JP2000064828A - Exhaust gas purification equipment for internal combustion engines - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve regeneration efficiency at the time of lean NOx catalyst regeneration. A heating element is disposed in an exhaust pipe upstream of a catalyst, and the exhaust gas is heated at the time of catalyst regeneration to easily reach a regeneration temperature and improve regeneration efficiency. Will be maintained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to carbon monoxide (C) contained in gas discharged from an internal combustion engine of an automobile or the like.
The present invention relates to a catalyst for purifying O), hydrocarbons (HC), and nitrogen oxides (NOx), and a catalyst device having a particularly high purification rate by controlling the exhaust gas temperature.

[0002]

2. Description of the Related Art In recent years, in the trend of resource saving and environmental protection, there is a social demand to operate an automobile gasoline engine by lean burn. Along with this, development of catalysts (lean NOx catalysts) for effectively purifying NOx in exhaust gas containing oxygen discharged from lean burn engines is being promoted at various places.

However, the lean NOx catalyst has a characteristic that it is poisoned by the sulfur content in gasoline and the catalytic activity decreases depending on the traveling distance. It is known that this poisoning by sulfur occurs when a compound of a catalyst component and a sulfur oxide is formed in the catalyst, but this compound decomposes at high temperature and returns to the original catalyst component. Therefore, in order to maintain the high activity of the catalyst, it is necessary to carry out a catalyst regeneration process in which the exhaust gas is heated to a high temperature to remove the sulfur content in the catalyst.

In order to raise the temperature of exhaust gas to a high temperature, it is generally necessary to operate the engine at high rotation and high load. This not only has a great adverse effect on fuel efficiency, but also becomes difficult to realize in normal driving conditions.

[0005]

In view of the above-mentioned problems of the prior art, the present invention facilitates catalyst regeneration by generating high temperature exhaust gas required for lean NOx catalyst regeneration even in a normal traveling state, and has a high purification rate. The present invention proposes an exhaust gas purifying apparatus and method for expressing the above.

[0006]

The invention for solving the above-mentioned problems is realized by providing a heating element for heating exhaust gas at an upstream portion of a catalyst in an exhaust pipe.

In the operating mechanism of the present invention, the exhaust gas is heated to the catalyst regeneration temperature by the heating element, so that the catalyst regeneration is efficiently performed. This not only reduces the load on the engine, but also reduces the adverse effect on fuel efficiency.

In addition to the lean NOx catalyst, the catalyst according to the present invention can efficiently use HC, even when the exhaust gas has a low temperature.
A catalyst that can purify CO (low temperature HC catalyst) or a generally used three-way catalyst alone or in combination can be applied.

In the present invention, when the exhaust gas temperature is lowered to the catalyst activation temperature or lower, the exhaust gas temperature is raised by a heating element to be used as a means for expanding the temperature range (temperature window) in which the catalyst works efficiently. Is also within the scope of the present invention.

[0010]

FIG. 1 shows an internal combustion engine system using the present invention.

FIG. 1 is a system diagram of a fuel injection type gasoline engine for an automobile. In FIG. 1, the air required for combustion is taken in through the intake port 2, and the air cleaner 1
It is mixed with gasoline in the intake pipe 8 through the throttle valve 5 for controlling the intake flow rate and introduced into the cylinder.

Gasoline required for combustion is sucked from a fuel tank 9 by a fuel pump 10, pressurized, and then passed through a fuel damper 11 and a fuel filter 12, and then from a fuel injection valve (injector) 13 into an intake pipe 8. Is jetted. The air mixed with gasoline in the intake pipe is burned by electric ignition in the cylinder. Exhaust gas generated by combustion is discharged to the outside of the system through the exhaust pipe 19 and the catalyst 20.

The combustion is controlled by the intake air amount signal detected by the intake air flow meter 3, the valve opening signal from the throttle sensor 18 provided in the throttle valve 5, and the crank provided in the distributor 16. An angle signal from the angle sensor is input to the control unit 15 to calculate an appropriate fuel injection amount / ignition timing and control the fuel injection valve 13 and the ignition device. At this time, a more precise control can be performed by detecting the combustion state in the cylinder by the oxygen concentration signal from the oxygen sensor 51 provided in the exhaust pipe 19 and performing feedback control.

A control unit 15 for performing this control
A block diagram of the above is shown in FIG. The input signal is passed to the MPU via I / O. In order to perform an appropriate control state, the MPU performs an operation using the input signal and the values of ROM and RAM, and outputs the operation result via I / O. This output is used as a control signal to control the fuel injection valve 13 and the ignition device.

By this control method, the combustion state in the cylinder is controlled to any of the theoretical air fuel consumption state (stoichi), excess fuel state (rich), and excess air state (lean).

Here, since the gas discharged from the engine 7 contains harmful components such as HC, CO, NOx, etc., these harmful components must be rendered harmless and then discharged out of the system. .

Therefore, an exhaust gas purifying catalyst 20 for purifying the exhaust gas by using a catalytic action is provided in the exhaust pipe 19. In the present invention, the heating element 21 for heating the exhaust gas and the temperature measuring sensor 22 are installed in the exhaust pipe upstream of the catalyst. The signal from the sensor is input to the control unit shown in FIG. 2, and the operation of the heating element is controlled after considering other input conditions. This allows the exhaust gas to be heated and controlled arbitrarily.

FIG. 3 shows a heating element using a resistor having a laminated structure such as a honeycomb. The heating element arranged in the exhaust pipe generates heat when energized to heat the exhaust gas. Similarly, FIG. 4 shows a heating element using a linear resistor such as a nichrome wire, and FIG. 5 shows a heating element using an electromagnetic wave generator.

FIG. 6 shows a control diagram of the heating element when the exhaust gas temperature decreases. When the exhaust gas temperature becomes lower than the catalyst activation temperature, the exhaust gas is heated by the heating element, and the temperature window of the catalyst can be widened.

7 and 8 are control diagrams relating to lean NOx catalyst regeneration. Although the activity of the lean NOx catalyst is lowered by the poisoning substances contained in the exhaust gas, the activity is restored by the regeneration treatment for raising the temperature of the exhaust gas. In FIG. 7, this reproduction is controlled by the traveling distance. Further, in FIG. 8, when the exhaust gas temperature rises, it is regenerated by heating it to a higher temperature with a heating element. Thereby, the exhaust gas temperature can be easily heated to the catalyst regeneration temperature, and regeneration can be performed efficiently. In addition, since the engine load at the time of reproduction can be reduced, reproduction can be performed during normal traveling, and adverse effects on fuel efficiency during reproduction can be reduced.

The heating element shown in FIG. 3 is mounted on a commercial vehicle, and the heating element shown in FIG.
The control shown in was performed. NOx, H in the catalyst at this time
Regarding the C purification rate, FIG. 9 shows the NOx purification rate, and FIG. 10 shows H.
C shows the purification rate. The engine control shown in FIGS. 1 and 2 maintained the engine in a stoichiometric combustion state.

It can be seen from FIGS. 9 and 10 that the temperature window as a catalyst device is widened according to the present invention.

The heating element shown in FIG. 3 was mounted on a commercially available lean burn vehicle, and the lean NOx catalyst was regenerated by the control shown in FIGS. 7 and 8. FIG. 11 shows the reproduction result. As shown in FIG. 11, the lean NOx catalyst decreases in activity in proportion to the traveling distance. Therefore, when the exhaust gas is heated to a high temperature, the activity is restored, but generally, in order to raise the temperature of the exhaust gas, it is necessary to set the engine to a high rotation and high load. However, exhaust gas did not stop sufficiently during normal running, and the lean NOx catalyst could not be sufficiently regenerated. According to the present invention, as shown in FIG. 11, a sufficient reproduction effect can be obtained.

[0024]

As is apparent from the embodiments, according to the present invention, NOx, HC and CO discharged from the engine can be efficiently purified.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an example of an automobile internal combustion engine system to which the present invention is applied.

FIG. 2 is a block diagram of an automobile engine system control unit.

FIG. 3 is a configuration diagram of an exhaust gas heating heating element using a honeycomb-shaped resistor.

FIG. 4 is a configuration diagram of an exhaust gas heating heating element using a wire-shaped resistor.

FIG. 5 is a configuration diagram of a heating element for heating exhaust gas using an electromagnetic wave generator.

FIG. 6 is a flowchart showing control of a heating element when the engine load is low.

FIG. 7 is a flowchart showing control of a heating element during regeneration of a lean NOx catalyst at a traveling distance.

FIG. 8 is a flow chart showing control of a heating element during regeneration of a lean NOx catalyst at exhaust gas temperature.

FIG. 9 is a characteristic diagram showing a NOx purification rate in a stoichiometric combustion state.

FIG. 10 is a characteristic diagram showing an HC purification rate in a stoichiometric combustion state.

FIG. 11 is a characteristic diagram showing a catalyst regeneration effect in a lean NOx catalyst.

[Explanation of symbols]

1 ... Air cleaner, 2 ... Intake port, 3 ... Intake flow meter, 5 ...
Throttle valve, 8 ... Intake pipe, 9 ... Fuel tank, 10 ... Fuel pump, 11 ... Fuel damper, 12 ... Fuel filter, 13 ... Fuel injection valve, 15 ... Control unit, 16 ... Distributor, 18 ... Throttle sensor, 19 ... exhaust pipe, 20 ... exhaust gas purifying catalyst, 21 ... heating element, 22 ... exhaust temperature sensor.

Continued front page    (72) Inventor Kanji Kanji             2520 Takaba, Oita, Hitachinaka City, Ibaraki Prefecture             Vehicle equipment technology research association (72) Inventor Yuichi Kitahara             Hitachinaka City, Ibaraki Prefecture 2520 Takaba             Ceremony Company Hitachi Automotive Systems Division (72) Inventor Osamu Kuroda             Hitachinaka City, Ibaraki Prefecture 2520 Takaba             Ceremony Company Hitachi Automotive Systems Division (72) Inventor Ryota Doi             Hitachinaka City, Ibaraki Prefecture 2520 Takaba             Ceremony Company Hitachi Automotive Systems Division (72) Inventor Takeshi Inoue             2477 Takaba, Hitachinaka City, Ibaraki Prefecture Stock Association             Inside Hitachi Car Engineering (72) Inventor Toshifumi Hiratsuka             Hitachinaka City, Ibaraki Prefecture 2520 Takaba             Ceremony Company Hitachi Automotive Systems Division (72) Inventor Kojiro Okude             7-1-1, Omika-cho, Hitachi-shi, Ibaraki Prefecture             Inside the Hitachi Research Laboratory, Hitachi Ltd. F term (reference) 3G091 AA02 AA12 AA17 AA23 AB02                       AB03 AB05 BA01 BA04 BA11                       BA14 BA15 BA19 BA32 BA33                       CA03 CA05 CB02 CB05 DC01                       EA05 EA07 EA17 EA26 EA28                       EA30 EA31 EA34 EA38 FA14                       FB03 FB10 FB11 FB12 FC01                       FC06 GA06 GA09 GB01Z                       GB17Z HA08 HA12 HA36                       HB01

Claims (13)

[Claims] 1. An exhaust gas purifying apparatus for an internal combustion engine, comprising an exhaust gas purifying catalyst, wherein an exhaust gas heating apparatus is provided in an exhaust pipe upstream of the catalyst. 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein an electric heater is used as the heat source for heating the exhaust gas. 3. The exhaust gas purifying apparatus for an internal combustion engine according to claim 2, wherein a wire-shaped resistor such as a metal wire is used as the electric heater for heating the exhaust gas. 4. The exhaust gas purifying apparatus for an internal combustion engine according to claim 2, wherein a resistor having a repeated laminated structure such as a metal honeycomb is used as an electric heater for heating the exhaust gas. 5. The exhaust gas purifying apparatus for an internal combustion engine according to claim 2, wherein a ceramic heater is used as the electric heater for heating the exhaust gas. 6. The exhaust gas purifying apparatus for an internal combustion engine according to claim 2, wherein an electromagnetic wave generator is used as the electric heater for heating the exhaust gas. 7. An exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein the electric heater is controlled so as to operate when the exhaust gas temperature becomes equal to or lower than a catalyst activation temperature. 8. The exhaust gas purifying apparatus for an internal combustion engine according to claim 7, wherein the operating condition of the electric heater is controlled by the load condition of the internal combustion engine and the operating time. 9. An internal combustion engine according to any one of claims 1 to 6, characterized in that an electric heater is used when the exhaust gas is heated to a high temperature in order to remove poisoning substances of the catalyst. Exhaust gas purification device. 10. The exhaust gas purifying apparatus for an internal combustion engine according to claim 9, wherein the operating condition of the electric heater is determined by the traveling distance. 11. The exhaust gas purifying apparatus for an internal combustion engine according to claim 9, wherein an operating condition of the electric heater is set when the internal combustion engine has a high load. 12. An exhaust gas purification system for an internal combustion engine according to any one of claims 1 to 11, wherein a temperature sensor is arranged below the electric heater for the purpose of controlling the electric heater. apparatus. 13. The nitrogen oxide in the exhaust gas according to claim 1, wherein an internal combustion engine for an automobile is used as the internal combustion engine, and nitrogen oxides in the exhaust gas can be efficiently removed even in the presence of a three-way catalyst and oxygen as the catalyst. Catalyst (lean NOx catalyst),
An exhaust gas purification device using a catalyst that is one or a combination of catalysts (low temperature HC catalysts) that can efficiently purify unburned hydrocarbons in exhaust gas even when the exhaust gas temperature is low. Exhaust gas purification device for internal combustion engine.