JPS6350239B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a hydraulic shock absorber that prevents nose dive (sinking) during braking in a two-wheeled vehicle.

Generally, in the front fork of a two-wheeled vehicle, a compression effect occurs due to the shift of the center of gravity and inertial force that occurs during braking, and the front fork sinks significantly during sudden braking, which significantly impairs steering stability.

As a measure against this, the applicant has previously proposed the first
A device as shown in the figure has been proposed.

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, and a piston 4 fixed to the tip thereof is oil-tightly connected to the inner circumferential surface of the outer tube 1 and the outer circumferential surface of the hollow tube 2. The piston 4 is in sliding contact with the piston 4, and oil chambers are defined on the upper and lower surfaces of the piston 4.

In the figure, A indicates an oil chamber that contracts during pressure side operation. When this oil chamber A contracts, the hydraulic oil flows into the expanding oil chamber at the upper part (not shown), and excess oil is divided into the entering volume of the inner tube. is aisle 5
From A, the relief valve 6 is pushed open and the oil flows out to the oil chamber B in the hollow tube 2 through the passage 5B.

Air or an inert gas is sealed in the upper part of this oil chamber B, and the gas is compressed in response to the inflow of oil.

The set pressure of the relief valve 6 is adapted to change depending on the braking force.

That is, a plunger 8 supporting one end of the relief spring 7 is movably provided within a cylinder 9, and a portion of pressure oil from a master cylinder of a brake device (not shown) is supplied to the end surface of the plunger 8 via a pipe 10. The plunger 8 is pushed in according to the brake circuit pressure.

That is, when the front fork attempts to sink during braking, the brake circuit pressure that increases at this time moves the plunger 8 and increases the set load of the relief spring 7.

As a result, excess oil that attempts to escape from oil chamber A to oil chamber B due to sinking becomes more difficult to flow out as the set load of the relief valve 6 increases, and the pressure in oil chamber A increases accordingly. This prevents the inner tube from entering, or sinking.

The pressure in the oil chamber A that produces this blocking effect increases as the set load of the relief valve 6 increases as the brakes are applied more suddenly, and therefore, it is possible to effectively prevent the phenomenon that the oil chamber tends to sink more when the brakes are applied more suddenly. .

However, in such a conventional hydraulic shock absorber, the modulator part that adjusts the spring load of the relief valve 6 mentioned above is attached externally to the side of the outer tube 1, so the protruding part In addition to having a negative impact on the design of the front fork, when applied to a rearing axle type front fork (a method in which the front fork is mounted offset from the axle to increase the effective stroke), it may cause the mounting height to be lower than that of the disc of the disc brake. There was a problem in that it was extremely difficult to install (in the extreme, it was impossible to install) because the parts matched each other.

Further, as mentioned above, there are difficulties in the installation work, and the manufacturing man-hours also increase due to an increase in the number of parts, resulting in an increase in costs.

Therefore, an object of the present invention is to solve the above problems by integrally incorporating the modulator section (including the relief valve mechanism) inside the outer tube bottom.

Note that if the flow path between the oil chambers is narrowed to suppress nose dive during braking, it may not be possible to absorb the upheaval from the road surface due to riding on bumps during braking, or the oil in the oil chamber may expand during braking. The flow is restricted and there is a risk that cavitation may occur on the oil chamber side, but the present invention also addresses this problem.

In order to achieve the above object, the present invention has an inner tube and an outer tube that slide against each other in the axial direction, and allows excess hydraulic oil in the oil chamber that contracts during pressure side operation to escape to the oil reservoir chamber. In a hydraulic shock absorber for a two-wheeled vehicle in which a relief valve mechanism is interposed in the relief passage and the set load of the relief valve mechanism is increased or decreased according to the braking force, the relief valve mechanism is attached in the closing direction by a relief spring. an annular relief valve that is energized; and a rod that can be fitted into a center hole of the relief valve and that fits closer to the center hole in response to an increase in braking force to narrow the relief passage and increase the set load of the relief valve. A second passage is formed in parallel with the relief passage through the inside of the relief valve and the rod to communicate the oil reservoir chamber and the oil chamber, and the second passage A check valve that allows only the flow of hydraulic oil from the oil sump chamber to the oil chamber is provided, and the relief valve mechanism and the modulator part adjust the degree of insertion of the rod into the relief valve center hole in accordance with the braking force. are integrally assembled inside the outer tube bottom.

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

FIG. 2 is a cross-sectional view of essential parts showing an embodiment of the present invention, and the same parts as in FIG. 1 will be described using the same reference numerals.

That is, in the figure, 1 is an outer tube and 2 is a hollow tube.

The hollow tube 2 projects downward through the center of the bottom partition 11 of the outer tube 1 and is pivotally supported on the outer tube 1 by a nut 12 screwed onto the outer periphery of the tip 2A.

Inside this hollow tube 2, the partition body 11
A relief valve mechanism 13 is installed above the boundary, and a modulator section 14 is installed below.

Further, a cylindrical modulator housing 15 is integrally formed below the partition wall 11 of the outer tube 1 so as to cover the downward protrusion of the modulator section 14, and the lower end opening thereof is closed by a cap 16. Ru.

A plurality of through holes 5 are formed on the outer periphery of the hollow tube 2 above the partition body 11, and the inner tube (not shown) is contracted through the lowering of a piston 4 attached to the tip of the inner tube (not shown) during pressure side operation. Excess oil flows out from the oil chamber A to the oil chamber (oil reservoir chamber) B in the hollow tube 2.

On the other hand, during the expansion side operation, there is a through hole 18 formed in the cylindrical tip 17A of the upper opening of the rod 17, which will be described later, and a through hole 19 formed below the through hole 5 of the hollow tube 2. Excess oil is returned from the oil chamber B to the expanding oil chamber A through the passage No. 2. Note that the outer periphery of the hollow tube 2 corresponding to the above-mentioned through hole 19 is formed by moving upward due to the pressure drop in the oil chamber A only during the expansion side operation, and forming the through hole 1.
An annular oil hole rod 20 serving as a suction check valve communicating between the oil chamber A and the oil chamber A is slidably fitted therein.

An annular relief valve 6 for regulating the flow rate of excess oil flowing out from the through hole 5 into the oil chamber B is housed in the hollow tube 2 so as to be slidable upward and downward. In the figure, 7 is the relief spring, and 7' is a spring receiver that supports the base end of the relief spring 7 above the hollow tube 2.

This relief valve 6 is supported by a rod guide 21 and a bearing 23 integrated with this guide 21 with a pin 22 etc. to freely slide vertically in its center hole 6A and the inside of the hollow tube 2 which can be freely inserted into the center hole 6A. The cylindrical tip 1 of the aforementioned rod 17
7A forms a valve port.

Further, the spring load of the relief valve 6 is variable depending on the degree of fitting between the center hole 6A and the cylindrical tip 17A.

In other words, the cylindrical tip 17A is deeply inserted into the center hole 6A due to the brake pressure described below, so that
Since the amount of lift required to open the valve port of the relief valve 6 increases, the set load of the relief spring 7 increases accordingly.

The rod 17 usually has a return spring 24 whose base end is supported by the rod guide 21.
The relief valve 6 is energized downward in the figure so as to be opened to the maximum extent. In other words, the spring receiver 2 supporting the tip of the return spring 24
5 is energized until it comes into contact with the bearing 23.

Furthermore, in this state, the relief spring 7 is precompressed by a predetermined stroke so that a predetermined gap l (play) is formed between the relief valve 6 and the cylindrical tip 17A.

In other words, the maximum amount of expansion of the relief spring 7 is forcibly regulated by the lower end surface of the relief valve 6 being locked to the upper end surface of the rod guide 21, and in this state, oil flow is allowed freely in both directions during the expansion and contraction operation. ing.

Then, a bearing 23 and a nut 2 are attached to the protruding tip 2A of the hollow tube 2 on the lower end surface of the rod 17 according to the brake circuit pressure described in FIG.
A plunger 8 that slides within a cylinder 9 formed on a modulator body 27 which is fastened together with the modulator body 27 is in contact with the modulator body 27 via a sealing device 28 and a separator 29 .

In the figure, reference numeral 30 denotes a bolt that connects the brake pipe 31 protruding inward from the side surface of the modulator housing 15 to the conduit 10.

Because of this structure, for extremely gentle braking, the oil chamber A is contracted by sliding the piston 4 in the pressure side direction, and the hydraulic oil in the oil chamber A flows into the expanding oil chamber at the top. At the same time, excess oil corresponding to the inflow volume of the inner tube enters the hollow tube 2 from the through hole 5, and from there the relief valve 6
While generating a predetermined damping force determined by the gap l, the oil flows into the oil chamber B defined above the relief valve 6 and performs a buffering action.

The gap 1 at this time becomes the so-called front leakage characteristic, but since the braking force is weak, the plunger 8 and the rod 1
The amount of movement of 7 is small, and the damping force can be set low in the range where this gap 1 exists, resulting in good riding comfort.

At the same time, by providing the gap 1 in this way, the damping resistance given to the hydraulic oil passing through this area during normal compression side operation (without braking) is reduced, preventing the compression side damping force from increasing unnecessarily. This improves the buffering characteristics in the normal operating range.

When the braking force increases, the plunger 8 and the rod 17 in contact with the plunger 8 are pulled further upward against the return spring 24 in accordance with the brake circuit pressure.

Along with this, the interval l is gradually narrowed,
The degree of fitting of the cylindrical tip 17A into the center hole 6A of the relief valve 6 also increases in proportion to the amount of upward movement of the rod 17, and as described above, the relief spring 7 is lifted to open the valve port. Since the amount increases, the set load of the relief valve 6 increases.

As a result, the flow from oil chamber A to oil chamber B via the through hole 5
A resistance corresponding to the spring load is applied to the flow of excess oil to the front fork, and the pressure in the oil chamber A increases, thereby effectively preventing nose dive of the front fork. This will not be communicated to the driver, and stable vehicle body posture and steering stability will be guaranteed.

In addition, during the expansion operation in which the oil chamber A expands, the oil hole rod 20 functions as a suction check valve and rapidly opens the second passage consisting of the through hole 19, etc., as described above. The oil in B is quickly returned to oil chamber A without any resistance. Therefore, the extension operation of the front fork is performed smoothly, and the occurrence of cavitation is also prevented.

In this embodiment, the relief valve mechanism 13 and the modulator part 14 are arranged and housed in tandem in the longitudinal direction at the bottom part of the outer tube 1, so there is no protruding part on the side of the outer tube 1. It has a good design and can be easily applied to a rearing axle type front fork.

In addition, a relief valve mechanism 13 is provided in the hollow tube 2.
Since it has a structure in which the parts can be assembled in one piece, there is no need for a special bubble body, and the number of parts can be reduced and assembly is simple, resulting in cost reduction.

Next, FIG. 3 shows another embodiment of this invention.

This is an example in which the modulator section 14 is formed in a cassette type with a short axial length and is detachably attached to the bottom section of the outer tube 1, and the basic structure is the same as that in FIG. 2.

That is, after fixing the modulator body 27 on which the conduit 10 is installed horizontally to the protruding tip 2A of the hollow tube 2 with the nut 26, the case 32 that previously covered the modulator body 27 is attached to the lower end boss portion 33 of the outer tube 1. It is designed to be tightened using a knot 34.

In the figure, 35 is a rotation prevention pin, and 36 is an air breather.

According to this, from Fig. 2, outer tube 1
As the axial length of
7, it can also be applied to a center axle type front fork.

As explained above, according to the present invention, the modulator section (including the relief valve mechanism) of the anti-nose dive mechanism is integrated into the outer tube bottom, which is good in terms of design and has a wide range of applications. This has the effect of providing a wide hydraulic shock absorber for two-wheeled vehicles.

In addition, in this invention, the gap between the center holes decreases as the degree of insertion of the rod into the center hole of the relief valve increases, that is, as the braking force increases, the effect of suppressing nose dive depends on the braking force. be appropriate. In addition, when a strong thrust is applied during braking, the relief valve lifts and suddenly opens the gap between the rod and the rod.
It can quickly absorb thrusts. Therefore, good steering stability is ensured even during the braking process.

In addition, this invention is provided with a suction check valve function that opens a second passage that communicates between both oil chambers during extension operation, so cavitation is prevented from occurring due to pressure drop in the return side oil chamber during extension operation. Furthermore, there is no risk.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway sectional view of a conventional example, FIG. 2 is a sectional view of a main part of the present invention, and FIG. 3 is a sectional view of a main part of another embodiment. 1... Outer tube, A... Oil chamber, B...
Oil chamber (oil reservoir chamber), 5...through hole, 6...relief valve,
7... Relief spring, 14... Modulator section, 8... Plunger, 17... Rod, 17
A... Cylindrical tip portion, 24... Return spring, 11... Bottom partition body, 2A... Protruding tip portion,
12, 26...nut, 27...modulator body.

Claims (1)

[Claims] 1. It has an inner tube and an outer tube that slide against each other in the axial direction, and allows surplus hydraulic oil in the oil chamber that contracts during pressure side operation to escape to the oil reservoir chamber, and a relief valve mechanism is installed in this relief passage. In addition, in the hydraulic shock absorber for a two-wheeled vehicle in which the set load of the relief valve mechanism is increased or decreased depending on the braking force, the relief valve mechanism is an annular relief valve biased in a closing direction by a relief spring;
and a rod which is fitably fitted into the center hole of the relief valve and fits closer to the center hole in response to an increase in braking force to narrow the relief passage and increase the set load of the relief valve. On the other hand, a second passage passing through the inside of the relief valve and the rod and communicating between the oil sump chamber and the oil chamber is formed in parallel with the relief passage, and a second passage is formed in the second passage from the oil sump chamber to the oil chamber. A check valve that only allows the flow of hydraulic oil is provided, and the relief valve mechanism and a modulator part that adjusts the degree of insertion of the rod into the center hole of the relief valve according to the braking force are integrated inside the outer tube bottom. A hydraulic shock absorber for a two-wheeled vehicle, characterized in that it can be assembled automatically.