JPS6160246B2 - - 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 gases has become a major social problem, regulations on exhaust gases have become even stricter, and various purification methods have been developed to minimize exhaust pollution while maximizing the effectiveness of automobiles. A method and purification device were developed and proposed.
Some 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.

A feature of the present invention is that the air-fuel ratio is operated with a slight excess of oxygen, for example, at a point where the oxygen excess ratio is around 1.0 or higher, so that the air-fuel mixture is combusted as completely as possible in the combustion chamber, and at the same time, the air-fuel mixture is completely combusted. Various means have been established to accomplish this.

Specifically, as shown in FIG. 1, the engine 4 has at least two spark plugs 2 and 3 arranged in one combustion chamber 1, and the ignition time difference θ between the two spark plugs 2 and 3 is determined by exhaust gas recirculation. A control means 9 is provided for controlling the amount of reflux gas in the device 8 in relation to the amount.

Here, the thermal reactor 7 is for oxidizing HC and CO.

The details of the present invention will be explained 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 Batsuteri, 1
5 is an ignition switch, 16 and 17 are first and second ignition coils, 18 and 19 are external resistors, and 20 and 21 are first and second distributors. Of course, it is also possible to form it into an integral structure. Reference numeral 22 denotes an ignition signal generator, which is composed of mechanical contacts or a semiconductor switch using a transistor. 23 is an intake pipe, and 24 is an exhaust pipe.

Figure 3 shows CO, HC, and
It shows NO, O ₂ , fuel efficiency, and torque.

With current exhaust countermeasures, it is difficult to treat
In order to avoid near the peak value of NO, countermeasures for rich mixtures near λ = 0.8 and measures for lean mixtures near λ = 1.2 to 1.4 are mainstream, but measures for rich mixtures lead to increased fuel consumption and Countermeasures against lean mixtures have the drawback of deteriorating drivability due to a decrease in output, and drastic measures are desired as a countermeasure for exhaust emissions.

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

As shown in Figure 4, the three-way catalyst has an oxygen excess rate λ
It has a characteristic that the purification rate of HC, CO, and NOx is over 90% when the ratio is around 1.0, so 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. becomes.

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

Then, by the action of the control circuit 11, the solenoid valve 1
2 is driven to accurately control the amount of fuel supplied.

Further, in the combustion chamber 1, a plurality of spark plugs 2,
3 are arranged, and the ignition time of these plugs is determined by the control means 9. Assuming that spark plug 2 is the reference side and spark plug 3 is the control side,
The spark plug 2 is the timing gear 25 of the engine 4.
While the spark plug 3 is ignited at the time determined by the spark plug 3, the ignition time of the spark plug 2 is detected and determined based on this. The ignition time of the control side plug 3 can be arbitrarily controlled within a range of a maximum of 15 degrees (crank angle) and a minimum of 1 degree (substantially 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 depends on the vacuum advance angle characteristics and governor advance angle characteristics of the distributor.
In contrast, the ignition time b of the control side spark 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 Alternatively, it may be controlled in conjunction with the control of the exhaust gas recirculation device, which will be described later (continuous control), and its selection can be determined by trends in regulation values, operating conditions, cost, etc.

As we all know, the exhaust gas recirculation system (EGR)
A portion of the exhaust gas is supplied to the intake system, lowering the maximum temperature during combustion and suppressing the generation of NO. NO.
One way to suppress the occurrence 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 will result in a better output for the same NO than retarding the ignition timing. Experimental data has been obtained showing that the decrease is small, and in this embodiment, a means is adopted to detect the exhaust gas recirculation rate and control the ignition 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 the relationship is as shown in the figure. It is effective to separate these relationships and control them independently.

FIG. 8 is an embodiment of the control means 9 for controlling the ignition time of the two spark plugs shown in FIG.
The figure is an explanatory diagram of the 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 transferred to the Zener diode 26.
The signal is applied to the base of transistor 27 through , turning on transistor 27 and turning on 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. A high voltage is induced in the first plug 2, and an arc is blown across the first plug 2.

On the other hand, the intermittent signal of the ignition signal generator 22 is detected, and the one-shot multivibrator circuit 31,
A predetermined delay time can be obtained by using 32 circuit constants.

FIG. 9 shows this state, where a is the potential difference due to on/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 multivibrator circuit 31, and d is one-shot multivibrator circuit 3
2 output pulse waveforms, e and f are the second coil 17
In the secondary voltage waveform of , e is the waveform when the delay time is the minimum, and f is the waveform when the delay time is the maximum.

Here, one-shot multivibrator circuit 3
1 delay time Tc ₁ setting is the resistance value of variable resistor 33
The time constant Tc ₁ ≈C ₃₄ ·R ₃₃ is determined by R ₃₃ and the capacitance C ₃₄ of the capacitor 34, and according to experiments, it is practically preferable to change within a range of 200 μS at the minimum and 3 ms at the maximum.

Furthermore, one-shot multivibrator circuit 3
The output of 2 is the capacitance C 35 of capacitor ₃₅ and resistor 3
An output pulse with a constant pulse width is derived from the time constant Tc ₂ ≈C ₃₅ ·R ₃₆ of the resistance value R ₃₆ of 6.

Therefore, by changing the constant of the resistor 33 or the capacitor 34, the ignition time between the first plug and the second plug can be changed arbitrarily. 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 to match the operating conditions. .

As described above, the present invention aims at stabilizing combustion by arranging at least two or more spark plugs in one combustion chamber, and also reduces NOx as the combustion speed increases.
The increase in fuel consumption is reduced by exhaust gas recirculation and by controlling the ignition time difference between the two plugs,
This system is designed to comprehensively improve exhaust purification and driveability in driving modes including acceleration, deceleration, constant speed, etc. in a well-balanced manner.

Therefore, unlike conventional devices, there is no fundamental flaw in the principle that improving one performance degrades the other, and it is suitable as a new system that can cope with future strict exhaust regulations.

[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. 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. DESCRIPTION OF SYMBOLS 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] 1. An engine in which at least two spark plugs are arranged in one combustion chamber, and a fuel supply device adjusted so that the air-fuel ratio of the mixture supplied to the engine is equal to or higher than the stoichiometric air-fuel ratio. a reactor installed on the exhaust side of the engine to oxidize CO and HC in the exhaust gas; an exhaust gas recirculation device that re-supplies a portion of the exhaust gas to the intake system; An automobile exhaust gas purification device comprising a control means for controlling an ignition time difference in relation to an amount of recirculated gas of the exhaust gas recirculation device.