JPH08233015A - Front fork - Google Patents

Abstract

PURPOSE: To always constantly and constantly retain internal pressure in a damper by sucking oil from an outside oil chamber through a suction valve when the internal pressure in the damper becomes lower than that in the outside oil chamber of a damper cylinder, and discharging the oil to the outside oil chamber through a relieve valve when the internal pressure in the damper becomes over a set prescribed value. CONSTITUTION: When internal pressure in an oil chamber in a damper 7 becomes smaller than that in an oil chamber 16 outside the damper 7 during an extending/ shrinking operation period, that is, when the internal pressure in the damper 7 becomes below a prescribed value, oil is introduced to an oil sump (a) from the passing hole (d) of the oil chamber 16 through a suction valve (f) so that the internal pressure in the damper 7 can be constantly retained at predetermined prescribed pressure. When oil leaked from the interval of an upper bearing 37 is collected in the oil sump (a) during the extending/shrinking operation period so that the internal pressure in the damper 7 becomes over the prescribed pressure and becomes higher than the internal pressure in the oil chamber 16, the oil in the oil sump (a) opens a relief valve (c) from a discharging port (b), further is discharged to the oil chamber 16 through a chamber (e) and the passing hole (d) so that the internal pressure in the damper 7 can be constantly retained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a front fork for a motorcycle which is interposed between a vehicle body side and a wheel side to serve as a shock absorber and a fork for damping vibrations from the road surface.

[0002]

2. Description of the Related Art As a front fork of this type, for example, one disclosed in Japanese Utility Model Laid-Open No. 3-130931 is known.

In this front fork, a wheel side inner tube is slidably inserted into a vehicle body side outer tube, a damper is built in the outer tube and the inner tube, and the damper is a damper cylinder connected to the outer tube. An inverted front fork including a piston rod coupled to the inner tube and a piston coupled to the piston rod and sliding in the damper cylinder.

In this front fork, the lower rod-side oil chamber and the upper anti-rod-side oil chamber are partitioned by the piston, and the anti-rod-side oil chamber is the amount of penetration of the piston rod that is partitioned by the elastic body outside the damper cylinder. It communicates with the volume compensation gas chamber. Further, the piston rod slides in the cylinder head through the seal material and the bearing.

[0005]

The front fork as described above is isolated from the oil chamber outside the damper cylinder through a sealing material or the like, but the internal pressure inside the damper is increased during repeated expansion and contraction operations. When the internal pressure of the oil chamber outside the damper becomes lower than the internal pressure of the damper cylinder, oil may enter from the oil chamber outside the damper cylinder through the gap. There is a case.

In addition, during expansion and contraction operation, the oil that has become an oil film may accumulate above the bearing from a minute gap in the inner circumference of the bearing, and the pressure in the damper may gradually rise, whereby the desired damping function can be exhibited. There is a problem that disappears.

Therefore, an object of the present invention is to provide a front fork capable of always maintaining a constant internal pressure in the damper.

[0008]

In order to achieve the above object, the structure of the present invention is such that an inner tube is slidably inserted into an outer tube and a damper is built in the outer tube and the inner tube. Is a damper cylinder that stands up from the center of the bottom of the outer tube,
It consists of a piston rod movably inserted through a piston equipped with a valve mechanism in the damper cylinder,
The piston rod is constantly urged in the direction of extension in conjunction with the inner tube, and the piston is installed in the damper cylinder in the front fork that divides the rod-side oil chamber and the anti-rod-side oil chamber. A through hole that communicates with the outer oil chamber of the damper cylinder is provided in the upper part, and a relief valve and a suction valve are provided in parallel between this through hole and the oil chamber on the rod side so that they can be opened and closed, and the internal pressure inside the damper is below a certain value. The internal pressure inside the damper is kept constant by sucking the oil from the oil chamber outside the damper cylinder through the suction valve when it reaches a certain value, and discharging the oil from the relief valve when the value exceeds a certain value.

In the upper cylinder head of the damper cylinder, there is provided a bearing and a sealing material which are in sliding contact with the piston rod, an oil reservoir is defined between the bearing and the sealing material, and an oil chamber outside the damper cylinder is further provided in the cylinder head. A valve seat is provided between the through hole and the oil reservoir, and the valve seat is provided with a suction port and a discharge port for communicating the through hole and the oil reservoir with each other. A suction valve is preferably provided at the outlet end of the port so as to be openable and closable, and a relief valve is preferably provided at the outlet end of the discharge port so as to be openable and closable.

[0010]

[Operation] When the internal pressure in the damper becomes lower than the internal pressure in the outer oil chamber of the damper cylinder, oil is sucked from the outer oil chamber via the suction valve, and when the internal pressure in the damper exceeds a set value, the relief valve is activated. The oil is discharged to the outer oil chamber of the damper cylinder via the oil.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings.

The front fork 1 includes a wheel-side outer tube 2 and bearings 3 in the outer tube 2.
5, the inner tube 6 on the vehicle body side slidably inserted through the seal 4, the outer tube 2, and the damper 7 built in the inner tube 6 constitute an upright front fork.

The damper 7 comprises a damper cylinder 8 standing upright from the center of the bottom portion of the outer tube 2 and a piston rod 10 movably inserted into the damper cylinder 8 via a piston 9. The upper end of the piston rod 10 is an inner member. It is coupled to the upper end cap of the tube 6 and interlocks with the inner tube 6.

A hollow cylinder head 11 is coupled to the upper end of the damper cylinder 8 and stands upright. The upper end support portion 11a of the cylinder head 11 guides the inner circumference of the inner tube 6 via a bearing 12, and , The support 1
A suspension spring 13 is provided between 1a and the cap of the inner tube 6 directly or through a seat 14.
The suspension spring 13 constantly biases the inner tube 6 and the piston lot 10 in the extending direction.

Outer tube 2 and inner tube 6
Upper and lower oil chambers 15 and 16 are defined inside, and the upper and lower oil chambers 1
5 and 16 are through holes 17 provided above the cylinder head 11.
Through the. A gas chamber is defined above the upper oil chamber 15.

On the outer periphery of the lower part of the damper cylinder 8, a hollow cylindrical oil hole rod 18 which is open upward is arranged upright.
Further, the oil hole rod 18 is provided on the inner circumference of the lower end portion of the inner tube 6.
An oil lock piece 19 that can enter the outer periphery of the inner tube 6 is provided, and the oil lock piece 19 is fitted into the oil hole rod 18 near the time when the inner tube 6 is most compressed, and the cushion and the oil lock are gradually activated. There is.

The piston 9 defines a rod-side oil chamber 20 and a non-rod-side oil chamber 21 inside the damper cylinder 8.

The two oil chambers 20 and 21 communicate with the expansion side port 22 and the compression side port 23 provided in the piston 9 through the passages 24 and 25 provided in the piston rod 10, and the outlet end of the expansion side port 22. An expansion side leaf valve 26 is openably and closably provided, a check valve 27 is openably and closably provided at an outlet end of the pressure side port 23, and a needle valve 28 is openably and closably inserted between the passages 24 and 25. There is.

The needle valve 28 is pushed upward by a spring and abuts on the control rod 29,
The control rod 29 is interlocked with a manual or electric drive mechanism provided on the upper end cap of the inner tube 6, and the control rod 29 adjusts the opening degree of the needle valve 28. The needle valve may be another valve.

A seal holder 3 is provided in the cylinder head 11.
0, a pressing plate 31, a valve seat 32, a hollow guide member 33, a bearing holder 34, and a spring seat 35 are inserted in series.

A seal material 36 is interposed between the seal holder 30 and the piston rod 10.

An oil storage chamber a is defined by an arbitrary gap in the inner circumference of the valve seat 32 and the guide 33.

The guide 33 has an upper small diameter portion and a lower hollow large diameter portion, a bearing holder 34 is held in the large diameter portion, and a bearing 37 for guiding the piston rod 10 is provided inside the bearing holder 34. ing.

A chamber e is defined between the spring seat 32 and the guide 33. The oil reservoir chamber a has ports b and g formed in the spring seat 32, the chamber e, and a through hole formed in the cylinder head 11. Oil chamber 16 outside the damper via d
Is in communication with.

A discharge port b and a suction port g are formed in parallel on the spring seat 32, and the port b and the suction port g connect the chamber e and the oil reservoir a.

A relief valve c biased in a closing direction by a spring h is openably and closably provided at the outlet of the discharge port b of the spring seat 32. The relief valve c is the internal pressure of the oil reservoir a, that is, the damper 7. The oil is discharged to the oil chamber 16 side only when the internal pressure in the inside becomes a certain value or more.

Similarly, a suction valve f is openably and closably provided at the outlet of the suction port g of the spring seat 32, and when the internal pressure in the damper falls below a certain value, the through hole d-chamber e-
A small amount of oil is sucked into the oil reservoir chamber a from the suction port g through the suction valve f.

The bearing 37 guides the piston rod 10, and the oil in the rod-side oil chamber 20 gradually becomes an oil film and is guided to the oil reservoir chamber a from a gap in the inner periphery thereof.

The spring seat 35 supports the cushion spring 38, and the cushion spring 38 comes into contact with the outer peripheral stepped portion 10a of the piston rod 10 when the piston rod 10 is most extended, thereby exerting a cushion.

A pressure side valve mechanism 40 is provided below the inside of the damper cylinder 8.

The pressure side valve mechanism 40 includes a hollow valve body 41 and a partition member 42 provided on the valve body 41.
It has and.

A pressure side port and an expansion side port are formed in the partition member 42, a pressure side leaf valve is openably and closably provided at the outlet end of the pressure side port, and a check valve is openably and closably provided at the outlet end of the expansion port. ing.

The partition wall member 42 divides the anti-rod side oil chamber 21 and the lower oil chamber 47.

The valve body 41 has a passage communicating with the oil chambers 21 and 47, and a needle valve 49 is provided in the middle of the passage so as to be freely opened and closed.
The opening degree can be adjusted from the outside of the lower part through the push rod 50.

Inside the oil hole rod 18, a bag 51 made of an elastic material such as bellows or rubber is attached to the outer periphery of the lower part of the damper cylinder 8 via upper and lower holders 52, 53. Defines an oil chamber 54 that compensates for the amount of oil that penetrates the piston rod.

At the bottom of the damper cylinder 8, an oil chamber 47,
A through hole 55 communicating with 54 is formed.

At the time of extension operation, the piston 9 rises, and at this time, the oil in the rod side oil chamber 20 flows out to the opposite rod side oil chamber 21 through the through holes 24 and 25 and the extension port 22, and at this time, the extension side leaf. The expansion side damping force is generated by the valve 26 and the needle valve 28, and the oil of the discharge volume of the piston rod 10 is the oil in the oil chamber 54 inside the bag 51 and the pressure side valve mechanism 4 below.
It is sucked into the anti-rod side oil chamber 21 via the extension port at 0 and the check valve.

On the other hand, during the pressure side operation, the piston 9 descends, and a part of the oil in the anti-rod side oil chamber 21 flows into the rod side oil chamber 20 through the through holes 24, 25, the pressure port 23 and the check valve 27. .

A part of the oil in the oil chamber 21 flows into the oil chamber 47 through the pressure port, the pressure side leaf valve, the through hole and the needle valve 55 in the lower valve mechanism 40, and further through the through hole 25. It is introduced into the oil chamber 54 for volume compensation, and at this time, a compression side damping force is generated by the pressure side leaf valve 45 and the needle valve 55.

Near the time of maximum compression, the oil lock piece 19 of the inner tube 6 penetrates into the outer circumference of the oil hole rod 18 to gradually exert a cushion.

When the internal pressure of the oil chambers 20, 21, 45 inside the damper 7 becomes smaller than the internal pressure of the oil chamber 16 outside the damper 7 during the expansion and contraction operation, that is, when the internal pressure inside the damper 7 becomes a certain value or less, A small amount of oil in 16 is introduced into the oil reservoir chamber a through the through hole d and the suction valve f, so that the internal pressure in the damper 7 can be maintained at a predetermined constant pressure.

Further, when the oil leaking from the gap of the upper bearing 37 during the expansion and contraction operation is accumulated in the oil reservoir chamber a and the internal pressure in the damper 7 becomes a certain pressure or more and becomes higher than the internal pressure in the oil chamber 16,
The oil in the oil sump chamber a opens the relief valve c from the discharge port b, is further discharged into the oil chamber 16 through the chamber e and the through hole d, and keeps the internal pressure inside the damper 7 constant.

As described above, according to the present invention, a small amount of oil inside and outside the damper 7 circulates through the check valve f and the relief valve c to keep the internal pressure inside the damper 7 at a constant value.

[0044]

According to the present invention, since the oil chamber on the rod side in the damper and the oil chamber on the outer side of the damper cylinder are opened and closed via the openable and closable relief valve and the suction valve, the internal pressure in the damper is increased. Is below a certain value, a small amount of oil in the oil chamber outside the damper cylinder is sucked in via the suction valve, and when the internal pressure in the damper is above a certain value, a small amount of oil in the damper is discharged to the outside of the damper via a relief valve. As a result, the internal pressure in the damper can always be maintained at a constant value, and a predetermined damping force can always be generated.

[Brief description of drawings]

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

FIG. 2 is a partially enlarged sectional view of FIG.

[Explanation of symbols]

 1 Front Fork 2 Outer Tube 6 Inner Tube 7 Damper 8 Damper Cylinder 9 Piston 10 Piston Rod 11 Cylinder Head 16 Outer Oil Chamber 20 Rod Side Oil Chamber 21 Anti Rod Side Oil Chamber 36 Sealing Material 37 Bearing 51 Bag Body 54 Oil Chamber a Oil Reservoir b Port c Relief valve d Through hole e Chamber f Suction valve g Suction port h Spring

Claims (2)

[Claims] 1. An inner tube is slidably inserted into the outer tube, a damper is built in the outer tube and the inner tube, and the damper is a damper cylinder standing upright from the lower center of the outer tube, and a valve in the damper cylinder. It is composed of a piston rod movably inserted through a piston equipped with a mechanism, the piston rod is always urged in the extension direction in conjunction with the inner tube, and the piston is in the damper cylinder and the rod side oil chamber and the anti-rod. In the front fork that separates from the side oil chamber, a through hole communicating with the outer oil chamber of the damper cylinder is provided above the rod side oil chamber, and the relief valve is provided between this hole and the rod side oil chamber. And the suction valve are arranged in parallel so that they can be opened and closed freely. When the internal pressure in the damper falls below a certain value, the damper cylinder Front fork, characterized in that to keep the suction oil through the suction valve from the side oil chamber, by discharging oil from the relief valve when a certain value or more the internal pressure of the damper constant. 2. A bearing and a seal member, which are in sliding contact with the piston rod, are provided in an upper cylinder head of the damper cylinder, an oil reservoir is defined between the bearing and the seal member, and the cylinder head is provided outside the damper cylinder. A through hole that opens to the oil chamber is formed, and a valve seat is provided between the through hole and the oil reservoir chamber, and the valve seat is provided with a suction port and a discharge port that connect the through hole and the oil reservoir chamber. The front fork according to claim 1, wherein a suction valve is openably and closably provided at an outlet end of the suction port, and a relief valve is openably and closably provided at an outlet end of the discharge port.