JPH04244492A - Frame for motorcycle - Google Patents

Abstract

PURPOSE:To facilitate molding of a frame for a motorcycle forming two-division structure of upper and lower parts and to facilitate variation of the characteristics of a rear wheel suspension device. CONSTITUTION:An upper frame body 10 comprises a head pipe 12, a front down frame 13, a main frame 15, a rear down frame 17, and a pivot plate 5. A link bracket 20 being a support part for a link mechanism L is formed integrally with a lower frame body 11 extended to the lower part of an engine 2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frame for a two-wheeled motor vehicle, and more particularly to a frame having an upper frame body and a lower frame body divided into upper and lower parts.

0002

[Prior Art] Such a frame structure is known,
For example, there is one described in Japanese Utility Model Publication No. 57-11833. This thing has an upper frame body in which the frame structure that forms a closed loop as a whole is divided into upper and lower halves, and the head pipe, the upper part of the front down frame, the upper part of the main frame, and the upper part of the rear down frame are integrally provided.
A lower frame body that integrates the lower part of the front down frame, the under frame, and the lower part of the rear down frame is formed in advance, and these divided bodies are bolted to each other, and the engine is supported in a closed loop structure. . Although the rear wheel suspension system is not shown in this known example, a pivot plate that swingably connects the front end of the swing arm of the rear wheel suspension system is usually provided at the rear and lower end of the frame. In addition, when adopting a known mono-suspension structure as a type of rear wheel suspension system, one rear cushion unit is arranged in the vertical direction, its upper end is connected to the upper rear end of the frame, and the lower end There is one in which the parts are connected via a link mechanism to a cross pipe and a swing arm that are horizontally suspended between pivot plates.

0003

[Problems to be Solved by the Invention] By the way, if one attempts to apply the latter mono-suspension structure to the former known example, it is necessary to attach the pivot plate to the rear and lower end of the lower frame body (i.e., the lower part of the rear down frame). It is considered common practice to provide one. However, with this structure, the lower frame body becomes relatively large due to the integral provision of the pivot plate, and the supporting part of the link mechanism must be provided integrally with this large lower frame body, making it extremely difficult to mold. It becomes difficult. Also, if you try to change the ratio of the rear wheel suspension system, for example, you will need to change the dimensions of the support part of the link mechanism, which means that you will have to completely replace the entire lower frame body, which is a large part. Change is not easy. moreover,
It is also desired to increase the rigidity against the tensile load applied from the rear wheel suspension system via the support portion of the link mechanism. This application aims to solve such problems.

0004

[Means for Solving the Problems] In order to solve the above problems, a frame for a two-wheeled motor vehicle according to claim 1 includes a frame having a loop shape in side view, an engine supported by the frame, and a rear part of the frame. A swing arm whose front end is swingably connected to a pivot plate provided on the frame, a rear wheel rotatably supported by the rear end of the swing arm, and an upper end connected to the rear upper side of the frame. It also includes a rear cushion unit whose lower end is connected to the rear lower side of the frame and the swing arm via a link mechanism, and the frame is divided into upper and lower halves into an upper frame body and a lower frame body which can be detachably connected. In the manufactured motorcycle, the upper frame body includes a head pipe that rotatably supports the steering shaft of the front wheel, a main frame extending rearward from the head pipe, and a rear down frame extending downward from the rear of the main frame. , a pivot plate provided at the lower end of the rear down frame and a front down frame extending downward from the front end of the main frame are integrally connected, and the lower frame body has at least a portion passing under the engine. Additionally, the support portion of the link mechanism is integrally formed. According to a second aspect of the present invention, in the frame for a two-wheeled motor vehicle, the lower frame body is provided with a lateral protrusion, and the lower front surface of the upper frame body is abutted against the back surface of the lateral protrusion.

[0005]

According to the first aspect of the invention, since the pivot plate is integrated with the upper frame body, the lower frame body can be made relatively compact. Therefore, if the support portion of the link mechanism is provided on the lower frame body, molding becomes easier because the lower frame body is a relatively small member. Further, when changing the characteristics of the rear wheel suspension system, the change can be easily made by replacing the small lower frame body in which the support portion of the link mechanism is provided. According to the invention of claim 2, when a rearward tensile force is applied from the rear wheel suspension side to the lower frame body through the support part of the link mechanism, the lower frame body Since it is supported by the lower front surface of the frame body, the rigidity against such tensile loads is increased.

[0006]

Embodiment FIGS. 1 to 6 show an embodiment applied to a motocross motorcycle. Fig. 2 shows the left side appearance of this two-wheeled motor vehicle. A frame 1 forming a closed loop supports an engine 2 in the closed loop, and a front fork 3
The front wheel 4 is supported through the swing arm 6, and the rear wheel 7 is supported through the swing arm 6 which is swingably attached to the pivot plate 5 which forms a part of the rear wheel. Reference numeral 8 is a rear cushion unit, the lower end of which is connected to the link mechanism L.
is supported by the swing arm 6 and the rear lower end of the frame 1. These swing arm 6, rear cushion unit 8, and link mechanism L constitute a rear wheel suspension system in the present application. The reference numeral 9a in the figure is an engine hanger, and 9b and 9c are engine mount brackets, respectively.

FIG. 1 shows a side profile of a frame 1, and FIG. 3 shows an exploded view thereof. In FIG. 1, the frame 1 is approximately 4 in side view.
It forms a side-shaped closed loop, and the upper frame body 10
and a lower frame body 11. The upper frame body 10 has a head pipe 12, a front down pipe 13,
It is composed of a gusset 14, a main frame 15, a cushion mounting bracket 16, a rear down frame 17, and a pivot plate 5, and is integrally formed of a light alloy such as aluminum. Note that the front end of a seat rail 18 is attached to the cushion attachment bracket 16, and the lower end of a rear stay 19 is attached to the rear of the pivot plate 5. The lower frame body 11 is an iron member installed in the longitudinal direction of the vehicle body to support the engine 2 downwardly. The front ends are connected by bolts 22. The rear end of the connecting rod 21 is connected to one vertex of a substantially triangular link plate 24 by a bolt 23. The connecting rod 21 and the link plate 24 constitute a link mechanism L. One of the other apexes sandwiching the bolt 23 is connected to the lower end 26 of the rear cushion unit 8 by a bolt 25, and another apex is connected to the lower part of the swing arm 6 by a bolt 27. Note that the front end of the swing arm 6 is rotatably connected to the pivot plate 5 by a bolt 28. Reference numeral 29 is a step bracket. The upper frame body 10 and the lower frame body 11 are connected by two bolts 30 from the sides at the front part.
bolts 31 and 32 from the side at the rear.
Furthermore, the front end 33 of the pivot plate 5 corresponding to the lower front end of the upper frame body 10 is projected rearward against a part of the two-way connection bracket 34 welded to the rear part of the lower frame body 11. In this state, the abutting portions are fastened to each other from the front with bolts 35, so that the whole is connected and integrated. As is clear from FIG. 3, the upper frame body 10 and the lower frame body 11 are divided into upper and lower halves and manufactured separately. In FIG. 3, the front down pipe 13 whose upper end is welded to the front end of the main frame 15 extends downward into left and right branches, and a joint portion 36 is provided at each lower end, where a bolt 30 is attached. Two through holes 37 are provided. The cushion mounting bracket 16 that protrudes rearward from the rear end of the main frame 15 is provided with a bolt through hole 40 for mounting the upper connecting portion 38 of the rear cushion unit 8 with a bolt 39. In addition, the rear down frame 17 whose upper end is welded to the rear end of the main frame 15 is
It extends downward into left and right branches, and the upper end of the pivot plate 5 is welded to each lower end. Two through holes 41, 42 for bolts 31, 32 are provided in the lower side of the pivot plate 5. In addition, bolts 31, 3
2 fastens the step bracket 29 together. The front end surface of the lower front end portion 33 of the pivot plate 5 forms an abutting surface 43, which will be described in detail later, and a screw hole 44 is provided rearward from this surface.

FIG. 4 is a partially cutaway view showing the planar shape of the connection between the upper frame body 10 and the lower frame body 11 on the rear side of the frame 1, and FIG. FIG. 6 is a diagram showing the side shape of the entire lower frame body 11. As is clear from these figures and FIG. 3, the underframes 45 constituting the lower frame body 11 extend in the front and back direction in left and right pairs, and the rear ends are welded to both ends of the cross pipe 46. There is. Under frame 45 and cross pipe 46
A reinforcing pipe 47 is obliquely welded to the corner. A pair of link brackets 20 extend rearward from the middle part of the cross pipe 46, and bolt through holes 4 are provided at the tips of the link brackets 20.
8 is provided. The front portions of the two-way connecting brackets 34 provided at the rear ends of the left and right underframes 45 have a cut shape similar to when a cylinder is cut diagonally, and a side protrudes outward at the rear of this cut portion. A side protrusion 50 is integrally provided. The side protrusion 50 is a portion on the back surface of which the contact surface 43 of the pivot plate 5 is abutted,
and a through hole 51 for the bolt 35 that connects these abutting parts to each other.
is formed. The rear portion of the two-way connection bracket 34 from the side protrusion 50 forms a flat plate portion 52 extending rearward along the inner surface of the pivot plate 5, through which the bolts 31 and 32 corresponding to the through holes 41 and 42 are inserted. Holes 53 and 54 are provided. These through holes 53, 5
The bolts 31 and 32 passed through the holes 4 are fastened with nuts 55 and 56. The nut 55 is integrally welded to the cross pipe 46. The lateral protrusion 50 may be formed separately from the two-way connecting bracket 34 and welded together, or may be formed into an integral structure by machining, forging, or the like.

As shown in FIGS. 3 and 6, the front end of the underframe 45 stands obliquely upward, and a joint bracket 57 having a substantially L-shaped cross section is welded to the tip. This joint bracket 57 can fit along two sides of the joint part 36 of the front down pipe 13, and is provided with two through holes 58 corresponding to the through holes 37 of the bolts 30, and is inserted through these through holes 58. 2 bolts 3
A nut 59 (only one is shown) is fastened to each end of the nut 59. An engine mount bracket 9b is integrally formed with the joint bracket 57. As is clear from FIG. 3, three brackets 61 for mounting the skid plate 60 are provided at the intermediate portions of the cross pipe 46 and the left and right underframes 45, 45, and one bolt 62 (one bolt) is provided through each bracket 61 for mounting the skid plate 60. The skid plate 60 is attached to the lower surface of the under frame 45 by fastening the nuts (shown) to three nuts (not shown) provided on the mounting bracket 61, respectively. Code 63 is bolt 6
This is the second seat.

Next, the operation of this embodiment will be explained. As is clear from FIGS. 1 and 3, the lower frame body 11 is considerably smaller than the upper frame body 10 by providing the pivot plate 5 and the front down pipe 13 on the upper frame body 10 side. Moreover, since the link bracket 20 is provided on the lower frame body 11 side, which is a relatively small member, compared to the case where it is provided integrally on the upper frame body 10 side (pivot plate 5 side), which is a considerably large member. , the difference in the number of molding steps is significant, making molding extremely easy. In particular, when the upper frame body 10 is made of a light alloy such as aluminum as in this embodiment, the link bracket 20 made of iron cannot be welded thereto, so that molding becomes even easier. In addition, when changing the ratio of the rear wheel suspension system, the lower frame body 11
It is sufficient to completely replace the link bracket 20 with another lower frame body 11 having a different size, and this replacement is easy and economical because the lower frame body 11 is miniaturized. Furthermore, since the upper frame body 10, which is a large part, is made of light alloy, and the lower frame body 11, which is a small part, is made of iron, it is possible to reduce the overall weight and lower the center of gravity of the vehicle body. Since the frame body 11 is made of iron, a structure that is resistant to ground hits can be obtained. Moreover, as shown in FIG. 4, as the rear wheel 7 moves up and down, a tensile load F is applied from the rear wheel suspension to the connecting rod
1 to the link bracket 20, the lower frame body 11 is pulled rearward. However, since the lower front end portion 33 of the pivot plate 5 is abutted against the back surface of the lateral protrusion 50 with the contact surface 34 in the direction of this tensile load F, the upper frame body 10 absorbs this tensile load F in the compression direction. As a result, the frame rigidity against the tensile load F increases. In addition, the upper frame body 1
The two-way connection bracket 34 between the pivot plate 5 and the lower frame body 11 is fastened with bolts 31 and 32 from two orthogonal directions, that is, from the sides, and with a bolt 35 from the front, so that the connection strength is extremely high.

[0011]

According to the invention as claimed in claim 1, the lower frame body can be made smaller by placing the pivot plate on the upper frame body side, and the supporting portion of the rear wheel suspension system is provided on this small lower frame body. This made molding extremely easy. Further, when changing the characteristics of the rear wheel suspension system, it is only necessary to replace the lower frame body, which is a small component, so changing the characteristics can be done easily and economically. According to the second aspect of the invention, the rear end of the upper frame is provided with a lateral protrusion, and the lower front surface of the lower frame is brought into contact with the rear end of the protrusion, so that the tensile load applied to the lower frame from the suspension system is reduced. It can be received by the upper frame, increasing frame rigidity.

[Brief explanation of the drawing]

[Fig. 1] Side view of main parts including the frame of the embodiment

[Fig. 2] Left side view of the motorcycle according to the example

[Fig. 3] Developed perspective view of main parts according to the embodiment

[Fig. 4] Partially cutaway plan view of main parts according to the embodiment

[Fig. 5] Partially cutaway enlarged side view of main parts according to the embodiment

[Fig. 6] Side view of main parts according to the embodiment

[Explanation of symbols]

1 Frame 2 Engine 5 Pivot plate 6 Swing arm 8 Rear cushion unit 10 Upper frame body 11 Lower frame body 33 Lower front end of pivot plate 34 Contact surface (lower front of upper frame body) 20 Link bracket (of rear wheel suspension system) Support part) 50 Lateral protrusion L Link mechanism

Claims (2)

[Claims] [Claim 1] A frame having a loop shape in side view;
An engine supported by the frame, a swing arm whose front end is swingably connected to a pivot plate provided at the rear of the frame, and a rear wheel rotatably supported by the rear end of the swing arm. An upper frame body that includes a rear cushion unit whose upper end is connected to the rear upper side of the frame and whose lower end is connected to the rear lower side of the frame and the swing arm via a link mechanism, and to which the frame can be detachably connected. In a motorcycle manufactured by dividing into upper and lower halves, the upper frame body includes a head pipe that rotatably supports the steering shaft of the front wheel, a main frame extending rearward from the head pipe, and a main frame body. A rear down frame extending downward from the rear of the frame, a pivot plate provided at the lower end of the rear down frame, and a front down frame extending downward from the front end of the main frame are integrally connected, and the lower frame body A frame for a two-wheeled motor vehicle, wherein at least a part of the frame passes under the engine, and a support part for the link mechanism is integrally formed. [Claim 2] A lateral protrusion is provided on the lower frame body,
2. The frame for a two-wheeled motor vehicle according to claim 1, wherein the lower front surface of the upper frame body is abutted against the back surface of the lateral protrusion.