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Abstract

To provide a shock absorber capable of improving ride comfort on a vehicle by changing friction force according to the vibration states of a vehicle boy.SOLUTION: A shock absorber D includes a shaft 1 rotatable in the peripheral direction, a first friction disc 2 mounted to the shaft 1 in a peripherally non-rotatable manner and rotatable in the peripheral direction together with the shaft 1, a second friction disc 3 non-rotatable in the peripheral direction for, when it abuts on the first friction disc 2 and then the first friction disc 2 is rotated, generating friction force between the first friction disc 2 and itself to suppress the rotation of the shaft 1, and a first cam unit C1 having an annular cam 15 and a cam follower 16 movable relative to the cam 15 in the axial direction of the shaft 1, and having an axial length changed with the rotation of the shaft 1 in the state that the cam 15 is mounted to the shaft 1. With the change in the axial length of the first cam unit C1, a contact surface pressure between the first friction disc 2 and the second friction disc 3 is changed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0007]

[0001] The present invention relates to a shock absorber.

Background Art

[0002] As shock absorbers that absorb vibration energy and attenuate the vibration of the object to be vibration-damped, there are, in addition to hydraulic shock absorbers that utilize the viscous resistance of hydraulic oil, those that utilize inertial mass as resistance and those that utilize frictional force as resistance.

[0003] Generally, hydraulic shock absorbers are often used in vehicle suspensions. However, due to the problem of responsiveness caused by the compressibility of hydraulic oil, there have been attempts to use shock absorbers that utilize frictional force, which is excellent in responsiveness, in suspensions.

[0004] Such a shock absorber includes, for example, a cylinder, a rod-shaped piston slidably inserted into the cylinder, a friction pad inserted into the cylinder with its axial movement restricted and slidably contacting the side surface of the piston, and an elastic body that presses the friction pad toward the side surface of the piston. When the piston moves axially with respect to the cylinder, a damping force is generated that hinders the movement of the piston due to the frictional force generated between the piston and the friction pad (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Here, the hydraulic shock absorber used in a suspension has a damping force characteristic that increases the damping force as the expansion and contraction speed increases, suppresses the vibration of the vehicle body according to the vibration situation of the vehicle body, and maintains a good ride comfort in the vehicle.

[0007] However, while conventional shock absorbers that utilize friction are superior to hydraulic shock absorbers in that they can generate damping force with better responsiveness, they can only output a constant damping force for the vertical displacement of the vehicle body relative to the wheels because the frictional force between the friction pad and the piston remains constant.

[0008] Therefore, if the damping force of a conventional shock absorber that utilizes friction is set to a small value suitable for vehicle body vibrations during small-amplitude strokes, the shock absorber cannot generate the damping force required for large-amplitude strokes, and thus cannot adequately suppress vehicle body vibrations.

[0009] However, if the damping force of a conventional friction-based shock absorber is set to a large value to suit the vibration of the vehicle body during large strokes, the damping force generated by the shock absorber during small strokes will be excessive, thus compromising the ride comfort of the vehicle.

[0010] Thus, conventional shock absorbers that utilize frictional force have the problem of compromising ride comfort in vehicles because they cannot generate damping force according to the vibration conditions of the vehicle body.

[0011] Therefore, the present invention aims to provide a shock absorber that can improve ride comfort in a vehicle by changing the damping force according to the vibration conditions of the vehicle body. [Means for solving the problem]

[0012] To solve the aforementioned problems, the shock absorber of the present invention comprises a shaft that is circumferentially rotatable, a first friction disc that is mounted on the shaft in a manner that prevents circumferential rotation and is circumferentially rotatable with the shaft, a second friction disc that is not circumferentially rotatable and contacts the first friction disc, generating a frictional force that suppresses the rotation of the shaft when the first friction disc rotates, and a first cam unit having an annular cam and a cam follower that is relatively movable relative to the cam in the axial direction of the shaft, with one of the cam and the cam follower mounted on the shaft and the axial length changing with the rotation of the shaft, and the contact pressure between the first friction disc and the second friction disc is changed by the change in the axial length of the first cam unit. The damping force increases whether the shaft is rotated clockwise or counterclockwise from its neutral position. The shock absorber configured in this way moves the second friction disc axially toward the first friction disc according to the rotation angle from the neutral position of the shaft, thereby changing the contact pressure between the first and second friction discs and changing the frictional force between them, thus reducing the damping force according to the rotation angle from the neutral position of the shaft. Large It is possible.

[0013] Also, Other inventions The shock absorber is A first cam unit comprising a shaft rotatable in the circumferential direction, a first friction disc mounted on the shaft so as not to rotate in the circumferential direction and rotatable with the shaft, a second friction disc which is not rotatable in the circumferential direction and contacts the first friction disc, generating a frictional force that suppresses the rotation of the shaft when the first friction disc rotates, and a first cam unit having an annular cam and a cam follower that is relatively movable relative to the cam in the axial direction of the shaft, with one of the cam and the cam follower mounted on the shaft and the axial length changing with the rotation of the shaft, The device comprises a third friction disc that is unable to rotate in the circumferential direction and contacts the side of the first friction disc opposite to the second friction disc, generating a frictional force that suppresses the rotation of the shaft when the first friction disc rotates, and a second cam unit having an annular cam and a cam follower that is movable relative to the cam in the axial direction of the shaft, with one of the cam and the cam follower attached to the shaft and positioned on the side of the first friction disc opposite to the first cam unit, and whose axial length changes with the rotation of the shaft, The contact pressure between the first friction disc and the second friction disc is changed by changing the axial length of the first cam unit. The contact pressure between the first and third friction discs is changed by altering the axial length of the second cam unit. ru .

[0014] In this type of shock absorber, a single first friction disc is sandwiched between the second and third friction discs, generating frictional forces between the first and second friction discs, and between the first and third friction discs. This allows for the generation of a large damping force with a small number of parts. Furthermore, because the structure involves sandwiching a single first friction disc between the second and third friction discs and applying a load to the first friction disc 2, no moment is applied that would cause the first friction disc to deflect radially, thus improving the durability of the shock absorber.

[0015] Furthermore, the shock absorber may include a first elastic body positioned between the first cam unit and the second friction disc, which biases the second friction disc toward the first friction disc. In this configuration, the biasing force of the first elastic body that biases the second friction disc toward the first friction disc changes according to the rotation angle of the shaft from the neutral position, so that the damping force can be changed according to the rotation angle of the shaft from the neutral position, and tuning of the damping force is also made easier.

[0016] Furthermore, the shock absorber may include a second elastic body positioned between the second cam unit and the third friction disc, which biases the third friction disc toward the first friction disc. In this configuration, the biasing force of the second elastic body that biases the third friction disc toward the first friction disc changes according to the rotation angle of the shaft from the neutral position, so that the damping force can be changed according to the rotation angle of the shaft from the neutral position, and tuning of the damping force is also made easier.

[0017] Furthermore, the cam may have an arc-shaped cam surface corresponding to the cam follower, and the cam surface may also include a flat portion and a pair of inclined portions provided on both sides of the flat portion in the circumferential direction, which are inclined to rise in the axial direction. With a shock absorber configured in this way, the damping force increases whether the shaft rotates clockwise or counterclockwise from the neutral position. Therefore, when installed on a vehicle, a large damping force can be generated when the stroke increases on both the compression side, when the vehicle body approaches the wheels, and the extension side, when the vehicle body moves away from the wheels.

Advantages of the Invention

[0018] As described above, according to the shock absorber of the present invention, the damping force can be changed according to the vibration state of the vehicle body, thereby improving the riding comfort of the vehicle.

Brief Description of the Drawings

[0019] [Figure 1] It is a cross-sectional view of a shock absorber in one embodiment. [Figure 2] It is a view showing a shock absorber in one embodiment in a state of being installed on a vehicle body. [Figure 3] It is a side view of a shock absorber in one embodiment in a state of being installed on a vehicle body. [Figure 4] It is a perspective view of a shock absorber in one embodiment. [Figure 5] It is a developed view of a cam in the first cam unit of a shock absorber in one embodiment. [Figure 6] It is a developed view of a cam in the second cam unit of a shock absorber in one embodiment. [Figure 7] It is a view showing the damping force characteristics of a shock absorber in one embodiment.

Embodiments for Carrying Out the Invention

[0020] Hereinafter, the present invention will be described based on the embodiments shown in the drawings. In the present specification, when simply referring to the axial direction, it refers to the direction along the axial direction of the shaft 1 in the shock absorber D.

[0021] As shown in FIGS. 1 to 3, a shock absorber D in one embodiment includes a shaft 1 rotatably inserted in a circumferential direction in a cylindrical case 7, and the shaft 1 toThe shock absorber D comprises a first friction disc 2 mounted so as not to rotate circumferentially and rotatable circumferentially with the shaft 1, a second friction disc 3 in contact with the first friction disc 2, a third friction disc 4 in contact with the side of the first friction disc 2 opposite the second friction disc 3, a first cam unit C1 and a second cam unit C2, a first elastic body 5 positioned between the first cam unit C1 and the second friction disc 3, and a second elastic body 6 positioned between the second cam unit C2 and the third friction disc 4. The shock absorber D is interposed between the vehicle body B and the wheel W, for example, with the case 7 attached to the vehicle body B, and the shaft 1 connected to a rod A supporting the wheel W in the vehicle via arms 8a and 8b attached to both ends of the shaft 1. Furthermore, when the vehicle body B and the wheels W move closer together or further apart in the vertical direction, the shock absorber D rotates the shaft 1, generating frictional forces between the first friction disc 2 and the second friction disc 3, and between the first friction disc 2 and the third friction disc 4, thereby suppressing the rotation of the shaft 1 and exerting a damping force that suppresses the relative displacement between the vehicle body B and the wheels W.

[0022] The following describes the various parts of the shock absorber D in detail. As shown in Figures 1 to 4, the case 7 is cylindrical and has eight key grooves 7a formed along the axial direction on its inner circumference. Annular caps 9 and 10 are attached to the left and right ends of the case 7 in Figure 1, respectively.

[0023] The shaft 1 protrudes from the case 7 at both ends through the inner circumference of the caps 9 and 10, and is supported by bearings 11 and 12 provided on the inner circumference of the caps 9 and 10, allowing for rotation in the circumferential direction. A first annular friction disc 2 is fixedly mounted on the outer circumference of the center of the shaft 1. The first friction disc 2 is annular and has friction surfaces 2a and 2b on both sides in the axial direction of the shaft 1, providing high frictional resistance. The outer diameter of the first friction disc 2 is smaller than the inner diameter of the case 7, allowing it to rotate circumferentially with the shaft 1 relative to the case 7. The first friction disc 2 has a keyway 2c that fits into a key 1a provided on the shaft 1 along its axial direction, restricting rotation in the circumferential direction relative to the shaft 1, but allowing movement along the axial direction of the shaft 1. The first friction disc 2 may also be mounted in such a way that it restricts not only rotation in the circumferential direction but also movement in the axial direction relative to the shaft 1.

[0024] The second friction disc 3 is annular in shape and contacts the right-side friction surface 2a of the first friction disc 2 in Figure 1, and is held by an annular holder 13. The holder 13 is annular in shape, with the second friction disc 3 mounted at its left end in Figure 1, and also has eight keys 13a provided at equal intervals on its outer circumference, which are inserted into the key grooves 7a of the case 7.

[0025] The inner diameters of the second friction disc 3 and the holder 13 are larger than the outer diameter of the shaft 1, and the shaft 1 is inserted through the inner circumferences of the second friction disc 3 and the holder 13. When the holder 13 is housed in the case 7, the key 13a is slidably inserted into the keyway 7a, so that it cannot rotate circumferentially relative to the case 7, but it is allowed to move axially. Therefore, the second friction disc 3 is restricted from rotating circumferentially relative to the case 7, but it can move axially, and the shaft 1 can rotate circumferentially within the case 7 without interfering with the inner circumferences of the second friction disc 3 and the holder 13. In this embodiment, the second friction disc 3 is held by the holder 13, and its rotation relative to the case 7 is restricted by the key 13a and the keyway 7a, but the rotation of the second friction disc 3 circumferentially may be restricted by other means, and the holder 13 may be omitted if the rotation of the second friction disc 3 circumferentially can be suppressed.

[0026] Next, the first cam unit C1 includes an annular cam 15 and a cam follower 16 that is relatively movable relative to the cam 15 in the axial direction of the shaft 1. The cam 15 and the cam follower 16 are positioned with the cam 15 facing the cap 9 side and the cam follower 16 facing the second friction disk 3 side.

[0027] The cam 15 is annular in shape, and in Figure 1, four arc-shaped cam surfaces 15a are continuously provided circumferentially at the left end. The maximum number of cam surfaces 15a that can be installed on the cam 15 is determined according to the movable angle of the shaft 1. In the shock absorber D of this embodiment, the shaft 1 is set to swing within a range of 90 degrees with respect to the circumferential direction of the case 7, so the maximum number of cam surfaces 15a that can be installed is 4, which is 360 degrees divided by 90 degrees. Any number of cam surfaces 15a can be installed as long as it is less than or equal to the maximum number. Therefore, for example, if the movable range of the shaft 1 is set to 120 degrees, the number of cam surfaces 15a that can be installed should be 3 or less.

[0028] The four cam surfaces 15a are arc-shaped, dividing the ring into four sections. As shown in the unfolded view of the cam 15 in Figure 5, each surface has a flat section 15a1 which is the lowest surface, and a pair of inclined sections 15a2 and 15a3 which are continuously provided on both sides of the flat section 15a1 in the circumferential direction and are inclined to rise in the axial direction.

[0029] Furthermore, the surface of the flat portion 15a1 and the surfaces of the inclined portions 15a2 and 15a3 are smoothly connected, the inclination angle θ1 formed by the flat portion 15a1 and the inclined portion 15a2 is greater than the inclination angle θ2 formed by the flat portion 15a1 and the inclined portion 15a3, and the two inclination angles θ1 and θ2 are different from each other.

[0030] In this embodiment of the buffer D, the maximum height from the lowest part of the flat portion 15a1 of the inclined portion 15a2 and the inclined portion 15a3 is the same, and the four cam surfaces 15a are provided continuously in the circumferential direction of the cam 15. As shown in Figure 5, the ends of the inclined portions 15a2 and 15a3 of adjacent cam surfaces 15a are connected to each other, and the shape of the cam 15 is such that four peaks formed by the inclined portions 15a2 and 15a3 of the cam surfaces 15a appear in the circumferential direction. The cam surfaces 15a may be provided independently of each other and not continuous with the cam 15. Also, the shape after reaching the maximum height of the end portion of the inclined portion 15a2 and the inclined portion 15a3 opposite to the flat portion 15a1 may be a flat surface. Furthermore, if the maximum heights of the inclined portion 15a2 and the inclined portion 15a3 are different, a step may be formed at the boundary between the inclined portion 15a2 and the inclined portion 15a3 on the adjacent cam surface 15a.

[0031] Furthermore, the outer diameter of the cam 15 is smaller than the inner diameter of the case 7. In the shock absorber D of this embodiment, the cam 15 is fixed to the outer circumference of the shaft 1 and rotates together with the shaft 1 when the shaft 1 rotates relative to the case 7.

[0032] The cam follower 16 is mounted on an annular base 17 which is ring-shaped, has an inner diameter larger than that of the shaft 1, has the shaft 1 inserted through its inner circumference, and has eight keys 17a provided at equal intervals on its outer circumference.

[0033] Specifically, four cam followers 16 are provided at equal intervals in the circumferential direction at the end of the base 17 facing the cam 15. Each cam follower 16 comprises a bracket 16a rising from the base 17 and a roller 16b rotatably mounted on the bracket 16a. The roller 16b of each cam follower 16 abuts against the corresponding cam surface 15a of the cam 15, allowing it to travel smoothly on the cam surface 15a. Note that if the cam follower 16 can travel smoothly on the cam surface 15a, the roller 16b may be omitted.

[0034] Furthermore, when the base 17 is housed in the case 7, the key 17a is slidably inserted into the keyway 7a, so that it cannot rotate circumferentially relative to the case 7, but it is allowed to move axially. Thus, the cam follower 16, together with the base 17, cannot rotate circumferentially relative to the case 7, but it is allowed to move axially. The base 17 has an annular projection 17b that protrudes axially from the inner circumference of the end opposite to the end facing the cam 15, which is provided with the four cam followers 16.

[0035] As the shaft 1 rotates, the cam 15 rotates, and the roller 16b of the cam follower 16 travels on the cam surface 15a and moves from the flat portion 15a1 onto the inclined portions 15a2 and 15a3. As a result, the base 17 that holds the cam follower 16 moves away from the cam 15 in the axial direction. Conversely, as the roller 16b travels from the inclined portions 15a2 and 15a3 to the flat portion 15a1, the base 17 is biased by the first elastic body 5 (described later) and moves towards the cam 15 in the axial direction. In other words, as the shaft 1 rotates, the first cam unit C1 changes its overall length from the end face of the cam 15 to the end face of the base 17 in the axial direction. It is preferable to have as many cam surfaces 15a and cam followers 16 as possible so that the load is applied to the base 17 as evenly as possible in the circumferential direction.

[0036] In the shock absorber D of this embodiment, assuming that the shaft 1 is in the neutral position when each cam follower 16 is in contact with the center of the flat portion 15a1 of the cam surface 15a, when the shaft 1 rotates clockwise from the neutral position as viewed from the left in Figure 1, each cam follower 16 rides up onto the left-side inclined portion 15a2 of the flat portion 15a1 of the cam surface 15a in Figure 5. When the shaft 1 rotates counterclockwise from the neutral position as viewed from the left in Figure 1, each cam follower 16 rides up onto the right-side inclined portion 15a3 of the flat portion 15a1 of the cam surface 15a in Figure 5.

[0037] Furthermore, since the inclination angle θ1 formed by the flat portion 15a1 and the inclined portion 15a2 of the cam 15 is greater than the inclination angle θ2 formed by the flat portion 15a1 and the inclined portion 15a3, the speed at which the base 17 moves away from the cam 15 differs depending on whether the shaft 1 rotates clockwise or counterclockwise from the neutral position at the same speed when viewed from the left in Figure 1. More specifically, the speed at which the base 17 moves away from the cam 15 is faster when the shaft 1 rotates clockwise from the neutral position at the same speed when viewed from the left in Figure 1 than when the shaft 1 rotates counterclockwise from the neutral position at the same speed when viewed from the left in Figure 1.

[0038] Furthermore, a first elastic body 5, composed of an annular disc spring, is interposed between the base 17 that holds the cam follower 16 and the holder 13 that holds the second friction disc 3. The inner circumference of the first elastic body 5 fits onto the outer circumference of a projection 17b provided on the base 17, and is interposed between the base 17 and the holder 13 in a flexed state, constantly biasing the second friction disc 3 toward the first friction disc 2, and applying a load to bring the second friction disc 3 and the first friction disc 2 into close contact. The first elastic body 5 may be composed of multiple stacked disc springs.

[0039] Since the inner circumference of the first elastic body 5 is fitted onto the outer circumference of the protrusion 17b provided on the base 17, it is positioned without radial displacement relative to the base 17, and therefore, it is offset in the circumferential direction relative to the second friction disc 3 and the first friction disc 2. RinaIt can withstand a load.

[0040] Therefore, when the shaft 1 is in the neutral position, the cam follower 16 contacts the lowest flat portion 15a1 on the cam surface 15a of the cam 15 and is furthest from the second friction disc 3. As a result, the amount of deflection of the disc spring, which is the first elastic body 5, is minimized, and the load that the first elastic body 5 exerts on the second friction disc 3 is minimized. Thus, when the shaft 1 is in the neutral position, the frictional force between the first friction disc 2 and the second friction disc 3 is minimized. In contrast, when the shaft 1 rotates from the neutral position and the cam follower 16 rides onto the inclined portions 15a2 and 15a3, the cam follower 16 approaches the second friction disc 3 axially, increasing the amount of deflection of the disc spring, which is the first elastic body 5. As a result, the frictional force between the first friction disc 2 and the second friction disc 3 becomes greater than when the shaft 1 is in the neutral position.

[0041] As the rotation angle of shaft 1 from the neutral position increases, the cam follower 16 moves toward the end of the inclined portions 15a2 and 15a3. As a result, the amount of movement of the cam follower 16 toward the second friction disc 3 also increases, and the frictional force between the first friction disc 2 and the second friction disc 3 increases. Depending on the allowable rotation angle from the neutral position of shaft 1, the cam follower 16 may not reach the maximum height portion of the boundary with the inclined portions 15a2 and 15a3. However, the further away from the center of the cam surface 15a the cam follower 16 is, the higher the height of the inclined portions 15a2 and 15a3 becomes. Therefore, when the rotation angle of the cam follower 16 from the neutral position reaches the maximum allowable angle, the deflection of the disc spring, which is the first elastic body 5, becomes maximum, the load that the first elastic body 5 exerts on the second friction disc 3 becomes maximum, and the frictional force between the first friction disc 2 and the second friction disc 3 becomes maximum.

[0042] Next, on the side of the first friction disc 2 opposite to the second friction disc 3 and the first cam unit C1, the third friction disc 4, the second elastic body 6, and the second cam unit C2 are arranged.

[0043] The third friction disc 4 is annular in shape and abuts against the left-hand friction surface 2b in Figure 1, which is opposite to the second friction disc 3 in the axial direction of the first friction disc 2, and is held by an annular holder 14. The holder 14 is annular in shape, with the third friction disc 4 mounted at its right end in Figure 1, and also has eight keys 14a provided at equal intervals on its outer circumference, which are inserted into the key grooves 7a of the case 7.

[0044] The inner diameters of the third friction disc 4 and the holder 14 are larger than the outer diameter of the shaft 1, and the shaft 1 is inserted through the inner circumferences of the third friction disc 4 and the holder 14. When the holder 14 is housed in the case 7, the key 14a is slidably inserted into the keyway 7a, so that it cannot rotate circumferentially relative to the case 7, but it can move axially. Therefore, the third friction disc 4 is restricted from rotating circumferentially relative to the case 7, but can move axially, and the shaft 1 can rotate circumferentially within the case 7 without interfering with the inner circumferences of the third friction disc 4 and the holder 14. In this embodiment, the third friction disc 4 is held by the holder 14, and the rotation of the third friction disc 4 relative to the case 7 is restricted by the key 14a and the keyway 7a, but the rotation of the third friction disc 4 relative to the case 7 may be restricted by other means, and the holder 14 may be omitted if the rotation of the third friction disc 4 circumferentially can be suppressed. 。

[0045] The second cam unit C2, like the first cam unit C1, comprises an annular cam 18 and a cam follower 19 that is relatively movable relative to the cam 18 in the axial direction of the shaft 1. The cam 18 and cam follower 19 are positioned with the cam 18 facing the cap 10 side and the cam follower 19 facing the third friction disk 4 side.

[0046] The cam 18 is annular in shape, and in Figure 1, four arc-shaped cam surfaces 18a are provided continuously in the circumferential direction at the right end. The maximum number of cam surfaces 18a that can be installed on the cam 18 is determined according to the movable angle of the shaft 1, similar to the cam surface 15a on the cam 15, and any number of cam surfaces 18a may be installed as long as it is less than or equal to the maximum number.

[0047] The four cam surfaces 18a are arc-shaped, dividing the annulus into four sections. As shown in the unfolded view of the cam 18 in Figure 6, each surface has a flat section 18a1 which is the lowest surface, and a pair of inclined sections 18a2 and 18a3 which are continuously provided on both sides of the flat section 18a1 in the circumferential direction and inclined to rise in the axial direction. In the shock absorber D of this embodiment, the cam surface 18a of the cam 18 has a symmetrical shape with respect to the cam surface 15a of the cam 15 and the first friction disk 2, that is, it has the same shape as a mirror image of the cam surface 15a.

[0048] Therefore, the surface of the flat portion 18a1 and the surfaces of the inclined portions 18a2 and 18a3 are smoothly connected, the inclination angle θ1 formed by the flat portion 18a1 and the inclined portion 18a2 is greater than the inclination angle θ2 formed by the flat portion 18a1 and the inclined portion 18a3, and the two inclination angles θ1 and θ2 are different from each other.

[0049] In this embodiment of the buffer D, the maximum height from the lowest part of the flat portion 18a1 of the inclined portion 18a2 and the inclined portion 18a3 is the same, and the four cam surfaces 18a are provided continuously in the circumferential direction of the cam 18. As shown in Figure 6, the ends of the inclined portions 18a2 and 18a3 of adjacent cam surfaces 18a are connected to each other, and the shape of the cam 18 is such that four peaks formed by the inclined portions 18a2 and 18a3 of the cam surfaces 18a appear in the circumferential direction. However, since the cam surface 18a is the same shape as the mirror image of the cam surface 15a, the inclined portion 18a2 with a large inclination angle θ1 with the flat portion 18a1 is located to the right of the flat portion 18a1 in Figure 6, and the inclined portion 18a3 with a small inclination angle θ2 with the flat portion 18a1 is located to the left of the flat portion 18a1 in Figure 6.

[0050] Furthermore, even with respect to the cam 18, the cam surfaces 18a may be provided independently of each other and not continuous with respect to the cam 18. Also, the shape after reaching the maximum height of the end portion opposite to the flat portion 18a1 of the inclined portion 18a2 and the inclined portion 18a3 may be a flat surface. Moreover, if the maximum heights of the inclined portion 18a2 and the inclined portion 18a3 are different, a step may be formed at the boundary between the inclined portion 18a2 and the inclined portion 18a3 of adjacent cam surfaces 18a.

[0051] Furthermore, the outer diameter of the cam 18 is smaller than the inner diameter of the case 7. In the shock absorber D of this embodiment, the cam 18 is fixed to the outer circumference of the shaft 1 and rotates together with the shaft 1 when the shaft 1 rotates relative to the case 7.

[0052] The cam follower 19 is mounted on an annular base 20 which is ring-shaped, has an inner diameter larger than that of the shaft 1, has the shaft 1 inserted through its inner circumference, and has eight keys 20a provided at equal intervals on its outer circumference.

[0053] Specifically, four cam followers 19 are provided at equal intervals in the circumferential direction at the end of the base 20 facing the cam 18. Each cam follower 19 comprises a bracket 19a rising from the base 20 and a roller 19b rotatably mounted on the bracket 19a. The roller 19b of each cam follower 19 contacts the corresponding cam surface 18a of the cam 18, allowing it to travel smoothly on the cam surface 18a. Note that if the cam follower 19 can travel smoothly on the cam surface 18a, the roller 19b may be omitted.

[0054] Furthermore, when the base 20 is housed in the case 7, the key 20a is slidably inserted into the keyway 7a, so that it cannot rotate circumferentially relative to the case 7, but it is allowed to move axially. Thus, the cam follower 19, together with the base 20, cannot rotate circumferentially relative to the case 7, but it is allowed to move axially. The base 20 has an annular projection 20b that protrudes axially on the inner circumference of the end opposite to the end facing the cam 18, which is provided with the four cam followers 19.

[0055] As the shaft 1 rotates, the cam 18 rotates, and the roller 19b of the cam follower 19 travels on the cam surface 18a and moves from the flat section 18a1 onto the inclined sections 18a2 and 18a3. As a result, the base 20 that holds the cam follower 19 moves away from the cam 18 in the axial direction. Conversely, as the roller 19b travels from the inclined sections 18a2 and 18a3 to the flat section 18a1, the cam follower 19 is biased by the second elastic body 6 (described later), causing the base 20 to move closer to the cam 18 in the axial direction. In other words, as the shaft 1 rotates, the second cam unit C2 changes its overall length from the end face of the cam 18 to the end face of the base 20 in the axial direction. It is preferable to have as many cam surfaces 18a and cam followers 19 as possible so that the load is applied to the base 20 as evenly as possible in the circumferential direction.

[0056] In the shock absorber D of this embodiment, assuming that the shaft 1 is in the neutral position when each cam follower 19 is in contact with the center of the flat portion 18a1 of the cam surface 18a, when the shaft 1 rotates clockwise from the neutral position as viewed from the left in Figure 1, each cam follower 19 rides up onto the right-side inclined portion 18a2 of the flat portion 18a1 of the cam surface 18a in Figure 6. When the shaft 1 rotates counterclockwise from the neutral position as viewed from the left in Figure 1, each cam follower 19 rides up onto the left-side inclined portion 18a3 of the flat portion 18a1 of the cam surface 18a in Figure 6.

[0057] Furthermore, since the inclination angle θ1 formed by the flat portion 18a1 and the inclined portion 18a2 of the cam 18 is greater than the inclination angle θ2 formed by the flat portion 18a1 and the inclined portion 18a3, the speed at which the base 20 moves away from the cam 18 differs depending on whether the shaft 1 rotates clockwise or counterclockwise from the neutral position at the same speed when viewed from the left in Figure 1. More specifically, the speed at which the base 20 moves away from the cam 18 is faster when the shaft 1 rotates clockwise from the neutral position at the same speed when viewed from the left in Figure 1 than when the shaft 1 rotates counterclockwise from the neutral position at the same speed when viewed from the left in Figure 1.

[0058] Furthermore, a second elastic body 6, composed of an annular disc spring, is interposed between the base 20 that holds the cam follower 19 and the holder 14 that holds the third friction disc 4. The second elastic body 6 is interposed between the base 20 and the holder 14 in a flexed state, with its inner circumference fitted onto the outer circumference of a projection 20b provided on the base 20, and constantly biases the third friction disc 4 toward the first friction disc 2, applying a load to bring the third friction disc 4 and the first friction disc 2 into close contact. The second elastic body 6 may be composed of multiple stacked disc springs.

[0059] Since the inner circumference of the second elastic body 6 is fitted onto the outer circumference of the protrusion 20b provided on the base 20, it is positioned without radial displacement relative to the base 20 and the holder 14, so that a load can be applied to the third friction disc 4 and the first friction disc 2 without bias in the circumferential direction.

[0060] Therefore, when the shaft 1 is in the neutral position, the cam follower 19 contacts the lowest flat portion 18a1 on the cam surface 18a of the cam 18 and is furthest away from the third friction disc 4. As a result, the amount of deflection of the disc spring, which is the second elastic body 6, is minimized, and the load that the second elastic body 6 exerts on the third friction disc 4 is minimized. Thus, when the shaft 1 is in the neutral position, the frictional force between the first friction disc 2 and the third friction disc 4 is minimized. In contrast, when the shaft 1 rotates from the neutral position and the cam follower 19 rides up onto the inclined portions 18a2 and 18a3, the cam follower 19 approaches the third friction disc 4 axially, increasing the amount of deflection of the disc spring, which is the second elastic body 6. As a result, the frictional force between the first friction disc 2 and the third friction disc 4 becomes greater than when the shaft 1 is in the neutral position.

[0061] As the rotation angle of shaft 1 from the neutral position increases, the cam follower 19 moves toward the end of the inclined portions 18a2 and 18a3. As a result, the amount of movement of the cam follower 19 toward the third friction disc 4 also increases, and the frictional force between the first friction disc 2 and the third friction disc 4 increases. Depending on the allowable rotation angle from the neutral position of shaft 1, the cam follower 19 may not reach the maximum height portion of the boundary with the inclined portions 18a2 and 18a3. However, the further away from the center of the cam surface 18a the cam follower 19 is, the higher the height of the inclined portions 18a2 and 18a3 becomes. Therefore, when the rotation angle of the cam follower 19 from the neutral position reaches the maximum allowable angle, the deflection of the disc spring, which is the second elastic body 6, becomes maximum, the load that the second elastic body 6 exerts on the third friction disc 4 becomes maximum, and the frictional force between the first friction disc 2 and the third friction disc 4 becomes maximum.

[0062] The shock absorber D is configured as described above, and its operation will be explained below. The shock absorber D has a case 7 attached to the vehicle body B, and a shaft 1 connected to a rod A that supports the wheel W via arms 8a and 8b attached to both ends, and is interposed between the vehicle body B and the wheel W in parallel with the suspension spring S. As mentioned above, the case 7 is used to hold the caps 9 and 10 that support the shaft 1 and to restrict the circumferential rotation of the second friction disc 3, third friction disc 4, and cam followers 16 and 19, but the circumferential rotation of the second friction disc 3, third friction disc 4, and cam followers 16 and 19 may be restricted using something other than the case 7. The cylindrical shape of the case 7 protects each part of the shock absorber D housed inside the case 7, but the caps 9 and 10 may be connected by a connecting rod instead of the case 7, and this connecting rod may be used to restrict the circumferential rotation of the second friction disc 3, third friction disc 4, and cam followers 16 and 19. Furthermore, a reduction gear may be provided between the arms 8a, 8b and the shaft 1.

[0063] The suspension spring S is compressed by the weight of the vehicle body B, generating an elastic force that supports the vehicle body B, thereby elastically supporting the vehicle body B and maintaining the vehicle height at a predetermined height when the vehicle body B is not vibrating. The shock absorber D in this embodiment is installed on the vehicle such that the shaft 1 is in the aforementioned neutral position when the vehicle height is maintained at a predetermined height by the suspension spring S.

[0064] As the vehicle moves, the wheels W travel over uneven surfaces, causing the vehicle body B and the wheels W to approach each other in the vertical direction. As a result, the shaft 1 rotates counterclockwise relative to case 7 when viewed from the left in Figure 1, starting from its neutral position.

[0065] As shaft 1 rotates counterclockwise from its neutral position, the cams 15 and 18 in the first cam unit C1 and the second cam unit C2 rotate, causing the cam followers 16 and 19 to move on the cam surfaces 15a and 18a of cams 15 and 18 from the flat portions 15a1 and 18a1 towards the inclined portions 15a3 and 18a3. In response to this rotation of shaft 1, the shock absorber D generates a damping force that suppresses the rotation of shaft 1, which is the sum of the frictional force generated between the first friction disc 2 and the second friction disc 3 and the frictional force generated between the first friction disc 2 and the third friction disc 4.

[0066] Here, if the rotation angle of shaft 1 counterclockwise from the neutral position is small, and the cam followers 16 and 19 move only on the flat sections 15a1 and 18a1 without riding up onto the inclined sections 15a3 and 18a3, the cam followers 16 and 19 are not pushed up toward the first friction disc 2 by the cams 15 and 18. Therefore, the axial lengths of the first cam unit C1 and the second cam unit C2 do not change, and the biasing force of the first elastic body 5 on the second friction disc 3 and the biasing force of the second elastic body 6 on the third friction disc 4 do not change. In this way, when the cam followers 16 and 19 move only on the flat sections 15a1 and 18a1, the total frictional force between the first friction disc 2 and the second friction disc 3 and between the first friction disc 2 and the third friction disc 4 is minimized.

[0067] Therefore, even if the vehicle body B and the wheels W are displaced so that they move closer to each other in the vertical direction, if the rotation angle of the shaft 1 is small and the cam followers 16 and 19 move only on the flat parts 15a1 and 18a1, the damping force generated by the shock absorber D will be minimized. In other words, the shock absorber D generates the minimum damping force when the relative stroke in the approaching direction between the vehicle body B and the wheels W is small.

[0068] In contrast, if the rotation angle of shaft 1 from the neutral position is larger than before, and the cam followers 16 and 19 ride up onto the inclined portions 15a3 and 18a3, the cam followers 16 and 19 are pushed upward toward the first friction disk 2 by the cams 15 and 18, increasing the axial length of the first cam unit C1 and the second cam unit C2, and compressing the first elastic body 5 and the second elastic body 6 by the amount of the displacement of the cam followers 16 and 19 toward the first friction disk 2. Therefore, when the rotation angle of shaft 1 becomes larger than before, and the cam followers 16 and 19 ride up onto the inclined sections 15a3 and 18a3, the biasing force of the first elastic body 5 on the second friction disc 3 and the biasing force of the second elastic body 6 on the third friction disc 4 become larger than when the cam followers 16 and 19 move only on the flat sections 15a1 and 18a1, and the contact pressure between the first friction disc 2 and the second friction disc 3 and the contact pressure between the first friction disc 2 and the third friction disc 4 increases. Also, when the cam followers 16 and 19 travel on the inclined sections 15a3 and 18a3, as the rotation angle of shaft 1 from the neutral position increases, the biasing force of the first elastic body 5 on the second friction disc 3 and the biasing force of the second elastic body 6 on the third friction disc 4 also increase.

[0069] Therefore, as the vehicle body B and the wheels W are displaced so that they move closer to each other in the vertical direction, and the rotation angle of the shaft 1 from the neutral position increases, causing the cam followers 16 and 19 to travel on the inclined sections 15a3 and 18a3, the axial lengths of the first cam unit C1 and the second cam unit C2 increase, and the contact pressure between the first friction disc 2 and the second friction disc 3 and the contact pressure between the first friction disc 2 and the third friction disc 4 increases. Consequently, the frictional force between the first friction disc 2 and the second friction disc 3 and the frictional force between the first friction disc 2 and the third friction disc 4 increases. Therefore, the damping force generated by the shock absorber D becomes greater than the damping force when the cam followers 16 and 19 travel on the flat sections 15a1 and 18a1, and increases in proportion to the increase in the rotation angle of the shaft 1 from the neutral position.

[0070] Therefore, as shown in Figure 7, when shaft 1 strokes in the direction that brings the vehicle body B and wheel W closer together, the damping force characteristics of the shock absorber D are such that the damping force remains constant until the cam followers 16 and 19 reach the inclined portions 15a3 and 18a3, and thereafter the cam followers 16 and 19 reach the inclined portions 15a3 and 18a3, the damping force increases in proportion to the increase in the rotation angle of shaft 1.

[0071] After the vehicle body B and the wheel W are in maximum proximity, when the vehicle body B and the wheel W begin to move in a direction that separates them vertically, the rotation direction of the shaft 1 reverses from counterclockwise to clockwise when viewed from the left in Figure 1, and the cam followers 16 and 19 move from the higher part to the lower part of the inclined section 15a3 and 18a3. In this situation, when the rotation direction of the shaft 1 switches to clockwise and the cam followers 16 and 19 are traveling on the inclined section 15a3 and 18a3, the cam followers 16 and 19 are displaced in a direction that separates them axially from the first friction disk 2. Therefore, the axial lengths of the first cam unit C1 and the second cam unit C2 are shortened, and as the rotation angle from the neutral position of the shaft 1 decreases, the biasing force of the first elastic body 5 on the second friction disc 3 and the biasing force of the second elastic body 6 on the third friction disc 4 decrease, the contact pressure between the first friction disc 2 and the second friction disc 3 and the contact pressure between the first friction disc 2 and the third friction disc 4 decreases, and the frictional force between the first friction disc 2 and the second friction disc 3 and the frictional force between the first friction disc 2 and the third friction disc 4 decreases.

[0072] Therefore, when the vehicle body B and the wheels W are in maximum proximity and then displaced to separate from each other in the vertical direction, and the cam followers 16 and 19 are traveling on the inclined sections 15a3 and 18a3, the damping force generated by the shock absorber D decreases as the rotation angle from the neutral position of the shaft 1 decreases.

[0073] Furthermore, as the vehicle body B and the wheels W continue to displace so that they move apart in the vertical direction, and the cam followers 16 and 19 move from the inclined sections 15a3 and 18a3 to the flat sections 15a1 and 18a1, the cam followers 16 and 19 move as far away from the first friction disc 2 as possible, thus minimizing the damping force generated by the shock absorber D. The shock absorber D minimizes the damping force generated as the cam followers 16 and 19 maintain their maximum distance from the first friction disc 2 until the vehicle body B and the wheels W continue to displace so that they move apart in the vertical direction, and the cam followers 16 and 19 reach the inclined sections 15a2 and 18a2 on the opposite side of the flat sections 15a1 and 18a1.

[0074] Therefore, as shown in Figure 7, when the vehicle body B and the wheels W are in a state where they are closest to each other and the suspension strokes in a direction that moves them apart, the damping force characteristics of the shock absorber D are such that when the cam followers 16 and 19 are traveling on the inclined sections 15a3 and 18a3, the damping force decreases with decreasing rotation angle from the neutral position of the shaft 1, and when the cam followers 16 and 19 reach the flat sections 15a1 and 18a1 and travel on them, the damping force remains constant regardless of the rotation angle from the neutral position of the shaft 1.

[0075] Furthermore, as the vehicle body B and the wheels W continue to displace so that they move apart in the vertical direction, the shaft 1 rotates clockwise when viewed from the left in Figure 1, and the clockwise rotation angle of the shaft 1 from its neutral position increases, causing the cam followers 16 and 19 to ride up from the flat sections 15a1 and 18a1 to the inclined sections 15a2 and 18a2. In this way, as the shaft 1 rotates clockwise from its neutral position and the cam followers 16 and 19 ride up to the inclined sections 15a2 and 18a2, the cam followers 16 and 19 are pushed up toward the first friction disc 2 by the cams 15 and 18. This compresses the first elastic body 5 and the second elastic body 6 by the amount of the displacement of the cam followers 16 and 19 toward the first friction disc 2. Therefore, when the clockwise rotation angle of shaft 1 from the neutral position is large, and the cam followers 16 and 19 ride up onto the inclined sections 15a2 and 18a2, the biasing force of the first elastic body 5 on the second friction disc 3 and the biasing force of the second elastic body 6 on the third friction disc 4 become larger than when the cam followers 16 and 19 move only on the flat sections 15a1 and 18a1. Also, when the cam followers 16 and 19 travel on the inclined sections 15a2 and 18a2, as the clockwise rotation angle of shaft 1 from the neutral position increases, the biasing force of the first elastic body 5 on the second friction disc 3 and the biasing force of the second elastic body 6 on the third friction disc 4 also increase.

[0076] Therefore, when the vehicle body B and the wheels W are displaced so that they are separated from each other in the vertical direction, and the clockwise rotation angle of the shaft 1 from the neutral position increases, causing the cam followers 16 and 19 to travel on the inclined sections 15a2 and 18a2, the damping force generated by the shock absorber D becomes greater than the damping force when the cam followers 16 and 19 travel on the flat sections 15a1 and 18a1, and increases in proportion to the increase in the clockwise rotation angle of the shaft 1 from the neutral position.

[0077] Therefore, when the shaft 1 strokes in a direction that separates the vehicle body B and the wheel W, starting from the neutral position, the damping force characteristics of the shock absorber D are as shown in Figure 7. The damping force remains constant until the cam followers 16 and 19 reach the inclined portions 15a2 and 18a2, and thereafter the cam followers 16 and 19 reach the inclined portions 15a2 and 18a2, the damping force increases in proportion to the increase in the rotation angle of the shaft 1.

[0078] Furthermore, since the inclination angle θ1 formed by the inclined sections 15a2, 18a2 and the flat sections 15a1, 18a1 is greater than the inclination angle θ2 formed by the inclined sections 15a3, 18a3 and the flat sections 15a1, 18a1, the rate of increase in damping force with respect to the stroke amount between the vehicle body B and the wheel W is greater when the shaft 1 rotates clockwise compared to when it rotates counterclockwise, as shown in Figure 7.

[0079] After the vehicle body B and the wheels W are separated to their maximum extent, when the vehicle body B and the wheels W begin to stroke in a direction that brings them closer together in the vertical direction, the rotation direction of the shaft 1 reverses from clockwise to counterclockwise, and the cam followers 16 and 19 move from the higher part to the lower part of the inclined section 15a2 and 18a2. In this situation, when the rotation direction of the shaft 1 switches to counterclockwise and the cam followers 16 and 19 are traveling on the inclined section 15a2 and 18a2, the cam followers 16 and 19 are displaced in a direction that moves them away from the first friction disc 2 in the axial direction. In addition, as the rotation angle of the shaft 1 from the neutral position decreases, the biasing force of the first elastic body 5 on the second friction disc 3 and the biasing force of the second elastic body 6 on the third friction disc 4 decrease.

[0080] Therefore, when the vehicle body B and the wheels W are separated to their maximum extent and then displaced to move closer to each other in the vertical direction, and the cam followers 16 and 19 are traveling on the inclined sections 15a2 and 18a2, the damping force generated by the shock absorber D decreases as the rotation angle of the shaft 1 decreases to its neutral position.

[0081] Furthermore, as the vehicle body B and the wheels W continue to displace so that they move closer to each other in the vertical direction, and the cam followers 16 and 19 move from the inclined sections 15a2 and 18a2 to the flat sections 15a1 and 18a1, the cam followers 16 and 19 move as far away from the first friction disc 2 as possible, thus minimizing the damping force generated by the shock absorber D. The shock absorber D minimizes the damping force generated as the cam followers 16 and 19 maintain their maximum distance from the first friction disc 2 until the vehicle body B and the wheels W continue to displace so that they move further apart in the vertical direction, and the cam followers 16 and 19 reach the inclined sections 15a3 and 18a3 on the opposite side of the flat sections 15a1 and 18a1.

[0082] Therefore, as shown in Figure 7, when the vehicle body B and the wheels W are stroking in a direction that brings them closer together from a state where they are maximally separated, the damping force characteristics of the shock absorber D are such that, when the cam followers 16 and 19 are traveling on the inclined sections 15a2 and 18a2, the damping force decreases with decreasing rotation angle from the neutral position of the shaft 1, and when the cam followers 16 and 19 reach the flat sections 15a1 and 18a1 and travel on them, the damping force remains constant regardless of the rotation angle from the neutral position of the shaft 1.

[0083] As described above, the shock absorber D of this embodiment comprises a shaft 1 that is rotatable in the circumferential direction, a first friction disc 2 that is mounted on the shaft 1 so as not to rotate in the circumferential direction and can rotate circumferentially with the shaft 1, a second friction disc 3 that is not rotatable in the circumferential direction and contacts the first friction disc 2, generating a frictional force that suppresses the rotation of the shaft 1 between itself and the first friction disc 2 when the first friction disc 2 rotates, a first cam unit C1 having an annular cam 15 and a cam follower 16 that is relatively movable relative to the cam 15 in the axial direction of the shaft 1, the cam 15 being mounted on the shaft 1 and whose axial length changes with the rotation of the shaft 1, and a first elastic body 5 that is positioned between the first cam unit C1 and the second friction disc 3 and biases the second friction disc 3 toward the first friction disc 2.

[0084] In this configuration, when the vehicle body B is displaced vertically relative to the wheels W around the vehicle height, if the displacement is small, the rotation angle of the shaft 1 from the neutral position is small, generating sufficient damping force to suppress the displacement of the vehicle body B. However, when the vehicle body B vibrates significantly relative to the wheels W, the rotation angle of the shaft 1 from the neutral position increases, resulting in a larger damping force in proportion to the stroke of the vehicle body B. In other words, the shock absorber D changes the biasing force of the first elastic body 5 that biases the second friction disc 3 toward the first friction disc 2 according to the rotation angle of the shaft 1 from the neutral position, thus allowing the damping force to change according to the rotation angle of the shaft 1 from the neutral position.

[0085] Therefore, the shock absorber D of this embodiment can not only exert a small damping force suitable for suppressing vibrations of the vehicle body B when the vehicle body B vibrates with a small stroke, but can also generate a large damping force required when the vehicle body B vibrates with a large stroke, and can generate an appropriate damping force according to the vibration conditions of the vehicle body B. In this way, the shock absorber D of this embodiment can improve ride comfort in the vehicle by changing the damping force according to the vibration conditions of the vehicle body B.

[0086] As described above, the first elastic body 5 is interposed between the cam follower 16 and the second friction disc 3. However, the first elastic body 5 and the holder 13 may be eliminated, and the second friction disc 3 may be installed on the cam follower 16, which moves axially due to the rotation of the shaft 1. Even in this case, the axial length of the first cam unit C1 changes due to the rotation of the shaft 1. to do As a result, the contact pressure between the first friction disc 2 and the second friction disc 3 changes, which in turn changes the frictional force between the first friction disc 2 and the second friction disc 3, allowing the shock absorber D to change its damping force according to the rotation angle from the neutral position of the shaft 1. However, if a first elastic body 5 is provided, the damping force of the shock absorber D can be tuned by setting the spring constant of the first elastic body 5, making it easier to tune the damping force of the shock absorber D.

[0087] In this embodiment, the shock absorber D has the cam 15 in the first cam unit C1 attached to the shaft 1. However, the cam 15 may be made axially movable relative to the shaft 1, and a cam follower 16 may be attached to the shaft 1 via or directly to the base 17 instead of the cam 15. The axial arrangement of the cam 15 and the cam follower 16 may be reversed, and the first elastic body 5 may be interposed between the cam 15 and the second friction disk 3.

[0088] Furthermore, in the shock absorber D of this embodiment, the second friction disc 3 is positioned between the first cam unit C1 and the first friction disc 2. However, the second friction disc 3 may be made immovable in the axial direction, and the first friction disc 2, which is immovable on the shaft 1 and movable in the axial direction, may be positioned between the first cam unit C1 and the second friction disc 3, so that the first cam unit C1 directly presses the first friction disc 2 toward the second friction disc 3. Alternatively, a structure may be adopted in which a first elastic body 5 is interposed between the first cam unit C1 and the first friction disc 2, and the first elastic body 5 biases the first friction disc 2 toward the second friction disc 3.

[0089] Furthermore, in the shock absorber D of this embodiment, the first elastic body 5 is a disc spring, but it is sufficient for it to be interposed between the first cam unit C1 and the second friction disc 3 so as to bias the second friction disc 3 while bringing it into contact with the first friction disc 2, and other elastic bodies such as coil springs, spring washers, gas springs, rubber, and synthetic resins can also be used.

[0090] Furthermore, the shock absorber D of this embodiment includes a third friction disc 4 that is unable to rotate in the circumferential direction and contacts the side surface of the first friction disc 2 opposite to the second friction disc 3, generating a frictional force that suppresses the rotation of the shaft 1 between it and the first friction disc 2 when the first friction disc 2 rotates; a second cam unit C2 having an annular cam 18 and a cam follower 19 that is relatively movable relative to the cam 18 in the axial direction of the shaft 1, with the cam 18 attached to the shaft 1 and positioned on the side of the first friction disc 2 opposite to the first cam unit C1; and a second elastic body 6 positioned between the second cam unit C2 and the third friction disc 4, biasing the third friction disc 4 toward the first friction disc 2.

[0091] In the shock absorber D configured in this way, one first friction disc 2 is sandwiched between the second friction disc 3 and the third friction disc 4, generating frictional forces between the first friction disc 2 and the second friction disc 3, and between the first friction disc 2 and the third friction disc 4. This allows for the generation of a large damping force with a small number of parts. Furthermore, because the structure is designed to apply a load to the first friction disc 2 by sandwiching it between the second friction disc 3 and the third friction disc 4, no moment is applied that would cause the first friction disc 2 to deflect radially, thus improving the durability of the shock absorber D. In this case, if the first friction disc 2 is mounted on the shaft 1 so as to be movable in the axial direction, the moment that would cause the first friction disc 2 to deflect radially is canceled out, further improving the durability of the shock absorber D.

[0092] As described above, a second elastic body 6 is interposed between the cam follower 19 and the third friction disc 4. However, the second elastic body 6 and the holder 14 may be eliminated, and the third friction disc 4 may be installed on the cam follower 19, which moves axially due to the rotation of the shaft 1. In this case as well, the axial length of the second cam unit C2 changes due to the rotation of the shaft 1, which changes the contact pressure between the first friction disc 2 and the third friction disc 4, and thus changes the friction force between the first friction disc 2 and the third friction disc 4. Therefore, the shock absorber D can change its damping force according to the rotation angle from the neutral position of the shaft 1. However, if the second elastic body 6 is provided, the damping force of the shock absorber D can be tuned by setting the spring constant of the second elastic body 6, making it easier to tune the damping force of the shock absorber D.

[0093] Furthermore, in the shock absorber D of this embodiment, a third friction disc 4 is positioned between the second cam unit C2 and the first friction disc 2. However, the third friction disc 4 may be made immovable in the axial direction, and a first friction disc 2 that is immovable on the shaft 1 and movable in the axial direction may be positioned between the second cam unit C2 and the third friction disc 4, so that the second cam unit C2 directly presses the first friction disc 2 toward the third friction disc 4. Alternatively, a second elastic body 6 may be interposed between the second cam unit C2 and the first friction disc 2, and the second elastic body 6 may bias the first friction disc 2 toward the third friction disc 4. Furthermore, when pressing the first friction disc 2 toward the third friction disc 4, if the first friction discs 2 are arranged on both sides in the axial direction with the third friction disc 4 as the center, and the first and second cam units C1 and C2 press each first friction disc 2 toward the third friction disc 4, then the third friction disc 4 does not need to be fixed in the axial direction because it is subjected to pressing force from both sides in the axial direction.

[0094] Furthermore, in the shock absorber D of this embodiment, the cams 15 and 18 have arc-shaped cam surfaces 15a and 18a corresponding to the cam followers 16 and 19, and the cam surfaces 15a and 18a include flat portions 15a1 and 18a1, and a pair of inclined portions 15a2, 15a3, 18a2, and 18a3 provided on both sides of the flat portions 15a1 and 18a1 in the circumferential direction and inclined to rise in the axial direction. With the shock absorber D configured in this way, a large damping force can be generated as the stroke increases, both on the contraction side when the vehicle body B approaches the wheel W and on the extension side when the vehicle body B moves away from the wheel W.

[0095] Furthermore, in the shock absorber D of this embodiment, the inclination angle θ1 of one of the inclined sections 15a2, 18a2 with respect to the flat sections 15a1, 18a1 is different from the inclination angle θ2 of the other inclined section 15a3, 18a3 with respect to the flat sections 15a1, 18a1. With the shock absorber D configured in this way, the damping force characteristics on the contraction side when the vehicle body B approaches the wheel W and on the extension side when the vehicle body B moves away from the wheel W can be set independently and made different, thereby effectively improving the ride comfort in the vehicle.

[0096] In this embodiment, the shock absorber D is equipped with a second friction disc 3, a first elastic body 5, and a first cam unit C1 on one side of the first friction disc 2, and a third friction disc 4, a second elastic body 6, and a second cam unit C2 on the other side of the first friction disc 2. hand However, the third friction disc 4, the second elastic body 6, and the second cam unit C2 may be omitted. Alternatively, the first friction disc 2 and the second friction disc 3 may be used as a single friction force generating unit, and multiple such friction force generating units may be provided in the axial direction of the shaft 1. Furthermore, multiple such friction force generating units may be provided in the axial direction of the shaft 1 between the first cam unit C1 and the second cam unit C2.

[0097] Furthermore, in the shock absorber D of this embodiment, the cam surfaces 15a and 18a of the cams 15 and 18 are mirror images of each other, but the design can be arbitrarily changed according to the damping force characteristics for the desired stroke (rotation angle of the shaft 1). For example, the inclination angles θ1 and θ2 of the inclined portions 15a2, 15a3, 18a2, and 18a3 can be set to the same angle, so that the damping force characteristics of the shock absorber D are the same on the extension side and the contraction side. Alternatively, if the shock absorber D does not need to increase the damping force on the contraction side when the vehicle body B approaches the wheel W, the inclined portion corresponding to the contraction side among the inclined portions 15a2 and 15a3 (18a2, 18a3) on the cam surface 15a (18a) can be eliminated, and the cam surface 15a (18a) can be formed to have an inclined portion on only one side in the circumferential direction.

[0098] Furthermore, if the damping force is to increase as the rotation angle from the neutral position of shaft 1 increases, the height of both sides of the cam surfaces 15a and 18a in the circumferential direction should be made higher than the center. In this way, when the shock absorber D is installed on a vehicle, the damping force increases as the vibration stroke of the vehicle body B increases, effectively suppressing the vibration of the vehicle body B. Therefore, if such damping force characteristics are to be obtained, for example, the cam surfaces 15a and 18a can be made to have only inclined sections on both ends, with a concave center and higher ends, without a flat section, and the maximum heights of inclined section 15a2 and inclined section 15a3 may be different. Moreover, the inclined sections 15a2, 15a3, 18a2, and 18a3 may be composed of inclined surfaces in which the inclination angle changes along the way.

[0099] Furthermore, the starting points of the inclined portions 15a2 and 15a3 do not necessarily have to be set at an equidistant distance from the position where the cam follower 16 contacts the flat portion 15a1 when the shaft 1 is in the neutral position. Also, in the case of the shock absorber D of this embodiment, the neutral position is defined as the position where the shaft 1 is positioned circumferentially relative to the case 7 when the vehicle body B is stationary and maintained at a constant vehicle height by the suspension spring S. However, the neutral position can be changed arbitrarily, and the neutral position does not necessarily have to be a position in the rotational direction of the shaft 1 such that the cam followers 16 and 19 are located at the circumferential center of the cam surfaces 15a and 18a.

[0100] In this embodiment, the shock absorber D is described as being interposed between the vehicle body B and the wheels W to dampen vibrations of the vehicle body B. However, the shock absorber D can also be used for vibration damping of structures, buildings, and various machines and equipment in civil engineering, in addition to vehicle vibration damping.

[0101] Although preferred embodiments of the present invention have been described in detail above, modifications, alterations, and changes are permitted as long as they do not deviate from the scope of the claims. [Explanation of Symbols]

[0102] 1...Shaft, 2...First friction disc, 3...Second friction disc, 4...Third friction disc, 5...First elastic body, 6...Second elastic body, 15,18...Cam, 15a,18a...Cam surface, 15a1,18a1...Flat section, 15a2,15a3,18a2,18a3...Inclined section, 16,19...Cam follower, C1...First cam unit, C2...Second cam unit, D...Bowser

Claims

1. A shaft that can rotate in the circumferential direction, A first friction disk is attached to the shaft so as not to rotate in the circumferential direction and is rotatable together with the shaft in the circumferential direction, A second friction disc that is unable to rotate in the circumferential direction and contacts the first friction disc, generating a frictional force that suppresses the rotation of the shaft when the first friction disc rotates, A first cam unit having an annular cam and a cam follower that is movable relative to the cam in the axial direction of the shaft, wherein one of the cam and the cam follower is attached to the shaft and the axial length changes with the rotation of the shaft, A third friction disk that is unable to rotate in the circumferential direction and contacts the side surface of the first friction disk opposite the second friction disk, and generates a frictional force that suppresses the rotation of the shaft when the first friction disk rotates, A second cam unit comprises an annular cam and a cam follower that is movable relative to the cam in the axial direction of the shaft, wherein one of the cam and the cam follower is attached to the shaft and positioned on the side of the first friction disk opposite the first cam unit, and the axial length of the second cam unit changes with the rotation of the shaft. The contact pressure between the first friction disk and the second friction disk is changed by changing the axial length of the first cam unit. The contact pressure between the first friction disk and the third friction disk is changed by changing the axial length of the second cam unit. A buffer characterized by the following features.

2. The first cam unit is provided with a first elastic body positioned between the first cam unit and the second friction disk, which biases the second friction disk toward the first friction disk. The shock absorber according to feature 1.

3. The device comprises a second elastic body positioned between the second cam unit and the third friction disk, which biases the third friction disk toward the first friction disk. A shock absorber according to claim 1 or 2, characterized by the features described above.

4. The cam has an arc-shaped cam surface that faces the range of motion of the cam follower, The cam surface has a flat portion and a pair of inclined portions provided on both sides of the flat portion in the circumferential direction, which are inclined to rise in the axial direction. A buffer according to any one of claims 1 to 3, characterized by the following:

5. The angle of inclination of one of the inclined portions relative to the flat portion is different from the angle of inclination of the other inclined portion relative to the flat portion. The shock absorber according to feature 4.

Images