JP2019113007A - Indirect injection diesel engine - Google Patents

Abstract

To provide an indirect injection diesel engine which is improved to suppress the generation of PMs by reviewing and devising the shape of a recess formed in the ceiling wall of a piston.SOLUTION: The indirect injection diesel engine includes a main combustion chamber, an auxiliary chamber provided in a site eccentric from the main combustion chamber and communicated therewith via an injection hole 8, and a single receiving recess r formed in a site f of a ceiling wall 1A of a piston 1 where combustion stream of air 10 injected from the injection hole 8 into the main combustion chamber is blown, the receiving recess r being formed as a circular recess 21 including the site f to be blown in a central area in plan view.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an engine of a type in which fuel is injected into an auxiliary combustion chamber provided in a cylinder head, that is, an auxiliary chamber diesel engine.

  In the sub-chamber type diesel engine, the main combustion chamber of the engine and the sub-chamber provided at a location eccentric to the main combustion chamber are communicated via the injection hole, and the combustion flow from the sub-chamber to the main combustion chamber through the injection hole Is configured to spout. Generally, the injection hole is formed to be inclined toward the center of the main combustion chamber so that the combustion air flow coming out of the injection hole is sprayed obliquely to the top surface of the piston reaching near the top dead center. It is done. For example, the one disclosed in Patent Document 1 is known.

  Compared with the direct injection type (direct injection type), the sub-chamber type can easily obtain a stable combustion state in all rotation regions, and since the combustion time is long, the pressure and temperature change at the time of combustion is gentle and nitrogen oxides It has the advantage of low generation of hydrocarbons, low noise (diesel knock) and suitable for high speed operation. Therefore, there are many applications in industrial diesel engines and the like.

  On the other hand, since the thermal energy generated by the combustion and explosion of the fuel is conducted as heat to the cooling water in the cylinder head and the cylinder block, the heat loss is large compared to the direct injection type. Therefore, it is inferior to the direct injection type in terms of thermal efficiency and disadvantageous in terms of power and fuel consumption.

JP 2002-61514 A

  Therefore, conventionally, as disclosed in Patent Document 1 (see FIGS. 1 and 3 and the like), the top surface side of the top wall of the piston is recessed at a position corresponding to the injection hole, that is, a recess (6, 7, 7 Literature 1) is often formed. That is, by providing the combustion chamber at the top dead center of the piston with a recess at the top of the piston, the mixing of fuel and air is easily promoted, and the thermal efficiency can be improved.

  However, in the combustion chamber of the conventional structure, the distance between the piston top surface and the injection hole (base) is small, and the spray in the middle of combustion tends to be easily quenched when it collides with the piston top surface. There is a problem that Particulate Matter (Particulate matter) is easily generated.

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

The present invention relates to a sub-chamber type diesel engine
A main combustion chamber 9 and a sub chamber 6 provided at a location eccentric to the main combustion chamber 9 communicate with each other through an injection hole 8,
A single receiving recess r is formed in a portion f of the ceiling wall 1A of the piston 1 to which the combustion air flow 10 ejected from the injection hole 8 into the main combustion chamber 9 is blown.

According to a second aspect of the present invention, there is provided a sub-chamber type diesel engine according to the present invention,
The receiving recess r is characterized in that it is formed in a circular recess 21 including in the central area the point f to be sprayed in a plan view.

According to a third aspect of the present invention, there is provided a sub-chamber type diesel engine according to the present invention,
The receiving recess r is characterized by including an area f to be sprayed in a plan view and being formed in an elliptical recess 22 which is long in the direction of the ejection path w of the combustion air flow 10.

According to a fourth aspect of the present invention, there is provided a sub-chamber type diesel engine according to the present invention,
The receiving recess r includes a portion f to be sprayed in a plan view, and is formed in a trapezoidal recess 24 which is long on the downstream side and short on the upstream side of the ejection path w of the combustion air flow 10. Do.

According to a fifth aspect of the present invention, there is provided a sub-chamber type diesel engine according to the present invention,
The receiving recess r is characterized in that it is formed in a large circular recess 25 having a circular shape concentric with the piston 1 and including the portion f to be sprayed in a plan view.

According to the present invention, since the receiving recess, which is a recess, is formed immediately below the injection hole in the ceiling wall of the piston, that is, at the position where the combustion air flow ejected from the injection hole into the main combustion chamber is blown. The distance between the hole and the top surface of the piston can be increased compared to conventional products, and the volume of the main combustion chamber immediately below the injection hole can be locally increased.
Therefore, the increase in volume immediately below the injection hole promotes the mixing of the air-fuel mixture ejected from the injection hole and the air in the main combustion chamber, thereby suppressing the quenching of the spray during combustion.

  As a result, by modifying and devising the shape and the like of the recess formed in the piston ceiling wall, it is possible to provide an improved sub-chamber type diesel engine in which the generation of PM is suppressed.

Longitudinal sectional view of the main part showing the combustion chamber part of the sub-chamber type diesel engine (A) An enlarged cross-sectional view of the main part showing the sub-chamber in FIG. 1, (b) a plan view of the sub-chamber forming die (A) A plan view showing a piston, (b) a sectional view of a recess portion (A) A plan view of the piston of the first alternative structure, (b) a sectional view of the recess portion (A) The piston top view of the 2nd separate structure, (b) The piston top view of the 3rd separate structure

  Hereinafter, an embodiment of a sub-chamber type diesel engine according to the present invention will be described with reference to the drawings.

  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 movably fitted inside. The 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 called a swirl chamber or a swirl chamber) 6 functioning as a sub combustion chamber.

The cylinder head 5 is provided with a fuel injection nozzle 7 penetrating therethrough, and a tip end injection portion 7 a of the fuel injection nozzle 7 is disposed so as to face the sub chamber 6. The sub chamber 6 is in communication with the main combustion chamber 9 formed in the cylinder 3 via an injection hole 8 provided at an eccentric position of the main combustion chamber 9.
The injection hole 8 is formed in an inclined hole having an injection port 8 a toward the piston axial center (= cylinder axial center) P in a direction substantially tangent to the inner peripheral surface of the sub chamber 6.

  The configuration of sub-chamber 6 will be described. As shown in FIGS. 1 and 2, a sub chamber forming hole 5A in the state of opening to the cylinder 3 is formed at a position eccentric to the cylinder peripheral wall side from the axial center P of the piston 1 in the cylinder head 5 An auxiliary chamber forming die (chamber) 4 is housed in the formation hole 5A. The sub-chamber forming hole 5A is located at a position deeper than the large-diameter opening 12, the small-diameter trunk portion housing portion 13, and the trunk portion housing portion 13 sequentially from the head bottom surface 5a facing the main combustion chamber 9 of the cylinder head 5. And a hollow portion 14 to be formed.

  The opening 12 accommodates the bottom 4A of the auxiliary chamber forming nozzle 4 formed in a cup shape. The body accommodating portion 13 is a place where the body 4B of the auxiliary chamber forming die 4 is accommodated, and has a diameter smaller than that of the opening 12. The hollow portion 14 is formed in a substantially hemispherical concave portion which is slightly larger than a hemispherical portion, and is connected to the trunk portion accommodation portion 13 by a stepped surface (not shown). The auxiliary chamber forming die 4 may have the opening 12 and the body accommodating portion 13 having the same diameter or substantially the same diameter. Reference numeral 23 in FIG. 2 denotes a glow plug.

  As shown in FIG. 1 and FIGS. 2 (a) and 2 (b), the auxiliary chamber forming die 4 is formed by a stepped cylindrical fitting including a cylindrical body 4B and a bottom 4A. . The bottom portion 4A is formed as a flange-like portion protruding in the circumferential direction with a diameter larger than the outer diameter of the trunk portion 4B at one end side of the trunk portion 4B. On the other end side of the body 4B, a substantially hemispherical sub-chamber forming concave portion 15 which is slightly smaller than a hemisphere from the upper end surface of the body 4B is formed. That is, the sub chamber 6 is configured by the hollow portion 14 and the sub chamber forming recess 15. In the bottom 4A of the sub-chamber forming nozzle 4, an injection hole 8 is formed to allow the sub-chamber forming recess 15 and the main combustion chamber 9 to communicate with each other.

  As shown in FIGS. 2 (a) and 2 (b), the injection hole 8 has a pair of sub injection holes 17 and 17 integrally formed to project from the main injection hole 16 at the center and both sides thereof. And a substantially three-leaf shaped communication hole. The injection hole 8 communicating the sub chamber 6 with the main combustion chamber 9 is provided in an inclined manner so as to be directed from the sub chamber 6 to the central portion of the main combustion chamber 9. When the combustion air flow 10 spouts from the sub chamber 6 through the injection hole 8 into the main combustion chamber 9, the combustion air flow 10 is on the top surface 11 of the piston head 1A which is the ceiling wall of the piston 1 reaching near the top dead center. It is configured to be sprayed obliquely.

  Further, as shown in FIGS. 2A and 2B, the auxiliary injection holes 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, 20 is located at a position away from the axial center P of the piston 1 with respect to the injection hole 8, that is, with the bottom 4A at the axial center P of the piston 1 It is formed in a small diameter vertical hole which is penetrated along and opened to the main combustion chamber 9. Therefore, the combustion air flow 10 is spouted into the main combustion chamber 9 in a state of facing the piston head 1A even when passing through the auxiliary injection holes 20, 20 from the sub chamber 6.

Embodiment 1
Next, the piston 1 will be described. As shown in FIGS. 2 (a) and 3 (a) and 3 (b), the portion f of the piston head 1A of the piston 1 to which the combustion air flow 10 ejected from the injection hole 8 into the main combustion chamber 9 is blown. , A single receiving recess r is formed. The receiving recess r is a recessed portion for receiving the combustion air flow 10 by the piston head 1A, and is formed in the circular recess 21 including a portion f to be sprayed in a plan view (view in the axial center P direction of the piston 1) It is done. The circular recess 21 is a recess having a circular shape, with the portion f to be sprayed included in the central region (central region of the circular shape).

The circular recess 21 is along or substantially along the ejection path w of the combustion air flow 10 ejected from the injection hole 8 in the top surface 11 of the piston 1 into the main combustion chamber 9 and the diameter of the piston 1 (the bore diameter of the cylinder Is formed into a circular recess having a diameter of about half that of Further, as shown in FIG. 3B, the circular recess 21 is formed in the piston head 1A in a recessed state having a peripheral edge 21a (ra) exhibiting a smooth corner R and a recessed bottom surface 21b (rb) There is.
Inside the circular recess 21, as shown in FIG. 3 (a), swirling flows h and h traveling along the outer periphery along the shape are generated, the presence of the swirling flow h, and the swirling of the jet path w left and right There is also an effect that mixing of air-fuel mixture and air is promoted by collision of streams h and h.

Second Embodiment
As shown in FIGS. 4 (a) and 4 (b), the receiving recess r is formed into an elliptical recess 22 which includes a point f to be sprayed in a plan view and which is long in the direction of the ejection path w of the combustion air stream 10. It may be the one being done. The elliptical recess 22 is formed in an elliptical recess that is long in the direction along the direction of the ejection path w. The long side length of the elliptical recess 22 is drawn to be about 3/4 of the diameter of the piston 1 (the bore diameter of the cylinder), but other sizes may be used. The elliptical recess 22 also has a smooth corner R peripheral edge 22a (ra) and a flat recess bottom surface 22b (rb).

  By making the receiving recess r an elliptical recess 22, as shown in FIG. 4A, the mixing is performed by the swirling flow h, h generated inside the elliptical recess 22 as compared with the circular recess 21. There is an advantage that the area which can be promoted can be expanded from the injection port 8a along the ejection path w to a distant place in the state of left and right object.

Third Embodiment
As shown in FIG. 5A, the receiving recess r includes a portion f to be sprayed in a plan view, and the trapezoidal recess 24 is long on the downstream side of the ejection path w of the combustion air flow 10 and short on the upstream side. It may be formed. The trapezoidal recess 24 is a recess having a long side extending in the direction in which the downstream side intersects the ejection path w in the ejection path w and a trapezoidal recess in the short side extending in the direction in which the upstream side intersects the ejection path w The downstream side of the path w is formed in a long trapezoidal recess. That is, the trapezoidal recess 24 has a long wall (long side) 24 a, a short wall (short side) 24 b, a pair of inclined walls 24 c and 24 c, and a bottom surface 24 d. It is convenient if the bottom surface 24d is an inclined bottom surface which is shallow on the short wall 24b side and deep on the long wall 24a side.

  In the configuration having the trapezoidal recess 24, the combustion air flow 10 coming out of the injection port 8a can flow smoothly on the top surface 11 of the piston 1 by flowing to the inclined bottom surface 24d immediately below it, and the jet flow is made into the main combustion chamber It can lead to a wide range in 9. In addition, one or more of the long wall 24a, the short wall 24b, and the pair of inclined walls 24c, 24c are angled so that the area of the trapezoidal recess 24 in plan view becomes wider toward the top surface 11 (opening side). It may be formed on a sloped wall.

Embodiment 4
As shown in FIG. 5 (b), the receiving recess r is formed in a large circular recess 25 including a point f to be sprayed in a plan view and having a circular shape concentric with the axis P of the piston 1. It may be The diameter of the large circular recess 25 having the inner peripheral wall 25a and the bottom surface 25b is a large circular recess slightly (or slightly) smaller than the diameter of the piston 1, and a concave outer peripheral wall 26 is formed. The diameter of the large circular recess 25 is set to about 65% to 90% of the diameter of the piston 1, and more desirably 70% to 85%. The depth of the large circular recess 25 is made sufficiently deeper than that of the first to third embodiments described above.

  In the configuration in which the large circular recess 25 is provided, the temperature of the flame in the main combustion chamber 9 at the completion of compression in the vicinity of the liner of the cylinder rises, so that the combustion state in the vicinity of the liner wall is improved. That is, since the compression ratio at the outer peripheral wall 26 in the main combustion chamber 9 at the piston top dead center is slightly increased, the combustion efficiency near the liner is improved, and as a result, the effect of contributing to PM reduction can be obtained.

The sub-chamber type diesel engine according to each embodiment can provide the following effects (1) to (5).
(1) The distance in the axial center P direction of the piston 1 between the injection hole 8 (the injection hole 8a) and the top surface 11 of the piston 1 (specifically, the recess bottom surface rb) can be larger than in the conventional case. The volume immediately below (or immediately after) the hole 8 can be locally increased (embodiments 1 to 4).

(2) Since the receiving recess r (the circular recess 21, the elliptical recess 22 and the large recess 25) is circular in plan view (piston movement direction), a swirling flow is generated in the receiving recess r, Mixing of the air-fuel mixture ejected from the injection hole 8 and the air in the main combustion chamber is promoted by the swirling flow, and the conventional problem that "a spray in the middle of combustion is quenched" is further suppressed or eliminated. (Embodiments 1, 2, 4).

(3) The top surface 11 of the piston 1 has no recess other than the conventional receiving recess r such as a valve recess or a fan-shaped recess, and the portion other than the receiving recess r has a flat surface. It is possible to minimize the resistance when air is introduced from the main combustion chamber 9 to the sub-chamber 6 through the injection holes 8 with the rise (embodiments 1 to 4).

(4) As a result of the above (1) to (3), since the receiving recess r is provided immediately below the injection hole 8, the jet flow from the injection hole 8 to the main combustion chamber 9 is the top of the piston 1 compared to the prior art. It becomes difficult to collide with the surface 11 (recessed bottom surface rb), the amount of air in contact with the jet in the main combustion chamber 9 can be increased, the cooling of the combustion flow 10 in the main combustion chamber 9 becomes gentle, and the generation of PM It comes to be suppressed (embodiments 1 to 4).

The depth of each of the circular recess 21, the elliptical recess 22, the trapezoidal recess 24, and the large circular recess 25 is preferably 0.7 to 1.1 mm, preferably 0.9 mm. If set in such a depth range, the reduction of the compression ratio and the volume ratio can be suppressed and the startability at cold time is improved, and the combustion air flow 10 ejected from the injection hole 8 is the top surface of the piston 1 Quenching at the time of hitting is suppressed, and the effect of PM reduction is also obtained.

Reference Signs List 1 piston 1A ceiling wall 6 auxiliary chamber 8 injection hole 9 main combustion chamber 10 combustion air flow 21 circular recess 22 elliptical recess 24 trapezoidal recess 25 large circular recess f spraying point r receiving recess w ejection path

Claims (5)

A main combustion chamber and a sub-chamber provided at a location eccentric to the main combustion chamber are communicated via an injection hole,
A sub-chamber type diesel engine in which a single receiving recess is formed at a portion of a ceiling wall of a piston where a combustion air flow ejected from the injection hole into the main combustion chamber is blown.   The sub-chamber type diesel engine according to claim 1, wherein the receiving recess is formed in a circular recess including in a central region a portion to be sprayed in a plan view.   The sub-chamber type diesel engine according to claim 1, wherein the receiving recess includes a portion to be sprayed in a plan view, and is formed in an elliptical recess which is long in a direction of an ejection path of the combustion air flow.   The sub-chamber type according to claim 1, wherein the receiving recess includes a portion to be sprayed in a plan view, and is formed in a trapezoidal recess having a long downstream side and a short upstream side in the ejection path of the combustion air flow. diesel engine.   The sub-chamber type diesel engine according to claim 1, wherein the receiving recess includes a portion to be sprayed in a plan view, and is formed in a large circular recess concentric with the piston.

Images