JP2010127122A - Supercharging pressure control device of cylinder injection type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a supercharging pressure control device of a cylinder injection type internal combustion engine for properly controlling the air-fuel ratio, by cooperatively controlling fuel pressure and a supercharger system. <P>SOLUTION: The feasible richest prediction A/F is determined based on present fuel pressure FPrea1, supercharging pressure Pb and an engine speed Ne (Step S1-S8), and when the prediction A/F is larger than a present target A/F(TAF'), the supercharging pressure is restricted (Step S9-S13) by controlling ETV and W/G-V so as to become the target A/F(TAF'). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a supercharging pressure control device for a direct injection internal combustion engine that controls a supercharger provided in the internal combustion engine in which fuel is directly injected into a cylinder.

  2. Description of the Related Art A cylinder injection internal combustion engine that directly injects fuel into a cylinder is equipped with a turbocharger or other supercharger.

JP 2003-254072 A

  In the case of an in-cylinder injection type internal combustion engine, the pressure of fuel (hereinafter referred to as fuel pressure) is increased by a high-pressure fuel pump, and fuel is directly injected into the cylinder. The fuel pressure is a key when controlling the fuel injection amount. On the other hand, in a cylinder injection internal combustion engine equipped with a supercharger, the amount of air taken in is controlled not only by the throttle valve, but also by the components that make up the supercharger system (for example, turbocharger, wastegate valve, etc.) Will be. Therefore, in a cylinder injection internal combustion engine equipped with a supercharger, if the fuel pressure and the supercharger system are not controlled so as to cooperate, an appropriate fuel injection amount cannot be supplied to the intake air amount, and the air-fuel ratio becomes low. Inappropriate conditions could lead to exhaust gas deterioration and engine damage.

  The present invention has been made in view of the above problems, and an object thereof is to provide a supercharging pressure control device for a direct injection internal combustion engine that controls the fuel pressure and the supercharger system in a coordinated manner to appropriately control the air-fuel ratio. To do.

A supercharging pressure control device for a direct injection internal combustion engine according to a first invention for solving the above-described problem is
Fuel injection means for directly injecting fuel into the cylinder of the internal combustion engine;
Fuel pressure detection means for detecting the pressure of fuel supplied to the fuel injection means;
Supercharging means for supercharging intake air sucked into the cylinder;
A supercharging pressure detecting means for detecting a supercharging pressure of the intake air supercharged by the supercharging means;
A rotational speed detection means for detecting the rotational speed of the internal combustion engine;
A predicted air-fuel ratio is obtained based on the current fuel pressure, the supercharging pressure, and the rotational speed detected by the fuel pressure detecting means, the supercharging pressure detecting means, and the rotational speed detecting means, and the current target air pressure of the internal combustion engine is determined. When the predicted air-fuel ratio is larger than the fuel ratio, control means for limiting the supercharging pressure by the supercharging means,
It is characterized by providing.

A supercharging pressure control device for a direct injection internal combustion engine according to a second invention for solving the above-mentioned problems is
In the supercharging pressure control apparatus for a direct injection internal combustion engine according to the first invention,
The control means includes
The richest air-fuel ratio that can be realized is obtained based on the maximum injection amount that can be injected with the current fuel pressure, and the obtained air-fuel ratio is set as the predicted air-fuel ratio.

A supercharging pressure control device for a direct injection internal combustion engine according to a third invention for solving the above-described problem is
In the supercharging pressure control device for a direct injection internal combustion engine according to the second invention,
The control means includes
Based on the fuel weight corresponding to the maximum injection amount and the target air-fuel ratio, the intake air weight as a control target is obtained, and the supercharging pressure by the supercharging means is limited based on the obtained intake air weight. It is characterized by.

A supercharging pressure control device for a direct injection internal combustion engine according to a fourth aspect of the present invention for solving the above-described problem is provided.
In the supercharging pressure control device for a direct injection internal combustion engine according to any one of the first to third inventions,
The control means includes
The first control valve provided in the intake system of the internal combustion engine and the second control valve provided in a bypass passage that bypasses the supercharging means in the exhaust system of the internal combustion engine are controlled to control the opening degree. The supercharging pressure by the supply means is limited, and when the supercharging pressure is limited, the second control valve is controlled after the first control valve is controlled.

A supercharging pressure control apparatus for a direct injection internal combustion engine according to a fifth aspect of the present invention for solving the above-described problem is provided.
In the supercharging pressure control device for a direct injection internal combustion engine according to any one of the first to fourth inventions,
The control means includes
Based on the number of revolutions detected by the number of revolutions detecting means, prediction correction of the number of revolutions when fuel is injected from the fuel injection means is performed.

  According to the present invention, when the predicted air-fuel ratio is larger than the target air-fuel ratio, that is, when the lean air condition is reached from the target air-fuel ratio, the boost pressure side is limited based on the current fuel pressure, Since the fuel ratio is controlled, the air-fuel ratio can be properly controlled, and exhaust gas deterioration and engine damage can be suppressed.

  Hereinafter, an embodiment of a supercharging pressure control device for a direct injection internal combustion engine according to the present invention will be described in detail with reference to FIGS.

Example 1
FIG. 1 is a schematic configuration diagram showing an example of an embodiment of a supercharging pressure control device for a direct injection internal combustion engine according to the present invention, and FIGS. 2 and 3 respectively show the direct injection shown in FIG. It is the block diagram and flowchart explaining the control in the supercharging pressure control apparatus of a type internal combustion engine.

  In this embodiment, an internal combustion engine (hereinafter referred to as an engine) 10 is an in-cylinder injection type gasoline engine that directly injects fuel into a cylinder, and supercharges air (intake air) sucked into the cylinder. A supercharger (supercharging means) is provided. Although the engine 10 has a plurality of cylinders, only one cylinder is illustrated in FIG. 1 and the configuration thereof will be described.

  As shown in FIG. 1, the engine 10 includes a cylinder 11 that constitutes a cylinder, and a piston 12 that is provided in the cylinder 11 and reciprocates along the inner wall of the cylinder 11. The space formed by is the combustion chamber 13.

  Further, the engine 10 has, as an intake system mechanism, an air cleaner 14 that cleans the sucked air when sucking air from the outside, an air flow sensor 15 that detects the flow rate of the cleaned air, and a combustion chamber. Intake pipes 16, 18, and 21 that lead to 13 are provided.

  The intake pipe 16 is connected to a turbocharger 17 (supercharging means) that supercharges the intake air using exhaust gas, and the air supercharged by the turbocharger 17 passes through the intake pipe 18. Then, it is guided to the intercooler 19. After the air guided to the intercooler 19 is cooled by the intercooler 19, the air amount is controlled by an electronically controlled throttle valve (first control valve; hereinafter abbreviated as ETV) 20, and the intake pipe 21 is Via, it is guided to the combustion chamber 13. At that time, the supercharging pressure of the air supercharged in the combustion chamber 13 is detected using a supercharging pressure sensor 22 (supercharging pressure detecting means) provided in the intake pipe 21.

  Further, the engine 10 functions as a fuel system mechanism by adjusting the pressure of the pressurized fuel supplied to a high-pressure fuel pump 23 that pressurizes the fuel supplied from a fuel tank (not shown) to a high pressure and an injector 26 described later. A fuel pressure sensor 24 (fuel pressure detection means) for detecting, a delivery pipe 25 for distributing the high-pressure fuel, and an injector 26 (fuel injection means) connected to the delivery pipe and directly injecting fuel into the combustion chamber 13 ).

  Therefore, the air supplied from the intake system mechanism and the fuel supplied from the fuel system mechanism are ignited by the spark plug 27 provided in the combustion chamber 13 and combusted.

  The engine 10 is connected to the combustion chamber 13 as an exhaust system mechanism, and is provided in the exhaust pipes 28 and 31 for exhausting the fuel (exhaust gas) combusted in the combustion chamber 13 and the exhaust pipe 31 to purify the exhaust gas. The fuel (exhaust gas) combusted in the combustion chamber 13 is discharged to the outside through this exhaust system mechanism. A turbocharger 17 is provided between the exhaust pipe 28 and the exhaust pipe 31, and the turbocharger 17 is driven using the force of the exhaust gas passing through the exhaust pipe 28 and the exhaust pipe 31. I am trying to pay.

  Between the exhaust pipe 28 and the exhaust pipe 31, a bypass passage 29 for bypassing the turbocharger 17 and a wastegate valve (second control valve; provided in the bypass passage 29 for controlling the amount of exhaust gas to be bypassed; Hereinafter, abbreviated as W / G-V.) 30 is provided so that the exhaust gas can bypass the turbocharger 17.

  The engine 10 is provided with a crank angle sensor 34 that detects the angle of the crankshaft 33 connected to the piston 12, and the engine speed Ne of the engine 10 is determined based on the detected value of the crank angle sensor 34. Is calculated (rotational speed detection means).

  The detected values in the supercharging pressure sensor 22, the fuel pressure sensor 24, and the crank angle sensor 34 are input to an ECU (Electronic Control Unit) 35, and based on these input values, ETV 20, W / G-V30 is controlled, and the supercharging pressure limitation described later is performed.

  Next, the control in the supercharging pressure control device of the present embodiment will be described with reference to FIGS.

  First, the engine speed Ne calculated using the crank angle sensor 34 is acquired (step S1), and the supercharging pressure Pb is acquired using the supercharging pressure sensor 22 (step S2).

  Next, the engine speed acquired based on the map data (engine speed Ne, data of intake air weight Gair (g / st) corresponding to the boost pressure Pb corresponding to the supercharging pressure Pb) acquired in advance by the ECU 35. The intake air weight Gair is obtained from Ne and the supercharging pressure Pb (step S3, block B1). The map data shown in the block B1 is a graph called an equal intake air amount line, and as the intake air amount increases, the equal intake air amount line tends to move in a direction in which the engine speed Ne and the boost pressure Pb increase. There is.

  Next, a period during which fuel can be injected is obtained based on the acquired engine speed Ne, and a maximum injection amount Qstd per injection at the standard fuel pressure is calculated from the obtained period during which fuel injection is possible (step S4, block) B2). As can be seen from the map data shown in block B2, the maximum injection amount Qstd tends to decrease as the engine speed Ne increases. The acquired engine speed Ne itself may be used as the engine speed Ne. However, when actual control is performed based on the acquired engine speed Ne in consideration of detection delay, control delay, etc., that is, The engine rotational speed when fuel is injected from the injector 26 may be predicted and corrected. This is effective when the engine speed changes greatly, for example, when accelerating or decelerating.

Next, a coefficient Kfp for correcting the difference between the actual fuel pressure FPreal and the standard fuel pressure FPstd is calculated based on the actual fuel pressure FPreal actually obtained using the fuel pressure sensor 24 and the standard fuel pressure FPstd used for calculation (step S5, Block B3). The coefficient Kfp is obtained from the following equation.
[Factor KFP] = {[actual fuel FPreal] / [Standard fuel pressure FPstd]} ^1/2

The maximum injection amount Qmax that can be injected with the current fuel pressure is obtained using the maximum injection amount Qstd obtained in step S4 and the coefficient Kfp obtained in step S5 (step S6, block B4). The maximum injection amount Qmax is obtained from the following equation.
[Maximum injection amount Qmax] = [maximum injection amount Qstd] × [coefficient Kfp]

The maximum injection amount Qmax is converted into the fuel weight Gmax using the maximum injection amount Qmax obtained in step S6 and the fuel specific gravity which is a known value (step S7). The fuel weight Gmax is obtained from the following equation.
[Fuel weight Gmax] = [maximum injection amount Qmax] × [fuel specific gravity]

A predicted A / F is obtained using the intake air weight Gair obtained in step S3 and the fuel weight Gmax obtained in step S7 (step S8, block B5). Prediction A / F is calculated | required from the following formula | equation. This predicted A / F is the richest air-fuel ratio that can be actually realized.
[Predicted A / F] = [Intake air weight Gair] / [Fuel weight Gmax]

  Based on the map data (engine speed Ne, target A / F (TAF) data corresponding to the load) acquired in advance in the ECU 35, the current target A / F (TAF) is calculated from the engine speed Ne and the load. Obtained (step S9).

A target A / F (TAF ′) that anticipates the margin α (α is a positive number) is obtained (step S10). The target A / F (TAF ′) is obtained from the following equation. The margin α is a safety coefficient that makes the actually controlled A / F become rich, that is, does not become lean. As described above, in this embodiment, the target A / F (TAF ′) that anticipates the margin is used in the comparison and control described later, but the target A / F (TAF) without the margin obtained in step S9 is used. It may be used in comparison and control described later.
[Target A / F (TAF ′)] = [Target A / F (TAF)] − [Margin α]

  The predicted A / F obtained in step S8 is compared with the target A / F (TAF ') obtained in step S10 (step S11). If the prediction A / F> the target A / F (TAF '), the process proceeds to step S12. If the prediction A / F> the target A / F (TAF') is not satisfied, the series of control procedures is terminated.

If predicted A / F> target A / F (TAF ′) in step S11, the intake air weight TGair as the control target is obtained using the target A / F (TAF ′) and the fuel weight Gmax. (Step S12). The intake air weight TGair is obtained from the following equation.
[Intake air weight TGair] = [Target A / F (TAF ′)] × [Fuel weight Gmax]

  The ECU 35 controls the ETV 20 and W / G-V30 so as to limit the supercharging pressure so that the actual intake air weight becomes the intake air weight TGair obtained in step S12 (step S13). That is, when the calculated prediction A / F is leaner than the target A / F (TAF ′), the current fuel pressure is sucked in until the air-fuel ratio becomes richer than the target A / F (TAF ′). Limit the air weight (supercharging pressure) side. Thereafter, a series of control procedures is terminated.

  In order to limit the weight of the air to be sucked in, W / G-V30 is controlled after controlling ETV20, and (1) ETV20 and (2) W / G-V30 are performed in this order. This is because the ETV 20 (the air weight increases when it is opened) is quick in terms of air weight control. On the other hand, W / G-V30 (the air weight decreases when opened) is efficient in controlling the air weight.

  In the above control, based on the current engine speed, supercharging pressure, and fuel pressure, the air-fuel ratio that affects the exhaust temperature is obtained as the richest predicted air-fuel ratio that can be realized, and the predicted air-fuel ratio is larger than the target air-fuel ratio. In this case, since the boost pressure side is limited based on the current fuel pressure, the actual air-fuel ratio can be properly controlled, exhaust gas deterioration and engine damage can be prevented, and the exhaust system temperature rise is delayed. And control in consideration of the margin.

(Example 2)
FIGS. 4 and 5 are a block diagram and a flowchart for explaining the control in the supercharging pressure control device for the direct injection internal combustion engine of the present embodiment, respectively.

  Also in the present embodiment, the engine may be an in-cylinder injection type and a supercharger. Therefore, as an example of the configuration, the engine 10 shown in FIG. 1 of the first embodiment will be referred to, and the control in the supercharging pressure control device of the present embodiment will be described using FIGS. 4 and 5. Detailed description of the same components as those in the first embodiment will be omitted.

  First, the engine speed Ne calculated using the crank angle sensor 34 is acquired (step S21), and the supercharging pressure Pb is acquired using the supercharging pressure sensor 22 (step S22).

  Next, the lower limit fuel pressure is obtained from the acquired engine speed Ne and boost pressure Pb based on the map data (the engine speed Ne and lower limit fuel pressure data corresponding to the boost pressure Pb) acquired in advance by the ECU 35. (Step S23, block B11). The map data shown in the block B11 is obtained by obtaining the lower limit fuel pressure corresponding to the engine speed Ne and the supercharging pressure Pb so that the air-fuel ratio A / F = 13.

  Next, the actual fuel pressure actually acquired using the fuel pressure sensor 24 is compared with the lower limit fuel pressure obtained in step S23 (step S24). If the actual fuel pressure <the lower limit fuel pressure, the process proceeds to step S25. If the actual fuel pressure <the lower limit fuel pressure is not satisfied, the series of control procedures is terminated.

  Next, based on the map data (the engine speed Ne, the supercharging pressure Pb corresponding to the lower limit fuel pressure, that is, the data obtained by reverse lookup of the data shown in the block B11) acquired in advance by the ECU 35. From the acquired engine speed Ne and the lower limit fuel pressure obtained in step S23, a limit supercharging pressure is obtained (step S25, block B12). As the engine speed Ne, the acquired engine speed Ne itself may be used. However, as in the first embodiment, when the control is actually performed, that is, the engine when fuel is injected from the injector 26. The rotational speed may be predicted and corrected.

  The ECU 35 controls the ETV 20 and W / G-V30 so as to limit the weight of air to be sucked so that the actual weight of the intake air is equal to or less than the limit supercharging pressure obtained in step S25 (step S26). That is, the intake air weight is limited so that the air-fuel ratio becomes rich when the actual fuel pressure is less than the lower limit fuel pressure. Thereafter, a series of control procedures is terminated.

  The intake air weight is limited in the order of (1) ETV20 and (2) W / G-V30, as in the first embodiment.

  In the above control, the lower limit fuel pressure is obtained based on the current engine speed and the boost pressure, and the boost pressure is limited based on the obtained lower limit fuel pressure. And engine damage can be prevented. As described above, the air weight is not limited to the first embodiment, and the air-fuel ratio can be appropriately controlled by the control shown in the second embodiment. In the first embodiment, the control is performed after the predicted A / F is calculated. However, in the present embodiment, the calculation of the predicted A / F is unnecessary, and the control can be simplified.

  In the first and second embodiments, a turbocharger is shown as a supercharger. However, the present invention can also be applied to other superchargers such as a supercharger.

  The present invention is suitable for a direct injection internal combustion engine provided with a supercharger.

It is a schematic block diagram which shows an example of embodiment of the supercharging pressure control apparatus of the cylinder injection type internal combustion engine which concerns on this invention. It is a block diagram explaining the control in the supercharging pressure control apparatus of the direct injection type internal combustion engine shown in FIG. 2 is a flowchart illustrating control in a supercharging pressure control device for a direct injection internal combustion engine shown in FIG. 1. It is a block diagram explaining the other example of the control about the supercharging pressure control apparatus of the cylinder injection type internal combustion engine which concerns on this invention. It is a flowchart explaining another example of the control about the supercharging pressure control apparatus of the direct injection internal combustion engine which concerns on this invention.

Explanation of symbols

10 Engine 17 Turbocharger 20 ETV
22 Supercharging pressure sensor 23 High pressure fuel pump 24 Fuel pressure sensor 26 Injector 29 Bypass passage 30 W / G-V
34 Crank angle sensor 35 ECU

Claims (5)

Fuel injection means for directly injecting fuel into the cylinder of the internal combustion engine;
Fuel pressure detection means for detecting the pressure of fuel supplied to the fuel injection means;
Supercharging means for supercharging intake air sucked into the cylinder;
A supercharging pressure detecting means for detecting a supercharging pressure of the intake air supercharged by the supercharging means;
A rotational speed detection means for detecting the rotational speed of the internal combustion engine;
A predicted air-fuel ratio is obtained based on the current fuel pressure, the supercharging pressure, and the rotational speed detected by the fuel pressure detecting means, the supercharging pressure detecting means, and the rotational speed detecting means, and the current target air pressure of the internal combustion engine is determined. When the predicted air-fuel ratio is larger than the fuel ratio, control means for limiting the supercharging pressure by the supercharging means,
A supercharging pressure control device for a cylinder injection type internal combustion engine. The supercharging pressure control device for a direct injection internal combustion engine according to claim 1,
The control means includes
Based on the maximum injection amount that can be injected with the current fuel pressure, the richest possible air-fuel ratio is obtained, and the obtained air-fuel ratio is set as the predicted air-fuel ratio. Supply pressure control device. The supercharging pressure control device for a direct injection internal combustion engine according to claim 2,
The control means includes
Based on the fuel weight corresponding to the maximum injection amount and the target air-fuel ratio, the intake air weight as a control target is obtained, and the supercharging pressure by the supercharging means is limited based on the obtained intake air weight. A supercharging pressure control device for a direct injection internal combustion engine. The supercharging pressure control device for a direct injection internal combustion engine according to any one of claims 1 to 3,
The control means includes
The first control valve provided in the intake system of the internal combustion engine and the second control valve provided in a bypass passage that bypasses the supercharging means in the exhaust system of the internal combustion engine are controlled to control the opening degree. A cylinder injection type internal combustion engine that restricts a supercharging pressure by a supply means, and controls the second control valve after controlling the first control valve when limiting the supercharging pressure. Engine supercharging pressure control device. In the supercharging pressure control device for a direct injection internal combustion engine according to any one of claims 1 to 4,
The control means includes
A boost pressure control for a cylinder injection type internal combustion engine, wherein a prediction correction of a rotation speed when fuel is injected from the fuel injection means is performed based on the rotation speed detected by the rotation speed detection means. apparatus.

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