Compression control system for an internal combustion engine and control method therefor

A compression control system for an internal combustion engine which includes an engine cylinder block defining therein a plurality of engine cylinders and a cylinder head mounted on said cylinder block and defining therein an intake port for introducing an air/fuel mixture through an induction system and an exhaust port for exhausting an exhaust gas created in a combustion chamber defined by the engine cylinder and the cylinder block comprising:

• sensor means including an engine speed sensor for detecting the revolution speed of the engine and producing an engine speed signal, an engine load sensor for detecting the load on the engine and producing an engine load signal, an engine coolant temperature sensor for detecting the engine coolant temperature and producing a temperature signal, a crank angle sensor for producing a crank reference angle signal, and a crank position signal indicative of a given angle of rotation of a crankshaft of the engine;
• a mixture recirculating circuit defined in said cylinder head for feeding some of the air/fuel mixture in said combustion chamber back to said induction system;
• valve means incorporated in said mixture recirculating circuit for controlably establishing and blocking communication between said combustion chamber and said mixture recirculating circuit;
• a valve actuator for operating said valve means in order to control the amount of said air/fuel mixture to be fed back to said induction system, said valve actuator being responsive to a control signal to be energized to open said valve means to establish said communication for a period defined by the duration of said control signal;
• and
• a controller associated with said valve actuator for outputting thereto said control signal, said controller being responsive to said engine speed signal, said engine load signal, said temperature signal, and said starter signal, as well as to said crank reference angle signal and said crank position signal, and including a memory for storing a plurality of predetermined duration values of said controlled signal in the form of a look-up table which is read out in terms of said engine speed, engine load, and said engine temperature parameters for determining the control signal duration, and where it said controller further includes means for producing reference values respectively representative of given engine speed thresholds, a given engine load threshold, and a given engine coolant temperature threshold to be compared respectively to the engine speed signal value, engine load signal value, and said engine coolant temperature signal value, said controller assigning the duration of said control signal the appropriate one of the values described as follows:
• a first value when said engine speed signal value and said engine load signal value are respectively greater than said engine speed threshold and said engine load threshold and said engine coolant temperature signal value is less than said engine coolant temperature threshold;
• a second value when said engine speed signal value, said engine load signal value and said engine coolant temperature signal value are respectively greater than said engine speed threshold, said engine load threshold and said engine coolant temperature threshold;
• a third value when said engine speed signal value and said engine load signal value are not both greater than said engine speed threshold and said engine load threshold and said engine coolant temperature signal value is greater than said engine coolant temperature threshold;
• and
• a fourth value when said engine speed signal value, and said engine load signal value are not both greater than said engine speed threshold and said engine load threshold and said engine coolant temperature signal value is less than said engine coolant temperature threshold.

In an internal combustion engine having an engine cylinder block defining therein a plurality of engine cylinders and a cylinder head mounted on said cylinder block and defining therein an intake port and an exhaust port for introducing an air/fuel mixture into a combustion chamber defined in each engine cylinder, and exhausting an exhaust gas created in said combustion chamber,

• a method for controlling the compression ratio in said combustion chamber comprising the steps of:
• defining a feedback circuit for feeding some of the air/fuel mixture in said combustion chamber back to an induction system of the engine;
• providing a compression control valve in said feedback circuit;
• detecting an engine operating parameter;
• comparing the detected engine operating parameter with a predetermined threshold value to determine an open period of said compression control valve depending on said engine operating parameter;
• detecting engine operational position in terms of the engine stroke cycle;
• and
• determining a timing at which to open said compression control valve based on said detected engine operational position so that said compression control valve is operated in synchronism with the engine revolution, said opening period being determined in such a manner that:
• said valve is open for a first duration when said engine speed and said engine load are respectively higher than an engine speed threshold and an engine load threshold, and said engine coolant temperature is lower than an engine coolant temperature threshold;
• said valve is open for a second duration when said engine speed, said engine load and said engine coolant temperature are respectively higher than said engine speed threshold, said engine load threshold and said engine coolant temperature threshold;
• said valve is open for a third duration when said engine speed and said engine load are not both respectively higher than said engine speed threshold and said engine load threshold and said engine coolant temperature is higher than said engine coolant temperature threshold;
• said valve is open for a fourth duration when said engine speed and said engine load are both respectively higher than said engine speed threshold and said engine load threshold and said engine temperature is lower than said engine temperature threshold;
• and
• said valve is open for a fifth duration when said starter switch is ON.

A compression control system for an internal combustion engine which includes an engine cylinder block defining therein a plurality of engine cylinders and a cylinder head mounted on said cylinder block and defining therein an intake port for introducing an air/fuel mixture through an induction system and an exhaust port for exhausting an exhaust gas created in a combustion chamber defined by the engine cylinder and the cylinder block, comprising:

• sensor means associated with said engine for detecting an engine operating condition and producing an engine operating condition-indicative signal representative of an engine operational parameter;
• a mixture recirculating circuit defined in said cylinder head for feeding some of the air/fuel mixture in said combustion chamber back to said induction system;
• valve means incorporated in said mixture recirculating circuit for controllably establishing and blocking communication between said combustion chamber and said mixture recirculating circuit;
• a valve actuator for operating said valve means in order to control the amount of said air/fuel mixture to be fed back to said induction system, said valve actuator being responsive to a control signal to be energized to open said valve means to establish said communication for a period defined by the duration of said control signal;
• and
• a controller associated with said valve actuator for outputting thereto said control signal, said controller being operable to compare said engine operating condition-indicative signal value with a predetermined threshold value to derive the duration of said control signal depending upon the difference between the engine operating condition-indicative signal value and said threshold value and producing said control signal having said duration.

A compression control system for an internal combustion engine comprising:

• an engine cylinder defining a combustion chamber therein;
• an induction system for introducing an air/fuel mixture into said combustion chamber;
• a return passage defined in said engine cylinder and connecting said combustion chamber to said induction system for conducting some of the air/fuel mixture in said combustion chamber back to said induction system;
• a compression control valve provided in said return passage and movable between a first position in which communication between said combustion chamber and said induction passage via said return passage is blocked and a second position in which said communication is established;
• a sensor for detecting at least one preselected engine operation parameter for producing a sensor signal indicative thereof;
• and
• a controller for controlling the operation of said compression control valve depending on an engine operating condition as represented by said sensor signal, said controller producing a control signal to actuate said compression control valve from said first position to said second position for a duration corresponding to the duration of said control signal, and said controller being operable to compare said sensor signal value with a predetermined threshold value to derive a first shorter duration of said control signal when said sensor signal value is equal to or less than said threshold value and a second longer duration of said control signal when said sensor signal value is greater than said threshold value.