JPH0321771B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a damping force generating device in a front fork used in a motorcycle or the like.

A front fork is a shock absorber that generally supports the front wheel of a motorcycle using a shock absorbing method.A front fork is a shock absorber that supports the front wheel of a motorcycle, etc., and has an inner cylinder and an outer cylinder that are slidably fitted together, and a seat pipe that is inserted and fixed into the outer cylinder. There is a known mechanism in which an auxiliary piston is provided that is slidable within the inner cylinder, and the impact generated in the vertical direction of the wheel is alleviated by hydraulic oil sealed inside.

In this type of front fork, the oil chamber formed between the inner cylinder and the seat pipe is divided into upper and lower parts by a check valve fitted on the inner circumference of the lower part of the inner cylinder, and the oil on the side that contracts as the front fork expands and contracts. Oil flows from the chamber to the oil chamber in the seat pipe and the expansion side oil chamber through an oil hole drilled in the seat pipe to generate damping force, absorbing and mitigating the impact received by the wheels. For this reason, the damping force increases in proportion to the square of the front fork's telescoping speed. Therefore, even if a preferable damping force is set in the low speed range of the telescoping speed, a higher damping force will occur in the high speed range. This problem tends to occur, and it is not possible to obtain a good riding comfort.

Therefore, as shown in FIG. 1, an annular valve seat 2 is slidably fitted onto the seat pipe 1, and a check valve 3 is slidably removed from a circular projection protruding from the center of the lower surface of the valve seat 2. Along with fitting,
A damping force generating device has been proposed in which the lower surface of the check valve 3 is supported by an annular protrusion 6 formed on the upper surface of an oil lock collar 5 inserted into the inner periphery of the lower end of the inner cylinder 4. The valve seat 2 has a radial groove formed on its upper surface and a plurality of oil holes on the bottom surface of the groove, and the upper surface is pressed by a disc spring 7. Further, 8 is a spring seat having an oil hole on its inner periphery. In this damping force generating device, when the extension speed of the front fork becomes high, the check valve 3 is bent downward and opened, and oil flows from the upper contraction side oil chamber to the lower expansion side oil chamber. Furthermore, when the compression speed increases, the check valve 3 and the valve seat 2 move upward, and the space between the annular protrusion 6 and the check valve 3 opens, so that the oil chamber flows from the lower contraction side oil chamber to the upper expansion side oil chamber. and the oil flows. Therefore, according to this device, there is no longer a problem that a high damping force is generated in the high speed range of the telescopic operation speed as in the conventional art. However, when assembled with the axis of the seat pipe misaligned with the axes of the inner and outer cylinders, the valve seat is fitted onto the seat pipe, so the oil lock collar disposed inside the inner cylinder is formed on the upper surface of the valve seat. There was a problem in that the force, position and area for pressing the check valve between the annular protrusion and the outer periphery of the lower surface of the valve seat varied, making it impossible to obtain the designed damping force.

This invention proposes a damping force generating device for a front fork with the aim of solving the above problems.
A check valve in which an annular valve seat is fitted on the inner periphery of the lower part of the inner cylinder to partition an oil chamber formed between the inner cylinder and the seat pipe, an oil hole is bored in the valve seat, and the check valve opens when extended. and a check valve that opens during compression.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

FIG. 2 is a longitudinal sectional front view showing a main part of a front fork having a device according to an embodiment of the present invention, and FIG. 3 is an enlarged view showing an embodiment of the present invention. 9 is an inner cylinder, 10 is an outer cylinder, and the gap between the sliding fitting portions is sealed by an oil seal 11. 12
is inserted into the outer cylinder 10, and its base end is connected to the bolt 1.
This is a seat pipe which is fixed to the bottom of the outer cylinder 10 at 3 and has an auxiliary piston 14 fixed to the tip thereof which allows the inner cylinder 9 to slide freely. Further, an oil lock piece 15 is externally fitted and fixed to the base end of the seat pipe 12. On the other hand, on the inner periphery of the lower end of the inner cylinder 9,
An annular spring seat 17 having a plurality of oil holes 16, an annular oil passage 18 formed between the inner peripheral surface of the spring seat 17 and an outer peripheral surface of the seat pipe 12, and a plurality of oil holes 19 on the outer peripheral side thereof. A perforated valve seat 20, a check valve 21 made of an annular leaf spring that contacts the lower surface of the valve seat 20 to open and close the oil hole 19, and an oil lock collar 22 are installed in this order. Note that 23 is a check valve that opens and closes the annular oil passage 18, and is pressed against the upper surface of the oil passage 18 by a spring 24. Also 2
5 and 26 are oil holes bored in the sheet pipe 12.

In the front fork with the above configuration,
During the compression stroke in which the front fork contracts, the inner cylinder 9 enters the outer cylinder 10, and the oil in the oil chamber inside the outer cylinder flows into the seat pipe 12 through the oil hole 26, causing attenuation proportional to the square of the compression speed. force is generated. At this time, as shown in FIG. 3, the upper and lower oil chambers formed between the inner cylinder 9 and the seat pipe 12 are blocked, but as the compression speed increases, the internal pressure in the lower oil chamber increases and the spring 24 The check valve 23 is pushed upward by overcoming the elastic force of the annular oil passage 18.
To open the oil chamber, oil flows from the lower oil chamber to the upper oil chamber.
The damping force does not increase excessively. Also, during the extension stroke, the oil in the lower oil chamber of the auxiliary piston 14 is transferred to the oil hole 2.
5 and into the seat pipe 12, but when the expansion speed increases, the check valve 21 bends downward and the oil hole 19 is opened, and the oil flows from the upper oil chamber to the lower oil chamber, similar to when compressing. The damping force will not increase significantly.

According to the present invention, as described above, the damping force does not increase excessively even in the high speed range of the telescopic operation speed, and the ride comfort is significantly improved when used for medium-sized and large-sized on-road vehicles. . Furthermore, the opening and closing of the check valve, that is, the damping force, can be adjusted as desired by adjusting the strength of the spring, the number of leaf springs, the thickness, etc. Furthermore, even if the seat pipe is assembled so that its axial center is misaligned with the axes of the inner and outer cylinders, the force, position, and area for pressing the check valve do not change, and a stable damping force can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an enlarged view showing a conventional damping force generating device for a front fork, Fig. 2 is a longitudinal sectional front view showing the main parts of a front fork having an embodiment of the device of the present invention, and Fig. 3 is an enlarged view showing a damping force generating device of a conventional front fork. It is an enlarged view showing an example. In the figure, 9...Inner cylinder, 10...Outer cylinder, 12...Seat pipe, 14...Auxiliary piston, 15...Oil lock piece, 16, 19, 25, 26...
Oil hole, 17... Spring seat, 18... Annular oil passage, 20... Valve seat, 21, 23...
Check valve, 24...spring.

Claims (1)

[Claims] 1. The inner cylinder and the outer cylinder are slidably fitted together, and an auxiliary piston that is slidable inside the inner cylinder is provided at the tip of a sheet pipe that is inserted and fixed into the outer cylinder, and
In a front fork having hydraulic oil sealed inside, an annular valve seat is fitted on the inner periphery of the lower part of the inner cylinder to partition an oil chamber formed between the inner cylinder and the seat pipe, and a plurality of valve seats are fitted on the inner periphery of the lower part of the inner cylinder. A check valve consisting of an annular leaf spring that opens when extended is provided on the lower surface of the oil hole, and an annular oil passage formed between the inner circumferential surface of the valve seat and the outer circumferential surface of the seat pipe. A damping force generating device for a front fork, comprising a check valve that opens against a spring when compressed.