JP2002048000A - Intake device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a more powerful swirl stream in a combustion chamber in an intake device for an engine in which a valve seat arranged at an inner end in an intake port generating swirl in the combustion chamber is fixed to a cylinder head at a position deviated from the center of the combustion chamber and a stem of an intake valve is slidably fitted into a guide cylinder provided in the cylinder head coaxially with the center of the valve seat. SOLUTION: The intake port 70 on a projection drawing for a plane crossing an axial line of a cylinder bore orthogonally is formed into such shape that has a first passage part 70a extending in the direction of tangent of the guide cylinder 98 on an outer side more than the guide cylinder 98 and a second passage part 70b continuous with the first passage part 70a and curved and tapered so as to wind a part of the guide cylinder 98. An opposing wall 39a covering an umbrella part of the intake valve and the valve seat 97 except a part where it is overlapped on the first and second passage parts 70a, 70b on the projection drawing is provided in the cylinder head 39 by opposing to a part of the umbrella part and the valve seat 97.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake device for an engine, and more particularly, to a cylinder head in which a swirl-shaped intake port is formed in a combustion chamber facing a top of a piston slidably fitted in a cylinder bore. An intake valve provided with a ring-shaped valve seat disposed at an inner end of the intake port, fixed to a cylinder head at a position deviated from the center of the combustion chamber, and having an umbrella portion capable of being seated on the valve seat; The present invention relates to an improvement of an intake system of an engine in which a stem is slidably fitted to a guide cylinder provided on a cylinder head coaxially with the center of the valve seat.

[0002]

2. Description of the Related Art Conventionally, such an intake device is already known, for example, from Japanese Patent Application Laid-Open No. Hei 4-17707, and has a spiral shape in which an inner end is passed through a circular intake valve opening formed by a valve seat. An intake port is provided in the cylinder head.

[0003]

SUMMARY OF THE INVENTION In the above prior art,
A swirling flow that winds the stem of the intake valve is formed in the inner end of the intake port on the back side of the umbrella portion of the intake valve, and the momentum of the intake air-fuel mixture generated in the upstream straight portion of the intake port This is used for the rotational force with a small radius around the stem, and the flow rate of the air-fuel mixture flowing from the intake port into the combustion chamber is greatly reduced. Also, when the intake valve opens, the air-fuel mixture swirling on the back side of the umbrella portion of the intake valve flows into the combustion chamber in the cylinder axis direction, and the swirling direction and the suction direction to the combustion chamber are different. It is difficult to increase the flow rate of the air-fuel mixture into the combustion chamber, and swirl formation in the combustion chamber is insufficient.

[0004] The present invention has been made in view of such circumstances, and has as its object to provide an intake device for an engine capable of forming a stronger swirl flow in a combustion chamber.

[0005]

In order to achieve the above object, an invention according to claim 1 is characterized in that a swirl is formed in a combustion chamber facing a top of a piston slidably fitted in a cylinder bore. An intake port is provided in the cylinder head, and a ring-shaped valve seat disposed at an inner end of the intake port is fixed to the cylinder head at a position off the center of the combustion chamber, and can be seated on the valve seat. In an engine intake device in which a stem of an intake valve having an umbrella portion is slidably fitted to a guide cylinder provided on a cylinder head coaxially with the valve seat, projection onto a plane orthogonal to the axis of the cylinder bore. The intake port on the drawing has a first passage portion extending tangentially to the guide cylinder outside the guide cylinder, and a part of the guide cylinder connected to the first passage portion. The second of narrowing earlier was curved to the memorial service
And a facing wall that covers the umbrella portion and the valve seat of the intake valve except for a portion that overlaps the first and second passage portions on the projection view. Are provided on the cylinder head so as to face a part of the cylinder head.

According to such a configuration, the intake port is
On a projection on a plane perpendicular to the axis of the cylinder bore,
It is formed so as to have a first passage portion along a tangential direction of the guide cylinder and a second passage portion which is curved so as to wind a part of the guide cylinder and narrows down, and overlaps the intake port in the projection view. Since the umbrella portion of the intake valve and the valve seat are covered with the opposing wall except for the part, the air-fuel mixture introduced at the intake port is drawn into the combustion chamber by winding a part of the outer periphery of the stem provided in the intake valve. Therefore, since the air-fuel mixture is not swirled in the intake port, the air-fuel mixture flows into the combustion chamber while avoiding a decrease in flow velocity, and a strong swirl can be formed in the combustion chamber. And the intake port is
Any shape that allows the air-fuel mixture to flow smoothly can be used, so that the passage resistance in the intake port can be reduced.

[0007] The invention according to claim 2 provides the above-described claim 1.
In addition to the configuration of the invention described above, the shape of the second passage portion on the projection view is formed in a shape that avoids intersecting with a straight line connecting the center of the combustion chamber and the center of the guide cylinder. According to this configuration, it is possible to reliably prevent the flow of the air-fuel mixture flowing from the intake port into the combustion chamber in a direction opposite to the swirl flow generated in the combustion chamber, and to reduce the swirl in the combustion chamber. It can be even more powerful.

According to a third aspect of the present invention, in addition to the configuration of the first or second aspect of the present invention, an inner surface of the intake port at a portion corresponding to an inner outline of the second passage portion is provided. According to such a configuration, the suction range of the air-fuel mixture into the combustion chamber is accurately determined, and is formed on the cylinder axis. The intake port can be inclined so that the angle between the plane and the plane orthogonal to the plane becomes smaller, and the swirl flow in the combustion chamber can be further increased.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on one embodiment of the present invention shown in the attached drawings.

FIGS. 1 to 8 show an embodiment of the present invention. FIG. 1 is a side view of a motorcycle, and FIG.
FIG. 3 is a cross-sectional view of the power unit taken along line 2, and FIG.
4 is an enlarged sectional view taken along line 4-4 of FIG. 2, FIG. 5 is a sectional view taken along line 5-5 of FIG. 4, FIG. 6 is a view taken along arrow 6 of FIG. 5, and FIG. FIG. 8 is a sectional view taken along line 8-8 of FIG. 5 in which the intake port is projected onto a plane orthogonal to the axis.

Referring to FIG. 1, a motorcycle body frame 15 has a front pipe W provided at a front end thereof with a front wheel W.
A front fork 17 that supports F is pivotally supported so as to be steerable. A bar handle 18 is connected to an upper end of the front fork 17, and a front fender 19 that covers an upper part of the front wheel WF is supported by the front fork 17. A rear fork 20 that supports the rear wheel WR is pivotally supported at an intermediate portion of the body frame 15, and a rear cushion 21 is provided between the rear portion of the body frame 15 and the rear fork 20.

A power unit P composed of a water-cooled spark-ignition four-cycle engine E and a transmission M is supported at an intermediate portion of the body frame 15, and the output of the transmission M is transmitted through an endless chain 22. The power is transmitted to the rear wheel WR.

An air cleaner 23 and a radiator 24 disposed above the engine E are supported by the vehicle body frame 15, and a fuel tank 25 disposed above the transmission M is provided. The storage box 26 disposed above the storage frame 25 is supported by the vehicle body frame 15.

An exhaust pipe 27 for guiding exhaust gas from the engine E is connected to an exhaust muffler 28 disposed between the power unit P and the rear wheels WR.

The front portion of the vehicle body frame 15, the engine E, the air cleaner 23, and the radiator 24 are covered with a leg shield 29 made of synthetic resin and attached to the vehicle body frame 15. The rear part of the body frame 15, the fuel tank 25 and the storage box 26
A rear fender 31 is provided on the rear cover 30 to cover an upper rear portion of the rear wheel WR. On the rear cover 30,
A seat 32 is provided so that the upper end opening of the storage box 26 can be opened and closed, and a driver can sit on the seat 32.

In front of the driver sitting on the seat 32, a light-transmitting wind screen 33 is arranged.
Is attached to the handle cover 34 that covers the cover.

2 to 5, the engine body 37 of the engine E has a combustion chamber 45 between a cylinder block 38 having a cylinder bore 44 into which a piston 43 is slidably fitted and a top of the piston 43. Cylinder head 39 formed and coupled to cylinder block 38
And a crankcase 40 rotatably supporting a crankshaft 47 connected to the piston 43 via a connecting rod 46 and coupled to a cylinder block 38. The cylinder block 38, the cylinder head 39, and the crankcase A plurality of cases 40, for example, four
It is fastened by the through bolts 41 of the book. Further, the crankcase 40 is configured such that the right crankcase half 40a and the left crankcase half 40b are connected to each other with a plane including the operating axis of the piston 43 as a mating surface. A crank chamber 42 is formed. Further, the engine body 37 is supported by the body frame 15 with a cylinder head 39 disposed immediately after the front wheel WF disposed at a front portion and an axis of the cylinder bore 44, that is, a cylinder axis substantially horizontal.

The transmission M has a main shaft 51 and a counter shaft 52 having an axis parallel to the crank shaft 47 and rotatably supported by the crank case 40.
And a plurality of gear trains 53 provided between the main shaft 51 and the counter shaft 52 to enable selective establishment.
Shift drum 54 that rotates to selectively establish 3
Is rotatably supported.

One end of a crankshaft 47 projecting from the right crankcase half 40a is connected to a drive gear 56 via a centrifugal clutch 55.
The driven gear 57 meshing with the right crankcase half 40
and is rotatably supported on one end side of a main shaft 51 protruding from a. The driven gear 57 is connected to a clutch outer 60 of a clutch 59 via a damper rubber 58.
The clutch 59 includes a clutch inner 62 and a clutch outer 60 which are connected to the main shaft 51 by the action of a release cam mechanism 61 in accordance with the operation of the driver.
This is a multi-plate clutch that disconnects and connects between the gear trains, and allows the gear train 53 to be selectively established with the clutch 59 disconnected. The centrifugal clutch 55 and the clutch 59 are covered with a right cover 63 connected to the right crankcase half 40a.

A driving sprocket 64 around which the chain 22 is wound is fixed to an end of the counter shaft 52 protruding from the left crankcase half 40b, and the rear wheel WR from the driving sprocket 64 via the chain 22.
Power is transmitted to.

A rotor 66 of a generator 65 is fixed to the other end of the crankshaft 47 protruding from the left crankcase half 40b, and is connected to the left crankcase half 40b so as to cover the generator 65. Left cover 68
, The stator 67 of the generator 65 is fixed.

The cylinder block 38 and the cylinder head 39 of the engine body 37 are provided with a jacket 48 for flowing cooling water. The cylinder head 39 has a pair of spark plugs having different ignition timings. 49 and 50 are attached so as to face the combustion chamber 45.

An intake port 70 for supplying an air-fuel mixture to the combustion chamber 45 is provided in the cylinder head 39 so as to open upward at an upper portion of the cylinder head 39, and exhaust gas from the combustion chamber 45 is discharged. Exhaust port 71 is provided so as to open downward at the lower portion of the cylinder head 39. Thus, the intake port 7
0 is connected to an air cleaner 23 via a carburetor (not shown), and the exhaust port 71 is connected to an exhaust pipe 27.

An intake valve 74 for switching the communication between the intake port 70 and the combustion chamber 45, and an exhaust port 71
Exhaust valve 75 for switching between communication and shutoff between the combustion chamber 45
Is provided on the cylinder head 39 so as to be capable of opening and closing, and the intake valve 74 and the exhaust valve 75 are spring-biased in the valve closing direction.

The intake valve 74 and the exhaust valve 75 are opened and closed by a valve mechanism 76. The valve mechanism 76 includes a cylinder head 39 and the cylinder head 3
9 is housed in a valve operating chamber 79 formed between the head cover 78 and a plurality of bolts 77.

The valve mechanism 76 includes a crankshaft 4
7, which is rotatably supported by the cylinder head 39 with an axis parallel to that of the cam 7, and on the intake side and exhaust side cams 81, 8.
And a camshaft 80 provided with the camshaft 8
The intake-side and exhaust-side rocker shafts 83 and 84 supported by the cylinder head 39 and having an axis parallel to 0, and the intake-side rocker shaft 83 driven by the intake-side cam 81 to open and close the intake valve 74. An exhaust-side rocker arm 85 is swingably supported, and an exhaust-side rocker arm 86 is swingably supported by an exhaust-side rocker shaft 84 to open and close the exhaust valve 75 following the exhaust-side cam 82.

Referring to FIG. 2, a driving sprocket 87 is fixed to the crankshaft 47 between the left crankcase half 40b of the crankcase 40 and the generator 65, and corresponds to the driving sprocket 87. A chain passage 88 is provided between the left crankcase half 40 b, the cylinder block 38, and the cylinder head 39.

On the other hand, a driven sprocket 89 is provided at an end of the camshaft 80 at a portion corresponding to the chain passage 88.
Is fixed, and an endless chain 90 that can run in a chain passage 88 is wound around the driven sprocket 89 and the driving sprocket 87.

The chain 90 between the driving sprocket 87 and the driven sprocket 89 is connected to the cylinder block 3.
8 around the idle sprocket 91 and the chain 90 between the idle sprocket 91 and the driving sprocket 87.
A tension is applied by a tensioner 92 disposed at 0b.

A water pump 93 having a rotation axis coaxial with the camshaft 80 of the valve mechanism 76 is mounted on the cylinder head 39. A thermostat 95 is provided in a pump housing 94 of the water pump 93 so that the cooling water of the jacket 48 returns to the jacket 48 via the thermostat 95 and the water pump 93 when the engine E is in a cold state. When the engine E is warmed up and the engine E has been warmed up, the cooling water from the jacket 48 is supplied to the radiator 24 and the thermostat 9.
5 and return to the jacket 48 via the water pump 93.

Paying particular attention to FIG. 5, the cylinder head 39 is provided with the intake port 7 at a position shifted from the center of the combustion chamber 45.
0, the ring-shaped valve seat 97 arranged at the inner end
It is fixed by press fitting or the like. The intake valve 74 includes an umbrella portion 74a that can be seated on the valve seat 97, and a stem 74b coaxially and integrally connected to the umbrella portion 74a.
The stem 74b is slidably fitted to a guide cylinder 98 provided at the bottom. In addition, a valve spring 99 is provided between the upper end of the stem 74b protruding from the guide cylinder 98 and the cylinder head 39 to exert a spring force for seating the umbrella portion 74a on the valve seat 97. The intake side rocker arm 85 of the valve mechanism 76 is interlocked and connected.

The inner end of the exhaust port 71 is arranged such that the center of the combustion chamber 45 is located between the inner end of the intake port 70 and the inner end of the intake port 70 on one diameter line of the combustion chamber 45. Umbrella part 75 which is located at the inner end of 71 and is seated on a valve seat (not shown) fixed to cylinder head 39.
An exhaust valve 75 having an a is a guide cylinder (not shown) fixed to the cylinder head 39 in the same manner as the intake valve 74.
The valve spring 100 is supported so as to be openable and closable in the valve closing direction.
The exhaust valve 75 urged (see FIG. 3) is linked to and connected to the exhaust-side rocker arm 86 of the valve operating mechanism 76.

In FIG. 6, an intake port 70 is provided in the cylinder head 39 so as to generate a swirl in the combustion chamber 45. A pair of spark plugs 49, 50 attached to the cylinder head 39 are used for combustion. Room 4
The heat value is set so as to increase as the distance from the intake port 70 increases along the swirl flow direction 101 in 5. That is, the heat value of the ignition plug 49 immediately downstream of the intake port 70 along the flow direction 101 is lower than the heat value of the ignition plug 50 at a position separated from the intake port 70 along the flow direction 101. In this embodiment, an ignition port 49 having a low heat value is arranged along the flow direction 101 on the upstream side of the exhaust port 71, that is, the exhaust valve 75.
Along the exhaust port 71, that is, on the downstream side of the exhaust valve 75, an ignition plug 50 having a high heat value is arranged.

Further, the engine E has its cylinder bore 4
4 is mounted on the vehicle body frame 15 with the axis thereof being substantially horizontal.
Since 0 is arranged, in the combustion chamber 45, the ignition plug 49 having a low heat value is arranged at the opening end of the intake port 70 to the combustion chamber 45, that is, immediately below the intake valve 74.

The intake port 70 has such a shape as to generate swirl in the combustion chamber 45, and as shown in FIG. 7 on a projection on a plane perpendicular to the axis of the cylinder bore 44, as shown in FIG. The port 70 has a first passage portion 70a extending outwardly of the guide tube 98 in a tangential direction of the guide tube 98, and is curved so as to wind a part of the guide tube 98 so as to be continuous with the first passage portion 70a. It is formed in a shape having a narrowed second passage portion 70b.

The first passage portion 70a is connected to the combustion chamber 45, for example.
Line 1 connecting the center C1 of the guide cylinder 98 and the center C2 of the guide cylinder 98
It extends in a straight line in the tangential direction of the guide cylinder 98 while being orthogonal to 02. Further, the second passage portion 70b is formed in a curved shape so as to wind a part of the guide tube 98 so as not to intersect with the straight line 102 on the projection view.

Referring also to FIG. 8, the cylinder head 3
9, the first and second passage portions 7 of the intake port 70 are provided.
Except for the portion overlapping with the first valve 0a and the second valve 70b, the umbrella portion 7 of the intake valve 74 is removed.
4a and the opposing wall 39a covering the valve seat 97 (FIG. 7).
Are indicated so as to face the umbrella portion 74a and a part of the valve seat 97. That is, a part of the valve seat 97 which is formed in a ring shape and disposed at the inner end of the intake port 70 substantially functions as the intake valve port 103. The intake valve port 103, which is a region excluding the portion covered by the wall 39a, is opened.

The inner surface of the intake port 70 at a portion corresponding to the inner outline of the second passage portion 70b is provided on the cylinder head 39 so as to be orthogonal to the opposing wall 39a. The wall 39b (see FIG. 5) is formed.

Next, the operation of this embodiment will be described. The intake port 70 projected on a plane perpendicular to the axis of the cylinder bore 44 is located outside the guide cylinder 98 for guiding the opening and closing operation of the intake valve 74. A first passage portion 70a extending in a tangential direction of the guide cylinder 98 on the side of the first passage portion 70a;
And a second passage portion 70b, which is curved so as to wind a part of the guide cylinder 98, and has a narrowed tapered portion. The first and second passage portions 70a, 7
Except for the portion overlapping with Ob, the umbrella portion 74a of the intake valve 74 and the valve seat 97 are opposed to the opposite wall 39 of the cylinder head 39.
a.

Therefore, the air-fuel mixture introduced at the intake port 70 is drawn into the combustion chamber 45 so as to wind around a part of the outer periphery of the stem 74b of the intake valve 74. Since the air-fuel mixture is not swirled, the air-fuel mixture can flow into the combustion chamber 45 while avoiding a decrease in flow velocity, and a strong swirl can be formed in the combustion chamber 45. Moreover, the intake port 70
Any shape that allows the air-fuel mixture to flow smoothly can be used, so that the passage resistance in the intake port 70 can be reduced.

Also, it is assumed that the shape of the vertical wall 39b, which is a wall at the tip of the second passage portion 70b in the projection, intersects a straight line 102 connecting the center C1 of the combustion chamber 45 and the center C2 of the guide cylinder 98. Since it is formed in a shape to avoid, it is possible to reliably prevent the flow of the air-fuel mixture flowing into the combustion chamber 45 from the intake port 70 in a direction opposite to the swirl flow generated in the combustion chamber 45, Thereby, the swirl in the combustion chamber 45 can be further enhanced.

Further, the inner side surface of the intake port 70 at a portion corresponding to the outer shape line on the inner side of the second passage portion 70b is
9a is formed by the vertical wall 39b provided on the cylinder head 39 so as to be orthogonal to the cylinder 9a.
The intake port 70 can be inclined so as to accurately define the suction range to the intake port and to form a smaller angle with a plane perpendicular to the cylinder axis, thereby increasing the swirl flow in the combustion chamber 45. Things.

The cylinder head 39 is provided with a plurality of, for example, a pair of spark plugs 49, 50 for reducing the fuel consumption and improving the exhaust characteristics.
The ignition plugs 49 and 50 have different heat values from each other, and the swirl flow direction 101 in the combustion chamber 45 is set so as to face the inside of the combustion chamber 45 in an empty space avoiding the air. The heat value of the ignition plug 49 closer to the intake port 70 along the
Is set lower than the heat value of the ignition plug 50 farther from the ignition plug 50.

That is, the ignition plug 50 is exposed to a relatively high temperature combustion gas by the combustion of the air-fuel mixture which has become relatively thin due to the progress of vaporization and diffusion of the air-fuel mixture in the combustion chamber 45.
The heat value of the intake port 7 is set relatively high.
The heat value of the ignition plug 49, which may be cooled by contact with the relatively rich air-fuel mixture flowing from 0 to the combustion chamber 45, is set to a relatively low value. Can be prevented from occurring.

The engine body 37 is mounted on the body frame 15 with the cylinder axis substantially horizontal, and the combustion chamber 45 is located above the ignition plug 49 having the lowest heat value.
Since the intake port 70 is provided in the cylinder head 39 so as to open into the inside, even if the fuel transmitted through the lower inner surface of the intake port 70 without being atomized flows into the combustion chamber 45, the fuel is Since the heat value of the spark plug 49 that may come into contact with the spark plug 49 is the lowest among the spark plugs 49 and 50, it is possible to avoid the occurrence of smoldering due to the contact with the non-atomized fuel, and the It is possible to prevent ignition failure due to smoking.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the appended claims. It is possible.

[0047]

As described above, according to the first aspect of the present invention, it is possible to form a strong swirl in the combustion chamber by flowing the air-fuel mixture into the combustion chamber while avoiding a decrease in the flow velocity. In addition, the passage resistance in the intake port can be reduced.

According to the second aspect of the present invention, it is possible to reliably prevent the flow of the air-fuel mixture flowing from the intake port into the combustion chamber in a direction opposite to the swirl flow generated in the combustion chamber. The swirl in the can be further enhanced.

Further, according to the third aspect of the present invention, it is possible to incline the intake port so that the angle formed by the plane perpendicular to the cylinder axis becomes smaller, and the swirl flow in the combustion chamber can be further enhanced. Things.

[Brief description of the drawings]

FIG. 1 is a side view of a motorcycle.

FIG. 2 is a sectional view of the power unit taken along line 2-2 of FIG.

FIG. 3 is an enlarged view taken along line 3-3 of FIG. 2;

FIG. 4 is an enlarged sectional view taken along line 4-4 of FIG. 2;

FIG. 5 is a sectional view taken along line 5-5 in FIG. 4;

6 is a view taken in the direction of arrow 6 in FIG. 5;

FIG. 7 is a projection view of the intake port on a plane perpendicular to the axis of the cylinder bore.

FIG. 8 is a sectional view taken along line 8-8 in FIG. 5;

[Explanation of symbols]

 39: Cylinder head 39a: Opposing wall 39b: Vertical wall 43: Piston 44: Cylinder bore 45: Combustion chamber 70: Intake port 70a: First passage 70b ..Second passage portion 74: intake valve 74a: umbrella portion 74b: stem 97: valve seat 98: guide cylinder 102: straight line E: engine

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Ryo Kubota 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. (Reference) 3G024 AA10 AA14 DA01 DA03 DA04 DA09 DA16 EA04

Claims (3)

[Claims] A combustion chamber (4) facing a top of a piston (43) slidably fitted in a cylinder bore (44).
5) Intake port (70) shaped to produce swirl
Is provided on the cylinder head (39), and a ring-shaped valve seat (97) arranged at the inner end of the intake port (70) is located at a position off the center of the combustion chamber (45). ), And a stem (74b) of an intake valve (74) having an umbrella (74a) that can be seated on the valve seat (97) is attached to the valve seat (9).
7) In an intake device for an engine which is slidably fitted to a guide cylinder (98) provided on a cylinder head (39) coaxially with 7), a projection on a plane orthogonal to the axis of the cylinder bore (44). Said intake port at (70)
A first passage portion (70a) extending tangentially to the guide cylinder (98) outside the guide cylinder (98);
The guide tube (98) connected to the first passage portion (70a).
The second passage portion (7), which is curved so as to wind a part of the
0b) and an umbrella portion (74a) of the intake valve (74) and a valve seat (74) except for a portion overlapping the first and second passage portions (70a, 70b) on the projection view. An intake device for an engine, characterized in that an opposing wall (39a) covering the cylinder head (97) is provided on the cylinder head (39) so as to oppose the umbrella part (74a) and a part of the valve seat (97). 2. A second passage portion (70b) on the projection view.
2 is formed in a shape that avoids intersecting with a straight line (102) connecting the center of the combustion chamber (45) and the center of the guide cylinder (98).
An intake device for the engine as described. 3. An inner surface of the intake port (70) at a portion corresponding to an inner outline of the second passage portion (70b),
3. The intake device for an engine according to claim 1, wherein the intake device is formed by a vertical wall (39 b) provided on the cylinder head (39) so as to be orthogonal to the opposing wall (39 a). 4.