JPH0733787B2 - Air-fuel ratio controller for electronic fuel injection engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air-fuel ratio control device for an electronic fuel injection type engine, and in particular to increasing the fuel pressure of a fuel injection valve to suppress bubbling of fuel. Regarding improvement.

(Prior Art) Conventionally, as an air-fuel ratio control device for an electronic fuel injection type engine, a fuel injection valve for supplying fuel is provided in an intake passage of the engine as disclosed in, for example, Japanese Patent Laid-Open No. 58-126440. At the same time, an exhaust sensor for detecting the air-fuel ratio of the air-fuel mixture supplied to the engine by the oxygen concentration component in the exhaust gas is provided in the exhaust passage, and the air-fuel ratio of the air-fuel mixture becomes the target value based on the output of the exhaust sensor. In addition, there is known one in which the fuel injection valve is feedback-controlled.

(Problems to be Solved by the Invention) By the way, when operating an electronic fuel injection engine equipped with such an air-fuel ratio control device, for example, in a state where the fuel temperature is high, the fuel pressure of the fuel injection valve is increased. By suppressing the bubbling, the fuel density is prevented from lowering and the responsiveness of the feedback control is ensured.

However, in this case, since the control of the fuel injection valve is performed by increasing or decreasing the valve opening period regardless of the fuel pressure, when the fuel pressure increases, the fluctuation amount of the fuel injection amount, that is, the fluctuation amount of the air-fuel ratio becomes large. The air-fuel ratio does not easily reach the target value,
There is a problem that the feedback control response and convergence are poor.

The present invention has been made in view of the above point, and an object of the present invention is to improve the responsiveness and convergence of the feedback control by correcting the feedback control according to the increase of the fuel pressure. .

(Means for Solving the Problems) In order to achieve the above object, the present invention is to increase the control gain of the feedback control according to the increase of the fuel pressure of the fuel supply means.

Specifically, the solution means taken by the present invention is, as shown in FIG. 1, a fuel supply means 23 for supplying fuel to an engine and an air-fuel ratio detection means for detecting an air-fuel ratio of an air-fuel mixture supplied to the engine. 18, a control means 25 for receiving the output of the air-fuel ratio detection means 18 and performing feedback control of the fuel supply means 23 so that the air-fuel ratio of the engine reaches a target value, and a specific means for detecting a specific operation time when the fuel foams Receiving the output of the operation detecting means 26 and the specific operation detecting means 26, the pressure of the fuel supply means 23 with respect to the fuel injection valve is increased and the control means is also provided.
The correction means 27 for increasing the control gain of the feedback control in 25 is provided.

(Operation) With the above configuration, in the present invention, during a specific operation of the engine in which the fuel foams, the pressure of the fuel supply means 23 to the fuel injection valve increases, the foaming of the fuel is suppressed, and the fuel density is maintained constant. The responsiveness of feedback control is secured.

In this case, the amount of change in the air-fuel ratio of the air-fuel mixture increases as the fuel pressure increases, but the control gain of the feedback control increases, so the air-fuel ratio of the air-fuel mixture is controlled to converge to the target value with good responsiveness.

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 2 shows an electronic fuel injection type engine equipped with an air-fuel ratio control device according to the present invention, where 1 is an engine and 2 is an engine 1.
The combustion chamber 5, which has a variable volume formed by the piston 4 slidably inserted in the cylinder 3, has one end communicating with the atmosphere,
An air intake passage having the other end opened to the combustion chamber 2 for supplying intake air to the engine 1, and an exhaust gas 6 having one end opened to the combustion chamber 2 and the other end opened to the atmosphere to exhaust the exhaust gas. A throttle valve 7 for controlling the intake air amount and a fuel injection valve 8 for injecting fuel on the downstream side of the throttle valve 7 are disposed in the intake passage 5 in the passage. An intake valve 9 is provided at the opening of the intake passage 5 to the combustion chamber 2, and an exhaust valve 10 is provided at the opening of the exhaust passage 5 to the combustion chamber 2. Further, a spark plug 11 for igniting the air-fuel mixture in the combustion chamber 2 is arranged at the top of the combustion chamber 2.

Further, the fuel injection valve 8 is provided with an intake pressure responsive pressure regulator 12 for adjusting the fuel pressure to a predetermined pressure. The pressure regulator 12 is in communication with the intake passage 5 downstream of the throttle valve 7 via a three-way solenoid 13, and when the three-way solenoid 13 is turned on, negative pressure is supplied to the pressure regulator 12 to inject fuel by the pressure regulator 12. When the pressure on the valve 8 is increased and the three-way solenoid 13 is turned off, the atmospheric pressure is supplied to the pressure regulator 12 and the fuel injection valve 8
The pressure for the fuel is matched with the discharge pressure of the fuel pump. Therefore, the fuel injection valve 8, the pressure regulator 12, and the three-way solenoid 13 described above constitute fuel supply means 23 for supplying fuel to the engine 1.

Further, 15 is an air flow sensor that detects the amount of intake air on the upstream side of the throttle valve 7 in the intake passage 5, 16 is an opening sensor that detects the opening of the throttle valve 7, and 17 is the temperature of the engine 1 based on the engine cooling water temperature. An engine temperature sensor for detecting, 18 is an exhaust sensor as an air-fuel ratio detecting means provided in the exhaust passage 7 for detecting an air-fuel ratio of the air-fuel mixture based on an oxygen concentration component in the exhaust gas, and 19 is a rotation speed sensor for detecting an engine speed. The air flow sensor 15 and the distributor 19 detect the operating state of the engine 1. Also,
Reference numeral 20 is an intake air temperature sensor that detects the intake air temperature. And
The detection signals of the sensors 15 to 20 are input to the controller 24, and the controller 24 causes the fuel injection valve 8 to operate.
The spark plug 11 and the three-way solenoid 13 are controlled.

Next, the operation of the controller 24 will be described based on the flowchart of FIG. 3. First, after initialization is performed in step S ₁ , signals of various sensors 15 to 20 are input in step S ₂ and then step S ₂ is performed. _{In step 3} , the basic fuel injection pulse width Tp corresponding to the operating state of the engine 1 is calculated, and in step S ₄ , it is determined whether the air-fuel ratio is in the feedback control zone.
If NO in the feedback zone, the fuel injection pulse width T is calculated by T = Tp × C _{K in} step S _{5 using} the basic fuel injection pulse width Tp and the constant correction coefficient C _K.

On the other hand, if YES in the feedback zone, step S _{6 is performed} to determine whether the engine 1 is in the hot start mode.
Whether the cooling water temperature or the intake air temperature is below the set temperature, or the elapsed time after the engine is started
Determines s) less than or not, it is judged not to be the time of hot start when the cooling water temperature or the elapsed time after the following or the engine start intake air temperature setting temperature is a predetermined time or more, in the feedback control in Step S ₇ a control gain of proportional control and integral control, respectively, and a ', the fuel injection pulse width T these control gains F _CB in step S ₁₂
The according to expression _{T = Tp × C K × F} CB.

On the other hand, it is determined to be in state easy to foam the fuel there during hot start when the elapsed time after and engine start at the cooling water temperature or the intake air temperature is a set temperature or higher in step S ₆ is equal to or less than the predetermined time, step the three-way solenoid 13 at S ₈
The fuel pressure of the fuel injection valve 8 is increased by turning it on. Furthermore, the air-fuel ratio of the mixture is determined whether rich at step S _9, the process proceeds to step S ₇ when the NO is not rich, those the rich determination in step S ₁₀ is affirmative (YES) is rich is first Therefore, it is determined whether the lean determination has not yet been reversed, and if NO in the first rich determination, it is determined that the change in the air-fuel ratio of the air-fuel mixture is converging. Proceed to ₇ . On the other hand, 1
Times eye when YES is rich determination, it is determined that the amount of fluctuation of the air-fuel ratio of the mixture by increasing the fuel pressure increases, respectively control gain of proportional control and integral control in the feedback control in the next step S ₁₁ A, From A ′
B, increased to B ', and calculates the fuel injection pulse width T in step S _12.

In the above flow, constituted by step S _12, receiving the output of the exhaust sensor 18 (air-fuel ratio detecting means), a control unit 25 for feedback controlling the fuel supply means 23 such that the air-fuel ratio of the engine 1 becomes the target value At the same time, step S ₆ constitutes the specific operation detection means 26 for detecting the specific operation time when the fuel foams, and steps S ₈ and S ₁₁
Thus, the output of the specific operation detection means 26 is received, and the correction means 27 is configured to increase the pressure of the fuel supply means 23 to the fuel injection valve 8 and increase the control gain of the feedback control in the control means 25.

Therefore, at the time of hot start, the fuel pressure of the fuel injection valve 8 increases, so that the bubbling of the fuel is suppressed, the decrease of the fuel density is prevented, and the responsiveness of the feedback control is secured.

Moreover, at that time, the control gain of the feedback control is corrected to be large, so that it is possible to prevent the responsiveness and the convergence of the feedback control from being deteriorated due to the increase in the variation amount of the air-fuel ratio due to the increase in the fuel pressure. Therefore, the air-fuel ratio of the air-fuel mixture is controlled to converge to the target value with good responsiveness.

In the above-described embodiment, the hot start is assumed as the specific operation, but the same can be applied to other operation areas where the fuel foams.

(Effects of the Invention) As described above, according to the air-fuel ratio control device for an electronic fuel injection type engine of the present invention, during the specific operation of the engine in which the fuel foams, the fuel pressure is increased and the feedback control of the air-fuel ratio is performed. Since the control gain is increased, it suppresses the foaming of the fuel and prevents the feedback control response and convergence from deteriorating due to the increase in the amount of air-fuel ratio fluctuations that accompanies the air-fuel ratio to the target value. The convergence control can be performed well, and the controllability of the feedback control can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of the present invention. 2 and 3 show an embodiment of the present invention, FIG. 2 is an overall schematic configuration diagram, and FIG. 3 is a flow chart diagram for explaining the operation of the controller. 1 ... Engine, 8 ... Fuel injection valve, 18 ... Exhaust sensor, 23 ... Fuel supply means, 25 ... Control means, 26 ... Specific operation detection means, 27 ... Correction means

Front Page Continuation (72) Inventor Shoji Tokuda 3-1, Shinchi Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) Reference JP-A-61-108843 (JP, A)

Claims (1)

[Claims] 1. A fuel supply means for supplying fuel to an engine, an air-fuel ratio detecting means for detecting an air-fuel ratio of an air-fuel mixture supplied to the engine, and an output of the air-fuel ratio detecting means for receiving an engine air-fuel ratio The control means for feedback-controlling the fuel supply means so that the target value is reached, the specific operation detection means for detecting the specific operation time when the fuel foams, and the fuel of the fuel supply means for receiving the output of the specific operation detection means. An air-fuel ratio control apparatus for an electronic fuel injection engine, comprising: a correction unit that increases a pressure applied to an injection valve and increases a control gain of feedback control in the control unit.