JPH0233434A - Fuel injection device for engine - Google Patents

Abstract

PURPOSE:To control the air-fuel ratio accurately by controlling the fuel injection quantity on the basis of a fuel adhesion model for estimating the adhering characteristic of the injected fuel to the intake inner wall and a carburetion model for estimating the carburetion characteristic of the adhered fuel. CONSTITUTION:A target injection quantity calculating means 31 calculates the basic injection quantity from the intake air quantity and the engine speed, and the target injection quantity adding each kind of correction. The target injection quantity (Iob, n) is corrected by estimating the tube wall adhering fuel quantity and the carbureted fuel quantity by means of a tube adhesion simulation model 32 and a carburetion simulation model 33 and calculating the correction quantity from the difference between the target injection quantity and that of the preceding cycle by means of a PID control 34 so as to obtain the fuel injection quantity (In) and supply the fuel quantity (Qn) into an engine through the tube characteristic. The air-fuel ratio can be thus controlled accurately and responsively even at a transition time.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to the adhesion characteristics of fuel injected into intake air from a fuel injection valve to the inner wall surface of an intake system, and the vaporization characteristics of the adhering fuel into intake air. The present invention relates to a fuel injection device for an engine that improves the accuracy of air-fuel ratio control during transient times by controlling the fuel injection amount based on a fuel transport model that predicts.

[Prior Art] The fuel injection amount is controlled based on the intake air amount detected by the intake air amount detection means, and the air-fuel ratio (A/F) of the mixture is set to a predetermined value (for example, the stoichiometric air-fuel ratio A/F=14). 7) is well known. Conventionally, all the fuel injected from the fuel injection valve into the intake air is in a cycle corresponding to the above fuel injection (hereinafter referred to as
The fuel injection amount was controlled by assuming that the fuel would flow into the combustion chamber during the current cycle (referred to as the current cycle). In this application, the cycle is defined as suction stroke - compression stroke - explosion stroke →
Refers to one repeated operation of the exhaust stroke.

[Problem to be solved by the invention] However, the fuel injected from the fuel injection valve into the intake air is
Not all of the fuel flows into the combustion chamber during the current cycle, but a considerable amount of fuel may be combusted in the next cycle or later depending on various factors such as fuel adhesion to the inner wall of the intake passage, fuel vaporization/atomization state, and intake speed. flows into the room. For this reason, if the fuel injection amount is controlled on the assumption that all the fuel injected from the fuel injection valve will flow into the combustion chamber in the current cycle, as in conventional fuel injection systems, the fuel injection amount will remain constant over time. In a steady state, the rate at which the injected fuel adheres to the inner wall of the intake passage and the rate of vaporization from the inner wall of the intake passage are approximately equal, so fuel flows into the combustion chamber at the planned flow rate; During transient times when the fuel injection amount changes over time, such as during acceleration, the fuel deposition speed and vaporization speed differ, so that the planned amount of fuel does not flow into the combustion chamber.

For example, during acceleration, the amount of fuel injected increases over time, so the fuel deposition rate increases immediately, but the vaporization rate of the deposited fuel, which is controlled by the amount of fuel deposited on the inner wall of the intake passage, quickly decreases. does not increase.

Therefore, in the current cycle, the air-fuel mixture flowing into the combustion chamber becomes lean, which causes problems such as deterioration of acceleration response at the start of acceleration and occurrence of misfire. On the other hand, during deceleration, the vaporization rate of the adhering fuel does not immediately decrease as the amount of fuel injection decreases, resulting in the problem that the air-fuel mixture becomes rich at the start of deceleration, making it impossible to obtain the expected deceleration feeling. .

A possible solution to the above problem is to actually measure the flow rate of fuel flowing into the combustion chamber or the vaporization rate of fuel from the inner wall surface of the intake passage, and control fuel injection based on this. , such a measuring device has not been put into practical use. Furthermore, an engine has been proposed in which various operating states of the engine that cannot be actually measured are predicted theoretically and various controls are performed based on the predicted results (for example, Japanese Patent Laid-Open No. 60-98151 (see publication)
, I have not seen any attempts to improve engine responsiveness by appropriately controlling the amount of fuel supplied during transient times.

The present invention has been made in view of the above-mentioned conventional problems, and in an ennon in which the target fuel injection amount is determined based on the intake air amount, even during a transient period when the fuel injection amount changes over time, An object of the present invention is to provide a fuel injection device for an engine that can improve acceleration/deceleration response and combustibility by maintaining the air-fuel ratio of a mixture flowing into a combustion chamber at a predetermined appropriate value. do.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes an intake air amount detection means and a fuel injection valve, and provides fuel target injection determined based on the intake air amount detected by the intake air amount detection means. A fuel adhesion model that predicts the adhesion characteristics of fuel injected into intake air from a fuel injection valve to the inner wall surface of the intake system in an engine that injects fuel based on the amount of fuel, and A fuel injection device for an engine is provided, characterized in that it includes a fuel injection control means for controlling the amount of fuel to be injected based on a vaporization model that predicts vaporization characteristics into the fuel.

[Operations and Effects of the Invention] According to the present invention, the amount of fuel injected from the fuel injection valve adhering to the inner wall surface of the intake passage and the amount directly flowing into the combustion chamber are estimated based on a fuel adhesion model. On the other hand, the amount of fuel adhering to the inner wall of the intake passage that vaporizes into the intake air is estimated based on the vaporization model. Then, from the estimated value of the amount of fuel flowing directly into the combustion chamber in the current cycle and the estimated value of the amount of fuel flowing into the combustion chamber after being vaporized from the inner wall surface of the intake passage,
The actual amount of fuel flowing into the combustion chamber in the current cycle can be estimated. In this way, the actual amount of fuel flowing into the combustion chamber in each cycle can be predicted, and the amount of fuel injected from the fuel injection valve is adjusted so that this predicted value matches the target amount of fuel injection for the intake air amount. By controlling the air-fuel ratio of the mixture supplied into the combustion chamber, it is always maintained at a predetermined appropriate value (for example,
The stoichiometric air-fuel ratio A/F=14.7) can be maintained. Therefore, it is possible to prevent response delays in fuel supply during transient times such as acceleration and deceleration, thereby improving acceleration/deceleration responsiveness and combustion performance.

[Example] Examples of the present invention will be specifically described below.

As shown in FIG. 1, a four-cylinder engine CE equipped with the first to fourth cylinders #1 to #.1 has, for example, intake air ( mixture)
an intake stroke in which the mixture is inhaled, a compression stroke in which the mixture is compressed by a piston (not shown), an explosion stroke in which the compressed mixture is ignited and combusted by a spark plug (not shown), and the combustion gas is exhausted. The exhaust stroke from the boat 4 to the independent exhaust passage 5 is repeated continuously (hereinafter, such a series of strokes is referred to as a cycle), and for the second to fourth cylinders #2 to #4. has a similar configuration.

In order to supply intake air to each combustion chamber 2 of the first to fourth cylinders #l to #4, a common intake passage 7 is provided. An air cleaner 8 that removes air intake, an air flow meter 9 that detects the amount of intake air from moment to moment, and a throttle valve 11 that opens and closes in conjunction with an accelerator pedal are provided.

The common intake passage 7 is a branch part I2, and is connected to the first to fourth cylinders #.
It branches into four independent intake passages 13 that communicate with each intake boat 2 numbered #1 to #4. And each independent intake passage 1
3 are each provided with an injector +4 (fuel injection valve) that injects fuel into intake air near the intake boat 2.

On the other hand, the independent exhaust passages 5 of the first to fourth cylinders #1 to #4 are gathered into one common exhaust passage 16 at a gathering part 15, and this common exhaust passage 16 is equipped with a three-way catalyst for purifying exhaust gas. The used exhaust gas purification device 17 is interposed.

By the way, in order to perform various controls on the engine CE, an engine controller 1 composed of a microcomputer is used.
This engine controller 18 is provided with control information such as the intake temperature in the air flow meter 19 detected by the first intake temperature sensor 19, the throttle opening detected by the throttle valve opening sensor 2I, and the second The intake air temperature in the independent intake passage 13 is detected by the intake air temperature sensor 22, the cooling water temperature is detected by the water temperature sensor 23, the engine speed is detected by the first crank angle sensor 24, and the engine speed is detected by the second crank angle sensor 25. The top dead center timing etc. are input.

The engine controller 1 is an engine C including a fuel injection control means as set forth in the claims of the present application.
It is a comprehensive control device for the E, and as shown functionally in Fig. 2, it controls the target fuel injection amount Io in the usual way based on the intake air amount.
A target injection amount calculation unit 31 that calculates b and n, and a fuel injection valve 14 based on a predetermined fuel adhesion simulation model.
The adhesion amount Rn of the fuel injected from the intake boat 2 to the inner wall surface of the independent intake passage 13 (hereinafter referred to as the fuel adhesion surface), and the amount of fuel flowing directly into the combustion chamber 2 Qf,n a fuel adhesion amount calculation unit 32 that estimates the amount of fuel adhering to the fuel adhesion surface Kn based on a predetermined vaporization simulation model; and Kn, that is, the estimated value Q of the amount of fuel flowing into the combustion chamber 2 in the current cycle
Deviation En(
Fuel injection @ based on En = Iob, n-Qs, n)
(Proportional/integral/differential operation CPTD operation of n) for feedback control. Note that, in reality, the fuel inflow 1i Q n into the combustion chamber 2 is determined for the fuel injection It r n by the internal characteristics of the intake boat 2 or the independent intake passage 13; Since Qn cannot be directly measured, the estimated fuel inflow amount Qs,n calculated by the method described above is used instead.

Hereinafter, a method of controlling fuel injection by the engine controller 18 will be explained according to the flowchart shown in FIG.

When the control is started, in step Sl, the fuel injection 1i1 n-1 (I = I
.

2.3...) are stored in memory. As shown by the polygonal line G1 in FIG. 4, the fuel is injected from the injector 14 in a substantially pulsed manner. As shown by curve G, a time difference occurs in the fuel flowing into 2.

In step S2, the fuel inflow m Q r , n that directly flows into the combustion chamber 2 is calculated using a fuel adhesion simulation model expressed by the following equation.

Qf, n=In'ao+ In-+"a++In-t'
ay+ I n-s 1 as In the above formula, I n, I n-++ T n-t,
I n-s are respectively n-th cycle (current cycle) ~
This is the fuel injection amount in the (n-3)th cycle. As described above, the fuel injected from the injector 14 in a certain cycle flows into the combustion chamber 2 in the current cycle, the next cycle, the next cycle, and so on. +
a l ) a t *a, in the fuel injected in each cycle, does not adhere to the fuel adhesion surface and directly enters the combustion chamber 2 in the current cycle, the next cycle, the next cycle, and the next cycle, respectively. It is a predetermined constant determined experimentally that indicates the ratio of inflowing fuel to the total fuel injection amount,
This is common to all cycles. Therefore, the fuel flowing into the combustion chamber 2 in the current cycle is the same as that of the injected fuel in the current cycle, except for the vaporization needle of the adhering fuel.

and the amount of fuel injected in the previous cycle.

(the current cycle corresponds to the next cycle from the previous cycle), an amount equivalent to the amount of fuel injected in the cycle before the previous cycle, and an amount equivalent to 8 (the amount of fuel injected in the cycle before the previous cycle). Therefore, Qf,n calculated by the above formula is the nth cycle (current cycle) of the fuel injected in the nth cycle (n-3) cycle.
indicates the amount of fuel flowing directly into the combustion chamber 2. Although there is a possibility that the fuel injected before the (n-4)th cycle directly flows into the combustion chamber 2 in the nth cycle, the amount can be substantially ignored, so in this example, He is trying to calculate the amount of fuel flowing into the combustion chamber 2 in the current cycle from the fuel injection amount after the (n-3)th cycle.

In step S3, the vaporization 11 K n of the fuel adhering to the fuel adhering surface in the n-th cycle (current cycle) is calculated using the vaporization simulation model expressed by the following equation.

Kn-b・(Rn-Co+Rn-+・C++Rn-,・
Ct+Rn-a・C3) b=b,・b.

In the above equation, Rn, Rn-+, Rn-t, and Rn-5 are the amounts of fuel adhered to the fuel adhesion surface in the nth cycle (current cycle) to (n-3)th cycle, respectively. Co, C+, Ct, and C3 represent the ratio of fuel vaporized in the current cycle, the next cycle, the next cycle, and the next cycle, respectively, in the fuel attached to the fuel adhesion surface in each cycle. This is a predetermined constant determined by the system, and is common to all cycles. Further, b is a vaporization coefficient, and is a first vaporization coefficient.

It is expressed as the product of and the second vaporization coefficient S. And, b is the characteristic of the vaporization rate of the adhering fuel with respect to the engine rotation speed N (intake flow velocity) as shown by curve G3 in FIG. 5, and it increases as the engine rotation speed N increases. When the rotational speed N exceeds a certain level, it becomes almost constant. Also, b
, as shown by curve G4 in FIG. 6, is a characteristic of the vaporization rate of the adhering fuel with respect to the tube surface temperature T of the fuel adhering surface, and increases as the tube surface temperature T increases. Therefore, Kn calculated by the above formula is calculated from the inflow of fuel that vaporizes in the nth cycle (current cycle) of the fuel that adheres to the fuel adhesion surface in the nth cycle (n-3) cycle and flows into the combustion chamber 2. 1 is shown.

In step S4, an estimated value Qs,n of the amount of fuel flowing into the combustion chamber 2 in the n-th cycle (current cycle) is calculated using the following equation.

Qs n=Qf n+Kn In the above formula, Qf and n are calculated in step S2, and Kn is calculated in step S3.

In this way, the total fuel Qs,n that flows into the combustion chamber 2 in the n-th cycle (current cycle) is divided into the fuel portion Qf,n that directly flows into the combustion chamber 2, and the fuel that adheres to the fuel adhesion surface and then becomes air again. This is the sum of the amount of fuel Kn that flows into the combustion chamber 2.

In step S5, the correction amount 1h,n of the fuel injection amount for the nth cycle (current cycle) is calculated using the following equation.

I h, r+= I h, n-++Ki-Bn+Kp・
(En-En-1)+Kd・(En-2En-++En
-t) En= fob, n-Qs, n In the above formula, Ih, n-+ is the (n-1)th cycle (
It is the fuel injection amount correction value of the previous cycle), and Iob, n
is the target fuel injection amount determined based on intake air 1.

Ki, Kp, and Kd are the integral operating constant, proportional operating constant, and differential operating constant, respectively, in ordinary digital PID control, and are set to predetermined values by, for example, the limit sensitivity method, so that the control system is stable. Ru. Fuel target injection amount rob
, n are calculated in a conventional manner, for example, by the following equation.

job, n=α・K−Q/N In the above formula, Q is the output value of the air flow meter 9, N is the engine rotation speed, and K is for calculating the basic fuel injection amount for one intake amount. is a predetermined constant. Further, α is a correction coefficient based on operating conditions such as intake temperature and acceleration zone.

In step S6, the fuel injection amount In for the nth cycle (current cycle) is calculated using the following equation.

In=Iob,n+rh,n That is, the actual fuel injection amount In is determined by correcting the fuel target injection 11ob,n with the fuel injection correction amount 1h,n.

In step S7, a control pulse signal I pulses,n for the injector 14 is transmitted according to the following equation, the solenoid of the injector 14 is driven, and fuel is injected from the injector 14.

1 pulse, n=In-++Tbat In the above equation, K1 is a coefficient for converting the fuel injection amount In into a fuel injection pulse width, and Tbat is an invalid injection time for compensating for the response delay of the injector 14. In this way, fuel corresponding to the amount of intake air is supplied to the combustion chamber 2 in the n-th cycle (current cycle).

After this, the control goes to step S! will return and continue.

As described above, according to the present invention, the air-fuel ratio (A/
F) can be well controlled, and responsiveness and combustibility can be improved.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of a four-cylinder engine equipped with a fuel injection device according to the present invention. FIG. 2 is a functional diagram showing the information processing mechanism of the Ennon controller shown in FIG. 1. FIG. 3 is a flowchart showing a method of controlling fuel injection by the engine controller. FIG. 4 is a diagram showing the characteristics of the fuel injected from the injector and the amount of the fuel flowing into the combustion chamber with respect to time. FIG. 5 is a diagram showing the characteristics of the first vaporization coefficient with respect to the engine rotation speed. FIG. 6 is a diagram showing the characteristics of the second vaporization coefficient with respect to the tube surface temperature of the fuel adhering surface. CE...engine, #l to #4...first to fourth cylinders, l...intake boat, 2...combustion chamber, 3...spark plug, 7...common intake passage, 9 ...Air flow meter, 11・Throttle valve, 13・Independent intake passage, 14
・Injector, 19...first intake temperature sensor, 21
... Throttle valve opening sensor, 22... Second intake temperature sensor, 23... Water temperature sensor, 24... First crank angle sensor, 25... Second crank angle sensor. Figure 2 Patent issuer Mazda Motor Corporation agent Patent attorney Maeda Hoshi and one other person

Claims (1)

[Claims] (1) In an engine that includes an intake air amount detection means and a fuel injection valve, and in which fuel is injected based on a fuel target injection amount determined based on the intake air amount detected by the intake air amount detection means, from the fuel injection valve. Fuel injection is based on a fuel adhesion model that predicts the adhesion characteristics of fuel injected during intake to the intake system inner wall surface, and a vaporization model that predicts the vaporization characteristics of fuel adhering to the intake system inner wall surface into intake air. A fuel injection device for an engine, characterized in that it is provided with a fuel injection control means for controlling the amount of fuel injection.