JP4115677B2 - Atmospheric pressure detection device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an atmospheric pressure detection device for an internal combustion engine, and more particularly to a technique for detecting atmospheric pressure by an in-cylinder pressure detecting means for detecting an in-cylinder pressure of each cylinder of the engine.
[0002]
[Prior art]
Conventionally, in order to perform engine control of an internal combustion engine with high accuracy, atmospheric pressure correction is performed on detection values of each pressure sensor.
For example, an in-cylinder pressure detection device for an internal combustion engine described in JP-A-11-193743 is detected by an in-cylinder pressure sensor in a predetermined crank angle range in which the in-cylinder pressure is estimated to take a pressure value close to atmospheric pressure. The calculated in-cylinder pressure is used as a reference in-cylinder pressure, and a differential pressure between the reference in-cylinder pressure and the absolute pressure in the intake pipe detected by the intake pressure sensor in the predetermined crank angle range is calculated. The atmospheric pressure correction of the detected in-cylinder pressure is performed by correcting with.
[0003]
[Problems to be solved by the invention]
However, since the above-mentioned conventional apparatus does not directly detect the atmospheric pressure, it is difficult to guarantee the detection accuracy even though it is complicated. Further, only the atmospheric pressure correction can be performed only with the in-cylinder pressure, and when the atmospheric pressure correction is performed on the detection value of the pressure sensor other than the in-cylinder pressure sensor, it is necessary to provide a separate atmospheric pressure sensor.
[0004]
The present invention has been made in view of the above circumstances, and an object thereof is to easily and accurately detect an atmospheric pressure using an in-cylinder pressure sensor provided for each cylinder of an engine.
[0005]
[Means for Solving the Problems]
Therefore, the invention according to claim 1 is an apparatus that detects the in-cylinder pressure of a cylinder in which at least one of an intake valve and an exhaust valve is open as an atmospheric pressure when the operation of the engine is stopped, and FIG. As shown in FIG. 2, in-cylinder pressure detecting means for detecting the in-cylinder pressure of each cylinder provided in each cylinder of the engine, and in-cylinder pressure memory for storing the in-cylinder pressure of each cylinder detected by the in-cylinder pressure detecting means before starting the engine. Among the in-cylinder pressure stored in the in-cylinder pressure storage means, the state determination means for determining the open / close state of the intake valve and the exhaust valve of each cylinder at the time of detecting the in-cylinder pressure before the engine start, Atmospheric pressure detecting means for detecting, as atmospheric pressure, the in-cylinder pressure of the cylinder determined by the state determination means that at least one of the intake valve and the exhaust valve was opened at the time of detecting the in-cylinder pressure before starting the engine. Characterized by being composed
[0006]
According to a second aspect of the present invention, when there is a plurality of cylinders in which at least one of the intake valve and the exhaust valve is determined to be open, the atmospheric pressure detecting means detects the in-cylinder pressure stored by the in-cylinder pressure storage means. Of these, the average value of the in-cylinder pressures of the plurality of cylinders is detected as atmospheric pressure.
[0007]
According to a third aspect of the present invention, the state determination means is configured to start the engine before starting the engine based on the rotation angle of the crankshaft from the start of engine start to cylinder discrimination completion and the crank angle position of each cylinder at the time of cylinder discrimination completion. you characterized to determine the opening and closing states of the intake and exhaust valves of each cylinder.
[0008]
【The invention's effect】
According to the first aspect of the present invention, the in-cylinder pressure detected by the in-cylinder pressure detecting means for detecting the in-cylinder pressure of each cylinder is stored, and the intake valve and the exhaust valve of each cylinder at the time of detecting the in-cylinder pressure are stored. And determining the open / close state of the cylinder, and detecting the in-cylinder pressure detected in the cylinder in which at least one of the intake valve and the exhaust valve is open among the stored in-cylinder pressure as an atmospheric pressure, The in-cylinder pressure of the cylinder that is reliably equivalent to the atmospheric pressure can be detected as the atmospheric pressure. Thereby, atmospheric pressure can be detected easily and with high accuracy using the in-cylinder pressure detecting means.
[0010]
According to the second aspect of the present invention, when there are a plurality of cylinders that are determined to have opened at least one of the intake valve and the exhaust valve when the in-cylinder pressure is detected before starting the engine, the plurality of cylinders are detected. By detecting the stored average value of the in-cylinder pressure as the atmospheric pressure, it is possible to detect the atmospheric pressure while suppressing variations between the in-cylinder pressure detecting means.
[0011]
According to the third aspect of the present invention, the completion of cylinder discrimination is because the crankshaft rotation angle from the start of the engine and the crank angle position from the reference position of each cylinder are known. By calculating backward the crank angle (crankshaft rotation angle) from the engine start to the completion of cylinder discrimination with respect to the angular position, it is possible to calculate the crank angle position at the time of detecting the in-cylinder pressure before starting the engine for each cylinder. The open / close state of the valve and the exhaust valve can be determined.
[0012]
Then, by comparing the calculation result of the crank angle position with a crank angle position where the intake valve or exhaust valve is opened in advance, the intake valve or exhaust valve is opened when the in-cylinder pressure is detected before the engine is started. The cylinder that has been used can be easily determined.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 2 is a system diagram of an internal combustion engine showing an embodiment of the present invention.
In FIG. 2, an air flow meter 3 that detects an intake air flow rate Qa is provided in an intake passage 2 of an engine (internal combustion engine) 1, and an intake air amount Qa is controlled by a throttle valve 4.
[0014]
Each cylinder of the engine 1 is provided with an electromagnetic fuel injection valve 6 that injects fuel into the combustion chamber 5, and an ignition plug 7 that performs spark ignition in the combustion chamber 5. The fuel is injected from the fuel injection valve 6 by electronic control to the generated air to form a predetermined air-fuel mixture, the air-fuel mixture is compressed in the combustion chamber 5 and ignited by spark ignition by the spark plug 7. To do.
[0015]
Here, by individually controlling the fuel injection valves 6 provided for the respective cylinders, it is possible to form air-fuel mixtures having different air-fuel ratios for the respective cylinders.
Exhaust gas from the engine 1 is discharged from the combustion chamber 5 to the exhaust passage 10 through the exhaust valve 9, and is released into the atmosphere through an exhaust purification catalyst and a muffler (not shown).
The control unit (C / U) 20 includes a microcomputer, and includes an intake air amount signal Q from the air flow meter 3, a throttle valve opening signal TVO from the throttle sensor 11, and a crank angle signal from the crank angle sensor 12. The cylinder discrimination signal from the cam sensor 14, the coolant temperature signal Tw from the water temperature sensor 14, the combustion pressure signal P from the in-cylinder pressure sensor 15 and the like are input, the fuel injection amount by the fuel injection valve 6, the ignition timing of the spark plug 7 Control etc.
[0016]
Here, the air flow meter 3 detects the intake air amount of the engine 1 as a mass flow rate, and the throttle sensor 11 detects the opening degree TVO of the throttle valve 4 with a potentiometer.
The crank angle sensor 12 outputs a unit angle signal for each unit crank angle and a reference angle signal for each reference crank angle position, and the cam sensor 13 outputs a cylinder discrimination signal that is different for each cylinder. The water temperature sensor 14 detects the cooling water temperature Tw in the water jacket of the engine 1.
[0017]
The rotational speed Ne of the engine 1 can be calculated by measuring the number of unit angle signals output from the crank angle sensor 12 within a predetermined time or the generation period of the reference angle signal, and the unit from the reference crank angle position can be calculated. The crank angle position for each unit crank angle is detected by counting the angle signal.
Further, cylinder discrimination is performed by detecting a cylinder discrimination signal generated between the reference angle signals.
[0018]
The in-cylinder pressure sensor 15 (in-cylinder pressure detecting means) is composed of a ring-shaped piezoelectric element mounted as a washer for the spark plug 7 as disclosed in, for example, Japanese Utility Model Laid-Open No. 63-17432, and It is a sensor that detects the combustion pressure as a relative pressure with respect to the tightening load of the plug 7 and is installed for each ignition plug 7 of each cylinder to detect the in-cylinder pressure P (combustion pressure) of each cylinder.
[0019]
The in-cylinder pressure sensor 15 is of a type that detects the in-cylinder pressure as an absolute pressure by directing the sensor portion directly into the combustion chamber in addition to the type that is mounted as a washer of the spark plug 7 as described above. Also good.
Here, the control of the injection amount injected from the fuel injection valve 6 is performed by the C / U 20 as follows.
[0020]
First, the basic fuel injection amount Tp (= K × Q) corresponding to the target air-fuel ratio based on the intake air amount Q detected by the air flow meter 3 and the engine speed Ne calculated from the detection signal from the crank angle sensor 12. / Ne; K is a constant).
Next, the basic fuel injection amount Tp includes a combustion torque fluctuation amount (combustion pressure fluctuation rate) calculated based on a correction according to operating conditions such as the coolant temperature Tw and the combustion pressure signal P, and a predetermined target value. The final fuel injection amount Ti is obtained by performing correction such that
[0021]
Then, a drive pulse signal having a pulse width corresponding to the fuel injection amount Ti is output to the fuel injection valve 6 at a predetermined timing.
Fuel that is adjusted to a predetermined pressure by a pressure regulator (not shown) is supplied to the fuel injection valve 6, and an amount of fuel that is proportional to the pulse width of the drive pulse signal is injected and supplied. An air-fuel mixture with a fuel ratio is formed.
[0022]
The C / U 20 is configured to detect atmospheric pressure using the in-cylinder pressure sensor 15. That is, in a state where the in-cylinder pressure is equivalent to the atmospheric pressure, in this embodiment, the in-cylinder pressure of the cylinder when the engine is stopped and at least one of the intake valve and the exhaust valve is opened. Detect and make this atmospheric pressure.
Specifically, the in-cylinder pressure of each cylinder is detected and stored immediately before starting the engine, and after the cylinder discrimination is completed, the open / close state of the intake valve and the exhaust valve of each cylinder when the stored in-cylinder pressure is detected is determined afterwards. . Of the stored in-cylinder pressure, the in-cylinder pressure of the cylinder determined to have been opened is detected as the atmospheric pressure.
[0023]
The detection of atmospheric pressure by the in-cylinder pressure sensor will be described with reference to the timing chart of FIG.
First, the output of the in-cylinder pressure sensor of each cylinder immediately before the start of engine start (S) is detected and stored. Next, the detection of the crankshaft rotation angle by the detection of the unit angle signal is started simultaneously with the start of the engine start. When the cylinder discrimination is completed, the crankshaft rotation angle (n0) from the engine start start (S) to the cylinder discrimination completion (K) is stored.
[0024]
Also, the crank angle position (n1, n2, n3, n4) with respect to the reference crank angle position (in this embodiment, the TDC of the compression stroke) of each cylinder at the time of completion of cylinder discrimination is counted as a unit angle signal from the reference angle signal. To calculate.
Then, from the calculated crank angle position (n1, n2, n3, n4) to the reference crank angle position of each cylinder, the stored crankshaft rotation angle (n0) from the start of engine start (S) to the completion of cylinder discrimination (K). ) Is subtracted, the crank angle position (n1 '= n1-n0, n2' = n2-n0, n3 '= n3) with respect to the reference crank angle position of each cylinder before the engine is started, that is, when the stored in-cylinder pressure is detected. -N0, n4 '= n4-n0).
[0025]
The crank angle (n1 ', n2', n3 ', n4') with respect to the reference crank angle position of each cylinder before starting the engine is set in advance as a period during which at least one of the intake valve and the exhaust valve is open. If it is within the crank angle with respect to the reference crank angle position (T1 to T2 or T1 'to T2'), it is determined that the cylinder is in an equivalent state to the atmospheric pressure before the engine is started, and the read cylinder pressure sensor Among the outputs, the cylinder pressure sensor output of the cylinder is detected as atmospheric pressure.
[0026]
The atmospheric pressure detection by the above in-cylinder pressure sensor is shown in the flowchart of FIG.
In step 1 (denoted as S1 in the figure, the same applies hereinafter), the output P1 of the in-cylinder pressure sensor 15 of each cylinder (# 1, # 2, # 3, # 4) before engine start (engine start start position S), Read and store P2, P3, and P4.
In step 2, the detection of the crankshaft rotation angle from the engine start start position (S) is started simultaneously with the start of the engine.
[0027]
In step 3, it is determined whether or not cylinder discrimination is completed.
If the cylinder discrimination is completed, the process proceeds to step 4 and the crankshaft rotation angle (n0) from the engine start start position (S) to the cylinder discrimination completion position (K) is stored.
In step 5, the crank angle position (n1, n2, n3, n4) with respect to the reference crank angle position (compression stroke TDC) of each cylinder at the completion of cylinder discrimination (K) is calculated from the cylinder discrimination result.
[0028]
In step 6, the open / close state of the intake valve or exhaust valve of each cylinder at the time when the output of the in-cylinder pressure sensor is read in step 1 is determined.
Here, as described above, the determination of the open / closed state of the intake valve or the exhaust valve of each cylinder is performed from the crank angle position (n1, n2, n3, n4) of each cylinder at the completion of cylinder discrimination to the completion of cylinder discrimination. By going back by the crankshaft rotation angle (n0), each crank position of each cylinder before the start of engine start is calculated.
[0029]
In step 7, the average value of the in-cylinder pressure sensor output calculated in step 6 is stored as the atmospheric pressure.
As described above, it is possible to easily detect the atmospheric pressure using the in-cylinder pressure sensor by detecting the in-cylinder pressure of the cylinder when the engine is stopped and at least one of the intake valve and the exhaust valve is opened. .
[Brief description of the drawings]
FIG. 1 is a block diagram showing an in-cylinder pressure detecting device according to the present invention.
FIG. 2 is a system diagram of an engine according to an embodiment of the present invention.
FIG. 3 is a timing chart of each cylinder of the engine according to the present invention.
FIG. 4 is a flowchart showing detection of atmospheric pressure according to the present invention.
[Explanation of symbols]
1 Engine 2 Intake passage 3 Air flow meter 4 Throttle valve 6 Fuel injection valve 7 Spark plug 9 Exhaust valve 10 Exhaust passage 11 Throttle sensor 12 Crank angle sensor 13 Cam sensor 14 Water temperature sensor 15 In-cylinder pressure sensor 20 Control unit

Claims (3)

An atmospheric pressure detection device for an internal combustion engine that detects an in-cylinder pressure of a cylinder in which at least one of an intake valve and an exhaust valve is open as an atmospheric pressure when the operation of the engine is stopped ,
In-cylinder pressure detecting means provided in each cylinder of the engine for detecting the in-cylinder pressure of each cylinder;
In-cylinder pressure storage means for storing the in-cylinder pressure of each cylinder detected by the in-cylinder pressure detection means before the engine is started,
State determination means for determining the open / close state of the intake valve and the exhaust valve of each cylinder after detection of the in-cylinder pressure before starting the engine;
Of the in-cylinder pressure stored by the in-cylinder pressure storage means, the in-cylinder pressure of the cylinder determined by the state determination means that at least one of the intake valve and the exhaust valve has been opened when the in-cylinder pressure is detected before the engine is started. Atmospheric pressure detecting means for detecting the atmospheric pressure as atmospheric pressure;
An atmospheric pressure detecting device for an internal combustion engine, comprising: When there are a plurality of cylinders determined that at least one of the intake valve and the exhaust valve is open, the atmospheric pressure detecting means has a plurality of cylinders out of the cylinder pressures stored in the cylinder pressure storage means. 2. The atmospheric pressure detection device for an internal combustion engine according to claim 1 , wherein an average value of the internal pressure is detected as atmospheric pressure. The state determination means is configured to determine an intake valve and an exhaust valve of each cylinder before starting the engine based on a crankshaft rotation angle from the start of engine startup to cylinder discrimination completion and a crank angle position of each cylinder at the time of cylinder discrimination completion. atmospheric pressure detecting device for an internal combustion engine according to claim 1 or claim 2, wherein determining the open or closed state of the.

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