JPS607274Y2 - Front fork of a motorcycle - Google Patents

Description

[Detailed explanation of the invention] When a motorcycle is running, if the brakes are applied suddenly, the rider's weight is applied to the front fork due to inertia, which is extremely compressed, which impairs running stability and makes it difficult to operate the steering wheel. become.

For this reason, some front forks are equipped with a valve mechanism linked to the brake to prevent the steering wheel from sinking as described above, but the mechanism is complicated, the fork has a large external shape, and the price is high. be.

The present invention utilizes Bernoulli's theorem regarding fluids, has an extremely simple structure, does not have the above-mentioned drawbacks, and prevents the steering wheel from sinking when the brakes are applied.

Fig. 1 is a longitudinal sectional view of an embodiment of the present invention, and Fig. 2 is a partially enlarged view showing that the lower part of a fork pipe 2 is slidably fitted into a cylindrical bottom case 1, and the above-mentioned The piston 4 at the upper end of the seat pipe 3 installed at the bottom of the bottom case is fitted into the inside of the fork pipe 2, and an oil seal 5 is provided at the upper end of the bottom case 1. It is filled with oil.

In addition, a vehicle suspension spring 6 is stretched between the piston 4 and the upper part of the fork pipe 2, and an oil lock collar 7 is provided at the lower end of the fork pipe 2, which is opened when the fork pipe descends and is opened when the fork pipe is raised. Check valve S to close
is the provision.

Furthermore, a small oil hole 9 is provided in the upper part of the seat pipe 3, and an oil hole 10 of an appropriate size is formed in the lower part, an oil lock piece 11 is fitted to the lower part, and the seat pipe and the oil lock are secured with bolts 12. Place the piece in the bottom case 1
It is fixed to .

A collar 13 is formed on this oil lock piece 11, and an O-ring 15 made of rubber or the like is fitted into an annular groove 14 provided on the periphery of the collar, and a gap of, for example, 0.5 mm is formed between the O-ring and the inner surface of the bottom case 1. A very small gap 16 is provided.

Also, oil holes 18 and 19 are formed to connect the annular oil chamber 17 formed at the lower part of the collar 13 to the inside of the seat pipe 3.

In the above-mentioned front fork, when the fork pipe 2 descends during normal running, the check valve 8 opens, so oil corresponding to the volume of the fork pipe that has entered the oil passes through the oil holes 9 and 10 and flows into the seat pipe. Flows into the inside of 3.

At the same time, it flows into the oil chamber 17 from the gap 16, and further flows into the oil hole 1.
8, 19 into the pipe, the fork is easily compressed by the relatively small damping force.

Also, when the fork pipe 2 rises, the valve S closes, so
The oil between the seat pipe 3 and the fork pipe 2 flows into the seat pipe 3 through only the small oil hole 9, thereby generating a large damping force and providing good riding comfort.

However, when the brakes are applied while driving at high speed, a large force is applied to the front fork, causing the pipe 2 to descend rapidly.

In such a case, the flow rate of oil passing through the gap 16 between the O-ring 15 and the inner surface of the bottom case 1 becomes extremely high, so the pressure in the gap decreases according to Bernoulli's theorem, and the above-mentioned O
The force of arrow p is applied to the ring to enlarge it.

Therefore, when this force becomes larger than the tightening force due to the elasticity of the O-ring 15, the diameter of the O-ring expands and the gap 16 becomes smaller, so that a large damping force is generated in this portion.

In addition, due to the expansion of the O-ring, high oil pressure is applied to the upper surface and even behind it in the oil chamber between the seat pipe 3 and the bottom case 1. The oil chamber 17 is in close contact with the inner surface of the flange 13, thereby blocking the oil chamber 17 from the oil chamber 17 at the bottom of the collar 13.

Therefore, the oil in the seat pipe 3 flows into the interior of the pipe only through the oil holes 9 and 10, and the damping force increases rapidly.

That is, as shown in FIG. 3, when the descending speed V of the fork pipe 2 exceeds a value vl of, for example, about 0.3 m/s, the damping force F increases rapidly and prevents the pipe from descending. This prevents sinking and allows stable operation.

4, 5, and 6 are longitudinal cross-sectional views of the same portion as in FIG. 2 in other embodiments of the present invention, and FIG. 7 is a cross-sectional view of the portion shown in FIG. In the figure, the upper part of the collar 13 has a small diameter, and in FIG. 5, a plurality of small holes 20 are formed in the upper part of the groove 14.

Furthermore, in the embodiments shown in FIGS. 6 and 7, a plurality of notches 21 are formed in the upper part of the groove 14, and in both cases, a hole is formed between the seat pipe 3 and the bottom case 1 on the upper surface or back surface of the O-ring 15. Since hydraulic pressure is easily applied, the above-mentioned gap 16 is reliably closed and the damping force can be increased.

As described above, the present invention has an extremely simple structure and can prevent the steering wheel of a two-wheeled vehicle from sinking, thereby allowing stable driving.

Furthermore, the outer shape of the front fork does not increase, and good riding comfort is always obtained due to the appropriate damping force characteristics.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is an enlarged view of a part of FIG. 1, FIG. 3 is an example of the characteristic curve of the device of the present invention, FIGS. 4 and 5, 6 is a longitudinal cross-sectional view of the same portion as FIG. 2 in another embodiment of the present invention, and FIG. 7 is a cross-sectional view of the portion shown in FIG. 6. In addition, in the figure, 1 is a bottom case, 2 is a fork pipe, 3 is a seat pipe, 4 is a piston, 13 is a collar,
15 is an O-ring, 16 is a gap, 17 is an oil chamber, 18, 19
is an oil hole.

Claims (1)

[Scope of utility model registration request] A lower part of a fork pipe is slidably fitted into a cylindrical bottom case with a bottom, and a piston at an upper end of a seat pipe installed at the bottom of the bottom case is fitted into the inside of the fork pipe. Filling the inside of the case and fork pipe with oil, fitting an O-ring around the periphery of a collar formed at the bottom of the seat pipe to provide a minute gap between the O-ring and the inner surface of the bottom case, A front fork for a two-wheeled vehicle, further comprising an oil hole that connects an oil chamber formed at the lower part of the brim to the inside of the seat pipe.