Patent ID: 8886427

Claim:
A hydraulic control apparatus for an automatic transmission that supplies oil discharged from an oil pump that operates in conjunction with a drive source to both a starting apparatus that is connected to the drive source and an automatic speed change mechanism that is connected to the starting apparatus, comprising: a circulating oil supply passage that is configured to always supply oil that has been discharged from the oil pump into a common oil passage to the starting apparatus as circulating oil; a circulating oil discharge passage that is configured to always discharge the circulating oil from the starting apparatus; a speed change mechanism oil supply passage that supplies oil in the common oil passage to the automatic speed change mechanism; a first flow rate changing device configured with a small flow rate oil passage having therein a flow rate restricting member that restricts a slow flow rate through the small flow rate oil passage, and a large flow rate oil passage that enables a large flow rate through the large flow rate oil passage, the large flow rate being larger than the slow flow rate, the first flow rate changing device being arranged in the circulating oil discharge passage and configured to change a flow rate of the circulating oil in predetermined stepped increments; and a first flow rate instructing portion that outputs a command to the first flow rate changing device to change the flow rate of the circulating oil according to an amount of oil discharged from the oil pump; a drive shaft that is connected to the drive source; an input shaft that is connected to the automatic speed change mechanism; a clutch that is configured to connect the drive shaft to the input shaft, an engagement state of the clutch being controlled by a difference between an engagement pressure supplied to a hydraulic servo of the clutch and a pressure of the circulating oil; a line pressure regulating portion that regulates a pressure of the oil discharged from the oil pump as line pressure, wherein the circulating oil of the starting apparatus is supplied based on the line pressure regulated by the line pressure regulating portion; and the first flow rate instructing portion outputs the command to the first flow rate changing device to change the flow rate such that the flow rate of the circulating oil decreases when the amount of oil discharged from the oil pump is small.