JP5402757B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine suitable for executing air-fuel ratio control of an internal combustion engine mounted on a vehicle.

  2. Description of the Related Art Conventionally, as disclosed in, for example, Patent Document 1, an internal combustion engine that employs an air amount preceding / fuel injection amount tracking control system that first determines an intake air amount and controls an air-fuel ratio by following the fuel injection amount. Engine control devices are known. Further, in Patent Document 1, the target throttle opening calculated from the accelerator opening is delayed by a predetermined delay time so as to control the electronically controlled throttle to the target throttle opening, so that the throttle when the intake valve is closed is disclosed. Predicting the opening is disclosed. In addition, Patent Document 1 discloses that the fuel injection amount is calculated from the intake air amount estimated from the predicted throttle opening and the like and the target air-fuel ratio, and the air-fuel ratio is controlled to the target air-fuel ratio. . In Patent Document 1, the intake air intake valve is closed by switching the throttle opening prediction method when the intake valve is closed in accordance with the longitudinal relationship between the throttle control after a predetermined time delay and the intake valve closing time of the fuel injection cylinder. The intake air amount when the valve is closed is estimated accurately.

Japanese Patent No. 3733669 Japanese Patent Laid-Open No. 11-117793 JP-A-10-205370

  However, the conventional control device for an internal combustion engine does not take into account the case where the accelerator opening changes after the fuel injection amount is calculated. When calculating the fuel injection amount, it is not possible to predict future changes in the accelerator opening, so that after the fuel injection amount is calculated, the accelerator opening changes, and a delay time elapses before the intake valve is closed. It may be controlled and the throttle opening may change. In such a case, in the conventional control device, the intake air amount estimated from the throttle opening or the like when calculating the fuel injection amount and the actual intake air amount when the intake valve is closed are greatly different. . Therefore, the estimation accuracy of the intake air amount is remarkably deteriorated, and the accuracy of the air-fuel ratio control is also deteriorated.

  The present invention has been made to solve the above-described problem, and after the fuel injection amount is calculated, the accelerator opening changes, and the throttle is controlled after a delay time elapses until the intake valve is closed. Even if it is a case, it aims at providing the control apparatus of the internal combustion engine which can maintain the precision of air fuel ratio control highly.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
Fuel injection amount calculating means for calculating the fuel injection amount based on the throttle opening;
Target throttle opening calculating means for calculating a target throttle opening corresponding to the accelerator opening;
After the target throttle opening is calculated by the target throttle opening calculating means, the throttle control means for controlling the throttle to the target throttle opening after a predetermined delay time has elapsed,
If the delay time elapses before the intake valve closing timing and the fuel injection amount is calculated within a predetermined period before and after the change in the accelerator opening, the delay time is extended. And a delay time extending means.

  According to the first invention, when the elapsed time of the delay time is before the intake valve closing timing, and when the fuel injection amount is calculated is within a predetermined period before and after the change of the accelerator opening degree. The delay time can be extended. By extending the delay time, the amount of change in the throttle opening until the intake valve is closed can be reduced. As a result, it is possible to reduce the difference between the intake air amount at the time of calculating the fuel injection amount and the intake air amount at the intake valve closing timing. Therefore, according to the present invention, even when the throttle opening is changed after the fuel injection amount is calculated and the throttle is controlled after the delay time elapses until the intake valve is closed, the air-fuel ratio control is performed. High accuracy can be maintained.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. In Embodiment 1 of the present invention, the accelerator opening changes after the fuel injection amount is calculated, the target throttle opening delay time tdly elapses until the intake valve is closed, and the throttle valve 32 reaches the target throttle opening. It is a figure for demonstrating the condition controlled. It is a figure which shows the experimental result regarding the estimation error of the intake air amount which arises in the situation of FIG. It is a figure for demonstrating the characteristic control and effect in Embodiment 1 of this invention. In Embodiment 1 of this invention, it is a flowchart of the control routine which ECU50 performs. In Embodiment 1 of this invention, it is a figure for demonstrating the predetermined period 70 memorize | stored in ECU50.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
[System Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes an internal combustion engine (hereinafter simply referred to as “engine”) 10 used as a power source for a vehicle. An intake passage 12 and an exhaust passage 14 are connected to the engine 10.

  The engine 10 is, for example, an in-line four cylinder engine. FIG. 1 shows a cross section of one of the cylinders. Each cylinder is provided with an intake port communicating with the intake passage 12 and an exhaust port communicating with the exhaust passage 14. In the intake port, an injector 16 for injecting fuel is disposed. The engine 10 is not limited to the configuration shown in the figure, and may be a system in which fuel is directly injected into the cylinder.

  Each cylinder has an intake valve 18 that opens and closes between the intake port and the combustion chamber, an exhaust valve 20 that opens and closes between the exhaust port and the combustion chamber, and ignition for igniting an air-fuel mixture in the combustion chamber. A plug 22 is provided.

  The reciprocating motion of the piston of each cylinder is converted into the rotational motion of the crankshaft 26 via the crank mechanism. A crank angle sensor 28 for detecting a rotation angle CA of the crankshaft 26 is attached in the vicinity of the crankshaft 26. According to the output of the crank angle sensor 28, the engine speed NE can also be detected.

  An air flow meter 30 is disposed in the intake passage 12. A throttle valve 32 is disposed downstream of the air flow meter 30. The throttle valve 32 is an electronically controlled throttle valve that is driven to open and close by a throttle motor 34 in accordance with a command from the ECU 50 described later. In the vicinity of the throttle valve 32, a throttle position sensor 36 for detecting the throttle opening is disposed.

  The exhaust passage 14 is provided with an air-fuel ratio sensor 37 that detects the air-fuel ratio of the exhaust gas. A catalyst 38 for purifying exhaust gas is installed downstream of the air-fuel ratio sensor 37. As the catalyst 38, for example, a three-way catalyst, a NOx catalyst, or the like is used.

  The system of this embodiment includes an ECU (Electronic Control Unit) 50. On the input side of the ECU 50, in addition to the crank angle sensor 28, the air flow meter 30, the throttle position sensor 36, the air-fuel ratio sensor 37, an operation position (accelerator opening) of an accelerator pedal provided in the driver's seat of the vehicle is detected. Various sensors such as an accelerator opening sensor 48 are connected. Further, on the output side of the ECU 50, various actuators such as the injector 16, the spark plug 22, and the throttle motor 34 are connected. The ECU 50 controls the operating state of the engine 10 by executing predetermined programs based on input information from various sensors and operating various actuators. Note that the target air-fuel ratio is set to the stoichiometric air-fuel ratio (stoichiometric).

[Characteristic Control in Embodiment 1]
In the system of the present embodiment, control is performed that adopts an air amount preceding / fuel injection amount tracking control method in which the intake air amount is determined first and the fuel injection amount follows this to control the air-fuel ratio. Here, the intake air amount can be estimated from the throttle opening, the engine speed NE, and the like. For example, Japanese Patent No. 3733669 discloses a model for estimating the intake air amount from the throttle opening or the like. Therefore, description of the model is omitted in this specification. Further, the fuel injection amount can be calculated based on the estimated intake air amount and the target air-fuel ratio.

  Further, in the system of the present embodiment, the accelerator opening is set as a driver request, and the throttle opening of the electronically controlled throttle valve 32 is controlled according to the driver request. This will be specifically described. First, the ECU 50 calculates and temporarily stores the target throttle opening of the electronically controlled throttle valve 32 according to the current operation position (accelerator opening) of the accelerator pedal by the driver. Then, the ECU 50 holds the control signal corresponding to the target throttle opening for a predetermined delay time, and outputs it to the throttle motor 34 after the delay time has elapsed.

  Therefore, the current operation position of the accelerator pedal is intentionally delayed by a slight delay time and transmitted to the throttle motor 34. The throttle valve 32 follows the operation position of the accelerator pedal with a delay by this delay time. This delay time is longer than the time until the time when the intake valve 18 of the fuel injection cylinder closes at a predetermined engine speed NE (for example, medium rotation) frequently used in the engine 10. Is set to

  Incidentally, the time until the intake valve 18 is closed mainly depends on the engine speed NE. Table 1 is a table showing the relationship between the fuel injection interval and the engine speed NE in an in-line four cylinder (L4) engine. As shown in Table 1, the lower the rotation speed, the longer the fuel injection interval, and the longer the time required for one intake stroke, the later the closing timing of the intake valve 18 in the intake stroke. Therefore, at the time of low rotation, the elapsed time of the above-described delay time may come before the closing timing of the intake valve 18. As a result, at the time of low rotation, the above-described delay time may elapse until the intake valve 18 is closed, and the throttle valve 32 may be controlled to the target throttle opening degree.

  Next, regarding the deterioration in the accuracy of estimation of the intake air amount that occurs when the delay time elapses before the closing timing of the intake valve 18 and the accelerator opening changes after the fuel injection amount is calculated. This will be described with reference to FIGS. Such a situation may occur when starting (acceleration from low rotation).

  FIG. 2 shows that in the first embodiment of the present invention, the accelerator opening changes after calculation of the fuel injection amount, the delay time tdly of the target throttle opening elapses until the intake valve is closed, and the throttle valve 32 is set to the target. It is a figure for demonstrating the condition controlled by throttle opening. FIG. 3 is a diagram showing an experimental result regarding an estimation error of the intake air amount generated in the situation of FIG.

  2 and 3A, time t0 is the current time, which is the timing for calculating the fuel injection amount (corresponding to the fuel injection timing). A broken line 60 represents the throttle opening originally intended to be predicted at time t0 when the fuel injection amount is calculated. Time t1 is the timing at which the operation of the accelerator pedal is started after fuel injection. A broken line 62 represents the target throttle opening calculated in accordance with the accelerator opening. Time t2 is a timing at which control of the throttle valve 32 is started after the delay time tdly has elapsed since the operation of the accelerator pedal was started. A solid line 64 represents a change in the throttle valve 32 controlled according to the target throttle opening after the delay time tdly has elapsed. Time t3 is the closing timing of the intake valve 18.

  FIG. 2 shows a situation where the accelerator pedal is depressed at time t1 after the fuel injection amount is calculated at time t0. At time t0, it cannot be predicted whether the driver will operate the accelerator pedal at time t1 in the future. Since the future operation position (accelerator opening) of the accelerator pedal is unknown, the target throttle opening calculated based on the accelerator opening cannot be predicted. Therefore, at time t0, the intake air amount is estimated from the above-described model with the throttle opening A as the target throttle opening, and the fuel injection amount is calculated according to the intake air amount.

  However, actually, the delay time tdly of the target throttle opening has elapsed until the intake valve 18 is closed (time t3), and the throttle opening when the intake valve 18 is closed changes to B. It becomes. That is, the throttle opening increases to B when the intake valve 18 is closed, even though it is A when the fuel injection amount is calculated. Therefore, the actual intake air amount is excessive with respect to the fuel injection amount calculated based on the throttle opening A. Therefore, the air-fuel ratio control is deviated to the lean side from the target air-fuel ratio.

  The error between the intake air amount estimated when calculating the fuel injection amount and the actual intake air amount when the intake valve 18 is closed is as shown in FIG. 3B when calculating the fuel injection amount. There is an experimental result that increases when the value is set between time ta and the vicinity of time t1. The time ta is a fuel injection timing at which the control of the throttle valve 32 after the delay time tdly has elapsed and the time when the intake valve 18 is closed (time t2 and time t3) are equal.

  As described above, after calculating the fuel injection amount (time t0), the accelerator opening changes (time t1), and until the intake valve is closed (time t3), the delay time tdly elapses and the control of the throttle valve 32 is started. In the case of being performed (time t2), the amount of air supplied into the cylinder fluctuates after the calculation of the fuel injection amount, so that the accuracy of the air-fuel ratio control deteriorates. In other words, when the elapsed time of the delay time tdly is earlier than the closing timing of the intake valve 18, the fuel injection timing is a period from time ta to the vicinity of time t1 (hereinafter, an air amount estimation error occurrence period). In the case of 68), the amount of air supplied into the cylinder fluctuates after calculation of the fuel injection amount, so that the accuracy of the air-fuel ratio control deteriorates.

  Therefore, in the system of the present embodiment, in order to solve such a problem, the elapsed time of the delay time tdly is earlier than the closing timing of the intake valve 18 and the fuel injection amount is calculated (fuel When the injection timing) is in a predetermined period before and after the change in the accelerator opening, control for temporarily extending the delay time tdly is performed.

  More specific control contents and effects thereof will be described with reference to FIG. FIG. 4 is a diagram for describing characteristic control and effects in the first embodiment of the present invention. In the characteristic control in the present embodiment, the delay time tdly is extended by the predetermined time 72 when the fuel injection amount is calculated (time t0) is within the predetermined period 70 before and after the change in the accelerator opening (time t1). . By extending the delay time tdly, the control start timing of the throttle valve 32 is delayed (solid line 74). As a result, the target throttle opening is C at the closing timing of the intake valve 18 (time t3).

  Therefore, when the fuel injection amount is calculated (time t0), the throttle opening originally intended to be reduced also decreases from B to C (broken line 76). Since the throttle opening originally desired to be reduced decreases from B to C, the deviation from the actual throttle opening A can be reduced. As a result, it is possible to suppress a decrease in the estimation accuracy of the intake air amount estimated from the throttle opening according to the decrease in the deviation (arrow 78). By suppressing the decrease in the estimation accuracy of the intake air amount, the accuracy of the air-fuel ratio control can be kept high.

(Control routine)
FIG. 5 is a flowchart of a control routine executed by the ECU 50 in order to realize the above-described operation. The routine shown in FIG. 5 is executed when the elapsed time of the delay time tdly is before the closing timing of the intake valve 18 and the accelerator opening changes. A change in the accelerator opening is detected by an accelerator opening sensor 48. In this routine, first, in step 100, it is determined whether or not the period etfwd from the time ta to the time t2 is longer than the delay time tdly. If this determination condition is not satisfied, the air amount estimation error generation period 68 does not occur, and thus the processing of this routine ends.

  On the other hand, since the air amount estimation error generation period 68 occurs when the determination condition is satisfied, next, at step 110, whether or not there is a timing for calculating the fuel injection amount within a predetermined period before and after the change in the accelerator opening degree. Is determined. The ECU 50 stores a predetermined period 70 before and after the accelerator opening change (time t1) as a predetermined period (FIG. 6). As the predetermined period 70, a period in which the error between the estimated value of the intake air amount and the actual value is larger than the predetermined value is determined based on the experiment and simulation results shown in FIG. If the determination condition in step 110 is not satisfied, the process of this routine is terminated.

  On the other hand, if the determination condition in step 110 is satisfied, the ECU 50 extends the delay time tdly until the electronically controlled throttle valve 32 is controlled (step 120). The delay time tdly is temporarily extended in the current intake stroke of the fuel injection cylinder. The extension time is set in a range not exceeding the time when the intake valve 18 is closed.

  As described above, according to the routine shown in FIG. 5, the change in the throttle opening until the intake valve 18 is closed can be reduced by extending the delay time tdly. As a result, it is possible to reduce a deviation between the intake air amount estimated from the throttle opening and the like when calculating the fuel injection amount and the actual intake air amount when the intake valve is closed. Therefore, according to the system of the present embodiment, the accelerator opening changes after the fuel injection amount is calculated, and the throttle is controlled to the target throttle opening after the delay time tdly has elapsed until the intake valve 18 is closed. Even in this case, the accuracy of the air-fuel ratio control can be maintained high. In particular, since the determination condition shown in FIG. 5 is likely to be established immediately after the start (before the air-fuel ratio sensor activation, before the feedback control is started, and the low engine speed), it is possible to suppress a decrease in the estimation accuracy of the intake air amount immediately after the transmission, A suitable exhaust emission can be realized.

  Further, according to the system of the present embodiment, when the fuel injection amount is calculated outside the air amount estimation error generation period 68, the delay time tdly is not extended, so that the responsiveness of the engine 10 felt by the driver is as much as possible. Operation control can be performed without deteriorating. In addition, since inaccurate control is not performed such that the delay time tdly is changed according to the engine speed NE having a large fluctuation, it is possible to realize suitable drivability and emission.

  By the way, in the system of Embodiment 1 mentioned above, it is supposed that the change of an accelerator opening will arise in the case of acceleration, However, The change of an accelerator opening is not limited to this. For example, even during deceleration, the above control works favorably because the intake air amount changes due to a change in the accelerator opening.

  In the first embodiment described above, the “delay time extending means” according to the first aspect of the present invention is realized by the ECU 50 executing the processing of steps 110 to 120 described above.

10 Engine 16 Injector 18 Intake valve 22 Spark plug 28 Crank angle sensor 32 Throttle valve 34 Throttle motor 38 Catalyst 48 Accelerator opening sensor 50 ECU
68 Air amount estimation error occurrence period A, B, C Throttle opening tdly delay time

Claims (1)

Fuel injection amount calculating means for calculating the fuel injection amount based on the throttle opening;
Target throttle opening calculating means for calculating a target throttle opening corresponding to the accelerator opening;
After the target throttle opening is calculated by the target throttle opening calculating means, the throttle control means for controlling the throttle to the target throttle opening after a predetermined delay time has elapsed,
If the delay time elapses before the intake valve closing timing and the fuel injection amount is calculated within a predetermined period before and after the change in the accelerator opening, the delay time is extended. Means for extending the delay time,
A control device for an internal combustion engine, comprising:

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