JP5946283B2 - Motorcycle - Google Patents

Description

  The present invention relates to an improvement in a motorcycle including a body frame.

  2. Description of the Related Art A motorcycle including a body frame in which one main frame extends rearward of the vehicle is known (see, for example, Patent Document 1 (FIGS. 2 and 3)).

  As shown in FIG. 2 and FIG. 3 of Patent Document 1, the body frame (100) (the numbers in parentheses indicate the symbols described in Patent Document 1. The element names have been changed. The same applies hereinafter) is the head pipe (110). ), The left and right main frames (120L, 120R) extending from the head pipe (110) to the rear of the vehicle, and the middle portions in the longitudinal direction of the left and right main frames (120L, 120R). Pivot frames (160L, 160R) extending downward from the section and exhibiting a plate shape.

  By the way, in the technique of Patent Document 1, the length of the joint between the left and right main frames (120L, 120R) and the pivot frame (160L, 160R) is the vehicle longitudinal direction of the upper end of the pivot frame (160L, 160R), respectively. It becomes length. Thus, when the length of the joint portion of the pivot frame (160L, 160R) is limited, the load tends to concentrate on the joint portion. It is preferable if there is a technique in which a load applied to the joint portion between the pivot frame and the main frame is dispersed and a proper bending can be maintained in each part of the vehicle body frame.

JP 2010-58762 A

  It is an object of the present invention to provide a technique for distributing load input applied to a joint portion between a pivot frame and a main frame so that the vehicle body frame is appropriately bent.

The invention according to claim 1 is a head pipe that rotatably supports the steering shaft, a main frame that extends rearward from the head pipe, and a pivot that is joined to the main frame and pivotally supports the rear arm. In a motorcycle provided with a frame, the main frame is a mono frame and has a circular cross section, and extends to the rear of the vehicle from the pivot frame. The pivot frame has a T-shape when viewed from the side of the vehicle. has a shaped portion, the pivot axis the the top of the T-shaped portion has a weld intends along the longitudinal axis of the main frame and swingably supported downward and the rear arm of the T-shaped portion The pivot frame (35) is provided with a constricted portion having a length in the vehicle longitudinal direction that is shorter than the other portions. Made is characterized in that is.

In the invention according to claim 2, the main frame is a circular portion in which the cross-sectional shape of the middle portion in the longitudinal axis direction is circular, the cross-sectional shape of the rear end portion is an oval portion exhibiting an oval, and a T-shaped portion The upper part of this has a welding part with a circular part , It is characterized by the above-mentioned.

In the invention according to claim 3 , the main frame is curved so that the middle portion in the longitudinal axis direction becomes the lowermost end, and the pivot frame has a welded portion where the lowermost end portion of the main frame is welded. Features.

In the invention according to claim 1, the main frame is a mono frame, has a circular cross section, and extends further to the rear of the vehicle than the pivot frame. Since the upper part of the T-shaped part of the pivot frame is welded along the longitudinal direction of the main frame, the input from the pivot frame is dispersed while increasing the weld length of the joint between the pivot frame and the main frame, Appropriate deflection can be maintained in the body frame. Further, since the upper part of the T-shaped part is brought into contact with the longitudinal direction of the main frame, welding work can be easily performed.
In the present invention, the pivot frame is provided with a constricted portion. The constricted portion has a smaller cross-sectional area than other parts and is lighter than other parts. As a result, the material cost of the pivot frame can be kept low.

  In the invention which concerns on Claim 2, a main frame consists of a circular diameter part and an ellipse part. The upper part of the T-shaped part of the pivot frame is welded to the main frame at a circular part instead of an oval part. If the circular portion has a larger radius of curvature than the oval portion, the area where the pivot frame is abutted against the main frame is increased, so that the welding operation can be easily performed.

In the invention according to claim 3 , since the pivot frame is welded to the lowermost end portion of the main frame, the length of the pivot frame extending upward can be shortened. The pivot frame can be reduced in size by the shortened length, and the pivot frame can be reduced in weight. Further, if the seat is placed on the lowermost end portion of the main frame, the seat height does not increase, so that passengers can easily get on and off.

1 is a left side view of a motorcycle according to the present invention. It is a left view of a vehicle body frame. It is a top view of a body frame. It is a disassembled perspective view of the junction part of a head pipe and a main frame. FIG. 5 is a view taken along line 5-5 in FIG. 2. It is a side view of a pivot frame and its peripheral part. It is a 7-7 line arrow directional view of FIG. FIG. 8 is a view on arrow 8-8 in FIG. 6. It is a 9-9 line arrow directional view of FIG. It is a 10-10 line arrow directional view of FIG. It is a 11-11 line arrow directional view of FIG. It is a top view of a seat rail. FIG. 13 is a sectional view taken along line 13-13 of FIG. FIG. 14 is a cross-sectional view taken along line 14-14 of FIG. It is principal part sectional drawing of the vehicle width direction center. It is a perspective view explaining the arrangement structure of an air cleaner box. It is a perspective view of a body frame.

  Hereinafter, embodiments of the present invention will be described in detail. In the drawings and examples, “up”, “down”, “front”, “rear”, “left”, and “right” respectively indicate directions viewed from the driver who rides the motorcycle. The drawings are viewed in the direction of the reference numerals.

Embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a motorcycle 10 includes a body frame 11, a front wheel steering support portion 15 that is provided at a front portion of the body frame 11 and supports a front wheel 13 so as to be steerable, and a rear portion of the body frame 11. A rear wheel suspension portion 16 provided to swingably support the rear wheel 14, an engine 17 that is suspended on the vehicle body frame 11 between the front wheel 13 and the rear wheel 14 and serves as a drive source for the rear wheel 14, A fuel tank 18 supported by the vehicle body frame 11 at an upper position and a seat 19 that extends continuously to the rear of the vehicle and is supported by the vehicle body frame 11 and on which an occupant sits are provided. Is a straddle-type vehicle that rides over.

  The front wheel steering support portion 15 includes a steering shaft 22 that is rotatably supported by the head pipe 21 of the vehicle body frame 11, a steering handle 23 that is provided integrally with the steering shaft 22 and that is operated by a passenger. Similarly, the front fork 24 is provided integrally with the steering shaft 22 and supports the front wheel 13.

  A headlight 51 and a meter panel 52 are attached to the top of the front fork 24. A rear fender 53 for preventing mud from the rear wheel 14 is attached to a seat rail 27 that constitutes a rear portion of the vehicle body frame 11 and supports the seat 19, and a taillight 54 is attached to the rear fender 53.

  The engine 17 includes an engine body 63 including a crankcase 61, a cylinder portion 62 extending obliquely forward and upward from the crankcase 61, and takes in outside air and supplies the outside air and fuel to the cylinder portion 62 at a predetermined ratio. An intake system 65 and an exhaust system 66 for guiding exhaust gas generated after combustion in the cylinder portion 62 are included.

  The intake system 65 includes an air cleaner 71, a carburetor 72 that is connected to the air cleaner 71 in front of the air cleaner 71 and generates an air-fuel mixture, and an intake pipe 73 that extends from the carburetor 72 and is connected to the rear wall of the cylinder portion 62. Thus, an air cleaner 71, a carburetor 72, and a cylinder portion 62 are sequentially arranged from the rear in the vehicle longitudinal direction toward the front. The exhaust system 66 includes an exhaust pipe 75 extending from the front wall of the cylinder portion 62 and a silencer 76 connected to the downstream side of the exhaust pipe 75.

Next, the structure of the body frame will be described.
As shown in FIG. 2, the vehicle body frame 11 includes a head pipe 21, a main frame 25 extending from the head pipe 21 to the rear of the vehicle, and a seat joined to the rear end 26 of the main frame and extending to the rear of the vehicle. Rail 27, plate-like reinforcing members 31L and 31R (only reference numeral 31L on the front side of the figure) welded to the lower portion of head pipe 21 and gusset 32, and diagonally below these reinforcing members 31L, 31R and gusset 32 A down frame 33 extending rearward, a pivot frame 35 joined to the main frame 25 and supporting a rear arm (reference numeral 30 in FIG. 1) in a swingable manner, and welded so as to extend downward to the left and right of the seat rail 27 Rear cushion bolt brackets 42L, 42R having a substantially triangular plate shape in a side view (only reference sign 42L on the front side in the figure) To. A), rear cushion bolts bracket 42L, 42R and the sub-frame 36L to be stretched between the pivot frame 35, 36R (showing only the viewer's side of the drawing symbols 36L.) And the main element. A front end 28 of the seat rail is joined to the rear end 26 of the main frame. The rear cushion bolt brackets 42L and 42R have rear cushion bolts 41L and 41R (only the reference numeral 41L on the front side is shown) to which the upper end of the rear cushion is attached.

  The rear cushion bolt brackets 42L and 42R constituting the connecting portion between the seat rail 27 and the sub frames 36L and 36R are members obtained by bending a plate-like member. The pipe-like subframes 36L and 36R are not directly joined to the pipe-like seat rail 27, and the subframes 36L and 36R are connected to the seat rail 27 via the rear cushion bolt brackets 42L and 42R. Rear cushion bolt brackets 42 </ b> L and 42 </ b> R in which plate-like members are processed are joined to the pipe-like seat rail 27. For this reason, compared with the case where pipe-shaped members are joined, since sufficient butt | matching length can be ensured, welding work can be performed easily. Further, since the pipe-shaped subframes 36L and 36R are welded to the rear cushion bolt brackets 42L and 42R, a sufficient butt length can be ensured and welding work can be easily performed.

  Tank support pins 78 extending in the vehicle width direction and supporting the front portion of the fuel tank (FIG. 1, reference numeral 18) are welded to the reinforcing members 31L and 31R. A plate-like regulator stay 82 for attaching the regulator 81 is welded to the upper surface of the main frame 25 in front of the pivot frame 35, and the rear portion of the fuel tank 18 and the seat ( A stay member 83 for fixing the front part of FIG.

  As shown in FIG. 3, the main frame 25 is a mono frame and extends further to the rear of the vehicle than the pivot frame 35. A seat rail 27 that is closed toward the front of the vehicle and opened toward the rear of the vehicle is joined to the rear end 26 of the main frame in a plan view. The seat rail 27 is a member obtained by bending a single pipe frame, and has a U shape in plan view. The front end 28 of the seat rail on the closed side is joined to the rear end 26 of the main frame. The seat rail 27 has left and right straight portions 103L and 103R extending in the vehicle longitudinal direction, and a seat cross pipe 44 is passed between the left and right straight portions 103L and 103R in the vehicle width direction. In addition, although the seat rail of a present Example exhibits U shape by planar view, it may exhibit V shape open | released toward a vehicle rear.

  In FIG. 1, a pivot shaft 46 extends in the vehicle width direction on a pivot frame 35 extending downward from the main frame 25, and the rear arm 30 is supported by the pivot shaft 46 so as to be swingable. The rear arm 30 extends rearward of the vehicle, the rear wheel 14 is attached to the rear end 30b of the rear arm, and rear cushions 40, 40 that relieve shock applied to the rear arm 30 between the rear end 30b of the rear arm and the seat rail 27. (Only the reference numeral 40 on the front side of the figure is shown). Rear cushion bolts 41L and 41R are attached to connecting portions (rear cushion bolt brackets 42L and 42R) between the seat rail 27 and the pivot frame, and rear cushion upper ends 40a and 40a are attached to the rear cushion bolts 41L and 41R. The pivot frame 35 can be said to be a member that supports the rear arm 30 in a swingable manner.

  The upper ends 40a and 40a of the rear cushion are respectively attached to the rear cushion bolt brackets 42L and 42R. The load applied to the rear cushions 40, 40 can be received by both the seat rail 27 and the sub-frames 36L, 36R. As a result, the load applied to the seat rail 27 can be dispersed.

  A seat 19 on which an occupant sits is provided above the seat rail 27, and the front end 20 of the seat is disposed in front of the front end portion 28 of the seat rail. Details of the seat mounting structure will be described later.

  An engine hanger 47 is attached to the lower end of the down frame 33, a crankcase front portion 61 a is supported on the engine hanger 47, and a crankcase rear portion 61 b is supported on the pivot frame 35.

Next, the structure of the connecting portion between the head pipe and the down frame will be described.
As shown in FIG. 4, a down frame 33 is disposed below the head pipe 21 obliquely rearward and downward such that its longitudinal axis extends obliquely rearward and downward of the head pipe 21. The down frame 33, the main frame 25, and the head pipe 21 The U-shaped cross-section reinforcing member 31 is welded to the head pipe 21 and the main frame 25 from the rear of the vehicle so that the gusset 32 having the U-shaped cross section is 33 and the reinforcing member 31, and the gusset 32 is welded to the head pipe 21, the down frame 33 and the reinforcing member 31.

2, the reinforcing member 31 and the gusset 32 are welded, the gusset 32 and the head pipe 21 are welded, and the gusset 32 and the down frame 33 are welded. . The reinforcing member 31 is welded to the head pipe 21 and the main frame 25.
The down frame 33 is separated from the head pipe 21 and the main frame 25. The welding structure around the down frame 33 will be described with reference to the next figure.

Next, the structure among the down frame 33, the reinforcing member 31, and the gusset 32 will be described.
As shown in FIG. 5, the down frame 33 is held so as to be surrounded by the reinforcing member 31 and the gusset 32. Gusset 32 is covered from the outside of the reinforcing member 31, and the boundary between the gusset 32 and the reinforcing member 31 is welded along the left and right ends in the vehicle width direction.

In the following, the structure of the pivot frame and its periphery will be described with reference to FIGS.
As shown in FIG. 6, the cross-sectional circular pipe-shaped main frame 25 extending in the longitudinal direction of the vehicle gradually collapses in the vehicle width direction at the rear portion of the main frame 25, and as shown in FIG. 9 described later, The rear end portion 26 has an elliptical cross section. The main frame 25 is curved so that the middle portion 25m in the longitudinal axis direction is the lowest end. A pivot frame 35 is welded along the longitudinal axis direction of the main frame 25 in a region having a circular cross section. The pivot frame 35 is welded to the lowermost end 25 b of the main frame 25.

  A pivot frame 35 is welded to the lowermost end 25 b of the main frame 25. Since the pivot frame 35 is welded to the lowermost end 25b portion of the main frame 25, the length of the pivot frame 35 extending upward can be shortened. The pivot frame 35 can be reduced in size by the shortened amount, and the weight of the pivot frame 35 can be reduced. Further, if the seat 19 is placed in the vicinity of the lowermost end portion 25b of the main frame 25, the height of the seat 19 does not increase, so that passengers can easily get on and off.

Next, a pivot frame joint portion to which the pivot frame is joined will be described.
As shown in FIGS. 7 and 8, one end 38L of the left pivot plate whose upper end is formed in an L-shaped section is overlapped with one end 38R of the right pivot plate whose upper part is formed in an L-shaped section. Then, welding was performed along the overlapped portion. Upper ends 39L and 39R of the left and right pivot plates constituting the left and right upper ends of the pivot frame 35 extend along the longitudinal axis direction of the main frame 25, and boundary portions between these left and right upper ends 39L and 39R and the main frame 25 Is welded.

  As shown in FIG. 9, the main frame 25 is a circular portion 87 in which the cross-sectional shape of the intermediate portion 25 m in the longitudinal axis is circular, and the main frame 25 to which the front end portion (reference numeral 28 in FIG. 6) of the seat rail is joined. The cross-sectional shape of the rear end 26 is an oval part 88 that exhibits a wide oval shape in the vehicle width direction.

  In FIG. 6, the pivot frame 35 has a T-shaped portion 90 whose upper portion extends along the longitudinal axis direction of the main frame in a side view of the vehicle and has a substantially T shape, and the upper portion of the T-shaped portion. The (upper end portion 91) is abutted and welded along the longitudinal axis direction of the main frame 25. The upper portion (upper end portion 91) of the T-shaped portion is welded to the circular portion 87 of the main frame 25.

  Since the upper portion (upper end portion 91) of the pivot frame 35 is brought into contact with and welded along the longitudinal axis direction of the main frame 25, the pivot frame is secured while increasing the welding length between the pivot frame 35 and the main frame 25. The input from 35 can be distributed. As a result, the vehicle body frame 11 can maintain an appropriate deflection. Moreover, since the upper part (upper end part 91) of a T-shaped part is contact | abutted along the longitudinal axis direction of the main frame 25, a welding operation can be performed easily and productivity at the time of welding can be improved.

  Furthermore, the upper part (upper end part 91) of the T-shaped part is welded to the circular part 87 instead of the oval part 88. Welding is performed on a circular portion 87 having a larger radius of curvature than the oval portion 88. Since the area where the upper part (upper end part 91) of a T-shaped part will face will become large if it is the circular part 87, welding work can be performed easily.

  As shown in FIG. 10, a constricted portion 93 having a length in the vehicle longitudinal direction shorter than other portions is provided on the pivot frame 35 at the intermediate portion 92 of the T-shaped portion. The constricted portion 93 is thinner and smaller than the other portions. The cross section of the constricted portion 93 has a substantially cross-sectional shape. The constricted portion 93 is arranged such that a left pivot plate 37L formed in a U-shaped cross section and a right pivot plate 37R formed in a U-shaped cross section are arranged to open to the center side in the vehicle width direction. The right pivot plate 37R, which is longer in the vehicle longitudinal direction than the left pivot plate 37L, is superimposed on the pivot plate 37L so that the right pivot plate 37R is positioned outward from the left pivot plate 37L. The left pivot plate 37L and the right pivot plate 37R are welded along the end of the pivot plate 37R.

  In FIG. 6, in the pivot frame 35, the portion having a smaller load load than the other portions is the constricted portion 93. Therefore, the weight of the pivot frame 35 can be reduced, and the material cost of the pivot frame 35 can be kept low. .

Next, the sub-frame joining portion where the sub-frame is joined will be described.
As shown in FIG. 11, the lower portion of the pivot frame 35 is substantially U-shaped on the horizontal cross section as described above, and the left and right walls 95L and 95R of the pivot frame are partially recessed to the center side in the vehicle width direction. Left and right recesses 96L and 96R that can be engaged with the front end of the subframe.

  As described above, the pivot frame 35 is formed by welding the left and right pivot plates 37L and 37R (left and right drawing plates) formed from steel plates to each other. That is, the pivot frame 35 is formed by welding a steel plate. If it is a steel plate, material cost will be reduced. In addition, since the steel plate is formed into the pivot frame 35, a predetermined rigidity can be obtained relatively easily.

  6 to 11, the pivot frame 35 is formed by joining the left pivot plate 37L formed by drawing a steel plate and the right pivot plate 37R formed by drawing the same steel plate. It has been explained that it is a member having a constricted portion 93 having a letter-like shape, an intermediate portion having a substantially square shape in a horizontal section, and a lower portion in a horizontal section having a U-shape.

Hereinafter, the structure of the seat rail will be described in detail with reference to FIGS.
As shown in FIG. 12, the seat rail 27 bends the first pipe member 101 into a substantially U shape in plan view of the vehicle, and as shown in FIG. The second pipe members 102 and 102 having an outer diameter that fits the inner diameter of the first pipe member 101 are inserted into the straight portions 103L and 103R from the rear of the vehicle, and as shown in FIG. The rear portion of 103R is formed so as to be crushed from the vehicle width direction, thereby forming a vertically long member having no space. The rigidity of the left and right straight portions 103L and 103R is increased by inserting the second pipe member 102 into the left and right straight portions 103L and 103R extending from the rear of the first pipe member 101 to the vehicle.

Next, the fuel tank support structure and the seat support structure will be described.
As shown in FIG. 15, the front portion of the fuel tank 18 is supported by a shaft-shaped tank support pin 78 welded to the left and right reinforcing members 31 </ b> L and 31 </ b> R and extending horizontally in the vehicle width direction. The projecting stay 105 projecting rearward is extended to the stay member 83, and the projecting stay 105 is fastened to the main frame 25 by the fastening member 106 from above the projecting stay 105.

  Next, after the seat stay 107 extends downward from the seat bottom plate at the front end portion of the seat 19, the seat stay 107 extends forward, and a notch (not shown) is formed in the seat stay 107 toward the rear of the vehicle. The front end portion of the seat 19 is fixed to the main frame 25 so as to be sandwiched between the upper surface of the protruding stay 105 and the fastening member 106.

Next, the structure and the like of the seat load receiving portion (support portion) will be described.
As shown in FIG. 16, a seat cross pipe 44 extends in the vehicle width direction at the longitudinal axis intermediate portion of the seat rail 27, and is formed on the seat cross pipe 44 by an elastic member and receives a load of the seat 19. A load receiving portion 111 is provided. Left and right second load receiving portions 112L and 112R that are formed of an elastic member and receive the load of the seat 19 are provided at the front ends on the straight portions 103L and 103R of the seat rail 27 in front of the first load receiving portion 111 in the vehicle. Referring also to FIG. 15, the seat 19 is mounted on the first load receiving portion 111 attached to the rear cross member (seat cross pipe 44) extending in the vehicle width direction and the straight portions 103 </ b> L and 103 </ b> R of the seat rail 27. It is mounted on the left and right second load receiving portions 112L and 112R.

  Since the first load receiving portion 111 is provided in the rear cross member (seat cross pipe 44) at the center in the vehicle width direction, it is possible to reliably support the load at the center in the vehicle width direction where a large load is easily applied. The seat 19 is supported at least by the first load receiving portion 111 and the second load receiving portions 112L and 112R. Since the sheet 19 is supported by the plurality of load receiving portions 111, 112L, and 112R, the sheet 19 can be supported more reliably.

  In FIG. 15, a seat 19 on which an occupant sits is provided above the seat rail 27, and the front end 20 of the seat is disposed in front of the front end portion 28 of the seat rail. The seat stay 107 provided at the front end 20 of the seat is supported by the main frame 25 by being fastened by the stay member 83 and the fastening member 106.

  The front portion of the seat 19 is supported by the main frame 25 via the seat stay 107, and the rear portion of the seat 19 is supported by the seat rail 27 via the load receiving portions 111, 112L, and 112R. If the seat 19 is supported by both the main frame 25 and the seat rail 27, the seat load can be dispersed and supported, and the load on the seat rail 27 can be reduced. If the load on the seat rail 27 is reduced, the frame member can be optimized, for example, the rigidity of members around the seat rail 27 can be reduced, and the weight of the vehicle body frame 11 can be reduced.

Next, an air cleaner box mounting structure and the like will be described.
In FIG. 16, an air cleaner box (air cleaner 71) that cleans the air entering the engine is screwed into the small stay 114 fixed to the stay member 83 horizontally from the left side in the vehicle width direction. It is attached to the main frame 25 via a member 83. In FIG. 15, the upper, lower, left, and right sides of the air cleaner 71 are disposed so as to be surrounded by the main frame 25, the sub cross pipe 121, the pivot frame 35, and the rear fender 53, so that the air cleaner 71 can be protected by these members. .

Next, supplementary explanation will be given for the components of the body frame.
As shown in FIG. 17, the sub cross pipe 121 is passed between the left and right sub frames 36L and 36R. A lower cross member 122 is passed between the left and right walls 95L and 95R in the vicinity of the lower end of the pivot frame 35, and a pivot shaft (see reference numeral 46 in FIG. 1, between the left and right walls 95L and 95R above the lower cross member 122. ) Through which a pivot collar 123 passes. In addition, hanger bolts 125 and 126 for suspending the engine (reference numeral 17 in FIG. 1) are passed between the left and right walls 95L and 95R below the pivot frame 35.

The operation of the motorcycle of the present invention described above will be described next.
The seat rail 27 is a member obtained by bending a pipe frame, and the front end portion 28 of the seat rail is joined to the rear end 26 of the main frame.

  Since the closed portion (front end portion 28) of the seat rail is directly joined to the rear end 26 of the main frame, a separate bracket or the like for joining the seat rail 27 to the main frame 25 becomes unnecessary. In addition, since the seat rail 27 only needs to bend one pipe, the number of parts can be reduced as compared with two seat rails. In addition, the productivity of the body frame 11 can be improved.

  In FIG. 15, the pivot frame 35 extends below the circular portion 87 of the main frame 25, and the pivot frame 35 is joined to the circular portion 87 of the main frame 25. A front end portion 28 of the seat rail is joined to the main frame 25 at a circular portion 88. Since the pivot frame 35 and the seat rail 27 are joined at different positions of the main frame 25, the members can be easily brought into contact with each other and the welding workability can be improved.

Further, the front end portion 28 of the seat rail is joined to the main frame rear end 26 that exhibits a wide ellipse in the vehicle width direction.
Conventionally, in welding between circular pipe frames, since the end portions of both members have curvature, it is difficult to make a uniform contact within a predetermined tolerance in a mass production process. For this reason, in order to facilitate uniform matching, for example, a flat member having a flat surface is interposed.

  In this regard, in the present invention, the cross-sectional shape of the main frame rear end 26 includes a flat portion (FIG. 9, reference numerals 118 and 118), so that the pipe members are made uniform using these flat portions 118 and 118. It can be easily matched and welded. As a result, productivity related to welding can be increased.

  The air cleaner box 71 is disposed at the rear portion of the main frame 25 in front of the front end portion 28 of the seat rail. Since the cross-sectional shape of the rear part of the main frame 25 gradually changes from a circle to a wide ellipse in the vehicle width direction, the space above the air cleaner box 71 can be widened. As a result, a large capacity of the air cleaner box 71 can be easily secured.

  Although the present invention is applied to a motorcycle in the embodiment, it can also be applied to a tricycle and can be applied to a general straddle-type vehicle.

  The present invention is suitable for motorcycles.

  DESCRIPTION OF SYMBOLS 10 ... Motorcycle, 21 ... Head pipe, 22 ... Steering shaft, 25 ... Main frame, 25m ... Middle part of main frame, 26 ... Rear end of main frame, 30 ... Rear arm, 35 ... Pivot frame, 37L, 37R ... Aperture Molded plates (left and right pivot plates), 46 ... pivot shaft, 87 ... circular part, 88 ... oval part, 90 ... T-shaped part, 93 ... constriction part.

Claims (3)

A head pipe (21) rotatably supporting the steering shaft (22), a main frame (25) extending from the head pipe (21) to the rear of the vehicle, and a rear arm (25) joined to the main frame (25). 30) a motorcycle (10) provided with a pivot frame (35) for pivotally supporting 30),
The main frame (25) is a mono frame and has a circular cross section, and extends to the vehicle rear side than the pivot frame (35).
The pivot frame (35), T-shaped portion having a substantially T-shaped when viewed from the side of the vehicle has a (90), the longitudinal axis of the upper before SL main frame of the T-shaped portion (90) (25) Having a weld along the direction ,
The length of the vehicle in the longitudinal direction of the pivot frame (35) is lower than that of the other portion of the pivot frame (35) below the T-shaped portion (90) and above the pivot shaft (46) supporting the rear arm (30) so as to be swingable. A short constriction (93) is provided,
The constricted part (93) has a horizontal section and an intermediate part formed in a substantially square shape,
Motorcycle characterized by that. The main frame (25) is a circular portion (87) in which the cross-sectional shape of the intermediate portion in the longitudinal axis direction is circular, and the oval portion (88) in which the cross-sectional shape of the rear end (26) is elliptical,
The motorcycle according to claim 1, further comprising a welded portion with the circular portion (87) at an upper portion of the T-shaped portion (90). The main frame (25), the middle portion in the longitudinal axis direction (25 m) is curved so that the lowermost end, the pivot frame (35) is lowermost portion is welded of the main frame (25) The motorcycle according to claim 1, wherein the motorcycle has a welded portion .

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