Four stroke engine with secondary air introducing system
A four stroke engine has an engine body that defines a cylinder bore. The cylinder bore has a longitudinal axis. A piston is reciprocally disposed within the cylinder bore. A crankshaft is rotatable with a movement of the piston. A valve actuating mechanism actuates intake and exhaust valves. The crankshaft drives the valve actuating mechanism. A first portion of the valve actuating mechanism is positioned at least adjacent to the exhaust valve. A second portion of the valve actuating mechanism is positioned adjacent to the crankshaft. The engine body defines an inner passage through which secondary air flows to the exhaust passage. The inner passage has an end at a surface of the engine body. The longitudinal axis intersects the surface.
The present application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2004-059173, filed on Mar. 3, 2004, the entire contents of which is expressly incorporated by reference herein.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention generally relates to a four stroke engine with a secondary air introducing system, and more particularly relates to a four stroke engine that has an introducing system through which secondary air is introduced into an exhaust passage.
2. Description of the Related Art
Typically, four stroke engines have an engine body that defines a cylinder bore. A piston is reciprocally disposed within the cylinder bore. The piston defines a combustion chamber with the engine body in the cylinder bore. The engine body defines an intake passage through which the ambient air is introduced into the combustion chamber and an exhaust passage through which exhaust gases are discharged from the combustion chamber.
The exhaust gases preferably contain no unburnt gases. In reality, however, the exhaust gases can contain some unburnt gases. The unburnt gases include hydrocarbon (HC) and carbon monoxide (CO). Conventionally, a secondary air introducing system is provided to introduce secondary air into the exhaust passage. The secondary air can be mixed with the exhaust gases in the exhaust passage. The exhaust gases can be burnt in a recombustion device such as, for example, a catalytic device located downstream of the exhaust passage. Thus, the unburnt gases are removed prior to being discharged to the atmosphere. Because an end of the secondary air introducing system is placed at a location in the exhaust passage, the secondary air can be efficiently introduced into the exhaust passage by the exhaust pulsation caused in the exhaust passage while the engine operates. For example, Japanese Patent Publication P2002-4849A discloses a four stroke engine having such a secondary air introducing system.
The four stroke engines typically have intake and exhaust valves that connect or disconnect the intake and exhaust passages with the combustion chamber, respectively. The engine disclosed in Japanese Patent Publication P2002-4849A includes a camshaft and rocker arms to actuate the intake and exhaust valves. The camshaft and the rocker arms are disposed around the intake and exhaust valves. The secondary air introducing system thus has a relatively complicated structure to reach the exhaust passage because the secondary air introducing system should make a detour to avoid the camshaft and the rocker arms.
SUMMARY OF THE INVENTIONAn aspect of the present invention involves the recognition of the need for a four stroke engine incorporating a secondary air introducing system that does not have a complicated structure to introduce secondary air to an exhaust passage of the engine.
To address such a need, an aspect of the present invention involves a four stroke engine comprising an engine body that defines a cylinder bore. The cylinder bore has a longitudinal axis. A piston is reciprocally disposed within the cylinder bore. The piston is movable along the longitudinal axis. The piston defines a combustion chamber with the engine body in the cylinder bore. The engine body defines a first intake passage through which primary air is introduced into the combustion chamber and an exhaust passage through which exhaust gases are discharged from the combustion chamber. An intake valve is arranged to connect or disconnect the first intake passage with the combustion chamber. An exhaust valve is arranged to connect or disconnect the exhaust passage with the combustion chamber. A crankshaft is rotatable with a movement of the piston. A valve actuating mechanism is arranged to actuate the intake and exhaust valves. The crankshaft drives the valve actuating mechanism. A first portion of the valve actuating mechanism is positioned at least adjacent to the exhaust valve. A second portion of the valve actuating mechanism is positioned adjacent to the crankshaft. The engine body further defines a second intake passage through which secondary air flows to the exhaust passage. The second intake passage has an end at a surface of the engine body. The longitudinal axis intersects the surface.
In accordance with another aspect of the present invention, a four stroke engine comprises an engine body defining a cylinder bore. The cylinder bore has a longitudinal axis. A piston is reciprocally disposed within the cylinder bore. The piston is movable along the longitudinal axis. The piston defines a combustion chamber with the engine body in the cylinder bore. The engine body defines a first intake passage through which primary air is introduced into the combustion chamber and an exhaust passage through which exhaust gases are discharged from the combustion chamber. An intake valve is arranged to connect or disconnect the first intake passage with the combustion chamber. An exhaust valve is arranged to connect or disconnect the exhaust passage with the combustion chamber. A crankshaft is rotatable with a movement of the piston. A valve actuating mechanism is arranged to actuate the intake and exhaust valves. The crankshaft drives the valve actuating mechanism. A first portion of the valve actuating mechanism is positioned at least adjacent to the exhaust valve. A second portion of the valve actuating mechanism is positioned adjacent to the crankshaft. The engine body further defines a second intake passage through which secondary air flows to the exhaust passage. The second intake passage has an end at a surface of the engine body. The longitudinal axis intersects the surface.
BRIEF DESCRIPTION OF THE DRAWINGSThese and other features, aspects and advantages of the present invention are now described with reference to the drawings of a preferred embodiment, which embodiment is intended to illustrate and not to limit the present invention. The drawings comprise eleven figures in which:
With reference to
As used through this description, the terms “forward” and “front” mean at or to the side where a leading end of the motorcycle 30 is situated when the motorcycle 30 proceeds, and the terms “rear” and “rearward” mean at or to the opposite side of the front side, unless indicated otherwise or otherwise readily apparent from the context use. The arrow Fr of
Also, as used in this description, the term “horizontally” means that the subject portions, members or components extend generally parallel to the ground when the motorcycle 30 stands normally on the ground. The term “vertically” means that portions, members or components extend generally normal to those that extend horizontally.
Further, as used through the description, the term “right hand side” means the side where the right hand of the rider of the motorcycle 30 is positioned, and the term “left hand side” means the side where the left hand of the rider is positioned.
The motorcycle 30 preferably comprises a frame 34, a front wheel 36, a rear wheel 38, a front fork 42, a rear arm 44, a seat unit 46 and a fuel tank 48 other than the engine 32.
The frame 34 preferably forms a basic framework of the motorcycle 30. A front portion of the frame 34 preferably supports the front fork 42 for pivotal movement about a generally vertically extending axis. With the pivotal movement of the front fork 42, the motorcycle 30 can be directed rightward or leftward. The front fork 42 preferably carries the front wheel 36. The front fork 42 also carries a handle bar 50 atop thereof. The rider of the motorcycle 30 can steer the front fork 42 with the handle bar 50.
A rear portion of the frame 34 preferably supports the rear arm 44. The rear arm 44 preferably carries the rear wheel 38. The rear wheel 38 is a propulsive wheel in the illustrated embodiment. A mid portion of the frame 34 preferably mounts the engine 32. An output or motive power of the engine 32 is transmitted to the rear wheel 38 through a transmission 52.
The frame 34 also supports the seat unit 46. The illustrated seat unit 46 is a tandem type one and comprises a main seat 54 for the rider who drives the motorcycle 30 and a sub seat 56 for another rider, if any. The riders straddle the respective seat 54, 56.
The fuel tank 48 in the illustrated embodiment is generally positioned above the engine 32. The fuel tank 48 preferably contains fuel that is supplied to the engine 32 for combustion.
Overall Construction of Engine With reference to
With reference to
The front and rear banks FB, RB extend upward from the crankcase 62 to generally form a V configuration. That is, respective top ends of the banks FB, RB are spaced apart from each other more than respective bottom ends thereof. Because both of the banks FB, RB are almost similar to each other, the rear bank RB can represent the respective banks FB, RB in the description below unless otherwise described.
With reference to
A piston (not shown) is reciprocally disposed in the cylinder bore 68. The piston is movable along the cylinder axis 66. The cylinder head assembly 64 closes a top end of the cylinder bore 68. The piston defines a combustion chamber 70 together with the cylinder block 60R and the cylinder head assembly 64 in the cylinder bore 68.
With reference to
With reference to
As best shown in
With reference to
With reference to
The carburetor 80 preferably is disposed in a space between the respective banks FB, RB below the fuel tank 48. The carburetor 80 preferably has an air inlet. The ambient air enters the carburetor 80 through the air inlet when the engine 32 is in the intake stroke. That is, the air is pulled because a negative pressure is generated in each combustion chamber 70 when the piston moves toward the crankcase 62. The carburetor 80 also has an air adjusting mechanism such as, for example, a throttle valve mechanism therein. A throttle valve actuator preferably is placed on the handle bar 50. When the rider operates the throttle valve actuator, the throttle valve moves between an open position and a closed position to adjust an amount of the air in response to a degree of the operation of the throttle valve actuator. The air is introduced into each combustion chamber 70 through the outer intake passage 82 and the inner intake passage 84. The outer intake passage 82 preferably is defined in an intake conduit 86 that connects the carburetor 80 and the cylinder head body 64a with each other. The inner intake passage 84 preferably is defined in the cylinder head body 64a to extend toward the combustion chamber 70. As best shown in
The engine 32 also has a fuel supply system through which fuel is supplied to the combustion chambers 70 from the fuel tank 48. Preferably, the carburetor 80 also works as a part of the fuel supply system. The fuel is metered within the carburetor 80 in accordance with the amount of the air adjusted by the throttle valve mechanism. The fuel is mixed with the air to form an air/fuel charge in the carburetor 80. As indicated by the arrows 90 of
Other charge formers such as, for example, a fuel injection device can replace the carburetor. The carburetor and the fuel injection device can be disposed at any places in the intake system. In this alternative, for example, an intake conduit or a plenum chamber member can be placed in the space where the carburetor of this embodiment is disposed.
With reference to
Exhaust valves 118 are reciprocally disposed on the cylinder head body 64a. Each exhaust valve 118 is associated with the respective exhaust port 108 and is movable between an open position and a closed position. When the exhaust valves 118 are in the open position, the inner exhaust passage 106 communicates with the combustion chamber 70. In other words, the exhaust passage 106 and the combustion chamber 70 are connected with each other when the exhaust ports 108 are open. When the exhaust valves 118 are in the closed position, the inner exhaust passage 106 does not communicate with the combustion chamber 70. In other words, the inner exhaust passage 106 and the combust; on cha 70 are disconnected from each other when the exhaust ports 108 are closed.
An exhaust bias spring 120 is provided at each exhaust valve 118 to urge the exhaust valve 118 toward its closed position. The exhaust valves 118 can be moved toward its open position by the valve actuating mechanism 96. As indicated by the arrows 119 of
With reference to
The crankcase 62 journals the camshaft 122. The camshaft 122 extends adjacent to the crankshaft 72 and parallel to the crankshaft 72. The crankshaft 72 drives the camshaft 122 through a drive mechanism (not shown). As schematically shown in
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With reference to
The tubular section 128a preferably extends transversely above the rocker arm mount 64b. That is, longitudinal axes 137 of the respective tubular sections 128a extend parallel to each other in the transverse direction of the engine 32 and generally normal to the cylinder axis 66. The tubular sections 128a are spaced apart from each other and interpose the spark plugs 100 therebetween. Preferably, the tubular sections 128a are positioned generally symmetrically relative to a vertical plane that extends generally vertically and includes the cylinder axis 66 and respective axes of the spark plugs 100. A rocker arm shaft 136 preferably extends through each tubular section 128a. In the illustrated embodiment, each tubular section 128a is pivotable about the longitudinal axis 137 thereof relative to the rocker arm shaft 136.
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As best shown in
In operation of the valve actuating mechanism 96, the camshaft 122 rotates when the crankshaft 72 drives the camshaft 122. Each cam surface 132 moves the associated lifter 124 upward. The lifter 124 thus lifts the associated push rod 126. Each push rod 126 pushes the associated driven arm 128c of the rocker arm unit 128 when the lifter 124 lifts the push rod 126. Thus, the tubular section 128a pivots about the longitudinal axis 137 thereof. With the pivotal movement of the tubular section 128a, the drive arms 128b in turn push the intake or exhaust valves 92, 118. The intake or exhaust valves 92, 118 move to their open positions against the urging force of the bias springs 94, 120. The intake ports 88 open and the air/fuel charge enters the combustion chamber 70, or the exhaust ports 108 open and the burnt charge is discharged from the combustion chamber 70. After awhile, the cam surface 132 leaves the lifter 124. The lifter 124 moves downward and no longer lifts the push rod 126. The rocker arm unit 128 thus moves back to its initial position. The intake or exhaust valves 92, 118 return to their closed positions.
The motorcycle 30 or the engine 32 can have other systems, devices, components and members. For example, the engine 32 preferably has a lubrication system 142 (
The illustrated engine 32 further comprises a secondary air ing system 150. The secondary air introducing system 150 preferably introduces the ambient air into the inner exhaust passage 106. Unburnt gases such as, for example, hydrocarbon (HC) and carbon monoxide (CO) are mixed with the air in the inner and outer exhaust passages 106, 112 and can be burned within the catalytic device 116.
With reference to
The inner passage 152 of the rear bank RB extends generally vertically along the cylinder axis 66. A bottom end of the inner passage 152 opens to the inner exhaust passage 106, while a top end 160 of the inner passage 152 opens in an area of the top surface 71 of the head cover 64c. Preferably, the bottom end of the inner passage 152 is positioned in the close vicinity of the intake ports 108, and the inner passage 152 opens generally at a center of the top surface 71.
The illustrated inner passage 152 comprises an upper portion 152a, a mid portion 152b and a lower portion 152c. The upper portion 152a has the top end 160. The lower portion 152c opens to the inner exhaust passage 106. The mid portion 152b connects the upper and lower portions 152a, 152c with each other.
The rocker arm mount 64b and the cylinder head body 64a define the mid portion 152b. The illustrated mid portion 152b is formed in casting processes of the rocker arm mount 64b and the cylinder head body 64a. That is, one recess is formed in a bottom surface of the rocker arm mount 64b, while another recess is formed in a top surface of the cylinder head body 64a. Both of the recesses are coupled with each other to define the mid portion 152b.
The head cover 64c and the rocker arm mount 64b preferably define the upper portion 152a. Also, the cylinder head body 64a preferably defines the lower portion 152c. The illustrated upper and lower portions 152a, 152c are circular apertures formed in a drilling process. In the illustrated embodiment, the upper portion 152a generally extends along the cylinder axis 66 and the lower portion 152c slightly inclines relative to the cylinder axis 66 as is shown in
The upper portion 152a preferably is positioned next to the rocker arm units 128. The rocker arm units 128 in the illustrated embodiment interpose the upper portion 152 therebetween. Also, the upper portion 152a preferably is positioned next to the spark plugs 100, and the spark plugs 100 interpose the upper portion 152a therebetween.
The air introducing conduit 156 preferably has a flange 164 at an end thereof. The outer passage 154 penetrates the flange 164. The flange 164 preferably is affixed to the top surface 71 of the head cover 64c by bolts 166 such the outer passage 154 communicates with the inner passage 152. The air introducing conduit 156 preferably curves and extends toward the airflow regulator 158 along the top surface 71 except for its portion that has the flange 164.
The airflow regulator 158 preferably is positioned between the front and rear banks FB, RB below the fuel tank 48 and on a left hand side of the motorcycle 30. The airflow regulator 158 preferably has a housing that is affixed to the frame 34 or a bracket extending from the engine body. The other end of the air introducing conduit 156 preferably is inserted into the housing of the airflow regulator 158. That is, two air introducing conduits 156 extend from the front and rear banks FB, RB and meet together within the housing of the airflow regulator 158.
The housing of the airflow regulator 158 preferably has an air inlet. The air inlet is defined at a suitable location of the housing to introduce the ambient air into an internal space of the housing. The airflow regulator 158 incorporates an airflow amount regulating unit in the housing. The airflow amount regulating unit preferably comprises a one-way valve or check valve and an air amount regulating valve. The one-way valve allows the air to flow toward the inner exhaust passage 106 and prevents the air from flowing in the reverse direction. The air amount regulating valve regulates an amount of the air that is introduced into the secondary air introducing system 150. Preferably, the regulating valve is adjustable outside of the housing.
The ambient air is introduced into the inner exhaust passage 106 through the airflow regulator 158, the outer passage 154 of the air flow introducing conduit 156 and the inner exhaust passage 106 of the cylinder head assembly 64 as indicated by the arrow 168 of
In the illustrated embodiment, the cylinder head assembly 64 only has the rocker arm units 128 as a part of the valve actuating mechanism 96 and the rest parts of the valve actuating mechanism 96 (i.e., the push rods 126, the lifters 124 and the camshaft 122) are placed out of the cylinder head assembly 64. Thus, relatively large room can be provided for the inner passage 152 of the secondary air introducing system 150. The inner passage 152 can generally straightly extend within the cylinder head assembly 64. In other words, the inner passage 152 does not have a complicated structure.
A relatively large part of the air passage of the secondary air introducing system 150 is defined in the cylinder head assembly 64 and the foregoing part of the air passage can be simply made by the casting processes or the drilling process in this embodiment. The secondary air introducing system 150 thus can be quite easily completed.
Also, the illustrated inner passage 152 extends next to and between the rocker arm units 128 or the spark plugs 100. This arrangement further contributes to making the inner passage 152 simpler.
In addition, because the end of the illustrated inner passage is positioned in the top surface of the head cover where no cooling fins are provided, a total area of the cooling fins cannot be reduced. Thus, the cooling effect of the engine body cannot be hampered by the secondary air introducing system.
The engine can be an OHC type instead of the OHV type. In this alternative, a first portion of the valve actuating mechanism includes a camshaft and a second portion of the valve actuating mechanism includes a timing belt or chain that is wounds around the camshaft and the crankshaft.
The spark plugs can be disposed in a fore to aft direction of the motorcycle 30 than in the transverse direction. The engine can have a single spark plug than two spark plugs. In some arrangements, the top end of the inner passage can be positioned at a location out of the rocker arm units that does not exist in an area surrounded by the rocker arm units.
Although this invention has been disclosed in the context of certain preferred embodiment, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiment to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiment may be made and still fall within the scope of the invention. It should be understood that various features and aspects of the disclosed embodiment can be combined with or substituted for one another in order to form varying modes of the disclosed invention. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiment described above, but should be determined only by a fair reading of the claims that follow.
Claims
1. A four stroke engine comprising an engine body defining a cylinder bore, the cylinder bore having a longitudinal axis, a piston reciprocally disposed within the cylinder bore, the piston movable along the longitudinal axis, the piston defining a combustion chamber with the engine body in the cylinder bore, the engine body defining a first intake passage through which primary air is introduced into the combustion chamber and an exhaust passage through which exhaust gases are discharged from the combustion chamber, an intake valve arranged to connect or disconnect the first intake passage with the combustion chamber, an exhaust valve arranged to connect or disconnect the exhaust passage with the combustion chamber, a crankshaft rotatable with a movement of the piston, and a valve actuating mechanism arranged to actuate the intake and exhaust valves, the crankshaft driving the valve actuating mechanism, a first portion of the valve actuating mechanism being positioned at least adjacent to the exhaust valve, a second portion of the valve actuating mechanism being positioned adjacent to the crankshaft, the engine body further defining a second intake passage through which secondary air flows to the exhaust passage, the second intake passage having an end at a surface of the engine body, and the longitudinal axis intersecting the surface.
2. The engine as set forth in claim 1, wherein the valve actuating mechanism additionally comprises a third portion that couples the first and second portions with each other, the third portion extends generally along the longitudinal axis.
3. The engine as set forth in claim 2, wherein the third portion includes push rods.
4. The engine as set forth in claim 1, wherein the first portion of the valve actuating mechanism comprises at least one rocker arm associated with the exhaust valve, the rocker arm and the second intake passage are positioned next to each other.
5. The engine as set forth in claim 4, wherein the valve actuating mechanism additionally comprises at least one push rod that couples the rocker arm with the second portion.
6. The engine as set forth in claim 1, wherein the first portion of the valve actuating mechanism comprises a pair of rocker arms associated with the intake and exhaust valves, the rocker arms generally interpose the second intake passage therebetween.
7. The engine as set forth in claim 1 additionally comprising a spark plug configured to make a spark in the combustion chamber, the spark plug and the second intake passage being positioned next to each other.
8. The engine as set forth in claim 1 additionally comprising a pair of spark plugs each of which is configured to make a spark in the combustion chamber, the spark plugs generally interpose the second intake passage therebetween.
9. The engine as set forth in claim 1, wherein the longitudinal axis generally extends vertically, the surface of the engine body is generally located at a top of the engine body.
10. The engine as set forth in claim 1, wherein the engine body has a plurality of cooling fins, the fins extend outward from another surface of the engine body.
11. The engine as set forth in claim 1, wherein the second portion of the valve actuating mechanism includes a camshaft extending next to the crankshaft.
12. A four stroke engine comprising a cylinder block defining a cylinder bore, a cylinder head closing one end of the cylinder bore, a piston reciprocally disposed within the cylinder bore the piston defining a combustion chamber with the cylinder block and the cylinder head in the cylinder bore, the cylinder head defining an exhaust passage through which exhaust gases are discharged from the combustion chamber, an exhaust valve arranged to connect or disconnect the exhaust passage with the combustion chamber, a crankshaft rotatable with a movement of the piston, and a valve actuating mechanism arranged to actuate the exhaust valve, the crankshaft driving the valve actuating mechanism, a first portion of the valve actuating mechanism being positioned adjacent to the exhaust valve, a second portion of the valve actuating mechanism being positioned adjacent to the crankshaft, the cylinder head further defining an intake passage through which air flows to the exhaust passage, the intake passage having an end at a surface of the cylinder head.
13. The engine as set forth in claim 11, wherein the cylinder bore has a longitudinal axis, and the longitudinal axis intersects the surface.
Type: Application
Filed: Mar 3, 2005
Publication Date: Sep 8, 2005
Inventor: Tomoki Kaneshiro (Shizuoka-ken)
Application Number: 11/072,004