KR100534921B1 - Engine torque control method - Google Patents

Abstract

The present invention relates to an engine torque control method, comprising: calculating a required torque according to an engine torque reduction request; Calculating and controlling the ignition timing by using the required torque; Calculating an exhaust gas modeling temperature and a catalyst modeling temperature; Returning an ignition timing to a basic ignition timing when the exhaust gas modeling temperature and the catalyst modeling temperature are larger than a preset value; Calculating a control torque using the ignition timing determined as described above; If the control torque is greater than the required torque, controlling the fuel cutoff for each cylinder; Calculating a lambda set point and a cylinder shutoff time at full load; Adjusting a lambda set point if the cylinder shutoff time is greater than or equal to a preset time; Comprising the step of calculating the control torque according to the fuel cut, it is possible to prevent the rise of the temperature of the exhaust gas and catalyst when the engine torque is reduced to improve the durability of the exhaust system as well as to prevent damage to the catalyst It works.

Description

Engine torque control method {Engine torque control method}

The present invention relates to an engine torque control method, and more particularly, to an engine torque control method for preventing the temperature of the exhaust gas and the catalyst from increasing when the engine torque is reduced.

In general, when the traction control system is operated in the engine torque control system, the gear shift of the automatic transmission vehicle occurs, the engine speed reaches the maximum value, or the vehicle speed reaches the maximum value, in each case Control by reducing the required torque.

For example, the engine torque is reduced when the traction control system is operated to reduce the driving force of the vehicle, thereby smoothly controlling the vehicle on roads having different coefficients of friction. The engine control unit (ECU) calculates the required torque, and calculates the control torque using the ignition timing and the fuel cut-off control method for each cylinder.

However, in the above-described method, the exhaust gas temperature rises due to the excessive ignition timing perception during torque reduction operation, and the A / F fluctuates suddenly when the fuel cut-off operation for each cylinder causes the unburned fuel to be exhausted. Or after-burn occurs in the catalyst.

This leads to an increase in catalyst temperature and exhaust gas temperature, which not only deteriorate the durability of the exhaust system, but also cause catastrophic damage to the catalyst, which is a direct cause of increased exhaust gas.

Accordingly, the present invention is designed to solve the conventional problems as described above, it is possible to prevent the rise of the exhaust gas and the catalyst temperature at the time of reducing the engine torque to improve the durability of the exhaust system as well as to damage the catalyst. It is an object of the present invention to provide an engine torque control method for preventing the engine torque.

An engine torque control method according to the present invention for achieving the above object comprises the steps of: calculating a required torque according to an engine torque reduction request; Calculating and controlling the ignition timing by using the required torque; Calculating an exhaust gas modeling temperature and a catalyst modeling temperature; Returning an ignition timing to a basic ignition timing when the exhaust gas modeling temperature and the catalyst modeling temperature are larger than a preset value; Calculating a control torque using the ignition timing determined as described above; If the control torque is greater than the required torque, controlling the fuel cutoff for each cylinder; Calculating a lambda set point and a cylinder shutoff time at full load; Adjusting a lambda set point if the cylinder shutoff time is greater than or equal to a preset time; And calculating a control torque according to the fuel cutoff.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a flowchart of an engine torque control method according to the present invention, which is executed by the engine control unit 10 shown in FIG.

As shown in FIG. 1, in step S1, it is determined whether the engine control unit 10 satisfies the engine torque reduction requirement, and if so, step S2 is performed. In other words, it is determined that the engine torque reduction requirement is satisfied in one of four cases including traction control system operation, gear shift operation, maximum engine speed reached, and maximum vehicle speed reached.

In step S2, the engine control unit 10 calculates the required torque. That is, when the traction control system is operated, the required torque is obtained by multiplying the maximum engine torque by the slip ratio, and the minimum engine torque is calculated as the required torque when the gear shift operation, the maximum engine speed, and the maximum vehicle speed are reached. Decide

Next, in step S3, the engine control unit 10 calculates and controls the ignition timing. In other words, the ignition timing is calculated by dividing the required torque by the ignition timing efficiency. The ignition timing is retarded as much as the required torque. In this case, the ignition timing efficiency is a numerical value indicating the reduction of the torque amount according to the ignition timing perception amount.

Next, in step S4, the engine control unit 10 calculates the exhaust gas modeling temperature. At this time, the exhaust gas modeling temperature is calculated by multiplying the basic exhaust gas temperature read from a calibration map determined according to the engine speed and the engine load by (basic ignition timing efficiency-current ignition timing efficiency) by the engine maximum torque. It is calculated by adding the exhaust gas temperature.

Next, in step S5, the engine control unit 10 calculates the catalyst modeling temperature. In this case, the catalyst modeling temperature is calculated by adding an exothermic reaction temperature to an exhaust gas modeling temperature, and the exothermic reaction temperature is read from a measurement map determined according to an oxygen storage capacity (OSC) according to a catalyst.

Subsequently, in step S6, the engine control unit 10 determines whether the exhaust gas modeling temperature is larger than a preset value (preferably 800 ° C.), and performs step S7 if it is large, otherwise step S9. Perform

In operation S7, the engine control unit 10 determines whether the catalyst modeling temperature is greater than a predetermined value (preferably 850 ° C.), and performs step S8 when the engine control unit 10 is larger. Perform

In step S8, the engine control unit 10 returns the ignition timing to a preset ignition timing, and then in step S9, the control torque according to the ignition timing perception is calculated. That is, the control torque amount is determined by multiplying the engine torque by the torque ignition timing correction amount. The engine torque is read from the measurement map (engine characteristic function) determined according to the engine speed and the engine load, and the torque ignition timing correction amount is the ignition timing. The amount of torque that decreases with the amount of crust is read from the measurement map (engine characteristic curve).

Then, in step S10, the engine control unit 10 compares the control torque and the required torque, and performs the step S11 when the control torque is larger than the required torque.

In the step S11, the engine control unit 10 performs the fuel cutoff control for each cylinder. That is, in the case of a four-cylinder engine, fuel is selectively cut off from one to four cylinders in some cases. As an example, assuming that the engine torque generated per cylinder is constant and the engine torque that can be generated per cylinder is 25 Nm, in the step S10, when the control torque is 100 Nm and the required torque is 25 Nm, the three cylinders are shut off. That is, the number of cylinders cut off the fuel is determined according to the difference between the control torque and the required torque.

Subsequently, in steps S12 and S13, the engine control unit 10 reads the throttle position from the throttle position sensor to determine whether it is full load, and if it is full load, performs step S14. If no load, step S18 is performed. That is, when a signal indicating that the throttle position is 70% or more is input from the throttle position sensor, it is determined as full load.

In step S14, the engine control unit 10 calculates a lambda set point. That is, the initial value of the lambda set point is read from the measurement map (engine characteristic curve) determined in order to maintain the maximum performance at full load.

Next, in step S15, the engine control unit 10 calculates the fuel cutoff time for each cylinder. That is, the time is counted at the time when the fuel cutoff for each cylinder is started by using the timer provided in the cylinder.

Subsequently, in step S16, the engine control unit 10 determines whether the fuel cut-off time for each cylinder is larger than a preset time (preferably 20 seconds), and performs step S17 if it is large. Otherwise, step S18. ).

In step S17, the engine control unit 10 adjusts the lambda set point, and changes the existing lambda from about 0.8 to 1.0.

Next, in step S18, the engine control unit 10 calculates the control torque according to the fuel cutoff. That is, the control torque amount is determined by adding the torque fuel cutoff correction amount to the torque ignition timing correction amount calculated in the step S9, and the fuel cutoff correction amount is determined by multiplying the engine torque by the number of fuel cutoff cylinders / total cylinders. do.

As described above, according to the present invention, the exhaust gas and the catalyst temperature are prevented from rising during engine torque reduction, thereby improving durability of the exhaust system and preventing damage to the catalyst.

1 is a flowchart of an engine torque control method according to the present invention;

2 is a diagram illustrating input and output of an engine control unit for performing an engine torque control method according to the present invention.

<Explanation of symbols for main parts of the drawings>

10: engine control unit

Claims (1)

Calculating the required torque according to the engine torque reduction request; Calculating and controlling the ignition timing by using the required torque; Calculating an exhaust gas modeling temperature and a catalyst modeling temperature; Returning an ignition timing to a basic ignition timing when the exhaust gas modeling temperature and the catalyst modeling temperature are larger than a preset value; Calculating a control torque using a basic ignition timing or an ignition timing corrected according to the exhaust gas temperature and the catalyst temperature according to a result of comparing each of the exhaust gas modeling temperature and the catalyst modeling temperature with a preset value; If the control torque is greater than the required torque, controlling the fuel cutoff for each cylinder; Calculating a lambda set point and a cylinder shutoff time at full load; Adjusting a lambda set point if the cylinder shutoff time is greater than or equal to a preset time; And calculating a control torque according to the fuel cutoff.