EP2217797B1

EP2217797B1 - Internal combustion engine and vehicle mounted with the same

Info

Publication number: EP2217797B1
Application number: EP08834678A
Authority: EP
Inventors: Nobuhisa Jingu
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2007-09-25
Filing date: 2008-09-24
Publication date: 2011-11-09
Anticipated expiration: 2028-09-24
Also published as: WO2009041706A3; WO2009041706A2; JP4888302B2; JP2009074510A; ATE532956T1; EP2217797A2

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

Technical Field

The present invention relates to an internal combustion engine and a vehicle on which the internal combustion engine is mounted.

Background Art

A known vehicle includes an engine disposed at a lower side of a rear portion seat, as disclosed, for example, in JP6-80032 A ). In a vehicle having this kind of prior art arrangement, the internal combustion engine is disposed in a posture leaning forwardly of the vehicle. In this case, an intake manifold of the engine is disposed at a front side of an engine main body (cylinder) in an overlapping manner with the engine as viewed from the front of the vehicle.
Including the above-mentioned document, the applicant is aware of the following document as a related art of the present invention.
DE 44 32 915 A1 discloses an internal combustion engine having two cylinders mutually adjacent to each other and having intake pipes running along two sides of the cylinders.

Disclosure of Invention

The abovementioned prior art is such that the intake manifold is disposed in an overlapping manner with the front side of the engine main body. In this arrangement, therefore, the engine main body is hidden behind the intake manifold relative to the direction of an airflow that is produced as the vehicle runs.
The prior art therefore poses a problem, in that the intake manifold prevents the airflow from sufficiently contacting the engine main body when the vehicle runs, making it difficult to cool the engine main body efficiently with the airflow.
The prevent invention has been made to solve the foregoing problem and it is an obj ect of the prevent invention to provide an internal combustion engine having an overall compact arrangement and allowing the cylinder and the intake pipe to be efficiently cooled and a vehicle on which the internal combustion engine is mounted.
The above object is achieved by an internal combustion engine which comprise two parallel cylinders juxtaposed mutually adjacently to each other. The internal combustion engine comprise two intake pipes disposed at positions to embrace the two cylinders from both sides in a juxtaposed direction of the cylinders.
The internal combustion engine comprise an exhaust pipe connected to a corresponding one of the cylinders at a position between the two intake pipes.
In a second aspect of the present invention, the two intake pipes according to the first aspect of the present invention may be disposed in a condition, in which at least part thereof protrude outwardly in the juxtaposed direction from a cylinder block in which each of the cylinders is disposed.
In a third aspect of the present invention, the internal combustion engine may further comprise a cylinder head disposed at a leading end side of the two cylinders and having intake ports open at portions disposed on both sides in the juxtaposed direction. The internal combustion engine may comprise a head cover covering the cylinder head.
And, the internal combustion engine may comprise a surge tank disposed at a central portion on top of the head cover and having connection ports of the intake pipes at portions disposed on both sides in the juxtaposed direction. Moreover, the two intake pipes may be connected to the connection ports on both sides of the surge tank and the intake ports in the cylinder head.
In a fourth aspect of the present invention, the cylinder head may include two exhaust ports disposed between the intake ports and open in a mutually same direction. And, the exhaust pipes may be connected to corresponding ones of the exhaust ports.
In a fifth aspect of the present invention, the cylinder head may include an exhaust port disposed between the intake ports and open at a single position to an outside of the cylinder head after being merged inside the cylinder head. And, the exhaust pipe is connected to the exhaust port.
In a sixth aspect of the present invention, the above object is achieved by a vehicle which comprise the internal combustion engine according to any one of the first aspect to the fifth aspect of the present invention. The vehicle comprise a seat having a seat cushion portion and a backrest. The vehicle comprise a vehicle body. And, the internal combustion engine includes the two cylinders juxtaposed in a width direction of the vehicle body and each of the cylinders is disposed in a position inclined rearwardly of the vehicle body. And, part of the internal combustion engine is disposed at a lower side of the seat cushion portion of the seat.
In a seventh aspect of the present invention, the cylinder according to the sixth aspect of the present invention may have a central axis that is obliquely upwardly inclined toward a rear of the vehicle body.
In an eighth aspect of the present invention, Each of the cylinders of the internal combustion engine may have a leading end side disposed rearwardly of the seat cushion portion of the seat.
In accordance with the first aspect of the present invention, the two intake pipes can be disposed on both sides (outside) of the two juxtaposed cylinders. Each of the intake pipes can therefore be disposed at a position away toward either side from the cylinder as a heat source during operation of the engine, i.e., at an outside position with a low ambient temperature. Accordingly, since an intake temperature of the internal combustion engine can be decreased, detonation or the like can be suppressed, resulting in improvement of drivability and fuel consumption. Additionally, with an arrangement in which a cooling air flows perpendicularly to a direction in which the cylinders are aligned, the cooling air can be made to contact efficiently not only the cylinders but also the intake pipes disposed on both sides thereof. This improves cooling efficiency of the cylinders and the intake pipes.
In accordance with the second aspect of the present invention, at least part of the two intake pipes can be disposed in a condition of protruding outside the cylinder block. This allows the intake pipes to be sufficiently away from structures on the side of the cylinder block, helping make the ambient temperature near the intake pipes low. It is also possible to dispose intermediate portions of the intake pipe spaced from the structure on the side of the cylinder block, so that thermal conduction from these structures to the intake pipes can be suppressed.
In accordance with the third aspect of the present invention, the intake pipes on both sides can be formed symmetrically about the surge tank. Accordingly, an inertia charge of an intake air (phenomenon in which intake pulsation charges the intake air into the cylinder) can be efficiently generated by appropriately setting, for example, an opposing distance of open ends of the intake pipes opening to the surge tank, capacity of the surge tank, diameter and length of each intake pipe, and the like. This increases an amount of intake air of the internal combustion engine and improves acceleration and other driving performance.
In accordance with the fourth aspect of the present invention, the exhaust pipes can be collectively disposed between the intake pipes. Accordingly, the exhaust pipes that become hot during operation of the engine can be disposed at a single place, so that effect of heat emanated from each of the exhaust pipes can be minimized relative to surrounding parts.
Additionally, for example, of the four surfaces surrounding the cylinder, the intake pipes can be disposed on both sides of the cylinder and the exhaust pipes can be disposed on another surface. As a result, there is no need to dispose any of the internal combustion engine parts on the remaining one surface. Other structures or the like may therefore be disposed on the remaining surface and this space will be effectively used.
In accordance with the fifth aspect of the present invention, the exhaust port extended from the two cylinders can be merged inside the cylinder head. The merged exhaust port can be open to an outside of the cylinder head at a single location. One exhaust pipe can then be connected to this opening. This allows the exhaust pipes to be centralized at an even more central portion and the number of exhaust pipes to be reduced. Accordingly, the exhaust pipes can be kept sufficiently away from the intake pipes. Effect of heat emanated from the exhaust pipe can be minimized relative to surrounding parts including the intake pipes.
In accordance with the sixth aspect of the present invention, on the other hand, the internal combustion engine can be disposed sideways in the vehicle. An airflow generated as the vehicle runs can therefore be made to flow from a side of the crankcase to a side of the cylinder head in areas around the internal combustion engine. As a result, the cylinders and the intake pipes do not overlap each other relative to a direction of the airflow, so that each can contact the airflow efficiently.
Since the cylinders and the intake pipes can therefore be cooled individually by the airflow, cooling efficiency of these portions can be improved. In addition, a portion of each intake pipe connected to the intake port, a temperature of which is particularly easy to rise, can be exposed to the airflow, so that heat dissipation of this portion can be sufficiently enhanced.
In addition, at least part of the internal combustion engine is disposed at the lower side of the seat. This allows a vehicle interior space to be more spacious, while allowing the entire vehicle to be formed compactly. Moreover, each cylinder is disposed in a posture of being inclined rearwardly of the vehicle body, which allows the exhaust pipe to be extended rearwardly of the vehicle body from a lower surface of a leading end side of the cylinder. Specifically, there is no need to extend the exhaust pipe in a space under the crankcase or the cylinder block. The internal combustion engine can therefore be mounted at a sufficiently low position.
This also makes it possible to keep the position of the seat sufficiently low, so that an interior height of the vehicle (in particular, a space in which the head of an occupant seated in the seat is positioned) can be easily assured. In addition, a ground clearance of the vehicle can be made low. This helps reduce air resistance during running sufficiently, so that fuel consumption can be improved. Further, the exhaust pipe does not extend on the underside of the crankcase or the cylinder block. This prevents heat emanated from the exhaust pipe from being transmitted to the crankcase and the cylinder. This allows such structures as a heat shielding plate, an oil cooler, and the like to be omitted or simplified, thus promoting cost reduction and weight reduction.
Additionally, for example, of the four surfaces surrounding the cylinder, the intake pipes can be disposed on both sides of the cylinder and the exhaust pipes can be disposed on the lower surface side. As a result, there is no need to dispose any of the internal combustion engine parts on the remaining upper surface side. Other onboard structures or the like may therefore be disposed on this upper surface side and this space will be effectively used.
In accordance with the seventh aspect of the present invention, the central axis of the cylinder is obliquely upwardly inclined toward the rear of the vehicle body. This allows a space to be assured for disposing the exhaust pipes, for example, at the lower side of the cylinder head without making high the position of the crankcase at the front side. Parts can therefore be laid out easily with the internal combustion engine held in a low position.
Additionally, the cylinder head can be held at a position higher relative to the crankcase. As a result, oil can easily return from the cylinder head to the crankcase. A PCV apparatus (blowby gas reduction system) can thereby be simply structured, promoting cost reduction. Moreover, the amount of oil can be reduced, which achieves weight reduction and low friction, contributing to improvement in fuel consumption.
In accordance with the eighth aspect of the present invention, the leading end side of each of the cylinders of the internal combustion engine can be disposed in a rearwardly bulged condition from the seat cushion portion of the seat. This allows the internal combustion engine to be easily inclined upwardly without making the position of the seat high.

Brief Description of Drawings

Fig. 1 is a side elevational view showing an internal combustion engine according to the first embodiment of the present invention.
Fig. 2 is a plan view to show in the state that broke one part of the internal combustion engine of Fig. 1.
Fig. 3 is a cross-sectional view taken along the line A-A of Fig. 2, showing the internal combustion.
Fig. 4 is a side elevational view showing the vehicle according to the first embodiment of the present invention.
Fig. 5 is a plan view of the vehicle to show in Fig.1.
Fig. 6 is a cross-sectional view like Fig. 3 to show an internal combustion engine by the first modified example of the present invention.
Fig. 7 is a cross-sectional view as Fig. 3 to show an internal combustion engine by the second modified example of the present invention.

Best Mode for Carrying Out the Invention

First Embodiment

[Configuration of the internal combustion engine]

A first embodiment of the prevent invention will be described below with reference to Figs. 1 through 6. Fig. 1 is a side elevational view showing an internal combustion engine 1 according to this embodiment. Fig. 2 is a plan view of the internal combustion engine 1. As shown in those figures, the internal combustion engine 1 is configured as, for example, an in-line two-cylinder engine having a crankcase 2 and a cylinder block 3.
The cylinder block 3 is formed as, for example, a slender, substantially rectangular metal block. The cylinder block 3 has its base end mounted in the crankcase 2. Two cylinders 4 are disposed in proximity to each other inside the cylinder block 3. Specifically, in this embodiment, the two cylinders 4 are formed in the single cylinder block 3. A piston 5 is fitted into each of these cylinders 4 so as to reciprocate. The piston 5 is connected to a crankshaft 6 by a connecting rod or the like.
A cylinder head 7 is mounted on the top end 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 rectangular metal block having four side faces. These side faces include an upper face 7A, a lower face 7B, and right and left side faces 7C as shown in Figs. 4 and 5 to be described later. Specifically, when mounted in a vehicle 21, the upper face 7A faces upwardly, the lower face 7B faces downwardly, and the side faces 7C are disposed on both sides of the cylinder head 7 in the width direction of the vehicle 21 (the direction in which the two cylinders 4 are juxtaposed).
As shown in Fig. 2, two intake ports 8 are formed inside the cylinder head 7, each of which is located on one of the sides in which the cylinder 7 is provided. Each of these intake ports 8 is in communication with its respective cylinder 4 and penetrates the side face 7C of the cylinder head 7. Also formed inside the cylinder head 7 are two exhaust ports 9, which are disposed between the intake ports 8. Each of these exhaust ports 9 is in communication with its respective cylinder 4 and penetrates the lower face 7B of the cylinder head 7 at a position close to that of the other exhaust port. In this manner, each of the exhaust ports 9 is open in the same direction (downwardly when mounted on the vehicle).
In addition , other devices such as, for example, a fuel injection valve, an ignition plug, an intake valve, and an exhaust valve (none of these are shown) are mounted on the cylinder head 7. Further, the upper portion of the cylinder head 7 is covered with a head cover 10.
The internal combustion engine 1 includes a surge tank 11, two intake pipes 12, and two exhaust pipes 13. The surge tank 11 is disposed at the center of the top face of the head covey 10. An intake path (not shown), through which an outside air is allowed to flow into the surge tank 11 as an intake air, is connected to the surge tank 11. Further, connection ports 11A are formed for the intake pipes 12 on the right and left side faces of the surge tank 11 with respect to the direction in which the cylinders 4 are juxtaposed.
The two intake pipes 12 each connect the connection port 11A of the surge tank 11 and the intake port 8 of the cylinder head 7. The intake air of the internal combustion engine 1 therefore first flows into the surge tank 11 from the outside and then flows through each of the intake pipes 12 before drawn into the intake port 8 of each cylinder 4.
The two exhaust pipes 13 (only one of them is shown) are connected to the exhaust ports 9 open on the lower face 7B of the cylinder head 7 as shown in Fig. 1. The two exhaust pipes 13 extend in proximity to each other toward the side of the head cover 10 from the lower side of the cylinder head 7.

(Arrangement of the intake and exhaust systems)

Arrangement of the intake system and exhaust system of the internal combustion engine 1 will hereunder be described in detail. The two intake pipes 12 are disposed so as to sandwich the two cylinders 4 from both sides in the direction in which the cylinders 4 are juxtaposed, that is, the right and left directions of Fig. 2. Specifically, each of the intake pipes 12 is disposed separately on either of the right and left sides (outside) of the cylinder head 7 as shown in Fig. 2. Each of the intake pipes 12 is bent substantially into an L shape from either of the right and left sides of the surge tank 11 and extends along either of the right and left side faces 7C of the cylinder head 7 and of the head cover 10, reaching a connection position with the intake port 8.
In this case, each of the intake pipes 12 is kept away from the cylinder head 7 and the head cover 10 except the connection portion with the intake port 8 in order to suppress thermal conduction from the cylinder head 7 and the head cover 10. Fig. 3 is a cross-sectional view taken along the line A-A of Fig. 2, showing the internal combustion engine 1 as viewed from direction of the arrow A of Fig. 2. As shown in Fig. 3, the intake pipes 12 protrude substantially perpendicularly from the right and left side faces 7C of the cylinder head 7, respectively, at the respective connection portions with the intake ports 8.
Accordingly, major portions of the intake pipes 12 are disposed in such a manner as to protrude to the right and left sides more from the cylinder block 3 in the juxtaposition direction of the cylinders 4. As a result, each of the intake pipes 12 can be held at a position sufficiently away from the cylinder block 3, a heat source during operation of the engine, more specifically, at an outward position of low ambient temperature. Accordingly, the intake temperature of the internal combustion engine 1 can be reduced, so that engine knocking or the like can be prevented and driving performance and fuel consumption can be enhanced.
If the internal combustion engine 1 is disposed sideways on the vehicle (with the axis of the crankshaft 6 directed to the lateral direction of the vehicle) as described later, an airflow (cooling air) can be generated during driving in the direction perpendicular to the juxtaposition direction of the cylinders 4 as shown by the arrow W in Fig. 2. This airflow can efficiently be made to contact not only the cylinder block 3, but also the intake pipes 12 disposed on both sides thereof. Accordingly, in this case, efficiency in cooling the cylinders 4 and the intake pipes 12 can be further improved.
In addition, the surge tank 11 and each of the intake pipes 12 are formed symmetrically about, for example, the axis M-M shown in Fig. 2 passing through the center of the surge tank 11. In this case, the open ends of the two intake pipes 12 into the surge tank 11 are disposed so as to face each other in the direction perpendicular to the axis M-M.
Accordingly, an inertia charge of an intake air (phenomenon in which intake pulsation charges the intake air into the cylinder 4) can be efficiently generated at any desired engine speed by appropriately setting, for example, the distance between the open ends of the intake pipes 12, volume of the surge tank 11, diameter and length of each intake pipe 12, and the like. This increases an amount of intake air into the internal combustion engine 1 and improves acceleration and other driving performance.
The two exhaust pipes 13, on the other hand, protrude substantially perpendicularly from the lower face 7B of the cylinder head 7 at positions between the intake pipes 12 and extend in parallel with each other. Specifically, the exhaust ports 9, to which the exhaust pipes 13 are connected, are open in the same direction on the lower face 7B of the cylinder head 7 between the right and left intake pipes 12.
As a result, the two exhaust pipes 13 can be disposed close to each other, so that these exhaust pipes 13 can be extended in the same direction. This allows the two exhaust pipes 13 that become hot during operation of the engine to be put together at a single location. Effect of heat from each of the exhaust pipes 13 on surrounding parts can also be minimized.
In addition, each of the intake pipes 12 can be disposed on each of the side face 7C of the cylinder head 7, and each of the exhaust pipes 13 can be disposed on the lower face 7B of the cylinder head 7. As a result, it can be avoided that parts of the internal combustion engine 1 are disposed on the side of the upper face 7A of the cylinder head 7. Accordingly, other structural members can be disposed on the side of the upper face 7A of the cylinder head 7, when mounted on the vehicle as described later. A space above the upper face 7A can therefore be efficiently used. [Configuration of a vehicle on which the internal combustion engine is mounted]
A vehicle on which the internal combustion engine 1 is mounted will be described below with reference to Figs. 4 and 5. Fig. 4 is a side elevational view showing the vehicle 21 according to this embodiment with the front side thereof omitted. Fig. 5 is a plan view of the vehicle 21. As shown in these figures, the vehicle 21 is configured as what is called a midship type, four-wheel passenger vehicle. A vehicle body 22 constituting a main body portion of the vehicle 21 includes right and left front wheels (not shown) and right and left rear wheels 23 as drive wheels. Rear wheel axles 24 support these rear wheels 23 individually.
In addition, two front seats 25 and two rear seats 26, on which occupants are seated, are mounted on the vehicle body 22. In this case, the rear seat 26 includes a seat cushion portion 26A and a backrest 26B. A connection portion between the seat cushion portion 26A and the backrest 26B is a bent portion 26C bent substantially into an L shape. Further, the vehicle body 22 includes a floor 27 on which the occupants seated on the seats 25 and 26 place their feet. The floor 27 is disposed at the lower end of a leg space in which the occupants' legs are disposed.
The internal combustion engine 1 is mounted on the rear side of the vehicle body 22 at a position ranging from the lower side of the rear seat 26 to the front side of the rear wheel axle 24. In this case, the internal combustion engine 1 is mounted under a condition that takes into consideration size reduction of the vehicle, cooling performance of the internal combustion engine 1, and the like as described later. In addition, the vehicle body 22 includes an airflow inlet port (not shown) disposed on the side of the lower face thereof. The airflow inlet port admits the airflow that is produced during running of the vehicle into areas near the internal combustion engine 1.
A transmission 28 is mounted on the crankcase 2 of the internal combustion engine 1 as shown in Fig. 5. Further, a differential gear 29 compensating for a difference in speed between the rear wheels 23 is disposed between the right and left rear wheel axles 24. A power transmission element 30 is also connected to the transmission 28 and to the differential gear 29. An output of the internal combustion engine 1 is transmitted to the rear wheel axles 24 via the transmission 28, the power transmission element 30, the differential gear 29, and the like, thereby driving the right and left rear wheels 23. It is to be noted that the rear wheel axles 24, the transmission 28, the power transmission element 30, and the like are omitted in Fig. 4.

(Arrangement of the internal combustion engine)

Arrangement of the internal combustion engine 1 on the vehicle body 22 will now be described in detail. The internal combustion engine 1 is disposed sideways, as it is called, on the vehicle body 22 and, at the same time, in a position in which each of the cylinders 4 face rearwardly of the vehicle body 22. In this case, the internal combustion engine 1 is disposed sideways when the axis 01 of the crankshaft 6 is in parallel with the width direction of the vehicle body 22 (vehicle width direction), specifically, when the two cylinders 4 are juxtaposed in the vehicle width direction.
At least part of the internal combustion engine 1 is disposed on the lower side of the seat cushion portion 26A of the rear seat 26 in a side view. In this case, in the example of this embodiment, the whole crankcase 2 and the base end side of the cylinder block 3 are disposed on the lower side of the seat cushion portion 26A.
Through the foregoing arrangement, the airflow produced as the vehicle 21 runs flows around the internal combustion engine 1 in the direction of the arrow W from the side of the crankcase 2 to the side of the cylinder head 7 as shown in Fig. 2. As a result, the cylinder block 3 and the two intake pipes 12 do not overlap each other with respect to the direction of the airflow, so that they can be efficiently in contact with the airflow.
Accordingly, the cylinder block 3 and each of the intake pipes 12 can be individually cooled by the airflow, so that efficiency in cooling these portions can be improved. In addition, the portion of the intake pipe 12 connected to the intake port 8, at which temperature particularly tends to increase easily, can be exposed to the airflow, so that heat dissipation from the portion can be sufficiently enhanced.
Further, at least part of the internal combustion engine 1 is disposed on the lower side of the rear seat 26. This arrangement allows the interior space of the vehicle to be made spacious, while allowing the entire vehicle to be formed compact. In this embodiment in particular, the in-line two-cylinder type internal combustion engine 1 is used. This allows the internal combustion engine 1 to be built compact and the intake and exhaust systems to be disposed compact as compared with, for example, an internal combustion engine 1 of a V type or a horizontal opposed type. As a result, the internal combustion engine 1 can be easily accommodated on the lower side of the rear seat 26.
Further, disposing each of the cylinders 4 leaned rearwardly of the vehicle body 22 allows the exhaust pipe 13 of each of the cylinders 4 to be extended rearwardly of the vehicle body from the lower face 7B of the cylinder head c 7. Specifically, there is no need to extend the exhaust pipe 13 under the crankcase 2 or cylinder block 3. This allows the internal combustion engine 1 to be mounted at a sufficiently low position on the vehicle body 22.
This also allows the position of the rear seat 26 to be made sufficiently low. The interior height of the vehicle (in particular, a space in which the head of an occupant seated on the rear seat 26 is disposed) can also be ensured easily. In addition, the ground height below the vehicle body 22 can be made small. The ground height below the rear portion of the vehicle, in particular, which greatly influences vehicle aerodynamic characteristics, can be kept to a low level. This helps reduce air resistance during running sufficiently, so that fuel consumption can be improved.
Further, the exhaust pipe 13 of each of the cylinders 4 does not extend below the crankcase 2 or the cylinder block 3. This prevents heat from the exhaust pipe 13 from being transmitted to the crankcase 2 and the cylinder 4. This allows such structures as a heat shielding plate, an oil cooler, and the like to be omitted or simplified, thus promoting cost reduction and weight reduction. Moreover, the two exhaust pipes 13 are collectively extended rearwardly from the center of the lower face 7B of the cylinder head 7 in the vehicle width direction. Accordingly, each of the exhaust pipes 13 can be compactly laid out as a unit of two.
The top end side of the cylinder block 3 (each of the cylinders 4), the cylinder head 7, the head cover 10, the surge tank 11, and the like are, on the other hand, disposed rearward of the vehicle body 22 relative to the seat cushion portion 26A and, at the same time, forward of the rear wheel axle 24 (differential gear 29). These portions are covered with an engine cover 31 from above as shown in Fig. 4. A luggage space (not shown) for loading cargoes and the like on the rear side of the vehicle 21 is disposed at the upper side of the engine cover 31.
In this case, in this embodiment, the intake pipes 12 are disposed the right and left side faces 7C of the cylinder head 7, respectively. This eliminates the need for disposing parts of the internal combustion engine 1 on the side of the upper face 7A of the cylinder head 7, so that the engine cover 31 and the like can be mounted at a lower position. A sufficiently spacious luggage space can therefore be provided on the upper side of the engine cover 31, so that the product value of the vehicle can be enhanced.
In addition, the internal combustion engine 1 is inclined obliquely upwardly with respect to the rear of the vehicle body 22 as shown in Fig. 4. Specifically, the axis 02 of each cylinder 4 is inclined, for example, at an angle of θ, so as to be higher in level toward the rear of the vehicle body 22. In this case, the internal combustion engine 1 can be easily inclined without having to raise the position of the rear seat 26, by disposing part of the internal combustion engine 1 rearwardly from the seat cushion portion 26A of the rear seat 26.
Further, by inclining the internal combustion engine 1 so that the rear side thereof (the side of the cylinder head 7) is higher, a space for disposing the exhaust pipes 13 on the underside of the cylinder head 7 can be formed without having to make the position of the crankcase 2 located at the front side higher. Parts can therefore be laid out easily with the internal combustion engine 1 kept at a low position.
Additionally, the cylinder head 7 can be held at a position higher relative to the crankcase 2. As a result, oil can be more easily returned from the cylinder head 7 to the crankcase 2. A PCV apparatus (blowby gas reduction system) can thereby be simply structured, promoting cost reduction. Moreover, the amount of oil can be reduced, which enables weight reduction and low friction, contributing to improvement of fuel consumption.
In this embodiment, the positional relationship between the bent portion 26C of the rear seat 26 and the boundary between the crankcase 2 and the cylinder block 3 is set such that the bent portion 26C is disposed near the boundary. Generally, the bent portion 26C between the seat cushion portion 26A and the backrest 26B is a portion that is disposed at the lowest position among others of the rear seat 26. The boundary portion between the crankcase 2 and the cylinder block 3 is, on the other hand, concavely shaped. Accordingly, by disposing the bent portion 2-6C near the boundary between the crankcase 2 and the cylinder block 3, the rear seat 26 can be disposed even closer to the internal combustion engine 1. This allows the position of the rear seat 26 to be made particularly low.
In the first embodiment, referring to Fig. 3 , the two intake pipes 12 are adapted to protrude substantially perpendicularly from the side faces 7C of the cylinder head 7. The present invention is not, however, limited to this. For example, the two intake pipes 12 may be modified as shown in modified examples shown in Figs. 6 and 7. In a first modified example shown in Fig. 6, two intake pipes 12' protrude in an obliquely inclined condition from intake ports 8' opened on the side face 7C of the cylinder head 7. The intake pipes 12' are inclined in a direction away from the exhaust pipes 13.
In a second modified example shown in Fig. 7, intake ports 8" are open in the lower face 7B of the cylinder head 7. Two intake pipes 12" protrude from the lower face 7B outwardly in the cylinder juxtaposition direction and are disposed at positions to sandwich the cylinders 4 from both sides. In this case, each of the intake pipes 12" is extended in a direction away from an exhaust pipe 13'. An exhaust port 9' is, on the other hand, formed into a substantially Y shape, disposed between the intake ports 8" . Specifically, the exhaust port 9' has a first end side extending from each of the two cylinders 4 before merged inside the cylinder head 7. The exhaust port 9' has a second end side that is open at one location in the lower face 7B of the cylinder head 7. A single exhaust pipe 13' is connected to the opening of the exhaust port 9'.
Accordingly, in accordance with the second modified example, the exhaust pipe 13' can be put together at the central portion and the number of exhaust pipes 13' can be reduced. Consequently, the exhaust pipe 13' can be sufficiently away from the intake pipes 12", so that effect of heat from the exhaust pipe 13' can be minimized for parts including the intake pipes 12" surrounding the exhaust pipe 13'.
In the first embodiment, part (on the side of the crankcase 2) of the internal combustion engine 1 is disposed on the lower side of the seat cushion portion 26A of the rear seat 26, and the side of the cylinder head 7 is disposed rearward of the seat cushion portion 26A. The present invention is, however, not limited to these. Rather, the whole of the internal combustion engine 1 covering from the crankcase 2 to the surge tank 11 may be disposed at the lower side of the seat cushion portion 26A.
In addition, in the first embodiment, the internal combustion engine 1 is inclined at an angle of θ relative to a horizontal plane. The present invention is, however, not limited to this. Rather, the internal combustion engine 1 may be disposed horizontally with the cylinder head 7 oriented rearwardly.
Furthermore, in the first embodiment, the internal combustion engine 1 is mounted sideways in the vehicle body 21. The present invention is, however, not limited to this. Rather, the internal combustion engine 1 may be mounted in the vehicle lengthways (the axis 01 of the crankshaft 6 extends in the front-back direction of the vehicle) as may be necessary.

Claims

An internal combustion engine (1) comprising:
two parallel cylinders (4) juxtaposed mutually adjacently to each other;

two intake pipes (12,12',12") disposed at positions to sandwich the two cylinders (4) from opposite sides in a juxtaposed direction of the cylinders (4); and

an exhaust pipe (13,13') connected to a corresponding one of the cylinders (4) at a position between the two intake pipes (12,12',12").
The internal combustion engine (1) according to claim 1,
wherein the two intake pipes (12,12',12") are disposed in a condition, in which at least part thereof protrude outwardly in the juxtaposed direction from a cylinder block (3) in which each of the cylinders (4) is disposed.
The internal combustion engine (1) according to claim 1 or 2, further comprising:
a cylinder head (7) disposed at a leading end side of the two cylinders (4) and having intake ports (8,8',8") open at portions disposed on both sides in the juxtaposed direction;

a head cover (10) covering the cylinder head(7); and

a surge tank (11) disposed at a central portion on top of the head cover (10) and having connection ports (11A) of the intake pipes (12,12',12") at portions disposed on both sides in the juxtaposed direction;

wherein the two intake pipes (12,12',12") are connected to the connection ports (11A) on both sides of the surge tank (11) and the intake ports (8,8',8") in the cylinder head (7).
The internal combustion engine (1) according to claim 3,
wherein the cylinder head (7) includes two exhaust ports (9) disposed between the intake ports (8,8') and open in a mutually same direction; and
wherein the exhaust pipes (13) are connected to corresponding ones of the exhaust ports(9).
The internal combustion engine (1) according to claim 3,
wherein the cylinder head (7) includes an exhaust port (9') disposed between the intake ports (8") and open at a single position to an outside of the cylinder head (7) after being merged inside the cylinder head(7); and
wherein the exhaust pipe (13') is connected to the exhaust port (9').
A vehicle (21) comprising:
the internal combustion engine (1) according to any one of claims 1 to 5;

a seat (26) having a seat cushion portion (26A) and a backrest(26B); and

a vehicle body(22) ;

wherein the internal combustion engine (1) includes the two cylinders (4) juxtaposed in a width direction of the vehicle body (22) and each of the cylinders (4) is disposed in a position inclined rearwardly of the vehicle body (22); and

wherein part of the internal combustion engine (1) is disposed at a lower side of the seat cushion portion (26A) of the seat(26).
The vehicle (21) according to claim 6,
wherein the cylinder (4) has a central axis that is obliquely upwardly inclined toward a rear of the vehicle body (22).
The vehicle (21) according to claim 6 or 7,
wherein each of the cylinders (4) of the internal combustion engine (1) has a leading end side disposed rearwardly of the seat cushion portion (26A) of the seat (26).