JPH0332511B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a frame structure for a straddle type vehicle including a motorcycle, a tricycle, and the like.

Background Art For example, the frame that forms the skeleton of a motorcycle is not only sturdy but also has a certain degree of flexibility.
Moreover, requirements such as being lightweight and thin are desired. A conventional frame structure is shown in FIGS. 1a and 1b. The frame structure shown in FIGS. 1a and 1b is disclosed in, for example, Japanese Patent Laid-Open No. 54-51143. As shown in the figure, in the conventional frame structure, a main frame connects a head pipe 1 that rotatably supports a front fork (not shown) and a pivot bearing 2 that swingably supports a rear fork (not shown). 3 is composed of four steel pipes in total, two on each side of the vehicle body extending in the longitudinal direction of the vehicle body, and a large number of stays 3a installed and welded between these steel pipes. There is.

In order to increase the rigidity of the entire frame structure in the conventional frame structure described above, for example, it is conceivable to increase the cross-sectional dimensions of the upper two steel pipes among the four steel pipes that constitute the main frame 3. However, simply increasing the cross-sectional dimension not only results in an increase in the size and weight of the frame structure, but also requires that both steel pipes be installed externally due to the need to accommodate other auxiliary equipment between the two steel pipes. Extend towards the
There is a disadvantage that the area where the driver's knees touch, the so-called knee grip area, widens, making it impossible to obtain a good riding feeling.

On the other hand, in the case of the double cradle type frame structure shown in Figures 1a and b, the main frame, which is the main part of the casing, is formed from a total of four steel pipes, one pair on each left and right as shown in the figure, and the assembly method is as follows: The manufacturing and assembly costs are extremely high, as the main work involves sliding the pipes together one by one at the joint, and then welding them together with the installation of reinforcing gusset plates, etc. We are destined to do so.

Summary of the Invention [Object of the Invention] The present invention has been made in view of the circumstances of the conventional frame structure, and its purpose is to provide the desired rigidity, slim and light weight, and improve the driver's comfort. To provide a frame structure for a straddle type vehicle that has a large degree of freedom in riding posture, has good workability during vehicle assembly, and ultimately greatly reduces manufacturing man-hours, which is close to the ideal. It is in.

[Structure of the Invention] The frame structure for a straddle type vehicle according to the present invention includes a head pipe that is arranged on both sides of the vehicle body and rotatably supports the front fork, and a pivot bearing that rotatably supports the rear fork. a pair of main frames that are linearly connected in side view and have a generally rectangular cross-sectional shape over the entire length;
a rear frame joined to the rear upper surface of the main frame, the main frame is bent inward of the vehicle body at a predetermined position in the longitudinal direction of the vehicle body, and is bent toward the rear of the vehicle body behind the bent portion to form a knee grip portion. The main frame has a dimension in a direction parallel to the pipe center axis of the head pipe that is substantially equal to the length of the head pipe throughout its entire length, and a bending position of the main frame in the longitudinal direction of the vehicle body at the knee grip portion. It is characterized by forming a bent line substantially along the vertical direction of the vehicle body by making the curves vary in the height direction of the vehicle body.

[Operation of the Invention] In the frame structure having such a configuration, the number of constituent members of the main frame is reduced to the utmost limit and made into a single member, and the main frame is made slim and lightweight, has great mechanical strength, and is easy to assemble the vehicle. Good workability and good riding feeling can be obtained.

Embodiments Hereinafter, frame structures of straddle-type vehicles, particularly motorcycles including tricycles, which are embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 2, 4a indicates a main frame, and 5 indicates a rear frame. A pair of main frames 4a are disposed on both sides of the vehicle body, and each main frame 4a is formed so that its overall cross-sectional shape is approximately rectangular over its entire length, and its shape when viewed from the side in the direction of arrow A is approximately linear. In other words, the line connecting the head pipe 6 into which the front fork (not shown) is fitted and the pivot bearing 7 which swingably supports the rear fork 8 is substantially straight.

What this means is that while the usual method of dealing with external forces acting on the car body from all angles has been to adopt a case frame structure made of multiple steel pipes, etc. as shown in Figure 1, The idea is to eliminate as much as possible the members on each side of the skeleton that share external forces and make it into a single member. The most efficient direction for consolidating each member into a single member is to form members on a line connecting the head pipe 6 and the pivot bearing 7, which are diagonal in this case. Therefore, in the case of the embodiment, the main frame 4a has a structural design that can withstand external forces acting from all angles.

The structure of the main frame 4a is made of thin steel plates, aluminum, etc., as well as synthetic resin materials such as FRP and CFRP, and as shown in Fig. 3, the main frame 4a is made of plate 4a ₁ and plate 4a ₂ , which are press-formed as outer plates. The tube has a substantially rectangular cross-sectional shape over its entire length, and its upper surface is flat. The space inside this tube is formed as a structure filled with honeycomb cores 9 which are separated into a large number of mutually independent chambers. Specifically, by filling the honeycomb core 9 as shown in the figure and using it as a reinforcing member, it is possible to cope with the external force acting particularly from the direction of the arrow A, and the entire frame is lightened and has the necessary cross-sectional performance. will have the following. That is, the isolated holes 9a of the honeycomb core 9 consisting of independent chambers are connected to the plate 4.
By filling substantially perpendicularly to the inner walls of each of a ₁ and 4a ₂ , we aim to achieve the effect of exhibiting the unique load-bearing strength of a honeycomb member.

In this case, it is assumed that the plate 4a ₁ and the plate 4a ₂ are caulked together using a pot rivet 10. Further, the head pipe 6 described above is detachably attached to the main frame 4a, and is designed to make the setting of the caster angle of the front wheels variable.

As shown in FIG. 2, the main frame 4a is
The dimension of the head pipe 6 in the direction parallel to the pipe center axis is approximately equal to the length K of the head pipe 6 over approximately its entire length. Because of this configuration, combined with the above-mentioned rectangular cross-sectional configuration of the main frame, the moment of inertia of the main frame 4a in the vertical direction of the vehicle body is extremely large over the entire length, which reduces the rigidity of the frame structure as a whole, especially in the vertical direction of the vehicle body. The stiffness has further increased.

As shown in Figure 2, both the left and right main frames 4
In a, the part where the driver's knees touch is first bent inward of the vehicle body, and a second bent portion 4d is bent toward the rear of the vehicle body behind the first bent portion 4c. A knee grip portion is formed by the knee grip portion. As is clear from the figure, the bending position of the main frame 4a at the knee grip portion in the longitudinal direction of the vehicle body differs over the height direction of the vehicle body. For more information,
The bending position seems to move linearly toward the lower part of the vehicle body and gradually toward the rear of the vehicle body. With this configuration, the knee grip portion of the main frame 4a has two grips that cross the main frame 4a diagonally with respect to its longitudinal direction. Parallel linear bending lines of the book are formed. In this way, the bending line is the main frame 4a.
By diagonally crossing the curve, the length of the bending line increases, and the rigidity of the main frame at the knee grip portion, particularly in the vertical direction of the vehicle body, becomes extremely large.

Next, a rear frame 5 shaped like a tail wing is attached to the rear upper surfaces of the left and right main frames 4a so as to straddle the two main frames.
The rear frame 5 serves as a skeleton for assembling seats, etc., and is made of a honeycomb structure as shown in Fig. 4.
It is framed by a pair of substantially symmetrical press-molded panels 5a, 5a including a core 9. The panels 5a, 5a have a V-shape in which the bottoms of the panels widen toward each other, and each lower leg seat surface is bent outward as shown in the figure, and is flat and has a sufficient length L. 5b. However,
These flange seats 5b, 5b are placed on the rear upper surface of the main frame 4a having a flat surface 4b.
1, the main frame 4a and rear frame 5 are assembled by caulking. In addition, 12 in the figure is a cross member that tightens the main frame 4a and the rear frame 5 together and serves as a reinforcing material for the entire structure.

As described above, each of the pair of left and right main frames 4a connecting the pivot bearing 7 that supports the rear fork 8 and the head pipe 6 is arranged so that it extends linearly when viewed from the side and has a cross-sectional shape as a whole. It is formed into a single member by molding it into a substantially rectangular shape over its entire length and reducing the number of constituent members to the utmost.
Because of this structure, it is possible to obtain rigidity that can cope with external forces acting from all directions, such as torsion and bending, as well as various moments due to tension and compression, with a slim and lightweight structure. Compared to a frame structure made by combining steel pipes, it is possible to expect significant improvements in both design and manufacturing man-hours, resulting in a reduction in costs.

Further, both the main frames are bent inward of the vehicle body at predetermined positions in the longitudinal direction of the vehicle body, and bent toward the rear of the vehicle body at the rear of the bent portions to form a knee grip portion.

That is, since the knee grip portion is formed by making the distance between the substantially rear half portions of the pair of left and right main frames 4a narrower than the distance between the front portions thereof, the narrow rear half portion of the main frame including the knee grip portion is The slim body of the vehicle increases the degree of freedom in the driver's riding position, providing a good riding feeling, and does not increase weight, reducing torsional moment, especially in the front half of the wide main frame. This also ensures rigidity against moments caused by lateral loads.

Also, based on the above configuration, mainframe 4
The dimension of a in the direction parallel to the central axis of the head pipe is made approximately equal to the length of the head pipe over approximately its entire length. Because of this configuration, combined with the above-mentioned rectangular cross-sectional configuration of the main frame, the moment of inertia of the main frame in the vertical direction of the vehicle body is extremely large over the entire length, which reduces the rigidity of the frame structure as a whole, especially the rigidity in the vertical direction of the vehicle body. This further increases the need for reinforcing members such as those found in conventional frame structures made of steel pipes, resulting in a significant weight reduction and reduced manufacturing man-hours.

Further, by varying the bending position of the main frame in the longitudinal direction of the vehicle body in the height direction of the vehicle body, a bent line is formed substantially along the vertical direction of the vehicle body. Therefore, the bending line is the main frame 4a.
Since the main frame extends diagonally with respect to the longitudinal direction, the length of the bent line increases, and the rigidity of the main frame at the knee grip portion, particularly in the vertical direction of the vehicle body, becomes extremely large. In addition, in this configuration, the front portions of the left and right main frames 4a at the bent position are expanded toward each other downward, making it easy to store the engine and the like thereunder. Workability when assembling is good.

Effects of the Invention As detailed above, in the frame structure for a straddle type vehicle according to the present invention, the head pipe and the rear fork, which are arranged on both sides of the vehicle body and rotatably support the front fork, are swingably supported. The main frame includes a pair of main frames linearly connected to the pivot bearing in a side view and having a generally rectangular cross-sectional shape over the entire length, and a rear frame joined at the rear upper surface of the main frames. A frame structure for a straddle type vehicle in which the frame is bent inward at a predetermined position in the longitudinal direction of the vehicle body, and bent toward the rear of the vehicle body at the rear of the bent portion to form a knee grip portion. The main frame has a dimension in a direction parallel to the central axis of the head pipe that is substantially equal to the length of the head pipe over its entire length, and the bending position of the main frame in the front-rear direction of the vehicle body at the knee grip portion is approximately equal to the length of the main frame in the direction parallel to the center axis of the head pipe. By making the curves different from each other, a curved line is formed substantially along the vertical direction of the vehicle body.

That is, in the frame structure for a straddle-type vehicle according to the present invention, each of the pair of left and right main frames connecting the pivot bearing that supports the rear fork and the head pipe is arranged such that it extends linearly in side view. The cross-sectional shape as a whole is formed into a substantially rectangular shape over the entire length, and the number of constituent members is reduced to the utmost, thereby forming a single member. Because of this structure, it is possible to obtain rigidity that can cope with external forces acting from all directions, such as torsion and bending, as well as various moments due to tension and compression, with a slim and lightweight structure. Compared to a frame structure made by combining steel pipes, it is possible to expect significant improvements in both design and manufacturing man-hours, and thus a reduction in costs has been achieved.

Further, both the main frames are bent inward of the vehicle body at predetermined positions in the longitudinal direction of the vehicle body, and bent toward the rear of the vehicle body at the rear of the bent portions to form a knee grip portion.

In other words, since the knee grip portion is formed by making the distance between the rear half portions of the pair of left and right main frames narrower than the distance between the front portions thereof, the narrow rear half portion of the main frame including the knee grip portion is narrower than the front portion of the main frame. As a result, the degree of freedom of the driver's riding posture is increased, and a good riding feeling is obtained, without causing an increase in weight, and especially for the front half of the wide main frame, torsional moment and lateral This ensures rigidity against moments caused by loads.

Further, in the frame structure for a straddle type vehicle according to the present invention, based on the above configuration, the dimension of the main frame in a direction parallel to the central axis of the head pipe is approximately equal to the length of the head pipe over approximately the entire length thereof. are doing. Because of this configuration, combined with the above-mentioned configuration of the main frame having a substantially rectangular cross section, the cross-sectional moment of inertia of the main frame in the vertical direction of the vehicle body becomes extremely large over the entire length.
The overall rigidity of the frame structure, especially the rigidity in the vertical direction of the vehicle body, has been further increased, and there are almost no reinforcing members like in the conventional frame structure that combines steel pipes, and a significant weight reduction has been achieved. This requires less man-hours.

Furthermore, in the frame structure according to the present invention,
By making the bending position of the main frame in the knee grip portion different in the longitudinal direction of the vehicle body, a bending line is formed substantially along the vertical direction of the vehicle body. Therefore, since the bending line extends diagonally with respect to the longitudinal direction of the main frame, the length of the bending line increases, and the rigidity of the main frame at the knee grip portion, especially in the vertical direction of the vehicle body, becomes extremely large. There is.
In addition, in this configuration, the front portions of the left and right main frames at the bent position expand downward toward each other, making it easy to store the engine, etc. below the main frames. Workability during assembly is now good.

[Brief explanation of drawings]

1A and 1B are plan and side views of a conventional frame structure, FIG. 2 is a perspective view showing an embodiment of the present invention, and FIG. 3 is a partial perspective sectional view showing the panel structure of the main frame. , and FIG. 4 is a partial perspective view showing how the rear upper surface of the main frame is assembled with the rear frame. Explanation of symbols of main parts, 4a... Main frame, 4a ₁ , 4a ₂ ... Outer plate, 4b... Flat surface, 4
c, 4d...Bending portion, 5...Rear frame, 6...
... Head pipe, 7 ... Pivot bearing, 9 ... Honeycomb core, 10, 11 ... Potprivet,
12...Cross member.

Claims (1)

[Claims] 1. A head pipe arranged on both sides of the vehicle body that rotatably supports the front fork and a pivot bearing that swingably supports the rear fork are linearly connected in side view, and the overall cross-sectional shape extends over the entire length. It includes a pair of substantially rectangular main frames and a rear frame joined at the rear upper surface of the main frames, the main frames are bent inward of the vehicle body at a predetermined position in the longitudinal direction of the vehicle body, and the rear frame is bent toward the inside of the vehicle body at a predetermined position in the longitudinal direction of the vehicle body. A frame structure for a straddle type vehicle, which is bent toward the rear of the vehicle body to form a knee grip part, wherein the main frame has a dimension in a direction parallel to the central axis of the head pipe that extends over substantially the entire length of the main frame. The length of the main frame is approximately equal to the length of the head pipe, and the bending position of the main frame in the longitudinal direction of the vehicle body at the knee grip portion is made different across the height direction of the vehicle body, thereby forming a bending line substantially along the vertical direction of the vehicle body. A frame structure characterized by: