JPH0452503Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of the Invention) The present invention relates to a damping force generating device for a front fork of a motorcycle.

(Prior art) In general, a front fork of a motorcycle has an inner tube and an outer tube that are slidable relative to each other, and a piston at the upper end that is fixed to the bottom of the outer tube and is slidable on the inner tube. It consists of a sheet pipe fitted to the In this type of front fork,
Many mechanisms generate push-side damping force by drilling an orifice into the peripheral wall of the seat pipe, but in the case of an orifice, the damping force is generated in proportion to the square of the piston speed. Therefore, the low speed range of piston speed is
The damping force is low, and the damping force increases rapidly in the high-speed range, but the range of choices is narrow and it is difficult to set the damping force to match the rider's preferences and riding style. In particular, in the case of a front fork with a long stroke such as an off-road vehicle, if an attempt is made to generate damping force using only the orifice, the damping force will change drastically between the low speed range and the high speed range, resulting in the above problem.

(Purpose of the invention) Therefore, the purpose of the invention is to develop a front fork of a motorcycle that is configured to avoid a sudden change in damping force from a low speed range to a high speed range and to increase the setting range of the damping force. An object of the present invention is to provide a damping force generating device.

(Structure of the invention) In order to achieve the above object, according to the invention, a relief valve is slidably attached to the upper end of the rod provided along the axis at the bottom of the seat pipe,
This relief valve is biased by a spring so as to always close the opening of a valve seat installed in the seat pipe, and a spring receiving seat that receives the opposite side of the spring from the relief valve is fixed to the upper end of the rod, The outer periphery of the spring receiving seat is formed into a cylindrical shape to constitute a yoke member, and an orifice is provided in the peripheral wall of the seat pipe between the relief valve and the yoke member in series with the yoke member, and an orifice is provided in the seat pipe below the relief valve. Oil holes may be provided in the peripheral wall.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 2 shows a longitudinal section of a front fork of a motorcycle equipped with the damping force generating device of the present invention. Reference numeral 1 denotes an outer tube configured as a bottom case, the upper end of which is open, and an inner tube 2 configured as a fork pipe is slidably fitted into the outer tube 1.
A seat pipe 4 having a piston 3 at its upper end is fixed to the bottom of the outer tube 1 with bolts via an oil lock piece 5 and a base 5'. An oil hole 6 is provided at the upper end of the seat pipe 4.

An oil lock collar 8 that fits into the oil lock piece 5 at the end of the pushing process is attached to the lower end of the inner tube 2, and a free valve 10 having a flow path between it and the fixing ring 9 is arranged above it. and
A groove 11 extending in the radial direction is formed on the upper surface of the free valve 10. 12 is a rebound spring. A sealing mechanism 13 is attached to the upper end of the outer tube 1 to slidably seal the gap with the inner tube 2, and a suspension spring 14 is attached between the upper end of the inner tube 2 and the piston 3 of the seat pipe 4. There is.

According to the present invention, a damping force generating device 20 is provided at the bottom of the seat pipe 4. Figure 1 shows an enlarged view.

A rod 21 is inserted along the axis of the seat pipe 4 from above the base 5' to which the lower end of the seat pipe 4 is screwed.
extends upward, and a relief valve 22 is slidably mounted approximately at the center of this rod 21, and its lower surface is supported by a stop ring 23. Below the relief valve 22, a valve seat 24 having an annular opening is attached to the inner peripheral surface of the seat pipe 4. This valve seat is configured as a check valve by being biased upward by a spring 25 supported by the base 5'. The upward movement of the valve seat 24 is limited by a stop ring 26 in the seat pipe 4. relief valve 2
2 is a spring 2 so as to keep the opening of the valve seat 24 closed at all times.
7 is biased downward. The opposite side of the spring 27 from the relief valve 22 is supported by a spring receiving seat 28 fixed to the upper end of the rod 21 with a nut, and the outer circumference of the spring receiving seat 28 is formed into a cylindrical shape in the axial direction, and the spring receiving seat 28 is formed into a cylindrical shape in the axial direction. It is configured as. An orifice 29 is provided on the peripheral wall of the seat pipe 4 at a position between the yoke member 28 and the relief valve 22, that is, in series with the yoke member 28.
An oil hole 30 is provided at a position below the check valve 24. Further, an orifice 31 is provided on the peripheral wall of the seat pipe 4 at a position that is always closed by the outer peripheral surface of the check valve 24.

In FIG. 1, the interior of the front fork includes an internal chamber A of the seat pipe 4, an external chamber B,
Chamber C between the piston 3 of the seat pipe 4 and the free valve 10 of the inner pipe 2, the inner pipe 2 above the piston 3
The inner chamber D and the chamber E in the seat pipe 4 below the relief valve 22 are divided, and the upper part of the chamber D is filled with gas, and all other chambers are filled with oil.

Next, the operation of the front fork damping force generating device 20 configured as above will be explained.

When the inner tube 20 descends during the pushing process, the oil in the B chamber pushes up the free valve 10 and flows into the C chamber without resistance, and at the same time the damping force generating device 20 acts to generate a pushing side damping force. That is, when the flow of oil in chamber B is slow and the speed is low, the oil in chamber B outside the seat pipe 4 passes through the upper orifice 29 of the seat pipe 4 as shown by arrow F and flows into chamber A inside the seat pipe 4. After that, the upper part 2
8 and the annular gap between the sheet pipe 4, and the resistance when flowing through this annular gap becomes the push-side damping force. This is clear from Figure 3, which shows the relationship between piston speed and damping force, in the low speed range,
This is because the damping force (straight line) caused by the yoke member contributes more as the push-side damping force than the damping force (quadratic curve) caused by the orifice. When the flow inside the B chamber outside the seat pipe 4 becomes faster (high-speed range), the damping force when passing through the upper orifice 29 of the seat pipe 4 increases with the damping force when flowing around the outer periphery of the yoke member 28, as shown in FIG. Since the proportion contributing to the push-side damping force is greater than the force, the resistance when flowing through the orifice 29 acts as the push-side damping force, increasing the rate of increase in the push-side damping force.
When the oil pressure in the B chamber exceeds a certain pressure set by the relief spring 27, the oil flowing from the B chamber into the E chamber as indicated by arrow G pushes up the relief valve 22 and flows into the A chamber through the opening. This prevents the damping force from further increasing secondarily (see point A in Figure 3).

When the inner pipe 2 rises during the extension process, the free valve 10 lowers and seats on the oil lock collar 8, so that the oil in the C chamber flows into the A chamber in the seat pipe 4 through the oil hole 6. A damping force on the extension side is generated due to the flow path resistance when passing through the oil hole 6. Also, B
When the flow of oil in the room is slow and the speed is low, the oil in chamber A in the seat pipe 4 passes through the outer periphery of the yoke member 28 due to the negative pressure in the chamber B, and then flows to the upper side of the seat pipe 4 as shown by arrow H. It passes through the orifice 29 and replenishes the oil in the A chamber. Then, when the negative pressure in chamber B becomes higher than a certain pressure, check valve 24 is sucked through oil hole 30 against spring 25, and oil in chamber A is generated between relief valve 22 and check valve 24. Arrow I through the gap
The oil in the A chamber flows into the B chamber through the orifice 31 adjacent to the check valve 24 to replenish the oil.

(Effects of the invention) As described above, in the present invention, the outer periphery of the spring receiving seat of the relief valve provided at the bottom of the seat pipe is formed into a cylindrical shape to constitute a yoke member, and the seat pipe is connected in series with the yoke member. Since the orifice is provided on the peripheral wall, the damping force can be generated by the chain yoke member in the low speed range of the piston speed and by the orifice in the high speed range, and the setting range of the damping force can be increased. In addition, due to the above-mentioned arrangement of the orifice and the choke member in series, the oil passes through the orifice and is squeezed by the choke member during the pushing process, so the oil pressure after passing through the orifice is not significantly reduced, and the occurrence of cavitation can be suppressed. Therefore, the damping force becomes stable. Further, since the spring receiving seat of the relief valve is constructed as a yoke member, there is an advantage that there is no need to provide a special part as a yoke member in addition to the relief valve.

[Brief explanation of the drawing]

Fig. 1 is a partially enlarged vertical cross-sectional view of a damping force generating device of the present invention for a front fork, Fig. 2 is a longitudinal cross-sectional view of a front fork equipped with a damping force generating device of the present invention, and Fig. 3 is a damping force generator of the present invention. 3 is a graph showing the relationship between damping force and piston speed of the force generator. 1... Outer tube, 2... Inner tube, 3... Piston, 4
... Seat pipe, 21 ... Rod, 22 ... Relief valve, 24 ... Valve seat, 27 ... Spring, 2
8...Chiyoke member, 30...Oil hole.

Claims (1)

[Scope of utility model registration request] an inner tube and an outer tube that are slidable relative to each other;
In a front fork damping force generating device consisting of a seat pipe that is fixed to the bottom of the outer pipe and whose upper end piston is fitted into the inner pipe, a rod is provided along the axis at the bottom of the seat pipe. A relief valve is slidably attached to the upper end of the
This relief valve is biased by a spring so as to always close the opening of a valve seat installed in the seat pipe, and a spring receiving seat that receives the opposite side of the spring from the relief valve is fixed to the upper end of the rod, The outer periphery of the spring receiving seat is formed into a cylindrical shape to constitute a yoke member, and an orifice is provided in the peripheral wall of the seat pipe between the relief valve and the yoke member in series with the yoke member, and an orifice is provided in the seat pipe below the relief valve. A damping force generating device characterized by having oil holes in the peripheral wall.