Abstract: A hydraulic continuously variable speed transmission includes means for detecting a speed reduction ratio of said continuously variable speed transmission, means for detecting an accelerator opening, and means for detecting vehicle speed. During running, when the means for detecting the accelerator opening detects that the accelerator opening has been fully closed, the means for detecting speed the reduction ratio detects the speed reduction ratio at the moment, and then an operation initiating vehicle speed of said clutch valve is determined based on the detected speed reduction ratio, and when the vehicle speed detected by the means for detecting vehicle speed is reduced to the operation initiating vehicle speed, the clutch valve starts to open.

Abstract: A hydraulic continuously variable speed transmission includes a hydraulic pump and a hydraulic motor, at least one of said hydraulic pump and motor being of variable displacement type. A hydraulic path is formed in a member of the pump which rotates in synchronism with an output shaft of engine, for communicating hydraulic a pressure chamber of the hydraulic pump with a drain. A check valve is provided in the hydraulic path for closing the hydraulic path under centrifugal force created by the rotation of the member when this member is in rotation faster than a predetermined speed, and for opening the hydraulic path against a centrifugal force when the member is in rotation slower than the predetermined speed.

Abstract: A continuously variable speed transmission in which a bypass line is formed between two hydraulic lines disposed between a hydraulic pump and a hydraulic motor to constitute a hydraulic closed circuit, and a opening control valve is disposed to open or close the bypass line. The opening control valve is opened when the reduction rate of the engine speed or the vehicle speed exceeds a given in order to short-cut the two lines and create a neutral condition.

Abstract: A method of controlling clutch operation, for a vehicle having a transmission and clutch means comprises setting a reference capacity of said clutch means corresponding to a parameter representing vehicle speed and an accelerator opening representing the driver's intention of acceleration or deceleration: and controlling said degree of the engine power transmitted to the wheels by adjusting the capacity of said clutch means so as to coincide with said reference capacity.

Abstract: The transmission ratio of an automotive continuously variable transmission is controlled on the basis of the difference between a target rotational speed of the engine which is preset according to an indication of the driver's intention of acceleration or deceleration and a detected rotational speed of the engine. The gain of the rate of change of the transmission ratio is reduced as the detected rotational speed of the engine becomes higher, and the gain of the rate of change of the transmission ratio is increased as the detected rotational speed of the engine becomes lower. Alternatively, the gain of the rate of change of the transmission ratio is of a relatively small value when the detected rotational speed of the engine is equal to or higher than a preset speed, and the gain of the rate of change of the transmission ratio is of a relatively large value when the detected rotational speed of the engine is lower than said preset speed.

Abstract: A hydraulic continuously variable speed transmission with a direct clutch valve comprises a hydraulic pump, a hydraulic motor, a hydraulic closed circuit for hydraulically connecting the both, a direct clutch valve placed in the closed circuit, a speed reduction ratio control actuator, and a direct clutch valve controlling device for controlling operations of said direct clutch valve to block the closed circuit when the speed reduction ratio becomes substantially "1". The direct clutch valve controlling device maintains a direct connecting state when an actual engine speed is higher than a direct clutch disconnecting reference engine speed at the speed reduction ratio of approximately "1". Then, the direct clutch valve control device releases the blocking of the closed circuit by the direct valve when a drop of the actual engine speed from the direct clutch disconnecting reference engine speed exceeds a predetermined amount corresponding to the vehicle speed.

Abstract: A hydraulic servo cylinder device for controlling a speed reduction ratio or clutch operation in a continuously variable transmission comprises cylinder and a piston slidably fitted in a cylinder chamber of the cylinder. The cylinder chamber is divided by the piston into a rod-side cylinder chamber and a head-side cylinder chamber, the rod-side cylinder chamber being supplied with a hydraulic line pressure, the head-side cylinder chamber being supplied with a hydraulic control pressure. When the piston is moved to a position near a head-side stroke end, the control pressure in the head-side cylinder chamber is so set that a hydraulic force which the piston receives from said control pressure is in equilibrium with a hydraulic force which the piston receives from the line pressure.

Abstract: A continuously variable speed transmission comprises a continuously variable speed change mechanism, a ratio control actuator, a controller controlling operational direction and speed of the ratio control actuator, and a speed reduction ratio detection sensor. The controller, in the case of outputting a command to reverse the operational direction of the ratio control actuator, keeps the ratio control actuators actuating at a maximum actuation speed in the reverse operation direction, until the speed reduction ratio detection sensor detects a fact that the speed reduction ratio of the mechanism has changed into the reversed direction after output of the command.

Abstract: A hydraulically operated continuously variable transmission includes a hydraulic pump coupled to an input shaft, a variable-displacement hydraulic motor coupled to an output shaft, and a closed hydraulic circuit interconnecting the hydraulic pump and the hydraulic motor and including a passage connecting the inlet and outlet ports of the hydraulic pump. A servomotor makes and breaks the hydraulic circuit respectively by opening and closing the outlet port. A clutch valve continuously varies the cross-sectional area of the passage to change the amount of power transmitted between the hydraulic pump and the hydraulic motor. A control system independently controls the servomotor and the clutch valve, the control system being arranged to hold the servomotor in a position to open the outlet port when the clutch valve is opened beyond a prescribed degree.