A valve is interposed between a source of pressure fluid and a clutch of a transmission such that the valve initially passes the pressure fluid at a high rate to take up slack in the clutch whereafter the supply of pressure fluid to the clutch is sharply reduced during clutch engagement and subsequently gradually increased. The valve includes first and second chambers which are respectively fed with the pressure fluid being supplied to the clutch, one of the chambers being fed with delay.
A pressure modulation valve, for supplying a smooth pressure increase, having desired characteristics, to a load port in a hydraulic control system. A single spool provides initial and final bypass phases of rapid pressure rise, and an intermediate modulated phase. The pressure characteristics can be adjusted by varying the loads and openings.
A pressure control circuit for use in connection with an automatic transmission of a vehicle is disclosed which comprises a pressure regulating valve for regulating a hydraulic pressure discharged from a pressure source and for actuating frictional engaging means, said pressure regulating valve including an accumulator, a valve spool and a spring urging said valve spool in one direction, said accumulator including a hydraulic chamber, into which is supplied the hydraulic pressure which will mechanically impart an additional force to said spring at a given value of the hydraulic pressure.
A control valve system for controlling the capacity of a hydraulic clutch in a power transmission mechanism wherein the clutch torque established by the hydraulic clutch will be nearly equal to the engine torque for the engine with which the transmission is used, thereby resulting in a smooth clutch engagement as a torque transmitting path is established from the engine to a driven member.
The present invention discloses a control apparatus for an oil pressure operated transmission in an automotive vehicle. The apparatus comprises a transmission with at least two stages of low speed and high speed forward driving trains and it is so arranged that, in an automatic shift range of a manual valve connected through first oil passage to an oil pressure source, low speed and high speed oil pressure clutches are selectively supplied with pressure oil through a shift valve in communication with the manual valve through a second oil passage. In a hold range of the manual valve, the valve is interposed between the low speed oil pressure clutch and the shift valve means for dividing the oil passage into third oil passage on its upstream side and fourth oil passage on its downstream side, having no communication between third and fourth passage and establishing a communication between fourth and first oil passage without through the shift valve means. At the same time the communication between first and second oil passage is disrupted.
The present invention provides an apparatus for controlling a hydraulic pressure usable for a clutch wherein the apparatus is employed for a transmission mounted on a construction machine or the like in such a manner that it is provided separately for a plurality of clutches and it is controlled individually. The apparatus includes a first valve for allowing a large amount of hydraulic oil to flow in the clutch and a second valve for electronically controlling a clutch pressure so that the termination of filling and the clutch pressure are detected by a simple structural arrangement on the basis of a displacement of a spool for the first valve and a separately disposed piston. In addition, appearing of an overshoot pressure on the termination of filling is prevented by providing a difference in pressure receiving areas on the spool for the first valve.
