JPS6121348Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a front fork of a motorcycle or the like, and particularly to a so-called anti-nose dive type front fork.

When a motorcycle or the like is suddenly braked while traveling at high speed, the rider's weight is added to the steering wheel due to inertia, which causes the vehicle to sink significantly, impairing steering performance and creating an extremely dangerous situation. In order to eliminate this drawback, the applicant previously proposed, in Japanese Patent Application No. 54-112989, a very simple mechanism to prevent the fork from sinking, and to provide a front panel that can maintain a buffering effect against the impact received from the road surface in that state. Suggested fork. The present invention is a further improvement.

FIG. 1 is a partially vertical side view of an embodiment of the present invention, in which the lower part of a fork pipe 1 whose upper end is attached to the handlebar of a motorcycle is slidably fitted inside a bottom case 2, and the bottom The case 2 is filled with oil, and the piston at the upper end of the sheet pipe 3 embedded in the bottom of the case 2 is slidably fitted inside the fork pipe 1 to connect the upper end of the sheet pipe 3 and the upper end of the fork pipe 1. A vehicle suspension spring 4 is stretched between them. The bottom case 2 has a mounting hole 5 formed at its lower end into which a front wheel shaft is fitted, and an oil seal 6 is provided at its upper end. Further, a check valve 7 is provided on the inner periphery of the lower end of the fork pipe 1, and an orifice 8 is formed on the upper peripheral wall of the seat pipe 3. The check valve 7 is as shown in FIGS. 2A and B.
Either oil grooves 7a are provided at n locations (two locations in FIG. 2) at the bottom of the check valve 7, or oil holes 7b penetrating through the check valve 7 in the axial direction are provided at n locations as shown in FIGS. 3A and 3B.
The check valve is provided at two locations (two locations in FIG. 3), and the other shapes are the same as the conventional check valve. FIG. 4 is an enlarged longitudinal cross-sectional view of a part of FIG. The oil lock piece 10 is provided with oil holes 11 and 12, respectively, and the bottom case 2 is formed with an oil passage consisting of oil holes 13, 14 and 15,
A valve seat 16 is slidably fitted into this oil passage.
Further, a spring receiver 19 is slidably fitted to a cylindrical screw 18 screwed onto the bottom case 2 via an O-ring 17, and a spring 20 is stretched between the spring receiver 19 and the screw 18. The spring receiver 1 is attached to the screwed bolt 21.
9 are pressed together, and an O-ring 22 is fitted onto the bolt 21. Further, a plunger 25 fitted with an O-ring 23 and with a sealing material 24 such as rubber attached to the tip is slidably fitted into the oil passage 15, and a spring 26 is inserted between the plunger 25 and the valve seat 16.
A flexible cable 29 connected to the control mechanism of the motorcycle is screwed to a cylindrical screw 28 screwed into the bottom case via an O-ring 27, and its core wire 30 is stretched.
is opposed to the upper end of the plunger 25. Further, an annular check valve 31 is provided at the upper end of the oil lock piece 10 and is slidably fitted into the seat pipe 3, and an oil hole 32 is formed in the lower part of the check valve 31 in the seat pipe 3. be.

Next, at the bottom of the fork pipe 1, the oil chamber between the seat pipe 3 and the bottom case 2 is set to A, and at the top of the check valve 7, the oil chamber between the seat pipe 3 and the fork pipe 1 is set to B, and the seat The oil chamber in the pipe 3 is designated as C, and the conventional operation, that is, the one in which the check valve 7 is normal, will be described first.

(1) Normal contraction stroke In this state, the sealing material 24 is separated from the valve seat 16, so the outside of the seat pipe 3 is connected to the oil passage 1.
3, 15, and 14, and an oil passage consisting of oil holes 12 and 11. Therefore, when the fork pipe 1 moves downward due to uneven road surfaces, the volume of the oil chamber A decreases, and the oil flows through the oil passages 13, 15, 1.
4, and enters the oil chamber C through the oil holes 12 and 11.
On the other hand, when the volume of the oil chamber B increases, the check valve 7 opens to replenish oil.

(2) Normal extension stroke In this case, contrary to the contraction stroke, the volume of the oil chamber B decreases and the check valve 7 closes, so the oil in the oil chamber B enters the oil chamber C via the orifice 8. At this time, a large damping force is generated. On the other hand, when the volume of the oil chamber A increases, the check valve 31 opens and oil is replenished from the oil chamber C.

(3) During control In this state, the plunger 25 is lowered by the core wire 30 interlocking with the brake lever, and the sealing material 24 closes the oil hole in the valve seat 16. Therefore, since oil chamber A and oil chamber C are shut off, the oil in oil chamber A has nowhere to escape, and the handle is prevented from sinking.

In this case, if the wheel runs onto a stone or the like during control, measures are needed to absorb the impact. In this operation, when the oil chamber A is compressed during control, the internal oil pressure increases. When the hydraulic pressure overcomes the pushing force of the spring 20, the valve seat 16 is pushed down and the oil hole in the valve seat 16 is opened, and the oil flows into the oil chamber C and absorbs the shock.

However, at the same time, the check valve 7 opens due to an increase in the oil pressure in the oil chamber A, making it impossible to prevent oil from flowing through the orifice 8. Therefore, the valve seat 16
Since the check valve 7 opens and the oil flows more easily through the orifice 8 than when oil flows through the oil hole, it is possible to effectively prevent the steering wheel from sinking during braking. Must not be.

The present invention eliminates such conventional drawbacks by making the orifice 8 of the seat pipe smaller in cross-sectional area than the conventional one, so that the oil chamber A is closed during braking.
By reducing the amount of oil flowing into the oil chamber C through the orifice 8, and on the other hand, allowing the oil to flow as much as possible through the oil hole in the valve seat 16, it is possible to effectively prevent the steering wheel from sinking during braking. At the same time, the oil groove 7a or oil hole 7b of the check valve 7 prevents the damping force from becoming too large during the normal extension stroke.

In this way, during the normal extension stroke, the oil in the oil chamber B flows through the orifice 8 and the oil groove 7a or oil hole 7b at the bottom of the check valve 7, thereby reducing the damping force.
Occur. If this total damping force is made to be the same as the damping force generated only by the conventional orifice 8, a front fork that is no different from the conventional one during normal running can be obtained. Of course, there is no change in the normal contraction process from the conventional one.

As described in detail above, according to the present invention, the simple structure does not impair ride comfort and has the effect of maintaining more stable steering performance.

[Brief explanation of the drawing]

Fig. 1 is a partially longitudinal side view of an embodiment of the front fork of the present invention, Fig. 2 shows an example of a check valve, A is a plan view, B is a cross-sectional view of Fig. A, and Fig. 3 1 shows another example of a check valve, A is a plan view, B is a cross-sectional view taken from A, and FIG. 4 is an enlarged longitudinal sectional view of a part of FIG. 1. 1...Fork pipe, 2...Bottom case,
3... Seat pipe, 7... Check valve, 7a... Oil groove at the bottom, 7b... Oil hole, 8... Orifice, 1
1, 12... oil hole, 13, 14, 15... oil path,
16... Valve seat, 20... Spring, 24... Seal material, 25... Plunger, 26... Spring, 29
... Flexible cable, 30 ... Core wire.

Claims (1)

[Scope of utility model registration request] A piston of a sheet pipe, which is slidably fitted into the lower part of the fork pipe and planted at the bottom of a bottom case filled with oil, is slidably fitted into the inside of the fork pipe, and An orifice is formed on the upper circumferential wall to communicate the oil chamber in the seat pipe and the oil chamber in the fork pipe, and a check valve that closes only during the extension stroke is disposed on the inner periphery of the lower end of the fork pipe. In a so-called anti-nose type front fork, an oil passage communicating between the inner and outer oil chambers of the seat pipe is formed in the lower side wall of the case, and the oil passage is closed during braking to prevent the vehicle body from sinking. , the cross-sectional area of the orifice of the seat pipe is reduced, and a plurality of oil grooves or oil holes are formed at the bottom of the check valve, so that during the extension stroke of the front fork, the cross-sectional area of the orifice of the check valve is reduced. A front fork for a motorcycle, etc., characterized in that it is configured to generate a damping force via an orifice of the seat pipe.