JPH04219538A - Front fork of motorcycle - Google Patents

Abstract

PURPOSE:To reduce a change in control characteristics following extension and contraction of a front fork by giving suitable flexibility even under the contracted state of the front fork. CONSTITUTION:In the front fork 20 of a motor cycle equipped with an outer tube 60 held on a head pipe side, an inner tube 62 slidably inserted into the outer tube 60 from downside, and an axle bracket 64 attached to the bottom end of this inner tube 62 and holding the front wheel 22, a groove 84 positioned in the neighborhood of the upper edge of the above-mentioned axle bracket 64 is formed in the above-mentioned inner tube 62.

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 using a so-called inverted telescopic fork having a large diameter outer tube at the top and a small diameter inner tube at the bottom.

0002

2. Description of the Related Art In motorcycles using telescopic forks, the rigidity of the fork has a large effect on maneuverability. For example, if the rigidity of the fork is too high, vibrations transmitted from the road surface to the vehicle body and running handlebars will increase, and small changes in road surface conditions will have a greater impact on maneuverability. Conventionally, therefore, the inner tube itself was given a suitable degree of flexibility to obtain a suitable degree of rigidity for the entire fork.

In this case, the flexibility of the inner tube can be utilized when the inner tube has fully withdrawn from the outer tube, but when the inner tube has entered deeply into the outer tube and the fork has become short, the flexibility of the inner tube cannot be used. This will cause the stiffness of the fork to increase rapidly. For example, if the front brake is applied during a turn, the front fork will contract significantly due to centrifugal force and forward load movement, making the fork excessively rigid. This causes problems such as changes in handling characteristics, such as an increase in understeer characteristics.

0004

[Problem to be Solved by the Invention] Therefore, the problem to be solved by the present invention is to minimize changes in handling characteristics caused by expansion and contraction of the front fork by providing the front fork with appropriate flexibility even in the retracted state. It is to be.

[0005]

[Means for Solving the Problems] According to the present invention, this problem can be solved by providing an outer tube held on the head pipe side;
In the front fork of a motorcycle, the front fork of a motorcycle includes an inner tube slidably inserted into the outer tube from below, and an axle bracket attached to the lower end of the inner tube to hold the front wheel. This is achieved by a front fork of a motorcycle characterized by forming a groove located near the upper edge.

[0006]

[Embodiment] Fig. 1 is a side view of an embodiment of the present invention, Fig. 2 is a partially sectional view of the front fork in a full bump state, Fig. 3 is an enlarged view of a part thereof, and Fig. 4 is an internal structure omitted. 4 is a sectional view taken along the line IV-IV in FIG. 3. FIG.

In FIG. 1, reference numeral 10 denotes a vehicle body frame, which is a combination of a front frame 12 and a rear frame 14. The front frame 12 has a head pipe 16 and a pair of left and right side frames 18 (only one of which is shown) extending obliquely downward and rearward from the head pipe 16. The side frame 18 is formed by joining two sheet metal members each having a U-shaped cross section facing each other to form a box shape with a square cross section, and the rear part of the side frame 18 is curved downward. Two front forks 20 are held in the head pipe 16 so as to be rotatable left and right, and a steering front wheel 22 is attached to the lower end of the forks. This front fork 2
0 will be described later.

The rear frame 14 is composed of a seat rail 24 and an auxiliary seat rail 26. Seat trail 24
is formed of a pair of left and right upper tubes 24a and a lower tube 24b supporting them from below, and the front ends of these upper and lower tubes 24a, 24b are fixed to the side frame 18.

The auxiliary seat rail 26 has a pair of left and right tubes.
The bridges 26a, 26a are connected to each other by front and rear bridges 28, 30 to form an integral body. Tubes 26a, 26
The front half part of a is bent diagonally downward and forward, and this descending part is bolted to the rear end of the upper tube 24a of the seat rail 24 and the rear lower part of the lower tube 24b. .

Reference numeral 32 denotes a rear wheel, the front end of which is held at the rear end of a rear arm 34 which is pivotally supported by the side frame 18. The rear arm 34 is elastically supported by a cushion unit (not shown). Note that a rear fender 36 is attached to this rear arm 34.

38 is a V-type two-stroke, two-cylinder, liquid-cooled engine. This engine 38 is mounted on the side frame 18 so that a V-shaped space formed between two V-shaped cylinders faces forward. 40 is an exhaust expansion pipe for the upper cylinder, and 42 is an exhaust expansion pipe for the lower cylinder. 44
is a cooling radiator for the engine 38, and 46 is a fuel tank. The front part of the fuel tank 46 rests on the side frame 18, and the rear part rests on the upper tube 24a of the seat rail 24. 48 is a driver's seat, and a fuel tank 46
It is attached to the upper tube 24a of the seat rail 24 at the rear of the seat rail 24. A lubricating oil tank 50 and a battery 52 are housed below the driver's seat 48.

A passenger seat 54 is attached to the auxiliary seat rail 26, and a license plate 56 is attached to the passenger seat 54.
, tail lights 58, direction indicators, luggage boxes, tool bags, and other parts for city driving are attached.

Next, the front fork 20 will be explained based on FIGS. 2 to 4. The front fork 20 is of an inverted type and has an upper outer tube 60, a lower inner tube 62, and an axle bracket 64 fixed to the lower end of the inner tube 62. The upper part of the outer tube 60 is fixed to upper and lower brackets 66 and 68 (see FIG. 1), which are held by the head pipe 16 so as to be rotatable left and right. Axle hole 70 of axle bracket 64
(FIG. 2) holds the axle of the front wheel 22.

A long rod 72 is fixed to the upper end of the outer tube 60 as shown in FIG. A piston 74 fixed to the lower end of the rod 72 slides within a damper tube 76 fixed to the axle bracket 64 side, thereby forming a small shock absorber using the damper tube 76 as a cylinder. A main coil spring 78 is housed in the gap between the damper tube 76 and the inner tube 62. The lower end of this spring 78 is supported by the axle bracket 64. Further, the upper end of the spring 78 is supported by the lower end of a seat pipe 80 fixed to the upper end of the outer tube 60. In addition, in Figure 2,
82 is a rebound coil spring.

An annular groove 84 is formed in the inner tube 62 and is located near the upper edge of the axle bracket 64 (FIGS. 3 and 4). This groove 84 provides flexibility to the inner tube 84 at the lower part of the inner tube 62, that is, near the upper edge of the axle bracket 64.

According to this embodiment, the front fork 2
When a compression force is applied to the damper tube 76, the inner tube 62 moves into the outer tube 60 while compressing the spring 78, and at this time, the oil in the damper tube 76 pushes against the piston 74.
The damping force is generated by passing through an orifice provided in the Further, when the inner tube 62 is sufficiently retracted from the outer tube 60, the fork 20 can have sufficiently large flexibility due to the elasticity of the entire inner tube 62 when it is curved.

[0017] When applying the front brake, the fork 20
When the inner tube 6 is close to a full bump, the inner tube 6
2 deeply enters the outer tube 60. Therefore, the flexibility associated with the curvature of the inner tube 62 itself can hardly be utilized. However, since the groove 84 is not located inside the outer tube 60, the flexibility of the vicinity of the groove 84 can be utilized to maintain a sufficiently large flexibility of the entire fork 20.

In this embodiment, an annular groove 84 is formed in the inner tube 62, but as in the embodiment shown in FIG.
, 84A may be provided. According to this embodiment, only the rigidity in the longitudinal direction can be lowered without lowering the rigidity in the lateral direction of the fork 20A.

In the above embodiments, the grooves 84 and 84A are provided on the outer surface of the inner tube 62, but in the present invention, similar effects can be obtained even if the grooves are formed on the inner surface.

[0020]

[Effects of the Invention] As described above, the present invention provides a lower inner
Since the tube has a groove located near the top end of the axle bracket, the inner tube has increased flexibility near this groove, and when the fork is compressed and near a full bump, the inner tube near this groove increases. The flexibility of the fork can be used to prevent the fork from becoming too stiff. Therefore, maneuverability near full bumps can be improved.

[Brief explanation of the drawing]

FIG. 1 is a side view of an embodiment of the invention.

FIG. 2 is a partial sectional view showing the front fork in a full bump state.

FIG. 3 is a partially enlarged view.

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3, with the internal structure omitted.

FIG. 5 is a sectional view of another embodiment at a position corresponding to line IV-IV.

[Explanation of symbols]

16 Head pipe 20 Fork 22 Front wheel 60 Outer tube 62, 62A Inner tube 64 Axle bracket

Claims (1)

[Claims] Claim 1: An outer tube that is held on the head pipe side, an inner tube that is slidably inserted into the outer tube from below, and an axle bracket that is attached to the lower end of the inner tube and holds the front wheel. In the front fork of a motorcycle,
A front fork for a motorcycle, characterized in that the inner tube has a groove located near an upper edge of the axle bracket.