JP2921158B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly to improving the starting characteristics of an exhaust gas purifying apparatus provided with a catalytic converter in an exhaust passage.

[0002]

2. Description of the Related Art Generally, a catalytic converter such as a three-way catalyst, which is used as an exhaust gas purifying device for an internal combustion engine, is not activated due to a low temperature for a while after being started.
The exhaust gas purification function cannot be sufficiently exhibited, and hydrocarbons (HC) and other harmful substances in the exhaust gas are released into the atmosphere without any treatment. This can be one of the causes of air pollution, so some measures need to be taken. 47-
In the prior art described in Japanese Patent No. 3110,
An ignition plug is provided in the exhaust pipe of an internal combustion engine, and when the temperature is low, the ignition plug is operated to reignite the exhaust gas, the exhaust gas is reburned, and the heat reactor is heated by the heat, and the temperature is rapidly raised to the reaction temperature. It is going to rise.

[0003]

Since the exhaust gas is a gas that has just undergone combustion in the combustion chamber of the internal combustion engine, even if the exhaust gas contains unburned components, the exhaust gas does not react with non-combustible components such as nitrogen, carbon dioxide or water. Since the concentration of unburned matter is not high, it is a gas that is very difficult to ignite in practice, and is not easily ignited even by discharge of a spark plug. Therefore, in the above-mentioned prior art, there is no guarantee that exhaust gas can be reliably reignited at any time, and it is considered that reburning of exhaust gas often becomes incomplete. The purpose of the prior art, which is released into the atmosphere and heats the thermal reactor by the heat of reburning the exhaust gas to rapidly increase the temperature, is not considered to be sufficiently achieved.

[0004] The present invention addresses this problem of the prior art and provides a means for the catalytic converter to be heated and activated during a period of time.
Combustible components such as HC are reliably burned by means other than the catalytic converter to prevent the combustible components from being directly released into the atmosphere, and the catalytic converter is quickly warmed up and has an exhaust gas purifying action as soon as possible. It is an object of the present invention to provide an effective means for achieving this.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is provided in an internal combustion engine provided with a catalytic converter in an exhaust passage for purifying exhaust gas, and an exhaust passage upstream of the catalytic converter. Hydrogen generating means for generating hydrogen for supply to the hydrogen supply means, a hydrogen supply means connecting between the hydrogen generating means and a hydrogen inflow opening provided in the exhaust passage, and a hydrogen supply means near the hydrogen inflow opening in the exhaust passage. and air supply means for supplying additional air, and forced ignition means provided in the inlet opening near the hydrogen to ignite to ignited and burnt in the hydrogen supplied to the exhaust passage, the catalytic converter Provided is an exhaust gas purifying apparatus for an internal combustion engine, comprising: control means for operating each of the means when the temperature of a catalyst is equal to or lower than a predetermined value.

[0006]

When the temperature of the catalytic converter is low, such as when the internal combustion engine is started, the catalyst is not activated.
Although there is no ability to purify pollutants in the exhaust, at this time, an appropriate amount of hydrogen is sent from the hydrogen generator to the hydrogen inlet of the exhaust passage through the hydrogen supply unit by the control unit, and is discharged into the exhaust passage. The hydrogen is mixed with air sent from the air supply means into the exhaust passage, and is ignited and burned by being forcibly ignited by the ignition means.
The temperature of the surrounding exhaust gas is increased to ignite and burn unburned components in the exhaust gas, thereby rendering pollutants such as HC harmless.

Further, when the high temperature hydrogen and the combustion gas of the exhaust gas burned in the exhaust passage flow into the catalytic converter, the catalyst is rapidly heated and its temperature rises, and the catalyst is quickly activated and activated. The internal combustion engine does not emit harmful pollutants immediately after starting, because it purifies the pollutants of interest. In this case, instead of hydrogen
For example, when normal fuel is supplied into the exhaust passage, it
Hazardous hydrocarbons (HC) are emitted until the time of fire,
Even after ignition, incomplete combustion is likely to occur,
Hazardous substances such as hydrogen chloride and carbon monoxide are discharged to the outside.
On the other hand, in the present invention, the point
Fire and burned hydrogen are very diffusible compared to fuel
It is easy to burn completely, so it is easy to completely burn it.
It is unlikely to be emitted outside and is harmful by combustion
No significant emissions.

[0008]

FIG. 1 shows a system configuration of an embodiment of the present invention. The catalytic converter 1 is disposed in the exhaust passage 12 of the internal combustion engine 10.
4 is connected, and air is supplied to the upstream side from an air supply device 16 such as an electric air pump, for example.
An appropriate amount of hydrogen is supplied from a hydrogen generator 18 such as a water electrolyzer via a control valve 20 such as an electromagnetic valve in a timely manner. The opening and closing of the control valve 20 is controlled by a control signal of, for example, an electronic control unit (ECU) 22. An ignition plug 26 such as a spark ignition plug or a glow plug is provided on the downstream side of the hydrogen injection nozzle 24 that is open to the exhaust passage 12.
The ignition plug 26 is electrically energized by the control signal of the ECU 22 so that the ignition plug 26 performs the ignition action at the same time as the injection from the ignition plug 4. Output signals from the catalyst temperature sensor 28 for detecting the temperature of the catalyst bed of the catalytic converter 14 or the water temperature sensor 30 for detecting the cooling water temperature of the internal combustion engine 10 are input to the ECU 22. As described above, the control signal is output to the hydrogen control valve 20, the air supply device 16, the ignition plug 26 and the like.

Next, the control valve 2 for hydrogen by the ECU 22
0, a specific control example of the air supply device 16 and the ignition plug 26 will be described. FIG. 2 is a flowchart specifically illustrating a routine program 100 in the case where the control is performed based on the catalyst bed temperature. FIG. 3 is a flowchart for setting an initial value in the program 100 when the control of the internal combustion engine 10 is started prior thereto. 2 illustrates a routine program 200.
At the same time that the operation control of the internal combustion engine 10 is started, the initialization routine program 200 of FIG. 3 is executed, and a flag which is an index indicating whether hydrogen and air are supplied to the exhaust passage 12 as described later. H ₂ airflag value is step 2
In step 202, the control valve 20 for supplying hydrogen is reset to 0 in step 01, the air supply device 16 for supplying air is in step 203, and the spark plug 26 for re-ignition is in step 204. Is turned off by giving a control signal of OFF from
This is the initial state of control. Subsequently, the catalyst warm-up routine 100 shown in FIG. 2 is repeatedly executed at a short time interval such as one time per one revolution of the internal combustion engine 10 to interrupt the main program of the operation control of the internal combustion engine 10. You.

When the catalyst warm-up routine program 100 shown in FIG. 2 is started, first, at step 101, it is determined whether or not the internal combustion engine 10 is currently in a starting state. The “starting state” is determined by whether or not a starter switch (not shown) for starting the internal combustion engine is turned on, that is, whether or not the starter motor is energized. Even if it has already been turned off after temporarily reaching 0N, the “starting state” may be set until the rotation speed of the internal combustion engine 10 reaches a predetermined value.

If the internal combustion engine is "starting", the routine proceeds to step 102, where hydrogen and air are
Is determined from the value of the flag H ₂ airflag. Flag H ₂ airflag
Is terminated when the value of the flag H ₂ airflag is 0, that is, when hydrogen and air are not supplied to the exhaust passage 12,
Proceeding to step 103, it is determined whether or not the signal of the catalyst bed temperature (may be the engine water temperature detected by the temperature sensor 30) output from the temperature sensor 28 is larger than a predetermined value CT. If it is larger than CT, the catalytic converter 14 has already been warmed up and does not need to take any special measures because it has a sufficient exhaust gas purifying function. If it is determined in step 103 that the catalyst bed temperature is not higher than the predetermined value CT,
Since contaminants such as HC in the exhaust gas pass through the catalytic converter 14 and are released into the atmosphere, it is necessary to take some measures.

Accordingly, in accordance with the characteristics of the present invention, in step 104, a control signal for electrically energizing the spark plug 26 is issued from the ECU 22 to start spark discharge of the spark plug 26, or in the case of a glow plug. Makes it glow red by energization. In the next step 105, the air supply device 16 is driven by the control signal of the ECU 22 to send fresh air into the exhaust passage 12. Step 106
Then, the ECU 22 issues a control signal to open the control valve 20 and causes the hydrogen of the hydrogen generator 18 to be ejected from the nozzle 24 toward the ignition plug 26 in the exhaust passage 12. The hydrogen injected from the nozzle 24 is mixed with the air from the air supply device 16 and easily ignited by the spark plug 26, and burns in the exhaust passage 12 upstream of the catalytic converter 14, thereby reducing the temperature of the surrounding exhaust gas. Since the temperature rises remarkably, flammable components such as HC in the exhaust gas, which are relatively difficult to ignite, are also ignited, and re-combustion of the exhaust gas is started. And step 10
At 7, the flag H ₂ airflag, which is an index during the execution of hydrogen injection and reignition, is set to 1, and the routine ends. In this way, a reburn state of exhaust gas is established in the exhaust passage 12 on the upstream side of the catalytic converter 14 in a short time, and unburned components such as HC in the exhaust gas are burned to purify the exhaust gas.

When the starter switch (not shown) is turned off and the rotation speed of the internal combustion engine 10 rises to a predetermined value, the result of the determination in step 101 is that the engine is not in the "starting state", the process proceeds to step 108. It is determined whether the flag H ₂ airflag is “1”. When the flag H ₂ airflag is 1 proceeds to step 109, the elapsed time after start of the engine whether exceeds a predetermined value T ₁ is is determined. When it exceeds the predetermined value T _1,
In step 110, the ECU 22 issues a control signal to close the control valve 20, and stops injecting hydrogen from the nozzle 24. Further, in step 111, the electrical bias of the ignition plug 26 is also released. However, since the temperature in the exhaust passage 12 has already risen, the reburning of the exhaust gas has been established, so that the combustion is not immediately stopped by the supply of hydrogen or the stop of the ignition.

In the example shown in FIG. 2, in step 112, it is determined whether or not the elapsed time after the start of the internal combustion engine exceeds a _second predetermined value T2. When the predetermined time T ₂ has passed, the catalytic converter 14 is heated by the exhaust of the heat afterburning hydrogen burned in the exhaust passage 12. Particularly, since is sufficiently warmed up has become activated state In addition, the catalytic converter 14 has the ability to purify exhaust gas, and does not require auxiliary means. Therefore, step 11
Proceeding to 3, the driving of the air supply device 16 is stopped, and the sending of air into the exhaust passage 12 is also stopped. That is, the operating state of the internal combustion engine is set to a normal state. Then, in step 114, the flag H ₂ airflag is reset to 0, and the routine ends. Step 108, 109 or 112
If any of the determination results in the above is NO, the routine is immediately terminated, and the subsequent steps are not executed.

FIG. 4 shows the result of measuring the result of this control for the embodiment. With the elapsed time on the horizontal axis and the temperature and concentration on the vertical axis, the HC concentration in the exhaust gas discharged, the catalyst bed temperature of the catalytic converter 14 detected by the temperature sensor 28, and the temperature of the exhaust gas upstream of the catalytic converter 14 (particularly, Time changes are shown for each of the temperature of the exhaust gas at the outlet of the catalytic converter 14 and the temperature of the exhaust gas at the outlet of the catalytic converter 14). The HC concentration becomes so high that it instantaneously scales out when the internal combustion engine is started. However, immediately after hydrogen is injected from the nozzle 24 and the ignition plug 26 performs an ignition action, recombustion in the exhaust passage 12 starts. , The HC concentration drops sharply. The time T ₁ for supplying hydrogen is set to 10 seconds in the illustrated example. The reason why the HC concentration continues to decrease even after the supply of hydrogen is stopped and the catalyst bed temperature and the catalyst outlet temperature are increased is that the reburning of exhaust gas continues in the exhaust passage 12 even after the supply of hydrogen is stopped. This indicates that the catalytic converter 14 is being warmed up and activated. As a result, the exhaust gas purifying function of the catalytic converter 14 itself starts up quickly.

[0016]

According to the present invention, when starting a low-temperature internal combustion engine in which the catalytic converter does not have an exhaust gas purifying ability, hydrogen having excellent ignitability is supplied to the exhaust passage on the upstream side of the catalytic converter, and air is further supplied. Supply and forced ignition hands
Since burning in the exhaust passage to ignite earlier hydrogen flammability by the stage, which is unburned in the exhaust by the heat HC
In addition to causing combustion to make it harmless, the high temperature combustion gas flows into the catalytic converter to warm up the catalyst,
The catalyst can be quickly activated and the original exhaust gas purifying function of the catalyst can be exhibited at an early stage.

According to the present invention, the upstream side of the catalytic converter
Supply hydrogen instead of normal fuel into the exhaust passage
Emissions of harmful hydrocarbons by the time of ignition as fuel
There is no danger of fire and incomplete combustion occurs after ignition
When harmful substances such as hydrocarbons and carbon monoxide are discharged to the outside
Without fear, hydrogen diffuses well with the supply and
In addition, it is extremely easy to ignite
Since the entire combustion occurs, the exhaust gas is reburned by the heat and touched.
The temperature of the medium converter can be rapidly increased.
Therefore, not only is the exhaust gas cleaned from the start of operation of the internal combustion engine, but even if hydrogen supplied to the exhaust passage is released without being ignited due to a failure of the ignition means or the like. Since hydrogen is not a problem as an air pollutant, harmful substances are discharged to the outside.
Harmful emissions from combustion or combustion
No, there is no possibility that the cause of the pollution. In any case,
According to the present invention, an internal combustion engine with much lower emission than a conventional internal combustion engine can be obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a system configuration according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a control program of the device of the present invention.

FIG. 3 is a flowchart illustrating an initialization routine program executed before executing the program of FIG. 3;

FIG. 4 is a diagram illustrating the operation and effect of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 ... Exhaust passage 14 ... Catalytic converter 16 ... Air supply device 18 ... Hydrogen generator 20 ... Control valve 26 ... Spark plug

Claims (1)

(57) [Claims] 1. A hydrogen generating means provided in an internal combustion engine having a catalytic converter in an exhaust passage for purifying exhaust gas, for generating hydrogen to be supplied to an exhaust passage on an upstream side of the catalytic converter; A hydrogen supply unit that connects between the hydrogen generation unit and a hydrogen inflow opening provided in the exhaust passage, an air supply unit that supplies additional air near the hydrogen inflow opening of the exhaust passage, and forced ignition means provided in the vicinity of the inflow opening of the hydrogen to ignite to ignited and burnt in the hydrogen supplied to the temperature of the catalytic converter catalyst activates the respective means when a predetermined value or less An exhaust gas purification device for an internal combustion engine comprising a control means .