JP2013194559A - Compression self ignition engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a cooling loss in a compression self ignition engine.SOLUTION: A piston 14 includes a piston-side recess 14a formed on its crown surface. The piston-side recess 14a is configured by inclining its sidewall with respect to an axial center X direction of a cylinder 11 so that the diameter is increased from the bottom of the piston-side recess 14a toward an opening of the piston-side recess 14a. A squish generating part 14c is formed at the outer peripheral part of the sidewall in order to generate a squish flow S, flowing along the inner wall of the piston-side recess 14a from the radial outside toward the center in the late phase of the compression stroke, together with the lower surface of a cylinder head 13. An intermediate part 14d is formed on the radial inside of the squish generating part 14c on the sidewall. A fuel injection valve 17 injects fuel mist F into the piston-side recess 14a.

Description

  The present invention relates to a compression self-ignition engine that burns fuel supplied into a cylinder by compression self-ignition.

  Conventionally, various methods have been proposed for improving combustion of a lean air-fuel mixture in an engine. For example, in Patent Document 1, a squish flow that flows along the combustion chamber ceiling surface and the piston crown surface is generated from the intake side and exhaust side squish areas at the end of the compression stroke, respectively, and the air-fuel mixture is collected in the center of the combustion chamber. Thus, there is described a spark ignition engine that improves the ignitability of fuel and realizes lean combustion.

  In addition, for the purpose of improving the combustion of a lean air-fuel mixture, it is already known to perform compression self-ignition combustion that shortens the combustion period and burns. According to this compression self-ignition combustion, by increasing the effective expansion ratio, it is possible to reduce exhaust loss and improve engine operating efficiency. In compression self-ignition combustion, it is necessary to increase the in-cylinder temperature at the time of ignition, so the amount of residual gas that leaves hot burned gas in the combustion chamber is controlled, the intake gas temperature is increased, The compression ratio is increased. Here, if the geometric compression ratio is increased, the engine operation efficiency can be improved, but the volume of the combustion chamber at the compression top dead center is reduced.

Japanese Utility Model Publication No. 5-83328

  By the way, in a compression self-ignition engine, in order to suppress premature ignition and combustion noise at the time of high load operation and high rotation operation, fuel may be injected from the combustion injection valve at the latter stage of the compression stroke.

  However, in a compression self-ignition engine with a high compression ratio in which the volume of the combustion chamber becomes smaller in the latter half of the compression stroke, when fuel is injected in the latter half of the compression stroke, the injected fuel reaches the wall surface of the combustion chamber, and even in the vicinity of the combustion chamber wall surface. There is a problem that the air-fuel mixture concentration increases, and high-temperature combustion gas comes into contact with the wall surface of the combustion chamber to increase the cooling loss. In particular, as the geometric compression ratio increases, the air-fuel mixture in the cylinder is compressed and the combustion gas temperature increases, so that the amount of heat released through the combustion chamber wall surface increases. Therefore, in the case of higher compression than before, the above-mentioned problem becomes particularly remarkable.

  The present invention has been made in view of the above points, and the object of the present invention is to reduce cooling loss in a compression self-ignition engine in which fuel supplied into a cylinder is burned by compression self-ignition. .

  In order to solve the above problems, the present invention generates a squish flow that flows from the outside in the radial direction toward the center along the inner wall of the recess formed in the crown surface of the piston in the latter half of the compression stroke. It is characterized by.

  Specifically, the present invention includes a cylinder block in which a cylinder is formed, a cylinder head disposed on the cylinder block, a piston fitted into the cylinder, the cylinder block, and the cylinder head. And a fuel injection valve that injects fuel spray into the combustion chamber defined by the piston, and sets the period during which the fuel spray is injected by the fuel injection valve in the latter half of the compression stroke and injects the fuel spray into the combustion chamber The following solution was taken for a compression self-ignition engine that self-ignites the fuel spray.

  That is, in the first invention, a concave portion is formed on the crown surface of the piston, and the side wall of the piston extends from the bottom of the concave portion toward the concave opening so that the side wall of the piston is the shaft of the cylinder. The squish flow that is inclined with respect to the central direction and that flows from the outer side of the recess toward the center along the inner wall of the recess at the later stage of the compression stroke is formed on the outer surface of the side wall of the cylinder head. A squish generating part that is generated together with the squish generating part, and an intermediate part that is continuous with the bottom wall of the recess and the squish generating part is formed inside the squish generating part in a radial direction of the side wall of the squish generating part. Is arranged in the cylinder head along the axis of the cylinder and injects fuel spray into the recess.

  According to this, since the squish flow is caused to flow from the outside in the radial direction toward the center along the inner wall of the recess formed in the crown surface of the piston in the latter half of the compression stroke, the fuel spray injected in the latter half of the compression stroke Spreading to the tip side can be suppressed (air-blocked) by the squish flow, and fuel spray can be prevented from reaching (collising) the crown surface (inner wall of the recess) of the piston. As a result, the combustion gas can be prevented from coming into contact with the crown surface of the piston, and the cooling loss can be reduced.

  The cooling loss is determined by cooling loss = heat transfer coefficient × heat transfer area × (gas temperature−combustion chamber section screen temperature). As described above, air block increases the heat transfer coefficient. However, the cooling loss is reduced as compared with the conventional case where the fuel injected in the latter half of the compression stroke reaches the section screen of the combustion chamber and the heat of the combustion gas is released through the combustion chamber section screen.

  According to a second aspect of the present invention, in the first aspect, the concave portion is formed with a raised portion that protrudes from the outer side in the radial direction toward the center on the bottom wall.

  According to this, since the raised portion is formed on the bottom wall of the recess so as to rise from the outside in the radial direction toward the center, the squish flow is directed from the outside in the radial direction toward the center along the side wall of the raised portion. Can be shed. Thus, an air layer (air curtain) can be formed between the raised portion and the fuel spray, and the fuel spray can be further suppressed from reaching the crown surface of the piston. As a result, the combustion gas can be further suppressed from coming into contact with the crown surface of the piston, and the cooling loss can be further reduced.

  Further, since the raised portion is formed on the bottom wall of the recess, the volume of the combustion chamber can be reduced.

  A third invention is characterized in that, in the first or second invention, a heat insulating layer is provided on at least a lower surface of the cylinder head in a section screen defining the combustion chamber.

  According to this, since the heat insulation layer is provided at least on the lower surface of the cylinder head in the section screen that partitions the combustion chamber, the combustion chamber can be insulated and the cooling loss can be further reduced.

  According to the present invention, the squish flow is caused to flow from the outside in the radial direction toward the center along the inner wall of the recess formed in the crown surface of the piston in the late stage of the compression stroke. Can be suppressed by the squish flow, and the fuel spray can be prevented from reaching the crown surface of the piston. As a result, the fuel spray is injected into the combustion chamber in the latter half of the compression stroke. Cooling loss can be reduced in a compression self-ignition engine with a high compression ratio that is injected and the volume of the combustion chamber is reduced in the latter half of the compression stroke.

It is a figure showing roughly the composition of the diesel engine concerning the embodiment of the present invention. It is a figure which shows the structure of a fuel injection valve, (a) is a fragmentary sectional view which shows the structure of the lower part of a fuel injection valve, (b) is sectional drawing which shows the structure of the principal part of a fuel injection valve. . It is a graph which shows the relationship between a squish flow velocity and a crank angle. It is a figure which shows schematically the structure of the modification of a diesel engine.

  Hereinafter, the diesel engine which concerns on embodiment is demonstrated based on drawing. The following description of the preferred embodiment is merely exemplary in nature. FIG. 1 shows a schematic configuration of an engine 1 according to the embodiment. The engine 1 is a compression self-ignition internal combustion engine that is mounted on a vehicle such as an automobile and is supplied with a fuel mainly composed of light oil, and only one cylinder is shown in the figure. Cylinder) 11. Although the output shaft of the engine 1 is not shown, it is connected to drive wheels via a transmission. The vehicle is propelled by the output of the engine 1 being transmitted to the drive wheels. The engine 1 includes a cylinder block 12 and a cylinder head 13 mounted thereon, and a cylinder 11 is formed inside the cylinder block 12. A piston 14 is slidably inserted in each cylinder 11, and the piston 14 defines a combustion chamber 15 together with the cylinder 11 and the cylinder head 13.

  On the lower surface of the cylinder head 13 (the ceiling surface that defines the upper surface of the combustion chamber 15), a conical central recess 13a whose inner wall (inner surface) is inclined downward from the center in the radial direction outward. Is formed in a recessed fit. The center side recess 13 a is arranged so that the center axis thereof coincides with the axis X of the cylinder 11. On the lower surface of the cylinder head 13, an outer peripheral recess 13 b that is annular when viewed from the axial center X direction of the cylinder 11 and is substantially triangular in cross section is recessed in the radial direction of the central recess 13 a. Is formed. The outer peripheral side recess 13b is arranged so that its central axis coincides with the axis X of the cylinder 11, and its inner peripheral surface is inclined upward from the center in the radial direction outward. Moreover, the outer peripheral side recessed part 13b has the outer peripheral surface extended in parallel with the axial center X of a cylinder. On the lower surface of the cylinder head 13, an annular intermediate portion 13 c is formed between the central concave portion 13 a and the outer peripheral concave portion 13 b as viewed from the axial center X direction of the cylinder 11. The intermediate portion 13 c is arranged with a central axis that coincides with the axis X of the cylinder 11 and is perpendicular to the axis X of the cylinder 11.

  A substantially frustoconical piston-side recess 14 a is formed in the crown surface of the piston 14 so as to be recessed. The piston-side concave portion 14a is arranged so that its central axis coincides with the axis X of the cylinder 11, and in this example, the bottom wall (bottom surface) has a substantially frustoconical shape that protrudes from the outside in the radial direction toward the center. The raised portion 14b is formed. The raised portion 14b is arranged so that its central axis coincides with the axis X of the cylinder 11, and its side wall (side surface) has a shape corresponding to the fuel spray F injected by the fuel injection valve 17 described later, and the fuel spray. It is formed in a shape along F. In addition, the top wall of the raised portion 14 b is inclined with respect to the direction perpendicular to the axis X of the cylinder 11 so that the top portion of the raised portion 14 b sinks from the outside in the radial direction toward the center. Further, the side wall of the piston-side recess 14a is inclined with respect to the axis X direction of the cylinder 11 so that the diameter of the piston-side recess 14a increases from the bottom of the piston-side recess 14a toward the opening of the piston-side recess 14a. . An annular squish generating portion 14c is formed on the side wall of the piston-side concave portion 14a at the outer peripheral portion thereof and at a portion corresponding to the outer peripheral-side concave portion 13b when viewed from the axis X direction of the cylinder 11. The squish generating part 14c is arranged with its central axis aligned with the axis X of the cylinder 11, and extends parallel to the inner peripheral surface of the outer peripheral recess 13b corresponding to the inner peripheral surface of the outer peripheral recess 13b. . Further, the side wall of the piston-side recess 14a has an annular shape when viewed from the direction of the axis X of the cylinder 11 that is continuous with the bottom wall of the piston-side recess 14a and the squish generation part 14c inward in the radial direction of the squish generation part 14c. The intermediate portion 14d is formed. The intermediate portion 14d is arranged such that its central axis coincides with the axis X of the cylinder 11, and the inclination of the cylinder 11 with respect to the direction of the axis X is the same as that of the squish generating portion 14c. Further, the side walls of the intermediate part 14d and the raised part 14b are smoothly continuous so that the continuous part is curved.

  In this way, in this engine 1, a high geometry is provided by the squish area 16 defined by the central recess 13 a, the piston recess 14 a, the raised portion 14 b, the inner peripheral surface of the outer periphery recess 13 b and the squish generating portion 14 c. The compression ratio is realized. In the present embodiment, the geometric compression ratio is preferably 20 or more, more preferably 25 or more and 40 or less.

  The cylinder head 13 is formed with two intake ports and two exhaust ports (not shown) for each cylinder 11, and an intake valve and an exhaust for opening and closing the intake port and the exhaust port on the combustion chamber 15 side. Each valve (not shown) is provided.

  The cylinder head 13 is provided with a fuel injection valve 17 for each cylinder 11. The fuel injection valve 17 is disposed along the axis X of the cylinder 11 and is attached to the cylinder head 13 with a known structure such as using a bracket. The tip of the fuel injection valve 17 faces the center of the ceiling surface of the combustion chamber 15 (inner wall of the central recess 13a).

  As shown in FIG. 2, the fuel injection valve 17 is an outer valve-opening injector having an outer valve 19 that opens and closes a nozzle port 18 that injects fuel spray F into the combustion chamber 15. The nozzle port 18 is formed in a tapered shape whose diameter increases toward the distal end side at the distal end portion of the fuel pipe 20 extending along the axis X of the cylinder 11. The proximal end of the fuel pipe 20 is connected to a case 21 in which a piezo element (not shown) is disposed. The outer opening valve 19 has a valve main body 19a and a connecting portion 19b connected from the valve main body 19a through the fuel pipe 20 to the piezo element. A portion of the valve body 19a on the side of the connecting portion 19b has substantially the same shape as the nozzle port 18, and when the portion is in contact (sitting) with the nozzle port 18, the nozzle port 18 is closed. . At this time, the tip side portion of the valve main body 19 a is in a state of protruding to the outside of the fuel pipe 20.

  The piezo element lifts the outer open valve 19 from a state in which the nozzle port 18 is closed by pressing the outer open valve 19 toward the combustion chamber 15 in the axial direction X of the cylinder 11 by deformation due to application of voltage. The nozzle port 18 is opened. At this time, the fuel spray F is injected from the nozzle port 18 into the combustion chamber 15 (specifically, in the piston-side recess 14a) in a cone shape (specifically, a hollow cone shape) centering on the axis X of the cylinder 11. When the application of voltage to the piezo element stops, the piezo element returns to its original state, and the outer valve 19 closes the nozzle port 18 again.

  Thus, in this engine 1, an injection period in which the fuel spray F is injected by the fuel injection valve 17 is within the range of the generation period of the squish flow S that is generated (generated) by the squish area 16 in the latter half of the compression stroke. For example, when the engine speed is 2000 rpm, BTDC is set to 20 ° to 30 ° CA (near the compression stroke top dead center). The generation period of the squish flow S ranges from BTDC 50 ° to 60 ° CA to top dead center, for example, as shown in FIG. In this example, the squish flow rate gradually increases and reaches a maximum in the vicinity of BTDC 5 ° CA, and then gradually decreases to zero at the top dead center. The squish flow velocity in FIG. 3 indicates the average flow velocity of the squish flow S in the boundary portion between the squish generating portion 14c and the intermediate portion 14d (the boundary portion between the outer peripheral recess 13b and the intermediate portion 13c) in the combustion chamber 15. Yes. Further, in the expansion stroke, a reverse squish flow is generated.

  Here, the symbol Y in the figure is the central axis of the nozzle port 18 (the spray axis of the fuel spray F), and this central axis Y is the cone-shaped open portion (FIG. The straight line at each position passing through the center of () is shown.

  Further, as shown in FIG. 1, the combustion chamber 15 is partitioned by the wall surface of the cylinder 11, the crown surface of the piston 14, the lower surface of the cylinder head 13, and the surfaces of the valve heads of the intake valve and the exhaust valve. The combustion chamber 15 is thermally insulated by providing a heat insulating layer 22 having a configuration to be described later on the lower surface of the cylinder head 13. The heat insulating layer 22 may be provided on all of these section screens, or may be provided on a part of these section screens including at least the lower surface of the cylinder head 13. In addition, the thickness of the heat insulation layer 22 illustrated in FIG. 1 does not indicate an actual thickness, but is merely an example.

  The heat insulation structure of the combustion chamber 15 will be described in further detail. As described above, the heat insulation structure of the combustion chamber 15 is constituted by the heat insulation layer 22 provided on the lower surface of the cylinder head 13 in each section screen defining the combustion chamber 15. In order to suppress the release of the heat of the combustion gas through the section screen, the thermal conductivity is set lower than that of the metal base material constituting the combustion chamber 15. Here, the cylinder head 13 is a base material for the heat insulating layer 22 provided on the lower surface of the cylinder head 13. Therefore, the material of the base material is aluminum alloy or cast iron for the cylinder head 13.

  In addition, the heat insulating layer 22 preferably has a volumetric specific heat smaller than that of the base material in order to reduce cooling loss. In other words, the gas temperature in the combustion chamber 15 fluctuates with the progress of the combustion cycle, but in a conventional engine that does not have a heat insulation structure of the combustion chamber, the cooling water flows in the water jacket formed in the cylinder head or cylinder block. Thus, the temperature of the surface defining the combustion chamber is maintained substantially constant regardless of the progress of the combustion cycle.

  On the other hand, since the cooling loss is determined by cooling loss = heat transfer coefficient × heat transfer area × (gas temperature−temperature of the section screen), the cooling temperature increases as the temperature difference between the gas temperature and the wall surface temperature increases. The loss will increase. In order to suppress the cooling loss, it is desirable to reduce the difference temperature between the gas temperature and the temperature of the partition screen. However, as described above, when the temperature of the partition screen of the combustion chamber 15 is maintained substantially constant, It is inevitable that the temperature difference will increase as the temperature changes.

  Therefore, it is preferable that the heat insulating layer 22 has a small heat capacity, and the temperature of the section screen of the combustion chamber 15 changes following the fluctuation of the gas temperature in the combustion chamber 15.

As an example of the heat insulating layer 22, the heat insulating layer 22 may be formed of a zirconia (ZrO ₂ ) or partially stabilized zirconia (PSZ) film formed on the lower surface of the cylinder head 13 by, for example, plasma spraying. . Zirconia or partially stabilized zirconia has a relatively low thermal conductivity and a relatively low volumetric specific heat, so that the thermal conductivity is lower than that of the base material and the specific heat of volume is the same as or lower than that of the base material. Layer 22 is constructed.

  Here, in the engine 1, the cooling loss of the cylinder head 13 is larger than that of the piston 14 as the cooling water flows through the water jacket formed in the cylinder head 13 as described above.

  A state in the combustion chamber 15 in the latter half of the compression stroke will be described. In the latter half of the compression stroke, as the piston 14 moves up, the air in the portion sandwiched between the inner peripheral surface of the outer peripheral recess 13b and the squish generating portion 14c that inclines downward from the outer side in the radial direction toward the center. Is pushed from the squish area 16 along the inner wall of the piston-side recess 14a (the side wall of the piston-side recess 14a and the side wall of the raised portion 14b) toward the center from the outside in the radial direction. A squish flow S that flows through is generated. Then, in the vicinity of the top dead center of the compression stroke, the fuel spray F enters the combustion chamber 15 from the nozzle port 18 of the fuel injection valve 17 and radially outward from the position of the axis X of the cylinder 11 and in the piston-side recess 14a. It is sprayed in a cone shape toward the side wall. At this time, the central axis Y of the nozzle port 18 intersects the side wall of the piston-side recess 14a at the top dead center.

  A negative pressure is generated in the vicinity of the tip of the fuel injection valve 17 as the fuel spray F is injected, so that the fuel spray is respectively applied to the upper side and the lower side (the radially outer side and the inner side) of the fuel spray F. After flowing away from F, a spray vortex flow R is generated that flows toward the tip of the fuel injection valve 17 (in the direction opposite to the spray direction of the fuel spray F). The spray vortex R on the upper side of the fuel spray F (on the cylinder head 13 side) is larger in magnitude than the spray vortex R on the lower side of the fuel spray F (on the piston 14 side). In addition, a funnel flow (not shown) that flows upward toward the tip of the fuel injection valve 17 also occurs at the center of the combustion chamber 15.

  Here, as described above, the squish flow S is radiated outward along the inner wall of the piston-side recess 14a (the squish generating portion 14c, the side wall of the piston-side recess 14a, and the side wall of the raised portion 14b) later in the compression stroke. The squish flow S suppresses (air-blocks) the fuel spray F injected near the top dead center of the compression stroke from flowing toward the center. The fuel spray F can be prevented from reaching (collising) the crown surface of the piston 14 (side wall of the piston-side recess 14a). As a result, the combustion gas can be prevented from coming into contact with the crown surface of the piston 14, and the cooling loss can be reduced.

  In addition, the squish flow S is formed radially outward along the side wall of the raised portion 14b by forming a raised portion 14b that rises from the radially outer side toward the center on the bottom wall of the piston-side recessed portion 14a. It can flow from the center to the center. Thus, an air layer (air curtain) can be formed between the raised portion 14b and the fuel spray F, and the fuel spray F can be further suppressed from reaching the crown surface of the piston 14. As a result, the combustion gas can be further suppressed from coming into contact with the crown surface of the piston 14, and the cooling loss can be further reduced.

  Further, the intermediate portion 14d (side wall of the piston-side recess 14a) and the side wall of the raised portion 14b are smoothly continued so that the continuous portion has a curved surface, thereby allowing the squish flow S to flow into the side wall of the piston-side recess 14a. And it can flow smoothly along the side wall of the protruding part 14b, and it can suppress that the squish flow S flows toward the fuel spray F.

  Further, by forming the raised portion 14b on the bottom wall of the piston-side concave portion 14a, the central space in the fuel spray F injected in a cone shape as the piston 14 is raised can be compressed by the raised portion 14b. It is possible to further suppress the fuel spray F from reaching the crown surface of the piston 14. As a result, the combustion gas can be further suppressed from coming into contact with the crown surface of the piston 14, and the cooling loss can be further reduced.

  Further, since the raised portion 14b is formed on the bottom wall of the piston-side recess 14a, the spray vortex R below the fuel spray F spreads outward in the radial direction as the fuel spray F spreads outward in the radial direction. The bulging portion 14 b can suppress the spreading to the direction, and the spray vortex R below the fuel spray F can be concentrated in the center of the combustion chamber 15.

  Moreover, the shape of the fuel spray F can be maintained by forming the raised portion 14b in a shape corresponding to the fuel spray F and the shape of the side wall corresponding to the fuel spray F.

  Furthermore, by inclining the top wall of the raised portion 14b with respect to the direction perpendicular to the axis X of the cylinder 11 so that the raised portion 14b top portion sinks from the outside in the radial direction toward the center, The top wall of the raised portion 14b can be shaped to correspond to the spray vortex flow R below the fuel spray F, and the fuel vortex R below the fuel spray F is surely secured by the top wall of the raised portion 14b. It can be made to flow upward toward the tip.

  Further, by injecting the fuel spray F into the piston-side recess 14a, the fuel spray F can be prevented from reaching the lower surface of the cylinder head 13 (inner wall of the center-side recess 13a) having a large cooling loss. An air layer (air curtain) can be interposed between the inner wall of the side recess 13a and the fuel spray F. As a result, the combustion gas can be prevented from coming into contact with the lower surface of the cylinder head 13, and the cooling loss can be further reduced.

(Other embodiments)
In addition, although the protruding part 14b is formed in the bottom wall of the piston side recessed part 14a, as shown in FIG. 4, for example, it is not necessary to form a protruding part. That is, the bottom wall of the piston-side recess 14 a is configured by a surface perpendicular to the axis X of the cylinder 11. At this time, the squish flow S flows from the radially outer side toward the center along the inner wall of the piston-side concave portion 14a, whereby the fuel spray F injected near the top dead center of the compression stroke spreads to the tip side. This can be suppressed by the squish flow S, and the fuel spray F can be prevented from reaching the crown surface of the piston 14, and as a result, the cooling loss can be reduced.

  Further, the ridge portion 14 b is inclined with respect to the direction in which the top wall is orthogonal to the axis X of the cylinder 11, but the ridge portion is a surface whose top wall is perpendicular to the axis X of the cylinder 11. It may be constituted by.

  Furthermore, although the magnitude | size of the inclination with respect to the axial center X of the cylinder 11 of the inner wall of the center side recessed part 13a is the same over the perimeter, as long as it does not become 0, you may change the magnitude | size. Similarly, the inclination of the inner peripheral surface of the outer peripheral recess 13b, the side wall of the piston recess 14a, and the side wall of the raised portion 14b may also change.

  Further, the squish generating part 14c extends in parallel with the inner peripheral surface of the outer peripheral side recessed part 13b. However, the squish generating part causes the squish generating part S to extend from the outer side in the radial direction along the inner wall of the piston side recessed part 14a. As long as it flows toward the inner side, it may be inclined with respect to the inner peripheral surface of the outer peripheral recess 13b.

  Further, although the fuel injection period is set near the top dead center of the compression stroke, the fuel injection period may be set as appropriate within the latter half of the compression stroke and within the generation period of the squish flow S.

  Moreover, although the heat insulation layer 22 is comprised with the film | membrane of zirconia or a partially stabilized zirconia, a heat insulation layer may be comprised with the film | membrane of ceramic type | system | groups other than a zirconia, a non-ceramic type | system | group, or a silicon-type resin, for example. Good.

  Furthermore, although the engine 1 is comprised with the diesel engine, you may comprise an engine with a gasoline engine, for example. At this time, the engine is operated in the HCCI mode, for example.

  Further, although the fuel injection valve 17 employs a piezo element as an actuator, the fuel injection valve may employ, for example, a solenoid as an actuator.

  As described above, the compression self-ignition engine according to the present invention can be applied to applications that require a reduction in cooling loss.

1 Engine 11 Cylinder
12 Cylinder block 13 Cylinder head 13a Center side recessed part 13b Outer peripheral side recessed part 13c Intermediate part 14 Piston 14a Piston side recessed part 14b Raised part 14c Squish generating part
14d Intermediate part 15 Combustion chamber 16 Squish area 17 Fuel injection valve 18 Nozzle port 22 Thermal insulation layer F Fuel spray R Spray vortex S Squish flow X Cylinder axis Y Center axis of nozzle port

Claims (3)

A cylinder block in which a cylinder is formed, a cylinder head disposed on the cylinder block, a piston fitted into the cylinder, and a combustion defined by the cylinder block, the cylinder head, and the piston A fuel injection valve that injects fuel spray into the chamber, and sets the period during which the fuel spray is injected by the fuel injection valve in the latter half of the compression stroke, and also performs self-ignition of the fuel spray injected into the combustion chamber A self-ignition engine,
The piston has a recess formed in its crown surface,
The recess is configured such that its side wall is inclined with respect to the axial direction of the cylinder so that the diameter of the recess increases from the bottom of the recess toward the opening of the recess. And a squish generating portion that generates a squish flow that flows from the outside in the radial direction toward the center along the inner wall of the concave portion together with the lower surface of the cylinder head. An intermediate portion is formed continuously with the bottom wall of the recess and the squish generating portion,
The compression self-ignition engine, wherein the fuel injection valve is disposed in the cylinder head along an axis of the cylinder and injects fuel spray into the recess. The compression self-ignition engine according to claim 1,
The compression self-ignition engine according to claim 1, wherein a raised portion is formed on the bottom wall of the concave portion so as to rise from the outside in the radial direction toward the center. The compression self-ignition engine according to claim 1 or 2,
A compression self-ignition engine, wherein a heat insulating layer is provided on at least a lower surface of the cylinder head in a section screen defining the combustion chamber.

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