Control apparatus for an internal combustion engine and method for controlling the same

Abstract

In a control apparatus for an internal combustion engine having a valve timing control portion controlling the timing opening and closing of an intake valve disposed in an intake port communicating with a cylinder of the internal combustion engine, when the internal combustion engine is being started from a cold condition, multi-stroke operation is set, in which one combustion cycle of the internal combustion engine includes two or more intake and compression strokes, formed by a first intake stroke and the first compression stroke and a second intake stroke and compression stroke, followed by a combustion stroke and an exhaust stroke. The valve timing control portion controls a lift of the intake valve during the first intake stroke and the first compression stroke to a low lift amount, which is smaller than the normal lift amount required for intake of a requested intake air amount, and controls the lift of the intake valve in a second intake and a second compression stroke to the normal lift amount.

1 . A control apparatus for an internal combustion engine comprising:
 a variable valve driving device that changes the timing of the opening and closing and lift amount of an intake valve disposed in an intake port that communicates with a cylinder of the internal combustion engine;   a valve timing control portion that controls the timing of the opening and closing and lift amount of the intake valve by the variable valve driving device;   a cold start determining portion that determines whether the internal combustion engine is being started from a cold start; and   a multi-stroke operation setting portion that sets a multi-stroke operation, in which one combustion cycle of the internal combustion engine includes two or more intake and compression strokes, when the cold start determining portion determines that the internal combustion engine is being started from the cold start, wherein the multi-stroke operation is formed by a first intake stroke and a first compression stroke and a second intake stroke and a second compression stroke, followed by a combustion stroke and an exhaust stroke,   wherein the valve timing control portion controls the lift of the intake valve during the first intake and the compression strokes to a low lift amount, which is smaller than the normal lift amount required for intake of a requested intake air amount, and controls the lift of the intake valve in the second intake and the second compression stroke to the normal lift amount.   
   
   
       2 . The control apparatus according to  claim 1 , wherein
 the low lift amount is the lift at which the pumping loss during the first intake and the first compression stroke is maximized.   
   
   
       3 . The control apparatus according to  claim 1 , further comprising:
 an ignition timing control portion that controls ignition timing by a spark plug disposed in the cylinder, wherein the ignition timing control portion prohibits ignition during the first intake and the first compression stroke.   
   
   
       4 . The control apparatus according to  claim 1 , wherein
 the multi-stroke operation setting portion sets the execution of, during one combustion cycle, a plurality of repetitions of the first intake stroke and the first compression stroke, followed by performing the second intake stroke and the second compression stroke.   
   
   
       5 . The control apparatus according to  claim 1 , further comprising:
 a multi-stroke operation termination determining portion that determines whether or not multi-stroke operation is to be terminated; and   a four-stroke operation setting portion that sets one combustion cycle of the combustion of the internal combustion engine to four-stroke operation, which includes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke, if the multi-stroke operation termination determining portion determines that multi-stroke operation is to be terminated.   
   
   
       6 . The control apparatus according to  claim 5 , further comprising:
 a temperature detector that detects a temperature in the cylinder wherein   the multi-stroke operation termination determining portion determines that multi-stroke operation is to be terminated if a temperature in the cylinder is greater than or equal to a threshold cylinder temperature.   
   
   
       7 . The control apparatus according to  claim 5 , further comprising:
 a coolant temperature detector that detects a temperature of the coolant of the internal combustion engine wherein   the multi-stroke operation termination determining portion determines that multi-stroke operation is to be terminated if the temperature of the coolant is greater than or equal to a threshold coolant temperature.   
   
   
       8 . The control apparatus according to  claim 5 , further comprising:
 a requested load calculation portion that calculates a requested load on the internal combustion engine wherein   the multi-stroke operation termination determining portion determines that multi-stroke operation is to be terminated if the calculated requested load is greater than or equal to a threshold engine load.   
   
   
       9 . The control apparatus according to  claim 5 , further comprising:
 a cylinder temperature predicting portion that predicts, before starting the first intake stroke and the first compression stroke, in one combustion cycle, a temperature in a cylinder after performing the second intake stroke and the second compression stroke wherein   the multi-stroke operation termination determining portion determines that multi-stroke operation is to be terminated if the predicted temperature in the cylinder is greater than or equal to a threshold predicted cylinder temperature.   
   
   
       10 . The control apparatus according to  claim 6 , wherein
 the internal combustion engine uses a fuel including alcohol as a fuel, and the control apparatus further includes a determining value setting portion that sets any one of the threshold cylinder temperature, the threshold coolant temperature, the threshold engine load, and the threshold predicted cylinder temperature in accordance with the concentration of alcohol in the fuel.   
   
   
       11 . The control apparatus according to  claim 1 , wherein
 the internal combustion engine has a first cylinder group and a second cylinder group, and wherein   the control apparatus operates only cylinders belonging to the first cylinder group and includes   a reduced-cylinder operation setting portion that sets cylinders belonging to the second cylinder group to reduced cylinder operation, in which the cylinders are stopped, and   an all-cylinder operation setting portion that sets all cylinders belonging to the first cylinder group and cylinders belonging to the second cylinder group to all-cylinder operation, in which all cylinders are operated, wherein   the cold start determining portion determines whether restoration of operation of the cylinders belonging to the second group of cylinders is a cold start when the engine transitions from reduced-cylinder operation to all-cylinder operation, and   the multi-stroke operation setting portion sets the operation of cylinders belonging to the second cylinder group to multi-stroke operation when the cold start determining portion determines that restoration of operation of the cylinders belonging to the second cylinder group of cylinders is the cold start.   
   
   
       12 . The control apparatus according to  claim 1 , wherein
 the variable valve driving device has an intake cam that drives the opening and closing of the intake valve and an electrical motor rotationally driving the intake cam, wherein the valve timing control portion controls the valve timing by controlling the rotational drive of the intake cam using the electrical motor.   
   
   
       13 . A method for controlling an internal combustion engine comprising:
 determining whether the internal combustion engine is being started from a cold start;   executing multi-stroke operation, which includes, in one combustion cycle in the internal combustion engine, two or more intake and compression strokes, formed by a first intake stroke and a first compression stroke and a second intake stroke and compression stroke, followed by a combustion stroke and an exhaust stroke; and   controlling a lift of an intake valve during the first intake stroke and the first compression stroke to a low lift amount, which is smaller than the normal lift amount required for intake of a requested intake air amount, and controlling the lift of the intake valve in the second intake stroke and the second compression stroke to the normal lift amount.   
   
   
       14 . The control apparatus according to  claim 7 , wherein
 the internal combustion engine uses a fuel including alcohol as a fuel, and the control apparatus further includes a determining value setting portion that sets any one of the threshold cylinder temperature, the threshold coolant temperature, the threshold engine load, and the threshold predicted cylinder temperature in accordance with the concentration of alcohol in the fuel.   
   
   
       15 . The control apparatus according to  claim 8 , wherein
 the internal combustion engine uses a fuel including alcohol as a fuel, and the control apparatus further includes a determining value setting portion that sets any one of the threshold cylinder temperature, the threshold coolant temperature, the threshold engine load, and the threshold predicted cylinder temperature in accordance with the concentration of alcohol in the fuel.   
   
   
       16 . The control apparatus according to  claim 9 , wherein
 the internal combustion engine uses a fuel including alcohol as a fuel, and the control apparatus further includes a determining value setting portion that sets any one of the threshold cylinder temperature, the threshold coolant temperature, the threshold engine load, and the threshold predicted cylinder temperature in accordance with the concentration of alcohol in the fuel.