JP3463151B2 - Front fork for motorcycle - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a front fork for elastically supporting a front wheel of a motorcycle with respect to a vehicle body.

[0002]

2. Description of the Related Art As this type of front fork, various types such as a direct sliding type and a hydraulic shock absorber built-in type have been widely used conventionally.

For example, FIG. 12 schematically shows an example of a direct sliding type front fork, which is an outer tube 1 for supporting a front wheel of a motorcycle.
On the other hand, the inner tube 2 which is operably linked to the vehicle body side from above is slidably inserted.

A hollow pipe 3 is erected from the lower bottom of the outer tube 1 inside the inner tube 2. The hollow pipe 3 communicates with the inside of the outer tube 1 at the lower part and is provided at the upper end. It comes into sliding contact with the inner peripheral surface of the inner tube 2 through the auxiliary piston 4.

A main piston (not shown) is attached to the lower end of the inner tube 2 so as to face the auxiliary piston 4 on the hollow pipe 3 side, and the main piston slides on the outer peripheral surface of the hollow pipe 3.

Thus, the auxiliary piston 4 and the main piston cooperate with each other to form the inner tube 2 and the hollow pipe 3.
A variable volume chamber 5 that changes its capacity according to the expansion and contraction operation of the front fork, that is, the relative displacement of the outer tube 1 and the inner tube 2 is defined between and.

The variable volume chamber 5 passes through an expansion side damping force generating element (not shown) and a pressure side suction element (not shown) arranged in parallel with the main piston, and also through the inside of the hollow pipe 3 to the auxiliary piston 4. It communicates with the upper oil reservoir 6 in the inner tube 2 partitioned by.

The upper part of the oil reservoir 6 is a gas chamber 7,
A suspension spring 8 is interposed between the oil reservoir chamber 6 and the gas chamber 7 between the inner tube 2 and the auxiliary piston 4, and the suspension spring 8 connects the outer tube 1 and the inner tube 2 to each other. It is elastically supported.

As a result, when the outer tube 1 and the inner tube 2 are compressed due to the relative displacement between the vehicle body and the front wheels of the motorcycle, the hydraulic oil in the outer tube 1 is provided on the main piston of the inner tube 2 on the pressure side. Through the suction element it is sucked into the variable volume chamber 5, which then expands in volume.

Further, in addition to the above, a quantity of hydraulic oil corresponding to the intrusion volume of the inner tube 2 with respect to the outer tube 1 is pushed out of the outer tube 1 through the hollow pipe 3 into the oil reservoir chamber 6 in the inner tube 2. .

On the other hand, when the outer tube 1 and the inner tube 2 are extended, the working oil in the variable volume chamber 5 that reduces the volume is introduced into the outer tube 1 through the expansion side damping force generating element of the main piston. The extension side damping force is generated by the flow resistance of the hydraulic oil that passes through the extension side damping force generating element.

At the same time, the amount of hydraulic oil corresponding to the withdrawal volume of the inner tube 2 with respect to the outer tube 1 is sucked into the outer tube 1 from the oil reservoir 6 through the hollow pipe 3.

On the other hand, the suspension spring 8 is compressed and expanded as the outer tube 1 and the inner tube 2 are compressed and expanded.

At the same time, the inner tube 2
The upper end of the oil container approaches or moves away from the auxiliary piston 4, and the volumes of the oil reservoir chamber 6 and the gas chamber 7 decrease.

As a result, the working oil surface of the oil reservoir 6 moves up and down as the outer tube 1 and the inner tube 2 are compressed and expanded, and the gas chamber 7 is compressed and expanded.

As a result, the suspension action of the front wheels with respect to the vehicle body is elastically performed by the synergistic action of the suspension spring characteristic of the suspension spring 8 that compresses and extends and the gas spring characteristic due to the compression and expansion actions of the gas chamber 7. Be seen.

Therefore, the combined spring characteristic of the front fork as a whole is a combination of the suspension spring characteristic a of the suspension spring 8 and the gas spring characteristic b of the gas chamber 7, as shown by the curve c in FIG. .

The above-mentioned composite spring characteristic c is not limited to the direct sliding type front fork described above,
Basically, there is no change in the built-in hydraulic shock absorber and other types of front forks.

[0019]

However, in such a front fork, the gas spring constant and the suspension spring 8 depending on the volume of the gas chamber 7 are taken into consideration in order to give importance to the riding comfort as a motorcycle. It is common to select a low spring constant of to set soft spring characteristics.

Therefore, not only when sudden braking is applied, the front fork largely compresses due to the increase in front wheel load even during normal braking,
There is a problem that the front of the vehicle body is excessively sunk and the vehicle posture is greatly tilted forward, which deteriorates driving and steering stability.

Therefore, an object of the present invention is to provide a two-wheeled vehicle front fork capable of ensuring both riding comfort as a motorcycle and suppression of changes in vehicle posture.

[0022]

According to the present invention, the above object is to divide the gas chamber above the oil reservoir into two by a partition member, and to divide the partition member into the inside and outside of the partition member. This is achieved by providing an aperture that communicates with.

Further, the oil reservoir chamber is divided into two by the partition member, the inside of the partition member is further divided into an independent oil reservoir chamber and a gas chamber, and the partition member is divided into two parts. This is also achieved by providing a throttle that connects the oil reservoirs inside and outside with each other.

[0024]

In other words, according to the above construction, in the normal operating speed range of the front fork where the throttle provided in the partition member does not exert throttle resistance, the operation of the gas in the gas chamber inside or outside the partition member or the oil reservoir chamber The oil flows back and forth through the squeezer without resistance.

As a result, the gas chambers inside and outside the partition member are expanded and contracted while maintaining the same pressure. Therefore, the front fork is soft and comfortable to ride as in the conventional case. It will expand and contract under the spring characteristics.

On the other hand, as in braking,
In the high-speed operation range of the front fork where the throttle resistance by the throttle is effective, the gas chamber or the oil reservoir inside the partition wall member is cut off from the external gas chamber or the oil reservoir by the action of the throttle. It becomes a state.

Therefore, in this case, the same result as that in which the volume of the gas chamber actually acting is reduced by the volume of the gas chamber in the partition member, and therefore the gas spring constant becomes large and the suspension is used. The combined spring characteristic with the spring is improved, and the front fork is prevented from sinking and the forward leaning posture of the vehicle body is suppressed.

Moreover, in the former construction in which the gas chamber above the oil sump chamber is divided into two by the partition member, in particular, when arranging the diaphragm for communicating the inside and outside of the partition member, the diaphragm is connected to the front fork. If it is configured to be positioned in the hydraulic oil in the oil reservoir over the entire stroke, the forward leaning posture of the vehicle body in the high speed operating range can be more effectively suppressed by utilizing the viscosity of the hydraulic oil.

Further, by constructing the throttle so as to enter the hydraulic oil from the middle of the stroke of the compression operation,
It is possible to suppress the forward leaning posture of the vehicle body while maintaining the ride comfort by keeping the composite spring characteristic relatively low in the normal stroke range and enhancing the composite spring characteristic from the desired position of the compression stroke. .

Further, in these cases, in particular, if a check valve that opens in parallel with the expansion operation of the front fork is provided in parallel with the throttle for the partition wall member, the resistance due to the throttle during the expansion operation of the front fork is increased. Regardless of the size, the pressure of the gas chamber inside and outside the partition member is kept the same, and the resistance action by the above-mentioned throttle is guaranteed from the initial stage of the compression operation.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Here, in order to facilitate the understanding of the present invention, a description will be given in advance by using a principle diagram.

FIG. 1 shows an example in which the present invention is applied to a direct sliding type front fork, and the basic structure of the front fork itself is no different from that of the conventional example described above. Therefore, the description of the configuration and the operation is omitted by giving the same reference numerals to the same parts here.

That is, in FIG. 1, the partition member 9 is arranged above the gas chamber of the conventional example described above, and the partition member 9 is provided on the inner surface of the upper end of the inner tube 2 at the upper end of the suspension spring 8. By pressing, the partition wall member 9 divides the gas chamber into two gas chambers 7a and 7b.

A diaphragm 10 is provided for the partition wall member 9.
And two gas chambers 7a, 7b are provided through the aperture 10.
Communicated with each other.

As a result, the diaphragm 10 provided on the partition wall member 9
In the normal operating speed range of the front fork where C does not exert throttling resistance, the gas in the two gas chambers 7 a and 7 b can freely flow back and forth through the throttle 10.

As a result, the gas chambers 7a and 7b expand and contract while maintaining the same pressure as the working oil surface of the oil reservoir chamber 6 moves up and down by the action of the inner tube 2 entering and leaving.
As can be seen from the above, the composite spring characteristic c of the front fork is
In the same manner as in the conventional case, the vehicle expands and contracts while maintaining a soft spring constant that is comfortable to ride.

On the other hand, when the compression speed of the front fork exceeds the normal speed range and becomes high, such as during braking, the throttle 10 starts to work, and the compression ratio on the gas chamber 7a side is higher than that on the gas chamber 7b side. Becomes larger and the gas spring constant rises.

Therefore, the composite spring characteristic with the suspension spring 8 rises from, for example, c to d as shown in FIG. 2, thereby suppressing forward leaning of the vehicle body.

Further, when the compression speed of the front fork reaches a higher speed by sudden braking, the flow resistance due to the throttle 10 approaches infinity and the gas chamber 7b is shut off, so that only the gas chamber 7a is compressed. This means that the volume of the gas chamber as a whole is reduced by the volume of the gas chamber 7b in the partition member 9.

As a result, the gas spring constant increases and the combined spring characteristic with the suspension spring 8 rises to a higher value e in FIG. 2, whereby the front fork is prevented from sinking and the vehicle body leans forward. Suppress.

In FIG. 3, the throttle 10 provided on the partition wall member 9 is attached to the oil storage chamber 6 over the entire stroke of the front fork.
2 shows an example of a case in which it is positioned in the hydraulic oil.

According to this, the flow resistance by the throttle 10 is further increased by utilizing the viscosity of the hydraulic oil, and the combined spring characteristic c with the suspension spring 8 is further increased as shown in f and g of FIG. Thus, the forward leaning posture of the vehicle body can be suppressed more effectively.

Further, FIG. 5 shows that the hydraulic shock absorber 12 is interposed between the outer tube 1 and the inner tube 2 while keeping the hydraulic shock absorber 12 in an upright state (state in which the piston rod is upward), and An example in which the present invention is applied to an upright type hydraulic shock absorber built-in type front fork in which the inside of the inner tube 2 has an oil reservoir 6 is shown.

In the example of FIG. 5, the throttle 10 provided on the partition wall member 9 is located above the hydraulic oil surface of the oil reservoir 6 in the most extended state of the front fork, and the latter half of the compression stroke is performed. As shown in FIG. 6, the throttle 10 is configured to penetrate into the hydraulic oil in the oil sump chamber 6.

Therefore, according to this, the hydraulic shock absorber 12 performs the expansion and contraction motion together with the expansion and contraction motion of the front fork, and the expansion force or both the expansion side and the compression side damping force is generated by the hydraulic shock absorber 12. To do.

Further, in parallel with the above, since the throttle 10 penetrates into the working oil in the oil reservoir 6 from the latter half of the compression stroke, the gas spring constant in the latter half of the stroke sharply rises at this point. However, the composite spring characteristics c, h and i as shown in FIG. 7 are shown according to the compression speed.

As a result, the composite spring characteristic of the suspension spring 8 in the normal stroke range is kept relatively low to ensure riding comfort, and the composite spring characteristic from the desired position of the compression stroke is enhanced to increase the forward lean of the vehicle body. The posture can be suppressed.

As described above, according to each of the above-mentioned examples, the gas spring constant can be increased corresponding to the compression speed of the front fork, and the composite spring characteristic with the suspension spring can be increased to suppress the forward leaning of the vehicle body. You can understand that.

However, even with these things, the aperture 1
Depending on the setting value of the throttle resistance by 0, the pressure in the gas chamber 7b becomes higher than the pressure in the gas chamber 7a due to the difference in speed between the expansion and compression operations of the front fork, and the composite spring characteristic rises from the initial stage of the compression stroke. There is a fear.

Therefore, in order to prevent this, as shown in each of the above-described examples, a check valve 11 that opens toward the gas chamber 7a side in parallel with the diaphragm 10 is provided to the partition member 9. I should do it.

The above-mentioned matters are not limited to the upright front forks of the direct sliding type and the hydraulic shock absorber built-in type shown in the respective examples, but can be appropriately applied to various types of front forks. It's obvious, not to mention.

FIG. 8 shows that the present invention is actually applied to an inverted front fork F having a built-in hydraulic shock absorber in which the hydraulic shock absorber 12 is kept upright and interposed between the inner tube 2 and the outer tube 1. An example in the case of doing is shown.

That is, the front fork F is an outer tube 1 located above, and an inner tube slidably inserted from the lower end opening of the outer tube 1 into the inside through the bearings 13 and 14 and the seal 15. Two
The hydraulic shock absorber 12 is provided inside the outer tube 1 and the inner tube 2.

The outer tube 1 is steerably attached to the vehicle body side of the motorcycle via a bracket (not shown), and the inner tube 2 is rotatably supported by the front wheel of the motorcycle through an axle bracket 16 that seals the lower end. To do.

The hydraulic shock absorber 12 connects the lower end of the cylinder, which is the main body, to the lower bottom of the inner tube 2, and
By connecting the upper end of the piston rod 17 extending from the cylinder to a cap 18 screwed to the upper end of the outer tube 1, the outer tube 1 and the inner tube 2 are attached while maintaining an upright state.

Between the outer and inner tubes 1 and 2 and the hydraulic shock absorber 12, the gas chamber 7 is left in the upper portion to form the oil reservoir chamber 6 of the hydraulic shock absorber 12, and thus, the front fork F. With the expansion and contraction operation, the hydraulic shock absorber 12 expands and contracts together to generate expansion side and compression side damping forces.

Piston rod 1 in hydraulic shock absorber 12
A partition member 9 is fitted around the outer circumference of the spacer 7 with a spacer 19 sandwiched between it and the cap 18. A suspension spring is provided between the collar portion 9a of the partition member 9 and the upper end of the cylinder of the hydraulic shock absorber 12. 8 is installed.

As a result, the suspension spring 8 pushes the outer tube 1 downward through the cylinder of the hydraulic shock absorber 12 and pushes the inner tube 2 upward through the spacer 19 from the partition member 9 to push the inner tube 2 against the inner tube 1. The tube 2 is elastically supported.

Further, in addition to the above, the spacer 19 keeps the partition member 9 at a predetermined position in the oil reservoir 6 and the gas chamber 7 in the outer tube 1, and in this state, the lower end of the partition member 9 is the front fork. It is arranged such that it is always located in the oil reservoir 6 over the entire stroke of F.

As can be seen from the detailed view of FIG. 9, the lower end of the partition member 9 is closed by a lid 21 screwed with the valve spring receiver 20, and the lid 21 is vertically penetrated through the lid 21. A through hole 22 is provided.

The upper end of the partition wall member 9 is sealed by a seal 23 interposed between it and the piston rod 17, and the lower end is a seal 24 interposed between the valve spring receiver 20 and the piston rod 17. It is hermetically sealed and the partition member 9 divides the gas chamber 7 above the oil reservoir chamber 6 into two gas chambers 7a and 7b.

A check valve 11 is disposed on the outlet side of a through hole 22 penetrating through the lid 21, and a return spring 25 is provided between the check valve 11 and the valve spring receiver 20. It is held on the lower surface of the lid 21 with.

Further, the check valve 11 is provided with a throttle 10, which allows the two gas chambers 7a and 7a to be connected to each other.
b is connected in parallel with each other through the throttle 10 and the chuck valve 11 which opens toward the gas chamber 7a side.

Thus, according to this embodiment, the expansion and compression damping forces are generated by the hydraulic shock absorber 12 as the front fork F expands and contracts, and at the same time the two gas chambers 7a and 7b and the throttle are closed. By the action of 10, the composite spring characteristic similar to the case of the principle diagram of FIG. 3 can be achieved.

Moreover, in this embodiment, for example, the amount of hydraulic oil in the oil reservoir 6 or the length of the spacer 19 is appropriately selected so that the lower end of the partition member is gas over the entire stroke of the front fork F. It can be understood that the synthetic spring characteristics similar to those of the principle diagrams of FIGS. 1 and 5 can be obtained by locating the chamber in the chamber 7a or by intruding into the oil reservoir chamber 6 in the middle of the compression stroke. .

FIG. 10 shows an inverted front fork of the hydraulic shock absorber built-in type in which the hydraulic shock absorber 12 is set upside down in the embodiment of FIG. 8 and is interposed between the inner tube 2 and the outer tube 1. An example in which is applied is shown.

Note that, in FIG. 10, when this is actually applied, since the hydraulic shock absorber 12 is placed upside down in FIG. 8 and the other basic structure does not change at all, so here, As in the case of the examples of FIGS. 1, 3 and 5, the explanation will be given using the principle diagram.

That is, as shown in FIG. 10, in the case where the hydraulic shock absorber 12 is interposed in the front fork while maintaining the inverted state, the thickest cylinder portion of the hydraulic shock absorber 12 is the front fork. Will come up.

Therefore, although the inner diameter of the outer tube 1 is larger than that of the inner tube 2,
The cross-sectional space of the gas chamber 7 between the outer tube 1 and the cylinder portion of the hydraulic shock absorber 12 becomes small.

Therefore, it is impossible to secure a margin for partitioning two gas chambers having a desired volume in this portion.

Therefore, in the example of FIG. 10, a partition member 9 is arranged below the oil reservoir 6 in the inner tube 2, and the free piston 26 is slidably inserted into the partition member 9. The inside of the partition member 9 is divided into an independent oil reservoir chamber 6a and a gas chamber 7c.

Then, the diaphragm 10 is attached to the partition wall member 9.
The oil reservoir chamber 6 in the inner tube 2 and the oil reservoir chamber 6a in the partition member 9 are communicated with each other through the throttle 10, and in this example, the oil reservoir chamber 6 is arranged in parallel with the throttle 10. A check valve 11 is provided which allows only the flow of hydraulic oil from 6a toward the oil sump 6.

As a result, the diaphragm 10 provided on the partition member 9
In the normal compression speed range of the front fork where the throttle valve does not exert throttling resistance, the working oil in the oil reservoir chamber 6 passes through the throttle 10 to the oil reservoir chamber 6a in the partition wall member 9 and the gas chamber 7
The gas of c is compressed and flows freely.

As a result, the front fork performs a compressing operation while increasing the hydraulic oil pressures in the oil reservoir chambers 6 and 6a at the same pressure, and as in each of the previous examples, the compression ratio is low, that is, the riding comfort. The compression operation is performed while maintaining a good and soft spring constant.

On the other hand, when the compression speed of the front fork becomes higher than the normal speed range such as during braking, resistance is started to be generated by the throttle 10 and flows into the oil reservoir 6a in the partition member 9. The amount of oil decreases.

This results in the same result as that the degree of compression of the gas chamber 7c in the partition wall member 9 is reduced and the gas capacity in the front fork is reduced accordingly, and the gas chambers 7 and 7c of the front fork as a whole are reduced. The compression ratio rises, the gas spring constant rises, and the composite spring characteristic with the suspension spring 8 becomes high, suppressing the tendency of the vehicle body to lean forward.

Further, when the compression speed of the front fork reaches a higher speed by sudden braking, the flow resistance due to the throttle 10 approaches infinity and the oil reservoir chamber 6a in the partition member 9 is shut off from the oil reservoir chamber 6. Becomes

As a result, the same result is obtained as if the gas capacity of the front fork were reduced by the volume of the gas chamber 7c in the partition member 9, and the gas spring constant was further increased to combine with the suspension spring 8. The spring characteristics are maximized and the body is prevented from leaning forward significantly.

In FIG. 11, the elastic member 27 containing gas is inserted into the partition member 9 so that the partition member 9 is closed.
2 shows an example of a case where the inside of is divided into an oil reservoir chamber 6a and a gas chamber 7c.

According to this, the compression and expansion actions of the gas chamber 7c associated with the expansion and contraction operation of the front fork are performed under non-friction as compared with the free piston 26. Therefore, the description of FIG. The control of the gas spring constant can be obtained in a more stable state.

Note that the basic operation of the example of FIG. 11 is exactly the same as the example of FIG. 10 described above, and it can be easily understood based on the description of FIG. 10, so the description thereof is omitted here. To do.

[0082]

As described above, according to the first aspect of the invention, the spring characteristic is kept soft when the front fork is expanded and contracted in the normal speed range to secure the riding comfort and to increase the compression speed. Along with this, the throttle acts to increase the gas spring constant by the throttle resistance, and the forward leaning posture of the vehicle body can be suppressed.

According to the invention of claim 2, while maintaining the softness of the spring characteristics when the front fork is expanded and contracted in the normal speed range to secure the riding comfort, the hydraulic oil passing through the throttle as the compression speed increases By utilizing the viscosity, the gas spring constant can be increased, and the forward leaning posture of the vehicle body can be suppressed more effectively.

According to the third aspect of the present invention, while maintaining the softness of the spring characteristic when the front fork expands and contracts in the normal speed range to ensure riding comfort, and the throttle operates from the middle of the stroke as the compression speed increases. By advancing into the oil, the gas spring constant from the desired position of the compression stroke can be increased and the forward leaning posture of the vehicle body can be suppressed.

According to the fourth aspect of the present invention, even if the inverted front fork has a built-in hydraulic shock absorber in which the hydraulic shock absorber is set upside down and is interposed between the inner tube and the outer tube, the normal front fork of the front fork is used. While maintaining the softness of the spring characteristics when expanding and contracting in the speed range to ensure riding comfort, and increasing the gas spring constant by using the viscosity of the hydraulic oil that passes through the throttle as the compression speed increases, the body leans forward Can be effectively suppressed.

[0086]

[0087]

Further, according to the invention of claim 5, the pressure difference between the two gas chambers caused by the difference between the expansion and compression operation speeds of the front fork can be eliminated, and the above respective effects can be reliably exhibited. Of.

[Brief description of drawings]

FIG. 1 is a principle view showing a front fork for a motorcycle according to the present invention.

FIG. 2 is a graph showing a spring characteristic of the front fork.

FIG. 3 is a principle view of a two-wheeled vehicle front fork showing another example of the present invention.

FIG. 4 is a graph showing the spring characteristics of the front fork.

FIG. 5 is a principle diagram of a front fork for a motorcycle showing still another example of the present invention.

FIG. 6 is a principle diagram showing a compression operation state of the front fork.

FIG. 7 is a graph showing the spring characteristics of the front fork.

FIG. 8 is a partially cutaway front view showing a motorcycle front fork according to an embodiment of the present invention.

FIG. 9 is a partial vertical cross-sectional view showing only the main part of the same by half cutting.

FIG. 10 is a principle view of a two-wheeled vehicle front fork showing another example of the present invention.

FIG. 11 is a principle diagram of a two-wheeled vehicle front fork showing a modification example of the above.

FIG. 12 is a principle view showing a conventional front fork for a motorcycle.

FIG. 13 is a graph showing a spring characteristic of the front fork.

[Explanation of symbols]

F front fork 6,6a Oil reservoir 7, 7a, 7b, 7c Gas chamber 9 Partition member 10 aperture 11 check valves 26 Free piston 27 Elastic body containing gas

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) F16F 9/00-9/58 B62K 25/00-27/16

Claims (5)

(57) [Claims] 1. A two-wheeled vehicle characterized in that a gas chamber above an oil reservoir is divided into two by a partition member, and a diaphragm that connects the inside and outside of the partition member is provided to the partition member. Front fork. 2. A gas chamber above the oil sump chamber is divided into two by a partition member, and a diaphragm for communicating the inside and outside of the partition member is provided for the partition member, and the diaphragm is a front fork. A front fork for a motorcycle, which is configured to be located in the hydraulic oil in the oil reservoir over the entire stroke of. 3. A gas stroke above the oil sump chamber is divided into two by a partition member, and a diaphragm for communicating the inside and outside of the partition member is provided for the partition member, and a compression stroke of the front fork. A front fork for a two-wheeled vehicle, wherein the throttle is configured to enter the hydraulic oil in the oil reservoir from the middle thereof. 4. A gas chamber is provided above the oil sump chamber , the oil sump chamber is divided into two by a partition member, and the inside of the partition member is further divided into an independent oil sump chamber and a gas chamber, and A front fork for a motorcycle, wherein the diaphragm member is provided with a throttle for communicating the oil reservoirs inside and outside the partition member with each other. 5. The front fork for a motorcycle according to claim 1, 2, 3 or 4, further comprising a check valve provided in parallel with the diaphragm on the partition wall member so as to open the valve along with the extension operation of the front fork.