Hydraulic control system for automatic transmission

摘要

A hydraulic control system for an automatic transmission comprises a first shift valve and a second shift valve which are coupled with a first port and a second port of a manual valve, respectively. The first shift valve receives a forward drive range pressure from the first outlet port of the manual valve when the manual valve is set in D or II or I range. The second shift valve receives a forward drive and reverse drive range pressure from the second outlet port of the manual valve when the manual valve is set in D or R or N range. The second shift valve is also coupled with a third outlet port of the manual valve to receive a manual range pressure when the manual valve is set in II or I range. The second shift valve is urged by the manual range pressure to shift to a downshift state wherein an outlet port thereof is allowed to communicate only with a drain port thereof.