JPH031536B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverted front fork in which an inner cylinder is arranged at the bottom and an outer cylinder is arranged at the top, and the inner cylinder is connected to the axle side and the outer cylinder is connected to the vehicle body side.

The so-called upright type front fork has an inner cylinder on top and an outer cylinder on the bottom, and the upper part of the inner cylinder is connected to the vehicle body through upper and lower brackets, and the lower part of the outer cylinder is connected to the axle side. be. Therefore, it is necessary to provide a fitting length below the lower bracket that is necessary for the stroke length of the inner cylinder and the outer cylinder and for the strength of the overlap between the inner cylinder and the outer cylinder when the front fork is fully extended. For this reason, in the case of such an upright front fork,
The overall length must be long, which poses many design difficulties, especially for vehicles that require a long stroke such as off-road vehicles.

The present invention was made in view of such circumstances,
The purpose of the invention is to ensure a sufficiently long stroke and obtain stable damping characteristics.
To provide an inverted front fork that can be manufactured at low cost.

In order to achieve such an object, the present invention provides a front fork in which an inner cylinder is disposed at the bottom and an outer cylinder is disposed at the top, and these inner and outer cylinders are slidably fitted together, and the present invention provides a front fork in which the inner cylinder is arranged at the bottom and the outer cylinder is arranged at the top, and the inner and outer cylinders are fitted together so as to be slidable. The inner and outer chambers of the seat pipe provided are gas chambers, and an annular spring holder equipped with an oil passage communicating with these gas chambers is screwed to the lower end of the seat pipe, and the spring holder and a cap member at the lower end of the inner cylinder are screwed together. A coil spring is stretched between them, and an annular check valve is installed on the outer periphery below the oil hole of the seat pipe, which opens during the pushing stroke and closes during the pulling stroke, and the upper end of the inner cylinder The gist is that a relief valve is installed that opens when the gas chamber pressure exceeds a certain level.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a half-cut side view of a front fork according to the present invention, and FIG. 2 is an enlarged sectional view of a main part of the front fork.

In the front fork 1 shown in FIG.
is an outer cylinder located above, and an upper part of an inner cylinder 3 is fitted into the outer cylinder 2 from below so as to be vertically slidable. An oil seal 4 that slides on the outer periphery of the inner cylinder 3 is fitted on the inner periphery of the lower part of the outer cylinder 2, and an oil seal 4 made of a soft material such as oil-impregnated plastic is fitted on the outer periphery of the lower part of the outer cylinder 2. A moving member 5 is fitted onto the outside.

In addition, there is a seat pipe 6 in the upper part of the outer cylinder 2 as shown in the figure.
The lower end of the seat pipe 6 is in sliding contact with the inner periphery of the inner cylinder 3 via an annular check valve 7 fitted on the outer periphery of the seat pipe 6. The check valve 7 is of a type that opens during the push stroke of the front fork 1 and closes during the pull stroke.

Further, an annular spring holder 8 having an oil passage 8a and an oil passage 8b is screwed to the inner periphery of the lower part of the seat pipe 6, and an oil hole 6 is provided at the lower part of the side wall of the seat pipe 6.
A is drilled. Note that the cross-sectional area of the oil passage 8b is set larger than the cross-sectional area of the oil passage 8a.

On the other hand, the upper end of the inner tube 3 is in sliding contact with the outer periphery of the seat pipe 6 via a guide member 9 fitted on the inner circumference side of the inner tube 3. As shown in the figure, a coil spring 11 is stretched between the cap member 10 and a cap member 10 provided to close the lower end of the cap member.

A cylindrical axle stay 12 is fitted on the outer periphery of the lower part of the inner cylinder 3, and a cylindrical protector 13 is attached to the axle stay 12 so as to cover the sliding parts of the inner and outer cylinders 3 and 2. The bottom edge is fixed.

The interior of the front fork 1 is divided into chambers A, B, C, and D as shown in the figure.
Hydraulic oil is sealed in chambers C and D, and in particular the upper portions of chambers A and D are occupied by gas. A rebound spring 14 is provided inside the chamber B.

In the front fork 1 described above, the upper end of the outer cylinder 2 is connected to the vehicle body side, and the lower end of the inner cylinder 3 is connected to the axle side via the axle stay 12.

Next, the function of the front fork 1 will be explained.

During the pushing stroke in which the wheel receives an impact and the inner cylinder 3 enters the outer cylinder 2, the spring receiver 8 provided on the seat pipe 6 enters the inner cylinder 3 while compressing the coil spring 11, and the spring receiver 8 Decrease the volume of the lower chamber C. Therefore, the hydraulic oil in the chamber C flows through the oil passages 8a and 8b provided in the spring receiver 8 to the inside of the seat pipe 6.
It is fed into the outer chambers B and D, where it generates push-side damping force. At this time, the volume of chamber B increases, but an amount of oil commensurate with this volume increase flows into chamber B through the oil passage 8b, check valve 7, and oil hole 6a, and oil flows into chamber B. will be replenished.

As the stroke of the push stroke progresses, the gas occupying the upper portions of chambers A and D is compressed and acts as a gas spring, and its reaction force increases, so that the so-called bottoming out phenomenon is prevented from occurring. If necessary, it is also possible to provide annular oil lock pieces and collars on the outer periphery of the seat pipe 6 and the inner periphery of the inner cylinder 3, respectively, to forcibly activate the oil lock.

Next, the outer cylinder 2 moves upward with respect to the inner cylinder 3 due to the reaction force of the gas spring and the reaction force of the coil spring 11, and the front fork 1 shifts to a retraction stroke. At this time, the volume of the chamber B will decrease, but since the check valve 7 is operated in the closing direction by hydraulic pressure, the hydraulic oil in the chamber B flows only from the oil hole 6a to the chamber D inside the seat pipe 6. and generates a pull-side damping force.

The guide member 9 provided in the inner cylinder 3 is the seat pipe 6
When the front fork 1 is located below the oil hole 6a, the chamber B is in a sealed state and the front fork 1 is in an oil lock state on the extension side.

In the above, since the front fork 1 has the inner cylinder 3 located at the bottom and the outer cylinder 2 at the top, it is possible to shorten the overall length compared to the conventional upright type, and it is assumed that the overall length is the same. This has the advantage of allowing a longer stroke, and the design constraints of off-road vehicles, which require a particularly long stroke, are relaxed.

Furthermore, since the connection of the inner and outer cylinders 3 and 2 to the axle side and the vehicle body side can be achieved through a dedicated mounting member (for example, the axle stay 12), these inner and outer cylinders 3 and 2 are made of steel. This also makes it possible to significantly reduce the cost of the front fork 1.

Furthermore, among the oil passages 8a and 8b provided in the spring receiver 8,
Since the cross-sectional area of one oil passage 8b is made larger than that of the other oil passage 8a, replenishment of oil to chamber B is ensured, and the pull-side damping force characteristics are stabilized.

In addition, according to the present invention, since the coil spring 11 is always under the oil level, phenomena such as so-called oil level shortage do not occur, the damping force is stabilized, and the spring receiver 8 and the seat pipe 6 are screwed together. Therefore, the spring receiver 8 can be replaced as desired, and thereby the push-side damping force can be adjusted as desired.

By the way, in the embodiment described above, the chambers D and A inside and outside the sheet pipe are partitioned by the sheet pipe, and oil easily flows into the chamber A through the gap between the guide member 9 and the sheet pipe, so a type of pumping is performed. Due to this phenomenon, the amount of oil increases each time the inner and outer cylinders slide, and the oil level heights in chambers A and D become different.

Therefore, if this state is left as is, room D
Since the oil level may drop below the oil hole 6a, the buffering function of the front fork will be significantly impaired, and there is also a risk that oil may flow out from the seal portion due to an increase in the internal pressure of the chamber A.

Therefore, the present invention provides for the interior and exterior of the sheet pipe.
The guide member 9 provided at the upper end of the inner cylinder 3 in the above embodiment was used as a relief valve 109 in order to automatically adjust the oil level height and not impair the buffer function.
Note that the relief valve 109 opens when the pressure in the chamber A reaches a certain value or more.

Thus, according to the present invention, in addition to the effects obtained in the embodiments described above, the oil level height of the chambers inside and outside the seat pipe is automatically adjusted to provide a stable buffering function. It will be done.

According to the present invention, the above effects can be obtained.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a half-cut side sectional view of a front fork according to the present invention, and FIG. 2 is an enlarged sectional view of the main part of the front fork. In the drawing, 1 is the front fork, 2 is the outer cylinder, and 3 is the front fork.
is an inner cylinder, 6 is a seat pipe, 7 is a check valve, 8 is an annular spring holder, 9 is a guide member, 11 is a coil spring,
109 is a relief valve, and A, B, C, and D are chambers.

Claims (1)

[Scope of Claims] 1. An inverted front fork in which an inner cylinder is arranged at the bottom and an outer cylinder is arranged at the top, these inner and outer cylinders are slidably fitted together, and hydraulic oil is sealed inside. The inner and outer chambers of the sheet pipe installed in the upper part of the outer cylinder form gas chambers, and an annular spring holder having an oil passage communicating with these gas chambers is screwed to the lower end of the sheet pipe. A coil spring is stretched between the seat pipe and the cap member at the lower end of the inner cylinder, and an annular check valve is installed on the outer periphery of the seat pipe below the oil hole. An inverted front fork characterized by having a relief valve disposed at the upper end of the cylinder that opens when the pressure in the gas chamber outside the seat pipe exceeds a certain level. 2. The oil passage formed in the annular spring receiver is characterized in that an oil passage area leading to a gas chamber on the outside of the seat pipe is larger than an oil passage area leading to a gas chamber inside the seat pipe. The inverted front fork described in item 1.