Patent ID: 7409937

Claim:
A hydraulic control system for an internal combustion engine, comprising: a driven mechanism driven by hydraulic pressure fed under pressure from an oil pump of the internal combustion engine; a flowing passage change-over valve for controlling hydraulic pressure supplied from the oil pump to the driven mechanism; a section defining a supplying passage fluidly disposed between the oil pump and the flowing passage change-over valve; and a section defining an oil passage fluidly disposed between the flowing passage change-over valve and the driven mechanism, wherein the flowing passage change-over valve includes a valve body formed with a plurality of ports which are respectively communicated with the supply passage and the oil passage, and a spool valve body slidably disposed in the valve body to open and close the plurality of ports, the ports including a supplying port directly communicated with the supplying passage, wherein a maximum cross-sectional area of the supplying port is larger than a minimum cross-sectional area of the supplying passage, wherein the flowing passage change-over valve is supplied with electric current to heat hydraulic fluid kept in the flowing passage change-over valve so as to lower a viscosity of the hydraulic fluid.