| 摘要 |
<p>PURPOSE:To have two-speed changeover without blackout by overlapping motions of No.1 and No.2 clutches forming No.1 and No.2 change gear ratios, respectively. CONSTITUTION:When the main engine shifts from the high-speed range in which a clutch 13 is in engagement to the low-speed changeover revilutions, a selector valve 27 is energized and another selector valve 26 deenergized. As supply of the working oil to passages 29, 40 is shut off, a selector valve 39 is put into the neutral position and the working oil in a passage 28 is put into communication with passages 31 and 32, and thereby pressure control valves 35, 36 retain the oil pressure at the rated pressure. The set pressure by a relief valve 22 and the pressure control valve 35 is high enough to put the clutch 13 in engagement, so that the clutch 13 continues to be in engagement even after the selector valve 26 is deenergized. The changing-over will send the oil pressure in the passage 32 to clutch 17 through a passage 38, and when the oil pressure in this passage 38 attains the setting pressure of the relief valve 22 the selector valve 39 is turned to the changeover positon.</p> |
