JPS58176461A - Air-fuel ratio controlling apparatus for internal- combustion engine - Google Patents

Abstract

PURPOSE:To enable to improve startability of an engine in re-starting the engine when its temperature is high, by providing a means for operating a pneumatic control valve on the basis of both of a cranking signal and an output signal of an oxygen sensor. CONSTITUTION:In starting an engine, it is cranked by closing an ignition switch 30 and a starter switch. Since the temperature of an oxygen sensor 18 is higher than its operation temperature when the engine temperature is high, the output of a comparison circuit 40 is made H and a regulator switch 50 is also closed with starting of a starter. Further, an H-output of an AND-circuit 54 is applied to an electromagnetic pneumatic valve 34 via a transistor 56, a changeover switch 44 and a driving circuit 46 and opens the pneumatic valve 34 a prescribed angle to prevent excessive enriching of mixture, thus improving startability of the engine. On the other hand, when the engine temperature is low, the output of the comparison circuit 40 is made L and the switch 50 is turned OFF when the starter is stopped after starting of the engine. Resultantly, the AND-circuit 54 is turned OFF and an integration circuit 42 is connected to a driving circuit 46 for executing ordinary feedback control of the air-fuel ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device for an internal combustion engine equipped with a carburetor. An electromagnetic air control valve is installed, and a control circuit is provided to control the opening and opening of the electromagnetic air control valve based on a signal from an oxygen sensor installed in the exhaust system of the engine, thereby feedback controlling the air-fuel ratio of the intake mixture. The present invention relates to improvements in air-fuel ratio control devices for internal combustion engines.

In the above-mentioned type of conventional air-fuel ratio control device, when the engine is restarted, feedback control is performed in an open loop, and the electromagnetic air control valve is forcibly closed. By the way, if you stop the engine after driving the vehicle under conditions of high outside temperature, such as during the summer, the temperature inside the engine room will rise and the carburetor will heat up, causing damage to the float chamber of the carburetor, fuel supply passage, etc. fuel vapor is generated. Therefore, the liquid fuel in the shift float chamber and the fuel supply passage oozes into the air horn of the carburetor due to the pressure of the fuel vapor, and the intake air-fuel mixture becomes excessively rich when the engine is restarted. However, as mentioned above in conventional air-fuel ratio control devices, the electromagnetic air control valve is closed when the engine is restarted, so the intake air-fuel mixture is
Since the highly concentrated gas is sent to the first combustion chamber without being diluted by the 4' air, restartability of the engine deteriorates.

The present invention has been devised in view of the problem of ramping up in the prior art, and improves restartability of the engine in high temperature conditions by adding a simple means to the conventional air-fuel ratio control device of the above type. The purpose is to

For this reason, the present invention provides an air-fuel ratio control device of the above type with a means for opening the electromagnetic air control valve based on both the cranking signal of the engine at the time of restart and the signal from the oxygen sensor. The present invention is characterized in that bypass air is added to the intake air-fuel mixture to dilute the rich air-fuel mixture when the engine is restarted in a high temperature state. Since the oxygen sensor has a characteristic that it can output a signal of the rated voltage only when heated to a predetermined temperature, the oxygen sensor outputs a signal when the engine is in a high temperature state when the engine is restarted.

On the other hand, if some time has passed after the engine has stopped and the engine has cooled down enough to dissipate heat and the fuel vapor in the fuel supply passage and float chamber has condensed again, the oxygen sensor itself will drop below its operating temperature. No signal is output because it is being cooled.

Therefore, according to the present invention, if the electromagnetic air control valve can be opened at the time of restart based on both the oxygen sensor signal and the cranking signal, the intake air-fuel mixture is supplied with bypass air only when the engine is in a high temperature state. Can be diluted. When the engine is restarted when it is sufficiently cooled, the oxygen sensor signal is not output, so bypass air is not introduced, and the intake mixture is diluted unnecessarily, resulting in poor restart performance. does not get worse.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram illustrating the outline of a conventional air-fuel ratio control device to which the present invention is applied, in which air taken in from an air cleaner 10 passes through a carburetor 12 and becomes an intake air-fuel mixture at a throttle valve 1 and 4. After the flow rate is controlled by
Enter 6. The combustion exhaust gas is discharged through an exhaust pipe 20 to which an oxygen sensor 18 is attached. A bypass passage 22 is provided to bypass the carburetor, and an electromagnetic air control valve 24 is provided in this bypass passage.
I am able to control my inner airflow of envy.

A control circuit 26 is connected between the oxygen sensor 18 and the solenoid of the air control valve 24, and the air control valve 24 is controlled to open or open based on the output signal from the oxygen sensor 18, as is well known. It has become.

Figure 2 is a graph explaining the output characteristics of oxygen sensors used today.
Unless it is heated to the order of degrees Celsius, it cannot output a voltage higher than the standard voltage vr.

FIG. 3 is a block diagram of the air-fuel ratio control device of the present invention.
32 is an ignition switch, 32 is a battery, 34 is a solenoid for the electromagnetic air control valve 24, and 36 is a control circuit. Oxygen sensor 18 with resistor 38 connected in series
is connected to a comparator circuit 4o), and as is well known, this comparator circuit 40 sets the output voltage from the oxygen sensor to a standard voltage 71.
When above, it outputs the signal "l#", and when it is below, it outputs a signal.
The comparator circuit 40 outputs a signal of t O''.
This integrating circuit integrates the output signal of the comparator circuit 4o and outputs a control signal indicating whether the intake air-fuel mixture is rich or lean. tell. The drive circuit 46 amplifies the control signal to control the air control valve solenoid 34. An output section of an open loop circuit 48 is connected to the integrating circuit 42 . The input section of the open loop circuit 48 receives signals A, . is entered. This open loop circuit has a function of making the integrating circuit 42 open roots based on the various signals mentioned above.

A switch 5o is provided at the L terminal of the engine's alternator regulator (not shown). When power is applied to the starter for starting and cranking the engine, the second regulator terminal is closed. Therefore, the switch 5o A cranking signal representing the cranking state of the engine can be output.

The switch 50 is connected to the open loop circuit 48 via an inverter 52 and to one input of an AND circuit 54 . The signal from the comparator circuit 40 is input to the other input section of the AND circuit 54. The output of the AND circuit 54 is connected to a Darlington connected transistor 56.

The output part of the M circuit 54 is also connected to the changeover switch 44, and when this AND circuit outputs a signal, it connects the emitter of the transistor 56 and the drive circuit 46, and when there is no signal, it connects the integrator circuit 42 and the drive circuit. 46 can be alternatively connected.

Next, the operation of this embodiment will be described. To start the engine, the ignition switch 30 is closed and a starter switch (not shown) is closed to start the starter and crank the engine.

Since the oxygen sensor 18 is maintained at a temperature above its operating temperature when the engine is at a high temperature, the comparator circuit 40 outputs a signal of 1'' to one input of the AND circuit 54. With the activation of the regirator, the switch 50 of the regirator is closed, and a signal is sent to the other input section of the AND circuit 54.

Therefore, the AND circuit 54 operates and outputs a signal.

This signal is amplified by transistor 56 and sent to changeover switch 44. This signal is also transmitted to the selector switch 44.
is switched upward to connect transistor 56 to drive circuit 46. Therefore, the signal output from the AND circuit and amplified by the transistor 56 flows to the drive circuit 46, and opens the electromagnetic air control valve 34 by a predetermined opening degree. As a result, the intake air-fuel mixture supplied to the combustion chamber is diluted by the air from the gas passage 22, so the air-fuel mixture does not become too rich even when the engine is at high temperature. is reliably ignited and the engine is easily restarted.

In contrast to the above, when the engine is being cooled by heat radiation, the oxygen sensor 18 does not output a signal, so bypass air is not supplied during cranking. Therefore, the intake air-fuel mixture is not diluted unnecessarily when the engine is cold. Further, after the engine is started, the starter is stopped, so the switch 50 is cut off, and the output signal of the AND circuit 54 disappears, so the changeover switch 44 is rotated downward.
Integrating circuit 42 is connected to drive circuit 46 . the result,
The control circuit 14 can perform feedback control of the air-fuel ratio as in the prior art.

As described above, since the air-fuel ratio control device of the present invention is provided with a means for operating the air control valve based on both the cranking signal and the signal from the oxygen sensor, the air-fuel ratio control device of the present invention is provided with means for operating the air control valve based on both the cranking signal and the signal from the oxygen sensor. This has the effect of significantly improving the startability of the engine.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a conventional air-fuel ratio control device, FIG. 2 is a graph showing output characteristics of an oxygen sensor, and FIG. 3 is a block diagram of an embodiment of the present invention. 12... vaporizer, 18... is sensor, 22...
9. Pass passage, 24.--Solenoid air control valve, 34.
... Solenoid of electromagnetic air control valve, 40 ... Comparison circuit, 42 ... Integral circuit, 44 ... Selector switch, 4
6... Drive circuit, 50... Regulator switch, 54... AND circuit, 56... Transistor. (9) Patent applicant Toyota Motor Corporation Patent agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney Kyosuke Tsuchinakayama Patent attorney Akira Yamaguchi (10)

Claims (1)

[Claims] A bypass passage that bypasses the carburetor is provided in the intake system of the internal combustion engine, and an electromagnetic air control valve is installed in the 24797 passage, and the electromagnetic air control valve is operated based on a signal from an oxygen sensor provided in the exhaust system of the engine. In an air-fuel ratio control device that is equipped with a control circuit that controls the opening and opening of a valve to feedback control the air-fuel ratio of the intake air-fuel mixture, the cranking signal of the engine and the oxygen sensor are used when the engine is restarted after stopping. An air-fuel ratio control device for an internal combustion engine, characterized in that the air-fuel ratio control device for an internal combustion engine is provided with means for opening the electromagnetic air control valve at the time of restarting the engine in a high temperature state based on both the signal and the signal.