| 摘要 |
<p>PURPOSE:To simplify the structure so as to reduce the cost of manufacture by using negative control pressure so as to make a pressure signal act upon a pilot valve for decelerating by means of a high pressure selecting shuttle valve and a low pressure selecting valve in a hydraulic circuit for engine control of a hydraulic shovel or the like. CONSTITUTION:A high pressure selecting shuttle valve 40 is connected to a low pressure selecting valve 41 in parallel on an oil passage which intercommunicates oil passages 37L, 37R of center by-pass outlet side to each other. A pilot valve 46 is connected to a decelerating cylinder 43 which is con nected to an adjusting rod 44 for governor 21, through a slow return valve 49. The high pressure selecting shuttle valve 40 is connected to an oil passage 52 for holding low pressure boost pressure through a shuttle valve 50. A high pressure pilot pressure receiving portion 47 of the pilot valve 46 is connected to the shuttle valve 50, and a low pressure pilot pressure receiving portion 48 is connected to the low pressure selecting valve 41 respectively. Owing to the above arrangement, various kinds of control are performed using negative control pressure, and thereby the structure can be simplified and as well the cost of manufacture can be reduced.</p> |
