JPS6116236Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a hydraulic shock absorber incorporating an anti-nose dive mechanism.

An example of a front fork for a two-wheeled vehicle that incorporates an anti-nose dive mechanism that suppresses the movement of the center of gravity during braking and the sudden compression operation caused by inertia force is shown in FIG. 1.

In the figure, 1 is an outer tube connected to the axle, and 2 is a hollow tube erected from the bottom of the outer tube.

An inner tube (not shown) connected to the vehicle body side is slidably inserted into the outer tube 1.
A piston 4 fixed to the tip thereof is in sliding contact with the inner peripheral surface of the outer tube 1 and the outer peripheral surface of the hollow tube 2 in an oil-tight manner, thereby defining oil chambers on the upper and lower surfaces of the piston 4.

In the figure, A indicates an oil chamber that contracts when the pressure side is operated. When this oil chamber A contracts, the hydraulic oil flows into the expanding oil chamber at the top (not shown), and excess oil corresponding to the entering volume of the inner tube is released. The oil flows out from the upper end opening 14 of the valve housing 12 to the oil reservoir chamber B in the hollow tube 2 through the through holes 5 and 13.

A relief valve 6 slidably housed within the valve housing 12 regulates the flow of this excess oil.
The relief valve 6 is urged in the closing direction by the relief spring 7 carried by the plunger 8. The relief valve 6 is pushed open by the flow of excess oil against the urging force of the relief spring 7, and the opening amount of the relief valve 6 at this time is determined by the set load of the spring 7 and the oil chamber A. It is determined by the differential pressure with the oil reservoir chamber B, and provides resistance to the flow of excess oil and generates a predetermined damping force to absorb and alleviate vibrations received from the road surface during normal driving.

The set pressure of the relief valve 6 is adapted to change in accordance with braking. That is, the plunger 8 supporting one end of the relief spring 7
is disposed coaxially with the relief valve 6 and is slidably supported by a bottomed cylindrical lid 20 fitted into the rear part of the valve housing 12. This plunger 8
is biased by a return spring 22 supported between the flange 23 and the spring receiver 21 so as to penetrate the bottom of the lid 20 and protrude outward;
This protruding end portion 24 is linked to a brake arm 25 pivotally supported on the outer tube 1 via a link mechanism 26. And brake arm 25 during braking
The plunger 8 is moved by the return spring 22 by one end of the link mechanism 26 which rises as the plunger 8 swings.
It's starting to push against the curve.

The relief spring 7 is deflected by this sliding movement of the plunger 8, increasing the set pressure of the relief valve 6. Since the amount of deflection of the spring 7 is proportional to the lift amount of the plunger 8, the relief spring 7 is deflected.
The set pressure will be increased according to the braking force of the brake. As a result, excess oil attempting to flow from oil chamber A to oil reservoir chamber B will be subjected to greater resistance due to the increased set load of relief spring 7, and the pressure in oil chamber A will increase during braking. As a result, nose dive of the front fork is effectively prevented.

Note that reference numeral 16 is a passage that returns hydraulic oil from the oil reservoir chamber B to the expanding oil chamber during the expansion side operation, and in the middle of the passage 16 is a check valve 17 that opens only during the expansion side operation.
is interposed.

Incidentally, the front fork of an off-road vehicle that is used to drive on rough roads such as mountain roads is constantly subjected to fairly severe vibrations from the road surface. Conventionally, with such front forks, in order to absorb and alleviate large vibrations, the set pressure of the relief valve (in other words, the spring constant of the relief spring) is reduced and the damping force is set low over a wide range, thereby softening the expansion and contraction of the fork. This improves the ability to follow the road surface.

However, although this configuration improves the ride comfort when driving on rough roads, on the other hand, the set pressure of the relief valve 6 cannot be increased unless the relief spring 7 is bent considerably during braking, which reduces the effectiveness of the anti-nose dive. The problem is that it gets worse.

Therefore, in order to solve this problem, this invention provides an auxiliary spring in parallel with the relief spring that is deflected after the plunger has made a predetermined stroke during braking, and rapidly increases the set pressure of the relief valve during braking. The purpose of the present invention is to provide a hydraulic shock absorber that is designed to do the following.

Embodiments of the present invention will be described below with reference to the drawings. Note that the same parts as in FIG. 1 are denoted by the same reference numerals.

FIG. 2 is an enlarged sectional view of the main parts, and 6 is a relief valve slidably housed in the valve housing 12;
8 is a plunger disposed coaxially with the relief valve 6 and slides in response to a brake device, and 7 is a relief spring supported between the relief valve 6 and the plunger 8.

Between this relief valve 6 and plunger 8,
An auxiliary spring 30 is provided in parallel with the relief spring 7.

The auxiliary spring 30 has a spring constant higher than that of the relief spring 7, and has one end supported by the plunger 8 and the other end attached to the outer periphery of a cylindrical spring receiver 31 formed in the relief valve 6 and located in the middle of the relief spring 7. Inserted into free state. That is, an initial play l is provided between the free end 32 of the spring 30 and the relief valve 6 in the closed position.

The flange 33 of the plunger 8, which supports the auxiliary spring 30 and the relief spring 7, is formed to have a diameter larger than the inner diameter of the relief valve 6, and hits the rear end surface of the relief valve 6 when the plunger 8 slides. The maximum lift amount is now regulated.

With this configuration, during normal driving, the relief valve 6 is biased in the closing direction only by the relief spring 7 and is not subjected to the elastic force of the auxiliary spring 30, so its set pressure is equal to the set load of the relief spring ( Spring constant) is determined only by
Therefore, the oil chamber A shrinks as the pressure side operates.
The damping resistance given to the excess oil flowing from the damper to the oil sump chamber B increases gradually in accordance with the damper speed (that is, the flow rate of the excess oil), as shown by the line P in FIG. This damping resistance can be set lower over a wider range as the spring constant of the relief spring is made smaller.

On the other hand, when a braking action is applied as shown in FIGS. 3A and 3B, the relief spring 7 is deflected by the sliding movement of the plunger 8, and at the same time, the play l of the auxiliary spring 30 is reduced by the amount of movement of the plunger 8. be done. Therefore, the set pressure of the relief valve 6 increases rapidly as the initial load increases according to the amount of deflection of the relief spring 7, and the elastic force of the auxiliary spring 30 acts from the time when the play l is eliminated. In the case of FIG. 3A, where the braking is gentle, the damping force increases rapidly from the middle of the spring 30 starting to take effect, as shown by the Q line in FIG. 4, and in the case of FIG. 3B, where the braking is applied further. , as shown by line R in FIG. 4, rises sharply from the time when the relief valve 6 begins to open and increases linearly.

Therefore, by only slightly moving the plunger 8, the set pressure of the relief valve 6 can be rapidly increased, which improves the effectiveness of the anti-nose dive during braking.

As explained above, this invention weakens the acting force of the relief spring during normal driving, softens the expansion and contraction of the front forks, absorbs large and violent vibrations, improves the ability to follow the road surface, and improves ride comfort. On the other hand, when braking, the auxiliary spring installed in parallel with the relief spring is activated, and the set pressure of the relief valve can be suddenly increased, which improves the effectiveness of anti-nose dive during braking, for example when driving on a rough road. This makes it ideal as a front fork for off-road use.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway sectional view of the conventional device, Fig. 2 is an enlarged sectional view of the main part of the present invention, Fig. 3 A and B are enlarged sectional views of the main part showing the operating state during braking, and Fig. 4 is an attenuation characteristic diagram. 6...Relief valve, 7...Relief spring, 8...Plunger, 30...Auxiliary spring, l...Play, 31...Spring receiver.

Claims (1)

[Scope of utility model registration request] In a hydraulic shock absorber, a relief valve is provided in the passage that releases hydraulic oil from the oil chamber to the oil reservoir chamber during pressure side operation, and this relief valve is activated during braking.The relief spring of the relief valve is activated in response to the braking force. A hydraulic shock absorber characterized in that an auxiliary spring is interposed between a deflecting plunger and a relief valve in parallel with the relief spring to provide initial play.