JP2011179395A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly accurately control air volume to achieve target torque even in a condition where an engine speed is changed, when a throttle delay control for delaying timing of outputting target throttle opening to a throttle is performed. <P>SOLUTION: The future engine speed by a delay time Δt than present is predicted. The air volume required for achieving the target torque at the predicted engine speed is calculated as a target air volume. Further, throttle opening required for achieving the target air volume at the predicted engine speed is calculated as target throttle opening. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine capable of controlling torque by the opening of a throttle, and more specifically, from calculating a target throttle opening based on the target torque to outputting the target throttle opening to the throttle. The present invention relates to a control device for an internal combustion engine having a predetermined delay time therebetween.

  In an internal combustion engine equipped with an electronically controlled throttle, a target throttle opening is calculated based on the target torque, and the throttle is operated according to the target throttle opening. As a method for calculating the target throttle opening from the target torque, it is known to use an inverse model of the response model of the intake system as disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-200466. In the technique described in this publication, the target torque is converted into a target air amount, and the target throttle opening for realizing the target torque is calculated by inputting the target air amount into the inverse model. Use of the inverse model of the intake system response model for calculation of the target throttle opening is useful for improving the torque control accuracy.

  In addition, so-called throttle delay control is known in which a delay time is intentionally provided between the time when the target throttle opening is calculated and the time when the target throttle is output. The specific contents are described in, for example, Japanese Patent Laid-Open No. 10-169469. According to the throttle delay control, the actual throttle opening can be changed by a delay time from the target throttle opening, so the future throttle opening is set to the target throttle opening before the delay by the delay time. It is possible to predict from.

  The throttle delay control is useful for improving the control accuracy of the air-fuel ratio. In the technique described in Japanese Patent Laid-Open No. 10-169469, the throttle opening at the closing timing of the intake valve is predicted, and the fuel injection amount is calculated based on the air amount obtained from the predicted throttle opening. Since the air amount is determined when the intake valve is closed, it is possible to predict the air amount with high accuracy by predicting the throttle opening degree at that point by throttle delay control.

JP 2006-200466 A

JP-A-10-169469

  As a method of torque control and air-fuel ratio control of an internal combustion engine, it is conceivable to combine the above two known techniques. However, the problem in that case is the effect of changes in the engine speed.

  When the engine speed changes during the delay time by the throttle delay control, even if the throttle is operated according to the target throttle opening, the target torque cannot be realized with high accuracy. This is because the relationship between the throttle opening and the air amount depends on the engine speed. In the technique described in JP-A-10-169469, the target throttle opening is calculated from the target air amount using the current engine speed as a parameter. For this reason, if the engine speed changes during the delay time, there is a difference between the air amount realized by operating the throttle according to the target throttle opening and the target air amount.

  Furthermore, the relationship between torque and air volume also depends on the engine speed. For this reason, when the engine speed changes during the delay time, even if the target air amount can be realized, there is a difference between the torque realized thereby and the target torque.

  The present invention has been made in view of the above-described problems, and in a situation where the engine speed is changing when a delay time is provided between the time of calculation of the target throttle opening and the time of output to the throttle. An object of the present invention is to provide a control device for an internal combustion engine that can achieve a target torque by controlling the air amount with high accuracy.

In order to achieve the above object, a control device for an internal combustion engine of the present invention comprises:
In the control device for an internal combustion engine, a predetermined delay time is provided between a calculation time point of the target throttle opening based on the target torque and an output time point of the target throttle opening to the throttle.
Target torque setting means for setting the target torque;
Engine speed prediction means for predicting the future engine speed by the delay time from the present time;
A target air amount calculating means for calculating, as a target air amount, an air amount necessary for realizing the target torque under the predicted engine speed;
A target throttle opening calculation means for calculating a throttle opening required for realizing the target air amount under the predicted engine speed as the target throttle opening;
It is characterized by having.

  According to the control apparatus for an internal combustion engine of the present invention, the target air amount is based on the predicted engine speed in the future by the delay time from the present time, that is, the predicted engine speed at the timing when the target throttle opening is output to the throttle. Furthermore, the target throttle opening is calculated based on the predicted engine speed, so even if the engine speed is changing, the air volume is accurately controlled to obtain the target torque. Can be realized.

It is a figure which shows the structure of the control apparatus of embodiment of this invention. It is a figure for demonstrating the effect on the torque control by the control apparatus of embodiment of this invention.

  An embodiment of the present invention will be described with reference to FIGS.

  A control device according to an embodiment of the present invention is applied to an internal combustion engine (hereinafter referred to as an engine) that has an electronically controlled throttle and whose torque can be controlled by the throttle opening. A specific example of such an engine is a spark ignition type four-stroke reciprocating engine.

  FIG. 1 is a block diagram showing the configuration of the control device 2 of the present embodiment. As shown in FIG. 1, the control device 2 includes a target torque setting unit 4, a target air amount calculation unit 6, a target throttle opening calculation unit 8, a delay control unit 10, and an engine speed prediction unit 12 for each function that the control device 2 has. Can be divided into These elements 4, 6, 8, 10, and 12 are specially expressed only in the elements related to the operation of the throttle 20 for torque control among various functional elements of the control device 2. It is. Therefore, FIG. 1 does not mean that the control device 2 is composed of only these elements 4, 6, 8, 10, and 12. Each of the elements 4, 6, 8, 10, and 12 may be configured by dedicated hardware, or the hardware may be shared and configured virtually by software.

  The control device 2 sets a target torque to be output to the engine in the target torque setting unit 4. The target torque setting unit 4 sets the target torque based on the amount of operation of the accelerator pedal by the driver and a signal from a vehicle control system such as VSC, TRC, or ECT.

  The control device 2 inputs the target torque to the target air amount calculation unit 6. The target air amount calculation unit 6 is provided with an air amount map. The air amount map is a map in which the torque and the air amount are associated with each other using various engine information including the engine speed as a key. The target air amount calculation unit 6 converts the target torque into an air amount value using the air amount map. The current engine information is used for searching the air amount map. However, regarding the engine speed, the air quantity map is searched using the predicted engine speed by the engine speed prediction unit 12 described later, instead of the current engine speed.

  Next, the control device 2 inputs the target air amount to the target throttle opening calculation unit 8. The target throttle opening calculation unit 8 is provided with an air inverse model. A physical model of the intake system in which the response of the air amount to the operation of the throttle is modeled based on fluid dynamics is an air model, and the air inverse model is the inverse model. By inputting the target air amount to the air inverse model, the target throttle opening for realizing it is calculated. A model calculation formula representing the air inverse model includes a plurality of coefficients. At least some of them are variables, and engine information is used to determine their values. The engine information used is basically the engine information at the present time. However, with respect to the engine speed, not the engine speed at the current time but the predicted engine speed by the engine speed prediction unit 12 described later is used.

  The control device 2 inputs the target throttle opening to the delay control unit 10. The delay control unit 10 delays the input target throttle opening by a predetermined delay time. The delay time can be set arbitrarily. The control device 2 outputs the target throttle opening after the delay by the delay control unit 10 to the throttle 20 as an opening command value. As a result, the actual throttle opening changes with a delay time from the target throttle opening, so the future throttle opening is predicted from the target throttle opening before the delay by the delay time. Is possible.

  The engine control by the control device 2 includes not only torque control but also air-fuel ratio control. In the air-fuel ratio control, the control device 2 predicts the throttle opening at the closing timing of the intake valve from the target throttle opening before the delay. Then, the fuel injection amount for realizing the target air-fuel ratio is calculated based on the air amount calculated from the predicted throttle opening. That is, the delay of the target throttle opening output by the delay control unit 10 is performed for the purpose of improving the control accuracy of the air-fuel ratio.

  The engine speed predicting unit 12 predicts the engine speed at a future time, that is, the timing at which the calculated target throttle opening is output to the throttle by the delay time from the present time. As the method, for example, a method of calculating the actual engine speed change speed in a predetermined period until now and calculating the engine speed after the delay time has elapsed using the change speed can be adopted. In addition, since the target torque set at the present time is reflected in the output torque after the delay time, it is assumed that the change in the target torque from before the delay time to the present is the change in the output torque from now on, and is delayed by the equation of motion. You may calculate the change of the engine speed after progress of time. As described above, the predicted engine speed (future engine speed for the delay time from the present time) is used for calculation of the target air quantity by the target air quantity calculation unit 6 and the target throttle opening degree calculation unit 8 sets the target. Used to calculate throttle opening.

  The above is description about the function of each element 4, 6, 8, 10, 12 which comprises the control apparatus 2 of this Embodiment. Next, the effect on torque control obtained by the functions of these elements 4, 6, 8, 10, 12 will be described with reference to FIG.

  FIG. 2 shows a control result obtained when there is a prediction of the future engine speed by Δt from the current time t when the target torque changes in a situation where the engine speed is changing (the control of the present embodiment). The control result by the device 2) and the control result obtained when the engine speed is not predicted (the control result when the target air amount and the target throttle opening are calculated using the current engine speed) are compared. It is a figure shown. Δt in FIG. 2 is a time from when the target throttle opening is calculated until it is output to the throttle 20, that is, a delay time in the throttle delay control.

  In the uppermost stage of FIG. 2, the change over time of the target torque and the change over time of the output torque when there is a prediction of the engine speed (NE) are indicated by solid lines, and the output torque when there is no prediction of the engine speed. The time change is shown by a broken line. The second stage of FIG. 2 shows a situation in which the engine speed decreases during Δt. In the third row of FIG. 2, the change over time of the target air amount when the engine speed is predicted and the change over time of the actual air amount are shown by solid lines. Moreover, the time change of the target air amount when there is no prediction of the engine speed is shown by a broken line. The bottom line in FIG. 2 shows the change over time in the target throttle opening when the engine speed is predicted and the change over time in the actual throttle opening when the target throttle opening is delayed and output. Show. Moreover, the time change of the target throttle opening when there is no prediction of the engine speed is shown by a broken line.

  As can be seen by comparing the target torque with the output torque (solid line) at the top of FIG. 2, the target torque is realized even if the engine speed changes during that time by predicting the future engine speed by Δt It becomes possible to do. However, when the engine speed is not predicted, the target torque cannot be realized as understood by comparing the target torque with the output torque (broken line). As shown in the third and bottom stages of FIG. 2, the target air amount (broken line) cannot be calculated accurately, and the target throttle opening (broken line) can be calculated accurately. It is because it is not possible.

  As described above, according to the control device 2 of the present embodiment, the target air amount and the target throttle opening are calculated based on the predicted engine speed at the time when the target throttle opening is output to the throttle 20. Therefore, even when the engine speed is changing, the target torque can be realized by accurately controlling the air amount.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

2 Controller 4 Target torque setting unit 6 Target air amount calculation unit 8 Target throttle opening calculation unit 10 Delay control unit 12 Engine speed prediction unit 20 Electronically controlled throttle

Claims (1)

In the control device for an internal combustion engine, a predetermined delay time is provided between a calculation time point of the target throttle opening based on the target torque and an output time point of the target throttle opening to the throttle.
Target torque setting means for setting the target torque;
Engine speed prediction means for predicting the future engine speed by the delay time from the present time;
A target air amount calculating means for calculating, as a target air amount, an air amount necessary for realizing the target torque under the predicted engine speed;
A target throttle opening calculation means for calculating a throttle opening required for realizing the target air amount under the predicted engine speed as the target throttle opening;
A control device for an internal combustion engine, comprising:

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