Patent ID: 7918753

Claim:
A hydraulic control unit, which has a power transmission system arranged on a route from a prime mover to a wheel, an oil receiving device to which oil is fed and which controls a power transmitting condition of the power transmission system on the basis of a feeding condition of the oil, and an oil reserving device for feeding the oil to the oil receiving device, wherein the oil reserving device comprises: a first hydraulic chamber, which is connected with the oil receiving device, and a second hydraulic chamber, which is positioned on the other side of the first hydraulic chamber across a piston capable of moving between the first and the second hydraulic chambers; wherein the piston has a first pressure receiving face forming the first hydraulic chamber and a second pressure receiving face forming the second hydraulic chamber, and an area of the first pressure receiving face is larger than that of the second pressure receiving face; further comprising: an oil pump, which is driven by the prime mover to establish oil pressure; an oil feeding amount control device for feeding the oil in the first hydraulic chamber to the oil receiving device, by raising the oil pressure in the second hydraulic chamber to operate the piston; and wherein the oil feeding amount control device includes a selector valve for connecting the discharge outlet of the oil pump with the second hydraulic chamber until the oil pressure discharged from the first hydraulic chamber reaches a preset value, and for disconnecting the discharge outlet of the oil pump with the second hydraulic chamber after the oil pressure discharged from the first hydraulic chamber reaches the preset value.