JPH0764301B2 - Motorcycle body frame - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cast body frame of a motorcycle having a large number of reinforcing ribs.

(Prior Art) Conventionally, for example, Japanese Unexamined Patent Publication No.
There is one disclosed in Japanese Patent Publication No. 53285. According to this
A steering shaft tube that supports the front fork so that it can be steered freely, a pair of left and right main frames extending rearward and downward from the steering shaft tube, and a rear arm attached to the rear end of each of these main frames. And a rear arm bracket for supporting.

In the above structure, when casting the vehicle body frame, it is conceivable to integrally cast the left and right main frames and the rear arm brackets attached to these respective main frames.

Further, the external force applied to each of the main frames is considered to be smaller in the rear portion than in the front portion of the main frame. It is conceivable to reduce the weight of the main frame by narrowing the area.

(Problems to be Solved by the Invention) As described above, when the left and right main frames and the rear arm bracket are integrally cast, the left main frame to be cast and the rear arm bracket attached to the left main frame are formed. Left side assembly,
It is required to set a core between the right main frame to be cast and the right assembly composed of the rear arm bracket attached thereto, which may complicate the casting.

Further, as in the above configuration, when the vertical width of each main frame is made narrower as it goes downward and rearward, the rear lower portion of the main frame becomes lighter than the front upper portion, and as a result, the body weight of the vehicle becomes higher, This causes the inconvenience of going against the low center of gravity of the vehicle body required for motorcycles.

(Object of the Invention) The present invention has been made in view of the above circumstances. When casting a vehicle body frame, this casting can be easily performed, and an external force applied to each part of the vehicle body frame. The purpose is to provide the body frame with a strength commensurate with, and to lower the center of gravity of the vehicle body.

(Structure of the Invention) A feature of the present invention for achieving the above-mentioned object is that the left and right main frames are made to have a narrower vertical width dimension as they proceed downward, and a plurality of ribs are provided on each main frame. On the other hand, in the vehicle body frame of the motorcycle in which a plurality of ribs are formed on each of the rear arm brackets around the support portion of the rear arm of the rear arm bracket attached to the rear end of each of the main frames, the left and right main frames, and A pair of left and right assemblies is configured with the rear arm brackets attached to each of the main frames, and each of the assemblies is a cast product, and the ribs are formed on each side surface of the main frame and the rear arm bracket. The ribs formed on the rear arm bracket are more reinforced than the ribs formed on the main frame. The point is that they are densely arranged.

(Operation) The operation of the above configuration is as follows.

A plurality of ribs are formed on each of the left and right main frames 11, while a plurality of ribs are formed on each of the rear arm brackets 15 around the support portion of the rear arm 6 of the rear arm bracket 15 attached to the rear end of each of the main frames 11. In this case, the left and right main frames 11 and the main frames 11
A pair of left and right assemblies is formed with the rear arm bracket 15 attached to each of the above, and each of these assemblies is a cast product, and the above ribs 11a to 11e and 15a to 15e are attached to the side surfaces of the main frame 11 and the rear arm bracket 15. It is formed on.

Therefore, when the body frame 2 is to be cast, the left side main frame 11 and the rear arm bracket 15 attached to the left side main frame 11 and the right side main frame 11 and the rear arm bracket 15 attached to the left side main frame 11 are assembled. The assembled right assembly may be cast separately.

That is, in this case, when the left and right assemblies are integrally cast, the core of the mold to be set between the two assemblies to be cast is unnecessary.

Particularly, the ribs 11a to 11e and 15a to 15e are attached to the left and right main frames 1
1 and each side surface of the rear arm bracket 15 attached to each of the main frames 11, the gap between the lower part of the rear arm bracket 15 and the traveling ground (so-called minimum ground clearance) is the ribs 11a to 11e. , 15a to 15e prevent narrowing.

Then, in this case, if the die during the casting for the rib is performed sideways, and as described above, the left side assembly and the right side assembly are individually cast, the rib die cutting is performed. This is easy and the die cutting when casting one assembly is not obstructed by the other assembly.

Further, the vertical width of each left and right main frame 11 is reduced as it goes rearward and downward, and each of these main frames 11 and the rear arm brackets attached to each of these main frames 11 are reduced.
When a plurality of ribs 11a to 11e and 15a to 15e are formed on the respective side surfaces of the rib 15, the ribs 15a to 15e formed on the rear arm bracket 15 are formed more than the ribs 11a to 11e formed on the main frame 11. Are more densely arranged.

Therefore, a large external force is applied from the rear wheel 7 side around the supporting portion of the rear arm 6 in the rear arm bracket 15 via the rear arm 6, but as described above, the ribs 15a to 15e formed on the rear arm bracket 15 are formed. Since they are arranged more densely, a large external force applied to the rear arm bracket 15 can be dealt with.

In the above case, since the main frame 11 has a shape in which the vertical width dimension becomes narrower as it goes downward and rearward, this causes the vehicle body center of gravity to be increased.
Since the ribs 15a to 15e formed on the rear arm bracket 15 are more closely arranged than the ribs 11a to 11e formed on
It is prevented that the weights of 15a to 15e become heavy and the weight of the vehicle becomes high.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

1 to 4, reference numeral 1 denotes a motorcycle, a front wheel 4 is supported on a front portion of a vehicle body frame 2 via a front fork 3, and a handle (not shown) is supported on an upper portion of the front fork 3. It On the other hand, a rear arm 6 is supported on the rear portion of the vehicle body frame 2, and a rear wheel 7 is supported on the rear end of the rear arm 6.

To explain the body frame 2 in more detail,
This body frame 2 is of a double cradle type.

That is, a steering shaft tube 9 is provided in the front portion of the vehicle body frame 2, and the steering shaft tube 9 supports the steering shaft 3a provided on the front fork 3 through bearings 8 and 8. There is. Frames 11 and 11 are extended rearward and downward from both left and right side portions of the upper portion of the steering shaft tube 9, and further rear arm brackets 15 for supporting the rear arms 6 are provided from the rear portions of the main frames 11. It extends toward the lower front.

Also, a pair of left and right sub-frames 12 and 12 are extended rearward from both left and right sides of the lower portion of the steering shaft tube 9 and the rear end of the sub-frame 12 is connected to the lower end of each rear arm bracket 15. . Further, in this case, each sub-frame 12 is located below the main frame 11. An engine (not shown) is supported in the frame of the frame formed by the left and right main frames 11 and the sub-frame 12.

A rear frame 13 is screwed by a bolt 14 so as to project rearward from the rear portion of the main frame 11, and a seat (not shown) is supported on the rear frame 13.

The vehicle body frame 2 is formed by casting a light alloy aluminum (including aluminum alloy). In this case, the vehicle body frame 2 is a left and right half-divided type, and specifically has the following configuration. There is.

The steering shaft tube 9 is divided into left and right, that is, the steering shaft 3a is sandwiched from the left and right sides.
It is composed of a pair of left and right supporting members, which are semi-cylindrical bodies 17, 17, which support 3a. The main frame 11 extends from the upper part of the semi-cylindrical body 17 toward the lower rear.

Each of the main frames 11 has a shape in which the vertical width dimension thereof gradually narrows as it goes downward.

Further, an upper rib 11a is formed on the upper edge of the outer surface of each main frame 11, a lower rib 11b is formed on the lower edge, and an intermediate rib 11 connecting these upper and lower ribs 11a, 11b to each other.
c, 11d, 11e are formed.

On the other hand, a front rib 15a is formed on the front edge of the outer surface of each of the rear arm brackets 15, a rear rib 15b is formed on the rear edge, and further, an intermediate rib 15c connecting these front and rear ribs 15a, 15b, 15d and 15e are formed.

Further, in the above case, the ribs 15a to 15e of the rear arm bracket 15 are formed around the supporting portion of the rear arm 6, and these ribs 15a to 15e are more than those of the ribs 11a to 11e formed on the main frame 11. The arrangement is dense.

Then, the semi-cylindrical body 17 and the main frame 11, and the rear arm bracket 1 extending from the main frame 11.
5. Further, the left and right assemblies of the sub-frame 12 are each flat in shape, and they are integrally formed by casting.

The body frame 2 is formed by joining the left and right assemblies to each other as follows.

That is, the two semi-cylindrical bodies 17, 17 are screwed by four bolts 18. Also, in order to firmly connect the upper and lower ends of both semi-cylindrical bodies 17, 17 respectively, these semi-cylindrical bodies 17, 17
Connection rings 19, 19 are press-fitted onto the outer peripheral surfaces of the upper and lower ends, respectively. On the other hand, each main frame 11 and each sub-frame
Connection holes 20, 20 are formed at the respective rear ends of 12, and both ends of the connection pipes 21, 21 are fitted and welded into these left and right connection holes 20, 20. Then, as described above, by connecting the left and right main and sub frames 11 and 12 to each other,
The body frame 2 is molded.

Next, referring to FIG. 5, showing a state of the assembly during casting, 22 is a mold, and this mold 22 has a lower mold 23 and an upper mold 24. The assembly is cast between 24 and. More specifically, both inner circumferential sides of the semi-cylindrical body 17,
The inner side of each of the main frame 11 and the sub-frame 12 in the vehicle width direction is formed by the upper surface of the lower mold 23, and the main frame 11 and the sub-frame 12 including the outer peripheral side of the same semi-cylindrical body 17 and the ribs 11a and 11b. Each vehicle width direction outer surface side is formed by the lower surface of the upper mold 24. 25 is a runway. In this case, since the assembly has a flat shape as described above, a small mold 22 is sufficient for this casting.

Although the above is based on the illustrated example, the rear frame 13 may be integrally cast with the main frame 11 and the sub frame 12. Further, the two semi-cylindrical bodies 17, 17 may be joined together by welding.

(Effects of the Invention) According to the present invention, a plurality of ribs are formed on each of the left and right main frames, and on the other hand, the rear arm brackets are attached to the rear arm brackets around the rear arm support parts of the rear arm brackets attached to the rear ends of the main frames. When a plurality of ribs are formed, the left and right main frames and the rear arm brackets attached to the respective main frames form a pair of left and right assemblies, and each of these assemblies is a cast product. Are formed on each side of the main frame and the rear arm bracket.

Therefore, when casting a vehicle body frame, a left-side assembly composed of the left main frame and a rear arm bracket attached to it, and a right assembly composed of the right main frame and a rear arm bracket attached to this The assembly and the assembly may be cast separately.

That is, in this way, in the case of integrally casting these left and right side assemblies, the core of the mold to be set between these two assemblies to be cast becomes unnecessary, and thus, Therefore, the body frame can be easily cast.

Particularly, since the ribs are formed on the left and right main frames and on the side surfaces of the rear arm brackets attached to the main frames, the lower part of the rear arm bracket,
A clearance (so-called minimum ground clearance) between the vehicle and the traveling ground is prevented from being narrowed by the ribs, and good steering performance is maintained.

Then, in this case, if the die during the casting for the rib is performed sideways, and as described above, the left side assembly and the right side assembly are individually cast, the rib die cutting is performed. In addition to being easy to perform, the die cutting when casting one assembly can be performed without being disturbed by the other assembly, and therefore, the body frame can be easily cast.

Further, in the case where the left and right main frames are made to have a narrower widthwise dimension as they go rearward and downward, and a plurality of ribs are formed on each of the main frames and on each side surface of the rear arm bracket attached to each of the main frames, The ribs formed on the rear arm bracket are arranged more densely than the ribs formed on the main frame.

Therefore, a large external force is applied around the rear arm support portion of the rear arm bracket from the rear wheel side via the rear arm, but as described above, the ribs formed on the rear arm bracket are arranged more densely. It is possible to more sufficiently cope with a large external force applied to the rear arm bracket, and the strength of supporting the rear arm with respect to the rear arm bracket is improved.

Moreover, in the above case, considering the shape of the main frame,
As a result of increasing the body weight of the vehicle, since the ribs formed on the rear arm bracket are arranged more closely than the ribs formed on the main frame as described above, the ribs on the rear arm bracket are arranged more densely. It is prevented that the vehicle becomes heavy and the center of gravity of the vehicle becomes high, that is, the center of gravity of the vehicle body is lowered.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 1 is a simplified side view of a motorcycle, FIG. 2 is an exploded perspective view of a vehicle body frame, and FIG. 3 is a sectional view taken along the line III-III in FIG. FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1 of the same as above, and FIG. 5 is a side sectional view when casting the left part of the divided body frame. 1 ... Motorcycle, 2 ... Body frame, 3 ... Front fork, 6 ... Rear arm, 9 ... Steering shaft tube, 11 ...
… Main frame, 11a …… Upper rib, 11b …… Lower rib, 11c, 11
d, 11e …… Intermediate rib, 15 …… Rear arm bracket, 15a
…… Front rib, 15b …… Rear rib, 15c, 15d, 15e …… Intermediate rib.

Claims (1)

[Claims] 1. A pair of left and right main frames extending rearward and downward from the steering shaft tube so as to be separated from each other, and a rear arm bracket for supporting a rear arm is attached to a rear end of each of the main frames. The vertical width of the frame is made narrower as it goes downward, and a plurality of ribs are formed on each main frame as above, while a plurality of ribs are formed on each rear arm bracket around the rear arm support portion of each rear arm bracket. In the vehicle body frame of the motorcycle, the left and right main frames,
A pair of left and right assemblies is configured with the rear arm brackets attached to each of the main frames, and each of the assemblies is a cast product, and the ribs are formed on each side surface of the main frame and the rear arm bracket. A motorcycle body frame in which the ribs formed on the main frame are more closely arranged.