JPH0447401Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a four-stroke water-cooled diesel engine suitable for outboard motor engines and the like.

In conventional diesel engines, the cylinder block and cylinder head are made of cast iron, so there are problems in that the weight is large and the output per unit weight is small. In addition, in conventional products, the cylinder block and cylinder head are separate parts, and they are fastened together with bolts with a gasket in between, so there is a problem that the number of parts increases and there is a risk that the seal at the gasket part may be incomplete. There are other problems.

In order to solve the above-mentioned conventional problems, the present invention aims to provide a diesel engine in which the cylinder block and cylinder head are integrally molded from aluminum (including aluminum-based alloys). .

In FIG. 1, which is a vertical cross-sectional view, the center line CC of the crankshaft 1 is vertical, and the flywheel 2 is attached to the upper end of the crankshaft 1. The illustrated engine is for an outboard motor, and an involute spline 3 is provided on the inner periphery of the lower end of a crankshaft 1 to connect an output shaft (not shown). In the illustrated engine, two cylinders 5 are arranged vertically, and the center line OO of each cylinder extends horizontally in the longitudinal direction of the ship. 6 is a piston, and 7 is a connecting rod.

The cylinder block 10 and cylinder head 11 are integrally molded from a cast product whose main component is aluminum. A cooling water chamber 12 is provided inside the cylinder block 10 and cylinder head 11. Cooling water is supplied to the chamber 12 by a cooling water pump (not shown). An exhaust port 13 and an intake port 14 are provided within the cylinder head 11. In addition, the cylinder head 11 has the stems 17 of the exhaust valve 15 and the intake valve 16,
18 and the cylindrical boss 22 forming the peripheral wall of the mounting hole of the unit injector 50.
is provided.

The cylindrical boss 22 is integrally provided from a ceiling 45 forming the explosion surface 35 of the cylinder head 11 to a wall 45' on the opposite side facing the ceiling 45 with the cooling water chamber 12 in between. An exhaust manifold 28 (FIG. 5) is also provided integrally with the cylinder head 11. One exhaust valve 15 and one intake valve 16 are provided for each cylinder 5. A total of four valves 15 and 16 are arranged vertically in a horizontal position,
They are driven by a common camshaft 23 via a valve arm 24 as will be described later. camshaft 23
Case 26 of the valve arm chamber 25 in which the valve arm 24 is housed
has approximately the same width as the width of the cylinder head 11, and is secured to the end surface 47 of the cylinder head 11 by a belt.

The crankcase 27 is the part 2 on the block 10 side.
9 and a portion 30 on the opposite side. Portion 29 is integrally molded with block 10, and portion 30 is connected to portion 29 by bolt 34.
is fixed. The mating surfaces of both parts 29 and 30 include the crankshaft centerline C--C and are perpendicular to the cylinder centerline O--O. Portion 30 is also made of the same material as cylinder block 10.

Next, the structure of each part will be explained in detail. In FIG. 2, which is an enlarged partial view of FIG. 1, a liner 31 forming the sliding surface of the piston 6 is made of cast iron and is incorporated into the cylinder block 10 by casting. An alloy layer is formed on the contact surface between the liner 31 and the cylinder block 10 during casting, and the alloy layer allows the liner 31 to contact the cylinder block 10.
is fixed to. The tip 32 of the liner 31 is located a short distance closer to the cylinder head 11 than the top ring 33 of the piston 6 at the top dead center position shown in the figure.
₁ and is located relatively far from the explosion surface 35 of the cylinder head 11. That is, the distance from the explosion surface 35 to the liner tip 32 is set as large as possible within a range that does not hinder the sliding of the ring 33. Reference numeral 36 indicates a corner portion near the outer periphery of the explosion surface 35, in other words, a portion where the cylinder block 10 and the cylinder head 11 are continuous in the vicinity of the combustion chamber 37. Combustion chamber 37 in this part 36
The cross section of the corner surface 36' facing is formed into a circular arc shape with a radius R, and the crank chamber side end 36'' of the corner surface 36' is located at the top dead center position of the piston 6, as shown in FIG. It is located closer to the explosion surface 35 than the top spring 33 of the.

By employing the above structure, the strength of the corner portion 36 can be sufficiently increased against the explosive force within the combustion chamber 37. That is, stress caused by the above-mentioned explosive force tends to concentrate on the corner portion 36, but by rounding the corner surface 36', the stress on the portion 36 can be dispersed and cracks etc. can be prevented from occurring in the portion 36. Moreover, since the length of the portion 36 is set large, the radius R can be set large, and therefore the stress dispersion effect can be enhanced and sufficiently high strength can be obtained.

It has been confirmed through tests that the strength of the portion 36 can be sufficiently increased if the radius R is set to a value of about 2% or more of the cylinder inner diameter and less than a distance to allow movement of the piston 6. That is, if the ratio of the radius R to the cylinder inner diameter is r%, then
As shown in FIG. 3, in a range where the ratio r is smaller than about 2%, the stress δ decreases more rapidly as the comparison r increases, but when the comparison r exceeds about 2%, the amount of change in the stress δ is small. Therefore, if the comparison r is about 2% or more, the density of the portion 36 in FIG. 2 can be sufficiently increased.

Also, the crank chamber side end 3 of the corner surface 36'
6" is located closer to the explosion surface 35 than the top ring 33 of the piston 6 at the top dead center position,
Piston ring 33 at piston top dead center position
This prevents the piston ring 33 from coming into contact with the corner surface 36', preventing deformation of the piston ring 33 due to contact between the piston ring 33 and the corner surface 36', and preventing leakage from the combustion chamber to the crank chamber side. Sealing performance against gas can be improved.

In FIG. 2, there is a cylinder block portion 39 surrounding the tip end 38 of the liner 31 and the cylinder head 1.
1 bulges outward (in the direction of arrow S) from the cylinder block portion 40 closer to the crankcase.
When the portion 39 has a thick structure in this manner, it is possible to prevent the portion 39 from being significantly deformed outward S when subjected to explosive force, and to prevent a gap from forming between the portion 39 and the liner 31. Therefore, the combustion chamber 37
The gas inside the liner 31 and the cylinder block 10
There is no leakage into the crank chamber between the holes, allowing high engine performance to be maintained. Since not much explosive force is applied to the crankcase side portion 40 of the cylinder block 10, there is no strength problem even if the portion 40 is made thinner, and the weight can be reduced by making the portion 40 thinner. At the same time part 3
When 9 is thickened, the cross-sectional area of the portion 39 becomes larger, and the area of the portion 39 that receives the force in the cylinder direction applied to the explosion surface 35 becomes larger, so that the stress in the corner portion 36 can also be reduced.

In FIG. 4, which is an enlarged schematic diagram of FIG. 2,
The inner surface of the liner 31 is honed. The honing surface 41 is provided on the inner surface of the liner from a portion on the crank chamber side to a portion 42 near the tip. The portion 42 is located at a distance ₂ of about 1 to 4 mm from the top spring 33 at the top dead center position toward the explosion surface 35, and the top spring 33
always slides on the honing surface 41. The inner circumferential surface portion 43 from the portion 42 of the liner 31 to the tip 32 is relative to the honing surface 41.
It is deflected radially outward by a distance ₃ of about 0.1 to 0.2 mm to form a honing relief. This provides the following advantages: That is, the honing tool is inserted into the liner 31 from the crank chamber side, but since the cylinder head 11 gets in the way at that time, honing cannot be performed up to the liner tip 32. Therefore, if the liner 31 before honing has the same inner diameter up to the tip 32, a honing boundary (step) will occur near the tip after honing, and the inner peripheral surface of the tip will have a smaller diameter than the honed surface 41. As a result, the piston 6 gets caught in the small-diameter tip portion of the piston 6, but in the illustrated structure, the tip portion 43 has a clearance, so such a problem does not occur. Also, since the honing relief 43 is provided in the liner 31, the cylinder block 10 (aluminum) is not honed and therefore the honing tool is not clogged.

In FIG. 4, the outer surface 6' of the outer periphery of the top of the piston 6 is formed into a curved surface that approaches the corner surface 36' of the corner portion 36 with almost no gap;
This makes it possible to increase the compression ratio of the engine and improve performance, especially in diesel engines.

In FIG. 2, the ceiling 45 of the cylinder head 11 forming the explosion surface 35 has a wall surface 46 opposite to the explosion surface 35 facing the cooling water chamber 12. Cooling water chamber 1
2, the chamber 12a near the center of the cylinder is farther from the explosion surface 35 than the chamber 12b near the outer periphery, and the ceiling 4
The wall thickness (for example, h) of No. 5 is larger at the center portion than at the outer periphery portion. By changing the wall thickness of the ceiling 45 in this way, the explosion surface 3
The strength of the ceiling 45 can be sufficiently increased against the explosive force applied to the ceiling 45, and the average wall thickness of the ceiling 45 can be reduced to reduce the weight. In the illustrated embodiment, the wall thickness of the ceiling 45 changes in stages, but it is also possible to make the entire wall surface 46 generally tapered so that the wall thickness of the ceiling 45 increases smoothly toward the center. By doing so, the strength can be further increased.

As shown in Fig. 1, the cylinder head 11 has intake and exhaust valves 15, 16 and ports 13, 14 inside.
, the total height H from the explosion surface 35 to the end surface 47 is large. Moreover, inside the cylinder head 11, the boss 20 and ports 13, 14 are provided.
and a large number of ribs 48 that constitute partition walls of the cooling water chamber 12.
is provided. In this way, the total height H of the cylinder head 11 is large, and there are many bosses 20 and ribs 4.
8, the strength of the cylinder head 11 is high.

In FIG. 5, which is a - sectional view of FIG. 1,
The boss 22 for the fuel injection nozzle 21 also increases the strength of the cylinder head 11. The boss 22 extends from near the center of the ceiling 45 roughly along the center of the cylinder, and is integrally provided to a wall 45' (FIG. 1) on the opposite side facing the ceiling 45 with the cooling water chamber 12 in between. Since there is another boss 20 (Fig. 1) rib 4
8, the reinforcing effect on the cylinder head 11 is greater. Also, the nozzle 21 is a fuel injection pump 49.
The unit injector 50 is configured in combination with the cylinder head 11, and the injector 50 is attached to the boss 22 as described below, thereby further increasing the strength of the cylinder head 11.

First, the general structure of the unit injector 50 will be explained. The unit injector 50 is the pump 49
The sleeve 98 of the nozzle 21 is attached to the tip of the body 91 of the
By reciprocating the plunger 93 within the barrel 92 attached inside the body 91, the high pressure fuel oil passage 9 inside the body 91 is directly connected.
4, fuel is supplied from the pump 49 to the nozzle 21. The unit injector 50 is provided with an annular step 95 near the tip of the body 91 and in the middle of the sleeve 98.
The portion protruding from the first boss 22 is fastened to the cylinder head 11 by a presser metal fitting 96. Therefore, the unit injector 5 is located in the center of the ceiling 45.
0, an initial compressive force is applied that opposes the explosive force, and in this respect as well, the strength of the cylinder head 11 is increased and the amount of deformation of the ceiling 45 is reduced.

Further, the unit injector 50 has a large diameter portion that constitutes the pump 49, and the large diameter portion (large diameter portion of the body) is also adapted to fit into the boss 22. Therefore, the boss 22 becomes a large reinforcing portion with a large diameter, and in this respect as well, the strength of the cylinder head 11 can be increased.

The nozzle 21 opens its injection port when high pressure is supplied from the pump 49. As described above, in the unit injector 50, the pump 49 and the nozzle 21 are connected only by the short oil passage 94 in the body 91, so that the fuel pressure in the pump 49 is accurately transmitted to the nozzle 21. Therefore, fuel can be injected from the nozzle 21 in a manner that accurately corresponds to the pressure inside the pump 49 over the entire range of changes in engine speed and the entire range of changes in the fuel injection amount, and secondary injection can be prevented. Moreover, since the pressure loss within the oil passage 94 can be significantly reduced, the injection pressure of the nozzle 21 can be increased and the atomization of the spray can be promoted. Furthermore, the injection operation of the nozzle 21 is not delayed with respect to the pressurizing operation of the pump 49. In this way, secondary injection and injection delay can be prevented, and the atomization of the spray can be promoted, so the best combustion state can be maintained and engine performance can be improved. Furthermore, since injection delays can be prevented, performance during high-speed operation can be improved. Moreover, unlike conventional products, there is no need to provide a timer for adjusting the injection timing, and the structure can be simplified.

The tip of the nozzle 21 is exposed in the combustion chamber 37 at approximately the center of the explosion surface 35, and the cylinder head 11 is not provided with a swirl chamber (auxiliary combustion chamber). Since the engine is of the direct injection type, the unit injector 50 can be supported over the entire height H of the head 11. Therefore, the mounting condition of the unit injector 50 is stabilized, and the distance from the explosion surface 35 to the other end (protector 65) of the unit injector 50 is reduced.
The entire engine can be downsized. That is, although the unit injector 50 has a long overall length, by making the engine a direct injection type, it is possible to prevent the engine from becoming larger. Incidentally, if the swirl chamber is provided in the cylinder head 11, the unit injector 50 will be located away from the explosion surface 35 by the amount of the swirl chamber, so the cylinder head 11 and the case 26 will need to be made larger.

By using a direct injection system, the following advantages can also be obtained. In other words, if a vortex chamber is provided,
When the flame jets out from the swirl chamber to the combustion chamber 37, a large thermal load is applied to the inner surface of the communication passage between the swirl chamber and the combustion chamber 37. On the other hand, in the direct injection type, no large local heat load is applied to the cylinder head 11 or cylinder block 10. Therefore, although aluminum has low heat resistance, the cylinder head 11 and cylinder block 10 will not be damaged by heat.

Also, since aluminum has low heat resistance but high thermal conductivity, the heat added to the cylinder block 10 and cylinder head 11 from the combustion chamber 37 is quickly transferred to the cylinder block 10 and the cylinder head 11.
It is discharged to the cooling water in 2. Therefore, the cylinder block 10 and the cylinder head 11 are not subjected to vortex heat, and damage due to heat can also be prevented in this respect.

The piston 6 has a depression in the center of the top that will become the combustion chamber 37, and the outer surface 6' (Fig. 4) of the outer periphery of the top of the piston has a portion other than the depression at the top dead center of the explosion surface 35 and its surroundings. The curved surface 6' (fourth
Figure).

Although the illustrated explosion surface 35 is flat, the explosion surface 35
5 can also be formed into a tapered (conical) concave surface. By doing so, the strength of the arch structure composed of the cylinder block 10 and the cylinder head 11 in the illustrated cross section, that is, the arch structure in which the blocks 10 on both sides of the piston 6 are the legs and the cylinder head 11 is the ceiling, can be increased. Since this increases the strength of the cylinder block 10 and cylinder head 11, it is possible to increase the strength of the cylinder block 10 and cylinder head 11.

Next, valves 15 and 16 (valve 16 in FIG.
(only shown in the figure) and the drive mechanism of the pump 49 will be explained.
In addition to the camshaft 23 and the valve arm 24, a valve arm 51 for the pump 49 is also accommodated in the valve arm chamber 25.
Further, the stems 17, 18 of the valves 15, 16 and the pump 49 protrude from the cylinder head 11 and enter into the valve arm chamber case 26. O ₁ -O ₁ is a vertical center plane including the center of the cylinder, and the stems 17 and 18 are adjacent to, for example, the left side of the center plane O ₁ -O ₁ when viewed in the direction of movement of the hull. The tips of the stems 17 and 18 are located relatively close to the head end surface 47. Stem 17,1
A protector 52 is attached to the tip of 8.
An adjusting screw 54 fixed to one end of the valve arm 24 by a lockite 53 is in contact with the protector 52. The valve arm 24 is provided with a tappet 55 in its intermediate portion, and the tappet 55 is adapted to be driven by a cam 56 on the camshaft 23. Total of 4 valve arms 24
The other end is supported by a common valve arm shaft 57.
The valve arm shaft 57 is supported by the valve arm chamber case 26. In addition, the valve arm shaft 57 is located away from the center plane O ₁ -O ₁ to the left, and its outer peripheral surface is close to the head end surface 47.
The center 57' of the protector 52 of the valves 15, 16 is in the closed position.
Approximately 2 to 3 mm from the end surface (the contact surface of the screw 54)
(approximately 1/3 of the valve lift) is located closer to the end face 47.

The camshaft 23 is located at the rear of the valve arm 24 (on the side opposite to the end surface 47) and to the left of the nut 53, and is supported by the valve arm chamber case 26. Valve arm shaft 5 of valve arm 51 for unit injector
9 extends vertically at a position adjacent to the right side of the center plane O ₁ -O ₁ and is lined up to the right of the camshaft 23 . Valve arm shaft 59 for unit injector
The valve arm chamber case 26 also supports the valve arm chamber case 26, and is provided so as to extend in the center of the valve arm chamber case 26 in parallel to the crankshaft. The two valve arms 51 (only one is shown) are supported at their intermediate portions by a common shaft 59, and a cam follower 60 provided at one end abuts a cam 61 on the camshaft 23 from behind.
An adjusting screw 63 is fixed to the other end of the valve arm 51 by a lockite 62. The tip of the screw 63 is in contact with the protector 65 at the tip of the plunger 93. The screw 63 is located relatively far to the right with respect to the center plane O ₁ −O ₁ , and therefore the injector 5
0 as a whole becomes central plane O ₁ as it moves towards the nozzle 21 side
−O It is inclined to approach ₁ .

An opening 66 is provided on the rear surface of the valve arm chamber case 26 from the right end to a portion slightly toward the left end. A lid 67 for closing the opening 66 is attached to the valve arm chamber case 26 by bolts 68. A lever-type decompression mechanism 70 is attached to the left side of the valve arm chamber case 26. The decompression mechanism 70 is used to manually open the valve from the outside when starting the engine, and the valve arm 24 is provided with an arm 71 that is driven by the decompression mechanism 70.

According to the above structure, the rotation of the camshaft 23 causes the cam 56 to drive the valves 15 and 16 via the valve arm 24, and at the same time, the cam 61 drives the plunger 93 of the pump 49 via the arm 51. Valve 1
The drive timing of 5, 16 and pump 49 is determined by screw 5.
It can be adjusted by changing the positions of 4 and 63.
Since the screw 63 and the lock nut 62 face the opening 66, the position of the screw 63 from the opening 66 can be easily adjusted by removing the cover 67. Also, the shaft 2 is connected to the screw 54 and lock nut 53.
3 and 59 are separated from each other on the left and right, so the axes 23 and 59
Adjustment of the screw 54 can be easily performed from the opening 66 through the gap 72 between them.

As shown in FIG. 1, the camshaft 23 is supported by a case 26 at both ends and a middle portion. In each cylinder 5, valve driving cams 56, 56 are distributed above and below a pump driving cam 61. Also cam 61
is at the same height as the cylinder centerline O-O. camshaft 2
A pump shaft 74 of a lubricating oil pump 73 is connected to the lower end of the lubricating oil pump 3 . The pump 73 is bolted to the lower surface of the case 26. The inlet of the pump 73 is connected to an oil pan (not shown) through an oil passage 75 made of a drilled hole provided in the case 26, head 11, and block 10. Oil pan is crankshaft 1
It is formed by a case surrounding an output shaft (not shown) extending downward from the output shaft. The outlet of the pump 73 is connected to various parts of the engine through the case 26, the head 11, and a bore hole oil passage (not shown) in the block 10.

The upper end of the camshaft 23 protrudes from the case 26, and a pulley 76 fixed to the protruding upper end is connected to a pulley 77 fixed to the upper part of the crankshaft 1 via a timing belt 78. A power generating device 79 is attached to the flywheel 2 above the pulley 77 . A ring gear 80 is provided on the outer periphery of the flywheel 2, and a starter 81 for driving the gear 80 is attached to the crankcase portion 30. At the top of the bottom wall (front wall) of the case portion 30, there is a filler port 82 that projects obliquely upward.
is provided. A governor 83 is attached to the cylinder block 10, and a fuel injection amount increasing device 87 for starting is attached to the cylinder head 11. The governor 83 is driven by a timing belt 78. Governor 83 and increase device 8
7 is connected to a plunger 93 of the fuel injection pump 49 in FIG. 5 via a lever mechanism 86.

As shown in FIG. 5, at a position adjacent to the rear of the crankcase 27, a governor 83 is provided on the right side of the cylinder block 10, and a lubricating oil strainer 84 is provided on the left side of the block 10. Further, the fuel injection pump 49 is integrated into the head 11 together with the nozzle 21 as described above. In this way, in the illustrated engine, among the large equipment attached to the engine, the pump 49 is built into the head 11, and the governor 83 and lubricating oil strainer 84 are built into the block 1.
Since the engine is distributed to the left and right sides of 0, the entire engine becomes approximately egg-shaped when viewed from above as shown in FIG. 5, and has a shape suitable for an outboard motor engine. Note that the entire engine is covered with an outboard motor case (not shown).

Reference numeral 85 denotes an intake pipe, one end of which is connected to the intake port 14 on the right side of the head 11, and the other end opened near the bottom of the crankcase 27. Intake pipe 8
5 is a cylinder block 10 and a crankcase 2
7, and the inlet side part wraps around to the front of the crankcase 27 to form the center plane O ₁
It has reached the vicinity of −O ₁ . By employing such a long intake pipe 85, it is possible to enhance the intake inertia effect and improve engine performance.

As mentioned above, the intake pipe 85 wraps around from the right side of the crankcase 27 to the front, and the starter 81 protrudes from the crankcase 27 to the left front.
In this respect as well, the left-right balance of the entire engine can be maintained. Inside the valve arm case 26,
By protruding the injector 50 to the right, providing the valve arm 51 in the center, and providing the camshaft 23 and the valve arm 24 on the left side, the left-right balance of the case 26 can be maintained.

According to the structure explained above, the cylinder block 10 and cylinder head 11 of the diesel engine
Since the cylinder block and head are integrally molded from aluminum, the weight can be reduced compared to conventional cylinder blocks and heads made of cast iron. Furthermore, by reducing the weight, it is possible to achieve higher output compared to conventional products of the same weight. There is no need to connect block 10 and head 11 with head bolts,
Of course, since there is no need to arrange a gasket between the two parts 10 and 11, the number of parts can be reduced, the weight can be reduced, and the assembly work can be simplified. Furthermore, head 1
Since there is no gasket between block 1 and block 10 as a heat insulating material, the flow of heat between them is improved and the cooling effect is also increased. Since there is no need for tightening with head bolts, there is no risk of deformation of the liner 31. Although the cylinder pressure is high in a diesel engine, there is no risk of combustion gas, cooling water, or lubricating oil leaking between the head 11 and block 10. In other words, it is possible to increase the cylinder pressure and achieve high output without considering gas leakage or the like. In conventional products, it was necessary to increase the thickness of the mating surface between the cylinder block and cylinder head in order to support the gasket, but the present invention eliminates such a thick part.
Weight reduction can be achieved.

Furthermore, as described above, by making various improvements to each part, the strength of the cylinder block 10 and cylinder head 11 can be sufficiently increased. Therefore, in a diesel engine with high cylinder pressure, the block 10 and head 11 are made of integrally molded aluminum.
In addition, the cylinder pressure can be increased to the extent that the desired high output can be obtained. In particular, in this invention, the corner portion 3 where explosive force is likely to concentrate is
The cross-sectional radius R of the corner surface 36' facing the combustion chamber 37 of the piston 6 is 2% or more of the cylinder inner diameter, and the piston 6
Since the value is set to a value less than the distance to allow movement of the corner portion 36, as explained in detail in connection with FIG. I can do it.

Furthermore, according to the present invention, a curved surface that approaches the corner surface 36' formed into an arcuate cross section as described above with almost no gap is formed on the outer surface of the outer periphery of the piston top, so that the compression ratio of the engine is reduced. This can improve performance, especially in diesel engines.

In addition, since the end 36'' of the corner surface 36' on the crank chamber side is located closer to the explosion surface 35 than the top ring 33 of the piston 6 at the top dead center position, the piston ring 33 and the piston ring 33 at the top dead center position There is no contact with the corner surface 36',
It is possible to prevent deformation of the piston ring 33 due to contact between the piston ring 33 and the corner surface 36', and therefore, it is possible to improve sealing performance against gas that tends to leak from the combustion chamber to the crank chamber side.

Furthermore, the boss 22 of the cylinder head 11 that forms the peripheral wall of the mounting hole of the unit injector 50 is
Since the ceiling 45 that forms the explosion surface 35 of the cylinder head 11 is provided integrally with the opposite wall 45' that faces the ceiling 45 with the cooling water chamber 12 in between, the cylinder head 11 has sufficient strength. can be increased to

Also, unlike a simple fuel injection valve, the unit injector 50 is connected to the combustion chamber case 26 by the valve arm 51.
Since it is pushed from the side, the unit injector 50
The head 11, which is attached to the center thereof, is also reinforced by this force.

Furthermore, the present invention is directed to a direct injection type diesel engine in which fuel is injected from a unit injector 50 located approximately in the center of the cylinder head 11 into the combustion chamber 37 formed by the recessed portion of the piston 6. The cylinder block 10 and cylinder head 11 of the engine are integrally molded from aluminum, and the camshaft 23 and valve arm shafts 57 and 59 for driving the unit injector 50 and the intake and exhaust valves 15 and 16 are supported. ,
In addition, a valve arm chamber case 26 having approximately the same width as the cylinder head 11 is bolted to the cylinder head 11, and a valve arm shaft 59 for driving the unit injector 50 among the valve arm shafts is provided. A central portion of the valve arm chamber case 26 is provided so as to extend parallel to the crankshaft 1.

According to this configuration, the valve arm chamber case 26 is reinforced by the camshaft 23 and the valve arm shafts 57 and 59, and the cylinder head 11 is reinforced by such a valve arm chamber case 26.
is reinforced, and deformation of the cylinder head 11 is effectively prevented.

In particular, the crankshaft 1 is placed in the center of the valve arm chamber case 26.
The above-mentioned deformation prevention effect is sufficiently enhanced because the valve arm shaft support 59 is positioned parallel to the valve arm and the width of the valve arm chamber case 26 is approximately the same as the width of the cylinder head 11.

Furthermore, the corner surface 36' formed into the above-mentioned arcuate cross section will be explained from another point of view as follows.

Generally, when adopting a direct injection combustion chamber in which the top clearance of the piston is kept as small as possible, the internal volume of the main combustion chamber (bowl) is made as large as possible, and squish flow is expected, and the cylinder inner diameter D is, for example, 100 mm, and For a small diesel engine, the relationship between the top clearance (δ1) and the corner radius (R: Fig. 2) is as follows, for example.

δ1/D=0.7mm/100mm=7/1000 R/D=2/100=20/1000 The piston (radial direction) clearance when cold is generally δ2/D=0.5mm/100mm=5/1000. Therefore, when R is set large as in the present invention, R becomes 3 to 4 times or more as compared to δ1 and δ2.

If the peripheral edge of the top of the piston is chamfered and a tapered surface (a surface with a straight cross-sectional shape) is formed in place of the curved corner surface 36' formed into the circular arc cross section shown in the figure, the cylinder internal volume increases accordingly. However, when R=1.3mm and D=100mm, the increase is as follows.

R ² (4.9348×D/2−2.8404R) −πR ² ((1/2)D−(2/3)R) = 410.75−260.86=149.89 = approx. 150 According to this, 100 (inner diameter) × 100 mm In the engine, the stroke volume = 785398 mm ³ , the compression ratio = 21, and by taking the volume after compression (R) of 1963 mm ³ , the dead volume is reduced by 150/1963 = approximately 8%.

Furthermore, when the internal volume of the cylinder is expanded by employing the tapered surface, the squishing strength decreases, and carbon tends to accumulate due to the lowered flow velocity, which tends to cause scuffing.

Note that when embodying the present invention, the layout of each part of the engine can be reversed left and right. The crankcase part 29 can also be provided separately from the cylinder block 10. The present invention can also be applied to engines with a single cylinder or three or more cylinders. The engine of the present invention can also be used for applications other than outboard motors. The present invention can also be applied to an engine in which the cylinder centerline 0-O is vertical.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view of the embodiment, Fig. 2 is an enlarged partial view of Fig. 1, Fig. 3 is a graph showing the relationship between corner radius and stress, and Fig. 4 is an enlarged partial schematic view of Fig. 2. , FIG. 5 is a - sectional view of FIG. 1. 10... Cylinder block, 11... Cylinder head, 23... Camshaft, 26... Valve arm chamber case, 36... Corner portion, 36'... Corner surface,
37... Combustion chamber, R... Section radius, 50... Unit injector, 57, 59... Valve arm axis.

Claims (1)

[Scope of utility model registration request] The cylinder block and cylinder head of a direct-injection diesel engine, in which fuel is injected from a unit injector placed approximately in the center of the cylinder head into the combustion chamber formed by the concave portion of the piston, are integrally molded from aluminum. A valve arm chamber case that supports a camshaft and a valve arm shaft for driving the actuator and the intake/exhaust valve and has a width that is approximately the same as the width of the cylinder head is bolted to the cylinder head, and the valve arm is fixed to the cylinder head with bolts. The valve arm shaft for driving the unit injector inside the shaft,
The central part of the valve arm chamber case is provided so as to extend parallel to the crankshaft, and the cross-sectional shape of the corner face facing the combustion chamber at the corner where the block and head are continuous is made into an arc shape, and the cross-sectional radius is made into an arc. Set to a value of 2% or more of the cylinder inner diameter, a curved surface is formed on the outer surface of the outer circumference of the top of the piston that approaches the corner surface with almost no gap, and is closer to the crank chamber than the curved surface on the outer circumference of the piston. Attach a top ring to the part, and position the end of the corner surface on the crank chamber side closer to the explosion surface than the top ring of the piston at the top dead center position to form the peripheral wall of the unit injector mounting hole. A four-cycle water-cooled diesel engine characterized in that a cylinder head boss is integrally provided from the ceiling that forms the explosion surface of the cylinder head to the opposite wall that faces the ceiling with a cooling water chamber in between. engine.