JP2594044Y2 - diesel engine - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sub-chamber type diesel engine provided with an EGR device.

[0002]

In recent years, enhanced exhaust gas regulations for diesel engines, a further reduction of the NO _X and the discharge amount of smoke is required. Therefore, exhaust gas (inert gas)
Some of lowering the mixture to the combustion temperature in the intake, EGR apparatus that suppress the formation of the NO _X are used in some.

By the way, the combustion mechanism of the sub-chamber diesel engine is as follows. First, fuel is injected from the fuel injection nozzle into the sub-chamber, where it ignites and combustion starts. The combustion gas is blown out to the main combustion chamber through the communication hole therebetween, and then the combustion is further progressed by fresh air in the main combustion chamber. Because of the high heat generation rate in the premixed combustion in the auxiliary chamber, a large part of the NO _X has been found to be generated at this stage, while in the diffusion combustion in the main combustion chamber, was refluxed by EGR device If the exhaust gas concentration is high and the combustion state is inert,
It has been confirmed that HC and smoke emissions increase.

Therefore, as proposed in Japanese Patent Application Laid-Open No. 63-85248, for example, in the suction stroke, exhaust gas is directly introduced into the sub-chamber and only the exhaust gas is charged into the sub-chamber. by filling only the fresh air in the chamber, while suppressing the generation of the NO _X lowers the combustion temperature in the premixed combustion in the secondary chamber, diesel to St. prevent inactivation of the diffusion combustion in the main combustion chamber Engines are known.

[0005]

[Problem to be Solved by the Invention] By the way, the ratio of the sub-chamber volume of the sub-chamber diesel engine is generally about 2.5% of the cylinder volume including the sub-chamber when the piston is at the bottom dead center. On the other hand, when the piston is at the top dead center, the volume of the combustion chamber (main combustion chamber + subchamber) is generally
It is about 50%.

Therefore, the above-mentioned conventional diesel engine is configured such that, in the intake stroke, the sub-chamber is filled only with the exhaust gas, while the main combustion chamber is filled only with the fresh air, as described above. EGR in sub-chamber before compression
Although the rate becomes 100%, fresh air in the cylinder is compressed during the compression stroke and flows into the sub-chamber through the communication hole,
The EGR rate in the sub-chamber after compression eventually becomes about 5%. That is, high heat release rate, the premixed combustion in the secondary chamber where most of the NO _X is produced, substantially EG
The R rate is limited to at most about 5%.

[0007] However, an attempt to reduce NO _X emissions to allow clear exhaust gas regulation values, EGR rate in the secondary chamber after compression, usually about 20-30%, better to approximately 50% in some cases Therefore, the above-mentioned conventional diesel engine cannot sufficiently increase the EGR rate and cannot be practically practically used.

In view of the above problems, the present invention can sufficiently increase the EGR rate in the compressed sub-chamber, and furthermore, the sub-chamber is intensively filled with the exhaust gas recirculated by the EGR device. On the other hand, it is an object of the present invention to provide a diesel engine capable of reducing both the emission of NO _X and the amount of smoke by introducing fresh air into the main combustion chamber.

[0009]

In order to achieve the above object, the diesel engine of the present invention has a plurality of intake valves provided in a diesel engine provided with a sub-chamber communicating with a main combustion chamber. The EGR passage communicates with at least one of the intake passages that is opened and closed, and the opening timing of the intake valve on the side where exhaust is sucked is delayed from the opening timing of the intake valve on the side where only fresh air is sucked. This is a configuration in which a valve mechanism is provided.

[0010]

[Operation] Since the diesel engine of the present invention has the above configuration, in the intake stroke, before opening the intake valve on the side from which exhaust gas is sucked, only the fresh air is supplied from the intake valve that opens first. Is sucked and introduced toward the back of the cylinder, that is, near the piston. Then, after a lapse of a predetermined delay time,
Exhaust gas is sucked from an intake valve that opens later, and is introduced into the cylinder closer to the valve, that is, closer to the sub chamber.

Therefore, the intake air containing only fresh air and the intake air containing exhaust gas are distributed in layers in the cylinder. In the compression stroke, the concentration of exhaust gas introduced toward the valve, that is, toward the sub-chamber, is compared. The sub-chamber can be preferentially filled with a relatively high intake air. In addition, in the suction stroke, the intake air including the exhaust gas is once introduced into the cylinder, and is charged into the sub-chamber in the compression stroke.
It is possible to sufficiently cope with the case where the R rate is set to be higher.

[0012]

[Embodiment] Next, an embodiment of the diesel engine of the present invention will be described with reference to the drawings. Embodiment 1 of the present invention shown in FIGS. 1 to 5 is one in which the present invention is applied to a vortex chamber type diesel engine 1. This diesel engine 1
Is a three-valve engine having a first intake valve 2, a second intake valve 3, and an exhaust valve 4.

A first valve opened and closed by a first intake valve 2
Although only fresh air from an intake manifold (not shown) is sucked into the intake port 5, the second intake port 6 opened and closed by the second intake valve 3 has:
Fresh air from the intake manifold and exhaust gas from the EGR passage 7 are sucked in a mixed state. An EGR valve 8 is provided in the EGR passage 7, and the EGR rate can be arbitrarily adjusted by adjusting the opening degree of the EGR valve 8.

FIG. 3 shows a diesel engine 1 according to this embodiment.
As shown in FIG. 1, a subchamber 12 communicating with a main combustion chamber 11 is formed by fitting a hot plug 10 having a communication hole 9 therein. The subchamber 12 has a fuel injection nozzle 13 and a glow plug. 14 are provided. The first intake valve 2
As shown in FIG. 4, the valve mechanism for opening and closing the second intake valve 3 includes a first cam 15 for determining the opening / closing timing of the first intake valve 2 and a lift amount, and a timing for opening / closing the second intake valve 3. A second cam 16 for determining the lift amount is provided.

In this embodiment, the opening / closing timing of the first intake valve 2 and the second intake valve 3 and the opening / closing timing of the exhaust valve 4 operated by the valve mechanism are shown in a cam diagram shown in FIG. And the valve opening timing of the second intake valve 3 is delayed from the valve opening timing of the first intake valve 2, and the lift amount of the second intake valve 3 is made smaller than the lift amount of the first intake valve 2. I have.

Accordingly, in the intake stroke, before the second intake valve 3 on the side where the exhaust gas recirculated by the EGR device is sucked is opened, only fresh air is sucked from the first intake valve 2 which opens earlier. Then, it is introduced toward the back of the cylinder 17, that is, near the piston 18. After a predetermined delay time has elapsed, exhaust gas is sucked from the second intake valve 3 that opens later, and is introduced into the cylinder 17 closer to the valve, that is, closer to the sub chamber 12.

With such a valve mechanism, the exhaust gas sucked from the second intake port 6 can stay in the vicinity of the sub-chamber 12, and the intake air containing only fresh air and the intake air containing the exhaust gas are supplied to the cylinder. In the compression stroke, the intake air having a relatively high exhaust gas concentration introduced into the sub-chamber 12 can be intensively filled in the sub-chamber 12 in the compression stroke.

Further, in the suction stroke, the intake air containing the exhaust gas can be once introduced into the cylinder 17 and can be charged into the sub-chamber 12 in the compression stroke.
It is possible to sufficiently cope with the case where the GR rate is set to be higher. For example, when the EGR rate in the sub-chamber 12 after compression by adjusting the opening of the EGR valve 8 is set to 30%, fresh air occupies 85% of the whole intake air, and the exhaust gas recirculated by the EGR device is exhausted. First, the fresh air is mainly introduced into the lower part so as to occupy 15% of the total intake air, while the intake air with high exhaust gas concentration is introduced into the upper part later, and the stratified To be distributed.

In the compression stroke, almost all of the exhaust gas and a portion of the fresh air flow into the sub-chamber 12, so that the compressed air in the sub-chamber 12 after compression contains 30% of the exhaust gas and 70% of the fresh air. %, And the main combustion chamber 11 is almost completely filled with fresh air. Thus, lowering the combustion temperature in the premixed combustion in the auxiliary combustion chamber 12 within, it is possible to suppress the generation of NO _X, the through hole 9 combustion gas ejected from the secondary chamber 12,
Since it is possible to completely burn by diffusion combustion in the main combustion chamber 11, smoke can also be effectively reduced.

Further, in the intake stroke, the recirculated exhaust gas is once introduced into the cylinder 17 from the second intake port 6, and the exhaust gas is charged into the sub chamber 12 in the next compression stroke. Therefore, a sufficient amount of exhaust gas can be recirculated, and it is possible to cope with a case where the EGR rate is set high. In the present embodiment, since the flange-shaped guide portion 3b is formed below the sealing surface 3a of the second intake valve 3, the guide portion 3b guides the second intake valve 3 from the second intake port 6 into the cylinder 17. The inflow direction of the intake air can be changed in the horizontal direction, and the intake air having a high exhaust gas concentration is retained in the upper layer in the cylinder 17, so that the intake air containing only fresh air and the intake air containing exhaust gas Layered distribution can be performed more reliably.

Next, a second embodiment of the present invention shown in FIGS.
The present invention is applied to a diesel engine 1 of a pre-combustion chamber type. The diesel engine 1 of the present embodiment has
As in the first embodiment, two intake valves are provided,
Only fresh air is introduced from the first intake port 5, while fresh air and exhaust gas from the EGR passage 7 are mixed from the second intake port 6. It is being introduced.

The first intake valve 2 and the second intake valve 3
As shown in FIG. 8, a valve mechanism for opening / closing the first intake valve 2 determines the opening / closing timing and the lift amount of the first intake valve 2.
A cam 15 and a second cam 16 for determining the opening / closing timing and lift of the second intake valve 3 are provided. In this embodiment, the opening and closing timing of the first intake valve 2 and the second intake valve 3 operated by the valve mechanism, and
The opening and closing timing of the exhaust valve 4 is set as shown in the cam diagram of FIG. 9, and the opening and closing timing of the second intake valve 3 is delayed from the opening and closing timing of the first intake valve 2.

In this embodiment, the flange-shaped guide portion 3b as in the first embodiment is not formed in the second intake valve 3, but by making the closing timing of the first intake valve 2 earlier, The intake of fresh air alone is performed in the first half of the intake stroke, the intake of exhaust gas containing exhaust gas is performed in the second half of the intake stroke, and the fresh air and the intake air containing exhaust gas are sucked in layers while being separated as much as possible. ing.

In this embodiment, as in the first embodiment, almost all of the exhaust gas and a part of the fresh air flow into the sub-chamber 12 in the compression stroke, and the main combustion chamber 11 is almost completely fresh air. It will be 100% full. Therefore, lowering the combustion temperature in the premixed combustion in the auxiliary combustion chamber 12 within, it is possible to suppress the generation of NO _X, also it is possible to suppress the generation of smoke in the diffusion combustion in the main combustion chamber 11 .

[0025]

According to the diesel engine of the present invention, a plurality of intake valves are provided in a diesel engine having a sub-chamber communicating with the main combustion chamber, and at least one of the intake passages opened and closed by the intake valves. Since the valve mechanism that communicates with the EGR passage and delays the opening timing of the intake valve on the side where the exhaust is sucked is provided later than the opening timing of the intake valve on the side where only fresh air is sucked, the following effects are provided. Can be played.

Before the intake valve on the exhaust gas intake side is opened in the intake stroke, only fresh air is sucked from the intake valve that opens first, and is introduced toward the back of the cylinder, that is, toward the piston. After a predetermined delay time,
Exhaust gas can be sucked from an intake valve that opens later, and introduced into the cylinder closer to the valve, that is, closer to the sub chamber.

Therefore, the intake air containing only fresh air and the intake air containing exhaust gas can be distributed in layers in the cylinder.
Thereby, in the compression stroke, the exhaust gas introduced toward the valve, that is, toward the sub-chamber can be preferentially charged into the sub-chamber. Further, it is possible to fill was refluxed exhaust intensively in auxiliary combustion chamber, it is possible to suppress the occurrence of the NO _X lowers the combustion temperature in the premixed combustion, further satisfying the main combustion chamber by fresh air Therefore, the combustion state in diffusion combustion can be improved, and the generation of smoke can be reduced.

Further, in the suction stroke, first, the intake air including the exhaust gas is once introduced into the cylinder, and is then charged into the sub-chamber in the next compression stroke.
It is possible to sufficiently cope with the case where the GR rate is set to be higher.

[Brief description of the drawings]

FIG. 1 is a schematic view of an intake and exhaust system of a diesel engine according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of the diesel engine according to the first embodiment of the present invention, showing an open state of an intake valve.

FIG. 3 is a cross-sectional view around the sub-chamber of the diesel engine according to the first embodiment of the present invention.

FIG. 4 is a side view of a cam that opens and closes an intake valve of the diesel engine according to the first embodiment of the present invention.

FIG. 5 is a cam diagram showing opening and closing timings and lift amounts of intake and exhaust valves of the diesel engine according to the first embodiment of the present invention.

FIG. 6 is a cross-sectional view of a main part showing an open state of an intake valve of the diesel engine according to the second embodiment of the present invention;

FIG. 7 is a cross-sectional view around a sub-chamber of a diesel engine according to a second embodiment of the present invention.

FIG. 8 is a side view of a cam for opening and closing an intake valve of the diesel engine according to the second embodiment of the present invention.

FIG. 9 is a cam diagram showing opening and closing timings and lift amounts of intake and exhaust valves of the diesel engine according to the second embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 diesel engine 2 intake valve (first intake valve) 3 intake valve (second intake valve) 5 intake passage (first intake port) 6 intake passage (second intake port) 7 EGR passage 11 main combustion chamber 12 sub-chamber 15 Valve mechanism (first cam) 16 Valve mechanism (second cam)

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 13/02 F02D 13/02 K 21/08 301 21/08 301H 41/02 320 41/02 320 (58) Fields surveyed ( Int.Cl. ⁶ , DB name) F02M 25/07 570 F02M 25/07 580 F01L 1/08 F01L 1/26 F02B 29/08 F02D 13/02 F02D 21/08 301 F02D 41/02 320

Claims (1)

(57) [Scope of request for utility model registration] A diesel engine provided with a sub-chamber communicating with a main combustion chamber is provided with a plurality of intake valves, and an EGR passage is communicated with at least one of intake passages each opened and closed by the intake valves. A diesel engine provided with a valve mechanism that delays the opening timing of the intake valve on the side where air is sucked from the opening timing of the intake valve on the side where only fresh air is sucked.