JPS595206Y2 - front fork - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a front fork provided with means for preventing air from entering the pressure chamber for generating damping force during the extension stroke.

A conventionally known front fork is shown in FIG. 2.

This conventional front fork is provided with a check valve 2 on its piston body 1 to guide oil in a pressure chamber 3 into a pressure chamber 4 during a compression stroke of the front fork.

When the front fork is extended, oil in the oil tank 5 is sucked into the pressure chamber 3 via the hollow vibro and the orifice 7.

As described above, when the front fork is extended, the oil in the oil tank 5 is sucked into the pressure chamber 3, but air is mixed into the oil sucked into the pressure chamber 3, especially in the high-speed extension speed range of the front fork.

That is, in the process of flowing from the oil tank 5 to the pressure chamber 3, it has to pass through the small-diameter hollow vibro and the orifice 7, so the flow rate inside the hollow vibro becomes extremely high in the above-mentioned high-speed expansion speed range.

Therefore, a swirling flow occurs inside the hollow vibro, but
Since the air in the oil tank 5 is mixed in this swirling flow, this air flows into the pressure chamber 3.

In this way, when the oil mixed with air flows into the pressure chamber 3 during the extension stroke of the front fork, the next stroke,
In other words, during the compression stroke, the oil mixed with the air,
It will flow into the pressure chamber 4.

When the above oil flows into the pressure chamber 4, the damping force during the extension stroke becomes unstable.

As a result, the desired damping force characteristics cannot be obtained, and the riding comfort is significantly impaired.

The purpose of this invention is to provide a front fork that does not affect the damping force characteristics during the extension stroke, even if oil mixed with air is sucked in from the oil tank during the extension stroke, especially in the high extension speed range. Make it.

This will be explained below with reference to the illustrated embodiment.

An inner tube 12 connected to the vehicle body side is slidably inserted into an outer tube 11 connected to the wheel side, and a piston body 13 is provided at the lower end of the inner tube 12.

A hollow pipe 14 is provided at the bottom of the outer tube 11.
At the same time, an auxiliary piston 15 formed at the upper end of the hollow pipe 14 is made to face inside the inner tube 12.

The inner diameter of the piston body 13 is the same as that of the hollow pipe 1.
4, and maintains a slight gap between the piston body 13 and the hollow pipe 14, and an annular groove 16 is formed on the inner circumference thereof.

In this annular groove 16, a ring-shaped closing member 17 is fitted into the hollow pipe 14 in an oil-tight and slidable manner and maintains a required gap between it and the bottom surface of the annular groove 16. It is disposed so as to be vertically movable within the groove 16.

Therefore, the closing member 17 is displaced according to the pressure difference between the pressure chambers 18 or 19 divided by the piston body 13, and no matter whether the closing member 17 is in the upper or lower position, the pressure chambers 18 and 19 are This is to cut off the distribution of

In this way, the purpose of providing the closing member 17 on the piston body 13 is to integrate the piston body and attach it to the hollow pipe 14.
If the hollow pipe 14 is in oil-tight contact with the piston body, and if the hollow pipe 14 is even slightly inclined, the piston body and the hollow pipe 14 may come into uneven contact, which may impede the vertical movement of the piston body. This is to prevent such things.

That is, since the closing member 17 is located within the annular groove 16 and has some leeway in the radial direction, even if the hollow pipe 14 is slightly inclined, it will not be affected in any way.

The auxiliary piston 15 has an outer diameter slightly smaller than the inner diameter of the inner tube 12 to form a gap 20 therebetween, and an annular groove 21 on its outer periphery.

Inside the annular groove 21, the outer periphery is connected to the inner tube 12.
A ring-shaped check valve 22 that is oil-tight and slidable is disposed within the annular groove 21 so as to be vertically movable.

The ring-shaped check valve 22 has an inner circumference and an annular groove 2.
A gap 23 is formed between the bottom surface and the bottom surface, and notches 24 are formed at required locations on the bottom surface.

During the compression stroke in which the inner tube 12 descends, the pressure inside the pressure chamber 19 becomes lower than the pressure in the oil tank 25;
As the ring-shaped check valve 22 follows the inner tube 12, the check valve 22 is pressed against the lower side of the annular groove 21.

Therefore, the pressure chamber 19 and the oil tank 25 communicate with each other via the gap 20.23 and the notch 24.

Also, during the extension stroke when the inner tube 12 rises,
As the pressure in the pressure chamber 19 increases, the ring-shaped check valve 22 is pressed against the upper side of the annular groove 21, and the pressure in the pressure chamber 19 increases.
This is to cut off communication between the oil tank 25 and the oil tank 25.

In addition, by providing the ring-shaped check valve as described above, even if the hollow pipe is slightly tilted, the auxiliary piston will not come into uneven contact with the inner tube, similar to the screw I/N body described above. .

During the compression stroke of the front fork, the pressure in the pressure chamber 18 increases, and the orifice 26 generates a damping force on the compression side.

At this time, since the ring-shaped check valve 22 is open, the oil in the oil tank 25 flows into the pressure chamber 19, but air does not mix with this flowing oil.

Next, during the extension stroke, the ring-shaped check valve 22 closes,
As the pressure inside the pressure chamber 19 increases, the orifice 2
7 generates a damping force.

At this time, oil is supplied from the oil tank 25 to the pressure chamber 18 via the hollow pipe 14 and the orifice 26, but some air is mixed into this oil.

However, since this air-mixed oil does not flow into the pressure chamber 19, it does not affect the damping force at the time of extension.

In other words, even though the damping force characteristics during compression are not necessarily constant, if they are kept constant during extension,
It does not adversely affect riding comfort, and therefore, some amount of air is allowed to enter the pressure chamber 18.

In addition, at the time of maximum extension, the closing member 17 closes the orifice 27, creating an oil lock.

As is clear from the above explanation, the structure of this invention is such that an inner tube with a piston body at its lower end is slidably inserted into an outer tube, and the upper end of a hollow pipe whose lower end is fixed to the bottom of the outer tube. By providing an auxiliary piston in the inner tube and facing the inner tube, a pressure chamber is formed between the auxiliary piston and the piston body, and this pressure chamber is inserted into the hollow pipe through a predetermined orifice. In the front fork that communicates with
A concave groove is formed around the auxiliary piston, and a ring-shaped check valve that is movable up and down with respect to the concave groove is provided. The feature is that only the flow to the pressure chamber formed between the two is allowed.

With the above configuration, even if air is mixed into the oil sucked into the pressure chamber via the hollow pipe during the extension stroke of the front fork, it will have an adverse effect on the damping force characteristics during the extension stroke. Not affected.

Since the damping force characteristics are stabilized in this way, the riding comfort is also improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of this invention, and FIG. 2 is a sectional view showing a conventional front fork. 11... Outer tube, 12...
Inner tube, 13... Piston body, 14
...Hollow pipe, 15 ... Auxiliary piston, 16 ... Annular groove, 17 ... Closing member, 1B, i9 ... Pressure chamber , 20...
・Gap, 21... Annular groove, 22...
Ring-shaped check valve, 24... Notch, 25.
...Oil tank.

Claims (1)

[Scope of utility model registration request] An inner tube with a piston body provided at the lower end is slidably inserted into the outer tube, and an auxiliary piston is provided at the upper end of the hollow pipe whose lower end is fixed to the bottom of the outer tube, and this auxiliary piston is inserted facing the inner tube. In the front fork, a pressure chamber is formed between the auxiliary piston and the piston body, and this pressure chamber is communicated with the inside of the hollow pipe through a predetermined orifice. A pressure chamber formed below the body is separated and partitioned by the piston body, and the flow of oil in the pressure chamber is blocked.A groove is formed around the auxiliary piston, and a groove is formed in the groove. A ring-shaped check valve that can freely move up and down is provided, and this check valve is configured to only allow flow from the oil tank in the inner tube to the pressure chamber formed between the auxiliary piston and the piston body. front fork.