Front fork

One of a pair of the hydraulic shock absorbers each mounted in the right and left sides of a front wheel for a two-wheel vehicle includes a contraction-side damping valve (5a) disposed in a flow passage (11) communicating a rod-side oil chamber (R1) with a piston-side oil chamber (R2), the contraction-side damping valve (5a) permitting an operating oil to flow from the piston-side oil chamber (R2) to the rod-side oil chamber (R1) only when a volume in the piston-side oil chamber (R2) is reduced, and a contraction-side check valve (6) disposed in a flow passage (10) communicating the piston-side oil chamber (R2) with the reservoir (R), the contraction-side check valve (6) permitting the operating oil to flow from the reservoir (R) to the piston-side oil chamber (R2) only when a volume in the piston-side oil chamber (R2) is increased.

FIELD OF THE INVENTION

The present invention relates to a front fork, and in particular, to a front fork in a front wheel side of a two-wheel vehicle.

BACKGROUND OF THE INVENTION

JP2004-44643A published by the Japan Patent Office in 2004 has disclosed a front fork, which is provided with one fork body including a hydraulic shock absorber for production of an expansion-side damping force performing production of an expansion-side damping force, and the other fork body including a hydraulic shock absorber for production of a contraction-side damping force performing production of a contraction-side damping force.

SUMMARY OF THE INVENTION

According to the front fork disclosed in JP2004-44643A, in each hydraulic shock absorber for producing the expansion-side or contraction-side damping force, lack of an operating oil possibly occurs in a cylinder when the hydraulic shock absorber operates in the opposite direction to the direction for producing the damping force. Therefore, after the lack of the operating oil occurs, in a case where the hydraulic shock absorber reverses its motion in the opposite direction and operates toward the direction for producing the damping force, a predetermined, stable damping force is not possibly produced.

In view of the above, there exists a need for a front fork which overcomes the above-mentioned problems in the related art. The present invention addresses this need in the related art, as well as other needs, which will become apparent to those skilled in the art from this disclosure.

An object of the present invention lies in that in a case where, when a hydraulic shock absorber produces one of expansion-side and contraction-side damping forces, lack of an operating oil does not occur in a cylinder at the time the hydraulic shock absorber operates in the opposite direction to the direction for producing a damping force, and thereafter, the hydraulic shock absorber reverses its motion in the opposite direction and operates in the direction for producing the damping force, a predetermined damping force is securely produced.

In order to achieve above object, this invention provides a front fork comprising a pair of hydraulic shock absorbers each mounted in the right side and left side of a front wheel for a two-wheel vehicle. Each of the pair of the hydraulic shock absorbers includes a cylinder, a piston rod inserted in the cylinder to enter into and go out from the cylinder. Each of the pair of the hydraulic shock absorbers includes a piston received in the cylinder and connected to the piston rod, the piston defining a rod-side oil chamber and a piston-side oil chamber inside the cylinder and having a first flow passage to communicate the rod-side oil chamber with the piston-side oil chamber. Further each of the pair of the hydraulic shock absorbers includes a reservoir communicated through a second flow passage with the rod-side oil chamber and the piston-side oil chamber. One of the pair of the hydraulic shock absorbers includes a contraction-side damping valve and a contraction-side check valve. The contraction-side damping valve is disposed in the first flow passage, and permits an operating oil to flow from the piston-side oil chamber to the rod-side oil chamber when travel of the piston decreases a volume in the piston-side oil chamber, and prohibits the operating oil to enter from the rod-side oil chamber to the piston-side oil chamber when travel of the piston increases the volume in the piston-side oil chamber. The contraction-side check valve is disposed in the second flow passage, and prohibits the operating oil to flow from the piston-side oil chamber to the reservoir when travel of the piston decreases the volume in the piston-side oil chamber, and permits the operating oil to flow from the reservoir to the piston-side oil chamber when travel of the piston increases the volume in the piston-side oil chamber.

This invention also provides a front fork comprising a pair of hydraulic shock absorbers each mounted in the right side and left side of a front wheel for a two-wheel vehicle. Each of the pair of the hydraulic shock absorbers includes a cylinder, a piston rod inserted in the cylinder to enter into and go out from the cylinder. Each of the pair of the hydraulic shock absorbers includes a piston received in the cylinder and connected to the piston rod, the piston defining a rod-side oil chamber and a piston-side oil chamber inside the cylinder and having a first flow passage to communicate the rod-side oil chamber with the piston-side oil chamber. Further each of the pair of the hydraulic shock absorbers includes a reservoir communicated through a second flow passage with the rod-side oil chamber and the piston-side oil chamber. One of the pair of the hydraulic shock absorbers includes an expansion-side damping valve and an expansion-side check valve. The expansion-side damping valve is disposed in the first flow passage, and permits an operating oil to flow from the rod-side oil chamber to the piston-side oil chamber when travel of the piston decreases a volume in the rod-side oil chamber, and prohibits the operating oil to enter from the piston-side oil chamber to the rod-side oil chamber when travel of the piston increases the volume in the rod-side oil chamber. The expansion-side check valve is disposed in the second flow passage, and prohibits an operating oil to flow from the reservoir to the rod-side oil chamber when travel of the piston decreases the volume in the rod-side oil chamber, and permits the operating oil to flow from the reservoir to the rod-side oil chamber when travel of the piston increases the volume in the rod-side oil chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention will be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following description of the embodiment of the present invention is provided for illustration only, and not for the purpose of limiting the present invention as defined by the appended claims and their equivalents.

A front fork of the present invention is provided with a pair of hydraulic shock absorbers, which are mounted respectively in the right side and left sides of a front wheel for a motorbike. One of the pair of the hydraulic shock absorbers each mounted in the right side and left side of the front wheel for the motorbike is formed of a unitary flow structure, in which an expansion-side damping force is not produced at the expansion operation time, and a predetermined contraction-side damping force is produced at the contraction operation time.

A hydraulic shock absorber for production of a contraction-side damping force is, as shown inFIG. 1, arranged with an outer tube1and an inner tube2, which is inserted in the outer tube1so that the inner tube2enters into the outer tube1and goes out from the outer tube1under a water proof structure. The outer tube1and the inner tube2define a fork body in the front fork.

A suspension spring S is disposed between the outer tube1and the inner tube2where the inner tube2is biased by the suspension spring S to go out from the outer tube1such that the fork body expends.

The hydraulic shock absorber is provided with a damping portion in an axis of the fork body. In the damping portion, a cylinder3is disposed at an axis of the inner tube2, and a piston rod4is disposed at an axis of the outer tube1where the piston rod4is inserted in the cylinder3to enter into or go out from the cylinder3.

InFIG. 1, an opening in the upper side of the cylinder3is closed by a head member3athrough which the piston rod4penetrates at the axis, and an opening of the lower side of the cylinder3is closed by a bottom member2aof the inner tube2.

A piston5connected to an end of the piston rod4is slidably received in the cylinder3, thereby defining a rod-side oil chamber R1and a piston-side oil chamber R2within the cylinder3.

A reservoir R is defined between an outer wall of the cylinder3and an inner wall of the inner tube2. The reservoir R is communicated with the rod-side oil chamber R1through a flow passage12disposed in the head member3awith no resistance, namely, freely, and is communicated with the piston-side oil chamber R2through a flow passage10disposed in the bottom member2a. A contraction-side check valve6is disposed in the flow passage10.

The contraction-side check valve6permits flow of an operating oil from the reservoir R to the piston-side oil chamber R2, and prohibits flow of the operating oil from the piston-side oil chamber R2to the reservoir R.

The piston5is provided with a flow passage11communicating between the piston-side oil chamber R2and the rod-side oil chamber R1. In addition, the flow passage11is provided with a contraction-side damping valve5atherein for producing a predetermined contraction-side damping force. The contraction-side damping valve5apermits flow of the operating oil from the piston-side oil chamber R2to the rod-side oil chamber R1, and prohibits flow of the operating oil from the rod-side oil chamber R1to the piston-side oil chamber R2where, when the operating oil flows from the piston-side oil chamber R2into the rod-side oil chamber R1, a predetermined contraction-side damping force is produced.

Accordingly, in the hydraulic shock absorber for production of the contraction-side damping force, when the inner tube2enters into the outer tube1, namely at the contraction operation time the piston rod4enters into the cylinder3, the operating oil in the piston-side oil chamber R2flows through the contraction-side damping valve5ainto the rod-side oil chamber R1where the operating oil passes through the contraction-side damping valve5a, thereby producing a predetermined contraction-side damping force.

An amount of the operating oil corresponding to the piston entering volume becomes an extra oil amount in the rod-side oil chamber R1among the operating oil flown into the rod-side oil chamber R1, and the extra oil amount flows out through the flow passage12disposed in the head member3aof the cylinder3into the reservoir R.

On the other hand, when the inner tube2goes out from the outer tube1, namely at the expansion operation time the piston rod4goes out from the cylinder3, the contraction-side damping valve5adisposed in the piston5prohibits flow of the operating oil from the rod-side oil chamber R1to the piston-side oil chamber R2, and the operating oil flows out through the flow passage12disposed in the head member3afrom the rod-side oil chamber R1into the reservoir R.

Then, an amount of an operating oil corresponding to the rod retreat volume lacking in the piston-side oil chamber R2is supplied through the contraction-side check valve6from the reservoir R to the piston-side oil chamber R2.

As described above, according to the present invention a predetermined contraction-side damping force is produced in the contraction-side damping valve5adisposed in the piston5in the hydraulic shock absorber of a unitary flow structure at the contraction operation time, and when the hydraulic shock absorber reverses its motion from the contraction operation to the expansion operation, the operating oil lacking in the piston-side oil chamber R2is supplied directly through the contraction-side check valve6from the reservoir R.

In the hydraulic shock absorber defining a front fork disclosed in JP2004-44643A, when the operating oil lacks in the lower oil chamber, the operating oil is flown from the reservoir to the upper oil chamber firstly, and then, the flown operating oil is supplied through a valve disposed in a piston to the lower oil chamber. That is, the operating oil is supplied indirectly to the lower oil chamber. In contrast, according to the preferred embodiment of the present invention, the operating oil lacking in the piston-side oil chamber R2is supplied through the contraction-side check valve6from the reservoir R. That is, the operating oil is supplied directly to the piston-side oil chamber R2. Therefore, supply insufficiency of the operating oil in the piston-side oil chamber R2at the expansion operation time is prevented, and as a result, when the hydraulic shock absorber reverses its motion from the expansion operation to the contraction operation, during the contraction operation the stable contraction-side damping force is produced.

As described above, in the front fork in use of the hydraulic shock absorber for production of the contraction-side damping force, a predetermined contraction-side damping force can be obtained at the contraction-side operation time without insufficiency of the operating oil in the piston-side oil chamber R2at the expansion operation time.

Next, an expansion-side hydraulic shock absorber which is the other of the pair of the expansion-side hydraulic shock absorber and the contraction-side hydraulic shock absorber, namely, a hydraulic shock absorber for production of an expansion-side damping force will be explained with reference toFIG. 2.

The hydraulic shock absorber for production of the expansion-side damping force produces a predetermined expansion-side damping force at an expansion operation time, and does not produce a contraction-side damping force at a contraction operation time when the hydraulic shock absorber reverses its motion from the expansion operation time. The hydraulic shock absorber for production of the expansion-side damping force is formed of a unitary flow structure the same as in the hydraulic shock absorber for production of the contraction-side damping force shown inFIG. 1.

A hydraulic shock absorber for production of an expansion-side damping force shown inFIG. 2is arranged with an outer tube1′ and an inner tube2′, which is inserted in the outer tube1′ so that the inner tube2′ enters into the outer tube1′ and goes out from the outer tube1′ under a water proof structure. The outer tube1′ and the inner tube2′ define a fork body in the front fork.

A suspension spring S′ is disposed between the outer tube1′ and the inner tube2′ where the inner tube2′ is biased by the suspension spring S′ to go out from the outer tube1′ such that fork body expands.

The hydraulic shock absorber is provided with a damping portion at an axis of the fork body. In the damping portion, a cylinder3′ is disposed at an axis of the inner tube2′, and a piston rod4′ is disposed at an axis of the outer tube1′ where the piston rod4′ is inserted in the cylinder3′ to enter into or go out from the cylinder3′.

InFIG. 2, an opening in the upper side of the cylinder3′ is closed by a head member3a′ through which the piston rod4′ penetrates at the axis, and an opening of the lower side of the cylinder3′ is closed by a bottom member2a′ of the inner tube2′.

A piston5′ connected to an end of the piston rod4′ is slidably received in the cylinder3′, thereby defining a rod-side oil chamber R1′ and a piston-side oil chamber R2′ within the cylinder3′.

A reservoir R′ is defined between an outer wall of the cylinder3′ and an inner wall of the inner tube2′. The reservoir R′ is communicated with the piston-side oil chamber R2′ through a flow passage10′ disposed in a bottom member2a′ with no resistance, namely, freely, and is communicated with the rod-side oil chamber R1′ through a flow passage12′ disposed in a head member3a′. An expansion-side check valve7is disposed in the flow passage12′.

The expansion-side check valve7permits flow of an operating oil from the reservoir R′ to the rod-side oil chamber R1′, and prohibits flow of the operating oil from the rod-side oil chamber R1′ to the reservoir R′.

The piston5′ is provided with a flow passage11′ communicating between the piston-side oil chamber R2′ and the rod-side oil chamber R1′. In addition, the flow passage11′ is provided with an expansion-side damping valve5bfor producing a predetermined expansion-side damping force. The expansion-side damping valve5bpermits flow of the operating oil from the rod-side oil chamber R1′ to the piston-side oil chamber R2′, and prohibits flow of the operating oil from the piston-side oil chamber R2′ to the rod-side oil chamber R1′ where, when the operating oil flows from the rod-side oil chamber R1′ to the piston-side oil chamber R2′, a predetermined expansion-side damping force is produced.

Accordingly, in the hydraulic shock absorber for production of the expansion-side damping force, when the inner tube2′ goes out from the outer tube1′, namely at the expansion operation time the piston rod4′ goes out from the cylinder3′, flow of the operating oil in the rod-side oil chamber R1′ to the reservoir R′ is blocked by the expansion-side check valve7, and enters into the piston-side oil chamber R2′ where the operating oil passes through the expansion-side damping valve5b, thereby producing a predetermined expansion-side damping force.

An amount of the operating oil corresponding to the volume of a rod retreat of the piston rod4′ becomes insufficient in the piston-side oil chamber R2′, and the insufficient operating oil is supplied through the flow passage10′ disposed in the bottom member2a′ of the inner tube2′ from the reservoir R′ to the piston-side oil chamber R2′.

On the other hand, when the inner tube2′ enters into the outer tube1′, namely at the contraction operation time the piston rod4′ enters into the cylinder3′, the expansion-side damping valve5bdisposed in the piston5′ prohibits flow of the operating oil from the piston-side oil chamber R2′ to the rod-side oil chamber R1′, and the operating oil flows out through the flow passage10′ disposed in the bottom member2a′ from the piston-side oil chamber R2′ into the reservoir R′.

Then, an amount of an operating oil corresponding to the rod entering volume lacking in the rod-side oil chamber R1′ is supplied through the expansion-side check valve7from the reservoir R′ to the rod-side oil chamber R1′.

As described above, according to the present invention a predetermined expansion-side damping force is produced at the expansion-side damping valve5bdisposed in the piston5′ at the expansion operation time of the hydraulic shock absorber of a unitary flow structure, and when the hydraulic shock absorber reverses its motion from the expansion operation to the contraction operation, the operating oil lacking in the rod-side oil chamber R1′ is supplied directly through the expansion-side check valve7from the reservoir R′.

In the hydraulic shock absorber defining a front fork disclosed in JP2004-44643A, when the operating oil lacks in the upper oil chamber, the operating oil is flown from the reservoir to the lower oil chamber firstly, and then, that operating oil is supplied through a valve disposed in a piston to the lower oil chamber. That is, the operating oil is supplied indirectly to the lower oil chamber. In contrast, according to the preferred embodiment of the present invention, the operating oil lacking in the rod-side oil chamber R1′ is supplied through the expansion-side check valve7from the reservoir R′. That is, the operating oil is supplied directly to the rod-side oil chamber R1′. Therefore, supply insufficiency of the operating oil in the rod-side oil chamber R1′ at the contraction operation time is prevented, and as a result, when the hydraulic shock absorber reverses its motion from the contraction operation to the expansion operation, during the expansion operation the stable expansion-side damping force is produced.

An example where a two-wheel vehicle equipped with a front fork is a motorbike is explained in the preferred embodiment, but the two-wheel vehicle may be a bicycle, in which the identical function/effect can be achieved.

In addition, a pair of hydraulic shock absorbers for production of a contraction-side damping force and an expansion-side damping force are disposed in a front wheel of the two-wheel vehicle, but only either one of the hydraulic shock absorbers for production of the contraction-side damping force and the expansion-side damping force may be disposed.

That is, one of hydraulic shock absorbers in a front fork may be arranged as a hydraulic shock absorber in a unitary flow structure according to the present invention, and the other of the hydraulic shock absorbers may be arranged as a hydraulic shock absorber other than the hydraulic shock absorber in a unitary flow structure.