JP4888302B2 - Internal combustion engine and vehicle equipped with the same - Google Patents

Abstract

An internal combustion engine 1 includes two cylinders 4 juxtaposed mutually adjacently to each other, two intake pipes 12, and two exhaust pipes 13. Each of the intake pipes 12 is disposed at a position to embrace the two cylinders 4 from either of both sides in a juxtaposed direction of the cylinders. In addition, the exhaust pipes 13 are connected to the cylinders 4 at positions between the intake pipes 12. This allows each of the intake pipes 12 to be held at a position away in either side from the cylinders 4 that serve as a heat source during operation of the engine, specifically, at an outside position with a low ambient temperature. Accordingly, an intake temperature of the internal combustion engine 1 can be reduced, so that detonation or the like can be prevented from occurring for improved drivability and fuel consumption.

Description

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

  2. Description of the Related Art Conventionally, as disclosed in, for example, Patent Document 1 (Japanese Patent Laid-Open No. 6-80032), a vehicle having a configuration in which an engine is disposed below a rear seat is known. A vehicle according to this type of prior art is arranged in a posture in which the internal combustion engine falls toward the front of the vehicle. In this case, the intake manifold of the engine is disposed so as to overlap the front side of the engine body (cylinder) when viewed from the front of the vehicle.

Japanese Patent Laid-Open No. 6-80032

  In the above-described prior art, the intake manifold is disposed so as to overlap the front side of the engine body. However, with this configuration, the engine body is hidden behind the intake manifold with respect to the direction of the flow of the traveling wind that occurs when the vehicle travels.

  For this reason, the conventional technology has a problem that when the vehicle travels, the intake manifold becomes in the way and the traveling wind does not sufficiently contact the engine body, and it is difficult to efficiently cool the engine body by the traveling wind. .

  The present invention has been made to solve the above-described problems. An internal combustion engine capable of efficiently cooling a cylinder and an intake pipe while having a compact structure as a whole, and a vehicle equipped with the same The purpose is to provide.

An internal combustion engine according to a first invention includes two cylinders arranged adjacent to each other,
Two intake pipes provided at positions sandwiching the two cylinders from both sides of the cylinder in the arrangement direction, and connected to the individual cylinders;
An exhaust pipe connected to each cylinder at a position between the two intake pipes;
It is characterized by providing.

  Further, according to the second invention, the two intake pipes are arranged in a state in which at least a part protrudes outside the cylinder block in which the cylinders are arranged in the arrangement direction.

Further, the third invention is a cylinder head mounted on the front end side of the two cylinders, each having an intake port opened at portions located on both sides in the arrangement direction,
A head cover covering the cylinder head;
A surge tank provided at a central portion on the head cover and provided with connection ports of the intake pipes at portions located on both sides of the arrangement direction;
The two intake pipes are respectively connected between connection ports on both sides of the surge tank and the intake ports of the cylinder head.

  According to a fourth aspect of the invention, the cylinder head includes two exhaust ports that are located between the intake ports and open in the same direction, and the exhaust pipes are connected to the exhaust ports, respectively. It is said.

  According to a fifth aspect of the present invention, the cylinder head includes an exhaust port that is located between the intake ports and merges in the cylinder head and opens at one location outside the cylinder head. The pipe is configured to be connected to this exhaust port.

On the other hand, a vehicle according to a sixth invention is a vehicle in which the internal combustion engine according to any one of the first to fifth inventions and a seat having a seat portion and a backrest are mounted on a vehicle body,
The internal combustion engine is arranged in a state in which the two cylinders are aligned in the width direction of the vehicle body, and the cylinders are tilted toward the rear of the vehicle body,
At least a part of the internal combustion engine is arranged below the seat portion of the seat.

  According to the seventh invention, the central axis of the cylinder is inclined obliquely upward so as to become higher toward the rear side of the vehicle body.

  Further, according to an eighth aspect of the invention, the tip end side of each cylinder of the internal combustion engine is arranged behind the seat portion of the seat.

  According to the first invention, two intake pipes can be arranged on both sides (outside) of two cylinders arranged side by side. For this reason, each intake pipe can be held at a position away from both sides of the cylinder that becomes a heat source during engine operation, that is, at an outer position where the ambient temperature is low. Accordingly, the intake air temperature of the internal combustion engine can be lowered, and the occurrence of knocking or the like can be suppressed and the drivability and fuel consumption can be improved. Further, when the cooling air is configured to flow perpendicularly to the direction in which the cylinders are arranged, the cooling air can be efficiently brought into contact not only with each cylinder but also with the intake pipes arranged on both sides thereof. Thereby, the cooling efficiency of a cylinder and an intake pipe can be improved.

  Further, according to the second invention, at least a part of the two intake pipes can be arranged in a state of protruding outside the cylinder block. Thereby, the intake pipe can be sufficiently separated from the structure on the cylinder block side, and the ambient temperature in the vicinity of the intake pipe can be lowered. Further, it is possible to separate the midway portion of the intake pipe and the structure on the cylinder block side, and heat conduction from these structures to the intake pipe can be suppressed.

  According to the third invention, the intake pipes on both sides can be formed symmetrically on the left and right with the surge tank interposed therebetween. For this reason, for example, by appropriately setting the facing distance of the opening end of each intake pipe that opens into the surge tank, the capacity of the surge tank, the diameter and length of each intake pipe, etc., the inertial supercharging of the intake air ( A phenomenon in which intake air is supercharged into the cylinder by intake pulsation) can be efficiently generated. As a result, the intake air amount of the internal combustion engine can be increased, and driving performance such as acceleration can be improved.

  Further, according to the fourth invention, the exhaust pipe can be arranged in a state of being gathered between the intake pipes. As a result, exhaust pipes that become hot during engine operation can be collected in one place, and the influence of heat released from each exhaust pipe can be minimized with respect to surrounding components.

  Further, for example, among the four peripheral walls surrounding the cylinder, the intake pipes can be arranged on both sides of the cylinder, and the exhaust pipes can be arranged together on the other one surface. As a result, since it is not necessary to arrange the components of the internal combustion engine on the remaining one surface, other structures and the like can be arranged on this vacant surface, and the space can be used effectively.

  According to the fifth aspect, the exhaust ports extending from the two cylinders can be merged in the cylinder head. The merged exhaust port can be opened at one location outside the cylinder head, and one exhaust pipe can be connected to the opening. As a result, the exhaust pipes can be more centralized, and the number of exhaust pipes can be reduced. Therefore, the exhaust pipe can be sufficiently separated from the intake pipe, and the influence of the heat released from the exhaust pipe on the surrounding parts including the intake pipe can be minimized.

  On the other hand, according to the sixth aspect of the present invention, the internal combustion engine can be disposed in the vehicle in a horizontal state. As a result, traveling wind generated when the vehicle travels can be circulated from the crankcase side toward the cylinder head side around the internal combustion engine. As a result, the cylinder and each intake pipe do not overlap with each other in the flow direction of the traveling wind, and can efficiently contact each other with the flow of the traveling wind.

  Therefore, the cylinder and each intake pipe can be individually cooled by the traveling wind, and the cooling efficiency of these parts can be improved. In addition, a portion of the intake pipe that is particularly connected to the intake port where the temperature is likely to rise can be exposed to the flow of the traveling wind, and the heat dissipation of this portion can be sufficiently enhanced.

  Further, by disposing at least a part of the internal combustion engine below the seat, the space in the vehicle can be widened while the entire vehicle is compactly formed. In addition, the exhaust pipe can be extended from the lower surface on the front end side of the cylinder to the rear side of the vehicle body by arranging each cylinder in a posture in which it is tilted to the rear side of the vehicle body. That is, since it is not necessary to pass the exhaust pipe below the crankcase or the cylinder block, the internal combustion engine can be mounted at a sufficiently low position.

  Thereby, the position of the seat can also be made sufficiently low, and the interior height of the vehicle (particularly, the space in which the head of the occupant seated on the seat is arranged) can be easily secured. Moreover, the ground clearance of the vehicle body can be lowered. Thereby, the air resistance at the time of driving | running | working can fully be reduced and a fuel consumption can be improved. Moreover, since the exhaust pipe does not pass below the crankcase or the cylinder block, it is possible to suppress the heat released from the exhaust pipe from being transmitted to the crankcase or the cylinder. Thereby, structures, such as a heat shield board and an oil cooler, can be omitted or simplified, for example, and cost reduction and weight reduction can be promoted.

  Further, for example, among the four peripheral walls surrounding the cylinder, the intake pipes can be arranged on both sides of the cylinder, and the exhaust pipes can be arranged together on the lower surface side of the cylinder. As a result, since it is not necessary to arrange the components of the internal combustion engine on the upper surface side of the cylinder, other in-vehicle structures and the like can be disposed on the upper surface side, and space can be used effectively.

  Further, according to the seventh invention, the center axis of the cylinder can be inclined obliquely upward so as to become higher toward the rear side of the vehicle body. As a result, even if the position of the crankcase on the front side is not increased, for example, an arrangement space for the exhaust pipe can be secured below the cylinder head, and the component layout in a state where the internal combustion engine is held at a low position It can be done easily.

  Further, the cylinder head can be held at a high position with respect to the crankcase. As a result, the oil easily returns from the cylinder head toward the crankcase, so that the structure of the PCV device (blow-by gas reduction device) can be simplified and cost reduction can be promoted. Further, since the amount of oil can be reduced, it is possible to realize weight reduction and friction reduction, which can contribute to improvement in fuel consumption.

  Further, according to the eighth invention, the front end side (cylinder head side) of each cylinder in the internal combustion engine can be arranged in a state of protruding to the rear side from the seat portion of the seat. As a result, the internal combustion engine can be easily inclined upward without increasing the seat position.

Embodiment 1 FIG.
[Configuration of internal combustion engine]
The first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a side view of an internal combustion engine 1 according to the present embodiment, and FIG. 2 shows a plan view of the internal combustion engine 1. As shown in these drawings, the internal combustion engine 1 is configured as, for example, an in-line two-cylinder engine, and includes a crankcase 2 and a cylinder block 3.

  The cylinder block 3 is formed, for example, as an elongated, substantially rectangular metal block, and the base end side is mounted on the crankcase 2. Further, two cylinders 4 and 4 arranged adjacent to each other are provided inside the cylinder block 3. That is, in this embodiment, two cylinders 4 are formed in a single cylinder block 3. Pistons 5 are inserted into these cylinders 4 so as to be able to reciprocate. The piston 5 is connected to the crankshaft 6 by a connecting rod or the like.

  A cylinder head 7 is mounted on the tip side of the cylinder block 3 (each cylinder 4). As shown in FIGS. 1 and 2, the cylinder head 7 is formed, for example, as a substantially square metal block and has four side surfaces. As shown in FIGS. 4 and 5 described later, these side surfaces include an upper surface 7A directed upward when mounted on the vehicle 21, a lower surface 7B directed downward, and the width direction of the vehicle 21 (two cylinders). 4), the left and right side surfaces 7C and 7C are located on both sides of the cylinder head 7.

  Further, as shown in FIG. 2, two intake ports 8, 8 are formed inside the cylinder head 7 so as to be located on both sides in the direction in which the cylinders 4 are arranged. These intake ports 8 communicate with the individual cylinders 4 and open on the side surfaces 7C and 7C of the cylinder head 7, respectively. Further, two exhaust ports 9 and 9 are formed in the cylinder head 7 between the intake ports 8. These exhaust ports 9 communicate with the individual cylinders 4 and open on the lower surface 7B of the cylinder head 7 at positions close to each other. In this way, the exhaust ports 9 are opened in the same direction (downward in the vehicle-mounted state).

  Further, the cylinder head 7 is equipped with devices (all not shown) such as a fuel injection valve, a spark plug, an intake valve, and an exhaust valve. Further, the upper side of the cylinder head 7 is covered with a head cover 10.

  On the other hand, the internal combustion engine 1 includes a surge tank 11 provided at the center of the head cover 10, two intake pipes 12, 12, and two exhaust pipes 13, 13. The surge tank 11 is connected to an intake passage (not shown) that allows outside air to flow into the surge tank 11 as intake air. Further, on the left and right side surfaces of the peripheral wall of the surge tank 11 located on both sides of the cylinder 4 in the arrangement direction, connection ports 11A of the intake pipe 12 are formed.

  The two intake pipes 12 are connected between the connection ports 11A of the surge tank 11 and the intake ports 8 of the cylinder head 7, respectively. As a result, the intake air of the internal combustion engine 1 flows into the surge tank 11 from the outside and then flows through the intake pipes 12 to be sucked into the intake ports 8 of the individual cylinders 4.

  On the other hand, as shown in FIG. 1, the two exhaust pipes 13 (only one is shown) are connected to the exhaust ports 9 opened on the lower surface 7B of the cylinder head 7 and are connected to the lower side of the cylinder head 7 in close proximity to each other. To the head cover 10 side.

(Arrangement of intake and exhaust system)
Here, the arrangement of the intake system and the exhaust system of the internal combustion engine 1 will be described in detail. First, the two intake pipes 12 are provided at positions sandwiching the two cylinders 4 from both sides in the arrangement direction in the arrangement direction of the cylinders 4 arranged in the left and right directions in FIG. That is, each intake pipe 12 is arranged separately on the left and right sides (outside) of the cylinder head 7 as shown in FIG. Each intake pipe 12 is bent in a substantially L shape from both the left and right sides of the surge tank 11, and is connected to the intake port 8 along the left and right side surfaces 7C and 7C of the cylinder head 7 and the head cover 10. Extends to position.

  In this case, each intake pipe 12 is held apart from the cylinder head 7 and the head cover 10 except for the connection position with the intake port 8 in order to suppress heat conduction from the cylinder head 7 and the head cover 10. . 3 is a cross-sectional view of the internal combustion engine 1 as viewed from the direction of arrows AA in FIG. As shown in FIG. 3, each intake pipe 12 protrudes substantially vertically from the left and right side surfaces 7 </ b> C of the cylinder head 7 at the connection position with the intake port 8.

  Accordingly, the main portion of each intake pipe 12 is arranged in a state of projecting to the left and right sides of the cylinder block 3 in the arrangement direction of the cylinders 4. For this reason, each intake pipe 12 can be held at a position sufficiently away from the cylinder block 3 that is a heat source during engine operation, that is, at an outer position where the ambient temperature is low. Therefore, the intake air temperature of the internal combustion engine 1 can be lowered, and the occurrence of knocking or the like can be suppressed to improve drivability and fuel consumption.

  Further, when the internal combustion engine 1 is arranged in a horizontal state as in a vehicle-mounted state, which will be described later, as shown by an arrow W in FIG. ) Can be generated. And this running wind can be efficiently contacted not only with the cylinder block 3 but also with the intake pipes 12 arranged on both sides thereof. Therefore, in this case, the cooling efficiency of each cylinder 4 and the intake pipe 12 can be further improved.

  Further, the surge tank 11 and each intake pipe 12 are formed symmetrically on the left and right, for example, with the axis MM in FIG. 2 passing through the center of the surge tank 11 as the center. In this case, the opening ends where the two intake pipes 12 open into the surge tank 11 are arranged so as to face each other in a direction perpendicular to the axis MM.

  For this reason, for example, by appropriately setting the facing distance of the opening end of each intake pipe 12, the capacity of the surge tank 11, the diameter and length of each intake pipe 12, the inertia of the intake air at a desired engine speed Supercharging (a phenomenon in which intake air is supercharged into the cylinder 4 by intake pulsation) can be efficiently generated. As a result, the intake air amount of the internal combustion engine 1 can be increased, and driving performance such as acceleration can be improved.

  On the other hand, the two exhaust pipes 13 protrude substantially perpendicularly from the lower surface 7B of the cylinder head 7 at a position between the intake pipes 12 and extend in parallel to each other. That is, the exhaust ports 9 to which the exhaust pipes 13 are connected open in the same direction on the lower surface 7B of the cylinder head 7 between the left and right intake pipes 12.

  As a result, the two exhaust pipes 13 can be arranged close to each other, and these exhaust pipes 13 can be extended in the same direction. As a result, the two exhaust pipes 13 that are at a high temperature during engine operation can be combined in one place, and the influence of heat released from each exhaust pipe 13 can be minimized with respect to surrounding components.

  Further, each intake pipe 12 can be arranged on the side surface 7C side of the cylinder head 7, and each exhaust pipe 13 can be arranged on the lower surface 7B side of the cylinder head 7. As a result, it is possible to avoid the components of the internal combustion engine 1 being disposed on the upper surface 7A side of the cylinder head 7. Accordingly, other structures can be arranged on the upper surface 7A side of the cylinder head 7 as in the case of vehicle mounting described later, and the space on the upper surface 7A can be effectively utilized.

[Configuration of vehicle equipped with internal combustion engine]
Next, with reference to FIG.4 and FIG.5, the vehicle carrying the internal combustion engine 1 is demonstrated. FIG. 4 shows a side view in which the front side of the vehicle 21 according to this embodiment is omitted, and FIG. 5 shows a plan view of the vehicle 21. As shown in these drawings, the vehicle 21 is configured as a so-called midship type passenger four-wheeled vehicle. The vehicle body 22 constituting the main body portion of the vehicle 21 is provided with left and right front wheels (not shown) and left and right rear wheels 23 that form drive wheels. These rear wheels 23 are supported by individual rear wheel shafts 24.

  The vehicle body 22 is equipped with two front seats 25 and two rear seats 26 on which passengers sit. In this case, the rear seat 26 has a seat portion 26A and a backrest 26B. Further, the connecting portion between the seat portion 26A and the backrest 26B is a bent portion 26C that is bent in a substantially L shape. Furthermore, the vehicle body 22 includes a floor surface 27 on which a rider seated on each seat 25 and 26 places his / her foot. The floor surface 27 is located at the lower end of the leg space in which the passenger's feet are arranged.

  On the other hand, the internal combustion engine 1 is mounted on the rear side of the vehicle body 22 at a position extending from the lower side of the rear seat 26 to the front side of the rear wheel shaft 24. In this case, the mounting state of the internal combustion engine 1 takes into account the compactness of the vehicle, the cooling performance of the internal combustion engine 1 and the like as will be described later. Further, a traveling wind intake (not shown) is provided on the lower surface side of the vehicle body 22 for taking traveling wind generated during traveling of the vehicle in the vicinity of the internal combustion engine 1.

  As shown in FIG. 5, a transmission 28 is attached to the crankcase 2 of the internal combustion engine 1. Further, a differential gear 29 is provided between the left and right rear wheel shafts 24 to absorb the difference in rotational speed between the rear wheels 23. A power transmission element 30 is connected between the transmission 28 and the differential gear 29. The output of the internal combustion engine 1 is transmitted to each rear wheel shaft 24 via the transmission 28, the power transmission element 30, the differential gear 29, and the like, thereby driving the left and right rear wheels 23. In FIG. 4, the rear axle 24, the transmission 28, the power transmission element 30 and the like are omitted.

(Arrangement of internal combustion engine)
Here, the arrangement of the internal combustion engine 1 on the vehicle body 22 will be described in detail. First, the internal combustion engine 1 is placed in a so-called horizontal state on the vehicle body 22, and each cylinder 4 is disposed in a posture in which the cylinder 4 is tilted toward the rear of the vehicle body 22. In this case, the horizontally placed state is a posture in which the axis O1 of the crankshaft 6 is parallel to the width direction (vehicle width direction) of the vehicle body 22, that is, a state where the two cylinders 4 are aligned in the vehicle width direction. It is posture.

  Further, the internal combustion engine 1 is disposed at least partially below the seat portion 26A of the rear seat 26 in a side view. In this case, in the example shown in the present embodiment, the entire crankcase 2 and the base end side of the cylinder block 3 are arranged below the seat portion 26A.

  With these arrangements, the traveling wind generated when the vehicle 21 travels flows around the internal combustion engine 1 in the direction indicated by the arrow W from the crankcase 2 side toward the cylinder head 7 as shown in FIG. become. As a result, the cylinder block 3 and the two intake pipes 12 do not overlap each other in the direction of travel wind flow, and can efficiently contact each other with respect to the flow of travel wind.

  Therefore, the cylinder block 3 and each intake pipe 12 can be individually cooled by the traveling wind, and the cooling efficiency of these parts can be improved. In addition, a portion of the intake pipe 12 that is particularly connected to the intake port 8 where the temperature is likely to rise can be exposed to the flow of traveling wind, and the heat dissipation of this portion can be sufficiently enhanced.

  Further, by disposing at least a part of the internal combustion engine 1 below the rear seat 26, it is possible to widen the space in the vehicle while forming the entire vehicle compact. In particular, in the present embodiment, since the in-line two-cylinder internal combustion engine 1 is used, the internal combustion engine 1 can be reduced in size as compared with, for example, a V-type or a horizontally opposed internal combustion engine, and an intake / exhaust system is also provided. It can be arranged compactly. For this reason, the internal combustion engine 2 can be easily accommodated under the rear seat 26.

  Further, by disposing each cylinder 4 in a posture in which it is tilted toward the rear side of the vehicle body 22, the exhaust pipe 13 of each cylinder 4 can be extended from the lower surface 7B of the cylinder head 7 to the rear side of the vehicle body. That is, since it is not necessary to pass the exhaust pipe 13 below the crankcase 2 and the cylinder block 3, the internal combustion engine 1 can be mounted at a sufficiently low position on the vehicle body 22.

  Thereby, the position of the rear seat 26 can also be sufficiently lowered, and the interior height of the vehicle (particularly, the space in which the head of the passenger seated on the rear seat 26 is disposed) can be easily secured. In addition, the ground clearance of the vehicle body 22 can be lowered, and in particular, the ground clearance at the rear of the vehicle that greatly affects the aerodynamic characteristics of the vehicle can be kept low. Thereby, the air resistance at the time of driving | running | working can fully be reduced and a fuel consumption can be improved.

  Further, since the exhaust pipe 13 of each cylinder 4 does not pass below the crankcase 2 or the cylinder block 3, it is possible to suppress the heat released from the exhaust pipe 13 from being transmitted to the crankcase 2 or the cylinder 4. Thereby, structures, such as a heat shield board and an oil cooler, can be omitted or simplified, for example, and cost reduction and weight reduction can be promoted. Moreover, the two exhaust pipes 13 extend rearward in a state in which two exhaust pipes 13 are collected from the center of the lower surface 7B of the cylinder head 7 in the vehicle width direction. For this reason, it is possible to perform compactly in a state where two layouts of each exhaust pipe 13 are combined.

  On the other hand, the front end side of the cylinder block 3 (each cylinder 4), the cylinder head 7, the head cover 10, the surge tank 11, and the like protrude from the seat portion 26A to the rear side of the vehicle body 22 and are rear wheel shafts 24 ( It is arranged at a position on the front side of the differential gear 29). And these parts are covered from the upper side with the engine cover 31, as shown in FIG. Further, on the upper side of the engine cover 31, a luggage space (not shown) for loading luggage or the like on the rear side of the vehicle 21 is provided.

  In this case, in the present embodiment, the intake pipes 12 are arranged on the left and right side surfaces 7C, 7C, etc. of the cylinder head 7. Thereby, since it is not necessary to arrange the components of the internal combustion engine 1 on the upper surface 7A side of the cylinder head 7, the engine cover 31 and the like can be attached to a lower position accordingly. Therefore, a sufficiently large luggage space can be provided on the upper side of the engine cover 31 and the commercial value of the vehicle can be improved.

  Further, as shown in FIG. 4, the internal combustion engine 1 is inclined obliquely upward with respect to the rear of the vehicle body 22. That is, the axis O2 of each cylinder 4 is inclined by, for example, an angle θ so as to increase toward the rear side of the vehicle body 22. In this case, by causing a portion of the internal combustion engine 1 to protrude rearward from the seat portion 26A of the rear seat 26, the internal combustion engine 1 can be easily tilted without increasing the position of the rear seat 26. it can.

  Then, by tilting the rear side (cylinder head 7 side) of the internal combustion engine 1 so as to be higher, the exhaust pipe 13 is located below the cylinder head 7 without increasing the position of the crankcase 2 on the front side. Arrangement space can be secured, and component layout in a state where the internal combustion engine 1 is held at a low position can be easily performed.

  Further, the cylinder head 7 can be held at a high position with respect to the crankcase 2. As a result, the oil easily returns from the cylinder head 7 toward the crankcase 2, so that the structure of the PCV device (blow-by gas reduction device) can be simplified and cost reduction can be promoted. Further, since the amount of oil can be reduced, it is possible to realize weight reduction and friction reduction, which can contribute to improvement in fuel consumption.

  In the present embodiment, the positional relationship between the bent portion 26 </ b> C of the rear seat 26 is set so that the bent portion 26 </ b> C is positioned near the boundary between the crankcase 2 and the cylinder block 3. In general, the bent portion 26C between the seat portion 26A and the backrest 26B is a portion arranged at the lowest position in the rear seat 26. On the other hand, the boundary portion between the crankcase 2 and the cylinder block 3 has a concave shape. Therefore, by arranging the bent portion 26 </ b> C near the boundary between the crankcase 2 and the cylinder block 3, the distance between the rear seat 26 and the internal combustion engine 1 can be made closer. For this reason, the position of the rear seat 26 can be particularly lowered.

  In the first embodiment, as shown in FIG. 3, the two intake pipes 12 are configured to protrude substantially vertically from the side surface 7 </ b> C of the cylinder head 7. However, the present invention is not limited to this. For example, the present invention may be configured as modified examples shown in FIGS. Here, in the case of the first modification shown in FIG. 6, the two intake pipes 12 ′ protrude in an inclined state from the intake port 8 ′ opened in the side surface 7 C of the cylinder head 7. Is in a direction away from the exhaust pipe 13.

  Further, in the case of the second modification shown in FIG. 7, the intake port 8 ″ is open to the lower surface 7B of the cylinder head 7. The two intake pipes 12 ″ are arranged in the cylinder arrangement direction from the lower surface 7B. It protrudes outside and is provided at a position sandwiching the cylinder 4 from both sides. In this case, each intake pipe 12 ″ extends in a direction away from the exhaust pipe 13 ′. On the other hand, the exhaust port 9 ′ is located between the intake ports 8 and is formed in a substantially Y shape. That is, the exhaust port 9 'extends from the two cylinders 4 at one end side and joins in the cylinder head 7. The other end side of the exhaust port 9' is at one place on the lower surface 7B of the cylinder head 7. One exhaust pipe 13 'is connected to the opening of the exhaust port 9'.

  Therefore, according to the second modification, the exhaust pipes 13 'can be gathered more centrally, and the number of the exhaust pipes 13' can be reduced. Therefore, the exhaust pipe 13 'can be sufficiently separated from the intake pipe 12 ", and the influence of heat released from the exhaust pipe 13' on the surrounding parts including the intake pipe 12" is minimized. Can do.

  Further, in the first embodiment, a part of the internal combustion engine 1 (on the crankcase 2 side) is disposed below the seat portion 26A of the rear seat 26, and the cylinder head 7 side is disposed behind the seat portion 26A. It was. However, the present invention is not limited to this, and the entire configuration from the crankcase 2 to the surge tank 11 of the internal combustion engine 1 may be arranged below the seat portion 26A.

  In the first embodiment, the internal combustion engine 1 is inclined by an angle θ with respect to the horizontal plane. However, the present invention is not limited to this, and the internal combustion engine 1 may be arranged horizontally with the cylinder head 7 facing rearward.

  Furthermore, in the first embodiment, the internal combustion engine 1 is mounted on the vehicle 21 in a horizontally placed state. However, the present invention is not limited to this, and the internal combustion engine 1 may be mounted on the vehicle in a vertically placed state (a state where the axis O1 of the crankshaft 6 extends in the front or rear direction of the vehicle) as necessary.

1 is a side view showing an internal combustion engine according to Embodiment 1 of the present invention. FIG. 2 is a plan view showing the internal combustion engine of FIG. 1 in a partially broken state. It is sectional drawing which looked at the internal combustion engine from the arrow AA direction in FIG. It is a side view which shows the vehicle by Embodiment 1 of this invention. It is a top view of the vehicle shown in FIG. FIG. 5 is a cross-sectional view similar to FIG. 3 showing an internal combustion engine according to a first modification of the present invention. FIG. 6 is a cross-sectional view similar to FIG. 3 showing an internal combustion engine according to a second modification of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Crankcase 3 Cylinder block 4 Cylinder 5 Piston 6 Crankshaft 7 Cylinder head 7A Upper surface 7B Lower surface 7C Left and right side surface 8, 8 ', 8 "Intake port 9, 9' Exhaust port 10 Head cover 11 Surge tank 11A Connection port 12, 12 ', 12 "Intake pipe 13, 13' Exhaust pipe 21 Vehicle 22 Car body 23 Rear wheel 24 Rear wheel axle 25 Front seat 26 Rear seat 26A Seat portion 26B Backrest 26C Bend portion 27 Floor 28 Transmission 29 Differential Gear 30 Power transmission element 31 Engine cover

Claims (6)

Two cylinders that are arranged side by side so that their axis lines are parallel to each other in the same plane, and the direction perpendicular to the respective axis lines is the alignment direction ;
Two intake pipes provided at positions sandwiching the two cylinders from both sides of the cylinder in the arrangement direction, and connected to the individual cylinders;
An exhaust pipe connected to each cylinder at a position between the two intake pipes;
A cylinder head mounted on the front end side of the two cylinders and having intake ports opened at portions located on both sides of the arrangement direction;
A head cover covering the cylinder head;
A surge tank provided at a central portion on the head cover and provided with connection ports of the intake pipes at portions located on both sides of the arrangement direction ;
The two intake pipes are arranged in a state in which at least a part protrudes outside the cylinder block in which the cylinders are arranged, and the connection ports on both sides of the surge tank and the cylinder head An internal combustion engine characterized by being connected to each intake port . 2. The internal combustion engine according to claim 1 , wherein the cylinder head includes two exhaust ports located between the intake ports and opening in the same direction, and the exhaust pipe is connected to the exhaust ports. organ. The cylinder head includes an exhaust port that is located between the intake ports, merges in the cylinder head, and opens at one location outside the cylinder head, and the exhaust pipe is connected to the exhaust port. The internal combustion engine according to claim 1 . A vehicle in which the internal combustion engine according to any one of claims 1 to 3 and a seat having a seat portion and a backrest are mounted on a vehicle body,
The internal combustion engine is arranged in a state in which the two cylinders are aligned in the width direction of the vehicle body, and the cylinders are tilted toward the rear of the vehicle body,
At least a part of the internal combustion engine is configured to be disposed below the seat portion of the seat. The vehicle according to claim 4 , wherein the center axis of the cylinder is inclined obliquely upward so as to become higher toward the rear side of the vehicle body. The vehicle according to claim 4 or 5 , wherein a tip side of each cylinder of the internal combustion engine is arranged behind the seat portion of the seat.

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