JPH0816494B2 - Front forks for motorcycles equipped with a valve device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a motorcycle front fork provided with a valve device, and more particularly to a motorcycle front fork, and more specifically, an outer pipe and a slidable inside the outer pipe. An inner tube that fits in
A seat pipe whose lower end is fixed to the bottom of the outer pipe, a cylindrical oil lock piece whose lower end is fixed to the bottom of the outer pipe outside the seat pipe, and an oil chamber inside and outside the seat pipe. The present invention relates to a front fork for a motorcycle, which includes a valve device for circulating or shutting off oil between the two.

[Prior art]

In the case of known front forks of this kind, the valve arrangement consists of relief valves and check valves provided at different points of the front fork. This relief valve opens when the pressure in the oil chamber outside the seat pipe increases due to front fork compression, and allows the oil to flow from the oil chamber outside the seat pipe to the oil chamber inside. The check valve opens when the pressure in the oil chamber outside the seat pipe decreases due to the extension of the front fork, and serves to flow oil from the oil chamber inside the seat pipe to the oil chamber outside.

[Disadvantages of conventional technology]

In this valve device, the relief valve is provided in the damping mechanism part, the check valve is provided in the seat pipe wall, and the check valve is separately formed, so that the structure is complicated and a wide space is required for installation. To do.

[Object of the Invention]

An object of the present invention is to provide a motorcycle fork having a simple and compact valve device structure.

[Structure of Invention]

For this purpose, according to the present invention, a tubular valve body is provided slidably in a vertical direction between a seat pipe and an oil lock piece, and is urged by springs from above and below to be opened and closed by the valve body. This is achieved by forming the oil hole in the seat pipe and the oil lock piece on the side of the valve body.

〔Example〕

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

The entire front fork according to this embodiment is partially cut away and shown in FIG. In this figure, 1 is an outer tube as a bottom case attached to an axle at the lower end, 2
Is an inner pipe as a fork pipe slidably fitted to the outer pipe 1 and attached to the vehicle body at the upper end. A seat pipe 3 is fixed to the bottom of the outer pipe 1 by a bolt 4, and a piston 5 that slides relatively to the inner surface of the inner pipe 2 is attached to the upper end of the seat pipe. A spring 6 for urging the inner pipe 2 in the extension direction is provided between the piston 5 and the upper end portion of the inner pipe 2. A valve 7 is slidably attached to the outer surface of the seat pipe 3 near the lower end of the inner pipe. This valve 7 has a large flow passage when the front fork is compressed, and acts so as to narrow the flow passage so as to generate a damping force when the front fork is extended. A is an oil chamber inside the seat pipe 3 and an oil chamber inside the inner pipe 2 communicating with this, and air is enclosed in the upper end portion thereof. B is an oil chamber outside the seat pipe 3.

At the lower end of the front fork, a damping mechanism 8 that operates according to the internal pressure is arranged. FIG. 1 shows the damping mechanism in an enlarged manner. In FIG. 1, reference numeral 9 denotes a valve case of a damping mechanism, a lid 11 having an air vent hole is screwed on the upper side thereof, and a cap 12 is further mounted thereon.

A cylindrical spool 13 having an upper end closed is slidably accommodated in the valve case 9. The spool 13 is biased by a return spring 14 from above. Return spring 14
Is supported by a spring receiver 15 at its upper end, and its amount of bending can be adjusted by a screw type adjuster 16. The upper side of the spool 13 is open to the atmosphere through a hole 17 provided in the spring receiver 15 and the air vent hole 10.

The spool 13 has a vertical groove 18 and a side opening 19. A screw 20 is fitted in the vertical groove 18, which prevents the spool 13 from rotating and also functions as a stopper for the spool descending movement. The lateral openings 19 act as orifices that produce a variable damping force, as described below.

The inner chamber 9'of the valve case 9 communicates with the oil chamber B through a passage 21, and the passage 22, the passage 24 formed in the oil lock piece 23, and the hole 25 formed in the seat pipe 3.
Through the oil chamber A. The oil lock piece 23 is fixed to the bottom portion of the outer pipe 1 by the bolt 4 together with the seat pipe 3. A valve device according to the present invention is provided between the oil lock piece 23 and the seat pipe 3. The valve body 26 of this valve device is formed in a tubular shape and is vertically slidable between the oil lock piece 23 and the seat pipe 3. The valve body 26 is urged by a spring 27 as a check spring from the upper side and by a spring 28 as a relief spring from the lower side, and an oil hole formed in the oil lock piece 23 in accordance with the pressure in the oil chambers A and B. 29 and the oil hole 30 formed in the seat pipe 3 are opened and closed.

Next, the operation of the front fork having the above structure will be described.

When the front fork is compressed, the inner pipe 2 descends, and the valve 7 reduces the volume of the oil chamber B. At the beginning of this compression stroke, the oil reaching the passage 21 from the oil chamber B flows into the valve case inner chamber 9'through the side opening 19 of the spool 13 as shown by the arrow, and then the passages 22 and 24 and the hole 25. To reach the oil chamber A.

When the compression stroke further progresses, the pressure in the oil chamber A increases due to the compression of the enclosed air. This pressure is due to holes 25 and passages 24,22.
And is transmitted to the valve case inner chamber 9 ', and presses the inner bottom surface of the spool 13, that is, the pressure receiving surface 31, upward. When this pressing force becomes larger than the reaction force of the return spring 14, the spool 13 is pushed up and its side opening 19 narrows or closes the flow path with the edge of the passage 21. As a result, the flow of oil from the oil chamber B to the oil chamber A is limited, and the damping force becomes large, so that the front wheels do not largely sink even when riding on a bump on the road surface or suddenly stopping. Therefore, the operation stability is improved.

In this case, the pressure receiving surface 31 is arranged along the flow path between the oil chambers A and B so that the dynamic pressure of the oil flowing from the oil chamber B to the oil chamber A does not act on the pressure receiving surface 31. Therefore, since the movement of the spool 13 is not affected by the dynamic pressure, the flow passage can be accurately and surely throttled according to the pressure transmitted from the oil chamber A.

Further, since a large load is applied to the front wheels during a sudden stop or a curve, the side opening 19 of the spool 13 may be closed. In this state, if you ride on the protrusion of the road surface,
The front fork is further compressed, and the pressure of the oil in the oil chamber B rises. This pressure pushes the valve body 26 against the spring 28, releasing the hydraulic pressure 30. Therefore, the oil in the oil chamber B flows into the oil chamber A through the oil hole 30 and absorbs the shock.

In the extension stroke of the front fork, the pressure in the oil chamber B decreases, so the valve body 26 rises against the spring 27 and the oil hole 29
Open up. As a result, the oil in the oil chamber A becomes
It flows into the oil chamber B through 29.

〔The invention's effect〕

As described above, in the present invention, the tubular valve body is provided slidably in the vertical direction between the seat pipe and the oil lock piece, and is biased by the spring from the upper side and the lower side, and Since the oil hole to be opened and closed is formed in the seat pipe and the oil lock piece on the side of the valve body, the valve body functions as both a check valve and a relief valve. Therefore, there is an effect that the structure of the valve device is very simple and compact.

[Brief description of drawings]

FIG. 1 is a sectional view showing a valve device according to an embodiment of the present invention, and FIG. 2 is a partial sectional view showing an entire front fork provided with the valve device of FIG. 1 …… Outer pipe, 2 …… Inner pipe, 3 …… Seat pipe, 23 ……
Oil lock piece, 26 …… Valve element, 27,28 …… Spring, 29,
30 ... Oil hole, A, B ... Oil chamber

Claims (1)

[Claims] 1. An outer pipe, an inner pipe slidably fitted in the outer pipe, a seat pipe having a lower end fixed to a bottom portion of the outer pipe, and a lower end outside the seat pipe having a bottom portion of the outer pipe. In a motorcycle fork front fork equipped with a tubular oil lock piece fixed to the vehicle and a valve device for circulating or shutting off oil between the oil chamber inside the seat pipe and the oil chamber outside the seat pipe, the tubular valve The body (26) is provided slidably in the vertical direction between the seat pipe (3) and the oil lock piece (23), and is biased by the springs (27, 28) from the upper side and the lower side, and the valve body ( A front fork for a motorcycle, characterized in that an oil hole (29, 30) opened and closed by means of (26) is formed in the seat pipe (3) and the oil lock piece (23) on the side of the valve body.