JP2000097272A - Motorcycle front fork - Google Patents

Abstract

(57) [Problem] To provide a front fork of a motorcycle in which a frequency response of vibration acceleration is improved with a simple structure in addition to a vibration absorbing system using a spring and an oil damper. SOLUTION: An outer tube 2 and an inner tube 3 are slidably fitted to each other, and a piston rod 11 having one end fixed to an end member of the outer tube 2 extends coaxially in the outer tube 2 via a bearing member 7. A piston 12 with an orifice, which is inserted into the hydraulic oil chamber 8 of the inner tube 3 and is provided at the tip of the piston rod 11, is slidably fitted into the hydraulic oil chamber 8, and an air chamber 13 in the outer tube 2 is provided. In the front fork 1 of a motorcycle in which a spring 14 is interposed between the end member 10 of the outer tube 2 and the bearing member 7, the air chamber 13 in the outer tube 2 and the external air chamber 16 have an orifice 15a. A front fork of a motorcycle communicated through a passage 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a structure of a front fork of a motorcycle.

[0002]

2. Description of the Related Art A front fork for supporting a front wheel of a motorcycle is composed of a metal spring and a damper utilizing oil resistance in order to absorb a shock applied to the wheel from a road surface. FIG. 5 shows an example of the conventional front fork (Japanese Utility Model Publication No. Sho 58-1103).

[0003] An outer tube 01 and an inner tube 02 are slidably fitted to each other, and the inner tube 02 also serves as a cylinder and forms a hydraulic oil chamber 03 therein.
A piston rod 06 extending from the end member 04 of the inner tube 02 slidably penetrates a bearing member 05 at the end of the inner tube 02, and a piston 07 with an orifice 08 provided at the tip of the piston rod 06 has a hydraulic oil chamber 03. Inside, the inner tube 02 is slidably fitted to form a damper.

A spring 010 is provided between an end member 04 and a bearing member 05 of the outer tube 01 in an air chamber 09 inside the outer tube 01.
Is interposed. The end member 04 screwed into the end of the outer tube 01 has a concave portion 04a formed toward the outside,
A cap 011 is covered so as to cover the recess 04a.

The end member 04 has the air chamber 09 and the concave portion 04.
a, and a ventilation hole 013 communicating the outside with the recess 04a. The ventilation hole 013 is covered with a skirt portion of the cap 011. Can open outward.

Accordingly, when the front fork receives a shock and vibration from the road surface via the front wheels, the spring 010 converts between the outer tube 01 and the inner tube 02 into a telescopic movement to absorb the shock and vibration. The expansion and contraction motion is attenuated by the flow resistance of the oil based on the sliding of the piston 07 in the hydraulic oil chamber 03.

The ventilation holes 012 and 013 of the end member 04 prevent the air chamber 09 from becoming a high pressure in the compression step by escaping the air to the atmosphere, and the air chamber 09 becomes extremely negative pressure. Has been prevented.

[0008]

As described above, the conventional front fork absorbs the impact received from the road surface by the spring effect of the spring 010 and the damper effect of the oil damper to attenuate the vibration. The air chamber 09 has ventilation holes 012.
, 013, and hardly acts as a damper, and the air chamber 09 does not actively contribute to the buffer.

[0009] The frequency characteristic of the vibration acceleration of the vibration absorption system by the spring of the front fork and the oil damper is:
Normally, as shown by a broken line in FIG. 4, it has a primary resonance point and a secondary resonance point, and the acceleration at the low frequency primary resonance point is particularly greater than that at the secondary resonance point.

In this vibration absorbing system, if the damping coefficient is uniformly increased to lower the acceleration at the primary resonance point, the acceleration at the primary resonance point decreases, but the frequency range between the primary resonance point and the secondary resonance point is reduced. Then, a high acceleration state continues. That is, with a damper using an incompressible fluid such as an oil damper, it was not possible to change only the acceleration at the primary resonance point by changing the damping coefficient, and it was difficult to improve the frequency response.

[0011] The present invention has been made in view of such a point,
An object of the present invention is to provide a front fork of a motorcycle in which the frequency response of vibration acceleration is improved with a simple structure in addition to a vibration absorbing system including a spring and an oil damper.

[0012]

In order to achieve the above object, according to the present invention, an outer tube and an inner tube are slidably fitted to each other, and one end is fixed to an end member of the outer tube. A piston rod extends coaxially in the outer tube and is inserted into the hydraulic oil chamber of the inner tube via a bearing member, and a piston with an orifice provided at the tip of the piston rod is slidably fitted in the hydraulic oil chamber. In a front fork of a motorcycle in which a spring is interposed between an end member of the outer tube and the bearing member in an air chamber in the outer tube, an air chamber in the outer tube and an outer air chamber have an orifice. It is a front fork of a motorcycle that is communicated through the communication passage provided.

A vibration absorbing system of an oil damper and a spring in which a piston with an orifice slides in the hydraulic oil chamber,
Furthermore, with a simple structure in which an air damper of compressible fluid that connects the air chamber in the outer tube and the external air chamber through a communication path with an orifice is added, vibration between the primary resonance point and the secondary resonance point The acceleration at the primary resonance point can be reduced without increasing the vibration acceleration in several regions, and the frequency response of the vibration acceleration can be improved.

According to a second aspect of the present invention, in the front fork according to the first aspect, the communication path is connected to an end member of the outer tube.

[0015] An external air chamber can be connected by connecting a communication pipe having a communication passage provided with an orifice to a conventional air release through hole of an end member of the outer tube, and a conventional front fork body can be used. And cost reduction can be achieved. Further, the frequency characteristics can be easily changed by changing the volume of the external air chamber or the passage area of the orifice without changing the structure of the front fork body.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described with reference to FIGS. FIG. 1 shows an overall sectional view of a front fork 1 according to the present embodiment,
FIG. 2 is an enlarged view of the main part.

The outer tube 2 and the inner tube 3 are slidably fitted to each other via a slide metal 20 bearing, and a separate cylinder 4 is provided inside the inner tube 3 and provided at an end of the inner tube 3. Bracket 5
One end of the cylinder 4 is closed by a plug member 6 screwed into the cylinder 4, and the other end of the cylinder 4 is closed by fitting of a rod guide 7 fixed in the inner tube 3, and a hydraulic oil chamber 8 is provided in the cylinder 4. Are formed.

The working oil chamber 8 is filled with oil, and a free piston 9 is loosely fitted. The piston rod 11 extending from the end member 10 of the outer tube 2 is
Slidably penetrates a rod guide 7 fixed therein, and is inserted into a hydraulic oil chamber 8 in the cylinder 4.
A piston 12 with an orifice 12a provided at the tip of 11 is slidably fitted to the cylinder 4 in the hydraulic oil chamber 8 to constitute an oil damper.

A spring is provided between the end member 10 of the outer tube 2 and the rod guide 7 in the air chamber 13 in the outer tube 2.
14 are interposed. Referring to FIG. 2, a connecting pipe 15 is fitted into a through hole to which an air bleeding plug is connected to the end member 10 of the outer tube 2, and a communication pipe 17 extending from an external air tank 16 is connected to the connecting pipe 15. It is connected to the.

The connecting pipe 15 has an orifice 15a in the internal communication passage. Therefore, the air chamber 13 in the outer tube 2 is connected to an external air tank 16 through a communication path of the connection pipe 15 having the orifice 15a and the communication pipe 17.

The air tank 16 is airtightly closed and communicates only with the air chamber 13 via the orifice 15a. Therefore, when the outer tube 2 and the inner tube 3 expand and contract, the air moves through the orifice 15a in the air chamber 13 and the inside of the air tank 16 to form an air damper using air of a compressive fluid.

The frequency characteristic of the damping force of the air damper is shown by an upwardly convex curve as shown in FIG. 3, showing a maximum damping force at a certain frequency, and a smooth damping force at frequencies before and after the frequency. Is declining.

The frequency characteristics of the vibration acceleration having the primary resonance point and the secondary resonance point shown by the broken lines in FIG. 4 can be obtained by the spring effect of the spring 14 and the damper effect of the oil damper with the oil as the incompressible fluid. Further, in the front fork 1, the characteristic of the damping force by the air damper as shown in FIG. 3 is added, and the frequency characteristic of the vibration acceleration as shown by the solid line in FIG. 4 can be obtained.

That is, the acceleration at the primary resonance point is reduced without increasing the acceleration in the frequency range between the primary resonance point and the secondary resonance point, and the frequency response of the vibration acceleration is improved. Air chamber 13 of outer tube 2 and external air tank 16
Can be improved through a simple structure that communicates with the orifice 15a through the orifice 15a.

The connecting pipe 15 is fitted into the air vent through hole of the end member 10 of the outer tube 2 and the connecting pipe 15 is connected to the communicating pipe 17 extending from the external air tank 16. You can use the old one,
It is not necessary to manufacture a special dedicated front fork, cost can be reduced, and an existing front fork can be easily improved.

The volume of the air tank 16 or the orifice 15a
By changing the passage area of the front fork, the frequency response of the vibration acceleration can be easily changed without changing the structure of the front fork main body, and it is easy to obtain an appropriate frequency response according to the vehicle type.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of a front fork according to an embodiment of the present invention.

FIG. 2 is an enlarged view of the main part.

FIG. 3 is a diagram illustrating a frequency characteristic of a damping force of an air damper.

FIG. 4 is a diagram illustrating frequency characteristics of vibration acceleration.

FIG. 5 is a sectional view of a conventional front fork.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Front fork, 2 ... Outer tube, 3 ... Inner tube, 4 ... Cylinder, 5 ... Bracket, 6 ... Plug member, 7 ... Rod guide, 8 ... Hydraulic oil chamber, 9 ... Free piston, 10 ... End member, 11 ... piston rod, 12 ... piston, 13 ... air chamber, 14 ... spring, 15 ... connecting pipe, 16 ... air tank, 17 ... communication pipe, 20 ... slide metal.

Claims (2)

[Claims] An outer tube and an inner tube are slidably fitted to each other, and a piston rod having one end fixed to an end member of the outer tube extends coaxially in the outer tube and the inner tube via a bearing member. A piston with an orifice provided at the tip of the piston rod is slidably fitted in the hydraulic oil chamber, and an end member of the outer tube and an air chamber in the outer tube are inserted into the hydraulic oil chamber. A front fork for a motorcycle in which a spring is interposed between bearing members, wherein an air chamber in the outer tube and an external air chamber are communicated through a communication passage having an orifice. . 2. The front fork according to claim 1, wherein the communication passage is connected to an end member of the outer tube.