JP4477561B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine.

  When the engine is started, particularly when the engine is cold, combustion is likely to deteriorate, and the engine speed may become unstable. When combustion deteriorates, problems such as deterioration of engine startability, deterioration of engine exhaust properties, vibration due to unstable rotation speed after start-up, and noise increase occur. For this reason, various control devices have been proposed for stabilizing the engine speed by preventing the deterioration of combustion when the engine is started.

  In this type of control device, for example, the throttle valve opening (engine intake air amount), ignition timing, fuel injection amount, etc., so that the engine speed coincides with a predetermined target speed during idling after the engine is started. Is controlled so as to keep the idle speed constant.

  In such a control device, the engine speed control itself is started at the time of engine start (in this application, the period from the start of the engine start operation (cranking) to the steady idle operation is referred to as “engine start”). The timing to do will have an important meaning. That is, in general, the engine speed increases rapidly when combustion is started in all cylinders of the engine after the start operation is started, and after reaching the starting peak speed, it decreases again to a constant speed. Here, the engine speed control at the time of engine start requires that the engine speed be converged to a predetermined target engine speed in a short time, but the engine speed has changed as described above after the engine start operation is started. In the state, the time until the rotation speed converges after the rotation speed control is started differs depending on the timing at which the rotation speed control is started.

  In this connection, Patent Document 1 includes means for detecting that the engine rotational speed has reached the peak rotational speed at the start after the engine starting operation is started, and the rotational speed is detected when the arrival of the peak rotational speed is detected. A control apparatus for an internal combustion engine that starts control is disclosed. And here, the engine speed control is started from the time when the engine speed reaches the starting peak speed. By doing so, the engine speed can be converged to the target speed in a short time. It is because it is thought that it can do.

  That is, the starting peak rotational speed is generated because the air stored in the intake passage on the downstream side of the throttle valve before the engine is started is drawn into the engine all at once. For this reason, the fact that the engine speed has reached the starting peak speed means that the entire amount of air stored in the intake passage on the downstream side of the throttle valve is sucked into the engine, and the engine speed can be controlled with high accuracy. It means that. Therefore, it is considered that the engine speed can be converged to the target speed in a short time by starting the speed control from the time when the engine speed reaches the starting peak speed.

JP 2001-90581 A JP 2001-59443 A

  By the way, as described above, when the engine speed control is started from the time when the engine speed reaches the starting peak speed, it is determined whether or not the engine speed has reached the starting peak speed. Although important, this determination is usually made by determining whether or not the engine speed has reached a peak when the engine is started. For this reason, for example, when a disturbance to the engine load such as the operation of the air conditioner or the operation of the air pump occurs when the engine speed increases immediately after the engine start operation, the rotation speed control may be started. That is, the engine speed temporarily decreases due to the disturbance to the engine load, thereby causing a peak of the engine speed. It may start inappropriately early.

  The present invention has been made in view of the above points, and an object of the present invention is to start a predetermined control based on a timing at which the engine speed is determined to be a peak at the time of starting the engine. In the control device for an internal combustion engine to be determined, the control device for the internal combustion engine is provided which can start the predetermined control more reliably at an appropriate timing.

  The present invention provides a control device for an internal combustion engine described in each claim as a means for solving the above-mentioned problems.

  The invention according to claim 1 is provided with means for determining whether or not the engine speed has reached a peak at the time of starting the engine, and is controlled in advance based on the timing at which the engine speed has been determined to have reached the peak. In the control apparatus for an internal combustion engine in which the timing for starting the engine is determined, it is determined whether or not the engine speed has reached a peak during a predetermined period after the load element that is operated using the power of the internal combustion engine is activated A control device for an internal combustion engine is provided.

  In the case where the timing for starting the predetermined control is determined based on the timing at which the engine speed is determined to have reached a peak at the time of starting the engine, the internal combustion engine is increased when the engine speed increases immediately after the engine starting operation. When a load element that is operated using the motive power is activated, the predetermined control may be started at an inappropriate timing. That is, when the load element is activated, the engine speed temporarily decreases, so that a peak engine speed occurs, and it is determined that the engine speed reaches the peak at that time. In such a case, it is determined that the engine speed has reached a peak earlier than the expected timing. Therefore, based on this determination timing, the above-described predetermined control is inappropriately performed early. It will start.

  On the other hand, in the first aspect of the present invention, it is prohibited to determine whether or not the engine speed has reached a peak for a predetermined period after the load element operated using the power of the internal combustion engine is activated. It is supposed to be. In this way, by appropriately setting the predetermined period, it is possible to prevent the engine speed from being determined to have reached the peak with respect to the engine speed peak caused by the engine speed reduction caused by the activation of the load element. it can. As a result, it can be determined that the engine speed has reached a peak earlier than the expected timing, and the predetermined control can be prevented from being started at an inappropriate timing. . That is, according to the first aspect of the invention, the predetermined control can be started more reliably at an appropriate timing.

  The load element includes an element that indirectly uses the power of the internal combustion engine through a compressor or a generator connected to the internal combustion engine such as an air conditioner, an air pump, and other various electric devices.

  According to a second aspect of the present invention, in the first aspect of the present invention, the timing at which the engine speed is determined to be a peak is the timing at which the predetermined control is started, and A control device for an internal combustion engine is provided in which the predetermined control is feedback control of ignition timing so that the engine speed becomes a predetermined target speed.

  According to the second aspect of the invention, it is possible to more reliably start the feedback control of the ignition timing so that the engine speed becomes the predetermined target speed. As a result, when the engine is started, the engine speed can be more reliably converged to the target speed in a short time.

  The invention described in each claim is the control device for an internal combustion engine in which the timing for starting the predetermined control is determined based on the timing at which the engine speed is determined to be the peak at the time of starting the engine. The common effect is that the control can be started more reliably at an appropriate timing.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an example in which the control device for an internal combustion engine of the present invention is applied to a direct injection spark ignition internal combustion engine mounted on a vehicle. The present invention may be applied to another spark ignition type internal combustion engine.

  As shown in FIG. 1, the engine body 1 includes a cylinder block 2, a piston 3 that reciprocates within the cylinder block 2, and a cylinder head 4 fixed on the cylinder block 2. A combustion chamber 5 is formed between the piston 3 and the cylinder head 4. The cylinder head 4 is provided with an intake valve 6, an intake port 7, an exhaust valve 8, and an exhaust port 9 for each cylinder.

  As shown in FIG. 1, the cylinder block 2 is provided with a cooling water temperature sensor 27 for detecting the engine cooling water temperature. A spark plug 10 is disposed at the center of the inner wall surface of the cylinder head 4, and a fuel injection valve 11 is disposed around the inner wall surface of the cylinder head 4. A cavity 12 extending from the lower side of the fuel injection valve 11 to the lower side of the spark plug 10 is formed on the top surface of the piston 3. Note that F in FIG. 1 indicates the fuel injected into the combustion chamber 5.

  The intake port 7 of each cylinder is connected to a surge tank 14 via a downstream intake pipe 13, and the surge tank 14 is connected to an air cleaner 16 via an upstream intake pipe 15. A throttle valve 18 driven by a step motor 17 is disposed in the intake pipe 15. On the other hand, the exhaust port 9 of each cylinder is connected to an exhaust pipe 19, and the exhaust pipe 19 is connected to an exhaust purification device 20.

  The electronic control unit (ECU) 31 is a known type of digital computer in which a RAM (Random Access Memory), a ROM (Read Only Memory), a CPU (Microprocessor), an input port and an output port are connected to each other via a bidirectional bus. Consists of. In the present embodiment, a throttle opening sensor 43 for detecting the opening of the throttle valve 18, an intake air temperature sensor 44 for detecting the temperature of intake air (intake air temperature), and the intake pipe 15 are detected. An intake pressure sensor 45 is provided for detecting the pressure of intake air (intake pressure), and output signals from these sensors are input to the ECU 31. Further, the output signal of the cooling water temperature sensor 27 described above is also input to the ECU 31.

  A load sensor 47 is connected to the accelerator pedal 46, and an output signal of the load sensor 47 is input to the ECU 31. The crank angle sensor 48 generates an output pulse every time the crankshaft rotates 15 degrees, for example, and this output pulse is input to the ECU 31. The ECU 31 calculates the engine speed NE from the output pulse of the crank angle sensor 48 and also calculates the engine speed change speed ΔNE. Further, in the present embodiment, the activation of a load element that is operated using the power of the internal combustion engine, such as an air conditioner, various electric devices, and an air pump mounted on the vehicle, is detected, and the signal is input to the ECU 31. It is like that.

  On the other hand, the spark plug 10, the fuel injection valve 11, the step motor 17, and the like described above are connected to the ECU 31 and controlled by signals from the ECU 31. That is, the ECU 31 performs various calculations necessary for controlling the internal combustion engine based on the signals from the various sensors as described above, and controls the internal combustion engine by driving each operating device based on the result. It has become. Note that the ECU 31 also performs various calculations and controls related to the rotational speed control at the time of starting the engine, which will be described later.

  By the way, in general, when the engine is started, especially when the engine is cold started, combustion is likely to deteriorate, and the engine speed may become unstable. Deterioration of combustion causes problems such as deterioration of engine startability, deterioration of engine exhaust properties, vibration due to unstable rotational speed after start-up, and increased noise. It is desirable to stabilize the number. For this reason, conventionally, feedback control of the throttle valve opening (engine intake air amount), ignition timing, fuel injection amount, and the like is performed so that the engine speed matches the predetermined target speed when the engine is started. It has been proposed.

  And when performing such rotation speed control, the timing which starts the control itself has an important meaning. That is, in general, the engine speed increases rapidly when combustion starts in all cylinders of the engine after the start operation (cranking) is started, and after reaching the start peak speed, it decreases again to a constant speed. Become. Here, the engine speed control at the time of engine start requires that the engine speed be converged to a predetermined target engine speed in a short time, but the engine speed has changed as described above after the engine start operation is started. In the state, the time until the rotation speed converges after the rotation speed control is started differs depending on the timing at which the rotation speed control is started.

  In this regard, there is an idea that the engine speed can be converged to the target speed in a short time by starting the speed control from the time when the engine speed reaches the starting peak speed. . That is, the starting peak rotational speed is generated because the air stored in the intake passage on the downstream side of the throttle valve before the engine is started is drawn into the engine all at once. For this reason, the fact that the engine speed has reached the starting peak speed means that the entire amount of air stored in the intake passage on the downstream side of the throttle valve is sucked into the engine, and the engine speed can be controlled with high accuracy. It means that. Therefore, it is considered that the engine speed can be converged to the target speed in a short time by starting the speed control from the time when the engine speed reaches the starting peak speed.

  As will be described in detail later, in the present embodiment, based on the above, the ECU 31 performs a stable idle operation when the engine is started, that is, after the engine warm-up is completed from the start of the engine start operation (cranking). Until the engine speed NE is reached, the engine speed NE is maintained at a predetermined target speed (generally, a fast idle speed for promoting engine warm-up) NEp. . More specifically, in the present embodiment, the ignition timing Itm is feedback-controlled so that the engine speed NE coincides with the predetermined target speed NEp when the engine is started. The feedback control of the ignition timing Itm is started when the engine speed NE reaches the starting peak speed.

  By the way, when the engine speed NE is started from the time when the engine speed NE reaches the starting peak speed in this way, it is determined whether or not the engine speed NE has reached the starting peak speed. However, this determination is usually made by determining whether or not the engine speed NE has reached a peak based on a change in the engine speed at the time of starting the engine. Specifically, for example, in this embodiment, the duration Tkn after the change in the engine speed per unit time (that is, the engine speed change speed) ΔNE is less than the predetermined change speed ΔNEc (> 0) is determined in advance. When it is determined that the predetermined duration time Tkc or longer, it is determined that the engine speed NE has reached a peak.

  For this reason, for example, when a disturbance to the engine load such as the operation of the air conditioner or the operation of the air pump occurs when the engine speed NE increases immediately after the engine start operation, the speed control may start. That is, the engine speed NE temporarily decreases due to the disturbance to the engine load, thereby causing a peak of the engine speed NE. There is a risk that control will start inappropriately early.

  When the rotational speed control is performed by the feedback control of the ignition timing Itm as in the present embodiment, the ignition timing Itm may be erroneously advanced by starting the rotational speed control early in this way. As a result, there is a risk of emission deterioration due to delay in catalyst temperature rise and overrun due to excessive torque generation.

  In view of the above, in the present embodiment, special control as described below is performed so that the rotation speed control can be started more reliably at an appropriate timing. Hereinafter, the control performed in the present embodiment will be described in detail with reference to FIGS. 2 and 3. First, FIG. 2 is a flowchart showing a control routine of control executed in order to determine the start of the rotational speed control in the present embodiment. This control routine is started at the same time when the ECU 31 is activated and the start operation (cranking) is started. Then, for example, it is performed every 8 msec.

  When this control routine is started, first, at step 101, it is determined whether or not a basic condition for executing the rotational speed control is satisfied. In the present embodiment, the basic condition for executing the rotational speed control is satisfied when the engine coolant temperature is within a predetermined temperature range and the intake air temperature is within a predetermined temperature range. That is, at step 101, it is determined whether or not the engine coolant temperature at that time is within a predetermined temperature range and the intake air temperature is within a predetermined temperature range. If it is determined in step 101 that the basic condition for executing the rotational speed control is not satisfied, the rotational speed control is not started, the present control routine is terminated, and the basic condition for executing the rotational speed control is satisfied. If it is determined, the process proceeds to step 103.

  In step 103, it is determined whether or not the peak determination flag Pjf is ON. As will be described in detail later, this peak determination flag Pjf is simply turned off before the engine speed NE reaches a peak, and turned on when the engine speed NE reaches a peak. is there. In the present embodiment, whether the peak determination flag Pjf is set to ON or OFF is actually determined by performing the control shown in the control routine of FIG. 3 described later. That is, in step 103, the result of performing the control shown in the control routine of FIG. 3 is taken in, and the determination is made based on the result.

  If it is determined in step 103 that the peak determination flag Pjf is ON, the process proceeds to step 105. In this case, the rotational speed control is started in step 105, and this control routine ends. On the other hand, if it is determined in step 103 that the peak determination flag Pjf is not ON, that is, it is OFF, the process proceeds to step 107.

  When the routine proceeds to step 107, it is determined whether or not the engine speed NE at that time is equal to or greater than a predetermined target speed NEp. Here, the target rotational speed NEp can be set to 1200 rpm, for example. When it is determined in step 107 that the engine speed NE at that time is equal to or higher than the predetermined target speed NEp, the routine proceeds to step 105, where the rotational speed control is started and this control routine ends. On the other hand, if it is determined in step 107 that the engine speed NE at that time is less than the predetermined target speed NEp, the routine proceeds to step 109.

  In step 109, it is determined whether or not the elapsed time Tes after the start operation (cranking) is started is equal to or longer than a predetermined elapsed time Tec. Here, the predetermined elapsed time Tec can be set to 5 seconds, for example. If it is determined in step 109 that the elapsed time Tes is equal to or longer than the predetermined elapsed time Tec, the process proceeds to step 105, where the rotational speed control is started and the present control routine is terminated. On the other hand, if it is determined in step 109 that the elapsed time Tes is less than the predetermined elapsed time Tec, the present control routine is terminated without starting the rotational speed control.

  As understood from the above description, in the present embodiment, in addition to the case where the peak determination flag Pfj is turned ON, the case where the engine speed NE is equal to or higher than the predetermined target speed NEp, and the start operation ( Cranking) The rotational speed control is also started when the elapsed time Tes after the start becomes equal to or longer than a predetermined elapsed time Tec.

  Next, FIG. 3 will be described. FIG. 3 is a flowchart showing a control routine of control executed to determine whether or not the engine speed NE has reached a peak in the present embodiment. More specifically, the peak determination flag Pjf is turned ON or OFF. It is a flowchart which shows the control routine of the control implemented in order to determine whether or not. This control routine is also started at the same time when the ECU 31 is activated and the start operation (cranking) is started. Note that the peak determination flag Pjf is turned off at the start of this control routine.

  When this control routine is started, first, in step 201, after the start operation is started, detection of activation of a load element that is operated using the power of the internal combustion engine, such as an air conditioner, various electric devices, an air pump, etc. mounted on the vehicle is detected. It is determined whether or not it has been done. If it is determined in step 201 that the activation of the load element has been detected, the process proceeds to step 203. If it is determined that activation of the load element has not been detected, the process proceeds to step 205.

  When the routine proceeds to step 203, it is determined whether or not the elapsed time Tas since the activation of the load element is detected is equal to or longer than a predetermined elapsed time Tac. As will become apparent from the following description, this predetermined elapsed time Tac corresponds to a period in which the engine speed is affected by the activation of the load element, and during this period, the engine speed NE peaks. In order to prevent erroneous determination that the starting peak rotational speed has been reached when the rotational speed decreases due to the activation of the load element, as described above, is prohibited. The predetermined elapsed time Tac is appropriately set in advance by experiments or the like for this purpose, and can be set to 1 second here, for example.

  If it is determined in step 203 that the elapsed time Tas is equal to or longer than the predetermined elapsed time Tac, the step 205 is performed in the same manner as in the case where it is determined in step 201 that the activation of the load element is not detected. Proceed to On the other hand, if it is determined in step 203 that the elapsed time Tas is less than the predetermined elapsed time Tac, the process proceeds to step 207.

  When the routine proceeds to step 205, it is determined whether or not the engine speed NE has reached a peak. More specifically, in the present embodiment, in step 205, the engine speed change per unit time (that is, engine speed change speed) ΔNE is continued after being less than a predetermined change speed ΔNEc (> 0). It is determined whether or not the time Tkn is equal to or longer than a predetermined duration Tkk. In the present embodiment, when it is determined that the duration Tkn is equal to or longer than the predetermined duration Tkk, it is determined that the engine speed NE has reached a peak.

  If it is determined in step 205 that the continuation time Tkn is equal to or longer than the predetermined continuation time Tkc, that is, if it is determined that the engine speed NE has reached a peak, the process proceeds to step 209 and the peak determination flag Pjf is turned on. This control routine ends. On the other hand, if it is determined in step 205 that the continuation time Tkn is less than the predetermined continuation time Tkc, the process proceeds to step 211, and this control routine is terminated while the peak determination flag Pjf is kept OFF.

  On the other hand, when it is determined in step 203 that the elapsed time Tas is less than the predetermined elapsed time Tac and the routine proceeds to step 207, the duration time Tkn is reset (that is, made zero). Then, the process proceeds to step 211, and this control routine is terminated while the peak determination flag Pjf is kept OFF.

  As is apparent from the above description, in the present embodiment, the engine speed NE is set to the predetermined target speed NEp at the timing when it is determined that the engine speed NE has peaked at the time of engine start. Feedback control of the ignition timing Itm is started. In particular, in the present embodiment, it is prohibited to determine whether or not the engine speed NE has reached a peak during a predetermined period Tac after the load element that is operated using the power of the internal combustion engine is activated. ing.

  By doing so, it is possible to prevent erroneous determination that the starting peak rotational speed has been reached when the rotational speed is reduced due to the activation of the load element, and feedback control of the ignition timing Itm can be further performed. It can be started reliably at an appropriate timing. As a result, when the engine is started, the engine speed NE can be more reliably converged to the target speed NEp in a short time.

  FIG. 4 is a diagram illustrating an example of changes over time of the engine speed NE, the load element activation signal Las, the peak determination flag Pjf, and the ignition timing Itm when the engine speed control at the start is performed. Here, the load element activation signal Las is a signal that is turned ON when activation of a load element that is operated using the power of the internal combustion engine, such as an air conditioner, various electric devices, an air pump, etc., mounted on the vehicle is detected. It is.

  In the figure, the solid line indicates the case where the control shown in the control routines of FIGS. 2 and 3 is performed, and the dotted line indicates the case where the conventional control is performed. In addition, only the solid line is shown in the part where the solid line and the dotted line overlap, and the load element activation signal Las is related only when the control shown in the control routine of FIGS. It is shown.

  In the example of this figure, the starting operation (cranking) is started at time t0, and then the load element is activated at time t1. With the activation of the load element, the engine speed NE starts decreasing from the time t1, and the peak of the engine speed NE occurs there.

  When the conventional control is performed, as indicated by the dotted line, the peak determination flag Pjf is turned ON because the starting peak rotational speed is reached at time t1, and the rotational speed control, that is, here, Feedback control of the ignition timing Itm has been started. At time t1, since the engine speed NE is less than the target speed NEp, the ignition timing Itm is advanced, whereby the engine speed NE is rapidly increased. When the engine speed NE reaches the target speed NEp at time t3, the ignition timing Itm is controlled to the retard side. However, the engine speed NE continues to increase for a while after that, and the ignition timing is thereby affected. It is at time t6 that the engine speed NE converges to the target speed NEp by the feedback control of Itm.

  On the other hand, when the control shown in the control routine of FIG. 2 and FIG. 3 described above is performed, the load element activation signal Las is ON at time t1, as indicated by the solid line, During the determined elapsed time Tac, it is prohibited to determine whether or not the engine speed NE has reached a peak. Thus, it is avoided that the engine speed NE is determined to be a peak at time t1 and the peak determination flag Pjf is turned on.

  As a result, it is then determined that the engine speed NE has reached a peak at time t4 when the engine speed NE has reached the starting peak speed, and the peak determination flag Pjf is turned on. Here, feedback control of the ignition timing Itm is started. In this case, the ignition timing Itm is gradually retarded, and the engine speed NE converges to the target speed NEp at time t5 earlier than time t6.

  As described above, when the control shown in the control routines of FIGS. 2 and 3 is performed, the feedback control of the ignition timing Itm is performed so that the engine speed NE becomes the predetermined target speed NEp. As a result, the engine speed NE can be more reliably converged to the target speed NEp in a short time when the engine is started.

  In the above, the case where the feedback control of the ignition timing Itm that causes the engine speed NE to become a predetermined target speed NEp is started when it is determined that the engine speed NE has reached a peak at the time of engine start. Although described as an example, the present invention is not limited to this, and other controls are started when it is determined that the engine speed NE has reached a peak when the engine is started or other controls are started. The present invention can also be applied to a case where the engine speed NE is determined at a time other than when it is determined that the engine speed NE is determined to be a peak.

FIG. 1 is a schematic view showing an example in which the control device for an internal combustion engine of the present invention is applied to a direct injection spark ignition type internal combustion engine mounted on a vehicle. FIG. 2 is a flowchart showing a control routine of control executed to determine the start of the rotational speed control in the embodiment of the present invention. FIG. 3 is a flowchart showing a control routine of control executed to determine whether or not the engine speed has reached a peak in one embodiment of the present invention. More specifically, the peak determination flag Pjf is set to ON. It is a flowchart which shows the control routine of the control implemented in order to determine whether to make or OFF. FIG. 4 is a diagram illustrating an example of changes over time of the engine speed NE, the load element activation signal Las, the peak determination flag Pjf, and the ignition timing Itm when the engine speed control at the start is performed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine main body 5 Combustion chamber 6 Intake valve 7 Intake port 8 Exhaust valve 9 Exhaust port 10 Spark plug 11 Fuel injection valve 18 Throttle valve 27 Coolant temperature sensor 31 Electronic control unit (ECU)
44 Intake air temperature sensor 48 Crank angle sensor

Claims (2)

  An internal combustion engine comprising means for determining whether or not the engine speed has reached a peak at the time of starting the engine, wherein a timing for starting a predetermined control is determined based on a timing at which the engine speed has been determined to have reached a peak. In an engine control apparatus, an internal combustion engine control apparatus for prohibiting determination of whether or not the engine speed has reached a peak for a predetermined period after activation of a load element operated using power of an internal combustion engine .   The timing at which it is determined that the engine speed has reached the peak is the timing at which the predetermined control is started, and the predetermined control is performed so that the engine speed becomes a predetermined target speed. The control device for an internal combustion engine according to claim 1, wherein the control device is feedback control of ignition timing.

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