JPS61197740A - Exhaust gas purifying device for diesel engine - Google Patents

Abstract

PURPOSE:To enable efficient purification of NOX in a condition to reduce fuel consumption and prevent decrease of an output, by a method wherein, when an air-fuel ratio is decided to be lean by means of an air-fuel ratio sensor, feedback control is performed so that the air-fuel ratio of exhaust gas forms a reduction air-fuel ratio. CONSTITUTION:When engine rotation, engine load, and a car speed, detected by an engine rotation sensor 42, an engine load sensor 44, and a car speed sensor 46, exceed their respective set values, a control valve 38 is forced into an opening state through an ECU 48. Fuel, injected from a surplus injection port 30E of a fuel injection pump 28 and stored in a storage tank 36, is injected to an exhaust system 12 through a control valve 38. A current fuel injection quantity controlled by the control valve 38 is decided so that, based on oxygen concentration information obtained by an O2 sensor 40, a fuel deficient amount causes an equivalent ratio of exhaust gas to be adjusted to about 1, and feedback control is effected. This enables an air-fuel ratio to be controlled to exhaust gas atmosphere under which a three-dimensional catalyst 22 can purity NOX most efficiently.

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention relates to an exhaust gas purification device for a diesel engine, and particularly relates to an exhaust gas purification device for a diesel engine that connects a three-way catalyst to an exhaust gas passage to purify C exhaust gas. . [Prior Art] A means for reducing NOx in the exhaust gas of a diesel engine, especially a diesel engine for automobiles, is so-called exhaust gas recirculation (hereinafter referred to as EGR), which recirculates a part of the exhaust gas to the engine intake system. There are various methods, such as those based on timing retard, those based on intake throttle, those based on lowering the injection rate or extending the injection period, and those using a combination of these.

[Problems to be solved by the invention]

However, these various NOx reduction means have problems in that they are accompanied by deterioration in fuel efficiency, reduction in output, deterioration in exhaust gas, and the like. Further, the EGR also has the problem of increasing other exhaust gases such as HC and Co, and causing wear and corrosion of various parts. Also, the intake throttle is as follows:
In addition to deterioration of fuel efficiency and output, there are also problems such as deterioration of noise. -h, the applicant is Japanese Patent Application Publication No. 58-72664, Japanese Patent Application Publication No. 58-72664,
8-72665 etc. as a NOx reduction device in exhaust gas C
1 By controlling the amount of EGR in the exhaust gas based on the oxygen concentration information from the 02 sensor installed in the exhaust manifold,
We propose a system that controls the air-fuel ratio by feedback 1BLJ to the set value.

[There is. However, according to the above proposal, 1 bl of EGR amount
The problem with J-control alone is that it is difficult to efficiently purify NOx in the exhaust gas in the high-speed, high-load range where there are many NOx-generating layers while minimizing the reduction in fuel consumption and output. OBJECTS OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and is capable of efficiently purifying NOx in exhaust gas while minimizing reductions in fuel consumption and output. It is an object of the present invention to provide an exhaust gas purification device for a diesel engine that can prevent an increase in other substances such as Co, HC, etc. and also prevent noise deterioration.

[Means to solve the problem]

The present invention provides a three-way catalyst □ disposed in an exhaust gas passage;
an air-fuel ratio sensor for exhaust gas disposed in the exhaust gas passage on the downstream side of the three-way catalyst; a fuel supply means for supplying fuel to the exhaust gas passage on the upstream side of the three-way catalyst; NO/multi-occurrence area detector that detects frequent operating areas;
When the NOx-rich region detection means is activated and the air-fuel ratio of the exhaust gas is determined to be lean by the air-fuel ratio sensor, the fuel supply means is activated so that the air-fuel ratio of the C1 exhaust gas becomes the reducing air-fuel ratio. The above object can be achieved by providing a feedback control means for controlling feedback I' so that the feedback I' is controlled. Further, in embodiment III of the present invention, the fuel supply means is a surplus injection boat of this summer □゛C using a single injection bonno with at least one more cylinders than the number of cylinders of the engine. , an injector distributed in the exhaust gas passage, a fuel pipe communicating with the injector and the above-mentioned jet boat, a storage tank disposed in the fuel pipe, and an I
By providing the IIJ control valve, the above objective i can be achieved without providing a separate C fuel injection cylinder. □

[Effect]

In the present invention, fuel is injected into the exhaust gas passage on the upstream side of the three-way catalyst, and the equivalence ratio (theoretical air-fuel ratio/actual air-fuel ratio) in an operating region with a large amount of NOx-soil is set to a sharp condition. By controlling the fuel supply stage in feedback mode and backing up the reducing air-fuel ratio by 9 degrees, it is possible to control the exhaust gas atmosphere to an atmosphere in which the three-way catalyst can purify NOx more efficiently than the three-way catalyst. Wear. Accordingly, it is possible to not only effectively reduce NOx while suppressing the reduction in fuel efficiency and output to a small extent, but also to prevent the increase in other exhaust gases such as O and noise, but also to reduce other exhaust gases and reduce noise. It is possible to reduce the In general, the normal running condition of a diesel engine is when the air-fuel ratio is about 25, which is lean C, and the condition where the equivalence ratio is large is the condition when the air-fuel ratio is about 17, which is in the high rotation/high load range C, where the amount of NOx generated is large. This refers to the case where the mixture becomes rich, and in this case, the equivalent ratio is 14.5/17-0.85.

【Example】

Embodiment □ of the exhaust gas purification device for a diesel engine according to the present invention will be described in detail below with reference to the drawings. The automotive diesel engine 10 of this embodiment includes a first
As shown in the figure, the exhaust system 12 and intake system 14 are passed through,
an exhaust gas recirculation passage (hereinafter referred to as an EGR passage) 16 that guides a portion of exhaust gas to the intake system 14;
An exhaust gas recirculation amount control valve (hereinafter referred to as an EGR valve) 18 is provided to control the effective passage area of C% and the flow rate of exhaust gas flowing through the EGR passage 16. The EGR valve 18 controls the effective passage area of the EGR passage 16 according to the negative pressure acting on its diaphragm chamber 18A, and the EGR valve 18 controls the effective passage area of the EGR passage 16 according to the negative pressure acting on its diaphragm chamber 18A. The control negative pressure is provided by adjusting the negative pressure generated by a negative pressure pump (not shown) with a pressure control valve. The control negative pressure generated by the pressure control valve C is controlled according to the output of a load sensor such as an accelerator sensor that detects the engine load and the output of a rotation sensor that detects the engine speed. The above is the same configuration as the conventional one, but in this example, C is
Furthermore, a three-way catalyst 22 disposed in the exhaust gas passage 120,
An exhaust gas air-fuel ratio sensor disposed in the exhaust gas passage 20 on the downstream side of the three-way catalyst 22;
A fuel supply means 24 that injects and supplies fuel to the exhaust gas passage 20 on the upstream side of the three-way catalyst 22, and a NOx high generation region detection means 2 that detects an operating region where a large amount of NOx is generated.
5, when the NOx high generation area detection means 25 is activated and the air-fuel ratio of the exhaust gas is determined to be lean by the 02 sensor 40, the fuel supply means 24 is activated and the NOx high generation area detection means 25 is activated.
A feedback control means 26 is provided for performing feedback control so that the air-fuel ratio of the exhaust gas becomes the reduced air-fuel ratio. The fuel supply means 24 is 0, and the fuel injection pump 28 for the number of cylinders one more than the number of cylinders of the engine 10, that is, the fuel injection pump 28 having injection ports 30A-E is used in the engine 10. Extra injection port 30E
, an injector 32 disposed in the exhaust gas passage 20 , the injector 32 and the surplus injection port 3
A fuel vibe 34E communicating with 0E and the fuel pipe/3
It is composed of a storage tank 36 and a control valve 38 arranged at 4E. In addition, the injection boats 30A-D are fuel pi/3
It is connected to the injection nozzle 50 of the engine 10 via 4A-E. The NOx high generation area detection means 25 includes an engine rotation sensor 42 that detects engine rotation, an engine load sensor 44 that detects engine load, and a vehicle speed sensor 46 that detects vehicle speed, and detects signals obtained by these sensors. It is comprised of an electronic control unit (hereinafter referred to as ECtJ) 48 that determines an operating region in which a lot of NOx occurs based on the above-mentioned information and performs C detection. The feedback control means 26 includes an 02 sensor 4o provided in the exhaust gas passage 20 downstream of the three-way catalyst 22;
An ECU 48 is configured to detect the air-fuel ratio of the exhaust gas based on the oxygen concentration information from the 02 sensor 40, and feedback-control the fuel supply means 24 so that the air-fuel ratio becomes around the equivalent ratio 1. As shown in FIG. 2, when the engine speed and the upper engine load are both higher than the set value, and the vehicle speed is in the range higher than the set value (shaded area in the figure), the ECU 48 controls the fuel flow. The control valve 38 of the supply means 24 is controlled to be in an open state. Further, the adjustment of the fuel injection amount in the control valve 38 is determined by the amount of insufficient fuel measured by the front 1aoz sensor 40r, and the ECLI 48 is feedback-controlled so that the equivalence ratio of exhaust gas is always around 1. Next, the operation of this embodiment will be explained. When the upper engine rotation speed, upper engine load, and vehicle speed each reach the set values, the control valve 38 is opened via the ECLJ 48, and fuel is injected from the excess injection port 30E of the fuel injection cylinder 28 and stored in the storage tank 36. Fuel is injected into the exhaust system 12 via the control valve 38. The amount of fuel injected by the control valve 38 at this time is feedback-controlled so that the amount of insufficient fuel τ is determined to make the equivalence ratio of exhaust gas near 1 based on the oxygen concentration information obtained from the 02 sensor 40'C. Under these operating conditions, since the exhaust gas temperature is high, a sufficient catalytic reaction temperature is ensured, and the ambient temperature is also sufficient for oxygen concentration detection by the O2 sensor. Therefore, when τ, the exhaust gas atmosphere can be controlled to an atmosphere in which the three-way catalyst 22 can purify NOx most efficiently. As a result, NOx can be effectively reduced while minimizing fuel consumption and output reduction. Incidentally, in order to explain the configuration in an easy-to-understand manner, the exhaust system is shown in Figure 1. Therefore, in implementing the present invention, in order to improve the performance of the three-way catalyst 22 and the O2 sensor 40, it is desirable to arrange the three-way catalyst 22 and the O2 sensor 40 as close as possible to the exhaust manifold 13 side. . In addition, considering the durability of the injector 32 due to heat, it is possible to change the type of injector 32 from direct mounting to indirect mounting with 7 lunges, or adding a fuel pipe. In this example, in order to eliminate sudden start and sudden acceleration conditions, in addition to the conditions in which the number of revolutions per lunge and the engine load exceed the set values, a condition in which the vehicle speed exceeds the set value is added. However, the present invention is not limited to this, and the condition that the vehicle speed is equal to or higher than the set value may be removed. That is, the vehicle speed setting is not necessarily a necessary condition for the operation of the control valve 38. Moreover, the injector 32
There are types that simply turn on and off, tights that have a needle valve to widen the spray angle, and tights that are used in the electronically controlled fuel injection system of gasoline engines and whose injection amount is determined by the energization time of the C tie/ECU. In this case, the control valve 38 may be a simple on-off tie/ll'', etc. In addition, if the upper engine to which the present invention is applied has two cylinders, the fuel injection pump 28 may have three to four cylinders. The fuel injection pump for cylinders will be used; in the case of a 3-cylinder engine, the fuel injection pump for 4 to 6 cylinders will be used, and in the case of a 4-cylinder engine, the fuel injection pump for 5 to 8 cylinders will be used. Therefore, it is possible to easily implement the present invention by changing the gas distributor head, cam face, etc.The fuel injection bong/28 is different from the one in the above embodiment. Although the fuel injection pump of an engine with a larger number of cylinders than the engine concerned is used, the present invention is not limited to this, and other dedicated pumps etc. may be used.
C is also good. [Effects of the Invention] As explained above, according to the present invention, fuel is injected only in areas where NOx emissions are high in the high rotation/high load range, reducing NOx in C exhaust gas and effectively reducing NOx. In addition, excellent effects such as minimizing the reduction in fuel consumption and output due to NOx reduction, ensuring the durability of each part of the engine, and preventing deterioration of noise are achieved.

[Brief explanation of drawings]

FIG. 1 is a pipe diagram including a partially cutaway diagram and a block diagram showing the configuration of an embodiment of the exhaust gas purification device for a diesel engine according to the present invention, and FIG. 2 is a control valve of the same embodiment. There is an engine speed/load diagram showing the operating range of the engine. 1;, O...engine, 16...exhaust gas recirculation (EGR) passage, 20...
Exhaust gas passage, 22... Three-way catalyst, 24... Fuel supply means, 26... Feedback control means, 28... Fuel injection pump, 32... Injector,
40...02 sensor, 48...electronic control unit (ECLJ).

Claims (2)

[Claims] (1) A three-way catalyst disposed in the exhaust gas passage, an exhaust gas air-fuel ratio sensor disposed in the exhaust gas passage downstream of the three-way catalyst, and an exhaust gas upstream of the three-way catalyst. a fuel supply means for supplying fuel to the passage; a NO_x high generation region detection means for detecting an operating region in which a large amount of NO_x is generated;
When the O_x frequent occurrence region detection means is activated and the air-fuel ratio of the exhaust gas is determined to be lean by the air-fuel ratio sensor, the fuel supply means is activated so that the air-fuel ratio of the exhaust gas becomes a reduced air-fuel ratio. An exhaust gas purification device for a diesel engine, comprising: a feedback control means for performing feedback control. (2) The fuel supply means includes a redundant injection port of a fuel injection pump for a cylinder number at least one more than the number of cylinders of the engine, an injector disposed in an exhaust gas passage, the injector and the redundant injection port. 2. The exhaust gas purification device for a diesel engine according to claim 1, comprising a fuel pipe communicating with the fuel pipe, and a storage tank and a control valve disposed in the fuel pipe.