JP2003269306A - Ignition timing control device of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a temperature rise of the exhaust gas when an engine is in the decelerative transient and suppress deterioration of an exhaust emission purifying catalyst. <P>SOLUTION: An increment of the residual gas rate due to a motion delay is calculated when a variable valve train is controlled in the idling range so as to minimize the valve overlapping amount, and the MBT ignition timing corresponding to the increment is calculated, and when the actual engine revolution speed is greater than the target value, a control is made into the MBT ignition timing to suppress the temperature rise of the exhaust gas, and an delay angle correction is made to the MBT ignition timing after the actual engine revolution speed approaches the target value to a certain extent and as the difference is getting small, and thereby the margin of the ignition advance angle for the accessories load input is secured. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a technique for controlling ignition timing of an engine.

[0002]

2. Description of the Related Art In a spark ignition engine for a vehicle, it is common to perform EGR in which a part of the exhaust gas is returned to the intake system in a partial region, whereby the inert gas in the cylinder is increased. , Slow combustion and NO
x can be reduced, and at the same time, the intake pressure in the cylinder can be increased to reduce pumping loss and improve fuel efficiency.

[0003]

However, in the EGR system, there is a problem that the cost is increased due to the installation of the EGR control valve and the bypass pipe, and the layout is restricted. Therefore, for the purpose of reducing NOx and reducing fuel consumption as well, there is a technique of increasing the amount of residual gas which is an inert gas by increasing the valve overlap amount of the intake / exhaust valve by using a variable valve mechanism. If the amount of residual gas increases too much, combustion becomes slow and combustion stability deteriorates.

In the system provided with the variable valve mechanism described above, if the amount of inert gas, that is, the amount of residual gas is large during idle operation, combustion deteriorates, so the valve overlap amount is negative (intake valve and exhaust valve). There is one that controls the valve timing so that the open period of is not overlapped). However, the response of the variable valve is slow during the deceleration transition during the transition from the partial operation range to the idle operation during deceleration operation. The amount becomes large and the combustion becomes slow. For this reason, if the ignition timing is set during steady idle operation, the combustion end timing is delayed, and the exhaust gas temperature rises during deceleration, which adversely affects the catalyst.

In Japanese Patent Laid-Open No. 2001-152889, the ignition timing is advanced according to the valve overlap amount. However, during transient operation, the engine speed, which is an influential factor of residual gas that affects the combustion speed, Intake negative pressure,
Since the valve overlap amount fluctuates, there is a problem that the ignition timing required value does not match with advance angle correction based only on the valve overlap amount.

Further, if the ignition timing during idle operation is set to the required ignition timing, that is, MBT, there is no margin for increasing the torque by advancing the ignition timing, and there is a large delay in torque correction due to the amount of air that is conventionally used. It was not possible to satisfactorily suppress fluctuations in rotation due to machine driving. The present invention has been made in view of such a problem, and suppresses the exhaust gas temperature rise during transient operation to suppress the deterioration of the exhaust gas purification catalyst, and also the rotation fluctuation when the auxiliary machine is driven during idling. It is an object of the present invention to provide an ignition timing control device for an engine that suppresses the ignition.

[0007]

Therefore, the invention according to claim 1 is characterized in that the residual gas amount in the combustion chamber is estimated and the ignition timing is controlled based on the estimated residual gas amount. According to the invention according to claim 1, while estimating the residual gas amount which varies depending on various conditions of the engine, and appropriately controlling the ignition timing based on the estimated residual gas amount, the delay of the end of combustion is suppressed. As a result, an increase in exhaust temperature can be suppressed, and deterioration of the exhaust purification catalyst can be suppressed.

Further, the invention according to claim 2 is characterized in that the residual gas amount is estimated based on parameters including the valve overlap amount of the intake / exhaust valve, the engine speed and the intake pressure. . According to the invention of claim 2, the valve overlap time is determined by the valve overlap amount of the intake / exhaust valve and the engine speed, and the blow-through amount (volume amount) during the valve overlap can be calculated.
The residual gas amount (volume amount) can be calculated by adding the blow-through amount to the basic value (volume amount) of the residual gas amount corresponding to the cylinder volume at the top dead center.

Further, the invention according to claim 3 is characterized in that the estimation of the residual gas amount is further carried out based on a parameter including the exhaust gas temperature. According to the invention of claim 3, by further using the exhaust temperature, the blow-through amount and the basic value of the residual gas amount can be obtained as the mass, and thus the residual gas amount can be calculated as the mass. .

The invention according to claim 4 is characterized in that the ignition timing to be controlled is set after the MBT ignition timing (maximum torque generation ignition timing) is calculated based on the residual gas amount. According to the invention of claim 4, the MBT ignition timing that is basically required for the ignition timing control can be calculated with high accuracy by calculating based on the residual gas amount. Control can be performed.

Further, the invention according to claim 5 is characterized in that the ignition timing at the time of idling is set to be delayed by a predetermined amount from the calculated MBT ignition timing. Further, the invention according to claim 6 is characterized in that the ignition timing at the time of idling is set to be delayed by a predetermined amount from the MBT ignition timing (maximum torque generation ignition timing).

According to the fifth or sixth aspect of the invention, the MBT ignition timing is set to be retarded by a predetermined amount, so that the increase in the required torque due to the drive of the auxiliary machine at the time of idling is advanced by the ignition timing. This can be covered by the correction, so that the rotation fluctuation can be suppressed well. Further, the invention according to claim 7 is characterized in that the predetermined amount of the retard angle is set to a smaller value as the actual rotation speed of the engine is higher than the target rotation speed.

According to the seventh aspect of the present invention, when the actual rotation speed is higher than the target rotation speed, there is a large margin for the reduction of the rotation speed due to the input of the auxiliary machine load. It can be small. This allows MB
It is possible to sufficiently exert the effect of suppressing the exhaust gas temperature rise by the ignition timing control advanced in proportion to the increase in the residual gas amount during the deceleration transition by setting the retard amount with respect to T to the necessary minimum.

On the other hand, when the actual rotation speed decreases near the target rotation speed, the increase in the residual gas amount also decreases and the influence of the rotation fluctuation due to the input of the auxiliary machine load increases. Therefore, by increasing the retard angle amount, Rotational fluctuation can be suppressed. Further, the invention according to claim 8 is characterized in that the engine is provided with a variable valve mechanism capable of varying the valve timing of at least one of the intake valve and the exhaust valve.

According to the invention of claim 8, when the valve timing is changed, the valve overlap amount is changed and the change of the residual gas amount is large. Therefore, the effect of applying each of the above inventions is great.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 showing a system configuration of an embodiment of the present invention, an intake valve 2 and an exhaust valve 3 of an engine (internal combustion engine) 1 are an intake valve cam 4 and an exhaust valve cam 5, respectively. Driven by a variable valve mechanism (VTC) 41 such as an electromagnetic brake type, a hydraulic control type (control of an electromagnetic hydraulic control valve), etc. Thereby, the valve timing of the intake valve 2 is variably controlled. However, in the application of the present invention, the valve timing of at least one of the intake valve and the exhaust valve may be variable, and the valve overlap amount of the intake and exhaust valves may be variable, and
The lift amount may be variable in addition to the valve timing.

At the center of the combustion chamber 6 of the engine 1, an ignition plug 8 is mounted which is driven by an ignition coil 7 containing a power transistor. In the intake passage 9 of the engine 1, an air cleaner 10, an electronically controlled throttle valve 11, and a fuel injection valve 12 for injecting fuel into each cylinder are installed from the upstream side. In the exhaust passage 13 of the engine 1, two exhaust purification catalysts 14 having the same or different functions,
15, a muffler 16 is provided.

As various sensors, an air flow meter 17 for detecting the intake air amount upstream of the throttle valve 11 in the intake passage 9 and an intake pressure sensor 1 for detecting the intake pressure downstream thereof.
8, an exhaust temperature sensor 19 for detecting the exhaust temperature on the upstream side of the exhaust purification catalyst 15 in the exhaust passage 14, and an air-fuel ratio sensor 2 for detecting the air-fuel ratio via the detection of the oxygen concentration in the exhaust gas.
0 is mounted, and further, a water temperature sensor 21 for detecting the engine cooling water temperature Tw is output to the engine body, a POS signal is output for each unit crank angle for engine speed detection, and a stroke phase difference between cylinders (720 ° / number of cylinders). ) Every RE
A crank angle sensor 22 that outputs an F signal, a cam sensor 23 that outputs a PHASE signal for cylinder discrimination in synchronization with the rotation of the intake valve cam 4, and an accelerator opening sensor 24 that detects an accelerator opening operated by a user. It is installed.

Detection signals from the various sensors are input to a control unit 31, and the control unit 31 controls various engines according to an operating state of the engine based on the input detection signals, specifically, the ignition coil. Ignition control by a spark plug 8 via 7, fuel injection control by a fuel injection valve 13, valve timing control of intake and exhaust valves by the intake valve cam 4 and the exhaust valve cam 5. In particular, as the control according to the present invention, the ignition timing is controlled while estimating the residual gas amount in the combustion chamber, and the ignition timing at the time of shifting from the partial operation region to the idle operation by deceleration is adjusted to an optimum value to improve the operability. Improve.

An outline of the ignition timing control will be described with reference to the control block diagram of FIG. 2 and the flow chart of the main routine of FIG. In FIG. 2, the residual gas rate calculation unit is
Engine speed Ne, valve overlap amount O / L,
Based on the intake pressure Pa downstream of the throttle valve, the exhaust temperature Et, and the intake air amount Qa, the residual gas rate in the combustion chamber according to the current engine state is estimated and calculated.

The MBT ignition timing calculation unit calculates the MBT ignition timing (maximum torque generation ignition timing) based on the residual gas ratio. The idle determination unit determines idle operation based on the engine operating state, the idle time ignition timing correction unit sets a correction amount (delay angle amount) for the MBT at idle, and the ignition unit makes the MBT during idle. The ignition is performed at the set ignition timing by correcting

FIG. 3 shows a flow chart of the main routine of the ignition timing control. In step 1, the MBT ignition timing MBTCAL is calculated. In step 2, based on the signal from the accelerator opening sensor 24, it is determined whether or not the engine is idling. When it is determined to be the idle operation, the routine proceeds to step 3, where a retard correction amount RETIDLE from the MBT ignition timing MBTCAL for securing a torque margin amount to be described later during the idle operation is calculated.

In step 4, based on the MBT and the retard correction amount RETIDLE, the ignition timing A at idle is set.
Calculate DVIDLE. In step 5, the ignition timing ADVIDLE at idle calculated as described above is set as the ignition timing ADV for controlling. On the other hand, when it is determined in step 2 that the engine is not in the idle operation, the routine proceeds to step 6, where the MBT ignition timing MBTCAL is set as the ignition timing ADV to be controlled.

In step 7, an ignition signal is output to the ignition plug 8 at the ignition timing AVT set in step 5 or step 6 to perform ignition. 4 is the same as FIG.
The MBT calculation routine performed in step 1 of FIG. In step 11, the basic fuel injection amount Tp calculated from the intake air amount Qa detected by the air flow meter 17 and the engine rotation speed Ne detected based on the signal of the crank angle sensor 22, and 100% filling The charging efficiency ITAC is calculated from the ratio with the fuel injection amount corresponding to the efficiency.

In step 12, the fuel weight equivalent coefficient FUELG is calculated from the ratio of the target equivalence ratio TFBYA set based on the detected value of the accelerator opening and the detected value of the engine speed to the theoretical air-fuel ratio of 14.5. . Step 13
Then, the residual gas mass MREG and the residual gas rate RATRE
Calculate G.

In step 14, the filling efficiency ITAC is set.
Then, a fresh air ratio ITAN, which is a ratio of the fresh air amount obtained from the stroke volume VS and the air density ATRDENS, the in-cylinder gas weight obtained from the residual gas weight MREG, and the fresh air amount is calculated. In step 15, the unburned gas density basic value DENS is read from the engine speed Ne and the charging efficiency ITEC with reference to the unburned gas density basic value map.

In step 16, the engine speed Ne
And the charging efficiency ITEC, the laminar flame velocity basic map FLMN is read by referring to the laminar flame velocity basic map. In step 17, the equivalence ratio correction coefficient RMDHS is read from the target equivalence ratio TFBYA by referring to the equivalence ratio correction coefficient map.
In step 18, the cylinder total gas mass MASSC is calculated from the charging efficiency ITAC, the fuel weight equivalent coefficient FULG, and the fresh air ratio ITAN.

In step 19, the laminar flame velocity basic value F
LML, equivalence ratio correction coefficient RMDHS, and residual gas ratio RAT
The flame speed FLV is calculated from REG. Step 20
Then, the unburned gas density basic value DENS and the equivalence ratio correction coefficient R
The unburned gas density ROU is calculated from MDHS. In step 21, the MBT ignition timing M is calculated from the total mass of gas in the cylinder MASSC, the flame velocity FLV, and the unburned gas density ROU.
Calculate BTCAL.

FIG. 5 shows a subroutine for calculating the residual gas ratio RATEREG executed in step 13. In step 31, based on the detected exhaust gas temperature, as shown in FIG.
Set the residual gas mass basic value by referring to the table shown in. In step 32, the valve overlap amount (angle) O / L is set based on the VTC operating angle by referring to the table shown in FIG.

In step 33, it is determined whether the valve overlap amount O / L is a positive value larger than 0. When it is determined that the valve overlap amount O / L is a positive value, the routine proceeds to step 34, where the valve overlap valve overlaps based on the valve overlap amount O / L and the engine speed Ne. Calculate O / L time.

In step 35, the valve overlap O / L is calculated based on the O / L time and the intake pressure Pa.
The volume of gas (exhaust gas) blown into the combustion chamber through the exhaust port during the time is calculated with reference to the map shown in FIG. In step 36, the mass of the blow-through gas is calculated based on the volume of the blow-through gas and the exhaust temperature as shown in FIG.
It is calculated by referring to the map shown in.

In step 37, the residual gas mass is calculated by adding the blown-through gas mass to the residual gas basic value as in the following equation. Residual gas mass = residual gas basic value +
In the blow-through gas mass step 38, the residual gas ratio is calculated based on the residual gas mass and the intake air mass as in the following equation.

Residual gas rate = residual gas mass / (residual gas mass + intake air mass) × 100 [%] In step 33, the valve overlap amount O / L
However, when it is determined that the blow-through gas mass is 0 or less,
Then, the process proceeds to step 27. In this case, the residual gas mass is the residual gas basic value. FIG. 10 shows a subroutine for calculating the ignition timing retard correction amount executed in step 3 of FIG.

In step 41, an engine target rotational speed at idle determined by the engine water temperature Tw detected by the water temperature sensor 21 and the auxiliary machine load is calculated. In step 42, the difference DELTN between the target rotation speed and the actual rotation speed
E (actual rotation speed-target rotation speed) is calculated. In step 43, when the current rotation speed is higher than the target rotation speed, the difference according to the difference DELTNE (> 0) shown in FIG.
The torque margin amount IDLETRQ by the ignition timing retard correction is calculated with reference to the map shown in FIG. Specifically, the smaller the difference DELTNE is, that is, the closer the actual rotation speed is to the target rotation speed, the larger the torque margin amount IDLETRQ is set in preparation for the input of the auxiliary load. When the actual rotation speed is higher than the target rotation speed, there is a large margin for the reduction of the rotation speed due to the input of the auxiliary machine load.
ETRQ may be small. As a result, the effect of suppressing the increase in exhaust gas temperature can be sufficiently exerted by the ignition timing control that is advanced in proportion to the increase in the residual gas amount during the deceleration transition by minimizing the retard amount with respect to the MBT. On the other hand, when the actual rotation speed decreases near the target rotation speed, the increase in the residual gas amount also decreases and the influence of the rotation fluctuation due to the input of the auxiliary machine load increases. Therefore, increasing the retardation amount reduces the rotation fluctuation. Can be suppressed.

In step 44, the torque allowance ID
Based on LETRQ and the residual gas rate, referring to the map shown in FIG. 12, the ignition timing retard amount RETID from the MBT
Calculate LE. FIG. 13 shows a state of ignition timing control during a deceleration transition according to this embodiment. If the operating state shifts from the partial range to the idle range during deceleration transition and the VTC operating angle target value is set to a value that minimizes the valve overlap amount O / L, the actual operating angle changes due to the VTC operation delay. Therefore, the valve overlap amount O / L becomes larger than the target value. As a result, an increase in the valve overlap amount O / L with respect to the target value and a transient increase in residual gas determined by the engine speed Ne and the intake pressure are generated.

Since the combustion becomes slower due to the increase in the residual gas at the transition time, the required ignition timing, that is, the MBT is set to the advance side with respect to the MBT at the time of steady idling. And
According to the characteristics of the map of FIG. 11, the actual rotation speed is larger than the target rotation speed, the delay correction is not performed at MBT in the initial stage of the deceleration transition, and then the actual rotation speed approaches the target rotation speed by a certain amount or more. As the speed difference decreases, the retard correction amount is increased, and after the steady idle state is reached, the retard amount is retarded to an amount that can secure the torque allowance by the input of the auxiliary drive.

FIG. 14 shows the relationship between the ignition timing and the exhaust temperature when the engine is idling in which the amount of residual gas is small and when the vehicle is decelerating and transitioning where the amount of residual gas is large. At the time of steady idling, the amount of torque allowance is secured, so that the ignition timing is controlled by retarding the MBT, and the torque and exhaust temperature at this time are shown in FIG. If the ignition timing is controlled to be switched to the steady idle state during the deceleration transition, the torque decreases and the exhaust temperature rises excessively as shown in FIG.

Therefore, during deceleration transition, by controlling the ignition timing with the advance angle corrected in accordance with the estimated increase in the residual gas amount, the torque and the exhaust temperature are within the permissible range as shown by c1 to c2 in the figure. Can be changed.

[Brief description of drawings]

FIG. 1 is a system configuration diagram according to an embodiment of the present invention.

FIG. 2 is a control block diagram of the above embodiment.

FIG. 3 is a flowchart of a main routine of ignition timing control.

FIG. 4 is a flowchart of a subroutine of MBT ignition timing calculation.

FIG. 5 is a flowchart of a subroutine for similarly calculating a residual gas rate.

FIG. 6 is also a table of residual gas mass basic values.

FIG. 7 is a table of valve overlap amount O / L.

FIG. 8 is a similar map of blow-through gas volume.

FIG. 9 is a map of the mass of blown gas.

FIG. 10 also shows a subroutine for calculating an ignition timing retard correction amount.

FIG. 11 is a map for similarly calculating a torque margin amount.

FIG. 12 is a map for similarly calculating the ignition timing retard amount.

FIG. 13 is a time chart showing how various state quantities change during the same control.

FIG. 14 is a diagram showing the relationship between the ignition timing and the exhaust temperature during the steady idle state where the residual gas amount is small and during the deceleration transition where the residual gas amount is large.

[Explanation of symbols]

1 engine 2 intake valve 3 exhaust valve 4 Intake valve cam 6 Combustion chamber 11 Throttle valve 12 Fuel injection valve 18 Intake pressure sensor 19 Exhaust temperature sensor 22 Crank angle sensor 23 Cam sensor 24 Accelerator position sensor 31 Control Unit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) F02M 25/07 F02M 25/07 550R 550 F02P 5/15 B E F term (reference) 3G022 CA03 CA05 DA02 FA06 GA01 GA02 GA05 GA06 GA07 GA08 GA09 3G062 AA10 BA08 CA03 GA06 GA09 3G084 BA03 BA13 BA17 BA23 CA03 CA06 DA19 EB08 FA07 FA10 FA11 FA20 FA27 FA29 FA33 FA38 FA39 3G092 AA11 BA09 BB01 DA03 DA12 EC09 FA37 GA04 GA13 HAZ HD05 HE01 HD

Claims (8)

[Claims] 1. An ignition timing control device for an engine, which estimates an amount of residual gas in a combustion chamber and controls an ignition timing based on the estimated amount of residual gas. 2. The engine according to claim 1, wherein the residual gas amount is estimated based on parameters including a valve overlap amount of intake and exhaust valves, an engine rotation speed, and an intake pressure. Ignition timing control device. 3. The ignition timing control device for an engine according to claim 2, wherein the estimation of the residual gas amount is further performed based on a parameter including exhaust temperature. 4. The ignition timing to be controlled is set after the MBT ignition timing (maximum torque generation ignition timing) is calculated based on the residual gas amount.
An ignition timing control device for an engine according to any one of 1. 5. The calculated ignition timing at idle is M
The engine ignition timing control device according to claim 4, wherein the ignition timing control device is set to be delayed by a predetermined amount from the BT ignition timing. 6. An engine ignition timing control device, characterized in that the ignition timing during idling is set with a predetermined delay from the MBT ignition timing (maximum torque generation ignition timing). 7. The ignition timing of the engine according to claim 5, wherein the predetermined amount of the retard angle is set to a smaller value as the actual rotation speed of the engine is higher than the target rotation speed. Control device. 8. The engine according to any one of claims 5 to 7, wherein the engine is provided with a variable valve mechanism that can vary the valve timing of at least one of an intake valve and an exhaust valve. Ignition timing control device.