JPH0529596B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scooter type motorcycle in which a unit swing type power unit is pivotally connected to an underbone type frame.

[Conventional technology]

Generally, an underbone type frame is often used in small motorcycles called scooter type. This frame includes a single down tube extending downward from the head pipe, and a pair of left and right backstays that support the footrest board are connected to the lower end of the down tube. The backstays extend rearward approximately horizontally and are spaced apart from each other in the left and right direction, and the rear portions of these backstays are
It is raised behind the footrest board.
An engine bracket is provided at the rising portion of the backstay, and the front end of a unit swing type power unit is pivotally connected to the engine bracket.

By the way, in this power unit, a transmission case that extends rearward is integrally provided on one side of the engine crankcase, and the rear wheel is supported at the rear end of the transmission case, and the rear wheel is mounted inside the transmission case. It is configured to house a transmission that drives the vehicle, and the engine is designed to swing together with the rear wheels and transmission. For this reason, the power unit as a whole becomes heavy and large, and when the power unit is swung, a large load is applied to the rising portion of the backstay through the engine bracket.

[Problem to be solved by the invention]

However, in the case of the above-mentioned underbone type frame, the backstay is the main frame of the frame and is not supported by other pipes, so the load due to the swinging of the power unit is applied to the rising part of the backstay. When a shock is applied in a concentrated manner, the rigidity of this rising portion may be insufficient. In particular, when the engine cylinder is tilted forward to a nearly horizontal angle and this cylinder is interposed between the lower part of the rising part,
Since the space between these rising parts becomes a space for allowing the cylinder to swing in the vertical direction, it is no longer possible to connect the rising parts with a special cross member, which reduces the rigidity of the pivot joint of the power unit. It becomes extremely difficult to raise it.

Furthermore, if the backstay is made to be able to sufficiently withstand the load from the power unit, the backstay and the bracket will become larger, and the frame itself will become heavier and larger.

Therefore, in the present invention, when the space between the rising parts of the left and right backstays is used as a space for allowing the swinging of the cylinder, the power unit including the cylinder can be used to improve the torsional rigidity and lateral rigidity of the frame. It is possible to support heavy and large power units reliably by supporting them at high points.
The purpose of the present invention is to provide a scooter type motorcycle that can prevent an increase in the weight of the frame.

[Means for Solving the Problems] Therefore, in the present invention, a down tube extending downward is connected to the head pipe, and a down tube extending rearward substantially horizontally and spaced apart from each other in the left and right direction is attached to the lower end of the down tube. A pair of backstays arranged in the same way are connected, and a footrest board for resting the driver's feet is installed on these backstays, and the rear part of the backstay is raised behind the footrest board, and the rising part of these backstays is connected. An engine bracket is provided in the middle of the engine, and a unit swing type power unit is attached to the engine bracket, which is composed of an engine and a transmission case that extends rearward from one side of the crankcase of the engine and has a rear wheel at its rear end. In a scooter-type motorcycle, the front part of which is pivotably mounted, the engine has a cylinder extending approximately horizontally from the front end of the crankcase toward the front footrest board; A seat is interposed between the lower parts of the rising parts to provide a space between these rising parts to allow vertical swing of the cylinder, and a seat is placed between the upper ends of the rising parts of the backstay. The engine bracket, which is connected to each other by two members, the supporting seat post and the cross member, and is located midway through the rising portion, is positioned closer to the joint with the seat post and the cross member than the lower end of the rising portion. It is characterized by being installed in an uneven position.

[Effect]

According to this configuration, the engine bracket installed at the rising part is biased toward the part of the rising part that is connected by the two members of the seat post and the cross member, so the left and right parts are installed near the engine bracket. This means that the rising portions of are connected. From this, when a large impact is applied to the rising part of the motorcycle through the power unit while the motorcycle is running, this impact is effectively absorbed not only by the rising part but also by the seat post and the cross member. It is possible,
A heavy and large power unit can be supported by a portion of the rising portion that has high torsional and lateral rigidity. For this reason, the space between the left and right rising parts is
This is a space for allowing the cylinder to swing, and although it is impossible to connect the rising portion in this area, it is possible to ensure sufficient rigidity of the part where the engine bracket is installed.

Therefore, the power unit can of course be supported reliably, and there is no need to make the backstay thicker, making it possible to reduce the size and weight of the frame.

〔Example〕

The present invention will be explained below based on an embodiment shown in the drawings.

Reference numeral 1 in the figure is an underbone frame, and a front fork 3 is pivotally supported on a head pipe 2 at the front end of the frame. A downwardly extending down tube 4 is welded to the lower rear surface of the head pipe 2. A lower end portion of the down tube 4 extends horizontally toward the rear, and a pair of back stays 6 are connected to the rear end portion of the extended portion 4a via a gusset 5. The backstay 6 extends substantially horizontally rearward continuously from the rear end portion of the extension portion 4a, and is arranged substantially parallel to the left and right with an interval therebetween. A footrest board 7 is placed on the extension portion 4a of the down tube 4 and the upper surface of the backstay 6, on which the driver's feet rest. The rear portions of the left and right backstays 6 are raised rearward and diagonally upward behind the footrest board 7. A footrest bracket 8 is welded to the lower end of these rising portions 9 and the front end of the backstay 6, respectively. As shown in FIG. 2, the footrest brackets 8 do not fit between the backstays 6 and the rising portions 9, but protrude toward the left and right outer sides of the backstays 6 and the rising portions 9, respectively. The footrest board 7 is fastened and fixed to. The upper end portion of the rising portion 9 extends rearward substantially horizontally to form left and right seat rails 10, and the rear end portions of these seat rails 10 are connected by a reinforcement reinforcement 11. A U-shaped seat post 12 and a cross pipe 13 are installed at the upper end of the rising portion 9 and extend forward and diagonally upward. A seat 15 is supported.

On the other hand, engine brackets 16 are welded to intermediate portions of the rising portions 9, respectively. As shown in FIG.
It is installed at a position that is largely biased toward the connection portion with the seat post 12 and cross pipe 13 above the attachment portion of the footrest bracket 8. Therefore, as shown in FIG.
3 are spaced apart from each other to the left and right without being connected to each other.

A swinging link 17 is pivotally supported on the engine bracket 16, and these swinging links 1
A front end portion of a unit swing type power unit 19 is pivotally connected between the two parts 7 via a pivot shaft 18. This power unit 19 includes a two-stroke engine 20 and a crankcase 21 of this engine 20.
A transmission case 22 integrally extending rearward from the left side of the
It is equipped with A rear end portion of the transmission case 22 is suspended from the left seat rail 10 via a hydraulic shock absorber (not shown), and a rear wheel 24 is cantilevered from the rear end portion of the transmission case 22. This rear wheel 24 is rotationally driven by a belt type transmission (not shown) housed within the transmission case 22.

Further, as shown in FIG. 1, the cylinder 25 of the engine 20 projects approximately horizontally from the front surface of the crankcase 21 toward the forward footrest bracket 8, and the cylinder head covers the front end of the cylinder 25. 26 is inserted between the lower portions of the left and right rising portions 9. Therefore, there is a space 30 between the rising portions 9 to allow the cylinder 25 and the cylinder head 26 to swing in the vertical direction.
It is becoming.

Note that the area from the area around the engine of the power unit 19 to the area around the seat 15 is covered with a cover 27.

According to this configuration, the upper ends of the rising portion 9 of the backstay 6 are connected to each other by two members, the seat post 12 and the cross pipe 13, and the engine bracket 16 welded to the rising portion 9 is connected to the upper end portions of the rising portion 9 of the backstay 6. Since the rising portion 9 is provided at a position that is largely biased toward the portion connected by the two members of the seat post 12 and the cross pipe 13, the left and right rising portions 9 are located close to the engine bracket 16. It will be combined. That is, when a large impact is applied to the rising portion 9 through the power unit 19 while the motorcycle is running, this impact is effectively absorbed not only by the rising portion 9 but also by the seat post 12 and the cross pipe 13. The heavy and large power unit 19 can be supported at a position within the rising portion 9 with high torsional rigidity and lateral rigidity. Therefore, as the cylinder 25 and the cylinder head 26 are tilted forward greatly, the space between the left and right rising portions 9 is occupied as a space 30 for allowing the cylinder 25 and the cylinder head 26 to swing. Although it is impossible to connect the rising portion 9 at a portion, sufficient rigidity of the mounting portion of the engine bracket 16 can be ensured.

Therefore, the power unit 19 can be supported reliably, and there is no need to make the backstay 6 thicker or to provide special reinforcement to the welded portion of the engine bracket 16, and the weight of the frame 1 can be reduced.

〔Effect of the invention〕

When a large impact is applied to the rising part of a motorcycle through the power unit while the motorcycle is running, this impact can be effectively absorbed not only by the rising part but also by the seat post and the cross member. The power unit can be supported at a position with high torsional rigidity and lateral rigidity among the rising parts. Because of this, the space between the left and right rising parts is occupied as a space to allow the cylinder to swing, and even though it is impossible to connect the rising parts in this area, the mounting part of the engine bracket Sufficient rigidity can be ensured, and heavy and large power units can be reliably supported. At the same time, there is no need to make the backstay thicker or provide special reinforcement to the engine bracket attachment part, which has the advantage of making it possible to reduce the weight of the frame.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, in which Figure 1 is a side view of the frame, Figure 2 is a plan view of the frame, and Figure 3 is a side view of the frame.
The figure is a side view of a scooter type motorcycle. 2...Head pipe, 4...Down tube, 6...
Back stay, 7...Footrest board, 9...Rising part, 12...Seat post, 13...Cross member (cross pipe), 16...Engine bracket, 19...Power unit, 20...Engine, 21
...Crank case, 22...Transmission case, 24...Rear wheel, 25...Cylinder, 30...Space.

Claims (1)

[Scope of Claims] 1. A down tube extending downward is connected to the head pipe, and a pair of back stays are provided at the lower end of the down tube extending rearward substantially horizontally and spaced apart from each other in the left and right direction. A footrest board for resting the driver's feet is installed on these backstays, the rear part of the backstay is raised behind the footrest board, and an engine bracket is installed in the middle of the rising part of these backstays. The front part of a unit swing type power unit, which is composed of an engine and a transmission case that extends rearward from one side of the engine's crankcase and has a rear wheel at its rear end, is mounted on this engine bracket so as to be able to swing. In the scooter type motorcycle, the engine has a cylinder extending substantially horizontally from the front end of the crankcase toward the front footrest board, and the front part of the cylinder is interposed between the lower part of the rising part. The space between these rising parts is made into a space for allowing the cylinder to swing in the vertical direction, and the space between the upper ends of the rising parts of the backstay is
The seat post and cross member that support the seat are connected to each other by two members, and the engine bracket, which is located in the middle of this rising part, is connected to the seat post and the cross member closer to the lower end of the rising part. A scooter-type motorcycle characterized by being installed in a position that is biased to the side.