JP2010096002A - Control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a computation error of an amount of fresh air and an amount of EGR gas flowing in a cylinder when controlling an internal combustion engine and an exhaust gas recirculation device affixed to the same. <P>SOLUTION: At a time point of calculating an air amount before intake valve closing timing, when calculating the partial pressure of the fresh air and the partial pressure of the EGR gas at the intake valve closing timing, an actual opening degree of an EGR valve at the intake valve closing timing is estimated based on an EGR valve opening degree at the calculation time point, a time difference from the calculation time pint to the intake valve closing timing and a valve opening speed or a valve closing speed of the EGR valve. Namely, the opening degree is estimated as estimated opening degree=actual opening degree+(time difference×opening or closing speed). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an internal combustion engine and a control device that controls an exhaust gas recirculation device incidental thereto.

  In an internal combustion engine such as an automobile, an EGR is performed in which an intake system and an exhaust system are connected via an exhaust gas recirculation passage, and a part of the exhaust gas is returned to the intake system via the EGR passage. ing. The EGR passage is provided with an EGR valve that opens and closes the EGR passage, and controls the exhaust gas recirculation rate (or recirculation amount) and recirculation timing by manipulating the opening degree of the EGR valve according to the operating condition of the internal combustion engine. To do.

  In controlling this type of internal combustion engine, it is essential to know the amount of fresh air (intake air) and EGR gas flowing into the cylinder in order to calculate the required fuel injection amount according to the operating conditions. . In order to know these new air amount and EGR gas amount, it is necessary to detect the intake pressure in the vicinity of the intake port of the cylinder and the partial pressure of EGR gas occupying it at the intake valve closing timing.

  On the other hand, the fuel injection amount must already be calculated before entering the intake stroke. In reality, it is often the case that fuel injection is started before the intake stroke.

From the above situation, the existing internal combustion engine control system pre-reads the intake pipe pressure. That is, the value of the intake pipe pressure at the intake valve closing timing is predicted at the time of calculating the air amount before the intake valve closing timing (see, for example, the following patent document).
JP 2004-197613 A

  However, for the opening degree of the EGR valve that is the basis for calculating the EGR gas partial pressure, the actual opening degree at the time of calculating the air amount is used as it is, without predicting the opening degree at the intake valve closing timing.

  Therefore, if the air amount calculation is performed while the EGR valve is being opened / closed, there will be a divergence between the opening of the EGR valve at the time of air amount calculation and that at the intake valve closing timing. Then, an error is mixed in the calculated values of the fresh air amount and the EGR gas amount flowing into the cylinder. As a result, the fuel injection amount does not become an optimal value and may become overlean or overrich, leading to deterioration of exhaust gas or reduction of engine output.

  The present invention has been made by paying attention to the above problems for the first time, and an object thereof is to reduce calculation errors of the amount of fresh air and the amount of EGR gas flowing into the cylinder.

  The present invention is a control device that controls an internal combustion engine or an exhaust gas recirculation device that accompanies the internal combustion engine, and at a calculation time prior to a predetermined time for determining the amount of air flowing into the cylinder, fresh air at the predetermined time is determined. Is calculated based on the EGR valve opening at the time of calculation, the time difference from the time of calculation to the predetermined time, and the valve opening speed or valve closing speed of the EGR valve. In addition, the EGR valve opening at the predetermined time point is predicted. Here, the “predetermined time point for determining the amount of air flowing into the cylinder” refers to the intake valve closing timing or a predetermined timing within a period in which the opened intake valve is closed.

  In short, in the present invention, the opening degree of the EGR valve at a predetermined time such as the intake valve closing timing is predicted at the time of calculating the air amount. According to the present invention, it is possible to reduce calculation errors of the amount of fresh air and EGR gas flowing into the cylinder, and it is possible to suppress problems such as deterioration of exhaust gas and reduction of engine output.

  According to the present invention, it is possible to reduce calculation errors in the amount of fresh air and the amount of EGR gas flowing into the cylinder.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. An internal combustion engine 100 schematically showing the configuration of one cylinder in FIG. 1 is mounted on, for example, an automobile. The intake system 1 of the internal combustion engine 100 is provided with a throttle valve 11 that opens and closes according to the amount of depression of an accelerator pedal (not shown), and an intake manifold 12 that integrally has a surge tank 13 downstream of the throttle valve 11. Is attached. A spark plug 8 is provided at the ceiling of the combustion chamber 21 formed at the top of the cylinder 2, and a fuel injection valve 3 is provided at the end of the intake manifold 12 on the intake port side.

  An exhaust manifold 51 is attached to the exhaust system 5 of the internal combustion engine 100, and a three-way catalyst 52 is attached downstream thereof. The intake system 1 and the exhaust system 5 are connected via an exhaust gas recirculation device 6.

  The exhaust gas recirculation device 6 includes an EGR passage 61 having a start end communicating with the exhaust manifold 51 and a terminal end communicating with the surge tank 13, and an external EGR valve 62 provided on the EGR passage 61. The EGR valve 62 controls the flow rate of exhaust gas (EGR gas) that recirculates through the EGR passage 61 through its opening operation.

  The control device that controls the internal combustion engine 100 and the exhaust gas recirculation device 6 is mainly composed of the ECU 4. The ECU 4 is a microcomputer system having a central processing unit 41, a storage device 42, an input interface 43, an output interface 44, and the like. The input interface 43 includes an intake negative pressure signal a output from a pressure sensor 71 that detects intake negative pressure, a rotation speed signal b output from a rotation speed sensor 72 that detects engine rotation speed, and a vehicle speed sensor that detects vehicle speed. 73, a vehicle speed signal c output from the idle switch 74, an IDL signal d output from the idle switch 74, a water temperature signal f output from the water temperature sensor 76 for detecting the cooling water temperature, and a knocking sensor for detecting the knocking state by a change in the combustion pressure. The knocking signal e output from 75, the crank angle signal and cylinder discrimination signal g output from the timing sensor 93 at the end of the intake camshaft 91, and 240 ° from the timing sensor 94 at the end of the exhaust camshaft 92. An exhaust cam signal h or the like output every CA (crank angle) rotation is input. From the output interface 44, a fuel injection signal n is output to the fuel injection valve 3, an ignition signal m is output to the spark plug 8, a valve opening signal o is output to the EGR valve 62, and the like.

  The central processing unit 41 interprets and executes a program stored in advance in the storage device 42, thereby controlling the operation of the internal combustion engine 100. That is, various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine 100 are acquired through the input interface 43, and based on these, the fuel injection amount that is a control input, The ignition timing, the opening degree of the EGR valve 62, and the like are calculated, and control signals m, n, and o corresponding to the control input are applied via the output interface 44.

  The ECU 4 refers to the intake negative pressure signal a output from the pressure sensor 71, the rotation speed signal b output from the rotation speed sensor 72, the opening degree of the EGR valve 62, and the like, and the amount of fresh air flowing into the cylinder 2 and EGR Estimate the amount of gas. Further, referring to the water temperature signal f output from the water temperature sensor 76, the required fuel injection amount, that is, the engine load is calculated. After that, the signal n is input to the fuel injection valve 3 for the fuel injection time corresponding to the required fuel injection amount (energization time for the fuel injection valve 3), and fuel is injected into the intake system 1. In addition, the opening degree of the EGR valve 62 necessary to achieve the target EGR rate corresponding to the operating state of the internal combustion engine 100 is calculated, the opening degree signal o is input to the EGR valve 62, and the EGR valve 62 is operated. The ECU 4 also refers to the knocking signal e output from the knocking sensor 75 to calculate the ignition timing (retard amount or advance amount) according to the operating state and knocking state of the internal combustion engine 100, and the ignition The signal m is input to the spark plug 8 at the timing, and the mixture in the cylinder 2 is ignited.

  The calculation of the required fuel injection amount needs to be completed before entering the intake stroke. For this purpose, the ECU 4 calculates the amount of fresh air and EGR gas flowing into the cylinder 2 at the time of calculating the amount of air before the intake valve closing timing. Actually, the air amount calculation is repeatedly executed every 4 to 8 milliseconds.

  The ECU 4 predicts the opening degree of the EGR valve 62 at the intake valve closing timing at the time of calculating the air amount, and as a result, predicts the intake pressure near the intake port at the intake valve closing timing and the partial pressure of the EGR gas occupied therein. To do.

A method of predicting the opening degree of the EGR valve 62 will be supplemented with reference to FIG. The ECU 4 determines the actual opening degree of the EGR valve 62 at the time of calculating the air amount, the time difference from the time of calculating the air amount to the intake valve closing timing, the valve opening speed or the valve closing speed of the EGR valve 62, (target EGR rate, The EGR valve 62 at the intake valve closing timing based on the target opening (calculated as a control input by the ECU 4) that should be realized after the intake valve closing timing (to achieve the target intake pressure or the like). Calculate the predicted value of the opening. The valve opening speed or valve closing speed of the EGR valve 62, that is, hardware operating characteristic data is stored in the storage device 42 of the ECU 4 in advance. Basically,
Predicted opening = actual opening + (time difference x switching speed)
The predicted value of the opening degree of the EGR valve 62 can be calculated according to the relational expression. However, if the predicted opening value in the above equation exceeds the target opening, that is, if the target opening is reached before the intake valve closing timing arrives, the target opening will open the EGR valve 62. Predicted value of degree.

  If the predicted value of the opening degree of the EGR valve 62 at the intake valve closing timing is obtained, the intake pressure at the intake valve closing timing and the partial pressure of the EGR gas occupied therein are calculated in the same manner as in the existing internal combustion engine control system. can do. Since the intake pressure is the sum of the partial pressure of fresh air and the partial pressure of EGR gas, the amount of fresh air flowing into the cylinder 2 and EGR are calculated from the predicted values of the intake pressure and EGR gas partial pressure at the intake valve closing timing. The amount of gas can be estimated.

  According to this embodiment, it is the control device 4 that controls the internal combustion engine 100 or the exhaust gas recirculation device 6 incidental thereto, rather than a predetermined time point (intake valve closing timing) at which the amount of air flowing into the cylinder 2 is determined. When calculating the partial pressure of fresh air and the partial pressure of EGR gas at the predetermined time at the previous calculation time, the opening of the EGR valve 62 at the calculation time and the time difference from the calculation time to the predetermined time Since the opening degree of the EGR valve 62 at the predetermined time point is predicted based on the valve opening speed or the valve closing speed of the EGR valve 62, the calculation error of the fresh air amount and the EGR gas amount flowing into the cylinder 2 is determined. This makes it possible to reduce problems such as exhaust gas deterioration and engine output reduction.

  The present invention is not limited to the embodiment described in detail above. In the above-described embodiment, the intake valve closing timing is the predetermined time point for determining the amount of air flowing into the cylinder 2, but the calculation is executed with the predetermined timing within the period during which the opened intake valve is closed as the predetermined time point. I will not prevent it.

  Moreover, although the internal combustion engine in the said embodiment was a spark ignition engine, this may be a diesel engine.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

The figure which shows schematic structure of the internal combustion engine, exhaust-gas recirculation apparatus, and control apparatus in one Embodiment of this invention. The figure explaining the prediction method of an EGR valve opening.

Explanation of symbols

0 ... Internal combustion engine 4 ... ECU (control device)
6 ... Exhaust gas recirculation device 62 ... EGR valve

Claims (1)

A control device that controls an internal combustion engine or an exhaust gas recirculation device that accompanies the internal combustion engine, and at a calculation time prior to a predetermined time for determining the amount of air flowing into the cylinder, In calculating the partial pressure of gas and the partial pressure of EGR gas,
Predicting the EGR valve opening at the predetermined time based on the EGR valve opening at the calculation time, the time difference from the calculation time to the predetermined time, and the valve opening speed or the valve closing speed of the EGR valve. Control device characterized.

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