JPH0524344B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fuel injection control device for an internal combustion engine, particularly a gasoline internal combustion engine, and more particularly to a fuel injection control device that injects fuel independently for each cylinder. It is.

[Prior Art] Conventionally, as one type of fuel injection control device for an internal combustion engine, there is a so-called independent injection type fuel injection control device that independently injects fuel for each fuel injection valve provided in each cylinder.

This independent injection type fuel injection control device first calculates the fuel injection amount to optimize the air-fuel ratio according to the internal combustion engine speed and intake air amount, and also makes corrections according to other operating conditions. In addition, in accordance with the determined fuel injection amount, the fuel injection valve is opened for each cylinder at an arbitrary stroke of the cylinder, that is, when a predetermined crank angle is reached, and fuel injection control is performed. It's summery.

In this way, the amount of fuel injection is calculated according to the driving conditions, but the start timing of fuel injection is fixed, and the timing of starting fuel injection is not controlled according to the driving conditions. In particular, no consideration is given to the fact that the degree of negative pressure in the intake pipe affects the flight time of the injected fuel until it reaches the intake valve of the cylinder.

Further injected fuel reaches the intake valve of the cylinder, but conventionally, control has not been performed that takes into account the relationship between the time when the last injected fuel reaches the intake valve and the intake speed of the intake valve. In other words, if the intake speed is not high enough when the last injected fuel is taken into the intake valve,
There are problems in that the fuel may adhere to the wall surface or the fuel may not be atomized sufficiently.
Therefore, in the past, there was a possibility that unburned air-fuel mixture remained. Furthermore, if the intake speed is low at the time when the last injected fuel reaches the intake valve, there is a problem that the swirling flow of the air-fuel mixture within the cylinder is insufficient and knocking occurs.

For example, in recent years, internal combustion engines using fuel injection valves have been equipped with air assist systems to improve the atomization effect of the fuel, but as mentioned above, the flight time of the fuel due to the negative pressure in the intake pipe and the final The intake velocity at the time the fuel reaches the intake valve should be considered.

The air assist system directs intake air upstream of the throttle valve to the vicinity of the fuel injection port of the injection valve without passing through the throttle valve.
The negative pressure downstream of the throttle valve blows out air, improving the fuel atomization effect.

However, the degree of negative pressure varies depending on the degree of load on the internal combustion engine. Therefore, the ejection speed of the atomized fuel differs, which affects the flight time for the fuel to reach the intake valve of the cylinder. Therefore,
Depending on the level of load, fuel is no longer always drawn into the cylinder in the same pattern, resulting in differences in how the fuel adheres to the intake pipe and how it mixes with the air, making injection start timing different from the previously fixed injection start timing. However, in terms of fuel combustion stability, fuel consumption, exhaust gas, transient response, etc., this may not necessarily be the optimal fuel injection start timing corresponding to the operating condition of the internal combustion engine.

[Object of the Invention] Therefore, an object of the present invention is to calculate the opening timing of a fuel injection valve according to the operating state of an internal combustion engine by taking into account the intake speed at the time when the last fuel reaches the intake valve. It is an object of the present invention to provide a fuel injection control device that reduces unburned air-fuel mixture and prevents knocking.

[Configuration of the Invention] The configuration of the present invention to achieve the above object is as follows.
As shown in the figure, the operating state detection means M3 of the internal combustion engine M2, and the fuel injection means M provided for each intake pipe of each cylinder.
4, the fuel injection time is calculated according to the operating state of the internal combustion engine M2, and the flight time required for the fuel injected into the intake pipe of each cylinder to reach the intake valve of the corresponding cylinder is calculated. detecting the rotational speed of the fuel injection time, the flight time, the rotational speed, the valve closing time of the fuel injection means M4, and the crank angle at which the intake speed of the intake valve becomes the highest. Calculating the fuel injection start time at which the intake speed is the highest at the time when the last fuel injected from the means M4 reaches the intake valve, and calculating the fuel injection start time from the fuel injection start time to the fuel injection time, and from the fuel injection start time to the fuel injection means M4. The gist of the present invention is a fuel injection control device for an internal combustion engine M2, which is characterized in that it includes a control means M7 that outputs a fuel injection signal.

[Operation] According to the fuel injection control device for an internal combustion engine of the present invention, the operating state detection means detects the operating state of the internal combustion engine, and the fuel injection means provided for each intake pipe of each cylinder injects fuel. The control means calculates the fuel injection time according to the operating state of the internal combustion engine, and determines the flight time required for the fuel injected into the intake pipe of each cylinder to reach the intake valve of the corresponding cylinder. Further, the rotational speed of the internal combustion engine is detected by the operating state detection means. The control means includes fuel injection time, flight time,
Based on the rotational speed, the closing time of the fuel injection means, and the crank angle at which the intake velocity of the intake valve is the highest, fuel injection is such that the intake velocity is at its highest when the last fuel injected reaches said intake valve. Calculate the start time. Then, a fuel injection signal is outputted to the fuel injection means for the fuel injection time from the fuel injection start timing.

This results in control that takes into account the time point at which the last injected fuel reaches the intake valve and the intake velocity of the intake valve. In other words, the fuel injection start timing is calculated so that the intake speed is at its highest when the last injected fuel is taken into the intake valve. As a result, among the fuel injected toward the intake valve, the last fuel, which has a high possibility of adhering to the wall surface or not being sufficiently atomized, is inhaled at the highest intake speed. Therefore, even the last fuel is prevented from adhering to the wall surface, and secondary atomization of the fuel at the intake valve position is promoted. This leads to a reduction in unburned mixture. Furthermore, since the intake speed is the highest when the last fuel is taken in, the swirling flow of the air-fuel mixture within the cylinder can be increased, and knocking can also be prevented.

Embodiments of the present invention will be described below based on the drawings.

[Embodiment] First, FIG. 2 is a schematic system diagram showing a four-cycle, four-cylinder internal combustion engine and its peripheral devices, in which the fuel injection control device of the present invention is mounted.

1 is the internal combustion engine body, 2 is the exhaust pipe, 3 is the intake pipe,
4 is a fuel injection valve that injects fuel into the intake air of the internal combustion engine 1; 5 is a surge tank that prevents pulsation of the intake air; 6 is a cold start fuel injection valve; 7
8 is a throttle valve, 9 is an auxiliary intake pipe, and 10 is an air flow meter.

The above-mentioned auxiliary intake pipe 9 sucks air from the upstream side of the throttle valve 8, controls the flow rate to achieve the target rotational speed of the internal combustion engine when the internal combustion engine 1 is idling, and also controls the flow rate when the internal combustion engine 1 is idling. is a flow control valve 9a for idle speed control that is controlled to maintain a certain amount of opening (hereinafter referred to as
Intake air is sent to the tip of the fuel injection valve 4 through an ISCV (ISCV). Due to this,
If the ISCV 9a is open, the amount of intake air will be injected to the tip of the fuel injection valve 4 through the auxiliary intake pipe 9. In this way, the intake air that has passed through the sub-intake pipe 9 exerts an effect as assist air for fuel injection.

Further, the air valve 7 similarly takes in intake air from the upstream portion of the throttle 8, and when the air valve 7 is open, the intake air directly flows out to the surge tank 5. The air valve 7 opens when the internal combustion engine 1 is in a cold state.

Further, the fuel in the fuel tank 11 is passed through a fuel filter 12 to a fuel pump 13 to a fuel injection valve 4.
is pumped to. At the same time, it is also pressure-fed to the cold start injection valve 6.

Separately, the fuel pumped by the fuel pump 13 is divided into a regulator 15 that controls the fuel pressure. The regulator 15 is connected to the fuel tank 1 depending on the degree of insertion of the conical control valve 15b into the inlet 15a.
1 and the fuel injection pressure of the fuel injection valve 4. This fuel pressure is basically applied to the diaphragm 1 on which the control valve 15b is installed.
It is determined by the pressing force of the spring 15d pressing the spring 5c from the opposite side. However, the pressure of assist air is introduced into the storage chamber 15e of the spring 15d from the auxiliary intake pipe 9 near the tip of the fuel injection valve 4 to finely adjust the control valve 15b. When the pressure of the assist air is high, the fuel inlet 15a becomes narrow, the amount of recirculation decreases, and the fuel pressure increases. Conversely, when the pressure of the assist air is low, the amount of recirculation of the fuel increases, and the fuel pressure increases. descend. As a result, the relative pressure of the fuel to the assist air is made constant, and the fuel injection amount can be precisely controlled.

The distributor 16 also includes a rotation angle sensor 16a that rotates in synchronization with the crankshaft of the internal combustion engine 1 and generates a pulse signal proportional to the rotation, and a cylinder discrimination sensor 16b that detects the top dead center of a specific cylinder. are provided, each outputting a detection signal. Furthermore, a water temperature sensor 17 is installed in the cylinder and outputs a signal corresponding to the cooling water temperature of the cylinder.

Next, 18 is an electronic control circuit which inputs detection signals from a throttle position sensor 8b and an air flow meter 10 which output a fully closed signal and an opening signal in conjunction with the throttle valve 8, and receives the data. A signal to adjust the opening time of the fuel injection valve 4 as necessary, a signal to control the opening state of the air valve 7, a signal to control the opening state of the cold start fuel injection valve 6, and a sub-intake. It outputs a signal that controls the opening area of ISCV 9a that controls the air flow rate of pipe 9.

FIG. 3 shows an enlarged partial sectional view of the tip of the fuel injection valve 4 described above. Intake air supplied from the auxiliary intake pipe 9 flows into the gap 24 between the adapter 22 provided at the nozzle 21 portion of the fuel injection valve 4 and the fuel injection valve mounting hole 23, and then flows around the adapter 22. Air flows into the vicinity of the tip of the nozzle 21 from the provided air intake hole 25 . Thereafter, the intake air is injected into the intake air of the intake manifold 3 from the jet port 26 provided in the adapter 22 together with the fuel injected from the nozzle 21 of the fuel injection valve 4 . Here, 27 is an O-ring, and the adapter 22
A ring-shaped insulator 28 is provided between the fuel injection valve 4 and the fuel injection valve mounting hole 23 on the opposite side from the position of the O-ring 27. , gap 2
4 is kept airtight.

Among the above-mentioned devices, a throttle position sensor 8b, an air flow meter 10, a rotation angle sensor 1
6a, cylinder discrimination sensor 16b and water temperature sensor 17
or a group consisting of these sensors plus an intake pipe pressure sensor (not shown) corresponds to the operating state detection means, the fuel injection valve 4 corresponds to the fuel injection means, and the auxiliary intake pipe 9 corresponds to the air introduction means. However, the combination of the throttle position sensor 8b and the air flow meter 10, or alternatively a not-shown intake pipe pressure sensor, corresponds to the internal combustion engine load detection means, and the electronic control circuit 18 corresponds to the control means.

Next, FIG. 4 shows a block diagram of the electronic control circuit 18.

30 inputs and calculates data output from each sensor according to a control program, and
A central processing unit (hereinafter simply referred to as CPU) performs processing for controlling the operation of various devices such as the ISCV 9a, and 31 is a read-only memory (31) in which the control program and initial data such as a target rotation speed map are stored. 32 is a random access memory (hereinafter simply referred to as ROM) in which data input to the electronic control circuit 18 and data necessary for arithmetic control are temporarily read and written.
33 is a backup random access memory (hereinafter simply referred to as backup RAM) backed up by a battery so as to retain data necessary for subsequent internal combustion engine operation even when the key switch is turned off; 34 is a diagram Inputs equipped with input ports not shown, a waveform shaping circuit provided as necessary, a multiplexer that selectively outputs the output signal of each sensor to the CPU 30, an A/D converter that converts analog signals to digital signals, etc. Each section is represented by a section. 35 is provided with an output port (not shown) and other ports as necessary.
An output section 36 is equipped with a drive circuit etc. that drives the ISCV 9a etc. according to the control signal of the CPU 30.
Each element such as CPU 30, ROM 31, etc. and input section 3
4. Bus lines connecting the output section 35 and through which each data is sent are shown.

The above control of ISCV9a by CPU30 is as follows:
This is executed using a pulse signal with a duty corresponding to the aperture area of the ISCV 9a.

In addition, in the CPU 30, the cooling water temperature is determined based on the signals from each sensor in the main routine (not shown).
Tw, throttle opening TH, intake air amount Q, internal combustion engine rotation speed N, etc. are calculated, and the injection pulse width τi corresponding to the fuel injection amount is calculated based on each calculated data value. . Since this process is well known, it will be omitted, and next we will discuss an example of setting the fuel injection timing, which is the main process related to the present invention, that is, setting the opening start timing of the fuel injection valve and controlling the injection pulse output. This will be explained in detail with reference to.

The flowchart shown in the first control example in FIGS. 5A and 5B represents processing that is executed once every two revolutions of the internal combustion engine for each cylinder. FIG. 5A shows the injection pulse start timing setting subroutine. When the process is started, first, in step 110, the cooling water temperature Tw, throttle opening TH, and
Various data values such as intake air amount Q, internal combustion engine rotation speed N, injection pulse width τi, etc. are read, and then step 120
to move to.

Next, in step 120, Q/N [l/rev] representing the load of the internal combustion engine is obtained from the values of Q and N read in step 110, and based on this value, the function f(Q/N) or f B is calculated from the map corresponding to (Q/N). B represents the fuel flight time from the fuel injection valve 4 to the intake valve 1a. A map corresponding to this function f(Q/N) is shown in FIG. 6, for example.

Next, the process of step 130 is executed, and the valve opening start timing θs of the fuel injection valve 4 is calculated using the following equation (1).

θs=θ−6×N×10 ^-3 ×(τi+A+B)... (1) In the above equation (1), the valve opening start timing θs is based on the intake top dead center (the top dead center of the piston during the intake stroke). It is expressed in crank angle [°CA], and specifically represents the output start timing of the injection pulse signal which is the valve opening signal of the fuel injection valve 4, that is, the injection pulse start timing. θ is the predetermined crankshaft setting angle based on intake top dead center [°CA]
represents. A is the closing time of the fuel injection valve 4 [msec]
represents.

In the above equation (1), the unit of the internal combustion engine rotation speed N is [rpm], the unit of the injection pulse width τi is [msec], and the unit of the fuel flight time B is [msec].

When the valve opening start timing θs is calculated through the process described above, after this process, the fuel injection valve 4 is opened at the time θs in the injection pulse output subroutine shown in FIG. It will be carried out. In the injection pulse output subroutine, in step 150, the crank angle waits until the crank angle reaches θs, and when it reaches θs, it is judged as "YES", and step 160 is executed.
An injection pulse with a pulse width τi is output, and fuel injection for τi is performed.

Next, the valve opening start timing calculated using the above equation (1) will be explained with reference to the opening/closing timing chart of the fuel injection valve 4 and the intake valve 1a shown in FIG. In addition, in the figure, TDC is the top dead center of the piston,
BDC is bottom dead center, INO is intake valve opening timing,
INC represents the intake valve closing timing, and EXC represents the exhaust valve closing timing.

In the above calculation formula (1), θ is a predetermined setting angle [°CA] based on TDC, which is the intake top dead center. This is to preset the timing when the last injected fuel reaches the intake valve 1a, and is set at 60° CA or after the intake top dead center.
A value of 120° CA is desirable, and as shown in the figure, in this embodiment, it is set to 80° CA after intake top dead center. Also, the reason for this is 60 [°CA] after intake top dead center or
The intake speed at the intake valve 1a position at 120 [°CA] is the fastest, and the intake speed at the intake valve 1a position is the fastest.
Since point a is the widest opening, if this point is taken as the final arrival point of the fuel, it will be possible to suppress fuel adhesion to the wall surface and further promote secondary atomization of the fuel at the intake valve 1a position. It is.

Next, 6 × N × 10 ^-3 × (τi + A + B) in equation (1) is the difference between the fuel injection pulse width τi [msec] obtained in the main routine and the actual fuel injection valve 4.
The valve closing time A [msec] required for the valve to close, and the flight time B [msec] required for the last fuel injected from the fuel injection valve 4 to reach the intake valve 1a.
This value is used to convert into a crank angle, and by subtracting this value from the set angle θ, the valve opening start timing θs of the fuel injection valve 4 can be determined.

As mentioned above, the relationship between the flight time B and the value Q/N representing the load is expressed as B=f(Q/N),
As shown in Figure 6, as Q/N increases, f
(Q/N) also increases. This is because the air pressure inside the intake pipe 3 increases due to an increase in Q/N, which reduces the blowing speed of air that has passed through the sub-intake pipe 9 and is close to the outside pressure, thereby extending the flight time. be.

As mentioned above, this embodiment attempts to perform more precise control by calculating the flight time B from the value of the internal combustion engine load Q/N, and the intake speed is adjusted after all the fuel is inhaled. Since this is the highest, the swirling flow of the air-fuel mixture within the cylinder can be increased, and knocking can also be prevented.

As a second control example, FIG. 8 shows a flowchart of the injection pulse start timing setting subroutine. This injection pulse start timing setting subroutine is used in combination with the injection pulse output subroutine of the first control example shown in FIG. 5B. Here, to obtain the flight time B, the intake pipe pressure P is used as a parameter representing the load.

However, in this flowchart, 21
Steps 0 and 230 perform the same processing as steps 110 and 130 in the flowchart of the first control example, respectively.

Further, in step 220, the flight time B [msec] is calculated based on the value of the intake pipe pressure P using the function g(P) or a map corresponding thereto. The above map is expressed in a graph as shown in FIG. 9, where P is an absolute pressure. As P increases, g
(P) tends to increase because as the intake pipe pressure P, which represents the load, increases, the speed of air blowing from the auxiliary intake pipe 9 decreases, resulting in an increase in flight time.

According to this control example, P has faster response to load changes than Q and N, so more accurate control is possible.

[Effects of the Invention] As described in detail above, in the present invention, control is executed in consideration of the relationship between the time when the last injected fuel reaches the intake valve and the intake speed of the intake valve. In other words, the fuel injection start timing is calculated so that the intake speed is at its highest when the last injected fuel is taken into the intake valve. As a result, among the fuel injected toward the intake valve, the last fuel, which has a high possibility of adhering to the wall surface or not being sufficiently atomized, is inhaled at the highest intake speed. Therefore, even the last fuel is prevented from adhering to the wall surface, and the second part of the fuel at the intake valve position is suppressed.
Secondary atomization is promoted. This leads to a reduction in unburned mixture. Furthermore, since the intake speed is the highest when the last fuel is taken in, the swirling flow of the air-fuel mixture within the cylinder can be increased, and knocking can also be prevented.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the basic configuration of the present invention, Fig. 2 is a schematic system diagram showing an internal combustion engine equipped with an embodiment of the fuel injection control device and its peripheral equipment, and Fig. 3 is a fuel injection valve. Figure 4 is an enlarged partial sectional view of the vicinity of the tip, and Figure 5 is a block diagram showing the configuration of the electronic control circuit used there.
A flowchart showing the injection pulse start timing setting process in the control example, FIG. , FIG. 7 is a valve opening/closing timing chart of the fuel injection valve and intake valve representing the operation of this embodiment, FIG. 8 is a flowchart of the second control example, and FIG. 9 is a flowchart of the second control example.
The figure is a graph showing a map for determining the fuel flight time from P. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 1a... Intake valve, 3... Intake pipe, 4... Fuel injection valve, 8... Throttle valve, 9
... Sub-intake pipe, 10... Air flow meter, 16a... Rotation angle sensor, 18... Electronic control circuit.

Claims (1)

[Scope of Claims] 1. A means for detecting the operating state of an internal combustion engine, a fuel injection means provided for each intake pipe of each cylinder, and a fuel injection time calculated according to the operating state of the internal combustion engine, The flight time required for the fuel injected into the pipe to reach the intake valve of the corresponding cylinder is determined, the rotation speed of the internal combustion engine is detected, and the fuel injection time, the flight time, the rotation speed, and the fuel injection means are determined. Based on the valve closing time of and the clamp angle at which the intake velocity of the intake valve is the highest, fuel injection is performed such that the intake velocity is the highest at the time when the last fuel injected from the fuel injection means reaches the intake valve. A fuel injection control device for an internal combustion engine, comprising: a control means for calculating a start time, and outputting a fuel injection signal to the fuel injection means for the fuel injection time from the fuel injection start time.