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AssigneeYamaha Motor Corporation, U.S.A.
InventorsDavid T. Takamoto, Jack R. Auld, John C. Dunne, Jr., Harry Adam Dupre, III, Eric N. Anderfaas, Dean W. Banks, Gregory E. Mott
Estimating the term…
An all terrain vehicle has a frame carried by a group of wheels. At least one of the wheels is steerably connected to the frame. A steering handle assembly is rotatably connected to the frame. A servo valve has an input shaft connected to the steering handle assembly and an output shaft connected to a pitman arm. A linkage extends from the pitman arm to the steerable wheel or wheels. A pump draws fluid from a reservoir and passes the fluid through the servo valve before the fluid is returned to the reservoir. The servo valve redirects at least a portion of the flow to a cylinder to drive a ram within the cylinder in response to steering movement of the steering handle assembly. The ram, in turn, provides a power assist to the steerable wheel or wheels. A variable speed, constant displacement pump can be used to vary the flow rate in a manner that reduces the flow rate as the vehicle speed increases. Alternatively, a bypass can be used to vary a flow rate through the servo valve. A damping valve arrangement also can be provided to absorb shocks to the steering system such that the wheels can initially deflect and then return to the original position without substantial input from the steering handle assembly.
An all terrain vehicle comprising:
An all terrain vehicle comprising a steerable wheel, a frame supported by said steerable wheel, an engine supported by said frame, a seat disposed generally above said engine, a handle bar assembly pivotally attached to said frame, said handle bar assembly comprising a lock-to-lock sweep of between about 30 degrees and 180 degrees, a flow control valve connected to said handle bar assembly, a pitman arm connected to said flow control valve and a linkage extending between said pitman arm and said steerable wheel, a hydraulic cylinder extending between said frame and at least one of said flow control valve, said pitman arm and said linkage, a fluid tank connected to said flow control valve with a pressure line, a pump interposed along said pressure line between said flow control valve and said tank, said valve also being connected to said tank with a return line, and said flow control valve being connected to said hydraulic cylinder.
The vehicle of claim 16, wherein the input shaft is mechanically coupled to the lower portion of the steering column.
A method of controlling a power steering system for a recreational vehicle, said method comprising sensing a first vehicle speed, controlling flow characteristics in said power steering system to provide a first flow rate of fluid within a closed loop hydraulic path, sensing a second vehicle speed, comparing said first vehicle speed to said second vehicle speed, controlling flow characteristics in said power steering system to provide a second flow rate of fluid wherein said first flow rate is higher than said second flow rate if said first vehicle speed is lower than said second vehicle speed and said first flow rate is lower than said second flow rate if said first vehicle speed is higher than said second vehicle speed, and sensing a lock state if a lockable transmission and varying said first flow rate and said second flow rate based upon said sensed lock state.
A power steering system for use on all terrain vehicle, said power steering system comprising:
Dependencies are inferred from the claim text.