other in the axial direction L.

[0023] As an expanding structure, a first inclined surface 3A is formed on the inner circumferential surface of the sliding member 3, inclined with respect to the axial direction L. The adjustment mechanism 4 holds the sliding member 3 at an arbitrary holding position in the axial direction L of the first inclined surface 3A. With this configuration, this holding position is a constant position in the radial direction R from the axis X, and as the position of the axial direction L changes to a different position, the sliding member 3 expands radially outward R1 or, conversely, contracts radially inward R2. As a result, the position of the sliding surface 31A in the radial direction R changes. For example, depending on the holding position, the adjustment mechanism 4 may press the sliding member 3 from radially inward R2 to radially outward R1. In this case, the sliding member 3 expands radially outward R1, and the position of the sliding surface 31A moves radially outward R1. In this embodiment, the first inclined surface 3A is formed on the inner circumferential surface of the holding portion 32. The first inclined surface 3A, illustrated in Figure 2, is formed around the entire inner circumference of the holding portion 32, excluding the thin-walled portion 33.

[0024] The adjustment mechanism 4 comprises a support member 41 positioned radially inward R2 relative to the sliding member 3, and a relative movement mechanism 42 that moves the sliding member 3 and the support member 41 relative to each other in the axial direction L.

[0025] The support member 41 holds the retaining portion 32 from the radially inner side R2. In this embodiment, the support member 41 is a cylindrical member extending along the axial direction L. The retaining portion 32 is held by the support member 41 by the contact of its inner circumferential surface with the outer circumferential surface of the support member 41. In addition, the support member 41 is fixed to the tip portion 51 of the rod 5 by a relative movement mechanism 42. Specifically, the support member 41 has a hollow portion through which a male screw 53 provided on the tip portion 51 of the rod 5 can be inserted. The support member 41 is fixed to the rod 5 by the relative movement mechanism 42 with the male screw 53 provided on the tip portion 51 of the rod 5 inserted through its hollow portion. As a result, the retaining portion 32 is held by the rod 5 via the support member 41.

[0026] The support member 41 presses the holding portion 32 from the radially inner R2 toward the radially outer R1. As a result, the holding portion 32 expands toward the radially outer R1, and the sliding portion 31 held on the outer circumferential surface of the holding portion 32 moves toward the radially outer R1. The support member 41 illustrated in Figure 1 presses the inner circumferential surface of the holding portion 32 from the radially inner R2. More specifically, the support member 41 illustrated in Figure 1 presses the first inclined surface 3A.

[0027] The relative movement mechanism 42 changes the holding position in which the support member 41 holds the holding part 32 by moving the support member 41 relative to the holding part 32 in the axial direction L. The holding position is changed while keeping the radial distance R from the axis X constant. This holding position corresponds to the holding position described as the position in which the adjustment mechanism 4 holds the first inclined surface 3A.

[0028] A second inclined surface 4A is formed on the outer circumferential surface of the support member 41, facing and parallel to the first inclined surface 3A. The support member 41 holds the holding portion 32 by bringing the second inclined surface 4A into contact with the first inclined surface 3A. The contact position between the portion of the second inclined surface 4A located at the outermost radially outer R1 and the first inclined surface 3A corresponds to the aforementioned holding position. In the example shown in Figure 1, the portion of the second inclined surface 4A located at the outermost radially outer R1 is the axially inward end L2 of the second inclined surface 4A (inner end). Here, if the distance from the axis X to the inner end of the second inclined surface 4A is smaller than the distance from the axis X to the contact position between the axis X and the inner end of the second inclined surface 4A on the first inclined surface 3A, the holding portion 32 expands radially outward R1. The holding position can be changed by adjusting the relative position of the support member 41 with respect to the holding portion 32 in the axial direction L.

[0029] In this embodiment, the first inclined surface 3A is inclined radially inward R2 as it moves toward the side of the protruding portion 52 in the axial direction L. With this configuration, when the second inclined surface 4A moves relative to the first inclined surface 3A in the axial direction outward L1, the inner end of the second inclined surface 4A comes into contact with the portion of the first inclined surface 3A that narrows radially inward R2, causing the support member 41 to push and expand the holding portion 32 radially outward R1. As a result, the sliding surface 31A moves radially outward R1, and the contact pressure of the sliding surface 31A with respect to the sliding surface 11 increases.

[0030] The relative movement mechanism 42 includes a nut 43, a transmission unit 44 that transmits the relative movement of the nut 43 in the axial direction L with respect to the rod 5 to one of the sliding member 3 and the support member 41, and a restricting unit 45 that restricts the relative movement of the other of the sliding member 3 and the support member 41 with respect to the rod 5. In detail, the transmission unit 44 and the restricting unit 45 are positioned to sandwich the sliding member 3 and the support member 41 from both sides in the axial direction L. One of the sliding member 3 and the support member 41 is in contact with the transmission unit 44, and the other of the sliding member 3 and the support member 41 is in contact with the restricting unit 45. The nut 43 is screwed onto a male thread 53 provided on the rod 5. The transmission unit 44 and the restricting unit 45 are fixed to the tip 51 of the rod 5 by the nut 43. In the example shown in Figure 1, the restricting unit 45, the sliding member 3 and the support member 41, and the transmission unit 44 are arranged in the order described, from the axial outer L1 to the axial inner L2. These components are then pressed by nuts 43 from the axially inward L2 onto the stepped portion 54 of the male thread 53 formed on the tip portion 51 of the rod 5.

[0031] The nut 43, which is screwed onto the male thread 53 of the rod 5, moves relative to the rod 5 in either direction by rotating it in either direction. The transmission part 44 moves relative to the rod 5 in the axial direction L along with the relative movement of the nut 43 to the rod 5. By moving the transmission part 44 relative to the rod 5 in the axial direction L, one of the sliding member 3 and the support member 41 is moved relative to the rod 5 in the axial direction L.

[0032] In this embodiment, the transmission unit 44 transmits the relative axial movement L of the nut 43 with respect to the rod 5 to the support member 41. As described above, in the example shown in Figure 1, the transmission unit 44 and the nut 43 are positioned axially inward L2 relative to the support member 41. The transmission unit 44 illustrated in Figure 1 is the surface of the nut 43 that contacts the support member 41.

[0033] In this embodiment, the restricting portion 45 is attached to the tip portion 51 of the rod 5 and is a member that restricts the relative movement of the holding portion 32 in the axially outward L1 relative to the rod 5. As shown in Figure 1, the restricting portion 45 is positioned axially outward L1 relative to the sliding member 3.

[0034] In this embodiment, the restricting portion 45 includes a restricting member 451 fixed to a stepped portion 54 of a male screw 53 formed on the tip portion 51 of the rod 5. The restricting member 451 illustrated in Figure 1 is an annular member through which the male screw 53 is inserted. The restricting member 451 has a restricting edge portion 452 that protrudes axially inward L2 from its radially outward edge R1. The restricting edge portion 452 abuts against the holding portion 32 from the axially outward L1, restricting the holding portion 32 from moving axially outward L1.

[0035] Preferably, the restricting member 451 is elastically deformed in the axial direction L. In this embodiment, the restricting member 451 is elastically deformed in the axial direction L by being pressed in the axial direction L by the sliding member 3. With this configuration, when the sliding member 3 is restricted from moving in the axial direction L by the restricting member 451, the restricting member 451 restricts the movement of the sliding member 3 relative to the rod 5 in the axial direction L while undergoing elastic deformation. Therefore, the movement of the sliding member 3 is restricted more gradually compared to the case where the restricting member 451 is a highly rigid member that is difficult to elastically deform. In the restricting member 451 illustrated in Figure 1, the restricting edge 452 abuts against the support member 41 from the axially outer side L1. Therefore, when the support member 41 presses the restricting edge 452 from the axially inner side L2, the restricting member 451 deforms so that it is positioned axially outer L1 from the radially inner side R2 to the radially outer side R1.

[0036] The operation of the friction damper 100 in this embodiment will be described with reference to Figure 1. The friction damper 100 dampens the force transmitted from the load W to the structure S by moving the rod 5 axially inward L2 or axially outward L1 relative to the cylinder 1. After describing how to obtain the damping characteristics required for the friction damper 100, the operation of the friction damper 100 when the rod 5 moves relative to the cylinder 1 in the axial direction L will be described.

[0037] The damping characteristics required for the friction damper 100 are obtained by pre-adjusting the contact pressure of the sliding surface 31A with respect to the sliding surface 11 while the rod 5 is stationary relative to the cylinder 1. The contact pressure of the sliding surface 31A with respect to the sliding surface 11 while the rod 5 is stationary relative to the cylinder 1 is determined by fixing the relative position of the sliding member 3 with respect to the support member 41 in the axial direction L. In this embodiment, the sliding member 3 is restricted from moving outward in the axial direction L1 by a restricting member 451 and is pressed from inward in the axial direction L2 by the support member 41 and a nut 43. Therefore, the relative position of the sliding member 3 with respect to the support member 41 in the axial direction L can be determined by adjusting the tightening amount of the nut 43.

[0038] In this embodiment, the friction damper 100 operates differently depending on the direction of the force that the rod 5 receives from the load W and related mechanical elements.

[0039] When rod 5 is subjected to an axial inward force L2, rod 5 moves relative to cylinder 1 in the axial inward L2 direction. As rod 5 moves, the sliding body 2 also slides against the sliding surface 11 in accordance with rod 5's movement, and moves relative to cylinder 1 in the axial inward L2 direction.

[0040] The sliding body 2 moves axially inward L2 together with the rod 5 as the sliding member 3 is pressed axially inward L2 by the rod 5 via the restricting portion 45. In the example shown in Figure 1, the holding portion 32 of the sliding member 3 is pressed axially inward L2 by the restricting member 451. As the sliding member 3 moves relative to the cylinder 1 axially inward L2, a frictional force is generated between the sliding surface 11 and the sliding surface 31A axially outward L1. This frictional force acts as resistance to the relative movement of the sliding body 2 and the rod 5 relative to the cylinder 1 axially inward L2.

[0041] In this embodiment, the restricting member 451, which acts as the restricting portion 45, undergoes elastic deformation. As the frictional force acting on the sliding surface 31A is transmitted to the sliding member 3, the restricting member 451 elastically deforms outward in the axial direction L1. As the amount of deformation of the restricting member 451 increases, the pressing force that presses the sliding member 3 inward in the axial direction L2 also increases. Therefore, the pressing force gradually increases from immediately after the sliding member 3 begins relative movement with respect to the cylinder 1, resulting in a smooth increase in frictional force.

[0042] When rod 5 is subjected to an axial outward force L1, rod 5 moves relative to cylinder 1 in the axial outward direction L1. As rod 5 moves, the sliding body 2 also slides against the sliding surface 11 in accordance with rod 5's movement, and moves relative to cylinder 1 in the axial outward direction L1.

[0043] The sliding body 2 moves axially outward L1 together with the rod 5 as the sliding member 3 is pressed axially outward L1 by the rod 5 via the nut 43 and support member 41. In the example shown in Figure 1, the support member 41 is pressed axially outward L1 from the transmission portion 44, which is the contact surface between the support member 41 and the nut 43. Consequently, the support member 41 presses the holding portion 32 axially outward L1. As the sliding member 3 moves relative to the cylinder 1 axially outward L1, a frictional force is generated between the sliding surface 11 and the sliding surface 31A axially inward L2. This frictional force acts as resistance to the relative movement of the sliding body 2 and the rod 5 relative to the cylinder 1 axially outward L1.

[0044] In this embodiment, the first inclined surface 3A is inclined radially inward R2 as it approaches the protruding portion 52. Therefore, when the sliding body 2 and the rod 5 move relative to the cylinder 1 axially outward L1, the servo effect increases the resistance to the relative movement of the sliding body 2 as it moves. Specifically, the support member 41 presses the sliding member 3 axially outward L1, causing the first inclined surface 3A of the sliding member 3 to be pressed axially outward L1 by the second inclined surface 4A of the support member 41. This changes the contact position between the second inclined surface 4A and the first inclined surface 3A in the axial direction L. More specifically, the positional relationship between the first inclined surface 3A and the second inclined surface 4A changes so that the inner end of the second inclined surface 4A contacts the portion of the first inclined surface 3A that narrows radially inward R2. As a result, the sliding member 3 is pressed by the support member 41 from the radially inward R2 and expands radially outward R1, causing the sliding surface 31A to move radially outward R1. As the sliding surface 31A moves radially outward R1, the contact pressure of the sliding surface 31A with respect to the sliding surface 11 increases, and the frictional force experienced by the sliding surface 31A increases. This increases the resistance of the rod 5 and sliding body 2 to relative movement axially outward L1 relative to the cylinder 1. In addition, as the frictional force experienced by the sliding surface 31A increases, the force with which the nut 43 presses the support member 41 axially outward L1 increases, causing the support member 41 to move further relative to the sliding member 3 axially outward L1. Then, the sliding member 3 expands further radially outward R1, and the contact pressure of the sliding surface 31A with respect to the sliding surface 11 increases even further. Consequently, the frictional force generated between the sliding surface 11 and the sliding surface 31A axially inward L2 increases even further. In other words, as with the operation of the friction damper 100 described above, when the rod 5 is subjected to an axial outward force L1, a servo effect is obtained in which the resistance to this force gradually increases.

[0045] [Embodiment 2] The friction damper 100 of Embodiment 2 will be described with reference to Figure 3. The friction damper 100 of Embodiment 2 differs from the friction damper 100 of Embodiment 1 in that the sliding member 3 is divided in the circumferential direction C. Therefore, the following description will mainly focus on the differences between the friction damper 100 of Embodiment 2 and the friction damper 100 of Embodiment 1.

[0046] In this embodiment, the sliding member 3 is divided in the circumferential direction C. With this configuration, it is easier to increase the amount of movement of the sliding surface 31A in the radial direction R compared to a configuration in which the sliding surface 31A is moved in the radial direction R by deforming the sliding member 3 in the radial direction R. In the example shown in Figure 3, the sliding member 3 is divided into four parts in the circumferential direction C. The sliding member 3 is composed of four divided bodies 34. Each of the four divided bodies 34 has the same shape. Therefore, even if the sliding surface 31A of each divided body 34 moves in the radial direction R, the frictional force can be transmitted to the circumferential direction C of the sliding surface 11 without bias.

[0047] Furthermore, in this embodiment, preferably, the first inclined surface 3A is continuously formed over the entire circumferential region C of each divided body 34. The second inclined surface 4A is continuously formed over the entire circumferential region C of the outer circumferential surface of the support member 41. With this configuration, the pressing force applied by the second inclined surface 4A against the first inclined surface 3A is less likely to be disproportionately large at specific points in the circumferential region C. Therefore, the contact pressure between the sliding surface 11 and the sliding surface 31A is less likely to be disproportionately large at specific points in the circumferential region C.

[0048] [Embodiment 3] The friction damper 100 of Embodiment 3 will be described with reference to Figure 4. The friction damper 100 of Embodiment 3 differs from the friction damper 100 of Embodiment 1 in that the relative movement mechanism 42 includes a pressing device 6 that can apply an axial pressing force L to at least one of the sliding member 3 and the support member 41 by user operation, and can change the magnitude of this pressing force. In this embodiment, the pressing force is the force that moves the sliding surface 31A radially outward R1. With this configuration, the user can change the pressing force on the support member 41 and at least one of the support members 41 at any timing to appropriately change the damping characteristics. In the following description, the differences between the friction damper 100 of Embodiment 3 and the friction damper 100 of Embodiment 1 will be mainly described.

[0049] In this embodiment, the pressing device 6 applies an axial pressing force L to at least one of the sliding member 3 and the support member 41 in response to an electrical signal, and is capable of changing the magnitude of the pressing force. The pressing device 6 shown in Figure 4 is positioned between the stepped portion 54 of the male screw 53 and the regulating member 451 at the tip 51 of the rod 5. This allows the pressing device 6 to apply an axial pressing force L to the sliding member 3 via the support member 41. When the pressing device 6 presses the sliding member 3, the sliding member 3 moves relative to the support member 41 so that they move closer to each other in the axial direction L. As a result, the positional relationship between the first inclined surface 3A and the second inclined surface 4A changes so that the inner end of the second inclined surface 4A contacts the portion of the first inclined surface 3A that narrows radially inward R2. As a result, the pressing force exerted by the support member 41 against the sliding member 3, which has a sliding surface 31A, on the radially outward R1 increases, causing the sliding surface 31A to move radially outward R1 and increasing the contact pressure of the sliding surface 31A against the surface to be slid 11.

[0050] An example of a pressing device 6 capable of changing the magnitude of the pressing force in response to an electrical signal is a piezoelectric element that expands and contracts in the axial direction L when a voltage is applied. Alternatively, the pressing device 6 may consist of a drive source and a linear motion conversion mechanism that converts the power generated by the drive source into a pressing force in the axial direction L. For example, the drive source could be a motor that generates rotational force, and the linear motion conversion mechanism could be a ball screw that converts rotational force into motion in the axial direction L.

[0051] [Embodiment 4] The friction damper 100 of Embodiment 4 will be described with reference to Figure 5. The friction damper 100 of Embodiment 4 differs from the friction damper 100 of Embodiment 1 in that the transmission section 44 is composed of an elastic member 441. In the following description, the main differences between the friction damper 100 of Embodiment 4 and the friction damper 100 of Embodiment 1 will be explained.

[0052] In this embodiment, the transmission unit 44 is composed of an elastic member 441 that elastically deforms in the axial direction L. With this configuration, in the sliding member 3 and the support member 41, the member not restricted by the restricting member 451 is pressed by the elastic member 441. The elastic member 441 has the property that the elastic force it exerts in the axial direction L increases as the amount of deformation increases. For this reason, the force with which the elastic member 441 presses one of the sliding member 3 and the support member 41 in the axial direction L is smallest at the moment when the rod 5 starts to move in the axial direction L, and the pressing force increases as the amount of movement of the rod 5 to one side in the axial direction L increases. As a result, the rise in frictional force of the sliding surface 31A against the sliding surface 11 at the start of movement of the rod 5 becomes gradual. In the example shown in Figure 5, the elastic member 441 is positioned between the nut 43 and the support member 41 and transmits the relative movement of the nut 43 in the axial direction L with respect to the cylinder 1 to the support member 41. In detail, the elastic member 441 illustrated in Figure 5 is a coil spring inserted through a male thread 53 formed on the rod 5. With this configuration, when the rod 5 moves axially outward L1, the elastic member 441 is compressed by the support member 41 and the nut 43. Therefore, when the rod 5 moves axially outward L1, the frictional force of the sliding surface 31A against the sliding surface 11 gradually increases.

[0053] [Embodiment 5] The friction damper 100 of Embodiment 5 will be described with reference to Figure 6. The friction damper 100 of Embodiment 5 differs from the friction damper 100 of Embodiment 1 in that it comprises a plurality of sliding members 3 and support members 41. Each of the plurality of sliding members 3 is provided with a sliding surface 31A. Therefore, with this configuration, the damping characteristics can be set with high precision by adjusting so that frictional forces of different magnitudes are generated on each of the plurality of sliding surfaces 31A. In the following description, the main differences between the friction damper 100 of Embodiment 5 and the friction damper 100 of Embodiment 1 will be explained.

[0054] In this embodiment, the sliding member 3 comprises a first sliding member 3X positioned on one side in the axial direction L, and a second sliding member 3Y positioned on the other side in the axial direction L. In addition, the support member 41 comprises a first support member 4X positioned on one side in the axial direction L, and a second support member 4Y positioned on the other side in the axial direction L. In the example shown in Figure 6, the first sliding member 3X is positioned axially outward L1 relative to the second sliding member 3Y, and the first support member 4X is positioned axially outward L1 relative to the second support member 4Y. The first sliding member 3X is positioned so that its first inclined surface 3A faces the second inclined surface 4A of the first support member 4X. The second sliding member 3Y is positioned so that its first inclined surface 3A faces the second inclined surface 4A of the second support member 4Y. With this configuration, the sliding surface 31A of the first sliding member 3X and the sliding surface 31A of the second sliding member 3Y can be positioned at different locations in the radial direction R. Therefore, it is possible to set the sliding surface 31A of the first sliding member 3X and the sliding surface 31A of the second sliding member 3Y to generate frictional forces of different magnitudes with respect to the sliding surface 11, thereby enabling high-precision setting of the damping characteristics.

[0055] In addition, in this embodiment, the first support member 4X is positioned at an axial distance L from the second support member 4Y, and the first support member 4X and the second support member 4Y are held on the rod 5 so as to be able to move relative to each other in the axial distance L. With this configuration, as the first support member 4X moves relative to the second support member 4Y, the pressing force exerted by the first support member 4X against the first sliding member 3X and the pressing force exerted by the second support member 4Y against the second sliding member 3Y become different in magnitude. Therefore, frictional forces of different magnitudes are generated on the sliding surface 31A of the first sliding member 3X and the sliding surface 31A of the second sliding member 3Y with respect to the sliding surface 11, so that the damping characteristics can be set with high precision. In the example shown in Figure 6, the first support member 4X is held on the rod 5 by being sandwiched from both sides in the axial direction L by a regulating member 451 positioned axially outward L1 relative to the first support member 4X and a first sliding member 3X positioned axially inward L2 relative to the first support member 4X. The second support member 4Y is held on the rod 5 by being sandwiched from both sides in the axial direction L by a second sliding member 3Y positioned axially outward L1 relative to the second support member 4Y and a nut 43 positioned axially inward L2 relative to the second support member 4Y.

[0056] In the example shown in Figure 6, the first inclined surface 3A of the first sliding member 3X and the first inclined surface 3A of the second sliding member 3Y are inclined in opposite directions. With this configuration, the damping characteristics when the rod 5 moves relative to the cylinder 1 in the axial outward L1 and axial inward L2 can be individually set by separately setting the inclination angles of the first inclined surfaces 3A of the first sliding member 3X and the second sliding member 3Y. Therefore, the damping characteristics when the amount of protrusion of the rod 5 from the cylinder 1 is large and the damping characteristics when the amount of protrusion of the rod 5 from the cylinder 1 is small can be set with high precision.

[0057] Preferably, the first inclined surface 3A of the first sliding member 3X is inclined radially inward R2 as it moves axially inward L2, and the first inclined surface 3A of the second sliding member 3Y is inclined radially inward R2 as it moves axially outward L1. The transmission part 44 presses the second support member 4Y, and the restricting part 45 restricts the relative movement of the first support member 4X with respect to the rod 5 in the axially outward L1 direction. With this configuration, the damping characteristics when the rod 5 moves axially inward L2 relative to the cylinder 1 are determined by the first sliding member 3X, and the damping characteristics when the rod 5 moves axially outward L1 relative to the cylinder 1 are determined by the second sliding member 3Y. In addition, with this configuration, it is easy to arrange the first support member 4X so that it does not come into contact with the second sliding member 3Y from the axially outward L1 direction, thus simplifying the overall structure of the sliding body 2.

[0058] [Embodiment 6] The friction damper 100 of Embodiment 6 will be described with reference to Figure 7. The friction damper 100 of Embodiment 6 differs from the friction damper 100 of Embodiment 1 in the inclination direction of the first inclined surface 3A and the configuration of the transmission section 44 and the regulating section 45. In the following description, the main differences between the friction damper 100 of Embodiment 6 and the friction damper 100 of Embodiment 1 will be explained.

[0059] In this embodiment, the first inclined surface 3A is inclined so that it moves radially inward R2 as it moves axially inward L2. With this configuration, when the support member 41 moves relative to the sliding member 3 axially inward L2, the sliding surface 31A moves radially outward R1. Conversely, when the support member 41 moves relative to the sliding member 3 axially outward L1, the sliding surface 31A moves radially inward R2. Therefore, when the amount of protrusion of the rod 5 from the cylinder 1 is large, the contact pressure between the surface to be slid 11 and the sliding surface 31A of the sliding member 3 is smaller than the contact pressure between the surface to be slid 11 and the sliding surface 31A of the sliding member 3 when the amount of protrusion of the rod 5 from the cylinder 1 is small.

[0060] In this embodiment, the transmission portion 44 also includes a transmission member 442 positioned between the nut 43 and the sliding member 3. The transmission member 442 illustrated in Figure 7 is an annular member through which a male screw 53 is inserted. The transmission member 442 has a transmission edge portion 443 that protrudes axially outward L1 from its radially outward edge R1. The transmission edge portion 443 abuts the sliding member 3 from the axially inward L2 and transmits the relative axial movement L of the nut 43 with respect to the rod 5 to the sliding member 3. The regulating portion 45 is a stepped portion 54 of the male screw 53 formed on the tip portion 51 of the rod 5.

[0061] Preferably, the transmission member 442 is elastically deformed in the axial direction L. In the transmission member 442 shown in Figure 7, the transmission edge 443 is deformed so that it is positioned axially inward L2 from radially inward R2 to radially outward R1. With this configuration, the frictional force of the sliding surface 31A against the sliding surface 11 rises gradually at the timing when the rod 5 begins relative movement to the cylinder 1 in the axial direction L2.

[0062] [Other Embodiments] Next, other embodiments of the friction damper 100 will be described.

[0063] (1) In the above embodiment, it was explained that a male screw 53 is formed on the tip 51 of the rod 5. Here, the male screw 53 may be integrally formed with the tip 51 of the rod 5, or it may be a separate component from the tip 51 of the rod 5 that is fixed to the tip 51 of the rod 5.

[0064] (2) In the above embodiment, the holding portion 32 was described as supporting a sheet-like sliding portion 31 having a sliding surface 31A coated with friction material from the radially inner side R2. However, the holding portion 32 may be integrally formed from the same material as the sliding portion 31. Also, the friction material may be applied to the sliding surface 11, or it may be applied to both the sliding surface 31A and the sliding surface 11.

[0065] (3) In the above embodiment, the adjustment mechanism 4 was described as changing the position of the sliding surface 31A in the radial direction R by combining an expanding diameter structure and a relative movement structure. However, the adjustment mechanism 4 can be any mechanism that expands or contracts the sliding member 3 in the radial direction R, and is not limited to the combination of the expanding diameter structure and the relative movement structure specifically described in the above embodiment. For example, the adjustment mechanism 4 may be a mechanism that expands the sliding member 3 from the radially inner side R2 by hydraulic pressure.

[0066] (4) In the above embodiments, a sliding member 3 having an elastic structure or a segmented structure has been described. However, the sliding member 3 may have both an elastic structure and a segmented structure. Such a sliding member 3 may be composed of multiple segmented parts made of elastically deformable members, for example.

[0067] (5) In the above embodiment, the first inclined surface 3A and the second inclined surface 4A were described as being parallel. Here, the second inclined surface 4A being parallel to the first inclined surface 3A does not mean that the second inclined surface 4A is strictly parallel to the first inclined surface 3A; it is sufficient that when the first inclined surface 3A and the second inclined surface 4A are brought into contact, most of them are in contact with each other.

[0068] (6) In the above embodiment, the pressing force that the pressing device 6 applies to at least one of the sliding member 3 and the support member 41 was described as moving the sliding surface 31A radially outward R1. However, this pressing force may also be applied to move the sliding surface 31A radially inward R2. In this case, the pressing force acts to reduce the contact pressure of the sliding surface 31A with respect to the sliding surface 11. As a result, the damping force acting on the relative movement of the rod 5 with respect to the cylinder 1 is reduced.

[0069] (7) In the above embodiment, the elastic member 441 was described as a coil spring inserted through a male screw 53 formed on the rod 5. However, the elastic member 441 is not limited to a coil spring. Also, there may be multiple elastic members 441.

[0070] (8) In the above embodiment, as an example of having multiple sliding members 3 and support members 41, an example was described in which a first sliding member 3X and a second sliding member 3Y and a first support member 4X and a second support member 4Y corresponding to each of these were provided. However, the number of sliding members 3 and their corresponding support members 41 is not limited to two, but may be three or more.

[0071] (9) The configurations disclosed in the embodiments described above can be applied in combination with configurations disclosed in other embodiments, as long as no inconsistencies arise. With regard to other configurations, the embodiments disclosed herein are merely illustrative in all respects. Therefore, various modifications can be made as appropriate without departing from the spirit of this disclosure.

[0072] [Summary of this embodiment] The following is a summary of the embodiments relating to the friction damper 100 described above.

[0073] The friction damper (100) consists of a cylindrical cylinder (1) and With the direction along the axis of the cylinder (1) as the axial direction (L), a sliding body (2) slides against the inner circumferential surface of the cylinder (1) and reciprocates within the cylinder (1) in the axial direction (L), A rod (5) is connected to the sliding body (2) and moves back and forth in the axial direction (L) together with the sliding body (2), A friction damper (100) equipped with, The direction perpendicular to the axis of the cylinder (1) is defined as the radial direction (R), and the direction around the axis of the cylinder (1) is defined as the circumferential direction (C). The sliding body (2) is A sliding member (3) having a sliding surface (31A) that contacts the inner circumferential surface (11) of the cylinder (1), An adjustment mechanism (4) for changing the radial (R) position of the sliding surface 31A, Equipped with, The adjustment mechanism (4) is A support member (41) is positioned on the inner side (R2) in the radial direction (R) relative to the sliding member (3), A relative movement mechanism (42) that moves the sliding member (3) and the support member (41) relative to each other in the axial direction (L), Equipped with, The sliding member (3) comprises at least one of an elastic structure having elasticity in the circumferential direction (C) and a segmented structure divided in the circumferential direction (C). A first inclined surface (3A) is formed on the inner circumferential surface of the sliding member (3), which is inclined with respect to the axial direction (L). A second inclined surface (4A) is formed on the outer circumferential surface of the support member (41), facing the first inclined surface (3A) and parallel to the first inclined surface (3A).

[0074] With this configuration, the adjustment mechanism (4) changes the radial (R) position of the sliding surface (31A), thereby adjusting the contact pressure between the inner circumferential surface (11) of the cylinder (1) and the sliding surface (31A) of the sliding member (3). This allows the damping characteristics to be adjusted without replacing the components that make up the sliding surface (31A). Furthermore, as the first inclined surface (3A) and the second inclined surface (4A) move relative to each other in the axial direction (L), the first inclined surface (3A) is pushed radially (R) outward (R1), causing the sliding surface (31A) to move radially (R) outward (R1). In this way, the adjustment mechanism (4) can adjust the contact pressure between the inner circumferential surface (11) of the cylinder (1) and the sliding surface (31A) of the sliding member (3), allowing the radial (R) position of the sliding surface (31A) to be adjusted with high precision, making it easier to obtain the desired damping characteristics.

[0075] Here, the relative movement mechanism (42) is A nut (43) that screws onto a male thread (53) provided on the rod (5), A transmission unit (44) transmits the relative movement of the nut (43) in the axial direction (L) with respect to the rod (5) to one of the sliding member (3) and the support member (41), It is preferable to include a restricting portion (45) that restricts the relative movement of the sliding member (3) and the other support member (41) with respect to the rod (5).

[0076] With this configuration, the sliding member (3) and the support member (41) can be moved relative to each other in the axial direction (L) by rotating the nut (43) relative to the rod (5). Therefore, the contact pressure between the inner circumferential surface (11) of the cylinder (1) and the sliding surface (31A) of the sliding member (3) can be easily adjusted.

[0077] Furthermore, the relative movement mechanism (42) preferably includes a pressing device (6) that applies an axial (L) pressing force to at least one of the sliding member (3) and the support member (41) in response to an electrical signal, and that can change the magnitude of the pressing force.

[0078] With this configuration, the damping characteristics of the friction damper (100) can be changed by an electrical signal. Therefore, the damping characteristics can be appropriately changed according to the usage conditions of the friction damper (100).

[0079] Furthermore, the rod (5) is provided with a projection (52) that protrudes outward (L1) in the axial direction (L) relative to the cylinder (1), Preferably, the first inclined surface (3A) is inclined toward the inner side (R2) in the radial direction (R) as it moves toward the side (L1) of the protruding portion (52) in the axial direction (L).

[0080] In this configuration, when the sliding member (3) moves relative to the support member (41) toward the protruding portion (52) in the axial direction (L), the sliding surface (31A) moves radially (R) outward (R1). Conversely, when the sliding member (3) moves relative to the support member (41) toward the opposite side of the protruding portion (52) in the axial direction (L), the sliding surface (31A) moves radially (R) inward (R2). As a result, when the amount of protrusion of the rod (5) from the cylinder (1) is large, the contact pressure between the inner circumferential surface (11) of the cylinder (1) and the sliding surface (31A) of the sliding member (3) becomes larger than the contact pressure between the inner circumferential surface (11) of the cylinder (1) and the sliding surface (31A) of the sliding member (3) when the amount of protrusion of the rod (5) from the cylinder (1) is small. Therefore, it is easy to obtain damping characteristics suitable for use in vehicle suspensions. [Industrial applicability]

[0081] The technology relating to this disclosure can be used in a friction damper comprising a cylinder and a sliding body that slides against the inner circumferential surface of the cylinder and reciprocates inside the cylinder. [Explanation of Symbols]

[0082] 1: Cylinder, 2: Sliding body, 3: Sliding member, 3A: First inclined surface, 4: Adjustment mechanism, 4A: Second inclined surface, 5: Rod, 6: Pressing device, 11: Sliding surface (inner circumferential surface of cylinder), 31: Sliding part, 31A: Sliding surface, 41: Support member, 42: Relative movement mechanism, 43: Nut, 44: Transmission part, 45: Regulating part, 52: Protruding part, 53: Male screw, 100: Friction damper, C: Circumferential direction, L: Axial direction, L1: Axial outer direction, L2: Axial inner direction, R: Radial direction, R1: Radial outer direction, R2: Radial inner direction

Claims

1. A cylindrical cylinder, A sliding body that moves back and forth within the cylinder in the axial direction while sliding against the inner circumferential surface of the cylinder, with the direction along the axis of the cylinder as the axial direction, A rod connected to the sliding body and moving back and forth in the axial direction together with the sliding body, A friction damper equipped with, The direction perpendicular to the axis of the cylinder is defined as the radial direction, and the direction around the axis of the cylinder is defined as the circumferential direction. The sliding body is, A sliding member having a sliding surface that contacts the inner circumferential surface of the cylinder, An adjustment mechanism for changing the radial position of the sliding surface, Equipped with, The adjustment mechanism is, A support member positioned radially inward relative to the sliding member, A relative movement mechanism that moves the sliding member and the support member relative to each other in the axial direction, Equipped with, The sliding member comprises at least one of an elastic structure having elasticity in the circumferential direction and a segmented structure divided in the circumferential direction. A first inclined surface is formed on the inner circumferential surface of the sliding member, which is inclined with respect to the axial direction. A friction damper in which a second inclined surface is formed on the outer circumferential surface of the support member, facing the first inclined surface and parallel to the first inclined surface.

2. The aforementioned relative movement mechanism is A nut that screws onto a male thread provided on the aforementioned rod, A transmission unit that transmits the relative axial movement of the nut with respect to the rod to one of the sliding member and the support member, The friction damper according to claim 1, further comprising a restricting portion that restricts the relative movement of the sliding member and the other support member with respect to the rod.

3. The friction damper according to claim 1 or 2, wherein the relative movement mechanism includes a pressing device that applies an axial pressing force to at least one of the sliding member and the support member in response to an electrical signal, and is capable of changing the magnitude of the pressing force.

4. The rod has a projection that protrudes outward in the axial direction relative to the cylinder, The friction damper according to claim 1 or 2, wherein the first inclined surface is inclined radially inward as it approaches the protruding portion in the axial direction.

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