JP2016098786A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently suppress an engine stall and an increase of a rotating speed in a transient state while ensuring the stability of a control in a steady state when an intake amount and ignition timing are controlled on the basis of first and second demanded torques calculated in response to a rotating speed deviation ΔNE during idling driving.SOLUTION: When an engine rotating speed NE is lower than a target rotating speed NE0 in a transient state where a rotating speed deviation ΔNE is not smaller than a predetermined value, an increment of a second demanded torque by correcting ignition timing to be advanced is set larger than an increment of a first demanded torque by correcting an intake quantity to be increased. When the engine rotating speed NE is higher than the target rotating speed NE0 in the transient state, a decrement of the second demanded torque by correcting the ignition timing to be retarded is set greater than a decrement of the first demanded torque by correcting the intake quantity to be decreased.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a control device for an internal combustion engine that controls the engine speed during idle operation, and more particularly to a control technique suitable for a transient state in which the engine speed changes suddenly due to load fluctuations.

  Conventionally, in an internal combustion engine mounted on a vehicle or the like, feedback control is performed so that the engine speed during idle operation becomes a target speed, which is called ISC (Idle Speed Control) control. This is because the engine speed approaches the target speed by correcting the intake air amount and the ignition timing in accordance with the deviation between the current engine speed calculated based on the signal of the crank position sensor and the target speed. Is to control.

  The feedback gain of such ISC control is set so as not to cause instability of control such as hunting in a steady state where the engine speed fluctuation is relatively small. In a transient state in which the engine load greatly fluctuates due to a change in state, a sudden change in the engine speed cannot be sufficiently suppressed, and the rotation may temporarily drop or may be increased.

  In this regard, for example, the control device described in Patent Document 1 not only performs feedback correction based on the engine speed, but in parallel with this, the intake air amount is corrected by feedforward according to the operating state of the auxiliary machine. I have to. Thus, even if the feedback gain is not increased so much, the correction amount of the intake air amount becomes large in the transient state, and a sudden change in the engine speed can be suppressed to some extent.

JP 09-032612 A

  By the way, in the transient state in which the load greatly fluctuates as described above, the influence of the intake transport delay in the intake system of the internal combustion engine appears strongly, so that even if the correction amount of the intake air amount is increased, the cylinder is filled. The amount of intake air does not change immediately. Further, even if the engine speed is the same, the amount of intake air charged in the cylinder varies, and the ignition timing also varies toward an advance angle or a delay angle accordingly.

  For this reason, for example, when the engine speed drops due to a sudden increase in load and becomes lower than the target speed, the intake air amount is corrected to increase in accordance with the deviation in the engine speed, and the ignition timing is corrected to advance. However, the increase of the engine torque due to this could not be in time, and there was a risk of stalling. That is, since the intake air amount delay is large as described above, the intake air amount in the cylinder does not immediately increase sufficiently. If the ignition timing varies at this time, the engine torque increases. Because it will be delayed.

  On the other hand, if the engine speed becomes higher than the target speed due to a sudden decrease in load, the intake amount is corrected to decrease according to the deviation in the engine speed, and the ignition timing is retarded. In this case as well, the intake air amount in the cylinder does not decrease immediately. If the ignition timing varies at this time, the engine torque does not decrease in time and the rotation increases.

  In consideration of such problems, the object of the present invention is to sufficiently control engine speed during idle operation while ensuring stability of steady-state control and sufficient engine stall and rotation in a transient state. It is to suppress.

  The inventor of the present application pays attention to the fact that the delay of the intake air becomes large in the transient state as described above, and improves the controllability of the engine speed by more effectively controlling the ignition timing with less delay. did.

  Specifically, the present invention corrects the intake air amount and the ignition timing in accordance with the deviation of the engine speed from the target speed (rotational speed deviation) during the idling operation of the internal combustion engine, so that the engine speed becomes the target speed. A control device for an internal combustion engine that performs feedback control so as to approach the number, and this control device controls the first required torque for controlling the intake air amount and the ignition timing based on the rotational speed deviation. It is assumed that each of the second required torques is calculated.

  When the engine speed is lower than the target engine speed in a transient state where the engine speed deviation is larger than a predetermined value, the amount of increase in the second required torque for correcting the ignition timing leads to the intake air amount. The first and second required torques are calculated so as to be larger than the increase in the first required torque for correcting the increase amount. On the other hand, if the engine speed is higher than the target speed, the ignition timing is set. The first and second required torques are calculated so that the amount of decrease in the second required torque for correcting the retard angle is greater than the amount of decrease in the first required torque for correcting the amount of intake air. It was set as the structure to do.

  In the control device configured as described above, during the idling operation of the internal combustion engine, feedback control is performed so that the engine speed approaches the target speed by correcting the intake air amount and the ignition timing according to the speed deviation. The That is, the first and second required torques are calculated based on the rotational speed deviation, the intake amount is controlled based on the first required torque, and the ignition timing is controlled based on the second required torque. Is done.

  Here, first, if the first and second required torques are basically calculated so that even if the rotational speed deviation fluctuates, it does not change so much, a steady state where the fluctuation of the engine rotational speed is relatively small. Therefore, it is possible to prevent instability of control such as hunting. For this purpose, for example, the value of the proportional gain that is multiplied by the rotational speed deviation when calculating the required torque may be set to be small.

  Further, for example, in a transient state where the operating state of the auxiliary machine has changed and the rotational speed deviation has become larger than a predetermined value due to a load change, the increase change of the second required torque is made larger than the first required torque. . For example, when the auxiliary machine starts operation and the engine speed drops due to a sudden increase in load and the speed deviation becomes large, the increase in the second required torque for controlling the ignition timing is calculated as the intake air amount. It is made larger than the increase amount of the first required torque for controlling.

  In this way, the ignition timing is controlled to the advance side earlier based on the second required torque, and therefore the engine torque is quickly increased by the advance control of the ignition timing with high responsiveness. be able to. As a result, the engine speed that has fallen as described above increases, and engine stall is suppressed. That is, the engine stall resistance is improved.

  On the other hand, if the auxiliary machine stops operating, the engine speed increases due to a sudden decrease in load, and the engine speed deviation increases, the decrease in the second required torque for controlling the ignition timing is reduced by the intake amount. It is made larger than the reduction amount of the first required torque for control. In this way, the ignition timing is controlled earlier and more retarded based on the second required torque, and the engine torque can be quickly reduced by retarding the ignition timing with high responsiveness. Can do.

  Therefore, it is possible to sufficiently suppress the engine speed from rising exceeding the target rotational speed. Moreover, since the amount of decrease in the first required torque is relatively small, the amount of intake air controlled based on the first required torque is not so small. Therefore, even if the load suddenly increases thereafter, the delay of the intake amount that is increased accordingly becomes small, and this also improves the engine stall resistance.

  According to the present invention, during the idling operation of the internal combustion engine, the intake air amount and the ignition timing are set such that the engine speed approaches the target speed according to the first and second required torques calculated based on the speed deviation. When each control is performed, in a transient state in which the delay in control of the intake air becomes large, the control of the engine speed can be improved by effectively controlling the ignition timing with a small delay, thereby increasing the engine speed. And the rise of rotation can be sufficiently suppressed.

It is a figure showing a schematic structure of an engine concerning an embodiment. It is a graph which shows the relationship between the rotation speed of an engine and torque in the ISC control of embodiment. It is a flowchart figure which shows the flow of a specific process of ISC control. FIG. 3 is a view corresponding to FIG. 2 showing a required torque in a steady state. FIG. 3 is a view corresponding to FIG. 2 showing a required torque in a transient state.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, the case where the present invention is applied to a gasoline engine will be described as an example. However, the present invention is not limited to this, and an internal combustion engine using a gas engine or alcohol fuel may be used.

(Schematic configuration of the engine)
FIG. 1 shows a schematic configuration of an engine 1 according to the present embodiment. The engine 1 is a multi-cylinder gasoline engine as an example, and each cylinder 2 accommodates a piston 12 so as to define a combustion chamber 11. The piston 12 and the crankshaft 13 are connected by a connecting rod 14, and a crank position sensor 61 that detects the rotation angle (crank angle) of the crankshaft 13 is disposed below the cylinder block 17.

  On the other hand, a cylinder head 18 is fastened to the upper end of the cylinder block 17 to close the upper end of each cylinder 2. The cylinder head 18 is provided with a spark plug 20 so as to face the cylinder 2, and is supplied with a voltage from an igniter 21 controlled by an ECU 6 described later to discharge sparks. A water temperature sensor 62 that detects the cooling water temperature of the engine 1 is disposed on the upper side wall of the cylinder block 17.

  An intake passage 3 and an exhaust passage 4 are formed in the cylinder head 18 so as to communicate with the combustion chamber 11 in each cylinder 2. An intake valve 31 is disposed at the downstream end of the intake passage 3 facing the combustion chamber 11 (downstream end of the intake flow), and similarly, an exhaust valve 41 is disposed at the upstream end of the exhaust passage 4 (upstream end of the exhaust flow). It is installed. A valve operating system for operating the intake valve 31 and the exhaust valve 41 is provided in the cylinder head 18.

  As an example, the valve train of the present embodiment includes an intake camshaft 31a and an exhaust camshaft 41a that drive the intake valve 31 and the exhaust valve 41, respectively. The camshafts 31a and 41a are driven by the crankshaft 13 via a timing chain (not shown), so that the intake valve 31 and the exhaust valve 41 are opened and closed at a predetermined timing.

  In the intake passage 3, an air cleaner 32, an air flow meter 63, an intake air temperature sensor 64 (built in the air flow meter 63), and an electronically controlled throttle valve 33 are disposed. The throttle valve 33 is driven by a throttle motor 34 to adjust the intake air amount of the engine 1 by restricting the flow of intake air, and the opening degree (throttle opening degree) is controlled by an ECU 6 described later.

  The intake passage 3 is also provided with an injector 35 for fuel injection for each cylinder 2. The injector 35 is controlled by an ECU 6 to be described later and injects fuel into the intake passage 3. The fuel thus injected is mixed with the intake air and sucked into the cylinder 2, and is ignited by the spark plug 20 and burned. The burnt gas generated thereby flows out into the exhaust passage 4 and is purified by the catalyst 42. Note that an air-fuel ratio sensor 65 is disposed upstream of the catalyst 42.

-ECU-
The ECU 6 includes a known electronic control unit (Electronic Control Unit). Although not shown, the ECU 6 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a backup RAM, and the like. . The CPU executes various arithmetic processes based on the control program and map stored in the ROM. In addition, the RAM temporarily stores calculation results in the CPU, data input from each sensor, and the like, and the backup RAM stores data to be saved when the engine 1 is stopped, for example.

  As described above, the ECU 6 is connected to the crank position sensor 61, the water temperature sensor 62, the air flow meter 63, the intake air temperature sensor 64, the air-fuel ratio sensor 65, and the like. As shown in FIG. An accelerator opening sensor 67 for detecting the operation amount (accelerator opening) of the accelerator pedal 7 is also connected. Further, the ECU 6 receives signals indicating the operating states of various auxiliary machines. For example, a signal indicating ON / OFF of the air conditioner is input from an air conditioner controller 66 that controls the operating state of the air conditioner.

  Then, the ECU 6 executes various control programs based on signals input from the various sensors and the like, so that the target torque of the engine 1 is determined based on the accelerator opening, the load and rotation speed of the engine 1, or the vehicle speed. And control of the ignition timing by the spark plug 20, control of the throttle opening by the throttle motor 34 (ie, control of the intake air amount), and control of fuel injection by the injector 35 so as to output this target torque. To do.

  Here, the target torque of the engine 1 is a torque that can realize the behavior required by the driver with respect to the vehicle by cooperative control of the engine 1 and the transmission. By using the control based on “torque” that is closely related, drivability can be improved. That is, in the present embodiment, so-called torque demand type engine control is performed.

  In such torque demand type engine control, a torque required for the engine 1 is obtained by adding a torque corresponding to a loss such as friction that is lost in the engine 1 or the power transmission system to the driving force required by the driver for the vehicle. And the intake air amount, fuel injection amount, ignition timing, and the like are controlled so as to realize this. Further, as described below, the ECU 6 performs feedback control so that the engine speed (engine speed) during idle operation becomes the target speed (ISC control).

(ISC control)
In the ISC control, during the idling operation of the engine 1, the intake air amount and the ignition timing are fed back according to the deviation (NE-NE0: hereinafter, the rotational speed deviation ΔNE) so that the engine rotational speed NE becomes the target rotational speed NE0. It is to correct. In the present embodiment, torque demand type engine control is basically used, and therefore, in ISC control, the required torque for controlling the intake air amount and the ignition timing is calculated based on the rotational speed deviation ΔNE.

  That is, as an example, as shown in a graph N shown in FIG. 2, the engine 1 is preliminarily set with a torque necessary to compensate for a loss due to friction or the like and maintain the engine speed NE at the target speed NE0. . In this graph N, the value of “necessary torque” adapted by experiments and calculations is set as a map in consideration of the increase in mechanical friction and the shear resistance of the oil film as the engine speed NE increases. For example, it is stored in the ROM of the ECU 6.

  As shown in FIG. 2, the “necessary torque” becomes a graph N that rises to the right gradually increasing as the engine speed NE increases. On the other hand, the required torque during the idle operation is represented as a downward-sloping graph R that intersects the graph N at a point P0 corresponding to the target rotational speed NE0. In this way, the required torque at the target rotational speed NE0 matches the “necessary torque”, and the engine rotational speed NE is maintained at the target rotational speed NE0 by the balance of torque.

  For example, when the engine speed NE1 is lower than the target speed NE0 as indicated by a point P1 on the graph R, the required torque T1 calculated based on the speed deviation ΔNE1 is larger than the “necessary torque”. The output torque of the engine 1 (hereinafter referred to as engine torque) increases, and the engine speed NE increases. On the other hand, at the point P2 where the engine speed NE2 is higher than the target speed NE0, the required torque T2 calculated based on the speed deviation ΔNE2 becomes smaller than the “necessary torque”, and the engine speed NE decreases. become.

  That is, the engine rotational speed NE approaches the target rotational speed NE0 by increasing or decreasing the required torque calculated based on the rotational speed deviation ΔNE. As will be described in detail later, such required torque is obtained by multiplying a base value set based on the engine speed NE, the engine water temperature, and the like by correction coefficients kstb1 and kstb2 corresponding to the speed deviation ΔNE. The correction coefficients kstb1 and kstb2 are obtained as a function of the rotational speed deviation ΔNE and the proportional gains K1 and K2.

  In general, the proportional gain of feedback control is directly related to control responsiveness, and in this embodiment, in order to prevent instability of control such as hunting in a steady state where the fluctuation of the engine speed NE is small. It is set to a smaller value. For example, in a transient state where the operating state of an auxiliary machine such as an air conditioner compressor changes and the load fluctuates greatly, the values of the proportional gains K1 and K2 are changed in order to suppress a sudden change in the engine speed NE. Yes.

-Specific processing flow-
Hereinafter, a specific flow of processing of the ISC control will be described along the flowchart of FIG. 3 with reference to FIG. 2 and FIGS. This ISC control routine is executed at a predetermined timing in the ECU 6 after the engine 1 is started.

  First, in step ST1 after the start shown in FIG. 3, it is determined whether or not the engine 1 is idling based on a signal from the accelerator opening sensor 67. For example, if the accelerator opening is equal to or smaller than a predetermined threshold (substantially set to be zero in advance), an affirmative determination (YES) is made and the process proceeds to step ST2, while the accelerator opening exceeds the threshold. If so, a negative determination (NO) is made and the routine of ISC control is exited (END).

  In step ST2, “necessary torque” corresponding to the target rotational speed NE0 set according to the engine water temperature is read from the map of FIG. 2 and set (setting of required torque). If it is detected based on a signal from the air conditioner controller 66 that there is an operating auxiliary machine, a torque necessary for driving this auxiliary machine (preset for each auxiliary machine) is added. The “necessary torque” is set.

  In step ST3, a reserve torque set in advance to “necessary torque” is added to calculate a base value of the first required torque. The reason why the reserve torque is applied in this way is to adjust the engine torque by controlling the ignition timing with high responsiveness. That is, since there is a relatively large delay in the intake air amount control as described above, it is necessary to increase or decrease the engine torque by controlling the ignition timing with a high response.

  For this purpose, the ignition timing must be set to a retarded side to some extent with respect to MBT (Minimum Advance for Best Torque) in advance, but in the air amount control described later, the air-fuel ratio is the stoichiometric air-fuel ratio. Assuming that the ignition timing is MBT, the intake air amount (throttle opening) is controlled. Therefore, the “required torque” set on the assumption of the ignition timing is retarded. The decrease in torque due to is added as reserve torque.

  Therefore, as shown by a solid line graph R1 in FIG. 4, the base value of the first required torque is shown in the graph R described above with reference to the map of FIG. 2 (shown as a broken line graph R2 in FIG. 4). Compared with the reserve torque, the value is larger. Since the “necessary torque” may be used as the base value of the second required torque for controlling the ignition timing, this is as shown by a graph R2 indicated by a broken line in FIG.

  Subsequently, in step ST4, it is determined whether or not the engine 1 is in a steady state. For example, based on a signal from the air conditioner controller 66, a predetermined time after the air conditioner is switched from on to off or from off to on is a transient state in which the rotational speed deviation ΔNE of the engine 1 is larger than a predetermined value due to load fluctuation. Can be determined. It should be noted that the amount of change in the driving torque of an auxiliary device such as an air conditioner may be estimated, and the transient state determined by this.

  And when it determines with it being a transient state as mentioned above, it becomes negative determination (NO) in step ST4, and while progressing to step ST8 mentioned later, it affirmatively determines (YES) that it is a steady state in other cases. The process proceeds to step ST5. In step ST5, correction coefficients kstb1 and kstb2 for correcting the first and second required torques are calculated in accordance with the rotational speed deviation ΔNE of the engine 1.

  The correction coefficient kstb1 for correcting the first required torque is a function of the proportional gain K1 and the rotation speed deviation ΔNE suitable for air amount correction control, and the correction coefficient kstb2 for correcting the second required torque is This is a function of a proportional gain K2 and a rotational speed deviation ΔNE suitable for ignition timing correction control. As an example, the correction coefficients kstb1 and kstb2 can be calculated by the following equations. kstb1 = −K1 × ΔNE + 1, kstb2 = −K2 × ΔNE + 1

  The values of the correction coefficients kstb1 and kstb2 calculated in this way are kstb1 and kstb2 = 1 if the rotational speed deviation ΔNE = 0, and kstb1 and kstb2> 1 if ΔNE <0, and ΔNE>. If 0, 0 <kstb1, kstb2 <1. Further, the values of the proportional gains K1 and K2 are adapted by experiments and calculations, respectively, and are stored in the ROM of the ECU 6. In order to ensure the stability of the control, the values of the proportional gains K1 and K2 in the steady state are set to be small, and this is set to a one-dimensional map that becomes larger as the engine water temperature is lower. Also good.

  In step ST6, the first and second required torques are calculated by multiplying the base values of the first and second required torques by the correction coefficients kstb1 and kstb2, respectively. Specifically, the second required torque will be described with reference to the graph R2 (broken line graph) in FIG. 4. If the engine rotational speed NE matches the target rotational speed NE0 and the rotational speed deviation ΔNE = 0. For example, since the correction coefficient kstb2 = 1, the second required torque becomes the base value.

  Further, at a lower speed side than the target rotational speed NE0, the rotational speed deviation ΔNE <0, the correction coefficient kstb2> 1, and the second required torque becomes larger than the base value. At this time, the second required torque increases as the speed decreases. On the other hand, on the higher rotation side than the target rotation speed NE0, the rotation speed deviation ΔNE> 0, the correction coefficient kstb2 <1, and the second required torque becomes smaller than the base value. At this time, the second required torque is smaller as the speed is higher.

  As described above, the magnitudes of the proportional gains K1 and K2 for correcting the first and second required torques are reflected in the slopes of the graphs R1 and R2 in FIG. 4 via the correction coefficients kstb1 and kstb2. That is, for example, the slope of the graph R2 becomes gentler as the proportional gain K2 decreases, and the degree of change in the required torque with respect to the magnitude (absolute value) of the rotational speed deviation ΔNE decreases. Conversely, as the proportional gain K2 increases, the slope of the graph R2 becomes steeper, and the degree of change in the required torque with respect to the magnitude of the rotational speed deviation ΔNE increases.

  Based on the first required torque thus calculated, in step ST7, it is necessary to obtain the first required torque on the assumption that the air-fuel ratio is the stoichiometric air-fuel ratio and the ignition timing is MBT. The amount of intake air into the cylinder 2 (intake charging efficiency) is obtained, and the throttle opening is controlled in consideration of the engine speed NE and the intake air temperature and pressure. Further, the ignition timing is controlled by referring to a preset one-dimensional map based on the second required torque calculated as described above.

  As described above, in the steady state of the engine 1, the base value set in consideration of the operation of the auxiliary machine is corrected by the correction coefficients kstb1 and kstb2 based on the rotational speed deviation ΔNE to obtain the first and second required torques. Since the proportional gains K1 and K2 for the correction are set to smaller values, the engine speed NE is maintained at the target speed NE0 without causing instability of control such as hunting. can do.

-Switching gain in transient state-
In contrast to the above-described control in the steady state, in step ST8 that proceeds with a negative determination (NO) in step ST4 of the flow of FIG. 3 that the engine 1 has not reached the steady state, the rotational speed deviation ΔNE of the engine 1 becomes greater than a predetermined value. Therefore, the values of the proportional gains K1 and K2 are switched in order to suppress a drop in the engine speed NE and the like. As a result, the first and second required torques are changed to those suitable for the transient state.

  That is, in the transient state in which the rotational speed deviation ΔNE is large as described above, the influence of the intake transportation delay appears strongly, so that the intake air that is charged into the cylinder 2 even if the first required torque is changed. The amount does not change immediately. Further, even if the engine speed NE is the same, the amount of intake air charged in the cylinder 2 varies, and the ignition timing also varies toward an advance angle or a delay angle accordingly.

  For this reason, for example, when the air conditioner is turned on and the engine speed NE suddenly decreases due to a sudden increase in load, the intake air amount is corrected to increase according to the engine speed deviation ΔNE as described above, and the ignition timing is corrected to the advance side. However, the increase in engine torque due to this could not be in time, and there was a risk of stalling. This is because the amount of intake air in the cylinder 2 does not immediately increase sufficiently because the delay in the intake amount is large. If the ignition timing varies at this time, the increase in engine torque is delayed. Because it will end up.

  On the other hand, for example, when the compressor of the air conditioner is turned off and the engine speed NE becomes higher than the target speed NE0 due to a sudden decrease in the load, the intake air amount is corrected to decrease according to the rotational speed deviation ΔNE, and the ignition timing is retarded. In this case as well, the amount of intake air in the cylinder 2 does not decrease immediately. If the ignition timing varies at this time, the engine torque will not decrease in time, and the engine will not rotate. It blows up.

  In consideration of such problems, in the present embodiment, focusing on the fact that the delay of the intake air becomes large in the transient state as described above, by effectively performing the correction control of the ignition timing with a small delay, the engine rotation The controllability of several NEs is improved. Specifically, in step ST8, when the engine speed NE is lower than the target speed NE0, the proportional gain K1 is not changed and the value of the proportional gain K2 is increased. In step ST8, when the engine speed NE is higher than the target speed NE0, the value of the proportional gain K1 is decreased and the value of the proportional gain K2 is increased.

  The values of the proportional gains K1 and K2 in the transient state that are changed in this way are also adapted by experiments, calculations, and the like as in the steady state values, and are stored in the ROM of the ECU 6. The values of the proportional gains K1 and K2 in the transient state may also be set to a one-dimensional map that becomes larger as the engine coolant temperature is lower.

  When the values of the proportional gains K1 and K2 are changed as described above, the first and second required torque graphs R1 and R2 described above with reference to FIG. 4 change as follows. That is, the first required torque graph R1 related to the control of the intake air amount changes from a virtual line to a solid line in FIG. 5 and does not change on the low rotation side than the target rotation speed NE0, but the inclination on the high rotation side. Becomes loose.

  That is, when the engine 1 changes from the steady state to the transient state, the amount of increase in the first required torque corresponding to the rotational speed deviation ΔNE becomes the same as that in the steady state on the lower rotational side than the target rotational speed NE0. On the high speed side, the amount of decrease in the first required torque corresponding to the rotational speed deviation ΔNE is smaller than in the steady state.

  In addition, the second required torque graph R2 related to the ignition timing control changes from a virtual line to a wavy line in FIG. 5, and the slope is steep on both the low speed side and the high speed side of the target rotational speed NE0. Become. That is, the amount of increase in the second required torque corresponding to the rotational speed deviation ΔNE increases on the low rotational side from the target rotational speed NE0, and conversely, on the high rotational side, the second demand corresponding to the rotational speed deviation ΔNE. The amount of torque reduction increases.

  In other words, if the engine 1 changes from the steady state to the transient state, the increase in the second required torque becomes larger than the increase in the first required torque on the low rotation side from the target rotational speed NE0, On the rotation side, the decrease in the second required torque is larger than the decrease in the first required torque. In the present embodiment, the proportional gains K1 and K2 are switched only when the engine speed NE is equal to or lower than the predetermined speed NE *.

  In step ST7, the throttle opening is controlled based on the first required torque using the values of the proportional gains K1, K2 thus switched, and the ignition timing is determined based on the second required torque. Is controlled. Thereby, for example, when the air conditioner is turned on, the engine speed NE falls, and the speed deviation ΔNE increases, the ignition timing is further increased based on the second required torque that increases in accordance with this. It will be controlled to the more advanced side sooner.

  At this time, the throttle opening controlled based on the first required torque increases in the same manner as in the steady state. However, as described above, the control of the highly responsive ignition timing proceeds more quickly. Since the ignition timing on the corner side is controlled, the engine torque can be quickly increased. Therefore, the engine speed NE that has fallen as described above increases, and engine stall is suppressed. That is, the engine stall resistance is improved.

  On the other hand, for example, when the air conditioner is turned off and the engine speed NE rises and the engine speed deviation ΔNE increases, the ignition timing is further increased based on the second required torque that increases in accordance with this. It will be controlled to the retard side earlier. Therefore, the engine torque can be quickly reduced by the retarding control of the ignition timing with high responsiveness, and the engine speed increase that exceeds the target rotational speed NE0 can be sufficiently suppressed.

  At this time, since the amount of decrease in the first required torque corresponding to the rotational speed deviation ΔNE is smaller than that in the steady state, the throttle opening is not so small, but the intake amount has a large delay. Is small. Rather, since the throttle opening does not become too small and the intake air amount does not decrease too much, if the load suddenly increases after that, the delay in the intake air amount increased accordingly becomes small, and the The nature is further improved.

  Therefore, according to the ISC control of the present embodiment, the intake air amount and the ignition timing can be suitably controlled according to the first and second required torques calculated based on the rotational speed deviation ΔNE. That is, by setting the proportional gains K1 and K2 to a small value in the steady state and ensuring the stability of the control, in the transient state where the load fluctuates, the ignition timing is effectively controlled with little delay. The controllability of the engine speed NE can be improved, and engine stall and engine speed can be sufficiently suppressed.

(Other embodiments)
The description of the above-described embodiment is merely an example, and is not intended to limit the configuration or application of the present invention. That is, in the above-described embodiment, the proportional gain K1 of the ISC control in the transient state is not changed when the engine speed NE is lower than the target speed NE0, and is changed to a small value when the engine speed NE is higher than the target speed NE0. On the other hand, the value of the proportional gain K2 is increased regardless of the engine speed NE, but is not limited thereto.

  For example, the value of the proportional gain K1 may not be changed even in a transient state, or may be decreased regardless of the engine speed NE. Further, the value of the proportional gain K1 may be changed to a smaller value when the engine speed NE is lower than the target speed NE0, and may not be changed when the engine speed NE is higher than the target speed NE0.

  Furthermore, the value of the proportional gain K1 may be increased in the transient state, but even in this case, the increase amount of the proportional gain K1 is made smaller than the increase of the proportional gain K2. In other words, when the engine speed NE is lower than the target speed NE0 in the transient state, the increase in the second required torque is larger than the increase in the first required torque, but is higher than the target speed NE0. In this case, the values of the proportional gains K1 and K2 may be set so that the decrease amount of the second required torque is larger than the decrease amount of the first request torque.

  Alternatively, it is not limited to changing the values of the proportional gains K1 and K2, and for example, the first and second required torques are calculated by referring to a map or the like based on the rotational speed deviation ΔNE. May be. In this case, a transient state map is set separately from the steady state map, and as described above, the increase in the second required torque is the first increase amount on the lower side of the target rotational speed NE0 in the transient state. While the increase is larger than the increase in the required torque, the decrease in the second request torque may be larger than the decrease in the first request torque on the high rotation side.

  In the above embodiment, when the proportional gains K1 and K2 are switched in the transient state, the values of the proportional gains K1 and K2 are immediately changed to those corresponding to the transient state. The values of K1 and K2 may be gradually changed from those set corresponding to the steady state to those set corresponding to the transient state.

  Since the present invention can sufficiently suppress engine stalls and engine speed up against load fluctuations while ensuring stability of rotational speed control during idling, it can be applied to, for example, a gasoline engine installed in a passenger car. Excellent effect.

1 engine (internal combustion engine)
6 ECU (control device)
NE engine speed (engine speed)
NE0 Target rotational speed ΔNE rotational speed deviation (deviation)
R1 First required torque graph (first required torque)
R2 Second required torque graph (second required torque)

Claims (1)

An internal combustion engine that performs feedback control so that the engine speed approaches the target speed by correcting the intake air amount and the ignition timing according to the deviation of the engine speed from the target speed during idle operation of the internal combustion engine. An engine control device,
Based on the deviation, a first required torque for controlling the intake air amount and a second required torque for controlling the ignition timing are respectively calculated.
In a transient state where the deviation is larger than a predetermined value, when the engine speed is lower than the target speed, the increase in the second required torque for correcting the advance of the ignition timing is used to increase the intake amount. While calculating the first and second required torques so as to be larger than the increase in the first required torque,
If the engine speed is higher than the target speed in the transient state, the decrease in the second required torque for correcting the ignition timing is the same as the first required torque for correcting the intake amount to be reduced. A control apparatus for an internal combustion engine, characterized in that the first and second required torques are calculated so as to be larger than a decrease.

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