JPH0117512Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a spring load adjustment device for a front fork.

A front fork that supports the front wheel of a two-wheeled vehicle or the like has an inner cylinder and an outer cylinder that are slidably fitted together, and is equipped with an internal damping force generator and a spring to absorb shocks received by the front wheel. Here, the spring refers to a metal coil spring, but it is well known that a gas chamber is formed above the oil sealed in the inner cylinder, and that the function as a gas spring is performed even when this gas chamber contracts. It is a fact.

By the way, metal coil springs generally produce a spring reaction force that is proportional to the amount of contraction (called a stroke), whereas gas springs have a relationship of pv = constant (where p is pressure and v is specific volume). According to the equation, that is, the equation of isothermal change in gas, as the stroke becomes larger, the reaction force increases rapidly. Applying this to the front fork, when a large impact is applied to a front fork with a small gas chamber volume, the reaction force of the gas spring increases suddenly and the front fork becomes a kind of rigid body. This causes an inconvenience in that riding comfort is extremely reduced.

The present applicant previously proposed a spring load adjustment device, in which a piston that receives the upper end of the spring is slidably fitted into an inner cylinder, and the piston is moved up and down using hydraulic pressure, thereby adjusting the spring load of the spring. can be adjusted arbitrarily.

However, according to such a device, by moving the piston up and down within the inner cylinder, the spring load of the metal spring and the volume of the gas chamber change at the same time, resulting in the above-mentioned disadvantages. Furthermore, since the metal spring and the gas spring have to be adjusted at the same time, it is very difficult to make the desired adjustment.

The present invention was developed to effectively eliminate such inconveniences, and its purpose is to provide a front panel that can adjust only the spring load of the metal spring while maintaining the spring characteristics of the gas chamber constant. To provide Folk's spring load adjustment device.

In order to achieve such an object, the present invention has a front fork which is made up of an inner cylinder and an outer cylinder that are slidably fitted together, and a spring holder that receives the upper end of a spring is slidably fitted into the inner cylinder of the front fork. A hollow chamber is provided inside the fork bolt fixed to the upper part, and a piston integrally formed with a rod extending vertically is fitted into the hollow chamber so as to be slidable, dividing the hollow chamber into an upper chamber and a lower chamber. The upper chamber is communicated with a gas chamber in the inner cylinder, and the end face of the rod extending upward from the piston is hydraulically pressed so that the spring load of the spring can be adjusted, and the cross-sectional area of the hollow chamber is twice that of the rod. The gist of this is that it has been doubled.

A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional side view of a front fork equipped with a device according to the present invention, and FIGS. 2 and 3 are enlarged sectional side views of the upper part of the front fork.

In the front fork shown in FIG. 1, 1 is an outer cylinder, and an inner cylinder 2 is fitted into the outer cylinder 1 from above so as to be vertically slidable. An oil seal 3 is provided on the upper inner periphery of the outer cylinder 1 and slides on the outer periphery of the inner cylinder 2.
The upper end opening of the outer cylinder 1 is similarly closed with a dust seal 4 that slides on the outer periphery of the inner cylinder 2.

Also, a seat pipe 5 is installed at the bottom of the outer cylinder 1 with an oil lock piece 6 and bolts 7.
The enlarged diameter end portion 5a of the seat pipe 5 is in sliding contact with the inner periphery of the inner tube 2 as shown in the figure.

On the other hand, a free valve 8 that slides on the outer periphery of the seat pipe 5 is fitted into the lower inner periphery of the inner cylinder 2, and a fork valve 8 equipped with a spring load adjustment device 20 according to the present invention is attached to the upper end of the inner cylinder 2. Bolt 9 is screwed in. Furthermore, inside the inner cylinder 2 there is a spring receiver 1 as shown in the figure.
0 is fitted to be vertically slidable, and the spring receiver 10
A coil spring 11 is compressed between the upper end of the seat pipe 5 and the upper end of the seat pipe 5. In addition, the above spring receiver 10
A plurality of ventilation holes 10a... are bored in the.

By the way, a hollow chamber S is formed inside the fork bolt 9, as shown in detail in FIG. each rod 2
2 and 23 are integrally extended. The upper rod 22 is a circular hole 9a provided in the fork bolt 9.
The lower rod 23 is slidably inserted into the guide member 24, and its lower end abuts the spring receiver 10 as shown. Further, an oil passage 9b communicates with the circular hole 9a, and the oil passage 9b communicates with a hydraulic pressure generator (not shown) via a pipe connected to a plug 25 screwed onto the upper end of the fork bolt 9. ing.

The hollow chamber S is divided into an upper chamber _S1 and a lower chamber _S2 by the piston 21, and the upper chamber _S1 communicates with a gas chamber Sg, which will be described later, inside the inner cylinder 2 through a passage 9c. The lower chamber _S2 communicates with the atmosphere via a passage 9d. Here, the cross-sectional area A ₁ of the hollow chamber S (this is the piston 21
) is set equal to exactly twice the cross-sectional area A ₂ of the upper and lower rods 22 and 23 (A ₁ =2A ₂ ).

Hydraulic oil is sealed inside the front fork, and gas at a predetermined pressure is sealed in the upper part of the inner cylinder 2 to form a gas chamber Sg.

Next, the spring 1 is adjusted by the spring load adjusting device 20.
Adjustment of the spring load in step 1 will be explained.

FIG. 2 shows a state in which the piston 21 and the rods 22, 23 are at their upper limits, and accordingly, in this state, the spring receiver 10 is also at its upper limit, and at this time the spring 11 is at its maximum extension.

If a hydraulic pressure generating device (not shown) is driven from such a state to apply hydraulic pressure to the upper end surface of the upper rod 22, the rod 22 will move toward the piston 2 as shown in FIG.
1 and the lower rod 23, the spring bearing 10 also moves downward by the same amount, and the downward movement of the spring bearing 10 causes the spring 11 to contract by the stroke ΔS. The spring load of the spring 11 is adjusted high.

By the way, at this time, the rod 23 enters the gas chamber Sg of the inner cylinder 2, and the volume of the gas chamber Sg is smaller than that of the rod 2.
The intrusion volume of 3 is reduced by ΔV ₁ . Here, the intrusion volume ΔV ₁ is expressed by the following formula.

ΔV ₁ =A ₂ ·ΔS (1) On the other hand, the volume of the upper chamber S ₁ increases by the volume ΔV ₂ expressed by the following equation, and the volume of the lower chamber S ₂ decreases by the same volume ΔV ₂ .

ΔV ₂ = (A ₁ − A ₂ )・ΔS=A ₂・ΔS ……(2) From equations (1) and (2) above, both volumes are always equal regardless of the stroke ΔS, and moreover, the gas chamber Sg and the upper room
Since the gas chamber Sg is in communication with _S1 through the passage 9c, the decrease in the volume of the gas chamber Sg due to the entry of the rod 23 is offset by the increase in the volume of the upper chamber _S1 , and as a result, the spring load of the spring 11 is reduced. Even if the volume of the gas chamber Sg is adjusted, the volume of the gas chamber Sg remains constant.

In this way, it is possible to adjust only the spring load of the spring 11 while keeping the volume of the gas chamber Sg constant, so that the desired adjustment can be easily made, and the spring characteristics that occur in conventional ones can be adjusted. sudden changes cannot occur.

In addition, the air equivalent to the reduced volume _ΔV of the lower chamber S _{2 by 2} is passed through the passage 9.
d and then released into the atmosphere.

If the hydraulic pressure acting on the upper end surface of the rod 22 is lowered from this state, the piston 21 and both rods 22,
23 moves upward together, and as a result, the spring load of the spring 11 is adjusted low again.

As is clear from the above description, according to the present invention, a spring holder that receives the upper end of a spring is slidably fitted into the inner cylinder of the front fork, which is formed by slidably fitting an inner cylinder and an outer cylinder. A hollow chamber is provided inside the fork bolt fixed to the upper part of the inner cylinder, and a piston integrally formed with a rod extending vertically is fitted into the hollow chamber so as to be slidable, dividing the hollow chamber into an upper chamber and a lower chamber. The upper chamber is communicated with a gas chamber in the inner cylinder, and the end face of the rod extending upward from the piston is hydraulically pressed so that the spring load of the spring can be adjusted. Since it is made to be twice that, it is possible to adjust only the spring load of the spring while keeping the spring characteristics of the gas chamber constant.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a longitudinal sectional side view of a front fork, and FIGS. 2 and 3 are enlarged sectional side views of the upper part of the front fork. In the drawings, 1 is an outer cylinder, 2 is an inner cylinder, 9 is a fork bolt, 10 is a spring receiver, 11 is a coil spring,
20 is a spring load adjustment device, 21 is a piston, 2
2 and 23 are rods, S is a hollow chamber, S ₁ and S ₂ are upper and lower chambers, and Sg is a gas chamber.

Claims (1)

[Scope of utility model registration request] In a front fork comprising an inner cylinder and an outer cylinder that are slidably fitted together, and a damping force generator and a spring are provided inside, a spring receiver that receives an upper end of the spring is slidably fitted into the inner cylinder. , a hollow chamber is provided inside the fork bolt that is fixed to the top of the inner cylinder,
A piston integrally formed with a rod extending vertically is slidably fitted into the hollow chamber to divide the hollow chamber into an upper chamber and a lower chamber, and the upper chamber is communicated with a gas chamber in the inner cylinder. A rod extending further downward is brought into contact with the upper surface of the spring holder, and the end surface of the rod extending upward is pressed by hydraulic pressure to adjust the spring load of the spring, such that the cross-sectional area of the hollow chamber is equal to that of the rod. A front fork spring load adjustment device characterized by being doubled.