System for controlling a valve mechanism for an internal combustion engine

A valve timing control system of an engine having an intake valve mounted on a cylinder head for controlling an amount of intake air into a cylinder, an exhaust valve mounted on said cylinder head for controlling an amount of exhaust gas from said cylinder, an intake cam driven by an intake camshaft for urging said intake valve, an exhaust valve cam connected to an exhaust cam shaft for pushing said exhaust valve, variable means interposed between said valves and said cams for changing an open and close timing thereof, a throttle valve interposed between an injector and said cylinder for controlling power of said engine, an engine speed sensor for detecting an engine speed and for producing an engine speed signal, a coolant temperature sensor for detecting a temperature of said engine and for producing a temperature signal, a throttle position sensor for detecting an opening degree of said throttle valve and for producing a throttle signal, an air flow meter inserted in an intake passage for detecting an air flow induced into said cylinder and for producing an air flow signal, and an exhaust gas temperature sensor provided in a catalyst for detecting an exhaust gas temperature and for producing an exhaust gas temperature signal, the improvement of the system which comprises:

• judging means responsive to said speed signal and said temperature signal for determining whether said engine is in a cold state and for generating a state signal when an engine temperature of said engine is lower than a predetermined value;
• engine operating condition determining means responsive to said speed, said temperature, said throttle and said air flow signals for deciding an engine operating condition and for generating an engine operating condition signal;
• catalyst condition detecting means responsive to said exhaust gas temperature signal for sensing a catalyst condition and for producing a catalyst condition signal;
• valve timing determining means responsive to said speed signal, said engine operating signal and said catalyst condition signal for computing said open and close timing in dependency on said engine operating condition and for producing an exhaust valve open timing signal and an intake valve opening period signal so as to make an opening timing of said exhaust valve advanced and to make an opening duration of said intake valve short when said engine is in said cold state, to make said opening timing of said exhaust valve normal and to make said opening duration of said intake valve short when said engine is at an abnormally high temperature and to make said opening timing of said exhaust valve normal and to make said opening duration of said intake valve long when said engine is operated in high load;
• and
• a driver responsive to said exhaust valve open timing signal and an intake valve opening period signal for controlling said variable means in order to operate said engine in an optimum condition at any temperature.

A valve timing control system of an engine having an intake valve mounted on a cylinder head for controlling an amount of intake air into a cylinder, an exhaust valve mounted on said cylinder head for controlling an amount of exhaust gas from said cylinder, an intake cam driven by an intake camshaft for urging said intake valve, an exhaust valve cam connected to an exhaust cam shaft for pushing said exhaust valve, variable means interposed between said valves and said cams for changing an open and close timing thereof, a throttle valve interposed between an injector and said cylinder for controlling power of said engine, an engine speed sensor for detecting an engine speed and for producing an engine speed signal, a coolant temperature sensor for detecting a temperature of said engine and for producing a temperature signal, a throttle position sensor for detecting an opening degree of said throttle valve and for producing a throttle signal, an air flow meter inserted in an intake passage for detecting an air flow induced into said cylinder and for producing an air flow signal, and an exhaust gas temperature sensor provided in a catalyst for detecting an exhaust gas temperature and for producing an exhaust gas temperature signal, the improvement of the system which comprises:

• judging means responsive to said speed signal and said temperature signal for determining whether said engine is in a cold state and for generating a state signal when an engine temperature of said engine is lower than a predetermined value;
• engine operating condition determining means responsive to said speed, said temperature, said throttle and said air flow signals for deciding an engine operating condition and for generating an engine operating condition signal;
• catalyst condition detecting means responsive to said exhaust gas temperature signal for sensing a catalyst condition and for producing a catalyst condition signal;
• valve timing determining means responsive to said speed signal, said engine operating signal and said catalyst condition signal for computing said open and close timing in dependency on said engine operating condition and for producing an exhaust valve open timing signal and an intake valve opening period signal so as to change an exhaust valve advanced opening degree and phase when said engine is in the cold state and to decide an exhaust valve retarded opening phase when said catalyst is at an abnormally high temperature by a heavy load operating condition of said engine after the temperature of said catalyst reaches an activation temperature;
• and
• a driver responsive to said exhaust valve open timing signal for controlling said variable means in order to operate said engine in an optimum condition at any temperature.

A valve timing control system of an engine having an intake valve mounted on a cylinder head for controlling an amount of intake air into a cylinder, an exhaust valve mounted on said cylinder head for controlling an amount of exhaust gas from said cylinder, an intake cam driven by an intake camshaft for urging said intake valve, an exhaust valve cam connected to an exhaust cam shaft for pushing said exhaust valve, variable means interposed between said valves and said cams for changing an open and close timing thereof, a throttle valve interposed between an injector and said cylinder for controlling power of said engine, an engine speed sensor for detecting an engine speed and for producing an engine speed signal, a coolant temperature sensor for detecting a temperature of said engine and for producing a temperature signal, a throttle position sensor for detecting an opening degree of said throttle valve and for producing a throttle signal, an air flow meter inserted in an intake passage for detecting an air flow induced into said cylinder and for producing an air flow signal, and an exhaust gas temperature sensor provided in a catalyst for detecting an exhaust gas temperature and for producing an exhaust gas temperature signal, the improvement of the system which comprises:

• judging means responsive to said speed signal and said temperature signal for determining whether said engine is in a cold state and for generating a state signal when an engine temperature of said engine is lower than a predetermined value;
• engine operating condition determining means responsive to said speed, said temperature, said throttle and said air flow signals for deciding an engine operating condition and for generating an engine operating condition signal;
• catalyst condition detecting means responsive to said exhaust gas temperature signal for sensing a catalyst condition and for producing a catalyst condition signal;
• valve timing determining means responsive to said speed signal, said engine operating signal and said catalyst condition signal for computing said open and close timing in dependency on said engine operating condition and for producing an exhaust valve open timing signal and an intake valve opening period signal so as to decide an exhaust valve wide opening period when said engine is operated in the cold state until the temperature of said catalyst reaches an activation temperature and to decide an exhaust valve short opening period when said catalyst is at an abnormally high temperature by a heavy load operating condition of said engine after the temperature of said catalyst reaches the activation temperature;
• and
• a driver responsive to said exhaust valve open timing signal for controlling said variable means in order to operate said engine in an optimum condition at any temperature.