| 摘要 |
PURPOSE:To make it possible to regulate the speed shift timing of an automatic transmission with a high degree of accuracy, by using the operating pressure of one of friction elements as a signal pressure, and by controlling the initiation of change in hydraulic pressure of the other friction element with the use of a timing valve. CONSTITUTION:When a gear shift from, for example, a third speed stage down to a two speed stage is made, an oil passage 457 falls in a drain condition so that the hydraulic pressure of a clutch is lowered acting upon a port 902b of a 3-2 timing valve 900, and since a spool 904 is pushed downward overcoming a spring 906 just after initiation of lowering of the hydraulic pressure, the hydraulic pressure is fed into a brake through an oil passage 434. Further, when hydraulic pressure is gradually lowered through orifices 908, 910 down to a value less than the force of the spring 906 corresponding to the fastening force of the brake, the spool 904 is changed over so that the hydraulic passage 434 falls in a drain condition, resulting in fastening of the brake. Thus, the fastening timing of the brake and the engaging timing of the clutch may be regulated as desired due to the areas of the orifices 908, 910. |
