JP2012041852A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promptly boost a supercharging pressure while preventing overshoot of exhaust pressure during accelerating operation.SOLUTION: An engine 10 includes a VVT (variable valve timing system) 32 for setting a phase of an exhaust valve 30 variable; and a supercharger 34 which is variable capacity. An ECU 60 measures acceleration time t required for the exhaust pressure to boost from a state before the accelerating operation to a threshold, when the accelerating operation has started. The shorter the acceleration time t is, the later valve-opening period of the exhaust valve 30 is. As a result, the overshoot of the exhaust pressure is prevented, and thereby the ECU 60 decrease nozzle opening of the supercharger 34 at the accelerating operation and promptly boosts the supercharging pressure. Accordingly, the efficiency of supercharging is enhanced and accelerating performance is improved, while boost of the exhaust pressure is moderately prevented.

Description

  The present invention is suitably used for a diesel engine with a supercharger and the like, and particularly relates to a control device for an internal combustion engine having a variable valve mechanism.

  As a conventional technique, for example, as disclosed in Japanese Patent Application Laid-Open No. 2008-215327, an internal combustion engine control device including a supercharger and a variable valve mechanism is known. In the prior art, when the turbocharger is operated, the opening timing of the intake valve is advanced, the closing timing is retarded, and the opening timing of the exhaust valve is advanced. As a result, in the prior art, the exhaust pressure is increased during operation of the supercharger to improve the supercharging response.

JP 2008-215327 A JP 2004-245104 A JP 2007-192155 A

  By the way, in the prior art mentioned above, in order to improve a supercharging response, it is set as the structure which controls valve timing and raises exhaust pressure. However, when the supercharger is activated, the exhaust pressure first increases and then the supercharging pressure rises following the exhaust pressure. Therefore, a response delay accompanies the increase in the supercharging pressure. For this reason, in the prior art, if an attempt is made to quickly increase the supercharging pressure to the target pressure during acceleration operation, it is necessary to increase (overshoot) the exhaust pressure to a level higher than the pressure during steady operation prior to this. When trying to avoid this overshoot, there is a problem that the responsiveness of the supercharging pressure and the rising speed are limited in some cases.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to quickly increase the supercharging pressure while suppressing an exhaust pressure overshoot during acceleration operation. An object of the present invention is to provide a control device for an internal combustion engine.

The first invention includes a variable valve mechanism that variably sets at least the opening timing of the exhaust valve;
A turbine that receives exhaust pressure, a compressor that is driven by the turbine and that supercharges intake air, and a variable nozzle attached to the turbine, and a variable nozzle whose opening area increases as the opening of the variable nozzle increases. A capacity-type turbocharger;
Acceleration required time measuring means for measuring the time required for the exhaust pressure to rise from the state before the acceleration operation to a predetermined threshold when the acceleration operation is started, as the acceleration required time;
A means for delaying the valve opening timing of the exhaust valve by the variable valve mechanism when acceleration operation is performed, and a retard correction amount that is an amount for delaying the valve opening timing from that during steady operation, Exhaust retard correction means for increasing the shorter the required time,
A nozzle opening degree control means for reducing the opening degree of the variable nozzle of the supercharger as compared with the non-correction time of the valve opening time when correcting the valve opening timing by the exhaust retard angle correcting means;
It is characterized by providing.

  According to the second invention, the nozzle opening control means is configured to increase the opening of the variable nozzle when the exhaust pressure becomes a predetermined reference value or more.

According to a third aspect of the present invention, the most retarded angle correction amount that is the most retarded angle correction amount that most delays the opening timing of the exhaust valve within a range in which the pump loss is suppressed to an allowable limit or less is calculated based on the operating state of the internal combustion engine. Means for calculating the most retarded angle correction amount,
And a retard limiter for limiting the retard correction amount so that the valve opening timing set by the exhaust retard correction unit is earlier than the valve opening timing corresponding to the maximum retard correction amount.

  According to a fourth aspect of the present invention, when the exhaust pressure is higher than the exhaust pressure during normal operation after the exhaust valve opening timing is corrected by the exhaust retard correction means, the corrected exhaust pressure and the normal operation A corrected exhaust pressure control means for increasing the retardation correction amount as the difference from the exhaust pressure increases is provided.

According to a fifth aspect of the present invention, there is provided an exhaust pressure acquisition means for acquiring an exhaust pressure before correcting the valve opening timing by the exhaust retard angle correction means and an exhaust pressure after correcting the valve opening timing,
Learning means for calculating a pressure difference between the exhaust pressure before the correction and the exhaust pressure after the correction, and learning a relationship between the pressure difference and the retardation correction amount.

According to a sixth aspect of the present invention, in-cylinder pressure acquisition means for acquiring the in-cylinder pressure at the valve opening timing before and after correcting the valve opening timing by the exhaust retard angle correction means. When,
Learning means for calculating a pressure difference between the in-cylinder pressure before the correction and the in-cylinder pressure after the correction, and learning a relationship between the pressure difference and the retardation correction amount.

  7th invention is equipped with the threshold value setting means which sets the said threshold value based on the engine speed and fuel injection quantity of an internal combustion engine.

  According to the first aspect of the invention, when the acceleration operation is performed, the exhaust retard angle correction means shortens the acceleration required time, that is, increases the exhaust pressure increase rate, the exhaust valve closing timing (EVO). Can be increased. Thereby, it is possible to suppress an exhaust pressure overshoot that is likely to occur particularly during rapid acceleration. Further, by suppressing the increase in exhaust pressure in this way, the nozzle opening degree control means can drive the variable nozzle of the supercharger closer to the closed side than the prior art, and can quickly increase the supercharging pressure. . Accordingly, during acceleration operation, it is possible to improve supercharging efficiency and improve acceleration performance while suppressing exhaust pressure overshoot.

  According to the second aspect of the invention, the nozzle opening degree control means opens the variable nozzle to moderately suppress the increase in the supercharging pressure after the exhaust pressure has increased to a certain level, and overshoots (overshoots) the supercharging pressure. (Supercharging) can be prevented. Therefore, control for reducing the fuel injection amount and the supercharging amount in order to cope with overcharging becomes unnecessary, and it is possible to prevent a feeling of deceleration and a feeling of popping out during the acceleration operation.

  According to the third aspect, the most retarded angle correction amount calculating means calculates the most retarded angle correction amount at which the pump loss is suppressed to an allowable limit or less, and the retard angle limiting means is retarded by the most retarded angle correction amount. The angle correction amount can be limited. Therefore, it is possible to prevent the EVO from being retarded excessively by the exhaust retard angle correcting means, and to ensure drivability while exhibiting the retard effect of the EVO.

  According to the fourth aspect of the invention, the corrected exhaust pressure control means delays the EVO and exhausts the exhaust gas as the exhaust pressure after the EVO is corrected by the exhaust retard correction means deviates from the steady state to the high pressure side. The atmospheric pressure can be reduced. As a result, the exhaust pressure can be quickly converged to a steady state.

  According to the fifth invention, the learning means calculates a pressure difference between the exhaust pressure before the EVO is corrected by the exhaust retardation correction means and the corrected exhaust pressure, and the pressure difference and the retardation correction amount are calculated. And can learn the relationship. As a result, individual differences and changes with time of the internal combustion engine can be absorbed, and the retardation correction amount calculated based on the required acceleration time can be optimized. Therefore, the exhaust pressure can be accurately controlled by the exhaust retard angle correcting means.

  According to the sixth invention, the learning means calculates the pressure difference between the cylinder pressure before the EVO correction by the exhaust retardation correction means and the cylinder pressure after the correction, and the relationship between the pressure difference and the retardation correction amount. Can learn. As a result, individual differences and changes with time of the internal combustion engine can be absorbed, and the same effects as the fifth invention can be obtained.

  According to the seventh aspect, the threshold setting means calculates the threshold based on the engine speed of the internal combustion engine and the fuel injection amount, so that the magnitude of the threshold is appropriately set with respect to the exhaust pressure during steady operation. Can be set.

It is a whole block diagram for demonstrating the system configuration | structure of Embodiment 1 of this invention. This is map data for determining the retardation correction amount EVOh based on the acceleration required time t. This is map data for determining the retardation correction amount EVOh based on the differential pressure between the exhaust pressure after EVO correction and the steady exhaust pressure. It is a timing chart which shows the control state of the engine implement | achieved by Embodiment 1 of this invention. In Embodiment 1 of this invention, it is a flowchart of the control performed by ECU. In Embodiment 1 and 2 of this invention, it is explanatory drawing for demonstrating the content of learning control. In Embodiment 2 of this invention, it is a flowchart of the control performed by ECU.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
The first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an overall configuration diagram for explaining a system configuration according to the first embodiment of the present invention. The system of the present embodiment includes an engine 10 as an internal combustion engine composed of, for example, a diesel engine. Each cylinder of the engine 10 has a combustion chamber 14 formed by a piston 12, and the piston 12 is connected to a crankshaft 16. The engine 10 also includes an intake passage 18 that sucks intake air into each cylinder, and an exhaust passage 20 that discharges exhaust gas from each cylinder. The intake passage 18 is provided with an electronically controlled throttle valve 22 that adjusts the amount of intake air based on the accelerator opening and the like, and an intercooler 24 that cools the intake air. Each cylinder has a fuel injection valve 26 for injecting fuel into the combustion chamber 14 (in the cylinder), an intake valve 28 for opening and closing the intake passage 18 with respect to the cylinder, and an exhaust passage 20 in the cylinder. And an exhaust valve 30 that opens and closes.

  The engine 10 also includes a VVT (Variable Valve Timing system) 32 that variably sets the phase (at least the valve opening timing) of the exhaust valve 30. The VVT 32 has a known configuration as disclosed in, for example, Japanese Patent Laid-Open No. 2000-87769, and constitutes the variable valve mechanism of the present embodiment. In brief, first, the valve train of the exhaust valve 30 includes a cam shaft provided with an exhaust cam and a timing pulley provided on the cam shaft. During operation of the engine, rotation of the crankshaft 16 is transmitted to the timing pulley via the timing chain, and the camshaft (exhaust cam) is rotationally driven by the timing pulley. Thereby, the acting force of the exhaust cam is transmitted to the exhaust valve 30 via the rocker arm, and the exhaust valve 30 opens and closes at a predetermined timing. In this valve train, the VVT 32 includes an actuator that relatively rotates the camshaft and the timing pulley, and is configured to change the phase of the exhaust valve 30 in accordance with the relative rotation angle between the two.

  The engine 10 also includes a variable capacity supercharger 34 that supercharges intake air using exhaust pressure. The supercharger 34 has a known configuration, and includes a turbine 36 provided in the exhaust passage 20, a compressor 38 provided in the intake passage 18, a variable nozzle 40 attached to the turbine 36, and a variable nozzle 40. Actuator 42 for changing the opening degree (nozzle opening degree). When the supercharger 34 operates, the turbine 36 receives the exhaust pressure and drives the compressor 38, and the compressor 38 supercharges the intake air. Further, when the supercharger 34 opens the variable nozzle 40 and increases the nozzle opening, the opening area of the turbine 36 increases, and when the variable nozzle 40 is driven to the closed side and the nozzle opening is decreased, the turbine opening is increased. The opening area of 36 is configured to be reduced. Thereby, when the nozzle opening is decreased, the exhaust pressure is increased to improve the supercharging efficiency, and when the nozzle opening is increased, the exhaust pressure is decreased.

  Furthermore, the system according to the present embodiment includes a sensor system necessary for controlling the vehicle and the engine, and an ECU (Electronic Control Unit) 60 that controls the operating state of the engine 10. First, the sensor system will be described. The sensor system includes a crank angle sensor 44 that outputs a signal synchronized with the rotation of the crankshaft 16, an airflow sensor 46 that detects the intake air amount, and an in-cylinder pressure that detects the in-cylinder pressure. A sensor 48, an intake pressure sensor 50 that detects the pressure (supercharging pressure) of the intake air, an exhaust pressure sensor 52 that detects the exhaust pressure, and an accelerator opening sensor that detects the accelerator operation amount (accelerator opening) of the engine 54.

  In addition to the sensors 44 to 54, the sensor system includes, for example, a water temperature sensor that detects the temperature of engine cooling water, an air-fuel ratio sensor that detects an exhaust air-fuel ratio, and the like. Is connected to the input side. Various actuators including the throttle valve 22, the fuel injection valve 26, the VVT 32, the actuator 42 of the supercharger 34, and the like are connected to the output side of the ECU 60.

  Then, the ECU 60 detects operation information of the engine with a sensor system, and performs operation control by driving each actuator based on the detection result. Specifically, the engine speed (engine speed) and the crank angle are detected based on the output of the crank angle sensor 44, and the fuel injection is performed based on the intake air amount detected by the air flow sensor 46 and the engine speed. Calculate the amount. Further, the fuel injection timing is determined based on the crank angle, and the fuel injection valve 26 is driven. Further, the ECU 60 drives the VVT 32 according to the operating state of the engine to control the valve timing of the exhaust valve 30, and also drives the actuator 42 of the supercharger 34 to control the supercharging pressure and the exhaust pressure. .

[Features of Embodiment 1]
In an engine with a supercharger, when an acceleration operation is performed, first, the exhaust pressure rises. As a result, the rotational speed of the turbine 36 (turbo rotational speed) increases, and then the supercharging pressure rises. For this reason, in the prior art, if the boost pressure is quickly increased to the target pressure, the exhaust pressure needs to be increased more than the pressure during steady operation in consideration of the response delay. Shooting is likely to occur. If this overshoot is to be avoided, the responsiveness and the rising speed of the supercharging pressure are limited, and the acceleration feeling is deteriorated. Further, when the exhaust pressure rises greatly, overshoot (overcharge) also occurs in the supercharging pressure. For this reason, in the prior art, when overcharging occurs, control for reducing the fuel injection amount and the supercharging amount may be performed to ensure the reliability of the intake system and the like. However, when the fuel injection amount is decreased, a feeling of deceleration is likely to occur during acceleration operation. In addition, when the supercharging amount is decreased, the turbo pressure and the supercharging pressure are sequentially decreased after the exhaust pressure first decreases, so that the pump loss is temporarily reduced at the timing when only the exhaust pressure is decreased. As a result, the torque is relatively increased and an acceleration feeling (feeling of popping out) that is not related to the accelerator operation is likely to occur.

  For this reason, in the present embodiment, when acceleration operation is performed, the EVO retard angle correction control delays the valve closing timing (EVO) of the exhaust valve 30 according to the exhaust pressure rising speed, thereby reducing the exhaust pressure overshoot. Suppress. In parallel with the EVO retard angle correction control, the nozzle opening degree of the supercharger 34 is decreased by the nozzle opening degree control to improve the acceleration performance. Hereinafter, EVO retardation correction control and nozzle opening control will be described.

(EVO retard angle correction control)
In this control, EVO is delayed (retarded) greatly with respect to the valve opening timing during steady operation as the exhaust pressure increase rate during acceleration operation increases. The exhaust pressure increase rate is measured by the time required for the exhaust pressure to increase from the state before the acceleration operation to a predetermined threshold (hereinafter referred to as acceleration required time t). The setting of the threshold will be described later. In general, when the EVO is retarded, the EVO moves away from the explosion top dead center by that amount, so that blowdown from the cylinder to the exhaust passage is reduced, and an increase in exhaust pressure is suppressed.

  Therefore, in the EVO retard angle correction control, as shown in FIG. 2, the shorter the acceleration required time t, that is, the greater the exhaust gas increase rate, the more retarded the EVO is with respect to the valve opening timing during steady operation. The amount to be increased (hereinafter referred to as retardation correction amount EVOh) is increased, and the increase in exhaust pressure is suppressed in accordance with the retardation correction amount EVOh. Here, FIG. 2 is map data for determining the retardation correction amount EVOh based on the required acceleration time t, and is stored in the ECU 60 in advance. According to the EVO retard angle correction control, when the exhaust pressure increase rate is large, the EVO is largely corrected to the retard angle side, and an exhaust pressure overshoot that tends to occur particularly during sudden acceleration can be suppressed. In addition, when the exhaust pressure increase rate is relatively small, the retardation correction amount EVOh can be reduced to prevent the exhaust pressure from being suppressed more than necessary. Therefore, EVO can be appropriately controlled in accordance with the exhaust pressure increasing speed, and the exhaust pressure can be quickly increased within a range that does not overshoot.

  The above-described threshold is set by the ECU 60 with reference to the exhaust pressure during steady operation (hereinafter referred to as steady exhaust pressure). The steady operation time is a time point when the acceleration operation shifts from the transient state immediately after the start to the steady state. In the present embodiment, the threshold value is set to a value of about 90% of the steady exhaust pressure, for example. The steady exhaust pressure is calculated based on the engine speed and the fuel injection amount when the acceleration operation is started. The steady exhaust pressure has a characteristic that it increases as the engine speed increases and the fuel injection amount increases. The ECU 60 calculates the steady exhaust pressure based on the engine speed and the fuel injection amount. Map data is stored in advance. Therefore, an appropriate threshold value can be set according to the operating state of the engine.

  On the other hand, if EVO is retarded too much, pump loss increases, torque decreases, and drivability deteriorates. For this reason, in the EVO retard angle correction control, the most retarded angle correction amount EVOhmax, which is the retard angle correction amount that most delays the EVO within a range in which the pump loss is suppressed below the allowable limit, is calculated. Then, before actually correcting the EVO, the retardation correction amount EVOh is limited so that the corrected EVO is earlier than the valve opening timing corresponding to the maximum retardation correction amount EVOhmax. The latest valve opening timing within a range where the pump loss is less than or equal to the allowable limit varies depending on the operating state of the engine (for example, engine speed, intake air amount, etc.). Map data for calculating the most retarded correction amount EVOhmax based on the current EVO or the like is stored in advance. This data can be easily obtained by measurement with an actual machine.

  The ECU 60 calculates the most retarded angle correction amount EVOhmax based on the map data, and finally calculates the smaller one of the most retarded angle correction amount EVOhmax and the retarded angle correction amount EVOh calculated based on the required acceleration time t. Used as a retardation correction amount. In the present embodiment, the value of EVO is defined such that the retard direction is a positive direction, and is set to increase as the delay is delayed. Further, the range of EVO where the pump loss is less than the allowable limit is defined as a range where the decrease in torque caused by the pump loss is small enough to be ignored in practice. According to the above control, it is possible to prevent the EVO from being retarded excessively by the EVO retard angle correction control, and to ensure drivability while exhibiting the effect of the control.

  Further, after execution of the EVO retardation correction control, the corrected EVO control is executed in order to quickly converge the exhaust pressure to the steady exhaust pressure. Specifically, in the corrected EVO control, when the exhaust pressure after correcting the EVO (corrected exhaust pressure) is higher than the steady exhaust pressure, the differential pressure between the corrected exhaust pressure and the steady exhaust pressure is large. The retard correction amount EVOh is increased accordingly. This process is executed using the map data of FIG. FIG. 3 is map data for determining the retardation correction amount EVOh based on the differential pressure between the exhaust pressure after EVO correction and the steady exhaust pressure. According to the post-correction EVO control, after the execution of the EVO retard angle correction control, the exhaust gas pressure can be retarded and the exhaust pressure can be lowered as the post-correction exhaust pressure deviates from the steady exhaust pressure to the high pressure side. The exhaust pressure can be quickly converged to a steady state.

(Nozzle opening control)
In this control, when the EVO is corrected by the EVO retard angle correction control, the nozzle opening of the supercharger 34 is reduced as compared with the case where the EVO is not corrected (conventional technology). In the prior art, it is necessary to suppress the exhaust pressure that tends to overshoot below the upper limit reference value (criteria) in the design by opening the variable nozzle early during acceleration operation. The acceleration performance of the vehicle is limited. On the other hand, in the present embodiment, the exhaust pressure overshoot is suppressed by the EVO retard angle correction control. Therefore, in the nozzle opening control, the variable nozzle 40 can be driven closer to the closed side than in the prior art. Thereby, a supercharging pressure can be raised rapidly, a supercharging efficiency can be improved, and acceleration performance can be improved.

  In the nozzle opening control, when the exhaust pressure is less than a predetermined reference value (for example, the above-described threshold value), the nozzle opening is held in a reduced state as described above. When the exhaust pressure becomes equal to or higher than the reference value, the variable nozzle 40 is driven to the open side, and the nozzle opening is increased as compared with the case where the exhaust pressure is less than the reference value. Here, the reference value is set to a pressure value suitable for starting the overcharge suppression operation in consideration of a response delay of the supercharging pressure and the like. Note that the threshold value is not necessarily used as the reference value. According to this control, after the exhaust pressure has increased to a certain level, the variable nozzle 40 can be opened to moderately suppress the increase in the supercharging pressure and prevent oversupercharging. Therefore, control for reducing the fuel injection amount and the supercharging amount in order to cope with overcharging becomes unnecessary, and it is possible to prevent a feeling of deceleration and a feeling of popping out during the acceleration operation.

(Learning angle correction learning control)
Further, in the present embodiment, the amount of change in the exhaust pressure with respect to the EVO correction amount (retard angle correction amount EVOh) is learned. In this learning control, an exhaust pressure difference ΔP, which is a pressure difference between the exhaust pressure before correcting the EVO by the EVO retardation correction control (pre-correction exhaust pressure) and the corrected exhaust pressure, is calculated, and this exhaust pressure difference ΔP And the retardation correction amount EVOh are learned (see FIG. 6 described later). The result of the learning control is reflected in the map data in FIG. 2 that determines the retardation correction amount EVOh based on the acceleration required time t. As an example of this reflection method, the exhaust pressure difference ΔP is smaller than the target value even though the retard correction amount EVOh1 is calculated at an arbitrary acceleration required time t1 and EVO is corrected based on this calculated value. If this is the case, the characteristics of the map data are changed so that the retardation correction amount EVOh1 increases for the same required acceleration time t1. According to the learning control described above, it is possible to optimize the retardation correction amount EVOh calculated based on the required acceleration time t by absorbing individual differences and changes with time of the engine. Therefore, the exhaust pressure can be accurately controlled by the EVO retardation correction control.

  Next, with reference to FIG. 4, the effect at the time of performing said each control is demonstrated. FIG. 4 is a timing chart showing a control state of the engine realized by the first embodiment of the present invention. In this figure, the characteristic line according to the present embodiment is indicated by a solid line, and the characteristic line of the prior art is indicated by a dotted line. First, at the time point (a) in FIG. 4, when the acceleration operation is started, the exhaust pressure starts to rise, and the measurement of the acceleration required time t is started by the EVO retardation correction control. Further, the supercharging pressure control is executed by the ECU 60, and the target supercharging pressure (shown by a two-dot chain line) set by this control is gradually increased. At this time, the nozzle opening degree of the supercharger 34 is maintained in a state of being reduced from the prior art by the nozzle opening degree control before the time point (b) when the exhaust pressure reaches the threshold value, and EVO retardation correction control is performed. The supercharging efficiency is set high on the assumption that

  Next, when the exhaust pressure reaches the threshold value at the time point (b), the correction of the EVO by the EVO retard angle correction control is started, and the EVO is retarded based on the acceleration required time t. As a result, the exhaust pressure rises without overshooting within the range below the upper reference value. At this time, since the nozzle opening degree of the supercharger is set to be small by the nozzle opening degree control, the rising speed of the exhaust pressure becomes faster than that of the prior art. As a result, the supercharging pressure also rises quickly, but the nozzle opening is gradually increased by the nozzle opening control accordingly, so the supercharging pressure does not overshoot and is earlier than the prior art. In (c), the target boost pressure is reached. Further, during the period from the time point (c) to the time point (d) when the acceleration is finished, the nozzle opening degree is kept large, and the supercharging pressure is suppressed.

[Specific Processing for Realizing Embodiment 1]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 5 is a flowchart of the control executed by the ECU in the first embodiment of the present invention. In the routine shown in FIG. 5, first, in step 100, it is determined whether or not the acceleration operation has been started based on the accelerator opening or the like.

  When the acceleration operation is started, in step 102, as described above, the steady exhaust pressure Ps is calculated based on the engine speed and the fuel injection amount. In step 104, the exhaust pressure is calculated based on the steady exhaust pressure Ps. The threshold value is calculated. In step 106, the current exhaust pressure P1 detected by the exhaust pressure sensor 52 is read. In step 108, it is determined whether the exhaust pressure P1 is less than a threshold value. If this determination is established, the exhaust pressure P1 has not yet reached the threshold value, so the measurement of the acceleration required time t is started (continued) using the time measurement counter built in the ECU 60. In step 112, the nozzle opening control described above is executed, and the nozzle opening of the supercharger 34 is set to the decreasing side. Next, in step 114, it is determined whether or not the acceleration operation is continuing. If this determination is established, the process returns to step 102. If the determination in step 114 is not established, the time measurement counter is cleared in step 116 and the process is terminated.

  On the other hand, if the determination in step 108 is established, the exhaust pressure P1 is equal to or greater than the threshold value, and the required acceleration time t is determined. In step 118, as described above, the nozzle opening is gradually increased by nozzle opening control. Next, at step 120, the map correction data EVOh is calculated with reference to the map data shown in FIG. 2 based on the acceleration required time t. At step 122, the maximum retardation correction value EVOhmax is calculated as described above. Next, at step 124, it is determined whether or not the retard correction amount EVOh is less than the most retarded correction amount EVOhmax. If this determination is satisfied, the VVT 32 is driven in step 126, and EVO is corrected by the retardation correction amount EVOh. On the other hand, if the determination in step 124 is not established, in step 128, EVO is corrected by the most retarded correction amount EVOhmax.

  Next, at step 130, the exhaust pressure P2 after correcting the EVO is read. In step 132, an exhaust pressure difference ΔP (= P2−P1) before and after correction is calculated, and the relationship between this exhaust pressure difference ΔP and the actual retardation correction amount (EVOh or EVOhmax) used for correcting EVO. To learn. Then, the map data in FIG. 2 is updated based on the learning result.

  Next, at step 134, it is determined whether or not the corrected exhaust pressure P2 is higher than the steady exhaust pressure Ps. If this determination is not established, the routine proceeds to step 116 and the control is terminated. If the determination in step 134 is established, in step 136, a differential pressure (P2-Ps) between the corrected exhaust pressure P2 and the steady exhaust pressure Ps is calculated. In step 138, the post-correction EVO control described above is executed, and the EVO is corrected based on the differential pressure (P2-Ps). Further, in step 140, the corrected exhaust pressure P2 is read again, and the process returns to step 134. Thus, the corrected EVO control in steps 134 to 140 is repeatedly executed until the corrected exhaust pressure P2 becomes equal to or lower than the steady exhaust pressure Ps.

  In the first embodiment, step 110 shown in FIG. 5 shows a specific example of the acceleration required time measuring means in claim 1, step 120 shows a specific example of the exhaust delay angle correcting means, and steps 112 and 118. Shows specific examples of the nozzle opening degree control means in claims 1 and 2. Step 122 represents the most retarded angle correction amount calculating means in claim 3, and steps 124 to 128 represent specific examples of the retard angle limiting means. Further, steps 134 to 140 are specific examples of the corrected exhaust pressure control means in claim 4, steps 106 and 130 are specific examples of the exhaust pressure acquisition means in claim 5, step 132 is specific examples of learning means, and steps. Reference numeral 104 denotes a specific example of the threshold setting means in claim 7.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. The present embodiment is characterized in that, in the same system configuration as in the first embodiment (FIGS. 1 to 3), learning control is performed by the in-cylinder pressure difference instead of the exhaust pressure difference. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 2]
In the present embodiment, the in-cylinder pressure at the EVO is detected by the in-cylinder pressure sensor 48 before and after correcting the EVO by the EVO retard angle correction control. Then, an in-cylinder pressure difference ΔPc that is a pressure difference between the in-cylinder pressure in the EVO before correction and the in-cylinder pressure in the corrected EVO is calculated. In the learning control, as shown in FIG. 6, the relationship between the in-cylinder pressure difference ΔPc and the retardation correction amount EVOh is learned.

  FIG. 6 is an explanatory diagram for explaining the contents of learning control. As shown in this figure, a predetermined central characteristic (reference characteristic) is set between the retard correction amount EVOh and the in-cylinder pressure difference ΔPc (or the exhaust pressure difference ΔP) at the time of engine design or the like. . This central characteristic gives the amount of change in the in-cylinder pressure (exhaust pressure) with respect to the magnitude of the retard correction amount EVOh, and the map data in FIG. 2 described above assumes that the central characteristic at the time of design is maintained. Is set as However, when the influence of individual engine differences (hardware variations) or deterioration over time is large, the center characteristic may be shifted. For this reason, in the learning control, when a deviation occurs in the relationship between the in-cylinder pressure difference ΔPc (exhaust pressure difference ΔP) and the retardation correction amount EVOh, the deviation amount is learned, and the retardation correction amount EVOh is updated. It is configured. The contents of the learning control in the first embodiment described above are almost the same as those in the second embodiment except that the exhaust pressure difference ΔP is used.

[Specific Processing for Realizing Embodiment 2]
FIG. 7 is a flowchart of control executed by the ECU in the second embodiment of the present invention. In the routine shown in FIG. 7, first, in steps 200 to 220, processing similar to that in steps 100 to 120 in the first embodiment (FIG. 5) is executed. In step 222, the pre-correction EVO detected by the in-cylinder pressure sensor 48 is executed. Read in-cylinder pressure at. In steps 224 to 232, processing similar to that in steps 122 to 130 in FIG. 5 is executed. Next, in step 234, the in-cylinder pressure at the corrected EVO is read. In step 236, the in-cylinder pressure difference ΔPc before and after correction is calculated, the relationship between the in-cylinder pressure difference ΔPc and the retardation correction amount EVOh is learned, and the learning result is reflected in the map data in FIG. Further, in steps 238 to 244, processing similar to that in steps 134 to 140 in FIG. 5 is executed.

  As described above, according to the second embodiment, learning control can be performed based on the in-cylinder pressure difference ΔPc instead of the exhaust pressure difference ΔP, thereby obtaining substantially the same operational effects as in the first embodiment. it can. In the second embodiment, steps 206 and 232 in FIG. 7 show a specific example of the exhaust pressure acquisition means in claim 6, steps 222 and 234 show a specific example of the in-cylinder pressure acquisition means, and step 236 shows a step 236. The specific example of the learning means in Claim 6 is shown. Further, specific examples of other means in FIG. 7 are the same as those shown in FIG.

  In the first and second embodiments, the exhaust pressure and the in-cylinder pressure are detected by the sensors 48 and 52. However, in the present invention, without using these sensors, exhaust pressure and in-cylinder pressure are estimated based on engine operation information (engine speed, intake air amount, crank angle, ignition timing, valve timing, etc.). It is good also as composition to do.

  Further, the present invention is not limited to a diesel engine with a supercharger, but can be applied to a gasoline engine.

10 Engine (Internal combustion engine)
12 piston 14 combustion chamber 16 crankshaft 18 intake passage 20 exhaust passage 22 throttle valve 24 intercooler 26 fuel injection valve 28 intake valve 30 exhaust valve 32 VVT (variable valve mechanism)
34 Supercharger 36 Turbine 38 Compressor 40 Variable nozzle 42 Actuator 44 Crank angle sensor 46 Air flow sensor 48 In-cylinder pressure sensor 50 Intake pressure sensor 52 Exhaust pressure sensor 54 Accelerator opening sensor 60 ECU

Claims (7)

A variable valve mechanism that variably sets at least the opening timing of the exhaust valve;
A turbine that receives exhaust pressure, a compressor that is driven by the turbine and that supercharges intake air, and a variable nozzle attached to the turbine, and a variable nozzle whose opening area increases as the opening of the variable nozzle increases. A capacity-type turbocharger;
Acceleration required time measuring means for measuring the time required for the exhaust pressure to rise from the state before the acceleration operation to a predetermined threshold when the acceleration operation is started, as the acceleration required time;
A means for delaying the valve opening timing of the exhaust valve by the variable valve mechanism when acceleration operation is performed, and a retard correction amount that is an amount for delaying the valve opening timing from that during steady operation, Exhaust retard correction means for increasing the shorter the required time,
A nozzle opening degree control means for reducing the opening degree of the variable nozzle of the supercharger as compared with the non-correction time of the valve opening time when correcting the valve opening timing by the exhaust retard angle correcting means;
A control device for an internal combustion engine, comprising:   The control apparatus for an internal combustion engine according to claim 1, wherein the nozzle opening degree control means is configured to increase the opening degree of the variable nozzle when the exhaust pressure becomes a predetermined reference value or more. The most retarded angle correction amount that calculates the most retarded angle correction amount that is the most retarded angle correction amount that most delays the opening timing of the exhaust valve within a range in which the pump loss is suppressed to an allowable limit or less, based on the operating state of the internal combustion engine. A calculation means;
Delay angle limiting means for limiting the delay angle correction amount so that the valve opening timing set by the exhaust gas delay angle correction means is earlier than the valve opening timing corresponding to the maximum delay angle correction amount;
The control device for an internal combustion engine according to claim 1, comprising:   After correcting the valve opening timing of the exhaust valve by the exhaust retard correction means, if the exhaust pressure is higher than the exhaust pressure during normal operation, the difference between the corrected exhaust pressure and the exhaust pressure during normal operation is The control apparatus for an internal combustion engine according to any one of claims 1 to 3, further comprising a corrected exhaust pressure control means for increasing the retardation correction amount as the value increases. Exhaust pressure acquisition means for acquiring the exhaust pressure before correcting the valve opening timing by the exhaust retard angle correction means and the exhaust pressure after correcting the valve opening timing;
Learning means for calculating a pressure difference between the exhaust pressure before correction and the exhaust pressure after correction, and learning a relationship between the pressure difference and the retardation correction amount;
The control apparatus for an internal combustion engine according to any one of claims 1 to 4, further comprising: In-cylinder pressure acquisition means for acquiring the in-cylinder pressure at the valve opening timing before and after correcting the valve opening timing by the exhaust retard correction means, and
Learning means for calculating a pressure difference between the in-cylinder pressure before correction and the in-cylinder pressure after correction, and learning a relationship between the pressure difference and the retardation correction amount;
The control apparatus for an internal combustion engine according to any one of claims 1 to 4, further comprising:   The control device for an internal combustion engine according to any one of claims 1 to 6, further comprising threshold setting means for setting the threshold based on an engine speed and a fuel injection amount of the internal combustion engine.

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