JPH0577871B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection device for an engine equipped with a supercharger.

(Prior art) In an engine equipped with a supercharger, if intake air amount detection means for detecting the amount of intake air into the engine and outputting an intake air amount signal is provided downstream of the supercharger, the intake air Generally, the intake air amount detecting means is provided upstream of the supercharger because the amount detecting means is affected by pulsating changes in the intake pressure due to the opening and closing of the intake valve, and its detection accuracy is impaired.

By the way, there are supercharged engines, in addition to fully supercharged engines that provide supercharging over the entire operating range of the engine, as well as partially supercharged engines that have two intake passages for the engine, i.e. supercharged engines. A first intake passage that is not equipped with a turbocharger and introduces naturally aspirated air, and a second intake passage that is equipped with a supercharger and introduces supercharged intake air are provided in parallel. Natural intake is performed only from the intake passage, and in high-speed/high-load operating regions, in addition to the introduction of natural intake air from the first intake passage, near the end of the natural intake stroke, natural intake air is introduced from the second intake passage. An engine is known in which the amount of intake air is increased by introducing supercharged intake air (see, for example, Japanese Patent Laid-Open No. 58-20921).

However, regardless of whether the supercharging system is full supercharging or partial supercharging, in a supercharged engine, an intake air amount detection means is generally provided on the intake upstream side of the supercharger, and on the intake downstream side of the supercharger. In the case of a vehicle equipped with a control valve such as a throttle valve that controls the opening and closing of the intake passage, the flow of intake air pressurized by the supercharger may become temporarily discontinuous due to the opening and closing operation of the control valve. The intake air amount detected by the intake air amount detection means (referred to as the detected intake air amount in the following explanation) and the intake air amount actually filled into the engine (referred to as the actual charged intake air amount in the following explanation) There will be a temporary gap between them. Therefore, in such a case, since the fuel injection amount is set based on the detected intake air amount which is different from the actual intake air amount filled into the engine, the control valve is This causes a problem in that the air-fuel ratio changes greatly each time the opening/closing operation is performed, deteriorating the combustion characteristics of the engine.

(Objective of the Invention) The present invention is intended to solve the problems pointed out in the above-mentioned section of the prior art.A supercharger is provided in the intake passage, and the amount of intake air is detected on the intake upstream side of the supercharger. In an engine provided with a control valve for controlling the opening and closing of an intake passage downstream of the supercharger, the means is configured to reduce as much as possible fluctuations in the air-fuel ratio due to changes in the opening degree of the control valve. The purpose is to improve the combustion characteristics of the engine.

(Means for Achieving the Object) As a means for achieving the above object, the present invention provides an intake air amount detecting means for detecting an intake air amount and outputting an intake air amount signal, and an intake air amount detecting means for detecting an intake air amount and outputting an intake air amount signal. A charger is installed such that the supercharger is located on the intake downstream side of the intake air amount detection means, and a control valve for controlling opening and closing of the intake passage is installed at a position on the intake downstream side of the supercharger. In the installed engine, an intake pressure detection means for detecting intake pressure and outputting an intake pressure signal by detecting intake pressure at a position intermediate between the supercharger mounting position and the control valve mounting position in the intake passage; and calculation means for calculating the amount of change in intake pressure, and when the intake pressure detected by the intake pressure detection means is in an increasing state, the control valve is operating in the valve closing direction, and therefore the control valve is operated in the valve closing direction. It is determined that the actual intake air amount charged into the engine is smaller than the detected intake air amount (the difference causes the intake pressure to rise on the upstream side of the control valve), and in this case, the intake air amount is input to the control unit. The output of the above detected intake air amount signal is corrected to decrease, and when the intake pressure is in a decreasing state, the control valve operates in the valve opening direction, so that the actual intake air charged to the engine is lower than the above detected intake air amount. It is determined that the amount of intake air has increased (the difference is caused by the drop in the intake pressure), and in this case, the detected intake air amount that is input to the control unit is calculated by the calculation means. The larger the amount of change in intake pressure, the larger the correction is made to reduce the difference between the output of the detected intake air amount signal and the actual amount of intake air charged into the engine as much as possible.

(Function) In the present invention, the above means reduces as much as possible the difference between the detected intake air amount detected by the intake air amount detection means and the actual intake air amount filled into the engine. Fluctuations in the air-fuel ratio of the air-fuel mixture are suppressed as much as possible, and the combustion characteristics of the engine are improved accordingly.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS. 1 and 2.

(Structure) FIG. 1 shows a system diagram of an intake system of an engine 1 equipped with a fuel injection device according to an embodiment of the present invention.

The engine 1 has two intake ports, namely a main intake port 2 with a main intake valve 5, a sub-intake passage 3 with a sub-intake valve 6, and an exhaust port 4 with an exhaust valve 7. . These two intake ports 2 and 3
Of the exhaust ports 4 and 4, the main intake passage 7 is connected to the main intake port 2, and the auxiliary intake passage 8 is connected to the auxiliary intake port 3.
However, exhaust ports 4 are further connected to exhaust passages 9, respectively.

The main intake passage 7 and the auxiliary intake passage 8 are made to merge on the intake upstream side, and an air cleaner 11 and an air flow meter 12 are installed on the intake upstream side of the merging portion. Further, a main throttle valve 1 is provided on the intake downstream side of the main intake passage 7.
Further, an injector 15 is installed on the intake downstream side of the main throttle valve 13.

On the other hand, a surge tank 16 is formed in the middle of the sub-intake passage 8 . Furthermore, a mechanical supercharger 17 and an intercooler 18 driven by the engine 1 are installed on the intake upstream side of the surge tank 16 in the auxiliary intake passage 8.
is installed in a position upstream of the intake air from the intercooler 18. Further, an auxiliary throttle valve (corresponding to a control valve in the claims) 14 for opening and closing the auxiliary intake passage 8 is installed downstream of the surge tank 16 in the auxiliary intake passage 8 . The sub-throttle valve 14 remains open until the opening of the main throttle valve 13 reaches a predetermined opening (that is, while the engine is operating in a low-speed/low-load region). When the main throttle valve 13 opens beyond the predetermined opening degree, the main throttle valve 13 is opened from the fully closed position to the fully open position in conjunction with the opening operation of the main throttle valve 13. That is, the sub-throttle valve 14
The valve is opened only in the high speed/weak load operating range of the engine, and acts to enable supercharged intake air compressed and pressurized by the supercharger 17 to be introduced into the engine 1 side.

On the other hand, the surge tank 16 is connected to a relief air passage 23 that communicates the surge tank 16 with an intake passage between the confluence of the main intake passage 7 and the auxiliary intake passage 8 and the air flow meter 12. . A relief valve 24 is attached to the relief air passage 23 to regulate the maximum intake pressure within the surge tank 16. moreover,
A pressure sensor 21 (corresponding to intake pressure detection means in the claims) is attached to the surge tank 16 via a pressure outlet path 22. The intake pressure in the surge tank 16 detected by the pressure sensor 21 is output as a pressure signal A ₃ and input to the control unit 25 .

In addition to the pressure signal A ₃ , the control unit 25 also receives the engine rotation speed detected by the rotation speed sensor 26 as the rotation speed signal A ₁ and the intake air amount detected by the air flow meter 12 . are respectively input as the intake air amount signal _A2 . Further, the injector 15 is controlled in accordance with a fuel control signal _A4 output from the controller unit based on each of the input signals described above.

(Operation) Next, to explain the operation of the fuel injection device of this embodiment, when the engine 1 is started, the supercharger 1
7 is started, and depending on the operating state of the engine 1, natural intake air is introduced through the main intake passage 7,
The supercharged intake air is selectively introduced through the sub-intake passage 8. That is, when the operating state of the engine 1 is in the low-speed/low-load operating region, the sub-throttle valve 14 is closed, so that only natural intake air is introduced into the engine 1 via the main intake passage 7. Low output operation of the engine 1 is realized.

In this operating state, the supercharged intake air pressurized by the supercharger 17 is held at an increased pressure in the surge tank 16 in preparation for the start of supercharging operation.

On the other hand, the operating state of engine 1 is
When the engine is in a high-load operation region, both the main throttle valve 13 and the auxiliary throttle valve 14 are opened, so natural intake air is introduced through the main intake passage 7 and overflow air is introduced through the auxiliary intake passage 8. The intake and supply air is introduced in parallel with a predetermined phase. That is,
In this embodiment, the auxiliary intake passage 8 is opened near the end of the natural intake air introduction process through the main intake passage 7, and supercharged intake air is introduced through the auxiliary intake passage 8. I have to. Therefore, the amount of intake air supplied is increased, and high output operation of the engine 1 is realized.

Incidentally, the fuel injection amount is determined by the opening of the injector 15 based on the injection pulse width calculated from the intake air amount detected by the air flow meter 12 and the rotation speed sensor 26 detected by the rotation speed sensor 26. Controlled by adjusting the valve time.

However, since the air flow meter 12 is provided on the intake upstream side of the supercharger 17 and the sub-throttle valve 14 is provided on the intake downstream side of the supercharger 17, the sub-throttle valve 14 is provided on the intake downstream side of the supercharger 17. Depending on the opening/closing operation (change in opening degree) of the tutle valve 14,
An error occurs between the detected intake air amount directly detected by the air flow meter 12 and the actual charged intake air amount that is actually filled into the engine 1. Therefore, in order to maintain the air-fuel ratio of the air-fuel mixture at a predetermined air-fuel ratio, it is necessary to increase or decrease the output of the detected intake air amount signal so as to match the actual charged intake air amount. detects the fluctuation state of the intake pressure in the surge tank 16 located between the supercharger 17 and the sub-throttle valve 14, and calculates the difference between the detected intake air amount and the actual charged intake air amount based on the fluctuation state of the intake pressure. The direction and magnitude of the deviation are determined, and the output of the detected intake air amount signal by the air flow meter 12 is corrected to increase or decrease by a predetermined amount in a predetermined direction. In other words, a state in which the intake pressure in the surge tank 16 is changing in the upward direction is a state in which the sub-throttle valve 14 is operating in the closing direction, such as during deceleration operation, and the intake pressure in the surge tank 16 is changing in the upward direction. This is a state in which the actual charged intake air amount is decreasing. Therefore, in this case, the output of the intake air amount signal from the air flow meter 12 is corrected in a decreasing direction based on the output from the pressure sensor 21. On the other hand, a state in which the intake pressure in the surge tank 16 is changing in the downward direction is a state in which the sub-throttle valve 14 is operating in the opening direction, such as during acceleration operation, and the detected intake air This is a state in which the actual charged intake air amount is larger than the amount. Therefore, in this case, the output of the intake air amount signal by the air flow meter 12 is corrected in the increasing direction by the output from the pressure sensor 21.

Next, this correction control of the intake air amount signal output will be specifically explained with reference to the flowchart shown in FIG. First, the current engine speed Ne,
Read the current intake air amount (output of the air flow meter 12) Qa and the intake pressure in the surge tank 16 (output of the pressure sensor 21) P (step
S1, S2, S3).

Next, in step S4, the currently detected intake pressure P is compared with the previously detected intake pressure _P1 to determine the direction and magnitude of the change in intake pressure. As a result of the determination, if P = P ₁ , it means that the intake pressure is not changing (that is, the engine is operating at constant speed and constant load), and therefore, in this case, the detected intake air It is determined that the intake air amount and the actual filled intake air amount almost match, and the correction value Qb of the intake air amount signal output from the air flow meter 12 is determined.
Set Qb=0 (that is, the intake air amount signal output is not corrected).

On the other hand, if P≠P ₁ , the intake pressure is fluctuating (that is, the engine is in acceleration or deceleration operation), and therefore the intake air amount signal output by the air flow meter 12 cannot be corrected. determine that it is necessary. In this case, the difference between the previous intake pressure P ₁ and the current intake pressure P (P ₁ - P)
A correction value Qb (=V.(P ₁ -P): V is a constant) is calculated from (step S8). At this time, if (P ₁ > P) (that is, the intake pressure is in a decreasing state), the correction value Qb becomes a positive value, and the air flow meter 12
The output of the intake air amount signal is corrected to increase.
On the other hand, if (P ₁ <P) (that is, the intake pressure is in an increasing state), the correction value Qb becomes a negative value, and the output of the intake air amount signal by the air flow meter 12 is corrected to decrease. Further, the absolute amount of the correction value is set to increase or decrease in proportion to the deviation of the intake pressure.

After setting the correction value Qb, the current intake pressure P is rewritten as the previous intake pressure (step S9).

Next, from the detected intake air amount Qa and the correction value Qb, the intake air amount that should actually be used as a reference for setting the fuel injection amount, that is, the current actual charged intake air amount Q (=Qa + Qb)
(step S6), and based on the actual charged intake air amount Q, the fuel injection pulse width, that is, the fuel injection amount T
(=K.Q/Ne: K is a constant) (step S7). This completes the correction control of the intake air amount signal output.

In addition, in the above explanation, the mechanical supercharger 17
Although the description has been made regarding a partially supercharged engine equipped with a It can also be applied to engines.

(Effects of the Invention) As is clear from the above description, the engine fuel injection device of the present invention includes an intake air amount detection means provided upstream of the supercharger provided in the middle of the intake passage.
Further, in an engine provided with a control valve on the intake downstream side, the intake pressure between the supercharger and the control valve is detected, and the intake air amount signal is output from the intake air amount detection means in accordance with the amount of change in the intake pressure. The larger the amount of change in intake pressure, the greater the increase or decrease in the output of air-fuel mixture in order to match the actual amount of air charged into the engine as much as possible. The effect is that air-fuel ratio fluctuations are prevented as much as possible and the combustion characteristics of the engine are improved.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an engine equipped with a fuel injection device according to an embodiment of the present invention, and FIG. 2 is a control flowchart of the fuel injection device shown in FIG. 1... Engine, 7, 8... Intake passage, 9...
Exhaust passage, 12...Air flow meter (intake air amount detection means), 13...Main throttle valve, 1
4... Sub-throttle valve (control valve), 15...
Injector, 16...Surge tank, 17...
...Supercharger, 18...Intercooler, 21...Pressure sensor (intake pressure detection means).

Claims (1)

[Claims] 1. An intake air amount detection means for detecting the amount of intake air into the engine and outputting an intake air amount signal and a supercharger are installed in the intake passage of the engine. In an engine in which a control valve for controlling opening/closing of the intake passage is installed at a downstream side of the intake passage of the turbocharger, the supercharger installation position in the intake passage and the control valve are provided. At an intermediate position between the supercharger and the control valve, there is an intake pressure detection means for detecting the intake pressure in the intake passage located between the supercharger and the control valve and outputting an intake pressure signal; and a calculation means for calculating an amount of pressure change, and is configured to increase or decrease the output of the intake air amount detection means to a greater extent as the amount of change in intake pressure by the calculation means increases. Fuel injection device.