JP4432572B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine for suitably predicting a future amount of air taken into the internal combustion engine.

  For example, there is a technique for predicting in-cylinder charged air amount to be filled in a cylinder of an internal combustion engine in advance, calculating fuel injection amount based on the prediction result, and performing fuel injection control. In this case, as an air amount predicting means, one that predicts the in-cylinder charged air amount from the past two air amounts is known. Specifically, the intake air amount is calculated at a constant time period from the detection result of the sensor or the like, and extrapolated (extrapolated) using the two intake air amounts immediately before the calculation of the in-cylinder charged air amount. In-cylinder charged air amount is calculated.

  However, the predicting means cannot accurately predict the in-cylinder charged air amount when the inclination of the air amount change greatly changes due to a change in the throttle opening in the future. For example, if the air amount changes from increasing to decreasing in the future, the in-cylinder charged air amount will be excessively predicted regardless of the change. As a result, when the fuel injection amount is controlled based on the in-cylinder charged air amount, an error also occurs in the fuel injection amount, causing problems such as adversely affecting the exhaust emission.

  If the calculation period of the intake air amount is shortened, the prediction result of the in-cylinder charged air amount has less error, and a certain degree of prediction accuracy can be secured, but the intake air amount calculation cycle is set to reduce the processing load of a microcomputer or the like. If it is made longer, an error occurs in the prediction result.

For example, Patent Document 1 is known as an intake air amount prediction device. In this patent document 1, the intake air amount is repeatedly predicted at a constant cycle, and the physical amount corresponding to the intake air amount in the previous prediction, the intake valve closing time in the previous prediction, and the intake valve in the current prediction A physical quantity corresponding to the intake air amount in the current prediction is calculated based on the difference from when the valve is closed, and the intake air amount in the current prediction time is calculated based on the physical quantity. However, the technique of Patent Document 1 still has a problem that the cylinder air charge amount cannot be accurately predicted when the gradient of the air amount change greatly changes in the future.
JP 2002-130041 A

  An object of the present invention is to provide a control device for an internal combustion engine capable of accurately predicting a future air amount.

According to the first aspect of the present invention, the amount of air taken into the internal combustion engine is predicted with a predetermined prediction cycle, and a total period of a time corresponding to at least one cycle of the prediction cycle and a predetermined period is set. Means for calculating a first predicted air amount at a preceding time point, and means for calculating a second predicted air amount at a predicted point that is a time point preceding the predetermined period from a current calculation timing; At the timing, the first predicted air amount calculated as the air amount before the prediction point and the air amount after the prediction point among the first predicted air amount calculated for each prediction cycle are calculated. The second predicted air amount is calculated based on the first predicted air amount.
In this case, the second predicted air amount is calculated using the first predicted air amount calculated as the air amount before the prediction point and the first predicted air amount calculated as the air amount after the prediction point. Since the calculation is interpolated, even if the inclination of the air amount change changes in the future, it is possible to predict the air amount reflecting the future air amount change. As a result, the future air amount can be accurately predicted.

In particular, the first predicted air amount is calculated by preceding a total period of time of at least one predicted period and a predetermined period . Thereby, when calculating the second predicted air amount, it is possible to know the first predicted air amount ahead.

In the invention according to claim 2, calculates the second prediction air amount when it is preceded by a predetermined crank angle until Oite intake valve closed during operation of the fuel injection amount as the prediction point, the second In the configuration for calculating the fuel injection amount based on the predicted air amount, the first predicted air amount is calculated by adding a time period for at least one cycle of the predicted cycle and the predetermined crank angle for each predicted cycle. Calculated as the amount of air at the time of preceding. Thereby, when calculating the second predicted air amount, it is possible to know the first predicted air amount ahead. In particular, in this configuration, the amount of air at the timing when the intake valve closes (the amount of air charged into the cylinder) can be predicted with high accuracy, so that the fuel injection amount can be calculated appropriately and the fuel injection control can be suitably performed. .

In the invention according to claim 3 , the first predicted air amount is calculated using a predicted opening degree of the throttle opening degree installed in the intake passage as a parameter. In this case, since the air amount changes according to the throttle opening, the air amount prediction can be suitably performed.

In the invention described in claim 4 , the second predicted air amount is calculated by performing an interpolation operation using the first and second predicted air amounts. In this case, the desired second predicted air amount can be suitably calculated even at a timing that is not synchronized with the prediction cycle of the first predicted air amount.

According to the fifth aspect of the present invention, the air amount ahead of the intake valve closing timing is predicted, and the in-cylinder charged air amount is predicted using the prediction result. In this case, the amount of air charged in the cylinder is predicted using the predicted air amount ahead of the prediction time, so even if the slope of the air amount change changes in the future, it will reflect the future air amount change. It becomes possible to accurately predict the in-cylinder charged air amount.

Further, the amount of air ahead of the closing timing of the intake valve is preceded by a summing period of a time corresponding to at least one cycle of the prediction cycle and a predetermined crank angle from the calculation timing of the fuel injection amount until the intake valve is closed. Predicted from the amount of air at the time . Thereby, the air quantity ahead of the valve closing timing of the intake valve can be suitably predicted. Therefore, the cylinder air charge amount can be predicted with high accuracy, and the fuel injection amount can be calculated appropriately, and the fuel injection control can be suitably performed.

In the invention described in claim 6, the cylinder charge air amount is predicted at the timing of the angle synchronization of the internal combustion engine. That is, when the cylinder air charge amount is predicted in synchronization with the crank angle, the prediction timing is changed depending on the engine speed. In this case, the in-cylinder charged air amount can be suitably calculated using the predicted air amount calculated separately.

According to the seventh aspect of the present invention, the air amount at the time when the sum of the time of at least one predicted period and the predetermined crank angle is preceded is predicted, so that the closing timing of the intake valve is set. In addition to the previous air amount, the air amount before the closing timing of the intake valve is predicted, and the air amount before the closing timing of the intake valve and the air amount before the same timing are used to Predict the amount of air charged in the cylinder. In this case, the in-cylinder charged air amount can be interpolated using the two predicted air amounts before and after.

According to the eighth aspect of the present invention, an interpolation calculation using predicted air amounts before and after the closing timing of the intake valve is performed to predict the in-cylinder charged air amount. In this case, the in-cylinder charged air amount can be suitably calculated at an arbitrary timing between the preceding and following air amount prediction timings.

As described in claim 9 , instead of the amount of air taken into the internal combustion engine, the intake air pressure in the intake passage of the internal combustion engine may be predicted. In such a case, the future intake air pressure can be accurately predicted.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In the present embodiment, an engine control system is constructed for an in-vehicle multi-cylinder gasoline engine that is an internal combustion engine. In the control system, an electronic control unit (hereinafter referred to as ECU) is used as a center to control the fuel injection amount. And control of ignition timing. First, an overall schematic configuration diagram of the engine control system will be described with reference to FIG.

  In the engine 10 shown in FIG. 1, an air cleaner 12 is provided at the most upstream portion of the intake pipe 11, and an air flow meter 13 for detecting the intake air amount is provided downstream of the air cleaner 12. A throttle valve 14 whose opening degree is adjusted by a throttle actuator 15 such as a DC motor is provided on the downstream side of the air flow meter 13. The opening degree of the throttle valve 14 (throttle opening degree) is detected by a throttle opening degree sensor built in the throttle actuator 15. A surge tank 16 is provided downstream of the throttle valve 14, and an intake pipe pressure sensor 17 for detecting the intake pipe pressure is provided in the surge tank 16. The surge tank 16 is connected to an intake manifold 18 that introduces air into each cylinder of the engine 10. In the intake manifold 18, an electromagnetically driven fuel injection that injects fuel near the intake port of each cylinder. A valve 19 is attached.

  An intake valve 21 and an exhaust valve 22 are respectively provided in the intake port and the exhaust port of the engine 10, and an air / fuel mixture is introduced into the combustion chamber 23 by the opening operation of the intake valve 21, and the exhaust valve 22. By the opening operation, the exhaust gas after combustion is discharged to the exhaust pipe 24. A spark plug 27 is attached to the cylinder head of the engine 10 for each cylinder, and a high voltage is applied to the spark plug 27 at a desired ignition timing through an ignition device (igniter) (not shown) including an ignition coil. Is done. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 27, and the air-fuel mixture introduced into the combustion chamber 23 is ignited and used for combustion.

  The exhaust pipe 24 is provided with a catalyst 31 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas, and the air-fuel ratio of the air-fuel mixture is detected on the upstream side of the catalyst 31 with exhaust gas as a detection target. An air-fuel ratio sensor 32 (an O2 sensor, a linear A / F sensor, etc.) for detecting the above is provided. In addition, the cylinder block of the engine 10 includes a coolant temperature sensor 33 that detects the coolant temperature, and a crank angle sensor 34 that outputs a rectangular crank angle signal at every predetermined crank angle of the engine 10 (for example, at a cycle of 10 ° CA). Is attached. In addition, an accelerator sensor 35 is provided for detecting the amount of depression of the accelerator pedal (accelerator opening).

  The outputs of the various sensors described above are input to the ECU 40 that controls the engine. The ECU 40 is composed mainly of a well-known microcomputer comprising a CPU, ROM, RAM, etc., and executes various control programs stored in the ROM, thereby controlling the fuel injection amount and ignition timing according to the engine operating state. Implement air volume control.

  In addition, when calculating the fuel injection amount, the ECU 40 predicts the in-cylinder charged air amount to be filled in the engine cylinder and corrects the fuel injection amount based on the predicted in-cylinder charged air amount. This is to predict how much air amount is filled in the cylinder when the intake valve 21 is actually closed, and to control the fuel injection amount by reflecting the amount of filled air. An outline of such control will be described with reference to the time chart of FIG. FIG. 2 shows an example of a 6-cylinder engine. For convenience, the combustion order is # 1 cylinder → # 2 cylinder → # 3 cylinder → # 4 cylinder → # 5 cylinder → # 6 cylinder. The compression TDC position of each cylinder is set to # 1 TDC, # 2 TDC, # 3 TDC, and the like. In the figure, a two-dot chain line schematically shows a change in the actual air amount charged in the cylinder, and a solid line schematically shows a change in the air amount predicted in advance by a predetermined crank angle. Hereinafter, the # 1 cylinder will be described in detail as an example.

  In the present embodiment, the fuel injection amount is calculated at the TDC of each cylinder. In the case of the # 1 cylinder, the fuel injection amount is calculated at # 2 TDC, and fuel injection is started accordingly. In the next TDC (# 3 TDC), the calculation of the fuel injection amount is performed again, and the remaining fuel injection is performed accordingly. At this time, the fuel injection end timing is controlled by the fuel injection amount calculated by # 3 TDC, and in order to improve the fuel injection control, it is indispensable to accurately predict the in-cylinder charged air amount at # 3 TDC. . Therefore, in the present embodiment, the crank angle from # 3 TDC to the closing angle of the intake valve 21 (# 5 ATDC 60 ° CA in the figure) is 300 ° CA. Then, the fuel injection amount is calculated using the prediction result. In this case, in particular, the air amount prediction process is performed every 8 ms. For example, in # 3TDC, the in-cylinder charged air amount is predicted from the predicted air amount before and after that (predicted value every 8 ms). Note that the air amount prediction processing is performed in a time cycle because the processing load of calculation becomes very high when the engine is rotating at high speed when the angle synchronization is performed.

  In FIG. 2, a1, a2, a3, etc. with white circles represent predicted air amounts predicted every 8 ms, and b1, b2, b3 with black circles represent in-cylinder charged air amounts predicted by TDC. The former corresponds to the “first predicted air amount”, and the latter corresponds to the “second predicted air amount”.

  In this case, the predicted air amounts a1, a2, a3, etc. obtained every 8 ms are calculated by predicting the air amount ahead of 300 ° CA by one cycle of the prediction cycle. That is, for example, “a2” is calculated as the predicted air amount at timing t1 in FIG. 2, and “a3” is calculated as the predicted air amount at timing t2. In # 3TDC, “b3” is calculated as the in-cylinder charged air amount based on the predicted air amounts a2 and a3 before and after that. In # 3TDC, fuel injection is performed based on the in-cylinder charged air amount b3.

  Next, 8 ms processing and TDC processing performed by the ECU 40 will be described. FIG. 3 is a flowchart showing the 8 ms process. By this process, the predicted air amount is calculated at a cycle of 8 ms. In the present embodiment, the future throttle opening is predicted from the accelerator operation amount and the like, and the future intake air amount is predicted based on the predicted throttle opening. As a technique for predicting the throttle opening, a technique called “Load Prediction” technique is used.

  In step S101, calculation parameters necessary for throttle opening calculation, such as the accelerator opening detected by the accelerator sensor 35, are input, and in step S102, the target throttle opening is calculated based on the input accelerator opening. . Thereby, it is calculated to which opening the throttle valve 14 should actually be controlled. Thereafter, in step S103, an opening command signal calculated according to the target throttle opening is delayed by a predetermined crank angle (300 ° CA in the present embodiment) and output to the throttle drive circuit. In this case, a future throttle opening can be predicted by a predetermined crank angle based on the target throttle opening. In step S104, a predicted air amount is calculated based on the predicted throttle opening.

  FIG. 4 is a flowchart showing the TDC process. With this process, the fuel injection amount is calculated at a predetermined TDC timing for each cylinder.

  In FIG. 4, in step S201, the in-cylinder charged air amount predicted at the current TDC timing is calculated using the predicted air amount calculated in the 8 ms process. In this case, the in-cylinder charged air amount is interpolated using the predicted air amount before and after the current TDC timing. When calculating the in-cylinder charged air amount, for example, the current TDC timing is time-converted based on the engine speed and timer information between the TDCs, or the 8 ms processing timing is converted to an angle. Interpolation is performed.

  Thereafter, in step S202, it is determined whether or not fuel injection is currently in progress. In subsequent step S203, it is determined whether or not it is time to start fuel injection. More specifically, in the time chart of FIG. 2, in the case of # 1 cylinder, since steps S202 and S203 are both NO in # 1TDC, the fuel injection amount calculation is not performed. Moreover, since step S203 is YES in # 2TDC and step S202 is YES in # 3TDC, the fuel injection amount calculation is performed in step S204.

  In step S204, the injected fuel amount is calculated using the in-cylinder charged air amount calculated in step S201 as a parameter. Finally, in step S205, an injection period timer is set based on the calculated fuel injection amount. Thereby, fuel injection is implemented within the set time of the injection period timer. In the time chart of FIG. 2, after # 2 TDC, fuel injection is performed so as to straddle # 3 TDC.

  According to the embodiment described above in detail, the following excellent effects can be obtained.

  While the predicted air amount is repeatedly calculated at a predetermined time period, in the configuration in which the in-cylinder charged air amount is predicted by the TDC of each cylinder, the in-cylinder charged air amount is interpolated using the predicted air amount before and after the TDC. I predicted it. As a result, even if the inclination of the intake air amount change to the engine 10 changes due to a change in the throttle opening in the future, it becomes possible to predict the in-cylinder charged air amount reflecting the future air amount change. . As a result, the future in-cylinder charged air amount can be accurately predicted. Therefore, the accuracy of fuel injection control is improved, and as a result, beneficial effects such as improvement of exhaust emission can be obtained.

  Moreover, since the cylinder filling air amount can be accurately predicted by using the interpolation calculation method as described above, the prediction cycle of the predicted air amount does not need to be shortened more than necessary, and the processing load of the ECU 40 increases. Can contribute to restraint.

  In the 8 ms process, the predicted air amount is calculated with the air amount ahead of the predetermined crank angle (300 ° CA ahead in this embodiment) advanced by one cycle of the predicted cycle. In, it is possible to know the predicted air amount ahead of it.

  In addition, this invention is not limited to the content of description of the said embodiment, For example, you may implement as follows.

  In the above embodiment, the in-cylinder charged air amount is interpolated using two predicted air amounts before and after the TDC, but this is changed and two or more predicted air before or after the TDC is predicted. The amount of air charged in the cylinder may be predicted by interpolation using the amount.

  It is also possible to predict the in-cylinder charged air amount using the predicted air amount only after TDC. Even in such a case, since at least the future predicted air amount is used for the prediction of the in-cylinder charged air amount, even if the inclination of the change in the intake air amount to the engine 10 changes due to a change in the throttle opening in the future, the future It is possible to predict the amount of air charged in the cylinder reflecting the change in the air amount. However, in this case, only the predicted air amount after TDC may be used as the predicted air amount. However, the cylinder filled air is used by using the previous predicted value of the in-cylinder charged air amount, throttle opening information at TDC, or the like. It is advisable to carry out a quantity prediction.

  In the above-described embodiment, when the fuel injection amount is calculated by the TDC of each cylinder, the case where the fuel injection is started immediately after the calculation of the fuel injection amount has been described. It is good also as a structure to set. In other words, not only the timing of the end of fuel injection but also the timing of the start of fuel injection is controlled.

  In the above embodiment, as described in the time chart of FIG. 2 and the flowchart of FIG. 4, the fuel injection amount is calculated by # 2 TDC and # 3 TDC at the time of fuel injection of the # 1 cylinder. To do. For example, in # 3TDC concerning the end timing of fuel injection among # 2TDC and # 3TDC, the fuel injection amount calculated in # 2TDC may be corrected according to the currently estimated in-cylinder charged air amount.

  In the above-described embodiment, the cylinder charge air amount is predicted for each TDC. However, only in the TDC where the predetermined crank angle ahead (300 ° CA ahead in the above-described embodiment) is the valve closing timing of the intake valve 21, It is good also as a structure which estimates the amount of filling air. Referring to FIG. 2, in the case of the # 1 cylinder, the cylinder air charge amount is predicted only at # 3 TDC.

  Instead of the intake air amount, a configuration may be adopted in which the intake air pressure is predicted. In such a case, the future intake air pressure can be accurately predicted by using the above-described prediction method.

It is a block diagram which shows the outline of the engine control system in embodiment of invention. It is a time chart which shows the change of the prediction air quantity at the time of engine operation. It is a flowchart which shows 8 ms process. It is a flowchart which shows a TDC process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 11 ... Intake pipe, 21 ... Intake valve, 40 ... ECU.

Claims (9)

The first prediction at the time when the amount of air taken into the internal combustion engine is predicted at a predetermined prediction cycle, and the sum of a period of at least one cycle of the prediction cycle and a predetermined period is preceded. Means for calculating the amount of air;
Means for calculating a second predicted air amount at a predicted point that is a time point preceding the current calculation timing for a certain period of time,
The first predicted air amount calculated as the air amount before the prediction point in the first predicted air amount calculated for each prediction cycle at the current calculation timing and the air amount after the prediction point The control apparatus for an internal combustion engine, wherein the second predicted air amount is calculated based on the first predicted air amount calculated as: The time which has preceded the predetermined crank angle before closing the Oite intake valve during operation of the fuel injection amount calculates the second prediction air amount as the prediction point, the fuel injection based on the predicted air amount of the second In the configuration for calculating the quantity,
The first predicted air amount is calculated as an air amount at the time when a sum period of a time corresponding to at least one cycle of the prediction cycle and the predetermined crank angle is preceded for each prediction cycle . Control device for internal combustion engine.   The control apparatus for an internal combustion engine according to claim 1 or 2, wherein the first predicted air amount is calculated using a future predicted opening degree of a throttle opening degree installed in the intake passage as a parameter.   The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the second predicted air amount is calculated by performing an interpolation operation using the first and second predicted air amounts. In a control device for an internal combustion engine that predicts a cylinder charge air amount that is filled in a cylinder before the intake valve is closed, and calculates a fuel injection amount based on the cylinder charge air amount,
First prediction means for predicting the amount of air taken into the internal combustion engine at a predetermined prediction cycle;
Second prediction means for predicting the in-cylinder charged air amount using the prediction result of the first prediction means at the calculation timing of the fuel injection amount ;
The first predicting means predicts an air amount at a point in time when a sum period of at least one period of the prediction period and a predetermined crank angle from the calculation timing of the fuel injection amount until the intake valve is closed precedes. And predicting the air amount ahead of the closing timing of the intake valve,
The control apparatus for an internal combustion engine, wherein the second predicting means predicts the in-cylinder charged air quantity based on an air quantity ahead of a closing timing of the intake valve predicted by the first predicting means. . The control apparatus for an internal combustion engine according to claim 5, wherein the second prediction means predicts the in- cylinder charged air amount at an angle synchronization timing of the internal combustion engine. The first predicting means predicts an air amount at a time point when a sum period of at least one period of the prediction period and the predetermined crank angle is preceded, thereby leading to the closing timing of the intake valve. In addition to the amount of air, the air amount before the closing timing of the intake valve is predicted,
The said 2nd prediction means predicts the said cylinder filling air quantity using the air quantity before the valve closing timing of the said intake valve, and the air quantity before the same timing. Control device for internal combustion engine. 8. The control apparatus for an internal combustion engine according to claim 7, wherein the second predicting means predicts the cylinder air charge amount by performing an interpolation operation using predicted air amounts before and after the closing timing of the intake valve.   The control device for an internal combustion engine according to any one of claims 1 to 8, wherein the intake air pressure in the intake passage of the internal combustion engine is predicted instead of the amount of air taken into the internal combustion engine.