JP2903236B2 - Motorcycle body frame - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a body frame of a motorcycle, in particular, a structure of a cross member at a lower part of a vehicle body, and a screw applied to the cross member by a supporting force on a vehicle body side link. The torsion force can be reduced as much as possible to improve the strength.

[Conventional technology]

A vehicle body in which a rear arm bracket is connected to both ends of a cross member connected to the rear ends of the left and right down tubes, one end of a vehicle body side link is pivotally supported by the cross member, and a rear cushion (buffer) is connected to the vehicle body side link. There is a frame. The structure of the cross member of such a body frame,
There are various types of connection structures between the rear end of the down tube and the cross member.
There are those described in JP 3084 and those described in JP-A 1-237276. In these conventional products, the cross member is generally a bent or welded pipe or plate, or a cast product, and in each case, a pair of brackets project from the cross member. And the above-mentioned vehicle body side link is pivotally supported by this bracket. The vehicle body side link is supported by the bracket via a pivot pin or a support bolt. Stress is concentrated on the base of the bracket due to the support force on the vehicle body link acting on the pivot pin or the support bolt. In a motorcycle that travels on uneven terrain such as a motocross, the load on the vehicle body side link becomes an impact force, so that concentrated stress is large at the base of the bracket. For this purpose, various reinforcing structures for reinforcing the base of the bracket are employed. In addition, since the axis of the pivot pin or the support bolt is largely displaced from the horizontal axis of the cross member, the cross member is twisted by the support force on the vehicle body side link applied to the pivot pin or the support bolt. Can be It is necessary to strengthen the connection structure between the cross member and the rear end of the down tube and the connection structure between the rear arm bracket as the torsional force increases.

[Problems to be solved by the invention]

In order to reduce the stress concentration and torsional force of the cross member due to the support force on the vehicle body side link, and to simplify and strengthen the structure of the cross member, the cross member including the connection structure with the rear end of the down tube is included. The purpose is to devise a structure.

[Means for solving the problem]

Means taken to solve the above problem include a pair of left and right main frames extending rearward from the head pipe, and a pair of left and right rear arm brackets connected to the main frame, and a lower portion of the left and right rear arm brackets. Are premised on the body frame of a motorcycle in which are connected by a cross member.

(B) Left and right circular holes are provided in the cross member, and the bottoms of the circular holes are used as bearings. (Ii) A recess is provided between the two bearings. One end of the cross member is inserted into the recess, and is supported by a support bolt inserted into the hole of the bearing portion. (D) The rear portions of the pair of left and right lower down tubes are inserted into the pair of left and right mounting portions of the cross member. And welded, the central extension line of the rear end of the lower down tube in plan view,
The vehicle body side link is directed to the left and right bearings with respect to the support bolt.

[Action]

Left and right circular holes are provided in the cross member, the bottom of the circular holes is used as the bearing, a recess is provided between the two bearings, and one end of a vehicle body side link is inserted into the recess. With the support bolts inserted into the holes, the vehicle body side link can be pivotally supported by the cross member without projecting the support bracket for the vehicle body side link from the cross member. Therefore, the problem of stress concentration caused by projecting the support bracket on the cross member does not occur.

Further, in such a support structure of the vehicle body side link, the misalignment between the support center of the cross member by the rear arm bracket and the axis of the support bolt can be made as small as possible. As a result, the torsional moment of the cross member is reduced as much as possible.

Further, the rear portions of the pair of left and right lower down tubes are inserted into the pair of left and right mounting portions of the cross member and welded,
Since the central extension line at the rear end of the lower down tube is directed to the left and right bearings with respect to the support bolt of the vehicle body side link in plan view, the tensile force and the compression force applied to the left and right down tubes are equal to the cross member. Act on each of the bearing portions, the bending moment on the cross member due to the tensile force and the compressive force is extremely small.

As described above, by reducing the torsional moment and the bending moment, the load applied to the cross member is reduced, and the strength of the cross member of the present invention is significantly improved (the torsional moment and the bending moment described above). A structure in which a concave portion is provided in each of the two bearing portions and one end of a vehicle body side link is inserted into the concave portion without causing a problem in strength by reducing the relative strength of the vehicle body. Can be said to have been realized).

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings.

The motorcycle according to this embodiment is used for, for example, a motocross game that runs on uneven terrain. A head pipe 2 constituting a body frame 1 has a front fork 3.
A front wheel 4 is provided at a lower end of the front fork 3. A front fender 5 is attached to the front fork 3, and a fixed fender that does not follow the vertical movement of the front wheel 4 is used as the front fender 5.

The head pipe 2 and a frame member 6 extending rearward and downward from the head pipe 2 are integrally formed. An integral member of the head pipe 2 and the frame member 6 is formed of an extruded material extruded in the head pipe axial direction. ing.

A pair of left and right substantially straight main frames 7 each having a substantially wide vertical cross section as viewed from the side are connected to the upper portion of the head pipe 2, and the rear of the main frame 7 is bent slightly downward. A pair of left and right rear arm brackets 8 are welded. This rear arm bracket 8
A rear arm pivot 9 is provided therebetween. A rear arm 10 is pivotally supported by the rear arm pivot 9, and a rear wheel 11 is supported at a rear portion of the rear arm 10.

As described above, the upper part of the head pipe 2 and the rear arm pivot 9 are connected by the pair of right and left substantially linear main frames 7 each having a vertical width and a rectangular cross section when viewed from the side, and the main frames 7 are formed of extruded material. A reinforcing plate 12 is welded to a lower front portion of the main frame 7.

The frame member 6 of the head pipe 2 is hung downward and rearward, and an upper down tube 13 is connected to the frame member 6 by welding, and the frame member 6 is shaped so as to smoothly connect to the upper down tube 13. From the lower side of the upper down tube 13 to the lower side of the frame member 6,
The reinforcing plate 14 is fixed by welding to reinforce the connection between the lower side of the upper down tube 13 and the frame member 6. The frame member 6 integrated with the head pipe 2 is thicker as the thickness is closer to the head pipe 2.
It has a shape corresponding to the stress distribution. Further, by forming the extruded member, the cross-sectional change of the frame member 6 can be freely set, and the frame member 6 can be smoothly connected to the upper down tube 13. Further, inside the pair of left and right frame members 6, a rib 6a for connecting the frame member 6 and the head pipe 2 is formed, and the rib 6a disperses stress and has a reinforcing effect by the rib itself. I have. The upper down tube 13 is welded by abutting the front of the connection frame 15 on the upper side of the center thereof, and a reinforcing plate 16 is welded between the upper down tube 13 and the connection frame 15 above the connection portion, A reinforcing plate 17 is welded between the upper down tube 13 and the connecting frame 15 below the connection portion, and the reinforcing plate 16
And the connection portion of the connection frame 15 is reinforced. The lower portion of the upper down tube 13 is connected to a pair of left and right lower down tubes 19 via one connecting member 18, and the lower down tube is similarly formed of extruded material, and is bent at the center thereof and extends rearward. ing. Connecting member 18 is upper down tube 13
And an extruded material extruded in a direction perpendicular to a plane formed by the pair of left and right lower down tubes 19. The connecting member 18 has an upper mounting portion 18a having a U-shaped end formed by extrusion and a pair of lower mounting portions 18b. A rib 18c is formed in a V shape inside the upper mounting portion 18a, and a rib 18d is formed on a wall facing the inside of the lower mounting portion 18b.
Are formed continuously to ensure strength and rigidity.

The lower part of the upper down tube 13 is the upper mounting part 18 of the connecting member 18.
a, and the lower part of the reinforcing plate 14 is welded to the front side of the upper mounting part 18a so as to contact the front side of the rib 18c, and the rear part of the upper mounting part 18a is reinforced. The lower part of the plate 17 is joined and welded so as to fit on the rear side of the rib 18c.

The upper part of the lower down tube 19 is the lower mounting part 18 of the connecting member 18.
b, the front side and the rear side are joined and welded so as to fit to the rib 18d.

The rear part of the pair of left and right lower down tubes 19 is a cross member
It is inserted and welded to a pair of right and left mounting portions 20a.
The cross member 20 is formed of an extruded material extruded in the left-right direction. Further, the cross member 20 is formed with holes 20b to 20d in the extrusion direction for weight reduction. The lower portions of a pair of left and right rear arm brackets 8 are welded to both sides of the cross member 20 in such a manner as to abut against a direction perpendicular to the axial direction of the cross member 20. The inside of the rear arm bracket 8 is covered with a lid 8a.

As described above, the pair of left and right rear arm brackets 8 are connected by the cross member 20 formed of the extruded material in the left and right direction, and by using the extruded material, it is possible to secure stable strength at the connecting portion of the rear arm bracket 8. it can. In addition, the thickness can be freely changed by the load applied to the body frame 1, and the shape can be smoothly changed. The rear arm bracket 8 is welded to the cross member 20 by abutting the rear arm bracket 8 in a direction perpendicular to the axial direction, so that the load applied to the cross member 20 can be directly received by the rear arm bracket 8, and a shear force is applied to the welded portion. Since it is not applied, the strength of the continuous portion is ensured. In addition, windows 20e and 20f are formed on the lower wall that defines the holes 20b and 20c of the cross member 20, respectively.
Water and mud entering the 20b and 20c are discharged downward. Further, both sides 20g of the cross member 20 are cut obliquely to secure a bank angle. A notch 20h is provided between the mounting portions 20a of the lower down tube 19.
Are formed, and both sides 20g are cut obliquely to avoid stress concentration. Furthermore, by fitting and welding the rear portions of the pair of left and right lower down tubes 19 to the mounting portion 20a, the strength can be secured without welding a reinforcing plate or the like, and the predetermined welding length can be easily adjusted. Can be secured.

A circular hole 20i is formed in the cross member 20 by cutting the hole formed by extrusion from both sides in the left-right direction, and a bearing 21 is formed at the bottom of the circular hole 20i. A concave portion 22 is formed between the bearing portions 21, a support bolt 23 is inserted from one of the bearing portions 21, and a nut 24 is screwed to a screw portion inserted into the other bearing portion 21 and screwed. You.

The mounting of the support bolts 23 is performed by forming the cross member 20 with an extruded material, and cutting out the extruded hole formed in the left-right direction from a circular hole portion 20i formed. Therefore, the mounting portion of the support bolt 23 can be easily formed without forming the above.

A pair of collars 25 are inserted opposite to the support bolts 23, and the ends of the vehicle body side links 28 of the link mechanism 27 are supported by the collars 25 via needle bearings 26. Oil seals 29 are provided at both ends.

A pair of rear arm side links 30 is rotatably provided on the vehicle body side link 28 of the link mechanism 27, and the end of the rear arm side link 30 is turned to a bracket 32 of a cross member 31 provided between the left and right rear arms 10. It is movably provided. The lower end of the rear cushion 33 is located at the end of the vehicle body side link 28.
34 is pivotally supported, and an upper portion 35 of the rear cushion 33 is connected to a rear portion of the connection frame 15.

As described above, since the link mounting portion 36 of the link mechanism 27 is provided in the cross section in the side direction of the cross member 20 connecting the pair of right and left rear arm brackets 8 and the link fulcrum is within the width of the rear arm bracket 8, The load applied to the link mounting portion 36 can be received by the entire cross member 20, and local concentration of stress is reduced.

Also, an extension line L of the axis of the pair of lower down tubes 19 on the left and right.
However, they face the center of each bearing portion 21 when viewed from the plane direction. Since the tensile force or the compressive force applied to the lower down tube 19 acts in the direction toward the bearing 21, the moment applied to the cross member 20 by the tensile force or the compressive force is extremely small. The extension line of the shaft of the pair of lower down tubes 19 on the left and right sides
Is preferably formed so as to face the center.

Therefore, the mounting strength of the link mechanism 27 that supports the rear arm 10 is improved, and since no special strength member or the like is used for this mounting portion, the strength can be improved with a simple structure, light weight, and more.

Further, the protrusion 37a of the step mounting bracket 37 is fitted into the circular hole 20i of the cross member 20. The step mounting bracket 37 has a flange portion 37b to be joined to the outer surface of the rear arm bracket 8, and this flange portion 37b is joined to the outer surface of the rear arm bracket 8, and the bolt 38 is inserted through the flange portion 37b to It is screwed into the nut 39 fixed inside and bolted. A step 40 is mounted on the mounting portion 37c of the step mounting bracket 37.

The load applied to the step 40 can be received by the circular hole 20i of the cross member 20 via the step mounting bracket 37, and the load applied to the bolted portion for mounting the step mounting bracket 37 to the rear arm bracket 8 is reduced. Forty mounting strengths can be improved.

The rear cushion 33 is disposed behind the pair of left and right main frames 7 and is substantially along the main frame 7 therebetween.
The upper part 35 of this one rear cushion 33 is
The front of the connecting frame 15 is located below the main frame 7 and the upper down tube
The lower part of the head pipe 2 and the upper part of the rear cushion 33 are connected to each other by a single linear connection frame 15 via an upper down tube 13. The vicinity of the rear part of the connection frame 15 and the main frame 7 are connected by a cross member 41, and the middle part of the connection frame 15 and the middle part of the main frame 7 are connected by a cross member 42.

A seat rail 43 is attached to each of the pair of left and right main frames 7. The seat rail 43 is supported by the rear arm bracket 8 with a back stay 44, and a seat 45 is attached to the seat rail 43.

A recessed space 46 is formed behind the head pipe 2 by the left and right main frames 7 and the connection frame 15, and a fuel tank 47 is disposed in the recessed space 46.

Engine mounting bracket in the middle of the connection frame 15
The cylinder 49a of the engine 49 is mounted on the engine mounting bracket 48. Also Engine 4
The front side and lower part of 9 are attached to upper down tube 13 and lower down tube 19 via engine mounting brackets 50 and 51. Further, the rear side of the engine 49 is connected to a rear arm pivot 9 provided on the rear arm bracket 8,
It is pivotally supported together with the rear arm 10.

A carburetor 52 is connected to the rear side of the cylinder 49a of the engine 49, and an air cleaner 54 is further connected to the carburetor 52 via a duct 53.The duct 53 is located on the left side of the vehicle body so as not to interfere with the rear cushion 33. It is arranged near. The air cleaner 54 is seated behind the rear cushion 33.
It is arranged at a position below 45 so as not to interfere with the rear cushion 33.

An exhaust pipe 55 is connected to the front side of the cylinder 49a of the engine 49. The exhaust pipe 55 is bent from the left side to the right side of the vehicle body below the front side of the lower down tube 19, and extends rearward from the right side.

A pair of left and right radiators 56 are arranged in front of the engine 49, and each of the radiators 56 is an upper down tube 13
Attached to. This radiator 56 is a pipe 57,
The engine 49 is connected to the cylinder 49a of the engine 49 via 58, and circulates cooling water to cool the engine 49.

FIG. 14 is a side view showing another embodiment of the rear arm bracket and the cross member. In this embodiment, the members denoted by the same reference numerals as those in the previous embodiment are configured in the same manner.
A description of this will be omitted. A support window 60 is formed below the pair of left and right rear arm brackets 8. A boss portion 20j formed in the cross member 20 to which the lower down tube 19 is connected is inserted into and supported by the support window 60, and a circular hole portion 20i is formed in the boss portion 20j.

〔The invention's effect〕

The cross member is provided with left and right circular holes, the bottom of the circular hole is the bearing, and a recess is provided between the two bearings.
One end of the vehicle body side link is inserted into the concave portion and supported by the support bolt inserted into the hole of the bearing portion, so that the support bracket for the vehicle body side link does not protrude from the cross member and the vehicle body side link is not provided. Can be pivoted to the cross member. Therefore, the problem of stress concentration as described above caused by projecting the support bracket on the cross member does not occur.

Further, in such a support structure of the vehicle body side link, the misalignment between the support center of the cross member by the rear arm bracket and the axis of the support bolt can be made as small as possible. As a result, the torsional moment of the cross member is reduced as much as possible.

Further, the rear portions of the pair of left and right lower down tubes are inserted into the pair of left and right mounting portions of the cross member and welded,
Since the center extension line of the rear end of the lower down tube is directed to the left and right bearing portions with respect to the support bolt of the vehicle body side link in plan view, the tensile force and the compressive force applied to the left and right down tubes are cross member. Act on each of the bearing portions, the bending moment on the cross member due to the tensile force and the compressive force is extremely small.

As described above, by reducing the torsional moment and the bending moment, the load applied to the cross member is reduced, and the strength of the cross member of the present invention is significantly improved.

As described above, in the present invention, the pair of left and right rear arm brackets are connected by the cross member, and the link mounting portion is provided in the cross section of the cross member. Therefore, the load applied to the link mounting portion is received by the entire cross member. Thus, local concentration of stress is reduced. Therefore, the mounting strength of the link mechanism that supports the rear arm is improved, and the strength can be improved with a simple structure and light weight because no special strength member or the like is used for the mounting portion.

[Brief description of the drawings]

FIG. 1 is a side view of a motorcycle to which the present invention is applied, and FIG.
FIG. 3 is a plan view of the vehicle body frame, FIG. 3 is an enlarged side view of the head pipe portion, FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. 3, FIG. Is a front view of the connecting portion of the down tube, FIG. 7 is a sectional view taken along line VII-VII of FIG. 6, FIG. 8 is a sectional view taken along line VIII-VIII of FIG. 6, and FIG. FIG. 10, FIG. 10 is a bottom view of FIG. 9, FIG. 11 is a cross-sectional view of a mounting portion of the link mechanism, and FIG.
11 is a sectional view taken along the line XII-XII, FIG. 13 is a sectional view taken along the line XIII-XIII in FIG. 9, and FIG. 14 is a side view showing another embodiment of the rear arm bracket and the cross member. Reference numeral 1 in the figure: body frame, 2: head pipe,
6 ... frame member, 7 ... main frame, 8 ...
Rear arm bracket, 9 ... Rear arm pivot, 10
…… Rear arm, 13 …… Top down tube, 15 …… Connection frame, 18 …… Connection member, 19 …… Down down tube,
20 ... cross member, 27 ... link mechanism, 33 ... rear cushion, 37 ... step mounting bracket, 40 ... step, 41, 42 ... cross member, 49 ... engine.

Claims (1)

(57) [Claims] 1. A motorcycle having a pair of left and right main frames extending rearward from a head pipe, and a pair of left and right rear arm brackets connected to the main frame, wherein lower portions of the left and right rear arm brackets are connected by a cross member. In the vehicle body frame, left and right circular holes are provided in the cross member, bottoms of the circular holes are used as bearings, recesses are provided between the bearings, and one end of a vehicle body side link is inserted into the recess. The lower part of the pair of left and right lower down tubes is inserted and welded to the pair of left and right mounting parts of the cross member, and is supported by the support bolts inserted into the holes of the bearing part. The center extension lines of the end portions are directed to the left and right bearing portions with respect to the support bolt of the vehicle body side link in plan view. Body frame for motorcycles.