WO2005056995A1

WO2005056995A1 - Engine control unit

Info

Publication number: WO2005056995A1
Application number: PCT/JP2003/015996
Authority: WO
Inventors: Takashi Yoshida; Mamoru Nemoto
Original assignee: Hitachi, Ltd.
Priority date: 2003-12-12
Filing date: 2003-12-12
Publication date: 2005-06-23
Also published as: JP4220518B2; JPWO2005056995A1

Abstract

An engine control unit provided with a variable valve train comprises an acceleration state detection means for detecting the acceleration state of the engine, a valve opening/closing control means which, when the acceleration state of the engine is detected by the acceleration state detection means, performs exhaust valve closing timing shifting control during acceleration for delaying the closing timing of the exhaust valve until the target closing timing. The valve opening/closing control means makes as small as possible the outflow of the exhaust gases remaining in the combustion chamber to an air suction passageway as by delaying, by a predetermined amount of time from the time the acceleration state is detected, the timing for starting the retard angle direction shift of the closing timing of the exhaust valve toward the target closing timing. Thereby, it becomes possible to charge the combustion chamber with a lot of fresh air, avoiding the generation of level difference in engine torque (torque decrease, torque shock) during acceleration, improving acceleration performance and drivability, and, further, smoothly increasing the inner EGR quantity, so that it also becomes possible to improve the air-fuel ratio control accuracy during acceleration.

Description

Engine control equipment

The present invention relates to an engine control device provided with a variable valve mechanism capable of changing the closing timing of an exhaust valve, and particularly to fuel efficiency and exhaust emission characteristics during acceleration (during transient operation). Valve timing with the intake valve delayed by closing the exhaust valve to improve

The present invention relates to a control system for an engine which is capable of minimizing a deterioration in driver's parity which occurs when a control for increasing a burlap amount is performed. Background art

2. Description of the Related Art In recent years, for the purpose of improving the fuel efficiency and exhaust emission characteristics of an automobile engine, a valve operating mechanism that makes opening and closing timings of an intake valve and an exhaust valve variable has become widespread. For example, Japanese Unexamined Patent Publication No. Hei. 8-170550 discloses that, in order to improve fuel efficiency during steady-state operation and to improve exhaust emission characteristics during transient operation (reduction of harmful emissions), During (transient operation), the opening timing of the intake valve is advanced (advanced) compared to the steady operation, and the variable valve mechanism is controlled so that the valve overlap amount of the intake and exhaust valves increases. Has been described.

However, as described in the above publication, if the pulp overlap amount is increased during acceleration, the intake valve is opened in a state where a large amount of exhaust gas remains in the combustion chamber, so that the residual exhaust gas flows into the intake passage ( As a result, the charge of fresh air into the combustion chamber is hindered, and the amount of fresh air sucked into the combustion chamber decreases sharply. As a result, a step (torque reduction, torque shock) occurs in the engine torque, especially during acceleration, which leads to a decrease in acceleration performance, a decrease in drivability (a feeling of backlash, etc.), and a sudden increase in the fresh air volume. With such a decrease, there is a problem that the air-fuel ratio of the air-fuel mixture supplied for combustion greatly deviates from the target air-fuel ratio, and the air-fuel ratio control accuracy also decreases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to delay the closing timing of an exhaust valve during acceleration to improve the fuel efficiency and exhaust emission characteristics. To control to increase the valve overlap amount with It is an object of the present invention to provide an engine control device capable of minimizing a torque reduction and a torque shock that occur in the same case and improving acceleration performance, dryability, air-fuel ratio control accuracy, and the like. Disclosure of the invention

In order to achieve the above object, an engine control device according to the present invention is basically applied to an engine having a variable valve mechanism capable of changing a closing timing of an exhaust valve. Acceleration state detection means for detecting a state, and acceleration-time exhaust valve closing timing shift control for delaying the closing timing of the exhaust valve to a target closing time when the acceleration state of the engine is detected by the acceleration state detecting means. And a valve opening / closing control unit adapted to perform the operation.

The valve opening / closing control means may be configured to detect the acceleration state of the engine by the acceleration state detection means, and then change the closing timing of the exhaust valve to the target closing timing. The acceleration-time exhaust valve closing timing shift control is performed so that the amount of the remaining exhaust gas flowing into the intake passage is reduced as much as possible. In a preferred aspect, the valve opening / closing control means delays a shift start timing of the closing timing of the exhaust valve from the target closing timing in the retard direction by a predetermined time from the acceleration state detection time.

The valve opening / closing control means preferably sets the predetermined time based on an operation state immediately before acceleration of the engine and / or a target operation state during acceleration.

In another preferred aspect, the valve opening / closing control means shifts the closing timing of the exhaust valve to an advanced direction during a period from the detection of the acceleration state until a predetermined time has elapsed, and the predetermined time has elapsed. At this time, the shift of the closing timing of the exhaust valve to the target closing timing in the retard direction is started.

In this case, the valve opening / closing control means preferably determines the amount of advance of the closing timing of the exhaust valve in the advance direction within the predetermined time based on an operating state immediately before acceleration of the engine and / or a target operating state during acceleration. To be set.

In another preferred aspect, the valve opening / closing control means is configured to determine a timing at which the closing timing of the exhaust valve is shifted to the target closing timing in a retarded direction from the time when the acceleration state is detected until a predetermined time elapses. To make it larger after the predetermined time has passed Is done.

On the other hand, in another preferred aspect of the control device according to the present invention, the control device further includes a pressure detection unit configured to detect a pressure in a passage downstream of a throttle valve in the intake passage of the engine, and the valve opening / closing control unit includes the acceleration state. After the detection point, when the pressure in the passage detected by the pressure detection means reaches a threshold value, the shift of the closing timing of the exhaust valve to the target closing timing in the retard direction is started. Is done.

In this case, the valve opening / closing control means preferably sets the threshold value based on an operation state immediately before acceleration of the engine and / or a target operation state during acceleration.

In another preferred aspect, the valve opening / closing control means shifts the closing timing of the exhaust valve to an advanced direction from the time of detection of the acceleration state until the pressure in the passage reaches the threshold value. When the threshold value is reached, the shift of the closing timing of the exhaust valve to the target closing timing in the retard direction is started.

Preferably, the valve opening / closing control means is configured to determine a shift amount in the advance direction of the closing timing of the exhaust valve until the pressure in the passage reaches the threshold value, in an operating state immediately before acceleration of the engine and / or during the acceleration. The setting is made based on the target operating state. In another preferred embodiment, the engine further includes pressure detection means for detecting a pressure at a passage downstream of a throttle valve in an intake passage of the engine, and the valve opening / closing control means includes a valve opening / closing valve for the exhaust valve from the time of detecting the acceleration state. The transition of the closing timing to the target closing timing in the retard direction is started, and when the retarded shifting amount reaches a predetermined amount, the closing timing at that time is reduced by the pressure in the passage detected by the pressure detecting means. It is kept until it exceeds the threshold.

In still another preferred aspect, the engine further includes pressure detection means for detecting a pressure in a passage downstream of a throttle valve in an intake passage of the engine, wherein the valve opening / closing control means detects the pressure by the pressure detection means from the time of detecting the acceleration state. Than the transition speed in the retard direction of the closing timing of the exhaust valve to the target closing timing until the pressure in the passage reaches the threshold value, after the passage pressure in the passage reaches the threshold value. It is made to make it bigger.

In a preferred embodiment of the engine control device according to the present invention having the above-described configuration, when the engine is accelerated, the transition of the closing timing of the exhaust valve to the target closing timing is performed, for example. For example, it is started after a predetermined time delay or after the intake passage pressure has become equal to or higher than the threshold, so that the delay of the closing timing of the exhaust valve to the target closing timing is started. At times, since the pressure in the intake passage is increasing, the amount of residual exhaust gas flowing into the intake passage (internal EGR amount) is significantly reduced, and more fresh air is charged into the combustion chamber 6. Becomes possible. As a result, it is possible to avoid the occurrence of steps (reduced torque, torque shock) in the engine torque during acceleration, and to improve the acceleration performance and the driveability. Furthermore, it is possible to smoothly increase the internal EGR amount. However, it is also possible to improve the accuracy of air-fuel ratio control during acceleration. Brief Description of Drawings

FIG. 1 is a system configuration diagram showing a first embodiment of a control device according to the present invention together with an engine to which the control device is applied.

FIG. 2 is a diagram showing an example of the opening / closing timing of the intake / exhaust valve in each operation region with the crank angle taken on the horizontal axis.

FIG. 3 is a time chart used for explaining an example of the control for shifting the exhaust valve closing timing during acceleration in the first embodiment.

FIG. 4 is a diagram provided for explaining an example of a method of setting a dead time until the start of the delay shift of the exhaust valve to the target phase in the first embodiment.

FIG. 5 is a diagram provided for explaining another example of the method of setting the dead time from the delay of the exhaust valve to the target phase to the start thereof in the first embodiment.

FIG. 6 is a flowchart illustrating an example of an acceleration-time exhaust valve closing timing shift control routine executed by the control unit according to the first embodiment.

FIG. 7 is a time chart provided for explaining an example of the control for shifting the exhaust valve closing timing during acceleration in the second embodiment.

FIG. 8 is a diagram provided for describing an example of a method of setting a dead time from the delay of the exhaust valve to the target phase to the start thereof in the second embodiment.

FIG. 9 is a diagram provided for explaining another example of the method of setting the dead time until the start of the delay shift of the exhaust valve to the target phase in the second embodiment.

FIG. 10 is a flowchart showing an example of an acceleration-time exhaust valve closing timing shift control routine executed by the control tut according to the second embodiment. FIG. 11 is a system configuration diagram showing a third embodiment of the control device according to the present invention together with an engine to which the control device is applied.

FIG. 12 is a time chart for explaining an example of the control of shifting the exhaust valve closing timing at the time of acceleration in the third embodiment.

FIG. 13 is a diagram provided for explaining an example of a method of setting a threshold value at the time of starting the delay shift of the exhaust valve to the target phase in the third embodiment.

FIG. 14 is a diagram that is used to describe another example of a method of setting a threshold value when starting the retard shift of the exhaust valve to the target phase in the third embodiment.

FIG. 15 is a flowchart illustrating an example of an acceleration-time exhaust valve closing timing shift control routine executed by the control unit according to the third embodiment.

FIG. 16 is a time chart for explaining an example of the control of shifting the exhaust valve closing timing during acceleration in the fourth embodiment.

FIG. 17 is a diagram provided for explaining an example of a retard shift amount (limiter) according to the fourth embodiment.

FIG. 18 is a diagram provided for explaining an example of a range of increase in the pressure in the intake passage in the fourth embodiment.

FIG. 19 is a flowchart illustrating an example of an acceleration-time exhaust valve closing timing shift control routine executed by the control unit according to the fourth embodiment.

FIG. 20 is a time chart provided for explaining an example of the control for shifting the exhaust-valve closing timing during acceleration in the fifth embodiment.

FIG. 21 shows the threshold for starting the retard shift of the exhaust valve to the target phase in the fifth embodiment! FIG. 6 is a diagram provided for describing an example of a method of setting values of /.

FIG. 22 is a diagram which is used for describing another example of a method of setting a threshold value and a value at the time of starting the delay shift of the exhaust valve to the target phase in the fifth embodiment.

FIG. 23 is a flowchart illustrating an example of an acceleration-time exhaust valve closing timing shift control routine executed by the control unit according to the fifth embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, some embodiments for carrying out the present invention will be described with reference to the drawings. [First Embodiment]

FIG. 1 is a system configuration diagram showing a first embodiment of a control device according to the present invention together with an engine to which the control device is applied. The engine 1 shown in FIG. 1 is, for example, an in-line four-cylinder engine having a cylinder block 3 and a cylinder head 5, and a cylinder block 3 in which the rotation of a crankshaft (not shown) is connected to a connecting rod 2. A biston 4 which is converted into reciprocating motion and transmitted via the slidably fits. Above the biston 4, a combustion chamber 6 is defined. The combustion chamber 6 has an intake port forming a downstream portion of the intake passage 12 and an exhaust port forming an upstream portion of the exhaust passage 22. It is communicated via an intake valve 7 and an exhaust valve 8 and a spark plug 9 is provided.

The intake valve 7 is provided with a variable valve mechanism 10 capable of changing the opening / closing timing (phase), and the exhaust valve 8 is also provided with a variable valve mechanism capable of changing the opening / closing timing (phase). 1 1 is provided.

In the intake passage 12, an air flow meter 15, a throttle valve 23, and a fuel injection valve 13 are arranged in this order from the upstream side.

The fuel injected into the intake passage 12 (intake port) by the fuel injection valve 13 is sucked into the combustion chamber 6 through the intake valve 7 together with air by the descending operation of the biston 4 (intake stroke). The mixture of fuel and air sucked into the chamber 6 is ignited by an ignition plug 9 and explosively burns, and the combustion gas (exhaust gas) is discharged through an exhaust valve 8 by the piston 4 ascending operation (exhaust stroke). The exhaust gas is discharged to the exhaust passage 22, and is purified by a catalytic converter or the like provided in the exhaust passage 22 and discharged to the outside. In addition to the above configuration, in the present embodiment, control of the variable valve mechanisms 10 and 11 (18), control of the fuel injection amount and fuel injection timing by the fuel injection valve 13 (19), ignition timing A control unit 14 is provided for performing engine control (17) and transmission control (20) such as control of the vehicle. The controller unit 14 includes, in addition to the intake air amount detected by the air flow meter 15 and the throttle opening detected by the throttle sensor 16, crank angle (engine speed), cylinder discrimination, and accelerator pedal depression. Various signals are supplied according to the amount, brake pedal depression amount, intake air temperature, water temperature, exhaust gas temperature, exhaust oxygen concentration, etc., and the control unit 14 performs the above various controls based on those signals. To be. In the present embodiment, the control unit 14 detects that the engine 1 is in an acceleration state (entered) based on, for example, a change rate (acceleration) of an accelerator pedal depression amount. The target engine speed and target engine load during acceleration are calculated based on the output signals from various sensors such as the throttle pedal depression amount, throttle opening sensor, etc., and the throttle is adjusted to satisfy these calculation results. The throttle opening and the opening / closing timing (phase) of the intake valve 7 and the exhaust valve 8 are set.

In the present embodiment, the phases of the intake valve 7 and the exhaust valve 8 are made variable by the variable valve mechanisms 10 and 11 provided for the intake valve 7 and the exhaust valve 8, and the opening and closing timing of each can be changed. It has become. This makes it possible to increase the variable expansion ratio and introduce a large amount of internal EGR (residual exhaust gas). In the partial load operation region, it is possible to reduce the Atkinson cycle and reduce pump loss, thereby improving fuel efficiency. . Further, by optimizing the opening / closing timing of the intake valve 7 and the exhaust valve 8, the scavenging efficiency is improved in the full load range, so that an output improving effect can be obtained.

Here, FIG. 2 shows an example of the opening and closing timing (phase) of the intake and exhaust valves 7 and 9 in each operation region. As can be seen from the figure, for example, when the operating state of the engine 1 is in the low-load operating range (steady operating state), the exhaust valve 8 is closed at, for example, 20 ° CA after the intake top dead center, and the intake valve is closed. When the engine is in the medium load operation area (steady operation state), the intake valve 7 is opened near the intake top dead center, and after the intake top dead center, for example, the exhaust valve 8 is opened at 20 ° CA. When the vehicle is shifted (accelerated) from the low-load operation region to the medium-load operation region (transient operation state), the target opening timing of the intake valve 7 is near the intake top dead center. The target closing timing of the exhaust valve 8 is set to, for example, 40 ° CA after the intake top dead center (the virtual line in the figure).

By the way, when the accelerator pedal is depressed to shift the operating state of the engine from the low-load operation range to the medium-load operation range, that is, when accelerating from the low-load operation range to the medium-load operation range, (Indicated by a broken line in FIG. 3), the advance of the opening timing of the intake valve 7 is started so as to increase the pulp overlap amount (time A), and at the same time, the delay of the closing timing of the exhaust valve 8 is started. Then, before the pressure in the intake passage increases sufficiently due to the expansion of the throttle opening, a large amount of exhaust gas remaining in the combustion chamber 6 flows out into the intake passage (internal EGR). Filling inside 6 is impeded, and the fresh air volume sharply decreases. As a result, a step (decrease in torque, torque shock) occurs in the engine torque during acceleration, leading to a decrease in acceleration performance and a deterioration in drivability (a feeling of backlash, etc.). In addition, a sharp decrease in the fresh air volume may lead to a decrease in air-fuel ratio control accuracy.

Therefore, in the present embodiment, as shown by the solid line in FIG. 3, the control unit 14 depresses the accelerator pedal, and the transition of the operating state of the engine from the low load operation area to the medium load operation area is started. In other words, when the start of acceleration from the low-load operation area to the medium-load operation area is detected based on, for example, the rate of change of the pedal travel of the accelerator pedal (time point A), the throttle opening increases (throttle opening). Initiation of the opening command value) and advancement of the phase (open timing) of the intake valve 7 to the target phase (open timing) (increase of the intake valve phase command value) are started. On the other hand, the phase shift (decrease of the exhaust valve phase command value) of the phase (close timing) of the exhaust valve 8 is delayed at the time B when a predetermined time (wasteful time T a) has elapsed from the time A when the acceleration start is detected. Get started.

The dead time T a is set here based on the operating state (engine speed, engine load) immediately before the start of acceleration, as can be clearly understood from FIG. In the low-rotation, low-load region immediately before the start of acceleration, the residual exhaust gas flows into the intake passage 12 because of the development of negative pressure in the intake passage and the long time required per cycle ( Internal EGR) Large amount. Therefore, in the low rotation speed and low load region, the dead time T a is set long. On the other hand, in the case of high rotation and 直前 load region immediately before the start of acceleration, the residual pressure of the intake passage 1 2 is low because the negative pressure in the intake passage has not developed and the time required per cycle is short. Outflow (internal EGR) is small. Therefore, in the high rotation and high load range, the dead time T a is set short. The dead time Ta may be set in consideration of not only the operation state immediately before the start of acceleration but also the target operation state. FIG. 5 shows a case where the dead time Ta is set based on the operation state immediately before the start of acceleration and the target operation state. In the figure, the dead time Ta is calculated from the difference between the engine speed immediately before the start of acceleration and the target engine speed, and the difference between the engine load immediately before the start of acceleration and the target engine load. .

Next, an example (routine) of the program executed at the time of the control of the control of the exhaust valve closing timing during acceleration as described above will be described with reference to a flowchart shown in FIG. In the acceleration exhaust valve closing timing transition control routine in FIG. 6, in step 1 (in the figure, denoted as S1, the same applies hereinafter), acceleration determination is performed. This acceleration determination determines whether or not acceleration has been started from a normal driving state (steady driving state). For example, the acceleration state is determined based on the detected value (change rate) of the accelerator pedal depression amount. This is done by detecting

If acceleration is detected, proceed to step 2. If acceleration is not detected, the following steps (S2 to S5) are skipped and normal control is executed. In step 2, the engine speed and the rate of change (acceleration) when the accelerator pedal is depressed are calculated from the crank angle signal and the accelerator pedal depression amount, and these calculated values and other various sensors are used. The target engine speed and the target engine load are calculated based on the output signal of the target. From these calculation results, the target throttle opening and the target opening / closing timing (phase) of the intake and exhaust valves 7, 8 are calculated.

In step 3, the exhaust valve is determined by referring to the map as shown in Fig. 4 or Fig. 5 from the engine speed and the engine load in the operating state immediately before detecting acceleration and in the target operating state. Set the dead time T a until the start of the delay shift of the closing timing in step 8.

In step 4, it is determined whether or not the waste time Ta set in step 3 has elapsed after detecting the acceleration state. Then, the process proceeds to step 5 after the dead time T a has elapsed.

In step 5, the closing timing of the exhaust valve 8 set in step 2 is retarded to the target closing time, and then the operation returns to the original state.

As described above, in the present embodiment, for example, when accelerating from the low-load operation region to the medium-load operation region, the advance of the opening timing of the intake valve 7 is shifted simultaneously with the start of acceleration (at time

A), the valve overlap with the exhaust valve 8 increases, but the transition of the closing timing of the exhaust valve 8 to the target closing timing for a predetermined time (based on the operating conditions immediately before the start of acceleration, etc.) And is started with a delay of a set dead time T a). In this case, during the dead time Ta, the throttle valve 23 is opened to the target opening and the pressure in the intake passage increases, so that the amount of residual exhaust gas flowing out into the intake passage 12 (internal

EGR amount) is greatly reduced, and more fresh air can be charged into the combustion chamber 6. As a result, the engine torque during acceleration (step reduction, torque Shock) can be avoided, acceleration performance and drivability can be improved, and the internal EGR amount can be increased smoothly, so that the air-fuel ratio control accuracy during acceleration can be improved. Become.

[Second Embodiment]

The second embodiment of the present invention has the same system configuration as the first embodiment described above (see FIG. 1), but differs in the mode of the exhaust valve closing timing shift control during acceleration. That is, FIG. 7 is a time chart provided for explaining an example of the control of shifting the exhaust valve closing timing at the time of acceleration in the second embodiment. The aspect of the exhaust valve closing timing transition control is different.

In the second embodiment, the closing timing of the exhaust valve 8 is advanced in the advance direction by a predetermined amount (here, the intake air) between the time A when the acceleration is detected and the time C when a predetermined dead time Tb elapses. When the dead time Tb has elapsed (time C), the shift of the closing timing of the exhaust valve 8 to the target closing timing in the retard direction is started. The amount of advance of the closing timing of the exhaust valve 8 in the advance direction during the dead time Tb is set based on the operating state immediately before acceleration of the engine and the target operating state during acceleration. You.

More specifically, when detecting the start of acceleration from the low load operation range to the medium load operation range based on, for example, the rate of change of the accelerator pedal depression amount (time A), the controller 1 Start the expansion of the opening (increase of the throttle opening command value) and the advancement of the phase (opening timing) of the intake valve 7 to the target phase (target opening timing) (increase of the intake valve phase command value).

On the other hand, the closing timing of the exhaust valve 8 is shifted (advanced) from time A in the direction opposite to the target phase (target closing timing). The amount of advance (the amount of advance) of the closing timing of the exhaust valve 8 in the advance direction from the time point A to the time point C when the dead time Tb elapses is set based on the operating state immediately before the start of acceleration. It is determined by the dead time Tb. Then, the phase shift (closed timing) of the exhaust valve 8 is retarded (decreased in the exhaust valve phase command value), and is started at the time point C when the dead time Tb has elapsed from the time point A when the acceleration start is detected. You.

The dead time Tb is, like the dead time Ta of the first embodiment described above, here, as shown in FIG. 8, the operating state (engine speed, engine load) immediately before the start of acceleration. Set based on If the rotation speed and load area are just before the start of acceleration, The amount of residual exhaust gas flowing into the intake passage 12 (internal EGR) is large due to the development of negative pressure in the air passage and the long time required per cycle. Therefore, the dead time Tb is set long in the low rotation and low load region. On the other hand, in the case of high rotation and high load regions just before the start of acceleration, since the negative pressure in the intake passage has not developed and the time required for one cycle is short, the residual exhaust gas enters the intake passage 12. Outflow (internal EGR) is small. Therefore, the dead time Tb is set short in a high rotation and high load region.

The dead time Tb may be set in consideration of not only the operation state immediately before the start of acceleration but also the target operation state. FIG. 9 shows a case where the dead time Tb is set based on the operation state immediately before the start of acceleration and the target operation state. In the figure, the dead time Tb is calculated from the difference between the engine speed immediately before the start of acceleration and the target engine speed, and the difference between the engine load immediately before the start of acceleration and the target engine load.

Next, an example (routine) of a program executed by the control unit 14 at the time of controlling the shift of the exhaust valve at the time of acceleration as described above will be described with reference to a flow chart shown in FIG.

In the acceleration-time exhaust valve closing timing transition control routine of FIG. 10, acceleration determination is performed in step 1 (shown as S 1 in the figure; the same applies hereinafter). This acceleration determination is for determining whether or not acceleration has been started from a normal driving state (steady driving state). For example, the acceleration state is determined based on the detected value (change rate) of the accelerator pedal depression amount. Perform by detecting.

If acceleration is detected, proceed to step 2. If acceleration is not detected, the following steps (S2 to S5) are skipped and normal control is executed. In step 2, the engine speed and the rate of change (acceleration) when the accelerator pedal is depressed are calculated from the crank angle signal and the accelerator pedal depression amount, and these calculated values and other various sensors are used. The target engine speed and the target engine load are calculated based on the output signal. From these calculation results, the target throttle opening and the target opening / closing timing (phase) of the intake and exhaust valves 7, 8 are calculated.

In step 31, based on the engine speed and engine load in the operating state immediately before detecting acceleration and in the target operating state, refer to the map shown in FIG. 8 or FIG. The time to continue the advance transition of the closing timing of 8, that is, The dead time Tb before the start of the retard shift of the closing timing of the valve 8 is set.

In step 4, it is determined whether or not the dead time Tb set in step 31 has elapsed after detecting the acceleration state. If it is determined that the dead time Tb has not elapsed, the closing timing of the exhaust valve 8 is advanced in step 41, and if it is determined that the dead time Tb has elapsed, the process proceeds to step 5. move on.

As described above, in the present embodiment, for example, when accelerating from the low-load operation region to the medium-load operation region, the advance of the opening timing of the intake valve 7 is started simultaneously with the start of acceleration (at time A). From the time A to the time C when the dead time Tb elapses, the closing timing of the exhaust valve 8 is shifted in the advance direction, so that the increase in the pulp overlap amount is suppressed, and the exhaust valve 8 After advancing the closing timing of the valve, the retarding transition to the target closing timing (target phase) is started, and during that time (during the dead time Tb), the pressure in the intake pipe passage increases. As a result, the amount of residual exhaust gas flowing out into the intake passage 12 (the amount of internal EGR) is significantly reduced, and more fresh air can be charged into the combustion chamber 6. For this reason, as in the first embodiment, a step difference is generated in the engine torque during acceleration.

(Reduction of torque and torque shock) can be avoided, acceleration performance and driveability can be improved, and the internal EGR amount can be increased smoothly, improving air-fuel ratio control accuracy during acceleration. It is also possible to make it.

[Third embodiment]

FIG. 11 shows a system configuration of a third embodiment of the present invention. The system configuration of the third embodiment differs from the system configuration of the first embodiment described above (see FIG. 1) in the intake passage 12. A pressure sensor 21 for detecting a pressure downstream of the throttle valve 23 is added. The output of the pressure sensor 21 (pressure in the intake passage) is input to the control unit 14, and the control unit 14 outputs the exhaust gas during acceleration based on the pressure in the intake passage detected by the pressure sensor 21. Valve closing timing shift control is performed.

FIG. 12 is a time chart used for explaining an example of the control for shifting the exhaust valve closing timing during acceleration in the third embodiment. The exhaust valve 8 shown in FIG. Of the timing to start the retard shift to the target closing timing (target phase) The method is different.

That is, in the first embodiment, the time point B at which the shift of the closing timing of the exhaust valve 8 to the target closing time (target phase) is started is set from the acceleration detecting time point A based on the operating state immediately before acceleration or the like. However, in the third embodiment, the time point D at which the delay of the closing timing of the exhaust valve 8 to the target closing timing (target phase) is started is determined by the pressure This is the time when the pressure in the intake passage detected by the sensor 21 becomes equal to or higher than a threshold value set as described later.

More specifically, as shown by the solid line in FIG. 12, the control unit 14 starts to shift the operating state of the engine from the low-load operation range to the medium-load operation range when the accelerator pedal is depressed. In other words, when the start of acceleration from the low-load operation range to the medium-load operation range is detected based on, for example, the rate of change of the pedal displacement of the accelerator pedal (time point A), the throttle opening expansion (throttle opening command Value) and advancing the intake valve 7 phase (opening timing) to the target phase (opening timing) (increasing the intake valve phase command value). On the other hand, the phase shift (closed timing) of the exhaust valve 8 is retarded (decrease of the exhaust valve phase command value) after the point A when the acceleration start is detected. Is started at a time point D when the threshold value becomes equal to or larger than a threshold value Ka set as described later.

Here, the threshold value Ka is set based on the operating state (engine speed, engine load) immediately before the start of acceleration, as can be clearly understood from FIG. In the low-rotation, low-load region immediately before the start of acceleration, the residual exhaust gas flows into the intake passage 12 due to the development of negative pressure in the intake passage and the long time required per cycle. (Internal EGR) Large amount. Therefore, the threshold value Ka is set to be high (large) in a low rotation speed and low load region. On the other hand, in the high-rotation, high-load region immediately before the start of acceleration, the negative pressure in the intake passage has not developed, and the time required for one cycle is short. Outflow to 2 (internal EGR) is small. Therefore, the threshold value Ka is set low (small) in a high rotation speed and high load region.

The threshold value Ka may be set in consideration of not only the operation state immediately before the start of acceleration but also the target operation state. FIG. 14 shows a case where the threshold value Ka is set based on the operating state immediately before the start of acceleration and the target operating state. In the figure, the The threshold value Ka is calculated from the difference between the engine speed and the target engine speed, and the difference between the engine load immediately before the start of acceleration and the target engine load.

Next, an example (routine) of a program executed by the control unit 14 when controlling the transition of the exhaust valve closing timing during acceleration as described above will be described with reference to a flowchart shown in FIG.

In the acceleration exhaust valve closing timing transition control routine in FIG. 15, step 1 (in the figure,

Notated as S1. In the following, acceleration determination is performed. This acceleration determination is for determining whether or not acceleration has been started from a normal driving state (steady driving state). For example, the acceleration state is determined based on the detected value (change rate) of the accelerator pedal depression amount. Perform by detecting.

If acceleration is detected, proceed to step 2. If acceleration is not detected, the following steps (S2 to S5) are skipped and normal control is executed. In step 2, the engine speed and the rate of change (acceleration) when the accelerator pedal is depressed are calculated from the crank angle signal and the accelerator pedal depression amount, and these calculated values and other various sensors are used. The target engine speed and target engine load are calculated based on the output signal. From these calculation results, the target throttle opening and the target opening / closing timing (phase) of the intake and exhaust valves 7, 8 are calculated.

Subsequently, in step 32, referring to a map as shown in FIG. 13 or FIG. 14 based on the engine speed and the engine load in the operating state immediately before detecting the acceleration and in the target operating state, respectively. The threshold value Ka of the pressure in the intake passage for detecting the start point D of the transition of the delay of the closing timing of the exhaust valve 8 is set.

In step 4, after detecting the acceleration state, it is determined whether or not the actual intake passage pressure has exceeded the threshold value Ka set in step 3. Then, the process proceeds to step 5 after waiting for the actual intake passage pressure to be equal to or higher than the threshold value Ka.

A), the amount of valve overlap with the exhaust valve 8 increases, but the transition of the closing timing of the exhaust valve 8 to the target closing timing occurs just before the intake passage pressure starts to accelerate. The operation is started after waiting for a threshold value Ka or more set based on the operating state of the vehicle. In this case, at the time D after the acceleration detection time A, the throttle valve 23 is opened to the target opening and the pressure in the intake passage is increased, so that the amount of the residual exhaust gas flowing into the intake passage 12 ( The internal EGR amount is greatly reduced, and more fresh air can be charged into the combustion chamber 6. As a result, a step (torque reduction, torque shock) in the engine torque during acceleration can be avoided, acceleration performance and drivability can be improved, and the internal EGR amount can be increased smoothly. However, it is also possible to improve the accuracy of air-fuel ratio control during acceleration.

[Fourth embodiment]

The fourth embodiment of the present invention has the same system configuration as that of the third embodiment described above (see FIG. 11), but differs in the mode of the exhaust valve closing timing shift control during acceleration. That is, FIG. 16 is a time chart provided for explaining an example of the control of the transition of the exhaust-valve closing timing during acceleration in the fourth embodiment, and the third embodiment described above (see FIG. 12) The mode of the exhaust valve closing timing shift control at the caro speed is different.

In the fourth embodiment, as shown in FIG. 16, when the accelerator pedal is depressed, the control unit 14 starts shifting the operating state of the engine from the low-load operation range to the medium-load operation range. In other words, when the start of acceleration from the low-load operation range to the medium-load operation range is detected based on, for example, the rate of change of the pedal displacement of the accelerator pedal (time point A), the throttle opening is increased (throttle opening). (Increase the opening command value) and start the advancement of the phase (open timing) of the intake valve 7 to the target phase (open timing) (increase the intake valve phase command value), and close the exhaust valve 8 Starts the delay shift (decrease of the exhaust valve phase command value) to the target closing timing (target phase).

Here, if the closing timing of the exhaust valve 8 is retarded to the target closing timing in a short time as in the related art, the pulp overlap amount becomes excessive. Therefore, before the closing timing of the exhaust valve 8 reaches the final target closing timing, the retarded shift amount of the closing timing (phase) of the exhaust valve 8 is changed.

(Retard value) is controlled by a limiter. When the amount of retarded movement of the exhaust valve 8 from the acceleration start point A reaches the predetermined amount set by the limiter 1, the closing timing at that time

(Retard value) until the pressure in the intake passage reaches the threshold value Kb. Thereafter, similarly, when the closing timing of the exhaust valve 8 reaches the retard value determined by the limiter 2, the retard value is held until the pressure in the intake passage reaches the threshold value Kc. . Hereinafter, similarly, the closing timing of the exhaust valve 8 is shifted to the target closing timing (target phase). The retard shift amount (limiter) from the start of the retard shift of the closing timing of the exhaust valve 8 to the arrival at the target closing timing will be described with reference to FIG. In the low-speed, low-load range, the amount of residual exhaust gas flowing out into the intake passage 12 (internal EGR) is due to the development of negative pressure in the intake passage and the long time required per cycle. There are many. Therefore, in the low rotation and low load range, the retard shift amount (limiter) is set small. On the other hand, in the high-speed and high-load region, the residual exhaust gas flows into the intake passage 12 because the negative pressure in the intake passage has not developed and the time required for one cycle is short. Internal EGR) Low volume. Therefore, in the high rotation and high load regions, the retard shift amount (limiter) is set to a high value (large). Subsequently, after the retard shift of the closing timing of the exhaust valve 8 is started, until the target closing timing is reached. The thresholds (K b, K c,...) Set between are described with reference to FIG. In the low-speed, low-load region, the residual exhaust gas flows into the intake passage 12 (internal EGR) due to the development of negative pressure in the intake passage and the long time required per cycle. There are many. Therefore, as shown in the figure, it is necessary to set the thresholds (Kb, Kc, ...) in the low-speed, low-load range by increasing the increase in the pressure in the intake passage. On the other hand, in the high rotation and high load range, since the negative pressure in the intake passage has not developed and the time required for one cycle is short, the residual exhaust gas flows into the intake passage 12 ( Internal EGR) Low volume. Therefore, as shown in the figure, it is necessary to set the threshold value (Kb, Kc, ...) by reducing the increase in the pressure in the intake passage in the high rotation and high load range.

Next, an example (routine) of the program executed by the control unit 14 in the control of shifting the exhaust valve closing timing during acceleration as described above will be described with reference to the flowchart shown in FIG.

In the acceleration-time exhaust valve closing timing transition control routine in FIG. 19, acceleration determination is performed in step 1 (referred to as S1 in the figure; the same applies hereinafter). This acceleration determination is for determining whether or not acceleration has been started from a normal driving state (steady driving state). For example, the acceleration state is determined based on the detected value (change rate) of the accelerator pedal depression amount. Perform by detecting.

If acceleration is detected, proceed to step 2.If acceleration is not detected, follow the steps below. Through the steps (S2 to S5), normal control is executed. In step 2, the engine speed and the rate of change (acceleration) when the accelerator pedal is depressed are calculated from the crank angle signal and the accelerator pedal depression amount, and these calculated values and output signals from various other sensors are calculated. The target engine speed and the target engine load are calculated based on From these calculation results, the target throttle opening and the target opening / closing timing (phase) of the intake and exhaust valves 7, 8 are calculated.

In the following step 33, the retard shift amount (limiter) and the limiter of the closing timing of the exhaust valve 8 are determined based on the engine speed and the engine load by referring to the maps shown in FIGS. Set thresholds Kb, Kc, ... to release. In step 41, it is determined whether or not the actual intake passage pressure has reached the threshold values Kb, Kc, ... set in step 33, and has reached the threshold values Kb, Kc, ... Wait and proceed to step 5.

In step 5, it is determined whether or not the closing timing of the exhaust valve 8 has reached the target closing time set in step 2. If the target closing time has been reached, this routine ends. If the target closing time has not been reached, the routine returns to step 33.

A), and at the same time, a delay shift (decrease in the exhaust valve phase command value) of the closing timing of the exhaust valve 8 to the target closing timing (target phase) is started, so that the closing timing of the exhaust valve 8 is delayed. In the angular shift, the amount of retard shift (retard value) of the closing timing (phase) of the exhaust valve 8 is controlled by a limiter before reaching the final target closing timing. Although the amount of parvo wrap increases, the amount of valve wrap does not increase excessively as in the past. Also, by providing a plurality of limiters before the retard shift to the target closing timing, the retard shift speed of the exhaust valve 8 changes, and the time during which the pressure in the intake pipe passage increases can be increased. As in the embodiment, the amount of residual exhaust gas flowing out into the intake passage 12 (internal EGR amount) is greatly reduced, and more fresh air can be charged into the combustion chamber 6. As a result, it is possible to avoid the occurrence of steps (torque reduction, torque shock) in the engine torque during acceleration, to improve the acceleration performance and the driver's piracy, and to increase the internal EGR amount smoothly. Therefore, it is possible to improve the air-fuel ratio control accuracy during acceleration. It becomes possible.

[Fifth Embodiment]

The fifth embodiment of the present invention has the same system configuration as the third embodiment described above (see FIG. 11), but differs in the mode of the exhaust valve closing timing shift control during acceleration. That is, FIG. 20 is a time chart provided for explaining an example of the control of the transition of the exhaust valve closing timing at the time of acceleration in the fifth embodiment, which is different from that of the third embodiment described above (see FIG. 12). The mode of shifting control of the exhaust valve closing timing during acceleration is different.

In the fifth embodiment, the closing timing of the exhaust valve 8 is advanced by a predetermined amount (here, from the time A at which the acceleration is detected until the pressure in the intake passage becomes equal to or higher than the threshold value Kf). Is shifted until the intake top dead center is reached. When the threshold value becomes equal to or higher than the threshold value Kf (time point F), the shift of the closing timing of the exhaust valve 8 to the target closing timing in the retard direction is started. It is made. Then, the amount of advance of the closing timing of the exhaust valve 8 in the advance direction from the time point A to the time point F is set based on the operating state immediately before the acceleration of the engine and the target operating state during the acceleration. You.

More specifically, when detecting the start of acceleration from the low load operation range to the medium load operation range based on, for example, the rate of change of the accelerator pedal depression amount (time A), the controller 1 Start the opening expansion (increase the throttle opening command value) and advance the intake valve 7 phase (open timing) to the target phase (target opening timing) (increase the intake valve phase command value).

On the other hand, the closing timing of the exhaust valve 8 is shifted (advanced) from time A in the direction opposite to the target phase (target closing timing). The amount of advance (the amount of advance) of the closing timing of the exhaust valve 8 in the advance direction from the time point A to the time point F at which the pressure in the intake passage becomes equal to or higher than the threshold value Kf is the operating state immediately before the start of acceleration. Is determined by the threshold value K f set based on Then, the retardation shift (decrease in the exhaust valve phase command value) of the phase (closing timing) of the exhaust valve 8 is started at the time point F when the pressure in the intake passage becomes equal to or higher than the threshold value Kf.

Here, the threshold value Kf is set based on the operating state (engine speed, engine load) immediately before the start of acceleration, as can be clearly understood from FIG. In the low-rotation, low-load region immediately before the start of acceleration, since the negative pressure in the intake passage has developed and the time required for one cycle is long, the intake passage for the residual exhaust gas 1

Outflow to 2 (internal EGR) is large. Therefore, in the low rotation and low load range, Set the threshold value K f higher (larger). On the other hand, in the high-rotation, high-load region immediately before the start of acceleration, the negative pressure in the intake passage has not developed, and the time required for one cycle is short. Outflow to 2 (internal EGR) is small. Therefore, the threshold value Kf is set low (small) in a high rotation and high load region.

The threshold value Kf may be set in consideration of not only the operation state immediately before the start of acceleration but also the target operation state. FIG. 22 shows a case where the threshold value Kf is set based on the operating state immediately before the start of acceleration and the target operating state. In the figure, the threshold value Kf is calculated from the difference between the engine speed immediately before the start of acceleration and the target engine speed, and the difference between the engine load immediately before the start of acceleration and the target engine load.

Next, an example (routine) of a program executed by the control unit 14 at the time of controlling the transition of the exhaust-valve closing timing during acceleration as described above will be described with reference to a flow chart shown in FIG.

In the acceleration-time exhaust valve closing timing shift control routine shown in FIG. 23, acceleration determination is performed in step 1 (referred to as S1 in the figure; the same applies hereinafter). This acceleration determination is for determining whether or not acceleration has been started from a normal operation state (steady operation state). For example, the acceleration state is determined based on a detected value (a change rate) of an accelerator pedal depression amount. Perform by detecting.

If acceleration is detected, proceed to step 2. If acceleration is not detected, the following steps (S2 to S5) are skipped and normal control is executed. In step 2, a change rate (acceleration) when the engine speed and the accelerator pedal are depressed is calculated from the crank angle signal and the accelerator pedal depression amount, and the calculated values and other various parameters are calculated. The target engine speed and the target engine load are calculated based on the output signal from the sensor. From these calculation results, the target throttle opening and the target opening / closing timing (phase) of the intake and exhaust valves 7, 8 are calculated.

In step 34, referring to a map as shown in FIG. 21 or FIG. 22 from the engine speed and the engine load in the operating state immediately before detecting acceleration and in the target operating state, respectively. The threshold value Kf for detecting how long the advance transition of the closing timing of the exhaust valve 8 is continued, that is, the threshold Kf for detecting the start timing of the retard transition of the closing timing of the exhaust valve 8

BX bridge _Q In step 42, it is determined whether or not the actual intake passage pressure has exceeded the threshold value Kf. If it is determined that it is not equal to or greater than the threshold value Kf, the closing timing of the exhaust valve 8 is advanced in step 43, and if it is determined that it is equal to or greater than the threshold value Kf, the process proceeds to step 5. .

As described above, in the present embodiment, for example, when accelerating from the low-load operation region to the medium-load operation region, the advance of the opening timing of the intake valve 7 is started simultaneously with the start of acceleration (at time A). By the time the actual intake passage 內 pressure becomes equal to or higher than the threshold value K f, the closing timing of the exhaust valve 8 is shifted in the advance direction, so that an increase in the valve overlap amount is suppressed, and After the closing timing of the exhaust valve 8 is advanced, the retarding transition to the target closing time (target phase) is started, and during that time (time A to time F), the pressure in the intake pipe passage increases. In this case, at the time point F after the acceleration detection time point A, since the throttle valve 23 is opened to the target opening and the pressure in the intake passage is increased, the amount of residual exhaust gas flowing out to the intake passage 12 is increased. (Internal EGR amount) is greatly reduced, and more fresh air can be charged into the combustion chamber 6. For this reason, as in the above-described embodiment, it is possible to avoid a step (torque reduction, torque shock) from occurring in the engine torque at the time of acceleration, thereby improving acceleration performance and drivability. Therefore, the accuracy of air-fuel ratio control during acceleration can be improved.

In the above-described embodiment, the variable valve mechanisms 10 and 11 of the intake valve 7 and the exhaust valve 8 that change only the phase while keeping the operating angle constant are used. However, the form of the variable valve mechanism is not limited as long as at least the closing timing of the exhaust valve 8 is made variable. For example, the variable valve mechanism has a variable operating angle or an operating angle. A variable valve mechanism for changing the lift amount and the phase may be used. Industrial potential

As is apparent from the above description, the engine control device according to the present invention delays the shift of the closing timing of the exhaust valve from the closing timing of the exhaust valve to the target closing timing by a predetermined time, or Wait until the pressure in the intake passage exceeds the threshold, then start At the start of the retarded transition of the exhaust valve closing timing to the target closing timing, the pressure in the intake passage is increasing, so the amount of residual exhaust gas flowing into the intake passage (internal

EGR amount) is greatly reduced, and more fresh air can be charged into the combustion chamber 6. As a result, it is possible to avoid the occurrence of steps (torque reduction, torque shock) in the engine torque during acceleration, to improve the acceleration performance and the driver's spirit, and to increase the internal EGR amount smoothly. However, it is also possible to improve the air-fuel ratio control accuracy during acceleration.

Claims

The scope of the claims

1. A control device for an engine having a variable valve mechanism capable of changing a closing timing of an exhaust valve, comprising: an acceleration state detecting means for detecting an acceleration state of the engine; And a valve opening / closing control unit configured to perform an acceleration-time exhaust valve closing timing shift control that delays a closing timing of the exhaust valve to a target closing timing when the acceleration state is detected.

The valve opening / closing control means may include an exhaust gas remaining in the combustion chamber during a period from when the acceleration state of the engine is detected by the acceleration state detection means to when the closing timing of the exhaust valve is shifted to the target closing timing. An engine control device, wherein the engine exhaust valve closing timing shift control is performed so as to minimize the amount of gas flowing out into the intake passage.

2. The valve opening / closing control means delays a start time of a shift of a closing timing of the exhaust valve to a target closing timing in a retard direction by a predetermined time from a time point of the detection of the acceleration state. 2. The control device for an engine according to 1.

3. The valve opening / closing control means is configured to set the predetermined time based on an operation state immediately before acceleration of the engine and / or a target operation state during acceleration. Engine control device.

4. The valve opening / closing control means shifts the closing timing of the exhaust valve in the advance direction until a predetermined time elapses after the detection of the acceleration state. 2. The engine control device according to claim 1, wherein a transition of a valve closing timing to a target closing timing in a retard direction is started.

5. The valve opening / closing control means sets the amount of advance of the closing timing of the exhaust valve in the advance direction within the predetermined time based on the operating state immediately before acceleration of the engine and the target operating state during acceleration. The engine control device according to claim 4, wherein the engine control device is configured to perform the control.

6. The valve opening / closing control means is configured to determine that the predetermined time period is longer than a transition speed of the exhaust valve closing timing to the target closing timing in the retard direction until a predetermined time period elapses from the detection of the acceleration state. 2. The engine control device according to claim 1, wherein the size of the engine control is increased after performing the control.

7. A pressure detecting means for detecting a pressure in a passage downstream of a throttle valve in an intake passage of the engine, wherein the valve opening / closing control means detects the pressure by the pressure detecting means at a time after the acceleration state detection time. 2. The engine control device according to claim 1, wherein when the pressure in the passage reaches a threshold value, the shift of the closing timing of the exhaust valve to the target closing timing in the retard direction is started.

8. The valve opening / closing control means, wherein the threshold value is set based on an operation state immediately before acceleration of the engine and a target operation state during acceleration. An engine control device according to any one of the preceding claims.

9. The valve opening / closing control means shifts the closing timing of the exhaust valve in the advance direction from the time when the acceleration state is detected until the pressure in the passage reaches the threshold value, and 8. The engine control device according to claim 7, wherein when it has reached, the shift of the closing timing of the exhaust valve to the target closing timing in the retard direction is started.

10. The valve opening / closing control means determines the amount of advance of the closing timing of the exhaust valve in the advancing direction until the pressure in the passage reaches the threshold value, in the operating state immediately before the acceleration of the engine and / or the acceleration. 10. The engine control device according to claim 9, wherein the setting is performed based on a target operation state at the time.

11. A pressure detecting means for detecting a pressure in a passage downstream of a throttle valve in an intake passage of the engine, wherein the valve opening / closing control means controls the target of closing timing of the exhaust valve from the time of detecting the acceleration state. The transition in the retard direction to the closing timing is started, and when the retarded transition amount reaches a predetermined amount, the closing timing at that time becomes equal to or higher than the threshold value in the passage detected by the pressure detecting means ′. The control device for an engine according to claim 1, wherein the control device is configured to hold the engine control device.

12. A pressure detecting means for detecting a passage pressure downstream of a throttle valve in an intake passage of the engine, wherein the valve opening / closing control means comprises a passage detected by the pressure detecting means from the time of detecting the acceleration state. The internal passage pressure after the passage internal pressure reaches the threshold value is lower than the transition speed of the exhaust valve closing timing to the target closing timing in the retard direction until the internal pressure reaches the threshold value. 2. The engine control device according to claim 1, wherein the control device is made larger.