JPH09324705A - Exhaust gas recirculation controller of veritable intake engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To aim at prevention of combustion from becoming worse on account of an excessive exhaust gas reflux quantity by composing such a control unit as allowing an eddy to take place by closing a variable intake valve according to the state of engine operation and enabling an exhaust gas recalculation to take place at a lapse of a preset period of time after closing the variable intake valve. SOLUTION: A diaphragm type EGR valve 41 is interposed, in an EGR passage 40 for communicating an exhaust manifold 9 with an air chamber 4, as an exhaust gas recirculation(EGR) system. EGR control is put in its practice when all of the constantly set operational conditions are satisfied. During a period in which any lag is generated in a change of an intake air flow immediately after start of variable intake air control and switching of a variable intake valve 20, exhaust gas recirculation is prohibited in its operation even if the present state seems to be applicable to the operational condition of the exhaust gas recalculation, so that its operation may be started from a time when the flow of the intake air is stabilized. Thereby, any deterioration of combustion caused by excessive exhaust gas recirculation quantity against the actual intake air quantity is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation control device for an engine having a variable intake mechanism, and more particularly,
Exhaust gas recirculation can be executed only when the variable intake mechanism is operated to generate a swirl in the combustion chamber.Exhaust gas recirculation is executed within a predetermined time after the variable intake mechanism is switched and operated. This is prohibited to stabilize the running performance.

[0002]

2. Description of the Related Art In recent years, there has been a so-called variable intake engine in which a part of the intake passage is closed by a variable intake valve to generate swirl flow such as swirl flow or tumble flow of air-fuel mixture in the combustion chamber to improve combustion efficiency. Variously developed. Further, in this type of engine, the variable intake valve is switched from closed to open in order to stop the generation of the vortex and enable the output-oriented operation at the time of high engine rotation or rapid acceleration of high load.

On the other hand, in recent vehicles, a part of the exhaust gas is recirculated to the intake side and burned together with fresh air, so that unburned components contained in the exhaust gas are reduced to improve emission. Exhaust gas recirculation (EGR)
The device is adopted (Japanese Patent Laid-Open No. 6-317223). In these conventional EGR devices, the operating conditions of the EGR are determined according to the operating state and operating region of the engine, and the EGR is operated immediately when these conditions are satisfied.

[0004]

This EGR device is naturally applied to a variable intake engine as well. In this case, the EGR is activated only when the variable intake valve is closed,
The EGR amount that is variably controlled is also set according to the state in which the flow of intake air is stable when the variable intake valve is closed. Therefore, if the EGR operates at the same time when the variable intake valve is switched from open to closed, there is a delay in the change of the intake air flow immediately after the variable intake valve is switched from open to closed. However, the EGR amount is not optimized, and combustion deteriorates. In some cases, there is a problem that a surge or a misfire occurs and the drivability of the vehicle is impaired.

In view of the above-mentioned circumstances, the present invention, in an EGR control device for a variable intake engine, inhibits the start of EGR operation for a predetermined time when the open / close state of the variable intake valve is switched, which deteriorates combustion. The purpose of this is to prevent surges and misfires resulting from this and to improve the drivability of the vehicle.

[0006]

In order to solve the above problems and to achieve the object of the present invention, an exhaust gas recirculation control device for a variable intake engine according to the present invention closes a part of an intake passage to form a combustion chamber. A variable intake valve that generates a swirl in the
An exhaust gas recirculation valve that opens the exhaust gas recirculation passage that connects the exhaust passage and the intake passage and recirculates the exhaust gas, and a variable intake valve that closes the variable intake valve to generate a swirl flow according to the engine operating state, and the variable intake valve is closed. And a control unit that enables exhaust gas recirculation after a lapse of a predetermined time.

With such a configuration, during the period in which there is a delay in the change of the intake air flow immediately after the variable intake valve is switched, the exhaust gas is exhausted even if the engine operating condition meets the exhaust gas recirculation operating condition. The operation of recirculation is prohibited, and the operation is started when the flow of intake air thereafter becomes stable. Therefore, deterioration of combustion caused by an excessive amount of exhaust gas recirculation with respect to the actual amount of intake air is prevented, and surges and misfires that affect the drivability of the vehicle are prevented.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
Will be described with reference to the system schematic diagram of FIG.

First, in FIG. 1, reference numeral 1 indicates a variable intake engine. The cylinder head 2 of the engine 1 is formed with an intake port 2a and an exhaust port 2b which communicate with the combustion chamber of each cylinder. An intake manifold 3 communicating with each intake port 2a is collected in an air chamber 4. Further, the air chamber 4 communicates with an intake pipe 6 via a throttle body 5, and sucks outside air via an air cleaner 7. A throttle valve 8 is provided in the throttle body 5. On the other hand, exhaust port 2b
The exhaust manifold 9 communicating with the exhaust manifold 9 is assembled on the downstream side thereof, and the exhaust pipe 10 is communicated with the collecting portion. Also, the exhaust pipe 19
A catalytic converter (not shown) is installed in the engine, and a muffler is connected to the downstream side of the catalytic converter.

On the other hand, an injector 10 is exposed immediately upstream of the intake port 2a of each cylinder of the intake manifold 3, and injects fuel at a predetermined timing for a predetermined time in response to a drive signal from an electronic control unit (ECU) 60. To do. The fuel in the fuel tank 11 is supplied to the injector 10 through the filter 13 by the fuel pump 12, and the fuel pressure thereof is adjusted to the set pressure by the pressure regulator 14. The drive of the fuel pump 12 is controlled by the ECU 60 via the pump relay 15.

Each intake manifold 3 is divided into two passages by a partition wall (not shown). One passage on one side is variable as a variable intake valve except when the engine is rotating at high speed or when the engine is rapidly accelerated. By closing the intake valve 20 and generating a tumble flow in the combustion chamber, the combustion efficiency is improved and the lean burn which will be described later is enabled. This variable intake valve 20
Is opened and closed by a diaphragm type actuator 21. The pressure chamber of the actuator 21 is connected to the air chamber 4 of the engine 1 via a variable intake solenoid valve 22 and a check valve 23. The variable intake solenoid valve 22 selectively operates the negative pressure and the atmospheric pressure of the air chamber 4 according to a signal from the ECU 60.
When the negative pressure is introduced, the variable intake valve 20 is closed by the actuator 21,
On the contrary, when the atmospheric pressure is introduced, the variable intake valve 20 is opened.

On the other hand, as a canister purge system,
The upper space of the fuel tank 11 is connected to the intake port 32a of the canister 32 through the 2-way valve 31 by the evaporation passage 30.
Is communicated to. In addition, the discharge port 32 of the canister 32
b is the air chamber 4 of the engine 1 due to the purge passage 33.
Is connected to the ECU, and the ECU is provided in the middle of the purge passage 33.
Purge solenoid valve 3 variably controlled by 60
4 is installed. Therefore, when the liquid fuel in the fuel tank 11 evaporates and the pressure in the fuel tank upper space increases, the two-way valve 31 is opened and the evaporated fuel accumulated in the fuel tank upper space is guided to the inside of the canister 32, so that the canister 32 Adsorbed on the activated carbon inside 32. Further, at the time of canister purging, the purge solenoid valve 34 is opened by a signal from the ECU 60, and the evaporated fuel adsorbed in the canister 32 together with the air introduced from the atmosphere opening port 32c of the canister 32 is taken into the suction negative pressure of the engine 1. Is purged into the air chamber 4 by
It is burned in the combustion chamber.

Next, as an exhaust gas recirculation (EGR) system, a diaphragm type EGR valve 41 is provided in an EGR passage 40 connecting the exhaust manifold 9 and the air chamber 4. The pressure chamber of the EGR valve 41 communicates with the dual duty solenoid valve 42. The dual duty solenoid valve 42 is used for the engine 1
Negative pressure side solenoid valve 4 communicating with the air chamber 4 of
2a and an atmospheric pressure side solenoid valve 42b for opening to the atmosphere, and E is set in accordance with a duty signal from the ECU 60.
The lift amount of the EGR valve 41 is controlled by variably setting the magnitude of the negative pressure introduced into the pressure chamber of the GR valve 41. The negative pressure side solenoid valve 42a is fully closed at a duty ratio of 0%, and the atmospheric pressure side solenoid valve 42b is fully closed at a duty ratio of 100%. Therefore, in order to keep the EGR valve 41 fully closed and deactivate the EGR, the duty ratios of the negative pressure side solenoid valve 42a and the atmospheric pressure side solenoid valve 42b are set to 0% and the pressure chamber of the EGR valve 41 is set. Apply atmospheric pressure to.

The engine 1 is equipped with various sensors and switches for detecting its operating state,
Those detection signals are transmitted to the ECU 60. First, in the intake system of the engine 1, an air flow meter 50 for detecting the amount of intake air is provided immediately downstream of the air cleaner 7, and a throttle opening sensor for outputting a voltage signal corresponding to the throttle opening to the throttle valve 8. 51 are arranged in a row. A water temperature sensor 52 is exposed to a cooling water passage (not shown) of the engine 1, and a crankshaft of the engine 1 is provided with a signal rotor 1a having a plurality of protrusions. A crank angle sensor 53 for detecting a crank angle is provided opposite to 1a. On the other hand, the above-mentioned EGR
The valve 41 is provided with a position sensor 54, which sends a voltage signal corresponding to the actual valve lift amount to the ECU.
Supply to 60.

Other sensors and switches are connected to the accelerator pedal and turned on when the accelerator is released.
An idle switch 55, a vehicle speed sensor 56 arranged in the power transmission system to detect the vehicle speed, and the like are provided, and respective signals are input to the ECU 60.

The control executed by the ECU 60 will be specifically described below. The ECU 60 mainly
CPU, ROM, RAM, backup RA not shown
It is composed of M and an input / output interface.
The ECU 60 processes the detection signals of the various sensors and switches described above and performs various calculations according to the control program, and the injector 10 and the variable intake solenoid valve 2
2. A control signal corresponding to the calculation result is output to the purge solenoid valve 34, the dual duty solenoid valve 42, and fuel injection control (lean burn control), variable intake control, canister purge control, and EGR control are executed respectively. To do.

The basic aim of the variable intake control is to open the variable intake valve 20 in a region where the engine 1 is required to output at a high rotation speed or a high load to bring it into a normal engine operating state, and in other regions. The variable intake valve 20 is closed to generate a tumble flow in the combustion chamber to improve combustion efficiency and enable lean burn.
Therefore, in the closing operation of the variable intake valve 20, the engine speed N calculated based on the detection signal of the crank angle sensor 53 is equal to or lower than the predetermined speed KNETCV, and the basic fuel injection amount T
Engine load LDATA according to p is a predetermined value KKDTC
This is executed when V or less and the throttle opening TVO detected by the throttle opening sensor 51 satisfies all conditions of a predetermined value TVOTCV or less.

The above-mentioned lean burn is realized by so-called lean burn control in which the fuel injection amount from the injector 10 is reduced as compared with the stoichiometric control to make the air-fuel ratio lean. Specifically, the intake air amount Q and the engine speed N
The basic fuel injection amount Tp calculated from is reduced and corrected by the lean correction coefficient. In particular, the lean correction coefficient is such that the engine rotation fluctuation, which is an index of the surge of the vehicle, reaches a predetermined upper limit value. Advance correction is made to the lean side unless it occurs, and retard correction is made to the rich side when engine rotation fluctuation of a predetermined level or more occurs. The lean burn control is based on the assumption that the variable intake valve 20 is closed in the variable intake control as described above, and in addition, the engine cooling water temperature TWN, the engine speed N, the engine load LDATA, the vehicle speed VSP,
It is executed in the lean burn operation mode in which all the various control conditions such as the throttle opening TVO are satisfied.

On the other hand, the EGR control according to the present invention is executed when all the following predetermined operating conditions 1 to 5 are satisfied. 1. After the engine warm-up in which the engine cooling water temperature detected by the water temperature sensor 52 is a predetermined value or higher, 2. During acceleration operation when the signal from the idle switch is OFF or during coasting when the vehicle speed detected by the vehicle speed sensor is equal to or higher than a predetermined speed. 3. The lean burn operation mode in which lean burn control is performed is not performed. 4. The variable intake valve 20 is closed. A predetermined time has passed since the variable intake valve 20 was closed. In particular, under the condition of 5, the EGR operation is prohibited during the unstable period immediately after the closing of the variable intake valve 20 in which the intake air amount changes with a delay, and deterioration of combustion is prevented.

When all of these conditions are satisfied, first, the transient correction which is set stepwise according to the basic lift amount ELBASE and the acceleration / deceleration level obtained from the map according to the engine speed N and the value of the load LDATA. Lift amount ELT
The target lift amount LIFTT of the EGR valve 41 is calculated from RN (LIFTT = ELBASE + ELTR
N). Then, the calculated target lift amounts LIFTT and E
The actual lift amount LIFT is changed to the target lift amount LIFT in accordance with the size of the deviation LIFTD from the actual lift amount LIFTP detected by the position sensor 54 of the GR valve 41.
The duty ratios of the negative pressure side solenoid valve 42a and the atmospheric pressure side solenoid valve 42b of the dual duty solenoid valve 42 are set so as to converge to T, and are output to the respective solenoid valves 42a and 42b.

Specifically, if the deviation LIFTD is within a predetermined range, the duty ratios of the negative pressure side solenoid valve 42a and the atmospheric pressure side solenoid valve 42b are set to 0% and 100%, respectively, and are held fully closed. Also, the deviation LIF
If TD is larger than the predetermined range, the duty ratio of the atmospheric pressure side solenoid valve 42b is fixed to 100% to be fully closed, and the duty ratio of the negative pressure side solenoid valve 42a is variably set according to the magnitude of the deviation LIFTD. EG
The pressure acting on the pressure chamber of the R valve 41 is controlled. Further, if the deviation LIFTD is smaller than the predetermined range, the duty ratio of the negative pressure side solenoid valve 42a is fixed to 0% and fully closed, and the duty ratio of the atmospheric pressure side solenoid valve 42a is changed according to the magnitude of the deviation LIFTD. Is set to control the pressure acting on the pressure chamber of the EGR valve 41.

As described above, the variable intake valve 20
Since the EGR is activated only when is closed and variable intake is performed, the basic lift amount map matches the engine speed N and the load LDATA so that the intake air by the variable intake control conforms to a stable state. It is determined in advance for each operating area determined by

The EGR control of the variable intake engine according to the present invention will be described below with reference to the flowchart of FIG.

First, in steps S101 to S107, the aforementioned EGR operating conditions 4 and 5 are determined. In step S101 corresponding to condition 4, the variable intake valve 2
It is determined whether 0 is closed and the variable intake control is being performed. If the variable intake control is not performed, the variable intake determination flag FLAG is cleared (FL) in step S107.
AG = 0), and the EGR is controlled to be inoperative in step S108. Specifically, the EGR valve 41 is fully closed,
That is, in order to set the lift amount to 0, the negative pressure side solenoid valve 42a of the dual duty solenoid valve 42 is
And the duty ratios of the atmospheric pressure side solenoid valve 42b are set to 0% and output.

On the other hand, if it is determined in step S101 that the variable intake control is being performed, the process proceeds to step S102 and the state of the variable intake determination flag FLAG is determined. Immediately after the start of the variable intake control, the flag FLAG has been cleared, so the routine proceeds to step S103, where it is set (FL
AG = 1), and further, in the next step S104, the variable intake control start timer TIMER is reset (TIME).
R = 0). On the other hand, when the flag FLAG is once set in step S102, the subsequent routines
The process moves from step S102 to step S105. In step S105, the timer TIMER is incremented, and the next step S1 corresponding to the EGR operating condition 5 is performed.
At 06, the current timer TIMER value is compared with the predetermined time KTEGRON to determine whether the predetermined time has elapsed after the variable intake control was started. When the predetermined time has not elapsed from the start of the variable intake control, the EGR operation is performed even if the current operating condition satisfies the other EGR operating conditions 1 to 3 determined in steps S109 to S112. And keep it inactive.

If it is determined in step S106 that the predetermined time has elapsed since the variable intake control was started,
In steps S109 to S112, the above EGR operating conditions 1 to 3 are determined. That is, condition 1
In step S109 corresponding to, the engine cooling water temperature TWN detected by the water temperature sensor 52 is set to the predetermined value KT.
It is determined whether or not it is greater than or equal to WEGR, and a predetermined value KTWEGR
When it is determined that the engine has been warmed up, the process proceeds to the next step S110 for determining the state of the idle switch and step S111 for determining the vehicle speed.

Steps S110 and S1 corresponding to condition 2
At 11, the idle switch is OFF and the driver is accelerating by depressing the accelerator pedal or the vehicle speed is VSP.
If it is determined that the vehicle is traveling at a speed equal to or higher than the predetermined vehicle speed KSPTCV, step S11 corresponding to condition 3 is performed.
In 2, it is determined whether or not the lean burn operation mode is currently set. In other words, this determination is a determination as to whether or not lean burn control is being executed. If a lean burn control execution condition is satisfied in a lean burn control program, a control flag is set, and in step S104, All you have to do is check the flags.

If the current fuel injection control is not the lean burn operation mode, that is, the stoichio operation mode in which the lean burn control is not executed, the engine speed N and the load LDATA as described above are determined in step S113. The variable EGR control according to is executed. If any one of the conditions from step S109 to step S112 is not satisfied, step S1
Moving to 08, the EGR is deactivated.

[0029]

As described above, according to the exhaust gas recirculation control device for a variable intake engine according to the present invention, the flow of intake air immediately after the variable intake control is started and the variable intake valve is switched. During the period when the change is delayed,
Even if the engine operating condition meets the exhaust gas recirculation operating conditions, the exhaust gas recirculation operation is prohibited,
The operation is started when the flow of the intake air thereafter becomes stable. Therefore, deterioration of combustion caused by an excessive amount of exhaust gas recirculation with respect to the actual intake air amount is prevented, and thereby surges and misfires that affect the drivability of the vehicle are prevented.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of a system of a variable intake engine including an exhaust gas recirculation control device according to the present invention.

FIG. 2 is a flowchart showing an example of an exhaust gas recirculation control program in the embodiment.

[Explanation of symbols]

 1 Engine 3 Intake Manifold 20 Variable Intake Valve 40 EGR Passage 41 EGR Valve 60 Electronic Control Unit

Claims (1)

[Claims] 1. A variable intake valve that closes a part of an intake passage to generate a swirl in a combustion chamber, and an exhaust gas recirculation valve that opens an exhaust gas recirculation passage that connects the exhaust passage and the intake passage to recirculate exhaust gas. A control unit that closes the variable intake valve to generate a swirl flow according to the engine operating state, and that enables exhaust gas recirculation after a predetermined time has elapsed since the variable intake valve was closed. An exhaust gas recirculation control device for variable intake engines.