U.S. patent application number 11/072004 was filed with the patent office on 2005-09-08 for four stroke engine with secondary air introducing system.
Invention is credited to Kaneshiro, Tomoki.
Application Number | 20050193725 11/072004 |
Document ID | / |
Family ID | 34747645 |
Filed Date | 2005-09-08 |
United States Patent
Application |
20050193725 |
Kind Code |
A1 |
Kaneshiro, Tomoki |
September 8, 2005 |
Four stroke engine with secondary air introducing system
Abstract
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.
Inventors: |
Kaneshiro, Tomoki;
(Shizuoka-ken, JP) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
34747645 |
Appl. No.: |
11/072004 |
Filed: |
March 3, 2005 |
Current U.S.
Class: |
60/305 ;
123/310 |
Current CPC
Class: |
Y02T 10/20 20130101;
F01N 2590/04 20130101; Y02T 10/12 20130101; F02B 61/02 20130101;
F01N 3/34 20130101 |
Class at
Publication: |
060/305 ;
123/310 |
International
Class: |
F01N 003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 3, 2004 |
JP |
2004-059173 |
Claims
What is claimed is:
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.
Description
PRIORITY INFORMATION
[0001] The present application is based on and claims priority
under 35 U.S.C. .sctn. 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 INVENTION
[0002] 1. Field of the Invention
[0003] 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.
[0004] 2. Description of the Related Art
[0005] 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.
[0006] 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.
[0007] 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 INVENTION
[0008] An 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.
[0009] 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.
[0010] 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 DRAWINGS
[0011] These 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:
[0012] FIG. 1 illustrates a side elevational view of a motorcycle
mounting an engine configured in accordance with certain features,
aspects and advantages of the present invention, wherein a fuel
tank is shown in phantom;
[0013] FIG. 2 illustrates a top plan view of the motorcycle of FIG.
1, wherein the fuel tank also is shown in phantom;
[0014] FIG. 3 partially illustrates a cross-sectional side view of
a rear bank of the engine;
[0015] FIG. 4 illustrates the rear bank looked in the direction
indicated by the arrows 4, 4 of FIG. 3, wherein bolts for coupling
a cylinder head assembly of the rear bank are removed;
[0016] FIG. 5 illustrates the rear bank without a head cover of the
cylinder head assembly and looked in the direction indicated by the
arrows 5, 5 of FIG. 3;
[0017] FIG. 6 illustrates the rear bank without the head cover and
a rocker arm mount of the cylinder head assembly and looked in the
direction indicated by the arrows 6, 6 of FIG. 3;
[0018] FIG. 7 illustrates a bottom side of a cylinder head body of
the cylinder head assembly;
[0019] FIG. 8 partially illustrates the rear bank looked in the
direction indicated by the arrows 8, 8 of FIG. 5, wherein the rear
bank except for rocker arms, push rods, tappets and a cam of a
camshaft is schematically shown in phantom;
[0020] FIG. 9 partially illustrates the rear bank looked in the
direction indicated by the arrows 9, 9 of FIG. 6;
[0021] FIG. 10 partially illustrates the rear bank looked in the
direction indicated by the arrows 10, 10 of FIG. 6, wherein the
head cover and the rocker arm mount of the cylinder head assembly
are shown in phantom; and
[0022] FIG. 11 partially illustrates the rear bank looked in the
opposite side of FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE
INVENTION
Overall Construction of Motorcycle
[0023] With reference to FIGS. 1 and 2, an overall construction of
a motorcycle 30 that mounts an internal combustion engine 32
configured in accordance with certain features, aspects and
advantages of the present invention is described. The motorcycle 30
merely exemplifies one type of machinery that is powered by the
engine 32. The engine 32 described below can be applied for other
types of machinery such as, for example, other land vehicles
including automobiles, motor scooters and mopeds; marine vehicles
and stationary machines. Such applications will be apparent to
those of ordinary skill in the art in light of the description
herein.
[0024] 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 FIGS. 1-8 and 11
indicates the front side of the motorcycle 30.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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
[0032] With reference to FIGS. 1-11, an overall construction of the
engine 32 is described.
[0033] With reference to FIGS. 1 and 2, the engine 32 preferably is
an OHV-type, four stroke engine. The engine 32 has an engine body
that is preferably made of aluminum alloy and can be produced in
casting processes. The engine body preferably comprises a front
cylinder block 60F, a rear cylinder block 60R, a crankcase 62 and a
pair of cylinder head assemblies 64. The front cylinder block 60F
and one of the cylinder head assemblies 64 together form a front
bank FB, while the rear cylinder block 60R and the other cylinder
head assemblies 64 together form a rear bank RB.
[0034] 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.
[0035] With reference to FIG. 3, the cylinder block 60R of the rear
bank RB preferably defines a cylinder bore 68. The cylinder bore 68
preferably has a longitudinal axis 66 that extends generally
vertically. The illustrated longitudinal axis 66 also is an axis of
the rear cylinder block 60R. Thus, the reference numeral 66 can
indicate the cylinder axis in the description below unless
otherwise described.
[0036] 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.
[0037] With reference to FIG. 1, the crankcase 62 closes a bottom
end of each cylinder bore 68 and journals a crankshaft 72 therein.
A longitudinal axis 73 of the crankshaft 72 transversely extends
through the crankcase 62. Each piston of the respective banks FB,
RB is connected to the crankshaft 72 through a respective
connecting rod. Thus, the crankshaft 72 rotates in the crankcase 62
with the reciprocal movement of the pistons.
[0038] With reference to FIGS. 3-11, each cylinder head assembly 64
preferably comprises a cylinder head body 64a, a rocker arm mount
64b and a head cover 64c. The cylinder head body 64a of the rear
bank RB abuts on a top surface of the cylinder block 60R and the
rocker arm mount 64b and the head cover 64c are put on top of one
another in this order. Preferably, the head cover 64c entirely
covers the rocker arm mount 64b. The head cover 64c thus has a top
surface 71. The cylinder axis 66 intersects the top surface 71.
[0039] As best shown in FIGS. 4 and 9, a plurality of stud bolts 74
extend upward and parallel to the cylinder axis 66 from the
cylinder block 60R. The cylinder block 60R and the cylinder head
body 64a define holes 75 having an inner diameter that is slightly
larger than an outer diameter of the bolts 74. Elongated nuts 76
are inserted into the holes 75 and are screwed onto the bolts 74.
The cylinder head body 64a thus is affixed to the cylinder block
60R. On the other hand, as best shown in FIG. 3, the rocker arm
mount 64b and the head cover 64c are together affixed to the
cylinder head body 64a by bolts 77 that extend through bolt holes
78. In addition, as shown in FIG. 5 and 9, the rocker arm mount 64b
is further affixed to the cylinder head body 64a by bolts 81.
[0040] With reference to FIGS. 1 and 3-11, each cylinder block 60F,
60R and each cylinder head body 64a in the illustrated embodiment
have a plurality of cooling fins 79 extending generally
horizontally from a side surface thereof. That is, the illustrated
fins 72 extend generally normal to the cylinder axis 66. The heat
of the engine body can be effectively radiated to the ambient air
from the fins 72 particularly while the motorcycle 30 travels.
[0041] With reference to FIGS. 1 and 3, the engine 32 preferably
has an intake system through which the ambient air is introduced
into the combustion chambers 70. The intake system preferably
comprises a carburetor 80, an outer intake passage 82 and an inner
intake passage 84.
[0042] 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 FIG. 7, the inner intake passage 84 in the
illustrated embodiment is bifurcated to define a pair of intake
ports 88 at the combustion chamber 70.
[0043] 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 FIGS.
3 and 7, the air and the fuels are introduced into each combustion
chamber 70 as the air/fuel charge through the intake ports 88 in
the intake stroke of the engine 32.
[0044] 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.
[0045] With reference to FIG. 3, intake valves 92 are reciprocally
disposed on the cylinder head body 64a. Each intake valve 92 is
associated with the respective intake port and the exhaust muffler
114. The exhaust muffler 114 preferably contains a catalytic device
116 therein.
[0046] 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.
[0047] 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
FIGS. 3, 4 and 7, the exhaust gases go out to the inner exhaust
passages 106.
[0048] With reference to FIGS. 3, 5, 8 and 9, each valve actuating
mechanism 96 preferably comprises a camshaft 122 (FIG. 8), a pair
of lifters (or oil tappets) 124, a pair of push rods 126 and a pair
of rocker arm units 128. In the illustrated embodiment, the
camshaft 122 is disposed within the crankcase 62, the rocker arm
units 128 are disposed within the cylinder head assembly 64, and
the lifters 124 and the push rods 126 art disposed on the right
hand side of the engine body. The rocker arm units 128 form a first
portion of the valve actuating mechanism 96. The camshaft 122 forms
a second portion of the valve actuating mechanism 96. The lifters
124 and the push rods 126 form a third portion of the valve
actuating mechanism 96.
[0049] 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 FIG. 8, the
camshaft 122 preferably has a pair of cam surfaces 132 which are
arranged off from each other in a circumferential direction of the
camshaft 122. The cam surfaces 132 can abut on a bottom surface of
the associated lifters 124 and can move the lifters 124 upward at
different moments.
[0050] As best shown in FIGS. 6 and 7, the illustrated engine 32
defines a recessed area 134 on the right hand side of the engine
body. The push rods 126 preferably extend generally vertically
through the recessed area 134. A bottom surface of each push rod
126 abuts on a top surface of the respective lifter 124. The
lifters 124 thus can lift the associated push rods 126 when the cam
surfaces 132 meet the associated lifters 124.
[0051] With reference to FIGS. 3, 5, 8 and 9, each rocker arm unit
128 preferably comprises a tubular section 128a, a pair of drive
arms 128b and a driven arm 128c.
[0052] 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.
[0053] As best shown in FIG. 9, the rocker arm mount 64b preferably
has a pair of support portions 138 to support the respective rocker
arm shafts 136. Preferably, one of the support portions 138 is
separable for easy setting of the rocker arm shaft 136. In the
illustrated embodiment, a top end of the support portion 138 on the
right hand side of the engine 32 is separable. The top end piece
preferably affixed to the rest part of the support portion 138 by
the bolts 81 that couples the rocker arm mount 64b to the cylinder
head body 64a.
[0054] As best shown in FIGS. 5 and 8, the driven arm 128c of each
rocker arm unit 128 extends to a top end of the respective push rod
126. In other words, each top end of the push rod 126 abuts on a
bottom surface of the associated driven arm 128c. On the other
hand, as best shown in FIGS. 3 and 5, the drive arms 128b of each
rocker arm unit 128 extend to respective top ends of the intake
valves 92 or respective top ends of the exhaust valves 118. In
other words, each bottom end of the drive arm 128b abuts on a top
end of the associated intake or exhaust valve 92, 118.
[0055] 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.
[0056] 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 (FIG. 3) that includes a
lubricant tank 144 and a lubrication pump 146. The lubrication pump
146 pressurizes the lubricant to circulate within the engine body
to lubricate portions of the engine body. Flows of the lubricant
are indicated by the arrows FL of FIGS. 5-7, 9 and 11.
Secondary Air Introducing System
[0057] 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.
[0058] With reference to FIGS. 1-6, 8, 9 and 11, the secondary air
introducing system 150 preferably comprises inner passages (or
second intake passages) 152 defined by the respective cylinder head
assemblies 64, outer passages 154 defined by air introducing
conduits or tubes 156 and a airflow regulator 158. In the
illustrated embodiment, the front bank FB and the rear bank RB each
has a set of one inner passage 152 and one outer passage 154. The
respective outer passages 154 preferably are connected with each
other above and between the front and rear banks FB, FR. Because
the respective sets of passages 152, 154 are almost similar to each
other, one set thereof on the rear bank RB can represent both of
the sets in the description below unless otherwise described.
[0059] 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.
[0060] 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.
[0061] 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.
[0062] 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 FIG. 3.
[0063] 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.
[0064] 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.
[0065] 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.
[0066] 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.
[0067] 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
FIGS. 3 and 4. The ambient air is pulled by negative pressure of
the exhaust pulsation in the inner exhaust passage 106. The exhaust
pulsation is generally caused by an interaction between the flow of
exhaust gases in the inner exhaust passage 106 and the movement of
the exhaust valves 118. Because the inner passage 152 opens in the
close vicinity of the exhaust ports 108, the exhaust pulsation
efficiently pulls the air.
[0068] 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.
[0069] 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.
[0070] 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.
[0071] 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.
[0072] 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.
[0073] 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.
[0074] 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.
* * * * *