JPS5925865B2 - Automobile exhaust gas purification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas purification device for automobiles, particularly automobiles equipped with gasoline engines.

Since air pollution caused by automobile exhaust gas has become a major social issue, regulations on exhaust gas have become even stricter, and various purification methods have been developed to minimize exhaust pollution while maximizing the effectiveness of automobiles. , purification devices have been developed and proposed, and some of the devices are being put into practical use.

However, these methods are focused on meeting regulatory values, at the expense of some vehicle performance or resources.

The present invention provides an effective device that satisfies strict regulatory values without sacrificing performance or fuel efficiency.

The present invention is characterized by operating the air-fuel ratio at a slightly excess oxygen state, for example, at a point where the oxygen excess ratio is around 1.0 or higher, and at the same time burning the air-fuel mixture as completely as possible in the combustion chamber. Various means are provided to achieve complete combustion.

Specifically, as shown in FIG. 1, there is an engine 4 in which at least two spark plugs 2 and 3 are arranged in one combustion chamber 1, and an exhaust gas sensor 10 that detects the oxygen concentration in exhaust gas.
Based on the output of this exhaust gas sensor, the air-fuel ratio from the fuel supply device 6 provided in the intake passage 5 is adjusted so that the oxygen excess rate λ in the exhaust gas is from around 1.0 to around 1.2. It is characterized in that it is equipped with a variable control circuit 11, a solenoid valve 12, and a three-way catalyst 13 that oxidizes HC and CO and simultaneously reduces NO using a single catalyst.

Note that the exhaust gas recirculation device 8 may also be controlled by the control circuit 11.

The thermal reactor 7 oxidizes CO and HC in the exhaust gas, and is provided as appropriate depending on the requirements of the engine.

The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 2 is a system diagram incorporating the features of the present invention shown in FIG.

Here, 14 is a battery, 15 is an ignition switch, 16.17 is a first and second ignition coil, respectively, and 18
, 19 are external resistors, and 20 and 21 are first and second I-IJ computers, which may be divided into separate units or formed into an integral structure, of course.

Reference numeral 22 denotes an ignition and signal generator, which is composed of a mechanical contact or a semiconductor switch using a transistor.

23 is an intake pipe, and 24 is an exhaust pipe.

Figure 3 shows CO and HC versus excess air ratio λ.

N0202, fuel efficiency, and torque are shown.

Current exhaust gas countermeasures mainly focus on measures for rich mixtures around λ = 0.8 and lean mixtures at λ = 1.2 to 1.4 in order to avoid the NO peak values that are difficult to treat. However, countermeasures for rich mixtures lead to increased fuel consumption.
Furthermore, countermeasures against lean mixtures have the drawback of deteriorating driveability due to a decrease in output, and drastic countermeasures are desired as a countermeasure against exhaust emissions.

On the other hand, a single catalyst oxidizes HC, CO and NOx at the same time.
A three-way catalyst 13 was developed to reduce .

As shown in Figure 4, the three-way catalyst has an oxygen excess ratio λ of 1.0.
Since it has the characteristic that the purification rate of HC, CO, and NOx is 90 or higher in the vicinity, it is possible to purify exhaust gas to a large extent by controlling the ratio of air and fuel in the mixture supplied to the engine. .

In FIG. 2, individual operations will be explained. The fuel supply device 6 measures and injects fuel corresponding to the amount of intake air, and supplies a mixture having a predetermined air-fuel ratio to the combustion chamber 1 in the engine 4.

In this embodiment, the air-fuel ratio is set to λ=1.0 or λ=1.0 or more.

Here, as a sensor for detecting λ=1.0, the exhaust gas sensor 10 that generates a predetermined output voltage with respect to the oxygen concentration in the exhaust gas is used, but the sensor is not limited to this, and the air-fuel ratio during combustion in the combustion chamber is A sensor that detects this is fine.

The solenoid valve 12 is driven by the control circuit 11 to accurately control the amount of fuel supplied.

Further, a plurality of spark plugs 2 and 3 are arranged within the combustion chamber 1, and the ignition times of these plugs are determined by a control means 9.

Assuming that the spark plug 2 is on the reference side and the spark plug 3 is on the control side, the spark plug 2 ignites at a time determined by the timing gear 25 of the engine 4;
The spark plug 3 is determined by detecting the ignition time of the spark plug 2 side and using this as a reference.

The ignition time of the control side plug 3 can be arbitrarily controlled within a range of a maximum of 15° (crank angle) and a minimum of 1° (approximately in phase) from the ignition time of the reference side plug.

This situation is shown in FIG. 5, where the ignition time a of the reference side spark plug 2 is predetermined by the vacuum advance characteristics of the distributor and the governor advance characteristics, whereas the ignition time a of the reference side spark plug 2 The ignition time of the plug 3 is set to have a certain time difference from the ignition time a of the reference side spark plug (constant time difference), or is controlled in conjunction with the control of the exhaust gas recirculation device, which will be described later. (continuous control), and the selection is based on the trend of regulatory values,
This is a factor that can be determined by operating conditions, cost, etc.

As is well known, the exhaust gas recirculation system (EGR) supplies part of the exhaust gas to the intake system, lowering the maximum temperature during combustion and increasing NO
This is to prevent the occurrence of

One way to suppress the generation of NO is to retard the ignition timing, but as shown in Figure 6, at the same air-fuel ratio, increasing the exhaust gas recirculation rate is better than retarding the ignition timing. Experimental data has been obtained that shows that there is little decrease in output, and in this embodiment, the exhaust gas recirculation rate is detected and a means is used to control the wearing time of the two plugs.

Figure 7 is an example of this.The exhaust gas recirculation rate, which is related to the intake negative pressure or intake air amount, and the ignition time difference (crank angle) between the two plugs have a relationship as shown in the figure, and during acceleration, deceleration,
It is effective to separate these relationships and perform independent control during startup, etc.

FIG. 8 is a diagram showing one embodiment of the control means 9 for controlling the ignition time of the two spark plugs shown in FIG. 2, and FIG. 9 is an explanatory diagram of its operation.

The configuration and operation will be explained below.

When the ignition signal generator 22 is turned off, the voltage charged in the capacitor 25 is applied to the base of the transistor 27 via the Zener diode 26, turning on the transistor 27 and turning on the transistor 28 as well.

Then, the base potential of the transistor 29 becomes zero potential, so the transistor 29 is turned off, and the last power transistor 30 is also turned off, cutting off the primary current of the first ignition coil 16 that should be ignited first, and turning off the secondary side. induces high voltage in
An arc is blown to the first plug 2.

On the other hand, an intermittent signal from the ignition signal generator 22 is detected, and a predetermined delay time is obtained by the circuit constants of the one-shot multi-bye break circuits 31 and 32.

FIG. 9 shows this situation, where a is the potential difference due to turning on and off of the breaker point, b is the secondary voltage waveform of the first coil 16, C is the output pulse waveform of the one-shot multi-by-break circuit 31, and d is the output pulse waveform of the one-shot multi-by-break circuit 32, e and f are the secondary voltage waveforms of the second coil 17, e is the waveform when the delay time is the minimum, and f is the waveform when the delay time is the maximum. be.

Here, the delay time Tc1 of the one-shot multi-bye break circuit 31 is set by a time constant Tc1L determined by the resistance value R33 of the variable resistor 33 and the capacitance C34 of the capacitor 34.
, C34 and R33, and according to experiments, the minimum is 2
Practically, it is preferable for the time to change within a range from 00 μS to 3 ms at maximum.

Furthermore, the output of the one-shot multi-bye break circuit 32 is the capacitance C35 of the capacitor 35 and the resistance value R of the resistor 36.
36 time constants TC2==, C35' and R36, an output pulse having a constant pulse width is derived.

Therefore, by changing the constant of the resistor 33 or the capacitor 34, it is possible to arbitrarily change the ignition time between the first plug and the second plug.

For example, by changing the resistance value of the resistor 33 in conjunction with changes in the opening of the throttle valve, fluctuations in the intake pipe negative pressure, or operation of the EGR control valve, it is possible to control the ignition time in accordance with the operating conditions.

As is clear from the above description, the present invention aims at stabilizing combustion by arranging at least two spark plugs in one combustion chamber, and also accurately controls the air-fuel ratio so that the three-way catalyst operates well. Therefore, it is possible to comprehensively reduce fuel consumption, improve drivability, and reduce harmful exhaust components.

[Brief explanation of the drawing]

Fig. 1 is a principle diagram of the present invention, Fig. 2 is a system diagram showing an embodiment of the present invention, Fig. 3 is a characteristic diagram showing the relationship between excess air ratio, exhaust gas components, and engine characteristics. A characteristic diagram of a three-way catalyst. Figure 5 is a characteristic diagram showing engine speed and advance characteristics of two spark plugs. Figure 6 is a diagram showing the amount of NO versus ignition timing delay and exhaust gas recirculation rate at the same air-fuel ratio. Figure 7 is a characteristic diagram showing the relationship between intake negative pressure or intake air amount, exhaust gas recirculation rate, and ignition time difference between the two plugs, Figure 8 is a characteristic diagram showing the relationship between the two spark plugs in Figure 2. FIG. 9 is a circuit diagram showing an embodiment of the means for controlling the ignition time of FIG. 9, and FIG. 9 is an operation waveform diagram explaining the operation of the embodiment of FIG. 1... Combustion chamber, 2, 3... Spark plug, 4... Engine, 5... Intake passage,
6... Fuel supply device, 7... Thermal reactor, 8... Exhaust gas recirculation device, 9...
Control means, 11... Control circuit, 13...
・Three-way catalyst.

Claims (1)

[Claims] an engine in which at least two spark plugs are arranged in eleven combustion chambers, a fuel supply device that supplies a mixture to the engine, an exhaust gas sensor that detects the oxygen concentration in exhaust gas, and an output of the exhaust gas sensor that detects the oxygen concentration in the exhaust gas. The receiver includes a control circuit that controls the mixture concentration from the fuel supply device so that the oxygen excess rate λ in the exhaust gas ranges from around 1.0 to around 1.2, and a single catalyst that oxidizes HC and CO. This is an automobile exhaust gas purification device that combines a three-way catalyst that simultaneously reduces NO.