JP2009250211A - Control device for engine - Google Patents

Abstract

An engine control device is provided that can realize good air-fuel ratio control with a simple configuration even during a transition of fuel pressure switching.
An actual fuel of an injector is set using an annealing calculation in which an annealing coefficient Ka is variably set based on an operating state of an engine 1 and converges to a set fuel pressure Pt with a response according to the annealing coefficient Ka. The injection pressure PF is estimated. As a result, the fuel pressure (actual fuel injection pressure PF) that actually acts on the injector 7 from the fuel line in the entire region including the transition time after switching the fuel pressure with a simple configuration without using a fuel pressure sensor or the like. It can be estimated accurately. Then, by setting the fuel injection pulse width Ti for the injector 7 based on the actual fuel injection pressure PF estimated in this way, it is possible to realize good air-fuel ratio control even during the transition of the fuel pressure switching. .
[Selection] Figure 3

Description

    The present invention relates to an engine control apparatus having a fuel system capable of switching the pressure of a fuel line acting on an injector in multiple stages.

    Conventionally, in a fuel system such as an engine with a supercharger or an in-cylinder injection type engine, a fuel pressure supplied to an injector is increased in order to appropriately cope with an operation region that requires a high fuel injection pressure. Many techniques for adjusting pressure by switching to a stage (for example, two stages of preset low pressure and high pressure) have been proposed. In general, such fuel pressure switching control is realized by switching the operating state of the pressure regulator and the circuit configuration of the fuel system. When the fuel pressure switching control is performed, the fuel pressure acting on the injector is physically Changes with a predetermined delay. Therefore, the operation control for the injector when the fuel pressure switching control is performed is generally switched to a new control after a preset delay time elapses. Disturbances occur in the air-fuel ratio and the like, and the exhaust gas characteristics tend to deteriorate. It should be noted that the speed of change caused by switching the fuel pressure is faster than the responsiveness of the air-fuel ratio feedback control, so it is difficult to absorb the air-fuel ratio disturbance during the fuel pressure switching transient by the air-fuel ratio feedback control.

To cope with this, for example, in Patent Document 1, in an engine having a fuel pressure changing means for changing a fuel pressure acting on an injector (injection valve), the fuel pressure acting on the injector is detected by a fuel pressure sensor, and the detection is performed. A technique for controlling the operation of the injector based on the fuel pressure is disclosed.
Japanese Patent Laid-Open No. 11-2145

    However, since the fuel pressure converges to a set value in a steady state, it is not necessary to detect the fuel pressure. However, as in the technique disclosed in Patent Document 1 described above, only an improvement in the air-fuel ratio at the time of transition of the fuel pressure is achieved. It is not preferable to add a fuel pressure sensor or the like for the purpose.

    The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an engine control device that can realize good air-fuel ratio control even during a transition of fuel pressure with a simple configuration. .

    The present invention is an engine control device comprising fuel pressure switching means for switching the fuel pressure of a fuel line for supplying fuel to an injector in multiple stages, wherein the fuel pressure is switched by the fuel pressure switching means. Fuel pressure estimating means for estimating the actual fuel pressure of the injector, and fuel injection control means for controlling the fuel injection amount of the injector based on the fuel pressure estimated by the fuel pressure means, the fuel pressure estimating means The actual fuel injection pressure is estimated based on a response delay time that is variably set according to the operating state of the engine.

    According to the engine control apparatus of the present invention, it is possible to realize a favorable air-fuel ratio control with a simple configuration even during a transition of fuel pressure switching.

    Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing an engine fuel system, FIG. 2 is a flowchart showing a fuel injection control routine, FIG. 3 is a flowchart showing an actual fuel injection pressure calculation subroutine, and FIG. FIG. 5 is a time chart showing the relationship between the target pressure and the fuel pressure.

    In FIG. 1, reference numeral 1 denotes an engine, and in this embodiment, an engine provided with a supercharger (not shown). An intake manifold 3 is communicated with an intake port 2a of each cylinder formed in the cylinder head 2 of the engine 1. An intake pipe 4 communicates with a collecting portion of the intake manifold 3, and a throttle valve 5 is interposed in the middle of the intake pipe 4. In addition, the code | symbol 2b in a figure is an exhaust port.

    In addition, a spark plug 6 whose tip is exposed to the combustion chamber is attached to the cylinder head 2 for each cylinder, and an injector 7 faces the upstream side of each intake port 2a of each cylinder of the intake manifold 3. . Each injector 7 is connected to a delivery pipe 8 for fuel distribution, and this delivery pipe 8 is connected to a fuel supply pipe 9. Further, an in-tank type fuel pump 11 installed in the fuel tank 10 is connected to the fuel supply pipe 9 via a fuel filter 12.

    The delivery pipe 8 is connected to two pressure regulators 14 and 15 as pressure regulating means arranged in parallel with each other. An electromagnetic valve 13 is interposed between the pressure regulator 14 and the delivery pipe 8. It is intervened. The pressure adjusting surplus fuel discharge port of one pressure regulator 14 and the pressure adjusting surplus fuel discharge port of the other pressure regulator 15 are both communicated with the fuel return pipe 16, and surplus fuel from the fuel return pipe 16 is connected to the fuel tank 10. Returned within.

    Here, both the pressure regulators 14 and 15 are provided with a fuel chamber into which the fuel pumped from the fuel pump 11 is introduced, and a spring that urges the pressure regulating valve in the closing direction by a diaphragm having a pressure regulating valve connected thereto. Is a regulator having a known configuration in which intake pipe pressure is introduced into the spring chamber through a negative pressure introduction passage that is partitioned by a spring chamber that houses the intake pipe 4 and communicates with the downstream side of the throttle valve 5 of the intake pipe 4. Is different.

    In the present embodiment, the set pressure of the pressure regulator 14 is set relatively lower than the set pressure of the pressure regulator 15. Specifically, the pressure regulator 14 opens the pressure regulating valve when the internal pressure of the fuel chamber reaches around 300 (kPa), and the pressure regulator 15 regulates the pressure when the internal pressure of the fuel chamber reaches around 500 (kPa). Open the valve. For convenience, the pressure regulator 14 is referred to as a low pressure regulator 14 and the pressure regulator 15 is referred to as a high pressure regulator 15.

    Next, an electronic control unit (ECU) 50 that electronically controls the engine 1 will be described. The ECU 50 is configured with a microcomputer at the center, and an igniter that discharges the ignition plug 6 connected to the secondary side by turning on and off the primary current of the injector 7, the fuel pump 11, the electromagnetic valve 13, and the ignition coil 17 described above. 18 and other various sensors / switches such as a throttle opening sensor, an intake air amount sensor, a water temperature sensor, an air-fuel ratio sensor, and a crank angle sensor are connected.

    When the ECU 50 detects the engine operating state by processing signals from various sensors and switches according to the control program stored in the memory, the ECU 50 calculates the optimal fuel injection amount, ignition timing, etc. from the detected engine operating state. Control signals to various actuators to control various engines.

    Here, as the fuel pressure Pt of the fuel line (delivery pipe 8 and fuel supply pipe 9) for supplying fuel to the injector 7, the ECU 50 has, for example, two different values P1 and P2 (for example, a low-pressure value P1 = 300 (kPa), high-pressure side value P2 = 500 (kPa)) can be selectively switched and set. The fuel pressure Pt is appropriately switched according to the operating state of the engine 1, and the ECU 50 is, for example, a value on the low pressure side as the fuel pressure Pt mainly when the supercharger of the engine 1 is inactive. P1 is set, and when the supercharger is in an operating state, a value P2 on the high pressure side is set as the fuel pressure Pt.

    When the low-pressure side value P1 is set as the fuel pressure Pt, the ECU 50 opens the electromagnetic valve 13. As a result, the low pressure regulator 14 having a low operating pressure preferentially acts on the regulation of the fuel line, and the fuel pressure is regulated to about 300 (kPa). On the other hand, when the value P2 on the high pressure side is set as the fuel pressure Pt, the ECU 50 closes the electromagnetic valve 13. As a result, the high pressure regulator 15 acts to regulate the fuel line, and the fuel pressure is regulated to about 500 (kPa).

    Further, the ECU 50 performs fuel injection control through the injector 7. In this fuel injection control, the ECU 50 estimates the fuel pressure that actually acts on the injector 7 (that is, the actual fuel injection pressure PF of the injector 7). The estimation of the actual fuel injection pressure PF is performed using an annealing calculation that converges the previous value PFn-1 of the fuel pressure to the fuel pressure Pt with a predetermined response. In this case, the ECU 50 variably sets a smoothing calculation coefficient (smoothing coefficient Ka) based on the operating state of the engine 1. Then, the ECU 50 controls the operation of the injector 7 based on the estimated actual fuel injection pressure PF. Thus, in this embodiment, ECU50 has each function as a fuel pressure estimation means, a coefficient setting means, and an operation control means.

    Next, the fuel injection control executed by the ECU 50 will be described according to the fuel injection control routine shown in FIG. This routine is repeatedly executed every set time. When the routine starts, the ECU 50 first estimates the actual fuel injection pressure PF in step S101 according to a fuel injection pressure calculation subroutine described later.

    In the subsequent step S102, the ECU 50 obtains the basic injection time of the injector 7 that determines the basic fuel injection amount with respect to the intake air amount Q per stroke of the engine 1, that is, the basic fuel injection pulse width Tp. Specifically, in this embodiment, the ECU 50 multiplies the value obtained by dividing the intake air amount Q detected by the intake air amount sensor by the engine speed Ne by the injector characteristic coefficient K0 to obtain the basic fuel injection pulse width Tp. Set (Tp = K0 × Q / Ne).

Then, the process proceeds to a step S103, ECU 50 reads the feedback correction coefficient Kα which is set based on the output of the O ₂ sensor. The feedback correction coefficient Kα is a correction value that increases or decreases around 0, and the basic fuel injection pulse width Tp is multiplied by a value (1 + Kα: so-called air-fuel ratio feedback correction coefficient) added to 1.0 that is the control center. This is reflected in the fuel injection time. As is well known, the air-fuel ratio feedback correction coefficient (feedback correction coefficient Kα) is updated by the proportional component and integral component of the proportional-integral control as the air-fuel ratio rich / lean inversion is determined based on the output of the O ₂ sensor. Is done.

    When the process proceeds from step S103 to step S104, the ECU 50 corrects the basic fuel injection pulse width Tp with the above-described air-fuel ratio feedback correction coefficient (1 + Kα), and further adds other corrections to set the effective injection pulse width Te. To do. As correction terms other than air-fuel ratio feedback, for example, a correction coefficient COEF related to cooling water temperature correction, acceleration / deceleration correction, full-open increase correction, post-idle increase correction, etc., and correction coefficient Kpf related to actual fuel injection pressure PF are calculated. These are multiplied by the basic fuel injection pulse width Tp to set the effective injection pulse width Te (Te = Tp × (1 + Kα) × COEF × Kpf).

Here, as is well known, the fuel injection amount q per unit time is affected by the actual fuel injection pressure P.
q∝P ^1/2
Therefore, if it is steady, the fuel injection amounts q1 and q2 per unit time when the actual fuel injection pressure is P1 and P2, respectively,
q1 = k × P1 ^1/2
q2 = k × P2 ^1/2
It becomes.
Here, in the case of the present embodiment in which the relationship between P1 and P2 is “P1 <P2,” the actual fuel injection pressure P2 has the same injection amount as that at the actual fuel injection pressure P1 and the injection time T1. The injection time T2 to obtain is
T2 = T1 × (P2 / P1) ^1/2
It becomes.
Therefore, for example, when the basic fuel injection pulse width Tp is set with reference to the actual fuel injection pressure P1 on the low pressure side, the correction coefficient Kpf is
Kpf = (PF / P1)
It becomes.

    When the process proceeds from step S104 to step S105, the ECU 50 corrects the voltage correction pulse width Ts0 for correcting the invalid injection time of the injector 7 based on the battery voltage with the correction coefficient Kpf related to the actual fuel injection pressure PF, and the invalid injection pulse. The width Ts is calculated (Ts = Ts0 × Kpf).

    In step S106, the ECU 50 sets the final fuel injection pulse width Ti by adding the invalid injection pulse width Ts to the effective injection pulse width Te (Ti = Te + Ts). After the injection pulse width Ti is set in the timer, the routine is exited. Thereby, the injector 7 of each cylinder is driven at a predetermined timing, and fuel is injected during the injection time determined by the fuel injection pulse width Ti.

    Next, the estimation of the actual fuel injection pressure PF executed in step S101 described above will be described according to the flowchart of the actual fuel injection pressure calculation subroutine shown in FIG. When this subroutine starts, the ECU 50 first reads out the fuel pressure Pt currently set in the fuel pressure regulation control for the fuel line in step S201.

    In subsequent step S202, the ECU 50 calculates the smoothing coefficient Ka as a parameter indicating the response of the actual fuel injection pressure PF when the fuel pressure Pt is switched based on the current operating state of the engine 1.

    That is, when the fuel pressure Pt is switched in the fuel pressure regulation control for the fuel line, the response delay of the actual fuel injection pressure PF depends on the operating state of the engine 1. For example, as shown in FIG. 5 (a), when the engine speed Ne is the same, the actual fuel injection pressure PF becomes more responsive as the fuel flow rate pumped by the fuel pump 11 to the fuel line increases. It converges to the fuel pressure Pt set for switching. Therefore, in the present embodiment, as shown in FIG. 4A, for example, the ECU 50 provides a fuel flow rate (specifically, control DUTY for the fuel pump 11) pumped by the fuel pump 11 and a smoothing coefficient Ka. A map showing the relationship is set and stored in advance by adaptation or the like, and the ECU 50 sets the smoothing coefficient Ka with reference to this map.

    Here, for example, as shown in FIG. 5B, when the fuel flow rate from the fuel pump 11 is the same, the actual fuel injection pressure PF is switched and set with higher responsiveness as the engine speed Ne is lower. It converges to the fuel pressure Pt. Therefore, for example, as shown in FIG. 4B, a map showing the relationship between the engine speed Ne and the smoothing coefficient Ka is set in advance by adaptation or the like, and the smoothing coefficient Ka is referenced with reference to this map. Can also be set. Furthermore, the smoothing coefficient Ka can be set with higher accuracy by using the fuel flow rate and the engine speed Ne as parameters indicating the operating state of the engine 1.

Then, when the process proceeds from step S202 to step S203, the ECU 50 uses the fuel pressure Pt and the smoothing coefficient Ka set as described above to calculate the actual fuel injection pressure PF by the following smoothing calculation, and then exits the subroutine. .
PF = PF _n-1 + (Pt-PF _n-1 ) × Ka
That is, the ECU 50 estimates the actual fuel injection pressure PF by using an annealing calculation that converges the previous value PF _n-1 of the actual fuel injection pressure to the target fuel pressure Pt with the response determined by the annealing coefficient Ka.

    According to such an embodiment, the annealing coefficient Ka is variably set based on the operating state of the engine 1, and the annealing calculation for converging to the fuel pressure Pt that is switched and set with responsiveness corresponding to the annealing coefficient Ka. Is used to estimate the actual fuel injection pressure PF of the injector 7 from the fuel line in the entire region including the transition time after switching the fuel pressure Pt with a simple configuration without using a fuel pressure sensor or the like. The fuel pressure that actually acts on the fuel (actual fuel injection pressure PF) can be accurately estimated. Then, by setting the fuel injection pulse width Ti for the injector 7 based on the actual fuel injection pressure PF estimated in this way, it is possible to realize good air-fuel ratio control even during the transition of the fuel pressure switching. .

Although the engine control apparatus according to the above embodiment uses smoothing calculation as a control method for converging the previous value PFn-1 of the actual fuel injection pressure to the target fuel pressure Pt, other control methods such as gradual change are used. It may be made to converge to fuel pressure Pt by control.

Explanatory drawing showing the fuel system of the engine Flow chart showing fuel injection control routine Flow chart showing actual fuel injection pressure calculation subroutine Explanatory drawing showing map for setting smoothing coefficient Time chart showing the relationship between set fuel pressure and actual fuel injection pressure

Explanation of symbols

1 ... Engine 7 ... Injector 8 ... Delivery pipe (fuel line)
9 ... Fuel supply piping ((fuel line)
DESCRIPTION OF SYMBOLS 10 ... Fuel tank 11 ... Fuel pump 13 ... Electromagnetic valve (pressure regulation means)
14 ... Pressure regulator
15 ... Pressure regulator
16 ... Fuel return piping 50 ... Electronic control unit Ka ... Smoothing coefficient (coefficient)
Kpf ... Correction factor Ne ... Engine speed PF ... Actual fuel injection pressure (fuel pressure acting on the injector)
Pt ... Fuel pressure

Claims (4)

An engine control device comprising fuel pressure switching means for switching the fuel pressure of a fuel line for supplying fuel to an injector in multiple stages,
Fuel pressure estimating means for estimating an actual fuel pressure of the injector when the fuel pressure is switched by the fuel pressure switching means;
Fuel injection control means for controlling the fuel injection amount of the injector based on the fuel pressure estimated by the fuel pressure means;
The engine control apparatus according to claim 1, wherein the fuel pressure estimating means estimates the actual fuel injection pressure based on a response delay time that is variably set according to an operating state of the engine.     The engine control device according to claim 1, wherein the response delay time is reduced as the flow rate of fuel pumped by the fuel pump to the fuel line increases.     3. The engine control device according to claim 1, wherein the response delay time is increased as the engine speed increases. 4. The engine control device according to claim 1, further comprising an operation control unit configured to control an operation of the injector based on the fuel pressure estimated by the fuel pressure estimation unit. 5.

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