JP6830057B2 - Sub-chamber diesel engine - Google Patents

Description

The present invention relates to an engine of a type that injects fuel into a sub-combustion chamber provided in a cylinder head, that is, a sub-chamber diesel engine.

In a sub-chamber type diesel engine, the main combustion chamber of the engine and the sub-chamber provided at a location eccentric from the main combustion chamber are communicated through the injection hole, and the combustion airflow from the sub-chamber to the main combustion chamber through the injection hole. Is configured to spout. Generally, the combustion chamber is formed so as to be inclined toward the center side of the main combustion chamber so that the combustion airflow emitted from the injection hole is blown diagonally to the top surface of the piston reaching near top dead center. Has been done. For example, those disclosed in Patent Document 1 are known.

Compared to the direct injection type (direct injection type), the sub-chamber type can easily obtain a stable combustion state in all rotation ranges, and since the combustion time is long, the pressure and temperature changes during combustion are gentle and nitrogen oxides are used. It has the advantages of low generation of hydrocarbons, low noise (diesel knock), and suitable for high rotation speed. Therefore, there are many examples of adoption in industrial diesel engines and the like.

On the other hand, the heat energy from the combustion explosion of the fuel is conducted as heat to the cooling water in the cylinder head and the cylinder block, so that the heat loss is larger than that of the direct injection type. Therefore, it is inferior to the direct injection type in terms of thermal efficiency, and is disadvantageous in terms of power and fuel efficiency.

JP-A-2002-61514

Therefore, conventionally, as disclosed in Patent Document 1 (see FIGS. 1, 3 and the like), a recess is provided at a position corresponding to a jet hole on the top surface side of the ceiling wall of the piston, that is, a recess (6, 7, 7: patent). Document 1) is often formed. That is, the combustion chamber at the top dead center of the piston has a shape that facilitates the mixing of fuel and air by providing a recess at the top of the piston, so that the thermal efficiency can be improved.

However, in a combustion chamber having a conventional structure, the distance between the top surface of the piston and the injection hole (mouthpiece) is small, and when the spray during combustion collides with the top surface of the piston, it tends to be rapidly cooled. As a result, PM ( There is a problem that a particulate matter (particulate matter) is likely to be generated.

An object of the present invention is to provide a sub-chamber diesel engine which is formed on a piston ceiling wall and is improved so as to suppress the generation of PM by reviewing and devising the shape of the recess.

The present invention relates to a sub-chamber diesel engine.
The main combustion chamber 9 and the sub chamber 6 provided at a position eccentric from the main combustion chamber 9 are communicated with each other through the injection hole 8, and one intake valve recess 18 and one intake valve recess 18 are connected to the ceiling wall 1A of the piston 1 . Exhaust valve recess 19 is formed,
The intake / exhaust valve recesses 18 and 19 are circular in a plan view and are circular in a plan view at a portion f of the ceiling wall 1A where the combustion airflow 10 ejected from the injection hole 8 into the main combustion chamber 9 is blown. A recess 21 directly underneath is formed so as to overlap each other .
The injection hole 8 is characterized in that the ejection path w of the combustion airflow 10 is set so as to pass between the intake valve recess 18 and the exhaust valve recess 19 in a plan view .

The second invention relates to the sub-chamber diesel engine of the present invention.
The ceiling wall 1A is characterized in that a fan-shaped receiving recess 22 extending downstream in the ejection direction is formed on the ceiling wall 1A with reference to a portion f corresponding to the injection hole 8 in a plan view .

A third aspect of the present invention is the sub-chamber diesel engine according to the present invention .
The intake valve recess 18 and the exhaust valve recess 19 and the recess 21 directly underneath are set to have different depths .

The fourth invention is the sub-chamber diesel engine of the second invention .
The direct recess 21 and the receiving recess 22 are set to have different depths from each other .

A fifth aspect of the present invention is the subchamber type diesel engine of the fourth aspect of the present invention .
The intake valve recess 18 and the exhaust valve recess 19 and the recess 21 directly underneath are set to have different depths .

The sixth invention is the sub-chamber diesel engine of the fifth invention.
The intake valve recess 18 and the exhaust valve recess 19 and the receiving recess 22 are set to have different depths from each other .

According to the present invention, a recess directly below the injection hole is formed on the ceiling wall of the piston, that is, at a position where the combustion airflow ejected from the injection hole into the main combustion chamber is blown. By increasing the distance between the piston and the top surface of the piston, the volume of the main combustion chamber directly under the injection hole can be locally increased.
Therefore, the increase in the volume immediately below the injection hole promotes the mixing of the air-fuel mixture ejected from the injection hole with the air in the main combustion chamber, and suppresses the rapid cooling of the spray during combustion.

Then, the combustion airflow with a small temperature drop in the direct recess flows smoothly to the intake / exhaust valve recesses in the main combustion chamber and propagates the flame, so that the combustion in the main combustion chamber is further promoted by the synergistic action having these three recesses. Become so.
As a result, it is possible to provide an improved sub-chamber diesel engine in which the generation of PM is suppressed by reviewing and devising the shape of the recess formed on the ceiling wall of the piston.

Vertical cross-sectional view of the main part showing the combustion chamber part of the sub-chamber diesel engine Enlarged sectional view of a main part showing an auxiliary chamber in the diesel engine of FIG. (A) Plan view showing the piston, (b) Plan view of the base for forming the auxiliary chamber (A) Piston plan view of the first separate structure, (b) Piston plan view of the second separate structure (A) Piston plan view of the third separate structure, (b) Piston plan view of the fourth separate structure (A) Piston plan view of the fifth separate structure, (b) Piston plan view of the sixth separate structure

Hereinafter, embodiments of the sub-chamber diesel engine according to the present invention will be described with reference to the drawings. The injection hole 8, the auxiliary injection hole 20, and the ejection path w (combustion airflow 10) depicted in FIG. 3A are not shown in FIGS. 4, 5 and 6.

As shown in FIG. 1, the sub-chamber type diesel engine E has a cylinder block 2 and a cylinder head 5, a cylinder 3 is provided in the cylinder block 2, and a piston 1 reciprocates up and down in the cylinder 3. It is fitted so that it can be moved. A cylinder head 5 is assembled on the upper side of the cylinder block 2, and the cylinder head 5 is provided with a sub chamber (also referred to as a vortex chamber or a vortex chamber) 6 that functions as a sub combustion chamber.

A fuel injection nozzle 7 is penetrating the cylinder head 5, and the tip injection portion 7a of the fuel injection nozzle 7 is arranged so as to face the inside of the sub chamber 6. The sub-chamber 6 communicates with the main combustion chamber 9 formed in the cylinder 3 via an injection hole 8 provided at an eccentric portion of the main combustion chamber 9.
The injection hole 8 is formed in an inclined hole having a injection port 8a in a substantially tangential direction of the inner peripheral surface of the sub chamber 6 and toward the piston axis (= cylinder axis) P.

The configuration of the sub-chamber 6 will be described. As shown in FIGS. 1 and 2, a subchamber forming hole 5A opened in the cylinder 3 is formed at a position eccentric from the piston axis P in the cylinder head 5 toward the cylinder peripheral wall side, and the subchamber forming hole 5A is formed. A cap (chamber) 4 for forming an auxiliary chamber is housed in 5A. The sub-chamber forming hole 5A is located behind the large-diameter opening 12, the small-diameter body housing portion 13, and the body housing portion 13 in order from the head bottom surface 5a facing the main combustion chamber 9 of the cylinder head 5. It is configured to have a hollow portion 14 to be formed.

The opening 12 accommodates the bottom 4A of the cup-shaped auxiliary chamber forming mouthpiece 4. The body portion accommodating portion 13 is a portion where the body portion 4B of the auxiliary chamber forming mouthpiece 4 is accommodated and has a smaller diameter than the opening portion 12. The hollow portion 14 is formed in a substantially hemispherical recessed portion slightly larger than the hemisphere, and is connected to the body portion accommodating portion 13 by a stepped surface (notation omitted). It should be noted that the sub-chamber forming base 4 in which the opening 12 and the body accommodating portion 13 have the same diameter or substantially the same diameter may be used. Note that 23 in FIG. 2 is a glow plug.

As shown in FIGS. 1, 2 and 3 (b), the auxiliary chamber forming mouthpiece 4 is formed of a stepped columnar metal fitting including a columnar body portion 4B and a bottom portion 4A. The bottom portion 4A is formed as a flange-shaped portion having one end side of the body portion 4B having a diameter larger than the outer diameter of the body portion 4B and protruding in the circumferential direction. On the other end side of the body portion 4B, a substantially hemispherical sub-chamber forming recess 15 slightly smaller than the hemisphere is formed from the upper end surface of the body portion 4B. That is, the sub chamber 6 is composed of a cavity 14 and a recess 15 for forming the sub chamber. A jet hole 8 for communicating the sub-chamber forming recess 15 and the main combustion chamber 9 is formed in the bottom 4A of the sub-chamber forming base 4.

As shown in FIGS. 2 and 3B, the injection hole 8 includes a main injection hole 16 in the center and a pair of auxiliary injection holes 17 and 17 integrally formed so as to project on both sides thereof. It is formed in a communication hole having a substantially trefoil shape in the direction of the piston axis P. The injection hole 8 that communicates the sub-chamber 6 and the main combustion chamber 9 is provided so as to be inclined from the sub-chamber 6 toward the central portion of the main combustion chamber 9. When the combustion airflow 10 is ejected from the sub chamber 6 through the injection hole 8 into the main combustion chamber 9, the combustion airflow 10 reaches the top surface 11 of the piston head 1A, which is the ceiling wall of the piston 1 reaching near the top dead center. On the other hand, it is configured to be sprayed diagonally.

Further, as shown in FIGS. 2 and 3, auxiliary injection holes 20 and 20 are formed in the vicinity of both sides of the injection hole 8 in the bottom 4A of the auxiliary chamber forming mouthpiece 4. The pair of auxiliary injection holes 20 and 20 piston the bottom 4A at a position closer to the side of the injection hole 8 from the piston axis P, that is, at a substantially central position in the direction of the piston axis P of the sub chamber 6. It is formed in a small-diameter vertical hole that is penetrated along the axis P and opens to the main combustion chamber 9. Therefore, even if the auxiliary chambers 6 pass through the auxiliary injection holes 20 and 20, the combustion airflow 10 is ejected into the main combustion chamber 9 in a state of facing the piston head 1A.

Next, the piston 1 will be described. As shown in FIGS. 1, 2, and 3 (a), the piston head 1A of the piston 1 has an intake valve recess 18 corresponding to an intake valve (not shown) and an exhaust valve corresponding to an exhaust valve (not shown). A recess 19 is formed, and a directly downward recess 21 forming a circular shape in a plan view is formed at a portion f in the piston head 1A where the combustion airflow 10 ejected from the injection hole 8 into the main combustion chamber 9 is blown.

The direct recess 21 overlaps both the intake valve recess 18 and the exhaust valve recess 19 in a plan view. Therefore, the direct recess 21 and the intake valve recess 18 and the direct recess 21 and the exhaust valve recess 19 are directly connected to each other. It is said that. In FIG. 3A, the overlapping length of the exhaust valve recess 19 and the recess 21 directly below, which is slightly smaller than the recess 18 of the intake valve, is longer than the overlapping length of the recess 18 directly below the intake valve recess 18. However, this is not the case.

In addition, as shown in FIG. 3A, a fan-shaped receiving recess 22 extending downstream in the ejection direction is also formed on the piston head 1A with reference to a portion f corresponding to the injection hole 8 in a plan view. .. The receiving recess 22 is a portion corresponding to the ejection path w of the combustion airflow 10 ejected from the injection hole 8 on the top surface 11 into the main combustion chamber 9. The ejection path w is the path of the combustion airflow 10 ejected from the main injection hole 16, and is actually from the pair of auxiliary injection holes 17 and 17 as shown by the arrow of the virtual line in FIG. 3A. Left and right sub-ejection paths (notation omitted) due to the ejected combustion airflow 10 are also generated.

Further, inside the circular recess 21 directly underneath, as shown in FIG. 3A, swirling flows h and h traveling on the outer peripheral side along the shape are generated. Due to the presence of the swirling flows h and h, and when the swirling flows h and h on the left and right of the ejection path w collide with each other on the downstream side of the flow, the effect of promoting the mixing of the air-fuel mixture and the air can be obtained. ..

The recess depths of these four recesses are in order from the deepest one, in the order of direct recess 21> intake valve recess 18 = exhaust valve recess 19> receiving recess 22. As shown in FIG. 3A, the receiving recess 22 has many overlapping portions with the direct recesses 21 and the intake / exhaust valve recesses 18 and 19, so that the depth relationship described above is combined with the outer diameter of the direct recess 21. It is divided into two parts and has a small area.

The sub-chamber diesel engine according to the first embodiment can exhibit the following effects (1) to (4).
(1) By providing the recess 21 directly below the piston head 1A, the distance between the injection hole 8, specifically the injection port 8a and the top surface 11 in the piston axis P direction becomes larger than before, and the main combustion chamber 9 The volume directly below (or immediately after) the injection hole 8 in the above can be locally increased.

(2) Since the recess 21 directly below has a circular shape in a plan view (view in the direction of piston movement), a swirling flow is generated in the recess 21 directly below, and the air-fuel mixture ejected from the injection hole 8 and the air in the main combustion chamber Mixing is promoted by the swirling flow, and the conventional problem of "the spray in the middle of combustion is rapidly cooled" becomes more suppressed or eliminated.

(3) Since the depth of the direct recess recess 21 is set deeper than the depth of the other recesses (intake / exhaust valve recesses 18 and 19 and the receiving recess 22), the functions of the intake / exhaust valve recesses 18 and 19 are minimized. As a limit, it is possible to promote combustion by utilizing a vortex that generates a flow from the recess 21 directly below the recess.

(4) As a result of the above (1) to (3), since the recess 21 directly underneath is provided, the jet flow from the injection hole 8 to the main combustion chamber 9 is less likely to collide with the top surface 11 of the piston 1. The amount of air in contact with the jet in the main combustion chamber 9 can be increased, the cooling of the combustion airflow 10 in the main combustion chamber 9 becomes gentle, and the generation of PM is suppressed.

[Embodiment 2]
As shown in FIG. 4A, intake / exhaust valve recesses 18, 19, direct recesses 21, and receiving recesses 22 are formed on the piston head 1A, and direct recesses 21> receiving recesses 22> intake valve recesses. A configuration in which the recess depths of 18 and the exhaust valve recess 19 are ordered. In this case, the depth of the intake valve recess 18 ≠ the depth of the exhaust valve recess 19, or the depth of the intake valve recess 18 = the depth of the exhaust valve recess 19 may be satisfied.

[Embodiment 3]
As shown in FIG. 4B, intake / exhaust valve recesses 18, 19, direct recesses 21, and receiving recesses 22 are formed on the piston head 1A, and the direct recesses 21 <receiving recess 22 <intake valve recesses. A configuration in which the recess depths of 18 and the exhaust valve recess 19 are ordered. In this case, the intake valve recess 18 = the exhaust valve recess 19, or the depth of the intake valve recess 18 ≠ the depth of the exhaust valve recess 19 may be satisfied.

[Embodiment 4]
As shown in FIG. 5A, intake / exhaust valve recesses 18 and 19, direct recesses 21, and receiving recess 22 are formed on the piston head 1A, and receiving recess 22 <intake valve recess 18 and exhaust valve. Recess 19 <Recess 21 directly below, which is a configuration in which the recess depths are ordered. In this case, the intake valve recess 18 = the exhaust valve recess 19, or the depth of the intake valve recess 18 ≠ the depth of the exhaust valve recess 19 may be satisfied.

[Embodiment 5]
As shown in FIG. 5B, intake / exhaust valve recesses 18, 19, direct recesses 21, and receiving recesses 22 are formed on the piston head 1A, and direct recesses 21 = receiving recesses 22 = intake valve recesses. There is no order in the recess depths of 18 and the exhaust valve recess 19, and they are all set to the same depth.

[Embodiment 6]
As shown in FIG. 6A, intake / exhaust valve recesses 18 and 19 and direct recesses 21 are formed on the piston head 1A, and the recess depth is such that direct recesses 21> intake valve recess 18 and exhaust valve recess 19. The configuration is ordered. In this case, the depth of the intake valve recess 18 ≠ the depth of the exhaust valve recess 19, or the depth of the intake valve recess 18 = the depth of the exhaust valve recess 19 may be satisfied.

[Embodiment 7]
As shown in FIG. 6B, the intake / exhaust valve recesses 18 and 19 and the direct recesses 21 are formed on the piston head 1A, and the recess depths such that the direct recesses 21 <intake valve recess 18 and exhaust valve recess 19 are formed. The configuration is ordered. In this case, the depth of the intake valve recess 18 ≠ the depth of the exhaust valve recess 19, or the depth of the intake valve recess 18 = the depth of the exhaust valve recess 19 may be satisfied.

1 Piston 1A Ceiling wall 6 Sub chamber 8 Injection hole 9 Main combustion chamber 10 Combustion airflow 18 Intake valve recess 19 Exhaust valve recess 21 Direct recess recess 22 Receiving recess f
w Eruption route

Claims (6)

A sub-chamber provided at a position eccentric from the main combustion chamber and the main combustion chamber are communicated with each other through the injection holes, the ceiling wall of the piston, one intake valve recess and one exhaust valve recess is formed, At the location on the ceiling wall where the combustion airflow ejected from the injection hole to the main combustion chamber is blown, a recess directly underneath is formed in a circular shape in a plan view and overlapping each of the intake / exhaust valve recesses in a plan view. Being done
The injection hole is a sub-chamber diesel engine in which the ejection path of the combustion airflow is set to pass between the intake valve recess and the exhaust valve recess in a plan view . The sub-chamber diesel engine according to claim 1, wherein a fan-shaped receiving recess extending downstream in the ejection direction is formed on the ceiling wall centering on a portion corresponding to the injection hole in a plan view . The sub-chamber diesel engine according to claim 1 or 2, wherein the intake valve recess and the exhaust valve recess and the recess directly under the exhaust valve are set to have different depths from each other . The sub-chamber diesel engine according to claim 2 , wherein the depths of the recess directly underneath and the recesses receiving the receiving recess are set to be different from each other . The sub-chamber diesel engine according to claim 4 , wherein the intake valve recess, the exhaust valve recess, and the recess directly below the intake valve recess are set to have different depths from each other . The sub-chamber diesel engine according to claim 5, wherein the intake valve recess, the exhaust valve recess, and the receiving recess are set to have different depths from each other .

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