JPS5841229B2 - front fork - 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 connected to the vehicle body side slidably fitted into an outer tube 1 connected to the wheel side. A hollow rod 3 fixed with a bolt 7 extends into the inner tube 2 from the bottom of the rod 1, and an auxiliary piston 5 is fixedly installed at the tip of the rod 3 to seal the gap with the inner tube 2. There is.

At the lower end of the inner tube 2, there is a main piston 4 that cooperates with an oil hole rod 8 to reduce the impact when the front fork is fully compressed, and a main piston 4 that closes the gap between it and the hollow rod 3 when the front fork is extended. Check valve 9 that opens when
is installed.

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

When the front fork is fully compressed when the inner tube 2 advances further, the oil in the chamber C' is discharged from the narrow annular gap between the inner periphery of the piston 4 and the outer periphery of the oil hole rod 8, thereby alleviating impacts such as bottoming out. are doing.

During the extension operation in which the inner tube 2 withdraws from the outer tube 1, oil in the pressure chamber A' blocked by the check valve 9 is discharged from the orifice 11 bored in the hollow rod 3 as the main piston 4 rises. It generates a damping force.

When the inner tube 2 reaches its maximum extension, the check valve 9 passes through the orifice 11, thereby placing the pressure chamber A' in a hydraulically locked state, and the spring 12 cushions the shock at the maximum extension.

In the conventionally known front fork constructed in this way, the inner tube 2 and the outer tube 1 are made to slide and both act as strength members, so that even when the front fork is fully extended, a constant fit is maintained. Therefore, the outer tube 2 inevitably becomes long.

Therefore, for example, when riding on rough terrain such as motocross,
Although the front fork of a motorcycle requires a long extension/contraction stroke, the distance between the mounting bracket 13 on the vehicle body side and the tip of the outer tube 1 must be at least equal to the extension/contraction stroke. Since the dust seal 14 has the problem of being damaged by hitting the bracket 13, the extension and retraction strokes of front forks whose vehicle height is regulated in advance are limited.

Furthermore, in recent years, as motorcycles have become lighter, the outer tube 1 has often been manufactured from non-ferrous metals such as aluminum alloys, and has become expensive.

Furthermore, if the inner tube 2 and the outer tube 1 made of aluminum alloy are allowed to slide directly, the degree of wear on the outer tube 1 side will be severe, the oil will become contaminated, the viscosity of the oil will decrease, and the sliding part will seize. , oil seal 17
This leads to problems such as damage to the equipment.

The present invention has been proposed in order to eliminate such drawbacks, and the length of the outer tube is shortened by an amount corresponding to the fitting length by using the inner tube and the hollow rod as a strength member, or, To provide a front fork that is capable of reducing the extension and contraction stroke by at least that length, and that further provides a gap between the outer tube and the inner tube to reduce wear on the outer tube and prevent oil contamination. The purpose is to

Embodiments of the present invention will be described below based on FIG. 2.

An inner tube 22 is slidably inserted into the outer tube 21 with a certain gap d, and a hollow rod 23 whose base end is fixed to the outer tube 21 with a bolt 27 is inserted into the inner tube 22. A pressure chamber A is defined by an auxiliary piston 25 fixedly attached to the upper end of the hollow rod 23 and slidingly contacting the inner surface of the inner tube 22, and a check valve 29 provided at the lower end of the inner tube 22.

Further, the main piston 24 disposed at the lower end of the inner tube 22 is in sliding contact with the circumferential surface of the hollow rod 23, and the lower surface of the piston 24, the button of the outer tube 21, and the hollow rod 2
3 to form a compartment C.

The inner tube 22 and the hollow rod 23 are in sliding contact via a main piston 24 button and an auxiliary piston 25 provided at their fitting ends, and both support the load acting on the front fork as a strength member.

An oil seal 37 is inserted to seal the gap d between the outer tube 21 and the inner tube 22, while the outer The lower inner periphery of the tube 21 bulges inward in a tapered shape and comes into sliding contact with the inner tube 22.

A hole 30 is provided in the hollow rod 23 for discharging oil from the chamber C during compression operation, and a hole 36 is also provided in the inner tube 22 for guiding this oil into the pressure chamber A via the check valve 29. It is.

The through hole 36 between the inner and outer tubes also has the role of guiding high pressure oil leaking from the gap between the inner tube 22 and the outer tube 21 to the pressure chamber Avc during the above-mentioned hydraulic lock state, and preventing high pressure from being applied to the oil seal 37.

Next, a limit stopper 35 is fixed to the hollow rod 23 in order to ensure a constant fitting length with the hollow rod 23 when the inner tube 22 is fully extended.

Therefore, the spring 32 for alleviating the impact at maximum extension and the damping orifice 31 are arranged below the limit stopper 35.

Here, the outer tube 21 is the inner tube 22.
Since the hollow rod 23 is configured as a strength member, there is no need to provide a predetermined fitting part to the outer tube 21 to provide strength, so it can be made shorter than the conventional one, and the inner tube 22 It is sufficient that the oil seal 37 provided at the tip of the outer tube 21 simply fits into the inner tube 22 when the outer tube 21 is in its most extended state, reaching a length that prevents oil from leaking to the outside. can be easily understood.

! In order to increase the extension stroke, the limit can be increased by lengthening the hollow rod 23 and fixing the limit stopper 35 at a position that ensures the minimum necessary fitting length when the inner tube 22 is at its maximum extension. The distance between the stopper 35 and the main piston 24 (check valve 29) becomes narrower, allowing the expansion and contraction stroke to be increased.

As the button extension stroke becomes sharper, the distance between the lower end of the inner tube 22 and the bottom of the outer tube 21 when fully extended also becomes shorter.
However, as mentioned above, since it is not necessary for the outer tube 21 to have a predetermined fitting length with the inner tube 22 as a strength member, at least There is no difference in the fact that the extension and contraction strokes can be made as long as the combined length.

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

Next, the operation of the present invention will be explained.

When the front fork is compressed, the inner tube 22 enters the outer tube 21 against the spring 26, and at this time, the oil in the chamber C flows through the through hole 36 and the check valve 29 to the pressure chamber A for generating damping force. The remaining oil flows into the oil reservoir chamber B through the hole 30 and the inside of the hollow rod 23.

At maximum compression, the inner tube 22 slides into contact with the bulging portion 21' of the outer tube 21 to create a hydraulic lock state and prevent bottoming out.

On the other hand, when the inner tube 22 is extended, oil in the pressure chamber A, which is contracting, flows out little by little from the orifice 31, producing a damping effect.

At the maximum extension, the check valve 29 closes the orifice 31.
The pressure chamber A is hydraulically locked to prevent full extension and to alleviate the impact.

In this way, the present invention allows the inner tube 22 and the hollow rod 23 to be fitted together as a strength member via the main piston 24 and the auxiliary piston 25, and the hollow rod 23 is fitted with the necessary minimum degree of fitting that is bent at least when fully extended. A limit stopper 35 is fixedly installed to ensure the length, and
Since a gap is formed between the outer tube 21 and the inner tube 22, the outer tube 21 can be substantially shortened, and therefore the expansion and contraction stroke can be reduced compared to the conventional method, and the cost can be reduced. It is also possible to provide a front fork that is extremely inexpensive.

Even if the outer tube 22 is made of non-ferrous metal such as aluminum alloy, it does not directly slide against the inner tube 22, so there is no oil contamination due to this abrasion, which reduces the viscosity of the oil and prevents seizure of the sliding parts. , there is no risk of problems such as damage to the oil seal.

[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, 22... Inner tube, 23... Hollow rod, 24... Main piston 2
5... Auxiliary piston, 29... Check valve, 31.
... Orifice, 35... Limiting stopper, A...
Pressure chamber, B... oil reservoir chamber, C... chamber.

Claims (1)

[Claims] 1. The inner tube and the hollow rod fixed in the outer tube are slidably fitted as strength members through the main piston fixed to the inner tube and the auxiliary piston fixed to the hollow rod, respectively, and the front fork A front fork for a two-wheeled vehicle configured to have a stopper fixed to a hollow rod to ensure a predetermined mating length between the inner tube and the hollow rod, which will collapse when fully extended.