JPH08319902A - Egr device for engine - Google Patents

Abstract

PURPOSE: To effectively introduce EGR(Exhaust Gas Recirculation) gas into a cylinder without complicating the outer construction of a multiple cylinder engine. CONSTITUTION: Respective cylinders 14, each of which is formed in a crank case 11 of a four-cylinder engine 10, is connected with an EGR-passage 19, which rectilinearly extends within a cooling water jacket 18, by means of a communicating passage 20 and a rotary valve 21 is installed in the EGR-passage 19. The system is controlled in such a way that, in a medium and low speed domain and in a medium and low load domain of the engine 10, the rotary valve 21 is opened so that the EGR passage 19 and the communicating passage 20 are connected with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR device for reducing the amount of NOx in engine exhaust gas by recirculating a part of engine exhaust gas into the cylinder of the engine.

[0002]

2. Description of the Related Art In a conventional multi-cylinder engine, a part of the exhaust gas extracted from the exhaust pipe is led to an intake manifold through an EGR pipe mainly in the medium and low rotation speed region and the medium and light load region, and this EGR gas is discharged. The amount of NOx in the exhaust gas is reduced by recirculating it to the cylinder. However, since the exhaust pressure in the exhaust pipe is low, the EGR pipe is relatively large in order to secure a sufficient amount of EGR gas. Therefore, the structure on the outer surface of the engine is likely to be complicated, and when cooling the EGR gas, a cooler or the like must be provided in the EGR pipe, so that the outer surface structure of the engine is further improved. It could be complicated.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to efficiently guide EGR gas into a cylinder without complicating the outer surface structure of a multi-cylinder engine.

[0004]

Therefore, an EGR device for an engine according to the present invention, in a multi-cylinder engine,
Connect the cylinders by a passage that does not pass through the intake and exhaust ports,
The exhaust gas is guided from the exhaust stroke cylinder to the intake stroke cylinder through the passage.

[0005]

In other words, since the cylinders are connected to each other through the passages that do not pass through the intake and exhaust ports and the EGR gas is guided into the cylinders during the intake stroke by the passages, the passages can be easily arranged in the engine body. EGR
Even if a device is attached, it is possible to easily avoid complication of the outer surface structure of the multi-cylinder engine, and use the difference between the cylinder pressure during the exhaust stroke and the cylinder pressure during the intake stroke to generate EGR gas. Since it can be introduced into the low pressure side cylinder,
The EGR action can be efficiently performed.

[0006]

Embodiments of the present invention shown in the drawings will be specifically described below. 1 and 2, the cylinder head 12 is provided on the crankcase 11 of the four-cylinder engine 10.
The first cylinder 14, the second cylinder 15, the third cylinder 16 and the fourth cylinder 17 each having the piston 13 inserted therein are provided by the above, and the cooling water jacket 18 of the crankcase 11 is provided. Is for each cylinder 14, 15, 16,
An EGR passage 19 linearly extending along the side of 17 is installed by casting a pipe, and each cylinder 14,
Communication passages 20 are provided at the bottoms of 15, 16 and 17 and are connected to the EGR passages 19 respectively.

Further, the cylindrical rotary valve 21 shown in FIG. 3 is disposed in the EGR passage 19, and the inclined valve 22 is formed in a portion of the rotary valve 21 facing each communication passage 20. The rotary valve 21 is driven by a step motor, a hydraulic motor, or a pneumatic motor whose rotation is controlled by an electronic control unit (not shown).
It rotates in the passage 19, and the communication area between the EGR passage 19 and each of the communication passages 20 can be adjusted according to the rotation angle thereof, and the EGR passage 19 can be adjusted in the high rotation speed region and the heavy load region of the engine 10. While the communication passages 20 are closed, the communication passages 20 are largely opened with respect to the EGR passage 19 as the rotation speed of the engine 10 is lower in the medium / low rotation speed region and the load is smaller in the medium / light load region. Is controlled.

FIG. 4 is a valve opening timing graph of the engine 10 with the first cylinder 14 as a reference (a solid line shows the opening of the exhaust valve and a broken line shows the opening of the intake valve). The exhaust stroke of the first cylinder 14 coincides with the intake stroke of the second cylinder 15, and the exhaust stroke of the third cylinder 16 and the first cylinder 1
4, the intake stroke of the fourth cylinder 17 coincides with the intake stroke of the third cylinder 16, and the second cylinder 15 has the same intake stroke.
Since the exhaust stroke of No. 4 and the intake stroke of the fourth cylinder 17 coincide with each other, when the rotary valve 21 is opened in the medium and low rotation speed region and the medium and light load region as described above, the communication passage 20 is opened to each cylinder. Unless the piston 13 is closed by the piston 13, E from the cylinder in the exhaust stroke to the cylinder in the intake stroke through the communication passage 20 and the EGR passage 19 as indicated by arrows.
GR gas flows, and this EGR gas is the EG installed in the cooling water jacket 18 of the crankcase 11.
When passing through the R passage 19, it is cooled by the cooling water.

In the above device, the difference between the pressure in the cylinder during the exhaust stroke and the pressure in the cylinder during the intake stroke is utilized by the opening degree of the rotary valve 21 depending on the rotational speed and load of the engine 10. An appropriate amount of EGR gas is introduced from the cylinder to the cylinder in the intake stroke, and at that time, the EGR gas is cooled by the engine cooling water to increase its density,
Even if the EGR passage 19 and the communication passage 20 are relatively small, the amount of EGR gas required for exhaust gas purification can be reliably supplied to each cylinder.

The rotary valve 21 can control the supply amount of EGR gas to each cylinder according to the opening degree to each cylinder, and the opening degree and opening / closing timing of the rotary valve 21 and the EGR passage 19 and the communication passage. If the conditions such as the cross-sectional area of 20 are the same for each cylinder, the supply amount of EGR gas to each cylinder will be substantially equal, and as a result, it will be easy to control the combustion state of all cylinders to be substantially uniform. There is an advantage that becomes possible.

Furthermore, the EGR passage 19 for guiding the EGR gas
Also, since the communication passage 20 is arranged inside the crankcase 11 and is not installed outside the crankcase 11, it is possible to easily avoid complication of the outer surface structure of the multi-cylinder engine 10. Since the outer shape of the engine 10 is reduced, it is possible to improve the mountability on the vehicle.

In the above embodiment, the EGR passage is arranged in the cooling water jacket of the crankcase by casting a pipe or the like.
Even if the GR passage is appropriately formed on the wall surface of the crankcase near each cylinder by punching or core casting,
It is needless to say that the same operational effects as those of the above-mentioned embodiment can be obtained, and the present invention can be applied to a multi-cylinder engine such as a 6-cylinder engine and an 8-cylinder engine in the same manner as described above.

[0013]

In the engine EGR device according to the present invention, since the passage for guiding the EGR gas into the cylinder in the intake stroke can be arranged in the engine body, even if the EGR device is attached, the multi-cylinder system is provided. It is possible to easily avoid complication of the outer surface structure of the engine, and use the difference between the cylinder pressure in the exhaust stroke and the cylinder pressure in the intake stroke to make E
Since the GR gas can be introduced into the cylinder on the low pressure side, E
The GR action can be efficiently performed, and the exhaust gas purification action can be reliably performed.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view in an embodiment of the present invention.

FIG. 2 is a schematic perspective view of the above embodiment.

FIG. 3 is an enlarged perspective view of a main part of the above embodiment.

FIG. 4 is an explanatory view of the operation of the above embodiment.

[Explanation of symbols]

 10 4-cylinder engine 11 Crankcase 14-17 Cylinder 18 Cooling water jacket 19 EGR passage 20 Communication passage 21 Rotary valve 22 Inclined hole

Claims (10)

[Claims] 1. An EGR device for a multi-cylinder engine, wherein the cylinders are connected by a passage that does not pass through an intake / exhaust port, and exhaust gas is guided from the cylinder in the exhaust stroke to the cylinder in the intake stroke through the passage. . 2. The EGR device for an engine according to claim 1, wherein the passage is arranged in the crankcase or integrally with the crankcase. 3. The EGR device for an engine according to claim 1 or 2, wherein the passage extends inside a cooling water jacket formed in the engine, or extends toward a surface of the cooling water jacket. . 4. The EGR device for an engine according to claim 3, wherein the passage extends into the cooling water jacket formed in the crankcase or extends toward the cooling water jacket. 5. The engine EG according to any one of claims 1 to 4, wherein an opening / closing control valve is provided in the passage.
R device. 6. The EGR device for an engine according to claim 5, wherein the opening / closing control valve is a rotary valve. 7. The EGR device for an engine according to claim 1, wherein the passage is connected to all cylinders. 8. The opening / closing control valve according to claim 7, wherein the passage comprises a first passage opening to each cylinder and a linear second passage to which all the first passages are connected. An engine EGR device provided in the second passage. 9. An EGR device for an engine configured such that an EGR passage for guiding engine exhaust gas to a cylinder in an intake stroke extends inside a cooling water jacket formed in the engine or extends so as to face the cooling water jacket. . 10. The EGR device for an engine according to claim 9, wherein the EGR passage is configured to extend inside a cooling water jacket formed in a crankcase or to extend toward a surface of the cooling water jacket.