JPH0237495B2 - FURONTOFUOOKUNOSHIZUMIKOMIBOSHISOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a front fork sinking prevention device during braking.

In motorcycles and the like, there is a phenomenon in which the front fork sinks (nose dive) due to the forward movement of the center of gravity during sudden braking, resulting in poor handling.

In order to prevent this, the present applicant has proposed a number of devices such as the one shown in FIG.

1 is an outer tube, 2 is an inner tube, and 3 is a hollow rod that is integrated with the outer tube 1. During pressure side operation when the inner tube 2 enters, the hydraulic oil in the lower oil chamber B is equal to the volume of the inner tube 2 that enters. The oil flows into the oil reservoir chamber C inside the hollow rod 3 via the oil passages 4 and 5.

The valve housing 6 does not provide any resistance to the flow of hydraulic fluid during steady operation, but in order to provide resistance during sudden braking, etc., and suppress the front fork from moving toward the pressure side, that is, from sinking. An internal ring-shaped damping valve 7 is urged by a spring 8 into contact with a cylindrical valve stopper 9.

Coaxially with the damping valve 7, a valve piston 10
is arranged, the valve piston 10 being axially displaced via a push rod 11 to reduce the predetermined gap normally maintained between it and the damping valve 7 during braking.

The outer diameter of the valve piston 10 is set to be slightly smaller than the inner diameter of the damping valve 7, so that the valve piston 10 can freely enter the inside of the damping valve 7.

The push rod 11 is slidably guided inside an adjusting sleeve 12 screwed into the valve housing 6, and the end 14 of the adjusting sleeve 12 comes into contact with the end surface of the valve stopper 9, while the return of the push rod 11 A spring 15 is housed inside the adjusting sleeve 12 and pushes the push rod 11 back outwards.

Further, an adjuster 16 of the push rod 11 is screwed into the adjuster sleeve 12, and a flange 17 provided on the push rod 11 abuts against the insertion end of the adjuster 16 to restrict its upper limit position.

The push rod 11 is interlocked with a brake arm (not shown) and is pushed inward as the brake is operated during braking.

In such a configuration, a predetermined gap is maintained between the valve piston 10 and the damping valve 7 during steady operation, and when the pressure side is operated, the lower oil chamber B
The hydraulic oil passing through the oil passages 4 and 5 is allowed to flow smoothly without giving almost any resistance. In addition,
The compression side damping force at this time is generated by applying resistance to the hydraulic oil flowing into the expanding upper oil chamber (not shown) by a pressure side damping valve installed in the piston portion 18 at the tip of the inner tube 2.

On the other hand, when braking, the push rod 11
is pushed in, the gap between the valve piston 10 and the damping valve 7 is reduced, and furthermore, the valve piston 10
overlaps with the damping valve 7 according to the braking stroke.

During braking, the front fork tends to sink in response to the braking acceleration, and the hydraulic oil in the oil chamber B flows to the oil reservoir chamber C side via the oil passages 4 and 5.

At this time, the hydraulic oil passes between the valve piston 10 and the damping valve 7, but when this gap disappears, the hydraulic oil pushes down the damping valve 7 against the spring 8 and flows.

Therefore, resistance is generated in the flow of the hydraulic oil, and this is added to the compression side damping force to provide resistance to the entry of the inner tube 2, thereby suppressing the sinking of the front fork during braking.

The generated damping force can be freely adjusted by adjusting the initial load of the valve spring 8 by moving the adjusting sleeve 12 forward or backward and changing the position of the valve stopper 9. In other words, the larger the initial deflection of the spring 8, the higher the damping force. can get.

Further, the initial gap adjustment between the valve piston 10 and the damping valve 7 is performed by moving the push rod 11 by moving the second adjuster 16 forward and backward.

According to this device, it is possible to effectively prevent sinking during braking as described above, but in this case, regardless of the braking acceleration, the valve piston 10 always strokes when braking is performed. The lapping with the damping valve 7 increases the valve cracking pressure.

Therefore, for example, when you continue to decelerate slowly while applying the brakes lightly after an instantaneous sudden braking, the front forks will not sink again, but the same result as during the sudden braking will occur. Sometimes there are gaps (unevenness) from the road surface.
When thrust is input, the front fork is in a hard state on the compression side, resulting in poor vibration absorption and poor riding comfort.

An object of the present invention is to improve ride comfort by increasing gap absorption during braking without exerting a large pressure damping force in a region where the compression speed is low even during braking.

The present invention provides a bypass port that bypasses the valve and allows hydraulic oil to flow in the braking area where the damping valve moves little when the valve piston and the damping valve overlap during braking. The valve piston or valve housing is opened at the valve piston or valve housing, and in the region where the compression speed is low, the compression side damping force is weakened by the flow of hydraulic oil by the bypass port, and the upthrust absorbability during slow braking is improved.

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

As shown in FIGS. 2 and 3, in the present invention, a bypass port 20 is formed in the valve piston 10, and a part of the hydraulic oil flows by bypassing the damping valve 7 during pressure side operation.

The bypass port 20 has an inlet 21 formed so as to constantly communicate with the oil passage 4 on the upstream side, and an outlet 22 that opens on the outer circumferential surface of the valve piston 10, that is, on the sliding surface with the damping valve 7.

The outlet 22 is formed at a position where it communicates with the oil passage 5 during slow braking when the damping valve 7 is in the initial position and the valve piston 10 wraps around the damping valve 7.

In addition to or instead of this bypass port 20, a bypass port 30 may be formed in the valve housing 6 to allow hydraulic fluid to flow so as to bypass the damping valve 7.

Of course, in this case as well, the damping valve 7 is connected to the spring 8.
When pushed down against this, the bypass port 30 is closed or located on the upstream side.

Other configurations are the same as in Figure 1,
Identical parts are denoted by the same reference numerals, and the operation will be explained next with reference to FIG.

The state shown in Fig. 2 shows a state of gentle braking, in which the valve piston 10 is pushed in through the push rod 11 due to braking and wraps with the damping valve 7, but since the sinking speed of the front fork is low, the hydraulic oil The amount of movement is small, and therefore the hydraulic oil flows through the bypass port 20 (or 30), so the compression side damping force does not increase so much.

Therefore, when the inner tube 2 and outer tube 1 are pushed up from the road surface during braking, the inner tube 2 and outer tube 1
compresses quickly and absorbs shock.

On the other hand, during sudden braking, the front fork tries to sink significantly, so a large amount of hydraulic oil moves, and the pressure difference between the front and rear of the damping valve 7 becomes large because the hydraulic oil cannot flow completely from the bypass port 20 (30). Eventually, the damping valve 7 is pushed down against the spring 8, the bypass port 20 (30) closes, and from then on, a compression-side damping force is generated by the damping valve 7.

What is shown by the dotted line in FIG. 4 is the conventional compression side damping characteristic, whereas in the present invention, the damping force is cut in the low compression speed range of the front fork to improve shock absorption.

As described above, according to the present invention, in the braking range where the compression speed is low, it is possible to prevent large damping force from being generated by the bypass port, improve the absorption of the gap during braking, and improve ride comfort. can.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional device. FIGS. 2 and 3 are cross-sectional views showing embodiments of the present invention, and FIG. 4 is an operational characteristic diagram. 1... Outer tube, 2... Inner tube, 4, 5... Oil path, 6... Valve housing, 7... Damping valve, 9... Valve stopper,
10... Valve piston, 11... Push rod, 20, 30... Bypass port, 21... Inlet, 22... Outlet.

Claims (1)

[Claims] 1. An annular damping valve and a valve piston that strokes and wraps with the damping valve according to the braking action are installed in the oil passage through which hydraulic oil flows as the front fork sinks, so that the displacement of the damping valve during braking is small. A sinking prevention device for a front fork, characterized in that a bypass port that allows hydraulic oil to flow by bypassing the damping valve only in the area where the damping valve slides is opened on the sliding contact surface of the damping valve of the valve piston or the valve housing.