Front fork

Abstract

The present invention comprises: a cylindrical cap (3) attached to one end-side opening of a vehicle body-side tube (2a) of an extendable fork body (2); a pressing body (4) slidably inserted into the cap (3); a spring bearing (6) that moves in the axial direction together with the pressing body (4) while supporting the upper end of a suspension spring (5) that biases the fork body (2) in an extension direction; a first seal (7) that seals the space between the pressing body (4) and the cap (3); and an actuator unit (8). The actuator unit (8) includes: a housing (9) detachably connected to the cap (3) and having a pressure chamber (P); a partition wall member (10) that, when inserted into the pressure chamber (P), keeps the pressure chamber (P) liquid-tight and can transmit the pressure of the pressure chamber (P) to the pressing body (4); and a pump (12) that supplies and discharges liquid to and from the pressure chamber (P).

Description

Front fork

[0001] The present invention relates to a front fork.

[0002] Some front forks that support the front wheel of a saddle-riding vehicle are interposed between the vehicle body and the axle of the front wheel to exert a damping force. Such front forks generally include a fork body that expands and contracts and includes a body-side tube that is connected to the vehicle body of the saddle-riding vehicle and a wheel-side tube that fits into the body-side tube and is connected to the axle, a damper cartridge that includes a cylinder and a rod and is housed within the fork body to exert a damping force as the fork body expands and contracts, and a suspension spring that biases the damper cartridge and fork body to expand.

[0003] The above-mentioned front fork may be provided with an adjuster device that adjusts the support position of the upper end of the suspension spring so that the vehicle height of a saddle-type vehicle can be adjusted to a desired vehicle height by the user, as disclosed in JP2010-084924A, for example.

[0004] Specifically, the adjuster device includes a bottomed cylindrical piston having a tubular portion slidably attached to the outer periphery of the lower end of a cap that closes the upper end of the vehicle body tube and a bottom portion that abuts against the upper end of a spring bearing that supports the upper end of the suspension spring, forming a pressure chamber between the cap and the piston, and a pump connected to the cap via a hose that can supply and discharge fluid into and out of the pressure chamber. When the pump supplies or discharges fluid into or out of the pressure chamber, the pressure chamber expands or contracts, causing the piston to move up and down, thereby adjusting the support position of the upper end of the suspension spring.

[0005] JP2010-084924A

[0006] In such front forks, a hose connected to a pump is attached to the cap, but when attaching the front fork to a saddle-riding vehicle, the upper end of the vehicle-side tube must be passed through a hole in the upper bracket of the saddle-riding vehicle.

[0007] However, because the pump could not pass through the hole in the upper bracket, in order to attach the front fork to the vehicle body, the hose and pump had to be removed from the vehicle body tube, the vehicle body tube passed through the upper bracket and the fork body attached to the vehicle body, then the hose connected to the pump was connected to the cap, and then oil had to be poured into the pressure chamber, a complicated installation process.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a front fork that can be easily attached to a vehicle body even when equipped with a pump for adjusting the vehicle height.

[0009] In order to achieve the above-mentioned object, the front fork of the present invention comprises: a fork body that is extendable and contractible and has a vehicle body side tube and a wheel side tube; a cylindrical cap that is attached to one end opening of the vehicle body side tube; a pressing body that is inserted into the cap so as to be slidable in the axial direction; a spring bearing that moves axially together with the pressing body while supporting the cap side end of a suspension spring that is housed in the fork body and biases the fork body in the extension direction; a first seal that seals between the pressing body and the cap; and an actuator unit that can drive the spring bearing in the axial direction relative to the cap via the pressing body, wherein the actuator unit comprises a housing that is detachably connected to the cap and has a pressure chamber; a partition member that, when inserted into the pressure chamber, keeps the pressure chamber liquid-tight and can transmit pressure from the pressure chamber to the pressing body; and a pump that supplies and discharges liquid to and from the pressure chamber.

[0010] With this configuration, the fork body is sealed and kept liquid-tight by the first seal, and the pressure chamber of the actuator unit is kept liquid-tight by the partition member, so the actuator unit can be separated from the fork body without risk of liquid leakage even if liquid remains in the pressure chamber. Because both the fork body and the actuator unit can be separated while maintaining a liquid-tight seal, the front fork can be installed on the vehicle body simply by attaching the fork body to the vehicle body and then connecting the actuator unit to the fork body cap. Therefore, with the front fork of the present invention, the front fork can be easily installed on the vehicle body without the need for the complicated task of adding oil to the pressure chamber after installation.

[0011] Fig. 1 is a side view of a saddle-riding vehicle equipped with a front fork according to an embodiment of the present invention. Fig. 2 is a longitudinal cross-sectional view of the front fork according to an embodiment of the present invention. Fig. 3 is an enlarged longitudinal cross-sectional view of the upper end of the front fork according to an embodiment of the present invention, showing a state in which the support position of the upper end of the suspension spring is in the lowest position. Fig. 4 is an enlarged longitudinal cross-sectional view of the upper end of the front fork according to an embodiment of the present invention, showing a state in which the support position of the upper end of the suspension spring is in the highest position. Fig. 5 is an enlarged longitudinal cross-sectional view of the upper end of the front fork according to a first modified embodiment of the present invention. Fig. 6 is an enlarged longitudinal cross-sectional view of the upper end of the front fork according to a second modified embodiment of the present invention.

[0012] The front fork 1 of the present invention will be described below based on the embodiment shown in the drawings. The same reference numerals used throughout the drawings indicate the same parts. As shown in FIG. 1, the front fork 1 of this embodiment is mounted between the body B and wheel W of a straddle-riding vehicle V. Furthermore, unless otherwise specified, the top and bottom of the front fork 1 mounted on the straddle-riding vehicle V will simply be referred to as "upper" and "lower."

[0013] 2, 3, and 4, the front fork 1 of the present invention comprises an extendable fork body 2 having a vehicle body-side tube 2a and a wheel-side tube 2b, a cylindrical cap 3 attached to one end opening of the vehicle body-side tube 2a, a pressing body 4 inserted into the cap 3 so as to be slidable in the axial direction, a spring bearing 6 that moves axially together with the pressing body 4 while supporting the upper end (the cap-side end) of a suspension spring 5 housed in the fork body 2 and biasing the fork body 2 in the extension direction, a first seal 7 that seals between the pressing body 4 and the cap 3, and an actuator unit 8 that can drive the spring bearing 6 in the axial direction relative to the cap 3 via the pressing body 4. The actuator unit 8 comprises a housing 9 that is detachable from the cap 3 and has a pressure chamber P, a partition member 10 that, when inserted into the pressure chamber P, keeps the pressure chamber P liquid-tight and can transmit the pressure of the pressure chamber P to the pressing body 4, and a pump 12 that supplies and discharges liquid to and from the pressure chamber P.

[0014] Below, we will explain each part of the front fork 1. As shown in Figure 2, the fork body 2 has a vehicle body side tube 2a and a wheel side tube 2b, is biased in the extension direction by a suspension spring 5 housed inside, and is equipped with a damper cartridge 13 that expands and contracts in accordance with the expansion and contraction of the fork body 2 to provide a damping force.

[0015] As shown in FIG. 1 , the vehicle-body side tube 2a is inserted into holes (not shown) in an upper bracket BR1 and an under bracket BR2 provided on the vehicle body B of a saddle-riding vehicle V, and is clamped and connected to the vehicle body B by bolts (not shown). The wheel-side tube 2b has a smaller diameter than the vehicle-body side tube 2a and is inserted into the vehicle-body side tube 2a from below. The fork body 2 expands and contracts when the vehicle-body side tube 2a and the wheel-side tube 2b move relative to each other in the axial direction. The upper end opening of the vehicle-body side tube 2a is closed by a cap 3, and the lower end of the wheel-side tube 2b is closed by an axle bracket 14 that clamps the axle Wa of the wheel W of the saddle-riding vehicle V. As shown in FIG. 2 , annular bearings 15, 16 are provided between the vehicle-body side tube 2a and the wheel-side tube 2b, allowing the vehicle-body side tube 2a and the wheel-side tube 2b to move smoothly in the axial direction. Furthermore, an annular seal member 17 is provided on the inner periphery of the lower end of the vehicle body side tube 2a, which is in sliding contact with the outer periphery of the wheel side tube 2b, thereby sealing the internal space of the fork body 2.

[0016] Thus, in this embodiment, the front fork 1 suspends the wheel W and elastically supports the body B of the saddle-ridden vehicle V, reducing vibration input to the body B from the wheel side and suppressing vibration of the body B by the damping force of the damper cartridge 13. Note that, in this embodiment, the front fork 1 is of a so-called inverted type in which the wheel-side tube 2b is inserted into the body-side tube 2a from below, but it may also be of a so-called upright type in which the body-side tube 2a has a smaller diameter than the wheel-side tube 2b and is inserted into the wheel-side tube 2b.

[0017] The damper cartridge 13 expands and contracts in accordance with the expansion and contraction of the fork body 2, thereby exerting a damping force. The damper cartridge 13 includes a cylinder 13a fixed to an axle bracket 14 that closes the lower end opening of the wheel-side tube 2b, a piston 13b slidably inserted into the cylinder 13a and dividing the interior of the cylinder 13a into an expansion-side chamber R1 and a compression-side chamber R2 that are filled with liquid, and a piston rod 13c connected to the piston 13b, inserted axially movably into the cylinder 13a, and connected to the cap 3 that closes the upper end opening of the vehicle-body-side tube 2a. An annular gap formed between the damper cartridge 13 and the wheel-side tube 2b is used as a reservoir R that is filled with liquid and gas. Although not shown, a suction passage that only allows liquid to pass from the reservoir R to the compression side chamber R2 and a damping passage that only allows liquid to pass from the compression side chamber R2 to the reservoir R and includes a base valve that provides resistance to the flow of liquid passing through. Therefore, liquid corresponding to the volume displaced within the cylinder 13a by the piston rod 13c that moves in and out of the cylinder 13a during extension and contraction is exchanged between the inside of the cylinder 13a and the reservoir R via the suction passage and the damping passage, thereby enabling volume compensation. Note that hydraulic oil can be used as the liquid, and any liquid that can generate a damping force can be used.

[0018] The piston 13b is annular and includes an expansion-side port 13b1 and a compression-side port 13b2 that communicate between the expansion-side chamber R1 and the compression-side chamber R2. An annular expansion-side leaf valve 13d that opens and closes the expansion-side port 13b1 is stacked at the lower end of the piston 13b in FIG. 2 , and an annular compression-side check valve 13e that opens and closes the compression-side port 13b2 is stacked at the upper end of the piston 13b in FIG. 2 . The piston 13b, the expansion-side leaf valve 13d, and the compression-side check valve 13e are all attached to the outer periphery of a piston connecting member 13f that is connected to the lower end of the piston rod 13c in FIG. 2 . The inner periphery of the expansion-side leaf valve 13d is fixed to the piston rod 13c, and when the outer periphery bends and moves away from the piston 13b, it opens the corresponding expansion-side port 13b1. The compression-side check valve 13e is slidably mounted on the inner periphery of the piston rod 13c and is pressed toward the piston 13b by a spring 13g to close the expansion-side port 13b1.

[0019] Additionally, a cylindrical rod guide 13h, into which the piston rod 13c is slidably inserted, is attached to the inner periphery of the upper end of the cylinder 13a. In addition to guiding the axial movement of the piston rod 13c, the rod guide 13h also functions as a spring bearing that supports the lower end of the suspension spring 5, and as an oil lock case that prevents further contraction of the damper cartridge 13 and fork body 2 by the entry of an oil lock piece 13i that is provided on the outer periphery midway along the piston rod 13c.

[0020] In the front fork 1 configured as described above, when the fork body 2 extends, the damper cartridge 13 also extends, and the expansion-side chamber R1 is compressed by the piston 13b. When the pressure in the expansion-side chamber R1 reaches the valve-opening pressure of the expansion-side leaf valve 13d, the liquid in the expansion-side chamber R1 moves to the compression-side chamber R2 through the expansion-side port 13b1. The expansion-side leaf valve 13d provides resistance to this liquid flow, creating a difference in pressure between the expansion-side chamber R1 and the compression-side chamber R2, and the front fork 1 exerts a damping force that suppresses the expansion operation. Note that when the damper cartridge 13 extends, the liquid equivalent to the volume of the liquid withdrawn from the cylinder 13a of the piston rod 13c flows from the reservoir R through the suction passage into the compression-side chamber R2, thereby compensating for the volume.

[0021] Furthermore, when the fork body 2 contracts, the damper cartridge 13 also contracts, and the compression-side chamber R2 is compressed by the piston 13b. Then, the pressure in the compression-side chamber R2 opens the compression-side check valve 13e, causing the liquid in the compression-side chamber R2 to move through the compression-side port 13b2 to the extension-side chamber R1, and the liquid equivalent to the volume of the liquid that has infiltrated into the cylinder 13a of the piston rod 13c is discharged from the compression-side chamber R2 to the reservoir R via the damping passage. The base valve provided in the damping passage provides resistance to the flow of liquid discharged from the compression-side chamber R2 to the reservoir R, causing a difference in pressure between the compression-side chamber R2 and the extension-side chamber R1, and the front fork 1 exerts a damping force that suppresses the contraction operation.

[0022] The above-described configuration of the damper cartridge 13 is merely an example, and the configuration of the damper cartridge 13 is not particularly limited as long as it can expand and contract together with the expansion and contraction of the fork body 2 to exert a damping force.

[0023] 2, 3, and 4, the cap 3 is cylindrical and includes a connecting portion 3a that is screwed to the upper end opening of the vehicle body side tube 2a, an intermediate portion 3b that is continuous with the lower end of the connecting portion 3a and has an outer diameter smaller than that of the connecting portion 3a, a guide portion 3c that is continuous with the lower end of the intermediate portion 3b and has an outer diameter smaller than that of the intermediate portion 3b, and is equipped with a pair of rectangular openings 3c1, 3c1 that face each other with a phase difference of 180 degrees on the sides, and a rod connecting portion 3d that is continuous with the lower end of the guide portion 3c and is formed by reducing the diameter so that its outer diameter is gradually smaller than that of the guide portion 3c.

[0024] A thread is formed on the inner periphery of the rod connecting portion 3d, and a thread provided on the outer periphery of the upper end of the piston rod 13c is screwed into the thread groove. In this way, the upper end of the piston rod 13c is screwed to the rod connecting portion 3d of the cap 3. A nut 19 is threadedly attached to the thread groove on the outer periphery of the upper end of the piston rod 13c and abuts against the lower end of the rod connecting portion 3d, so that the rod connecting portion 3d and the nut 19 are fastened together to prevent loosening and to firmly fasten the cap 3 and the piston rod 13c.

[0025] The connecting portion 3a has a threaded portion 3a1 on its outer periphery. The connecting portion 3a is connected to the vehicle body side tube 2a by threading the threaded portion 3a1 on its outer periphery into the threaded portion 2a1 formed on the inner periphery of the upper end opening of the vehicle body side tube 2a. A seal ring 20 that fits tightly against the inner periphery of the vehicle body side tube 2a is attached to the outer periphery of the connecting portion 3a above the threaded portion 3a1, thereby sealing the gap between the cap 3 and the vehicle body side tube 2a.

[0026] The intermediate portion 3b is cylindrical with an outer diameter smaller than that of the connecting portion 3a and an inner diameter smaller than that of the connecting portion 3a, and an annular groove 3b2 is formed at the upper end 3b1 facing the inside of the cap 3.

[0027] The spring bearing 6 comprises a cylindrical spring bearing main body 6a which is slidably mounted on the outer periphery of the guide portion 3c of the cap 3 and which supports the upper end of the suspension spring 5 at its lower end, and a regulating portion 6b which is stacked on the upper end of the spring bearing main body 6a.

[0028] The restricting portion 6b has an annular disk portion 6b1 inserted into the guide portion 3c, and two arms 6b2, 6b2 arranged on the outer periphery of the disk portion 6b1 with a phase difference of 180 degrees, each of whose tips protrudes outside the guide portion 3c through an opening 3c1 formed in the side of the guide portion 3c, and can move up and down relative to the guide portion 3c. Therefore, the spring bearing 6 can move up and down relative to the cap 3 within the range in which the arms 6b2 of the restricting portion 6b can move up and down within the opening 3c1.

[0029] The restricting portion 6b is connected to the pressing body 4, which is slidably inserted into the inner periphery of the intermediate portion 3b of the cap 3. Specifically, the pressing body 4 is inserted into the intermediate portion 3b of the cap 3, using the intermediate portion 3b as an insertion portion. The pressing body 4 is cylindrical and is inserted into the inner periphery of the disk portion 6b1 of the restricting portion 6b and connected to the restricting portion 6b. An annular first seal 7 is attached to the outer periphery of the pressing body 4 to seal between the outer periphery of the pressing body 4 and the inner periphery of the intermediate portion 3b. This seals the inside of the fork body 2.

[0030] In addition, the axial length of the pressing body 4 is set to a length that allows the end of the pressing body 4 to protrude upward from the intermediate portion 3b when the spring bearing 6 is in the uppermost position as shown in Figure 4 (when the arm portion 6b2 of the regulating portion 6b of the spring bearing 6 is positioned at the uppermost position within the opening 3c1 of the guide portion 3c of the cap 3).

[0031] In this embodiment, the restricting portion 6b is connected to the pressing body 4 by inserting the small diameter portion 4a provided at the lower end of the cylindrical pressing body 4 inside the disk portion 6b1 of the restricting portion 6b and fitting a C-pin 4b onto the outer periphery of the portion of the small diameter portion 4a that protrudes from the lower end of the disk portion 6b1. However, the method of connecting the restricting portion 6b to the pressing body 4 is not particularly limited. Furthermore, as long as the fork body 2 can be assembled, the restricting portion 6b and the pressing body 4 may be formed integrally.

[0032] Next, a detailed description will be given of the actuator unit 8. The actuator unit 8 has a housing 9 which is detachably attached to the cap 3 and has a pressure chamber P, a partition member 10 which, when inserted into the pressure chamber P, keeps the pressure chamber P liquid-tight and is capable of transmitting the pressure of the pressure chamber P to the pressing body 4, and a pump 12 which supplies and discharges liquid to and from the pressure chamber P.

[0033] More specifically, the housing 9 includes a cylindrical portion 9a that is inserted into the connecting portion 3a that serves as an attachment portion of the cap 3, and a bottom portion 9b that closes the lower end of the cylindrical portion 9a, which is the pressing body side end, and that is provided with a through hole 9b1 that faces the upper end of the pressing body 4 in the axial direction in FIG. 2. The bottom portion 9b also has a plurality of communication holes 9b2 that are arranged circumferentially outside the through hole 9b1, and the communication holes 9b2 face the axial direction and communicate with an annular groove 3b2 that is provided in the upper end 3b1 of the middle portion 3b of the cap 3. An annular seal ring 9b3 is provided on the outer periphery of the bottom portion 9b to seal the space between the connecting portion 3a and the bottom portion 9b.

[0034] Furthermore, an annular flange portion 9c is provided on the outer periphery of the cylindrical portion 9a of the housing 9 near the axial center. A plurality of holes 9c1 are formed in the flange portion 9c, and a plurality of bolt holes 3e are formed in the upper end of the cap 3, spaced circumferentially at equal intervals from the holes 9c1. The cylindrical portion 9a is inserted into the connecting portion 3a, and the flange portion 9c is abutted against the upper end of the cap 3 so that the holes 9c1 axially face the bolt holes 3e. Then, bolts 21 are threaded through the holes 9c1 and into the bolt holes 3e, thereby sandwiching the flange portion 9c between the heads of the bolts 21 and the upper end of the cap 3. This allows the housing 9 to be connected while inserted into the cap 3. Because the housing 9 is connected to the cap 3 by the bolts 21, the housing 9 can be separated from the cap 3 by removing the bolts 21. Therefore, the housing 9 is detachably connected to the cap 3. However, the method of connecting the housing 9 to the cap 3 is not particularly limited as long as it is detachable from the cap 3, and may be a method other than bolt fastening.

[0035] The partition member 10 includes a disk-shaped piston 10a that is axially movable while in sliding contact with the inner periphery of the cylindrical portion 9a and that defines a pressure chamber P within the housing 9, an output shaft 10b that protrudes from the lower end of the piston 10a (the bottom end of the housing 9) and is inserted into a through hole 9b1 while abutting against the upper end of the pressing body 4, and a second seal 10c that is provided on the outer periphery of the piston 10a and seals the pressure chamber P. The output shaft 10b is slidably inserted into the through hole 9b1, and axial movement of the output shaft 10b relative to the housing 9 is guided. Note that, because the piston 10a and the output shaft 10b are in sliding contact with the inner periphery of the housing 9, the partition member 10 can move axially without axial wobble, but the output shaft 10b does not need to be guided by the bottom portion 9b. The second seal 10c is fitted in an annular groove (not shown) provided on the outer periphery of the piston 10a and is in sliding contact with the inner periphery of the cylindrical portion 9a to provide a seal between the piston 10a and the cylindrical portion 9a. A gap G formed below the piston 10a in the housing 9 is in communication with the annular groove 3b2 via a communication hole 9b2 in the bottom portion 9b of the housing 9.

[0036] An annular cover member 22 is attached to the inner periphery of the upper end of the cylindrical portion 9a of the housing 9. A threaded portion 22a is provided on the inner periphery of the cover member 22, and one end of a hose (not shown) is connected to the inner periphery of the cover member 22 by screwing. The other end of the hose (not shown) is connected to the pump 12, and by driving the pump 12, liquid can be supplied to and discharged from the pressure chamber P. Although not shown, a seal member is also provided between the hose and the cover member 22. A seal ring 22b is attached to the outer periphery of the cover member 22 and makes sliding contact with the inner periphery of the cylindrical portion 9a of the housing 9 to seal between the cover member 22 and the cylindrical portion 9a, and the pressure chamber P is kept liquid-tight by a second seal 10c that is connected to the pump 12 and seals between the piston 10a and the cylindrical portion 9a.

[0037] There are no particular limitations on the shape of the hose or the method of attaching the hose to the housing 9. There are also no particular limitations on the type of pump 12, as long as it can supply and discharge liquid to and from the pressure chamber P. In this embodiment, the liquid supplied by the pump 12 is hydraulic oil, but other liquids such as water or an aqueous solution can also be used.

[0038] As described above, in this embodiment, the fork body 2 is sealed and kept liquid-tight by the first seal 7, and the pressure chamber P of the actuator unit 8 is kept liquid-tight by the partition member 10, so the actuator unit 8 can be separated from the fork body 2 without risk of liquid leakage even if liquid remains in the pressure chamber P.

[0039] In this way, because both the fork body 2 and the actuator unit 8 can be separated while maintaining a liquid-tight seal, the front fork 1 can be installed between the body B and wheel W of a saddle-ride vehicle V by inserting the vehicle-side tubes 2a of the fork body 2 from below into the holes in the upper bracket BR1 and the under bracket BR2, gripping the fork body 2 between the upper bracket BR1 and the under bracket BR2, and then connecting the actuator unit 8 to the cap 3 of the fork body 2. In this way, the installation work of the front fork 1 to the vehicle body B is completed simply by installing the fork body 2 to the vehicle body B and then connecting the actuator unit 8, which has already had liquid poured into the pressure chamber P, to the cap 3 of the fork body 2. This means that the front fork 1 can be easily installed to the vehicle body B without the need for the complicated work of pouring oil into the pressure chamber P after installing the front fork 1.

[0040] Next, a method for adjusting vehicle height using the front fork 1 of this embodiment will be described in detail. First, to raise the vehicle height, the pump 12 is driven to supply liquid into the pressure chamber P. Then, as shown in Figure 3, the partition member 10, whose upper end is in contact with the output shaft 10b, is pressed by the liquid supplied into the pressure chamber P and moves downward against the biasing force of the suspension spring 5 acting via the pressing body 4 and the spring bearing 6 and the pressure in the gap G. When the partition member 10 moves downward, the pressing body 4 and the spring bearing 6 are also pushed downward by the partition member 10, and the fork body 2 extends by the amount by which the support position of the upper end of the suspension spring 5 moves downward, thereby raising the vehicle height.

[0041] Conversely, to lower the vehicle height, the pump 12 is driven in the reverse direction to discharge the liquid from the pressure chamber P. Then, as shown in Figure 4, the partition member 10 is pressed upward by the biasing force of the suspension spring 5 acting via the pressing body 4 and the spring bearing 6 and the pressure of the gap G, causing it to move upward. When the partition member 10 moves upward, the pressing body 4 and the spring bearing 6 also move upward, and the support position of the upper end of the suspension spring 5 moves upward, causing the fork body 2 to contract by the amount corresponding to the upward movement, thereby lowering the vehicle height.

[0042] That is, in the front fork 1 of this embodiment, the partition member 10 moves up and down within the housing 9, and the actuator unit 8 expands and contracts, thereby allowing the vehicle height to be adjusted.

[0043] Since both the partition member 10 and the spring bearing 6 move in the vertical direction, the vertical stroke range of the partition member 10, like that of the spring bearing 6, is the range in which the arm portion 6b2 of the regulating portion 6b can move in the vertical direction within the opening 3c1.

[0044] Furthermore, as described above, in this embodiment, the gap G formed below the piston 10a inside the housing 9 is connected to the annular groove 3b2 of the cap 3, which prevents the pressure in the gap G from becoming high when the partition wall member 10 strokes toward the extension side (downward in the figure), allowing the partition wall member 10 to move smoothly and facilitating vehicle height adjustment. However, if the pressure in the gap G does not hinder the smooth movement of the partition wall member 10 when the partition wall member 10 strokes toward the extension side, the annular groove 3b2 and the communication hole 9b2 may be omitted.

[0045] Furthermore, when adjusting vehicle height by supplying or discharging liquid to or from the pressure chamber P using the pump 12, as in the front fork 1 of this embodiment, the higher the discharge capacity of the pump 12, the shorter the time required to adjust vehicle height and the wider the weight range for which vehicle height can be adjusted. However, a pump 12 with high discharge capacity requires a larger motor to drive the pump 12, and therefore becomes larger in size.

[0046] In contrast, as described above, in the front fork 1 of this embodiment, the actuator unit 8 can be separated from the fork body 2 without the risk of fluid leakage. Therefore, the vehicle-side tube 2a of the fork body 2 can be inserted from below into the holes in the upper bracket BR1 and the under bracket BR2 to attach the fork body 2 to the vehicle body B, and then the actuator unit 8 including the pump 12 can be connected to the cap 3 of the fork body 2. Because there is no need to pass the pump 12 through the holes in the upper bracket BR1 and the under bracket BR2, it does not matter if the pump 12 is larger than the holes in the upper bracket BR1 and the under bracket BR2. Therefore, in the front fork 1 of this embodiment, a pump 12 of any size can be selected, regardless of the size of the holes in the upper bracket BR1 and the under bracket BR2. Therefore, in the front fork 1 of this embodiment, a large pump 12 with a high discharge capacity can be used to shorten the time required for vehicle height adjustment and to widen the weight range for which vehicle height can be adjusted.

[0047] In this embodiment, the axial length of the pressing body 4 is set to a length that protrudes from the intermediate portion 3b of the cap 3 toward the connecting portion 3a when the spring bearing 6 is in its uppermost position, as shown in FIG. 4 . Furthermore, the axial length of the output shaft 10b of the partition member 10 is set to a length that protrudes downward from the bottom portion 9b of the housing 9 when the piston 10a is farthest from the bottom portion 9b of the housing 9 (when the upper end of the piston 10a is in contact with the lower end of the cover member 22), as shown in FIG. 4 . Therefore, when the actuator unit 8 and the fork body 2 are separated, the end of the pressing body 4 protrudes from the intermediate portion 3b of the cap 3, and the end of the output shaft 10b protrudes slightly from the bottom portion 9b of the housing 9. Therefore, if the front fork 1 is in a normal state, the pressing body 4 and the output shaft 10b can be seen from the outside when the actuator unit 8 and the fork body 2 are separated. Therefore, whether or not there is a defect in the assembly of the actuator unit 8 or the assembly of the pressing body 4 to the cap 3 can be easily confirmed by whether or not the pressing body 4 and the output shaft 10b can be seen from the outside, making it easier to discover defects in the front fork 1.

[0048] The length of protrusion of the pressing body 4 from the intermediate portion 3b of the cap 3 and the length of protrusion of the output shaft 10b from the bottom portion 9b of the housing 9 may be determined arbitrarily, but since it is sufficient to be visible from the outside, it is sufficient if they protrude even slightly. However, the pressing body 4 and the output shaft 10b do not have to protrude from the intermediate portion 3b of the cap 3 and the bottom portion 9b of the housing 9, respectively.

[0049] Furthermore, in this embodiment, the actuator unit 8 is detachably connected to the cap 3 of the fork body 2 by connecting the housing 9 to the cap 3 with the bolts 21. However, as long as the housing 9 is detachably connected to the cap 3, the method of connecting the housing 9 to the cap 3 is not limited to using the bolts 21. For example, the housing 9 may be fastened to the cap 3 by providing threaded portions on the inner periphery of the connecting portion 3a of the cap 3 and on the outer periphery of the tubular portion 9a of the housing 9, respectively, and threading the housing 9 onto the inner periphery of the connecting portion 3a. However, when the housing 9 is connected to the cap 3 with the bolts 21, the housing 9 does not rotate relative to the cap 3. Therefore, even if, for example, a hose (not shown) connected to the housing 9 via the cover member 22 is L-shaped and the orientation of the pump-side end of the hose is predetermined, or if the hose (not shown) is connected to a position radially offset from the center of the cap 3 and the circumferential connection position of the hose to the cap 3 is predetermined, connecting the housing 9 to the cap 3 with the bolts 21 does not change the orientation of the pump-side end of the hose or the circumferential connection position of the hose to the cap 3.

[0050] As described above, the front fork 1 of this embodiment comprises the extendable fork body 2 having the vehicle body side tube 2a and the wheel side tube 2b, the cylindrical cap 3 attached to one end opening of the vehicle body side tube 2a, the pressing body 4 inserted into the cap 3 so as to be slidable in the axial direction, the spring bearing 6 which moves in the axial direction together with the pressing body 4 while supporting the upper end (which is the cap side end) of the suspension spring 5 housed in the fork body 2 and which urges the fork body 2 in the extension direction, the first seal 7 which seals between the pressing body 4 and the cap 3, and the actuator unit 8 which is capable of driving the spring bearing 6 in the axial direction relative to the cap 3 via the pressing body 4, and the actuator unit 8 has a housing 9 which is detachably connected to the cap 3 and has a pressure chamber P, a partition member 10 which, when inserted into the pressure chamber P, keeps the inside of the pressure chamber P liquid-tight and is capable of transmitting the pressure of the pressure chamber P to the pressing body 4, and a pump 12 which supplies and discharges liquid to and from the pressure chamber P.

[0051] With the front fork 1 configured in this manner, the fork body 2 is sealed and kept liquid-tight by the first seal 7, and the pressure chamber P of the actuator unit 8 is kept liquid-tight by the partition member 10, so the actuator unit 8 can be separated from the fork body 2 without risk of liquid leakage even if liquid remains in the pressure chamber P. In this way, because both the fork body 2 and the actuator unit 8 can be separated while maintaining a liquid-tight seal, the installation work of the front fork 1 to the vehicle body B is completed simply by installing the fork body 2 to the vehicle body B and then connecting the actuator unit 8 to the cap 3 of the fork body 2. Therefore, with the front fork 1 of this embodiment, the front fork 1 can be easily installed to the vehicle body B without the need for the complicated work of filling the pressure chamber P with oil after installing the front fork 1.

[0052] Furthermore, with the front fork 1 of this embodiment, the vehicle-side tubes 2a of the fork body 2 can be inserted from below into the holes in the upper bracket BR1 and the under bracket BR2 to attach the fork body 2 to the vehicle body B, and then the actuator unit 8 including the pump 12 can be connected to the cap 3 of the fork body 2, eliminating the need to pass the pump 12 through the holes in the upper bracket BR1 and the under bracket BR2. Therefore, a pump 12 of any size can be selected regardless of the size of the holes in the upper bracket BR1 and the under bracket BR2. Therefore, with the front fork 1 of this embodiment, a large pump 12 with a high discharge capacity can be used, shortening the time required to adjust the vehicle height and widening the weight range for which the vehicle height can be adjusted.

[0053] Furthermore, in the front fork 1 configured as described above, the pressure in the pressure chamber P is transmitted to the pressing body 4 via the partition member 10, so that when the pump 12 is driven to supply liquid to the pressure chamber P, the partition member 10 is pressed by the liquid supplied into the pressure chamber P and moves downward. As a result, the pressing body 4 is pressed downward in the axial direction via the partition member 10, so the spring bearing 6 also moves downward together with the pressing body 4, and the support position of the upper end of the suspension spring 5 moves downward, thereby extending the fork body 2 and increasing the vehicle height. Conversely, when the pump 12 is driven in the reverse direction to discharge liquid from the pressure chamber P, the partition member 10 is pressed upward by the urging force of the suspension spring 5 acting via the pressing body 4, and moves upward. When the partition member 10 moves upward, the pressing body 4 and spring bearing 6 also move upward, and the support position of the upper end of the suspension spring 5 moves upward, causing the fork body 2 to contract and lower the vehicle height. In other words, in the front fork 1 of this embodiment, the pressure of the pressure chamber P is transmitted to the pressing body 4 via the partition member 10, so when the pump 12 supplies or discharges liquid to or from the pressure chamber P, the spring bearing 6 moves up and down together with the pressing body 4, making it possible to adjust the vehicle height.

[0054] In this embodiment, the first seal 7 is provided on the outer periphery of the pressing body 4, but the first seal 7 may be provided on the cap 3 side.

[0055] Furthermore, in this embodiment, the partition member 10 directly contacts the pressing body 4 to transmit the pressure of the pressure chamber P to the pressing body 4, but it is also possible to interpose another member between the partition member 10 and the pressing body 4 so that the partition member 10 contacts the pressing body 4 indirectly.

[0056] Furthermore, in the front fork 1 of this embodiment, the partition member 10 has a second seal 10c that seals the pressure chamber P. With this configuration, the pressure chamber P is sealed by the second seal 10c and maintained liquid-tight. While the second seal 10c is provided on the outer periphery of the partition member 10 in this embodiment, it may also be provided on the housing 9 side. Instead of the structure including the piston 10a described above, the partition member 10 may be an elastic partition such as a bladder, diaphragm, or bellows, as long as the pressure of the pressure chamber P can be transmitted to the pressing body 4 via the partition member. In this case, the second seal 10c can be omitted.

[0057] In the front fork 1 of this embodiment, the cap 3 is provided on its inner periphery with a cylindrical intermediate portion 3b (insertion portion) into which the cylindrical pressing body 4 is inserted, and a cylindrical connecting portion 3a (mounting portion) which is larger in diameter than the intermediate portion 3b and into which the housing 9 is inserted. The housing 9 has a cylindrical portion 9a inserted into the connecting portion 3a, and a bottom portion 9b which closes the pressing body side end of the cylindrical portion 9a and is provided with a through hole 9b1 which faces the pressing body 4 in the axial direction. The partition member 10 slides against the inner periphery of the cylindrical portion 9a while sliding against the inner periphery of the cylindrical portion 9a. and an output shaft 10b that protrudes from the bottom end of the piston 10a and is inserted into the through-hole 9b1 while abutting against the pressing body 4, the axial length of the output shaft 10b being set to a length that allows the end of the output shaft 10b to protrude from the bottom 9b when the piston 10a is at its farthest from the bottom 9b, and the axial length of the pressing body 4 being set to a length that allows the end of the pressing body 4 to protrude from the intermediate part 3b (insertion part) towards the connecting part 3a (mounting part) when the spring bearing 6 is at its uppermost position.

[0058] With the front fork 1 configured as described above, when the actuator unit 8 and the fork body 2 are separated, the end of the pressing body 4 protrudes from the middle portion 3b (insertion portion) of the cap 3, and the end of the output shaft 10b protrudes from the bottom portion 9b of the housing 9. Therefore, if the front fork 1 is in a normal state, the pressing body 4 and the output shaft 10b can be visually confirmed from the outside when the actuator unit 8 and the fork body 2 are separated. Therefore, whether the pressing body 4 and the output shaft 10b are visible from the outside can easily determine whether there is a problem with the assembly of the actuator unit 8 or the assembly of the pressing body 4 to the cap 3, making it easier to discover problems with the front fork 1. However, if the front fork 1 only performs the vehicle height adjustment function, the pressing body 4 and the output shaft 10b do not need to protrude from the middle portion 3b (insertion portion) of the cap 3 and the bottom portion 9b of the housing 9, respectively. Furthermore, although the pressing body 4 is formed in a cylindrical shape in this embodiment, the shape of the pressing body 4 is not particularly limited.

[0059] Furthermore, in the front fork 1 of this embodiment, the partition member 10 is composed of a disk-shaped piston 10a and an output shaft 10b that protrudes from the lower end of the piston 10a and abuts against the pressing body 4. However, as shown in FIG. 5 , the partition member 10A may be composed of only the disk-shaped piston 10a that is movable in the axial direction while making sliding contact with the inner periphery of the cylindrical portion 9a of the housing 9, and the axial length of the pressing body 4 may be increased so that the end of the pressing body 4 abuts against the piston 10a inside the housing 9.

[0060] Even with this configuration, the end of the pressing body 4 abuts against the lower end of the piston 10a that constitutes the partition member 10A, so the pressure of the pressure chamber P is transmitted to the pressing body 4 via the partition member 10A. Therefore, when the pump 12 supplies or discharges liquid to or from the pressure chamber P, the spring bearing 6 moves up and down together with the pressing body 4, making it possible to adjust the vehicle height.

[0061] Furthermore, with the front fork 1 configured as described above, the partition member 10 has a simple, disk-like shape, thereby reducing manufacturing costs. In the embodiment shown in FIGS. 2 to 4 , the output shaft 10b is slidably inserted into the through-hole 9b1 to guide its axial movement relative to the housing 9. However, when the partition member 10A is configured only with the piston 10a as shown in FIG. 5 , the output shaft 10b does not need to be in sliding contact with the through-hole 9b1. Therefore, when the partition member 10A is configured only with the piston 10a, as shown in FIG. 5 , the communication hole 9b2 provided in the bottom portion 9b of the housing 9 may be omitted, and the diameter of the through-hole 9b1 may be made larger than the outer diameter of the pressing body 4, so that the gap G communicates with the annular groove 3b2 via the through-hole 9b1. This eliminates the need to process the communication hole 9b2 in the bottom portion 9b, thereby facilitating manufacturing of the housing 9. However, the pressing body 4 may be slidably inserted into the through-hole 9b1 to guide its axial movement.

[0062] 6, the front fork 1 may have a partition member 10 that is movable in the axial direction within the housing 9, and the actuator unit 8 may be provided with a stroke sensor 23 that detects the stroke position of the partition member 10. Although not described in detail, the stroke sensor 23 includes a cylindrical housing portion 23a that is connected to the bottom portion 9b of the housing 9, and a movable rod 23b that is inserted into the housing portion 23a so as to be movable in the axial direction, and whose upper end that protrudes from the housing portion 23a is connected to the piston 10a and moves in the axial direction together with the piston 10a. The stroke position of the partition member 10 can be detected by detecting the position of a detectable element (not shown) that is provided on the movable rod 23b with a sensor (not shown) provided in the housing portion 23a.

[0063] In this way, if the front fork 1 is provided with a stroke sensor 23 that can detect the stroke position of the partition wall member 10, it is possible to adjust the vehicle height while keeping track of the vehicle height of the front fork 1. The type of stroke sensor 23 is not particularly limited as long as it can detect the stroke position of the partition wall member 10, and for example, the stroke sensor 23 may be composed of a detection element attached to the inner periphery of the bottom 9 b of the housing 9, and a rod-shaped probe that is housed in a hole that opens from the top end of the partition wall member 10 and detects the position of the detection element.

[0064] Furthermore, with the front fork 1 configured in this manner, the stroke sensor 23 is provided on the side of the actuator unit 8, which is separable from the fork body 2, making it easy to install the stroke sensor 23. Furthermore, in the event of a malfunction of the stroke sensor 23, the actuator unit 8 can be separated, making it easy to replace or repair the stroke sensor 23.

[0065] The stroke sensor for determining the vehicle height of the front fork 1 may be provided on the fork body 2 side, and may, for example, detect the stroke position of the pressing body 4 to determine the vehicle height of the front fork 1. Furthermore, if the pump 12 is a pump that includes a cylinder and a piston inserted into the cylinder, and supplies and discharges liquid into and from the pressure chamber P as the piston moves relative to the cylinder, the stroke sensor may detect the position of the piston relative to the cylinder to detect the stroke position of the partition member 10.

[0066] Although the preferred embodiment of the present invention has been described in detail, modifications, variations and changes can be made thereto without departing from the scope of the appended claims.

[0067] DESCRIPTION OF SYMBOLS 1: Front fork, 2: Fork body, 3: Cap, 3a: Connecting portion (mounting portion), 3b: Intermediate portion (insertion portion), 4: Pressing body, 5: Suspension spring, 6: Spring bearing, 7: First seal, 8: Actuator unit, 9: Housing, 9a: Cylindrical portion, 9b: Bottom portion, 9b1: Through hole, 10: Partition member, 10a: Piston, 10b: Output shaft, 10c: Second seal, 12: Pump, 23: Stroke sensor

Claims

1. A front fork comprising: a fork body that is extendable and contractible and has a vehicle body side tube and a wheel side tube; a cylindrical cap that is attached to one end opening of the vehicle body side tube; a pressing body that is inserted into the cap so as to be able to slide freely in the axial direction; a spring bearing that is housed in the fork body and moves in the axial direction together with the pressing body while supporting the cap side end of a suspension spring that urges the fork body in the extension direction; a first seal that seals between the pressing body and the cap; and an actuator unit that is capable of driving the spring bearing in the axial direction relative to the cap via the pressing body, wherein the actuator unit has: a housing that is detachably connected to the cap and has a pressure chamber; a partition member that, when inserted into the pressure chamber, keeps the pressure chamber liquid-tight and is capable of transmitting pressure from the pressure chamber to the pressing body; and a pump that supplies and discharges liquid to and from the pressure chamber.

2. A front fork according to claim 1, wherein the partition member has a second seal that seals the pressure chamber.

3. A front fork as set forth in claim 2, wherein the inner periphery of the cap is provided with a cylindrical insertion section into which the cylindrical pressing body is inserted, and a cylindrical attachment section having a diameter larger than that of the insertion section into which the housing is inserted, the housing having a cylindrical section inserted into the attachment section and a bottom section that closes the pressing body side end of the cylindrical section and has a through hole that faces the pressing body in the axial direction, the partition member having a disk-shaped piston that is in sliding contact with the inner periphery of the cylindrical section and can move in the axial direction, and an output shaft that protrudes from the bottom side end of the piston and is inserted into the through hole while abutting against the pressing body, the axial length of the output shaft being set to a length such that the end of the output shaft protrudes from the bottom when the piston is farthest from the bottom, and the axial length of the pressing body is set to a length such that the end of the pressing body protrudes from the insertion section towards the attachment section when the spring bearing is at its uppermost position.

4. A front fork as claimed in claim 2, wherein the partition member is a disc-shaped piston that is axially movable while in sliding contact with the inner periphery of the housing, and an end of the pressing body abuts against the piston inside the housing.

5. A front fork according to any one of claims 1 to 4, wherein the partition member is movable axially within the housing, and the actuator unit is provided with a stroke sensor that detects the stroke position of the partition member.

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