JPH0475381B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection control device for a fuel injection type engine.

[Prior art]

A fuel injection engine that uses an air flow meter to detect the intake air amount of the engine, and an engine rotation speed sensor to detect the engine rotation speed, and calculates the fuel injection amount from the intake air amount and engine rotation speed. In some cases, the amount of fuel injected during deceleration becomes too small compared to the required amount, resulting in an over-lean air-fuel ratio. That is,
During deceleration, when the throttle valve is fully closed, the air flow meter's compensation plate undershoots as the intake air amount rapidly decreases, causing the intake air amount detected by the air flow meter to be lower than the actual amount. I get used to it. If the detected intake air amount is small, the fuel injection amount will also be reduced. When the air-fuel ratio becomes over-lean due to such a transient phenomenon, torque fluctuations occur in the engine, and when this engine is installed in a vehicle, the vehicle body vibrates and the drivability of the vehicle deteriorates.

In order to eliminate such problems, conventionally a minimum fuel injection amount is set to regulate the lower limit value of the fuel injection amount, and the calculated fuel injection amount is prevented from becoming less than the set minimum fuel injection amount. However, the required minimum fuel injection amount changes depending on the engine speed, and in a relatively low speed range,
In order to reduce torque fluctuations, a relatively large minimum fuel injection amount is required, and in relatively high rotation ranges, torque fluctuations are not a problem, but harmful components in exhaust gas are. Requires small minimum fuel injection quantity. Therefore, a device has been proposed that changes the minimum fuel injection amount set in accordance with changes in engine speed. (Patent Application No. 56-152045) However, the air-fuel ratio becomes over lean due to transient phenomena during deceleration only at the moment when the throttle valve is closed. If you set the minimum fuel injection amount according to the engine speed and set the minimum fuel injection amount larger in the low rotation range than in the high rotation range, the engine speed may start to decelerate in the high rotation range and the engine speed will gradually decrease. Considering this, when deceleration starts in the high rotation range,
While the minimum fuel injection amount effectively fulfills the function of regulating the lower limit of the fuel injection amount, as the engine speed decreases and the set minimum fuel injection amount increases, the calculated fuel injection amount increases. Since the amount is not in the transition period of deceleration, it is calculated normally and the air-fuel ratio will not become over lean due to the fuel injection amount, but the minimum fuel injection amount is higher than the calculated fuel injection amount. becomes larger, causing the minimum fuel injection amount to inadvertently increase the fuel injection amount, which in turn may cause the air-fuel ratio to become overbalanced. If the air-fuel ratio becomes overbalanced during deceleration, harmful components in the exhaust gas will increase.

[Purpose of the invention]

In view of such conventional problems, an object of the present invention is to set the minimum fuel injection amount according to the engine speed, but to set the minimum fuel injection amount according to the engine speed when deceleration starts. By determining the minimum fuel injection amount and not changing it during deceleration, the minimum fuel injection amount may be inadvertently set to The purpose is to prevent the air-fuel ratio from becoming overbalanced by increasing the injection amount.

[Structure of the invention]

The configuration of the present invention for achieving this object will be explained with reference to FIG.

The intake air amount and engine speed of the engine are detected by an air flow meter and an engine speed sensor.

Also, the throttle switch detects that the throttle valve is in a fully closed state.

The minimum fuel injection amount calculation means calculates the minimum fuel injection amount preset for the engine speed at the time when the throttle switch detects that the throttle valve is fully closed. It is determined based on the engine rotation speed detected by the engine.

The fuel injection amount calculation means calculates the fuel injection amount from the intake air amount and engine rotation speed detected by the air flow meter and the engine rotation speed sensor, and the calculated fuel injection amount is determined by the minimum fuel injection amount setting means. If the amount of fuel injection is smaller than the minimum fuel injection amount set by Let be the final fuel injection amount.

The fuel injection means operates the fuel injection valve so that the amount of fuel calculated by the fuel injection amount calculation means is injected.

〔Effect of the invention〕

According to the present invention, the minimum fuel injection amount is set according to the engine speed at the time when the throttle valve is fully closed, so that overlean air-fuel ratio caused by a transient phenomenon at the start of deceleration can be avoided at that time. This can be effectively prevented according to the engine speed, and the minimum fuel injection amount does not change even if the engine speed subsequently decreases.
When the calculation of the fuel injection amount is normalized outside the transition period of the start of deceleration, the minimum fuel injection amount is
The fuel injection amount will not be larger than the calculated fuel injection amount, and it is possible to prevent the air-fuel ratio from becoming overbalanced during deceleration, and it is possible to suppress harmful components in exhaust gas.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic configuration diagram of one embodiment, and this engine is equipped with an air flow meter 2 provided downstream of an air cleaner (not shown), and the air flow meter 2 is rotated in a damping chamber. Compensation plate 2A freely installed
and a potentiometer 2B that detects the opening degree of the compensation plate 2A. Therefore, the amount of intake air is determined by potentiometer 2B.
It is detected as the voltage output from the Further, an intake temperature sensor 4 is provided near the air flow meter 2 to detect the temperature of intake air.

A throttle valve 6 is arranged downstream of the air flow meter 2, and the throttle valve 6 includes:
A throttle switch 18 is provided to detect the fully closed state of the throttle valve 6. Further, a surge tank 8 is provided downstream of the throttle valve 6. An intake manifold 10 is connected to the surge tank 8, and a fuel injection valve 12 is arranged to supply fuel into the intake manifold 10. The intake manifold 10 is connected to a combustion chamber 14A of the engine body 14, and the combustion chamber 14A of the engine is connected via an exhaust manifold 16 to a catalytic converter (not shown) filled with a three-way catalyst. Note that 20 is a spark plug, and 24 is a coolant temperature sensor that detects the engine coolant temperature.

The spark plug 20 of the engine body 14 is connected to a distributor 26, and the distributor 26 is connected to an igniter 28. The distributor 26 is provided with a cylinder discrimination sensor 30 and an engine rotation speed sensor 32, which are comprised of a pickup and a signal rotor fixed to the distributor shaft.
For example, the cylinder discrimination sensor 30 outputs a cylinder discrimination signal to the control circuit 34 at every 180 degrees of crank angle for a 4-cylinder engine, and every 120 degrees for a 6-cylinder engine, and outputs a cylinder discrimination signal to the control circuit 34.
2 outputs a crank angle signal to the control circuit 34, for example, every 30 degrees of crank angle.

The control circuit 34 is composed of a microcomputer, and as shown in FIG. ) 40 and the first input/output port 42
, a second input/output port 44, a first output port 46, and a second output port 48. port 44, first output port 46 and second output port 48
are connected by a bus 50.

The first input/output port 42 includes a buffer 52.
A, 52B, 52C, multiplexer 54, analog-to-digital (A/D) converter 56,
An air flow meter 2, a cooling water temperature sensor 24, and an intake air temperature sensor 4 are connected. The multiplexer 54 and A/D converter 56 are controlled by a signal output from the first input/output port 42, and the air flow meter 2, cooling water temperature sensor 24
The data detected by the intake temperature sensor 4 is sequentially converted into a digital signal and sent to the CPU 40 or
It is now imported into RAM36.

The second input/output port 44 includes a waveform shaping circuit 6
A cylinder discrimination sensor 30 and an engine rotation speed sensor 32 are connected through a buffer 58, and a throttle switch 18 is connected through a buffer 58. The first output port 46 is connected to the igniter 28 via a drive circuit 70, and the second output port 48 is connected to the fuel injection valve 12 via a drive circuit 72.

The ROM 38 of the control circuit 34 stores in advance a map of the basic ignition advance angle expressed by the engine speed and the intake air amount and the basic fuel injection amount.
The CPU 40 reads out the basic ignition advance angle and basic fuel injection amount based on the signal from the air flow meter 2 and the signal from the engine speed sensor 32, and also reads various signals including the signals from the cooling water temperature sensor 24 and the intake air temperature sensor 4. By the signal
Corrections are added to the basic ignition advance angle and basic fuel injection amount, and the igniter 28 and fuel injection valve 12
is controlled.

Such control of the ignition advance angle and fuel injection amount is achieved by executing a program stored in the ROM 38. Of this program, the characteristic τ calculation routine of the present invention is shown in FIG. This will be explained according to the flowchart.

This τ calculation routine is an interrupt processing routine that is executed every time a cylinder discrimination signal is generated from the cylinder discrimination sensor 30. When this routine is started, in step 11, the air flow meter 2 and the engine rotation speed sensor The intake air amount Q and engine speed N detected by 32 are taken in, and in step 112, the basic fuel injection time τp' is determined based on the taken in intake air amount Q and engine speed N.

In step 200, the minimum fuel injection amount τpMIN is determined by the method described later, and in step 113, it is determined whether the basic fuel injection time τp' determined in step 112 is smaller than the minimum fuel injection amount τpMIN determined in step 200. A judgment will be made. If the basic fuel injection time τp' is smaller than the minimum fuel injection amount τpMIN, the process proceeds to step 114, where the final basic fuel injection time τp is set as τpMIN,
If the basic fuel injection time τp' is larger than the minimum fuel injection amount τpMIN, the process proceeds to step 115 and the final basic fuel injection time τp is set as the basic fuel injection time τp'.

Next, in step 120, various corrections are applied to the finally determined basic fuel injection time τp to determine the actual injection time τ. In other words, the basic fuel injection time τp is multiplied by the correction coefficient Km determined by intake air temperature, cooling water temperature, etc., and the invalid injection time τv of the fuel injection valve is added to the multiplication result to obtain the actual injection time τ. It will be done. Then, in step 130, the actual injection time τ obtained in step 120 is output, and the fuel injection valve 12 is opened for this time to perform fuel injection.

FIG. 5 shows details of step 200 of FIG. First, in step 201, a signal from the throttle switch 18 is captured, and in step 202, it is determined whether the captured signal indicates that the throttle switch 18 is on. In other words, step
In steps 201 and 202, it is checked whether the throttle valve is fully closed.

When the throttle valve is fully closed and the throttle switch 18 is on, step 202 is executed.
Since the determination is affirmative, the process advances to step 204, where it is determined whether a flag F, which will be described later, is set. If flag F is not currently set, a negative determination will be made in step 204, so
Proceeding to step 205, the engine speed N is captured. Then, in the next step 206, a flag F is set to store that the throttle valve is fully closed and the engine speed N has been taken. Next, in step 207, the optimal minimum fuel injection amount τpmin is determined for the engine speed N taken in step 205 by a partial interpolation method using a map as shown in FIG.
seek. In step 208, the minimum fuel injection amount τpmin obtained in step 207 is set as τpMIN.

When the minimum fuel injection amount τpMIN is set in this way, even if the throttle valve remains fully closed, the throttle switch 18 is on, and step 202 is affirmed, flag F has already been set. Therefore, an affirmative determination is made in step 204, and the minimum fuel injection amount τpMIN is not set again.

After that, the throttle valve is opened and
When the throttle switch 18 is turned from on to off, a negative decision is made in step 202, so in step 203 flag F is reset and everything is returned to its initial state.

As a result of setting the minimum fuel injection amount τpMIN in this way, the transient decrease in fuel injection amount at the start of deceleration is regulated by the optimal minimum fuel injection amount τpMIN, but even if deceleration operation continues thereafter. Since the minimum fuel injection amount τpMIN is not reset, the minimum fuel injection amount τpMIN will not increase as the engine speed decreases. Therefore, the fuel injection amount after the transition period will depend on the intake air amount and engine This is determined by a calculation based on the rotational speed, and the problem of overbalancing the air-fuel ratio due to the fuel injection amount being regulated by an excessively large minimum fuel injection amount can be resolved, and an increase in harmful components in exhaust gas can be prevented. .

In the flowcharts of FIGS. 4 and 5, steps 201 to 208 correspond to the minimum fuel injection amount calculation means of the present invention, and steps 111 to 208 correspond to the minimum fuel injection amount calculation means of the present invention.
The process at step 115 corresponds to the fuel injection amount calculation means of the present invention, and the process at step 130 corresponds to the fuel injection control means of the present invention.

Although specific embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and includes various embodiments within the scope of the claims. For example, the minimum fuel injection amount preset for the engine rotation speed may be switched between a high rotation side and a low rotation side with a certain engine rotation speed as a boundary.

[Brief explanation of drawings]

FIG. 1 is a diagram corresponding to claims, FIG. 2 is a schematic configuration diagram of an embodiment of the present invention, FIG. 3 is a block diagram showing details of the control circuit in FIG. 2, and FIGS. 4 and 5. 3 is a flowchart showing the program contents of the microcomputer, and FIG. 6 is a diagram showing the minimum fuel injection amount set with respect to the engine rotation speed. 2... Air flow meter, 12... Fuel injection valve, 18... Throttle switch, 32... Engine rotation speed sensor, 34... Control circuit.

Claims (1)

[Claims] 1. An air flow meter that detects the intake air amount of the engine; an engine rotation speed sensor that detects the engine rotation speed; a throttle switch that detects that the throttle valve is in a fully closed state; When the fully closed state of the throttle valve is detected by the twinkle switch, the minimum fuel injection amount preset for the engine speed is changed to the engine speed detected by the engine speed sensor. A minimum fuel injection amount calculation means is used to calculate the fuel injection amount from the intake air amount and engine rotation speed detected by the air flow meter and the engine rotation speed sensor, and the obtained fuel injection amount is the minimum fuel injection amount. When it is smaller than the minimum fuel injection amount determined by the calculation means, the minimum fuel injection amount is used as the final fuel injection amount, and when the determined fuel injection amount is larger than the minimum fuel injection amount, the determined fuel injection amount is used as the final fuel injection amount. A fuel injection amount calculating means for determining the injection amount as a final fuel injection amount; and a fuel injection means for operating a fuel injection valve so that the amount of fuel calculated by the fuel injection amount calculating means is injected. A fuel injection control device for an engine, comprising: