Compression-side front fork and suspension device

Abstract

A compression-side front fork (FC) comprises a fork body (F) and a compression-side damper (DC) accommodated in the fork body (F). The compression-side damper (DC) comprises a cylinder (10), a piston rod (11), a piston (12) that partitions the inside of the cylinder (10) into an extension-side chamber (R1) and a compression-side chamber (R2), a compression-side damping valve (22) that applies resistance to the flow of liquid from the compression-side chamber (R2) toward the extension-side chamber (R1), a suction check valve (26) that allows only the flow of the liquid from a liquid storage chamber (R) toward the compression-side chamber (R2), and a passage (10b) that communicates the extension-side chamber (R1) and the liquid storage chamber (R). The entire amount of the liquid moving from the inside of the compression-side chamber (R2) during a contraction operation moves to the extension-side chamber (R1) by passing through the compression-side damping valve (22).

Description

Compression-side front fork and suspension device

[0001] The present invention relates to a compression-side front fork and a suspension device.

[0002] Conventionally, a suspension device interposed between the vehicle body of a saddle-riding vehicle and the front wheel is configured to include a pair of left and right front forks, and a damper is built into each front fork.

[0003] More specifically, each front fork includes, for example, a vehicle body side tube, an axle side tube that is axially movable relative to the vehicle body side tube, a cap that closes the upper end of the vehicle body side tube, and an axle bracket that closes the lower end of the axle side tube and holds the axle of the front wheel. It also includes a fork body and a damper housed in the fork body.

[0004] Further, as disclosed in, for example, JPH11-201214A, the damper includes a cylinder whose lower end is fixed to the axle bracket, a piston rod whose upper end is connected to the cap and is inserted into the cylinder, and a piston that is attached to the tip of the piston rod and is slidably inserted into the cylinder to partition the inside of the cylinder into an extension chamber and a compression chamber. It also includes a valve disk that partitions between a chamber inserted into the lower side of the cylinder and communicating with a liquid reservoir chamber outside the cylinder through a hole provided in the cylinder and the compression chamber, an extension port and a compression port provided in the piston, an extension damping valve that opens and closes the extension port and provides resistance to the flow of liquid from the extension chamber to the compression chamber, a compression check valve that opens and closes the compression port and allows only the flow of liquid from the compression chamber to the extension chamber, a compression damping port and a suction port provided in the valve disk, a compression damping valve that opens and closes the compression damping port and provides resistance to the flow of liquid from the compression chamber to the reservoir, and an extension check valve that opens and closes the suction port and allows only the flow of liquid from the reservoir to the compression chamber (see, for example, Patent Document 1).

[0005] JPH11-201214A

[0006] In conventional suspension systems, each damper in each front fork can generate both rebound and compression damping forces. However, adjusting these forces must be done individually for each damper, making the adjustment process cumbersome.

[0007] Therefore, by making the damper housed in one front fork a rebound damper that generates damping force only during extension, and the damper housed in the other front fork a compression damper that generates damping force only during compression, the rebound damping force can be adjusted using the rebound damper, and the compression damping force can be adjusted using the compression damper, making the adjustment process easier.

[0008] In a compression damper, the generation of extension damping force is unnecessary, so a structure is adopted that eliminates the extension damping valve that opens and closes the extension port. In a compression damper employing such a structure, when extension operation occurs, hydraulic fluid moves from the extension chamber to the compression chamber via the extension port, and the extension check valve opens, supplying hydraulic fluid from the reservoir to the compression chamber equivalent to the volume of hydraulic fluid released by the piston rod out of the cylinder. However, at high extension speeds, the amount of hydraulic fluid in the compression chamber tends to become insufficient.

[0009] Thus, even with a compression damper that eliminates the extension damping valve, if it extends at high speed, the pressure inside the compression chamber tends to drop excessively and fall below atmospheric pressure. Therefore, when the direction of expansion and contraction of the compression damper changes and it switches from extension to contraction, it takes time for the pressure inside the cylinder to rise.

[0010] Therefore, simply eliminating the extension damping valve in a suspension system to make the damper a one-sided compression damper that generates only compression damping force will cause problems with the responsiveness of the compression damping force generation when the direction of expansion and contraction of the compression damper changes and it switches from contraction to extension.

[0011] Therefore, the present invention aims to provide a compression-side front fork and a suspension system that primarily generate compression-side damping force, which can improve the responsiveness of damping force generation.

[0012] To solve the aforementioned problems, the compression front fork of the present invention comprises a fork body having a vehicle body side tube and an axle side tube, which expands and contracts as the vehicle body side tube and the axle side tube move relative to each other in the axial direction, and a compression damper housed within the fork body and generating damping force during contraction. The compression damper comprises a cylinder connected to either the vehicle body side tube or the wheel side tube, a piston rod connected to the other of the vehicle body side tube or the wheel side tube and inserted into the cylinder so as to be movable in the axial direction, a piston connected to the piston rod and inserted into the cylinder so as to be movable in the axial direction, which divides the inside of the cylinder into an extension chamber and a compression chamber, a compression damping valve that provides resistance to the flow of liquid from the compression chamber to the extension chamber, a suction check valve that allows only the flow of liquid from the liquid reservoir chamber to the compression chamber, and a passage connecting the extension chamber and the liquid reservoir chamber, wherein the entire amount of liquid moving from the compression chamber during contraction passes through the compression damping valve and moves to the extension chamber.

[0013] With this compression-side front fork configuration, when the compression damper contracts, the entire volume of liquid equal to the reduced volume of the compression chamber passes through the compression damping valve and moves to the extension chamber. At the same time, the extension chamber is connected to the liquid reservoir chamber via a passage, and the pressure in the extension chamber is kept low. Furthermore, with this compression-side front fork configuration, when the compression damper contracts, only the compression chamber is efficiently pressurized, allowing the entire surface of the piston facing the compression chamber to receive the pressure of the compression chamber.

[0014] Furthermore, the suspension system may also include an extension front fork having a body-side tube and an axle-side tube, which generates damping force when the body-side tube and the axle-side tube move relative to each other in the axial direction and contract, and a compression front fork. With a suspension system configured in this way, it is possible to improve the responsiveness of the compression damping force generation while enjoying the advantage of being able to easily adjust the extension damping force and compression damping force generated as a whole.

[0015] Figure 1 is a front view of a saddle-type vehicle to which a suspension device according to one embodiment of the present invention is applied. Figure 2 is a cross-sectional view of the extension-side front fork of the suspension device according to one embodiment of the present invention. Figure 3 is a cross-sectional view of the compression-side front fork of the suspension device according to one embodiment of the present invention. Figure 4 is a diagram showing the pressure fluctuation in the extension chamber when the extension damper is extended and retracted.

[0016] The present invention will be described below based on the embodiments shown in the figures. As shown in Figure 1, in one embodiment, the suspension device S comprises an extension front fork FE and a compression front fork FC, and is interposed between the body B and the front wheel W of a saddle-type vehicle V such as a motorcycle or trike to suspend the front wheel W.

[0017] The following describes in detail each part of the suspension system S. Note that the extension front fork FE and the compression front fork FC share several common components. When describing the components of the extension front fork FE and the compression front fork FC, unless otherwise specified in this document, the parts common to both the extension front fork FE and the compression front fork FC will be referred to as parts of both.

[0018] As shown in Figure 1, the suspension system S comprises an extension front fork FE, a compression front fork FC, and a pair of upper and lower brackets 1 and 2 that grip the upper ends of the extension front fork FE and the compression front fork FC. The brackets 1 and 2 are attached to a steering shaft that is rotatably inserted into a head pipe P located at the front of the body B of the saddle-type vehicle V, and are rotatably connected to the body B in the circumferential direction of the head pipe P. The upper ends of the extension front fork FE and the compression front fork FC are gripped by the brackets 1 and 2 that are rotatably connected to the body B in the circumferential direction of the head pipe P, and the axle Ws of the front wheel W is connected to the lower ends. In this way, the suspension system S suspends the front wheel W from the body B of the saddle-type vehicle V by a pair of left and right extension front forks FE and compression front forks FC.

[0019] As shown in Figures 2 and 3, the extension front fork FE and compression front fork FC each have a fork body F that can extend and retract due to the relative axial movement of the vehicle body tube 3 and the axle tube 4, a vehicle body tube 3, a vehicle axle tube 4 that is movable axially relative to the vehicle body tube 3, a cap 5 that closes the upper end of the vehicle body tube 3, and an axle bracket 6 that closes the lower end of the vehicle axle tube 4 and holds the axle Ws of the front wheel W, and a fork body F that can extend and retract due to the relative axial movement of the vehicle body tube 3 and the vehicle axle tube 4, and an extension damper DE or a compression damper DC housed within the fork body F. The extension damper DE is a one-sided damper that mainly exerts damping force during extension operation, and the compression damper DC is a one-sided damper that mainly generates damping force during contraction operation.

[0020] As shown in Figures 2 and 3, a cap 5 is attached to the open end of the upper end of the vehicle body side tube 3, and the cap 5 closes the upper end of the vehicle body side tube 3. The axle side tube 4 is inserted into the vehicle body side tube 3 from below and can move relative to the vehicle body side tube 3 in the axial direction. An annular bush 7 and an annular sealing member 8 are provided on the inner circumference of the lower end of the vehicle body side tube 3, which slide against the outer circumference of the axle side tube 4, and an annular bush 9 is attached to the outer circumference of the upper end of the axle side tube 4, which slides against the inner circumference of the vehicle body side tube 3. Therefore, the vehicle body side tube 3 and the axle side tube 4 can move axially without axial wobble from each other due to the bushes 7 and 9.

[0021] The lower end of the axle-side tube 4 is closed by an axle bracket 6 that grips the axle Ws of the front wheel W, and the fork body F is connected to the front wheel W by the axle bracket 6. The inside of the fork body F configured in this way is a space that is sealed from the outside by a sealing member 8. The axle bracket 6 is a bottomed cylindrical shape and is fixed to the outer circumference of the lower end of the axle-side tube 4 by screw fastening, and has a gripping portion 6a at its lower end for gripping the axle Ws. Although not shown in the figures, the axle bracket 6 is provided with mounting portions that allow for the attachment of brake calipers, fenders, etc.

[0022] The extension damper DE and compression damper DC housed within the fork body F each have a cylinder 10 connected to the axle-side tube 4 via an axle bracket 6, a piston rod 11 inserted into the cylinder 10 so as to be axially movable and whose upper end is connected to the vehicle-side tube 3 via a cap 5, and a piston 12 connected to the piston rod 11 and inserted into the cylinder 10, dividing the inside of the cylinder 10 into an extension chamber R1 and a compression chamber R2, which are filled with liquid. The extension and compression occur as the piston rod 11 moves in and out of the cylinder 10 in conjunction with the extension and compression of the fork body F. As mentioned above, the extension damper DE and compression damper DC are arranged upright within the fork body F with the cylinder 10 connected to the axle-side tube 4 and the piston rod 11 connected to the vehicle body-side tube 3, so that the cylinder 10 is at the bottom and the piston rod 11 is at the top. However, the cylinder 10 may be connected to the vehicle body-side tube 3 and the piston rod 11 may be connected to the axle-side tube 4, so that the cylinder 10 is at the top and the piston rod 11 is at the bottom within the fork body F, so that it is at the top.

[0023] When the extension damper DE and the compression damper DC are housed within the fork body F in this manner, a liquid reservoir R is formed outside the extension damper DE and outside the compression damper DC, respectively, within the fork body F, where liquid is stored.

[0024] Furthermore, a suspension spring 19 is housed within the fork body F, interposed between the cap 5 and the cylinder 10, and constantly biasing the fork body F in an extension direction. Therefore, when the suspension device S is interposed between the vehicle body B and the front wheel W of a saddle-type vehicle V, the extension-side front fork FE and the compression-side front fork FC elastically support the vehicle body B through the resilient force exerted by the suspension spring 19.

[0025] The components constituting the extension damper DE and the compression damper DC will be described below. The cylinder 10 is screw-connected to an adapter 13 housed on the inner circumference of the axle bracket 6 in the fork body F, and is connected to the axle bracket 6 via the adapter 13. The adapter 13 is a bottomed cylindrical shape with a flange 13a on the outer circumference of its bottom. The flange 13a is sandwiched between the bottom of the axle bracket 6 and the axle-side tube 4 which is screw-fastened to the axle bracket 6, and is fixed in a state where it is housed within the axle bracket 6. The cylinder 10 has a threaded portion (not shown) on the outer circumference of its lower end, which is screw-connected to the threaded portion provided on the inner circumference of the adapter 13 and connected to the axle bracket 6 via the adapter 13.

[0026] Furthermore, the cylinder 10 in the extension damper DE and the compression damper DC is provided with a through hole 10a that opens from the side of the lower end and connects the inside of the cylinder 10 with the liquid reservoir R outside the cylinder 10. In addition, the cylinder 10 in the compression damper DC is provided with a through hole 10b that opens from the side near the upper end and serves as a passage connecting the inside of the cylinder 10 with the liquid reservoir R outside the cylinder 10.

[0027] An annular rod guide 14 is attached to the upper open end of the cylinder 10 in the extension damper DE and the compression damper DC. The rod guide 14 is annular and slides against the outer circumference of the piston rod 11, which is screwed into the inner circumference of the upper end of the cylinder 10 and inserted through the inner circumference. The rod guide 14 closes the upper end of the cylinder 10 and guides the movement of the piston rod 11 in the vertical direction shown in Figures 2 and 3, which is the axial direction of the cylinder 10.

[0028] As shown in Figures 2 and 3, the piston rod 11 includes a small-diameter portion 11a provided at the lower end of the figure, which is the tip, and whose outer diameter is smaller than that of the upper side; a threaded portion 11b provided on the outer circumference of the tip of the small-diameter portion 11a; and a stepped portion 11c formed at the boundary between the small-diameter portion 11a and the upper side.

[0029] An annular piston 12 is connected to the outer circumference of the small-diameter portion 11a at the tip of the piston rod 11, and the piston rod 11 can move vertically within the cylinder 10 together with the piston 12 in the axial direction as shown in Figures 2 and 3. As described above, the piston 12 is annular and is inserted into the cylinder 10 so as to be movable in the axial direction, dividing the inside of the cylinder 10 into an extension chamber R1 and a compression chamber R2, both of which are filled with liquid. In the compression damper DC, the cylinder 10 is provided with a through hole 10b, so in the compression damper DC, the extension chamber R1, which is partitioned by the piston 12, is connected to a liquid reservoir chamber R outside the compression damper DC. In this case, the extension chamber R1 and the liquid reservoir chamber R are connected by a through hole 10b which is a passage provided in the cylinder 10, but the passage connecting the extension chamber R1 and the liquid reservoir chamber R may also be provided in the rod guide 14 in addition to the cylinder 10.

[0030] Furthermore, the piston 12 is equipped with a first piston port 12a and a second piston port 12b that connect the extension chamber R1 and the compression chamber R2. The cylinder 10 is filled with liquid, and the liquid reservoir chamber R is filled with gas in addition to the liquid that fills the cylinder 10. The liquid that fills the cylinder 10 and the liquid reservoir chamber R is generally hydraulic oil, but it may also be water, an aqueous solution, or the like.

[0031] In the extension damper DE, a first check valve 20 is stacked above the piston 12 in Figure 2, which allows only the flow of liquid from the compression chamber R2 to the extension chamber R1. In the extension damper DE, an extension damping valve 21 is stacked below the piston 12 in Figure 2, which provides resistance to the flow of liquid from the extension chamber R1 to the compression chamber R2.

[0032] In the extension front fork FE of this embodiment, the first check valve 20 consists of an annular valve body stacked above the piston 12 in Figure 2 and mounted axially movable on the small diameter portion 11a of the piston rod 11, a spring retainer fixed to the piston rod 11, and a spring interposed between the valve body and the spring retainer to bias the valve body toward the piston 12. The first check valve 20 opens with the entire valve body separated from the piston 12 in response to the flow of liquid passing through the second piston port 12b of the piston 12 from the compression chamber R2 to the extension chamber R1, thereby allowing the liquid flow with almost no resistance. On the other hand, the first check valve 20 also blocks the flow of liquid attempting to pass through the second piston port 12b of the piston 12 from the extension chamber R1 to the compression chamber R2 by closing the second piston port 12b. In this embodiment, the first check valve 20 is composed of a valve body, a spring, and a spring seat, and is a check valve that opens when the entire valve body separates from the piston 12. However, any valve that opens only when the liquid passes from the compression chamber R2 to the extension chamber R1 through the second piston port 12b and allows the liquid to flow with almost no resistance is acceptable.

[0033] In the extension front fork FE of this embodiment, the extension damping valve 21 is a laminated leaf valve constructed by stacking multiple annular plates and is stacked below the piston 12. Its inner circumference is fitted to the outer circumference of the small diameter portion 11a of the piston rod 11 and fixed by a piston nut 17 that is screw-connected to the threaded portion 11b, allowing for deflection of the outer circumference. The extension damping valve 21 opens by deflecting its outer circumference to allow the flow of liquid passing through the first piston port 12a of the piston 12 from the extension chamber R1 to the compression chamber R2, while simultaneously providing resistance to the liquid flow. On the other hand, the extension damping valve 21 also closes the first piston port 12a of the piston 12 to block the flow of liquid attempting to pass through the first piston port 12a of the piston 12 from the compression chamber R2 to the extension chamber R1. In this embodiment, the extension damping valve 21 is a laminated leaf valve in the extension front fork FE, but it may be a valve other than a laminated leaf valve, as long as it provides resistance while remaining open to the flow of liquid passing from the extension chamber R1 to the compression chamber R2.

[0034] In the compression damper DC, a compression damping valve 22 is stacked above the piston 12 in Figure 3, which allows only the flow of liquid from the compression chamber R2 to the extension chamber R1. In the compression damper DC, a sub-check valve 23 is stacked below the piston 12 in Figure 3, which provides resistance to the flow of liquid from the extension chamber R1 to the compression chamber R2.

[0035] In this embodiment of the compression-side front fork FC, the compression-side damping valve 22 is a laminated leaf valve constructed by stacking multiple annular plates and is stacked above the piston 12. Its inner circumference is fitted to the outer circumference of the small-diameter portion 11a of the piston rod 11 and fixed by a piston nut 17 that is screw-connected to the threaded portion 11b, allowing for deflection of the outer circumference. The compression-side damping valve 22 opens by deflecting its outer circumference to allow the flow of liquid passing through the second piston port 12b of the piston 12 from the compression chamber R2 to the extension chamber R1, while simultaneously providing resistance to the liquid flow. On the other hand, the compression-side damping valve 22 closes the second piston port 12b of the piston 12 to block the flow of liquid attempting to pass through the second piston port 12b of the piston 12 from the extension chamber R1 to the compression chamber R2. In this embodiment, the compression damping valve 22 is a laminated leaf valve in the compression front fork FC. However, other types of valves may be used as long as they provide resistance to the flow of liquid passing from the extension chamber R1 to the compression chamber R2 while remaining open.

[0036] In the compression-side front fork FC of this embodiment, the sub-check valve 23 consists of an annular valve body stacked below the piston 12 in Figure 3 and mounted so as to be axially movable on the small-diameter portion 11a of the piston rod 11, a spring retainer fixed to the piston rod 11, and a spring interposed between the valve body and the spring retainer to bias the valve body toward the piston 12. The sub-check valve 23 opens with the entire valve body separated from the piston 12 to allow the flow of liquid passing through the first piston port 12a of the piston 12 from the extension-side chamber R1 to the compression-side chamber R2, thereby allowing the liquid flow with almost no resistance. On the other hand, the sub-check valve 23 closes the first piston port 12a of the piston 12 to block the flow of liquid attempting to pass through the first piston port 12a of the piston 12 from the compression-side chamber R2 to the extension-side chamber R1. In this embodiment, the sub-check valve 23 is a check valve composed of a valve body, a spring retainer, and a spring, which opens when the entire valve body separates from the piston 12. However, any valve that opens only when the liquid passes through the first piston port 12a from the extension chamber R1 to the compression chamber R2, allowing the liquid to flow with almost no resistance, is acceptable.

[0037] Furthermore, in the extension damper DE and the compression damper DC, a disc 15 is fitted below the cylinder 10 in Figures 2 and 3, which defines the lower cylinder chamber R3 located within the cylinder 10 and below the compression chamber R2, communicating with the liquid reservoir chamber R via a through hole 10a.

[0038] The disc 15 is annular in shape and is held by a center rod 16 fixed to the adapter 13, and is fitted onto the inner circumference of the lower end of the cylinder 10. The disc 15 is equipped with a discharge port 15a and a suction port 15b that connect the pressure chamber R2 and the lower cylinder chamber R3.

[0039] The center rod 16 comprises a disc-shaped base portion 16a that is fixed to the adapter 13 by being sandwiched between the cylinder 10, which is placed on the bottom of the adapter 13 and screw-connected to the adapter 13, and the bottom of the adapter 13, and a shaft portion 16b that rises from the center of the base portion 16a and is inserted into the cylinder 10. In addition, the center rod 16 has a small-diameter portion 16c on the upper side of the shaft portion 16b in Figures 2 and 3, which has a smaller outer diameter than the lower side, as well as a threaded portion 16d provided on the outer circumference of the tip of the small-diameter portion 16c, and a stepped portion 16e formed in the middle of the shaft portion 16b at the boundary between the small-diameter portion 16c and the lower side.

[0040] The center rod 16 is connected to the vehicle body tube 3 via the adapter 13 and the axle bracket 6 to which the adapter 13 is fixed, and positions the fixed and held disc 15 within the cylinder 10, above the through hole 10a in Figures 2 and 3. Thus, the lower cylinder chamber R3 is always in communication with the liquid reservoir chamber R via the through hole 10a.

[0041] Furthermore, on the outer circumference of the shaft portion 16b of the center rod 16 in the extension damper DE, a suction check valve 24 is mounted on the upper part of the disc 15 in Figure 2, and a second check valve 25 is mounted on the lower part of the disc 15 in Figure 2.

[0042] In the extension front fork FE of this embodiment, the suction check valve 24 consists of an annular valve body stacked on the upper part of the disc 15 in Figure 2 and mounted so as to be axially movable on the small diameter portion 16c of the center rod 16, a spring retainer fixed to the center rod 16, and a spring interposed between the valve body and the spring retainer to bias the valve body toward the disc 15. The suction check valve 24 opens with the entire valve body separated from the disc 15 in response to the flow of liquid passing through the suction port 15b of the disc 15 from the lower cylinder chamber R3, which is connected to the liquid reservoir chamber R, toward the pressure side chamber R2, thereby allowing the liquid flow with almost no resistance. On the other hand, the suction check valve 24 also blocks the flow of liquid attempting to pass through the suction port 15b of the disc 15 from the pressure side chamber R2 toward the lower cylinder chamber R3 by closing the suction port 15b. In this embodiment, the suction check valve 24 in the extension front fork FE is composed of a valve body, a spring retainer, and a spring, and is a check valve that opens when the entire valve body separates from the disc 15. However, any valve that opens only when the liquid passes through the suction port 15b from the lower cylinder chamber R3 to the pressure chamber R2 and allows the liquid to flow with almost no resistance is acceptable.

[0043] The second check valve 25 is a check valve formed by laminating a plurality of annular plates in the extension-side front fork FE of the present embodiment, and is laminated below the disk 15. The inner peripheral side is fitted to the outer periphery of the small-diameter portion 16c of the center rod 16 and is fixed by a nut 18 screwed to the screw portion 16d, and the outer peripheral side is allowed to deflect. The second check valve 25 deflects the outer peripheral side to open the valve with respect to the flow of the liquid passing from the discharge port 15a in the disk 15 toward the lower cylinder chamber R3 communicating with the liquid reservoir chamber R from the pressure-side chamber R2, allows the flow of the liquid, and gives a little resistance to the flow of the liquid. The opening pressure of the second check valve 25 is higher than the opening pressure of the first check valve 20. When the extension-side damper DE contracts, the first check valve 20 opens earlier than the second check valve 25, and the liquid can smoothly move from the pressure-side chamber R2 to the extension-side chamber R1. On the other hand, the second check valve 25 closes the discharge port 15a to block the flow of the liquid with respect to the flow of the liquid passing from the lower cylinder chamber R3 toward the pressure-side chamber R2 in the disk 15. Although the second check valve 25 is formed by laminating a plurality of annular plates in the extension-side front fork FE of the present embodiment, as long as it gives a little more resistance than the first check valve 20 while opening the valve with respect to the flow of the liquid passing from the pressure-side chamber R2 to the lower cylinder chamber R3, it may be a valve other than the check valve having the above-described structure. Therefore, the second check valve 25 may be composed of a valve body, a spring receiver, and a spring, like the first check valve 20.

[0044] On the outer periphery of the shaft portion 16b of the center rod 16 in the pressure-side damper DC, a suction check valve 26 laminated above the disk 15 in FIG. 3 is mounted, and a plurality of washers 27 laminated below the disk 15 in FIG. 3 are mounted.

[0045] In the compression-side front fork FC of this embodiment, the suction check valve 26 consists of an annular valve body stacked on the upper part of the disc 15 in Figure 3 and mounted so as to be axially movable on the small-diameter portion 16c of the center rod 16, a spring receiver fixed to the center rod 16, and a spring interposed between the valve body and the spring receiver to bias the valve body toward the disc 15. The suction check valve 26 opens with the entire valve body separated from the disc 15 in response to the flow of liquid passing through the suction port 15b of the disc 15 from the cylinder lower chamber R3, which is connected to the liquid reservoir chamber R, toward the pressure-side chamber R2, thereby allowing the liquid flow with almost no resistance. On the other hand, the suction check valve 26 also blocks the flow of liquid attempting to pass through the suction port 15b of the disc 15 from the pressure-side chamber R2 toward the cylinder lower chamber R3 by closing the suction port 15b. In this embodiment, the suction check valve 26 in the compression-side front fork FC is composed of a valve body, a spring retainer, and a spring, and is a check valve that opens when the entire valve body separates from the disc 15. However, any valve that opens only when the liquid passes through the suction port 15b from the lower cylinder chamber R3 to the compression-side chamber R2 and allows the liquid to flow with almost no resistance is acceptable.

[0046] The washer 27 is a thick, annular shape, and multiple washers are stacked on the disc 15. It is fixed to the outer circumference of the small-diameter portion 16c of the center rod 16 by a nut 18, blocking the lower end of the discharge port 15a in Figure 3. The washer 27 does not bend and blocks the discharge port 15a even when subjected to the flow of liquid attempting to pass through the discharge port 15a from the pressure chamber R2 to the cylinder lower chamber R3 which communicates with the liquid reservoir chamber R. Similarly, the washer 27 continues to block the discharge port 15a even when subjected to the flow of liquid attempting to pass through the discharge port 15a from the cylinder lower chamber R3 to the pressure chamber R2. Therefore, the washer 27 blocks the discharge port 15a and does not allow any liquid flow. Thus, in the compression damper DC of the compression front fork FC, the discharge port 15a on the disc 15 is constantly blocked, and liquid cannot move from the pressure chamber R2 to the cylinder lower chamber R3. Thus, in the compression damper DC, there is no need to provide a discharge port 15a, so the disk 15 may have a structure that does not have a discharge port 15a and only has a suction port 15b. However, by adopting a structure that uses a washer 27 to block the discharge port 15a, it is possible to use a general disk used in dampers, which is advantageous because it eliminates the need to newly design and manufacture a disk that does not have a discharge port 15a. The number of stacked washers 27 can be arbitrarily changed in the design as long as the discharge port 15a is always blocked.

[0047] Although not shown in the diagram, both the extension damper DE and the compression damper DC are equipped with damping force adjustment valves. The damping force adjustment valve includes, for example, a bypass passage that opens from the lower end in Figure 2, which is the tip of the piston rod 11 facing the compression chamber R2, and leads to the side facing the extension chamber R1; a needle valve that can move within the bypass passage and adjust the flow area in the bypass passage; and an adjuster provided on the cap 5 that allows adjustment of the position of the needle valve within the bypass passage. The opening degree of the needle valve can be adjusted by operating the adjuster from the outside.

[0048] The extension front fork FE, the compression front fork FC, and the suspension device S are configured as described above, and their operations will be described below. First, when the extension front fork FE and the compression front fork FC in the suspension device S extend, both the extension damper DE and the compression damper DC extend.

[0049] When the extension damper DE and the compression damper DC extend, the piston 12 moves upward in FIGS. 2 and 3 within the cylinder 10, reducing the extension chamber R1 and expanding the compression chamber R2. In the extension front fork FE, as the extension damper DE extends, the liquid moves from the reducing extension chamber R1, which passes through the extension damping valve 21, to the expanding compression chamber R2. Since the extension damping valve 21 provides resistance to the flow of this liquid, the pressure within the extension chamber R1 increases. Further, as the piston rod 11 withdraws from the cylinder 10 with the extension operation of the extension damper DE, the liquid corresponding to the volume by which the piston rod 11 withdraws from the cylinder 10 within the cylinder 10 passes through the through hole 10a and the suction check valve 24 and moves to the compression chamber R2 from the liquid reservoir chamber R almost without resistance. Therefore, when the extension damper DE exhibits an extension operation, it generates an extension damping force that impedes the extension of the extension front fork FE by the extension damping valve 21.

[0050] On the other hand, in the compression-side front fork FC, as the compression-side damper DC extends, the liquid moves from the extension-side chamber R1, which is reduced, through the sub-check valve 23 to the compression-side chamber R2, which is expanded. However, the sub-check valve 23 provides almost no resistance to the flow of the liquid passing through it. Also, as the compression-side damper DC extends, the piston rod 11 retracts from the cylinder 10. As a result, the liquid equivalent to the volume of the piston rod 11 retracting from the cylinder 10 moves almost without resistance from the liquid reservoir chamber R to the compression-side chamber R2 through the through-hole 10a and the suction check valve 26. Therefore, when the compression-side damper DC extends, the pressure in the extension-side chamber R1 and the pressure in the compression-side chamber R2 become approximately equal. Consequently, the compression-side damper DC does not generate a damping force that hinders the extension operation of the compression-side front fork FC during its extension operation. Furthermore, when the compression damper DC extends, liquid equivalent to the volume of the piston rod 11 retracting from the cylinder 10 is supplied from the liquid reservoir chamber R. However, since the suction check valve 26 opens, allowing liquid to be supplied into the compression chamber R2, and the through-hole 10b, which acts as a passage, connects the extension chamber R1 and the liquid reservoir chamber R, allowing liquid to be discharged from the extension chamber R1 to the liquid reservoir chamber R via the through-hole 10b, the first piston port 12a and the sub-check valve 23 can be eliminated. However, by providing the sub-check valve 23, liquid can be moved from the extension chamber R1, which contracts during the extension operation of the compression damper DC, to the expansion of the compression chamber R2, thus preventing a shortage of liquid in the compression chamber R2 even when the compression damper DC contracts at high speed.

[0051] Therefore, when the extension front fork FE and the compression front fork FC are extended, the suspension system S suppresses the extension operation of the extension front fork FE and the compression front fork FC by the extension damping force generated by the extension damper DE in the extension front fork FE.

[0052] Next, when the extension front fork FE and compression front fork FC in the suspension system S contract, the extension damper DE and compression damper DC also contract.

[0053] When the extension damper DE and the compression damper DC contract, the piston 12 moves downward within the cylinder 10 as shown in Figures 2 and 3, reducing the compression chamber R2 and expanding the extension chamber R1.

[0054] In the extension front fork FE, as the extension damper DE contracts, the liquid moves from the compression chamber R2, which is reduced, through the first check valve 20 to the extension chamber R1, which is expanded. When the extension damper DE is contracted, the piston rod 11 enters the cylinder 10, so the volume of liquid that the piston rod 11 enters the cylinder 10 passes through the second check valve 25 and the through hole 10a, moving from the compression chamber R2 to the liquid reservoir chamber R. Although the opening pressure of the second check valve 25 is higher than the opening pressure of the first check valve 20, the first check valve 20 provides almost no resistance to the flow of liquid passing through it, and the resistance that the second check valve 25 provides to the flow of liquid passing through it is sufficiently small compared to the flow of liquid passing through the damping valve. Therefore, the pressure in the extension chamber R1 and the pressure in the compression chamber R2 become approximately equal, and the pressures in both the extension chamber R1 and the compression chamber R2 become slightly higher than those in the liquid reservoir chamber R. Therefore, the extension damper DE generates only a small damping force that hinders the extension front fork FE's extension operation during compression. Also, since the opening pressure of the second check valve 25 is higher than the opening pressure of the first check valve 20, the first check valve 20 opens before the second check valve 25. As a result, the extension damper DE prevents excessive liquid from being discharged from the compression chamber R2 to the liquid reservoir chamber R through the second check valve 25, allowing the liquid to move smoothly from the compression chamber R2 to the extension chamber R1, making it less likely for liquid to become deficient in the extension chamber R1. Therefore, as shown by the solid line in Figure 4, the pressure in the extension chamber R1 of the extension damper DE never falls below atmospheric pressure even during compression, and the situation where the inside of the extension chamber R1 is excessively depressurized and gas dissolved in the liquid appears as bubbles inside the extension chamber R1 does not occur. Figure 4 shows the pressure fluctuation in the extension chamber R1 from the fully extended state of the extension damper DE to its fully contracted state, and then from the fully contracted state to its fully extended state until the piston speed becomes 0. Note that when a structure is adopted in which the compression damping valve and suction check valve are eliminated from the damper in a conventional suspension system, the damper generates damping force only during extension operation. However, during contraction operation, the check valve, which allows the flow of hydraulic fluid from the compression chamber to the extension chamber in the expanding extension chamber, provides some resistance, so the pressure may become lower than atmospheric pressure, as shown by the dashed line in Figure 4.Therefore, when adopting a structure that eliminates the compression damping valve and suction check valve from the damper in a conventional suspension system, when the damper transitions from contraction to extension, it takes time for the pressure in the extension chamber, which has been reduced to below atmospheric pressure by the contraction, to rise, resulting in a deterioration of the response of the extension damping force generation.

[0055] In contrast, in the extension damper DE of this embodiment, even when the extension damper DE exhibits contraction operation, the pressure in the extension chamber R1 is maintained at or above atmospheric pressure and does not drop to a pressure lower than atmospheric pressure.

[0056] Therefore, in the extension damper DE of this embodiment, there is no tendency for the liquid in the extension chamber to become insufficient during contraction, and it is possible to suppress a situation in which the pressure in the extension chamber R1 drops excessively. As a result, even if the direction of expansion and contraction of the extension damper DE changes and it switches from contraction to extension, the pressure in the extension chamber R1 is quickly increased, and the responsiveness of the extension damping force generation is improved.

[0057] On the other hand, in the compression front fork FC, as the compression damper DC contracts, the liquid moves from the compression chamber R2, which is reduced in size, through the compression damping valve 22 to the extension chamber R1, which is expanded, and the compression damping valve 22 resists this liquid flow. Furthermore, because the discharge port 15a of the reduced compression chamber R2 is blocked by the washer 27, the liquid in the reduced compression chamber R2 moves only through the compression damping valve 22 to the extension chamber R1. Thus, when the compression damper DC contracts, the entire volume of liquid equivalent to the volume reduced in the compression chamber R2 by the piston 12 within the cylinder 10 moves through the compression damping valve 22 to the extension chamber R1.

[0058] Furthermore, when the compression damper DC is contracted, the piston rod 11 enters the cylinder 10, and the volume of liquid equivalent to the volume of the piston rod 11 entering the cylinder 10 moves from the extension chamber R1 to the liquid reservoir chamber R through the through hole 10b.

[0059] Therefore, when the compression damper DC is contracting, the pressure in the compression chamber R2 is increased, while the pressure in the extension chamber R1 becomes approximately equal to the pressure in the liquid reservoir chamber R. The compression damper DC generates a damping force equal to the value obtained by multiplying the cross-sectional area of ​​the piston 12 by the pressure in the compression chamber R2, in a direction that opposes the contraction operation of the compression damper DC. In this way, the compression damper DC increases the pressure only in the compression chamber R2 during contraction, making the pressure in the extension chamber R1 equal to the pressure in the liquid reservoir chamber R. Since the cross-sectional area of ​​the piston 12 can receive the pressure in the compression chamber R2 as the pressure-receiving area, the responsiveness of the generation of compression damping force can be improved.

[0060] Based on the above, the extension damper DE in the extension front fork FE is configured as a one-sided damper that primarily generates an extension damping force that hinders the extension operation during extension, thereby improving the responsiveness of damping force generation during extension operation.

[0061] Furthermore, the compression damper DC in the compression front fork FC is configured as a one-sided damper that primarily generates a compression damping force that hinders the compression operation during compression, thereby improving the responsiveness of damping force generation during compression.

[0062] As mentioned above, both the rebound damper DE and the compression damper DC are equipped with damping force adjustment valves (not shown). Therefore, the rebound damping force of the rebound damper DE can be adjusted by adjusting the opening of the needle valve by operating the adjuster on the rebound damper DE, and the compression damping force of the compression damper DC can be adjusted by adjusting the opening of the needle valve by operating the adjuster on the compression damper DC.

[0063] As described above, the compression front fork FC of this embodiment comprises a fork body F having a vehicle body side tube 3 and an axle side tube 4, which expand and contract as the vehicle body side tube 3 and the axle side tube 4 move relative to each other in the axial direction, and a compression damper DC housed within the fork body F and generating damping force when it contracts, the compression damper DC having a cylinder 10 connected to either the vehicle body side tube 3 or the axle side tube 4, and a component connected to the other of the vehicle body side tube 3 or the axle side tube 4 and inserted into the cylinder 10 so as to be movable in the axial direction The device comprises a piston rod 11, a piston 12 connected to the piston rod 11 and inserted into the cylinder 10 so as to be movable in the axial direction, dividing the inside of the cylinder 10 into an extension chamber R1 and a compression chamber R2, a compression damping valve 22 that provides resistance to the flow of liquid from the compression chamber R2 to the extension chamber R1, a suction check valve 26 that allows only the flow of liquid from the liquid reservoir chamber R to the compression chamber R2, and a through hole (passage) 10b that connects the extension chamber R1 and the liquid reservoir chamber R, so that the entire amount of liquid moving from the compression chamber R2 during contraction operation passes through the compression damping valve 22 and moves to the extension chamber R1.

[0064] With the compression-side front fork FC configured in this way, when the compression damper DC is contracted, the entire volume of liquid equal to the volume of the reduced compression chamber R2 passes through the compression damping valve 22 and moves to the extension chamber R1, and the extension chamber R1 is connected to the liquid reservoir chamber R via the through hole (passage) 10b, so that the pressure in the extension chamber R1 is kept at a low pressure. Therefore, with the compression-side front fork FC, when the compression damper DC is contracted, only the compression chamber R2 is efficiently pressurized, and the entire surface of the piston 12 facing the compression chamber R2 can receive the pressure of the compression chamber R2. With the compression-side front fork FC in this way, when the compression damper DC is contracted, the pressure of the compression chamber R2 is received over a wide pressure-receiving area, improving the responsiveness of the generation of compression damping force, and thus improving the ground contact of the front wheel W when the saddle-type vehicle V is running.

[0065] Furthermore, the compression damper DC in the compression front fork FC of this embodiment is equipped with a sub-check valve 23 that allows only the flow of liquid from the extension chamber R1 to the compression chamber R2. With the compression front fork FC configured in this way, the sub-check valve 23 opens when the compression damper DC extends, connecting the compression chamber R2 and the extension chamber R1, thus preventing a shortage of liquid in the expanding compression chamber R2 when the compression damper DC extends. As a result, the compression front fork FC does not tend to have a shortage of liquid in the compression chamber R2 when the compression damper DC extends, and it is possible to suppress a situation in which the pressure in the compression chamber R2 drops excessively. Therefore, even if the direction of expansion and contraction of the compression damper DC changes and it switches from an expansion operation to a contraction operation, the pressure in the compression chamber R2 is quickly increased, and the response of the compression damping force can be improved.

[0066] Furthermore, the extension front fork FE of this embodiment comprises a fork body F having a vehicle body side tube 3 and an axle side tube 4, which extend and retract as the vehicle body side tube 3 and the axle side tube 4 move relative to each other in the axial direction, and an extension damper DE housed within the fork body F and generating damping force during extension operation. The extension damper DE comprises a cylinder 10 connected to either the vehicle body side tube 3 or the axle side tube 4, a piston rod 11 connected to the other of the vehicle body side tube 3 or the axle side tube 4 and inserted into the cylinder 10 so as to be movable in the axial direction, and a component connected to the piston rod 11 inside the cylinder 10 The system includes a piston 12 that is inserted into the cylinder 10 so as to be movable in the axial direction and divides the inside of the cylinder 10 into an extension chamber R1 and a compression chamber R2, an extension damping valve 21 that provides resistance to the flow of liquid from the extension chamber R1 to the compression chamber R2, a first check valve 20 that allows only the flow of liquid from the compression chamber R2 to the extension chamber R1, a second check valve 25 that allows only the flow of liquid from the compression chamber R2 to a liquid reservoir chamber R located inside the fork body F and outside the extension damper DE, and a suction check valve 24 that allows only the flow of liquid from the liquid reservoir chamber R to the compression chamber R2, wherein the opening pressure of the second check valve 25 is higher than the opening pressure of the first check valve 20.

[0067] In the extension front fork FE configured in this way, both the first check valve 20 and the second check valve 25 are check valves that do not provide much resistance to the flow of liquid through which they pass. Since the opening pressure of the second check valve 25 is higher than the opening pressure of the first check valve 20, the first check valve 20 opens before the second check valve 25. Therefore, in the extension damper DE, when the extension damper DE is contracting, it is prevented that an excessive amount of liquid is discharged from the compression chamber R2 to the liquid reservoir chamber R through the second check valve 25, allowing the liquid to move smoothly from the compression chamber R2 to the extension chamber R1, and making it less likely for a shortage of liquid to occur in the extension chamber R1. Based on the above, the extension front fork FE prevents a tendency for insufficient fluid in the extension chamber during the compression operation of the extension damper DE, and suppresses situations where the pressure in the extension chamber R1 drops excessively. Therefore, even when the direction of extension and compression of the extension damper DE changes and it switches from compression to extension, the extension chamber R1 is quickly pressurized, improving the responsiveness of the extension damping force generation.

[0068] As described above, the extension front fork FE of this embodiment improves the response of extension damping force generation in the extension front fork FE, thereby improving the ground contact feel of the front wheel W when the saddle-type vehicle V is in motion.

[0069] Furthermore, if the opening pressure of the second check valve 25 is increased, the resistance exerted on the liquid flow through the second check valve 25 during the contraction operation of the extension damper DE increases, causing the extension damper DE to exert a damping force that hinders unintended contraction operation. In the suspension system S, if the extension front fork FE generates only an extension damping force that hinders extension operation, and the compression front fork FC generates only a compression damping force that hinders contraction operation, then tuning of the extension damping force can be done using only the extension damper DE, and tuning of the compression damping force can be done using only the compression damper DC, thus providing the advantage of easily adjusting the extension damping force and compression damping force generated by the suspension system S as a whole. On the other hand, if the extension damper DE unintentionally generates a high compression damping force that hinders contraction operation, tuning becomes complicated. Therefore, it is preferable that the opening pressure of the second check valve 25 be set to a value such that the extension chamber R1 does not fall below atmospheric pressure during the extension operation of the extension damper DE. In this way, when the opening pressure of the second check valve 25 is set to a value such that the extension chamber R1 does not fall below atmospheric pressure when the extension damper DE is extended, the damping force generated when the extension damper DE is contracted is reduced, and the response of the extension damping force can be improved without adversely affecting the characteristics of the compression damping force generated by the compression front fork FC in the suspension system S.

[0070] Furthermore, in the suspension system S, the compression damping force generated by the second check valve 25 when the extension damper DE in the extension front fork FE is in the contraction operation is set lower than the compression damping force generated by the compression front fork FC, which generates damping force when it is in the contraction operation. With the suspension system S configured in this way, it is possible to improve the responsiveness of the extension damping force generation while enjoying the advantage of easy adjustment of the extension damping force and compression damping force generated by the suspension system S as a whole. In addition, if the damping force generated by the extension damper DE when it is in the contraction operation is set to be sufficiently smaller than the damping force generated by the compression front fork FC when it is in the contraction operation, the responsiveness of the extension damping force generation can be further improved while enjoying the above advantages.

[0071] 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.

[0072] 3...Body-side tube, 4...Axle-side tube, 10...Cylinder, 10b...Through hole (passage), 11...Piston rod, 12...Piston, 22...Compression damping valve, 23...Sub-check valve, 24...Suction check valve, DC...Compression damper, F...Fork body, FC...Compression front fork, FE...Rebound front fork, S...Suspension system, R...Liquid reservoir chamber, R1...Rebound chamber, R2...Compression chamber

Claims

1. A compression front fork comprising: a fork body having a body-side tube and an axle-side tube, the body-side tube and the axle-side tube extending and retracting as they move relative to each other in the axial direction; a compression damper housed within the fork body and generating damping force during contraction; the compression damper comprising: a cylinder connected to either the body-side tube or the wheel-side tube; a piston rod connected to the other of the body-side tube or the wheel-side tube and inserted into the cylinder so as to be movable in the axial direction; a piston connected to the piston rod and inserted into the cylinder so as to be movable in the axial direction, dividing the cylinder into an extension chamber and a compression chamber; a compression damping valve that provides resistance to the flow of liquid from the compression chamber to the extension chamber; a suction check valve that allows only the flow of liquid from the liquid reservoir chamber to the compression chamber; and a passage connecting the extension chamber and the liquid reservoir chamber. A compression front fork in which, during contraction, the entire amount of liquid moving from the compression chamber passes through the compression damping valve and moves to the extension chamber.

2. A compression front fork according to claim 1, comprising a sub-check valve that allows only the flow of liquid from the extension chamber to the compression chamber.

3. A suspension system comprising: an extension front fork having a body-side tube and an axle-side tube, which generates a damping force when the body-side tube and the axle-side tube move relative to each other in the axial direction and extend; and a compression front fork as described in claim 1 or 2.

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