JP2001152842A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress rotating variation making ignition timing, injection timing, and torque generating in each cylinder using EGR coincide, and to enhance operativeness by in an engine in which an air/fuel ratio different each cylinder is set. SOLUTION: An EGR passage is installed independently in a lean operation cylinder and a rich operation cylinder, and EGR, ignition timing, and injection timing are controlled so as to evaluate rotation variations, based on data from a rotating sensor for measuring a rotating signal of the engine and reduce the rotating variation, and the workability of the engine is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine in which the air-fuel ratio of some of the cylinders is made lean and the other cylinders are operated under rich conditions in order to reduce the regulated components in the exhaust gas. The present invention relates to an exhaust gas purification device for an engine.

[0002]

2. Description of the Related Art Laws and regulations on fuel efficiency and exhaust gas of automobiles are becoming stricter year by year in each country. Conventionally NO
In order to increase the purification efficiency when purifying x, CO and HC with the three-way catalyst, the fuel injection rate is controlled with respect to the respective air amount so that the air-fuel ratio approaches the ideal air-fuel ratio (14.7) as much as possible. Technology has been developed. In order to improve fuel economy, many methods have been developed to reduce the pump loss by making the air-fuel ratio lean. However, in these methods, when a three-way catalyst is used, in particular, the NOx purification rate is significantly reduced.

Japanese Patent Application Laid-Open No. 4-365920 discloses a control system in which, for example, in a four-cylinder engine, three cylinders are operated lean, and the other one is operated slightly richer than the ideal air-fuel ratio. In this method, the exhaust of the cylinder operating in a rich manner passes through the ammonia generation catalyst, and the generated ammonia and NOx generated from the cylinder in the lean operation act on the denitration catalyst to reduce the NOx emission amount. Further, since the engine is operated in the lean region on average, it is possible to purify exhaust gas without substantially deteriorating fuel efficiency.

[0004]

SUMMARY OF THE INVENTION
In the system of 4-365920, the same engine mixes lean and rich cylinders, resulting in different torques for each cylinder, resulting in surge torque and rotational fluctuation, resulting in poor drivability. There is. Even under normal operating conditions in which the same control is applied to all cylinders to make the air-fuel ratio equal, the injection system, ignition system, or combustion differs slightly for each cylinder, causing a difference in the generated torque between cylinders. It causes rotation fluctuation. For this reason, in order to ensure drivability, the characteristics of the fuel injection device are determined in advance and corrected for each cylinder so that the air-fuel ratios of all cylinders match, or the air-fuel ratio is determined for each cylinder and feedback control is performed. Is used. In engines with different air-fuel ratios for each cylinder, suppression of surge torque and rotation fluctuation is an indispensable technology.

An object of the present invention is to provide an exhaust gas purifying apparatus for an internal combustion engine which suppresses rotational fluctuations and improves operability in an engine having a mixture of a lean cylinder and a rich cylinder.

[0006]

According to the present invention, the above object is attained by employing any of the following means.

A first invention is an engine having a plurality of cylinders, in which the intake manifold and the exhaust manifold are separated into those for some cylinders and those for other cylinders. This can be achieved by an exhaust gas purification device for an internal combustion engine, wherein a passage through which exhaust gas circulates is provided in the intake manifold.

The second invention is an engine having a plurality of cylinders, in which the intake manifold and the exhaust manifold are separated into those for some cylinders and those for other cylinders, and means for detecting in-cylinder pressure, This can be achieved by an exhaust gas purification device for an internal combustion engine having means for calculating the torque generated by each cylinder from the internal pressure signal for each cylinder, and controlling the combustion state of the engine based on the evaluation index.

A third aspect of the present invention is an engine having a plurality of cylinders, in which an intake manifold and an exhaust manifold are separated into one for some cylinders and another for other cylinders, and means for detecting rotation of a crankshaft; The exhaust gas purifying apparatus for an internal combustion engine has means for calculating a fluctuation in torque generated by the engine from the rotation signal thus obtained, and controls a combustion state of the engine based on the evaluation index.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an exhaust gas purifying apparatus for an internal combustion engine according to the present invention will be described in detail with reference to the drawings. FIG. 1 shows a configuration in which the present invention is applied to a four-cylinder engine 11 in one embodiment of the present invention. The intake manifold and the exhaust manifold are separated from the three cylinders from the first cylinder to the third cylinder and the fourth cylinder. The intake / exhaust manifold for the fourth cylinder has a passage 12 for recirculating exhaust gas to the intake manifold.
Adjust with valve 13. The EGR valve is driven by the EGR valve drive circuit 14. On the exhaust side of the fourth cylinder, there is a catalyst 15 that produces ammonia when operated under conditions slightly richer than the ideal air-fuel ratio, and further there is a denitration catalyst 16 downstream where exhaust from all cylinders is collected.

An ignition device 17 and an injection device 18 are provided in each cylinder, and are driven by an ignition device drive circuit 19 and an injection device drive circuit 20, respectively. The throttle valves 21 are provided in the respective intake manifolds, and are driven by a throttle drive circuit 22. A rotation sensor 23 is provided on the crankshaft of the engine, and an oxygen sensor 2 is provided on the exhaust side of the fourth cylinder.
4, which is an input of the arithmetic unit 25. JP
According to the method of 4-365920, the arithmetic unit operates such that the air-fuel ratio from the first cylinder to the third cylinder (hereinafter, referred to as lean cylinder) is lean, and the fourth cylinder (hereinafter, referred to as rich cylinder) becomes slightly rich. And outputs a signal for controlling the throttle valve and the injection device. This makes it possible to purify exhaust gas while preventing deterioration of fuel efficiency, but causes a problem of engine rotation fluctuation caused by a difference in air-fuel ratio between cylinders. FIG. 2 shows an example in which a passage for recirculating exhaust gas is provided in the intake and exhaust manifolds for the first to third cylinders.
At this time, the rotation sensor detects a rotation fluctuation caused by a difference in generated torque between the cylinders, and an ignition device,
The injection device and the EGR valve are controlled. Although the injection device is arranged in the intake pipe in FIGS. 1 and 2, the method of the present invention can be similarly applied even if it is arranged in the cylinder.

If the ignition timing of the rich cylinder or the lean cylinder is appropriately adjusted and the magnitude of the generated torque of each cylinder is made uniform, the rotational fluctuation can be suppressed to an allowable range as shown in FIG. FIG. 4 shows a flowchart of a process for suppressing the rotation fluctuation using the ignition device. Since the relationship between the rotation fluctuation and the ignition timing is not monotonous, a method of adjusting the ignition timing in a direction in which the rotation fluctuation decreases is employed. This process is started when the rotation fluctuation of the engine exceeds the allowable range. In step 41, the change width of the ignition timing is set to 1 degree. The rotation fluctuation is calculated from the rotation sensor, and if the rotation fluctuation is within the allowable range in step 42, this processing ends. If not, the ignition timing is advanced once. In step 43, when there is almost no change in the rotation fluctuation even if the ignition timing is advanced, even if the rotation fluctuation is equal to or more than the allowable value, it is determined that the ignition timing control has no effect, and the process is ended. In this case, the rotation fluctuation is reduced by another method described later. In step 44, if the rotation timing increases as a result of advancing the ignition timing, the range of change of the ignition timing is set to -1.
The ignition timing is delayed from the next time. The torque of each cylinder can be adjusted not only by the ignition timing but also by the injection timing, and the injection timing has the same relationship as in FIG.
Therefore, the method of adjusting the injection timing can be performed by the same processing as that in FIG.

If EGR (Exhaust Gas Recirculation) for recirculating exhaust gas to the intake manifold is applied to a rich cylinder or a lean cylinder in the configuration shown in FIGS. 1 and 2, it can be used as a means for adjusting rotation fluctuation. When the EGR valve is opened, exhaust gas flows into the cylinder in addition to air, the combustion state of the cylinder changes, and the generated torque also changes. Therefore, if an appropriate EGR valve opening is selected as shown in FIG. 5, the torque generated by each cylinder becomes substantially the same, and the rotation fluctuation becomes less than the allowable value. FIG. 6 is a flowchart describing a method of adjusting the EGR valve, and moves the EGR valve in a direction in which the rotational fluctuation decreases, similarly to the method of adjusting the ignition timing. This process is started when the rotation fluctuation becomes equal to or more than the allowable value M, and in step 51, the width of one change of the EGR valve is set to 1 degree.
In step 52, the rotation fluctuation is evaluated. If the rotation fluctuation is equal to or smaller than the allowable range M, the processing is stopped. Otherwise, the processing is continued. In step 53, the EGR valve is opened by the previously set change width. If the set width is negative and the EGR valve is already fully closed, it cannot be closed any more, so the process is stopped in step 54.
Further, if there is almost no change in the rotation fluctuation after the EGR valve is moved, even if it is moved further, there is a possibility that the combustion may be deteriorated, and the process ends in step 55. In step 56, when the EGR valve is opened (closed) by the set amount and the rotational fluctuation has increased as compared to before, the set amount is set in the opposite direction. These processes are repeated until the rotation fluctuation becomes equal to or smaller than the allowable value.

The above-mentioned method is a method of detecting rotation fluctuation by a rotation sensor attached to a crankshaft of an engine. As shown in FIG. 7, each cylinder is generated by an in-cylinder pressure sensor 26 provided for each cylinder. A method of directly measuring the applied torque is also possible. In this case, ignition, injection, EG
By using R to equalize the torque of each cylinder, rotation fluctuations are reduced.

FIG. 8 is a conceptual diagram showing a method of adjusting the ignition timing and the injection timing when the system of the present invention is applied to an engine having an injection device installed in a cylinder. In a rich cylinder, fuel is injected in an intake stroke, whereas in a lean cylinder, fuel is injected in a compression stroke. As shown in FIG. 8A, the ignition timing is set for each of the rich cylinder and the lean cylinder, but the torque of each cylinder may be different. Therefore, first, the ignition timing is adjusted for each cylinder so that the torques are matched as much as possible, and the remaining torque variation is controlled by controlling the injection timing for each cylinder as shown in FIG. This method is different from the method of measuring rotation fluctuations by a rotation sensor, and has the advantage that a cylinder with insufficient or excessive torque can be directly detected and the torque of that cylinder can be adjusted.

FIG. 9 is a flowchart illustrating this method. This process is started when the rotation fluctuation exceeds the allowable range. Step 91 and step 92
Thus, the torque adjustment starts from the first cylinder and adjusts all four cylinders. In step 93, the torque of each cylinder is calculated based on the in-cylinder pressure sensor of each cylinder. Subsequently, in step 94, the average value of the torque generated by each cylinder is determined. When the difference between the torque of the i-th cylinder in question at present and the previously obtained average torque is smaller than a predetermined value, the process proceeds to step 95 at the next cylinder. If not, the ignition timing is adjusted in step 96 and further in step 97
Then, the injection timing is adjusted. When the torque adjustment of the i-th cylinder is completed, the next cylinder is processed in step 98.

FIG. 10 shows a method of adjusting the ignition timing in the process of FIG. The adjustment of the injection timing can be performed by the same processing. In step 101, the change width for adjusting the ignition timing in one process is set to 1 degree. If the difference between the average torque of each cylinder and the torque of the corresponding cylinder is smaller than a predetermined value in step 102, the process ends. In step 103, the ignition timing is changed by the previously set value. As a result, if the changed torque is equal to or less than the predetermined value, the effect of the torque adjustment is hardly obtained under this condition. Otherwise, in step 105, the difference between the average torque of each cylinder and the torque of the i-th cylinder in question is evaluated. If the difference is increased by the current ignition timing adjustment, the direction of adjustment in step 106 is changed. Invert.

[0018]

According to the present invention, in an engine in which the air-fuel ratio is changed for each cylinder, the ignition timing, the injection timing, and the opening of the EGR valve are adjusted for each cylinder so that the torque generated by each cylinder is matched, and the torque of the engine is adjusted. Fluctuations and rotation fluctuations can be suppressed. This is also effective in improving fuel efficiency. These effects are also effective against individual differences and aging of engines and cylinders.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example in which an exhaust gas recirculation passage is provided in a rich cylinder in an embodiment of an engine exhaust gas purification apparatus according to the present invention.

FIG. 2 is a block diagram showing an example in which an exhaust recirculation passage is provided in a rich cylinder.

FIG. 3 is a graph showing a relationship between ignition timing and rotation fluctuation.

FIG. 4 is a flowchart illustrating a procedure for suppressing rotation fluctuations according to ignition timing.

FIG. 5 is a graph showing a relationship between EGR and rotation fluctuation.

FIG. 6 is a flowchart illustrating a procedure for suppressing rotation fluctuation by EGR.

FIG. 7 shows an embodiment of the present invention in which an in-cylinder pressure sensor is provided in each cylinder.

FIG. 8 is a conceptual diagram showing a torque adjustment method based on ignition timing and injection timing.

FIG. 9 is a flowchart illustrating a procedure of a torque adjustment method based on an in-cylinder pressure sensor.

FIG. 10 is a flowchart illustrating a procedure of a torque adjustment method based on ignition timing.

[Explanation of symbols]

11 ... engine, 12 ... recirculation passage, 13 ... EGR valve, 1
4: EGR valve drive circuit, 15: catalyst, 16: denitration catalyst,
17: ignition device, 18: injection device, 19: ignition device drive circuit, 20: injection device drive circuit, 21: throttle valve,
22 ... Throttle drive circuit, 23 ... Rotation sensor, 24 ...
Oxygen sensor, 25: arithmetic unit, 26: in-cylinder pressure sensor.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 41/02 301 F02D 41/02 301E 41/34 41/34 E 43/00 301 43/00 301B 301K 301H 301J 301N 45/00 368 45/00 368S F02M 25/07 550 F02M 25/07 550R 580 580B (72) Inventor Hiroshi Kimura 7-1-1, Omikacho, Hitachi City, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Shinji Nakagawa 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Research Laboratory Co., Ltd. (72) Inventor Youichi Iiboshi 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. (72) Inventor Shiro Yamaoka 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi, Ltd.Hitachi Research Laboratory (Reference) 3G062 AA06 BA05 BA08 ED10 ED11 GA04 GA05 GA06 GA15 GA18 GA21 GA26 3G084 BA05 BA13 BA15 BA17 BA20 DA11 DA22 FA21 FA33 FA38 3G091 AA02 AA11 AA12 AA13 AA13 AB14 AB CB02 CB03 CB05 CB07 DB10 DB13 EA01 EA12 EA31 EA34 FB10 FB11 FB12 HA01 HA08 HA36 HB02 HB03 HB05 3G092 AA01 AA05 AA09 AA13 AA17 BA09 BB01 BB06 DC02 DC03 DC09 DC14 DC15 DF01 FA02X05 FA01X02 3G301 HA13 HA18 JA04 JA15 LA00 LA01 MA01 MA11 MA18 PC01Z PE01Z PE02Z PE03Z

Claims (7)

[Claims] In an engine having a plurality of cylinders, an intake manifold and an exhaust manifold are separated into those for some cylinders and those for other cylinders, and for some cylinders, an exhaust manifold is changed from an intake manifold to an intake manifold. An exhaust gas purification device for an internal combustion engine, comprising a passage through which exhaust gas flows. 2. An engine having a plurality of cylinders, wherein an intake manifold and an exhaust manifold are separated into those for some cylinders and those for other cylinders, and means for detecting an in-cylinder pressure; An exhaust purification system for an internal combustion engine, comprising: means for evaluating the torque generated by each cylinder for each cylinder, and controlling the combustion state of the engine based on the evaluation index. 3. An engine having a plurality of cylinders, wherein an intake manifold and an exhaust manifold are separated into one for some cylinders and another for other cylinders, and means for detecting rotation of a crankshaft; An exhaust purification device for an internal combustion engine, comprising: means for evaluating a change in torque generated by an engine from the engine, and controlling a combustion state of the engine based on the evaluation index. 4. The engine according to claim 1, further comprising: means for detecting an in-cylinder pressure; and means for evaluating a torque generated by each cylinder from the detected in-cylinder pressure signal for each cylinder. An exhaust gas purifying apparatus for an internal combustion engine, comprising: 5. The engine according to claim 1, further comprising: means for detecting rotation of the crankshaft; and means for evaluating a change in torque generated by the engine based on the detected rotation signal. An exhaust gas purifying apparatus for an internal combustion engine, comprising: 6. An exhaust purification system for an internal combustion engine according to claim 2, wherein a variation of an evaluation index for each cylinder is controlled to a predetermined value or less by controlling a throttle valve, an exhaust ring flow rate, an ignition timing, an injection timing, and an injection amount. apparatus. 7. The throttle valve according to claim 3, wherein
An exhaust gas purification device for an internal combustion engine that controls an exhaust flow rate, an ignition timing, an injection timing, and an injection amount to set an evaluation index to a predetermined value or less.