JP2007146802A - Internal combustion engine and motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine excellent in noise insulation effect and cooling effect. <P>SOLUTION: In the air-cooled engine 50 in which an upper end of a cylinder block 52 is closed by a cylinder head 53 to define a combustion chamber 63 inside and a cylinder head cover 54 is attached onto the cylinder head 53, an outer peripheral part of the cylinder head cover 54 is formed in a double structure having a first vertical wall 87 and a second vertical wall 88, the first vertical wall 87 and the second vertical wall 88 are connected with ribs, a cavity 98 opened at a lower side is formed between the first vertical wall 87 and the second vertical wall 88, and a guide section is provided on the cylinder head cover 54 for guiding traveling wind flowing into the cavity 98 so that it flows toward an ignition plug 64. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an internal combustion engine and a motorcycle equipped with the internal combustion engine.

Cooling is extremely important in an internal combustion engine, and some air-cooled internal combustion engines have a cooling effect enhanced by providing cooling fins on a cylinder head cover (see, for example, Patent Document 1).
Japanese Utility Model Publication No. 63-196451

However, the cooling fin of the cylinder head cover has only a function as a heat radiating plate and does not have other functions.
Since the cooling fins of the cylinder head cover are arranged in parallel with the cooling fins of the cylinder block, only a very limited effect of improving the cooling effect by increasing the heat radiation area can be obtained. For example, in an internal combustion engine, cooling around the combustion chamber of the plug mounting portion is extremely important, but the specific portion cannot be actively cooled simply by providing cooling fins on the cylinder head cover as in the prior art.

Furthermore, the conventional cylinder head cover with cooling fins has an attachment having cooling fins formed separately from the cylinder head cover, and this attachment is attached to the cylinder head cover via a rubber gasket for preventing resonance. Not only will the number of points increase, but the number of assembly steps will also increase, resulting in increased costs.
Accordingly, the present invention provides an internal combustion engine having excellent soundproofing and cooling effects, and a motorcycle equipped with the internal combustion engine.

In order to solve the above-described problem, the invention according to claim 1 is configured such that the upper end of a cylinder block (for example, a cylinder block 52 in an embodiment described later) is closed by a cylinder head (for example, a cylinder head 53 in an embodiment described later). A combustion chamber (for example, a combustion chamber 63 in an embodiment to be described later) is formed inside, and a cylinder head cover (for example, a cylinder head cover 54 in an embodiment to be described later) is mounted on the cylinder head. In an engine (for example, an engine 50 in an embodiment to be described later), an outer peripheral portion of the cylinder head cover has double vertical walls (for example, a first vertical wall 87 and a second vertical wall 88 in an embodiment to be described later). It has a double structure.
By comprising in this way, since the outer peripheral part of a cylinder head cover has a double structure, the soundproofing effect can be heightened. Further, the heat radiation area of the cylinder head cover is increased, and the cooling effect can be enhanced.

The invention according to claim 2 is characterized in that, in the invention according to claim 1, the double vertical walls are connected to each other by a rib (for example, a rib 94 in an embodiment described later).
With such a configuration, the strength of the double structure portion can be ensured by the ribs, so that the vertical wall can be made thin, and the weight of the cylinder head cover can be reduced.
The invention according to claim 3 is characterized in that, in the invention according to claim 1, a lower side is opened and an upper side is closed between the double vertical walls.
With this configuration, the cylinder head cover can be further reduced in weight. Moreover, since air can enter and exit between the double vertical walls, the cooling effect is improved.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the cylinder head cover includes a recess (on the upper extension of a spark plug (for example, a spark plug 64 in an embodiment described later)) attached to the cylinder head. For example, a guide portion (for example, a blockage in an embodiment described later) having a recess 91 in the embodiment described later and guiding the traveling wind flowing between the double vertical walls to flow toward the spark plug. Wall 92F).
With this configuration, the traveling wind flows toward the spark plug, and the combustion chamber around the spark plug mounting portion can be efficiently cooled.

The invention according to claim 5 is a motorcycle equipped with the internal combustion engine according to claim 4, wherein the cylinder block of the internal combustion engine is disposed to be inclined forward toward the front of the vehicle body. .
With this configuration, the traveling wind that flows between the vertical walls of the cylinder head cover can easily hit the spark plug, and the internal combustion engine of the motorcycle can be efficiently cooled.

According to the invention which concerns on Claim 1, the soundproofing effect and cooling effect of an internal combustion engine can be heightened. Further, the merchantability of the appearance of the cylinder head cover can be improved, and the cooling performance around the plug can be improved without complicating the structure.
According to the invention which concerns on Claim 2 or Claim 3, a cylinder head cover can be made lightweight and the weight reduction of an internal combustion engine can be achieved. Further, according to the invention of claim 3, the cooling effect is further improved.
According to the invention which concerns on Claim 4, the combustion chamber around a spark plug attaching part can be cooled efficiently.
According to the invention which concerns on Claim 5, the internal combustion engine of a motorcycle can be cooled efficiently.

Embodiments of an internal combustion engine and a motorcycle according to the present invention will be described below with reference to the drawings of FIGS. Note that the directions such as front, rear, left and right in the following description are the same as those in the vehicle unless otherwise specified. In the figure, an arrow FR indicates the front of the vehicle, an arrow LH indicates the left side of the vehicle, and RH indicates the right side of the vehicle.
As shown in FIG. 1, a pair of left and right front forks 3 that pivotally support a front wheel 2 of a motorcycle (vehicle) 1 can be steered by a head pipe 6 provided at a front end portion of a vehicle body frame 5 via a steering stem 4. It is pivotally supported by. The swing arm 8 that pivotally supports the rear wheel 7 is pivotally supported by a pivot shaft 9 provided at a substantially center of the vehicle body frame 5 at its front end. The vehicle body frame 5 has a so-called diamond shape mainly composed of a main frame 11 that extends rearward from the upper portion of the head pipe 6 and then curves downward. A pivot plate 12 attached to both sides of the lower end of the main frame 11 The lower end of the down tube 13 extending obliquely rearward and downward from the lower portion of the head pipe 6 is connected to the front and rear of a crankcase 51 of an engine (internal combustion engine) 50 mounted at the center of the vehicle body. It is suspended from the vehicle body frame 5 via the pivot plate 12.

A front end portion of a seat frame 16 extending rearward is coupled to the upper rear side of the main frame 11, and an upper end portion of a sub frame 17 extending obliquely upward and rearward from the vicinity of the pivot shaft 9 is coupled to an intermediate portion of the seat frame 16. Has been. A rear cushion 18 is disposed behind the main frame 11 in a tilted posture. The upper end of the rear cushion 18 is connected to the main frame 11 and the lower end is connected to the swing arm 8.
A rear sprocket 19 is attached to the left side of the rear wheel 7, and a drive chain 22 is wound around the rear sprocket 19 and a drive sprocket 21 disposed on the left side of the rear part of the engine 50, so that the driving force of the engine 50 is Transmission to the wheel 7 is possible.
A fuel tank 24 is disposed above the engine 50, and a seat 25 is disposed behind the fuel tank 24.
A bar handle 32 is attached to the upper portion of the steering stem 4, and a front fender 33 is attached to an intermediate portion of the front fork 3. Further, a headlamp 34 and a front cowl 37 are attached to the steering stem 4 via a support stay (not shown).
Side covers 38 are mounted on both sides of the central portion of the body frame 5, a rear cowl 39 is mounted on the rear portion of the body frame 5, and a rear fender that covers the upper portion of the rear wheel 7 with a predetermined gap inside the rear cowl 39. 31 is disposed.

As shown in FIGS. 2, 4, and 5, the engine 50 includes a crankcase 51, a cylinder block 52, a cylinder head 53, a cylinder head cover 54, a piston 55, a crankshaft 56, and a connecting rod 57 as main components. The cylinder block 52 installed on the crankcase 51 is installed in a slightly forward inclined posture toward the front of the vehicle body.
As shown in FIG. 5, a piston 55 accommodated in the cylinder block 52 so as to be slidable in the axial direction and a crankshaft 56 rotatably installed in the crankcase 51 are connected by a connecting rod 57, The reciprocating motion of the piston 55 is converted into the rotational motion of the crankshaft 56.

  The crankshaft 56 is connected to the main shaft 60 of the shift drum transmission 59 via a primary drive gear 27, a primary driven gear 28, and a clutch mechanism 58 so as to be connectable / disconnectable. The main shaft 60 is connected to a countershaft via a transmission gear 61. The rotation of the crankshaft 56 can be transmitted to the countershaft 62. In FIG. 5, one set of the transmission gears 61 that are meshed is shown as a representative, and the other transmission gears are omitted. The above-described drive sprocket 21 is attached to the end of the counter shaft 62, and the rotation of the drive sprocket 21 is transmitted to the rear sprocket 19 by the drive chain 22 as described above.

A cylinder head 53 is attached to the upper side of the cylinder block 52, and a combustion chamber 63 is formed by being surrounded by the cylinder head 53 and the piston 55. The cylinder head 53 is provided with a spark plug mounting portion 68 at the approximate center on the right side. The spark plug 64 is screwed into the spark plug mounting portion 68 from obliquely upward to the combustion chamber 63, and the tip of the spark plug 64 is inserted. The electrode protrudes into the combustion chamber 63.
As shown in FIGS. 2 and 3, the cylinder head 53 is provided with an exhaust port 65 on the front side of the vehicle body and an intake port 66 on the rear side of the vehicle body, and continues to the combustion chamber 63. Each can be opened and closed by an exhaust valve and an intake valve (both not shown). As shown in FIG. 1, the exhaust port 65 is connected to a silencer 44 disposed on the right side of the rear part of the vehicle body via an exhaust pipe 43, and the intake port 66 is connected to an air cleaner 46 via a carburetor 45. .

The exhaust valve and the intake valve are urged in a valve closing direction by a valve spring (not shown), and resist the valve spring by a valve operating mechanism 70 (see FIG. 5) installed above the cylinder head 53. The valve can be opened at a predetermined timing. The valve mechanism 70 is a well-known technique and will not be described in detail, but includes a cam and cam shaft 71, a rocker arm (not shown), a tappet (not shown), and the like.
A holder 67 is fixed to the center upper portion of the cylinder head 53, and bearings 72, 72 that rotatably support the camshaft 71 of the valve mechanism 70 are sandwiched between the cylinder head 53 and the holder 67. A cam chain 81 is wound around a cam sprocket 73 fixed to one end of the camshaft 71 and a cam drive sprocket 80 fixed to the crankshaft 56, and the camshaft 71 is rotationally driven in conjunction with the crankshaft 56. .

  As shown in FIG. 4, the cylinder head 53 and the cylinder block 52 are fastened to the crankcase 51 by bolts 41 that pass through them and screwed into the crankcase 51, and the holder 67 connects the cylinder head 53 and the cylinder block 52. The nut bolt 43 that passes through the holder 67 is fastened to the stud bolt 42 that passes through and is screwed into the crankcase 51.

On the outer periphery of the cylinder block 52, cooling fins 82 extending in the circumferential direction project. Cooling fins 83 extending in the circumferential direction are also provided on the outer periphery of the cylinder head 53 so as not to interfere with the exhaust port 65, the intake port 66, and the spark plug mounting portion 68.
A gasket surface 84 is formed on the outer edge of the upper surface of the cylinder head 53, and the cylinder head cover 54 is installed on the gasket surface 84 via a rubber gasket 90.

FIG. 6 is a bottom view of the cylinder head cover 54 as viewed from below. The cylinder head cover 54 has a substantially rectangular shape in plan view, and a valve operating chamber 85 that accommodates the valve operating mechanism 70 described above is formed inside the center portion. As shown in FIGS. 2, 4, and 5, the valve operating chamber 85 is formed by a top plate portion 86 of the cylinder head cover 54 and an annular first vertical wall 87 extending downward from the top plate portion 86. It is surrounded. Further, the cylinder head cover 54 includes a second vertical wall 88 outside the first vertical wall 87, and the upper end of the second vertical wall 88 is connected to the outer peripheral edge of the top plate portion 86. In other words, the outer peripheral portion of the cylinder head cover 54 has a double structure including double vertical walls 87 and 88.
The bottom surface of the first vertical wall 87 is placed on the gasket surface 84 of the cylinder head 53 with the gasket 90 interposed therebetween. A gasket fitting groove 89 is provided on the bottom surface of the first vertical wall 87, and a convex portion formed on the upper portion of the gasket 90 is fitted into the gasket fitting groove 89. As shown in FIGS. 2, 4, and 5, the bottom surface of the second vertical wall 88 is positioned slightly higher than the bottom surface of the first vertical wall 87.

  The cylinder head cover 54 has a recess 91 that is recessed inward at the center on the right side. As shown in FIG. 6, the recess 91 is located on the upper extension of the spark plug 64. As shown in FIG. 5, the top plate portion 86, the first vertical wall 87, and the second vertical wall 88 are all recessed inward in the concave portion 91, and the second vertical wall 88 is blocked in the concave portion 91. The closing wall 92F on the front side of the vehicle body and the closing wall 92R on the rear side of the vehicle body are connected to the first vertical wall 87. The blocking walls 92F and 92R extend obliquely downward toward the spark plug 64. Further, the second vertical wall 88 is interrupted and closed on the rear side and the front side of the vehicle body, and the closed walls 93, 93... Are connected to the first vertical wall 87.

A cavity 98 is formed between the first vertical wall 87 and the second vertical wall 88. The cavity 98 is closed on the upper side by the top plate portion 86, but the lower side is open and air is free. You can go in and out. Further, the first vertical wall 87 and the second vertical wall 88 are connected by a pair of ribs 94 at the four corners and the left-side center in plan view. By providing the rib 94, it is possible to reduce the thickness of the second vertical wall 88 while ensuring a predetermined strength, and it is possible to reduce the weight of the cylinder head cover 54 and hence the engine 50.
As shown in FIG. 2, the cylinder head cover 54 is fastened by inserting a bolt 96 through a mounting hole 95 formed in the top plate portion 86 and screwing the bolt 96 into a holder 87. At that time, the gasket surface 84 of the cylinder head 53 and the bottom surface of the first vertical wall 87 of the cylinder head cover 54 are pressed against the gasket 90 and sealed.

  In the engine 50 of the motorcycle 1 configured as described above, the outer peripheral portion of the cylinder head cover 54 has a double structure including the first vertical wall 87 and the second vertical wall 88. Can be increased. Further, since the heat radiation area of the cylinder head cover 54 is increased as compared with the case where the second vertical wall 88 is not provided, the cooling effect can be enhanced.

  Further, during traveling, traveling wind can flow into the cavity 98 between the first vertical wall 87 and the second vertical wall 88 of the cylinder head cover 54, and in particular, as shown in FIG. When the traveling wind that has flowed into the cavity 98 strikes the obstruction wall 92F on the front side of the vehicle body in the recess 91, the flow changes diagonally downward and flows toward the spark plug 64. That is, the blocking wall 92F functions as a guide unit that guides the traveling wind so that it flows toward the spark plug 64. As a result, the combustion chamber 63 around the spark plug mounting portion 68 can be efficiently cooled without complicating the structure of the cylinder head cover. Further, the merchantability of the appearance of the cylinder head cover can be improved.

  In particular, in the motorcycle 1, the cylinder block 52 of the engine 1 is tilted forward, so that the traveling wind that has changed its flow upward by hitting the uppermost cooling fin 83 of the cylinder head 53 easily flows into the cavity 98. Therefore, the cooling effect around the spark plug mounting portion 68 described above is great. Therefore, the engine 50 of the motorcycle 1 can be efficiently cooled.

1 is a side view of a motorcycle according to the present invention. 1 is a right side view showing a part of an internal combustion engine according to the present invention in a cutaway manner. FIG. It is a right view for demonstrating the flow of the driving | running | working wind in the said internal combustion engine. It is sectional drawing of the said internal combustion engine. It is sectional drawing which expand | deploys and shows the transmission part of the said internal combustion engine. It is a bottom view of the cylinder head cover of the internal combustion engine.

Explanation of symbols

1 motorcycle 50 engine (internal combustion engine)
52 Cylinder block 53 Cylinder head 54 Cylinder head cover 63 Combustion chamber 64 Spark plug 87 First vertical wall 88 Second vertical wall 91 Recess 92F Closure wall (guide part)
94 Ribs

Claims (5)

In the air-cooled internal combustion engine in which the upper end of the cylinder block is closed with a cylinder head, a combustion chamber is formed inside, and a cylinder head cover is attached on the cylinder head.
An internal combustion engine having a double structure in which an outer peripheral portion of the cylinder head cover has a double vertical wall.   2. The internal combustion engine according to claim 1, wherein the double vertical walls are connected to each other by a rib.   2. The internal combustion engine according to claim 1, wherein a lower side is opened and an upper side is closed between the double vertical walls.   The cylinder head cover has a recess on an upper extension of a spark plug attached to the cylinder head, and guides the traveling wind flowing between the double vertical walls to flow toward the spark plug. The internal combustion engine according to claim 3, further comprising a portion.   A motorcycle equipped with the internal combustion engine according to claim 4, wherein the cylinder block of the internal combustion engine is inclined forward toward the front of the vehicle body.

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