JPS5836184B2 - Kuunen Pisei Gyo Souchinokeihou Cairo - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an abnormality warning circuit for an air-fuel ratio control device for an engine.

Recently, as a method for reducing harmful exhaust gases from automobiles, a feedback type air-fuel ratio control device has been provided that controls the air-fuel ratio based on information regarding engine exhaust gas components.

For example, as shown in FIG.
, 02, etc.) is detected by the exhaust sensor 3 provided in the exhaust pipe 2, and the control circuit 4 generates a control signal ((
For example, a proportional signal that is proportional to the deviation, an integral signal that integrates the deviation, or a signal that adds both signals, etc.) is generated, and the fuel metering device 5 (carburizer, fuel injection device, etc.) is controlled based on the control signal. By additionally controlling the fuel supply amount and air supply amount (the fuel metering device is naturally also controlled by other factors such as the driver operating the throttle valve), the mixture supplied to the engine 1 The air-fuel ratio is maintained at a set air-fuel ratio.

If this set air-fuel ratio is set, for example, to the optimum operating point of the exhaust purification device 6 (catalyst device, reactor device, etc.) (if a three-way catalyst is used as the exhaust purification device, the set air-fuel ratio is set to the stoichiometric air-fuel ratio). ), it is possible to efficiently reduce harmful substances in exhaust gas under various operating conditions.

If an abnormality occurs in the air-fuel ratio control device as described above,
Normal control may not be performed and the air-fuel mixture may become too rich or too lean.

When the air-fuel mixture becomes lean, engine drivability and stability deteriorate. Further, if the air-fuel mixture becomes too rich, problems such as an increase in harmful components in the exhaust gas occur, so it is necessary to promptly detect abnormalities in the air-fuel ratio control device and take appropriate measures.

An abnormality alarm circuit of a conventional air-fuel ratio control device has a configuration as shown in a portion 7 surrounded by a broken line in FIG.

That is, the abnormality detection circuit 8 detects an abnormality (
(often caused by an abnormality in the exhaust sensor or control circuit), and activates the alarm device 10 (lamp, buzzer, etc.) via the drive circuit 9 to warn of the occurrence of the abnormality.

However, when the engine temperature is low (such as immediately after starting), the output of the exhaust sensor 3 does not show a normal value, so in order to prevent this state from being mistakenly judged as an abnormality, a temperature sensor that detects the engine temperature (cooling water temperature, etc.) 11 and a gate circuit 12, the alarm circuit is configured to operate only when the engine temperature is above a predetermined value.

However, with the conventional abnormality alarm circuit as described above, the abnormality alarm circuit does not operate from the time the engine starts until the temperature reaches a predetermined value. The warning device will not operate for a while after the vehicle restarts after stopping the vehicle, that is, until the engine temperature reaches a predetermined value.

Therefore, even if a warning has been issued while driving, when the driver starts driving again, the warning will not be issued for a while, so there is a risk that some drivers may misunderstand that the abnormality has been fixed, and there may be a blank period in the operation of the abnormality warning device. This is very inconvenient.

The present invention has been made in view of the above points, and it is possible to determine the state of the abnormality alarm circuit immediately before the engine stops for a predetermined period of time from the next engine restart (the time until the engine temperature rises and the exhaust sensor output returns to normal). ) The purpose of the present invention is to provide an abnormality warning circuit that can issue a warning immediately when starting a new run if a warning was issued during the previous run by storing the information in the same state during the previous run. shall be.

The present invention will be explained in detail below based on the drawings.

FIG. 2 is a circuit diagram of an embodiment of the present invention, in which 13 is an abnormality detection circuit, 14 is a memory circuit, and 15 is a drive circuit.

The input terminal 16 of the abnormality detection circuit 13 is connected to the output of the exhaust sensor 3 shown in FIG. good) is given.

When the air-fuel ratio propellant system is normal, the output of the exhaust sensor 3 and the output of the control circuit 4 fluctuate up and down around the set value, but when an abnormality occurs, they maintain a constant value.

In other words, when an abnormality occurs in the exhaust sensor, the output of the exhaust sensor may become a constant value close to zero, which is impossible under normal conditions, regardless of the air-fuel ratio, and the output of the control circuit may stick to the upper or lower limit value. Alternatively, a device with a fail-safe function fixes the output to an appropriate constant value when an abnormality occurs.

Therefore, the input signal at the input terminal 16 is transferred to the capacitor C
diode D through a differentiator circuit consisting of 1 and resistor R1.
1 for half-wave rectification and charging the capacitor C2, the voltage of the capacitor C2 will be at a high level during normal operation and at a low level at abnormal time (as it is discharged through resistor R2, it will be at a low level when there is no input). Abnormalities can be detected.

When the voltage of capacitor C2 is at a high level, transistor Q is turned on, transistor Q2 is turned off, and transistor Q3 is turned on.

Therefore, the base of the transistor Q5 of the drive circuit is at a low level, and the transistor Q is off, so the alarm lamp LP1 does not light up.

When the voltage of capacitor C2 is at a low level, contrary to the above, transistor Q is turned off, transistor Q2 is turned on,
Since the transistor Q3 is turned off and the transistor Q is turned on, the alarm lamp LP4 lights up and issues an alarm.

Next, the switch S1 of the memory circuit 14 is a switch that is interlocked with the ignition switch of the engine (turns on when the ignition switch is on), and M is a storage element such as a memory ode, for example.

A switch S is connected to the charging terminal P1 of this memory ode M1.
The collector voltage of the transistor Q2 of the abnormality detection circuit 13 is applied through the transistor Q2 and the resistor R3.

Since the switch S1 is turned off in conjunction with the ignition switch when the engine is stopped, the memory ode M,
stores the collector voltage of transistor Q2 immediately before the engine stops.

An operational amplifier OP is connected to the detection terminal P2 of the memory node M1.
A voltage buffer circuit using 1 is connected.

Since the input impedance of this voltage buffer circuit is extremely high, almost no current flows, so that the memory ode M1 can retain its stored value for a long period of time (about one month).

When the air-fuel ratio control device is normal, transistor Q2 is off, so its collector voltage is at a high level, and a high-level signal is stored in memory node M1.

Therefore, the detection terminal P2 of the memory node M1 also goes to a high level, and the output of the operational amplifier OP also goes to a high level, so the transistor Q4 is turned on and the base potential of the transistor Q5 is kept at a low level.

When the engine is stopped in this state, the switch S1 is turned off and the memory node M1 remains at a high level.

Next, when the engine is restarted, the output of the exhaust sensor is abnormal until the engine temperature reaches a predetermined value, so the voltage of the capacitor C2 of the abnormality detection circuit 13 becomes a low level, and the transistor Q2 is turned on.

At this time, switch S1 is also on, so the charge in memory node M1 is gradually discharged via switch S1, resistor R3, and transistor Q2, but transistor Q4 is kept on during this discharge time. .

Therefore, during the period between restarting the engine and the above discharge (
(while the engine is at low temperature), the warning lamp LP1 does not light up even if the output of the exhaust sensor is abnormal.

If the input signal is abnormal even after the above discharge time has ended (when the air-fuel ratio control device is abnormal), the charge in memory node M1 is discharged, transistor Q4 is turned off, and transistor Q5 is turned on, causing noisy sound. The warning lamp LP1 lights up.

Next, before the engine stops, an abnormality occurs and the warning lamp LP1
If it is lit, as mentioned above, transistor Q2
is turned on, and the charge in memory node M1 is being discharged.

When the engine is stopped in this state, the memory node M remains at a low level.

When the engine is restarted, the output of memory node M1 is at a low level, so transistor Q4 is turned off.

At this time, the transistor Q1 is off, the transistor Q2 is on, and the transistor Q3 is off, so the transistor Q is turned on and the alarm lamp LP1 is immediately lit.

In other words, if the circuit in Figure 2 was normal before the engine was stopped, it will stop the alarm device from operating for a predetermined period of time after the engine is restarted (while the engine is at a low temperature), and if the circuit is abnormal before the engine is stopped, If there is, the alarm system will be activated to issue an alarm immediately after the engine is restarted.

In addition, after the air-fuel ratio control circuit becomes abnormal. If the system returns to normal for some reason, the warning lamp LP1 will immediately turn off.

As described above, according to the present invention, if a warning has been issued before the engine is stopped, the warning is issued immediately upon restart, so that the occurrence of an abnormality can be immediately confirmed.

Therefore, it will no longer be mistaken as normal even though it is abnormal.
This facilitates prompt maintenance of abnormal vehicles and helps improve safety and exhaust purification performance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of an abnormality alarm circuit of a conventional air-fuel ratio control device, and FIG. 2 is a circuit diagram of an embodiment of the present invention. Explanation of symbols, 1...Engine, 2...
Exhaust pipe, 3... Exhaust sensor, 4... Control circuit, 5... Fuel metering device, 6...
Exhaust purification device, 13.゜bending abnormality detection circuit, 14...
...Memory circuit, 15...Drive circuit, 16...
...Input terminal, M1...Memory ode, L
P... Warning lamp.

Claims (1)

[Claims] 1 Equipped with an exhaust sensor that detects the concentration of exhaust gas components of the engine, and a control circuit that outputs a control signal corresponding to the deviation between the output of the exhaust sensor and a set value, and controls a fuel metering device based on the control signal. In the air-fuel ratio control device to be controlled, an abnormality detection circuit that detects an abnormality in the output of the exhaust sensor or the signal of the control circuit, a drive circuit that activates an alarm device in response to the signal of the abnormality detection circuit, and a control circuit that detects an abnormality in the output of the exhaust sensor or the signal of the control circuit; and a memory circuit that stores the signal of the abnormality detection circuit and holds the input of the drive circuit at the stored signal for a predetermined period of time after restarting the engine. circuit.