JPS5838353A - System for controlling air-fuel ratio of internal- combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device for an internal combustion engine, and more specifically to a closed-loop control type air-fuel ratio control device. Hereinafter, the present invention will be described in detail based on the drawings.

In conventional air-fuel ratio control devices of this type, the stoichiometric air-fuel ratio (input = 1
) Detects the residual oxygen concentration in the exhaust gas using a three-way catalyst that efficiently purifies the three components of HC%CO and Hog in the nearby air-fuel ratio range.The supplied air-fuel ratio is determined based on the sensor's detection output. Feedback control was performed to keep the air-fuel ratio close to the same.

In the conventional device described above, when the supply air-fuel ratio is maintained near the stoichiometric air-fuel ratio by feedback control, if the vehicle starts without pressing the accelerator pedal, the engine is likely to stall. FIG. 1 shows the relationship between the engine rotation speed and the torque generated by the vehicle, and FIG. 2 shows the relationship between the supplied air-fuel ratio and the torque generated by the vehicle.

Located on the Tutsi side, input = around 0,9 (A/F = 12~1
3) is optimal. However, in the above diagram, the set idle speed is 800 rpm, and FIG. 2 shows the characteristics when the engine speed is so rpm.

Therefore, when the vehicle is started with the supplied air-fuel ratio controlled near the stoichiometric air-fuel ratio by the feedback control described above, and a load is applied to the engine, there is a drawback that the engine stalls easily because the idling sustaining force is small.

An object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that improves the starting performance of a vehicle.

The feature of the present invention is to detect the residual oxygen concentration in the exhaust gas, and calculate the amount of fuel supplied to each cylinder of the engine from the residual oxygen concentration, the amount of air taken into the throttle chamber, and the engine speed. An air-fuel ratio control device for an internal combustion engine that controls the fuel ratio to a stoichiometric air-fuel ratio, which includes means for detecting when the vehicle is started and means for detecting an idling state, and detects a detection output from the rain detecting means. The present invention is configured to correct the supplied air-fuel ratio to be richer than the stoichiometric air-fuel ratio when it is determined that the vehicle is starting and is in an idling state based on the following.

Embodiments of the present invention will be described below with reference to FIGS. 3 to 5. Figure 3 shows the overall configuration of the engine system, in which 1 is the engine, 2 is the air cleaner, 3 is the throttle chamber, 4 is the intake manifold that feeds air to each cylinder, and 6 is each cylinder. An exhaust manifold 16 introduces exhaust gas in the cylinder into an exhaust pipe 17, and 16 is a three-way catalyst. When the accelerator pedal (not shown) is operated, the opening t1' of the throttle valve 5 provided in the throttle chamber 3 is controlled, thereby controlling the amount of air supplied from the air cleaner 2 to each cylinder of the engine 1. be done.

The throttle valve 5 has a throttle sensor that detects whether the throttle valve 5 is fully closed or not, that is, whether the engine is in an idling state. It is measured by an air flow meter 7 provided upstream of the throttle valve 5, and its detection signal is input to the control circuit 14.

Furthermore, there is an O! near the outlet of the exhaust manifold 6 that detects the residual oxygen concentration in the exhaust gas. The control circuit 14 calculates the fuel injection amount so that the air-fuel ratio supplied to each cylinder becomes the stoichiometric air-fuel ratio based on the detection signal of the sensor 8 and the air amount detection signal, A control signal is output for injecting fuel at a predetermined timing and for a predetermined period of time to an injector 18 provided near the inlet of a cylinder of the engine 1. t 12 is an ignition circuit that sends an ignition signal to the ignition plug provided in each cylinder via the distributor 11, and an ignition coil next signal 13 is inputted from the ignition circuit 12 to the control circuit 14. Ru. This ignition coil next signal is processed by the control circuit 14 as an engine speed signal and is used as basic information in various engine controls including air-fuel ratio control.

Furthermore, 9 is a water temperature sensor that detects the engine cooling water temperature, and 10
is an intake temperature sensor that detects the temperature of intake air, and these detection outputs are also taken into the control circuit 14 and used for various engine controls.

Note that the fuel supply system is not the main point of the present invention, so a description thereof will be omitted.

Next, FIG. 4 shows a specific configuration of the control circuit 14, in which numeral 30 is a division circuit;
0 takes in the ignition-following signal 13 and outputs a pulse signal with a predetermined frequency division ratio to the basic injection amount calculation circuit 40.

The basic injection amount calculation circuit 40 outputs a basic injection pulse Tp having a pulse width based on the air amount detection signal from the air flow meter 7 to the injection amount correction circuit 50 via the diode 25 at the timing of the pulse signal of the frequency dividing circuit 30. With,
It is output to the interrupt control section 52 in the microcomputer '30. The injection amount correction circuit 50 takes in the detection outputs of the water temperature sensor 9 and the intake temperature sensor 10 and the air-fuel ratio correction signal 29 output from the microcomputer 60, and changes the pulse width of the basic injection pulse Tp based on these signals.
The injector drive pulse T1 is outputted to the output transistor 240 via the output transistor 23.

A current regulating resistor 22 and a parallel circuit of a solenoid 20m for controlling the injection valve of the injector 20 provided in each cylinder are connected in series between the collector of the output transistor 24 and the battery VB. Every time the injector drive pulse T1 is applied to the output transistor 24, an exciting current flows through the solenoid 18 of each injector 20, resulting in the valve opening time of the injector 20 (corresponding to the pulse width of the pulse T1), in other words, fuel injection. Amount controlled.

The basic injection pulse cut signal 27 is input to the injection amount correction circuit 30.
A fuel cut is performed. Furthermore, the or gate 23
An injection amount increase pulse 28 for increasing the fuel injection amount asynchronously with the injector drive pulse T1 is input under specific operating conditions of the engine (for example, during acceleration, idling, etc.).

Both the basic injection pulse cut signal 27 and the injection amount increase pulse 28 are output from the digital output port 56 within the microcomputer 60.

Next, the configuration of the microcomputer 60 will be explained. 42 is a central processing unit (CPU) that performs digital calculation processing related to air-fuel ratio control;
44 is a readable and writable memory element (RAM)
Furthermore, a round storage element (R
OM). Further, 48 is a timer, which measures the activation cycle of the interrupt processing program. 52 accepts various interrupts, outputs an interrupt signal to the CPU 42 via the pass line 70, takes in the basic injection pulse Tp, and monitors the rising and falling points of the basic injection pulse. ing. 54 is a digital input port that receives detection outputs from various sensors that output digital signals;
This digital input board 54 includes a 0° sensor 8 for detecting the residual oxygen concentration in the exhaust gas, and a throttle sensor 15 for detecting the open/closed state of the throttle valve 5. Starter switch 18 that detects the starting state of the engine. Detection outputs from a clutch switch 19 that detects a clutch depression state and a shift switch 33 that detects a transmission switching state are input. In this embodiment, the detection outputs of the clutch switch 19 and the shift switch 33 are used to determine when the vehicle is started.

Furthermore, there is an air flow meter 7 which outputs an analog signal to the 56ij A/D converter.
and the detection output of the water temperature sensor 9 are input and converted into digital signals. Reference numeral 58 denotes a digital output port for outputting a digital control signal, and the basic injection pulse 27 and the injection amount increasing pulse 28 are outputted from the digital output port 58 as described above. Further, 62 is a D/mu converter that outputs an analog control signal, and the D/mu converter 2 outputs the air-fuel ratio correction signal 29 described above.

In this way, the input/output ink face 80 composed of the digital input port 54, the digital output port 58, the mu/D converter 56, and the D/mu converter 2 takes in the detection outputs of various sensors and transfers them to the pass line 70.
The control signal is sent to the cPt 742 via the CPU 42, and after arithmetic processing is performed by the CPU 42 based on the control program stored in the ROM 46, the control signal is output from the digital output port 58 and the D/A converter 62 to the outside.

Next, FIG. 5 shows the processing contents of the air-fuel ratio control device according to the present invention. In the figure, when the air-fuel ratio control program is started in step 100, it is determined in the next step 102 whether or not the vehicle is starting, that is, whether the clutch switch 19 and shift switch 33 are both in the ON state. It will be judged. If it is determined in step 102 that the vehicle is not starting, the process moves to step 104, where air-fuel ratio feedback control is performed based on the detection output of the O-snow sensor.

Note that the air-fuel ratio feedback control itself is not the gist of the present invention, so a description thereof will be omitted. After air-fuel ratio feedback control is performed in step 104, the execution of the air-fuel ratio control program ends in step 106.

On the other hand, if it is determined in step 102 that the vehicle is starting, the process moves to step 108;
Then, it is determined whether the engine is in an idling operating state. If it is determined in step 10g that the engine is not in an idling state, the process moves to step 104, and the same process as described above is performed. If it is determined in step t & step 10g that the engine is in an idling operating state, then in step 110 the fuel injection amount is increased. That is, in addition to the injector drive pulse T1, the injection amount increase pulse 28 is output from the digital output port 58 through the OR gate 231- to the base of the output transistor 24, and as a result, the injection amount increase pulse 26 is outputted from the digital output port 58 to the base of the output transistor 24. The pulse width of the fuel injection amount pulse 28 is controlled to be so@r1c of the pulse width of the basic injection pulse.

As explained above, the present invention is configured to correct the air-fuel ratio supplied to each cylinder to be richer than the stoichiometric air-fuel ratio when the vehicle starts and is in an idling state. The starting performance of the vehicle can be improved.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relationship between engine speed and vehicle generated torque, Figure 2 is a characteristic diagram showing the relationship between supplied air-fuel ratio and vehicle generated torque, and Figure 3 is an overall configuration diagram of the engine system. , FIG. 4 is a block diagram showing the specific configuration of the control circuit 14, and FIG. 5 is a flowchart showing the processing contents of the air-fuel ratio control program. 1...Engine, 5...Throttle valve, 8...0. Sensor, 14... Control circuit, 19... Clutch switch, 20... Injector, 33... Shift switch, 40... Basic injection amount calculation circuit, 50... Injection amount correction circuit, 60. ...Microcomputer, 80...Input/output interface. Figure 1 Figure 2 Figure 3 Figure 4 Vs Figure 5 +06

Claims (1)

[Claims] (1) The residual oxygen concentration in the exhaust gas is detected, and the air-fuel ratio in each cylinder is calculated based on the residual oxygen concentration, the amount of air taken into the throttle chamber, and the engine speed. An air-fuel ratio control device for an internal combustion engine that controls the air-fuel ratio to a stoichiometric air-fuel ratio, comprising means for detecting when the vehicle is started and means for detecting an idling state, and based on the detection output from the rain detection means. 1. An air-fuel ratio control device for an internal combustion engine, which corrects the supplied air-fuel ratio to be higher than the stoichiometric air-fuel ratio when it is determined that the vehicle is starting and is in an idling state.