Shock absorber

Abstract

A shock absorber (10) has a free piston part (30) into which a first fluid can flow from a shock absorber body part (20). The free piston part (30) includes: a pressing means storage part (R4) storing a pressing means that is a fluid different from the first fluid; a first member (32) that is installed to be displaceable along an axis (CL2) of a free piston case part (40) and that is located at a position where the pressure of the first fluid and pressing force of the pressing means are balanced; and a second member (34) that is displaceable together with the first member (32) along the axis (CL2) of the free piston case part (40) and that is displaceable separately from the first member (32).

Description

Shock absorber

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

[0002] Vehicles such as two-wheeled vehicles are provided with a shock absorber to attenuate energy such as vibration input to wheels from the ground. As a conventional technology related to shock absorbers, there is a technology disclosed in Patent Document 1.

[0003] A shock absorber as disclosed in Patent Document 1 comprises: a shock absorber main body that is filled with oil inside and is capable of generating a damping force; and a free piston portion that allows oil to flow into and out of the shock absorber main body.

[0004] The free piston portion is filled with oil and nitrogen gas inside, and the free piston is provided between the oil and the nitrogen gas. The free piston is displaced to a position inside the case where the pressures of the oil and the nitrogen gas are balanced. By including the free piston portion, the characteristics of the damping force generated in the shock absorber main body can be stabilized.

[0005] Japanese Patent Laid-Open No. 2024-53137

[0006] The present inventors conducted research on a shock absorber having a free piston portion as disclosed in Patent Document 1, and found that it has the following problems.

[0007] For example, when the volume of oil in the shock absorber main body contracts at a low outside air temperature, the oil in the free piston portion corresponding to the contracted volume is returned into the shock absorber main body. In other words, the pressure of the nitrogen gas advances the free piston to deliver oil into the shock absorber main body. Also, when the shock absorber main body extends, oil corresponding to the volume of the rod flows from the free piston portion into the shock absorber main body. That is, the free piston advances also during the extension stroke of the shock absorber main body. Even if the shock absorber main body extends when the free piston is located at the forward limit inside the case due to the influence of outside air temperature, no more oil can be fed from the free piston portion into the shock absorber main body. It has been found that in this case, a delay may occur in the generation of damping force.

[0008] The present invention aims to provide a shock absorber that suppresses a decrease in the stability of its damping force characteristics.

[0009] The following describes this disclosure.

[0010] According to this disclosure, a shock absorber is provided, comprising: a shock absorber body portion filled with a first fluid as a working fluid and capable of generating a damping force; a free piston portion into which the first fluid can flow from the shock absorber body portion and which can return the first fluid to the shock absorber body portion; the shock absorber body portion comprising a cylindrical cylinder and a piston provided inside the cylinder that generates a damping force when displaced along the axis of the cylinder; the free piston portion comprising a free piston case portion which is a substantially cylindrical case, a pressing means housing portion which is a part of the free piston case portion and houses a pressing means, a first member provided so as to be displaceable along the axis of the free piston case portion and located at a position where the pressure of the first fluid and the pressing force of the pressing means are balanced; and a second member which is displaceable together with the first member along the axis of the free piston case portion and is displaceable independently of the first member.

[0011] According to the present invention, it is possible to provide a shock absorber that suppresses a decrease in the stability of its damping force characteristics.

[0012] This is a cross-sectional view showing the main part of the buffer according to Embodiment 1. This is an enlarged view of part 2 of Figure 1. Figure 3A is a diagram illustrating the state of the buffer body and free piston under normal conditions, Figure 3B is a diagram illustrating the details of the free piston in the state of Figure 3A, Figure 3C is a diagram illustrating the state of the buffer body and free piston when the volume of the first fluid is reduced or the amount of the first fluid is decreased, Figure 3D is a diagram illustrating the details of the free piston in the state of Figure 3C, Figure 3E is a diagram illustrating the state of the buffer body and free piston when the buffer body is extended from the state of Figure 3C, and Figure 3F is a diagram illustrating the details of the free piston in the state of Figure 3E. This is a schematic cross-sectional view showing the buffer according to Embodiment 2.

[0013] Embodiments of the present invention will be described below with reference to the attached drawings. Note that the embodiments shown in the attached drawings are examples of the present invention, and the present invention is not limited to these embodiments.

[0014] <Example 1> (Shock absorber 10) Refer to Figure 1. The shock absorber 10 is used, for example, as an inverted front fork connecting the front wheel and the body of a motorcycle. The cross-section of the shock absorber 10 shown in Figure 1 is near the lower end of the front fork.

[0015] The shock absorber 10 includes a shock absorber body 20 filled with oil that generates damping force when it expands and contracts, a free piston 30 through which oil can flow in and out of the shock absorber body 20, and a control unit 15 provided between the shock absorber body 20 and the free piston 30 to control the flow rate of the oil.

[0016] The oil filled inside the shock absorber 10 is the working fluid for generating damping force. Hereafter, the oil may be referred to as the first fluid.

[0017] (Shock absorber body 20) The shock absorber body 20 can use a well-known component that connects the front wheel to the vehicle body and generates damping force when it expands and contracts. The shock absorber body 20 includes a holder portion 21 connected to the front wheel, a cylindrical inner tube 22 whose lower end is fixed to the holder portion 21, a cylindrical cylinder 23 provided inside the inner tube 22, a piston rod 24 provided inside the cylinder 23 and displaceable relative to the cylinder 23, a piston 25 fixed to the piston rod 24 and generating damping force when displaced, and a sub-piston 26 provided at the lower end of the cylinder 23.

[0018] The axes of the inner tube 22, piston rod 24, piston 25, and sub-piston 26 coincide with the axis CL1 of the cylinder 23.

[0019] The shock absorber body 20 further includes an outer tube (not shown) whose upper end is connected to the vehicle body and which is relatively displaceable along the outer circumferential surface of the inner tube 22. The piston rod 24 is supported by the outer tube. The axis of the outer tube also coincides with the axis CL1 of the cylinder 23.

[0020] The piston rod 24, piston 25, and outer tube are displaceable along the axis CL1 of the cylinder 23 relative to the holder portion 21, inner tube 22, cylinder 23, and sub-piston 26. In other words, the piston rod 24, piston 25, and outer tube are displaceable relative to the holder portion 21, inner tube 22, cylinder 23, and sub-piston 26.

[0021] A cylindrical hole, a connecting hole 21a, is formed at the lower part of the holder portion 21 for connection to the axle. The shock absorber 10 is connected to the front wheel via the connecting hole 21a.

[0022] The inside of the cylinder 23 is divided into two chambers by the piston 25. The two chambers are a first chamber R1 located in front of the piston 25, whose volume decreases during the compression stroke, and a second chamber (not shown) located behind the piston 25, whose volume decreases during the extension stroke.

[0023] The space between the inner circumference of the inner tube 22 and the outer circumference of the cylinder 23 is a third chamber R3 to which oil can be supplied to and from the free piston portion 30. The third chamber R3 does not contribute to the generation of damping force.

[0024] The oil in the first chamber R1 flows to the control unit 15 via the sub-piston 26 during the compression stroke.

[0025] (Free piston section 30) The free piston section 30 includes a free piston case section 40 (hereinafter referred to as "case section 40") which is a case in which a part is integrally formed with the holder section 21, a first member 32 which is provided to be displaceable inside the case section 40, a restricting section 33 which extends from the first member 32 toward the bottom of the case section 40 and is capable of restricting the forward movement of the first member 32, and a second member 34 which passes through the center of the restricting section 33 and is provided to be movable inside the case section 40.

[0026] Refer to Figure 2. The interior of the case portion 40 is divided into multiple spaces by the first member 32 and the second member 34. The area enclosed by the case portion 40 and the first member 32, which is filled with nitrogen gas as a pressing means, is the pressing means housing portion R4. The area enclosed by the case portion 40 and the second member 34, which is filled with oil, is the first fluid filling portion R5. The space formed by the second member 34, the case portion 40, and the first member 32 is the rear first fluid filling portion R6.

[0027] The nitrogen gas filled in the pressing means housing section R4 is a fluid that presses the first member 32 toward the first fluid filling section R5. Hereinafter, the nitrogen gas may be referred to as the pressing means.

[0028] In addition to nitrogen gas, compressible fluids such as carbon dioxide or elastic bodies such as coil springs can also be used as the pressing means.

[0029] (Case portion 40) Refer to Figure 1. The case portion 40 has a case body portion 41 which is integrally formed with the holder portion 21 and has an open rear end, and a lid portion 42 which closes the opening of the case body portion 41.

[0030] The case body portion 41 includes a piston housing portion 41a in which the first member 32 and the second member 34 are housed, a case tip portion 41b formed at the end of the piston housing portion 41a into which the first member 32 and the second member 34 cannot enter, a contact portion 41c formed in a concave shape at the tip of the case tip portion 41b into which the tip of the restricting portion 33 can abut, a communication portion 41d opened radially near the bottom of the piston housing portion 41a, and an outer peripheral communication portion 41e opened radially from the rear first fluid filling portion R6 with reference to the first member 32 which is located at the forward limit.

[0031] The case tip 41b has a mortar-like shape, with its inner diameter continuously decreasing towards the tip. The inner diameter at the rear end of the case tip 41b is smaller than the inner diameter of the piston housing 41a. Therefore, a step is formed at the boundary between the piston housing 41a and the case tip 41b. This step acts as a stopper that restricts the forward movement of the second member 34.

[0032] The contact portion 41c is a concave portion with an inner diameter slightly larger than the outer diameter of the regulating portion 33.

[0033] The communication section 41d is a cylindrical hole and is connected to the control unit 15. The control unit 15 and the shock absorber body 20 are also connected in a way that allows oil to flow in and out. Therefore, it can be said that the communication section 41d is connected to the shock absorber body 20 via the control unit 15.

[0034] Refer to Figure 2. The communication portion 41d is formed in a position facing the side surface of the second member 34, which is located at its forward limit.

[0035] Refer to Figure 1. The outer peripheral communication portion 41e is a cylindrical hole and is connected to the control unit 15. The control unit 15 and the shock absorber body 20 are also connected in a way that allows oil to flow in and out. Therefore, it can be said that the outer peripheral communication portion 41e is connected to the shock absorber body 20 via the control unit 15. The outer peripheral communication portion 41e is formed at a position facing the side surface of the first member 32, which is located at the forward limit.

[0036] The lid portion 42 is formed in a bottomed cylindrical shape and opens toward the bottom of the piston housing portion 41a. The outer circumferential surface of the lid portion 42 is formed in a male thread shape and fastened to the inner circumferential surface of the case body portion 41. The outer circumferential surface of the lid portion 42 is provided with a first seal 42a, which is a seal that suppresses oil leakage, and a retaining ring 42b, which is a ring that prevents the lid portion 42 from coming off the case body portion 41. In addition, the inner circumferential surface of the lid portion 42 is provided with a second seal 42c, which is a seal that suppresses nitrogen gas leakage.

[0037] (First member 32) The first member 32 has a bottomed cylindrical shape and opens toward the top plate of the lid 42. The side surface of the first member 32 is along the inner circumferential surface of the lid 42 and is displaceable in the direction of the axis CL2 of the case 40.

[0038] (Regulating portion 33) The regulating portion 33 is a rod-shaped member that extends from the center of the bottom of the first member 32 along the axis CL2 of the case portion 40.

[0039] Refer to Figure 2. The length of the restricting portion 33 is set such that even when the first member 32 is located at the rear end and the second member 34 is located at the front end, the tip portion is located inside the second member 34.

[0040] The restricting portion 33 may be formed from a separate component from the first member 32. Furthermore, it may protrude toward the first member 32 from the case portion 40 side, as long as it can restrict the forward movement of the first member 32.

[0041] (Second member 34) Refer to Figure 2. The second member 34 has a disc-shaped large-diameter portion 34a that abuts the inner circumferential surface of the case portion 40, a small-diameter portion 34b that faces the communication portion 41d when the second member 34 is in the forward limit position and has a smaller outer diameter than the large-diameter portion 34a, and a restricting portion penetration portion 34c that is opened in the center and through which the restricting portion 33 passes.

[0042] The outer diameter of the large-diameter portion 34a is slightly smaller than the inner diameter of the piston housing portion 41a, and larger than the outer diameter of the first member 32.

[0043] A third seal 34d and a fourth seal 34e, which are seals that suppress the inflow of oil from the piston storage portion 41a to the rear first fluid filling portion R6, are provided on the outer circumference of the large diameter portion 34a and the inner circumference of the large diameter portion 34a.

[0044] Reference is made to FIG. 1. In a state where the first member 32 is positioned at the forward limit, the second member 34 can be further advanced. More specifically, the second member 34 can advance to the bottom of the piston storage portion 41a.

[0045] (Control Valve 15) The control valve 15 is stored in a bottomed cylindrical hole-shaped control valve storage portion 21b formed integrally with the holder portion 21. The control valve 15 is energized under a predetermined condition, and can switch opening and closing of the flow path by being energized. For example, in a state where the control valve 15 is open, oil delivered from the first oil chamber R1 flows into the inside of the free piston portion 30 via the communication portion 41d. On the other hand, when the control valve 15 is closed, the oil flows to another oil chamber not shown.

[0046] When the volume of the first fluid becomes excessively large, the first member 32 and the second member 34 are greatly displaced, and when a constant displacement is reached, the crush margin decreases due to the diameter expansion of the mating component on which the third seal 34d slides. At this time, the third seal 34d loses its sealing function, so that the first fluid filling portion R5 communicates with the rear first fluid filling portion R6, and excess oil is discharged to the rear first fluid filling portion R6. The discharged oil further flows into the third chamber R3 communicating with the rear first fluid filling portion R6.

[0047] (Operation of Shock Absorber 10) Next, the operation of the shock absorber 10 will be described.

[0048] Reference is made to FIGS. 3A and 3B. FIG. 3A shows the state of the shock absorber main body portion 20 and the free piston portion 30 in a normal state, and FIG. 3B shows the free piston portion 30 shown in FIG. 3A in more detail.

[0049] For example, when the ambient temperature is normal and the oil has just been filled, the shock absorber body 20 and the free piston 30 are in the state shown in Figures 3A and 3B. More specifically, refer to Figure 3B. The regulating portion 33 is spaced apart from the contact portion 41c, and the first member 32 is in a position where it can move forward and backward. In the state shown in Figure 3B, the oil pressure in the first fluid filling portion R5 and the gas pressure of the nitrogen gas in the pressing means housing portion R4 are in equilibrium.

[0050] Hereinafter, when we say that the first member 32 moves forward, we mean that the displacement of the first member 32 causes the oil to be discharged in the direction from the case body 41. In Figure 3B, this refers to displacement to the right. When we say that the first member 32 moves backward, we mean that the first member 32 is displaced in the opposite direction to when it moves forward. The same applies to the second member 34 and the regulating part 33.

[0051] Refer to Figures 3C and 3D. Figure 3C shows the state of the buffer body 20 and the free piston 30 when the volume of the first fluid is reduced or the amount of the first fluid is decreased, and Figure 3D shows the free piston 30 shown in Figure 3C in more detail.

[0052] For example, if the outside temperature drops, the volume of the oil will contract, and if the buffer 10 is used for a long time, the oil may leak out little by little. In such cases, the gas pressure of the nitrogen gas inside the pressing means housing R4 will be relatively higher. As a result, the first member 32 will move forward more than in its normal state. The first member 32 will move forward to a maximum extent until the restricting portion 33 contacts the contact portion 41c. In other words, the first member 32 can move forward to a position where its forward movement is restricted by the restricting portion 33.

[0053] Furthermore, if the temperature rises or if new oil is added, the oil pressure will relatively increase, causing the first member 32 to retract and return to its normal state (see Figure 3B).

[0054] Refer to Figures 3E and 3F. Figure 3E shows the state of the shock absorber body 20 and the free piston 30 when the shock absorber body 20 is extended from the state shown in Figure 3C, and Figure 3F shows the free piston 30 shown in Figure 3E in more detail.

[0055] As the vehicle moves, the shock absorber body 20 expands and contracts due to the effects of uneven ground, etc. Figure 3E shows the shock absorber body 20 in the extended state, as shown in Figure 3C.

[0056] As the first fluid-filled section R5 extends from the state shown in Figure 3C, the oil in the first fluid-filled section R5 flows towards the buffer body section 20. At this time, since the first member 32 is restricted from moving forward by the restricting section 33, only the second member 34 moves forward.

[0057] As the extended shock absorber body 20 returns to its original position, the second member 34 returns to the position shown in Figure 3D.

[0058] <Example 2> Next, Example 2 will be described based on the drawings.

[0059] Refer to Figure 4. In the buffer 10A according to Embodiment 2, the free piston portion 30A is integrally provided with the buffer body portion 20A. The free piston portion 30A is positioned to face the cylinder 23A. Other basic configurations are the same as those of the buffer 10 in Embodiment 1. Common components will use the same reference numerals and detailed explanations will be omitted as appropriate.

[0060] A boundary wall 35A is provided at the lower part of the cylinder 23A, which forms the boundary between the shock absorber body 20A and the free piston 30A. In other words, the part of the cylinder 23A below the boundary wall 35A can be said to be the case body 41A, which constitutes part of the case body 40A. The case body 41A is then covered with a lid 42A to form the case body 40A.

[0061] A first fluid passage hole 35Aa is provided in the boundary wall portion 35A, parallel to the axis CL3 of the cylinder 23A. Oil is supplied to and from the buffer body portion 20A to the free piston portion 30A through the first fluid passage hole 35Aa.

[0062] Multiple protrusions 32Aa may be formed on the surface of the first member 32A facing the second member 34A, projecting toward the second member 34A. This allows the second member 34A to be easily separated from the first member 32A. The protrusions 32Aa may also project from the second member 34A toward the first member 32A. The protrusions 32Aa may be provided on the first member 32 (see Figure 1) as shown in Embodiment 1.

[0063] The shock absorber 10A has a case portion 40A provided on the axis CL3 of the cylinder 23A. The axis CL3 of the cylinder 23A can also be said to be the axis CL3 of the case portion 40A.

[0064] The rear first fluid-filling section R6 may be connected to the second chamber R2 via a bypass passage section R7 to allow oil to be supplied in and out. When the second member 34A moves away from the first member 32A, the oil in the second chamber R2 flows into the rear first fluid-filling section R6 via the bypass passage section R7. Conversely, when the second member 34A approaches the first member 32A, the oil in the rear first fluid-filling section R6 is supplied to the second chamber R2 via the bypass passage section R7.

[0065] In addition, in the buffer 10A according to Embodiment 2, it is also possible to provide a control unit 15 between the buffer body 20A and the free piston portion 30A. Furthermore, instead of the boundary wall portion 35A, a disc without the first fluid passage hole portion 35Aa can be provided, and oil can be inserted into and removed from the buffer body 20A and the free piston portion 30A via the control unit 15 provided externally.

[0066] The buffers 10 and 10A described above are summarized below.

[0067] Refer to Figure 1. Firstly, the shock absorber 10 includes a shock absorber body 20 filled with a first fluid as a working fluid and capable of generating damping force, and a free piston 30 into which the first fluid can flow from the shock absorber body 20 and which can return the first fluid to the shock absorber body 20. The shock absorber body 20 includes a cylindrical cylinder 23 and a piston 25 provided inside the cylinder 23 that generates damping force when displaced along the axis CL1 of the cylinder 23. The free piston section 30 includes a case section 40 which is a substantially cylindrical case, a pressing means housing section R4 which is a part of the case section 40 and houses the pressing means, a first member 32 which is provided so as to be displaceable along the axis CL2 of the case section 40 and is located at a position where the pressure of the first fluid and the pressing force of the pressing means are balanced, and a second member 34 which is displaceable along the axis CL2 of the case section 40 together with the first member 32 and is displaceable independently of the first member 32.

[0068] Refer to Figure 3. The free piston 25 is composed of two members, a first member 32 and a second member 34, and the second member 34 is made separable from the first member 32. As shown in Figure 3D, the shock absorber body 20 may extend from a state where the first member 32 is at its forward limit, as shown in Figure 3E. In this case, as shown in Figure 3F, the second member 34 separates from the first member 32 and moves forward. In other words, even if the shock absorber body 20 extends when the first member 32 is at its forward limit, the first fluid can be returned to the shock absorber body 20. Therefore, damping force can be generated without delay during extension. A shock absorber 10 is provided that suppresses a decrease in the stability of the damping force characteristics. The same applies to the shock absorber 10A according to Embodiment 2.

[0069] Refer to Figure 1. Conventionally, the design sometimes considered the case where the free piston extended further when it was in its forward position. In this case, the first fluid filling section R5 was depressurized to a near-vacuum state, and oil was injected to a predetermined hydraulic pressure. This required assembly with the free piston positioned between its forward and reverse limits, which presented assembly difficulties. With the shock absorber 10, assembly can be performed with the first member 32 in its forward position, that is, in contact with the case section 40. Therefore, assembly is also improved.

[0070] Refer to Figure 1. Secondly, assuming the first shock absorber 10, the free piston portion 30 further has a restricting portion 33 that restricts the forward movement of the first member 32 while allowing the displacement of the second member 34, when displacement in the direction away from the pressing means housing portion R4 is considered forward movement and displacement in the direction toward the pressing means housing portion R4 is considered backward movement. This ensures that the forward movement of the first member 32 is reliably restricted, while also securing space for the second member 34 to be displaced while the forward movement of the first member 32 is restricted. The same applies to the shock absorber 10A according to Embodiment 2.

[0071] Thirdly, assuming the second buffer 10, the regulating portion 33 is a rod-shaped member that protrudes from the first member 32 and penetrates the second member 34. Because the regulating portion 33 penetrates the second member 34, the regulating portion 33 acts as a guide for the second member 34. The same applies to the buffer 10A according to Embodiment 2.

[0072] Fourthly, assuming the third buffer 10, the case portion 40 has a contact portion 41c that the tip of the restricting portion 33 can contact, and which restricts the forward movement of the first member 32 and the restricting portion 33 when the restricting portion 33 contacts it. This simple configuration allows for a reliable definition of the forward movement limit of the first member 32. The same applies to the buffer 10A according to Embodiment 2.

[0073] Refer to Figure 2. Fifth, assuming a third or fourth buffer 10, when the first member 32 is at its retracted limit and the second member 34 is at its forward limit, at least a part of the regulating portion 33 reaches the second member 34. When the first fluid flows into the free piston portion 30 when the second member 34 is at its forward limit, the second member 34 can be reliably guided. The same applies to the buffer 10A according to Embodiment 2.

[0074] Refer to Figure 1. Sixth, assuming any of the first to fifth shock absorbers 10, the outer diameter of the first member 32 is smaller than the outer diameter of the second member 34, and the rear first fluid-filled section R6, which is the space formed by the second member 34, the case section 40, and the first member 32, is filled with the first fluid. The oil seal forms a thin oil film between the seal itself and the part to be sealed, and this oil film provides the sealing performance. In each oil chamber separated by the oil seal, a very small amount of oil moves through the oil film when the seal slides. For this reason, in hydraulic equipment involving sliding, the amount of oil in each oil chamber is often not strictly controllable. Since the spaces in front of and behind the second member 34 are filled with the first fluid, oil movement occurs, and it is more likely that the oil will not be sufficiently filled. The same applies to the shock absorber 10A according to Embodiment 2.

[0075] Seventh, assuming the sixth shock absorber 10, the rear first fluid filling section R6 is connected to the shock absorber body 20. Since the first fluid inside the rear first fluid filling section R6 is used, there is no need to use a separate case or the like for filling the first fluid, and the number of parts can be reduced. Also, the oil seal forms a slight oil film between the seal itself and the part to be sealed, and the sealing performance is achieved by this oil film. In each oil chamber separated by the oil seal, a very slight movement of oil occurs through the oil film when the seal slides. For this reason, in hydraulic equipment that involves sliding, the amount of oil in each oil chamber is often not strictly controllable. Since the spaces in front of and behind the second member 34 are filled with the first fluid, oil movement occurs, and it is more likely that the oil will not be sufficiently filled. The same applies to the shock absorber 10A according to Embodiment 2.

[0076] Refer to Figure 2. Eighth, assuming any of the first to seventh buffers 10, the case portion 40 has a communication portion 41d into which the first fluid from the cylinder 23 flows, and the second member 34 has a large diameter portion 34a that abuts the inner circumferential surface of the case portion 40, and a small diameter portion 34b which faces the communication portion 41d when the second member 34 is at its forward limit, and has a smaller outer diameter than the large diameter portion 34a, when the displacement in the direction away from the pressing means housing portion R4 is forward and the displacement in the direction toward the pressing means housing portion R4 is backward. When the second member 34 is at its forward limit, the small diameter portion 34b is located in the part that faces the communication portion 41d. When the first fluid flows into the free piston portion 30, the first fluid can be easily guided into the space between the small diameter portion 34b and the large diameter portion 34a. This ensures that the second member 34 at its forward limit is reliably displaced. The same applies to the buffer 10A according to Embodiment 2.

[0077] Ninthly, assuming the eighth buffer 10, the communication portion 41d is opened radially in the case portion 40. The communication portion 41d can be shortened.

[0078] Refer to Figure 1. Tenth, assuming any of the first to ninth buffers 10, a control unit 15 for controlling the flow rate of the first fluid is provided between the buffer body 20 and the free piston 30. The flow rate of the first fluid flowing into the free piston 30 can be controlled. The same applies to the buffer 10A according to Embodiment 2.

[0079] Refer to Figure 4. Eleventh, assuming one of the first to tenth shock absorbers 10A, a free piston portion 30A is provided facing the cylinder 23A. The radial dimension of the shock absorber 10A can be reduced.

[0080] Although the shock absorbers 10 and 10A according to the present invention have been described using an inverted front fork as an example, the present invention is also applicable to upright front forks and rear cushions. Furthermore, the present invention is also applicable to vehicles other than motorcycles, such as saddle-type vehicles and passenger cars. Insofar as the functions and effects of the present invention are achieved, the present invention is not limited to the embodiments described.

[0081] The shock absorber of the present invention is suitable for the front fork of a saddle-type vehicle.

[0082] 10, 10A... Shock absorber 15... Control unit 20, 20A... Shock absorber body 23, 23A... Cylinder 25... Piston 30, 30A... Free piston section 32, 32A... First member 33... Regulating section 34, 34A... Second member, 34a... Large diameter section, 34b... Small diameter section 40, 40A... Free piston case section 41c... Contact section, 41d... Communication section R4... Pressing means housing section R6... Rear first fluid filling section CL1... Axis (of the cylinder) CL2... Axis (of the free piston case section) CL3... Axis (of the cylinder and free piston case section)

Claims

1. A shock absorber comprising: a shock absorber body portion filled with a first fluid as a working fluid and capable of generating a damping force; a free piston portion into which the first fluid can flow from the shock absorber body portion and which can return the first fluid to the shock absorber body portion, wherein the shock absorber body portion comprises a cylindrical cylinder and a piston provided inside the cylinder that generates a damping force when displaced along the axis of the cylinder, wherein the free piston portion comprises a free piston case portion which is a substantially cylindrical case, a pressing means housing portion which is a part of the free piston case portion and houses a pressing means, a first member provided so as to be displaceable along the axis of the free piston case portion and located at a position where the pressure of the first fluid and the pressing force of the pressing means are balanced, and a second member which is displaceable together with the first member along the axis of the free piston case portion and is displaceable independently of the first member.

2. The shock absorber according to claim 1, wherein the free piston portion further has a restricting portion that restricts the forward movement of the first member while allowing the displacement of the second member, when displacement in the direction away from the pressing means housing portion is considered forward movement and displacement in the direction toward the pressing means housing portion is considered backward movement.

3. The buffer according to claim 2, wherein the restricting portion is a rod-shaped member that protrudes from the first member and penetrates the second member.

4. The shock absorber according to claim 3, wherein the free piston case portion has a contact portion to which the tip of the restricting portion can abut, and which restricts the forward movement of the first member and the restricting portion when the restricting portion abuts.

5. The shock absorber according to claim 3, wherein at least a portion of the restricting portion reaches the second member when the first member is at its retracted limit and the second member is at its forward limit.

6. The shock absorber according to claim 1, wherein the outer diameter of the first member is smaller than the outer diameter of the second member, and the rear first fluid-filled portion, which is a space formed by the second member, the free piston case portion, and the first member, is filled with the first fluid.

7. The shock absorber according to claim 6, wherein the rear first fluid filling section is connected to the shock absorber body.

8. The shock absorber according to claim 1, wherein the free piston case portion has a communication portion into which the first fluid from the cylinder flows, and the second member has a large diameter portion that abuts the inner circumferential surface of the free piston case portion, and a small diameter portion that faces the communication portion when the second member is at its forward limit, when the displacement in the direction away from the pressing means housing portion is forward and the displacement in the direction toward the pressing means housing portion is backward, and has a smaller outer diameter than the large diameter portion.

9. The buffer according to claim 8, wherein the communication portion is opened radially in the free piston case portion.

10. The buffer according to claim 1, further comprising a control unit for controlling the flow rate of the first fluid between the buffer body and the free piston portion.

11. The shock absorber according to claim 1, wherein the free piston portion is provided so as to face the cylinder.

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