Leaning vehicle

Abstract

An EGR path (50) of a leaning vehicle (1) includes an EGR cooler path (52) between an EGR path exhaust side end (50a) positioned above the lowermost end of a cylinder body part (13), which is disposed such that the upper part of a cylinder axis (Cy) is positioned ahead of the lower part, and an EGR path intake side end (50b) positioned above the uppermost end of the cylinder body part. At least a portion of the EGR path, so that the condensed water generated in the EGR cooler path returns to an exhaust path (30), is disposed so as to face at least one side surface of the three side surfaces of the cylinder body part excluding a right side surface (13r) or a left side surface (13l) close to a camshaft drive mechanism (17), in a direction orthogonal to the cylinder axis, wherein the cylinder body part is disposed such that the lowest end of a rear side surface (13b) closer to a portion of an intake path (20) formed inside a cylinder head part (14) is positioned above the lowest end of a front side surface (13f) closer to a portion of the exhaust path formed inside the cylinder head part.

Description

Lean vehicle

[0001] The present invention relates to a lean vehicle having an EGR path.

[0002] Conventionally, an exhaust gas recirculation (EGR) path is known that recirculates a portion of exhaust gas discharged from an engine combustion chamber back into an intake path. For example, Patent Document 1 discloses a motorcycle having an EGR path. In Patent Document 1, a portion of the EGR path is formed in a body frame to efficiently supply cooled exhaust gas to the intake path, and the body frame dissipates heat from the exhaust gas. Patent Document 1 describes that by using the body frame to cool the exhaust gas, an EGR cooler provided in the EGR path can be downsized or eliminated.

[0003] Patent No. 5283898

[0004] Lean vehicles such as motorcycles are required to have an EGR path equipped with an EGR cooler while suppressing an increase in size in the left-right direction of the lean vehicle.

[0005] An object of the present invention is to provide a lean vehicle that has an EGR path provided with an EGR cooler, while preventing the lean vehicle from becoming larger in the left-right direction.

[0006] (1) A lean vehicle according to one embodiment of the present invention has the following configuration: (A) a body frame that leans to the right of the vehicle when turning right and leans to the left of the vehicle when turning left, (B) the engine having (B1) a cylinder section that includes a cylinder body section that forms at least one cylinder hole and a cylinder head section that is connected to the cylinder body section and that constitutes an end of the engine in the direction of at least one cylinder axis that is the center axis of the at least one cylinder hole, and that forms at least one combustion chamber, (B2) a crankshaft that rotates about an axis along the left-right direction of the vehicle, and (B3) a camshaft drive mechanism that is disposed inside the engine so as to be located to the right or left of the at least one cylinder hole formed in the cylinder body section in the left-right direction of the vehicle and that transmits the driving force of the crankshaft to at least one camshaft disposed inside the cylinder head section, and (C) an intake side end of at least one EGR path connected to an intake path connected to the at least one combustion chamber, and a cylinder head section that is connected to the at least one combustion chamber. a lean-fuel vehicle including an EGR path having an exhaust-side end of at least one EGR path connected to an exhaust path connected to a combustion chamber, the exhaust path having a first end connected to the combustion chamber and an exhaust port, the EGR path having a first end connected to the combustion chamber and an exhaust port, the EGR path having a first end connected to the combustion chamber and an exhaust port, the EGR path having a first end connected to the combustion chamber and an exhaust port, the EGR path having a first end connected to the combustion chamber and an exhaust port, the EGR path having a second ...At least a portion of the EGR path extending from the exhaust side end of the at least one EGR path via the EGR cooler path to the intake side end of the at least one EGR path is arranged to face at least one side surface of three side surfaces excluding the right side surface or left side surface near the camshaft drive mechanism of the cylinder body portion, which is arranged so that an upper portion of the at least one cylinder axis is located forward of a lower portion and a lowermost end of a rear side surface near a portion of the intake path formed inside the cylinder head portion is located higher than a lowermost end of a front side surface near a portion of the exhaust path formed inside the cylinder head portion, in a direction perpendicular to the at least one cylinder axis.

[0007] According to this configuration, at least a portion of the EGR path extending from the exhaust end of at least one EGR path via the EGR cooler path to the intake end of at least one EGR path is positioned perpendicular to at least one cylinder axis and faces at least one of three side surfaces, excluding the right or left side surface near the camshaft drive mechanism, of a cylinder body portion included in the cylinder portion, which is arranged so that the upper portion of at least one cylinder axis is forward of the lower portion and the lowermost end of the rear side surface forming a portion of the intake path is higher than the lowermost end of the front side surface forming a portion of the exhaust path, so that condensed water generated in at least the EGR cooler path returns to the exhaust path. Therefore, by utilizing the fact that the cylinder portion is arranged so that the upper portion of at least one cylinder axis is forward of the lower portion and the lowermost end of the rear side surface forming a portion of the intake path is higher than the lowermost end of the front side surface forming a portion of the exhaust path, the EGR path can be positioned so that condensed water generated in the EGR cooler path returns to the exhaust path. This allows the EGR path to be simplified. Furthermore, the exhaust-side end of at least one EGR path is located above a first plane perpendicular to the vehicle vertical direction, passing through a lowermost end of a cylinder body portion arranged so that an upper portion of at least one cylinder axis is located forward of a lower portion in the vehicle longitudinal direction. The intake-side end of at least one EGR path is located above an exhaust-side end of at least one EGR path in the vehicle vertical direction and above a second plane perpendicular to the vehicle vertical direction, passing through a uppermost end of a cylinder body portion arranged so that an upper portion of at least one cylinder axis is located forward of a lower portion. Therefore, it is easy to arrange at least a portion of the EGR path so that it faces the cylinder body portion in a direction perpendicular to at least one cylinder axis. By arranging at least a portion of the EGR path so that it faces at least one side surface of the cylinder body portion, interference between the EGR path and piping (e.g., coolant piping or exhaust pipe) or electrical components of a path other than the EGR path arranged around the cylinder body portion can be reduced. This allows the EGR path to be arranged while further suppressing an increase in the size of the lean vehicle in the left-right direction of the vehicle.Furthermore, when the camshaft drive mechanism is positioned close to the right side of the cylinder body, it is easier to ensure free space to the left of the left side of the cylinder body than to the right of the right side of the cylinder body. Conversely, when the camshaft drive mechanism is positioned close to the left side of the cylinder body, it is easier to ensure free space to the right of the right side of the cylinder body than to the left of the left side of the cylinder body. Therefore, by arranging at least a portion of the EGR path so that it faces at least one of the three side surfaces of the cylinder body, excluding the right side or left side surface close to the camshaft drive mechanism, in a direction perpendicular to at least one cylinder axis, the EGR path can be positioned while further suppressing the increase in size of the lean vehicle in the left-right direction. As described above, a lean vehicle can have an EGR path equipped with an EGR cooler, while suppressing the increase in size of the lean vehicle in the left-right direction.

[0008] (2) A lean-fuel vehicle according to one embodiment of the present invention may have the following configuration in addition to the configuration described in (1) above: The portion of the EGR path is arranged such that, of the right and left side surfaces of the cylinder section, which is arranged so that an upper portion of the at least one cylinder axis is located forward of a lower portion thereof and a lowermost end of a rear side surface that forms a portion of the intake path is located higher than a lowermost end of a front side surface that forms a portion of the exhaust path, the side surface other than the right side surface or the left side surface that is closer to the camshaft drive mechanism is the side surface that is closest to the portion of the EGR path.

[0009] With this configuration, the EGR path can be positioned while further minimizing the increase in size of the lean vehicle in the left-right direction compared to when a portion of the EGR path is positioned so that it faces the right or left side of the cylinder section that is close to the camshaft drive mechanism in a direction perpendicular to at least one cylinder axis, or when a portion of the EGR path is formed inside the cylinder section in a position close to the right or left side that is close to the camshaft drive mechanism.

[0010] (3) In addition to the configuration of (1) or (2) above, a lean-fuel vehicle according to one embodiment of the present invention may have the following configuration: The EGR cooler path is arranged so that the upper part of the at least one cylinder axis is located forward of the lower part and the lowest end of a rear side surface that forms a part of the intake path is located higher than the lowest end of a front side surface that forms a part of the exhaust path, and one of three side surfaces, excluding the right side surface or the left side surface that is closer to the camshaft drive mechanism, of the cylinder section is closest to the EGR cooler path, so that condensed water generated in at least the EGR cooler path returns to the exhaust path.

[0011] With this configuration, the EGR path can be positioned while further minimizing the increase in size of the lean vehicle in the left-right direction compared to when the EGR cooler path is positioned closer to the right or left side of the cylinder section, which is closer to the camshaft drive mechanism.

[0012] (4) In addition to the configuration of (3) above, a lean-fuel vehicle according to one embodiment of the present invention may have the following configuration: At least a portion of the EGR cooler path is arranged to face, in a direction perpendicular to the at least one cylinder axis, one of three side surfaces of the cylinder body portion, excluding the right side surface or the left side surface that is closer to the camshaft drive mechanism, of the cylinder body portion, which is arranged so that an upper portion of the at least one cylinder axis is located forward of a lower portion thereof and a lowermost end of a rear side surface that is closer to a portion of the intake path formed inside the cylinder head portion is located higher than a lowermost end of a front side surface that is closer to a portion of the exhaust path formed inside the cylinder head portion, so that condensed water generated in at least the EGR cooler path returns to the exhaust path.

[0013] With this configuration, the EGR cooler passage is arranged to face the side surface of the cylinder body in a direction perpendicular to at least one cylinder axis, so the EGR passage can be arranged while minimizing interference between the EGR cooler and the piping and electrical components arranged around the cylinder head. Furthermore, compared to when the EGR cooler passage is formed inside the cylinder, the EGR passage has greater design freedom. This allows the EGR passage to be arranged while minimizing the increase in size of the lean-engine vehicle in the lateral direction.

[0014] (5) A lean-fuel vehicle according to one embodiment of the present invention may have the following configuration in addition to the configuration described in (3) or (4) above: At least a portion of the EGR cooler path is arranged to face one of three side surfaces, excluding the right side surface or the left side surface that is closer to the camshaft drive mechanism, of the cylinder head portion, which is arranged so that an upper portion of the at least one cylinder axis is located forward of a lower portion and a lowermost end of a rear side surface that forms a portion of the intake path is located higher than a lowermost end of a front side surface that forms a portion of the exhaust path, in a direction perpendicular to the at least one cylinder axis, so that condensed water generated in at least the EGR cooler path returns to the exhaust path.

[0015] With this configuration, the EGR cooler path is arranged to face the side surface of the cylinder head in a direction perpendicular to at least one cylinder axis, so the EGR path can be arranged while minimizing interference between the EGR cooler and the piping and electrical components arranged around the cylinder body. Furthermore, compared to when the EGR cooler path is formed inside the cylinder, the EGR path has greater design freedom. This allows the EGR path to be arranged while minimizing the increase in size of the lean-engine vehicle in the lateral direction.

[0016] (6) In addition to the configuration of (3) above, a lean-fuel vehicle according to one embodiment of the present invention may have the following configuration: The EGR cooler path is arranged inside the cylinder body portion so that an upper portion of the at least one cylinder axis is located forward of a lower portion thereof and a lowermost end of a rear side surface near a portion of the intake path formed inside the cylinder head portion is located higher than a lowermost end of a front side surface near a portion of the exhaust path formed inside the cylinder head portion, the first cylinder body side surface being one of three side surfaces excluding the right side surface or the left side surface near the camshaft drive mechanism, is the side closest to the EGR cooler path out of four side surfaces of the cylinder body portion.

[0017] With this configuration, the EGR cooler path is formed inside the cylinder body, which makes it easy to shorten the path length of the EGR path. It also makes it easy to reduce interference between the EGR cooler and the piping and electrical components arranged around the cylinder head. Therefore, even if an EGR path with an EGR cooler is installed, it is easy to prevent the lean-engine vehicle from becoming too large in the lateral direction.

[0018] (7) A lean-fuel vehicle according to one embodiment of the present invention may have the following configuration in addition to the configuration described in (3) above: The EGR cooler path is arranged inside the cylinder head portion so that an upper portion of the at least one cylinder axis is located forward of a lower portion and a lowermost end of a rear side surface that forms a portion of the intake path is located higher than a lowermost end of a front side surface that forms a portion of the exhaust path, and the first cylinder head side surface is one of three side surfaces excluding the right side surface or the left side surface that is closer to the camshaft drive mechanism, and is the side closest to the EGR cooler path among the four side surfaces of the cylinder head portion.

[0019] With this configuration, the EGR cooler path is formed inside the cylinder head, which makes it easy to shorten the path length of the EGR path. It also makes it easy to reduce interference between the EGR cooler and the piping and electrical components arranged around the cylinder body. Therefore, even if an EGR path with an EGR cooler is installed, it is easy to prevent the lean-engine vehicle from becoming too large in the lateral direction.

[0020] In the present invention, the term "path" refers to a space through which an object such as a gas flows. This definition applies to the EGR path, the intake path, and the exhaust path in the present invention and the embodiments.

[0021] In the present invention and the embodiments, the vehicle up-down direction is the direction perpendicular to a horizontal plane when the lean vehicle is placed upright on the horizontal plane. The vehicle left-right direction is the left-right direction for a rider riding on the lean vehicle. The vehicle front-rear direction is the direction perpendicular to the vehicle up-down direction and the vehicle left-right direction, and is the front-rear direction for a rider riding on the lean vehicle. The vehicle forward direction is the direction in which the lean vehicle travels straight.

[0022] In the present invention and the embodiments, the body frame tilting to the right of the vehicle means that the body frame tilts to the right of the vehicle relative to the vertical direction of the vehicle. In other words, it means that the upper part of the body frame tilts so that it is positioned further to the right of the vehicle than the lower part. The definition of the body frame tilting to the left of the vehicle is the same as above.

[0023] In the present invention and the embodiments, the rotation axis of the crankshaft is aligned with the left-right direction of the vehicle. The rotation axis of the crankshaft may be parallel to the left-right direction of the vehicle when the lean vehicle is in an upright position.

[0024] In the present invention and the embodiments, the number of at least one combustion chamber formed by the cylinder section may be one or more. When the cylinder section forms multiple combustion chambers, the multiple combustion chambers formed by the cylinder section are arranged side by side in the left-right direction of the vehicle. In the present invention and the embodiments, the engine may be a single-cylinder engine or a multi-cylinder engine. The engine may be an in-line multi-cylinder engine having multiple combustion chambers arranged side by side in the left-right direction of the vehicle. The engine may be a V-type engine having a cylinder section having at least one combustion chamber and a rear cylinder section arranged rearward of the cylinder section. The rear cylinder section is not included in the cylinder section of the present invention.

[0025] In the present invention and its embodiments, the number of at least one cylinder hole formed by the cylinder body portion is the same as the number of at least one combustion chamber formed by the cylinder portion. The combustion chamber is formed by the cylinder hole, the piston disposed in the cylinder hole, and the cylinder head portion. When the cylinder body portion forms multiple cylinder holes, the multiple cylinder axes, which are the central axes of the multiple cylinder holes, are parallel to each other. In the present invention and its embodiments, the cylinder axis is not a line segment that exists only in the region where the cylinder hole exists, but a straight line that extends infinitely.

[0026] In the present invention and in the embodiments, the cylinder portion is configured so that the cylinder head portion and the cylinder body portion can be separated. The cylinder portion may include a gasket disposed between the cylinder head portion and the cylinder body portion. At least one cylinder axial end of the cylinder portion is at least one cylinder axial end of the cylinder head portion and at least one cylinder axial end of the cylinder body portion. In the present invention and in the embodiments, the cylinder portion has four side surfaces. The four side surfaces of the cylinder portion do not include at least one end surface in the cylinder axial direction. The four side surfaces of the cylinder portion intersect with at least one cylinder axial direction. The four side surfaces of the cylinder portion are a side surface (right side surface) seen when the cylinder portion is viewed to the left of the vehicle, a side surface (left side surface) seen when the cylinder portion is viewed to the right of the vehicle, a side surface (front side surface) seen when the cylinder portion is viewed in a direction perpendicular to the direction perpendicular to at least one cylinder axis and along the vehicle rearward direction, and a side surface (rear side surface) seen when the cylinder portion is viewed in a direction perpendicular to the direction perpendicular to at least one cylinder axis and along the vehicle frontward direction.

[0027] In the present invention and its embodiments, the cylinder head portion may be composed of multiple separable parts, or may be composed of a single, inseparable part. For example, the cylinder head portion may be composed of multiple parts including a head cover. The cylinder head portion has four side surfaces. The definition of the four side surfaces of the cylinder head portion is the same as the definition of the four side surfaces of the cylinder portion described above. In the present invention and its embodiments, the cylinder body portion may be composed of multiple separable parts, may be composed of a single, inseparable part, or may be composed of a part of a single, inseparable part. For example, the cylinder body portion and at least a portion of the crankcase portion may form a single part. In this case, the boundary between the cylinder body portion and the crankcase portion is located on a plane that passes through the end of at least one cylinder hole formed in the cylinder body portion and is perpendicular to at least one cylinder axis. The cylinder body portion has four side surfaces. The definition of the four side surfaces of the cylinder body portion is the same as the definition of the four side surfaces of the cylinder portion described above.

[0028] In the present invention and its embodiments, "the upper part of at least one cylinder axis is located forward of the lower part" means that, when at least one cylinder axis is divided into an upper part and a lower part by a plane perpendicular to the vehicle up-down direction, the upper part of at least one cylinder axis is located forward of the lower part of at least one cylinder axis in the vehicle longitudinal direction. In the present invention and its embodiments, "arranging a cylinder body portion so that the lowest end of its rear side surface, which is close to a portion of the intake path formed inside the cylinder head, is located higher than the lowest end of its front side surface, which is close to a portion of the exhaust path formed inside the cylinder head" means that the cylinder body portion is arranged to satisfy the following three requirements. The first requirement is that the rear side surface of the cylinder body portion is the side, among the four side surfaces of the cylinder body portion, that is closest to the portion of the intake path formed inside the cylinder head. The second requirement is that the front side surface of the cylinder body portion is the side, among the four side surfaces of the cylinder body portion, that is closest to the portion of the exhaust path formed inside the cylinder head. The third requirement is that the lowest end of the rear side surface of the cylinder body portion is located higher in the vehicle up-down direction than the lowest end of the front side surface of the cylinder body portion. In the present invention and embodiments, "arranging the cylinder portion so that the lowest end of its rear side surface, which forms part of the intake path, is located higher than the lowest end of its front side surface, which forms part of the exhaust path," means that the cylinder portion has a rear side surface which forms part of the intake path and a front side surface which forms part of the exhaust path, and the lowest end of the rear side surface of the cylinder portion is located higher in the vehicle vertical direction than the lowest end of the front side surface of the cylinder portion. In the present invention and embodiments, "arranging the cylinder head portion so that the lowest end of its rear side surface, which forms part of the intake path, is located higher than the lowest end of its front side surface, which forms part of the exhaust path," means that the cylinder head portion has a rear side surface which forms part of the intake path and a front side surface which forms part of the exhaust path, and the lowest end of the rear side surface of the cylinder head portion is located higher in the vehicle vertical direction than the lowest end of the front side surface of the cylinder head portion.

[0029] In the present invention and embodiments, the camshaft drive mechanism may be composed of, for example, a crankshaft, multiple sprockets or multiple pulleys provided on at least one camshaft, and a chain or belt wound around the multiple sprockets or multiple pulleys. The camshaft is provided to drive an intake valve that opens and closes the intake path and an exhaust valve that opens and closes the exhaust path. The camshaft drive mechanism is disposed inside the engine so as to be located to the right or left of at least one cylinder hole formed in the cylinder body in the vehicle transverse direction. A portion of the camshaft drive mechanism is disposed inside the cylinder portion so as to follow the right or left side surface of the cylinder portion. A portion of the camshaft drive mechanism is disposed inside the cylinder body so as to follow the right or left side surface of the cylinder body. The camshaft drive mechanism is closer to either the right or left side surface of the cylinder portion. When the camshaft drive mechanism is located to the left of at least one cylinder hole formed in the cylinder body in the vehicle transverse direction, the camshaft drive mechanism is closer to the left side of the right or left side surface of the cylinder portion. When the camshaft drive mechanism is located to the right of at least one cylinder hole formed in the cylinder body portion in the left-right direction of the vehicle, the camshaft drive mechanism is closer to the right side of the right and left side surfaces of the cylinder portion.

[0030] In the present invention and embodiments, the intake path is directly connected to at least one combustion chamber. Air supplied to at least one combustion chamber flows through the intake path. A portion of the intake path is formed inside the cylinder head. A portion of the intake path is arranged outside the engine and is formed by an intake pipe or the like. The intake path has at least one downstream end in the air flow direction. The number of at least one downstream ends of the intake path may be the same as or greater than the number of combustion chambers. One or two downstream ends of the intake path may be provided for one combustion chamber. When the number of downstream ends of the intake path is multiple, the portion of the intake path including the multiple downstream ends may have a branch shape that divides the air flow.

[0031] In the present invention and embodiments, the exhaust path is directly connected to at least one combustion chamber. Exhaust gas discharged from at least one combustion chamber flows through the exhaust path. A portion of the exhaust path is formed inside the cylinder head. A portion of the exhaust path is disposed outside the engine and is formed by an exhaust pipe or the like. The exhaust path has at least one upstream end in the flow direction of the exhaust gas. The number of at least one upstream ends of the exhaust path may be the same as or greater than the number of combustion chambers. One or two upstream ends of the exhaust path may be provided for one combustion chamber. When the number of upstream ends of the exhaust path is multiple, the portion of the exhaust path including the multiple upstream ends may be formed to collect exhaust gas flowing in from the multiple upstream ends.

[0032] In the present invention and embodiments, the EGR path is directly connected to the intake path and the exhaust path. In the present invention and embodiments, the EGR path has at least one EGR path exhaust end connected to the exhaust path. The number of the at least one EGR path exhaust end of the EGR path may be one or more. When the number of at least one upstream end of the exhaust path is one, the number of the at least one EGR path exhaust end of the EGR path is one. When the number of at least one upstream end of the exhaust path is multiple, the number of the at least one EGR path exhaust end of the EGR path may be one or more. When the number of at least one exhaust path is multiple and the number of at least one EGR path exhaust end of the EGR path is multiple, the multiple EGR path exhaust ends of the EGR path are located upstream of a position where exhaust gases flowing in from the multiple upstream ends of the exhaust path gather. When the number of upstream ends of at least one exhaust path is multiple and the number of exhaust-side ends of at least one EGR path is single, the exhaust-side end of one EGR path may be located downstream of or upstream from a position where exhaust gases flowing in from the multiple upstream ends of the exhaust path gather. When the cylinder unit has multiple combustion chambers, the EGR path may be connected to the exhaust path so that a portion of exhaust gas discharged from each of the multiple combustion chambers flows into the EGR path. When the cylinder unit has multiple combustion chambers, the EGR path may be connected to the exhaust path so that only a portion of exhaust gas discharged from at least one of the multiple combustion chambers flows into the EGR path. In the present invention and embodiments, the EGR path has at least one EGR path intake-side end connected to the intake path. The number of EGR path intake-side ends of the at least one EGR path may be one or multiple. In the present invention and the embodiments, the EGR path may be provided with an EGR valve that adjusts the flow rate of exhaust gas flowing through the EGR path. The EGR valve may be disposed, for example, between at least one EGR path intake end of the EGR path and the EGR cooler path.

[0033] In the present invention and in the embodiments, the EGR cooler is configured to cool the exhaust gas flowing through the EGR path. The EGR cooler may be configured to cool the exhaust gas using a coolant (e.g., water) that cools the engine. The EGR cooler may be configured to cool the exhaust gas using an airflow generated by running a lean vehicle. In the present invention and in the embodiments, the EGR cooler path is a portion of the EGR path that is formed within the EGR cooler.

[0034] In the present invention and embodiments, the EGR path is arranged so that condensed water generated in at least the EGR cooler path returns to the exhaust path. This sentence means that the EGR path is arranged so that condensed water generated in the EGR cooler path returns to the exhaust path. Furthermore, this sentence means that the EGR path may be arranged so that condensed water generated in a portion of the EGR path other than the EGR cooler path returns to the exhaust path. "Condensed water generated in the EGR cooler path returns to the exhaust path" means that condensed water generated in the EGR cooler path returns to the exhaust path by gravity. Condensed water is generated when water vapor in the exhaust gas is cooled and condensed.

[0035] In the present invention and embodiments, at least a portion of the EGR path is arranged to face at least one of three side surfaces of the cylinder body portion, excluding the right or left side surface close to the camshaft drive mechanism, in a direction perpendicular to at least one cylinder axis. Here, "three side surfaces of the cylinder body portion, excluding the right or left side surface close to the camshaft drive mechanism" refers to three of the four side surfaces of the cylinder body portion, excluding the right or left side surface close to the camshaft drive mechanism. Here, "at least one side surface" may be one side surface, two side surfaces, or three side surfaces. The phrase "at least a portion of the EGR path is arranged to face at least one side surface of the cylinder body portion in a direction perpendicular to at least one cylinder axis" does not matter what the flow direction of exhaust gas is in at least a portion of the EGR path. When a portion of the EGR path is arranged to face a first side surface of the cylinder body portion in a direction perpendicular to at least one cylinder axis, a pipe forming this portion of the EGR path may be arranged away from the first side surface of the cylinder body portion or in contact with the first side surface of the cylinder body portion.When at least a portion of the EGR cooler path is arranged to face a first side surface of the cylinder body portion in a direction perpendicular to at least one cylinder axis, the EGR cooler may be arranged away from the first side surface of the cylinder body portion or in contact with the first side surface of the cylinder body portion.

[0036] In the present invention and the embodiments, the lean vehicle may be, for example, a motorcycle or a three-wheeled motor vehicle having one or two front wheels. In the present invention and the embodiments, the lean vehicle may have, as a drive source, at least one of an electric motor that generates a drive force transmitted to a crankshaft and an electric motor that generates a drive force that is transmitted to drive wheels without passing through a crankshaft. The electric motor as a drive source does not include a starter motor that is used only to start the engine.

[0037] In the present invention and the embodiments thereof, the engine cooling system may be air-cooled or liquid-cooled using a coolant other than lubricating oil. Also, an air-cooled or liquid-cooled engine may be combined with lubricating oil cooling.

[0038] In the present invention and embodiments, the engine may be provided with a fuel supply device that supplies fuel. The fuel supply device may be arranged to supply fuel directly to the combustion chamber. In this case, at least a portion of the fuel supply device may be arranged in a hole formed in a rear side surface of the cylinder section, or in a hole formed in at least one end surface of the cylinder section in the cylinder axis direction. The fuel supply device may also be arranged to supply fuel to the intake path.

[0039] In the present invention and embodiments, the lean-fuel vehicle may or may not have a forced induction device that pressurizes air to supply the compressed air to the combustion chamber. The forced induction device may be a turbocharger, a mechanical supercharger, or an electric supercharger. The turbocharger may be an electrically assisted turbocharger that can pressurize air using exhaust gas pressure and an electric motor, or a turbocharger that pressurizes air using exhaust gas pressure alone. For example, the turbine wheel of the turbocharger may be disposed downstream in the exhaust gas flow direction from a position where the exhaust gas recirculation (EGR) path is connected to the exhaust side end of at least one EGR path. The turbine wheel of the turbocharger may be disposed upstream in the exhaust gas flow direction from a position where the exhaust gas recirculation (EGR) path is connected to the exhaust side end of at least one EGR path.

[0040] In the present invention and the embodiments, a lean vehicle may have a catalyst in the exhaust path that purifies exhaust gas. For example, the catalyst may be disposed in the exhaust path downstream in the exhaust gas flow direction from a position where the exhaust side end of at least one EGR path of the EGR path is connected.

[0041] In the present invention and the embodiments, the terms including, comprising, having, and their derivatives are used to encompass additional items in addition to the listed items and their equivalents. In the present invention and the embodiments, the terms mounted, connected, coupled, and supported are used broadly to specifically include not only direct mounting, connection, coupling, and support, but also indirect mounting, connection, coupling, and support. Furthermore, connected and coupled are not limited to physical or mechanical connections / couplings; they also include direct or indirect electrical connections / couplings.

[0042] Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification and claims have the same meaning as commonly understood by those skilled in the art to which this invention belongs. Terms, such as those defined in commonly used dictionaries, should be interpreted to have a meaning consistent with the meaning in the context of the relevant technology and this disclosure, and should not be interpreted in an idealized or overly formal sense.

[0043] It should be noted that in this specification, the term "may" is non-exclusive. "may" means "may, but is not limited to." In this specification, "may" implicitly includes the possibility that "may not."

[0044] Before describing the embodiments of the present invention in detail, it should be understood that the present invention is not limited to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The present invention may be practiced in embodiments other than those described below. The present invention may also be practiced in embodiments incorporating various modifications of the embodiments described below. Furthermore, the present invention may be practiced by appropriately combining the embodiments and modifications described below.

[0045] According to the lean vehicle of the present invention, it is possible to prevent the lean vehicle from becoming large in size in the left-right direction while having an EGR path provided with an EGR cooler.

[0046] Fig. 1 is a schematic diagram showing a plurality of examples of a lean vehicle according to a first embodiment of the present invention; Fig. 2 is a schematic diagram showing examples of a lean vehicle according to a second embodiment of the present invention and a lean vehicle according to a third embodiment; Fig. 3 is a schematic diagram showing other examples of the lean vehicle according to the second embodiment of the present invention and the lean vehicle according to the third embodiment; Fig. 4 is a schematic diagram showing examples of a lean vehicle according to a fourth embodiment of the present invention and a lean vehicle according to a fifth embodiment;

[0047] Arrows F, Re, U, D, L, and R shown in Figures 1 to 4 represent the forward, rearward, upward, downward, leftward, and rightward directions of the vehicle, respectively.

[0048] <First embodiment> A lean vehicle 1 according to a first embodiment of the present invention will be described below with reference to FIG. 1. Lean vehicles 1 according to second to fifth embodiments, which will be described later, have all of the configurations of the first embodiment. FIGS. 1(a) to 1(e) show five examples of the layout of an EGR path 50, which will be described later, that the lean vehicle 1 according to the first embodiment has. However, the lean vehicle 1 according to the first embodiment is not limited to the example shown in FIG. 1.

[0049] The lean vehicle 1 has a body frame 2. The body frame 2 leans to the right of the vehicle when the lean vehicle 1 turns right, and leans to the left of the vehicle when the lean vehicle 1 turns left.

[0050] The lean-fuel vehicle 1 has an engine 10. The engine 10 has a cylinder section 11 that defines at least one combustion chamber 12. The cylinder section 11 includes a cylinder body section 13 and a cylinder head section 14. The cylinder body section 13 defines at least one cylinder bore 15. The cylinder head section 14 is connected to the cylinder body section 13 and defines an end of the engine 10 in the direction of at least one cylinder axis Cy, which is the central axis of the at least one cylinder bore 15. The engine 10 also has a crankshaft 16 that rotates about an axis Cl that extends along the left-right direction of the vehicle. The engine 10 also has a camshaft drive mechanism 17. The camshaft drive mechanism 17 is configured to transmit the driving force of the crankshaft 16 to at least one camshaft 18 disposed inside the cylinder head section 14. While FIG. 1 illustrates the camshaft drive mechanism 17 having one at least one camshaft 18, the camshaft drive mechanism 17 may have multiple camshafts 18.

[0051] 1A to 1E each include a schematic diagram of the cylinder body 13 and an EGR path 50, described later, viewed in the direction of the cylinder axis Cy. In FIGS. 1A to 1E, the number of at least one combustion chamber 12 is two, but it may be one or more than two. The camshaft drive mechanism 17 is disposed inside the engine 10 so as to be located to the right or left of at least one cylinder hole 15 formed in the cylinder body 13 in the vehicle's left-right direction. In FIGS. 1A to 1E, the camshaft drive mechanism 17 is located to the right of at least one cylinder hole 15, but this is not limited thereto.

[0052] The cylinder body portion 13 is arranged so that an upper portion of at least one cylinder axis Cy is located forward of a lower portion. At least one combustion chamber 12 is connected to an intake path 20 and an exhaust path 30. The cylinder body portion 13 is arranged so that the lowest end of a rear side surface 13b, which is close to a portion of the intake path 20 formed inside the cylinder head portion 14, is located higher than the lowest end of a front side surface 13f, which is close to a portion of the exhaust path 30 formed inside the cylinder head portion 14. The cylinder portion 11 is arranged so that the lowest end of a rear side surface 11b, which forms a portion of the intake path 20, is located higher than the lowest end of a front side surface 11f, which forms a portion of the exhaust path 30.

[0053] The lean vehicle 1 has an EGR path 50. The EGR path 50 has at least one EGR path intake end 50b connected to an intake path 20 connected to at least one combustion chamber 12, and at least one EGR path exhaust end 50a connected to an exhaust path 30 connected to at least one combustion chamber 12. A portion of the exhaust gas passing through the exhaust path 30 flows into the EGR path 50 from at least one EGR path exhaust end 50a. The EGR path 50 is configured to recirculate the exhaust gas that has flowed into the EGR path 50 from at least one EGR path exhaust end 50a back to the intake path 20 from at least one EGR path intake end 50b. In FIGS. 1(a) to 1(e), the EGR path 50 has one at least one EGR path exhaust end 50a, but may have multiple EGR path exhaust ends 50a. In FIGS. 1A to 1E, the number of the intake side ends 50b of at least one EGR path in the EGR path 50 is two, but it may be one or more.

[0054] The exhaust end 50a of at least one EGR path is located above a first plane S1 that passes through the lowermost end of the cylinder body 13 and is perpendicular to the vehicle vertical direction, and that is arranged so that the upper part of the at least one cylinder axis Cy is located forward of the lower part in the vehicle longitudinal direction. The intake end 50b of at least one EGR path is located above the exhaust end 50a of the at least one EGR path in the vehicle vertical direction and above a second plane S2 that passes through the uppermost end of the cylinder body 13 and is perpendicular to the vehicle vertical direction.

[0055] The EGR path 50 includes an EGR cooler path 52 formed in an EGR cooler 51 that cools exhaust gas as it flows from at least one EGR path exhaust end 50 a to at least one EGR path intake end 50 b. The EGR path 50 may be provided with an EGR valve (not shown) that adjusts the flow rate of exhaust gas flowing through the EGR path 50.

[0056] As described above, the cylinder body portion 13 is disposed so that the upper portion of at least one cylinder axis Cy is located forward of the lower portion, and the lowest end of the rear side surface 13b, which is close to a portion of the intake path 20 formed inside the cylinder head portion 14, is located higher than the lowest end of the front side surface 13f, which is close to a portion of the exhaust path 30 formed inside the cylinder head portion 14. At least a portion of the EGR path 50 is disposed so as to face at least one of three side surfaces of the cylinder body portion 13 disposed as described above, excluding the right side surface 13r or the left side surface 13l, which is close to the camshaft drive mechanism 17, in a direction perpendicular to at least one cylinder axis Cy, so that condensed water generated in at least the EGR cooler path 52 returns to the exhaust path 30. The lowest end of the EGR cooler path 52 is located higher than the lowest end of at least one EGR path exhaust-side end 50a. 1(a) to 1(e), the region between a third plane S3 that passes through the bottom end of the cylinder body portion 13 and is perpendicular to at least one cylinder axis Cy, and a fourth plane S4 that passes through the top end of the cylinder body portion 13 and is perpendicular to at least one cylinder axis Cy, is hatched with dots. At least a portion of the EGR path 50 that is arranged to face at least one of three side surfaces of the cylinder body portion 13, excluding the right side surface 13r or the left side surface 13l that is closer to the camshaft drive mechanism 17, in a direction perpendicular to at least one cylinder axis Cy, is present in the region between the third plane S3 and the fourth plane S4.

[0057] In FIG. 1( a), a portion of the EGR path 50 is arranged to face the left side surface 13l and the rear side surface 13b of the cylinder body portion 13 in a direction perpendicular to at least one cylinder axis Cy. In FIG. 1( b), a portion of the EGR path 50 is arranged to face the left side surface 13l, the front side surface 13f, and the rear side surface 13b of the cylinder body portion 13 in a direction perpendicular to at least one cylinder axis Cy. In FIG. 1( c), a portion of the EGR path 50 is arranged to face the rear side surface 13b of the cylinder body portion 13 in a direction perpendicular to at least one cylinder axis Cy. In FIG. 1( d), a portion of the EGR path 50 is arranged to face the front side surface 13f and the rear side surface 13b of the cylinder body portion 13 in a direction perpendicular to at least one cylinder axis Cy. In FIG. 1( d), another portion of the EGR path 50 is formed inside the cylinder body portion 13. In Fig. 1(e), a portion of the EGR path 50 is disposed to face the rear side surface 13b of the cylinder body portion 13 in a direction perpendicular to at least one cylinder axis Cy. In Fig. 1(e), another portion of the EGR path 50 is formed inside the cylinder head portion 14. More specifically, the other portion of the EGR path 50 is formed inside the cylinder head portion 14 along the vehicle front-rear direction.

[0058] 1(a) to 1(e), at least one EGR path exhaust end 50a is located above a first plane S1 that passes through the lowest end of the cylinder body 13 and is perpendicular to the vehicle vertical direction, and above a fourth plane S4 that passes through the highest end of the cylinder body 13 and is perpendicular to at least one cylinder axis Cy. However, at least one EGR path exhaust end 50a may be located above the first plane S1 and below the fourth plane S4. For example, the position of the EGR path exhaust end 50a of the EGR path 50 in FIGS. 1(b) and 1(d) may be changed to be above the first plane S1 and below the fourth plane S4.

[0059] 1( e), the EGR path 50 is connected to the exhaust path 30 inside the cylinder head 14. However, as shown in FIG. 1( e), if a portion of the EGR path 50 is formed inside the cylinder head 14 along the vehicle longitudinal direction, the EGR path 50 may be connected to the exhaust path 30 outside the cylinder head 14. Also, if a portion of the EGR path 50 is not formed inside the cylinder head 14 along the vehicle longitudinal direction, the EGR path 50 may be connected to the exhaust path 30 inside the cylinder head 14.

[0060] 1(a) to 1(e), the EGR path 50 is connected to the intake path 20 outside the cylinder head portion 14. However, the EGR path 50 may be connected to the intake path 20 inside the cylinder head portion 14.

[0061] In Figures 1(a) to (e), it is preferable that a portion of the EGR path 50 is arranged so that the side surface of the cylinder portion 11 other than the right side surface (not shown) or the left side surface 11l that is closer to the camshaft drive mechanism 17 is the side surface closest to this portion of the EGR path 50.

[0062] In Figures 1(a) to (e), regardless of where the EGR cooler path 52 is located in the EGR path 50, the EGR cooler path 52 is located so that one of the three sides of the cylinder section 11, excluding the right side (not shown) or the left side 11l that is close to the camshaft drive mechanism 17, is the side closest to the EGR cooler path 52.

[0063] Second Embodiment Next, a lean vehicle 1 according to a second embodiment of the present invention will be described. Figures 2(a), 2(b), and 3(a) show an example of the second embodiment.

[0064] As described in the first embodiment, the cylinder body portion 13 is disposed so that the upper portion of at least one cylinder axis Cy is located forward of the lower portion, and the lowest end of the rear side surface 13b, which is close to a portion of the intake path 20 formed inside the cylinder head portion 14, is located higher than the lowest end of the front side surface 13f, which is close to a portion of the exhaust path 30 formed inside the cylinder head portion 14. In the second embodiment, at least a portion of the EGR cooler path 52 is disposed so as to face one of the three side surfaces of the cylinder body portion 13, excluding the right side surface 13r or the left side surface 13l, which is close to the camshaft drive mechanism 17, in a direction perpendicular to at least one cylinder axis Cy, so that condensed water generated in at least the EGR cooler path 52 returns to the exhaust path 30.

[0065] For example, as shown in FIG. 2( a), a portion of the EGR cooler path 52 may be arranged to face the left side surface 13l of the cylinder body portion 13 in a direction perpendicular to at least one cylinder axis Cy. FIG. 2( a) is a specific example of FIG. 1( a). Alternatively, as shown in FIG. 2( b), the entire EGR cooler path 52 may be arranged to face the left side surface 13l of the cylinder body portion 13 in a direction perpendicular to at least one cylinder axis Cy. FIG. 2( b) is a specific example of FIG. 1( b). Alternatively, as shown in FIG. 3( a), at least a portion of the EGR cooler path 52 may be arranged to face the rear side surface 13b of the cylinder body portion 13 in a direction perpendicular to at least one cylinder axis Cy. FIG. 3( a) is a specific example of FIG. 1( a). However, when at least a portion of the EGR cooler path 52 is arranged to face the rear side surface 13b of the cylinder body portion 13 in a direction perpendicular to at least one cylinder axis Cy, the EGR path 50 may be arranged, for example, as shown in Figure 1(b).

[0066] Third Embodiment Next, a lean vehicle 1 according to a third embodiment of the present invention will be described. Figures 2(a), 2(c), and 3(a) to 3(c) show an example of the third embodiment.

[0067] The cylinder head 14 is disposed so that an upper portion of at least one cylinder axis Cy is located forward of a lower portion thereof, and the lowest end of a rear side surface 14b, which forms part of the intake passage 20, is located higher than a lowest end of a front side surface 14f, which forms part of the exhaust passage 30. The configuration of this cylinder head 14 is the same as that of the first embodiment. In the third embodiment, at least a portion of the EGR cooler passage 52 is disposed to face one of three side surfaces of the cylinder head 14 disposed as described above, excluding a right side surface (not shown) or a left side surface 14l, which is close to the camshaft drive mechanism 17, in a direction perpendicular to at least one cylinder axis Cy, so that condensed water generated in at least the EGR cooler passage 52 returns to the exhaust passage 30.

[0068] For example, as shown in FIG. 2( a), a portion of the EGR cooler passage 52 may be disposed so as to face the left side surface 14l of the cylinder head portion 14 in a direction perpendicular to at least one cylinder axis Cy. FIG. 2( a) is a specific example of FIG. 1( a). Alternatively, as shown in FIG. 2( c), the entire EGR cooler passage 52 may be disposed so as to face the left side surface 14l of the cylinder head portion 14 in a direction perpendicular to at least one cylinder axis Cy. FIG. 2( c) is a specific example of FIG. 1( c). Alternatively, as shown in FIGS. 3( a) and 3( b), at least a portion of the EGR cooler passage 52 may be disposed so as to face the rear side surface 14b of the cylinder head portion 14 in a direction perpendicular to at least one cylinder axis Cy. FIG. 3( a) and FIG. 3( b) are specific examples of FIG. 1( a). However, when at least a portion of the EGR cooler path 52 is disposed to face the rear side surface 14b of the cylinder head portion 14 in a direction perpendicular to at least one cylinder axis Cy, a portion of the EGR path 50 may be disposed to face the front side surface 13f of the cylinder body portion 13 in a direction perpendicular to at least one cylinder axis Cy, as shown in FIG. 1B. Also, as shown in FIG. 3C, at least a portion of the EGR cooler path 52 may be disposed to face the front side surface 14f of the cylinder head portion 14 in a direction perpendicular to at least one cylinder axis Cy. FIG. 3C is a specific example of FIG. 1C. However, when at least a portion of the EGR cooler path 52 is arranged to face the front side surface 14f of the cylinder head portion 14 in a direction perpendicular to at least one cylinder axis Cy, a portion of the EGR path 50 may be arranged to face the left side surface 13l of the cylinder body portion 13 in a direction perpendicular to at least one cylinder axis Cy, as shown in Figure 1(c), for example.

[0069] Fourth Embodiment Next, a lean vehicle 1 according to a fourth embodiment of the present invention will be described. Fig. 4(a) shows an example of the fourth embodiment.

[0070] As described in the first embodiment, the cylinder body portion 13 is disposed so that an upper portion of at least one cylinder axis Cy is located forward of a lower portion thereof, and the lowest end of the rear side surface 13b, which is close to a portion of the intake passage 20 formed inside the cylinder head portion 14, is located higher than the lowest end of the front side surface 13f, which is close to a portion of the exhaust passage 30 formed inside the cylinder head portion 14. In the fourth embodiment, the EGR cooler passage 52 is disposed inside the cylinder body portion 13 so that a first cylinder body side surface, which is one of three side surfaces of the cylinder body portion 13 disposed as described above, excluding the right side surface 13r or the left side surface 13l, which is close to the camshaft drive mechanism 17, is the side surface closest to the EGR cooler passage 52 among the four side surfaces 13b, 13f, 13l, and 13r of the cylinder body portion 13, so that condensed water generated in at least the EGR cooler passage 52 returns to the exhaust passage 30.

[0071] Fifth Embodiment Next, a lean vehicle 1 according to a fifth embodiment of the present invention will be described. Fig. 4B shows an example of the fifth embodiment.

[0072] The cylinder head portion 14 is disposed so that an upper portion of at least one cylinder axis Cy is located forward of a lower portion thereof, and the lowest end of a rear side surface 14b, which forms a part of the intake passage 20, is located higher than a lowest end of a front side surface 14f, which forms a part of the exhaust passage 30. The configuration of this cylinder head portion 14 is the same as that of the first embodiment. In the fifth embodiment, the EGR cooler passage 52 is disposed inside the cylinder head portion 14 so that a first cylinder head side surface, which is one of three side surfaces of the cylinder head portion 14 disposed as described above, excluding the right side surface (not shown) or the left side surface 14l, which is close to the camshaft drive mechanism 17, is the side closest to the EGR cooler passage 52 among the four side surfaces of the cylinder head portion 14, so that condensed water generated in at least the EGR cooler passage 52 returns to the exhaust passage 30.

[0073] 1: lean vehicle, 2: vehicle body frame, 10: engine, 11: cylinder portion, 11b, 11f, 11l: side surface of cylinder portion, 12: combustion chamber, 13: cylinder body portion, 13b, 13f, 13l, 13r: side surface of cylinder body portion, 14: cylinder head portion, 14b, 14f, 14l: side surface of cylinder head portion, 15: cylinder bore, 16: crankshaft, 17: camshaft drive mechanism, 18: camshaft, 20: intake path, 30: exhaust path, 50: EGR path, 50a: exhaust side end of EGR path, 50b: intake side end of EGR path, 51: EGR cooler, 52: EGR cooler path, Cy: cylinder axis, S1: first plane, S2: second plane

Claims

1. (A) A vehicle body frame that tilts to the right of the vehicle when turning right and to the left of the vehicle when turning left; (B) an engine having (B1) a cylinder section that includes a cylinder body section that forms at least one cylinder hole, and a cylinder head section that is connected to the cylinder body section and constitutes an end of the engine in the direction of at least one cylinder axis that is the central axis of the at least one cylinder hole, and that forms at least one combustion chamber; (B2) a crankshaft that rotates about an axis along the left-right direction of the vehicle; and (B3) a camshaft drive mechanism that is disposed inside the engine so as to be located to the right or left of the at least one cylinder hole formed in the cylinder body section in the left-right direction of the vehicle, and that transmits the driving force of the crankshaft to at least one camshaft disposed inside the cylinder head section; (C) an EGR path having at least one EGR path intake side end connected to an intake path connected to the at least one combustion chamber, and at least one EGR path exhaust side end connected to an exhaust path connected to the at least one combustion chamber, a portion of exhaust gas passing through the exhaust path flows in from the at least one EGR path exhaust side end, and the exhaust gas that flows in is returned from the at least one EGR path intake side end to the intake path, the EGR path includes an EGR cooler path formed in an EGR cooler for cooling exhaust gas as the exhaust gas flows from an exhaust side end of the at least one EGR path that passes through a lowermost end of the cylinder body portion that is arranged so that an upper portion of the at least one cylinder axis is located forward of a lower portion in the vehicle longitudinal direction, and that is located above a first plane perpendicular to the vehicle vertical direction, to an intake side end of the at least one EGR path that passes through an uppermost end of the cylinder body portion that is arranged so that an upper portion of the at least one cylinder axis is located forward of a lower portion in the vehicle vertical direction, and that is located above a second plane perpendicular to the vehicle vertical direction,At least a portion of the EGR path from the exhaust side end of the at least one EGR path via the EGR cooler path to the intake side end of the at least one EGR path is arranged to face at least one of three side surfaces, excluding the right side surface or the left side surface near the camshaft drive mechanism, in a direction perpendicular to the at least one cylinder axis of the cylinder body portion, which is arranged so that the upper part of the at least one cylinder axis is located forward of the lower part and the lowest end of the rear side surface near the portion of the intake path formed inside the cylinder head portion is located above the lowest end of the front side surface near the portion of the exhaust path formed inside the cylinder head portion, so that condensed water generated in at least the EGR cooler path returns to the exhaust path.

2. A lean vehicle as described in claim 1, characterized in that a portion of the EGR path is arranged so that the upper part of the at least one cylinder axis is located forward of the lower part and the lowest end of the rear side surface forming part of the intake path is located above the lowest end of the front side surface forming part of the exhaust path, and the side other than the right side surface or left side surface closer to the camshaft drive mechanism is the side closest to the portion of the EGR path.

3. The lean vehicle described in claim 1 or 2, characterized in that the EGR cooler path is arranged so that the upper part of the at least one cylinder axis is located forward of the lower part and the lowest end of the rear side surface that forms part of the intake path is located above the lowest end of the front side surface that forms part of the exhaust path, so that condensed water generated in at least the EGR cooler path returns to the exhaust path, and one of three side surfaces, excluding the right side surface or left side surface that is close to the camshaft drive mechanism, is the side closest to the EGR cooler path.

4. The lean vehicle described in claim 3, characterized in that at least a portion of the EGR cooler path is arranged to face one of three side surfaces, excluding the right side surface or left side surface near the camshaft drive mechanism, of the cylinder body portion, which is arranged so that the upper part of the at least one cylinder axis is located forward of the lower part and the lowest end of the rear side surface near the portion of the intake path formed inside the cylinder head portion is located higher than the lowest end of the front side surface near the portion of the exhaust path formed inside the cylinder head portion, so that condensed water generated in at least the EGR cooler path returns to the exhaust path.

5. A lean vehicle as described in claim 3 or 4, characterized in that at least a portion of the EGR cooler path is arranged to face one of three side surfaces, excluding the right side surface or left side surface near the camshaft drive mechanism, of the cylinder head portion, which is arranged so that the upper part of the at least one cylinder axis is located forward of the lower part and the lowest end of the rear side surface forming part of the intake path is located above the lowest end of the front side surface forming part of the exhaust path, so that condensed water generated in at least the EGR cooler path returns to the exhaust path.

6. The lean vehicle according to claim 3, characterized in that the EGR cooler path is arranged inside the cylinder body portion so that an upper part of the at least one cylinder axis is located forward of a lower part and a lowermost end of a rear side surface near a portion of the intake path formed inside the cylinder head portion is located above a lowermost end of a front side surface near a portion of the exhaust path formed inside the cylinder head portion, so that condensed water generated in at least the EGR cooler path returns to the exhaust path, and a first cylinder body side surface which is one of three side surfaces excluding the right side surface or the left side surface which is close to the camshaft drive mechanism, is the side closest to the EGR cooler path among four side surfaces of the cylinder body portion.

7. The lean vehicle described in claim 3, characterized in that the EGR cooler path is arranged inside the cylinder head portion so that a first cylinder head side surface, which is one of three side surfaces excluding the right side surface or the left side surface close to the camshaft drive mechanism of the cylinder head portion, is the side closest to the EGR cooler path among the four side surfaces of the cylinder head portion, the first cylinder head side surface being one of three side surfaces excluding the right side surface or the left side surface close to the camshaft drive mechanism of the cylinder head portion, the first cylinder head side surface being one of three side surfaces excluding the right side surface or the left side surface close to the camshaft drive mechanism of the cylinder head portion, the first cylinder head side surface being the side closest to the EGR cooler path among the four side surfaces ... the side closest to the EGR cooler path among the four side surfaces of the cylinder head portion, the first cylinder head side surface being the side closest to the EGR cooler path among the four side surfaces of the cylinder head portion, the first cylinder head side surface being the side closest to the EGR cooler path among the four side surfaces of the cylinder head portion.

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