JPS59101571A - Exhaust-gas purification controller for engine - Google Patents

Abstract

PURPOSE:To secure the high traveling performance and economical fuel consumption by reducing the amount of the exhaust gas which returns into an intake system in comparison with that for the normal case, when an air-fuel ratio can not be feedback-controlled to the vicinity of the aimed air-fuel ratio. CONSTITUTION:An O2 sensor 2 as fuel-ratio sensor, exhaust-gas purifier 13 are installed into an exhaust passage 11, and an EGR valve 4 for varying passage area is installed into a recirculation passage 12 which communicates to an intake passage 10 and the exhaust passage 11. The trouble detection circuit 1c of a control unit 1 detects the state where feedback control for air-fuel ratio is impossible. That is, the detection circuit 1c detects a trouble by processing the output signal A of the O2 sensor 2 and outputs each signal I into an air-fuel ratio control circuit 1a, EGR amount control circuit 1b, and an EGR amount correction circuit 1e. By receiving the signal I, the EGR amount control circuit 1b suspends the operation, and the EGR amount correction circuit 1e cuts the exhaust gas which returns, and therefore, electric induction between an atmosphere-side solenoid 5a and a negative-pressure side solenoid 5b is suspended.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides feedback control of the air-fuel ratio of the air-fuel mixture of an engine to near the target value, and control for returning part of exhaust gas to the intake system. The present invention relates to an exhaust gas purification control device for an engine, which is equipped with a correction device that operates when the purification is not possible.

Conventionally, an air-fuel ratio sensor that detects the air-fuel ratio of the air-fuel mixture in the engine has been used to feedback control the air-fuel ratio to near a target value, and an engine sensor that controls the amount of exhaust gas recirculated to the intake system depending on the engine operating state. Exhaust gas purification control systems are known.

Generally, when performing the above air-fuel ratio control, the control signal depends on the detection number 16 of the air-fuel ratio sensor. Therefore, if the detection signal is not normal, it becomes difficult to adjust the fuel flow rate (air-fuel ratio) necessary for normal operation of the engine. ◇What to do when feedback control of the air-fuel ratio becomes impossible For example, in order to prevent instability in engine operation, a system is known in which feedback control based on a detection signal from an air-fuel ratio sensor is interrupted and open-loop control is performed (Japanese Patent Publication No. 54-25973).

However, even if the feedback control based on the air-fuel ratio detection fl is interrupted and oven loop control is performed, the air-fuel ratio does not reach the target air-fuel ratio, and the air-fuel ratio is leaner or leaner than the target air-fuel ratio. Be on the rich side. For this reason, if it is on the lean side, the combustibility will be poor and the engine operation will become unstable, and if it is on the rich side, fuel efficiency will tend to deteriorate.Especially, the intake system For vehicles equipped with an exhaust gas recirculation device that recirculates exhaust gas, the air-fuel ratio is preset to the lean side, assuming that normal air-fuel ratio control is being performed. Since the exhaust gas is recirculated, the supply of inert exhaust gas may worsen the bisque firing properties and make it impossible to drive.
If the exhaust gas is recirculated at around 7, where the air-fuel ratio is on the rich side, the fuel consumption will be significantly reduced.

Therefore, the present invention has been made in view of this.

If the air-fuel ratio cannot be feedback-controlled to near the target air-fuel ratio, it is possible to reduce the amount of exhaust gas that recirculates to the intake system compared to normal conditions.Engine exhaust gas that can ensure driving performance and fuel efficiency An object of the present invention is to provide a cleaning control device.

Embodiments of the present invention will be described below based on the drawings. FIG. 1.2 is a configuration diagram of an embodiment in which the fuel is controlled to be near the stoichiometric air-fuel ratio by a carburetor, and the amount of exhaust gas recirculated to the intake passage is controlled depending on the operating state.

In FIG. 1, an intake passage 10 of a gasoline engine 9 is provided with a carburetor 3 that adjusts fuel using an air-fuel ratio control solenoid valve (not shown).

The exhaust passage 11 includes an 02 sensor 2 as an air-fuel ratio sensor for detecting the oxygen concentration in the exhaust gas and an exhaust gas purification device (
A catalyst) 13 is provided. The recirculation passage 12 connects the intake passage 10 and the exhaust passage 11.
EGR pulp 4 that changes the passage area of 2 is provided. The EGR pulp 4 is composed of a valve 4b that changes the area of the recirculation passage 120, an EGR valve opening sensor 4a that detects the lift amount of the valve 4b, and an EGR valve negative pressure chamber 4c that operates the valve 4b. An EGR valve 5 for controlling the negative pressure in the EGR valve negative pressure chamber 4C is provided near the EGR pulp 4. In addition, as sensors for detecting the operating state of the gasoline engine 9, a cooling water temperature sensor 6, an engine rotation speed sensor 7, and a negative pressure sensor 8 are provided. The control circuit consists of a 13% EGR amount control circuit 1b, a failure detection circuit IC, a memory circuit 1d, and an EGRt correction circuit 1e.The failure detection circuit IC is a system for detecting a state in which air-fuel ratio feedbank control is disabled.
j11 failure detection device, which processes the output signal A of the 02 sensor 2 to detect a failure, and detects the air-fuel ratio control circuit 18% EGR1Th control circuit 1b and the EG
No. 2 is output to the Rjit correction circuit 1e. Above air fuel ratio? The ti control circuit 1a receives the signal A from the 02 sensor 2 and the signal I from the failure detection circuit 1C, and outputs a control signal B to the air-fuel ratio control solenoid valve that adjusts the fuel to be supplied. The EGR amount control circuit 1b is the failure detection circuit IC.

Cooling water mud sensor 6, rotation sensor 7, negative pressure sensor 8, EG
1 of each of the R valve deflection sensor 4a and the memory circuit 1d.
No. 1 1. Control signals G and H are output to the above EGR solenoid valve 5 so that the amount of exhaust gas that is recirculated in response to the EGR solenoid valves 5 and 5 is adjusted to be appropriate.

The storage circuit 1d stores the target lift amount of the valve 4b for each operating state. The EGR amount correction correction circuit functions as a correction device that corrects the exhaust gas recirculation amount in a decreasing direction when air-fuel ratio feedback control becomes impossible.
Upon receiving the failure detection signal I, the recirculation of exhaust gas is stopped.

Here, an air-fuel ratio feedback control device is constituted by the above-mentioned 02 sensor 2, air-FFI ratio control solenoid valve, and air-fuel ratio control circuit 1a, and the above-mentioned cooling main sensor 6, engine rotation sensor 7, negative pressure sensor 8, EGR valve 4,
The EGR solenoid valve 5, the recirculation pipe 12, and the EGR amount control circuit 1b constitute an exhaust gas recirculation device. This shows the operation when the fuel ratio is controlled. As is well known, the output A of the 02 Cenoza 2 is an on/off signal that fluctuates dramatically near the stoichiometric air-fuel ratio.

The air-fuel ratio control circuit 1a performs integral processing on the above output No. 14A to obtain an integral No. 16, and generates a pulse 1g@ according to the integral signal.
B is output to the desired fuel ratio control solenoid valve.

The air-fuel ratio control solenoid valve receives the above pulse signal B,
Have Ki 1hi device 3 adjust the supply of fuel to the ship. Thereby,
The air-fuel ratio is controlled near the stoichiometric air-fuel ratio.

On the other hand, the EGR control circuit 1b detects the operating state based on the detection signals C, D, and E of the cooling water temperature sensor 6, the engine rotation sensor 7, and the negative pressure sensor 8.
A signal J corresponding to the target lift amount t of b is determined. This value is set so that when the cooling water temperature is above the specified humidity, the recirculating exhaust gas is stopped to ensure operability, and when the cooling water temperature is above the specified humidity, the amount of exhaust gas is optimized. P The lift amount is memorized (mapped) for each operation category as shown in Fig. 3. On the other hand, the EGR pulp opening sensor 4a No. 1b F
is input to obtain the measured lift amount of the valve 4b.

Here, among the solenoid valves 5, the atmospheric side solenoid valve 5a
is a type of solenoid valve that shuts off the EGR pulp negative pressure chamber 4C from the atmosphere when energized, and opens the EGR valve chamber 4c to the atmosphere when the energization is stopped. On the other hand, the negative pressure side solenoid valve 5b is a type of solenoid that communicates the EGR negative pressure chamber 4c with the intake passage 10 when energized, and cuts off the EGR pulp chamber 4c from the intake passage 1 (:) when the energization is stopped. For example, if the actual lift amount lost is larger than the target lift amount, the atmospheric side solenoid valve 5a and the negative pressure side solenoid valve 5 are activated to reduce the actual lift amount.
It is sufficient to reduce the negative pressure in the EGR pulp negative pressure chamber 4C by stopping power supply to b, and if the actually measured lift Aft is small, in order to increase the actual lift) t, the atmospheric side solenoid valve 5
A and the negative pressure side solenoid valve 5b are energized to increase the EGR pulp negative pressure chamber 4c. 50-100 of these operations
By performing this at m5EC intervals, the actual lift amount can be maintained at the target lift amount.

Next, the operation when the 02 sensor 2 fails will be described.

When the air-fuel ratio is controlled near the stoichiometric air-fuel ratio, the signal A from the 02 sensor 2 repeats on and off, but if the 02 sensor 2 is damaged, the signal A immediately turns off. At this time, the failure detection circuit IC
Then, the air-fuel ratio control circuit 1 detects that the input signal does not turn on and off again within a predetermined period of time.
a, EGR amount control circuit 1b and EGR amount correction correction circuit 1e output fault detection signal 1;

In response to the failure detection signal I, the air-fuel ratio control circuit la&t
A fixed pulse signal that makes the air-fuel ratio on the lean side is output to the air-fuel ratio ilj control solenoid valve 5.The reason why the zero air-fuel ratio is made on the lean side is because NOx1HC%CO in the exhaust gas (At the 41st Δt, C...NOx
1d...lIC1e...CO) to reduce the load on the exhaust gas purification device (catalyst) and to prevent deterioration of fuel efficiency. On the other hand, in response to the above failure detection signal 1, The EGRjt correction circuit 1e interrupts the operation of the atmospheric side solenoid 5 in order to cant the recirculating exhaust gas.
energization is stopped to a and the negative pressure side solenoid 5b.

As is clear from this embodiment shown above, even when the 02 sensor 2 is damaged and the air-fuel ratio cannot be controlled to the stoichiometric air-fuel ratio, the air-fuel ratio is controlled to the lean side to prevent harmful exhaust gas from being emitted. On the other hand, since the recirculation of the exhaust gas is stopped, it is possible to prevent poor combustibility and unstable running performance.

In the above embodiment, when the feedback control of the air-fuel ratio becomes impossible, the recirculation of exhaust gas is stopped, but of course it is not completely stopped, but the amount is reduced and the recirculation is made to some extent. You may also do so. The degree may be appropriately set depending on the running performance and the like.

In this embodiment, only damage to the 02 sensor 2 was described as the cause of the failure in which the air-fuel ratio could not be controlled to the stoichiometric air-fuel ratio, but failure in the signal line of the 02 sensor 2 and the fuel supply system (carburizer, injector, etc.) The same can be said for .

Furthermore, in this embodiment, when a failure is detected, the air-fuel ratio is controlled to the lean side, but the air-fuel ratio may be controlled to the rich side within a range where the HC%C00j increase is allowed, with the aim of emphasizing drivability. However, even in this case, if the recirculation of exhaust gas is stopped, the problem of further deterioration of fuel efficiency can be solved.

As is clear from the above, according to the present invention, feedback control of the air-fuel ratio becomes impossible, and the air-fuel ratio changes to the lean side or rich side, which may impede driving performance or fuel efficiency. In this case, since the reflux of υ1 gas is stopped or the output debt is reduced, the degree of support 1&ic can be reduced as much as possible, and it can be suppressed to a level that does not pose a problem in practice.

[Brief explanation of the drawing]

Figure 8141 is an overall configuration diagram of the embodiment according to the present invention, Figure 2 is a book diagram of the hunt roll unit, and Figure 3 is 94b.
FIG. 4 is a characteristic diagram showing the relationship between the degree of harmful gas ijS and the air-fuel ratio. DESCRIPTION OF SYMBOLS 1... Control unit, la... Air-fuel ratio control circuit, lb... EGRt control circuit, 1c... Failure detection circuit, le... EGR@ correction circuit, 2... O2 sensor, 3...・・Ki (Heki, 4・EGR pulp, 5・
...EGR pulp solenoid valve. Patent agent Toyo Kogyo Co., Ltd.

Claims (1)

[Claims] (1) an air-fuel ratio feed batter control system R that feedback-controls the air-fuel ratio to a target value based on the output of an air-fuel ratio sensor that detects the air-fuel ratio of the air-fuel mixture supplied to the engine;
Control for detecting an uncontrollable state of air-fuel ratio feedback control and outputting a detection signal in an engine exhaust gas purification control device comprising an exhaust gas recirculation device that controls an exhaust gas claw that recirculates to an intake system according to operating conditions. The present invention is characterized by comprising a failure detection device, and a correction device that receives a detection signal from the failure detection device and reduces the amount of exhaust gas recirculation controlled by the exhaust gas recirculation device when the air-to-air ratio feedback control is not possible. Exhaust gas purification for engines with 1li
11-car device.