JPH08303517A - Front fork - Google Patents

Abstract

PURPOSE: To improve and stabilize damping force characteristics by enlarging the diameter of a damper cylinder, and effectively prohibit striking the bottom at the time of compression to the maximum stroke. CONSTITUTION: An upper end of a first spring is held close to a lower end part of a damper cylinder, a lower end of a second spring 29 is supported to a bottom part of a wheel side tube 2, a lower end of the first spring 28 and an upper end of the second spring 29 are connected to each other through a spring guide 30, and an oil lock case 34 to link the spring guide 30 to the upper end of the second spring 29 is vertically movably provided. The oil lock case 34 has a lower cylinder part 36 suspended downward from a guide part 37 slidably inserted to an outer circumference of a piston rod 7 to be disposed at an outer circumference of a lower end of the piston rod 7 to face a hollow oil hole lever 42, the lower cylinder part 36 is formed to have a diameter- contracted part 36a in which upper part inner circumference is formed smaller than a lower part inner circumference, and the diameter-contracted part 36a has a communication hole 39 which communicate with the outer side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of an inverted front fork mounted on a motorcycle.

[0002]

2. Description of the Related Art A front fork mounted on a motorcycle is installed in an inverted manner in order to reduce the weight on the wheel side of the motorcycle. There are various proposals for the front fork in the past.
In the front fork disclosed in Japanese Unexamined Patent Publication No. 2, a wheel-side inner tube is slidably inserted into a vehicle body-side outer tube, and a damper cylinder is attached downward at the center of the upper end of the vehicle-body-side outer tube. A piston rod is movably inserted through the piston, the lower end of this piston rod is connected to the center of the bottom of the wheel-side inner tube, and the intermediate outer periphery of the damper cylinder and the bottom of the wheel-side inner tube are connected. The suspension spring is installed in the.

Therefore, in the front fork,
As a result of the upper end of the suspension spring being carried on the outer periphery of the middle part of the damper cylinder, a space for interposing the suspension spring is required between the outer periphery of the damper cylinder and the inner periphery of the wheel-side inner tube. Inevitably, the outer diameter of the damper cylinder is set smaller than the inner diameter of the suspension spring.

However, in order to improve and stabilize the damping force characteristic of the front fork without increasing the overall diameter of the front fork, it is preferable to set the diameter of the damper cylinder as large as possible. In order to meet the request, the suspension spring mounting method as described above is restricted by the suspension spring and the diameter of the damper cylinder cannot be set sufficiently large.

Therefore, if the upper end of the suspension spring is supported on the lower end of the damper cylinder, the suspension spring is not distributed on the outer peripheral side of the damper cylinder,
Although it is possible to set the diameter of the damper cylinder to a large value, in that case, the overall length of the suspension spring tends to be shortened, and as a result, so-called bottom thrusting is likely to occur at the time of maximum compression of the front fork. There is a concern that

The present invention was devised in view of the above-mentioned circumstances, and its purpose is to increase the diameter of the damper cylinder to improve and stabilize the damping force characteristic, while It is an object of the present invention to provide a front fork that is optimal for effectively preventing bottom thrust during compression.

[0007]

In order to achieve the above-mentioned object, the structure of the present invention is constructed such that a wheel side tube is slidably inserted into a vehicle body side tube and a damper cylinder is directed downward to the vehicle body side tube. In a front fork in which a piston rod erected from the wheel side tube is movably inserted into the damper cylinder via the piston, and a suspension spring is interposed between the damper cylinder and the bottom of the wheel side tube, A first spring in which the suspension spring increases the wire diameter and the winding diameter; and a second spring in which the wire diameter and the winding diameter are smaller than that of the first spring, and the upper portion of which is present inside the first spring. The upper end of the first spring is supported near the lower end of the damper cylinder, and the lower end of the second spring is supported on the bottom of the wheel side tube. On the other hand, the lower end of the first spring and the upper end of the second spring are connected via a spring guide, and an oil lock case connected to the spring guide is provided at the upper end of the second spring so as to be vertically movable. The oil lock case has a lower cylindrical portion that is vertically provided downward from a guide portion that is slidably inserted into the outer periphery of the piston rod and that faces a hollow oil hole rod provided on the outer periphery of the lower end portion of the piston rod. It is assumed that the lower cylindrical portion has a diameter-reduced portion whose inner diameter is smaller than that of its lower inner diameter, and that the diameter-reduced portion has a through hole communicating with the outside.

[0008]

Therefore, in the front fork, the first
Also, since the suspension spring including the second spring is arranged below the vicinity of the lower end of the damper cylinder, there is no fear that the outer circumference of the damper cylinder interferes with the suspension spring, and as a result, the diameter of the damper cylinder can be set large. Enables improvement and stabilization of damping force characteristics.

Further, since the oil lock case is connected to the spring guide which connects the lower end of the first spring and the upper end of the second spring and is provided at the upper end of the second spring, the spring guide and the oil are provided. It makes it possible to replace the lock cases individually or both with different effects.

During the compression operation of the front fork, the second spring is first compressed and then the first spring is compressed.
Spring compresses.

The oil lock case provided on the upper end of the second spring exerts a cushioning effect between the lower cylinder portion and the lower hollow oil hole rod near the time when the front fork is most compressed.

At this time, the upper end portion of the oil hole rod is fitted into the lower tubular portion to provide a cushion, and the upper end portion of the oil hole rod is fitted into the reduced diameter portion of the lower tubular portion to lock the oil lock. As a result, a predetermined cushioning effect is exerted, and the bottom contact where the oil lock case and the oil hole rod hit the metal is prevented in advance.

Further, the through hole opened in the reduced diameter portion allows the working oil in the lower tubular portion to flow out to the outside oil chamber side when the upper end portion of the oil hole rod is fitted in the reduced diameter portion. Works, and therefore
The oil pressure at the time of the oil lock can be arbitrarily controlled depending on the setting of the diameter of the through hole.

The through hole opened in the reduced diameter portion is reversed from the above-mentioned most compressed state, and when the upper end of the oil hole rod comes out from the reduced diameter portion in the lower tubular portion, the oil chamber side which is the outside The working oil from the inside is allowed to flow into the inner peripheral side of the reduced diameter portion to prevent the occurrence of the vacuum phenomenon in the reduced diameter portion.

The hollow oil hole rod contributes to the tendency to reduce the weight of the lower end side of the piston rod, that is, the lower end side of the front fork.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below on the basis of an illustrated embodiment. In the illustrated front fork, an inner tube 2 as a wheel side tube is slidable inside an outer tube 1 as a vehicle body side tube. The damper 3 is inserted and the damper 3 is built in the outer tube 1 and the inner tube 2.

The damper 3 is connected to the center of the upper end cap 4 of the outer tube 1 and hangs downward from the damper cylinder 5, and a hollow cylinder movably inserted into the damper cylinder 5 via a piston 6. Piston rod 7
And the lower end of the piston rod 7 is joined to the bottom of the inner tube 2.

A spring receiver 8 having an L-shaped cross section is provided in the vicinity of the lower end of the damper cylinder 5, and a suspension spring 10 is provided between the spring receiver 8 and the upper surface of the lower end bottom portion 9 which is the bottom portion of the inner tube 2. This suspension spring 10 is interposed and constantly urges the damper cylinder 5 and the outer tube 1 in the extending direction.

At the center of the upper part of the damper cylinder 5, a pipe body 11 is attached downward, and a partition member member 12 is provided at the lower part of the pipe body 11. This partition member 12 is a damper cylinder. The oil chambers 13 and 14 are defined above 5.

A gas chamber 15 is provided above the oil chamber 13.

Further, the partition wall member 12 includes oil chambers 13 and 14
Is provided with a port 16 for opening and closing and a leaf valve 17,
The pipe body 11 is provided with a bypass 18 that connects the two oil chambers 13 and 14 with each other. In the bypass 18, a needle valve 19 for adjusting the opening degree by an external operation is provided so as to be vertically movable, and a leaf valve 17 is provided. And a needle valve is used to generate damping force.

The piston 6 on the damper 3 side divides the upper oil chamber 14 and the lower oil chamber 20 into two oil chambers 14, 2.
0 is communicated with the expansion side leaf valve 22 and the compression side leaf valve 23 that open and close the two expansion ports 2 provided in the piston 6.

A bypass 24, which connects the two oil chambers 14 and 20 to each other, is formed in the upper portion of the piston rod 7, and the opening of the needle valve 2 is freely adjustable in the bypass 24.
5, the needle valve 25 can be moved up and down via a control rod 26 inserted in the piston rod 7 and an adjuster 27 at the lower end.

The suspension spring 10 in this embodiment has the first spring 28 for increasing the wire diameter and the winding diameter.
And a second spring 29 having a wire diameter and a winding diameter smaller than that of the first spring 28. The upper end of the second spring 29 is assumed to be present below the first spring 28. There is.

Therefore, during the compression operation of the front fork, in this embodiment, first, the second wire having a small wire diameter and a small winding diameter is used.
The spring 29 of No. 1 compresses, and then the first spring 28 having a large wire diameter and winding diameter compresses,
The wire diameter may be set to be reversed so that the first spring 28 compresses first.

A spring guide 3 is provided between the lower end of the first spring 28 and the upper end of the second spring 29.
0 is distributed, and the lower end of the first spring 28 and the upper end of the second spring 29 are connected via the spring guide 30.

The spring guide 30 has a cylindrical portion 31, a flange portion 32 provided at the lower end of the cylindrical portion 31 toward the outside, and a support piece provided at the upper end of the cylindrical portion 31 toward the inside. 33, and the flange portion 32 supports the lower end of the first spring 28, and the support piece 33 supports the upper end of the second spring 29.

The upper end of the first spring 28 is carried by the lower end of the spring receiver 8, and the lower end of the second spring 29 is carried by the upper surface of the bottom 9.

On the other hand, between the inner tube 2 and the oil chamber R
An oil lock case 34 is vertically movably arranged on the outer periphery of the piston rod 7 which defines the section of the suspension rod 10. It is assumed that the outer circumference of the piston rod 7 moves up and down in conjunction with the expansion and contraction operation.

As described above, the oil lock case 3
4 is connected to the spring guide 30 and is provided at the upper end of the second spring 29, the spring guide 30 and the oil lock case 34 may be replaced individually or both with different effects. Will be possible.

The oil lock case 34 has a guide portion 37 slidably inserted into the outer circumference of the piston rod, and an upper cylindrical portion 35 formed in a cylindrical shape with a bottom from the guide portion 37 and standing upward. And the guide part 3
7, a lower cylindrical portion 36 formed in a cylindrical shape having a head and vertically extending downward.

The upper tubular portion 35 has an opening toward the upper side of the oil chamber R opposed to a hollow oil lock piece 40 arranged at the center of the lower end of the damper cylinder 5, and has an inner bottom portion for cushioning. The elastic body 38 of FIG.

The oil lock piece 40 has a through hole 41 that allows the hollow portion inside and the oil chamber R to pass therethrough, and a cushion spring 43 is provided below the piston 6.

On the other hand, the lower tubular portion 36 has its downward opening in the oil chamber R opposed to the hollow oil hole rod 42 arranged on the outer periphery of the lower end portion of the piston rod 7, while
A reduced diameter portion 36a whose inner diameter is reduced from its inner diameter
In addition, the reduced diameter portion 36a has a through hole 39 for communicating the inside and the outside of the oil chamber R.

The reduced diameter portion 36a is set so that the upper end portion of the lower oil hole rod 42 is projected and retracted in a fitted state.
Therefore, when the lower tubular portion 36 descends to fit the upper end portion of the oil hole rod 42 into the reduced diameter portion 36a, a cushioning effect is exerted with the oil hole rod 42.

That is, near the most compressed state of the front fork, the oil hole rod 42 is fitted in the lower cylinder portion 36 of the oil lock case 34, and the working oil in the lower cylinder portion 36 is the outer circumference of the oil hole rod 42. Then, the oil flows into the oil chamber R, which is the outside, and the resistance at this time acts as a cushion to suppress the descending speed of the oil lock case 34.

Further, subsequently, when the upper end of the oil hole rod 42 is further fitted into the lower tubular portion 36, the upper end portion of the oil hole rod 42 is fitted into the reduced diameter portion 36a of the lower tubular portion 36. As a result, the hydraulic oil is locked in the reduced diameter portion 36a, and the oil lock case 34 is prevented from descending.

The through hole 39 opened in the reduced diameter portion 36a is provided when the upper end portion of the oil hole rod 42 is fitted into the reduced diameter portion 36a.
It functions to let the hydraulic oil in the lower tubular portion 36 flow out to the oil chamber R side, and controls the amount of hydraulic oil trapped in the reduced diameter portion 36a.

Further, since the oil hole rod 42 is formed hollow, the weight of the lower end side of the piston rod 7 in which the oil hole rod 42 is arranged, that is, the lower end side of the front fork tends to be reduced. Will contribute.

Reversed from the above, when the front fork is extended, the lower tubular portion 36 is raised and the reduced diameter portion 36a.
The upper end of the oil hole rod 42 comes out from the inside, but at this time, hydraulic oil from the outside flows into the inner peripheral side of the reduced diameter portion 36a through the through hole 39 opened in the reduced diameter portion 36a. The occurrence of the vacuum phenomenon in the reduced diameter portion 36a is prevented in advance.

In the front fork according to this embodiment formed as described above, the damper 3 and the outer tube 1 are normally biased in the extending direction by the suspension spring 10.

From this state, when the front fork is compressed, for example, the oil in the upper oil chamber 14 flows out to the lower oil chamber 20 via the port 21 and the bypass 24, and at this time the leaf valve 23 and A damping force on the compression side is generated with the needle valve 25.

At this time, the oil corresponding to the fitting volume of the piston rod 7 is discharged to the oil chamber 13 which is a reservoir via the upper port 16 and the bypass 18, and the leaf valve 17
Therefore, the damping force on the compression side is generated by the needle valve 19.

During the above compression operation, the suspension spring 1
At 0, the second spring 29 having a small wire diameter and winding diameter compresses first, and then the first spring 28 having a large wire diameter and winding diameter compresses.

In the vicinity of the most compressed state, the oil hole rod 42 is fitted in the lower cylinder portion 36 of the oil lock case 34, and the working oil in the lower cylinder portion 36 intersects the outer circumference of the oil hole rod 42. The oil flows into the oil chamber R which is the outside, and the resistance at this time reduces the descending speed of the oil lock case 34.

Further, subsequently, when the upper end of the oil hole rod 42 is further fitted into the lower tubular portion 36, the upper end portion of the oil hole rod 42 is fitted into the reduced diameter portion 36a of the lower tubular portion 36. As a result, the working oil is confined in the reduced diameter portion 36a, and at this time, an oil lock occurs in the reduced diameter portion 36a.

As a result, even if the front fork is suddenly compressed with a large stroke, the cushion effect is exerted, and the oil lock case 34 and the oil hole rod 42 are provided.
The metal contact between and, that is, the bottoming is prevented.

The through hole 39 opened in the reduced diameter portion 36a is provided when the upper end of the oil hole rod 42 is fitted into the reduced diameter portion 36a.
Since the hydraulic oil in the lower tubular portion 36 functions to flow out to the oil chamber R side, the hydraulic pressure at the time of the oil lock can be controlled by setting the diameter of the through hole 39.

Incidentally, when the front fork is fully compressed, the upper oil lock piece 40 may be fitted into the upper cylindrical portion 35 of the oil lock case 34. In this case as well, the cushion and the oil lock are not locked. Of course, the cushioning effect is exerted.

At this time, the elastic body 38 prevents the oil lock piece 40 from hitting the oil lock case 34 against the metal.

During the extension operation of the front fork, the damper cylinder 5 rises, the oil in the lower oil chamber 20 flows out to the upper oil chamber 14 via the port 21 and the bypass 24, and the leaf valve 23 and the needle. An extension side damping force is generated with the valve 25.

In addition, the amount of oil which is insufficient in the upper oil chamber 14 due to the withdrawal of the piston rod 7 from the withdrawal volume of the piston rod 7 is increased from the oil chamber 13 to the upper port 16 and the bypass 1.
It is replenished to the oil chamber 14 via 8 and the damping force by the leaf valve and the needle valve 19 is generated also at this time.

[0053]

As described above, according to the present invention, the suspension spring is composed of the first spring for increasing the wire diameter and the winding diameter and the second spring for decreasing the wire diameter and the winding diameter. , The upper part of the second spring is arranged inside the first spring, and the first and second springs are connected by the spring guide. Therefore, as compared with the case where the suspension spring is composed of one spring, The axial length of the suspension spring can be significantly shortened, and the storage space for the suspension spring can be reduced.

As a result, by mounting the upper end of the suspension spring near the lower end of the damper cylinder, it is possible to prevent the outer periphery of the damper cylinder from interfering with the suspension spring. It becomes possible to improve and stabilize.

Further, since the oil lock case is connected to the spring guide which connects the lower end of the first spring and the upper end of the second spring and is provided at the upper end of the second spring, the spring guide and the oil are prevented. It makes it possible to replace the lock cases individually or both with different effects.

In the vicinity of maximum compression of the front fork, a hollow oil hole rod is fitted in the lower cylinder portion forming the oil lock case to provide a cushion, and an oil hole is formed in the reduced diameter portion of the lower cylinder portion. When the upper end of the rod is fitted, the oil lock works and a predetermined cushioning effect is obtained, and the bottom contact that is a metal contact between the oil lock case and the oil hole rod is effective. Can be prevented.

By forming the oil hole rod hollow, it contributes to the tendency to reduce the weight on the lower end side of the front fork having the piston rod in which the oil hole rod is arranged.

Further, when the upper end portion of the oil hole rod is fitted in the reduced diameter portion, the through hole opened in the reduced diameter portion allows the working oil in the lower tubular portion to flow out to the oil chamber side which is the outside. Because it works
The oil pressure at the time of the oil lock can be controlled depending on how the diameter of the through hole is set.

Since the reduced diameter portion has a through hole,
When the uppermost portion of the oil hole rod is pulled out from the inside of the reduced diameter portion of the lower tubular portion by reversing from the above-mentioned most compressed state, the working oil from the oil chamber side which is the outside flows into the inner peripheral side of the reduced diameter portion, It also prevents the occurrence of the vacuum phenomenon in the reduced diameter portion.

[Brief description of drawings]

FIG. 1 is a partially longitudinal 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 Outer tube which is a body side tube 2 Inner tube which is a wheel side tube 5 Damper cylinder 6 Piston 7 Piston rod 10 Suspension spring 28 First spring 29 Second spring 30 Sling guide 34 Oil lock case 35 Upper cylinder part 36 Lower cylinder part 36a Reduced diameter portion 37 Guide portion 39 Through hole 40 Oil lock piece 42 Oil hole rod

Claims (1)

[Claims] 1. A wheel-side tube is slidably inserted into a vehicle-body-side tube, a damper cylinder is attached downward to the vehicle-body-side tube, and a piston rod standing upright from the wheel-side tube is inserted into the damper cylinder through a piston. In a front fork in which the suspension spring is interposed between the damper cylinder and the bottom of the wheel side tube, the suspension spring has a first spring for increasing the wire diameter and the winding diameter, and A second spring whose wire diameter and winding diameter are smaller than those of the first spring and whose upper portion is present inside the first spring, and the upper end of the first spring is supported near the lower end of the damper cylinder, The lower end of the second spring is supported on the bottom of the wheel-side tube, while the lower end of the first spring and the upper end of the second spring are supported. Is connected via a spring guide, an oil lock case linked to the spring guide is provided at the upper end of the second spring so as to be vertically movable, and the oil lock case is slidably inserted into the outer circumference of the piston rod. Has a lower cylindrical portion which is hung downward from the lower portion and faces the hollow oil hole rod disposed on the outer periphery of the lower end portion of the piston rod, and the lower cylindrical portion reduces the inner diameter of its upper portion from the inner diameter of its lower portion. Front fork characterized by having a reduced diameter portion and a through hole communicating with the outside in the reduced diameter portion.