| 摘要 |
<p>PROBLEM TO BE SOLVED: To control the amount of pump unload in accordance with the pump discharge amount actually required and reliably decrease the pump driving loss in a pump unit which supplies oil pressure to a hydraulic circuit of an automatic transmission and the like. SOLUTION: This hydraulic pump for an automatic transmission is provided with first and second hydraulic pumps 32a, 32b driven by the engine, a drain passage 42 which communicates discharge pressure of one hydraulic pump 32b to the low pressure side, an unloading valve 30 interposed midway in the drain passage 42, detecting means to detect the required discharge amount of the hydraulic pump 32, and control means to control the opening/closing of the unloading valve 30 based on these detection results. In this case, when the required discharge is at or below the discharge amount of the first hydraulic pump 32a at that time, the discharge oil of the second hydraulic pump 32b is released to the low pressure side via the unloading valve 30.</p> |
