Information
-
Patent Grant
-
6378495
-
Patent Number
6,378,495
-
Date Filed
Tuesday, January 11, 200024 years ago
-
Date Issued
Tuesday, April 30, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Birch, Stewart, Kolasch & Birch, LLP
-
CPC
-
US Classifications
Field of Search
-
International Classifications
-
Abstract
To provide an engine with a valve resting function for resting at least one of a plurality of intake valves when the engine is in a specific operational region, which is capable of preventing the flow-in of the remaining fuel in a combustion chamber when the rested intake valve is switched to be opened/closed, thereby preventing the reduction in engine output and the increase in unburned hydrocarbon. A communication passage is provided in a cylinder head for enabling a fuel-air mixture to flow from an intake passage corresponding to an intake valve in a resting state to an intake passage corresponding to an intake valve in a resting state, when said engine is in a specific operational region.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an engine with a valve resting function, which is intended to rest at least one of a plurality of intake valves in a specific operational region.
2. Description of Background Art
The engine of this type has been known, for example, from Japanese Patent Publication No. Sho 62-56327.
The above-described related art engine is configured to rest one of a pair of intake valves in a specific operational region for allowing lean combustion by forming a swirl in a combustion chamber, thereby reducing fuel consumption. However, in a state in which one of the intake valves is rested, fuel remains in an intake passage corresponding to the rested intake valves, and consequently, when the operational state in which one of the intake valves is rested is switched into the operational state in which all of the intake valves are opened/closed, the remaining fuel flows in the combustion chamber to temporarily make dense the concentration of the fuel in the combustion chamber. This may reduce the engine output and increase the occurrence of unburned hydrocarbon.
SUMMARY AND OBJECTS OF THE INVENTION
In view of the foregoing, the present invention has been made, and an object of the present invention is to provide an engine with a valve resting function, which is capable of preventing the flow-in of the remaining fuel in a combustion chamber when the rested intake valve is switched to be opened/closed, thereby preventing the reduction in engine output and preventing the increase in unburned hydrocarbon.
To achieve the above object, according to the present invention there is provided an engine with a valve resting function, including a plurality of intake valve ports provided in a cylinder head in such a manner as to face to a combustion chamber. A plurality of intake passages are provided in the cylinder head in such a manner as to be individually connected to the intake valve ports; and a valve system is provided for driving a plurality of intake valves capable of individually opening/closing the intake valve ports, the valve system is configured such that it can rest at least one of the intake valves in a specific operational region. A communication passage for communicating the intake passage corresponding to the intake valve opened/closed even in the specific operational region to the intake passage corresponding to the intake valve rested in the specific operational region is provided in the cylinder head.
With this configuration, when at least one of a plurality of the intake valves is rested in a specific operational region, an air-fuel mixture flows from the intake passage corresponding to the rested intake valve to the intake passage corresponding to the opened/closed intake valve via the communication passage, with a result that it is possible to prevent the fuel from remaining in the intake passage corresponding to the rested intake valve. Accordingly, even if the operational state in which at least one of the intake valves is rested is switched into the operational state in which all of the intake valves are opened/closed, the remaining fuel does not flow in the combustion chamber, to prevent the mixing ratio of the air-fuel mixture flowing in the combustion chamber from being made unstable, thereby preventing the reduction in engine output and preventing the increase in occurrence of unburned hydrocarbon as much as possible.
According to the present invention an intake system including a carburetor common to the intake passages is connected to the intake passages. With this configuration, even if the intake system connected to a plurality of intake passages is configured to have the single carburetor, it is possible to avoid the inconvenience that the mixing ratio is made unstable when the operational state in which part of the intake valves is rested is switched into the operational state in which all of the intake valves are opened/closed. That is to say, it is possible to prevent the fuel from remaining in the intake passage corresponding to the intake valve which is rested due to the configuration of the present invention and hence to prevent the mixing ratio from being made unstable even by using the intake system with a simple structure in which the air-fuel mixture is formed by the carburetor common to respective intake passages.
According to the present invention the communication passage is formed as a hollow portion upon formation of the cylinder head by casting. With this configuration, it is possible to form the communication passage simultaneously with the formation of the cylinder head by casting, and hence to reduce the number of the steps of forming the cylinder head.
According to the present invention the communication passage is formed by cutting, from the combustion chamber side. With this configuration, the communication passage can be simply formed in the cylinder head without use of any special means.
According to the present invention, the communication passage is formed in such a manner as to be tilted toward the combustion chamber in the direction from the intake passage corresponding to the intake valve opened/closed even in the specific operational region to the intake passage corresponding to the intake valve rested in the specific operational region. With this configuration, the opening end of the communication passage to the intake passage corresponding to the intake valve rested in the specific operational region can be disposed at a position being as close to the combustion chamber as possible, so that when the intake valve is rested in the specific operational region, the intake passage corresponding to the rested intake valve can be communicated to the intake passage corresponding to the opened/closed intake valve at the position being as close to the combustion chamber as possible. This makes it possible to make the amount of the remaining fuel in the resting state of the intake valve as small as possible.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
FIG. 1
is a side view of a motorcycle according to a first embodiment;
FIG. 2
is a plan view seen from an arrow
2
of
FIG. 1
;
FIG. 3
is a partial vertical sectional view, taken on line
3
—
3
of
FIG. 5
, of an upper portion of an engine;
FIG. 4
is a transverse sectional view, taken on line
4
—
4
of
FIG. 5
, of the upper portion of the engine;
FIG. 5
is a bottom view, seen from arrows
5
—
5
of
FIG. 3
, of a cylinder head;
FIG. 6
is a partial transverse sectional view of the cylinder head near an intake port;
FIG. 7
is an enlarged vertical sectional view of a valve resting mechanism;
FIG. 8
is a perspective view seen from above a pin holder;
FIG. 9
is a perspective view seen from below the pin holder;
FIG. 10
is a perspective view of a slide pin;
FIG. 11
is a characteristic diagram showing the valve opening lift amounts of intake valves and exhaust valves;
FIG. 12
is a side view, seen from an arrow
12
of
FIG. 5
, of the cylinder head;
FIG. 13
is a sectional view showing a configuration of a hydraulic control valve;
FIG. 14
is a vertical sectional view showing a hydraulic passage of the cylinder block and a crank case; and
FIG. 15
is a sectional view, similar to
FIG. 6
, showing a second embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring first to
FIGS. 1 and 2
, a body frame
21
of this motorcycle includes a pair of right and left main frames
22
each being formed into an approximately U-shape opened upwardly. A head pipe
23
is provided at front ends of the main frames
22
. A connection frame
24
, that is formed into an approximately U-shape opened downwardly, is provided for connecting rear portions of the main frames
22
to each other. A seat stay
25
is connected to rear ends of the main frames
22
and extends rearwardly, obliquely upwardly therefrom. A front fork
26
for supporting a front wheel W
F
, is steerably supported by the head pipe
23
. A steering handle
27
is operatively connected to the front fork
26
. A rear fork
28
for supporting a rear wheel W
R
, is vertically swingably supported by a rear portion of one of the main frames
22
. A pair of cushion units
29
are provided between the seat stay
25
and the rear wheel W
R
.
An engine E is supported by the main frames
22
and the connecting frame
24
. Power from the engine E is transmitted to the rear wheel W
R
, via a transmission assembled in the engine E and a chain transmission
30
.
A fuel tank
31
is mounted on the right and left main frames
22
and the connection frame
24
in such a manner as to be positioned over the engine E. A tandem seat
32
is mounted on the seat stay
25
, and a radiator
33
is disposed in front of the engine E.
Referring additionally to
FIGS. 3 and 4
, the engine E is a multi-cylinder for example, a four-cylinder/four-cycle engine. A plurality (for example, four) of cylinder bores
37
are formed in a cylinder block
36
of the engine E in such a manner as to be arranged along the width direction of the body frame
21
. The cylinder bores
37
are tilted upwardly, forwardly in the running direction of the motorcycle. To be more specific, cylinder liners
38
for forming the cylinder bores
37
are fixed in the cylinder block
36
in such a manner as to be spaced from each other at intervals along the width direction of the body frame
21
. Each cylinder liner
38
is partially inserted in an upper crank case
39
connected to a lower portion of the cylinder block
36
.
A cylinder block
40
is connected to an upper portion of the cylinder block
36
. Recesses
41
that individually correspond to the cylinder bores
37
are provided in a connection plane of the cylinder head
40
to the cylinder block
36
. Combustion chambers
43
including the recesses
41
are formed between the cylinder head
40
and top portions of pistons
42
slidably fitted in the cylinder bores
37
.
Referring additionally to
FIG. 5
, a plurality (for example, a pair) of first and second intake valve ports
44
1
and
44
2
opened to the combustion chamber
43
, and a plurality of (for example, a pair) of first and second exhaust valve ports
45
1
and
45
2
opened to the combustion chamber
43
are provided in the cylinder head
40
. The first intake valve port
44
1
and the first exhaust valve port
45
1
are substantially symmetrically disposed with respect to the center of the combustion chamber
43
, and the second intake valve port
44
2
and the second exhaust valve port
45
2
are substantially symmetrically disposed with respect to the center of the combustion chamber
43
.
Referring additionally to
FIG. 6
, a first intake passage
46
1
connected to the first intake valve port
44
1
a second intake passage
46
2
connected to the second intake valve port
44
2
and an intake port
47
commonly connected to the first and second intake passages
46
1
and
46
2
and opened to one side surface
40
a
of the cylinder head
40
are provided in the cylinder head
40
. The one side surface
40
a
of the cylinder head
40
to which each intake port
47
is opened is disposed on the back side along the running direction of the motorcycle.
A first exhaust passage
48
1
connected to the first exhaust valve port
45
1
a second exhaust passage
48
2
connected to the second exhaust valve port
45
2
and an intake port
49
commonly connected to the first and second exhaust passages
48
1
, and
48
2
and opened to the other side surface
40
b
of the cylinder head
40
are provided in the cylinder head
40
for each combustion chamber
43
. The other side surface
40
b
of the cylinder head
40
to which each exhaust port
49
is opened is disposed on the front side along the running direction of the motorcycle.
An intake system
51
including a carburetor
50
common to the intake ports
47
is connected to the intake ports
47
. An exhaust system
53
including an exhaust muffler
52
is connected to the exhaust ports
49
. The exhaust muffler
52
is disposed on the right side of the rear wheel W
R
in a state being directed forwardly in the running direction of the motorcycle.
Referring to
FIGS. 3 and 4
, the communication and cutoff between the first intake valve port
44
1
and the first intake passage
46
1
is switched from each other by a first intake valve
56
1
and the communication and cutoff between the second intake valve port
44
2
and the second intake passage
46
2
is switched from each other by a second intake valve
56
2
. Meanwhile, the communication and cutoff between the first exhaust valve port
45
1
and the first exhaust passage
48
1
is switched from each other by a first exhaust valve
57
1
as an engine valve, and the communication and cutoff between the second exhaust valve port
45
2
and the second exhaust passage
48
2
is switched from each other by a second exhaust valve
57
2
as an engine valve.
Each of the first and second intake valves
56
1
and
56
2
includes a valve body
58
capable of closing the associated one of the intake valve ports
44
1
and
44
2
and a valve stem
59
having the base end integrally connected to the valve body
58
. Each of the first and second exhaust valves
57
1
and
57
2
includes a valve body
60
capable of closing the associated one of the exhaust valve ports
45
1
and
45
2
and a valve stem
61
having the base end integrally connected to the valve body
60
.
The valve stem
59
of each of the first and second intake valves
56
1
and
56
2
is slidably fitted in a guide cylinder
62
provided in the cylinder head
40
. The valve stem
61
of each of the first and second exhaust valves
57
1
and
57
2
is slidably fitted in a guide cylinder
63
provided in the cylinder head
40
.
A retainer
64
is fixed via split cotters (not shown) to an intermediate point of a portion, projecting upwardly from the guide cylinder
62
, of the valve stem
59
of the first intake valve
56
1
. A coil valve spring
65
1
is provided between the retainer
64
and the cylinder head
40
, whereby the first intake valve
56
1
is biased in the direction of closing the first intake port
44
1
by the valve spring
65
1
. Meanwhile, a retainer
64
is fixed via split cotters (not shown) to the leading end of a portion, projecting upwardly from the guide cylinder
62
, of the valve stem
59
of the second intake valve
56
2
. A coil valve spring
65
2
is provided between the retainer
64
and the cylinder head
40
, whereby the second intake valve
56
2
is biased in the direction of closing the second intake port
44
2
by the valve spring
65
2
.
A retainer
66
is fixed via split cotters (not shown) to an intermediate point of a portion, projecting upwardly from the guide cylinder
63
, of the valve stem
61
of the first exhaust valve
57
1
. A coil valve spring
67
1
is provided between the retainer
66
and the cylinder head
40
, whereby the first exhaust valve
57
1
is biased in the direction of closing the first exhaust port
45
1
by the valve spring
67
1
. Meanwhile, a retainer
66
is fixed via split cotters (not shown) to the leading end of a portion, projecting upwardly from the guide cylinder
63
, of the valve stem
61
of the second exhaust valve
57
2
. A coil valve spring
67
2
is provided between the retainer
66
and the cylinder head
40
, whereby the second exhaust valve
57
2
is biased in the direction of closing the second exhaust port
45
2
by the valve spring
67
2
.
An intake side valve system
68
I for driving the first and second intake valves
56
1
and
56
2
of the combustion chambers
43
includes a cam shaft
70
, bottomed cylindrical valve lifters
71
1
and bottomed cylindrical valve lifters
71
2
. The cam shaft
70
has first intake side valve system cams
69
1
corresponding to the first intake valves
56
1
and the second intake side valve system cams
69
2
corresponding to the second intake valves
56
2
. The valve lifters
71
1
are supported by the cylinder head
40
in such a manner as to be slidably driven by the first intake side valve system cams
69
1
. The valve lifters
71
2
are supported by the cylinder head
40
in such a manner as to be slidably driven by the second intake side valve system cams
69
2
.
The cam shaft
70
has an axial line perpendicular to the extensions of the axial lines of the valve stems
59
of the first and second intake valves
56
1
and
56
2
and is rotatably supported between the cylinder head
40
and a holder
55
connected to the cylinder head
40
. The valve lifters
71
1
are slidably fitted in the cylinder head
40
in such a manner as to be slidably movable in the same axial direction as the axial lines of the valve stems
59
of the first intake valves
56
1
. The outer surface of the closed end of each valve lifter
71
1
is in slide-contact with the associated one of the first intake side valve system cams
69
1
. The valve lifters
71
2
are slidably fitted in the cylinder head
40
in such a manner as to be slidably movable in the same axial direction as the axial lines of the valve stems
59
of the second intake valves
56
2
. The outer surface of the closed end of each valve lifter
71
2
is in slide-contact with the associated one of the second intake side valve system cams
69
2
.
The leading end of the valve stem
59
of the second intake valve
56
2
is in contact with the inner surface of the closed end of the valve lifter
71
2
via a shim
72
. The second intake valve
56
2
is, during the operation of the engine E, usually operated to be opened/closed by the second intake side valve system cam
69
2
. On the other hand, a valve resting mechanism
73
I is provided between the valve stem
59
of the first intake valve
56
1
and the valve lifter
71
1
. The valve resting mechanism
73
I can switch an acting state and a non-acting state of a pressing force applied from the valve lifter
71
1
to the first intake valve
56
1
in the valve opening direction. To be more specific, in a specific operational region, typically, a low speed operational region of the engine E, the valve resting mechanism
73
I creates the non-acting state of the pressing force, thereby turning the first intake valve
56
1
into the resting state irrespective of the sliding motion of the valve lifter
71
1
.
Referring to
FIG. 7
, the valve resting mechanism
73
includes a pin holder
74
slidably fitted in the valve lifter
71
1
. A slide pin
76
is slidably fitted in the pin holder
74
in such a manner as to form a hydraulic chamber
75
between the inner surface of the valve lifter
71
1
and the slide pin
76
. A return spring
77
is provided between the slide pin
76
and the pin holder
74
, for biasing the slide pin
76
in the direction of reducing the volume of the hydraulic chamber
75
. A stopper pin
78
, functioning as a rotation stopping means, is provided between the pin holder
74
and the slide pin
76
, for stopping the rotation of the slide pin
76
around its axial line.
Referring additionally to
FIGS. 8 and 9
, the pin holder
74
includes a ring portion
74
a
slidably fitted in the valve lifter
71
1
and a bridging portion
74
b
, integrated with the ring portion
74
a
, for connecting the opposed inner peripheral portions of the ring portion
74
a
along one diameter line of the ring portion
74
a.
The inner periphery of the ring portion
74
a
and both the side surface portions of the bridging portion
74
b
are partially cut off to reduce the weight. The pin holder
74
is made from a steel or an aluminum alloy by lost-wax casting or forging, or made from a synthetic resin. The outer peripheral surface of the metal made pin holder
74
, that is, the outer peripheral surface of the metal made ring portion
74
a
and the inner peripheral surface of the valve lifter
71
, are subjected to carbonization.
An annular groove
79
is formed in the outer peripheral portion of the pin holder
74
, that is, the outer peripheral portion of the ring portion
74
a.
A bottomed sliding hole
80
is provided in the bridging portion
74
b
of the pin holder
74
. The sliding hole
80
has an axial line along one diameter line of the ring portion
74
a,
that is, an axial line perpendicular to the axial line of the valve lifter
71
1
. One end of the sliding hole
80
is opened to the annular groove
79
and the other end thereof is closed. An insertion hole
81
for allowing the leading end of the valve stem
59
of the first intake valve
56
1
to pass therethrough is formed at the center of a lower portion of the bridging portion
74
b
in such a manner as to be opened to the sliding hole
80
. An extension hole
82
for containing the leading end of the valve stem
59
of the first intake valve
56
1
is provided at the center of an upper portion of the bridging portion
74
b
in such a manner as to be coaxial with the insertion hole
81
with the sliding hole
80
put between the insertion hole
81
and the extension hole
82
.
A containing cylinder portion
83
coaxial with the axial line of the extension hole
82
is integrally formed on a portion, facing to the closed end of the valve lifter
71
1
of the bridging portion
74
b
of the pin holder
74
. A disk-like shim
84
for blocking the end of the extension hole
82
on the closed side of the valve lifter
71
1
is partially fitted in the containing cylinder portion
83
. A projecting portion
85
to be in contact with the shim
84
is integrally formed at a central portion on the inner surface of the closed end of the valve lifter
71
1
.
The slide pin
76
is slidably fitted in the sliding hole
80
of the pin holder
74
. If the pin holder
74
is made from a synthetic resin, only the slide-contact portion of the pin holder
74
with the slide pin
76
may be made from a metal.
The hydraulic chamber
75
communicated to the annular groove
79
is formed between one end of the slide pin
76
and the inner surface of the valve lifter
71
1
. The return spring
77
is contained in a spring chamber
86
formed between the other end of the slide pin
76
and the closed end of the sliding hole
80
.
Referring additionally to
FIG. 10
, a containing hole
87
, which can be coaxially communicated to the insertion hole
81
and the extension hole
82
and also can contain the leading end of the valve stem
59
, is provided at the intermediate portion in the axial direction of the slide pin
76
. The end of the containing hole
87
on the insertion hole
81
side is opened to a flat contact plane
88
formed on the outer surface of the lower portion of the slide pin
76
in such a manner as to face to the insertion hole
82
. To be more specific, the contact plane
88
is relatively longer along the axial line direction of the slide pin
76
, and the containing hole
87
is opened in the contact plane
88
at a position offset to the spring chamber
86
side.
Such a slide pin
76
is slid in the axial direction in such a manner that hydraulic pressure of the hydraulic chamber
75
acting to one end of the slide pin
76
is balanced against a spring force of the return spring
77
acting to the other end side of the slide pin
76
. In the non-acting state in which the hydraulic pressure of the hydraulic chamber
75
is low, the slide pin
76
is moved to the right in
FIG. 7
for containing the leading end of the valve stem
59
inserted in the insertion hole
81
in the containing hole
87
and the extension hole
82
. In the acting state in which the hydraulic pressure of the hydraulic chamber
75
is high, the slide pin
76
is moved leftward in
FIG. 7
for offsetting the containing hole
87
from the axial lines of the insertion hole
81
and the extension hole
82
thereby bringing the leading end of the valve stem
59
into contact with the contact plane
88
.
When the slide pin
76
is moved to the position at which the containing hole
87
is coaxial with the insertion hole
81
and the extension hole
82
, the first intake valve
56
, remains at rest. To be more specific, at this time, the pin holder
74
and the slide pin
76
&are moved on the first intake valve
56
1
side along with the sliding motion of the valve lifter
71
1
by the pressing force acting from the first intake side valve system cam
69
1
. However, only the leading end of the valve stem
59
is contained in the containing hole
87
and the extension hole
82
, and the pressing force is not applied from the valve lifter
71
1
and the pin holder
74
to the first intake valve
56
1
in the valve opening direction. When the slide pin
76
is moved to the position at which the leading end of the valve stem
59
is in contact with the contact plane
88
, the first intake valve
56
1
is operated to be opened/closed. To be more specific, at this time, the pin holder
74
and the slide pin
76
are moved toward the first intake valve
56
1
side along with the sliding motion of the valve lifter
71
1
by the pressing force acting from the first intake side valve system cam
69
1
, so that the pressing force is applied to the first intake valve
56
1
in the valve opening direction. In this way, the first intake valve
56
1
is operated to be opened/closed in accordance with the rotation of the first intake side valve system cam
69
1
.
If the slide pin
76
is rotated around its axial line in the pin holder
74
, the axial line of the containing hole
87
is offset from those of the insertion hole
81
and the extension hole
82
so that the leading end of the valve stem
59
cannot be brought into contact with the contact plane
88
. To cope with such an inconvenience, the stopper pin
78
is provided for stopping the rotation of the slide pin
76
around its axial line.
The stopper pin
78
is mounted in mounting holes
89
and
90
which are coaxially provided in the bridging portion
74
b
of the pin holder
74
in such a manner as to put part of the sliding hole
80
on its one end side therebetween. The stopper pin
78
passes through a slit
91
which is provided on the one end side of the slide pin
76
in such a manner as to be opened to the hydraulic chamber
75
side. To be more specific, the stopper pin
78
is mounted in the pin holder
74
in a state in which it passes through the slide pin
76
while permitting the axial movement of the slide pin
76
. Accordingly, the stopper pin
78
is brought into contact with the inner closed end of the slit
91
, so that the movement end of the slide pin
76
toward the hydraulic chamber
75
side is restricted.
A coil spring
92
is provided for biasing the pin holder
74
on the side on which the shim
84
mounted on the pin holder
74
is in contact with the projecting portion
85
provided at the central portion on the inner surface of the closed end of the valve lifter
71
1
. To be more specific, the coil spring
92
is disposed between the pin holder
74
and the cylinder head
40
in such a manner as to surround the valve stem
59
at a position where the outer periphery of the coil spring
92
is not brought into contact with the inner surface of the valve lifter
71
1
. A pair of projections
93
and
94
are integrally provided on the bridging portion
74
b
of the pin holder
74
. The projections
93
and
94
function to position the end of the coil spring
92
in the direction perpendicular to the axial line of the valve stem
59
.
Each of the projections
93
and
94
, formed into a circular-arc centered at the axial line of the valve stem
59
, projects from the pin holder
74
by an amount less than the diameter of the coil spring
92
.
The projection
93
has a stepped portion
95
which is brought into contact with the end portion, on the first intake valve
56
1
side, of the stopper pin
78
, thereby preventing the movement of the stopper pin
78
on the first intake valve
56
1
side.
To prevent a change in pressure in the spring chamber
86
by the axial movement of the slide pin
76
, the slide pin
76
has a communication hole
96
through which the spring chamber
86
is communicated to the containing hole
87
. Meanwhile, to prevent a change in pressure of a space between the pin holder
74
and the valve lifter
71
1
due to temperature change, the pin holder
74
has a communication hole
97
through which the space is communicated to the spring chamber
86
.
The cylinder head
40
has a supporting hole
98
for slidably supporting the valve lifter
71
1
and an annular recess
99
is provided in the supporting hole
98
in such a manner as to surround the valve lifter
71
1
. The valve lifter
71
1
has a communication hole
100
through which the annular recess
99
is communicated to the annular groove
79
formed in the pin holder
74
irrespective of the sliding motion of the valve lifter
71
1
in the supporting hole
98
, and also has a release hole
101
. The release hole
101
is provided in the valve lifter
71
1
at such a position as to allow, when the valve lifter
71
1
is moved at the uppermost position in
FIG. 71
1
communication between the annular recess
99
to the inside of the valve lifter
71
1
through the lower portion of the release hole
101
positioned under the pin holder
74
but to block, as the valve lifter
71
1
is moved downwardly from the uppermost position in
FIG. 7
, the communication between the annular recess
88
and the inside of the valve lifter
71
1
. Lubricating oil is jetted in the valve lifter
71
1
through the release hole
101
.
The cylinder head
40
also has working oil feed passages
103
communicated to the annular recesses
99
of the combustion chambers
43
.
An exhaust side valve system
68
E for driving the first and second exhaust valves
57
1
and
57
2
of the combustion chambers
43
includes a cam shaft
106
, bottomed cylindrical valve lifters
107
1
and bottomed cylindrical valve lifters
107
2
. The can shaft
106
has first exhaust side valve system cams
105
1
corresponding to the first exhaust valves
57
1
and the second exhaust side valve system cams
105
2
corresponding to the second exhaust valves
57
2
. The valve lifters
107
1
are supported by the cylinder head
40
in such a manner as to be slidably driven by the first exhaust side valve system cams
105
1
. The valve lifters
107
2
are supported by the cylinder head
40
in such a manner as to be slidably driven by the second exhaust side valve system cams
105
2
.
The cam shaft
106
has an axial line perpendicular to the extensions of the axial lines of the valve stems
61
of the first and second exhaust valves
57
1
and
57
2
and is rotatably supported between the cylinder head
40
and the holder
55
connected to the cylinder head
40
like the cam shaft
70
of the intake side valve system
68
I. The valve lifters
107
1
are slidably fitted in the cylinder head
40
in such a manner as to be slidably movable in the same axial direction as the axial lines of the valve stems
61
of the first exhaust valves
57
1
. The outer surface of the closed end of each valve lifter
107
1
is in slide-contact with the associated one of the first exhaust side valve system cams
105
1
. The valve lifters
107
2
are slidably fitted in the cylinder head
40
in such a manner as to be slidably movable in the same axial direction as the axial lines of the valve stems
61
of the second exhaust valves
57
2
. The outer surface of the closed end of each valve lifter
107
2
is in slide-contact with the associated one of the second exhaust side valve system cams
105
2
.
The leading end of the valve stem
61
of the second exhaust valve
57
2
is in contact with the inner surface of the closed end of the valve lifter
107
2
via a shim
108
. The second exhaust valve
57
2
is, during operation of the engine E, usually operated to be opened/closed by the second exhaust side valve system cam
105
2
. On the other hand, a valve resting mechanism
73
E is provided between the valve stem
61
of the first exhaust valve
57
1
and the valve lifter
107
1
. The valve resting mechanism
73
E can switch an acting state and a non-acting state of a pressing force applied from the valve lifter
107
1
to the first exhaust valve
57
1
in the valve opening direction. To be more specific, in a specific operational region, typically, a low speed operational region of the engine E, the valve resting mechanism
73
E creates the non-acting state of the pressing force, thereby turning the first exhaust valve
57
1
into the resting state irrespective of the sliding motion of the valve lifter
107
1
. The valve resting mechanism
73
E has the same configuration as that of the valve resting mechanism
73
I of the intake side valve system
68
I.
In the non-acting state of the valve resting mechanism
73
I and
73
E, that is, in the state in which the first intake valve
56
1
and the first exhaust valve
57
1
are operated to be opened/closed, as shown by broken curves in
FIG. 11
, the first intake side valve system cam
69
1
and the first exhaust side valve system can
105
1
are operated in such a manner that the total opening angle is made relatively large and the angle at which the opening state of the first intake valve
56
1
is overlapped to that of the first exhaust valve
57
1
is made relatively large. However, as shown by solid curves in
FIG. 11
, the second intake side valve system cam
69
2
and the second exhaust side valve system cam
105
2
are operated in such a manner that the total opening angle is made relatively small and the angle at which the opening state of the second intake valve
56
2
is overlapped to that of the second exhaust valve
57
2
is made relatively small.
In accordance with such intake side and exhaust side valve systems
68
I and
68
E, in a low speed operational region as a specific operational region of the engine E, the first intake valve
56
1
and the first exhaust valve
57
1
are rested and only the second intake valve
56
2
and the second exhaust valve
57
2
are operated to be opened/closed. At this time, since the angle at which the opening state of the second intake valve
56
2
is overlapped to that of the second exhaust valve
57
2
is relatively small, the rear compression ratio in the combustion chamber
43
can be improved, and since swirl occurs by flow-in of the fuel-air mixture in the combustion chamber
43
only through the second intake passage
46
2
the fuel consumption can be reduced and the output torque is increased. In a high speed operational region, since the valve resting mechanisms
73
I and
73
E are turned into the acting state, not only the second intake valves
56
2
and the second exhaust valves
57
2
are usually operated to be opened/closed but also the first intake valve
56
1
and the first exhaust valve
57
1
are operated to be opened/closed, with a result that the output in the high speed operational region can be enhanced. Accordingly, in a wide operational region from a low speed operational region to a high speed operational region, it is possible to enhance the output and to reduce the fuel consumption.
As described above, in a low speed operational region of the engine E, the first intake valve
56
, is rested, and in such a state, fuel remains in the intake passage corresponding to the intake valve
56
1
, that is, the first intake passage
46
1
. When the operation for the low speed operational region is switched to the operation for a high speed operational region in which the intake valves
56
1
and
56
2
are operated to be opened/closed, the fuel thus remaining in the first intake passage
46
1
flows in the combustion chamber
43
, and thereby the concentration of the fuel in the combustion chamber
43
becomes temporarily dense. This may reduce the output of the engine E and cause an occurrence of unburned hydrocarbon.
To cope with such an inconvenience, as shown in
FIG. 6
, a communication passage
109
, which communicates the second intake passage
46
2
corresponding to the second intake valve
56
2
usually opened/closed upon operation of the engine E to the first intake passage
46
1
corresponding to the first intake valve
56
1
rested in a specific operation region upon the operation of the engine E, is formed in the cylinder head
40
. In the resting state of the first intake valve
56
1
the fuel-air mixture in the first intake passage
46
1
flows in the second intake passage
46
2
through the communication passage
109
as shown by an arrow
110
in FIG.
6
.
The communication passage
109
is formed in the cylinder head
40
obtained by casting, by cutting from the combustion chamber
43
side, in such a manner as to be tilted toward the combustion chamber
43
in the direction from the second intake passage
46
2
to the first intake passage
46
1
. The opening end of the communication passage
109
for communicating the first intake passage
46
1
to the second intake passage
46
2
is disposed at a position being as close to the combustion chamber
43
as possible.
Referring to
FIG. 5
, a containing hole
112
is provided in the cylinder head
40
at a position between the adjacent two, on the central side along the arrangement direction, of the four cylinder bores
37
. The cylinder head
40
is partitioned by the containing hole
112
into first and second head portions
40
1
and
40
2
.
A means such as a chain drive means for driving the cam shafts
70
and
106
of the intake side and exhaust side valve systems
68
I and
68
E is contained in the containing hole
112
.
Referring additionally to
FIG. 12
, a hydraulic control valve
113
is mounted on the one side surface
40
a
of the cylinder head
40
to which the intake ports
47
are opened at a position between a pair of the intake ports
47
disposed on the first head
40
1
side. The hydraulic control valve
113
is used for controlling a hydraulic pressure of working oil fed to the valve resting mechanism
431
and
43
E of the intake side and exhaust side valve systems
68
I and
68
E.
Referring to
FIG. 13
, the hydraulic control valve
113
is mounted on the one side surface
40
a
of the cylinder head
40
for switching the on/off of the communication between the opening end of a working oil intake passage
114
to the one side surface
40
a
of the cylinder head
40
and the opening end of a first working oil discharge passage
115
, to the one side surface
40
a
of the cylinder head
40
. The hydraulic control valve
113
includes an inlet
116
communicated to the working oil intake passage
114
, an outlet
117
communicated to the first working oil discharge passage
115
1
and a spool valve body
119
slidably fitted in a housing
118
mounted on the side surface
40
a
of the cylinder head
40
.
The housing
118
has a cylinder hole
121
with its upper end blocked by a cap
120
. The spool valve body
119
is slidably fitted in the cylinder hole
121
in such a manner as to form a hydraulic chamber
122
between the cap
120
and the spool valve body
119
. A spring chamber
123
is formed between the lower portion of the housing
118
and the spool valve body
119
. A spring
124
for biasing the spool valve body
119
upwardly, that is, in the closing direction is contained in the spring chamber
123
. The spool valve body
119
has an annular recess
125
for allowing communication between the inlet
116
and the outlet
117
. When the spool valve body
119
is moved upwardly as shown in
FIG. 13
, it blocks the communication between the inlet
116
and the outlet
117
.
In a state in which the housing
118
is mounted on the one side surface
40
a
of the cylinder head
40
, an oil filter
126
is held between the inlet
116
and the working oil intake passage
114
. The housing
118
also has an orifice hole
127
for communicating the inlet
116
to the outlet
117
. Accordingly, even in a state in which the spool valve body
119
is located at the closing position, the inlet
116
is communicated to the outlet
117
through the orifice hole
127
, so that a hydraulic pressure restricted by the orifice hole
127
is fed from the outlet
117
into the first working oil discharge passage
115
1
.
The housing
118
also has a bypass port
128
which is communicated to the outlet
117
through the annular recess
125
only in the state in which the spool valve body
119
is located at the closing position. The bypass port
128
is communicated to the upper inside portion of the cylinder head
40
.
The housing
118
also has a passage
129
usually communicated to the inlet
116
. The passage
129
is connected via a solenoid valve
130
to a connection hole
131
which is formed in the cap
120
in such a manner as to be communicated to the hydraulic chamber
122
. When the solenoid valve
130
is opened, a hydraulic pressure is fed into the hydraulic chamber
122
, and the spool valve body
119
is driven to be opened by the hydraulic pressure thus introduced into the hydraulic chamber
122
.
The housing
118
also has a leak jet
132
communicated to the hydraulic chamber
122
. The leak jet
132
is also communicated to the upper inside portion of the cylinder head
40
. When the solenoid valve
130
is closed, the hydraulic pressure remaining in the hydraulic chamber
122
is released through the leak jet
132
.
Referring to
FIG. 14
, a lower crank case
136
constituting part of a mission case
135
is connected to a lower portion of the upper crank case
39
. A crank shaft
137
is rotatably supported between both the crank cases
39
and
136
.
An oil pan
138
is connected to a lower portion of the lower crank case
136
. An oil pump
139
for pumping up working oil remaining in the oil pan
138
is contained in the mission case
135
. A projecting portion
135
a,
which projects upwardly from the upper crank case
39
, is provided on the mission case
135
. A starter motor
140
having a rotational axial line parallel to the crank shaft
137
is mounted on the projecting portion
135
a
at a position over the upper crank case
39
.
The working oil intake passage
114
for introducing working oil from the oil pump
135
to the hydraulic control valve
113
is provided in the cylinder head
40
, the cylinder block
36
, the upper crank case
39
, and the lower crank case
136
.
The working oil intake passage
114
includes a connection port
114
a
connected to the inlet
116
of the hydraulic control valve
113
and opened to the one side surface
40
a
of the cylinder head
40
. A first passage
114
b
is provided in the cylinder head
40
in such a manner as to be connected to the connection port
114
a
and extends in a straight line along the one side surface
40
a.
A second passage
114
c
is provided in the cylinder block
36
in such a manner as to be coaxially connected to the first passage
114
b.
A third passage
114
d
is provided in the lower crank case
39
in such a manner as to be coaxially connected to the second passage
114
c
and to extend in straight line. A fourth passage
114
e
is provided in the lower crank case
136
in such a manner as to be connected to the lower end of the third passage
114
d
and to extend in the vertical direction. A fifth passage
114
f
is provided in the lower crank case
136
in such a manner as to be connected to the lower end of the fourth passage
114
e
and to extend substantially in the horizontal direction. A sixth passage
114
g
is provided in the lower crank case
136
in such a manner as to extend substantially in parallel to the fifth passage
114
f.
A filter
141
interposed between the fifth and sixth passages
114
f
and
114
g
is mounted in the lower crank case
136
, and the sixth passage
114
g
is connected to a discharge port of the oil pump
139
.
The working oil intake passage
114
for introducing working oil from the oil pump
139
to the hydraulic control valve
113
is provided in the cylinder head
40
, the cylinder block
36
, the upper crank case
39
, and the lower crank case
136
.
A water jacket
145
is provided in the cylinder block
36
and the cylinder head
40
. The first passage
114
b
and the second passage
114
c,
corresponding to the cylinder block
36
and the cylinder head
40
, of the working oil intake passage
114
are disposed outside the waterjacket
145
.
Referring to
FIGS. 5 and 12
, the first head portion
40
1
of the cylinder head
40
has a first working oil discharge passage
115
1
for feeding working oil to the valve resting mechanisms
73
I and
73
E for each of the combustion chambers
43
disposed on the first head portion
40
1
side, and the second head portion
40
2
has a second working oil discharge passage
115
2
for feeding working oil to the valve resting mechanisms
73
I and
73
E for each of the combustion chambers
43
on the second head portion
40
2
side. The working oil feed passages
103
provided in the cylinder head
40
for the valve resting mechanisms
73
I and
73
E (see
FIG. 7
) are branched from the first and second working oil discharge passages
115
1
and
115
2
.
A mounting seat
146
is mounted on the one side surface
40
a
of the cylinder head
40
in such a manner as to cross between the first and second head portions
40
1
and
40
2
. The first and second working oil discharge passages
115
1
and
115
2
are provided in the cylinder head
40
in such a manner that one end thereof is commonly opened to the mounting seat
146
and the other end thereof is closed at a position near the containing hole
112
.
A cover
147
is fastened to the mounting seat
146
, and the working oil discharge passage
115
1
and
115
2
are communicated to each other via the cover
147
.
Next, the function of the first embodiment will be described. The communication passage
109
for communicating the second intake passage
46
2
corresponding to the second intake valve
56
2
opened/closed even in a specific operational region to the first intake passage
46
1
corresponding to the first intake valve
56
1
rested in the specific operational region is provided in the cylinder head
40
. Accordingly, when the first intake valve
56
1
is rested, a fuel-air mixture flows from the first intake passage
46
1
corresponding to the rested first intake valve
56
1
to the second intake passage
46
2
corresponding to the opened/closed second intake valve
56
2
via the communication passage
109
, so that it is possible to prevent the fuel from remaining in the first intake passage
46
1
in the resting state of the first intake valve
56
1
as much as possible. As a result, when the operation for the above specific operational region is switched to the operation for an operational region in which the intake valves
56
1
and
56
2
are both opened/closed, it is possible to eliminate the inconvenience that the remaining fuel flows in the combustion chamber
43
. This makes it possible to prevent the mixing ratio of the fuel-air mixture flows in the combustion chamber
43
from being made unstable, and hence to prevent the reduction in engine output and the occurrence of unburned hydrocarbon as much as possible.
Since the phenomenon in which the fuel remains in the first intake passage
46
1
in the resting state of the first intake valve
56
1
can be prevented as described above, even if the intake system
51
is simply configured to have the carburetor
50
common to the intake passages
46
1
and
46
2
it is possible to avoid the inconvenience that the mixing ratio of the fuel-air mixture flowing in the combustion chamber
43
is made unstable when the operation for the specific operational region in which the first intake valve
56
1
that is in a rest position is switched to the operation for the operational region in which the intake valves
56
1
and
56
2
are both opened/closed.
The communication passage
109
can be simply formed in the cylinder head
40
, having been obtained by casting, by cutting from the combustion chamber
43
side. Since the communication passage
109
is tilted toward the combustion chamber
43
in the direction from the second intake passage
46
2
to the first intake passage
46
1
the opening end of the communication passage
109
for communicating the first intake passage
46
1
that is rested in a specific operational region to the second intake passage
46
2
can be disposed at a position being as close to the combustion chamber
43
as possible. As a result, when the first intake valve
56
1
is rested in the specific operational region, the first intake passage
46
2
corresponding to the rested first intake valve
56
1
can be communicated to the second intake passage
46
2
at a position being as close to the combustion chamber
43
as possible, so that the remaining amount of fuel in the resting state of the first intake valve
56
1
can be made as small as possible.
The hydraulic control valve
113
for controlling the hydraulic pressure of working oil to the hydraulic valve resting mechanism
73
I and
73
E for resting the first intake valve
56
1
and the first exhaust valve
57
1
in a specific operational region are mounted on the side surface
40
a
of the cylinder head
40
to which a plurality of the intake ports
47
provided in the cylinder head
40
are opened. To be more specific, the hydraulic control valve
113
is mounted on the side surface
40
a
of the cylinder head
40
in the direction perpendicular to the arrangement direction of the cylinder bores
37
, that is, in the forward or rearward direction (in the rearward direction in this embodiment) of the body frame
21
. As a result, it is possible to avoid an inconvenience that the length of the multi-cylinder engine E extending along the arrangement direction of the cylinder bores
37
becomes large due to the mounting of the hydraulic control valve
113
to the cylinder head
40
. That is to say, in the motorcycle in which the engine E is mounted on the body frame
21
with the arrangement direction of the cylinder bores
37
set in the width direction of the body frame
21
, the length of the multi-cylinder engine E extending along the width direction of the body frame
21
can be made as small as possible.
Since the hydraulic control valve
113
is mounted on the side surface
40
a
of the cylinder head
40
at a position between the adjacent two of the intake ports
47
by making effective use of a space therebetween, it is possible to decrease the length of the multi-cylinder engine E along the width direction of the body frame
21
.
Since the working oil intake passage
114
for introducing working oil from the oil pump
139
to the hydraulic control valve
113
is provided in the cylinder head
40
, the cylinder block
36
, and the crank cases
39
and
136
, it is possible to eliminate the necessity of the provision of an additional pipe line for introducing the working oil from the oil pump
139
to the hydraulic control valve
113
, and hence to simplify the appearance of the multi-cylinder engine E.
Since the water jacket
145
is provided in the cylinder block
36
and the cylinder head
40
and the two parts, corresponding to the cylinder block
36
and the cylinder head
40
, of the working oil intake passage
114
are disposed outside the water jacket
145
, it is possible to effectively cool the working oil flowing in the working oil intake passage
114
.
The working oil intake passage
114
has at least the first passage
114
b
provided in the cylinder head
40
in such a manner as to extend in straight line along the side surface
40
a
between the one side surface
40
a
of the cylinder head
40
and the water jacket
145
. A second passage
114
c
is provided in the cylinder block
36
in such a manner as to be coaxial with the first passage
114
b.
A third passage
114
d
is provided in the upper crank case
39
in such a manner as to be coaxial with the second passage
114
c
and extend in straight line therefrom. As a result, it is possible to make the working oil passage from the oil pump
139
to the hydraulic control valve
113
as short as possible, and hence to make a loss in hydraulic pressure in the working oil intake passage
114
as small as possible.
The containing hole
112
, which contains the means for driving the cam shafts
70
and
106
, is provided in the cylinder head
40
at a position between the adjacent two, on the central side along the arrangement direction, of the four cylinder bores
37
. The cylinder head
40
is partitioned by the containing hole
112
into the first and second head portions
40
1
and
40
2
. As a result, it is possible to desirably keep the balance between the cylinder heads
40
along the arrangement direction of the cylinder bores
37
, and thereby the balance of the multi-cylinder engine E as a whole.
The first working oil discharge passage
115
1
for supplying working oil to the valve resting mechanism
73
I and
73
E for each of the combustion chambers
43
on the first head portion
40
1
side is provided in the first head portion
40
1
in such a manner as to be connected to the hydraulic control valve
113
mounted on the side surface
40
a
of the cylinder head
40
between a pair of the intake ports
47
disposed on the first head portion
40
1
side. The second working oil discharge passage
115
2
is provided for supplying working oil to the valve resting mechanism
73
I and
73
E for each of the combustion chambers
43
on the second head portion
40
2
side is provided in the second head portion
40
2
. The one-ends of the first and second working oil discharge passages
115
1
and
115
2
are opened to the mounting seat
146
which is formed on the side surface
40
a
of the cylinder head
40
in such a manner as to cross between the first and second head portions
40
1
and
40
2
. The first and second working oil discharge passages
115
1
and
115
2
are communicated to each other via the cover
147
fastened to the mounting seat
146
. Accordingly, the first and second working oil discharge passages
115
1
and
115
2
provided in the cylinder head
40
on both of the sides of the containing hole
112
can be simply communicated to each other, and thereby working oil discharged from the single hydraulic control valve
113
can be effectively supplied to the valve resting mechanism
73
I and
73
E for each of the combustion chambers
43
.
In the valve resting mechanism
73
I (or
73
E), the pin holder
74
is slidably fitted in the valve lifter
71
1
(or
107
1
) driven by the valve system cam
59
1
(or
105
1
). The slide pin
76
slidably fitted in the pin holder
74
is slidable between the position at which the leading end of the valve stem
59
(or
61
) is contained in the containing hole
87
and the position at which the leading end of the valve stem
59
(or
61
) is in contact with the contact plane
88
as the outer side surface of the slide pin
76
in accordance with the balance between the hydraulic force and the spring force applied to both the ends of the slide pin
76
. As a result, by controlling the hydraulic force applied to one end of the slide pin
76
, it is possible to switch the resting state and the opening/closing state of the first intake valve
56
1
(or the first exhaust valve
57
1
) from each other.
Since the rotation of the slide pin
76
around its axial line in the pin holder
74
is prevented only by the simple configuration in which the stopper pin
78
is mounted in the pin holder
74
, the valve resting mechanism
73
I (or
73
E) can be easily assembled with the stem
59
(or
61
) of the first intake valve
56
1
(or the first exhaust valve
57
1
) by mounting the valve lifter
71
1
(or
107
1
) to the cylinder head
40
in the state that the pin holder
74
in which the slide pin
76
has been fitted is fitted in the valve lifter
71
1
(or
107
1
).
The pin holder
74
has the insertion hole
81
into which the leading end of the stem
59
(or
61
) of the first intake valve
56
1
(or the first exhaust valve
57
1
) can be inserted, and also has the extension hole
82
, disposed coaxially with the insertion hole
81
, for containing the leading end of the valve stem
59
(or
61
). The sliding hole
80
in which the slide pin
76
is slidably fitted is put between the insertion hole
81
and the extension hole
82
. Accordingly, since in the resting state of the first intake valve
56
1
(or the first exhaust valve
57
1
), the leading end of the valve stem
59
(or
61
) is contained not only in the containing hole
87
but also in the extension hole
82
, the length of the containing hole
87
, that is, the diameter of the slide pin
76
can be made small. This makes it possible to miniaturize the pin holder
74
and hence to the miniaturize the entire valve resting mechanism
73
I (or
73
E).
The shim
84
for blocking the end portion of the extension hole
82
on the closed end side of the valve lifter
71
1
(or
107
1
) is mounted on the pin holder
74
in such a manner that it can be brought into contact with the closed end of the valve lifter
71
1
(
107
1
). To be more specific, it is required to block the end portion of the extension hole on the closed end side of the valve lifter for applying a pressing force from the valve lifter
71
1
(or
107
1
) to the pin holder
74
, and in this embodiment, the end portion of the extension hole
82
is blocked with the shim
84
which is brought into contact with the closed end of the valve lifter
71
1
(or
107
1
). Accordingly, it is possible to simplify the structure of the pin holder
74
, and to suitably adjust a gap at the valve head of the first intake valve
56
1
(or first exhaust valve
57
1
) by changing the thickness of the shim
84
.
The containing cylinder portion
83
coaxial with the axial line of the extension hole
82
is integrally formed on the pin holder
74
at a position facing to the closed end of the valve lifter
71
1
(or
107
1
), and the disk-like shim
84
is partially fitted in the containing cylinder portion
83
. As a result, it is possible to simply mount the relatively small shim
84
on the pin holder
74
.
The projecting portion
85
to be in contact with the shim
84
is integrally formed on the inner surface of the closed end of the valve lifter
71
1
(or
107
1
), and accordingly, the sliding motion of the valve lifter
71
1
(or
107
1
) with respect to the cylinder head
40
can be certainly performed along the axial line of the valve stem
59
(or
61
) in such a manner that the pressing force is applied from the valve lifter
71
1
(or
107
1
) to the pin holder
74
on the extension of the axial line of the valve stem
59
(or
61
) of the first intake valve
56
1
(or the first exhaust valve
57
1
). As a result, the sliding motion of the valve lifter
71
1
(or
107
1
) can be smoothened.
The coil spring
92
for biasing the pin holder
74
toward the closed end side of the valve lifter
71
1
(or
107
1
) is provided between the pin holder
74
and the cylinder head
40
. To be more specific, the coil spring
92
is disposed in such a manner as to surround the valve stem
59
(or
61
) at a position at which the outer periphery of the coil spring
92
is not in contact with the inner surface of the valve lifter
71
1
(or
107
1
). The projections
93
and
94
for positioning the end portion of the coil spring
92
in the direction perpendicular to the axial line of the valve stem
59
(or
61
) are provided on the pin holder
74
. As a result, it is possible to allow the spring force of the coil spring
92
to be certainly applied along the axial line of the valve stem
59
(or
61
), and to prevent the occurrence of frictional loss due to slide-contact of the outer periphery of the coil spring
92
with the valve lifter
71
1
(or
107
1
).
Since the projecting amount of each of the projections
93
and
94
is less than the diameter of the coil spring
92
, even if the coil spring
92
is contracted, it is not in slide-contact with the pin holder
74
. As a result, it is possible to prevent the occurrence of the frictional loss due to the slide-contact of the coil spring
92
with the pin holder
74
.
FIG. 15
shows a second embodiment of the present invention. As shown in
FIG. 15
, a communication passage
149
for communicating a first intake passage
46
1
corresponding to a first intake valve
56
1
rested in a specific operational region of the engine E to a second intake passage
46
2
corresponding to a second intake valve
56
2
opened/closed in the specific operational region is formed as a hollow portion upon the formation of the cylinder head
40
by casting.
According to the second embodiment, the communication passage
149
can be formed upon the formation of the cylinder head
40
by casting. As a result, it is possible to more easily form the communication passage
149
while reducing the number of the steps of forming the cylinder head
40
, and to increase the degree of freedom in shape and the arrangement position of the communication passage
149
.
While the embodiments of the present invention have been described in detail, the present invention is not limited thereto, and it is to be understood that many changes in design may be made without departing from the scope of the claims.
As described above, according to the present invention, it is possible to prevent the fuel from remaining in the intake passage corresponding to the rested intake valve, and hence to prevent the remaining fuel from flowing in the combustion chamber when the operational state in which part of the intake valves is rested is switched into the operational state in which all of the intake valves are opened/closed. As a result, it is possible to prevent the mixing ratio of the air-fuel mixture flowing in the combustion chamber from being made unstable, and hence to prevent the reduction in engine output and the increase in occurrence of unburned hydrocarbon as much as possible.
According to the present invention, even if the intake system connected to a plurality of intake passages is configured to have a single carburetor, it is possible to avoid the inconvenience that the mixing ratio is made unstable when the operational state in which part of the intake valves is rested is switched into the operational state in which all of the intake valves are opened/closed.
According to the present invention, it is possible to form the communication passage simultaneously with the formation of the cylinder head by casting, and hence to reduce the number of the steps of forming the cylinder head.
According to the present invention, the communication passage can be simply formed in the cylinder head without use of any special means.
According to the present invention, the opening end of the communication passage to the intake passage corresponding to the intake valve is positioned in the specific operational region can be disposed at a position being as close to the combustion chamber as possible, so that when the intake valve is positioned in the specific operational region, the intake passage corresponding to the position of the intake valve can be communicated to the intake passage corresponding to the opened/closed intake valve at the position being as close to the combustion chamber as possible. This makes it possible to make the amount of the remaining fuel in the resting state of the intake valve as small as possible.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
Claims
- 1. An engine with a valve resting function, comprising:a plurality of intake valve ports provided in a cylinder head in communication with a combustion chamber; a plurality of intake passages provided in said cylinder head to be individually connected to said intake valve ports, wherein a substantially equal portion of a fuel-air mixture is directed towards each of said intake valve ports; a plurality of intake valves operatively mounted relative to respective intake valve ports; and a valve system for driving intake valves and being capable of individually opening/closing said intake valve ports, said valve system also being capable of putting at least one of said intake valves into a resting state when said engine is in a specific operational region; wherein a communication passage is provided in said cylinder head for enabling a fuel-air mixture to flow from said intake passage corresponding to at least one of said intake valves in a resting state to said intake passage corresponding to said intake valve in an acting state, when said engine is in said specific operational region.
- 2. The engine with a valve resting function according to claim 1, wherein an intake system including a carburetor common to said intake passages is connected to said intake passages.
- 3. The engine with a valve resting function according to claim 1, wherein said communication passage is formed as a hollow portion upon formation of said cylinder head by casting.
- 4. The engine with a valve resting function according to claim 2, wherein said communication passage is formed as a hollow portion upon formation of said cylinder head by casting.
- 5. The engine with a valve resting function according to claim 1, wherein said communication passage is formed by cutting, from the combustion chamber side.
- 6. The engine with a valve resting function according to claim 2, wherein said communication passage is formed by cutting, from the combustion chamber side.
- 7. The engine with a valve resting function according to claim 5, wherein said communication passage is formed to be tilted toward said combustion chamber in the direction from said intake passage corresponding to said intake valve in said acting state to said intake passage corresponding to said intake valve capable of being put into said resting state when said engine is in said specific operational region.
- 8. An engine with a valve resting function, comprising:a cylinder head including a combustion chamber being formed therein; a plurality of intake valve ports provided in said cylinder head and being in communication with said combustion chamber; a plurality of intake passages provided in said cylinder head to be individually connected to said intake valve ports, wherein a substantially equal portion of a fuel-air mixture is directed towards each of said intake valve ports; a plurality of intake valves operatively mounted relative to respective intake valve ports; and a valve operator for imparting movement to said intake valves and being capable of individually opening/closing said intake valve ports, said valve system also being capable of putting at least one of said intake valves into a resting state when said engine is in a specific operational region; wherein a communication passage is provided in said cylinder head for enabling a fuel-air mixture to flow from said intake passage corresponding to at least one of said intake valves in a resting state to said intake passage corresponding to said intake valve in an acting state, when said engine is in said specific operational region.
- 9. The engine with a valve resting function according to claim 8, wherein an intake system including a carburetor common to said intake passages is connected to said intake passages.
- 10. The engine with a valve resting function according to claim 8, wherein said communication passage is formed as a hollow portion upon formation of said cylinder head by casting.
- 11. The engine with a valve resting function according to claim 9, wherein said communication passage is formed as a hollow portion upon formation of said cylinder head by casting.
- 12. The engine with a valve resting function according to claim 8, wherein said communication passage is formed by cutting, from the combustion chamber side.
- 13. The engine with a valve resting function according to claim 9, wherein said communication passage is formed by cutting, from the combustion chamber side.
- 14. The engine with a valve resting function according to claim 11, wherein said communication passage is formed to be tilted toward said combustion chamber in the direction from said intake passage corresponding to said intake valve in said acting state to said intake passage corresponding to said intake valve capable of being put into said resting state when said engine is in said specific operational region.
Priority Claims (1)
Number |
Date |
Country |
Kind |
11-004628 |
Jan 1999 |
JP |
|
Foreign Referenced Citations (1)
Number |
Date |
Country |
B2 6256327 |
Nov 1987 |
JP |