TW201422902A - Forced air-cooling type internal combustion engine and saddled vehicle having the same - Google Patents

Abstract

There is provided a forced air-cooling type internal combustion engine which excels in both castability and cooling efficiency of a cylinder head and/or a cylinder block. A forced air-cooling type internal combustion engine (101) includes: a cylinder block (103) molded by casting; a cylinder head (100) molded by casting and overlaid on the cylinder block; a shroud (130) covering at least a portion of the cylinder block and at least a portion of the cylinder head; and a fan (121) for rotating to introduce air to the inside of the shroud. At least one of the cylinder block and the cylinder head includes a cooling fin (10) formed at least in a portion covered by the shroud and a cross fin (20) provided so as to cross the cooling fin, the cross fin being connected to the cooling fin. A thickness (t') of the cross fin at a leading edge (20a) thereof is greater than a thickness (t) of the cooling fin at a leading edge thereof.

Description

Forced air-cooled internal combustion engine and straddle type vehicle having the forced air-cooled internal combustion engine

The present invention relates to an internal combustion engine, and more particularly to a forced air cooled internal combustion engine. Further, the present invention relates to a straddle type vehicle having a forced air-cooled internal combustion engine.

The internal combustion engine for a straddle type vehicle is roughly classified into a water-cooled type and an air-cooled type. The water-cooled type is a method of cooling a coolant such as water as a medium, and the air-cooling type is a method of cooling by air. In the air-cooled internal combustion engine, a plurality of cooling fins are provided on the surface of the internal combustion engine to improve the cooling efficiency (see, for example, Patent Document 1).

Further, as an air-cooled internal combustion engine, a natural air-cooled internal combustion engine and a forced air-cooled internal combustion engine are known. In the natural air-cooling type, cooling is performed by blowing wind on the cooling fins. The internal combustion engine disclosed in Patent Document 1 is of a natural air-cooling type. On the other hand, in the forced air cooling type, cooling is performed by driving the fan by the power of the internal combustion engine, and cooling air introduced into the enclosure (air deflector) by the fan is blown to the cooling. Chip.

[Previous Technical Literature] (Patent Literature)

Patent Document 1: Japanese Laid-Open Patent Publication No. 2010-159703

The inventors of the present invention have repeatedly conducted research on the structure of a cooling fin (heat sink) which is most suitable for a forced air-cooled internal combustion engine. Specifically, the inventors of the present invention studied the following matters: by reducing the thickness and pitch of the cooling fins (that is, arranging thinner cooling fins in a reduced interval manner), placing as many cooling fins as possible in the cylinder head and the cylinder In this way, the cooling efficiency is improved. As a result, it has been found that when the thinner cooling fins are arranged at a reduced interval, although the cooling efficiency is improved, when the cylinder head or the cylinder is formed by casting, the melt fluidity (filling property) around the fins may be Reduced, resulting in poor casting.

The present invention has been made in view of the above problems, and an object thereof is to provide a forced air-cooled internal combustion engine which is excellent in both castability and cooling efficiency of a cylinder head and/or a cylinder.

A forced air-cooled internal combustion engine according to the present invention includes: a cylinder formed by casting; a cylinder head formed by casting and provided so as to overlap with the cylinder; and a shroud covering the cylinder At least a portion and at least a portion of the aforementioned cylinder head; and a fan that introduces air into the enclosure by rotation; and at least one of the cylinder and the cylinder head is formed at least in the foregoing a cooling fin on a portion covered by the plate, and an intersecting piece provided to intersect with the cooling fin and connected to the cooling fin; a thickness of a front end portion of the cross piece is larger than a front end portion of the cooling fin thickness.

In a preferred embodiment, at least the cylinder head of the cylinder block and the cylinder head has the cross piece.

In a preferred embodiment, the cross piece is provided at an angle of 45 or less with respect to the rotation axis of the fan when viewed from the cylinder axis direction.

In a preferred embodiment, the cross piece is provided in such a manner as to overlap the combustion chamber when viewed from the cylinder axis direction.

In a preferred embodiment, further comprising a plurality of bolts that couple the cylinder block to the cylinder head; the plurality of bolts include two bolts located on the fan side with respect to a cylinder axis; the cross piece It is provided in such a manner that a part thereof is located between the two bolts.

In a preferred embodiment, the width of the cross piece along the cylinder axis direction is smaller than the width of the root portion of the cross piece at the front end portion of the cross piece.

In a preferred embodiment, the thickness of the cross piece increases as it goes from the front end side of the cross piece toward the root side.

In a preferred embodiment, the thickness of the cross-tab is larger as the cylinder is closer to the cylinder.

In a preferred embodiment, the position of the at least one of the cylinder and the cylinder head is located between the center of the cooling fin and the front end of the cooling fin.

In a preferred embodiment, at least one of the foregoing cylinder block and the aforementioned cylinder head has a plurality of the aforementioned cooling fins; The thickness of each of the front end portions is set to t (mm), and when the distance between the front end portions of the adjacent two cooling fins of the plurality of cooling fins is c (mm), the thickness t and the interval are c satisfies the relationship between t≦3 and t≦c≦3t.

In a suitable embodiment, the thickness t further satisfies the relationship of 1 ≦ t.

In a suitable embodiment, the interval c further satisfies the relationship of 3≦c.

In a preferred embodiment, the cooling fin has a draft angle of 1.0° or more and 2.0° or less.

The straddle type vehicle of the present invention includes the forced air-cooling type internal combustion engine having the above configuration.

The internal combustion engine of the present invention is a forced air-cooled internal combustion engine having a shroud and a fan. Therefore, even if the thickness and the pitch of the cooling fins are reduced (that is, even if the thinner cooling fins are arranged at a reduced interval), as many cooling fins as possible are provided, the cooling efficiency can be improved, and The cooling air is sufficiently transmitted in the gap between the adjacent cooling fins. Further, in the forced air-cooled internal combustion engine of the present invention, at least one of the cylinder block and the cylinder head has not only a cooling fin but also a cross piece which is provided to intersect with the cooling fin and is connected to the cooling fin. The thickness of the front end portion of the cross piece is larger than the thickness of the front end portion of the cooling fin. By providing such a cross piece, even if a thin cooling fin is disposed at a reduced interval to improve the cooling efficiency, the fluidity of the melt during casting can be prevented from being lowered, so that the occurrence of casting failure can be prevented. As a result, the forced air-cooled internal combustion engine of the present invention is excellent in both castability and cooling efficiency of the cylinder head and/or the cylinder block.

Preferably, at least the cylinder head has a cross piece in the cylinder block and the cylinder head. Usually, since the cylinder head is often more complicated than the cylinder shape, if a thin cooling fin is disposed at a reduced interval, the melt fluidity is likely to be lowered around the cooling fin. By providing a cross piece at least on the cylinder head, it is possible to effectively prevent the occurrence of casting defects.

If the cross piece is provided in such a manner that when viewed from the cylinder axis direction, the rotation axis of the fan is at an angle of 45 or less, it is not easy to generate resistance to the cooling air transmitted by the fan. Therefore, the reduction in cooling efficiency caused by the provision of the cross piece can be prevented.

Preferably, the cross piece is disposed in such a manner as to overlap the combustion chamber when viewed from the cylinder axis direction. That is, preferably, the cross piece is connected to the combustion chamber wall for defining the combustion chamber. By providing the cross piece in this way, since the heat generated in the combustion chamber can be transmitted to the cooling fin via the cross piece, the cooling efficiency is improved.

Typically, the internal combustion engine of the present invention includes a plurality of bolts that couple the cylinder block to the cylinder head; the plurality of bolts include two bolts on the fan side with respect to the cylinder axis. Preferably, the cross piece is disposed such that a portion thereof is located between the two bolts. By disposing the cross piece in this manner, since the cross piece can be brought close to the center of the combustion chamber, more heat can be transmitted to the cooling fin via the cross piece, and the cooling efficiency can be further improved.

The width of the cross piece along the cylinder axis direction may be such that a plurality of cooling fins are provided on the front end side if the width of the front end portion of the cross piece is smaller than the width of the root portion of the cross piece, and the cam chamber can be brought close to the combustion on the root side. The cylinder head is miniaturized on the side of the chamber. That is, it is possible to simultaneously achieve cooling and miniaturization.

Preferably, the thickness of the cross piece becomes larger as it goes from the front end side toward the root side of the cross piece. By setting the thickness of the cross piece in this way, more heat can be transferred from the combustion chamber to the cooling fin.

Further, it is preferable that the thickness of the cross piece is larger as it approaches the cylinder. By setting the thickness of the cross piece in this way, more heat can be transferred from the combustion chamber to the cooling fin.

Preferably, the division position of the cylinder and/or the cylinder head (mold dividing position at the time of casting) is located between the center of the cooling fin and the front end portion of the cooling fin. By setting the division position at such a position, it is easy to remove the burrs at the division position. On the other hand, if the division position is located between the center of the cooling fin and the root of the cooling fin, it is difficult to perform the operation of removing the burr.

Preferably, when the thickness of the front end portion of each of the plurality of cooling fins is t (mm), and the interval between the front end portions of the adjacent two cooling fins among the plurality of cooling fins is c (mm) The thickness t and the interval c satisfy the relationship between t≦3 and t≦c≦3t. By arranging a thinner cooling fin at a reduced interval while satisfying such a relationship, a plurality of cooling fins can be provided, and cooling efficiency can be improved.

Preferably, the thickness t of the front end portion of the cooling fin satisfies the relationship of 1 ≦ t. The smaller the thickness of the cooling fins, the more the number of cooling fins can be increased. However, if the thickness of the cooling fins is too small, it is difficult to remove heat from the cylinder block and the cylinder head. If the thickness t of the front end portion of the cooling fin is 1 mm or more (that is, 1 ≦ t), such a problem does not occur.

Preferably, the distance c between the front end portions of the adjacent two cooling fins satisfies the relationship of 3≦c. If the distance c between the front end portions of the adjacent two cooling fins is 3 mm or more (that is, 3 ≦ c), it is easy to supply cooling air to the cold. The root of the piece, therefore, the cooling efficiency is improved.

Preferably, the cooling fin has a draft angle of 2.0 or less. By reducing the draft angle to 2.0° or less, the interval between the root portions of the cooling fins can be enlarged, so that the cooling property can be further improved. However, from the viewpoint of easy release, the draft angle of the cooling fin is preferably 1.0 or more.

According to the present invention, there is provided a forced air-cooled internal combustion engine in which the cylinder head and/or the cylinder are excellent in both castability and cooling efficiency.

1‧‧‧Motorcycles (straddle-type vehicles)

10‧‧‧ Cooling film

10c‧‧‧Bending part of the cooling fin

10d‧‧‧ Straight line of the cooling fin

20‧‧‧cross piece

20a‧‧‧ front end of the cross piece

20b‧‧‧ root of the cross piece

20c‧‧‧The curved part of the cross piece

20d‧‧‧ Straight line of the cross piece

30‧‧‧fuel chamber wall

32‧‧‧ plug hole

40‧‧‧ Inhalation channel

40a‧‧‧ suction port

40b‧‧‧ openings

50‧‧‧Exhaust passage

50a‧‧‧Exhaust port (inlet of exhaust duct)

50b‧‧‧ openings (exit of the exhaust passage)

60‧‧‧Cooling air passage

60a‧‧‧Environment of the cooling air passage

60b‧‧‧Exit of the cooling air passage

70‧‧‧Cam chain room

80‧‧‧Buds (holders for bolts or bosses for head bolts)

80a, 80b, 80c, 80d‧‧‧ bolt holes

100‧‧‧ cylinder head

101‧‧‧ engine (internal combustion engine)

102‧‧‧ crankcase

103‧‧‧Cylinder block

105‧‧‧Cylinder head cover

106‧‧‧ cylinder

108‧‧‧Camshaft

110‧‧‧ combustion chamber

113‧‧‧Cam chain

121‧‧‧Fan

130‧‧‧

141‧‧‧ suction pipe

142‧‧‧Exhaust pipe

161‧‧‧ Inhalation valve

162‧‧‧Exhaust valve

CA‧‧‧Cooling air

D1‧‧‧Cylinder axis direction

L1‧‧‧Cylinder axis

L2‧‧‧Center line of the crankshaft (rotation axis of the fan)

P‧‧‧ split position

Fig. 1 is a right side view schematically showing a locomotive (straddle type vehicle) 1 in an embodiment of the present invention.

Fig. 2 is a cross-sectional view taken along line 2A-2A' in Fig. 1.

Fig. 3 is an enlarged view of the vicinity of an engine (internal combustion engine) 101 shown in Fig. 2.

FIG. 4 is a right side view of a portion of the engine 101.

Fig. 5 is a cross-sectional view of the left side of the engine 101.

Fig. 6 is a plan view schematically showing a cylinder head 100 provided in the engine 101 in the embodiment of the present invention.

Fig. 7 is a bottom view schematically showing the cylinder head 100 of the engine 101 according to the embodiment of the present invention.

Fig. 8 is a front view schematically showing a cylinder head 100 provided in the engine 101 in the embodiment of the present invention.

Figure 9 is a schematic view of an engine 101 in an embodiment of the present invention A rear view of the cylinder head 100 is provided.

Fig. 10 is a left side view schematically showing the cylinder head 100 of the engine 101 according to the embodiment of the present invention.

Fig. 11 is a right side view schematically showing the cylinder head 100 of the engine 101 according to the embodiment of the present invention.

Fig. 12 is a view schematically showing the cylinder head 100 of the engine 101 according to the embodiment of the present invention, which is a cross-sectional view taken along line 12A-12A' in Fig. 10.

Fig. 13(a) is a cross-sectional view schematically showing the cooling fins 10 of the cylinder head 100, and Fig. 13(b) is a cross-sectional view schematically showing the intersecting piece 20 of the cylinder head 100.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Furthermore, the present invention is not limited to the following embodiments.

In the first drawing, the straddle type vehicle 1 in the present embodiment is shown. The straddle type vehicle 1 shown in Fig. 1 is a scooter type locomotive. Furthermore, the straddle type vehicle of the present invention is not limited to the locomotive 1 of the Scooton type. The straddle type vehicle of the present invention may be a so-called moped type, an off-road type, and an on-road type. Further, the straddle type vehicle of the present invention refers to any vehicle that is ridden by a rider and is not limited to a two-wheeled vehicle. The straddle type vehicle of the present invention may be a tricycle or the like in the form of changing the traveling direction by tilting the vehicle body, or may be another straddle type vehicle such as an All Terrain Vehicle (ATV).

In the following description, the front, the rear, the left, and the right respectively refer to the front, rear, left, and right when viewed by the rider of the locomotive 1. Reference symbol F in the figure, Re, L, and R indicate front, back, left, and right, respectively.

As shown in FIG. 1, the locomotive 1 includes a vehicle body 2, a front wheel 3, a rear wheel 4, and an engine unit 5 that drives the rear wheel 4. The vehicle body 2 is provided with a handle 6 for the rider to operate, and a seat 7 for the rider to sit. The engine unit 5 is a so-called unit swing type engine unit that is supported by a vehicle body frame (not shown in Fig. 1) centered on the pivot shaft 8 in a swingable manner. That is, the engine unit 5 is supported by the vehicle body frame in a swingable manner.

Next, the configuration of the engine unit 5 of the locomotive 1 will be described more specifically with reference to FIGS. 2 to 5 . Fig. 2 is a cross-sectional view taken along line 2A-2A' in Fig. 1. Fig. 3 is an enlarged view of the vicinity of the engine 101 shown in Fig. 2. FIG. 4 is a right side view of a portion of the engine 101. Fig. 5 is a cross-sectional view of the left side of the engine 101.

As shown in FIG. 2, the engine unit 5 includes an engine (internal combustion engine) 101 and a v-belt type stepless transmission (hereinafter referred to as "continuously variable transmission (CVT)) 150. Further, in the example shown in FIG. 2, the engine 101 and the CVT 150 integrally constitute the engine unit 5. However, the engine 101 and the transmission may of course be separated.

The engine 101 is a single cylinder engine having a single cylinder. The engine 101 is a four-stroke engine that sequentially repeats an inhalation step, a compression step, a combustion step, and an exhaust step. The engine 101 includes a crankcase 102 and a cylinder 103 that is forward from the crankcase 102. (Further, the "front" described herein is not limited to the front in a strict sense, that is, it is not limited to the direction parallel to the horizontal line. , also extending from the direction of the horizontal line inclination and combined with the crankcase 102; the cylinder head 100 is coupled to the front portion of the cylinder block 103; and, the cylinder head cover 105 is connected At the front of the cylinder head 100.

The cylinder 103 is formed by casting (for example, gravity casting). The material of the cylinder 103 is, for example, an aluminum alloy or a cast iron. Inside the cylinder 103, a cylinder 106 is formed.

Further, the cylinder 106 may be formed by a cylinder liner or the like inserted into the body of the cylinder 103 (that is, a portion other than the cylinder 106 in the cylinder 103), or may be connected to the cylinder 103. The integration of the ontology. In other words, the cylinder 106 may be formed to be separable from the body of the cylinder 103 or may be formed so as not to be separated from the body of the cylinder 103. The piston 107 is slidably housed in the cylinder 106. The piston 107 is disposed to be reciprocally movable between a top dead center TDC (top dead center) and a bottom dead center BDC (bottom dead center).

The cylinder head 100 is superposed on the cylinder block 103 so as to cover the cylinder 106. The cylinder head 100 is formed by casting (for example, gravity casting). The material of the cylinder head 100 is, for example, aluminum alloy or cast iron. The combustion chamber 110 is defined by the cylinder head 100, the top surface of the piston 107, and the inner circumferential surface of the cylinder 106. The portion 30 of the cylinder head 100 that defines the combustion chamber 110 is referred to as the combustion chamber wall.

The piston 107 is coupled to the crankshaft 112 via a link 111. The crankshaft 112 extends leftward and rightward and is supported by the crankcase 102. The camshaft 108 is driven by a cam chain 113 coupled to the crankshaft 112. The cam chain 113 is housed in the cam chain chamber 70.

Further, in the present embodiment, the crankcase 102, the cylinder block 103, the cylinder head 100, and the cylinder head cover 105 are separate bodies, but these are not necessarily separate bodies, and may be appropriately integrated. For example, the crankcase 102 and the cylinder 103 may be integrally formed. The cylinder 103 and the cylinder head 100 may also be integrally formed. Further, the cylinder head 100 and the cylinder head cover 105 may be integrally formed.

As shown in FIG. 2, the CVT 150 includes a first pulley 151 which is a pulley on the driving side, a second pulley 152 which is a pulley on the driven side, and a V-shaped wound around the first pulley 151 and the second pulley 152. Belt 153. The left end portion of the crankshaft 112 protrudes leftward from the crankcase 102. The first pulley 151 is attached to the left end portion of the crankshaft 112. The second pulley 152 is attached to the main shaft 154. The main shaft 154 is coupled to the rear wheel shaft 155 via a gear mechanism (not shown). On the left side of the crankcase 102, a transmission housing 156 is provided. The CVT 150 is housed within the shifter housing 156.

A generator 120 is disposed at a right portion of the crankshaft 112. A cooling fan (hereinafter simply referred to as "fan") 121 is fixed to the right end portion of the crankshaft 112. The fan 121 rotates together with the crankshaft 112. The fan 121 is formed by sucking air to the left by rotation. The generator 120 and the fan 121 are housed in the enclosure 130. The shroud 130 is disposed to cover at least a portion of the cylinder 103 and at least a portion of the cylinder head 100.

As shown in Fig. 4, the engine 101 is a so-called transverse type engine, that is, the cylinder block 103 and the cylinder head 100 extend in the horizontal direction or in a direction slightly inclined from the front to the front in the horizontal direction. Reference symbol L1 in the figure denotes a line (cylinder axis) passing through the center of the cylinder 106. The cylinder axis L1 extends in a horizontal direction or a direction slightly inclined from the horizontal direction. However, the direction of the cylinder axis L1 is not particularly limited. For example, the inclination angle of the cylinder axis L1 with respect to the horizontal plane may be 0 to 15 degrees, or may be above the range. Furthermore, reference symbol L2 in the figure denotes a center line of the crankshaft 112.

An intake pipe 141 is connected to an upper portion of the cylinder head 100. Further, an exhaust pipe 142 is connected to the lower portion of the cylinder head 100. Inside the cylinder head 100, an intake passage 40 and an exhaust passage 50 are formed. The intake pipe 141 is connected to the intake passage 40, and the exhaust pipe 142 is connected to the exhaust passage 50. An intake valve 161 and an exhaust valve 162 are provided on the intake passage 40 and the exhaust passage 50, respectively.

The engine 101 of the present embodiment is an air-cooled engine that is cooled by air, and more specifically, a forced air-cooled engine. As shown in FIGS. 2 to 4, the cylinder 103 has a plurality of cooling fins 114 formed at least on a portion covered by the louver 130. The cooling fins 114 extend in a direction substantially orthogonal to the cylinder axis L1. Further, as will be described later, the cylinder head 100 also has a plurality of cooling fins 10 formed at least on the portion covered by the louver 130 (see FIGS. 8 to 10).

The shingle 130 has an inner member 131 and an outer member 132 which are formed by assembling the inner member 131 and the outer member 132. As shown in FIG. 4, the inner member 131 and the outer member 132 are fixed by bolts 133. The inner member 131 and the outer member 132 are formed, for example, of a synthetic resin.

A hole 131a is formed in the inner member 131, and an ignition device 115 such as a spark plug is inserted into the hole 131a. A suction port 132a is formed in the outer member 132. When the enclosure 130 is attached to the engine unit 5, the suction port 132a is disposed at a position facing the fan 121 (see FIG. 3). Reference symbol F in Fig. 4 denotes the outer circumference of the fan 121, and reference symbol B denotes the rotation direction of the fan 121.

The shroud 130 is attached to the crankcase 102, the cylinder 103, and the cylinder head 100, and extends forward along the cylinder 103 and the cylinder head 100. Coaming 130 covers the crankcase 102, the cylinder 103, and the right side portion of the cylinder head 100. Further, a part of the shingle 130 also covers the cylinder block 103 and a part of the upper side portion and the lower side portion of the cylinder head 100.

When the fan 121 rotates in accordance with the rotation of the crankshaft 112, the air outside the shingle 130 is introduced into the enclosure 130 through the suction port 132a. The air introduced into the enclosure 130 is blown onto the cylinder 103 and the cylinder head 100. The cylinder 103 and the cylinder head 100 are cooled by this air.

Next, the configuration of the cylinder head 100 included in the engine 101 in the present embodiment will be specifically described with reference to FIGS. 6 to 12 . 6 and 7 are a plan view and a bottom view schematically showing the cylinder head 100. 8 and 9 are a front view and a rear view schematically showing the cylinder head 100. 10 and 11 are a left side view and a right side view schematically showing the cylinder head 100. Further, Fig. 12 is a cross-sectional view taken along line 12A-12A' in Fig. 10. In the partial drawings, the cylinder axis direction is indicated by an arrow D1. Further, of course, the cylinder axis direction means a direction parallel to the cylinder axis L1. In the following description, one side of the intake pipe 141 is connected to the front side of the cylinder head 100 and will be described.

As shown in FIGS. 6 to 12, the cylinder head 100 has a plurality of cooling fins 10, a combustion chamber wall 30, an intake passage 40, an exhaust passage 50, and a cooling air passage 60.

As shown in FIGS. 8 , 9 , and 10 , a plurality of cooling fins 10 are provided on the outer side surface (more specifically, the left side surface) of the cylinder head 100 and protrude toward the outside of the cylinder head 100 . (that is, it is formed in such a manner as to extend in a direction substantially orthogonal to the cylinder axis direction D1). Further, a plurality of cooling fins 10 are arranged at a specific pitch along the cylinder axis direction D1. Again, cold The number of slices 10 is not limited to the number exemplified herein.

The combustion chamber wall 30 shown in Figures 7 and 10 is used to define the combustion chamber 110. The combustion chamber 110 is a space formed by the combustion chamber wall 30 of the cylinder head 100, the top surface of the piston 107, and the inner circumferential surface of the cylinder 106. As shown in Fig. 7, a plug hole 32 is formed in the combustion chamber wall 30 in addition to the intake port 40a and the exhaust port 50a which will be described later. In the plug hole 32, a spark plug of the ignition device 115 is mounted.

The intake passage 40 is a passage for sucking the combustion chamber 110. The opening 40a on the combustion chamber wall 30 side of the intake passage 40 is an intake port. The intake valve 161 is moved up and down to open and close the intake port 40a. An intake pipe 141 is connected to an opening 40b (on the front surface of the cylinder head 100) on the opposite side of the combustion chamber wall 30 of the intake passage 40.

The exhaust passage 50 is a passage for exhausting from the combustion chamber 110. The opening portion 50a of the exhaust passage 50 on the combustion chamber wall 30 side is an exhaust port. The exhaust valve 162 is moved up and down to open and close the exhaust port 50a. An exhaust pipe 142 is connected to the opening 50b of the exhaust passage 50 opposite to the combustion chamber wall 30.

Typically, a plurality of cooling fins 10 include cooling fins 10 extending from the exhaust passage walls defining the exhaust passage 50 (in Fig. 10, relatively on the right side). In the present embodiment, the plurality of cooling fins 10 further include a cooling fin 10 extending from the wall of the intake passage defining the intake passage 40 (in the tenth figure, relatively on the left side).

The cooling air passage 60 shown in Fig. 10 is a passage for passing cooling air. As shown in Fig. 7, the inlet 60a of the cooling air passage 60 is located on the left side of the cylinder head 100, and the outlet 60b of the cooling air passage 60 is located. The right side of the cylinder head 100. The cooling air CA introduced into the enclosure 130 by the fan 121 is introduced into the cooling air passage 60 from the inlet 60a. During the passage of the cooling air passage 60, the cylinder head 100 is cooled and discharged from the outlet 60b. The exterior of the cylinder head 100.

Further, as shown in Fig. 6, Fig. 7, and Fig. 12, the cylinder head 100 has a plurality of bolt holes 80a to 80d through which bolts are respectively inserted. The cylinder head 100 is coupled to the cylinder block 103 by bolts (typically stud bolts) inserted through the bolt holes 80a to 80d. The boss 80 having the bolt holes 80a to 80d is sometimes referred to as a boss for a bolt or a boss for a headless bolt.

The cylinder head 100 further has a cross piece 20 that is disposed to intersect the cooling fins 10 and is coupled to the cooling fins 10. In the present embodiment, two intersecting pieces 20 are provided. One of the two intersecting pieces 20 (in the tenth figure, relatively located on the side of the exhaust passage 50) is connected to the cooling extending from the wall of the exhaust passage. Slice 10. Further, the other (in the Fig. 10, relatively located on the side of the intake passage 40) is connected to the cooling fins 10 extending from the wall of the suction passage.

As shown in Fig. 10, the thickness t' of the front end portion of the cross piece 20 is larger than the thickness t of the front end portion of the cooling fin 10. Further, as shown in Fig. 13(a), actually, the front end of the cooling fin 10 has a curvature. That is, the cooling fin 10 has a curved portion 10c having a curved surface and a straight portion 10d having a flat surface. In the present specification, the thickness t of the front end portion of the cooling fin 10 means the thickness of the outermost side of the straight portion 10d, in other words, the thickness of the boundary between the curved portion 10c and the straight portion 10d. Further, as shown in Fig. 13(b), actually, the front end of the cross piece 20 is also curved. That is, the cross piece 20 has a curved portion 20c having a curved surface and a straight portion 20d having a flat surface. In the case of this case The thickness t' of the front end portion of the cross piece 20 refers to the thickness of the outermost side of the straight portion 20d, in other words, the thickness of the boundary between the curved portion 20c and the straight portion 20d. Further, in the 13th (a)th and 13th (b)th drawings, the draft angle of the cooling fins 10 and the cross sheets 20 are exaggeratedly shown.

As described above, the engine (internal combustion engine) 101 in the present embodiment is a forced air-cooled engine including the louver 130 and the fan 121. Therefore, even if the thickness and pitch of the cooling fins 10 are reduced (that is, even if the thinner cooling fins 10 are disposed at a reduced interval), as many cooling fins 10 as possible are provided, and the cooling efficiency is improved. The cooling air CA can be sufficiently transferred into the gap between the adjacent cooling fins 10.

Further, in the forced air-cooling type engine 101 of the present embodiment, the cylinder head 100 has the cross piece 20 which is provided so as to intersect the cooling fin 10. The cross piece 20 is attached to the cooling fin 10. The thickness t' of the front end portion of the cross piece 20 is larger than the thickness t of the front end portion of the cooling fin 10. By providing such a cross piece 20, even if the thin cooling fins 10 are disposed at a reduced interval to improve the cooling efficiency, the fluidity of the melt during casting can be prevented from being lowered, so that the occurrence of casting failure can be prevented.

As described above, the forced air-cooling engine 101 of the present embodiment is excellent in both the castability and the cooling efficiency of the cylinder head 100.

The thickness t' of the tip end portion of the cross piece 20 is preferably 1.5 times or more the thickness t of the tip end portion of the fin 10 from the viewpoint of more reliably preventing the decrease in the fluidity of the melt. Moreover, from the viewpoint of sufficiently ensuring the cooling property, the thickness t' of the tip end portion of the cross piece 20 is preferably 10 times or less the thickness t of the tip end portion of the cooling fin 10.

Further, in the present embodiment, the cylinder head 100 has the configuration in which the cross piece 20 is provided. However, in addition to or in place of the cylinder head 100, the cylinder 103 may be provided to intersect the cooling fins 114. And connected to the cross piece of the cooling fins 114. By including at least one of the cylinder 103 and the cylinder head 100 in addition to the cooling fins, the engine 101 is excellent in both the castability and the cooling efficiency of the cylinder head 100 and/or the cylinder block 103.

However, for the following reasons, it is preferable that at least the cylinder head 100 has the cross piece 20 in the cylinder 103 and the cylinder head 100 as exemplified in the present embodiment. Usually, since the cylinder head is often more complicated than the cylinder shape, if a thin cooling fin is disposed at a reduced interval, the melt fluidity is likely to be lowered around the cooling fin. According to the present embodiment, at least the cross piece 20 is provided on the cylinder head 100, whereby the occurrence of casting failure can be effectively prevented.

Preferably, the cross piece 20 is provided in such a manner as to be shown in Fig. 12, as viewed from the cylinder axis direction D1, with respect to the rotation axis of the fan 121 (with the center of the crank shaft 112 as in the present embodiment) Line L2 (shown in Figure 12 for reference) is at an angle of 45° or less. The cross piece 20 is provided in such a manner as to be an angle of 45 or less with respect to the rotation axis of the fan 121 when viewed from the cylinder axis direction D1 (if it is a horizontal type according to the present embodiment, it can be said that In the up-and-down direction, which is formed to extend in the direction closer to the left-right direction, it is not easy to generate resistance to the cooling air CA transmitted by the fan 121. Therefore, the reduction in cooling efficiency caused by the provision of the cross piece 20 can be prevented.

Further, it is preferable that the cross piece 20 is provided in such a manner as to overlap with the combustion chamber 110 when viewed from the cylinder axis direction as shown in Fig. 12. That is, the cross piece 20 is preferably connected to the combustion chamber wall 30 of the predetermined combustion chamber 110. By providing the cross piece 20 in this way, since the heat generated in the combustion chamber 110 can be transmitted to the cooling fins 10 via the cross piece 20, the cooling efficiency is improved.

The plurality of bolts included in the engine 101 in the present embodiment include two bolts (corresponding to the bolt holes 80c and 80d) on the side of the fan 121 with respect to the cylinder axis L1, as shown in Figs. 10 and 12. The cross piece 20 is disposed such that a portion thereof is located between the two bolts (that is, between the bolt holes 80c and 80d). By providing the cross piece 20 in this manner, since the cross piece 20 can be brought close to the center of the combustion chamber 110, more heat can be transmitted to the cooling fin 10 via the cross piece 20, and the cooling efficiency can be further improved.

The width w of the cross piece 20 along the cylinder axis direction D1 (see FIG. 10) is smaller than the width of the tip end portion 20a (see FIG. 12) of the cross piece 20 is smaller than the root portion 20b of the cross piece 20 (see FIG. 12). width. When the width w of the cross piece 20 is set in this way, the plurality of cooling fins 10 can be provided on the distal end portion 20a side, and the cam chamber can be brought closer to the combustion chamber 110 side on the side of the root portion 20b to reduce the size of the cylinder head 100. That is to say, it is possible to achieve both cooling performance and miniaturization.

Further, in Fig. 12, the thickness of the cross piece 20 is shown as being constant from the front end portion 20a to the root portion 20b, but the thickness of the cross piece 20 is preferably from the side of the front end portion 20a toward the side of the root portion 20b. Become bigger. By setting the thickness of the cross piece 20 in this way, more heat can be transferred from the combustion chamber 110 to the cooling fins 10.

Moreover, in Fig. 10, the thickness of the cross piece 20 is a pattern along The cylinder axis direction D1 does not change, but the thickness of the cross piece 20 is preferably larger as it approaches the cylinder 103 (i.e., from the upper side toward the lower side in Fig. 10). By setting the thickness of the cross piece 20 in this way, more heat can be transferred from the combustion chamber 110 to the cooling fins 10.

Further, the division position (the split position at the time of casting) P of the cylinder head 100 and/or the cylinder block 103 is preferably located at the center and the front end portion of the cooling fin 10 (or the cooling fins 114) as shown in Fig. 12 . More specifically, it is preferably located within 10 mm from the front end portion of the cooling fin 10 (or the cooling fins 114). By setting the division position P at such a position, it is easy to remove the burrs on the division position P. On the other hand, if the division position P is located between the center and the root of the cooling fin 10 (or the cooling fins 114), it is difficult to perform the operation of removing the burrs.

Preferably, the thickness t (mm) of the front end portion of each of the plurality of cooling fins 10 and the interval c (mm) between the front end portions of the two adjacent cooling fins 10 of the plurality of cooling fins 10 (refer to FIG. 10) ), satisfying the relationship between t≦3 and t≦c≦3t. That is, the thickness t is preferably 3 mm or less, and the interval c is preferably 1 time or more and 3 times or less the thickness t. By arranging the thinner cooling fins 10 at a reduced interval while satisfying such a relationship, a plurality of cooling fins 10 can be provided, and the cooling efficiency can be improved. Further, it is preferable that the thickness of the tip end portion of the plurality of cooling fins 114 provided on the cylinder block 103 and the distance between the tip end portions satisfy the same relationship (that is, the thickness of the tip end portion is preferably 3 mm or less. The distance between the front end portions is 1 time or more and 3 times or less the thickness of the front end portion.

The thickness t of the front end portion of the cooling fin 10 preferably satisfies the relationship of 1 ≦ t. That is, the thickness t of the front end portion of the cooling fin 10 is preferably 1 mm. on. The smaller the thickness of the cooling fins 10, the more the number of the cooling fins 10 can be increased. However, if the thickness of the cooling fins 10 is too small, it is difficult to carry heat away from the cylinder head 100. If the thickness t of the front end portion of the cooling fin 10 is 1 mm or more (that is, 1 ≦ t), such a problem does not occur. The cooling fins 114 of the cylinder block 103 are also the same, and preferably have a thickness of 1 mm or more at the front end portion.

Moreover, it is preferable that the distance c between the front end portions of the adjacent two cooling fins 10 satisfies the relationship of 3≦c. In other words, the interval c between the distal end portions of the adjacent two cooling fins 10 is preferably 3 mm or more. When the interval c is 3 mm or more (3 ≦ c), since the cooling air CA is easily supplied to the root of the cooling fin 10, the cooling efficiency is improved. The cooling fins 114 of the cylinder block 103 are also the same, and it is preferable that the distance between the front end portions of the adjacent two cooling fins 114 is 3 mm or more.

Preferably, the cooling fins 10 of the cylinder head 100 and/or the cooling fins 114 of the cylinder block 103 have a draft angle of 2.0 or less. By reducing the draft angle to 2.0° or less, the interval between the cooling fins 10 of the cylinder head 100 and/or the cooling fins 114 of the cylinder block 103 can be enlarged, so that the cooling performance can be further improved. However, from the viewpoint of easy mold release, the draft angle of the cooling fins 10 of the cylinder head 100 and/or the cooling fins 114 of the cylinder block 103 is preferably 1.0 or more.

Further, it is preferable that the plurality of cooling fins 10 of the cylinder head 100 include the cooling fins 10 extending from the exhaust passage wall for defining the exhaust passage 50. Since the exhaust passage 50 is a portion where the temperature is likely to become high in the cylinder head 100, the cooling efficiency can be improved by extending the cooling fin 10 from the exhaust passage wall. From the standpoint of sufficiently ensuring a higher cooling efficiency, more specifically, the cooling fins 10 extending from the wall of the exhaust passage are at least more than the bosses in the wall of the exhaust passage (headless The bolt boss 80 is extended closer to the cylinder axis L1 side (refer to FIG. 10), and the boss corresponds to the bolt hole (the bolt hole closest to the cooling fin 10 extending from the exhaust passage wall) 80c.

The internal combustion engine 101 according to the embodiment of the present invention is suitably used for various straddle type vehicles such as a locomotive and an ATV (All Terrain Vehicle). Also, it is also suitable for use in generators and the like.

[Industrial availability]

According to the present invention, there is provided a forced air-cooled internal combustion engine in which the cylinder head and/or the cylinder are excellent in both castability and cooling efficiency. The forced air-cooled internal combustion engine of the present invention is suitable for use in various straddle type vehicles including locomotives because of its excellent cooling efficiency.

10‧‧‧ Cooling film

20‧‧‧cross piece

30‧‧‧fuel chamber wall

40‧‧‧ Inhalation channel

50‧‧‧Exhaust passage

60‧‧‧Cooling air passage

80‧‧‧Buds (holders for bolts or bosses for head bolts)

80c, 80d‧‧‧ bolt holes

100‧‧‧ cylinder head

Claims (14)

A forced air-cooled internal combustion engine comprising: a cylinder body formed by casting; a cylinder head formed by casting and disposed to overlap the cylinder block; and a shroud covering at least the cylinder block a portion and at least a portion of the aforementioned cylinder head; and a fan that introduces air into the enclosure by rotation; and at least one of the cylinder and the cylinder head is formed at least in the enclosure a cooling fin on the covered portion and an intersecting piece provided to intersect with the cooling fin and connected to the cooling fin; the thickness of the front end portion of the cross sheet is larger than the thickness of the front end portion of the cooling fin. A forced air-cooled internal combustion engine according to claim 1, wherein at least the cylinder head of the cylinder block and the cylinder head has the cross piece. The forced air-cooled internal combustion engine according to claim 1 or 2, wherein the cross piece is provided at an angle of 45 or less with respect to a rotation axis of the fan when viewed from a cylinder axis direction. The forced air-cooled internal combustion engine according to claim 1 or 2, wherein the cross piece is provided in such a manner as to overlap with the combustion chamber when viewed from the cylinder axis direction. The forced air-cooled internal combustion engine according to claim 4, further comprising: a plurality of bolts that couple the cylinder block to the cylinder head; the plurality of bolts include two bolts located on the fan side with respect to a cylinder axis; The cross piece is provided such that a part thereof is located between the two bolts. The forced air-cooled internal combustion engine according to claim 1 or 2, wherein the width of the cross piece in the cylinder axis direction is smaller than the width of the root portion of the cross piece at the front end portion of the cross piece. The forced air-cooled internal combustion engine according to claim 1 or 2, wherein the thickness of the cross piece becomes larger as it goes from the front end side toward the root side of the cross piece. The forced air-cooled internal combustion engine according to claim 1 or 2, wherein the thickness of the cross piece is larger as the cylinder is closer to the cylinder. The forced air-cooled internal combustion engine according to claim 1 or 2, wherein the divided position of the at least one of the cylinder block and the cylinder head is located between a center of the cooling fin and a front end portion of the cooling fin. The forced air-cooled internal combustion engine according to claim 1 or 2, wherein at least one of the cylinder block and the cylinder head has a plurality of the cooling fins; and a front end portion of each of the plurality of cooling fins When the thickness is t (mm), and the interval between the front end portions of the adjacent two cooling fins among the plurality of cooling fins is c (mm), the thickness t and the interval c satisfy t≦3 and t. ≦c≦3t relationship. The forced air-cooled internal combustion engine according to claim 10, wherein the thickness t further satisfies a relationship of 1 ≦ t. The forced air-cooled internal combustion engine according to claim 10, wherein the interval c further satisfies a relationship of 3 ≦ c. The forced air-cooled internal combustion engine according to claim 1 or 2, wherein the cooling fin has a draft angle of 1.0° or more and 2.0° or less. A straddle-type vehicle provided with a forced air-cooled internal combustion engine according to any one of claims 1 to 13.