JP2850240B2 - Motorcycle front fork - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a motorcycle front fork that supports a front wheel so as to be steerable.

(Prior Art) A front wheel of a motorcycle is supported by a front fork so as to be steerable. The front fork is pivotally supported at the lower ends of two left and right fork members with a front wheel interposed therebetween, and a steering shaft integrally coupled is rotatably supported by a head pipe at a front upper end portion of the vehicle body. A handle is fixed to the upper end of the steering shaft.

FIGS. 8 and 9 show a simple and lightweight front fork used for a relatively small motorcycle disclosed in Japanese Utility Model Publication No. 57-46716.

Through a horizontally long bracket 1, a steering shaft 2 is connected to a central portion, and left and right fork members 3 are connected to both side portions. This bracket 1 is formed by bending a metal plate.
It has an upper plate 1a, a front plate 1b, and a lower plate 1c, and has a U-shaped cross section with an open rear surface. The steering shaft 2 and the fork member 3 are welded through the upper plate 1a and the lower plate 1c, respectively.

The fork member 3 includes an upper tube 3a and a lower tube 3b which is slidably inserted through the lower tube 3b and is pressed down by a spring 4, and a front wheel is pivotally supported at a lower end of the lower tube 3b. Numeral 5 denotes a rubber damper for cushioning at the time of full compression, 6 denotes a spring for cushioning at full length, 7 denotes a stopper for regulating the steering angle, and 8 denotes a dust seal. Arrow F indicates the front direction of the car.

However, in such a configuration, since a relatively strong force acts on the bracket 1 that supports the upper end of the fork member 3, the rigidity is insufficient in the U-shaped cross section, so that it is necessary to increase the plate thickness or reinforce the plate. May occur.

FIGS. 10 and 11 show a case in which a rear plate 9 separately provided by closing an open rear surface is welded, and upper and lower plates 1a and 1c are connected to each other at a rear edge thereof to form a rectangular closed cross section to increase rigidity. It is enhanced. However, as shown in FIG.
And the fork member 3 are offset (dimension S) forward and backward, so that the trailing edge of the bracket 1 has a complicated shape, and the welding line 10 is bent to increase the welding cost and increase the cost due to the increase in the number of parts. There's a problem.

In order to avoid such a problem, as shown in FIG. 12, the bracket 11 is formed by a square pipe having a closed cross section in advance, and the steering shaft 2 and the fork member 3 are formed.
Is welded. However, also in this case, it is necessary to use a flat square pipe having a large front and rear width depending on the offset amount (S), and the bracket 11 becomes larger than necessary. Further, in order to avoid interference with other objects at the time of turning, it is necessary to form the cut portions 12 at the left and right rear corners.

In addition, as shown in FIG. 13, there is a type using a bracket 13 in which a square pipe is bent to correspond to the offset amount (S). In this case, a thin square pipe having a substantially square cross section can be obtained, and the size and weight can be reduced. However, a large cost increase due to the bending of the square pipe is inevitable.

(Problems to be Solved by the Invention) In view of the above situation, according to the present invention, a bracket connecting a steering shaft and a fork member is formed by bending a single metal plate, and has high rigidity without adding another part. It is an object of the present invention to provide a front fork of a motorcycle in which the front fork is provided.

[Configuration of the invention]

(Means for Solving the Problems) In order to achieve the above object, a front fork of a motorcycle according to the present invention has a substantially U-shaped cross section formed by an upper plate, a front plate, and a lower plate, and has a substantially triangular shape in plan view. The bracket includes a front plate and a rear plate that connect the upper plate and the lower plate of the substantially triangular bracket, and cut off at the substantially triangular corners to open the left and right sides and the rear of the bracket. Forming
The rear plate of the bracket is constituted by a tongue piece extending from at least one of the upper plate and the lower plate, and the rear edge of the upper plate and the lower plate of the bracket are connected to each other by welding through the tongue. A steering shaft is provided at a central corner of the bracket, and left and right fork members are disposed on the left and right corners of the bracket so as to straddle the upper plate and the lower plate. The fork member penetrates the lower plate and abuts on the lower surface of the upper plate. Are fixed to the upper plate and the lower plate by welding.

(Function) In the front fork of the motorcycle according to the present invention, the front plate and the rear plate of the bracket having a substantially triangular shape in plan view have the front plate and the rear plate corresponding to the corners of the substantially triangular shape. The bending line that bends the tongue piece is a simple straight line and easy to process, while the upper end of the fork member extending through the lower plate can be welded to the lower surface of the upper plate at the left and right side opening, -Physical strength can be increased.

The front fork's bracket has a U-shaped cross section with the rear surface open as the main form, but the steering shaft and the fork member are welded over the upper and lower plates at the center corner and both side corner apex, and the left and right fork members Since the bracket at the portion where the bracket is fixed vertically is formed in a substantially closed cross section, the overall rigidity is high.

The tongue pieces are formed left and right independently by notching the rear plate, and the width parts of the individual tongue pieces can be formed in a straight line for easy processing, and it is easy to cope with the offset between the steering shaft and the fork member. The pieces can be simply bent and the rear edges of the upper and lower plates can be connected by welding, so that the workability is good and it can be formed with a minimum number of parts, which is advantageous in cost.

(Embodiment) FIG. 1 is a front view of a main part of a front fork according to an embodiment of the present invention, which is partially longitudinally cut, FIG. 2 is a plan view of the same cross section, and FIG. It is a side view.

A bracket 21 for connecting the steering shaft 22 and the fork member 23 has an upper surface 21a, a front surface 21b, and a lower surface 21c. It is a triangular shaped metal plate molded product.

A steering shaft 22 extends through the upper plate 21a and the lower plate 21b toward the rear of the center of the bracket 21, that is, at the vertex of a substantially triangular center in plan view, and the lower end of the shaft is welded to the lower plate 21c. You. 24 is the steering shaft 2
A stopper for restricting the rotation angle range which is welded concentrically to the upper plate 21a.

The upper end of the fork member 23 is welded to the position closer to the left and right front sides of the bracket 21, that is, at the position of the right and left corners of the triangular shape in plan view, while penetrating the lower plate 21c and in contact with the lower surface of the upper plate 21a. .

In the figure, reference numerals 25 and 26 denote a bracket front plate 21b and a fork member 23.
Guides such as brake cables welded to the front surface are shown. Reference numeral 27 denotes a welding line for each welded portion.
Refers to the front direction of the wheeled vehicle.

Next, at the rear edges of the upper plate 21a and the lower plate 21c, tongue pieces 28a, 28b and 29a, 29b which are bent inward are provided at the portions sandwiched between the steering shaft 22 and the fork member 23. The upper and lower tongues 28a and 29a and the leading edges of the upper and lower tongues 28a and 29b are welded against each other, and a rectangular closed cross section is formed at this portion (FIG. 5). The tongues 28a, 29a and 28b, 29b constitute the rear plate of the bracket 21, as shown in FIGS.

FIG. 4 is an exploded view of the bracket 21, that is, a cutout of the material of the bracket 21, and all the necessary surfaces are provided by one metal plate. The steering shaft 22 is inserted through the upper plate 21a, and a through hole 30a is formed to fit and weld the stopper 24, and the lower plate 21c is inserted into the lower plate 21c.
A through hole that penetrates and welds the lower end of the steering shaft 22
A through hole 31 that penetrates through 30a and fork member 33 and welds
Has been established. 32 is a straight bent line forming the upper plate 21a, the front plate 21b, and the lower plate 21c, and 33 is tongue pieces 28a, 28b, 29a, 29
b shows a straight bending line formed by b, by bending in the same direction along all bending lines 32, 33,
A bracket 21 is formed.

In this case, since the bending line 33 of the tongue piece is straight and has a relatively short setting, it is easy to incorporate such a straight structure into the shape of the rear surface of the bracket 21 according to the offset of the steering shaft 22, and therefore, the bending The entire bracket 21 can be formed only by processing, and the processing cost is reduced.

FIG. 6 shows another embodiment of the present invention, in which a rectangular closed cross section is formed by elongating the tongue piece 34 on the upper plate 21a side and welding it to the rear edge of the lower plate 21c.

FIG. 7 shows still another embodiment of the present invention,
The c-side tongue piece 35 is elongated and welded to the rear edge of the upper plate 21a to form a square closed cross section.

〔The invention's effect〕

As described above, the front fork of the motorcycle according to the present invention includes a bracket having a substantially U-shaped cross section formed by an upper plate, a front plate, and a lower plate and having a substantially triangular shape in plan view. The front and rear plates connecting the upper and lower plates,
The substantially triangular corners are notched to form openings that open to the left, right, right and rear of the bracket, and the rear plate of the bracket is a tongue piece extending from at least one of the upper plate and the lower plate. The upper plate and the lower plate of the bracket are welded to each other at the rear edges through welding,
A steering shaft is provided at the center corner of the bracket, and left and right fork members are disposed on the left and right corners of the bracket so as to straddle the upper plate and the lower plate. The fork member penetrates the lower plate and abuts on the lower surface of the upper plate, Since it is fixed to the upper plate and the lower plate by welding, the bending line of the bracket becomes a simple straight line and processing is easy, while the upper ends of the left and right fork members pass through the lower plate and abut on the lower surface of the upper plate. The left and right side openings allow welding to the upper plate and the lower plate, and the bracket has a closed section consisting of the upper plate, the front plate, the lower plate and the tongue (rear plate), so the rigidity is improved, Since the mechanical and physical strength can be increased, and the bracket is formed by bending only one metal plate, there is an effect that the processing is easy and the cost can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a partially longitudinal side view of a main part of a front fork showing an embodiment of the present invention, FIG. 2 is a plan view partially crossing the main part of the front fork, and FIG. 3 is FIG. FIG. 4 is an exploded view of the bracket of FIG. 1, FIG. 5 is a sectional view of FIG. 2 taken along the line BB, and FIG. 6 is another embodiment of the present invention. FIG. 7 is a cross-sectional view showing a tongue shape of a bracket according to another embodiment of the present invention; FIG.
FIG. 9 is a partially longitudinal front view showing the general configuration of the front fork, FIG. 9 is a partially longitudinal plan view showing the general configuration of the front fork, FIG. 10 is a perspective view showing the configuration of a conventional bracket, FIG. 11 is a longitudinal sectional side view showing the structure of a conventional bracket, and FIGS. 12 and 13 are perspective views each showing the structure of a conventional bracket using a square pipe. 21 Bracket, 21a Upper plate, 21b Front plate, 21c
... lower plate, 22 ... steering shaft, 23 ... fork member, 24 ... stopper, 27 ... welding line, 28a, 28b, 29
a, 29b, 34,35 …… Tongue (back plate).

Claims (1)

(57) [Claims] An upper plate, a front plate, and a lower plate form a U-shaped cross-section, and have a substantially triangular bracket in a plan view. The front plate and the rear plate connect the upper plate and the lower plate of the substantially triangular bracket. The plate is cut off at the substantially triangular corner vertex to form an opening that opens to the left, right, left and right of the bracket, and a rear plate of the bracket extends from at least one of the upper plate and the lower plate. The rear edge of the upper plate and the lower plate of the bracket are connected to each other by welding through the tongue pieces, while the steering shaft is provided at the central corner of the bracket, and the left and right corners are provided at the left and right corners of the bracket. The fork member is disposed over the upper plate and the lower plate, and the fork member penetrates the lower plate, abuts on the lower surface of the upper plate, and is fixed to the upper plate and the lower plate by welding. Front fork of motorcycle.