JPS58172434A - Air-fuel ratio control device of internal-combustion engine - Google Patents

Abstract

PURPOSE:To have an always stable idling operation by such an arrangement that the feedback control of fuel injection is commenced, when activation of an O2 sensor is judged, at the time of starting with low cooling-water temperature and that the feedback control is commenced immediately after or a certain while after the starting at the time of tarting with a higher temperature. CONSTITUTION:If the engine is started in the condition that the cooling-water temperature sensed by a thermo-sensor 15 is below a preset reference valve (for ex., below 40 deg.), a control circuit 16 judges activation of an O2 sensor 1 from the change of the sensor 1 from lean to rich signal. When the activation of O2 sensor 1 is thus judged, a built-in integration circuit is started to make feedback control of a fuel injection valve 7 on the basis of output from the O2 sensor 1. When the engine is started in the condition, on the other hand, that the cooling- water temperature is above reference valve, signal is sent regardless of the condition of O2 sensor 1 after a certain while which is set by a timer circuit, to make feedback control of the fuel injection valve 7 in such a manner as mentioned above.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention measures residual oxygen i in exhaust gas using an oxygen sensor installed in the exhaust system of a vehicle internal combustion engine, and feedback controls the fuel injection amount according to the result. This invention relates to improvements in air-fuel ratio control III for internal combustion engines.

In recent years, with the tightening of exhaust gas regulations, various exhaust gas purification measures have been proposed, one of which is an exhaust gas purification method using a catalyst. This method uses the three components of exhaust gas, 11c.
, Go, and NOx are removed by oxidation or reduction using an oxidation catalyst and a reduction catalyst.In order to evenly and effectively remove the three components of the exhaust gas, the amount of residual oxygen in the exhaust gas must be kept within a certain range. In other words, the air-to-fuel weight ratio of the mixture sent to the internal combustion engine,
That is, it was necessary to maintain the air-fuel ratio (A/F) within a certain range.

One way to maintain this air-fuel ratio within a certain range is to use an oxygen sensor to detect residual ia* in the exhaust gas, and use the results to perform feedback control on the air-fuel ratio of the air-fuel mixture sent to the internal combustion engine. An air-fuel ratio control device for an engine has been proposed.

However, in the conventional air-fuel ratio control device for an internal combustion engine, the output voltage is low when the oxygen sensor is not activated at the time of startup, as shown by the solid line in Figure 1. When the output voltage gradually increases (referred to as a lean signal) and exceeds a preset comparison voltage level for the first time (the output signal in this state is referred to as a rich signal), it is determined that the oxygen sensor has been activated, and control is performed. Since the circuit is configured to start feedback control, if the internal combustion engine (hereinafter referred to as the engine) is stopped when it has reached a sufficiently high temperature, for example after driving at high speed, and then restarted, the fuel temperature will increase. The temperature is approximately the same as the concentration of the engine's cooling water, making it a relatively high temperature state.As shown above, in an area where the temperature is approximately 60°C or higher, vapor is likely to occur in the fuel pipes, and when vapor occurs, the gas Due to the depleted fuel, the required amount of fuel is not supplied, and the air-fuel ratio becomes lean, and the oxygen sensor outputs a lean signal, indicating that the fuel is lean.If the engine is left in idle operation in this state, Then, the output of the oxygen sensor remains as a lean signal as shown by the broken line in Figure 1, and as mentioned above, the oxygen sensor changes from a lean signal to a rich signal, resulting in 11!
In a system that starts feedback control by determining the activation of the fuel sensor, it is impossible to start feedback control forever, and the system continues to operate in a lean state, resulting in misfires and other problems. This has led to the problem that the idle speed becomes extremely unstable.

The present invention detects the cooling water temperature of the engine, and when the cooling water temperature is lower than a preset temperature, that is, when starting in a low temperature state, feedback control of fuel injection is started by determining the activation of the oxygen sensor. When starting at a temperature higher than a preset temperature, that is, at a high temperature, fuel injection feedback control is started immediately after the start or after a preset time has elapsed, regardless of the state of the oxygen sensor, thereby solving the problems of the conventional method. The purpose of this invention is to provide an air-fuel ratio control system for an internal combustion engine that eliminates this problem.

Embodiments of the present invention will be described below with reference to FIGS. 2 to 4.

First, in FIG. 2, 1 is an II elementary sensor, 2 is an exhaust manifold from which engine exhaust gas is output, 3 is an exhaust valve that is opened and closed by a cam (not shown) to control the outflow of exhaust gas, and 4 is a cylinder 5 that also contains the air-fuel mixture. 6 is a spark plug; 7 is a fuel injection valve that injects fuel; 8 is an intake manifold that branches from the surge tank 9 described later and guides intake air to each cylinder 5;
Reference numeral 9 denotes a surge tank that branches the intake air to each cylinder 5, and this surge tank 9 prevents the air flow from undulating by restricting the intake air into each cylinder 5 by the intake valve 4. It is intended to prevent and 10
11 is an air meter that detects the intake air amount of the engine by the displacement of the measuring plate 12; and 13 is an ignition coil that sends high voltage current for ignition to the spark plug 6. an igniter including 14 a piston; 15
16 is an air-fuel ratio control circuit, and 17 is a start switch.

Furthermore, when the main parts of the configuration of the air-fuel ratio control circuit 16 of this embodiment are shown in the block diagram of FIG.
The cooling water temperature signal is input to a comparison circuit 18 corresponding to comparison means, and if it is higher than a preset reference value, an output signal indicating - is sent to the AND gate 19, and an engine start command is issued by the start switch 17. The signal is input to the timer circuit 20, and after a preset period of time has elapsed, an output signal indicating the negative is sent to the AND gate 19, and the signal from the oxygen sensor 1 is sent to the discriminating circuit 21 corresponding to discriminating means. When the signal is input and the signal exceeds a preset value, it is determined that the oxygen sensor 1 has been activated. 22,
If any of these inputs an ON signal, the OR gate 22 is opened, and the 16
Feedback control of fuel injection is started by sending a signal.

Therefore, if the coolant temperature detected by the temperature sensor 15 is below a preset reference value, for example 40°C or below, and the engine is started in this state, the control circuit will not be closed by the solid line in Fig. 1, but as shown in the graph. Oxygen sensor 1 changes from lean signal to rich signal of oxygen sensor 1.
The integration circuit 23 is started to start the fuel injection feedback ill, and the cooling water temperature is above a preset reference value, for example 40°C or above, and in this state, the start switch is turned off. When the start signal from 17 is input, the timer circuit 20 starts as shown in FIG. Feedback control is started, and even if the 811 prefecture sensor 1 does not change from a lean signal to a rich signal in the ^^ state, it is possible to automatically perform feedback control of the air-fuel ratio.

In this embodiment, the timer circuit 20 is used to start the feedback control one hour after the start signal is input, but the feedback control is started immediately after the start signal is input manually. For example, if the cooling water temperature is within the range of 40°C to 70°C, a timer circuit is used to provide a delay of, for example, 10 seconds, and if it is over 70°C, feedback control is started at the same time as the start. Also good.

Further, in this embodiment, the device is constructed by combining circuits having various functions as shown in FIG. good.

As described in detail above, the air-fuel ratio control device for an internal combustion engine of the present invention includes a comparison means for comparing the output of a temperature sensor that detects the temperature of cooling water with a preset value, and a comparison means that compares the output of a temperature sensor that detects the temperature of cooling water, and A means for determining activation of the oxygen sensor is provided in the feedback control system, and when the internal combustion engine is started with the cooling water temperature below a preset value, the activation signal of the oxygen sensor determines the amount of fuel injection. When feedback control is started and the internal combustion engine is started with the cooling water concentration being higher than a preset value, the preset value is set at the same time as the internal combustion engine is started or after the internal combustion aim is started, regardless of the state of the oxygen sensor. The system is configured to start returning the fuel injection amount Ill11ml after the elapse of the specified time.

Therefore, according to the present invention, even if the engine is restarted in a high temperature state and left in an idling state, fuel injection return IIJIIl is started regardless of the state of the oxygen sensor, so the idling becomes unstable. Conventional problems such as these can be solved.

[Brief explanation of drawings]

Fig. 1 is a graph showing the characteristics of the output signal and feedback control output signal of a conventional oxygen sensor, Figs. 2 to 4 show embodiments of the present invention, and Fig. 2 is applied to the present invention. FIG. 3 is a block diagram showing the main parts of the control circuit, and FIG. 4 is a graph showing the characteristics of the output signal of the oxygen sensor and the feedback control output signal. 1...Oxygen sensor 7...Fuel injection amount valve 11...Air flow meter 15...Temperature sensor 16...Control circuit 17...Start switch 18...Comparison circuit 19...AND gate 20... Timer circuit 21... Discrimination circuit 22... OR gate agent Patent attorney Tsutomu Addition

Claims (1)

[Claims] 1. The temperature at which the temperature of the cooling water is detected in the air-fuel ratio wJ device of an internal combustion engine that measures the amount of residual oxygen in exhaust gas using an oxygen sensor and feedback-controls the amount of fuel intake according to the result. Comparing means for comparing the output of the sensor with a preset value and means for determining activation of the oxygen sensor based on the output of the oxygen sensor are provided, and the internal combustion engine is started when the cooling water temperature is below the preset value. When the internal combustion engine is started with the cooling water temperature exceeding a preset value, the activation signal of the oxygen sensor starts the return control of the fuel injection amount. Regardless of the state, the air-fuel ratio control Il for an internal combustion engine is characterized in that the feedback control of the fuel injection amount is started at the start of the internal combustion engine or after a preset time m has elapsed after the start of the internal combustion IIIwj. @place.