WO2015142296A1

WO2015142296A1 - A rear arm truss structure for scooters

Info

Publication number: WO2015142296A1
Application number: PCT/TH2014/000009
Authority: WO
Inventors: Masayuki Tsutsui; Pakpum PROMMA; Kazuki Yamagishi; Ryosuke Sato
Original assignee: Honda Motor Company Limited
Priority date: 2014-03-18
Filing date: 2014-03-18
Publication date: 2015-09-24

Abstract

Problem to be solved: to provide a rear arm structure for a scooter that can be produced using cheaper materials without compromise in strength while enabling the distance between upper and lower portions of the rear arm to be increased without sacrificing strength and increasing weight to thereby enable elevated coupling to a muffler without occlusion of the rear arm from side view, thus allowing the aesthetic elements of the rear arm to be prominently displayed. Solution: In a scooter having a scooter frame and an engine unit being swingably coupled thereto, where the engine unit has an engine case and a belt converter extending therefrom for supporting a rear wheel on one side of the scooter, a rear arm truss structure is positioned on the other side of the scooter and connects between a rear portion of an engine case and an axle of the rear wheel with the scooter further having a muffler extending rearwardly and upwardly. The rear arm truss structure comprises a tubular upper arm having a front end coupled to an rear-upper mounting portion of said engine case and a rear end coupled to a rear-upper portion of said muffler, and a lower arm is located below said upper arm and having a front end coupled to a rear-lower mounting portion of said engine case and a rear end coupled to a rear wheel axis supporting portion for supporting said axle of the rear wheel. The tubular truss frame structure connects between said upper arm and said lower arm.

Description

A REAR ARM TRUSS STRUCTURE FOR SCOOTERS

TECHNICAL FIELD

This invention relates generally to a rear arm structure of scooters with a unit swing-type motorcycle engine.

BACKGROUND ART

Japanese Patent P2003-170879 describes a motorcycle (1) with a unit swing-type engine. The unit swing-type engine described has an engine case and a rear arm (2a, 2b) coupled to and extending therefrom. The rear arm (2a, 2b) supports a muffler (9) and a wheel pivot (3a) and is positioned opposite a belt converter (5).

DISCLOSURE / DESCRIPTION

Technical Problem

Due to the distance between the engine case and the wheel pivot, it is usual to cast the rear arm from high strength material. The high strength material used is typically aluminum. The use of casting material heightens production cost. Further, prior art describes a triangular rear arm connected at one corner to the axle of the rear wheel and at the other two corners to the engine case. This results in the rear arm being substantially overlapped by the muffler in side view which in turn eclipses the aesthetic features of the rear arm member such as its shapes, angles and/or curves, even though the rear arm is made from aluminum.

It is desired to provide a motorcycle rear arm which can be produced using cheaper materials without compromise in strength. It is further desired that the motorcycle rear arm be defined and positioned to enable its aesthetic features to be visibly displayed.

Technical Solution

This invention according to claim 1 is a rear arm truss structure including an upper rear arm, a lower rear arm and a truss frame. The upper rear arm has a front end coupled to an upper mounting portion an engine case and a rear end coupled to a rear mounting portion of a muffler. The lower rear arm having a front end coupled to a lower mounting portion of the engine case and a rear end coupled to a stub axle of a rear wheel of the motorcycle, characterized in that the motorcycle rear arm structure further comprises a truss frame comprising pipe structures extending between and interconnecting the upper rear arm and the lower rear arm.

This invention according to claim 2 has, in the rear arm truss structure of claim 1 , a characteristic in that the lower rear arm has an upward curving portion.

This invention according to claim 3 wherein, in the rear arm truss structure of claim 1 , a front mounting portion of the muffler and the front end of the lower rear arm are affixed to the same point at the lower mounting portion of the engine case.

This invention according to claim 4 wherein, in the rear arm truss structure of claim 1, one of the pipe structures of the truss frame extends from the upper rear arm to the rear end of the lower rear arm whereto the stub axle of the rear wheel is coupled.

This invention according to claim 5 wherein, in the rear arm truss structure of claim 4, the pipe structures of the truss frames forming triangular shape structures with the upper rear arm and a rear portion of the lower rear arm, the rear portion of the lower rear arm extending from the rear end to a curving portion of the lower rear arm, the curving portion being shaped to obliquely dispose the pipe structures from the upper rear arm for creating a structural bulge defining a bulge gap bounded by the triangular shaped structures and a frontal portion of the lower rear arm, the frontal portion extending between the curving portion and the front end of the lower rear arm, and a lubricant filling nozzle being positionable at the bulge gap.

This invention according to claim 6 has, in the rear arm truss structure of claim 5, a characteristic in that the curving portion of the lower rear arm is formed behind the muffler adjacent where a front mounting portion of the muffler is coupled with the lower rear arm. This invention according to claim 7 has, in the rear arm truss structure of claim 1 , a characteristic in that the rear end of the upper rear arm is substantially the same height from the stub axle of the rear wheel as a mounting portion of a belt converter whereto a lower end of a rear suspension actuator is coupled.

This invention according to claim 8 wherein, in the rear arm truss structure of claim 1 , a characteristic in that the pipe structures comprises a front pipe structure and a rear pipe structure extending rearward diagonally from the upper rear arm to the lower rear arm, and a middle pipe structure extending rearward diagonally from the lower rear arm to the upper rear arm, the angle of the front pipe structure to the upper rear arm being the same as the angle of the rear pipe structure to the upper rear arm.

This invention according to claim 9 has, in the rear arm truss structure of claim 1, a characteristic in that the upper rear arm projects rearwardly from the engine case while the lower rear arm projects rearwardly from the engine case in an upwards skewing direction.

Advantageous Effects

According to the invention disclosed in Claim 1, the casting of a rear arm truss structure for a scooter from a truss frame formed from pipe structures lowers production cost when compared with use of conventional aluminum rear arms. The use of the rear arm truss structure to inter-couple an upper arm and rear upper portion of a muffler enables the upper arm to be elevated to impede occlusion of the truss frame from side view and allows the truss frame's aesthetic elements to be prominently displayed. The use of the truss frame structure enables the distance between the upper arm and the lower arm to be increased without sacrificing strength and increasing weight. Production material cost is also kept low with the use of the truss frame.

According to the invention disclosed in Claim 3, the upward curving portion of the lower arm enables the distance between the upper arm and the lower arm to be reduced after the curving portion toward the rear wheel. This enables stiffness of the scooter rear arm truss structure to be increased. The upward curving portion also enables the lower arm to be accommodated easier while avoiding the tubular muffler, thereby simplifying coupling of the axle of the rear wheel at the rear end of the lower arm to the lower mounting portion of the engine case.

According to the invention disclosed in Claim 4, affixing a front mounting portion of the muffler and the front end of the lower arm to the same point reduces the number of bolts required. Further, shortening the mounting pitch of exhaust pipe and muffler improves overall mounting stiffness of the muffler.

According to the invention disclosed in Claim 5, as the rear wheel axis supporting portion is of comparatively high stiffness, and the rear wheel axis connecting portion and the lower arm are connected to said rear wheel axis supporting portion, the stiffness of the rear wheel axis connecting portion and the lower arm including the curving portion is kept high. As such result, it's possible to keep high stiffness of whole rear arm structure. According to the invention disclosed in Claim 6 , making the triangle shape direct to downward enables a wider lower portion for the like triangle shape space. The design of lubricant filling nozzle is then easier.

According to the invention disclosed in Claim 7 , as the upper and lower connecting portion is not located on the curving portion of the lower arm, it's so easy to connect the upper and lower connecting portion with the lower arm and to form the truss structure. And even though such curving portion is formed at the front of a connecting position where the upper and lower connecting portion is connected to the lower arm, such curving portion is almost hidden by the muffler and it enables the curving portion to be visually presented as being detached from the rest of the rear arm truss structure for scooter without impacting the visual appearance.

According to the invention disclosed in Claim 8, positioning the rear end of the upper arm at substantially the same height from the axle of the rear wheel as a mounting portion of a belt converter whereto a lower end of a rear suspension is coupled enables the upper arm to be higher and more visual to outward. It makes the rear arm design emphasis more effective. According to the invention disclosed in Claim 9, three pipes structure makes such truss structure most simple and optimum. Especially so, making both axis angles of the front pipe and the rear pipe almost parallel enables same triangle shape to be defined by three pipes and it's possible for the stiffness valance of truss rear arm to be made optimum.

According to the invention disclosed in Claim 2, the skewing of the general longitudinal axis of the lower arm from the longitudinal axis of the upper arm enables force received from below by the rear wheel to be better endured more effectively.

Brief Description of the Drawings

FIG. 1 is a partial right view of a motorcycle having a unit swing engine comprising a rear arm truss structure for a scooter according with an embodiment of the present disclosure.

FIG. 2 is a partial left view of the motorcycle of FIG. 1 with a belt convertor positioned on an opposite side of a rear wheel from the rear arm truss structure for the scooter in accordance with an embodiment of the present disclosure. FIG. 3 is a partial top view of the motorcycle of FIG. 1 with a partial top view of the rear arm truss structure in accordance with an embodiment of the present disclosure.

FIG. 4 is a rear view of the motorcycle of FIG. 1 with a partial rear view of the rear arm truss structure in accordance with an embodiment of the present disclosure.

FIG. 5 is a top view of the rear arm truss structure of FIG. 1 in accordance with an embodiment of the present disclosure with the right side of the figure being the front of the scooter. FIG. 6 is a bottom view of the rear arm truss structure of FIG. 1 in accordance with an embodiment of the present disclosure with the right side of figure being the front of scooter. FIG. 7 is a right side view of the rear arm truss structure of FIG. 1 in accordance with an embodiment of the present disclosure.

FIG. 8 is a front view of the rear arm truss structure of FIG. 1 in accordance with an embodiment of the present disclosure with the right side of the figure being the inside of scooter and the left side of the figure being the outside of scooter.

FIG. 9 is a rear view of the rear arm truss structure of FIG. 1 in accordance with an embodiment of the present disclosure with the right side of the figure being the outside of scooter and the left side of the figure being the inside of scooter.

Detailed Description of Example Embodiments

FIG. 1 is a partial right view of a scooter 18 with a rear arm truss structure 20 in accordance with an embodiment of the present disclosure. With reference to FIG. 1, the scooter comprises a unit swing-type motorcycle engine 22 ("unit swing engine 22"). With reference to each of FIGs. 1-4, in several embodiments, the motorcycle 20 is, or exhibits structural elements or features corresponding to, an underbone main frame type scooter, in a manner understood by one having ordinary skill in the relevant art. Thus, the scooter 18 includes an underlying structural a pair of frame 24 that is formed from a set of frame elements, tubes, or pipes under a seat. The unit swing engine 22 is then swingably attached to the cross frame member of said frame 24 with a pivot shaft 26. The pivot shaft 26 has a linkage member 27a connecting the cross frame member at a swing pivot 27b. More specifically, the unit swing engine 22 is constructed to hold a rear wheel 28 provided at a rear portion of the unit swing engine 22 such that the rear wheel 28 can swing about the swing pivot 27b.

Further referring to Fig.2, the unit swing engine 22 has an engine 30 with an engine case 32 that is integrated with a belt converter 36 on the left side of the rear wheel 28. A crankshaft is rotatably disposed in the engine case 32 for coupling with a piston placed in a cylinder of the engine 30 such that reciprocating motion of the piston within the cylinder translates into rotational cranking of the crankshaft which in turn drives the belt convertor 36 and the axle 54 of the rear wheel 28. An air cleaner 37a is connected to the engine 30 through an intake structure and mounted above the convertor 36.

The belt convertor 36 is a power transmission device for transmitting the driving force from the engine 30 to the rear wheel 28 in a unit, in a manner that permits swingable suspension of the unit together with the rear wheel 28 about the swing pivot 27b. To support the rear wheel 28 and to keep the rear wheel 28 aligned with the belt convertor 36 on the left side, the unit swing engine 22 further comprises the rear arm truss structure 20 extending from the engine case 32 for coupling supporting and coupling the rear wheel 28 to the engine case 32 on the right side of the rear wheel 28. The rear suspension 80 mounting on left side of the rear wheel 28 and connecting between the belt convertor 36 and the frame 24, absorbs the swing motion of the rear wheel 28 and the unit swing engine 22 generated by bumps and vibrations to provide improved ride and motorcycle handling characteristics.

The unit swing engine 22 further comprises a radiator 37b mounting the right end of the crankshaft and positioning the front of the rear arm truss structure 20. The radiator 37b is preferably positioned in the direction of airflow to allow coolant circulated from the engine 30 to be cooled by the passage of air fhereacross. Dissipation of heat from the coolant by the radiator 37b is further facilitated by a fan integrated with the engine 22.

With further reference to FIGs. 5-9, the rear arm truss structure 20 comprises an upper arm 40, a lower arm 42 and a truss frame 44. The truss frame 44 comprises pipe structures extending between and interconnecting the upper arm 40 and the lower arm 42. It is preferred that the upper arm 40 and the lower arm 42 be also formed from pipe structures. The upper arm 40 has a front end 46a for coupling to an upper mounting portion 48a of the engine case 32 while the lower arm 42 has a front end 50a for coupling to a lower mounting portion 48b of the engine case 32. The lower arm 42 further has a rear end 50b that terminates at a rear wheel support structure defining a rear wheel pivot 52 (a rear wheel axis supporting portion) whereto the axle 54 of the rear wheel 28 is coupled to enable rotational displacement of the rear wheel 28 thereabout. The rear wheel pivot 52 has comparatively the stiffness so as to support the rear wheel 28. So, the lower arm 42 enables keeping of the stiffness also by connecting the combination to the rear wheel pivot 52.

The engine 30 additionally includes an exhaust port and exhaust pipe 58 coupled to a muffler 56. The exhaust pipe 58 directs exhaust from the engine 30 to the rear of the motorcycle 18, through the muffler 56. The muffler 56 is therefore suspended with the exhaust pipe 58 and has to be coupled to the rear end 46b of the upper arm 40 at a rear mounting portion 60a of the muffler 56 in rear-upper portion of the muffler 56 to mount tightly therewith.

The muffler 56 has a front mounting portion 60b that is coupled to the lower mounting portion 48b of the engine case 32, coinciding with where the front end 50a of the lower arm 42 is coupled. This improves the stiffness and rigidity of the muffler 56 when in use and also reduces the number of bolts and wrenching points required since only a single bolt is required for coupling both the front end 50a of the lower arm 42 and the front mounting portion 60b of the muffler 56 to the same point on the engine case 32. A muffler cover 56a covers the outside and upper side of the muffler 56 and overlaps the rear end 46b of the upper arm 40 in the right side view. Production of the rear arm truss structure for scooter 20 from the truss frame 44 formed from pipe structures lowers production cost when compared with use of conventional casting aluminum rear arms. The connection between the upper arm 40 and rear-upper portion of the muffler 56 enables the rear arm truss structure 20 to be elevated by the upper arm 40 to impede occlusion of the muffler 56 from right side view, thereby enabling aesthetic elements of the upper arm 40 and the truss frame 44 to be prominently displayed. The use of the truss frame 44 also enables the wide distance between the upper arm 40 and the lower arm 42 to be kept with strength and to be achieved without increasing weight even though the material of aluminum is changed to steel pipe. Production material cost is also kept low with the use of the truss frame 44 formed from the pipe structures as the pipe structures allows use of lower cost materials such as steel without compromise to weight, strength and rigidity. When produced in the rear arm truss structure 20, in rear back side view, the upper arm 40 projects rearwardly and outwardly from the engine case 32 while the lower arm 42 projects rearwardly and inwardly from the engine case 32 in skewing direction. The skewing of the general longitudinal axis of the lower arm 42 from the longitudinal axis of the upper arm 40 enables force received from below and by the rear wheel 28 to be better endured and more effectively from road impact in running condition of scooter.

Further, the lower arm 42 has a curving portion 60 that is upwardly curving. The curving portion 60 of the lower arm 42 enables the distance between the upper arm 40 and the lower arm 42 to be further reduced at portions along the lower arm 42 between the curving portion 60 and the rear wheel pivot 52. This enables stiffness of the rear arm truss structure 20 to be improved. The upward curving portion 60 also enables the lower arm 42 to be easier designed for avoiding the tubular muffler 56, thereby simplifying coupling of the rear wheel supporting portion (rear wheel pivot) 52 at the rear end 50b of the lower arm 42 to the lower mounting portion 48b of the engine case 32.

The truss frame 44 of the rear arm truss structure 20 comprises a front pipe structure 62, a middle pipe structure 64 and a rear pipe structure 66, in especially referring to Fig.7. Configuratively, the front pipe structure 62 is positioned closest to towards the engine case 32, the rear pipe structure 66 is positioned towards the rear wheel 28 and the middle pipe structure 64 is positioned and connected generally between the front pipe structure 62 and the rear pipe structure 66. It is preferred that the rear pipe structure 66 extends from the upper arm 40 to the rear end 50b of the lower arm 42, terminating at the rear wheel pivot 52 (the rear wheel axis supporting portion) whereto the axle 54 of the rear wheel 28 is coupled. This improves the overall stiffness of the rear arm truss structure 20, without providing an additional structure for supporting the rear wheel 28 at the rear wheel pivot 52. Further, this enables the lower arm 42 to preserve its stiffness even with the incorporation of the upward curving portion 60 defined therealong because the rear wheel pivot 52 has to be of comparatively high stiffness so as to hold the axle 54 of rear wheel 28. So, the strength of rear wheel pivot 52 elevates not only the truss frame 44, but also the overall of the rear arm truss structure 20. The pipe structures of the truss frame form triangular shape structures (X,Y) with the upper arm 40 and a rear portion 72 of the lower arm 42 in upside down direction. The rear portion 72 of the lower arm 42 extends from the rear end 50b to the curving portion 60 thereof. A first triangular shape structure (Y) is defined to direct downwardly by the front pipe 62, the middle pipe 64 and a portion of the upper arm 40, while a second triangular shape structure (X) is defined to direct upwardly by the middle pipe structure 64, the rear pipe 66 and the rear portion 72 of the lower arm 42. A portion of the upper arm 40 extends further from the second triangular shape structure to meet the rear mounting portion 60a of the muffler 56.

The curving portion 60 is shaped to obliquely dispose the pipe structures of the truss frame 44 from the upper arm 40 for creating a triangle space. The triangle space defines a triangle shape space 70 bounded by the triangular shape structures and a frontal portion 68 of the lower arm 42. The frontal portion 68 extends between the curving portion 60 and the front end 50a of the lower arm 42. The triangle shape space 70 defined by the pipe structures of the front pipe 62 and the frontal portion 68, is wider at the bottom portion to enable a lubricant filling nozzle 74 to be positionable thereat and to facilitate easy access to a filling cap of the lubricant filling nozzle 74. Further, the curving portion 60 of the lower arm 42 is formed behind the muffler 56 adjacent where the front mounting portion 60b of the muffler 56 is coupled with the lower arm 42. The curving portion 60 is hidden by the muffler 56, and thus visually presented as being detached from the rest of the rear arm truss structure 20 without impacting the visual appearance of the scooter 18.

The front pipe 62 and the rear pipe 66 extend rearward diagonally and downwardly from the upper arm 40 to the lower arm 42, while the middle pipe 64 extends rearward diagonally and upwardly from the lower arm 42 to the upper arm 40. The axis angle of the front pipe 62 is preferably the same as the axis angle of the rear pipe 66. This configuration enables stiffness to be consistent throughout the truss frame 44. The three pipes structure makes such truss structure most simple and optimum. Especially, making both axis angles of the front pipe 62 and the rear pipe 66 almost parallel enables same or similar triangle shape to be defined by three pipes and makes it possible for the stiffness valance of truss rear arm to be made optimum.

Further, the rear end 46b of the upper rear arm 40 is substantially the same height from the stub axle 54 of the rear wheel 28 as a mounting portion 76 of the belt converter whereto a lower end 78 of a rear suspension actuator 80 is coupled. This substantially improves visual symmetrical balance between the left side and the right side of the motorcycle 18.

An inner rear fender 82a is attached to the unit swing engine 22 and disposed at front above portion of the rear wheel 28 for substantially preventing mud, debris, and water that has been picked up from the ground and directed upward and rearward as a result of rotation of the rear wheel 28 from traveling above and behind the inner rear fender 82a. A fender 82b is also mounted to the frame of scooter at the above and rear side of the rear wheel 28.

A step floor mounting at front of the seat supports the rider's feet when a rider is positioned on a seat of the scooter 18. Referring to FIGs. 2 and 4, the rear brake lever mounting at left handle bar, is coupled to the rear drum brake by a rear drum brake cable 86. The rear drum brake is covered by a rear drum brake panel 88. A pair of passenger steps 88L, R support a passenger's feet when the passenger is positioned on the seat of the scooter 18.

Aspects of particular embodiments of the present disclosure address at least one aspect, problem, limitation, and/or disadvantage associated with existing scooter side cover structures. While features, aspects, and/or advantages associated with certain embodiments have been described in the disclosure, other embodiments including various motorcycles, may also exhibit such features, aspects, and/or advantages, and not all embodiments need necessarily exhibit such features, aspects, and/or advantages to fall within the scope of the disclosure. It will be appreciated by a person of ordinary skill in the art that several of the above-disclosed structures, components, or alternatives thereof, can be desirably combined into alternative structures, components, and/or applications. In addition, various modifications, alterations, and/or improvements may be made to various embodiments that are disclosed by a person of ordinary skill in the art within scope of the present disclosure, which is limited only by the following claims.

Claims

1. A rear arm truss structure (20) for a scooter (18) comprising:

an engine unit (22) being swingably supported by the scooter frame (24), and has a belt converter (36) supporting a rear wheel (28), on one side of the scooter, said rear arm truss structure (20) being located on the other side of the scooter and connects between a rear portion of an engine case (32) and an axle (54) of the rear wheel (28), and a muffler (56) extending rearwardly and upwardly, characterized in that:

said rear arm truss structure (20) has a tubular upper arm (40) and lower arm (42),

said upper arm (40) having a front end (46a) coupled to an rear mounting portion (48a) of said engine case (32) and a rear end (46b) coupled to a rear- upper portion (60a) of said muffler (56), and

said lower arm (42) being located below said upper arm (40) and having a front end (50a) coupled to a rear mounting portion (48b) of said engine case

(32) and a rear end (50b) coupled to a rear wheel axis supporting portion (52) for supporting said axle (54) of the rear wheel (28); and

a tubular truss frame structure (44) connecting between said upper arm (40) and lower arm (42).

2. The rear arm truss structure (20) for the scooter (18) as in claim 1 , wherein said upper arm (40) extends rearwardly and outwardly in back side view from said engine case (32), and said lower arm (42) extends rearwardly and inwardly in back side view from said engine case (32) and both axis (40a,42a) of arms being in skewing position.

3. The rear arm truss structure (20) for the scooter (18) as in claim 1, wherein said lower arm (42) has an upward curving portion (60).

4. The rear arm truss structure (20) for the scooter as in claim 1, wherein a front mounting portion (60b) of said muffler (56) and said front end (50a) of the lower arm (42) are affixed to the same point at said rear mounting portion (48b) of said engine case (32).

5. The rear arm truss structure (20) for the scooter (18) as in claim 3, said truss frame structure (44) comprising a upper and lower connecting portion (62,64) for connecting between said upper arm (40) and lower arm (42), and a rear wheel axis connecting portion (66) for connecting between said rear wheel axis supporting portion (52) and said upper arm (40).

6. The rear arm truss structure (20) for the scooter (18) as in claim 5, wherein said upper and lower connecting portion (62,64) of said truss frame structure (44) comprising a front pipe(62) and rear pipe (64), forms a triangular shape structure directing downwardly, and said front pipe (62) is extending downwardly and rearwardly, and in like triangle shape space defined with said upper arm (40) and said lower arm (42) and said front pipe (62), a lubricant filling nozzle (74) is positioned.

7. The rear arm truss structure (20) for the scooter (18) as in claim 5, wherein said curving portion (60) of said lower arm (42) is formed at the front of a position (42b) where said upper and lower connecting portion (62,64) is connected to said lower arm (42), and also formed behind the muffler (56).

8. The rear arm truss structure (20) for the scooter (18) as in claim 1 , wherein said rear end (46b) of the upper arm (40) is substantially the same height as a position (76) for fixing a lower end (78) of a rear suspension (80) to said belt convertor (36).

9. The rear arm truss structure (20) for the scooter (18) as in claim 1, wherein said truss frame structure (44) comprises a front pipe(62), and a rear pipe(66) extending downwardly and rearward diagonally from said upper arm (40) to said lower arm (42), and a middle pipe (64) extending upwardly and rearward diagonally from said lower arm (42) to said upper arm (40), the axis (62a) angle of said front pipe (62) is almost parallel to the axis (66a) angle of said rear pipe (66).