Vehicle body frame structure and manufacturing method of same

Motor vehicles – Frame

Reexamination Certificate

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Details

C180S312000, C180S908000, C280S781000, C280S785000, C280S788000, C296S203010

Reexamination Certificate

active

06702058

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a body frame structure of a vehicle, particularly of a straddle-type vehicle for traveling on rough ground and also relates to a method of manufacturing the same.
A straddle-type vehicle is generally a small-sized vehicle suitable for traveling on a rough ground, and such vehicle is, for example, provided with a front wheel and a lateral pair of rear wheels. A rider straddles a rider's seat positioned at an upper portion of a vehicle body frame and steers a front wheel by operating a steering handle, and the vehicle runs through the driving of an engine mounted to the vehicle body frame.
Such body frame or frame structure of a vehicle is usually composed by interconnecting, by using coupling members, a plurality of lateral paired pipe or tube members each extending from the front portion towards the central portion of the vehicle so as to provide an integral frame structure, and then, a support bracket of a suspension device of a wheel or a reinforcing bracket is welded.
However, in the case of the frame structure of the vehicle body mentioned above, it is difficult to access or insert a welding torch or like into a frame structure at the time of welding a bracket or like member to the frame structure at the inside thereof and also difficult to automatically carry out the welding process by, for example, utilizing a robot. Thus, it is difficult to provide a good welding performance, which may increase working cost.
Moreover, since the brackets or like are welded after the construction of the frame structure, it is also difficult to reform deformation caused after the welding.
Furthermore, it is necessary to newly prepare a welding jig or like every time the change or modification of a specification or a model of an engine to be mounted or suspension stroke, which requires an increased cost.
SUMMARY OF THE INVENTION
An object of the present invention is to substantially eliminate defects or disadvantages encountered in the prior art mentioned above and to provide a vehicle body frame having an improved structure suitable for easy assembling and manufacturing thereof and for achieving improved workability.
This and other objects can be achieved according to the present invention, in one aspect, by providing a frame structure of a body of a vehicle in which a front wheel, which is steered, is disposed in front of a vehicle body frame and a rear wheel disposed to the rear side thereof, an engine is arranged between the front and rear wheels, and a rider's seat is disposed at a rear upper portion of the vehicle body frame, said vehicle body frame structure comprising:
a front frame unit provided with a support member for a front wheel suspension device and a support member for a steering shaft;
a center frame unit provided with a support member for a rear wheel suspension device and an engine mounting member; and
a rear frame unit supporting the rider's seat,
the front, center and rear frame units being assembled respectively individually and then coupled together integrally.
Further, it is to be noted that term “front”, “rear”, “upper”, “lower” and the like used herein are referred with reference to a vehicle in a normal standing (running) state or a state illustrated in the accompanying drawings which will be mentioned hereinlater.
In a preferred embodiment, the front frame unit comprises a lateral pair of flat front main frame members and a coupling member disposed so as to bridge the front main frame members, the support member of the front wheel suspension device is mounted to the front main frame members, and the support member of the steering shaft is mounted to the coupling member of the front frame unit.
The center frame unit also comprises a lateral pair of flat center main frame members, each having a horizontally curved U-shape so as to surround the engine from a vertical side and a rear side, and a coupling member disposed between the center main frame members so as to integrally couple the center main frame members, the support member of the rear wheel suspension device is provided for the center main frame members and the engine mounting member is provided for the coupling member disposed between the center main frame members.
The center main frame members include center lower tubes, respectively, which have rear half portions extending obliquely rearward upward, rear ends of the extended rear half portions of the center lower tubes are connected to substantially central lower portions of seat rail tubes constituting the rear frame unit to thereby constitute the rear half portions of the center lower tubes as support members of the seat rail tubes, and a rear cushion bracket supporting a rear cushion unit of the rear wheel suspension device is provided for a coupling member disposed so as to bridge rear end portions of the center lower tubes. The front frame unit includes coupling members disposed to vertical rear end portions of the front main frame members so as to connect the front main frame members and the vertical front end portions of the center main frame members of the center frame unit are coupled to the front frame unit through the coupling members of the front frame unit.
The front main frame members of the front frame unit are connected, at an upper end thereof, to each other through the upper coupling member, to which the support member of the steering shaft is attached. Furthermore, the front main frame members of the front frame unit are connected, at a lower end thereof, to each other through the lower coupling member, to which the engine mounting member is attached.
A lateral distance of the lower portion of the center frame unit is formed to be wider than a lateral distance of the lower portion of the front frame unit, the lower rear end portions of the front main frame members are connected to inside portions at both ends of the lower coupling member, the lower front end portions of the center frame unit are disposed so as to extend forward from the lower coupling member, the lower front portion of the center frame unit is bent inside in a width direction thereof, and the front end portion of the bent portion is connected to the rear end of the lower portion of the center frame unit from the outside in the width direction so that the connecting portions between the lower portion of the front frame unit, the lower portion of the center frame unit and the lower coupling member provide substantially a triangular shape in a plan view.
In another aspect, there is also provided a method of manufacturing a body frame structure of a vehicle in which a front wheel, which is steered, is arranged in front of a vehicle body frame, a rear wheel is arranged on a rear side of the vehicle body frame, an engine is arranged between the front and rear wheels, and a rider's seat is disposed at a rear upper portion of the vehicle body frame, the manufacturing method comprising the steps of:
preparing a front frame unit provided with a support member of a front wheel suspension device and a support member of a steering shaft, center frame unit provided with an engine mounting member and a rear frame unit supporting the rider's seat, the front, center and rear frame units being assembled independently; and
coupling integrally these front, center and rear frame units after being assembled independently.
In this method, the front frame unit is composed of a pair of lateral flat front main frame members which are coupled through a coupling member disposed therebetween after mounted with a bracket, a stay, a reinforcing member and the like member. The center frame unit is also composed of a pair of lateral flat front main frame members which are coupled through a coupling member disposed therebetween after mounted with a bracket, a stay, a reinforcing member and the like member.
According to the embodiments of the present invention mentioned above,
The vehicle body frame (structure) is constructed by coupling the front frame unit, the center frame unit and the rear frame unit, which are p

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