JP2010084926A - Front fork - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize adjustment of a spring force of a suspension spring in each pair of front forks on the front wheel side of a two-wheeled vehicle by operating a device provided at one place.
SOLUTION: The upper end position of a suspension spring S accommodated in a fork main body composed of a vehicle body side tube 1 and a wheel side tube 2 is moved up and down by a telescopic drive of a jack mechanism accommodated in the fork main body. In each front fork that makes a spring force adjustment possible, the jack mechanism communicates with a single fluid pressure supply / discharge source 100 disposed outside the fork main body to operate the fluid pressure supply / discharge source 100. On the other hand, the fluid pressure supply / exhaust source 100 is held by a fork bracket B that connects each fork main body to the handle side of the two-wheeled vehicle, and is also driven by the drive source 200 disposed along with the fork bracket B. This makes it possible to supply and discharge fluid pressure to the jack mechanism.
[Selection] Figure 1

Description

  The present invention relates to a front fork that is a hydraulic shock absorber that is mounted on the front wheel side of a two-wheeled vehicle and absorbs road surface vibrations that are input to the front wheel while suspending the front wheel of the two-wheeled vehicle. The present invention also relates to an improvement in the front fork that allows the spring force of the suspension spring to be adjusted in the fork body by the jack mechanism of the accommodation.

  A front fork that is a hydraulic shock absorber that is mounted on the front wheel side of a two-wheeled vehicle and absorbs road surface vibrations that are input to the front wheel while suspending the front wheel of the two-wheeled vehicle. There have been various proposals so far for a front fork that can adjust the spring force of the spring by a jack mechanism that is housed in the fork body.

  Among them, for example, in Patent Document 1, the spring force of each suspension spring in the front fork mounted on the front wheel side of the two-wheeled vehicle and the rear cushion unit mounted on the rear wheel side of the two-wheeled vehicle is described as a single pressure source. A proposal has been disclosed that the vehicle height in a two-wheeled vehicle can be adjusted by adjusting the operation of the pressure part.

  Incidentally, the jack mechanism disclosed in Patent Document 1 has a plunger that is a piston in series in contact with the upper end of the suspension spring in the fork body, and this plunger is a pressure from the outside of the fork body. Sliding in the axial direction of the suspension spring by supplying and discharging oil, the upper end position of the suspension spring is raised and lowered to adjust the spring force of the suspension spring.

Therefore, in the proposal disclosed in Patent Document 1, the height of the motorcycle can be adjusted by adjusting the spring force of the suspension spring in the rear cushion unit and adjusting the spring force of the suspension spring in the front fork.
Japanese Patent Laid-Open No. 4-8934 (see Claims, Fig. 1)

  However, in the proposal disclosed in Patent Document 1 described above, the spring force adjustment of the suspension spring in the front fork can be realized together with the spring force adjustment of the suspension spring in the rear cushion unit by a single operation. However, there is a slight problem when trying to adjust the spring force of the suspension spring in the fork body in the front fork that is on the front wheel side of the motorcycle and is paired on the left and right.

  That is, in a two-wheeled vehicle, when a front fork is mounted on the front wheel side, in most cases, it is a pair of left and right, and accordingly, each suspension in two hydraulic shock absorbers that are two front forks that are paired on the left and right Regarding the adjustment of the spring force of the spring, it can be said that the proposal disclosed in Patent Document 1 described above can be used.

  However, as disclosed in Patent Document 1 described above, devices for adjusting the spring force of each suspension spring in the front fork and the rear cushion unit are dispersed on the motorcycle body side below the seat, below the fuel tank, and the like. Has been.

  Therefore, it is difficult to divert this to the spring force adjustment of the suspension spring in each of the front forks that are paired on the left and right sides on the front wheel side of the two-wheeled vehicle in this dispersed mode.

  The present invention has been developed in view of such a current situation, and the object of the present invention is to adjust the spring force of the suspension spring in each of the front forks that are paired on the left and right sides of the front wheel side of the motorcycle. An object of the present invention is to provide a front fork that can be realized by operating the provided devices and is optimal for expecting an improvement in versatility.

  In order to achieve the above-mentioned object, the front fork according to the present invention is basically configured so that the upper end position of the suspension spring accommodated in the fork main body comprising the vehicle body side tube and the wheel side tube is the above fork main body. The above-mentioned jack mechanism is arranged outside the fork main body in each pair of left and right front forks that allows the spring force of the suspension spring to be adjusted by moving it up and down by the expansion and contraction drive of the jack mechanism inside. The fluid pressure supply / discharge source is connected to a single fluid pressure supply / discharge source, and the fluid pressure supply / discharge source connects the fork body to the handle side of the motorcycle. It is assumed that fluid pressure can be supplied to and discharged from the jack mechanism by driving a driving source that is held and disposed together with the fork bracket.

  Therefore, according to the present invention, the jack mechanism accommodated in the fork main body constituting the pair of front forks on the left and right sides communicates with a single fluid pressure supply / discharge source disposed outside the fork main body. Thus, the spring force of the suspension springs in the front forks that are paired on the left and right are adjusted simultaneously by the operation of the fluid pressure supply / discharge source.

  In the present invention, the fluid pressure supply / discharge source is held by a fork bracket that connects each fork main body to the handle side of the two-wheeled vehicle, and is driven by a drive source disposed along with the fork bracket. Since it operates, the supply and discharge of fluid pressure to the jack mechanism can be realized at one place, as well as the fluid pressure supply and discharge source and the drive source are held by the fork bracket, etc. Do not become worse or look bad.

  Hereinafter, the present invention will be described based on the illustrated embodiment. A front fork according to the present invention is mounted on the front wheel side of a two-wheeled vehicle and suspends the front wheel of the two-wheeled vehicle while inputting road surface vibrations input to the front wheel. Acts as a hydraulic shock absorber.

  In this front fork, as shown in FIG. 1, the upper end position of the suspension spring S accommodated in the fork main body composed of the vehicle body side tube 1 and the wheel side tube 2 is accommodated in the fork main body. It is possible to adjust the spring force of the suspension spring S by moving it up and down by driving the jack mechanism.

  In the figure, the fork body is set to be an inverted type in which the vehicle body side tube 1 is an outer tube and the wheel side tube 2 is an inner tube, but this is not shown in the embodiment of the present invention. However, contrary to the above, the fork main body may be set upright with the vehicle body side tube 1 as the inner tube and the wheel side tube 2 as the outer tube.

  The front fork shown in FIG. 1 will be described briefly. The front fork is configured by housing a suspension spring S, a jack mechanism, and a damper in a fork main body including a vehicle body side tube 1 and a wheel side tube 2.

  In the front fork, the suspension spring S is supported on the cylinder body 3 side of a damper, which will be described later, and the upper end of the suspension spring S via a cylindrical spacer S1. Rather, it is also locked by a jack mechanism, which will be described later, and biases the fork body in the extending direction in the direction in which the wheel side tube 2 protrudes from the vehicle body side tube 1.

  Specifically, the lower end of the suspension spring S is supported on the upper end of an oil lock case 5 provided continuously with the upper end of the cylinder body 3, and the upper end of the spacer S1 that locks the upper end of the suspension spring S is the upper end of the cylinder body 3. The cap member 11 that closes the opening is locked to the lower end of the piston member 12 constituting the jack mechanism.

  The oil lock case 5 is opposed to the oil lock piece 41 held by the rod body 4 of the damper, and the oil lock piece 41 is fitted into the oil lock case 5 when the fork body is fully contracted. In addition to exerting a cushioning effect, an oil lock phenomenon is manifested.

  And a damper is the cylinder body 3 which is a lower end side member standingly arranged in the wheel side tube 2, and the front-end | tip part used as a lower end part in the figure while it is suspended in the vehicle body side tube 1 and is used as an upper end side member. The rod body 4 is inserted into the cylinder body 3 so as to be able to appear and retract.

  Although not shown, the lower end portion of the cylinder body 3 is coupled to a bottom member 21 that closes the lower end opening of the wheel side tube 2, and the upper end portion of the rod body 4 is a cap member 11 that closes the upper end opening of the vehicle body side tube 1. Therefore, the damper is integrally connected to the fork main body and is expanded and contracted in synchronization with the expansion and contraction operation of the fork main body.

  Therefore, in the front fork according to the present invention, the axial direction which is the expansion / contraction direction of the damper coincides with the axial direction which is the expansion / contraction direction of the fork main body, and thus the smooth expansion / contraction operation of the damper with respect to the expansion / contraction fork main body is achieved. It becomes easy to guarantee.

  The damper has a piston part P that is slidably received in the cylinder body 3 while being held at the tip of the rod body 4, and the piston part P is shown in FIG. As shown, the upper body R1 and the lower chamber R2 are defined in the cylinder body 3 so as to be slidably received in the cylinder body 3 while being held by the tip member 43 constituting the tip portion of the rod body 4. It has a piston body 6.

  And in this piston part P, the piston body 6 has an extension side port 6a and a pressure side port 6b, and an extension side damping valve 6c that closes the downstream side end of the extension side port 6a so as to be openable, And a compression side damping valve 6d for closing the downstream side end of the compression side port 6b so as to be openable.

  By the way, the damping valves 6c and 6d on each side are made of annular leaf valves, are arranged in a manner that the outer peripheral end is fixed with the inner peripheral end fixed, and the hydraulic oil passes through the gap appearing there as the outer peripheral end bends. As a result, a predetermined damping action is realized.

  On the other hand, in the above damper, although not shown, the base valve portion is provided in the lower end portion of the cylinder body 3, and the outside of the cylinder body 3 is a reservoir chamber R (see FIG. 1). In addition, the lower chamber R2 in the cylinder body 3 can be communicated via the base valve portion.

  At this time, the base valve portion also has a pressure-side damping valve that allows the hydraulic oil in the lower chamber R2 in the cylinder body 3 to flow out toward the reservoir chamber R, and is parallel to the pressure-side damping valve, although not shown in the figure. Thus, a check valve that allows the hydraulic oil from the reservoir chamber R to flow into the lower chamber R2 in the cylinder body 3 is provided.

  Therefore, in the damper described above, the hydraulic oil in the lower chamber R2 in the cylinder body 3 is transferred to the piston portion P during the contraction operation in which the piston portion P descends in the cylinder body 3 in synchronization with the contraction operation of the fork main body. Flows into the upper chamber R1 through the pressure side damping valve 6d, and an amount of hydraulic oil corresponding to the rod intrusion integral that becomes redundant in the lower chamber R2 flows out into the reservoir chamber R through the pressure side damping valve in the base valve portion. Then, a predetermined compression side damping action is realized.

  In the damper, the hydraulic oil in the upper chamber R1 in the cylinder body 3 is transferred to the piston portion P during the extension operation in which the piston portion P rises in the cylinder body 3 in synchronization with the extension operation of the fork main body. An amount of hydraulic oil corresponding to the rod withdrawal volume that is deficient in the lower chamber R2 is replenished from the reservoir chamber R via the check valve in the base valve portion, while flowing out to the lower chamber R2 via the extension side damping valve 6c. A predetermined extension side damping action is realized.

  Incidentally, when the rod body 4 described above is formed of a pipe body having a through hole 4a in the shaft core portion as shown by a virtual diagram in the drawing, the weight of the rod body 4 can be reduced, This is advantageous in that the section modulus can be increased and the bending strength can be increased.

  Further, even in the above-described tip member 43, as shown by a virtual diagram in the drawing, when the passage 43a is formed of a through hole, in the piston portion P, the passage 43a is used as a bypass passage. A control valve that allows communication between the upper chamber R1 and the lower chamber R2 and that controls the flow rate of hydraulic oil passing through the bypass passage is disposed in the bypass passage, so that the damping valve on each side described above is provided. Thus, the height control of the damping action by 6c and 6d can be made possible.

  At this time, as described above, when the rod body 4 has the through hole 4a of the shaft core portion, the control rod connected to the control valve can be accommodated in the through hole 4a. Thus, the control rod can be driven by an actuator housed in a cap member 11 that closes the upper end opening of the vehicle body side tube 1.

  Incidentally, in the present invention, as described above, the spring force in the suspension spring S accommodated in the fork main body can be adjusted by the jack mechanism. Hereinafter, this jack mechanism will be described a little.

  First, as shown in FIG. 3, the jack mechanism is slidably connected to the lower end side portion 11 a of the cap member 11 that closes the upper end opening of the vehicle body side tube 1 and the lower end side portion 11 a of the cap member 11. It has a piston member 12 that defines a pressure chamber R3 that expands and contracts with the lower end side portion 11a.

  In the jack mechanism, the pressure chamber R3 is expanded by supplying / discharging the fluid pressure to / from the pressure chamber R3 from a single fluid pressure supply / discharge source 100 (see FIG. 1) arranged outside the fork main body. The piston member 12 is moved up and down with respect to the cap member 11, and the upper end position of the suspension spring S is moved up and down.

  Therefore, the cap member 11 has a through hole 11b in the shaft core portion, and this through hole 11b communicates with the pressure chamber R3 in the jack mechanism and through a passage L (see FIG. 1) disposed outside the fork main body. The fluid pressure supply / exhaust source 100 communicates with the above.

  On the other hand, the cap member 11 includes a lower end shaft portion 11c that protrudes downward from the lower end side portion 11a. The upper end of the rod body 4 is screwed under the presence of the lock nut 42.

  Also from this, as described above, in the damper, the upper end portion of the rod body 4 is screwed to the cap member 11 that closes the upper end opening of the vehicle body side tube 1, so that the cylinder body 3 is connected to the wheel side tube. In addition to being coupled to the fork main body, the axial direction as the expansion / contraction direction of the damper coincides with the axial direction as the expansion / contraction direction of the fork main body. It is possible to ensure proper telescopic operation.

  Incidentally, a seal 11d is interposed on the outer periphery of the main body portion in the cap member 11 to ensure liquid tightness with the vehicle body side tube 1.

  Meanwhile, the piston member 12 that defines the pressure chamber R3 between the lower end side portion 11a of the cap member 11 has an upper cylindrical portion 12a that is in sliding contact with the outer periphery of the lower end side portion 11a of the cap member 11, and an upper cylindrical portion. The lower part 12b which connects 12a to an upper end is comprised.

  In the piston member 12, the lower portion 12 b protrudes downward from the lower end side portion 11 a of the cap member 11, and the lower end shaft portion for screwing the upper end portion of the rod body 4 to the shaft core portion. In this state, the upper end of the spacer S1 formed in a cylindrical shape is locked via the spring sheet S2 in this state.

  Incidentally, a seal 11e is interposed on the outer periphery of the lower end side portion 11a of the cap member 11 to ensure liquid tightness with the upper cylindrical portion 12a of the piston member 12, and the lower portion of the piston member 12 A seal 12c is interposed on the inner periphery of 12b to ensure liquid-tightness between the cap member 11 and the lower end shaft portion 11c.

  Therefore, in the jack mechanism formed as described above, when the outer diameter of the piston member 12 is set to be smaller than the inner diameter of the wheel side tube 2 formed of the inner tube, Since the wheel side tube 2 entering the vehicle body side tube 1 can be prevented from interfering with the vehicle body side tube 1, it is not necessary to worry that the drive of the jack mechanism is hindered.

  In the jack mechanism, the outer diameter of the upper cylindrical portion 12a of the piston member 12 is made smaller than the inner diameter of the wheel side tube 2, while the lower end side of the cap member 11 that closes the upper end opening of the vehicle body side tube 1 is used. The pressure chamber R3 defined between the cap member 11 and the piston member 12 is slidably contacted with the outer periphery of the portion 11a. Thus, for example, when the inner diameter of the wheel side tube 2 is the same, the pressure receiving area in the pressure chamber R3 can be increased, and the operating efficiency with respect to the supply pressure can be improved.

  In addition, the jack mechanism is composed of a cap member 11 that closes the upper end opening of the vehicle body side tube 1 and a piston member 12 that is linked to the cap member 11 as compared with the proposal disclosed in Patent Document 1 described above. Therefore, the number of parts can be reduced, and a slight modification to the existing cap member 11 is sufficient.

  On the other hand, the fluid pressure supply / discharge source 100 described above is connected to the pressure chamber R3 of the jack mechanism in each front fork that is paired on the left and right via the respective passages L (see FIGS. 1 and 4). The operation of the fluid pressure supply / exhaust source 100 enables the expansion and contraction drive in the jack mechanism accommodated in each fork main body.

  The fluid pressure supply / discharge source 100 is provided in the present invention, as shown in FIGS. 4 and 5, in a fork bracket B for connecting the fork main body of each pair of front forks to the handle side of the two-wheeled vehicle. In addition to being held, it is possible to supply and discharge the fluid pressure to the jack mechanism described above by driving a driving source 200 described later disposed together with the fork bracket B.

  4 and 5, for convenience, FF indicates a front fork connected to the fork bracket B, SS indicates a steering shaft also connected to the fork bracket B, and the left side is the front wheel side in the motorcycle. Yes, the right side is the rear wheel side of the motorcycle.

  In the present invention, the fork bracket B in which the fluid pressure supply / discharge source 100 is held and a driving source 200 described later is disposed is composed of upper and lower two stages of an upper bracket and an under bracket (not shown). As long as this is the case, the fork bracket B may be either an upper bracket or an under bracket.

  However, when the fork bracket B is composed of an under bracket, the fluid pressure supply / discharge source 100 is positioned between the upper bracket and the under bracket. Therefore, the fork bracket B is defined as the upper bracket. As compared with the case where the fluid pressure supply / discharge source 100 is exposed on the upper bracket, the appearance will be improved.

  1 and 5, the fluid pressure supply / discharge source 100 includes a housing 101 formed in a headed cylinder shape having a fluid chamber R4 communicating with the passage L outside the fork main body, and the housing 101. And a piston 102 which is slidably received and defines the fluid chamber R4.

  In the fluid pressure supply / discharge source 100, when the piston 102 moves forward by the rotation operation of the drive shaft 103 and enters the housing 101, the fluid in the fluid chamber R4 is directed to the pressure chamber R3 in the jack mechanism. Leaked.

  Further, in the fluid pressure supply / discharge source 100, when the above external force is eliminated, that is, the drive shaft 103 is reversed and the piston 102 comes out of the housing 101 and is supplied to the jack mechanism. Return the fluid to flow into the fluid chamber R4.

  Further, in the fluid pressure supply / discharge source 100, the drive shaft 103 is formed in a hexagonal bolt shape, and the cap 105 is fixed to the inner periphery of the opening end of the housing 101 under the presence of the snap ring 104. The shaft core is screwed under a retaining structure (not shown) and the tip is brought into contact with the back surface of the piston 102.

  The fluid used for the fluid pressure supply / discharge source 100 may be, for example, hydraulic oil contained in the fork main body, but in order to reduce the amount of hydraulic oil used in the fork main body, Different oils may be used, or water instead of oil may be used, and even gas may be used. Especially when gas is used as the fluid, the air spring effect is exhibited by the expansion and contraction drive of the jack mechanism. Can be expected.

  Therefore, in the fluid pressure supply / discharge source 100 described above, since the spring force of the suspension spring S in each pair of front forks on the left and right is adjusted, a predetermined spring force adjustment in the suspension spring S is realized as set. The ride comfort of a motorcycle is not impaired.

  That is, in the proposal disclosed in Patent Document 1 described above, the spring force of each suspension spring in the rear cushion unit and the front fork is adjusted at the same time with a pressure portion that is a single pressure source. If the spring load on the rear wheel side is larger than the spring load on the front wheel side, the spring force of the suspension spring is adjusted to balance each spring load. It is expected that the vehicle height will be higher than the side, and there is a problem that the squat phenomenon at the start is likely to occur.

  On the other hand, in the present invention, since the spring force of the suspension spring S in each front fork paired on the left and right in the two-wheeled vehicle is adjusted equally at the same time, the front wheel side of the two-wheeled vehicle has a higher vehicle height than the rear wheel side. Therefore, the squat phenomenon at the start of the motorcycle is made difficult to appear.

  By the way, with respect to the operation of the fluid pressure supply / discharge source 100 described above, according to the present invention, a single drive source 200 shown in FIG. Each spring force in S is adjusted simultaneously.

  In other words, in a two-wheeled vehicle, the front fork that suspends the front wheel is often a pair of left and right, and as long as that is the case, the spring force of the suspension spring S on the front fork is adjusted. If it is not simultaneous, it will be irrational.

  In this respect, in the present invention, since the jack mechanism in each front fork is simultaneously extended and retracted by one drive source 200, the spring force of the suspension spring in the pair of front forks on the left and right can be adjusted simultaneously.

  Whereas the fluid pressure supply / discharge source 100 according to the present invention is formed as described above, the drive source 200 has a rotation source 201 such as a tank motor held by a fork bracket B as shown in FIG. The guide shaft 202 is rotated by the rotation source 201, and the drive shaft 103 is accommodated in a hexagonal hole (not shown) that the guide 202 has inside.

  Therefore, in the drive source 200 formed as described above, by rotating the drive shaft 103, the operation of the fluid pressure supply / discharge source 100, that is, the supply of the fluid pressure to the pressure chamber R3 in the jack mechanism is performed. Allows elimination.

  The driving of the driving source 200 may be performed manually by a rider of the two-wheeled vehicle. For example, detection results from detection means such as various sensors mounted on the two-wheeled vehicle body are processed. Then, it may be based on a so-called automatic operation that is input to the drive source 200.

  In the above description, the front fork has the jack mechanism and the spring force of the suspension spring S can be adjusted. In addition, the front fork also has an actuator that enables control of the damping action. It is also good.

  In this case, the actuator will be disposed at the shaft core portion of the cap member 11 so that the actuator has priority, so that this cap is provided at a portion eccentric from the shaft core of the cap member 11. I will.

  And as described above, the hydraulic shock absorber embodying the present invention is mounted on the front wheel side of the two-wheeled vehicle and is used as a pair of front forks that suspend the front wheel of the two-wheeled vehicle. In view of the intention of the invention, instead of the above, one of the two hydraulic shock absorbers may be a rear cushion unit as disclosed in Patent Document 1 described above. Of course, there is no difference.

It is a longitudinal cross-sectional view which shows the front fork by this invention partially fractured | ruptured. FIG. 2 is a partially enlarged longitudinal sectional view showing a piston portion as a damping portion in a damper built in the front fork of FIG. 1. FIG. 2 is a partially enlarged longitudinal sectional view showing an upper end portion of a vehicle body side tube in the front fork of FIG. 1. It is a fragmentary top view which shows the state by which the fluid pressure supply / discharge source was hold | maintained at the fork bracket connected with the front fork of this invention. FIG. 5 is a longitudinal sectional view showing a state in which a fluid pressure supply / discharge source is held on a fork bracket and a drive source is disposed at a position along line XX in FIG. 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Car body side tube 2 Wheel side tube 3 Cylinder body 4 Rod body 11 Cap member 11a Lower end side part 11b Through-hole 11c Lower end shaft part 12 Piston member 12a Upper cylinder part 12b Lower part 100 Fluid pressure supply / discharge source 101 Housing 102 Piston 103 Drive Shaft 200 Drive source B Fork bracket R3 Pressure chamber R4 Fluid chamber S Suspension spring S1 Spacer

Claims (9)

Adjustment of the spring force in the suspension spring by raising and lowering the upper end position of the suspension spring accommodated in the fork main body composed of the vehicle body side tube and the wheel side tube into the fork main body by the expansion and contraction drive of the jack mechanism of the accommodation. In each pair of left and right front forks that enables the above-mentioned jack mechanism, the above-mentioned jack mechanism communicates with a single fluid pressure supply / discharge source disposed outside the fork main body, and the fluid pressure supply / discharge source operates to expand and contract. On the other hand, the above-described jack mechanism is driven by a driving source that is held by a fork bracket that connects each fork main body to the handle side of the two-wheeled vehicle while driving. A front fork characterized in that fluid pressure can be supplied to and discharged from the front fork. The front member according to claim 1, wherein a cap member that closes an upper end opening of the vehicle body side tube has a through hole communicating with the jack mechanism, and the through hole communicates with the fluid pressure supply / discharge source. fork. The fork main body has a damper in the shaft core portion, the damper has a rod body that can be inserted into and retracted from the cylinder body, and an upper end portion of the rod body is screwed to the cap member. The front fork according to claim 1 or claim 2. The suspension spring is configured such that a lower end of a cylindrical spacer is brought into contact with the upper end while the lower end is held on the wheel side tube side, and the upper end of the spacer is engaged with the jack mechanism. The front fork according to claim 2 or claim 3. The fluid pressure supply / discharge source includes a housing having a fluid chamber communicating with the jack mechanism, and a piston slidably received in the housing to define the fluid chamber. 1, 2, 2, wherein when an external force is input to and released from the housing, the fluid in the fluid chamber can be supplied to and discharged from the jack mechanism. The front fork according to claim 3 or claim 4. The fluid pressure supply / discharge source has a drive shaft connected to the drive source, and fluid pressure can be supplied to and discharged from the jack mechanism by driving the drive shaft. The front fork according to claim 3, claim 4 or claim 5. The jack mechanism includes the cap member and a piston member that is connected to the cap member and defines a pressure chamber that expands and contracts with the cap member, and supplies fluid pressure to the pressure chamber. The pressure chamber is expanded and contracted by exhaust, the piston member is moved up and down with respect to the cap member, and the upper end position of the suspension spring is moved up and down. The front fork according to claim 4, claim 5 or claim 6. The piston member has an upper cylindrical portion that is in sliding contact with the outer periphery of the cap member, and an outer diameter of the upper cylindrical portion is set smaller than an inner diameter of a wheel side tube inserted into the vehicle body side tube. 7. The front fork according to 7. The piston member has a lower portion that is connected to the upper end of the upper cylindrical portion that is in sliding contact with the outer periphery of the cap member, and the lower portion is in sliding contact with the lower end shaft portion of the cap member. The front fork according to claim 8.

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