JP2008032059A - Front fork - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent nose diving in an inverted front fork incorporating a damper cylinder by increasing the pressure of a gas chamber in conjunction with a brake operation.
SOLUTION: In a front fork 10, an axle side tube 12 is slidably inserted into a vehicle body side tube 11, and a damper cylinder 21 is erected on the bottom of the axle side tube 12 so as to be supported by the vehicle body side tube 11. The body 27 is inserted into the damper cylinder 21, and a part on the upper end side of the piston support body 27 is formed as a hollow pipe 28, around the damper cylinder 21 and the piston support body 27 inside the vehicle body side tube 11 and the axle side tube 12. The oil reservoir chamber 34 and the first gas chamber 35 </ b> A above the oil reservoir chamber 34 are formed, and the second gas chamber 35 </ b> B is formed inside the hollow pipe 28 constituting the piston support 27.
[Selection] Figure 1

Description

  The present invention relates to a front fork such as a motorcycle.

  In Patent Document 1, in an upright front fork of a motorcycle, the pressure in the gas chamber is increased during braking to prevent nose dive, and the increase in pressure in the gas chamber after prevention of nose dive is suppressed. What improved the property is disclosed.

That is, in the front fork of Patent Document 1, the solenoid that has obtained the brake signal retracts the iron core upward, and the flow path that connects the lower chamber B to the upper chamber C is closed by a valve body fixed to the iron core, The pressure of B is raised to prevent nose diving, and when the pressure in the lower chamber B exceeds a predetermined level due to further compression of the front fork, the auxiliary valve body is opened and the pressure in the lower chamber B is blown into the upper chamber C. Thereby, the pressure in the lower chamber B is slightly weaker than before the auxiliary valve body is opened, and as a result, the compression of the front fork becomes smooth and the cushioning property can be secured.
JP 60-252085

  In the inverted front fork of a motorcycle, the nose dive prevention structure of Patent Document 1 cannot be applied as it is. That is, in an inverted front fork in which an axle side tube is slidably inserted into a vehicle body side tube, a damper cylinder is erected at the bottom of the axle side tube, and a piston rod supported by the vehicle body side tube is inserted into the damper cylinder, Two gas chambers cannot be formed in the upper part of the body side tube due to the entry of the axle side tube into the side tube and the arrangement of the piston rod inside the body side tube, resulting in a nose dive prevention structure. I can't.

  An object of the present invention is to prevent a nose dive by increasing the pressure of a gas chamber in conjunction with a brake operation in an inverted front fork incorporating a damper cylinder.

  According to the first aspect of the present invention, the vehicle body side tube and the axle side tube are slidably fitted, an oil reservoir chamber and a gas chamber are provided inside the vehicle body side tube and the axle side tube, and the gas chamber is provided as an oil reservoir chamber. A front fork comprising an upper first gas chamber and a second gas chamber communicating with the first gas chamber, and an open / close valve that closes the communication between the first gas chamber and the second gas chamber in conjunction with the brake operation , The axle side tube is slidably inserted into the vehicle body side tube, a damper cylinder is erected on the bottom of the axle side tube, and the piston support supported by the vehicle body side tube is inserted into the damper cylinder. A part of the upper end side is a hollow pipe, and an oil reservoir chamber and a first gas chamber above the damper cylinder and the piston support body are formed around the damper cylinder and the piston support tube inside the vehicle body side tube and the axle side tube. Structure Inside a hollow pipe which is obtained as by forming a second gas chamber.

  According to a second aspect of the present invention, in the first aspect of the invention, a communication port for the first gas chamber and the second gas chamber is provided at the upper end of the hollow pipe.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the first gas chamber is opened when the first gas chamber reaches a predetermined pressure with the on-off valve closed, and the first gas chamber is opened. Is provided with a blow valve communicating with the.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, the flow from the second gas chamber to the oil reservoir or the first gas chamber is allowed at the bottom of the second gas chamber. A check valve is provided.

(Claim 1)
(a) In the front fork, a part of the upper end side of the piston support body is a hollow pipe, and the oil reservoir chamber and the first upper part of the oil cylinder are disposed around the damper cylinder and the piston support body inside the vehicle body side tube and the axle side tube. While forming a gas chamber, the 2nd gas chamber was formed in the inside of the hollow pipe which comprises a piston support body. Therefore, the first and second gas chambers can be formed in the inverted front fork incorporating the damper cylinder.

  (b) When the brake is operated, the on-off valve closes the communication port between the first gas chamber and the second gas chamber. As a result, the pressure in the first gas chamber rises to increase the air spring constant, suppress the sinking of the front fork, and prevent nose diving. Riding comfort during normal driving is not deteriorated.

(Claim 2)
(c) Since the communication port of the first gas chamber and the second gas chamber is provided at the upper end of the hollow pipe, the oil in the oil reservoir chamber that moves up and down by the expansion and contraction of the front fork passes through the first gas chamber during normal travel. It is difficult to enter the second gas chamber from the communication port. Oil that enters the communication port throttles the communication port to generate a damping force, which deteriorates the riding comfort during normal driving. In addition, the oil that has entered from the communication port changes the volume of the second gas chamber and deteriorates the riding comfort during normal running, and the effect of preventing nose dive by a desired air spring cannot be obtained.

  (d) Since the communication port of the first gas chamber and the second gas chamber is provided at the upper end of the hollow pipe, the on-off valve can be placed on the upper end of the vehicle body side tube, and can be opened and closed by a solenoid installed at the upper end of the vehicle body side tube Valves can be connected directly.

(Claim 3)
(e) When the front fork is further compressed after the above (b) and the pressure in the first gas chamber becomes equal to or higher than a predetermined value, the blow valve is opened to blow the air in the first gas chamber into the second gas chamber. Suppresses the pressure increase in the gas chamber. As a result, the front fork has a gentle rise in the air spring during the compression stroke, and cushioning is improved. Riding comfort in the second half of the compression stroke is not deteriorated.

(Claim 4)
(f) When the front fork is compressed, the check valve is closed by increasing the oil pressure in the oil reservoir. When the front fork starts to extend after the brake is actuated, the first gas chamber expands. At this time, when the on-off valve is still closed, the first gas chamber becomes negative pressure, and the smooth extension operation of the front fork is inhibited. However, in the present invention, since the check valve is opened by the negative pressure of the first gas chamber and the second gas chamber communicates with the first gas chamber, the first gas chamber in the initial stage of the extension operation after the brake operation is performed. Eliminate the negative pressure to make the extension operation smooth. The oil that has entered the second gas chamber also returns to the oil reservoir chamber when the check valve is opened.

  1 is a sectional view showing a front fork, FIG. 2 is an enlarged sectional view of the lower portion of the front fork, FIG. 3 is an enlarged sectional view of the lower portion of the front fork, FIG. 4 is an enlarged sectional view of the upper portion of the front fork, and FIG. FIG.

  As shown in FIGS. 1 to 5, the front fork 10 is inverted by fitting a vehicle body side outer tube (vehicle body side tube) 11 to an axle side inner tube (axle side tube) 12 slidably. A suspension spring 13 is interposed between the tubes 11 and 12 and the single cylinder damper 14 is installed upright.

  A bush 15, an oil seal 16, and a dust seal 17 that are in sliding contact with the outer peripheral portion of the inner tube 12 are fitted to the inner peripheral portion of the lower end of the outer tube 11, and the inner peripheral portion of the outer tube 11 is attached to the upper peripheral portion of the inner tube 12. A bush 18 that comes into sliding contact is fitted.

  The outer tube 11 is supported on the vehicle body side via an upper bracket 19A and a lower bracket 19B, and the inner tube 12 is screwed to the axle bracket 20 and abutted against the axle bracket 20 via a sealing member 20A. The inner tube 12 is coupled to the axle via the axle bracket 20.

  At the bottom of the inner tube 12, the lower end of the damper cylinder 21 of the damper 14 is attached and stands upright. At this time, the damper cylinder 21 is fixed and held as described later by a bottom bolt 24 engaged with the axle bracket 20 from the outside via a bottom piece 51 described later.

  A large cylindrical portion 25A of the cap 25 is liquid-tightly inserted and screwed into the upper end portion of the outer tube 11 via an O-ring 26, and a piston is connected to the small cylindrical portion 25B following the large cylindrical portion 25A of the cap 25. A support 27 is screwed. The piston support 27 includes a hollow pipe 28 on the upper end side that is screwed to the small cylindrical portion 25 </ b> B, and a piston rod 29 on the lower end side that is coupled to the hollow pipe 28 via a connector 30. The lower end portion of the hollow pipe 28 is screwed to the connection tool 30, and the upper end portion of the piston rod 29 is screwed to the connection tool 30 and is locked by the lock nut 30 </ b> A. The hollow pipe 28 has a larger diameter than the piston rod 29. The lower end of the piston rod 29 is inserted into the damper cylinder 21.

  An oil lock collar 31 is screwed and fixed to the inner periphery of the upper end of the damper cylinder 21 inside the inner tube 12, and a spring receiver 32 is provided on the upper end of the oil lock collar 31. On the other hand, a spring receiver 33 formed by a stepped surface is provided on the outer periphery of the connecting tool 30 described above. The aforementioned suspension spring 13 is interposed between the spring receiver 32 and the spring receiver 33.

  Inside the outer tube 11 and the inner tube 12, an oil reservoir chamber 34 and a gas chamber 35 are provided on the outer peripheral portion of the damper 14, and the gas confined in the gas chamber 35 constitutes a gas spring. The hydraulic oil in the oil reservoir 34 adjusts the air spring constant of the gas chamber 35, lubricates the sliding contact bushes 15 and 18 of the outer tube 11 and the inner tube 12, and wets the oil seal 16 at the lower end of the inner tube 12. Contribute. And the elastic force of these suspension spring 13 and gas spring absorbs the impact force which a vehicle receives from a road surface.

  The damper 14 includes a piston valve device (extension-side damping force generation device) 40 and a bottom valve device (compression-side damping force generation device) 50. The damper 14 suppresses the expansion and contraction vibration of the outer tube 11 and the inner tube 12 due to the absorption of the impact force by the suspension spring 13 and the gas spring by the damping force generated by the piston valve device 40 and the bottom valve device 50.

  A rod guide 36 which is the lower end portion of the oil lock collar 31 is screwed and fixed to the upper end opening of the damper cylinder 21, and a bush 37 for slidingly guiding the piston rod 29 is press-fitted into the rod guide 36.

  A spring stopper 38A is fixed immediately below the rod guide 36 on the inner periphery of the damper cylinder 21, and the spring stopper 38A is compressed with a piston holder 41 (to be described later) when fully extended to rebound. 38 is held.

  Further, an oil lock piece 39 is held on the outer periphery of the piston rod 29 by a retaining ring 39A, and this oil lock piece 39 is caused to enter the oil lock collar 31 at the time of the most compression to perform a buffering action at the time of the most compression.

Hereinafter, the damping mechanism of the front fork 10 will be described.
(Piston valve device 40)
In the piston valve device 40, a piston holder 41 is mounted on the tip of the piston rod 29, and a piston 42 and a valve stopper 41C are mounted by a nut 41A and a valve stopper 41B that are screwed onto the piston holder 41. The piston 42 slidably contacts the inside of the damper cylinder 21 and divides the inside of the damper cylinder 21 into a piston side oil chamber 43A in which the piston rod 29 is not accommodated and a rod side oil chamber 43B in which the piston rod 29 is accommodated. The piston 42 includes an expansion side valve 44A, and includes an expansion side flow path 44 that enables communication between the piston side oil chamber 43A and the rod side oil chamber 43B, and a pressure side valve (check valve) 45A, and includes a piston side oil chamber 43A. And a pressure-side flow path 45 (not shown) that enables the rod-side oil chamber 43B to communicate with each other.

  Further, the piston valve device 40 includes a bypass path 46 that connects the piston-side oil chamber 43 </ b> A and the rod-side oil chamber 43 </ b> B in the piston holder 41, and an orifice 47 in the bypass path 46.

  Therefore, when the front fork 10 is compressed, when the relative speed between the damper cylinder 21 and the piston rod 29 is low, the oil in the piston-side oil chamber 43A is guided to the rod-side oil chamber 43B through the orifice 47 of the bypass passage 46, During this time, the damping resistance by the orifice 47 generates a compression side damping force.

  When the front fork 10 is compressed and the relative speed between the damper cylinder 21 and the piston rod 29 is medium to high, the oil in the piston-side oil chamber 43A passes through the pressure-side flow path 45 and opens the pressure-side valve 45A to open the rod-side oil chamber. 43B.

  Further, when the front fork 10 is extended, when the relative speed between the damper cylinder 21 and the piston rod 29 is low, the oil in the rod side oil chamber 43B is guided to the piston side oil chamber 43A through the orifice 47 of the bypass passage 46, During this time, the expansion side damping force is generated by the restriction of the orifice 47.

  Further, when the front fork 10 is extended and the relative speed between the damper cylinder 21 and the piston rod 29 is medium to high, the oil in the rod side oil chamber 43B passes through the extension side passage 44 to bend and deform the extension side valve 44A. It is guided to the piston side oil chamber 43A and generates an extension side damping force.

(Bottom valve device 50)
In the bottom valve device 50, a pressure side valve 56A, a valve housing 53, and a valve stopper 54 are held by a bolt 52 on a bottom piece 51 to which the damper cylinder 21 is fixed by a retaining ring 51A. The valve stopper 54 holds an extension side valve (check valve) 57A and a spring 57B between the valve housing 53 and the valve stopper 53. The valve housing 53 is in liquid-tight contact with the middle portion of the damper cylinder 21 and forms a bottom valve chamber 55 below the piston-side oil chamber 43A. The valve housing 53 includes a pressure-side flow path 56 that enables communication between the piston-side oil chamber 43A including the pressure-side valve 56A and the bottom valve chamber 55, and an extension-side valve (check valve) 57A. An extension-side flow channel 57 (not shown) that can communicate with the bottom valve chamber 55 is provided. The bottom valve chamber 55 can communicate with an oil reservoir 34 provided outside the damper cylinder 21 by an oil passage 58 provided on the wall surface of the damper cylinder 21.

  Therefore, when the front fork 10 is compressed, the oil corresponding to the volume of the piston rod 29 that has entered the damper cylinder 21 flows from the piston-side oil chamber 43A to the pressure-side flow path 56, the bottom valve chamber 55, and the wall surface of the damper cylinder 21. The oil is discharged to the oil reservoir chamber 34 through the passage 58. At this time, the oil passing through the pressure side flow passage 56 from the piston side oil chamber 43A bends and deforms the pressure side valve 56A and is guided to the bottom valve chamber 55 to generate a pressure side damping force.

  When the front fork 10 is extended, the oil corresponding to the retraction volume of the piston rod 29 that retreats from the damper cylinder 21 is recirculated from the oil reservoir chamber 34 to the piston side oil chamber 43A through the bottom valve chamber 55 and the expansion side flow passage 57. The

Accordingly, the front fork 10 performs a damping action as follows.
(When compressed)
When the front fork 10 is compressed, in the bottom valve device 50, the pressure side damping force is generated by the oil flowing through the pressure side valve 56A of the valve housing 53, and the piston valve device 40 generates almost no damping force.

(When stretched)
When the front fork 10 is extended, in the piston valve device 40, the expansion side damping force is generated by the oil flowing through the expansion side valve 44A or the orifice 47 of the piston 42, and the bottom valve device 50 generates almost no damping force.

  The damping force on the compression side and the extension side suppresses the stretching vibration of the front fork 10.

However, the front fork 10 has a nose dive prevention structure as follows.
As described above, in the front fork 10, a part of the upper end side of the piston support 27 is formed as the hollow pipe 28. Further, the front fork 10 divides the gas chamber 35 described above into a first gas chamber 35A above the oil reservoir chamber 34 and a second gas chamber 35B communicating with the first gas chamber 35A. Specifically, inside the outer tube 11 and the inner tube 12, an oil reservoir chamber 34 and a first gas chamber 35 </ b> A above the damper cylinder 21 and the piston support 27 are formed, and the piston support 27 is A second gas chamber 35B was formed inside the hollow pipe 28 to be configured.

  At this time, the upper partition wall member 61 that continues to the small cylindrical portion 25B of the cap 25 via the neck portion 25C is inserted into the inner periphery of the upper end side of the hollow pipe 28 via the O-ring 61A. A lower partition wall member 62 fixed to the upper end surface by a bolt 63 is inserted into the inner periphery of the lower end side of the hollow pipe 28 via an O-ring 62A, and the upper partition wall member 61 and the lower partition wall member 62 are inserted into the hollow pipe 28. The partitioned second gas chamber 35B is formed.

  Further, a hole-like communication port 64 is provided at the upper end portion of the hollow pipe 28, and a horizontal hole-like communication port 65 is provided in the radial direction of the neck portion 25 C of the cap 25, so that the neck portion 25 C of the cap 25 and the upper partition wall member 61 A longitudinal hole-shaped communication port 66 where the communication port 65 intersects is provided at the center. The first gas chamber 35A communicates with the second gas chamber 35B via the communication port 64 of the hollow pipe 28, the annular gap around the neck portion 25C of the cap 25, and the communication ports 65 and 66.

  The front fork 10 is provided with an on-off valve 70 that closes the communication between the first gas chamber 35A and the second gas chamber 35B in conjunction with the brake operation. A rod-like valve element 71 of the on-off valve 70 includes a valve housing 72 that is inserted and screwed into the center of the large cylindrical portion 25A of the cap 25 via an O-ring 72A, and the center of the small cylindrical portion 25B of the cap 25. It is inserted into a bush 73 inserted into the part through a O-ring 71A so as to be movable in a fluid-tight manner.

  The valve element 71 of the on-off valve 70 is pushed by the plunger 74A of the solenoid 74 when the solenoid 74 installed on the upper end surface of the cap 25 is turned on, and is brought into close contact with the valve seat 66A of the communication port 66 and the first gas chamber 35A. The communication of the second gas chamber 35B is closed. When the solenoid 74 is turned off, the valve element 71 of the on-off valve 70 is lifted by a restoring spring 75 interposed between the upper end surface of the bush 73 and is separated from the valve seat 66A of the communication port 66, and the first gas chamber. 35A communicates with the second gas chamber 35B.

  The front fork 10 opens when the first gas chamber 35A reaches a predetermined pressure in a state where the on-off valve 70 closes communication between the first gas chamber 35A and the second gas chamber 35B, and opens the first gas chamber 35A. A blow valve 80 communicating with the second gas chamber 35B is provided. The perforated cup-shaped valve body 81 of the blow valve 80 is pressed against the end face of the upper partition wall member 61 by a valve spring 84 backed up by a spring receiver 83 held by a retaining ring 82 provided inside the hollow pipe 28. The blow passages 85 provided at a plurality of positions around the center of the partition wall member 61 are closed. At this time, the central hole 81 </ b> A of the valve body 81 corresponds to the communication port 66 at the center of the upper partition wall member 61, and the valve body 81 does not block the communication port 66. When the pressure in the first gas chamber 35 </ b> A resists the urging force of the valve spring 84, the valve body 81 of the blow valve 80 is separated from the end face of the upper partition member 61 and opens the blow passage 85.

  The front fork 10 has a check valve that allows the flow of air and oil from the second gas chamber 35B to the oil reservoir 34 or the first gas chamber 35A to the lower partition wall member 62 constituting the bottom of the second gas chamber 35B. 90 is provided. An annular plate-like valve element 91 of the check valve 90 can move up and down along the outer periphery of the collar 92 held between the connecting tool 30 and the lower partition wall member 62 around the bolt 63 described above. The oil pressure in the oil reservoir chamber 34 during compression of the front fork 10 extends from the hole-like communication port 93 provided at the lower end of the hollow pipe 28 between the connector 30 and the lower partition wall member 62, and the valve body 91 is lowered by this oil pressure. Pressed by the lower end surface of the partition wall member 62, the communication paths 94 provided at a plurality of positions around the center of the lower partition wall member 62 are closed. When the front fork 10 starts to extend after the brake is actuated and the first gas chamber 35A expands and the first gas chamber 35A becomes negative pressure, the valve body 91 is peeled off from the lower end surface of the lower partition wall member 62 by this negative pressure. The communication path 94 is opened to allow the flow of air and oil from the second gas chamber 35B to the oil reservoir chamber 34 or the first gas chamber 35A.

  Note that the oil level of the oil reservoir 34 is in the vicinity of the lower partition member 62 during normal travel of the front fork 10.

According to the present embodiment, the following operational effects can be obtained.
(a) In the front fork 10, a part of the upper end side of the piston support 27 is formed as a hollow pipe 28, and the oil reservoir chamber 34 is disposed around the damper cylinder 21 and the piston support 27 inside the outer tube 11 and the inner tube 12. The first gas chamber 35 </ b> A at the upper portion thereof is formed, and the second gas chamber 35 </ b> B is formed inside the hollow pipe 28 constituting the piston support 27. Therefore, the first and second gas chambers 35A and 35B can be formed in the inverted front fork 10 incorporating the damper cylinder 21.

  (b) When the brake is operated, the on-off valve 70 closes the communication port 66 of the first gas chamber 35A and the second gas chamber 35B. As a result, the pressure in the first gas chamber 35A increases to increase the air spring constant, suppress the sinking of the front fork 10, and prevent nose diving. Riding comfort during normal driving is not deteriorated.

  (c) Since the communication port 64 of the first gas chamber 35A and the second gas chamber 35B is provided at the upper end of the hollow pipe 28, the oil in the oil reservoir chamber 34 that moves up and down by the expansion and contraction of the front fork 10 is It is difficult to enter the second gas chamber 35B from the communication port 64 through the first gas chamber 35A. The oil that enters the communication port 64 squeezes the communication port 64 to generate a damping force, thereby deteriorating riding comfort during normal driving. In addition, the oil that has entered from the communication port 64 changes the volume of the second gas chamber 35B and deteriorates the riding comfort during normal traveling, and the effect of preventing a nose dive by a desired air spring cannot be obtained.

  (d) Since the communication port 64 of the first gas chamber 35 </ b> A and the second gas chamber 35 </ b> B is provided at the upper end portion of the hollow pipe 28, the on-off valve 70 can be disposed on the upper end side of the outer tube 11. The on-off valve 70 can be directly connected to the installed solenoid 74.

  (e) When the front fork 10 is further compressed after the above (b) and the pressure in the first gas chamber 35A becomes equal to or higher than a predetermined value, the blow valve 80 is opened, and the air in the first gas chamber 35A is transferred to the second gas chamber 35B. Blows to suppress the pressure rise in the first gas chamber 35A. As a result, the front fork 10 has a gentle rise in the air spring during the compression stroke, and the cushioning property is improved. Riding comfort in the second half of the compression stroke is not deteriorated.

  (f) The check valve 90 is closed by the increase of the oil pressure in the oil reservoir chamber 34 when the front fork 10 is compressed. When the front fork 10 starts to extend after the brake is actuated, the first gas chamber 35A expands. At this time, when the on-off valve 70 is still closed, the first gas chamber 35A becomes negative pressure, and the smooth extension operation of the front fork 10 is hindered. However, in the present invention, the check valve 90 is opened by the negative pressure of the first gas chamber 35A, and the second gas chamber 35B communicates with the first gas chamber 35A. The negative pressure in one gas chamber 35A is eliminated, and the extension operation is smoothed. The oil that has entered the second gas chamber 35B also returns to the oil reservoir chamber 34 when the check valve 90 is opened.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and even if there is a design change or the like without departing from the gist of the present invention. It is included in the present invention.

FIG. 1 is a sectional view showing a front fork. FIG. 2 is an enlarged sectional view of the lower portion of the front fork. FIG. 3 is an enlarged cross-sectional view of an intermediate lower portion of the front fork. FIG. 4 is an enlarged cross-sectional view of the middle upper part of the front fork. FIG. 5 is an enlarged cross-sectional view of the upper portion of the front fork.

Explanation of symbols

10 Front fork 11 Outer tube (vehicle body side tube)
12 Inner tube (Axle tube)
21 damper cylinder 27 piston support 28 hollow pipe 34 oil reservoir 35 gas chamber 35A first gas chamber 35B second gas chamber 64 communication port 70 on-off valve 80 blow valve 90 check valve

Claims (4)

The vehicle body side tube and the axle side tube are slidably fitted, and an oil reservoir chamber and a gas chamber are provided inside the vehicle body side tube and the axle side tube,
An on-off valve that divides the gas chamber into a first gas chamber above the oil reservoir and a second gas chamber that communicates with the first gas chamber, and closes the communication between the first gas chamber and the second gas chamber in conjunction with the brake operation. In the front fork with
Insert the axle side tube slidably into the vehicle body side tube, install the damper cylinder upright on the bottom of the axle side tube, insert the piston support supported by the body side tube into the damper cylinder, and the upper end side of the piston support body A part of the hollow pipe,
Inside the vehicle body side tube and the axle side tube, an oil reservoir chamber and a first gas chamber above it are formed around the damper cylinder and the piston support, and a second gas is formed inside the hollow pipe constituting the piston support. A front fork characterized by forming a chamber.   The front fork according to claim 1, wherein a communication port of the first gas chamber and the second gas chamber is provided at an upper end portion of the hollow pipe.   3. The front according to claim 1, further comprising a blow valve that opens when the first gas chamber reaches a predetermined pressure with the on-off valve closed, and communicates the first gas chamber with the second gas chamber. fork.   The front fork according to any one of claims 1 to 3, wherein a check valve that allows a flow from the second gas chamber to the oil reservoir chamber or the first gas chamber is provided at a bottom portion of the second gas chamber.

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