JP3198879B2 - Engine structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine structure in which a cylinder head having a plurality of intake valves and swirl chambers is fixed to a cylinder block with six or more bolts to withstand high in-cylinder pressure.

[0002]

2. Description of the Related Art Diesel engines (internal combustion engines) include:
There is an engine called a vortex chamber type in which a spherical vortex chamber is provided in a cylinder head. This engine, during the compression stroke,
Compressed air flows into the swirl chamber and swirls at a high speed, and fuel is injected toward the air flow in the swirl chamber. Is burned in a combustion chamber between the lower surface and the lower surface.

[0003] The output of such diesel engines has been increasing. Specifically, the camshaft is arranged above the cylinder, and the OH that drives the intake valve and the exhaust valve is
2. Description of the Related Art A C (overhead camshaft) type valve train is adopted, or a plurality of intake valves are used to increase the number of valves.

[0004] However, even if such a structure is adopted, there is a limit in increasing the output of the engine. Therefore, in recent years, in order to further increase the output, it has been considered to set the in-cylinder pressure (in-cylinder pressure) to a considerably higher pressure than before so as to perform combustion.

[0005] When the in-cylinder pressure is increased in this manner, the seal between the cylinder head and the cylinder block is increased by four cylinder heads per cylinder. It has been found that it must be fixed with the quantity of the product and it cannot be secured.

Specifically, it has been found that the cylinder head and the cylinder block cannot be sealed unless the cylinder head is fixed to the cylinder block with six head bolts arranged at substantially equal intervals around the cylinder bore.

In addition, in order to maintain the same distance between the cylinders without interfering with the adjacent cylinders in the arrangement of the six head bolts, it is necessary to pass through the center of the cylinder bore and orthogonal to the axis of the crankshaft. It has been found that it is also necessary to insert six head bolts into each part of the cylinder bore around the cylinder bore at substantially equal intervals, with a pair of parts on or near the plane being bolt positions.

[0008]

In order to establish an OHC type diesel engine having a swirl chamber with such a fixed structure using six head bolts, it is necessary to arrange the swirl chamber so as to avoid the head bolt. It is considered good.

However, in addition to a multi-valve engine having a swirl chamber, that is, a swirl chamber, two intake valves and one exhaust valve are provided.
In the case of a single engine, the layout of the swirl chamber, the intake port including the intake valve, and the exhaust port including the exhaust valve,
Unlike when four far, fairly narrow since intends want affected by the span become six head bolt, vortex chamber allows position to ensure favorable combustion avoiding head bolt,
It is difficult to lay out the valve train equipment.

In particular, since the engine body is required to have compactness in which the height and width are suppressed as much as possible, the compactness is not impaired even if the layout of the swirl chamber and the valve train is established. Two intake valves,
It is difficult to establish a valve train that drives one exhaust valve.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to cope with an increase in the output around a cylinder head of an OHC type multi-valve structure having a swirl chamber by a high in-cylinder pressure. Another object of the present invention is to provide an engine structure that can be made compact.

[0012]

In order to achieve the above object, the invention described in claim 1 is directed to a cylinder block of an engine on an imaginary plane passing through the center of a cylinder bore and orthogonal to an axis of a crankshaft. Or a cylinder head fixed by six bolts including a pair of first bolts disposed in the vicinity thereof and screwed at substantially equal intervals around the cylinder bore, formed on one side of a virtual plane in the cylinder head, An intake port having one end opened on one side surface of the cylinder head in a direction along the virtual plane, and the other end branched into two branches and connected to two intake openings opening to the combustion chamber along the virtual plane, respectively, a cylinder head; Slidably mounted on
Is, first and second intake valves respectively opening and closing the two intake openings, is formed on the other side of the virtual plane in the cylinder head, one end opening to one side of the cylinder head, the other end the cylinder head An exhaust port connected to an exhaust opening that opens at a position that intersects a crank axis passing through the combustion chamber when projected onto a plane parallel to the lower surface of the cylinder, and an exhaust opening slidably provided in the cylinder head. An exhaust valve that opens and closes, and the other side of a virtual plane provided in the cylinder head.
Oite that at least a part does not interfere with other side of the first bolt position to and shea <br/> cylinder head on the cylinder bore
Swirl chamber formed at an appropriate position and the upper part of the cylinder head
Is disposed outside the cylinder bore in one side of the cylinder head, a rocker shaft that extends along the axis of the crankshaft, is formed with an arm portion which is inclined in the vertical direction, one end each of the rocker shaft First and second intake rocker arms which are swingably supported, the other ends of which extend toward the first and second intake valves and are respectively engaged with the base ends of the first and second intake valves; An exhaust rocker arm formed with an arm portion inclined in the direction, one end of which is swingably supported by the rocker shaft, and the other end of which extends toward the exhaust valve and is locked to the base end of the exhaust valve; Above the rocker shaft
It is rotatably disposed along the axis of the crankshaft to the top of Oite cylinder head, respectively the inclined arm portion of the first and second intake rocker arm and exhaust rocker arm
And a cam shaft for swinging each respective rocker arms has a contact with the cam portion, lies in the structure of the engine structure.

[0013] According to the first aspect of the present invention, an intake port having a bifurcated outlet end disposed along a virtual plane passing through the center of the cylinder bore and orthogonal to the axis of the crankshaft, Due to the arrangement of the exhaust ports and swirl chambers arranged on the opposite side of the plane,
The one intake valve, one exhaust valve, and the swirl chamber can be laid out at appropriate positions avoiding the six bolts used to increase the in-cylinder pressure.

A rocker shaft and a camshaft extending along a crankshaft arranged vertically in two stages outside the cylinder bore; and a base end of an intake valve and an exhaust valve supported by the rocker shaft from a cam portion of the camshaft. The valve system that combines the inclined intake rocker arm and exhaust rocker arm leading to the engine section has a structure in which the inclined arm portion of each rocker arm is pressed obliquely by the cam section of the camshaft. In addition, the intake valve and the exhaust valve can be opened and closed without increasing the width of the engine body.

As a result, the cylinder head having the vortex chamber and the OHC type multi-valve structure can be made compact while maintaining the seal due to the high in-cylinder pressure. Claim 2
The rocker shaft and the camshaft according to claim 1 are provided together with each rocker arm to achieve the installation of the valve drive system without being restricted by the bolts fixed to the cylinder block. And a structure in which the cam case is fixed to the upper portion of the cylinder head.

According to a third aspect of the present invention, in addition to the above object, in order to further minimize the arm portion protruding outward from the cylinder bore, the rocker arm of the first aspect is provided with an inclined arm portion which is formed on a base of a cam portion. In the vicinity of the circle, a horizontal arm portion is provided which is bent parallel to the lower surface of the cylinder head and extends.

In addition to the above object, the invention described in claim 4 is to prevent the camshaft from protruding outside the cylinder bore as much as possible while further ensuring the rocking motion of the rocker arm. Is arranged outside the cylinder bore so that the axial distance L between the camshaft and the rocker shaft is related to L ≦ 20 mm.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to one embodiment shown in FIGS. FIG. 1 is a cross-sectional view around the head of an internal combustion engine to which the present invention is applied, for example, a multi-valve vortex chamber type diesel engine in which the in-cylinder pressure is increased to increase the output, and FIG. FIG. 3 is a plan view taken along the line, FIG. 3 is a cross-sectional view taken along the line BB in FIG. 2, and 1 is a cylinder block constituting the engine body 1a.

A plurality of cylinders 3 accommodating a piston 2 are provided in the upper part in the cylinder block 1 in parallel in the front-rear direction (only one is shown). A crankshaft 4 is arranged in a lower part (not shown) in the cylinder block 1 along a direction in which the cylinders 3 are arranged.

A crank portion 4 a formed for each cylinder on the crankshaft 4 and each piston 2 are rotatably supported via a connecting rod 5. Also cylinder block 1
A block-shaped cylinder head 6 is mounted on the upper surface of the cylinder head 6. In addition, a gasket 7 as a sealing member is interposed between the upper surface of the cylinder block 1 and the lower surface of the cylinder head 6.

The cylinder head 6 is fixed with six head bolts 8 screwed into the cylinder block 1 from around each of the cylinder bores 3a. Specifically, in order to keep the distance between the cylinders as in the case of four head bolts without interfering with the adjacent cylinders, for example, the crankshaft passes through the center of the cylinder bore 3a indicated by α in FIG. A pair of portions on or near an imaginary plane orthogonal to the axis of the shaft are defined as bolt positions A and D, and portions B, C, E and F at substantially equal intervals around the cylinder bore 3a including the positions A and D. From the six head bolts 8 for the cylinder block 1
Is inserted.

Thus, the cylinder bore 3a is brought into close contact with the cylinder block 1 so as to withstand high in-cylinder pressure, so that gas is not leaked from the combustion chamber 9 to the outside. In the cylinder head 6, an intake port 10 and an exhaust port 11 are formed in parallel for each cylinder so as to avoid the head bolt 8.

Specifically, as shown in FIG. 2, the intake port 10 is formed along the virtual plane α so as to pass between the bolts on one side of the virtual plane α, and the left end serving as the inlet end is shown in FIG. As shown in FIG. 1, it is open on the left side of the cylinder head 6. The right end, which is the outlet end of the intake port 10, is branched into two branches, and these branched ends are arranged along the virtual plane α and open to the combustion chamber 9.
2, 12 are connected.

The exhaust port 11 is formed along the virtual plane α so as to pass through a substantially symmetrical position across the virtual plane α, specifically, between bolts on opposite sides. And
As shown in FIG. 3, the left end serving as the outlet end is opened on the left side surface of the cylinder head 6. The right end, which is the inlet end of the exhaust port 11, opens into the combustion chamber 9 at a position that intersects with the crankshaft 4 passing through the combustion chamber 9 when projected onto a plane parallel to the lower surface of the cylinder head 6. Connected to the exhaust opening 13.

The intake openings 12, 12 have intake valves 15, 15
(Corresponding to first and second intake valves), and an exhaust valve 16 is provided in the exhaust opening 13. These intake valves 1
5, the exhaust valve 16 has an intake opening 12 and an exhaust opening 1
An umbrella-shaped valve body 18 which comes in contact with and separates from a valve seat 17 in the valve body 3, and slidably penetrates a head portion directly above the intake opening 12 and the exhaust opening 13 from the valve body 18, and And a stem 19 projecting from

The stem 19 is controlled by a stem guide 20.
It is slidably supported in parallel with the axis of the cylinder bore 3a. A valve spring 22 is wound around the protruding stem portion by using a spring retainer 21 attached to the end of the stem, and the valve body 18 is attached to the valve seat 1.
7 is seated.

Thus, the intake valve 15 and the exhaust valve 16
Are designed to open and close the intake opening 12 and the exhaust opening 13 by a vertical movement parallel to the axis of the cylinder bore 3a.

A swirl chamber 24 is formed in a portion of the cylinder bore 3a having no ports, that is, in a portion of the cylinder head adjacent to the exhaust valve 16 so as not to interfere with the head bolt 8.

The swirl chamber 24 is located in a cylinder bore portion along the imaginary plane α on the right side of the exhaust opening 13 (portion on the other side of the cylinder head), which is a region without ports.
Is formed with a spherical chamber 24a.

Specifically, the spherical chamber 24a is disposed between the head bolts 8, 8 at the bolt positions A, F as shown in FIGS. 2 and 3, and communicates with the end side of the cylinder bore 3a. It is formed as follows. This avoids interference between the head bolts 8, 8 located at the same positions A, F.

More specifically, the portion where the swirl chamber 24 is formed is a portion substantially parallel to the intake openings 12 and 12 and parallel to the exhaust opening 13. Two intake valves 15, 1
5, one exhaust valve 16 and swirl chamber 24 are provided to increase the in-cylinder pressure by the arrangement of the swirl chamber 24 parallel to the exhaust opening 13 and the arrangement of the suction / exhaust port system described above. The layout is made at an appropriate position avoiding the six head bolts 8 used for the above.

A glow plug 25 and a fuel injection nozzle 26 are provided in the swirl chamber 24 as shown in FIG.
Reference numeral 27 denotes an outlet of the vortex chamber 24 that opens into the combustion chamber 9.

On the other hand, reference numeral 30 denotes a cam case mounted on the upper part of the cylinder head 6. The cam case 30 is formed, for example, in a frame shape corresponding to the frame-shaped installation seat 31 formed on the outer periphery of the upper end of the cylinder head 6, for example.
Further, of the lower end of the cam case 30, for example, the left side is formed in an inverted L-shape, and is used as a seat 30a.

A bolt 32 is screwed from the inverted L-shaped seat portion 30a toward the installation seat 31 of the cylinder head 6, and the entire cam case is detachably fixed to the cylinder head 6.

In the cam case 30, an OHC type valve driving system 33 which is combined with the intake / exhaust valves 15 and 16 of the cylinder head 6 is mounted. The valve drive system 33 has a rocker shaft 34 which is displaced leftward from the cylinder bore 3a (one side surface of the cylinder head 6) and is disposed on the upper portion of the cylinder head close to the cylinder bore 3a.

The rocker shaft 34 is disposed, for example, at approximately the same low position as the upper ends of the intake / exhaust valves 15, 16 and extends along the axis of the crankshaft 4. Both ends of the rocker shaft 34 are rotatably supported, for example, on the front and rear portions (not shown) of the peripheral wall constituting the cam case 30.

Immediately above the rocker shaft 34, at the same position as the axis of the rocker shaft 34 or slightly below it.
A camshaft 35 is disposed at a position shifted to the left. This camshaft 35 also extends along the axis of the crankshaft 4. For example, both ends of the camshaft 35 and a portion corresponding to a substantially middle portion between the cylinders are sandwiched from above and below by a rib-shaped base portion 45 and a cam cap 46 projecting inward from the left and right portions of the peripheral wall of the cam curse 30, respectively. It is rotatably supported in this way.

The camshaft 35 is connected to the crankshaft 4 via, for example, a timing gear and a timing belt (neither of which is shown), and receives a torque from the crankshaft 4 to rotate at a predetermined speed. is there.

The crankshaft 4 is provided with three cam portions 36a to 36c for each cylinder. Specifically, a cam portion 36a for driving an exhaust valve is provided on a rear (one side) crankshaft portion sandwiching the virtual plane α, and two intake valve driving portions are provided on a front (other side) crankshaft portion. Cam part 36b,
36c are provided in parallel.

As shown in FIG. 1, the rocker shaft 34 has a substantially V-shaped exhaust valve driving rocker arm 37 (corresponding to an exhaust rocker arm) corresponding to each of the cam portions 36a to 36c. Similarly, rocker arms 38, 38 (corresponding to first and second intake rocker arms) for driving the intake valves are provided.

That is, the rocker arm 3 for driving the exhaust valve.
7 is an inclined arm portion 37a that is inclined upward from one end.
have. One end of the rocker arm 37 is rotatably supported by the rocker arm 37. Also inclined arm 3
A rocker roller 39 is rotatably provided as a cam receiving portion at a portion which is substantially the top of 7a. Thus, the displacement of the cam portion 36a can be received from obliquely below the camshaft 35.

At the other end of the rocker arm 37, there is formed a horizontal arm portion 37b which is bent near the base circle 40 of the cam portion 36a and extends in parallel with the lower surface of the cylinder head 6, so that the entire rocker arm is substantially formed. It is shaped like a letter.

The other end of the rocker arm 37, that is, the end of the horizontal arm 37b, reaches the stem end (base end) of the exhaust valve 16, and the adjusting screw 41 located on the horizontal arm 37b is connected to the stem end (the stem end). (Proximal end).

The rocker arm 37 is provided with the valve spring 2
It is urged counterclockwise by the elastic force of 2. As a result, the rocker roller 39 and the cam surface of the cam portion 36a come into close contact (contact), and when the cam shaft 35 rotates,
The rocker arm 37 swings with the rocker shaft 34 as a fulcrum, following the cam curve of the cam portion 36a.

The rocker arms 38 for driving the intake valves also have the same structure as the rocker arm 37 for driving the exhaust valves. That is, the rocker arms 38, 38 also have inclined arm portions 38a that are inclined at one end side from one end upward.
Are formed. And these rocker arms 38,
One end of each is rotatably supported by a rocker arm 37.

A rocker roller 39 constituting a cam receiving portion is also provided on the inclined arm portion 38a, similarly to the rocker arm 37 for driving the exhaust valve. Similarly, the cam portions 36b, 36b Is received.

At the other end of each of the rocker arms 38, 38, a horizontal arm portion 38b which is bent near the base circle 40 and extends in parallel with the lower surface of the cylinder head 6 is formed, and a rocker arm for driving an exhaust valve is formed. Similar to 37, the entire rocker arm 38 is formed in a substantially rectangular shape.

The ends of these horizontal arms 38b and 38c are
Each reaches the stem end (base end) of the intake valve 15,15. Then, the adjusting screw portion 42 located on the horizontal arm portions 38b, 38c is locked to the stem end (base end). The horizontal arm 38c of the rocker arm 38 located farther from the virtual plane α is bent inward from the front of the rocker arm 38 located closer to the virtual plane α and faces the intake valve 15.

Each of the rocker arms 38, 38 is urged in the counterclockwise direction by the elastic force of the valve spring 22.
The cam surfaces b and 36c are brought into close contact (contact). Thus, like the rocker arm 37 on the exhaust side, when the camshaft 35 rotates, the rocker arms 38 and 38 use the rocker shaft 34 as a fulcrum and the cam portions 36b and
The oscillating movement follows the cam curve of 36c.

In the cam case 30 in which the rocker shaft 34, the cam shaft 35, and the rocker arms 37, 38, 38 are integrally arranged, the swirl chamber 24, the two intake valves 15, and the one exhaust O with valve 16
HC type valve operating structure is assembled.

At the upper end of the cam case 41, a cam cover 43 is provided to close the upper opening of the cam case 30 so that dust and the like do not enter from the outside. Thus, the diesel engine configured as described above has the cam portions 3 driven by the rotation of the crankshaft 4.
With the rotation of 6a to 36c, each rocker roller 39 follows the cam curve and is pressed obliquely downward.

Then, the rocker arms 37, 38, 38 on the exhaust side and the intake side are driven to swing about the rocker shaft 34 as a fulcrum. These rocker arms 37, 38,
38, the intake valves 15, 15, the exhaust valve 16
Is opened and closed at a predetermined opening and closing timing according to the reciprocating piston 2, and in each cylinder, that is, in each cylinder 3, a cycle of repeating an intake stroke, a compression stroke, an explosion stroke using the vortex chamber 24, and an exhaust stroke is repeated. Done.

According to such a cylinder head structure of a diesel engine, as described above, the cylinder bore 3a
And an intake port 10 whose outlet end is branched along an imaginary plane α orthogonal to the axis of the crankshaft 4 and is arranged in parallel on the opposite side across the imaginary plane α. Exhaust port 11 and swirl chamber 24
Two intake valves 15, 15, one exhaust valve 16, swirl chamber 2
4 can be laid out at appropriate positions where good combustion can be performed, avoiding the six head bolts 8 used to increase the in-cylinder pressure.

In addition, the rocker shaft 37 and the camshaft 38 which are disposed outside the cylinder bore in a two-
A valve train in which the rocker arms 37, 38, 38 are combined with the cam portions 36a to 36c of the cam shaft 38.
In this structure, the inclined arm portions of the rocker arms 37, 38, and 38 are pressed obliquely to drive the valve. Therefore, the height of the engine body 42 and the width of the engine body 42 do not greatly protrude, and the intake valve does not protrude. 15, 15, exhaust valve 16
Can be opened and closed.

This means that the cylinder head 6 can be made compact while maintaining the seal due to the high in-cylinder pressure. Therefore, the engine main body 1a can be made compact while coping with high output due to high in-cylinder pressure, even though the cylinder head 6 has an OHC multi-valve structure having the swirl chamber 24.

In particular, each rocker arm 3 on the exhaust side and the intake side
The inclined arm portions 37a, 38a of the 7, 38 are connected to the cam portions 36a to 36a.
In the vicinity of the base circle 36c of 36c, the structure having the horizontal arm portions 37b and 38b which bend and extend in parallel to the lower surface of the cylinder head 6 can suppress the arm portion projecting outward from the cylinder bore 3a as much as possible. Moreover, the camshaft 35 and the rocker shaft 3 shown in FIG.
4 is set to a value of L ≦ 20 mm, the camshaft 35 is connected to the cylinder bore 3a as much as possible while ensuring good rocking motion of the rocker arms 37 and 38.
Can be suppressed so as not to protrude outside,
Compactness around the cylinder head can be achieved.

The rocker shaft 34 and the camshaft 35, together with the rocker arms 37, 38, 38, are bolted to the upper part of the cylinder head 6 by the cam case 3.
When the structure integrally provided with the cylinder drive 6 is adopted, the valve drive system 33 can be installed without being restricted by the head bolts 6 for fixing the cylinder head 6 to the cylinder block 1 as shown in FIG. There are advantages. In addition, since the valve drive system 33 has an independent structure, there is an advantage that the degree of freedom in the layout of the intake port 10 and the exhaust port 11 and the layout of the intake and exhaust valves 15 and 16 is increased.

Although the present invention has been applied to the cylinder head 6 in which the valve drive system 33 is assembled to the cam case 30, it is needless to say that the present invention is also applied to a structure in which the valve drive system is incorporated in the cylinder head. It does not matter.

[0059]

As described above, according to the first aspect of the present invention, the area around the cylinder head of the OHC type multi-valve structure having the swirl chamber is made compact while coping with high output due to high in-cylinder pressure. can do.

According to the second aspect of the present invention, in addition to the effect of the first aspect, installation of the valve drive system can be achieved without being restricted by the bolts fixed to the cylinder block.

In addition, since the valve drive system has an independent structure, there is an effect that the layout of the intake port and the exhaust port and the layout of the intake and exhaust valves in the cylinder head can be increased.

According to the third aspect of the invention, in addition to the effect of the first aspect of the invention, an effect is obtained that the arm portion projecting outward from the cylinder bore can be suppressed as much as possible.

According to the fourth aspect of the present invention, in addition to the effect of the first aspect of the present invention, the camshaft is prevented from protruding outward of the cylinder bore as much as possible while ensuring good rocking movement of the rocker arm. The effect that it can be made is produced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the periphery of a cylinder head of a multi-valve engine having a swirl chamber according to an embodiment of the present invention.

FIG. 2 is a plan view of the valve drive system along the line AA in FIG. 1;

FIG. 3 is a sectional view around the vortex chamber along the line BB in FIG. 2;

FIG. 4 is a cross-sectional view for explaining that a cam case to which a valve drive system is assembled is detachably mounted on an upper portion of a cylinder head.

[Explanation of symbols]

 Reference Signs List 1a Engine body 1 Cylinder block 2 Piston 3 Cylinder 3a Cylinder bore 4 Crankshaft 6 Cylinder head 8 Head bolt (bolt) 10 Intake port 11 Exhaust port 12 Intake opening 13 Exhaust opening 15 Intake valve (first and second intake valves) 16 ... Exhaust valve 22 ... Valve spring 24 ... Swirl chamber 30 ... Cam case 33 ... Valve drive system 34 ... Rocker shaft 35 ... Cam shafts 36a to 36c ... Cam portion (for exhaust drive, 37. Rocker arm (exhaust rocker arm) 38. Rocker arm (intake rocker arm) 39. Cam roller 40. Base circle of cam section A to F. Bolt position α. Virtual plane.

Continuation of the front page (72) Inventor Toshikazu Akabane 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (56) References JP-A-62-282211 (JP, A) JP-A-3-3 121242 (JP, A) JP-A-1-219302 (JP, A) JP-A-5-312097 (JP, A) JP-A-6-58200 (JP, A) JP-A-60-61407 (JP, U) JP-B 3-72819 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) F01L 1/26 F01L 1/00 F01L 1/18 F02B 19/08 F02F 1/24

Claims (4)

(57) [Claims] 1. With respect to a cylinder block of an engine,
A pair of first first pair disposed on or near an imaginary plane passing through the center of the cylinder bore and orthogonal to the axis of the crankshaft.
A cylinder head including bolts and fixed by six bolts screwed around the cylinder bore at substantially equal intervals; formed on one side of the imaginary plane in the cylinder head, one end of the cylinder head in a direction along the imaginary plane; An intake port that is open to one side surface of the cylinder head, the other end of which is bifurcated and that is connected to two intake openings that open to the combustion chamber along the virtual plane, and that is slidably provided on the cylinder head. is, first and second intake valves respectively opening and closing the two intake openings, is formed on the other side of the virtual plane in the cylinder head, one end opening to the one side surface of the cylinder head, the other end An exhaust port connected to an exhaust opening that opens at a position that intersects with a crank axis passing through the combustion chamber when projected and viewed on a plane parallel to the lower surface of the cylinder head, An exhaust valve slidably provided on the cylinder head to open and close the exhaust opening; and an exhaust valve provided in the cylinder head, the other of the virtual plane
Positioned on the cylinder bore at least a portion on the side
And then and the cylinder other side surface side of the swirl chamber formed in the first bolt and so as not to interfere the position of the head, distribution outside of the cylinder bore in said one side surface of the upper portion of the cylinder head of the cylinder head A rocker shaft extending along the axis of the crankshaft , and an arm portion inclined in a vertical direction. One end is swingably supported by the rocker shaft, and the other end is the rocker shaft. First and second extending toward the first and second intake valves and locked to the proximal ends of the first and second intake valves, respectively.
An intake rocker arm and an arm portion inclined in the vertical direction are formed, one end of which is swingably supported by the rocker shaft, and the other end of which extends toward the exhaust valve and is provided at a base end of the exhaust valve. and locked exhaust rocker arm is, the rotatably arranged along the axis of the crankshaft at the top of Oite the cylinder head above the rocker shaft, the first and second intake rocker arm and the exhaust rocker arm Abut each inclined arm
Engine structure characterized by comprising a camshaft for each oscillating the respective rocker arms has a cam portion. 2. The engine structure according to claim 1, wherein said rocker shaft and said camshaft are provided integrally with each rocker arm in a cam case fixed to an upper portion of said cylinder head. . 3. The rocker arm according to claim 1, wherein the inclined arm portion of each rocker arm has a horizontal arm portion that is bent near the base circle of the cam portion and extends parallel to the lower surface of the cylinder head. The engine structure according to claim 1. 4. The camshaft is disposed outside the cylinder bore with respect to the rocker shaft, and an axial center distance L between the camshaft and the rocker shaft is L ≦ 20.
The engine structure according to claim 1, wherein the engine structure is set to mm.