JP2001132535A - Overhead valve type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a cooling property of an intake valve, an exhaust valve, and blocks with a simple structure so as to improve durability of those member, in an internal combustion engine wherein blocks into which the intake valve and the exhaust valve are assembled in fitted to a cylinder head. SOLUTION: In the overhead valve type internal combustion engine 2, a cylinder 8 and the cylinder head 9 are integrally molded, the intake valve 51 and the exhaust valve 53 are assembled into blocks 54, 55 having a intake valve seat 77, an intake valve guide 80, an exhaust valve seat 79, and an exhaust valve guide 82, and the blocks 54, 55 are fitted to fitting holes 71, 73, 72, 74 of the cylinder head 9 from the cylinder head 9 side. The fitting holes 71, 73, 72, 74 are opened to a ventilating path 44 formed on the cylinder head 9, and cooling fins 54a, 55a are disposed on an outer surface that is brought into contact with cooling air flowing the ventilating path 44 in the blocks 54, 55.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overhead valve type internal combustion engine in which a cylinder and a cylinder head are integrally formed, wherein a block in which an intake valve and an exhaust valve are assembled is fitted to the cylinder head. The present invention relates to a cooling structure of the block and a structure of an intake port and an exhaust port.

[0002]

2. Description of the Related Art There has been known a forced air-cooled overhead valve type internal combustion engine in which a cylinder and a cylinder head are integrally formed, and a block in which an intake valve and an exhaust valve are assembled is fitted to the cylinder head. JP-A-2-215908). In this internal combustion engine, the intake valve and the exhaust valve are assembled to valve seat members (blocks) for the intake valve and the exhaust valve each having a valve seat and a valve guide,
Both valve seat members are installed in mounting holes provided in the cylinder head.
It can be inserted and removed from the cylinder head side. This makes it possible to easily form the mounting portion of the intake valve and the exhaust valve as compared with the case where the mounting portion is processed from the inside of the cylinder, and to increase the valve clamping angle. Can be enhanced.

[0003]

In the prior art, since both valve seat members are mounted in cylindrical mounting holes formed in the cylinder head, the outer periphery of each valve seat member is surrounded by the cylinder head. ing. Therefore, on the outer peripheral side of each valve stem of the intake valve and the exhaust valve, there is a valve seat member and a cylinder head surrounding the outer periphery of the valve seat member,
Heat was not satisfactorily drawn from the intake valve and the exhaust valve heated by the combustion gas to the cylinder head via the valve seat member provided with the valve guide. As a result, the sliding motion is performed without sufficient cooling between the intake and exhaust valves and the valve guide, and there is room for improvement in the durability of the intake and exhaust valves and the valve seat member. was there.

[0004] In the prior art, since the intake port and the exhaust port are formed integrally with the cylinder head, the position of the connection end with the intake pipe and the exhaust pipe is fixed. When the internal combustion engine is mounted on a different vehicle, the arrangement of peripheral devices of the internal combustion engine is sometimes restricted.

Incidentally, in an overhead valve type internal combustion engine in which a valve box (block) having a valve seat and a valve guide and having an exhaust valve assembled thereto is fitted to a cylinder head, in order to improve the heat removal from the exhaust valve. In addition, there is also known a valve box in which a coolant passage through which the coolant passes is formed (Japanese Patent Publication No. 4-68076). However, in this case, it is necessary to form a coolant passage in the valve box, which complicates the structure of the valve box, increases the size of the valve box, and requires a structure for supplying the coolant to the valve box. There was also.

The present invention has been made in view of such circumstances, and according to the first to third aspects of the present invention, the cylinder and the cylinder head are integrally formed, and the cylinder head has an intake port. In an overhead-valve internal combustion engine in which a block in which a valve and an exhaust valve are assembled is fitted, the simple structure improves the cooling performance of the intake valve, the exhaust valve and the block, and the durability of the intake valve, the exhaust valve and the block is improved. A common goal is to improve the performance. It is still another object of the present invention to increase the degree of freedom of the position of the connection end of the intake port with the intake pipe and the position of the connection end of the exhaust port with the exhaust pipe.

[0007]

According to the first aspect of the present invention, a cylinder and a cylinder head are integrally formed, and an intake valve and an exhaust valve are respectively provided on the intake valve and the exhaust valve. An overhead valve assembled to a block having corresponding intake valve seats and intake valve guides and exhaust valve seats and exhaust valve guides, the blocks being fitted into fitting holes formed in the cylinder head from the cylinder head side. In the internal combustion engine, the fitting hole is opened in a cooling fluid passage formed in the cylinder head, and an overhead valve provided with a cooling fin on an outer surface of the block that comes into contact with the cooling fluid flowing through the cooling fluid passage. An internal combustion engine.

According to the first aspect of the present invention, the intake valve and the exhaust valve are separate from the cylinder head and are assembled to a block having a valve seat and a valve guide. In order to provide the valve guide, instead of processing the cylinder head integrally formed with the cylinder, it is only necessary to process the block. Therefore, the manufacturing cost of the internal combustion engine in which the cylinder and the cylinder head are integrally formed can be reduced.

In addition, the block has a simple structure in which the block is fitted in a fitting hole opened in the cooling fluid passage, and a cooling fin is provided on an outer surface of the block in contact with the cooling fluid flowing through the cooling fluid passage. Directly cooled by cooling fluid flowing through a cooling fluid passage in contact with the outer surface of the block,
In addition, since the contact area is increased by the cooling fins on the outer surface of the block, cooling is more efficiently performed.

Therefore, the heat removal from the intake valve through the intake valve guide of the block becomes good, and the heat removal from the exhaust valve through the exhaust valve guide of the block becomes good.
The cooling performance of the respective sliding portions of the intake valve and the exhaust valve and the intake valve guide and the exhaust valve guide is also improved. as a result,
The durability of the intake valve, exhaust valve and block is improved.

According to a second aspect of the present invention, in the overhead valve type internal combustion engine according to the first aspect, the intake valve and the exhaust valve are arranged at a top surface of the piston at a top dead center in an axial direction of a bore of the cylinder. The valve is driven to open via a rod for transmitting a valve opening driving force of a cam provided on a camshaft disposed closer to the crankshaft than the position.

According to the second aspect of the present invention, unlike the prior art, since the camshaft is not provided in the cylinder head, the large flow passage in the cylinder head is not restricted by the arrangement of the camshaft. The cooling fluid passage having a cross-sectional area can be formed, and the contact area between the block and the cooling fluid can be increased, so that the cooling performance of the intake valve, the exhaust valve, and the block can be further improved.

According to a third aspect of the present invention, in the overhead valve type internal combustion engine according to the first or second aspect, the block includes an intake passage having an intake port formed by the intake valve seat as one opening. An exhaust passage having an exhaust opening formed by the exhaust valve seat as one opening, and an opening of the block forming the other opening of each of the intake passage and the exhaust passage. And pipes forming exhaust ports, respectively, are connected from outside the cylinder head.

According to the third aspect of the invention, the connection of the pipe forming the intake port to the intake pipe depends on the shape of the pipe such as the length of the pipe forming the intake port and the exhaust port and the degree of curvature of the pipe. Since the connection end of the pipe forming the end and the exhaust port with the exhaust pipe can be set at any position, it is possible to select a pipe corresponding to the arrangement of the intake pipe and the exhaust pipe, and the pipe forming the intake port and the intake pipe The degree of freedom of the connection position with the exhaust pipe and the connection position between the pipe forming the exhaust port and the exhaust pipe increases. As a result, restrictions on the arrangement of the peripheral devices of the internal combustion engine due to the connection positions are reduced, and the optimal arrangement of the peripheral devices becomes possible.

Further, since the pipes forming the intake port and the exhaust port are respectively connected from the outside of the cylinder head, when the block is fitted to the cylinder head, the intake port and the exhaust port may interfere. Therefore, the fitting of the block to the cylinder head becomes easy.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view of a power unit having a four-cycle single-cylinder, forced-air-cooling, overhead-valve internal combustion engine according to an embodiment of the present invention, as viewed from the front, and FIG. 2 is a cross-sectional view of the power unit as viewed from the rear. FIG. 3 is a sectional view taken along line III-III in FIG.

A swing-type power unit 1 mounted on a motorcycle, as shown in FIGS.
An internal combustion engine 2 and a transmission 3 having a planetary gear type transmission 4 and a final reduction gear 5 disposed to the left of the internal combustion engine 2 are provided, and the power of the internal combustion engine 2 is controlled by a centrifugal starting clutch 4a.
And a transmission 4 having three planetary gear mechanisms 4b, 4c, 4d
Is transmitted from the final reduction gear 5 to the rear wheel 6 via the

The internal combustion engine 2 is arranged vertically so that the axis of the crankshaft 11 is oriented in the front-rear direction of the vehicle body, and the axis C of the bore 8a of the cylinder 8 is directed slightly obliquely to the right of the vehicle body. The crankcase 7 has a cylinder 8 having a large number of cooling fins 8a formed by a split surface passing through the axis of the crankshaft 11.
And an engine-side crankcase integrally formed by casting with a cylinder head 9 having a number of cooling fins 9a
7a and a transmission-side crankcase 7b serving as a part of a case of the transmission 4 located on the left side of the vehicle body.
In this specification, "front, rear, left and right" means "front, rear, left, and right" of the vehicle body.

An intake block 54 in which an intake valve 51 composed of a poppet valve and a supercharging valve 52 composed of a poppet valve are assembled, and an exhaust block 55 in which an exhaust valve 53 composed of a poppet valve is assembled are attached. An ignition plug 43 for igniting a mixture of fuel and air injected from a fuel injection valve provided in an intake pipe not provided in a combustion chamber
A cylinder head cover 10 is attached to the cylinder head 9 attached to the cylinder head 12.

As shown in FIG. 3, a crankshaft 11 connected via a connecting rod 14 to a reciprocating piston 13 fitted slidably in a bore 8a of the cylinder 8 has a pair of front-rear directions. It is held by the crankcase 7 by being rotatably supported by a pair of front and rear crankshaft holders 17 and 18 made of a pressed steel plate via the ball bearings 15 and 16, respectively. Each of the crankshaft holders 17 and 18 has a pair of cylindrical mounting portions formed on the crankshaft holders 17 and 18.
18a, 18a, is fixed to the engine side crankcase 7a by a pair of through bolts (the bolts 19, 19 of the crankshaft holder 18 are shown in FIG. 1).

Further, a drive gear 20 integrally formed with the crankshaft 11 meshes with an input gear 4e of the transmission 4 to transmit the power of the crankshaft 11 to the transmission 4. When the engine is started, the rotation of the starting motor 21 is transmitted to the crankshaft 11 via the pinion 22, the large gear 23 and the small gear 24 of the idler shaft, the starting driven gear 25, the one-way clutch, the input gear 4e, and the driving gear 20. Transmitted (see FIG. 1).

An AC generator 26 is disposed at the front end of the crankshaft 11. A rotor 26 a of the AC generator 26 fixed integrally to the crankshaft 11 has a cylinder 8 and a cylinder head 9 for cooling. A cooling fan 27 for sending air is integrally fixed. The cooling fan 27 is covered by a fan cover 28 provided with an air inlet, and extends from the fan cover 28 and is in contact with a portion of the cylinder head 9 between the cooling fin 9a closest to the cylinder head cover 10 and the cylinder head cover 10. By 29, the cooling air from the cooling fan 27 is guided toward the cylinder 8 and the cylinder head 9. Although not shown, the shroud 29 is provided so as to surround the outer circumferences of the cylinder 8 and the cylinder head 9.

At the rear end of the crankshaft 11, a timing gear 30 provided so as to rotate integrally with the crankshaft 11 meshes with a cam gear 31 which is press-fitted into a camshaft 32 and integrally connected thereto. And the camshaft 32 is
One rotation is made for each rotation.

In the direction of the axis C of the bore 8a of the cylinder 8, the rear side of the portion of the cylinder 8 near the crankshaft 11, which is closer to the crankshaft 11 than the position of the piston top surface at the top dead center. Is supported by a boss of the cam gear 31 rotatably supported by the crankshaft holders 17 and 18 via a ball bearing 33, and a rear end of the cam shaft 32 is provided with a ball bearing 34. , Is rotatably supported by a camshaft holder 35 formed of a pressed steel plate and fixed to the engine-side crankcase 7a.

The camshaft 32 is provided with an intake / exhaust cam 56 for driving the intake valve 51 and the exhaust valve 53 to open and a supercharging cam 57 for driving the supercharge valve 52 to open. The intake valve 51 is driven to open via an intake pull rod 61 that transmits a driving force for opening the intake and exhaust cams 56. That is, the intake pull rod 61 is brought into contact with the intake / exhaust cam 56 to swing and swing to the first intake rocker arm 58.
The intake valve 51 is driven to open by the second intake rocker arm 64 which is swung by the intake pull rod 61 pulled and pulled.

Similarly, the supercharging valve 52 is driven to open via a supercharging pull rod 62 that transmits a valve opening driving force of a supercharging cam 57. That is, the supercharging pull rod 62 is pulled by the first supercharging rocker arm 59 which swings in contact with the supercharging cam 57,
The supercharging valve 52 is driven to open by the second supercharging rocker arm 65 which is swung by the supercharged pull rod 62 pulled.

On the other hand, the exhaust valve 53 is driven to open via an exhaust pull rod 63 that transmits a driving force for opening the intake and exhaust cam 56. That is, the exhaust pull rod 63 is pulled by the first exhaust rocker arm 60 swinging in contact with the intake / exhaust cam 56, and the exhaust valve 53 is moved by the second exhaust rocker arm 66 swinged by the pulled exhaust pull rod 63. The valve is driven to open.

A first intake rocker arm shaft for swingably supporting the first intake and first supercharged rocker arms 64 and 65.
Both ends of the first exhaust rocker arm shaft 68 that swingably supports the first exhaust rocker arm 60 are fixed to the crankshaft holder 18 and the camshaft holder 35, respectively. In addition, the intake pull rod 61 and the supercharging pull rod 62,
The exhaust pull rod 63 passes through the inside of the two guide cylinders 69 and 70 fitted to the cylinder head 9 behind the cylinder 8.

A supercharged piston having a supercharger piston reciprocated by the rotation of a supercharger crankshaft 36b having a supercharger drive gear 36a engaged with the cam gear 31 is provided above the engine side crankcase 7a and the cylinder 8. Dynamic piston type supercharger 36
The air introduced from the auxiliary intake pipe into the supercharger 36 is compressed and discharged to a high pressure, and the internal combustion engine 2
Is supplied to the combustion chamber 12.

Further, a trochoid type oil pump 37 is provided behind the crankshaft 11, and a rotor attached to a hollow pump drive shaft 37a integrally fixed to the crankshaft 11 is fixed to the crankcase 7. It is rotationally driven inside the pump casing 37b.

The oil which is sucked into the oil pump 37 through the suction passage 39 from the oil reservoir 38 at the bottom of the crankcase 7 and discharged at a high pressure is lubricated to the internal combustion engine 2 and the transmission 4 through the oil passage. Supplied to the location. Among them, a valve operating mechanism constituted by sliding portions of the intake valve 51 and the exhaust valve 53 housed in the valve operating chamber 76 formed by the cylinder head 9 and the cylinder head cover 10 and the rocker arms 64, 65, 66 and the like. Oil pipe 40 for supplying oil to the inner plate
Connected to a double-structured cylinder head cover 10 composed of 10a and an outer plate 10b, supplied oil is
The fluid flows into a meandering oil passage 41 formed by processing the outer plate 10b into a corrugated shape, and is injected from a plurality of injection ports 42 provided in the middle of the oil passage 41, and the sliding portion and the dynamic Lubrication of the valve mechanism is performed. The oil after lubricating the valve operating mechanism returns to the oil reservoir 38 via a return pipe (not shown) connecting the valve operating chamber 76 and the oil reservoir 38.

Next, a structure for mounting each valve to the cylinder head 9 will be described. In the cylinder head 9,
A combustion chamber wall portion 9b forming the combustion chamber 12 and a combustion chamber wall portion 9b
The cooling fan guided by the shroud 29 is between the valve chamber wall portion 9c, which is a valve chamber wall located closer to the cylinder head cover 10 and spaced apart in the direction along the axis C of the bore 8a of the cylinder 8. An air passage 44 as a cooling fluid passage through which the cooling air as the cooling fluid from 27 flows is formed to penetrate the cylinder head 9 in the front-rear direction. The ventilation path 44 is located between the intake valve 51 and the exhaust valve 53 as shown in FIGS.

Further, in the cylinder head 9, an intake fitting hole 71 and an exhaust fitting hole 72 are formed in the combustion chamber wall 9b. In the wall portion 9c, an intake fitting hole 73 and an exhaust fitting hole 74 on the valve operating chamber side that open to the outer surface of the cylinder head 9 and the ventilation passage 44 are formed.

The intake block 54 and the exhaust block 55
These two intake fitting holes 71, 73 and both exhaust fitting holes 72, 74
The cylinder head 9 is fitted to the cylinder head 9 from the side opposite to the cylinder side, that is, from the cylinder head side, and is fixed to the cylinder head 9 by a pair of bolts. A pair of fixing bolts 75, 75 are shown). further,
In the intake and exhaust blocks 54 and 55, a large number of cooling fins 54a and 55a are formed on the outer surface exposed to the ventilation passage 44, respectively.

The material of the intake and exhaust blocks 54 and 55 is made of, for example, heat-resistant ferritic stainless steel in consideration of heat resistance, abrasion resistance, lubricity between the valve guide and the valve stem, and the like. You.

In the intake block 54, the intake valve seat 77 and the supercharge valve seat 78, which are the respective valve seats of the intake valve 51 and the supercharge valve 52, at the portion facing the combustion chamber 12, the intake valve 51 and the supercharge valve Inlet valve guides that slidably guide each of the 52 valve stems
An intake valve 51 formed with a supercharge valve guide 81 and further opened and closed to supply an air-fuel mixture in an intake pipe to the combustion chamber 12;
A supercharging valve 52 that is opened and closed to supply supercharging air from the supercharger 36 to the combustion chamber 12 is assembled.

The intake block 54 is provided with two spring receivers 83 and 84 corresponding to the intake valve 51 and the supercharging valve 52, respectively, near the spring receivers 83 and 84 and the valve ends of both valve stems. Valve spring 8 between the attached spring receivers 86 and 87
9,90 are installed.

Further, the intake block 54 includes an intake valve seat 77.
The intake passage formed by the opening formed by the opening 92 formed in a direction substantially orthogonal to the valve stem of the intake valve 51 incorporated in the intake block 54 is the other opening. An intake port pipe 97 made of a pipe material is attached to the opening 92 from the outside of the cylinder head 9 through an insertion hole 101 formed in the cylinder head 9 to form an intake port 99. ing. Since the intake port pipe 97 is formed from a pipe material,
The shape of the tube, such as its length and degree of curvature, can be appropriately selected as needed. The opening 92 is provided in the insertion hole 101.
Is provided in the intake block 54 located inside the inner surface of the cylinder head 9 having

The intake port pipe 97 is formed with a press-formed annular flange at a connection portion with the opening 92, and the outer diameter of the flange is made substantially equal to the inner diameter of the insertion hole 101. Insert 97 from outside of cylinder head 9 into insertion hole 101
And facilitates temporary fixing when connecting to the intake block 54. Then, with an O-ring mounted between the flange and the intake block 54, a fixing ring (not shown) for pressing the flange from the opposite side is fixed to the cylinder head 9, so that the intake port pipe 97 Is the intake block
Fixed to 54.

In the intake block 54, a supercharging path 95 and an opening corresponding to the intake path 94 and the opening 92 of the intake valve 51 are provided in the same manner as the supercharging valve 52, respectively. Regarding the supercharging valve 52, a supercharging port pipe and a supercharging port pipe insertion hole corresponding to the intake port pipe 97 and the insertion hole 101 of the intake port pipe 97 for the intake valve 51, respectively, are provided in the same manner. The shape of the supercharging port tube formed from the tube material, such as the length and degree of curvature of the supercharging port tube, can be appropriately selected as needed.

Further, the intake block 54 has second intake and second supercharged rocker arm shafts 103, 1 for swingably supporting the second intake and second supercharged rocker arms 64, 65, respectively.
Intake and supercharged rocker arm shaft holder 10 to which 04 is fixed
6, 107 are formed.

On the other hand, an exhaust valve seat 79 and an exhaust valve guide 82 for slidably guiding the valve stem of the exhaust valve 53 are formed in the exhaust block 55 at a portion facing the combustion chamber 12.
An exhaust valve 53 that is opened and closed to discharge the combustion gas from 12 to an exhaust pipe is assembled. The exhaust block 55 is provided with a spring receiver 85, and a valve spring 91 is mounted between the spring receiver 85 and a spring receiver 88 attached near the valve end of the valve stem.

The exhaust block 55 is provided with an exhaust path 96 and an opening 93 corresponding to the intake path 94 and the opening 92 of the intake valve 51 of the intake block 54 in the same manner. Intake port pipe 97 for 51
And an exhaust port tube 98 and an insertion hole 102 of the exhaust port tube 98 corresponding to the insertion hole 101 of the intake port tube 97, respectively.
It is provided in a similar form. Here, the pipe shape of the exhaust port pipe 98 formed of a pipe material, such as the pipe length and the degree of curvature, can be appropriately selected as needed.

Further, the exhaust block 55 is provided with an exhaust rocker arm shaft holder 108 to which a second exhaust rocker arm shaft 105 for swingably supporting the second exhaust rocker arm 66 is fixed.

[0045] Between the intake and exhaust blocks 54, 55 and the cylinder head 9 in which both the fitting holes 71, 72 on the combustion chamber side and the fitting holes 73, 74 on the valve train chamber side are formed, respectively. A seal member 110 is mounted. The seal member 110 may be an O-ring made of a heat-resistant synthetic resin or metal as shown in FIG. 1 or a seal member shown in FIGS. You may.

That is, what is shown in FIG. 4 is a seal member 111 whose cross section is formed of an annular piece having a "-" shape.
Sealing is performed by bending both ends of the annular piece with the open portion facing the combustion chamber. FIG. 5 shows an example of a seal member 112 having a cross section formed of an annular piece having a “C” shape, in which the annular piece is pressed in the radial direction of the poppet valve, as shown in FIG. Is an example in which the sealing member 113 is also formed of an annular piece having a C-shaped cross section, and the annular piece is pressed in the axial direction of the poppet valve. When the seal member is pressed in the axial direction as described above, a washer may be used instead of the annular piece. FIG. 7 shows a seal member 114 used when fitting the block into the tapered fitting hole. As shown in the enlarged view of FIG. 8, the seal member 114 has a truncated cone shape. A bead 114a projecting radially outward is formed on a tapered surface of a cylindrical annular piece (the bead 114a before deformation is shown by a two-dot line in FIG. 8). FIG.
As a material of the seal member illustrated in FIG. 7, a heat-resistant synthetic resin such as a fluororesin, a heat-resistant rubber, or a heat-resistant metal can be used.

With the intake and exhaust blocks 54 and 55 fitted to the cylinder head 9, the intake valve 51, the supercharging valve 52 and the exhaust valve 53 have respective inclination angles with respect to the axis C of the bore 8a. The intake valve 51 and the exhaust valve 53 are arranged so as to have a set included angle θ. The size of the included angle θ is set in consideration of the required size of the valve diameter, the size of the combustion chamber 12, and the like.

As shown in FIG. 2, the intake pull rod 61 and the exhaust pull rod 63
Also, they intersect at an angle substantially equal to the included angle θ between the intake valve 51 and the exhaust valve 53, which is also the angle as viewed from the front-back direction.
Therefore, the ventilation path 44 formed between the intake valve 51 and the exhaust valve 53 is located between the intake pull rod 61 and the exhaust pull rod 63.

Since the first embodiment is configured as described above, the following effects can be obtained. The intake valve 51 and the supercharging valve 52 include an intake valve seat 77, an intake valve guide 80, and a supercharging valve seat.
78, the exhaust valve 53 is assembled to the intake block 54 having the supercharging valve guide 81, and the exhaust valve 53 is assembled to the exhaust block 55 having the exhaust valve seat 79 and the exhaust valve guide 82.
In order to form the valve seats 77, 78, 79 and the valve guides 80, 81, 82 of 51, 52, 53, instead of processing the cylinder head 9 integrally formed with the cylinder 8, the intake and exhaust blocks 54 are formed. , 55, the manufacturing cost of the internal combustion engine 2 in which the cylinder 8 and the cylinder head 9 are integrally formed can be reduced.

In addition, the intake block 54 in which the intake valve 51 and the supercharging valve 52 are assembled is fitted in the intake fitting holes 71 and 73 opened in the ventilation passage 44, and the exhaust gas in which the exhaust valve 53 is assembled. The block 55 is fitted in the exhaust fitting holes 72, 74 opened in the ventilation passage 44, and the cooling fins 54a, 55a are provided on the outer surfaces of the intake and exhaust blocks 54, 55 which are exposed to the ventilation passage 44. The simple structure of the intake and exhaust blocks 54,
The block 55 is directly cooled by the cooling air from the cooling fan 27 flowing through the ventilation path 44 that contacts the blocks 54 and 55, and the contact area is increased by the cooling fins 54a and 55a on the outer surfaces of the blocks 54 and 55. Therefore, the cooling is performed more efficiently.

Therefore, the intake valve 51 and the supercharge valve 52 are slidably guided through the intake valve guide 80 and the supercharge valve guide 81 of the intake block 54 through the intake valve 51.
And the heat removal from the supercharging valve 52 is improved, and the exhaust valve
Through the exhaust valve guide 82 of the exhaust block 55, which guides the valve stem 53 slidably, the heat removal from the exhaust valve 53 is improved, and the valve stem of the intake valve 51, the valve stem of the supercharging valve 52, and the exhaust valve 53 Valve stem, intake valve guide 80, supercharging valve guide 81
Also, the cooling performance of each sliding portion with the exhaust valve guide 82 is improved. As a result, the intake valve 51, the supercharging valve 52, the exhaust valve 53,
The durability of the intake block 54 and the exhaust block 55 is improved.

The intake valve 51 and the supercharging valve 52 are connected to a camshaft 32 disposed on the rear side of a portion of the cylinder 8 near the crankshaft 11.
The exhaust valve 53 is driven to open via an intake pull rod 61 and a supercharge pull rod 62 that respectively transmit a valve opening driving force of an intake / exhaust cam 56 and a supercharging cam 57 provided in the exhaust valve 53.
Exhaust pull rod 63 that transmits the driving force for opening and closing cam 56
The valve is driven to open.

Therefore, since the camshaft 32 is not provided in the cylinder head 9, the ventilation passage 44 having a large flow passage cross-sectional area can be formed in the cylinder head 9 without being restricted by the arrangement of the camshaft 32. Since the contact area between the intake and exhaust blocks 54 and 55 and the cooling air can be increased, the cooling performance of the intake valve 51, the supercharging valve 52, the exhaust valve 53, the intake block 54 and the exhaust block 55 can be further improved. it can.

In addition, since the intake pull rod 61 and the exhaust pull rod 63 intersect at an angle substantially equal to the included angle θ when viewed from the front-back direction, the cross-sectional area of the air passage 44 can be increased. Therefore, the cooling performance of both blocks 54 and 55 can be further improved.

Since the intake and exhaust blocks 54 and 55 are separate bodies, the intake block 54 is hardly affected by the thermal influence of the exhaust block 55, and the intake air is suppressed from being heated by the exhaust, thereby reducing the volumetric efficiency. Can be suppressed. In addition, since the intake block 54 and the exhaust block 55 can be changed independently of each other, sharing of parts between different models is further promoted. For example, in an engine without the turbocharger 36, the exhaust block 55 may be used as it is, and only the intake block 54 may be changed to a block in which the supercharge valve 52 is not mounted and only the intake valve is mounted. It is possible.

Depending on the pipe shape such as the length of the intake port pipe 97, the supercharging port pipe and the exhaust port pipe 98 and the degree of curve of the pipe, the connection end of the intake port pipe 97 with the intake pipe, the supercharging of the supercharging port pipe, and the like. Since the connection end of the high-pressure air discharged from the feeder 36 with the discharge conduit and the connection end of the exhaust port pipe 98 with the exhaust pipe can be set at arbitrary positions, the arrangement of the intake pipe, the discharge pipe and the exhaust pipe is supported. Thus, the degree of freedom in the connection position between the intake port pipe 97 and the intake pipe, the connection position between the supercharging port pipe and the discharge pipe, and the connection position between the exhaust port pipe 98 and the exhaust pipe increases. As a result, restrictions on the arrangement of the peripheral devices of the internal combustion engine 2 due to the connection positions are reduced, and the optimal arrangement of the peripheral devices becomes possible.

Since the intake port pipe 97, the supercharging port pipe and the exhaust port pipe 98 are respectively connected from the outside of the cylinder head 9, when the intake block 54 and the exhaust block 55 are fitted to the cylinder head 9, the intake port pipe 97, the supercharge port pipe and the exhaust port pipe 55 are connected. The port pipe 97, the supercharging port pipe and the exhaust port pipe 98 do not interfere, and the fitting of the blocks 54 and 55 to the cylinder head 9 becomes easy.

Rocker arm shaft holders 106 and 107 are formed on the intake block 54 to which rocker arm shafts 103 and 104 for swingably supporting rocker arms 64 and 65 abutting on the intake valve 51 and the supercharging valve 52, respectively. Further, valve springs 89 and 90 are also assembled, and a rocker arm shaft holder 108 to which a rocker arm shaft 105 for swingably supporting a rocker arm 66 abutting on the exhaust valve 53 is fixed is formed in the exhaust block 55. Further, since the valve spring 91 is also assembled, the mechanism including the rocker arm and the valve is attached to the cylinder head 9 as one unit by fitting both the blocks 54 and 55 to the cylinder head 9. Is improved.

In the above embodiment, the valve seat is the intake block.
Although formed on the block itself of the exhaust block 54 and the exhaust block 55, as shown in FIG.
The valve seat member 121 may be formed separately from the valve seat member 121, and the valve seat member 121 may be assembled to the block 120 by, for example, screw connection. By doing so, the degree of freedom in selecting materials for the block 120 and the valve seat member 121 is increased. Therefore, by forming the block 120 from a material having good thermal conductivity, for example, aluminum, the heat dissipation from the block 120 can be improved, and the cooling performance of the block 120 can be further improved.

Further, in the above-mentioned one, each valve guide 80, 8
Although the reference numerals 1 and 82 are constituted by holes formed in the blocks 54 and 55 themselves, a valve guide may be constituted by fitting a sleeve into the holes formed in the blocks. In addition, pull rod 61,
Push rods can be used instead of 62 and 63.

Further, in the above, the intake valve 51 and the exhaust valve 53 are assembled in separate blocks 54 and 55, respectively. However, the intake valve and the exhaust valve may be assembled in a single block. In this case, a space through which the cooling air flowing through the ventilation passage 44 formed in the cylinder head 9 flows is formed in a portion between the intake valve and the exhaust valve in the block. The cooling fins formed on the outer surface of the fin are located.

In the above, the internal combustion engine 2 is of the air-cooling type, but may be of the water-cooling type. In this case, the passage corresponding to the ventilation passage 44 formed in the cylinder head 9 is A cooling water passage through which the cooling water flows.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a power unit including an internal combustion engine according to an embodiment of the present invention as viewed from the front.

FIG. 2 is a cross-sectional view of the power unit of FIG. 1 as viewed from the back.

FIG. 3 is a sectional view taken along line III-III of FIG. 1;

FIG. 4 is a sectional view of a main part when another sealing member is used.

FIG. 5 is a sectional view of a main part when another sealing member is used.

FIG. 6 is a sectional view of a main part when another sealing member is used.

FIG. 7 is a sectional view of a main part when another sealing member is used.

FIG. 8 is an enlarged view of a portion A in FIG. 7;

FIG. 9 is a sectional view of a main part of a block in which a valve seat is formed by a separate member.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 power unit 2 internal combustion engine 3 transmission device 4
... transmission, 5 ... final reduction gear, 6 ... rear wheel, 7 ... crankcase, 8 ... cylinder, 9 ... cylinder head, 10 ... cylinder head cover, 11 ... crankshaft, 12 ... combustion chamber, 13 ...
Piston, 14… Connecting rod, 15, 16… Ball bearing, 17, 18…
Crankshaft holder, 19 bolt, 20 drive gear, 21 starting motor, 22 pinion, 23, 24, 25 gear, 26 AC generator, 27 cooling fan, 28 fan cover, 29 shroud, 30 ... timing gear, 31 ... cam gear, 32 ... cam shaft, 33, 34 ... ball bearing, 35 ... cam shaft holder, 36 ... supercharger,
37 ... oil pump, 38 ... oil reservoir, 39 ... suction passage,
40 ... oil pipe, 41 ... oil passage, 42 ... injection port, 43 ... ignition plug, 44 ... ventilation passage, 51 ... intake valve, 52 ... supercharge valve, 53 ... exhaust valve, 54 ... intake block, 54a ... cooling fin, 55… Exhaust block, 55a…
Cooling fins, 56 ... intake and exhaust cams, 57 ... supercharged cams, 58, 59,
60 ... first rocker arm, 61, 62, 63 ... pull rod, 64,
65, 66 ... second rocker arm, 67, 68 ... first rocker arm shaft, 69, 70 ... guide cylinder, 71, 72, 73, 74 ... fitting hole, 75 ... bolt, 76 ... valve operating chamber, 77, 78, 79: Valve seat, 80, 81, 82: Valve guide, 83 to 88: Spring receiver, 89, 90, 91: Valve spring, 92,
93 ... opening, 94 ... intake path, 95 ... supercharging path, 96 ... exhaust path, 97
... intake port pipe, 98 ... exhaust port pipe, 99 ... intake port,
100 ... exhaust port, 101, 102 ... insertion hole, 103, 104, 105 ...
Second rocker arm shafts, 106, 107, 108: rocker arm shaft holders, 110 to 114: seal member 120: block, 121: valve seat member.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02F 1/24 F02F 1/24 F

Claims (3)

[Claims] 1. A cylinder and a cylinder head are integrally formed, and an intake valve and an exhaust valve have an intake valve seat, an intake valve guide, an exhaust valve seat, and an exhaust valve guide respectively corresponding to the intake valve and the exhaust valve. Assembled to the block,
In the overhead valve type internal combustion engine in which the block is fitted from the cylinder head side into a fitting hole formed in the cylinder head, the fitting hole is opened to a cooling fluid passage formed in the cylinder head. An overhead valve type internal combustion engine, wherein cooling fins are provided on an outer surface of the block, which contacts a cooling fluid flowing through the cooling fluid passage. 2. The cam valve according to claim 1, wherein the intake valve and the exhaust valve are provided on a camshaft disposed closer to a crankshaft than a position of a piston top surface at a top dead center in an axial direction of a bore of the cylinder. 2. The overhead valve type internal combustion engine according to claim 1, wherein the valve is driven to open via a rod transmitting the valve opening driving force. 3. The block has an intake passage having an intake opening formed by the intake valve seat as one opening, and an exhaust passage having an exhaust opening formed by the exhaust valve seat as one opening. A pipe forming an intake port and an exhaust port is connected from the outside of the cylinder head to an opening of the block forming the other opening of each of the intake path and the exhaust path. The overhead valve type internal combustion engine according to claim 1 or 2, wherein: