JPH0742626A - Exhaust gas feedback device for diesel engine - Google Patents

Abstract

(57) [Summary] [Purpose] Even if the operating conditions change, the distribution characteristics of recirculated exhaust gas are not deteriorated, and a uniform exhaust gas recirculation rate is always ensured in each cylinder. Prevent the deterioration. [Structure] An exhaust gas recirculation passage 12 is joined to a central portion of an intake collector 1 to which an intake branch portion 2 of each cylinder is connected, and an exhaust guide portion 11 is provided at a tip end portion thereof. The exhaust guide portion 11 has a first exhaust outlet 13 at the tip and a pair of second exhaust outlets 14 directed to both sides, and the exhaust guide portion 1
1, a flow path control valve 1 for controlling the flow rate ratio of both
5 are provided. The opening degree of the flow path control valve 15 is controlled by a predetermined map based on the engine load and the rotation speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of an exhaust gas recirculation system for a diesel engine.

[0002]

2. Description of the Related Art In an exhaust gas recirculation system for a multi-cylinder internal combustion engine, in addition to the structure in which recirculation exhaust gas is individually introduced into each cylinder, the tip of the exhaust gas recirculation passage is joined to an appropriate position of the intake collector so as to A configuration may be adopted in which exhaust gas is distributed to each cylinder. For example, JP-A-62-12955
Japanese Unexamined Patent Publication No. 8 discloses a configuration in which the tip of the exhaust gas recirculation passage is joined to the collecting portion of the intake manifold and is distributed to each branch portion together with the intake air flow.

[0003]

In the structure in which the recirculated exhaust gas is distributed and supplied to the branch portion of each cylinder as described above, the direction of the exhaust outlet provided at the confluent portion at the tip of the exhaust gas recirculation passage is devised. The exhaust amount distributed to each cylinder is kept as uniform as possible.

However, in a vehicle such as a diesel engine for automobiles, which has various operating conditions, the flow rate and flow velocity of the recirculated exhaust gas vary depending on the operating conditions.
Stable distribution characteristics cannot be obtained under each operating condition.

As a result, the actual exhaust gas recirculation rate of each cylinder may fluctuate widely around the target exhaust gas recirculation rate as shown in FIG. 10, and as a result, the exhaust particulate emission amount (average emission amount of each cylinder). However, there is a drawback that the amount becomes larger than the set emission amount corresponding to the target exhaust gas recirculation rate.

[0006]

Therefore, according to the present invention, the front end of the exhaust gas recirculation passage is joined to an appropriate position of the intake collector formed by connecting the intake branch portion of each cylinder, and the exhaust gas is exhausted to each cylinder in the collector. In an exhaust gas recirculation device for a diesel engine configured to distribute, an exhaust gas recirculation unit having a plurality of exhaust gas outlets each directed in a predetermined direction is provided at an exhaust gas recirculation passage leading end part joined in an intake air collector,
A flow control valve for variably controlling the flow rate from each exhaust outlet is arranged in the exhaust guide portion.

The flow path control valve is used, for example, for engine operating conditions,
It is controlled based on the intake temperature at a plurality of positions downstream of the intake collector, the exhaust temperatures of a plurality of cylinders, the in-cylinder pressure of a plurality of cylinders, and the like.

[0008]

The recirculated exhaust gas that merges from the exhaust gas recirculation passage into the intake collector flows in a plurality of directions through the plurality of exhaust outlets of the exhaust guide portion, and is sucked into the cylinders from the intake branch portion together with fresh air. It The flow rate ratio of the exhaust gas flowing out from each exhaust outlet is controlled by the flow passage control valve so that it is evenly distributed to each cylinder.

If the distribution of the recirculated exhaust gas becomes uneven, the intake air temperature toward each cylinder, the exhaust gas temperature from each cylinder, or the cylinder pressure of each cylinder fluctuates according to the change of the exhaust gas recirculation rate. By controlling the flow passage control valve, the exhaust gas recirculation rate of each cylinder becomes equal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a portion of a first embodiment of an exhaust gas recirculation system according to the present invention, which is a portion that joins with an intake system. In the figure, reference numeral 1 denotes an intake collector having a long and narrow box shape along the cylinder row direction, and a plurality of intake branch portions 2 corresponding to each cylinder are connected to the lower surface thereof. This embodiment is an example of an in-line 6-cylinder engine, and is provided with six intake branch portions 2 corresponding to the # 1 to # 6 cylinders.
A flat seat portion 3 is formed between the lower surface of the central portion of the intake collector 1, that is, between the intake branch portion 2 of the # 3 cylinder and the intake branch portion 2 of the # 4 cylinder, and a communication hole 4 is formed in the central portion. Is formed with an opening. The flange 6 at the tip of the exhaust gas recirculation tube 5 is fixed to the outer side surface of the seat portion 3 by a pair of bolts 7 and nuts 8, and the flange 10 of the exhaust passage 9 is attached to the inner surface of the seat portion 3 by the bolt 7 described above. , And nuts 8 together.

The exhaust passage 9 has a cylindrical exhaust guide portion 11 having a diameter substantially equal to that of the recirculation exhaust tube 5, and together with the communication hole 4 and the exhaust recirculation tube 5 constitutes an exhaust recirculation passage 12. The exhaust guide portion 11 is
The tip is opened as a first exhaust outlet 13, and the first exhaust outlet 13 is formed substantially perpendicular to the flange 10 so as to face the upper wall surface of the intake collector 1. Further, the intake collector 1 is provided on the lower side surface of the exhaust guide portion 11, respectively.
Pair of second exhaust outlets 14 opening in the longitudinal direction of the
Is provided. A butterfly valve type flow path control valve 15 is disposed between the first exhaust outlet 13 and the second exhaust outlet 14 in the exhaust guide portion 11. The opening degree of the flow path control valve 15 is controlled by an actuator such as a motor or a solenoid (not shown).

FIG. 2 shows an outline of a control system for the flow path control valve 15. As an engine operating condition detecting means, a rotation speed sensor 16 for detecting an engine rotation speed, and a fuel injection corresponding to the load of the engine. It has a lever opening sensor 17 for detecting the control lever opening of the pump, and these detection signals are inputted to the control unit 18. The control unit 18 is based on these detection signals,
With reference to the control map as shown in FIG. 3, the flow path control valve 15 is switch-controlled to three positions of fully open, half open and fully closed.

Next, the operation of the above embodiment will be described.

When the flow path control valve 15 is fully opened, as shown in FIG. 4, the flow rate ratio of the first exhaust outlet 13 at the tip is large and the flow rate ratio of the second exhaust outlet 14 is small. On the other hand, when the flow control valve 15 is fully closed, as shown in FIG.
As shown in, the flow rate ratio of the first exhaust outlet 13 is small,
Moreover, the flow rate ratio of the second exhaust outlet 14 increases.

FIG. 6 shows the actual exhaust gas recirculation rate of each cylinder. When the engine speed is low, as indicated by the solid line B,
A uniform exhaust gas recirculation rate can be obtained in each cylinder while the flow passage control valve 15 is fully opened. That is, the recirculated exhaust gas is distributed well. However, if the flow path control valve 15 is kept fully open when the engine is running at high speed, it is close to the exhaust guide section 11 as indicated by the solid line B.
Exhaust gas recirculation rate increases in 3 cylinders and # 4 cylinders,
The exhaust gas recirculation rate becomes low in the # 1 and # 6 cylinders. On the other hand, if the flow path control valve 15 is closed when the engine is running at high speed, the second exhaust outlet 1
Since the flow rate ratio of No. 4 increases, a uniform exhaust gas recirculation rate is obtained in each cylinder as indicated by the broken line C. In the medium speed range, when the flow path control valve 15 is fully opened, the deviation of the exhaust gas, which is weaker than the solid line B, occurs. Therefore, by opening the flow path control valve 15 halfway, a uniform exhaust gas recirculation rate can be obtained. Therefore, by controlling the flow path control valve 15 with the characteristics shown in FIG. 3, it is possible to constantly reduce the variation in the exhaust gas recirculation rate and prevent an increase in the exhaust particulate discharge amount.

Next, FIG. 7 shows a second embodiment of the present invention. In this embodiment, an intake air temperature sensor 21 is provided in each of the intake branch portions 2 of the # 1 cylinder and the # 3 cylinder in which the variation of the exhaust gas recirculation rate becomes remarkable due to the change of the exhaust gas flow rate and the like. The opening degree of the flow path control valve 15 is controlled by a control unit (not shown) so that the temperatures detected by the intake air temperature sensors 21 match each other.

That is, since the temperature of the exhaust gas introduced through the exhaust gas recirculation passage 12 is higher than the temperature of the fresh air introduced from the outside, the intake air temperature rises if the exhaust gas recirculation rate is relatively high, and conversely If the reflux rate is relatively low, the intake air temperature will drop. Therefore, by controlling the opening degree of the flow path control valve 15 so that the intake air temperatures of the # 1 cylinder and the # 3 cylinder are kept the same, as a result, the exhaust gas recirculation rate of each cylinder is kept uniform. .

Next, FIG. 8 shows a third embodiment of the present invention. In this embodiment, an exhaust temperature sensor 23 is provided in each of the exhaust pipes 22 of the # 1 cylinder and the # 3 cylinder. Then, the opening degree of the flow path control valve 15 is controlled by a control unit (not shown) so that the temperatures detected by the two exhaust gas temperature sensors 23 coincide with each other.

That is, when the exhaust gas recirculation rate differs between the cylinders, the combustion state changes, so that the exhaust gas temperature varies.
Therefore, by controlling the opening degree of the flow path control valve 15 so that the exhaust temperatures of the # 1 cylinder and the # 3 cylinder are kept the same, the exhaust gas recirculation rate of each cylinder is consequently kept the same. .

Next, FIG. 9 shows a fourth embodiment of the present invention. In this embodiment, in-cylinder pressure sensors 25 for detecting the in-cylinder pressure are arranged in the combustion chambers of the # 1 cylinder and the # 3 cylinder, specifically, in the swirl chamber 24. And
The opening degree of the flow path control valve 15 is controlled by a control unit (not shown) so that the maximum values of the in-cylinder pressures of both cylinders match each other.

That is, when the exhaust gas recirculation rate is different between the cylinders, the composition of the working gas is different, and the specific heat ratios thereof are also different, so that the maximum value of the in-cylinder pressure is different. Therefore,
By controlling the opening degree of the flow path control valve 15 so that the maximum cylinder pressures of the # 1 cylinder and the # 3 cylinder are kept the same, as a result, the exhaust gas recirculation rate of each cylinder is kept the same. is there.

[0023]

As is apparent from the above description, according to the exhaust gas recirculation system for a diesel engine of the present invention, the variation in the exhaust gas recirculation rate between the cylinders can be suppressed to be extremely small under various operating conditions. It is possible to prevent deterioration of exhaust particulate emission of the entire engine due to the above.

[Brief description of drawings]

FIG. 1 is a partially cutaway sectional view showing a first embodiment of an exhaust gas recirculation device according to the present invention.

FIG. 2 is a block diagram showing an outline of a control system of a flow path control valve.

FIG. 3 is a characteristic diagram showing characteristics of a control map of a flow path control valve.

FIG. 4 is an explanatory diagram showing the flow of exhaust gas when the flow path control valve is open.

FIG. 5 is an explanatory diagram showing the flow of exhaust gas when the flow path control valve is closed.

FIG. 6 is a characteristic diagram showing the exhaust gas recirculation rate of each cylinder.

FIG. 7 is a partially cutaway sectional view showing a second embodiment of the present invention.

FIG. 8 is a partially cutaway sectional view showing a third embodiment of the present invention.

FIG. 9 is a partially cutaway sectional view showing a fourth embodiment of the present invention.

FIG. 10 is a characteristic diagram showing a relationship between a variation in exhaust gas recirculation rate between cylinders and an exhaust particle emission amount in the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Intake collector 11 ... Exhaust guide part 12 ... Exhaust gas recirculation passage 13 ... First exhaust outlet 14 ... Second exhaust outlet 15 ... Flow path control valve 16 ... Rotation speed sensor 17 ... Lever opening sensor 18 ... Control unit 21 ... Intake Temperature sensor 23 ... Exhaust temperature sensor 25 ... In-cylinder pressure sensor

Claims (5)

[Claims] 1. A diesel engine constructed so that the front end of an exhaust gas recirculation passage is joined to an appropriate position of an intake collector to which an intake branch portion of each cylinder is connected, and the exhaust gas is distributed to each cylinder in the collector. In the exhaust gas recirculation device, an exhaust gas guide portion having a plurality of exhaust gas outlets each directed in a predetermined direction is provided at the front end portion of the exhaust gas recirculation passage joined in the intake air collector, and the flow rate from each exhaust gas outlet is provided in the exhaust gas guide portion. An exhaust gas recirculation device for a diesel engine, comprising a flow path control valve for variably controlling the ratio. 2. A means for detecting an operating condition of the engine,
The exhaust gas recirculation device for a diesel engine according to claim 1, wherein the flow path control valve is controlled in accordance with the engine operating condition. 3. The diesel engine according to claim 1, wherein intake passage temperature sensors are provided at a plurality of positions downstream of the intake collector, and the flow path control valve is controlled based on the intake air temperatures at the plurality of positions. Exhaust recirculation system. 4. The diesel engine according to claim 1, wherein an exhaust temperature sensor is provided in each of the exhaust passages of the plurality of cylinders, and the flow path control valve is controlled based on the exhaust temperatures of the plurality of cylinders. Exhaust recirculation system. 5. The diesel engine according to claim 1, wherein each of the plurality of cylinders has an in-cylinder pressure sensor, and the flow path control valve is controlled based on the in-cylinder pressures of the plurality of cylinders. Exhaust gas recirculation system for engines.