JPH09324672A - Fuel injection timing control device of lean-burn engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent torque fluctuation shocks and misfires by switching fuel injection timing in synchronism with switching of a variable intake valve which produces a vortex inside a combustion chamber, in a device wherein the operating mode is switched between the lean-burn operating mode and the stoichiometric operating mode when the variable intake valve is closed. SOLUTION: An intake manifold 3 is divided into two passages by a partition wall, and one of the passages is closed by a variable intake valve 20 to produce a tumbling flow inside a combustion chamber. Combustion efficiency is thereby enhanced and lean-burn operation is made possible. The closure of the variable intake valve 20 is effected if such requirements that engine speed be not more than a predetermined value, that engine load be not more than a predetermined value, and that throttle opening be not more than a predetermined value are met. If injection timing differs between before and after the variable intake valve 20 is switched between open and closed positions, fuel injection timing is gradually varied from the injection timing before the switching to that after the switching, thereby preventing torque fluctuation shocks.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection timing control device for a lean burn engine having a variable intake mechanism, and more particularly, when changing the variable intake mechanism, the fuel injection timing is switched, and when lean burn operation and stoichio operation mode are switched. It is intended to reduce the torque fluctuation shock of the engine and improve the combustion by not switching the fuel injection timing.

[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. 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 speed or rapid acceleration of high load.

Further, since the variable intake mechanism improves the combustion efficiency of the engine and enables the combustion of a lean mixture, the variable intake control is a so-called lean burn control for improving fuel efficiency. It is adopted in combination with. In this case, lean burn operation is performed only in the low engine load region and normal stoichio operation is performed in other regions in order to achieve both output-oriented driving such as acceleration and fuel efficiency-oriented driving such as steady running. However, normally, the lean burn operation region is executed in a steady running region which is a part of the variable intake control region.

On the other hand, in such a lean burn engine, the fuel injection timing during lean burn operation is delayed from that during stoichio operation, and fuel is injected during the intake stroke to perform stratified combustion to improve the combustion limit. There is a need. Therefore, two types of fuel injection timing tables are prepared, one for stoichio operation and one for lean burn operation, and these two tables are used while being switched in synchronization with the switching between lean burn operation and stoichio operation.

[0005]

However, in this type of variable intake type lean burn engine, if the fuel injection timing is switched at a time when combustion becomes unstable, such as immediately after switching between lean burn operation and stoichiometric operation, the engine will be In this case, a torque fluctuation shock or a misfire occurs, which deteriorates the drivability of the vehicle.

In view of the above circumstances, the present invention provides a fuel injection timing control device for a variable intake engine, in which the fuel injection timing table is switched in synchronism with the opening and closing of the variable intake valve to switch between lean burn operation and stoichiometric operation mode. The purpose is to prevent the occurrence of engine torque fluctuation shocks and misfires by not doing so.

[0007]

In order to solve the above-mentioned problems and to achieve the object of the present invention, a fuel injection timing control system for a lean burn engine according to the present invention is provided in a combustion chamber by closing a part of an intake passage. A variable intake valve that generates a swirl, an injector that injects fuel into the engine, a variable intake valve that closes the variable intake valve according to the engine operating state to generate a swirl, and a lean intake valve that is dependent on the engine operating state when the variable intake valve is closed. The control unit controls the fuel injection amount from the injector by switching between the burn operation mode and the stoichiometric operation mode, and further switches the fuel injection timing in synchronization with the switching of the opening and closing of the variable intake valve.

With such a configuration, the fuel injection timing does not change and is constant at the time of switching between the lean burn operation and the stoichiometric operation, so that fluctuation in engine torque due to switching of the injection timing and occurrence of misfire are prevented. . Further, since the fuel injection timing is set to the optimum timing for lean burn when the variable intake valve is closed before the lean burn operation is started, the lean burn effect can be maximized.

More preferably, when the fuel injection timing is switched in synchronism with the switching of the variable intake valve, the variable intake valve is switched because the injection timing before switching is gradually changed to the injection timing after switching. The torque fluctuation shock can be reduced.

[0010]

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), and one passage is variable as a variable intake valve except when the engine is rotating at high speed or when the engine is accelerated rapidly. 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 the normal engine operating state in the region where the engine 1 is required to output at high rotation or high load, and in the 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
V or less, the throttle opening TVO detected by the throttle opening sensor 51 is a predetermined value TVOTCV or less, the engine cooling water temperature TWN detected by the water temperature sensor 52 is a predetermined value KTWTCV or more when the engine is warmed up, and the vehicle speed sensor 56. The vehicle speed VSP detected at is the predetermined speed KSPTCV
It is executed when all the following conditions are met.

The above-mentioned lean burn is realized by so-called lean limit 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 basic fuel injection amount Tp calculated from the intake air amount Q and the engine speed N is reduced and corrected by a lean correction coefficient. In particular, the lean correction coefficient is set to a predetermined upper limit value. Until then, the advance correction is made to the lean side unless the engine rotation fluctuation, which is an index of the vehicle surge, is generated, and the retard correction is made to the rich side when the engine rotation fluctuation is equal to or higher than a predetermined level.

This lean burn control is based on the condition that the variable intake valve 20 is closed in the variable intake control as described above. In addition, the engine speed N is within a predetermined range, and the engine load LDATA is below a predetermined value LDLEAN. , The vehicle speed VSP is within a predetermined range and the throttle opening is in the lean burn operation mode in which all the various control conditions of the predetermined value KTVOLE or less are satisfied. These control conditions are included in the control conditions in the variable intake control, that is, the control region of the lean burn control is set to the steady running state corresponding to a part of the variable intake control region. Therefore, in accordance with the engine operating state, the variable intake valve 20 is opened to normally inhale, and the stoichio controlled region (for example, during rapid acceleration) and the variable intake valve 20 are closed to perform variable intake control. In addition, there are regions where stoichio control is performed (for example, during idling, slow acceleration, and deceleration) and regions where variable intake control and lean burn control are performed (for example, low speed traveling).

The stoichiometric control is a conventionally known control for controlling the air-fuel ratio to stoichiometric based on the signal from the O2 sensor, and a detailed description thereof will be omitted.

On the other hand, regarding the fuel injection timing control according to the present invention, the optimum injection timing is set in the table with the engine speed N as a parameter. The fuel injection timing is set in different tables corresponding to the open / closed state of the variable intake valve 20, that is, the operating state of the variable intake control. In this case, the first fuel injection timing table is set so as to comply with the stoichiometric control as usual, while the second table lags behind the first table in which injection is started during the intake stroke. The injection timing is set, and the injection timing is set to comply with lean burn control. The table data is set as a time or an angle from a predetermined reference angle signal detected by the crank angle sensor 53.

Thus, when the variable intake control is executed and the variable intake valve 20 is closed, or vice versa, when the variable intake valve 20 is closed and returns to normal intake, the fuel injection timing table is not switched. However, when the injection timing is different before and after the switching, the injection timing retrieved from the table before the switching is gradually changed to the injection timing retrieved from the table after the switching to prevent the torque fluctuation shock of the engine.

The fuel injection timing control of the lean burn engine according to the present invention will be described below with reference to the flow chart of FIG.

First, in step S101, the open / closed state of the variable intake valve 20 is determined. Here, if the control condition is not satisfied in the variable intake control described above and the variable intake valve 20 is opened, step S102 is performed.
Then, the injection timing TBLOPN suitable for the stoichiometric control is retrieved from the first fuel injection timing table according to the engine speed at that time and stored in the table data address (TBLINJ). On the other hand, when the control condition is satisfied in the variable intake control and the variable intake valve 20 is closed, the process proceeds to step S103, and the lean burn control is performed from the second fuel injection timing table according to the engine speed N at that time. The suitable injection timing TBLCLS is searched and stored in the table data address (TBLIN
J).

Next, in step S104 or S106, the table data TBLINJ stored in the table data address is compared with the output fuel injection timing INJTIM set in the previous routine, and INJTIM>
TBLINJ or INJTIM <TBLIN
J is determined. If the table data TBLINJ is different from the previous output fuel injection timing INJTIM, the output fuel injection timing INJTIM is set to the table data TBL in step S105 or S107, respectively.
Correction is performed gradually (every 1 bit) so as to approach INJ.

As described above, in the present invention, the variable intake valve 2 is processed by the processing of steps S101 to S103.
The injection timing table for stoichio control and the injection timing table for lean burn control are switched in synchronism with the switching of the open / closed state of 0. Therefore, the fuel injection timing is switched to lean burn control before switching from stoichio operation to lean burn operation, and the injection timing may switch in a situation where combustion is unstable at the time of switching between stoichio operation and lean burn operation. Since it is not present, deterioration of vehicle drivability due to torque fluctuation shock of the engine and misfire is prevented.

Further, different injection timings are searched for before and after the switching of the injection timing table synchronized with the switching of the open / close state of the variable intake valve 20, but at this time, the pre-switching is performed by the processing of steps S104 to S107. The table data (injection timing) is gradually changed to the switched table data (injection timing).

In the program example of FIG. 2, the engine speed may change and the injection timing retrieved from the table may change even while the lean burn operation or stoichiometric operation is continued. Even in that case, the injection timing is changed gradually from the previous injection timing to the injection timing retrieved this time.

[0031]

As described above, according to the fuel injection timing control device for a lean burn engine according to the present invention,
Switching from the fuel injection timing for stoichio operation to the fuel injection timing for lean burn operation is performed at the time of switching the variable intake valve before shifting to lean burn operation. Therefore, when combustion is unstable at the time of switching from stoichio operation to lean burn operation, the fuel injection timing does not change and is constant, so fluctuations in engine torque due to switching and occurrence of misfire are prevented. . Further, since the fuel injection timing is set to the optimum timing for lean burn when the variable intake valve is closed before the lean burn operation is started, the lean burn effect can be maximized. Furthermore, when the fuel injection timing is switched in synchronization with the switching of the variable intake valve opening / closing, the torque fluctuation shock when switching the variable intake valve can be reduced because the injection timing before switching is gradually changed to the injection timing after switching. .

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of a lean burn engine system according to the present invention.

FIG. 2 is a flowchart showing an example of a fuel injection timing control program in the embodiment.

[Explanation of symbols]

 1 Engine 3 Intake Manifold 10 Injector 20 Variable Intake Valve 60 Electronic Control Unit

Claims (2)

[Claims] 1. A variable intake valve that closes a part of an intake passage to generate a swirl in a combustion chamber, an injector that injects fuel into an engine, and the variable intake valve closes to generate a swirl according to an engine operating condition. And a control unit configured to control the fuel injection amount from the injector by switching between the lean burn operation mode and the stoichiometric operation mode according to the engine operating state when the variable intake valve is closed. A fuel injection timing control device for a lean burn engine, wherein the unit switches fuel injection timing in synchronization with opening / closing switching of the variable intake valve. 2. The lean burn according to claim 1, wherein when the fuel injection timing is switched in synchronism with the opening / closing switching of the variable intake valve, the injection timing before the switching is gradually changed to the injection timing after the switching. Engine fuel injection timing control device.