JP4178881B2 - Internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine.
[0002]
[Prior art]
Conventionally, during normal operation, in order to achieve both high engine speed output and low engine speed fuel efficiency, each cylinder has two types of cams (an output cam suitable for achieving high output and a lift from the output cam). Japanese Patent Laid-Open No. 8-260927 discloses a configuration in which fuel consumption cams having small amounts and operating angles and suitable for improving fuel efficiency are provided, and these cams are switched according to the load and rotation speed of the internal combustion engine. Such a variable valve mechanism can be applied to a V-type internal combustion engine.
[0003]
[Problems to be solved by the invention]
However, when a variable valve mechanism is applied to a V-type internal combustion engine, a shift in the central angle of each bank of the V-type internal combustion engine becomes a problem. For example, a deviation occurs in the central angle due to an assembly error of the internal combustion engine, an operation error of the continuous phase variable device, etc., but this deviation amount does not cause a large amount of intake air in operation with the intake valve that responds to the output cam, When operating with an intake valve that responds to a fuel consumption cam with a small operating angle, there is a difference in the intake air volume between the left and right banks and an imbalance in the residual gas ratio between the left and right banks. There is a problem that deterioration is invited.
[0004]
The present invention has been made in view of such problems, and corrects the phase difference so that the average in-cylinder pressure of each bank due to the deviation of the central angle of the left and right banks during fuel economy cam operation is substantially the same. An object is to provide an internal combustion engine to be corrected.
[0005]
[Means for Solving the Problems]
According to the present invention, a first cam for determining a lift amount and a valve opening period of the intake valve, a lift amount and a valve opening period of the intake valve are determined, and a lift amount and an operating angle are set smaller than those of the first cam. A plurality of banks provided with variable valve gears for switching the first cam and the second cam and setting the lift amount and the valve opening period of the intake valve according to the cam and the accelerator pedal depression amount and rotation speed of the internal combustion engine; The means for detecting the in-cylinder pressure of each cylinder, the means for calculating the average value of the in-cylinder pressure for each bank, and correcting the valve opening timing of the intake valve so that the average value of the in-cylinder pressure for each bank is the same. The internal combustion engine is characterized in that correction of the opening timing of the intake valve is performed during operation by the second cam and is not performed during operation by the first cam.
[0006]
【The invention's effect】
According to the present invention, in an internal combustion engine having a plurality of banks, since the phase of the intake valve is changed so that the average in-cylinder pressure for each bank is the same, an imbalance in the intake air amount of each bank is suppressed, Deterioration of fuel consumption, drivability, and emission can be suppressed.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0008]
FIG. 1 is a schematic view of an internal combustion engine to which the present invention is applied. This V-type internal combustion engine is provided with a variable valve operating device 1. The variable valve operating device 1 places importance on the output cam (first cam) and fuel efficiency of the cam 2 based on the rotational speed and the required load. The intake valve 3 is opened and closed by switching between the fuel consumption cam (second cam). Here, the operating angle (= opening period of the intake valve) of the output cam is set to 240 ° crank angle or less, and the fuel consumption cam is set to 180 ° crank angle or less.
[0009]
A control unit 4 composed of a microcomputer or the like for controlling the variable valve operating device 1 is installed. The control unit 4 includes an output of a sensor 5 for detecting an accelerator pedal depression amount (hereinafter referred to as APO). The output of the inhibitor switch 6 and the output of the rotational speed sensor 8 for detecting the rotational speed of the crankshaft 7 (= the rotational speed of the internal combustion engine) are input. Based on these input values, the control unit 4 calculates a fuel injection amount, for example, and controls an injector (not shown). Further, the selection of the cam and the phase to which the intake valve 3 responds is performed, and the lift amount, the valve opening period and the valve opening timing of the intake valve 3 are controlled.
[0010]
The variable valve operating device 1 has a variable valve configuration described in, for example, Japanese Patent Application Laid-Open No. 8-260927, and the control unit 4 has two solenoid valves for switching the fuel consumption cam and output cam and for changing the phase (configuration). The above is a total of three phase changeable electromagnetic switching valves because each bank is provided.) Is controlled based on the input value. A block diagram of the configuration of the control unit 4 is shown in FIG.
[0011]
The rotational speed from the rotation sensor 8, the APO from the sensor 5, and the in-cylinder pressure from the in-cylinder pressure detecting means are input to the control unit 4. Here, the detection of the in-cylinder pressure can be calculated based on the crank angular speed detected by the rotational speed sensor 8 using the technique disclosed in Japanese Patent Laid-Open No. 10-278585. Or you may detect by installing a piezoelectric sensor in the washer part of the spark plug which is not shown in figure desired in the combustion chamber of each cylinder. Furthermore, a piezoelectric element may be installed in the cylinder as desired, and detection may be performed using this element.
[0012]
The engine speed and APO are output to the cam switching determination unit 4a and the continuous variable phase conversion angle calculation unit 4b that constitute the control unit 4. The in-cylinder pressure is output to the left and right bank average pressure and average pressure variation calculation unit 4c, and the average pressure and average pressure variation calculated by the calculation unit 4c are output to the continuous variable phase conversion angle calculation unit 4b.
[0013]
The continuous variable phase conversion angle calculation unit 4b calculates the phase conversion angle according to the engine speed, APO, average pressure and average pressure variation, and outputs the phase conversion angle to the continuous variable phase instruction unit 4e. The continuous variable phase instruction unit 4e calculates Based on the phase conversion angle thus set, the phase variable solenoid valve installed in each bank is controlled.
[0014]
On the other hand, the cam switching determination unit 4a determines whether or not the cam switching is necessary according to the input value, and the switching solenoid instruction unit 4d controls the cam switching solenoid valve based on the determination result.
[0015]
FIG. 3 shows an example of the difference in characteristics between the fuel consumption cam and the output cam. As is clear from the figure, the fuel consumption cam is set to have a smaller valve lift and operating angle than the output cam. Further, the lift center angle of the fuel economy cam is advanced with respect to the lift center angle of the output cam, thereby greatly increasing the overlap between the intake valve and the exhaust valve to improve the fuel efficiency. Further, the pumping loss can be reduced by making the phase variable during driving with the fuel consumption cam, that is, by advancing, and the fuel efficiency can be further improved by operating the internal EGR.
[0016]
FIG. 4 is a diagram showing an example of the operation region of the fuel consumption cam and the output cam.
[0017]
FIG. 5 is a flowchart illustrating the in-cylinder pressure correction control content that is characteristic of the present invention. This control is executed by the control unit 4. In this flowchart, the in-cylinder pressure is detected for each cylinder.
[0018]
First, in step 1, the currently used cam is confirmed, and in the case of the fuel economy cam, the process proceeds to step 2, and in the case of the output cam, this determination is repeated. The in-cylinder pressure correction control is limited to the fuel efficiency cam operation because the intake air amount supplied to the engine is large during the output cam operation, so the sensitivity to the phase change of the center angle of the cam is low and the response is slow. Is not good and the effect is small. Furthermore, if the in-cylinder pressure correction control is performed during the operation of the output cam, hunting or the like occurs, which may lead to instability of the combustion state. For this reason, in-cylinder pressure correction is not performed during the output cam operation, and the calculation load is reduced.
[0019]
In step 2, the in-cylinder pressure for each cylinder in each bank is detected to determine whether it is within the allowable pressure. If it is within the permissible pressure, the process proceeds to step 3, and if greater than the permissible pressure, the process proceeds to step 4. Here, the determination is made in the next step by determining that the variation is large when the difference between the upper and lower limit values of the in-cylinder pressure during one cycle of the in-cylinder pressure detecting means or the standard deviation value of the detected pressure exceeds a predetermined value. Correct the phase. Alternatively, the difference between the upper and lower limit values may be divided by the average in-cylinder pressure of each bank and compared with another predetermined value. Since the phase is retarded when the in-cylinder pressure for each cylinder in each bank is not within the allowable pressure, the accuracy of the in-cylinder pressure correction control can be improved.
[0020]
In step 4, the phase is retarded according to the difference between the detected value and the allowable pressure. The retardation amount can be set based on a preset map or the like. Subsequently, it is determined whether or not the in-cylinder pressure is within the allowable pressure based on the phase corrected in step 5. If the determination is true, the process proceeds to step 3; if not, the process returns to step 4 to repeat the phase correction.
[0021]
In step 3, the average in-cylinder pressure in each of the left and right banks is calculated, the difference is obtained, and it is determined whether or not the difference is within the reference value. If it is within the reference value, the control is finished assuming that the combustion state of each cylinder is stable, and if not, the process proceeds to step 6 and the other bank is set with reference to the bank with the higher average in-cylinder pressure. The angle of the cam is retarded to reduce the angle.
[0022]
By such control, an imbalance in the intake air amount between the left and right banks can be suppressed, and deterioration of fuel consumption, drivability, and emission can be suppressed.
[0023]
In subsequent step 7, it is determined once again whether or not the difference in average in-cylinder pressure between the left and right banks is within the reference value. When it is within the reference value, the control is terminated because the combustion is stable, and when it is not within the reference value, the process returns to step 6 to repeat the retardation correction.
[0024]
The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea of the present invention.
[Brief description of the drawings]
FIG. 1 is a diagram showing a system configuration according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a control unit.
FIG. 3 is a diagram showing a difference in cam characteristics.
FIG. 4 is a diagram illustrating an example of an operation region of a fuel consumption cam and an output cam.
FIG. 5 is a flowchart for explaining in-cylinder pressure correction control performed by the control unit;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Variable valve apparatus 2 Cam 3 Intake valve 4 Control unit 5 APO sensor 6 Inhibitor switch 7 Crankshaft 8 Rotational speed sensor

Claims (5)

A first cam that determines the lift amount and valve opening period of the intake valve;
A second cam in which a lift amount and a valve opening period of the intake valve are determined, and a lift amount and an operating angle are set smaller than the first cam;
A plurality of banks provided with variable valve gears for switching the first cam and the second cam according to the accelerator pedal depression amount and the rotational speed of the internal combustion engine and setting the lift amount and valve opening period of the intake valve;
Means for detecting the in-cylinder pressure of each cylinder;
Means for calculating an average value of in-cylinder pressure for each bank;
Means for correcting the valve opening timing of the intake valve so that the in-cylinder pressure average value for each bank is the same;
With
The internal combustion engine according to claim 1, wherein the correction of the opening timing of the intake valve is performed during operation by the second cam and is not performed during operation by the first cam. A first cam that determines the lift amount and valve opening period of the intake valve;
A second cam in which the lift amount and valve opening period of the intake valve are determined, and the lift amount and operating angle are set smaller than the first cam;
A plurality of banks provided with variable valve gears for switching the first cam and the second cam according to the accelerator pedal depression amount and the rotational speed of the internal combustion engine and setting the lift amount and valve opening period of the intake valve;
Means for detecting the in-cylinder pressure of each cylinder;
Means for detecting variations in the detected in-cylinder pressure between the cylinders;
Means for correcting variation in cylinder pressure for each cylinder to a predetermined value or less;
Means for calculating an average value of in-cylinder pressure for each bank;
Means for correcting the valve opening timing of the intake valve so that the in-cylinder pressure average value for each bank is the same;
With
The internal combustion engine according to claim 1, wherein the correction of the opening timing of the intake valve is performed during operation by the second cam and is not performed during operation by the first cam. The internal combustion engine according to claim 1 or 2, wherein the cylinder arrangement is V-shaped. The internal combustion engine according to claim 1 or 2, wherein the opening timing of the intake valve of the bank with the smaller average cylinder pressure value for each bank is retarded. Means for detecting the rotational speed of the crankshaft;
The internal combustion engine according to claim 1 or 2, further comprising means for calculating an average value of the in-cylinder pressure based on the detected rotational speed.

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