JP3874385B2 - Front fork - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a front fork that serves as both a shock absorber and a fork that are interposed between a vehicle body such as a motorcycle and an axle and attenuates vibration from a road surface.
[0002]
[Prior art]
As this type of front fork, for example, one disclosed in Japanese Utility Model Laid-Open No. 4-80943 or Japanese Utility Model Publication No. 5-9550 has been developed.
[0003]
In the front fork disclosed in Japanese Utility Model Publication No. 4-80943, the wheel side inner tube is slidably inserted into the vehicle body side outer tube, and the damper cylinder is erected from the lower center of the wheel side inner tube. A piston rod is movably inserted through the piston, and a casing opened upward is provided at the upper portion of the damper cylinder. An elastic body is provided in the casing, and the other cushion is opposed to the elastic body on the outer periphery of the piston rod. A piece is provided, and the cushion piece is brought into contact with the elastic body in the vicinity of the most compressed state to absorb an impact caused by a sudden bottoming.
[0004]
Further, in the front fork disclosed in Japanese Utility Model Laid-Open No. 5-9550, a wheel-side inner tube is slidably inserted into a vehicle body-side outer tube, and a damper cylinder is erected at the lower center of the wheel-side tube. A piston rod is movably inserted through the piston, an oil lock case is provided on the upper part of the damper cylinder, an oil lock piece facing the oil lock case is provided on the outer periphery of the piston rod, and an oil lock is provided in the vicinity of the maximum compression. When the piece enters the oil lock case, oil lock pressure is generated to prevent sudden bottoming.
[0005]
[Problems to be solved by the invention]
The conventional front fork disclosed in the above publication is not particularly functionally defective, but it is desired to improve the following problems.
[0006]
(1) The front fork of Japanese Utility Model Laid-Open No. 4-80943 is an elastic cushion rubber that can relieve the shock at the time of the most compression, but to absorb a sudden shock when the piston speed is high. It is necessary to increase the volume of the cushion rubber. However, when the cushion rubber is enlarged as described above, there is a problem that the ride comfort of the vehicle is deteriorated because the repulsive force of the cushion rubber acts on the piston rod when shifting from the state of the maximum compression to the extension operation. Further, when the cushion rubber is large, the cushion piece hits the cushion rubber even in a compression stroke region other than a large input where bottoming occurs, resulting in an extra effect and poor ride comfort.
[0007]
(2) Since the front fork disclosed in Japanese Utility Model Publication No. 5-9550 is an oil lock case and an oil lock piece, the oil fork is effective when the piston compression speed is high. When the piston speed is low, the oil lock piece also enters the oil lock case at a low speed, which may weaken the oil lock and cause a shock. Therefore, in order to be able to absorb sufficient shock even when the piston speed is low, the oil lock case can be lengthened to increase the stroke of the oil lock action. There is a problem that the oil lock characteristic occurs in the stroke area other than the driving and the riding comfort is deteriorated.
[0008]
Accordingly, an object of the present invention is to provide a front fork which can obtain desired oil lock characteristics without requiring an elastic body such as cushion rubber or the like and without lengthening an oil lock case.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the means of the present invention, the wheel side tube is slidably inserted into the vehicle body side tube, the damper cylinder is erected from the lower center of the wheel side tube, and the piston is interposed in the damper cylinder. The piston rod is movably inserted, the piston rod is connected to the upper part of the vehicle body side tube, the piston rod and the vehicle body side tube are always urged in the extending direction via the suspension spring, and further the oil lock is placed on the upper part of the damper cylinder. A front fork having a case and an oil lock generating mechanism facing the oil lock case on the outer periphery of the piston rod, a holder in which the oil lock generating mechanism is fitted on the outer periphery of the piston rod, and an upper portion of the holder Nut that holds the holder on the outer periphery of the piston rod by screwing to the outer periphery, and the holder A cylindrical oil lock piece floating freely fitted to the outer periphery small diameter portion, constituted by a cylindrical cushion rubber disposed in series at the bottom of the holder, the cushion rubber and the oil lock piece in the uppermost compression vicinity oil lock The oil lock pressure is generated by intrusion into the case, and the cushion rubber is elastically brought into contact with the bottom surface of the oil lock case for maximum compression to prevent sudden bottoming .
[0010]
In this case, it is preferable that a stopper is provided on the outer periphery of the piston rod, and the stopper engages with the upper end of the holder and the inner peripheral upper wall of the nut to hold the holder and the nut at a predetermined position on the outer periphery of the piston rod.
[0011]
Also, preferably the diameter of the cylinder smaller than the diameter of the oil lock piece with the cushion rubber is made of a cylindrical body of the cross-section drum type which is fitted to the outer periphery of the piston rod.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
[0013]
In the front fork F of the present invention, like the conventional front fork, an inner tube 2 as a wheel side tube is slidably inserted into an outer tube 1 as a vehicle body side tube, and a damper cylinder 3 is inserted from the lower center of the inner tube 2. The piston rod 5 is erected and inserted into the damper cylinder 3 via the piston 4 so as to be movable. The piston rod 5 is connected to the upper cap of the outer tube 1, and the piston rod 5 and the outer tube 1 are connected via the suspension spring 6. An oil lock case 7 that is always urged in the extending direction and is opened upward at the top of the damper cylinder 3 is provided, and an oil lock generating mechanism 8 that faces the oil lock case 7 is provided on the outer periphery of the piston rod 5. Yes.
[0014]
In this case, the holder 9 in which the oil lock generating mechanism 8 is inserted into the outer periphery of the piston rod 5, the nut 11 that is screwed into the upper outer periphery of the holder 9 to hold the holder 9 on the outer periphery of the piston rod 5, and the outer periphery of the holder 9 A cylindrical oil lock piece 10 fitted to the small-diameter portion 9a so as to be floatable along the axial direction and a cylindrical cushion rubber 12 arranged in series below the holder 9 are configured.
[0015]
Further, a stopper 15 made of a snap ring or the like is provided on the outer periphery of the piston rod 5, and this stopper 15 engages the upper end of the holder 9 and the inner peripheral upper wall of the nut 11, so that the holder 9 and the nut 11 are connected to the outer periphery of the piston rod 5. It is held in place. That is, the nut 11 is prevented from moving downward by the stopper 15, and when the nut 11 is rotated and the holder 9 is pulled up, the stopper 15 is not raised further to the holder 9 and both are positioned at the position of the stopper 15. . A notch 13 is formed at the lower end of the oil lock piece 10.
[0016]
The cushion rubber 12 is formed of a drum body 12a having a drum section inserted into the outer periphery of the piston rod 5, and the diameter of the cylinder 12a is smaller than the diameter of the oil lock piece 10. Further, slits 12b and 12c are formed at the upper and lower ends and the center of the cylinder 12a.
[0017]
The oil lock case 7 is formed of a hollow cylinder, and a trumpet-shaped taper surface 7a is formed on the upper inner periphery, and a plurality of notches 7b are formed on the upper end of the cylinder to allow the oil to flow. The lower end of the suspension spring 6 is carried on the upper end of the oil lock case 7 via a seat 16.
[0018]
A large-diameter portion 5a is formed in the lower portion of the piston rod 5, and a cushion spring 14 is supported on the upper portion of the large-diameter portion 5a. The cushion spring 14 is adapted to apply the cushion when fully extended.
[0019]
At the time of the most compression, the cushion rubber 12 and the oil lock piece 10 enter the oil lock case 7 in the vicinity of the most compression, and between the inner periphery of the oil lock case 7 and the outer periphery of the cushion rubber 12 and the oil lock piece 10. Oil lock pressure is generated by the flow resistance of the oil flowing through the gap, and the cushion rubber 12 elastically contacts the bottom surface of the oil lock case 7, so that a shock due to a sudden bottom does not occur and the ride comfort of the vehicle is improved. improves.
[0020]
When shifting from the most compressed state to the extension operation, the oil is introduced below the oil lock case 7 through the notch 13 formed in the oil lock piece 10 and the slits 12b and 12c formed in the cushion rubber 12, and the negative pressure is reduced. Occurrence is prevented.
[0021]
【The invention's effect】
According to the present invention, the following effects can be obtained.
[0022]
1) According to the invention of each claim, the oil lock generating mechanism is composed of an oil lock piece and a cushion rubber provided in series on the outer periphery of the piston rod, and the oil lock piece and the cushion rubber are oil locks in the vicinity of the most compressed state. Oil lock pressure is generated by intruding into the case, and the cushion rubber elastically contacts the bottom of the oil lock case at the time of maximum compression to prevent sudden bottoming, preventing the occurrence of shock , The ride comfort of a vehicle with a front fork is improved.
[0023]
(2) Similarly, when the descending speed of the piston is high, the occurrence of shock is prevented by the oil lock pressure, so there is no need to increase the volume of the cushion rubber.
[0024]
(3) Similarly, when the piston speed is low, a shock can be generated by the elasticity of the cushion rubber, and the insufficient effect of the oil lock pressure can be covered by the elasticity of the cushion rubber.
[0025]
(4) Similarly, even if the oil lock case is shortened and the volume of the cushion rubber is reduced, the occurrence of shock can be prevented. As a result, no oil lock pressure is generated in the compression stroke range that does not reach the bottom. It can prevent the ride comfort from being deteriorated.
[0026]
(5) According to the invention of claim 2, the holder and the nut can be positioned by the stopper, and the oil lock generating mechanism is prevented from loosening or moving in the vertical direction, so that the desired oil can be reliably obtained at a predetermined position. Lock pressure can be generated.
[0027]
(6) According to the invention of claim 3, since the diameter of the cushion rubber is smaller than the diameter of the oil lock piece, the cushion rubber expands outward by the oil lock pressure when the cushion rubber is fitted in the oil lock case. As a result, a two-step gap can be formed outside the cushion rubber and the oil lock piece, and the oil lock can be applied in two steps. Further, since the cushion rubber has a drum-shaped outer surface, the penetration of the cushion rubber and the flow of oil are smooth.
[Brief description of the drawings]
FIG. 1 is a partially cut longitudinal front view of a front fork according to an embodiment of the present invention.
FIG. 2 is a partially enlarged cross-sectional view of FIG.
[Explanation of symbols]
1 Car body side tube 2 Wheel side tube 3 Damper cylinder 4 Piston 5 Piston rod 6 Suspension spring 7 Oil lock case 8 Oil lock generating mechanism 9 Holder 10 Oil lock piece 11 Nut 12 Cushion rubber 15 Stopper

Claims (3)

The wheel side tube is slidably inserted into the vehicle body side tube, the damper cylinder rises from the lower center of the wheel side tube, and the piston rod is movably inserted into the damper cylinder via the piston. It is connected to the upper part of the side tube, the piston rod and the vehicle body side tube are always urged in the extending direction via the suspension spring, and an oil lock case is provided on the upper part of the damper cylinder. In the front fork provided with the opposed oil lock generating mechanism, the oil lock generating mechanism is screwed into the outer periphery of the upper part of the holder, and the holder is held on the outer periphery of the piston rod. Fitted to the nut and the small outer diameter of the holder Jo of the oil lock piece, constituted by a cylindrical cushion rubber disposed in series at the bottom of the holder, the cushion rubber and the oil lock piece in the uppermost compression vicinity intrudes into the oil lock case generating an oil lock pressure The front fork is characterized in that the cushion rubber elastically contacts the bottom surface of the oil lock case to prevent sudden bottoming at the maximum compression .  The front fork according to claim 1, wherein a stopper is provided on the outer periphery of the piston rod, and the stopper engages with an upper end of the holder and an inner upper wall of the nut to hold the holder and the nut at a predetermined position on the outer periphery of the piston rod. Front fork according to claim 1 or 2 cushion rubber the diameter of the cylindrical body with consists tubular body of section drum type which is fitted on the outer periphery of the piston rod is characterized in that smaller than the diameter of the oil lock piece.

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