JPS6323957B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a front fork for a two-wheeled vehicle.

An example of a conventional inverted oil type front fork in which the outer tube is disposed above the inner tube is as shown in FIG. However, for convenience of drawing, the upper part of the front fork is shown on the left and the lower part on the right.

First, to explain this, inner tube 1
is slidably inserted into an outer tube 4 disposed above via a piston 2 fixed to its upper end and a bearing 3 such as a slide metal, and is inserted into an inner tube through an orifice 5 provided in the piston 2. The oil chamber A inside the outer tube 1 and the oil chamber B inside the outer tube 4 communicate with each other. The upper part of the oil level of the outer tube 4 is an air chamber 6, which is sealed and shut off from the outside air, and responds to the increase in the volume of entry into the inner tube 1 during compression operation. It contracts due to the rising oil level.

In order to obtain predetermined operating characteristics, the air chamber 6 must be set so that an appropriate compression ratio can be obtained with respect to the entry of the inner tube 1. Therefore, it was necessary to provide an axial margin b above the maximum raised position of the piston 2 to ensure at least a constant volume of the air chamber 6 at the time of maximum contraction.

By the way, the figure shows a state where the inner tube 1 is moving to the maximum extension side, and the symbol a indicates the area where the piston cannot slide from the upper end 7 of the outer tube 4 to the lower end of the spring stopper 8.
The code st is the piston 2 for the outer tube 4
shows the effective operating range of

Therefore, if the longest distance from the front fork upper end 7 to the upper end of the piston 2 is L, then L is the sum of a, st, and b. That is, the following equation is obtained.

L = a + st + b ... (1) In this way, in the case of the conventional front fork, there is a margin in the axial direction to secure the oil chamber B and the air chamber 6 when the inner tube 1 moves to the maximum pressure side. Since it is necessary to provide the outer tube 4, the length of the above L becomes relatively long, and as a result, the outer tube 4
or the overall length of the front fork has become longer,
Due to the limited distance between the handlebar and the axle, installation problems arose.

On the other hand, if the under bracket 9 is not extended and the distance (fitting length) between the piston 2 and the bearing part 3 is shortened, the balance will be lost and the operating characteristics will become unstable.

Another problem was that the sliding range st of the pushston 2 covered the fixed position of the under bracket 9.

Since the under bracket 9 is normally fixed by bolting, welding, etc., distortion occurs in the inner diameter of the outer tube 4, and when the piston 2 slides into the distorted position, the operating characteristics are significantly impaired.

Therefore, conventionally, as a measure to deal with the inner diameter distortion, an auxiliary pipe 10 is attached to the outer peripheral wall of the outer tube 4 and welded at a position outside the sliding range st of the piston 2. Although the under bracket 9 is fixed, there are problems such as an increase in the number of processing steps and weight.

This invention was made by focusing on such conventional problems, and it is designed to maintain a constant oil level in the oil chamber provided inside the inner tube regardless of the expansion and contraction of the front fork. The object of the present invention is to provide a front fork that solves the above-mentioned problems by providing an annular gap between the outer tubes to absorb the volume of hydraulic oil that has entered, thereby eliminating the need for the margin area b for ensuring the compression ratio. .

In order to achieve the above object, the present invention fixes an annular bearing part to the end of the inner tube, which slides in an oil-tight manner on the outer periphery of the piston rod and the inner periphery of the outer tube. The oil chamber B between the piston and the annular bearing section is communicated via a damping means, and the oil chamber C, which communicates with the oil chamber B via an orifice, is connected to the outer periphery of the inner tube, the inner periphery of the outer tube, and the annular bearing section. The cross-sectional area of the oil chamber C is set to be approximately equal to the cross-sectional area of the piston rod, and the oil chamber C absorbs oil level fluctuations, thereby eliminating the need for an upper air chamber.

This invention will be explained below based on the drawings.

FIG. 2 is an overall sectional view showing an embodiment of the present invention, and FIG. 3 is a sectional view of the main part of FIG.
For convenience of drawing, the upper part of the front fork is shown on the left and the lower part on the right.

First, to explain the structure, an inner tube 11 having a cylindrical shape with a bottom has an oil chamber A filled with oil, and an outer tube 12 disposed above the inner tube 11 via a bearing portion 13 such as a slide metal. It is inserted freely and slides freely. A piston rod 14 is interposed at the axis of the outer tube 12, and the piston rod 14 is fixed to the outer tube 12 via a fixing member 16 fixed near the cap 15 at the upper end of the outer tube 12. A piston 17 is fixed to the lower end of the piston rod 14, and an annular gap formed between the outer circumferential wall of the piston rod 14 and the inner circumferential wall of the outer tube 12 is provided at the upper end of the inner tube 11 in an oil-tight manner. An annular bearing portion 18 that slides freely is fixedly provided.

The annular sliding bearing part 18 is for completely oil-tightly separating the upper air chamber E from the lower oil chambers B and C, and includes a seal 18a for the piston rod 14 and a seal 18b for the outer tube. and its mounting bracket 18c and bracket 18c
and an integral stopper 18d. The air chamber E is formed between the cap 15 and the stopper 18d of the bearing part 18, and the air chamber E is formed between the cap 15 and the stopper 18d of the bearing part 18.
It communicates with the atmosphere through an air hole 20 located near the air hole 20 . Also, at the maximum compression, stopper 1
A conical cylindrical cushion rubber 21 that elastically abuts against the shock absorber 8d and softens the shock is fixed to the fixing member 16.

Between the piston 17 and the sliding bearing portion 18 is an annular oil chamber B in which a coil spring 22 disposed in the axial direction is interposed. This oil chamber B is piston 1
Check valve 23 and piston rod 14 provided at 7
The piston 17 is inserted through the orifice 24 that passes through the
It communicates with oil chamber A below. Also, the check valve 23 only allows flow from oil chamber A to oil chamber B.
The valve closes when the front fork operates on the rebound side.

An annular chamber formed between the outer circumferential wall of the inner tube 11, the inner circumferential wall of the outer tube 12, the annular sliding bearing portion 18, and the bearing portion 13 at the lower end of the outer tube 12 is an oil chamber C that serves as an escape path for oil. The oil chamber C communicates with the oil chamber B through an orifice 25 passing through the inner tube 11. Further, the length of the oil chamber C expands in the axial direction as the annular sliding bearing portion 18 rises along the piston rod 14, but the cross-sectional area of the oil chamber C increases depending on the amount of increase in the penetrating volume of the piston rod 14. The increase in volume of the oil chamber C is designed to be approximately equal.
Therefore, oil corresponding to the increase in the infiltration volume of the piston rod 14 during left-side operation flows from the oil chamber B to the oil chamber C through the orifice 25. In this way, the oil chamber C functions to absorb the oil that is removed from the oil chamber B due to the entry of the piston rod 14, thereby preventing fluctuations in the oil level.

Furthermore, a volume compensation chamber D is provided in the inner tube 11 to compensate for the volume expansion of oil due to temperature rise.
It is located at the bottom of the oil chamber A inside. The volume compensation chamber D is formed inside an elastic cylindrical body 26 made of highly elastic thin steel material, rubber, etc., and the elastic cylindrical body 26 is fixed to a stopper 27 so as to protrude toward the oil chamber A side. Therefore, the oil level in the oil chamber B is always constant due to the oil chamber C and the volume compensation chamber D, and therefore there is no need to form an air chamber above the oil chamber.

Further, a pressure side spring 28 is interposed in the oil chamber A between the piston 17 and the stopper 27 to absorb the shock when the front fork operates on the pressure side. 29 is an under bracket, and 30 is an upper bracket, and the under bracket 29 is mounted below the effective stroke of the bearing portion 18. 31 is an axle mounting portion, and 32 is a seal.

Note that the volume compensation chamber D may be formed using a free piston instead of the cylindrical elastic body 26.

In the above configuration, as mentioned above, the figure shows the state in which the inner tube 11 is moving to the maximum extension side, but when a load is actually applied,
The outer tube 12 moves relatively downward (to the right in the drawing) via the piston 17 while deflecting the spring 28 on the pressure side until it is balanced with the spring 28 on the pressure side.

When the inner tube 11 is pushed up from the road surface from the balanced position, the inner tube 11 moves upward while further compressing the spring 28.

In this way, when the front fork is operated on the compression side, the outer tube 12 moves down while sliding on the outer wall of the inner tube 11 against the biasing force of the left spring 28. At the same time, the piston 17 fixed to the piston rod 14, which is integrated with the outer tube 12, also slides down inside the inner tube 11, causing the oil chamber A to contract and the oil chamber B to expand. Oil flows from chamber A to oil chamber B.

At this time, due to the sliding of the annular bearing portion 18, the volume of the oil chamber C expands approximately equal to the increase in the volume of the piston rod 14, so that oil corresponding to the increase in the volume of the piston rod 14 removed from the oil chamber B is removed. is absorbed from oil chamber B to oil chamber C through orifice 25.

Note that during this pressure side operation, since the check valve 23 is open, almost no damping force is generated.

On the other hand, when operating on the extension side, inner tube 1
1 escapes, oil chamber B contracts and oil chamber A expands.

At that time, oil exits from oil chamber B to oil chamber A while being throttled by orifice 24 while producing a predetermined rebound damping force, but at the same time, oil is discharged from oil chamber C to oil chamber B through orifice 25. .

In this way, the oil level in the oil chamber in the inner tube 11 is always constant and does not fluctuate during the extension and contraction operation of the front fork, and the oil level in the oil chamber B, C and the air chamber E is maintained at all times.
Since there is an annular bearing portion 18 that completely oil-tightly separates the air chambers, no oil leakage occurs on the air chamber E side.

Therefore, the air chamber E can be communicated with the atmosphere via the air hole 20. Since the air chamber E is open to the atmosphere in this way, there is no need to provide a margin b (see FIG. 1) for ensuring a predetermined air compression ratio as in the conventional front fork.

Therefore, the longest distance L from the front fork upper end 15 to the upper end of the piston 17 is the sum of the non-slidable area a of the annular bearing part 18 and the effective operating area st of the inner tube 11. That is, the following equation is obtained.

L=a+st...(2) In this way, since there is no need to provide a margin b, the front fork upper end 15 and the annular bearing part 18
(This corresponds to the piston of the conventional device.) The distance L between the upper end is shortened, and the total length of the outer tube 12 is shortened.

As a result, the annular bearing portion (piston rod bearing portion) 18 can be easily slidably accommodated between the upper bracket 30 and the under bracket 29 as shown in the figure, and the operating characteristics are improved and the auxiliary pipe etc. This has the effect of making it unnecessary.

In addition, since the overall length of the front fork is shortened, the degree of freedom in mounting can be increased.

In addition, since the air chamber E and the oil chambers B and C are completely separated by the annular bearing part 18, oil may be blown up into the air chamber E or air may be dragged into the oil during the telescopic operation of a conventional front fork. This prevents air ration.

Note that the above embodiment is an example of a front fork structure in which the outer tube 12 is attached to the vehicle body side and the inner tube 11 is attached to the wheel side, but the oil chamber C is formed as an annular gap between both tubes and between the upper and lower bearing parts. Therefore, contrary to the above, the present invention can also be applied to a structure in which the inner tube 11 is on the vehicle body side and the outer tube 12 is on the wheel side.

As explained above, in this invention, since the oil chamber that absorbs oil level fluctuations is formed in the annular gap between the inner tube and the outer tube, the air chamber on the upper surface of the oil chamber is unnecessary, and the overall length of the front fork is shortened. It is possible to increase the degree of freedom at the time of mounting, and it is possible to obtain the effect that the mounting of the bracket becomes easy.

Furthermore, according to the present invention, the oil chamber and the air chamber are oil-tightly separated via the annular bearing, so that the air in the air chamber is prevented from getting caught up in the hydraulic oil during expansion and contraction operations. In other words, there is no risk of aeration, so stable operability can be achieved even under severe specification conditions.

[Brief explanation of the drawing]

Figure 1 is a longitudinal cross-sectional view of a conventional front fork.
FIG. 2 is a longitudinal cross-sectional view of one embodiment of the present invention, and FIG. 3 is an enlarged cross-sectional view of the main part of FIG. A, B, C...Oil chamber, E...Air chamber, D...Volume compensation chamber, 11...Inner tube, 12...
Outer tube, 13... bearing section, 14... piston rod, 17... piston, 18... annular sliding bearing section, 20... air hole, 23... check valve, 24... orifice, 25... orifice,
26...Elastic cylindrical body, 26...Compression side spring, 29...
Under bracket, 30... hot bracket.

Claims (1)

[Scope of Claims] 1. The inner tube is slidably inserted into the outer tube via the bearing part, and the piston rod of the piston that slides on the inner surface of the inner tube is fixed to the end of the outer tube, and the outer circumference of the piston rod and An annular bearing that slides oil-tightly on the inner circumference of the outer tube is fixed to the end of the inner tube, and an oil chamber A inside the inner tube is fixed to the end of the inner tube.
and an oil chamber B between the piston and the annular bearing section through a damping means, and an oil chamber C that communicates with the oil chamber B through an orifice between the outer periphery of the inner tube, the inner periphery of the outer tube, and the annular bearing section. A front fork characterized in that the cross-sectional area of the oil chamber C formed between the bearing parts is set to be approximately equal to the cross-sectional area of the piston rod. 2. The front fork according to claim 1, wherein the oil chamber A inside the inner tube is provided with a volume compensation chamber D formed of an elastic cylinder that absorbs volumetric expansion of hydraulic oil.