JPS5841230B2 - Front fork for motorcycles - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in front forks for two-wheeled vehicles.

Conventionally, as shown in Fig. 1, this type of front fork has an inner tube 2 that is connected to the vehicle body and is slidably fitted into an outer tube 1 that is connected to the wheel side. A hollow rod 3 fixed with a bolt γ extends into the inner tube 2 from the bottom of the tube 1, and an auxiliary piston 5 is fixed at the tip end to seal the gap with the inner tube 2. .

On the other hand, at the lower end of the inner tube 2 there is a main piston button 4 which cooperates with the oil hole frame 8 to reduce the impact when the front fork is fully compressed, and which closes the gap between it and the hollow rod 3 when the front fork is extended. A check valve 9 that is open during compression is provided.

The inner tube 2 has a spring 6 interposed between the upper part of the inner tube 2 and the upper end of the hollow rod 3.
In the compression operation in which the oil in the chamber C flows into the outer tube 1 against the pressure, the oil in the chamber C flows into the pressure chamber A for generating damping force through the check valve 9, and the excess oil flows through the hollow hole 10. It is guided to the oil reservoir chamber B via the rod 3.

When the front fork is fully compressed with the inner tube 2 further inserted, the oil in the chamber C is transferred to the inner circumference of the piston 4 and the oil hole frame 8.
By discharging the water through a narrow annular gap with the outer periphery of the pipe, shocks such as bottoming out are alleviated.

In the middle extension operation, oil in the pressure chamber A blocked by the check valve 9 is discharged from the orifice 11 bored in the hollow rod 3, thereby generating a damping force, and when it reaches near the maximum extension end, the orifice 11 is checked. By passing through the valve 9, a hydraulic lock is established with the pressure chamber A, thereby mitigating the impact.

In the conventionally known front fork configured in this way, the inner tube 2 and the outer tube 1 are
The high-pressure oil that has been hydraulically locked by the above may escape through these narrow gaps and act on the oil seal 17, thereby damaging the oil seal 17 and causing problems such as oil leakage.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to prevent the oil seal from being damaged or detached by preventing the high pressure oil generated when the front fork is most compressed from acting on the oil seal.

An embodiment of the present invention will be described below with reference to FIG.

A hollow rod 23 is vertically installed on the outer tube 21 via a bolt 27, an auxiliary piston 25 is fixed at the tip of the hollow rod 23, and a piston 24° installed at the lower end of the inner tube 22 forms a pressure chamber A. is formed.

The inner tube 22 is inserted with a gap d formed between it and the outer tube 21. Therefore, even if the inner surface of the outer tube 21 has a roughness of 11 or has some scratches, for example There is no effect on other functions.

The outer tube 21 has a sliding contact portion 21a whose lower inner surface bulges inward in a tapered shape, and the inner tube 22 It is designed to make sliding contact with the bottom edge of the.

A port 3 bored into the hollow rod 23 allows the oil in the chamber C to flow during compression operation.
0 into the oil reservoir chamber B, and a part of the oil flows into the pressure chamber A through the check valve 29 through the through hole 36 which is opened at the upper part of the main piston 24 of the inner tube 22. When the chamber C is in the hydraulic lock state at maximum compression, the inner surface of the outer tube 21 and the inner tube 22
The high pressure oil flowing from the annular gap to the gap d is guided to the pressure chamber A to prevent high pressure from being applied to the oil seal 17, thereby preventing the oil seal 17 from being damaged or detached.

1. Front forks attached to bicycles, buttons, and small-displacement motorcycles require only a hydraulic damping mechanism to reduce the shock at maximum extension and maximum compression, and reduce the damping force in the middle of the expansion and contraction stroke. In the case of a front fork that does not require the check valve 29, the orifice 31 bored in the inner tube 22 is configured as a hole of a size that does not generate damping force. 36 may be provided in the inner tube 22 so as to directly communicate the pressure chamber A and the gap d.

35 is when the inner tube 22 reaches its maximum extension state;
This is a limit stopper for ensuring a fixed length of fitting with the hollow rod 23.

Therefore, the spring 32 and the orifice 31 are arranged below the limit stopper 35.

In this embodiment, the outer tube 21 is composed of the inner tube 22 and the hollow rod 23 as the strength members of the front fork.
Since there is no need to provide strength by providing a fitting part with the inner tube 22, it is shorter than the conventional one, and simply when the inner tube 22 is at its maximum extension,
Oil seal 3 arranged at the tip of outer tube 21
It is sufficient that the inner tube 7 fits into the inner tube 22 and reaches a length that prevents oil from leaking to the outside.

In the figure, 26 is a buffer spring, 33 is a support bracket,
34 is a dust seal.

Next, the effect will be explained.

When the front fork is compressed, the inner tube 22
enters against the buffer spring 26 and while the port 30 is in communication with the chamber C, the oil in the chamber C flows through the port 30 into the interior of the hollow rod 23 as the main piston 24 moves. The check valve 2 is guided from the through hole 36 to the oil sump chamber B.
9 is opened to flow into the pressure chamber A.

Furthermore, when the inner tube 22 is contracted to the maximum compression, the sliding contact portion 21 between the inner tube 22 and the outer tube 21
a makes contact and holds chamber C in a hydraulically locked state to prevent shocks such as bottoming out.

At this time, the sliding contact portion 21a and the inner tube 22
High pressure oil leaking from the narrow annular gap between the oil seal 37 and the oil seal 37 escapes from the gap d to the pressure chamber A through the through hole 36.
High pressure does not act directly on the oil seal 37.
to prevent damage or detachment.

On the other hand, during the extension operation, the oil in the pressure chamber A is discharged only through the orifice 31, thereby producing a predetermined damping effect.

At the maximum extension, the piston 24 (check valve 29) contacts the limit stopper 35 via the spring 32, and at this time, communication between the orifice 31 and the pressure chamber A is cut off, so the pressure chamber A becomes in a hydraulic lock state. Prevents the front fork from stretching.

As described above, according to the present invention, when the front fork is fully compressed, the high pressure oil in the lowering chamber C is passed through the pressure chamber A through the passage hole 36.
In other words, since the oil is guided directly or indirectly to the oil reservoir chamber B, high pressure does not act on the oil seal 37.
Therefore, it is possible to prevent the oil seal 37 from being damaged or detached, or from leaking oil due to this.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a conventional front fork, and FIG. 2 is a longitudinal sectional view of the front fork of the present invention. 21... Outer tube, A... Pressure chamber, 22.
... Inner tube, B... Oil reservoir chamber, 23... Hollow rod, C... Chamber, 24... Piston, d...
Gap, 25 piston, 29...check valve, 30...
・Port, 36...Through hole, 37...Oil seal.

Claims (1)

[Claims] 1 The inner tube is slidably fitted to the outer tube via an oil seal, a gap is formed between the outer tube and the inner tube, and a hollow rod or the like fixed to the outer tube is attached to the inner periphery of the inner tube. A pressure chamber that is inserted through the piston and contracts between the inner tube and the hollow rod when the front fork is extended, and a sealed chamber that is partitioned between the outer tube and the inner tube when the front fork is fully compressed. A through hole is provided in the inner tube to guide leaked oil from the sealed chamber to the inside of the inner tube via the above-mentioned gap, and a check valve is arranged inside the inner tube in series with this through hole. A front fork for two-wheeled vehicles that is characterized by: