Engine fuel injection control method and device

Abstract

To maintain an ideal air-fuel ratio even if torque required for an engine is abruptly changed, in a method for controlling a fuel injection amount for estimating an air amount when air is mixed into fuel which is supplied to the engine on the basis of an air amount in an intake manifold.SOLUTION: An actually-controlled throttle passage air amount is calculated from an air amount in an intake manifold 6 which is calculated from a pressure value detected by an intake manifold pressure sensor 7 installed in the intake manifold 6 which connects a throttle 5 and a cylinder 2, and a pressure change in the intake manifold 6; a cylinder inhalation air amount at the actual mixing of fuel is predicted from the calculated air amount in the intake manifold 6 and the calculated throttle passage air amount; and the fuel is injected according to the predicted cylinder inhalation air amount.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for controlling the amount of fuel injection required to maintain a constant ratio of fuel to air (air-fuel ratio) supplied to an engine. [Background technology]

[0002] Conventionally, in order to control an engine with high precision in order to improve fuel economy and rotational performance, an appropriate fuel injection amount is supplied to the engine by appropriately mixing the fuel and air ratio (air-fuel ratio).

[0003] This engine fuel injection control method invention is directed to the widespread use of electronic throttle control devices that use an electronic control system to electronically open and close the throttle instead of mechanically opening and closing it through accelerator operation by the driver in order to perform engine control with high precision, with the aim of improving the fuel efficiency and driving performance of the vehicle. These devices are described, for example, in Japanese Patent Application Laid-Open Nos. 5-240073 and 2008-38872.

[0004] As a means for controlling the fuel injection amount at an appropriate air-fuel ratio, there is known a means for controlling the appropriate fuel injection amount by estimating the amount of air to be mixed with the fuel supplied to the engine based on the amount of air in the intake manifold calculated from the pressure value detected by a pressure sensor installed in the intake manifold, and this means is disclosed, for example, in JP 2001-521095 A.

[0005] As shown in Figure 1, the means for controlling the fuel injection amount disclosed in this publication and elsewhere comprises a throttle 5 provided in an intake pipe 4 that supplies air into cylinders 2 of engine 1 via a filter 3, and an intake manifold pressure sensor 7 that detects the pressure inside intake manifold 6, which is installed in intake manifold 6 located between each cylinder 2 and intake pipe 4. For example, an opening signal from an accelerator 8 is sent to an ECU (electronic control unit) 9, which has a storage means stored with a program for executing a fuel injection control method, to calculate the opening of throttle 5, and the calculated opening signal is sent to throttle 5, causing it to open to a predetermined opening.

[0006] The air that passes through the open throttle 5 is sent into the intake manifold 6, and the amount of air in the intake manifold 6 is calculated from the pressure value inside the intake manifold 6 detected by the intake manifold pressure sensor 7. The ECU 9 also calculates the optimum air-fuel ratio, and from that value, calculates the required amount of fuel. Based on the operating state detected using, for example, a signal from a crank angle sensor 12 provided on the engine 1, fuel is injected from injectors 10 located near each cylinder 2, and the air and fuel sent from the intake pipe 4 are mixed and sent into each cylinder 2, where they are ignited by spark plugs 11 and start the engine rotating. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 5-240073 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-38872 [Patent Document 3] Special Publication No. 2001-521095 Summary of the Invention [Problem to be solved by the invention]

[0008] Incidentally, the conventional means for controlling the fuel injection amount by estimating the amount of air to be mixed with the fuel supplied to the engine based on the amount of air in the intake manifold as described above calculates the amount of fuel injection from the pressure value detected by a pressure sensor installed in the intake manifold. When a sudden change in the torque required of the engine is required, for example, when the vehicle in which it is installed suddenly accelerates or decelerates, there is a sudden change in the amount of air passing through the throttle 5 located upstream of the intake manifold 6 of the intake pipe 4 shown in Figure 1, and this causes a discrepancy between the amount of air passing through the throttle 5 located upstream of the intake manifold 6 located downstream, and therefore, when fuel is injected according to the amount of air in the intake manifold 6, the fuel may be too lean or too rich compared to the actual amount of air, which is a problem.

[0009] An object of the present invention is to provide a method and device for controlling fuel injection of an engine, which has a means for controlling fuel injection amount by estimating the amount of air to be mixed with fuel supplied to the engine based on the amount of air in the intake manifold as described above, and which can maintain an ideal air-fuel ratio even if the torque required by the engine suddenly changes. [Means for solving the problem]

[0010] The engine fuel injection control method of the present invention, which has been made to solve the above problems, is characterized by calculating the amount of air in the intake manifold calculated from a pressure value detected by a pressure sensor installed in the intake manifold connecting the throttle and the cylinder, and the amount of air passing through the throttle that is actually being controlled from the pressure change in the intake manifold, predicting the amount of air intake into the cylinder when fuel is actually mixed from the calculated amount of air in the intake manifold and the calculated amount of air passing through the throttle, and injecting fuel according to this predicted amount of air intake into the cylinder.

[0011] The present invention focuses on the fact that the amount of air between the amount of air in the intake manifold and the amount of air passing through the throttle is the amount of air when fuel is actually mixed.The actual amount of air passing through the throttle that is being controlled is calculated from the amount of air in the intake manifold determined by the intake manifold pressure sensor and changes in pressure, and these are then used to calculate the amount of air when fuel is mixed.

[0012] Furthermore, in the present invention, in the process of determining the cylinder intake air amount when fuel is actually mixed, by using a pressure command value in the intake manifold that has been processed by a low-pass filter, it is possible to eliminate the influence of high-frequency noise generated by vibrations of the engine, etc. on the actual pressure value in the intake manifold and maintain a more accurate air-fuel ratio.

[0013] Furthermore, in the present invention, the amount of air in the intake manifold can be calculated from the pressure value detected by the pressure sensor installed in the intake manifold using the following formula.

[0014]

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[0015] Furthermore, in the present invention, the pressure change in the intake manifold connecting the throttle and the cylinder can be calculated from the amount of air in the intake manifold using the following formula.

[0016]

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[0017] Additionally, in the present invention, the throttle passing air amount actually controlled can be calculated from the calculated air amount in the intake manifold and the calculated change in pressure in the intake manifold using the following formula.

[0018]

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[0019] In addition, the engine fuel injection control device of the present invention is characterized in that a program for executing a fuel injection control method is stored in a memory means, a pressure signal detected by a pressure sensor installed in the intake manifold is input, the fuel injection signal is generated and output to the injector, and thereby the engine fuel injection control method of the present invention is executed. [Effects of the Invention]

[0020] As described above, according to the present invention, it is possible to provide a method and device for controlling fuel injection of an engine, which is capable of maintaining an ideal air-fuel ratio even if the torque required of the engine suddenly changes, by estimating the amount of air to be mixed with the fuel supplied to the engine based on the amount of air in the intake manifold and using a means for controlling the fuel injection amount. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic diagram of a fuel injection control device for an engine for carrying out a conventional example and an embodiment of the present invention; [Figure 2] 2 is a diagram showing changes over time in the amount of air passing through the throttle, the amount of air in the intake manifold, and the amount of air when fuel is mixed, when the throttle opening changes, for the embodiment shown in FIG. 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0023] FIG. 1 is a schematic diagram of an engine fuel injection control device for carrying out an embodiment of the present invention. The basic component configuration and control method are basically the same as those of the conventional example, but differ in that the actual throttle-passing air volume Qt being controlled is calculated from the air volume in the intake manifold 6 calculated from the pressure value detected by a pressure sensor 7 installed in the intake manifold 6 connecting the throttle and the cylinder 2, and from the pressure change in the intake manifold 6, and the cylinder intake air volume when fuel is actually mixed is predicted from the calculated intake manifold air volume Qa and the calculated throttle-passing air volume Qt, and fuel is injected according to this predicted cylinder intake air volume.

[0024] To explain in more detail, first, the amount of air Qa in the intake manifold, which is obtained from the intake manifold pressure sensor 7, is calculated by the following equation (1).

[0025] In equation (1) and the equations used below, Kc is the charging efficiency correction coefficient, ω is the engine speed, Vc is the volume inside the cylinder, R is the gas constant, Tm is the temperature inside the manifold, Pm is the pressure value inside the manifold, and Vm is the volume inside the manifold.

[0026]

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[0027] Next, the amount of air Qa in the intake manifold calculated by the above formula (1) is used to calculate the pressure change in the intake manifold 6 connecting the throttle 5 and the cylinder 2 by the following formula (2). In formula (2), Qt represents the amount of air passing through the throttle.

[0028]

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[0029] Furthermore, using the above formulas (1) and (2), the amount of air passing through the throttle Qt is calculated by the following formula (3).

[0030]

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[0031] At this time, the intake manifold pressure Pm is controlled to satisfy the following equation (4) using the pressure proportional gain Kpm and the pressure command value Pmref in the intake manifold.

[0032]

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[0033] Then, by substituting the above equation (4) into the above equation (3), the throttle passing air amount Qt can be rewritten as the following equation (5).

[0034]

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[0035] As shown in Figure 2, when a sudden change in the torque required of the engine is required, the amount of air changes suddenly, so it has been found that the ideal air-fuel ratio cannot be maintained unless fuel is injected for an air amount somewhere between the air amount Qa in the intake manifold and the air amount Qt passing through the throttle.

[0036] Here, the air amount Q is calculated as the intermediate amount between the air amount Qa in the intake manifold calculated by the above formula (1) and the air amount Qt passing through the throttle calculated by the above formula (5). B is the adjustment gain K PQB is used to estimate as shown in the following equation (6).

[0037]

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[0038] Therefore, using the above equation (6), the amount of air Qa in the intake manifold 6 calculated from the intake manifold pressure Pm, the amount of air passing through the throttle Qt calculated from the change in pressure in the intake manifold 6, and the amount of air Q when the fuel is mixed are calculated. B By injecting fuel in accordance with the above, appropriate fuel injection can be performed, and control to maintain an ideal air-fuel ratio becomes possible even when the torque required for the engine suddenly changes.

[0039] Furthermore, in actual use, the pressure value Pm in the intake manifold may be affected by high frequency noise due to vibrations that occur when the engine or the like is operating.

[0040] Therefore, as shown in the following equation (7), the pressure value Pm in the intake manifold is processed by a low-pass filter to obtain the pressure value P mMODEL By using this, the actual pressure value in the intake manifold can be prevented from being affected by high frequency noise caused by engine vibrations, etc., and a more accurate air-fuel ratio can be maintained.

[0041]

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[0042] Here, Δ is a constant for adjusting the sensitivity, and by putting it in the denominator, P mMODEL It is designed to prevent oscillation even when the input voltage approaches 0. [Explanation of symbols]

[0043] 1 engine, 2 cylinder, 3 filter, 4 intake pipe, 5 throttle, 6 intake manifold, 7 intake manifold pressure sensor, 8 accelerator, 9 ECU, 10 injector, 11 spark plug, 12 crank angle sensor, Qa air volume in intake manifold, Qt throttle air volume, Q B Amount of air when fuel is mixed

Claims

1. calculating an amount of air in the intake manifold using a pressure in the intake manifold detected by a pressure sensor installed in the intake manifold connecting the throttle and the cylinder and an engine speed; calculating a throttle-passing air amount using the air amount in the intake manifold and a pressure change in the intake manifold per unit time; using the amount of air in the intake manifold and the amount of air passing through the throttle, to estimate the amount of air intake into the cylinder when fuel is mixed; A method for controlling fuel injection in an engine, comprising injecting fuel in accordance with the amount of intake air in the cylinder.

2. A fuel injection control method for an engine as described in Claim 1, characterized in that the cylinder intake air volume is estimated using the following formula. [Equation 1] (where Q B is the cylinder intake air amount, K PQB is an adjustment gain, P mref is the pressure command value in the intake manifold, P m is the pressure in the intake manifold, and Q a is the air amount in the intake manifold).

3. A method for controlling fuel injection in an engine as described in claim 1, characterized in that the cylinder intake air volume is estimated using the following formula. [Equation 2] (where Q B is the cylinder intake air amount, K PQB is an adjustment gain, P mref is the pressure command value in the intake manifold, P mMODEL is the pressure in the intake manifold processed by a low-pass filter, Δ is a constant for adjusting sensitivity, and Q a is the air amount in the intake manifold).

4. 4. The method for controlling fuel injection in an engine according to claim 1, wherein the amount of air in the intake manifold is calculated using the following formula: [Equation 3] (However, Q ａ is the amount of air in the intake manifold, K ｃ is the charging efficiency correction coefficient, ω is the engine speed, V ｃ is the volume inside the cylinder, R is the gas constant, T ｍ is the temperature in the intake manifold, P ｍ is the pressure in the intake manifold)

5. A method for controlling fuel injection in an engine as described in claim 1, 2, 3 or 4, characterized in that the pressure change in the intake manifold per unit time is calculated using the following formula. [Equation 4] (where K pm is a pressure proportional gain, P mref is a pressure command value in the intake manifold, and P m is the pressure in the intake manifold).

6. 6. A method for controlling fuel injection of an engine according to claim 1, wherein the amount of air passing through the throttle is calculated using the following formula: [Equation 5] (where Qt is the amount of air passing through the throttle, Vm is the volume inside the intake manifold, Vc is the volume inside the cylinder, Kc is the charging efficiency compensation coefficient, ω is the engine speed, Pm is the pressure inside the intake manifold, and Qa is the amount of air in the intake manifold).

7. 10. An engine fuel injection control device characterized in that a program for executing a fuel injection control method is stored in a storage means, a pressure signal detected by a pressure sensor installed in an intake manifold is input, a fuel injection signal is generated and output to an injector, and the engine fuel injection control method according to claim 1, 2, 3, 4, 5 or 6 is executed.

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