JPH021579B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a rear fork for a motorcycle.

More specifically, we aim to prevent twisting and bending of the rear fork while making it lightweight, highly rigid, and improve the appearance design, and by reducing or eliminating the extension of welded parts, we are particularly able to prevent a decrease in precision and strength due to thermal distortion. The present invention relates to a method for manufacturing a novel light metal rear fork that can be suitably used in motorcycles subjected to high loads.

In the past, rear forks (swing arms) for motorcycles were generally made of steel pipes, but in recent years, efforts have been made to improve road tracking performance by reducing unsprung weight, reducing the load on shock absorbers, and further improving stability. For example, a rear fork is obtained from a light metal material such as aluminum alloy and extruded into a desired cross-sectional shape.
Known examples include No. 122537 (1982) and No. 146550 (Jitsu, Kai, and No. 1465).

The recent trend in the above rear fork is to pivot the shock absorber near the pivot part of the rear fork in order to obtain so-called progressive shock absorbing characteristics, so that the pivot part and the support shaft of the shock absorber come close to each other, and when the vehicle is running, the shock absorber is attached to the rear axle. The applied overhanging load causes a strong bending action on the rear fork, the vehicle body leans during cornering, and a torsional action is added, all of which act together in a complex manner, resulting in unstable running performance and poor handling. Significantly decreased. Therefore, in order to eliminate and prevent adverse effects such as twisting and bending of the rear fork, a separate U-shaped reinforcing member is installed on the underside of the rear fork, and its open end is attached to the area around the rear axle shaft attachment area. There has also been known a rear fork in which the so-called side surface is formed into a triangular shape, and one side is welded and fixed to the pivot shaft mounting portion through a connecting member.

Such a rear fork exhibits tremendous torsional bending rigidity against the torsional bending action caused by external thrust loads, but on the other hand, each member is fixed by welding, which increases the length of the welded part. Due to the influence of heat, the rear fork warps, thermal distortion such as bending occurs, and the strength also tends to decrease due to the decrease in accuracy and hardness.As a result, cracks occur around the welded part due to excessive repeated loads, resulting in breakage, etc. This creates an extremely dangerous situation for driving.

The above-mentioned phenomenon occurs intensively as a particularly amplified load is applied to the portions where the torsional bending moment is large around the mounting portion of the pivot shaft mounting portion and rear axle shaft mounting portion shock absorbing member.

The present invention is aimed at solving problems in view of the problems associated with welding of a rear fork formed using an extruded aluminum alloy member as described above, and a reinforcing member and a connecting member that are integrally connected to the rear fork. The purpose of this proposal is to improve strength, rigidity, and precision by reducing the extension of welded parts that induce thermal distortion or by eliminating fixing means such as welding. In order to achieve this, the present invention involves integrally extruding a rear fork arm with an arbitrary cross-sectional shape and a reinforcing member connected above and below through ribs, and bending the reinforcing member appropriately into a shape that resists bending moment. A rear fork is formed by fitting extruded sections between the rear fork arms and welding, screwing, or riveting them together.Further features and effects of the present invention will be described in accordance with the drawings attached below. It will be explained in detail.

Fig. 1 shows the rear fork body Rf (combined body) obtained by the present invention, A is a plan view, B is a side view, C is a rear view from arrow Z, 1R is the right upper rear fork arm, 1L is the left upper rear fork arm, 2 is the pivot shaft bearing, 3 is the cross arm, 4R is the lower rear fork arm which is the reinforcement member on the right side, 4L is the same lower rear fork arm on the left side, 5R is the right rib, 5L is Left side ribs 6R and 6L are connecting members on the left and right sides, respectively, and 7C is a connecting member at the center.

The left and right upper and lower rear fork arms 1R, 4R and the upper lower rear fork arms 1L, 4L in Fig. 1, which constitute the rear fork body Rf, are basically symmetrical, so the left upper lower rear will be referred to below. The method for manufacturing fork arms 1L and 4L will be described in detail. And the above Atsuparo Ariar Fork Arm 1
L and 4L are formed from a long shape M obtained by extrusion molding using an aluminum alloy die shown in FIG. 2A.

As shown in Fig. 2 (b), this profile M has an upper upper rear fork arm 1L and a lower lower rear fork arm 4L, which form two basic skeletons that overlap and connect in the vertical direction, and are extruded together through ribs 5L. The cross-sectional shapes of the upper rear fork arm 1L and the lower rear fork arm 4L are arbitrary, but as shown in the figure, they are formed into a so-called rectangular or rectangular shape with a closed cross section, and the lower rear fork arm 4L is made into a slightly smaller shape. This is favorable in terms of appearance design and provides sufficient strength and rigidity against torsion and bending stress.

The shape M obtained as described above is cut into a desired side shape and length. (Cutting lines C ₁ - _{C 2} - C ₃ - _{C 4} ) The thus obtained profile M ₁ is cut in the center of the rib 5L on the rear axle shaft side (around the right end in the figure) as shown in Fig. 2 (c). A hole 10 is appropriately drilled through the rib 5L, and a slit 17 is provided to cut in the longitudinal direction between the hole 10 and one end of the rib 5L (the left end in the figure) to divide the rib 5L into upper and lower parts. member 6R,
The fitting grooves 12, 13, 14 that fit into the parts 6L and 7C are cut out as shown in the figure using a press cut or the like, and a mounting part 8 for the pivot shaft bearing 2 is provided, and the lower rear fork arm _4L is attached to the left side in the figure ( The pivot shaft bearing 2 side) is bent downward to open the shape shown in Fig. 2 D, and the upper rear fork arm 1L is moved in the direction of arrow P ₂ (inward) shown in the perspective view of Fig. 2 E. The left rear fork RfL is formed by bending and bending the tip of the lower rear fork arm 4L inward in the arc shape shown in FIG. _1A in the direction of arrow P3. (The right rear fork RfR is also obtained in the same manner.) During or after the above steps, the rear axle shaft attachment hole 16 is opened.

In the above, left and right rear fork RfL,
As shown in Figure 3A, each RfR has the pivot shaft bearing 2 and the cross arm 3 attached to the front end (on the left side in the figure) with the bent portions facing inward, and the tips of the lower rear fork arms 4R and 4L are assembled and welded. They are fixed together by etc.

Next, the connecting members 6L and 6 shown in FIG.
R and 7C are molded by the following method.

First, the connecting member 6L shown in FIG. 3B is made by cutting a shape _M2 formed by extrusion molding of aluminum alloy into a required length as shown in the top view D of FIG. (Cutting line C ₅ ~
_C6 ) The cross-sectional shape of the profile _M2 is arbitrary, but it is advantageous in terms of strength if the ribs 11 are protruded from the upper and lower edges to form a closed square cross-sectional shape as shown in the cross-sectional view of FIG. 3E.

Furthermore, this shape _M2 has the unnecessary ribs 11 cut out (the downward diagonal line on the left in the figure) to reduce weight and improve rigidity, and the ribs 11 at both ends are replaced with the ribs 5L of the upper rear fork arm 1L and lower rear fork arm 4L. A concave fitting groove 15 is cut out (diagonal line downward to the right in the figure) to make it abut against the top of the figure, and is inserted into the fitting grooves 12 and 13 in Fig. 3A as shown in the side view of Fig. 3A. Cut off and provide at both ends.

The above connecting members 6L are common to the left and right, so 2
Each of them can be manufactured in the same shape and the other one can be used as the connecting member 6R.

Incidentally, as shown in the perspective view of FIG. 3C, the connecting member 7C can also be obtained by the same method as above using the same shape member _M2 , but the upper end portion is shaped so as to fit and match the cross-sectional shape of the pivot shaft bearing 2. Sufficient welding strength can be obtained by cutting in an arc shape.

The connecting members 6R and 6L obtained in the above manner are fitted into the fitting grooves 12 and 13, respectively, as shown in FIG.
The ribs 5L and 11 are inserted and fitted in a pressing manner to be fixed, and the abutting portions of the ribs 5L and 11 are further fixedly connected together by welding or the like.

The connecting member 7C has an upper end connected to the pivot shaft bearing 2 and a lower end connected to the lower rear fork arm 4.
After fixing and welding them into the fitting grooves 14 of R and 4L as described above, the extremely rigid rear fork body Rf shown in FIG. 1A, B, and C is formed.

In addition, as shown in Fig. 3, the rib 5L of the rear fork RfL can be sandwiched from both sides or one side, and the ends of the connecting members formed so as to be overlapped are arranged and fixed together by spot welding, and this can be done quickly and reliably. In addition, a high-quality rear fork body Rf with little thermal distortion can be formed, and if the spot welded parts are crimped and fixed using rivets, etc., as shown in Fig. 3, thermal distortion and heat generation can be avoided. Extremely high rigidity that does not cause any adverse effects such as changes in material quality or decrease in strength due to
Highly accurate rear fork body Rf can be obtained.

Of course, other than the above-mentioned rivet connection, it is obvious that connection means such as applying various adhesives to adhere the parts or screwing them with bolts and nuts may also be used.

The rear fork main body Rf described in detail above is obtained by forming the left and right rear forks RfL and RfR separately, assembling them together and then fixing them using the above-mentioned connecting means. The shown rear fork body Rf ₁ uses the shape M as described above.
By obtaining a lower rear fork arm 20 that is connected to the left and right as one unit, this eliminates any thermal distortion by eliminating welded parts, and further improves strength, rigidity, and precision, and in particular, prevents the weld bead from being exposed to the outside. The purpose of this embodiment is to obtain a high-yield rear fork with an excellent appearance design, and the same parts as those in the previous embodiment will be described with the same reference numerals.

That is, the profile M shown in FIG. 5A has a cross-sectional shape as indicated by the arrow _S0 , and is cut to a required length _l0 .
(Cutting lines _{C 1} to C ₂ ) As shown in FIG. A slit 17 that is drilled through and extends longitudinally between the holes 10.
In order to separate and form the upper rear fork arm 23 and the lower rear fork arm 24, and to connect the pivot shaft bearing 2 to the upper rear fork arm 23, a length l ₁ corresponding to this, that is, C ₂ to C ₄ lines and Cut the C ₅ to C ₆ lines up to the slit 17 of the rib 22 above, and follow the arrow S ₁ in Figure 4 C.
Atsupariar fork arm 23 as shown in
23' of the pivot shaft bearing 2 and the connecting member 6.
Fitting grooves 12, 13, 1 that fit with L, 6R, 7C
The main part of the rear fork body Rf ₁ is formed from the section M by cutting out the section 4 (the shaded part in the figure is the cutout part).

Next, as shown in _FIG .
As shown in S ₂ , the left and right sides are bent equally into a U-shape and
The upper rear fork arm 23 is bent in the direction of arrow _S3 in the figure, and the lower rear fork arm 24 is bent in the downward direction of _S4 , and the pivot shaft bearing mounting part 8 is provided at the front end of the protruding upper rear fork arm 23. The pivot shaft bearing 2 is fixedly connected by welding or the like to obtain the shape shown in Fig. 8.
Further, connecting members 6L, 6R, 7 are inserted into the fitting grooves 12, 13, 14 of each rib 22 of the upper rear fork arm 23 and the lower rear fork arm 24, respectively.
C is fitted as shown by the arrow, and then the tops of the rib portions that mainly abut are welded together or fixedly connected together using a connecting means as shown in FIG. Further, the cross arm 3 is also connected integrally. It should be noted that the welding method for each of the joints described above is by so-called MIG welding or TIG welding, but it is clear that electron beam welding, laser welding, etc. may also be used.

Further, this rear fork body Rf ₁ is configured to function by disposing a lower rear fork arm 24 as a reinforcing member of the upper rear fork arm 23 below the upper rear fork arm 23. As shown in Figure A, the upper part is bent and placed, a connecting member is fixed to the open part, the side surface is formed into a triangular shape as is known in the art, and a rear buffer member is placed between the top of this and the vehicle body frame (not shown). It may be mounted, and if a high load is to be received, it is especially advantageous in terms of strength if it is connected via two ribs R ₁ and R ₂ as shown in FIG. 10B.

In the embodiment shown in FIG. 10A, mounting holes for the axle shaft are provided in ribs R ₁ and R ₂ , and the cross-sectional shape of the lower rear fork arm is shown in FIG. It is molded to the same or slightly thicker shape and is most suitable for use as a rear fork for motorcycles that are subjected to relatively high loads.If the shaded area is removed as shown in the figure, it is effective in improving the external design and reducing the unsprung weight.

In the embodiment shown in Fig. 11A, an axle shaft mounting hole is provided in one rib _R3 , and the cross-sectional shape of the lower rear fork arm is horizontally plate-shaped.
_R4 is integrated into the vehicle to create a new exterior design.

Furthermore, FIG. 12A shows an upper rear fork arm and a hollow cylindrical lower rear fork arm 4L' as shown in FIG. By cutting the lower rear fork arm along the extension line as shown by diagonal lines, it is possible to advantageously improve the strength and reduce the weight.

In this way, the cross-sectional shapes of the upper rear fork arm and the lower rear fork arm can be freely selected according to the vehicle type, weight, and purpose of use and set in combination. Needless to say, this is not something that can be done.

In the above, although the mounting member of the rear side shock absorber is not particularly shown in the drawings in the present application, this is because the present invention includes a dedicated mounting member that matches various rear shock absorber types such as the so-called Pro Link, Full Floater, and Unitrack. It is clear that adding more will suffice. In addition, in order to further reduce the weight, the thickness of the profile of each of the above embodiments is made even thinner, and carbon fiber members are bonded together to form a composite material that is laminated on the outside and inside of this material, resulting in extremely strong strength. , it is possible to obtain an ultra-lightweight rear fork with excellent rigidity.

Although not shown in the drawings, a lower rear fork arm may be placed on the side of the upper rear fork arm via a rib, the side surface shape of the lower rear fork arm may be bent into a desired shape, or Separate rear fork arms may be provided at the upper and lower edges of the rear fork arm. Each of the above embodiments is shown in FIG.
It is shown in FIGS. 14 and 15.

Of course, an end plate may be attached to the rear end of the upper rear fork arm and the lower fork arm, and a mounting hole for the rear axle shaft may be provided therein.

According to the present invention as described above, an integrally molded light metal extruded section in which the upper rear fork arm and the lower rear fork arm forming the rear fork are connected via ribs is used, and this is cut into a desired shape. With one part of the rear end of the rib connected, the other part is separated, and the rear lower rear fork arm is bent and formed so that one side is open so as to resist the torsional bending moment. A fitting part is provided on the rib, a plurality of connecting members are fitted into this, and the rib part is mainly welded or joined together by riveting, screwing, gluing, etc. to form the rear fork body, so welded first. There is no thermal distortion or brittleness of the material due to the heat generated by the time, and even if high-load vibrations, shocks, etc. are applied, there is no occurrence of defects such as cracks as in the past. The arm and lower rear fork arm are connected around the rear axle using high-quality base materials, so this part has excellent strength, rigidity, and external design.The above manufacturing method also ensures stable quality. It is possible to mass produce the rear fork body.

Furthermore, since the extruded shape of aluminum alloy is used, the appearance is extremely beautiful and glossy, and it can be easily alumite-treated and colored in various colors, making it possible to mass-produce rear forks with particularly high fashionability at low cost. can.

Also, by using a composite material in which carbon fiber is laminated on the upper and lower rear fork arms, the wall thickness of the profile can be set thin, which makes it possible to obtain a rear fork that is particularly advantageous in reducing unsprung weight. It has various features and is an innovative and extremely practical method for manufacturing rear forks for motorcycles.

[Brief explanation of drawings]

Fig. 1 shows the rear fork body obtained by this invention, A is a plan view, B is a side view, C is a rear view, Fig. 2 A is a partial side view of the extruded section, and B is a side view of A. Rear view of the profile, C, D, and H are side and perspective views showing the forming process of the upper and lower rear fork arms from the profile, and Figure 3A is formed by assembling the left and right rear forks. B is a perspective view of the side connecting member, C is a perspective view of the central connecting member, D is a plan view of the molding method for obtaining the connecting member from an extruded shape, E is D _C5
~C ₆ line sectional view, F is a side view of the connecting member in D, G is a partially enlarged side view showing the state in which the connecting member is fitted and connected to the upper rear fork arm and the lower rear fork arm, and C and R are FIG. 4 is a perspective view of a rear fork body obtained in another embodiment, and FIG. 5A is a side view of the rear fork profile of FIG. 4. Figures B and C are side views showing the forming process; Figure 6 is a plan view showing the shape of Figure 5 C being bent and formed; Figure 7 is a perspective view showing the state after bending; Figure 8 is an explanatory perspective view of bending the lower rear fork and fitting the connecting member thereto; Figures 9 to 10 to 11;
Each A in FIG _. 12 shows various examples of the terminal treatment method of the rear _axle shaft part, _B in _FIGS .
14 and 15 are side views showing various embodiments of the rear fork body. 1R...Right side upper rear fork arm,
5R...Right side rib, 1L...Left upper rear fork arm, 5L...Left side rib, 4R...Right lower rear fork arm, 6R...Right side connecting member, 4L...Left lower rear fork arm, 6L... Left side connecting member.

Claims (1)

[Scope of Claims] 1. In a rear fork arm of a motorcycle formed from an extruded shape of a light metal material, the rear fork arm has an upper rear fork arm and a lower rear fork arm connected vertically and integrally via ribs. After cutting the extruded long light alloy metal shape to the required length, leave the ribs connected around the rear axle shaft attachment part, and divide the ribs on one side into upper and lower parts by making a slit in the longitudinal direction. The pivot side of the lower rear fork arm is bent downward so as to be arbitrarily opened, and the tip is bent inward in an arc shape, and the upper rear fork arms are fixed together via a connecting member. to form one side of left-right symmetry,
A method for manufacturing a rear fork for a motorcycle, characterized in that the rear fork is formed by fixing the tip of a lower rear fork arm of the same member on the other side. 2. The method of manufacturing a rear fork for a motorcycle according to claim 1, wherein the lower rear fork arms are bent into a U-shape so that the inner side faces face each other from the center.