| 摘要 |
A hydraulic drive unit is disclosed which is configured to prevent the occurence of cavitation when turning off a hydraulic motor, and, as a result, provides an improved sensation of deceleration and eliminates the associated noise. In one embodiment the present invention provides a hydraulic drive unit, comprising: first and second main circuits (1,2) for connecting an oil pressure source to a hydraulic motor (M); first and second return circuits (23, 24) connected to respective ones of the first and second main circuits (1, 2); first and second return check valves (25, 26) in respective ones of the first and second return circuits (23, 24); a by-pass circuit (27) connected to the first and second return circuits (23, 24) downstream of the first and second return check valves (25, 26); and a counter-balancing valve (3) connected to the first and second main circuits (1, 2) and the by-pass circuit (27), and being switchable between first and second positions, the counter-balancing valve (3) including first and second discharge passages (10, 11), first and second return passages (12a, 12b), first and second discharge check valves (13, 14) in respective ones of the first and second discharge passages (10, 11), first and second ports (28, 29) in respective ones of the first and second return passages (12a, 12b), and first and second branch passages (21, 22) connected to respective ones of the first and second discharge passages (10, 11) upstream of the respective ones of the first and second discharge check valves (13, 14); wherein the first discharge passage (10) connects the first main circuit (1), the first return passage (12a) connects the second main circuit (2) and the first branch passage (21) is connected to the by-pass circuit (27) when the counter-balancing valve (3) is in the first position, and the second discharge passage (11) connects the second main circuit (2), the second return passage (12b) connects the first main circuit (1) and the second branch passage (22) is connected to the by-pass circuit (27) when the counter-balancing valve (3) is in the second position. <IMAGE> |
