Control apparatus with range control to suppress interference for internal combustion engine, and method thereof

1. A control apparatus for an internal combustion engine equipped with:

a compression ratio variable mechanism configured to change a top dead center of a piston of the internal combustion engine to thereby change a mechanical compression ratio of the internal combustion engine; and

a variable valve mechanism configured to change a valve timing of an intake valve of the internal combustion engine,

the control apparatus comprising:

a first sub control apparatus including a first microcomputer configured to control the compression ratio variable mechanism;

a second sub control apparatus including a second microcomputer configured to control the variable valve mechanism; and

a main control apparatus including a third microcomputer configured to calculate a target mechanical compression ratio and output the calculated ratio to the first sub control apparatus, as well as calculate a target valve timing and output the calculated timing to the second sub control apparatus,

wherein the main control apparatus is configured to

calculate a first upper limit of a mechanical compression ratio based on the valve timing of the intake valve;

calculate a first target mechanical compression ratio based on an operation state of the internal combustion engine; and

compare the first upper limit and the first target mechanical compression ratio, and output a lower one of the first upper limit and the first target mechanical compression ratio as a second target mechanical compression ratio to the first sub control apparatus,

wherein the first sub control apparatus is configured to

calculate a second upper limit of the mechanical compression ratio based on the valve timing of the intake valve;

compare the second upper limit and the second target mechanical compression ratio, and output a lower one of the second upper limit and the second target mechanical compression ratio as a third target mechanical compression ratio, and

control the compression ratio variable mechanism based on the third target mechanical compression ratio.

2. The control apparatus for an internal combustion engine according to claim 1 , wherein:

the main control apparatus is further configured to

calculate a first limit value of the valve timing of the intake valve based on the mechanical compression ratio of the internal combustion engine;

calculate a first target valve timing based on the operation state of the internal combustion engine; and

compare the first limit value and the first target valve timing, and output a later one of the first limit value and the first target valve timing as a second target valve timing to the second sub control apparatus,

the second sub control apparatus is configured to

calculate a second limit value of the valve timing of the intake valve based on the mechanical compression ratio of the internal combustion engine;

compare the second limit value and the second target valve timing, and output a later one of the second limit value and the second target valve timing as a third target valve timing, and

control the variable valve mechanism based on the third target valve timing.

3. The control apparatus for an internal combustion engine according to claim 2 , wherein:

the compression ratio variable mechanism comprises a first sensor configured to detect the mechanical compression ratio of the internal combustion engine;

the main control apparatus and the first sub control apparatus are configured to receive a detection signal from the first sensor;

the main control apparatus is further configured to compare a detection value of the mechanical compression ratio, which is calculated from the detection signal of the first sensor, and a detection value of the mechanical compression ratio received from the first sub control apparatus to thereby select a higher one of the detection value calculated from the detection signal of the first sensor and the detection value received from the first sub control apparatus, and

calculate the first limit value based on the selected mechanical compression ratio.

4. The control apparatus for an internal combustion engine according to claim 3 , wherein:

the variable valve mechanism comprises a second sensor configured to detect a valve timing of the intake valve,

the main control apparatus and the second sub control apparatus are configured to receive a detection signal from the second sensor,

the main control apparatus is further configured to

compare a detection value of the valve timing, which is calculated from the detection signal of the second sensor, and a detection value of the valve timing received from the second sub control apparatus to thereby select an earlier one of the detection value calculated from the detection signal of the second sensor and the detection value received from the second sub control apparatus, and

calculate the first upper limit based on the selected valve timing.

5. The control apparatus for an internal combustion engine according to claim 4 , wherein:

the first sub control apparatus is further configured to compare the detection value of the valve timing, which is calculated from the detection signal of the second sensor, the detection value of the valve timing received from the second sub control apparatus, and the second target valve timing to thereby select the earliest one of them, and

calculate the second upper limit based on the selected valve timing.

6. The control apparatus for an internal combustion engine according to claim 5 , wherein:

the second sub control apparatus is further configured to

compare the detection value of the mechanical compression ratio, which is calculated from the detection signal of the first sensor, the detection value of the mechanical compression ratio received from the first sub control apparatus, and the second target mechanical compression ratio to thereby select the highest one of them, and

calculate the second limit value based on the selected mechanical compression ratio.