JP2019113008A - 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 h, and a receiving recess R formed in a ceiling wall 4A of a piston 4 to receive combustion stream of air g injected from the injection hole h, the receiving recess R having a direct recess part 25 formed in a site f where the combustion stream of air g injected from the injection hole h into the main combustion chamber is blown in the state of corresponding to the opening shape of the injection hole h, and a spread recess part 26 formed in the state of spreading wider as extending from the blown site f of the main combustion chamber 5 through an injection passage w for the combustion stream of air g to the downstream side, and being shaped corresponding to the opening shape of the injection hole h.SELECTED DRAWING: Figure 4

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 which is improved so as to suppress the 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
The main combustion chamber 5 and the sub chamber 9 provided at a location eccentric from the main combustion chamber 5 are communicated by the injection hole h, and the combustion air flow g ejected from the injection hole h to the ceiling wall 4A of the piston 4 Receiving recess R is formed to receive
The receiving recess R is formed at a location f where the combustion air flow g ejected from the injection hole h to the main combustion chamber 5 is blown in a state corresponding to the opening shape of the injection hole h A diffusion recess portion 26 formed in the main combustion chamber 5 in a state of being spread toward the downstream side along the ejection path w of the combustion air flow g from the blowing point f in the main combustion chamber 5; It is characterized in that

According to a second aspect of the present invention, there is provided a sub-chamber type diesel engine according to the present invention,
The injection hole h has a main injection hole 13 including a central injection hole 13 and a pair of side injection holes 14 integrally formed so as to project on both sides of the central injection hole 13;
The recess portion 25 directly below is formed corresponding to the base recess portion 27 formed corresponding to the central injection hole 13 and the pair of side injection holes 14 in a state of being connected to the base recess portion 27. And a pair of side recess portions 28 and 28.

According to a third aspect of the present invention, there is provided a sub-chamber type diesel engine according to the second aspect of the present invention,
The injection hole h has a pair of auxiliary injection holes 22 formed independently at both side positions of the central injection hole 13, and the recess portion 25 directly below is connected to the base recess portion 27. And a pair of auxiliary recess portions 29, 29 formed correspondingly to the pair of auxiliary injection holes 22, 22, respectively.

According to a fourth aspect of the present invention, in the sub-chamber type diesel engine according to the third aspect of the present invention,
The ceiling wall 4A is characterized in that an intake valve recess 30 corresponding to the intake valve and an exhaust valve recess 31 corresponding to the exhaust valve are formed.

According to a fifth aspect of the present invention, in the sub-chamber type diesel engine according to the fourth aspect of the present invention,
The intake valve recess 30 and the exhaust valve recess 31 are formed to be connected to the receiving recess R.

According to a sixth aspect of the present invention, in any one of the sub-chamber diesel engine according to the fifth to the present invention,
It is characterized in that the depth d of the receiving recess R is formed to be uniform.

According to a seventh invention, in any one of the sub-chamber type diesel engine according to the fifth invention of the present invention,
It is characterized in that the depth of the receiving recess R is formed so as to become shallower toward the downstream side in the ejection path w of the combustion air flow g.

  According to the present invention, the recess directly under the recess portion is formed immediately below the injection hole in the ceiling wall of the piston, that is, at a 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.

And since the diffusion recess part in the state which spreads to the lower stream side is also formed and it is considered as the receiving recess of the shape according to the opening shape of the injection hole, the air which contacts with all the combustion airflows (jet stream) which came out from the injection hole The amount will increase and the combustion efficiency will also be improved.
As a result, it is possible to provide an improved sub-chamber type diesel engine in which generation of PM is suppressed by reviewing and devising the shape and the like of the recess formed in the piston ceiling wall.

Longitudinal sectional view of the main part showing the combustion chamber part of the sub-chamber type diesel engine An enlarged sectional view of the main part showing the sub-chamber of FIG. 1 (A) Top view of the auxiliary chamber forming die, (b) Bottom view of the auxiliary chamber forming die Top view showing the ceiling wall of the piston Top view showing a ceiling wall of a piston having a recess of another shape

  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 6, and the cylinder block 2 is provided with a cylinder 3 in which a piston 4 is axially centered. It is internally fitted in P so that it can move up and down. A cylinder head 6 is assembled on the upper side of the cylinder block 2, and the cylinder head 6 is provided with a sub chamber (also called a swirl chamber or a swirl chamber) 9 functioning as a sub combustion chamber.

  The cylinder head 6 is provided with a fuel injection nozzle 19 penetrating therethrough, and a tip end injection portion 19 a of the fuel injection nozzle 19 is disposed so as to face the sub chamber 9. The sub chamber 9 is in communication with the main combustion chamber 5 formed in the cylinder 3 via an injection hole h provided at an eccentric position of the main combustion chamber 5. The injection hole h is formed in an inclined hole having an injection port 15 (see FIG. 2) toward the axial center (= cylinder axial center) P of the piston 4 substantially tangential to the inner peripheral surface of the sub chamber 9 There is.

  The configuration of sub-chamber 9 will be described. As shown in FIG. 2 and FIGS. 3A and 3B, the mounting hole (sub-chamber formed in the cylinder block 2 is opened at a position eccentric to the cylinder peripheral wall side from the cylinder center axis in the cylinder head 6). A hole 7 is formed, and the mounting hole 7 accommodates a base for forming a sub chamber (chamber) 8. The mounting hole 7 is a hollow located behind the large diameter opening 16, the small diameter trunk portion housing portion 17, and the trunk portion housing portion 17 in order from the head bottom surface 6 a facing the main combustion chamber 5 of the cylinder head 6. And a unit 18.

  The opening portion 16 accommodates the bottom portion 11 of the auxiliary chamber forming mouthpiece 8 formed in a cup shape. The body accommodating portion 17 is a place where the body portion 10 of the auxiliary chamber forming die 8 is accommodated, and has a smaller diameter than the opening 16. The hollow portion 18 is formed in a substantially hemispherical concave portion, and is connected to the trunk portion accommodation portion 17 by a stepped surface (not shown). The glow plug facing the sub-chamber 9 is omitted.

  As shown in FIGS. 1 and 2, the auxiliary chamber forming die 8 is formed of a stepped cylindrical fitting including a cylindrical barrel 10 and a bottom 11. The bottom portion 11 is formed in a state having a flange-like fitting flange portion 11A with one end side of the body portion 10 protruding in the circumferential direction with a diameter larger than the outer diameter of the body portion 10. On the other end side of the body portion 10, a substantially semispherical sub-chamber forming recess 12 is formed from the upper end surface of the body portion 10. Further, at the bottom portion 11 of the auxiliary chamber forming mouthpiece 8, an injection hole h for communicating the auxiliary chamber forming concave portion 12 with the main combustion chamber 5 is formed.

  As shown in FIG. 2, the hollow portion 18 and the trunk portion housing portion 17 are connected by a stepped surface (reference numeral is omitted), and the assembled state in which the auxiliary chamber forming cap 8 is fitted to the cylinder head 6 In this case, the inner peripheral surface 18a of the hollow portion 18 and the inner peripheral surface 12a of the auxiliary chamber forming recess 12 of the auxiliary chamber forming die 8 are configured to be substantially flush with each other. That is, a substantially spherical sub-chamber 9 is formed by the hollow portion 18 and the sub-chamber forming recess 12.

  As shown in FIG. 2 and FIGS. 3A and 3B, the injection hole h is formed in an inclined state substantially tangential to the inner peripheral surface of the sub chamber 9 and toward the cylinder center axis. By making the opening on the main combustion chamber 5 side the injection port 15, air entering into the sub chamber 9 at the time of compression is formed so as to generate a vortex in the sub chamber 9. A fuel injection nozzle 19 is penetrated through the cylinder head 6, and a tip injection portion 19 a of the fuel injection nozzle 19 is disposed so as to face the sub chamber 9.

  The injection holes h are configured to include the main hole 1 and a pair of auxiliary injection holes 22 located on both sides thereof. The main hole 1 has a central injection hole 13 located at the center (the left and right center with respect to the ejection path w), and a pair of side injection holes 14 and 14 integrally formed so as to protrude on both sides thereof. In the direction view of the piston axial center P, it is formed in the communication hole of a substantially three-leaf shape. The pair of side injection holes 14, 14 and the pair of auxiliary injection holes 22, 22 are distributed to one end side and the other end side of the central injection hole 13.

  The injection hole h communicating the sub chamber 9 with the main combustion chamber 5 is provided in an inclined manner so as to be directed from the sub chamber 9 to the central portion of the main combustion chamber 5. When the combustion flow g is ejected from the sub chamber 9 into the main combustion chamber 5 through the injection hole h, the top surface 4a of the piston head (ceiling wall) 4A of the piston 4 where the combustion flow g reaches near the top dead center It is configured to be sprayed obliquely.

  As shown in FIG. 2 and FIGS. 3A and 3B, the auxiliary injection holes 22 and 22 are formed in the vicinity of both sides of the bottom portion 11 on the bottom recessed portion 20A side of the injection hole h. The auxiliary injection hole 22 is formed in a vertical hole which penetrates the bottom portion 11 at a substantially central position of the sub chamber 9 and opens to the main combustion chamber 5. Therefore, the combustion air flow g is jetted from the sub chamber 9 into the main combustion chamber 5 in a state of facing the piston head 4A through the auxiliary injection holes 22 and 22.

  As shown in FIGS. 2 and 3 (a) and 3 (b), a recess 20 capable of forming a space s between the cylinder head 6 and the cylinder block 2 is formed on the outer surface (not shown) of the base. ing. The auxiliary chamber forming die 8 is formed with a heat insulating recessed portion 20 having a bottom recessed portion 20A and an outer peripheral recessed portion 20B. The outer surface of the base is a concept including the outer peripheral surface of the body portion 10, the upper surface of the bottom portion 11, the outer peripheral surface, and the bottom surface 11B.

  The bottom recess 20A is provided in the bottom 11 in a state of being opened in the bottom surface 11B of the bottom 11 (opening toward the top surface 2a of the cylinder block 2). That is, the bottom concave portion 20A of the curved shape formed on the bottom portion 11 of the overlapping portion of the auxiliary chamber forming die 8 and the cylinder block 2 in the vertical direction and having a concave shape is an outer peripheral arc along the outer periphery of the bottom portion 11. The surface 23 has an inner circumferential arc surface 24 whose curvature is smaller than that of the outer circumferential arc surface 23.

  That is, the bottom concave portion 20A is formed to be biased to the side opposite to the side where the injection holes h are present in the bottom portion 11. The bottom recessed portion 20A and the upper surface 2a of the cylinder block 2 form a space portion s for heat insulation via the gasket 21. The depth of the bottom recess 20A is set to a little less than half the thickness of the bottom 11.

  The outer peripheral recessed portion 20 </ b> B is provided on the outer periphery of the body 10 in a state of being opened to the cylinder head 6. The outer peripheral recessed portion 20B has an inclined peripheral surface 20b substantially along the inner peripheral surface 12a of the sub-chamber forming recess 12 and exhibits a substantially triangular cross-sectional shape continuous with the upper surface of the bottom 11 It is formed in the doughnut-shaped space part s covering the whole perimeter.

  Next, the piston 4 will be described. As shown in FIGS. 2 and 4, the piston head 4A of the piston 4 receives an intake valve recess 30 corresponding to an intake valve (not shown), an exhaust valve recess 31 corresponding to an exhaust valve (not shown), and A stop recess R is formed. The receiving recess R is provided as a recess for receiving the combustion air flow g ejected from the injection hole h. The intake and exhaust valve recesses 30 and 31 have a circular shape in plan view when they are alone.

  The receiving recess R is configured to have a recess portion 25 immediately below and a diffusion recess portion 26 on the downstream side of the ejection path w of the combustion air flow g. The recess portion 25 directly below is formed at a location f where the combustion flow g jetted from the injection hole h to the main combustion chamber 5 is blown in a state corresponding to the opening shape of the injection hole h. The diffusion recess portion 26 is formed so as to spread toward the downstream side in the ejection path w from the point f to be sprayed. That is, the receiving recess R is formed in a shape (cloud shape) conforming to the shape (opening shape) of the injection hole 15 which is the opening of the injection hole h.

  The recess portion 25 directly below is formed with a base recess portion 27 formed corresponding to the central injection hole 13, and a pair of side injection holes 14, 14 and a pair of auxiliary injection holes 22, 22 in a state of being connected to the base recess portion 27. And a pair of side recess portions 28 and 28 and a pair of auxiliary recess portions 29 and 29 formed correspondingly.

  The receiving recess R has a symmetrical shape or a shape close to that with respect to the ejection path w in plan view (viewing in the axial center P direction of the piston 4), and the intake valve recess 30 and the exhaust valve recess 31 receive The recess R is formed to be connected to the diffusion recess 26 in detail. As shown in FIG. 2, the depths of the intake and exhaust valve recesses 30 and 31 are set shallower than the depth of the receiving recess R set to the uniform depth d.

  The combustion air flow g ejected from the injection hole h to the main combustion chamber 5 is ejected from the central injection hole 13 to the base recess portion 27 and is ejected from the side injection holes 14 and 14 to the side recess portions 28 and 28. The injection holes 22, 22 are jetted to the auxiliary recess portions 29, 29 and then flow to the diffusion recess portion 26. The receiving recess R is shaped and set in a shape that matches the ejection state of the combustion air flow g.

〔Example〕
The depth range of each recess is as follows. Receiving recess R: 0.7 to 2.0 mm, quenching is suppressed when the combustion air flow g ejected from the injection hole h hits the top surface of the piston 4, and the effect of PM reduction is obtained, and blue and white It is also desirable from the point of smoke performance and cold startability. The intake valve recess 30: 0.5 to 1.0 mm, the exhaust valve recess 31: 0.5 to 1.0 mm, and the reduction of the compression ratio and the volume ratio can be suppressed without interference with the intake and exhaust valves, and blue and white Smoke performance and low temperature startability become good.

Second Embodiment
It may be a sub-chamber type diesel engine having a piston 4 shown in FIG. That is, the injection hole h is configured to have a main hole provided with the central injection hole 13 and a pair of side injection holes 14 integrally formed so as to project on both sides thereof. The recess portion 25 directly below is a pair of a base recess portion 27 formed corresponding to the central injection hole 13 and a pair formed corresponding to each of the pair of side injection holes 14 in a state of being connected to the base recess portion 27. Side recessed portions 28, 28 are composed. The auxiliary injection holes 22, 22 and the auxiliary recess portions 29, 29 are not present.

The sub-chamber type diesel engine E according to the present invention can achieve the following effects (1) to (6).
(1) Since the recess portion 25 directly below is provided, the time until the combustion air flow g ejected from the injection hole h to the main combustion chamber 5 collides with the top surface 4 a of the piston 4 (bottom surface of the receiving recess R) However, compared to the prior art, it becomes longer and therefore less likely to be quenched.
(2) In the main combustion chamber 5, the amount of air in contact with the combustion flow g jetted out to the main combustion chamber 5 can be increased.
(3) Since the shape of the receiving recess R is matched to the shape of the injection port 15, the functions and effects of the above (1) and (2) can be obtained more efficiently.

(4) Since the receiving recess R is formed, air can easily enter the injection hole h from the main combustion chamber 5 in the intake process.
(5) Mixing of the air in the main combustion chamber 5 and the mixture (combustion stream g) is promoted.
(6) By the above (1) to (5), it is possible to realize the output improvement, the fuel efficiency improvement and the PM reduction.

[Another embodiment]
The intake and exhaust valve recesses 30 and 31 may be deeper than the receiving recess R. In addition, the depth of the receiving recess R may be changed (shallow or deep) as going from the upstream side to the downstream side of the ejection path w. In particular, it is advantageous if the depth of the receiving recess R is formed so as to be shallower toward the downstream side in the ejection path w of the combustion air flow g.

DESCRIPTION OF SYMBOLS 1 main hole 4 piston 4A ceiling wall 5 main combustion chamber 9 sub chamber 13 central injection hole 14 side injection hole 22 auxiliary injection hole 25 immediately below recess 26 diffusion recess 27 base recess 28 side recess 29 auxiliary recess 30 intake valve Recess 31 Exhaust valve recess R Receiving recess d Depth f Sprayed point g Combustion air flow h Injection hole

Claims (7)

A main combustion chamber and a sub chamber provided at a location eccentric to the main combustion chamber are communicated by the injection hole, and a receiving recess for receiving the combustion air flow ejected from the injection hole is formed in the ceiling wall of the piston And
The receiving recess is formed at a location where the combustion air flow sprayed from the injection hole to the main combustion chamber is blown in a state corresponding to the opening shape of the injection hole, and the recess in the main combustion chamber A sub-chamber type diesel engine comprising a diffusion recess portion formed in a state where it spreads toward a downstream side in a blowout path of a combustion air stream from a portion to be blown, and configured in a shape matched to the opening shape. The injection hole has a central injection hole and a main hole provided with a pair of side injection holes integrally formed so as to project on both sides of the central injection hole.
The recess portion directly below is a base recess portion formed corresponding to the central injection hole, and a pair of side recess portions formed corresponding to the pair of side injection holes in a state of being connected to the base recess portion The sub-chamber type diesel engine according to claim 1, which is composed of:   The injection hole has a pair of auxiliary injection holes formed independently at positions on both sides of the central injection hole, and the recess portion directly below is connected to the base recess portion and the pair of auxiliary injection holes 3. The sub-chamber type diesel engine according to claim 2, further comprising a pair of auxiliary recess portions formed correspondingly to each of.   The sub-chamber type diesel engine according to any one of claims 1 to 3, wherein an intake valve recess corresponding to the intake valve and an exhaust valve recess corresponding to the exhaust valve are formed in the ceiling wall.   5. The sub-chamber type diesel engine according to claim 4, wherein the intake valve recess and the exhaust valve recess are formed to be connected to the receiving recess.   The sub-chamber type diesel engine according to any one of claims 1 to 5, wherein the receiving recess is formed to have a uniform depth.   The sub-chamber type diesel engine according to any one of claims 1 to 5, wherein the depth of the receiving recess is formed so as to be shallower toward the downstream side in the ejection path of the combustion air flow.

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