JP2884836B2 - Engine ignition timing control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition timing control device for an engine.

[0002]

2. Description of the Related Art Feedback control of the air-fuel ratio is a correction for always maintaining the air-fuel ratio at the stoichiometric air-fuel ratio in the feedback control range in order to make the three-way catalyst function efficiently. Published, Automotive Engineering, January 1986, pages 110 and 111).

The air-fuel ratio is detected by an oxygen sensor, and the average air-fuel ratio is controlled to the stoichiometric air-fuel ratio by changing the air-fuel ratio feedback correction coefficient α.

[0004] However, during warm-up, an air-fuel mixture richer than the stoichiometric air-fuel ratio is required. Therefore, the feedback control of the air-fuel ratio is stopped to increase the amount of fuel.

[0005]

By the way, when the temperature is in a certain temperature range corresponding to the middle of warm-up, the ignition timing is retarded more than the so-called MBT in order to improve the exhaust performance. The purification performance of the three-way catalyst is greatly affected by the catalyst temperature, and the purification performance drops at low temperatures.Therefore, by delaying the ignition timing, the temperature of the exhaust gas flowing into the catalyst is raised, and the three-way catalyst is quickly brought to the activation temperature. To try to raise it.

On the other hand, if the feedback control of the air-fuel ratio is stopped during warm-up, a change in intake air temperature, a slight load change,
Since the air-fuel ratio fluctuates due to a change in rotation or the like, the torque fluctuates under this influence, and a surge occurs. This tendency becomes remarkable when the ignition timing is retarded even if the supplied fuel amount is the same.

Therefore, during the warm-up period, it is desired to retard the ignition timing to quickly raise the temperature of the three-way catalyst, but it is not possible to sacrifice drivability, and to greatly retard the ignition timing. I can't do that.

Accordingly, an object of the present invention is to improve the exhaust performance by greatly retarding the ignition timing when the catalyst temperature rise condition is satisfied, and to improve the operability during warm-up by making the generated torque flat by improving the exhaust performance. I do.

[0009]

According to the present invention, as shown in FIG. 1, a sensor 3 for detecting an exhaust air-fuel ratio or an oxygen concentration is used.
A means 32 for determining whether or not a condition for rapidly raising the temperature of the three-way catalyst is provided, and the sensor detection value is set so that the actual air-fuel ratio becomes the target value even when the catalyst temperature rising condition is satisfied. Means 33 for feedback control of the air-fuel ratio based on
Means for calculating a basic ignition timing NGOV for raising the temperature of the catalyst, and for each injection based on the air-fuel ratio feedback correction amount α calculated by the air-fuel ratio feedback control means 33 when the catalyst temperature raising condition is satisfied. Means 35 for predicting the air-fuel ratio in the cylinder at every predetermined rotation speed
Means 36 for calculating an ignition timing correction amount NGCTADV such that the generated torque matches a predetermined required torque in accordance with the predicted value NGFBYA of the in-cylinder air-fuel ratio. Means 37 is provided for calculating the ignition timing ADV by correcting the timing NGOV, and a device 38 for performing ignition with a signal of the calculated ignition timing ADV.

[0010]

When the air-fuel ratio in the cylinder is predicted from the air-fuel ratio feedback correction amount α, the air-fuel ratio prediction value NGF is obtained.
BYA well represents the air-fuel ratio of the air-fuel mixture formed from the amount of fuel that flows into the cylinder with a delay due to wall flow.

According to the air-fuel ratio predicted value NGFBYA,
When the ignition timing is corrected so that the generated torque obtained from the predicted value matches a predetermined required torque, a flat torque characteristic is obtained.

Further, since a flat torque characteristic can be obtained by correcting the ignition timing, the basic ignition timing itself for raising the temperature of the catalyst can be greatly retarded. The exhaust time during warm-up is improved.

[0013]

In FIG. 2, the flow rate of intake air from an air cleaner 2 through an intake pipe 3 is controlled by a throttle valve 8 linked to an accelerator pedal, and flows into a cylinder. Fuel is injected from an injector (fuel supply device) 4 toward each intake port of the engine 1 based on an injection signal. A power transistor 1 for receiving an ignition signal
The gas in the cylinder is ignited by an ignition device including the ignition plug 4 and an ignition plug 15. The gas burned in the cylinder performs the work of pushing down the piston, generating torque. The exhausted combustion gas is introduced into a catalytic converter 6 through an exhaust pipe 5, where harmful components (CO, HC, NOx) in the combustion gas are purified by a three-way catalyst and discharged.

7 is an air flow meter for detecting the intake air amount Qa, 9 is a sensor for detecting the opening of the throttle valve 8, 10 is a crank angle sensor for detecting the engine speed N, and 11 is a cooling water temperature TW of the water jacket. And 12 are oxygen sensors having characteristics whose output rapidly changes at the stoichiometric air-fuel ratio, and these are input to a control unit 20 composed of a microcomputer.

As shown in FIG. 5, the control unit 20 obtains a basic injection pulse width Tp [ms] common to all cylinders according to the intake air amount Qa obtained from the air flow meter output and the engine speed N. Further, during start-up and during warm-up, the injector 4 is opened with a pulse width slightly larger than the pulse width Tp due to an increase coefficient, that is, a pulse width of Tp · COEF, so that the air-fuel mixture sucked into the cylinder is reduced from the theoretical air-fuel ratio. (Steps 21 and 21)
2).

When the warm-up is completed and the air-fuel ratio feedback control range is reached, the air-fuel ratio feedback correction coefficient α is multiplied by the basic pulse width Tp so that the three-way catalyst works effectively, so that the fuel injection pulse width Ti (= Tp · α + Ts) is calculated (step 22). Note that the air-fuel ratio feedback correction coefficient α is 1/1 of the engine based on the oxygen sensor output.
It is calculated once every two revolutions (one revolution in four cylinders).

The required ignition timing of the engine includes the engine speed N, the basic injection pulse width (an engine load equivalent amount).
Since it changes depending on conditions such as Tp and cooling water temperature TW, the control unit 20 calculates the basic ignition timing PADV [゜ BTDC] according to these conditions as follows (step 23, FIG. 6).

(1) Normal operating conditions An ADV map is searched to obtain a basic ignition advance value ADV [゜ BTD corresponding to the engine speed N and the basic injection pulse width Tp.
C] (steps 31 to 33), and this is set as the basic ignition timing PADV.

When the engine is started at a low temperature of 30 ° C. or less, the ADVCLD table is further searched and the advance correction amount A at a low temperature is calculated.
DVCLD is obtained and added to the basic ignition advance value ADV to improve startability (steps 34 to 3).
6).

(2) At idle The throttle valve comes to the fully closed position irrespective of the rotational speed. Therefore, a PGOV table different from the above-mentioned map is searched and the ignition advance value PGOV [゜ BTD corresponding to the engine rotational speed N is obtained.
C] is obtained and set as the basic ignition timing PADV (steps 31, 37, 36).

(3) When the condition for raising the temperature of the catalyst is satisfied (except during idling) When 30 ° C. <TW <50 ° C. (during warm-up), the NGOV table is searched and the ignition advance value corresponding to the rotation speed N is obtained. NGOV
[゜ BTDC] is obtained and set as the basic ignition timing PADV (steps 32, 38, 36).

The above map value ADV and table value PGO
V is a value set for MBT,
The value of ADV is T if N is the same as shown in FIG.
The larger the value of p, the more retarded, and the smaller the value of N if the same Tp, the more the retarded side.
The smaller the value of N is, the more the angle is retarded. As shown in FIG. 9, the value of ADVCLD is advanced as the temperature becomes lower in consideration of the fact that the combustion is delayed as the temperature becomes lower.

On the other hand, the value of NGOV is higher than that of MBT control in order to rapidly raise the temperature of the three-way catalyst.
As shown by 0, the angle is significantly retarded compared to PGOV.

By the way, when the air-fuel ratio feedback control is stopped when the catalyst temperature increasing condition is satisfied, a slight load change,
The air-fuel ratio fluctuates due to the rotation change, causing torque fluctuation. This torque fluctuation increases when the value of NGOV is retarded as described above.

In order to solve this, the control unit 20 performs the air-fuel ratio feedback control even when the catalyst temperature increasing condition is satisfied, and predicts the air-fuel ratio in the cylinder using the air-fuel ratio feedback correction coefficient α obtained by performing this control. And
The basic ignition timing (NGOV) for increasing the temperature of the catalyst is corrected by advancing or delaying it so that the generated torque is constant according to the predicted value.

For example, as shown in FIG. 3, if the value of the flag FNGOV is FNGOV = 1, it is determined that the catalyst temperature increasing condition is satisfied, and the cylinder is discriminated. If so, select n),
The value obtained by multiplying the air-fuel ratio feedback correction coefficient α by the weighted average is used to calculate the cylinder air-fuel ratio predicted value NGFB of the n-th cylinder.
It is calculated as YAn (step 3).

This is because the amount of fuel flowing into the cylinder greatly depends on the behavior of the wall flow of the fuel injected from the injector into the intake port during warm-up, and the wall flow fuel amount is substantially delayed by a first order. Therefore, in order to predict the in-cylinder air-fuel ratio, it is necessary to use a weighted average value of α.

Since the degree of the first-order lag of the wall-flow fuel increases as the wall-flow temperature decreases, the value of the weighted average coefficient X [%] decreases as the water temperature TW decreases, as shown in FIG. Old N
GFBYAn is the previous value.

The flag FNGOV may be set to "1" when searching the NGOV table, and set to "0" otherwise (steps 39 and 40 in FIG. 6).

The above-mentioned cylinder air-fuel ratio prediction value NGFBY
From the An, the NGCTADVn table is searched to calculate the ignition timing correction amount NGCTADVn [°] for the n-th cylinder (step 4).

The ignition timing correction amount NGCTADVn is
As shown in FIG. 12, when the air-fuel ratio predicted value NGFBYAn is smaller than 1.0 (a value with respect to the required air-fuel ratio) (that is, when the air-fuel ratio is on the lean side), the advance amount is given. If the air-fuel ratio of the n-th cylinder is leaner than the required value, the required torque (predetermined constant value) cannot be obtained, so the required torque is generated by advancing the ignition timing to increase the combustion pressure. It is.

Conversely, when the predicted air-fuel ratio value NGFBYAn is larger than 1.0 (when the air-fuel ratio is on the rich side), a torque greater than the required torque is generated in the n-th cylinder. By retarding, the generated torque is reduced to the required torque.

The ignition timing correction amount NGCTA thus determined
As shown in FIG. 4, when the catalyst temperature rise condition is satisfied, DVn is added to the basic ignition timing PADV (= NGOV), so that the ignition timing ADVn [ｎBTDC] of the n-th cylinder.
Is calculated (steps 12 and 13). This ignition timing AD
When Vn is set in the timer of the I / O port (step 14), ignition is performed in the nth cylinder at the timing of ADVn.

In this example, the air-fuel ratio in the cylinder is predicted using α while the air-fuel ratio feedback control is performed even at the time of idling or low load, and the air-fuel ratio predicted value FBYAn
The ignition timing correction amount CTADVn is calculated so that the generated torque is constant in accordance with the equation (1), and the exhaust performance is improved while preventing torque fluctuation in this operation range (steps 11 and 15). This point has already been filed (Japanese Patent Application No.
-261728).

On the other hand, when the engine is not idling or at a low load and the catalyst temperature rise condition is not satisfied, the basic ignition timing PAD
V is directly used as the ignition timing ADVn of the n-th cylinder (steps 11, 12, 16). This is because, in such an operating range, the engine rotation is stable, and the torque fluctuation does not matter so much, so that it is not necessary to correct the basic ignition timing.

Here, the operation of this example when the catalyst temperature increasing condition is satisfied will be described with reference to FIG.

If the air-fuel ratio feedback control is performed when the catalyst temperature raising condition is satisfied, a torque fluctuation occurs due to the periodic fluctuation of α by this control. This is because, as shown in FIG. 14, when the air-fuel ratio A / F shifts to the rich side or the lean side under a constant ignition timing, the generated torque is different. ,
It fluctuates slowly at a low frequency as shown by the broken line.

On the other hand, when the predicted value NGFBYAn of the in-cylinder air-fuel ratio is calculated from α in synchronization with the injection timing, the change in the predicted air-fuel ratio NGFBYAn coincides with the phase of the torque fluctuation indicated by the broken line. . When the predicted value of the air-fuel ratio NGFBYAn in the cylinder shifts to the rich side,
This is because the generated torque increases, and conversely, if it shifts to the lean side, the generated torque decreases, that is, the air-fuel ratio in the cylinder and the generated torque correspond one to one.

Therefore, when the ignition timing correction amount NGCTADVn is determined according to the air-fuel ratio predicted value NGFBYAn, the change in the correction amount NGCTADVn becomes exactly in phase with the torque fluctuation shown by the broken line, and the half cycle in which the torque decreases Then, a lead angle correction value corresponding to the degree of the decrease is given, and conversely, in a half cycle in which the torque increases, a retard angle correction value corresponding to the degree of the increase is given. As a result, the torque characteristic becomes flat as shown by the solid line, and no surge or the like is generated.

Conventionally, the ignition timing at the time of raising the temperature of the catalyst cannot be largely retarded (about 15 ° to 20 ° BTDC) in order to keep the operability from deteriorating. , Feedback correction amount NGCTAD
Since flat torque characteristics can be obtained by Vn,
The basic ignition timing (NGOV) for raising the temperature of the catalyst is set to, for example, 0
The angle can be greatly retarded from ゜ to 15 ° BTDC.

While the predicted value of the air-fuel ratio NGFBYAn is shifted to the rich side, the ignition timing correction amount NGCTA
Since DVn takes a negative value, it can be further retarded by | NGCTADVn | from the table value NGOV.

As a result, the time required for the three-way catalyst to reach the activation temperature can be shortened, and the exhaust performance during warm-up is further improved.

In the embodiment, the in-cylinder air-fuel ratio is predicted from the air-fuel ratio feedback correction coefficient α, but learning prediction can be performed using the oxygen sensor output itself.
Further, the predicted value NGFBYA of the in-cylinder air-fuel ratio and the ignition timing correction amount NGCTADV calculated from the predicted value may be obtained as values common to all cylinders, not for each cylinder. An air-fuel ratio sensor can be used instead of the oxygen sensor.

[0044]

According to the present invention, the air-fuel ratio feedback control is performed even when the catalyst temperature rise condition is satisfied, and the air-fuel ratio in the cylinder is predicted based on the air-fuel ratio feedback correction amount. The ignition timing is adjusted to increase or decrease so that the generated torque matches the predetermined required torque.Thus, the operability is improved by a flat torque characteristic, and the exhaust performance during warm-up is significantly improved by the large ignition timing delay. Can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of the present invention.

FIG. 2 is a control system diagram of one embodiment.

FIG. 3 is a flowchart for calculating an ignition timing correction amount NGCTADVn for each cylinder.

FIG. 4 is a flowchart for calculating an ignition timing ADVn.

FIG. 5 is a flowchart for calculating a fuel injection pulse width Ti.

FIG. 6 is a flowchart for calculating a basic ignition timing PADV.

FIG. 7 is a characteristic diagram of an ADV map.

FIG. 8 is a characteristic diagram of a PGOV table.

FIG. 9 is a characteristic diagram of an ADVCLD table.

FIG. 10 is a characteristic diagram of an NGOV table.

FIG. 11 is a characteristic diagram of a weighted average coefficient X with respect to a water temperature.

FIG. 12 is a characteristic diagram of an ignition timing correction amount NGCTADVn.

FIG. 13 is a characteristic diagram of generated torque with respect to ignition timing ADV.

FIG. 14 is a waveform chart for explaining an operation during warm-up of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 3 Intake pipe 4 Injector 7 Air flow meter 10 Crank angle sensor 11 Cooling water temperature sensor 12 Oxygen sensor 15 Spark plug 20 Control unit 31 Air-fuel ratio sensor or oxygen sensor 32 Catalyst temperature rise condition determination means 33 Air-fuel ratio feedback control means 34 Basic ignition Timing calculation means 35 In-cylinder air-fuel ratio prediction means 36 Ignition timing correction amount calculation means 37 Ignition timing calculation means 38 Ignition device

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F02P 5/15 F02D 43/00 301

Claims (1)

(57) [Claims] 1. A sensor for detecting an exhaust air-fuel ratio or an oxygen concentration, means for judging whether or not a condition for rapidly raising the temperature of a three-way catalyst is provided. Means for feedback-controlling the air-fuel ratio based on the sensor detection value so that the fuel ratio becomes a target value; means for calculating a basic ignition timing for increasing the temperature of the catalyst; Means for predicting the air-fuel ratio in the cylinder for each injection or for each predetermined number of revolutions based on the air-fuel ratio feedback correction amount calculated by the fuel ratio feedback control means, and generating torque in accordance with the predicted value of the cylinder air-fuel ratio. Means for calculating an ignition timing correction amount so as to match a predetermined required torque; and means for calculating the ignition timing by correcting the basic ignition timing with the ignition timing correction amount. And a device for performing ignition with the signal of the calculated ignition timing.