JP4989377B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device mounted on a vehicle.

  In automobile engine control, control parameters that affect engine torque (ignition timing, valve timing, etc.) must be manipulated due to demands for improved fuel consumption and reduced exhaust emissions, even in situations where there is no intention to change engine torque. You may not get. At this time, control is known in which torque is kept constant by adjusting other control parameters (electric throttle, etc.) capable of operating torque so that torque fluctuation does not occur. (Such control is hereinafter referred to as “constant torque control”.)

  As an example of constant torque control, there is an early catalyst temperature increase control by ignition retard (see FIG. 7) at the time of fast idling. As shown in FIG. 8, since the exhaust temperature rises by performing the ignition retard, the catalyst can be heated and activated early, but on the other hand, the engine torque is lowered and the rotational speed at the time of fast idling is lowered. A malfunction occurs.

  Patent Document 1 relates to a torque control device for an internal combustion engine. In order to prevent the above-described problem, the torque change rate due to ignition retard is calculated, and the required air amount is divided by the torque change rate to reduce the torque. A technique for increasing the throttle opening to compensate for the minute is disclosed.

  Another example of constant torque control is low fuel consumption control using a variable valve timing mechanism. In this control, as shown in FIG. 9, the valve phase angle is adjusted to increase the valve overlap amount, and the fuel efficiency is improved (see FIG. 10) by the pump loss reduction effect. Patent Document 2 relates to an electronic throttle control device for an internal combustion engine, and calculates a torque change rate resulting from an increase in overlap amount, and corrects a required air amount and thus a throttle opening by the torque change rate. Discloses a technique for controlling the engine torque to be constant.

JP 2003-278591 A JP 2002-303177 A

  The torque generation efficiency when the ignition retard or the valve phase angle is changed generally depends on the engine operating region (intake amount / engine speed). Therefore, when the operating region changes significantly before and after the throttle opening correction, there may occur a case where the torque generation efficiency η1 before the throttle opening correction and the torque generation efficiency η2 after the throttle opening correction are greatly different. In such a case, the conventional technique has a problem that the throttle opening correction amount set based on η1 does not match the η2 in the operation region of the transfer destination, and the accuracy of constant torque control is greatly impaired. there were.

  The present invention has been made in order to solve the above-described problems. Even when the torque generation efficiency of the control parameter related to the engine torque varies greatly depending on the operation region, the engine torque that performs the constant torque control with high accuracy. An object is to provide a control means.

  In order to solve the above-described problems, an engine control apparatus according to the present invention calculates a target torque when a control parameter related to engine torque is changed in engine control, and the engine is based on the target torque. In an engine control apparatus that compensates for engine torque by adjusting other control parameters related to torque, it is assumed that the other control parameters have been adjusted before performing the adjustment of the other control parameters. Predicting the operating state, calculating the predicted generated torque under the predicted operating state, and if the deviation between the target torque and the predicted generated torque is greater than or equal to a predetermined value, change the change amount of the control parameter, The calculation of the target torque and the predicted generated torque is recalculated.

  The engine control apparatus of the present invention uses a corrected target torque obtained by correcting the target torque based on a final torque generation efficiency when a deviation between the target torque and the predicted generated torque is equal to or less than a predetermined value. The engine torque is compensated for.

  In the engine control apparatus according to the present invention, the recalculation is limited to a predetermined number of times or less, and when the predetermined number of times is exceeded, the deviation and the target torque and the torque generation efficiency are minimized. The engine torque is compensated using the corrected target torque obtained by correcting the target torque based on the above.

  The engine control apparatus according to the present invention is characterized in that the recalculation is executed using a sequential search method or a binary search method.

  Further, in the engine control device of the present invention, the control parameters relating to the engine torque include throttle opening, fuel injection amount, ignition timing, valve timing, EGR valve opening, swirl control valve opening, variable intake pipe effective length, It is any one of the wastegate valve opening degree of a turbocharger.

  According to the present invention, even when the torque generation efficiency η of the control parameter related to the engine torque varies greatly depending on the operation region, the torque constant control that keeps the torque constant can be realized with high accuracy and stability. There is an effect.

  Hereinafter, the best mode for carrying out the present invention will be described based on examples.

[Example 1]
FIG. 1 shows a hardware configuration of an automobile gasoline engine with a variable valve mechanism to be controlled. An engine control unit (ECU) 118 determines a target valve opening according to the amount of depression of an accelerator pedal operated by a driver, and transmits an opening command value to an electronic control throttle valve (electric throttle) 103. When the electric throttle 103 achieves the target valve opening according to the command value, intake pipe negative pressure is generated and air is taken into the intake pipe.

  The air taken in from the intake pipe inlet passes through the air cleaner 100 and is introduced into the inlet of the electric throttle 103 after the intake air amount is measured by the airflow sensor 102 provided in the middle of the intake pipe 101. The measured value of the airflow sensor 102 is transmitted to the ECU 118. The ECU calculates the fuel injection pulse width of the injector 105 so that the air-fuel ratio becomes the stoichiometric air-fuel ratio, based on the measured value of the airflow sensor.

  The intake air that has passed through the electric control throttle 103 is introduced into the intake manifold after passing through the collector 104, and is mixed with the gasoline spray injected from the injector 105 in accordance with the fuel injection pulse width signal to become an air-fuel mixture, It is introduced into the combustion chamber 111 in the cylinder 1 in synchronization with the opening / closing of the intake valve 107. After that, when the intake valve 107 is closed and the air-fuel mixture compressed in the process of ascending the piston 112 is ignited by the spark plug 108 according to the ignition timing commanded by the ECU 118 in the vicinity immediately before the compression top dead center, And the piston 112 is pushed down to generate engine torque.

Thereafter, the exhaust stroke starts from the moment when the piston 112 rises and the exhaust valve 110 opens, and the exhaust gas is discharged to the exhaust manifold 113. A three-way catalyst 115 for purifying exhaust gas is provided downstream of the exhaust manifold 113. When exhaust gas passes through the three-way catalyst 115, hydrocarbon (HC), carbon monoxide (CO), nitrogen oxide ( The exhaust component of NOx is converted into water (H ₂ O), carbon dioxide (CO ₂ ), and nitrogen (N ₂ ). Note that a wide-range air-fuel ratio sensor 114 and an O ₂ sensor 116 are respectively installed at the inlet and outlet of the three-way catalyst, and the air-fuel ratio information measured by these sensors is transmitted to the ECU 118. The ECU performs air-fuel ratio feedback control by adjusting the fuel injection amount so that the air-fuel ratio becomes close to the theoretical air-fuel ratio based on such information.

  The command value for the valve opening of the electric throttle is set based on the target engine torque calculated in the ECU 118. The ignition timing is usually set near the ignition timing (MBT: Minimum advance for the Best Torque) that can generate torque most efficiently, but it may be set to the delay side according to the torque demand or exhaust reduction demand. is there. (This setting is hereinafter referred to as “ignition retard”.)

The opening / closing timings of the intake valve 107 and the exhaust valve 110 are determined by the cam phases of the intake camshaft and the exhaust camshaft, respectively. In the first embodiment, the intake camshaft 106 and the exhaust camshaft 109 are provided with cam phase angle changing actuators that are hydraulically driven, and the ECU calculates a command value according to the operating condition, and based on the command value The cam phase is changed by operating the cam phase angle changing actuator. As an example of cam phase angle optimization, in the low to medium rotation or low to medium load range, the intake cam is advanced with respect to the reference phase angle, and the exhaust cam is retarded with respect to the reference phase angle. Set the overlap larger than normal. Accordingly, and fuel economy improvement effect due to pumping loss reduction, it is possible to realize the NO _X reduction due to the combustion temperature decreases due to internal EGR increases.

  FIG. 2 shows a control block of the first embodiment in which the present invention is applied to torque-based (torque demand) type engine control corresponding to the engine configuration shown in FIG. The target engine torque calculation means 204 is a basic parameter for torque control based on input information such as the accelerator opening 201, the idle request torque 202, and the external request torque 203 (transmission request torque, traction control request torque, etc.). The air equivalent target torque 208 is calculated.

  The ignition retard amount calculation means 206 calculates an appropriate ignition retard amount 207 based on an exhaust reduction request typified by early catalyst activation immediately after engine startup. The torque generation efficiency η calculating means 210 calculates a torque generation efficiency η211 based on MBT based on the ignition retard amount 207. Next, the corrected air equivalent target torque 209 is calculated by dividing the air equivalent target torque 208 by the torque generation efficiency η211. Then, the target throttle opening calculation means 212 calculates the target throttle opening 213 based on the corrected air equivalent target torque, and outputs this to the electric throttle.

With the above configuration, for example, when an ignition retard amount 207 of 30 degrees is determined by the exhaust reduction request 205 while fast idle is being executed with the air equivalent target torque 208 being 20 Nm, torque is generated. The efficiency η calculating means 210 calculates η = 0.5, for example, as the torque generation efficiency corresponding to the retard amount. Next, when the air equivalent target torque 208 is divided by 0.5 and corrected to 40 Nm as the corrected air equivalent target torque, the torque generation efficiency is 0.5 for an air amount equivalent to 40 Nm. In addition,
40Nm × 0.5 = 20Nm
Thus, even if ignition retard is performed, the engine torque can be controlled to be constant. However, the algorithm assumes that the torque generation efficiency η211 does not change significantly at the operating points before and after the throttle. The torque generation efficiency η calculating means 210 for the purpose of calculating the torque generation efficiency η211 that satisfies the above conditions will be described below.

  FIG. 3 shows an overall block of the torque generation efficiency η calculating means 210. FIG. 4 shows a flowchart of the calculation. As a measure for solving the above-described problem, the calculation unit of the first embodiment does not output the torque generation efficiency η immediately, and determines whether the value is an appropriate value in advance for realizing constant torque control. Has an algorithm to verify.

Specifically, it is as follows.
a) Similar to the conventional algorithm, η1 in the current operation region (operating point) and the throttle opening correction amount based on η1 are calculated.
b) Next, η2 in the operation region (operating point) after the predicted throttle opening correction and the generated torque based on η2 are predicted.
c) Next, the deviation between the air equivalent target torque and the predicted generated torque is verified,
If the deviation is smaller than the predetermined value, output η2 as the final value of η,
When the deviation is larger than a predetermined value, the above-mentioned η1 and η2 are recalculated until the deviation from the air equivalent target torque becomes small (iteration), and η is output after convergence.
d) At the time of the iteration, the maximum number of operations Nmax is set, Nmax is divided into two at the center,
When N <Nmax / 2, the iteration is performed in the direction of adding η, which is the correction amount of η, in one direction with respect to η (1) of the initial calculation.
When Nmax / 2 <number of operations N ≦ Nmax, the iteration is performed in the direction in which Δη is integrated in the opposite direction to η (1) of the initial calculation,
• If the number of operations N> Nmax, η (N) with the smallest torque deviation is selected and output from the Nmax calculations.

Hereinafter, the calculation flow of the torque generation efficiency η calculation means will be described with reference to FIGS. 3 and 4.
Calculation step (1)
Set N (number of operations) = 1.
Calculation step (2)
Torque generation efficiency current value calculation means 301 calculates torque generation efficiency η1 (N) at the current operating point.
Calculation step (3)
Judge N> Nmax (maximum number of operations)
If Yes: Go to calculation step (14).
If No: go to calculation step ( 4 ) .
Calculated step (4)
Based on η1 (N), the operating point (engine load) after the throttle opening correction is predicted.
Specifically, the following calculation is performed.
Air equivalent target torque prediction value = Air equivalent target torque ÷ η1 (N)
Calculation step (5)
Using the predicted air equivalent target torque value as input, the torque generation efficiency future value calculation means 303 is used to calculate the torque generation efficiency prediction value η2 (N) at the predicted operating point.
Calculation step (6)
The predicted generation torque ESTRQ (N) is calculated using the following calculation formula.
ESTTRQ (N) = Air equivalent target torque ÷ η1 (N) × η2 (N)
Calculation step (7)
A torque error TRQ_ER (N) that is a difference between the predicted generation torque 305 and the air equivalent target torque 208 is calculated.
TRQ_ER (N) = | ESTTRQ (N) -TGTRQ |

Calculation step (8)
Judge TRQ_ER (N) ≤ ER_SL (torque error threshold)
If yes: go to calculation step (9)
If No: go to the calculation step (10).
Calculation step (9)
As η = η2 (N), η which is the final torque generation efficiency is output to the outside, and the calculation routine is terminated.
Calculation step (10)
N = N + 1 and the number of calculations is updated.
Calculation step (11)
Determine N ≦ Nmax / 2 (half value of the maximum number of calculations)
If yes: go to calculation step (12),
If No: go to calculation step (13).
Calculation step (12)
Δη (η correction value for iteration) is calculated by Δη calculating means 308, and η1 (N) is calculated by the following equation.
η1 (N) = η2 (N −1 ) + Δη
After the calculation, the process returns to the calculation step (3), and the calculation after the calculation step (3) is repeated.
Calculation step (13)
Similar to the calculation step (12), η1 (N) is calculated by the following equation using Δη.
When N = Nmax / 2 + 1, η1 (N) = η2 (1) −Δη
Otherwise, η1 (N) = η2 (N −1 ) −Δη
After the calculation, the process returns to the calculation step (3), and the calculation after the calculation step (3) is repeated.
Calculation step (14)
(Receiving the result that the determination in the calculation step (2) is Yes)

  Among the Nmax TRQ_ER (N) [N = 1 to Nmax] calculated so far, the minimum TRQ_ER (N) is investigated, and η2 (N) corresponding to the N is selected. Next, η = η2 (N) is set, and η, which is the final torque generation efficiency, is output to the outside, and the calculation routine is terminated.

  By executing the above calculation steps (1) to (14), the amount of change at the operating point before and after the throttle is small, and the torque generation efficiency η211 optimal for constant torque control can be calculated.

  FIG. 5 shows an example of the above calculation process. FIG. 5A shows an example in which the torque error is within an allowable range after one calculation. FIG. 5B shows an example of convergence when N ≦ Nmax / 2. FIG. 5C shows an example in which the torque error does not converge (rather diverges) when N ≦ Nmax / 2, but converges when Nmax / 2 <N ≦ Nmax. FIG. 5D shows an example in which the torque error does not converge when N ≦ Nmax. In this case, η 2 (N) indicating the smallest torque error is output.

  Note that the method for calculating the optimum η that minimizes the torque error is not limited to the above-described sequential search method (data search method for checking whether the target data is sequentially from the beginning). In a region that monotonously increases or decreases, the binary search method (divides the entire data in half to determine which region the target data is in, and further divides the region in half to search Can be applied, and a faster search algorithm such as a data search method that narrows the search range by half can be applied.

[Example 2]
FIG. 6 shows a control block diagram of Embodiment 2 in which the present invention is applied to a variable valve system. The difference from the first embodiment is that the input parameter to the torque generation efficiency calculating means 210 is changed from the ignition retard amount 207 to the valve phase angle 503.

  The target valve phase angle calculation means 502 calculates an optimal valve phase angle 503 considering valve overlap in response to a fuel consumption reduction request. Then, by executing the same algorithm as in the first embodiment, the optimum torque generation efficiency η211 is calculated based on the valve phase angle, and the corrected air equivalent target torque 209 is calculated by dividing the air equivalent target torque. After the calculation, the target throttle opening is calculated and output to the electric throttle, so that the air flow rate is accurately and accurately corrected, and high-precision torque constant control is realized.

  Compared to the torque generation efficiency η related to the ignition retard, the torque generation efficiency η related to the valve phase angle is more dependent on the operation region, so the second embodiment applied to the variable valve system is compared to the first embodiment, There is an effect that the accuracy improvement effect of the constant torque control becomes larger.

  Further, the algorithm of the present invention is not limited to ignition timing and variable valve system, but other parameters affecting engine torque (EGR valve opening, swirl control valve opening, variable intake pipe effective length, turbocharger wastegate It is also effective for cooperative torque control between the valve opening and the like) and the throttle.

The figure which shows the hardware constitutions of the gasoline engine for motor vehicles with a variable valve mechanism. FIG. 3 is a diagram illustrating a part of a control block according to the first embodiment. FIG. 3 is a block diagram illustrating the entire torque generation efficiency calculation unit according to the first embodiment. The figure which shows the flowchart of torque generation efficiency calculation. The figure which shows another process in the case of torque generation efficiency calculation. FIG. 6 is a diagram illustrating a part of a control block according to a second embodiment. The figure which shows the relationship of the cylinder pressure with respect to a crank angle. The figure which shows the relationship between the engine torque with respect to ignition retard amount, and exhaust temperature. The figure which shows the contents of a variable valve system and valve overlap. The figure which shows the relationship between the engine torque with respect to valve overlap amount, and a fuel consumption.

Explanation of symbols

1: Automotive gasoline engine (cylinder),
100: Air cleaner,
101: Intake pipe
102: Airflow sensor
103: Electric throttle,
104: Collector,
105: Injector,
106: intake cam,
107: intake valve,
108: Spark plug,
109: exhaust cam,
110: exhaust valve,
111: Combustion chamber
112: piston,
113: exhaust manifold,
114: Wide area air-fuel ratio sensor,
115: Three-way catalyst,
116: O ₂ sensor,
117: Accelerator pedal sensor,
118: Engine control unit,
207: ignition retard amount,
211: Torque generation efficiency η
213: Target throttle opening,
301: Torque generation efficiency current value calculation means,
302: Torque generation efficiency current value η1,
303: Torque generation efficiency future value calculation means,
304: Torque generation efficiency future value η2,
307: η calculation means after correction,
308: Δη calculation means,
503: Target valve phase angle

Claims (4)

In engine control, an engine that compensates for engine torque by calculating an estimated torque when the ignition timing related to the engine torque is changed, and adjusting a throttle opening related to the engine torque based on the estimated torque A control device of
Before performing the adjustment of the throttle opening , after calculating the torque generation efficiency, which is the torque ratio at the current operating point with respect to MBT,
Based on the torque generation efficiency, a predicted operating point after the throttle opening correction is predicted, a predicted torque generating efficiency that is a torque ratio at the predicted operating point with respect to MBT is calculated, and an estimated torque is calculated from the predicted torque generating efficiency And calculating a deviation between the target torque determined from at least the accelerator opening and the estimated torque ,
When the deviation exceeds a predetermined value , the predicted operating point after the throttle opening correction is predicted based on the torque generation efficiency, which is obtained by adding or subtracting a predetermined value to the predicted torque generation efficiency. , Calculating the predicted torque generation efficiency at the predicted operating point, calculating the estimated torque from the predicted torque generation efficiency, and repeatedly calculating at least the target torque determined from the accelerator opening and the estimated torque , Calculate and output the corrected target torque from the predicted torque generation efficiency when the deviation is minimized,
When the deviation is less than or equal to a predetermined value, the corrected target torque is calculated from the predicted torque generation efficiency at that time and output . The control device according to claim 1,
Wherein when the deviation of the target torque and the estimated torque is below a predetermined value, the deviation is calculated the predicted torque generation efficiency or al, compensation after the target torque at the time it reaches the predetermined value or less in the iterative calculation, the correction An engine control device that compensates for engine torque using a rear target torque . In the control device according to claim 1 or 2 ,
The iterative calculation is limited to a predetermined number of times or less , and within the predetermined number of times, a calculation based on a torque generation efficiency obtained by adding a predetermined value to the predicted torque generation efficiency and a predetermined value from the predicted torque generation efficiency. An engine control device that performs both of calculation based on torque generation efficiency obtained by subtracting a value . In the control device according to any one of claims 1 to 3 ,
The engine control apparatus is characterized in that the iterative calculation is executed using a sequential search method or a binary search method.

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