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A snowmobile power steering system on a snowmobile having a body with a chassis and a pair of laterally spaced steerable skis includes a source a hydraulic pressure including a reservoir for storing hydraulic fluid, a hydraulic cylinder which is mounted to the snowmobile body and has two chambers an

A snowmobile power steering system on a snowmobile having a body with a chassis and a pair of laterally spaced steerable skis includes a source a hydraulic pressure including a reservoir for storing hydraulic fluid, a hydraulic cylinder which is mounted to the snowmobile body and has two chambers and at least one end rod, a steering column, and a linkage arrangement including interconnected connecting rods and pivotal members which together transmit force from the steering column to the skis. The linkage arrangement is operably connected to the hydraulic cylinder end rod so that movement of the end rod rotates the skis. A selected connecting rod includes a valve which selectively directs hydraulic pressure to one hydraulic cylinder chamber to move the end rod so the skis rotate in the first direction when the selected connecting rod transmits a tensile force. The valve directs hydraulic pressure to the other cylinder chamber to move the end rod so the skis rotate in a second direction when the selected connecting rod transmits a compressive force. The selected connecting rod is able to transmit both tensile and compressive forces, and has at least one elastic member which biases a spool within the valve toward its central position. At least one of the orifices within the valve near the spool is ellipsoidal in shape.

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A power steering system for steering a snowmobile having a body with a chassis, and a pair of laterally spaced steerable skis, the power steering system comprising: (a) a source of hydraulic pressure including a reservoir for storing hydraulic fluid; (b) a hydraulic cylinder which is mounted to the

A power steering system for steering a snowmobile having a body with a chassis, and a pair of laterally spaced steerable skis, the power steering system comprising: (a) a source of hydraulic pressure including a reservoir for storing hydraulic fluid; (b) a hydraulic cylinder which is mounted to the snowmobile body and has two chambers and at least one end rod; (c) a steering column; and (d) a linkage arrangement including interconnected connecting rod and pivotal members which together transmit force from the steering column to the skis to selectively rotate the skis, wherein a selected connecting rod transmits a tensile force when the skis are being rotated in a first direction by force transmitted from the steering column, and a compressive force when the skis are being rotated in a second direction by force transmitted from the steering column, the linkage arrangement being operably connected to the hydraulic cylinder end rod so that movement of the end rod rotates the skis; and wherein the selected connecting rod includes a control valve means for selectively directing hydraulic pressure to a hydraulic cylinder chamber to move the end rod so the skis rotate in the first direction when the selected connecting rod transmits a tensile force and for selectively directing hydraulic pressure to the other hydraulic cylinder chamber to move the end rod so the skis rotate in the second direction when the selected connecting rod transmits a compressive force, the hydraulic cylinder thereby augmenting the force transmitted to the linkage arrangement by the steering column; wherein the selected connecting rod includes two connecting portions through which the control valve directing means is connected to a remainder of the linkage assembly, and the control valve directing means comprises a four-way, three-position control valve including: (i) a spool including a first, second, and third wide damper portions, a first narrow portion between the first and second wide damper portions, and a second narrow portion between the second and third wide damper portions, the spool being in rigid connected relation to one of the connecting portions; (ii) a valve housing which is in rigid connected relation to another of the connecting portions and has a back end; a front end; and axial bore which opens to at least the back end and which substantially contains the spool, a control portion of the axial bore having a diameter substantially equal to that of the spool wide damper portions, an inner surface of the control portion of the axial bore and narrow portions of the spool defining a first and second slidable passageways; a first return passageway communicating with the reservoir and with the axial bore in proximity to the spool first wide damper portion through a first return orifice; a first cylinder passageway located forwardly from the first return passageway and communicating with one of the hydraulic cylinder chambers and the axial bore at the first slidable passageway through a first cylinder orifice; a pressure passageway located forwardly from the first cylinder passageway and communicating with the source of hydraulic pressure and the axial bore in proximity to the spool second wide damper portion through a pressure orifice; a second cylinder passageway located forwardly from the pressure passageway and communicating with another of the hydraulic cylinder chambers and the axial bore at the second slidable passgeway through a second cylinder orifice; and a second return passageway located forwardly from the second cylinder passageway and communicating with the reservoir and with the axial bore in proximity to the spool third wide damper portion through a second return orifice; wherein the spool is axially slidable within the axial bore between: a rearward position in which hydraulic pressure is directed from the pressure passageway through the second slidable passageway to the second cylinder passageway, the spool third wide damper portion blocks hydraulic pressure from entering the second return passageway from the second slidable passageway, hydraulic fluid is exhausted from the first cylinder passageway through the first slidable passageway to the first return passageway, and the spool second wide damper portion blocks hydraulic pressure from entering the first slidable passageway from the pressure passageway; a central position in which the spool second wide damper portion at least partially blocks the pressure passageway so that the hydraulic pressure directed through the slidable passageways to the cylinder passageways, if any, is equal; and a forward position in which hydraulic pressure is directed from the pressure passageway through the first slidable passageway to the first cylinder passageway, the spool first wide damper portion blocks hydraulic pressure from entering the first return passageway from the first slidable passageway, hydraulic fluid is exhausted from the second cylinder passageway through the second slidable passageway to the second return passageway, and the spool second wide damper portion blocks hydraulic pressure from entering the second slidable passageway from the pressure passageway; and (iii) means for biasing the spool to the central position and for transmitting tensil and compressive forces through the valve housing and spool so that force can be transmitted from a connecting portion to the spool, through the spool central biasing and force transmitting means to the valve housing and then to the other connecting portion, and conversely.