METHOD AND DEVICE FOR CONTROLLING FUEL INJECTION TO ENGINE

Abstract

A method for controlling fuel injection to an engine may include calculating an amount of air passing through a throttle, which is actually controlled, from a calculated amount of air in an intake manifold, which is calculated from a pressure value detected by a pressure sensor installed in the intake manifold connecting the throttle and a cylinder to each other, and a calculated pressure change in the intake manifold. The method may further include predicting an actual amount of air to be sucked into the cylinder when mixed with fuel from the calculated amount of air in the intake manifold and the calculated amount of air passing through the throttle. The method may also include injecting an amount of fuel according to the predicted actual amount of air to be sucked into the cylinder.

Claims

1. A method for controlling fuel injection to an engine, the method comprising: calculating an amount of air passing through a throttle, which is actually controlled, from a calculated amount of air in an intake manifold, which is calculated from a pressure value detected by a pressure sensor installed in the intake manifold connecting the throttle and a cylinder to each other, and a calculated pressure change in the intake manifold; predicting an actual amount of air to be sucked into the cylinder when mixed with fuel from the calculated amount of air in the intake manifold and the calculated amount of air passing through the throttle; and injecting an amount of fuel according to the predicted actual amount of air to be sucked into the cylinder.

2. The method for controlling fuel injection according to claim 1, wherein the actual amount of air to be sucked into the cylinder when mixed with fuel is obtained using a pressure command value obtained by processing the pressure value in the intake manifold with a low-pass filter.

3. The method for controlling fuel injection according to claim 1, wherein the calculated amount of air in the intake manifold is calculated from the pressure value detected by the pressure sensor installed in the intake manifold using the formula: $Q_a=K_c\frac{\omega }{\pi }.Math.\frac{V_c}{R.Math.T_m}.Math.P_m\underset{\_}{;}$ and wherein Q.sub.a is the calculated amount of air in the manifold, K.sub.c is a filling efficiency correction coefficient, ω is a revolutions per minute (rpm) of the engine, V.sub.c is a volume in the cylinder, R is a gas constant, T.sub.m is a temperature in the intake manifold, and P.sub.m is a pressure in the intake manifold.

4. The method for controlling fuel injection according to claim 1, wherein the calculated pressure change in the intake manifold connecting the throttle and the cylinder to each other is calculated from the calculated amount of air in the intake manifold using the formula: $\frac{d}{\mathrm{dt}}{P}_m=\frac{R.Math.T_m}{V_m}.Math.\left(Q_t-Q_a\right)\underset{\_}{;}$ and wherein V.sub.m is a volume in the intake manifold, R is a gas constant, T.sub.m is a temperature in the intake manifold, P.sub.m is a pressure in the intake manifold, Q.sub.a is the calculated amount of air in the intake manifold, and Q.sub.t is the amount of air passing through the throttle.

5. The method for controlling fuel injection according to claim 1, wherein the amount of air passing through the throttle, which is actually controlled, is calculated from the calculated amount of air in the intake manifold and the calculated pressure change in the intake manifold using the formula: $Q_t=\left(1+\frac{V_m}{V_c}.Math.\frac{\pi }{K_c}.Math.\frac{1}{\omega }.Math.\frac{1}{P_m}.Math.\frac{d}{d_t}{P}_m\right).Math.Q_a\underset{\_}{;}$ and wherein Q.sub.t is the amount of air passing through the throttle, V.sub.m is a volume in the intake manifold, V.sub.c is a volume in the cylinder, K.sub.c is a filling efficiency correction coefficient, ω is a revolutions per minute (rpm) of the engine, P.sub.m is a pressure in the intake manifold, and Q.sub.a is the calculated amount of air in the manifold.

6. A device for controlling fuel injection to an engine, the device comprising: a program stored in a storage unit to execute the method for controlling fuel injection according to claim 1 via inputting a pressure signal detected by the pressure sensor installed in the intake manifold, generating a fuel injection signal, and outputting the fuel injection signal to an injector.

7. The method for controlling fuel injection according to claim 2, wherein the calculated amount of air in the intake manifold is calculated from the pressure value detected by the pressure sensor installed in the intake manifold using the formula: $Q_a=K_c\frac{\omega }{\pi }.Math.\frac{V_c}{R.Math.T_m}.Math.P_m;$ and wherein Q.sub.a is the calculated amount of air in the manifold, K.sub.c is a filling efficiency correction coefficient, ω is a revolutions per minute (rpm) of the engine, V.sub.c is a volume in the cylinder, R is a gas constant, T.sub.m is a temperature in the intake manifold, and P.sub.m is a pressure in the intake manifold.

8. The method for controlling fuel injection according to claim 2, wherein the calculated pressure change in the intake manifold connecting the throttle and the cylinder to each other is calculated from the calculated amount of air in the intake manifold using the formula: $\frac{d}{dt}{P}_m=\frac{R.Math.T_m}{V_m}.Math.\left(Q_t-Q_a\right);$ and wherein V.sub.m is a volume in the intake manifold, R is a gas constant, T.sub.m is a temperature in the intake manifold, P.sub.m is a pressure in the intake manifold, Q.sub.a is the calculated amount of air in the intake manifold, and Q.sub.t is the amount of air passing through the throttle.

9. The method for controlling fuel injection according to claim 2, wherein the amount of air passing through the throttle, which is actually controlled, is calculated from the calculated amount of air in the intake manifold and the calculated pressure change in the intake manifold using the formula: $Q_t=\left(1+\frac{V_m}{V_c}.Math.\frac{\pi }{K_c}.Math.\frac{1}{\omega }.Math.\frac{1}{P_m}.Math.\frac{d}{d_t}{P}_m\right).Math.Q_a;$ and wherein Q.sub.t is the amount of air passing through the throttle, V.sub.m is a volume in the intake manifold, V.sub.c is a volume in the cylinder, K.sub.c is a filling efficiency correction coefficient, ω is a revolutions per minute (rpm) of the engine, P.sub.m is a pressure in the intake manifold, and Q.sub.a is the calculated amount of air in the manifold.

10. A device for controlling fuel injection to an engine, the device comprising: a program stored in a storage unit to execute the method for controlling fuel injection according to claim 2 via inputting a pressure signal detected by the pressure sensor installed in the intake manifold, generating a fuel injection signal, and outputting the fuel injection signal to an injector.

11. The method for controlling fuel injection according to claim 3, wherein the calculated pressure change in the intake manifold connecting the throttle and the cylinder to each other is calculated from the calculated amount of air in the intake manifold using the formula: $\frac{d}{dt}{P}_m=\frac{R.Math.T_m}{V_m}.Math.\left(Q_t-Q_a\right);$ and wherein V.sub.m is a volume in the intake manifold, R is a gas constant, T.sub.m is a temperature in the intake manifold, P.sub.m is a pressure in the intake manifold, Q.sub.a is the calculated amount of air in the intake manifold, and Q.sub.t is the amount of air passing through the throttle.

12. The method for controlling fuel injection according to claim 3, wherein the amount of air passing through the throttle, which is actually controlled, is calculated from the calculated amount of air in the intake manifold and the calculated pressure change in the intake manifold using the formula: $Q_t=\left(1+\frac{V_m}{V_c}.Math.\frac{\pi }{K_c}.Math.\frac{1}{\omega }.Math.\frac{1}{P_m}.Math.\frac{d}{d_t}{P}_m\right).Math.Q_a;$ and wherein Q.sub.t is the amount of air passing through the throttle, V.sub.m is a volume in the intake manifold, V.sub.c is a volume in the cylinder, K.sub.c is a filling efficiency correction coefficient, ω is a revolutions per minute (rpm) of the engine, P.sub.m is a pressure in the intake manifold, and Q.sub.a is the calculated amount of air in the manifold.

13. A device for controlling fuel injection to an engine, the device comprising: a program stored in a storage unit to execute the method for controlling fuel injection according to claim 3 via inputting a pressure signal detected by the pressure sensor installed in the intake manifold, generating a fuel injection signal, and outputting the fuel injection signal to an injector.

14. The method for controlling fuel injection according to claim 4, wherein the amount of air passing through the throttle, which is actually controlled, is calculated from the calculated amount of air in the intake manifold and the calculated pressure change in the intake manifold using the formula: $Q_t=\left(1+\frac{V_m}{V_c}.Math.\frac{\pi }{K_c}.Math.\frac{1}{\omega }.Math.\frac{1}{P_m}.Math.\frac{d}{d_t}{P}_m\right).Math.Q_a;$ and wherein Q.sub.t is the amount of air passing through the throttle, V.sub.m is a volume in the intake manifold, V.sub.c is a volume in the cylinder, K.sub.c is a filling efficiency correction coefficient, ω is a revolutions per minute (rpm) of the engine, P.sub.m is a pressure in the intake manifold, and Q.sub.a is the calculated amount of air in the manifold.

15. A device for controlling fuel injection to an engine, the device comprising: a program stored in a storage unit to execute the method for controlling fuel injection according to claim 4 via inputting a pressure signal detected by the pressure sensor installed in the intake manifold, generating a fuel injection signal, and outputting the fuel injection signal to an injector.

16. A device for controlling fuel injection to an engine, the device comprising: a program stored in a storage unit to execute the method for controlling fuel injection according to claim 5 via inputting a pressure signal detected by the pressure sensor installed in the intake manifold, generating a fuel injection signal, and outputting the fuel injection signal to an injector.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0019] FIG. 1 is a schematic diagram of a device for controlling fuel injection to an engine for implementing an example of the conventional art and an embodiment of the present invention; and

[0020] FIG. 2 is a diagram showing temporal changes in an amount of air passing through a throttle, an amount of air in an intake manifold, and an amount of air to be mixed with fuel when an opened degree of the throttle is changed in the embodiment shown in FIG. 1.

DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0022] FIG. 1 is a schematic diagram of a device for controlling fuel injection to an engine for carrying out an embodiment of the present invention, and basic components and a control method thereof are basically similar to those in the above-described example of the conventional art, but are different in that an amount Qt of air passing through a throttle, which is actually controlled, is calculated from an amount of air in an intake manifold 6 calculated from a pressure value detected by a pressure sensor 7 installed in the intake manifold 6 connecting the throttle and a cylinder 2 to each other, and a pressure change in the intake manifold 6, an actual amount of air to be sucked into the cylinder when mixed with fuel is predicted from the calculated amount Qa of air in the intake manifold and the calculated amount Qt of air passing through the throttle, and fuel is injected according to the predicted amount of air to be sucked into the cylinder.

[0023] More specifically, first, the amount Qa of air in the intake manifold obtained by the intake manifold pressure sensor 7 is obtained according to the following Formula (1).

[0024] In Formula (1) and the formulas to be used below, Kc denotes a filling efficiency correction coefficient, ω denotes an rpm of the engine, Vc denotes a volume in the cylinder, R denotes a gas constant, Tm denotes a temperature in the manifold, Pm denotes a pressure value in the manifold, and Vm denotes a volume in the manifold.

[00004]$\begin{array}{cc}\left[\mathrm{Mathematical}\mathrm{formula}7\right]& \\ Q_a=K_c\frac{\omega }{\pi }.Math.\frac{V_c}{R.Math.T_m}.Math.P_m& \left(1\right)\end{array}$

[0025] Next, a pressure change in the intake manifold 6 connecting the throttle 5 and the cylinder 2 to each other is obtained according to the following Formula (2) using the amount Qa of air in the intake manifold obtained according to Formula (1). In Formula (2), Qt denotes an amount of air passing through the throttle.

[00005]$\begin{array}{cc}\left[\mathrm{Mathematical}\mathrm{formula}8\right]& \\ \frac{d}{\mathrm{dt}}{P}_m=\frac{R.Math.T_m}{V_m}.Math.\left(Q_t-Q_a\right)& \left(2\right)\end{array}$

[0026] In addition, the amount Qt of air passing through the throttle is obtained according to the following Formula (3) using Formulas (1) and (2).

[00006]$\begin{array}{cc}\left[\mathrm{Mathematical}\mathrm{formula}9\right]& \\ Q_t=\left(1+\frac{V_m}{V_c}.\frac{\pi }{K_c}.Math.\frac{1}{\omega }.Math.\frac{1}{P_m}.Math.\frac{d}{\mathrm{dt}}{P}_m\right).Q_a& \left(3\right)\end{array}$

[0027] At this time, the pressure Pm in the intake manifold is controlled to satisfy the following Formula (4) using a pressure proportional gain Kpm and a pressure command value Pmref in the intake manifold.

[00007]$\begin{array}{cc}\left[\mathrm{Mathematical}\mathrm{formula}10\right]& \\ \frac{d}{\mathrm{dt}}{P}_m=K_{\mathrm{pm}}.Math.\left(P_{\mathrm{mref}}-P_m\right)& \left(4\right)\end{array}$

[0028] Then, Formula (4) is put into Formula (3), and the amount Qt of air passing through the throttle is rewritten as the following Formula (5).

[00008]$\begin{array}{cc}\left[\mathrm{Mathematical}\mathrm{formula}11\right]& \\ Q_t=\left(1+\frac{V_m}{V_c}.Math.\frac{\pi }{K_c}.Math.\frac{K_{\mathrm{pm}}}{\omega }.Math.\frac{P_{\mathrm{mref}}-P_m}{P_m}\right).Math.Q_a=\left(1+K_{\mathrm{PQT}}.Math.\frac{P_{\mathrm{mref}}-P_m}{P_m}\right).Math.Q_a& \left(5\right)\end{array}$$\left(K_{\mathrm{PQT}}=\frac{V_m}{V_c}.Math.\frac{\pi }{K_c}.Math.\frac{K_{\mathrm{pm}}}{\omega }\right)$

[0029] Here, as shown in FIG. 2, it has been found that an ideal air-fuel ratio cannot be maintained unless fuel injection is performed with respect to a mid-amount of air between the amount Qa of air in the intake manifold and the amount Qt of air passing through the throttle, because the amount of air rapidly changes when a rapid change is required in the torque required for the engine.

[0030] Here, the mid-amount QB of air between the amount Qa of air in the intake manifold obtained according to Formula (1) and the amount Qt of air passing through the throttle obtained according to Formula (5) is estimated according to the following Formula (6) using an adjustment gain K.sub.PQB.

[00009]$\begin{array}{cc}\left[\mathrm{Mathematical}\mathrm{formula}12\right]& \\ Q_B=\left(1+K_{\mathrm{PQB}}.Math.\frac{P_{\mathrm{mref}}-P_m}{P_m}\right).Math.Q_a& \left(6\right)\end{array}$

[0031] Therefore, by injecting fuel according to the amount Qa of air in the intake manifold 6 obtained from the pressure Pm in the intake manifold, the amount Qt of air passing through the throttle obtained from the pressure change in the intake manifold 6, and the amount QB of air to be mixed with fuel using Formula (6), it is possible to appropriately inject fuel, thereby maintaining an ideal air-fuel ratio even if the torque required for the engine is rapidly changed.

[0032] In actual use, the pressure value Pm in the intake manifold may be influenced by noise in a high-frequency region due to vibration generated while the engine or the like is being operated.

[0033] Therefore, as shown in the following Formula (7), by using a pressure value P.sub.mMODEL in the intake manifold obtained by processing the pressure value Pm in the intake manifold with a low-pass filter, it is possible to maintain a more accurate air-fuel ratio by eliminating the influence of the noise in the high-frequency range or the like caused by the vibration of the engine or the like on the actual pressure value in the intake manifold.

[00010]$\begin{array}{cc}\left[\mathrm{Mathematical}\mathrm{formula}13\right]& \\ Q_B=\left(1+K_{\mathrm{PQB}}.Math.\frac{P_{\mathrm{mref}}-P_{\mathrm{mMODEL}}}{\Delta +P_{\mathrm{mMODEL}}}\right).Math.Q_a& \left(7\right)\end{array}$

[0034] Here, Δ is a constant for adjusting sensitivity, and is put in a denominator to prevent oscillation even when P.sub.mMODEL approaches 0 infinitely.