Patent ID: 7331416

Claim:
An oil-hydraulic vehicle comprising: an oil-hydraulic pump driven by an engine; and a means which makes use of the hydraulic oil fed from the oil-hydraulic pump to drive at least one wheel, the means for driving said at least one wheel including: an oil-hydraulic motor to drive said at least one wheel; and a means for controlling the rotational frequency of the oil-hydraulic motor, the oil-hydraulic motor including: an output shaft on which said at least one wheel is mounted; and a plurality of oil chambers, each oil chamber containing (i) a driving cogwheel which is mounted on, and drives, the output shaft and (ii) a driven cogwheel which engages with the driving cogwheel the means for controlling the rotational frequency of the oil-hydraulic motor including: a housing with a circular rotor chamber in it; and a rotor fitted in the circular rotor chamber for free rotation, an inlet port being made in the housing to let the hydraulic oil fed from the oil-hydraulic pump into the rotor chamber, outlets of the same number as the oil chambers being made in the housing and arranged in the directions of turn of the rotor, each outlet connecting with different one of the oil chambers, a feed channel being made in the rotor to connect the inlet port selectively to one of the outlets, made in the housing being an inlet (hereinafter “bypass inlet”) which connects with a hydraullic-oil outlet of the oil-hydraulic motor through a bypass and made in the rotor being a bypass connection to connect the bypass inlet to the other outlets than an outlet which is connected with the inlet port through the feed channel.