JP4554245B2 - Body frame for motorcycles - Google Patents

Description

  The present invention relates to a body frame for a motorcycle, and more particularly to a structure of a main frame extending rearward from a head pipe.

The body frame for a motorcycle mainly includes a head pipe that pivotally supports a steering shaft, a main frame that extends rearward from the head pipe, and a pivot frame (swing arm) that extends downward from the rear end of the main frame. And a plurality of frame parts such as a down tube extending downward from the head pipe. Of these frame parts, the main frame is formed in the middle structure by joining two long members whose cross section forms a channel shape from the left and right, and welding the upper and lower attachment parts along the longitudinal direction. (For example, refer to Patent Document 1).
JP-A-7-232681

  By the way, in the main frame which welded the upper and lower attachment parts as mentioned above, in order to ensure the rigidity of a to-be-welded part, an overlapping part is provided in an attachment part and it welds over the full length of a main frame in many cases. However, in this case, the weight is increased due to the overlapping portion, and the weight is also increased due to the welding beat generated over the entire length. Since the main frame is relatively long, an increase in the weight due to the overlapping portion of the attachment portion and the welding beat has a relatively large influence on the weight increase of the body frame.

  In a motorcycle equipped with an engine, the engine is fixed to the body frame via a bracket. The bracket is cast or forged separately from the body frame and welded to the body frame, but it must be connected to the body frame while maintaining rigidity in order to support a heavy engine. Therefore, it is necessary to remove the welding beat generated by welding and improve the consistency of the joint surface between the main frame and the bracket. However, in the case of a long main frame, the work of removing the welding beat is troublesome. .

  Further, in a body frame of a recent motorcycle, many lightweight aluminum members are being adopted. However, technically sophisticated work is required to weld aluminum members while ensuring a predetermined rigidity. Furthermore, since aluminum materials are easily distorted by welding heat, welding of aluminum members is particularly troublesome.

  Therefore, an object of the present invention is to provide a vehicle body frame for a two-wheeled vehicle including a main frame capable of suppressing weight while securing rigidity. It is another object of the present invention to provide a body frame for a motorcycle that can suppress distortion caused by welding and improve the assembly accuracy.

  The present invention has been made in view of the above-described circumstances, and the body frame for a motorcycle according to the present invention has a tubular main frame extending rearward from the head pipe and has a butting portion only at a lower portion of the body. It has a substantially annular cross section.

  In the case of the main frame having such a cross-sectional shape, the required rigidity can be ensured without welding the attached portion. Therefore, no welding beat is generated at the abutting portion, and it is not necessary to provide an overlapping portion, so that an increase in the weight of the body frame can be suppressed. Further, if the attachment portion is not welded, it can be connected with the engine bracket with good consistency, and the engine can be reliably supported by the main frame. Further, in consideration of the thickness of the main frame and the like, a part or all of the abutting portion may be welded as necessary. Even in this case, since the welding location is only the lower portion of the main frame, the weight of the vehicle body frame can be suppressed as compared with the conventional case. The main frame can be formed by pressing a metal plate.

  Further, a gusset for supporting both of the main frame and the down tube is provided, the gusset has a channel-shaped cross section that is open upward, and the main frame has an abutting portion on the inside. The main frame may be connected to the lower portion, and only a portion of the main frame located inside the gusset may be welded. In this case, it is possible to attach the gusset without being affected by the presence of the welding beat, and it is possible to prevent the attachment portion from opening because a part of the attachment portion is welded in the main frame. . Further, since the other portions are not welded in the associating portion, the engine bracket can be easily attached to the lower portion of the main frame without performing a cumbersome operation of removing the welding beat.

  The butted portion of the main frame may be recessed toward the inside of the main frame, and an engine bracket that supports the engine on the main frame may be connected to the butted portion from below. Since the engine bracket to be cast has a draft angle, the engine bracket can be joined to the main frame with good consistency without processing the draft angle flat by adopting the above-described configuration.

  The main frame may be made of an aluminum alloy. Compared to steel materials, aluminum materials are greatly distorted by heat, and it is relatively difficult to ensure assembly accuracy by suppressing deformation due to welding. However, since the number of welding locations can be reduced as much as possible by adopting the above-described configuration, a vehicle body frame can be formed using a member containing aluminum such as an aluminum alloy, and the vehicle body is lightweight and has high assembly accuracy. A frame can be easily realized.

  According to the vehicle body frame for a motorcycle according to the present invention, it is possible to provide a vehicle body frame for a motorcycle including a main frame that can suppress weight while securing rigidity. Furthermore, in addition to the above, it is possible to provide a body frame of a motorcycle that can suppress distortion due to welding and can improve the assembly accuracy.

  Hereinafter, a body frame for a motorcycle according to an embodiment of the present invention will be specifically described with reference to the drawings. FIG. 1 is a side view of a motorcycle 2 in which an engine E is mounted in a body frame 1. The motorcycle 2 illustrated in the present embodiment is a motocrosser type configured such that a rider rides on a seat S provided on a body frame 1 and can travel off-road. In addition, the concept of direction used in the following description is the same as the concept of direction viewed from the rider riding on the seat S.

  As shown in FIG. 1, the motorcycle 2 has a predetermined caster angle at the front portion of the body frame 1 and pivotally supports a steering shaft 3. The steering shaft 3 has a front fork 4 provided at a lower portion thereof. The front wheel 5 is pivotally supported via the via. A steering handle 6 is provided on the steering shaft 3.

  At the rear part of the body frame 1, the swing arm 10 is swingable so that the front end part thereof is pivotally supported, and the front end part of the swing arm 10 is connected to the upper part of the body frame 1 via the link mechanism 12 and the suspension unit 13. The neighborhood is supported. A rear wheel 11 is pivotally supported at the rear end of the swing arm 10. The suspension unit 13 reduces the impact that the vehicle body frame 1 receives from the ground through the rear wheel 11. Further, the rear wheel 11 is driven to rotate based on the power generated by the engine E mounted in the body frame 1.

  A fuel tank 14 is provided above the body frame 1 and in front of the seat S. Then, fuel burned in the engine E is supplied from the fuel tank 14 to the engine E.

  The vehicle body frame 1 shown in FIG. 2 is a semi-double cradle type, and is composed of a plurality of frame parts made of aluminum alloy. That is, the vehicle body frame 1 includes a substantially cylindrical head pipe 20 that pivotally supports the steering shaft 3, a main frame 21 that has a front portion connected to the head pipe 20 and extends backward, and the main frame 21. A pivot frame 22 connected to the rear portion and extending substantially downward and pivotally supporting the swing arm 10 and the suspension unit 13 is provided. Further, a down tube 23 having an upper portion connected to the head pipe 20 and extending downward, a lower frame 24 having a front end connected to a lower portion of the down tube 23, and a rear end portion of the lower frame 24 and a pivot frame A lower pipe 25 is provided to connect the lower end of 22. From the inside of the vehicle body frame 1, a gusset 26 is attached in contact with both the main frame 21 and the down tube 23 to support the main frame 21 and the down tube 23. A bracket 27 for attaching an ignition coil is attached to the gusset 26.

  As shown in FIG. 2, an engine E is mounted in the body frame 1. The engine E is supported by an engine bracket 28 or the like attached to the rear lower part of the main frame 21.

  FIG. 3 is an enlarged side view showing the main frame 21, the gusset 26, the bracket 27, and the engine bracket 28 in the body frame 1 of FIG. 2, and FIG. 4 shows the main frame 21, the gusset shown in FIG. It is a cross-sectional view when 26 and the bracket 27 are cut | disconnected by the IV-IV line. The main frame 21 according to the present embodiment is formed by pressing a metal plate material into a tubular shape. As shown in FIG. 3 and FIG. The surface has a substantially rectangular ring shape. The main frame 21 has left and right abutting portions 30 and 31 only at the lower portion, and only the predetermined section (welding section) Z located substantially at the center of the abutting portions 30 and 31 extending over the entire length of the main frame 21 is provided. It is welded (see FIG. 3).

  Thus, since the main frame 21 has a cross-sectional shape having the left and right attachment portions 30 and 31 only at the lower portion, it is possible to ensure a predetermined rigidity without welding the attachment portions 30 and 31. Further, in the present embodiment, since a part (welding zone Z) of the associating portions 30 and 31 is welded, it is possible to prevent the associating portions 30 and 31 from opening left and right.

  On the other hand, as shown in FIG. 4, the gusset 26 has a channel shape in which a cross section of a portion joined to the main frame 21 is opened upward, and a bracket 27 is erected at a lower portion thereof. The gusset 26 has a channel shape in which the cross section of the portion joined to the down tube 23 is open toward the down tube 23. The gusset 26 is in contact with the lower portion of the main frame 21 from below, with the mating portions 30 and 31 of the welding zone Z in the main frame 21 being inward. In other words, the upper end portions 26A and 26B of the gusset 26 are in contact with the lower portion of the main frame 21 so that the left and right upper end portions 26A and 26B sandwich the mating portions 30 and 31 therebetween. The left and right upper end portions 26A, 26B of the gusset 26 and the lower portion of the main frame 21 are welded. As a result, the lower portion of the main frame 21 is supported by the gusset 26, and the attachment portions 30 and 31 are more difficult to open, and the rigidity of the main frame 21 can be improved.

  FIG. 5 is a cross-sectional view of the main frame 21 and the engine bracket 28 shown in FIG. 3 taken along line VV. As shown in FIG. 3, the portion cut by the VV line in the main frame 21 does not include the welded portion Z, and the abutting portions 30 and 31 of this portion are not welded as shown in FIG. 5.

  On the other hand, the engine bracket 28 is forged or cast and has a symmetrical appearance on the left and right. And it is comprised from the junction part 34 which has the joining surface 33 joined to the main frame 21 on the upper surface, and the bolt fastening part 35 which passes the volt | bolt which supports the engine E in the lower part of this junction part 34. The engine bracket 28 has an external shape that is long in the front-rear direction, and is welded to the lower portion of the main frame 21 such that the longitudinal direction coincides with the main frame 21. More specifically, the joint surface 33 of the engine bracket 28 is joined to the mating parts 30 and 31 at the lower part of the main frame 21, and the space between the left and right side parts 34 </ b> A and 34 </ b> B of the joint part 34 and the lower part of the main frame 21 is between. Welded.

  As described above, since the abutting portions 30 and 31 of the main frame 21 to which the engine bracket 28 is attached are not welded, an operation for removing the welding beat is unnecessary, and the main frame 21 of the engine bracket 28 is not required. Easy to join. The main frame 21 shown in FIG. 5 is formed so that the bottom surface is flat. On the other hand, the joint surface 33 of the forged (or cast) engine bracket 28 is joined during forging (or casting). The draft formed on the upper surface of the portion 34 is cut to be flat. Therefore, the lower surface of the main frame 21 and the joint surface 33 of the engine bracket 28 are joined with good consistency.

  FIG. 6 shows a cross section of the main frame 210 and the engine bracket 280 that are different from the cross section of the main frame 21 and the engine bracket 28 shown in FIG. The main frame 210 shown in FIG. 6 is slightly recessed inwardly with the mating portions 300 and 310 provided at the lower portion thereof, and the lower surface of the main frame 210 has a concave shape. On the other hand, the joint surface 330 of the engine bracket 280 that has been forged (or cast) is a convex joint surface 330 in which the draft formed on the upper surface of the joint portion 340 is left as it is during forging (or during casting). Have. Therefore, the joint surface 330 of the engine bracket 280 is joined to the lower surface of the main frame 210 with good consistency. The left and right side portions 340 </ b> A and 340 </ b> B of the joint surface 340 of the engine bracket 280 are welded to the lower portion of the main frame 210.

  While it is relatively easy to mold the main frame 210 so that the bottom surface is concave, it is relatively cumbersome to cut the draft of the joint surface 330 of the engine bracket 280 to make it flat. It is often work. Therefore, with the configuration as described above, the main frame 210 and the engine bracket 280 can be joined with good workability, and the welding strength can be further improved.

  According to the above-described vehicle body frame 1 according to the present embodiment, the main frame 21 has the required rigidity, and the increase in weight and distortion are suppressed by reducing the number of welding points. Further, the attachment portions 30 and 31 are welded only in the section Z covered by the gusset 26 to prevent the attachment portions 30 and 31 from opening.

  The present invention is applicable not only to a body frame for a motorcycle but also to a body frame for a motorcycle not equipped with an engine. Further, the present invention is applicable not only to the motocrosser but also to various motorcycles such as American type and road racer type. Further, in addition to the semi-double cradle type, the present invention can be applied to various body frames such as a diamond type and a double cradle type.

1 is a side view of a motorcycle including a body frame according to an embodiment of the present invention. It is a side view of the vehicle body frame shown in FIG. It is a side view which expands and shows a main frame, a gusset, a bracket, and an engine bracket among the vehicle body frames of FIG. It is a cross-sectional view when the main frame, gusset, and bracket shown in FIG. 3 are cut along the IV-IV line. It is a cross-sectional view when the main frame and engine bracket shown in FIG. 3 are cut along the line V-V. FIG. 6 is a cross-sectional view of the main frame and the engine bracket showing a configuration different from the cross-section of the main frame and the engine bracket shown in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Body frame 2 Motorcycle 3 Steering shaft 14 Fuel tank 20 Head pipe 21 Main frame 22 Pivot frame 23 Down tube 24 Lower frame 25 Lower pipe 26 Gusset 27 Bracket (for ignition coil attachment)
28 Engine brackets 30 and 31 Attached part 33 Joint surface 34 Joint part 35 Bolt fastening part 210 Main frame 280 Engine brackets 300 and 310 Attached part 330 Joint surface 340 Joint part E Engine S sheet

Claims (3)

A tubular main frame extending rearward from the head pipe has a substantially annular cross section having a butting portion only at the lower part of the vehicle body,
Furthermore, a gusset for supporting both of the main frame and the down tube is provided, the gusset has a channel-shaped cross section that opens upward, and the main frame has an abutting portion on the inside, and A body frame for a two-wheeled vehicle, characterized in that it is connected to a lower part and the main frame is welded only at a part of the main frame located inside the gusset. A main frame having a substantially annular cross section having a butting portion only at a lower portion of the vehicle body, and an engine bracket connected to the main frame;
The engine bracket is connected to the main frame at the left and right portions sandwiching the butting portion between the engine bracket and the lower portion of the main frame .
A body frame for a motorcycle , wherein a portion of the lower surface portion of the main frame positioned between the left and right portions and the upper surface of the engine bracket are in contact with each other in alignment . A main frame having a substantially annular cross section having a butting portion only at a lower portion of the vehicle body, and an engine bracket connected to the main frame;
The engine bracket is connected to the main frame at the left and right portions sandwiching the butting portion between the engine bracket and the lower portion of the main frame.
The engine bracket has a convex upper surface due to a draft angle at the time of molding, and a lower portion of the main frame that contacts the upper surface of the engine bracket has an abutting portion on the upper side so as to match the draft angle. a body frame for two-wheeled vehicles, characterized in that it forms a concave so as to be positioned.

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