U.S. patent application number 09/848238 was filed with the patent office on 2001-09-06 for valve system for an engine.
This patent application is currently assigned to HONDA GIKEN KOGYO KABUSHIKI KAISHA. Invention is credited to Ichimura, Takashi, Kumagai, Yoshihiko, Tsukui, Takaaki.
Application Number | 20010018902 09/848238 |
Document ID | / |
Family ID | 11589352 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010018902 |
Kind Code |
A1 |
Tsukui, Takaaki ; et
al. |
September 6, 2001 |
Valve system for an engine
Abstract
A valve system for an engine including a valve resting mechanism
provided between an engine valve and a valve lifter supported by a
cylinder head. The valve resting mechanism can place the engine
valve into a resting state. The valve resting mechanism has a pin
holder which includes a sliding hole having an axis perpendicular
to the axis of a valve lifter, and an insertion hole for allowing a
valve stem to pass therethrough. The pin holder is slidably fitted
in the valve lifter. A slide pin is slidably fitted in the sliding
hole, with a hydraulic force and a spring force applied to both
ends of the slide pin. A containing hole is coaxially connectable
to the insertion hole, and a rotation stopping means for stopping
axial rotation of the slide pin is provided between the pin holder
and the slide pin.
Inventors: |
Tsukui, Takaaki; (Saitama,
JP) ; Ichimura, Takashi; (Saitama, JP) ;
Kumagai, Yoshihiko; (Saitama, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
HONDA GIKEN KOGYO KABUSHIKI
KAISHA
|
Family ID: |
11589352 |
Appl. No.: |
09/848238 |
Filed: |
May 4, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09848238 |
May 4, 2001 |
|
|
|
09480650 |
Jan 11, 2000 |
|
|
|
Current U.S.
Class: |
123/90.5 ;
123/90.27 |
Current CPC
Class: |
F01L 1/205 20130101;
F01L 1/143 20130101; F01L 13/0005 20130101; F01L 1/26 20130101;
F01L 2001/0537 20130101 |
Class at
Publication: |
123/90.5 ;
123/90.27 |
International
Class: |
F01L 001/02; F01L
001/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 11, 1999 |
JP |
HEI-11-004630 |
Claims
What is claimed is:
1. A valve system for an engine comprising: an engine valve having
an intake valve and an exhaust valve, each said intake and exhaust
valve having a valve body capable of closing one of an intake and
an exhaust port, the intake and exhaust ports being provided in a
cylinder head and opening to a combustion chamber; valve stems, one
stem being connected to each valve body; a valve lifter supported
in and axially slidable within said cylinder head; and a valve
resting mechanism disposed between the valve stems associated with
the valve and the valve lifter; wherein the valve resting mechanism
enables an acting state and a non-acting state of a pressing force
applied from the valve lifter to the valve in the valve opening
direction, the valve resting mechanism including: a pin holder
slidably fitted in said valve lifter, the pin holder having an
essentially cylindrical shape with an end abutting the valve lifter
opposite to a point wherein the valve lifter abuts a valve system
cam, and an axis substantially perpendicular to an axis of the
valve lifter, wherein a sliding hole is formed in the pin holder
and has an axis substantially perpendicular to the axis of the pin
holder, and an insertion hole opens in an inner surface of the
sliding hole so as to allow the valve stem associated with the
exhaust valve to be slidably inserted therethrough; a slide pin
slidably disposed in the valve lifter and having one end facing to
a hydraulic chamber, the slide pin having a containing hole
coaxially connected to said insertion hole; a return spring for
biasing the slide pin in the direction of reducing the volume of
the hydraulic chamber; and a rotation stopping member, the rotation
stopping member being provided between the pin holder and the slide
pin and being capable of stopping rotation of said slide pin about
its axis.
2. The valve system of claim 1, wherein said engine valve is
supported in said cylinder head and is biased in the direction of
closing said intake port and said exhaust port.
3. The valve system of claim 1, wherein when the engine is in a low
speed operational region, the valve resting mechanism enables the
non-acting state of the pressing force from the valve lifter,
thereby placing the exhaust valve into a resting state irrespective
of a sliding motion of the valve lifter.
4. The valve system of claim 1, wherein the slide pin is fitted in
said sliding hole and slidable between a position wherein said
containing hole is coaxially aligned to said insertion hole, for
allowing a leading end of said valve stem associated with the
exhaust valve to be contained in said containing hole at a position
wherein the leading end of said valve stem associated with the
exhaust valve is brought into contact with an outer side surface of
said slide pin.
5. The valve system of claim 4, wherein said rotation stopping
member is a stopper pin mounted in said pin holder so as to pass
through said slide pin while permitting movement of said slide
pin.
6. The valve system of claim 5, wherein said pin holder further
includes: an extension hole capable of containing the leading end
of said valve stem associated with the exhaust valve, said
extension hole being coaxial with said insertion hole, and said
sliding hole being disposed between said insertion hole and said
extension hole; and a shim for blocking an end portion of said
extension hole on a closed end side of said valve lifter, the shim
being mounted on said pin holder so as be engageable with the
closed end of the valve lifter.
7. The valve system of claim 6, wherein a containing cylinder
portion is coaxial with the axis of said extension hole and is
provided on said pin holder at a position facing to the closed end
of said valve lifter, wherein said shim has a disk shape and is
partially fitted in said containing cylinder portion.
8. The valve system of claim 7, wherein a projecting portion is
provided on the inner surface of the closed end of said valve
lifter and is engageable with said shim.
9. The valve system of claim 8, wherein: a coil spring for biasing
said pin holder toward the closed end of said valve lifter is
provided between said pin holder and said cylinder head so as to
surround said valve stem at a position wherein the outer periphery
of said coil spring is not in contact with an inner surface of said
valve lifter; and positioning portions for positioning an end
portion of said coil spring in a direction substantially
perpendicular to the axis of said valve stem associated with the
exhaust valve are provided on said pin holder.
10. The valve system of claim 9, wherein said positioning portions
are projections integrally formed with said pin holder, a
projecting amount of each of said projections being less than a
diameter of said coil spring.
11. The valve system of claim 9, wherein said positioning portions
are grooves provided in said pin holder, the depth of each of said
grooves being less than the diameter of said coil spring.
12. The valve system of claim 1, further comprising a second engine
valve having an intake valve and an exhaust valve, each of said
second intake and exhaust valves having a valve body capable of
closing one of a second intake and a second exhaust port, the
second intake and exhaust ports being provided in said cylinder
head and opening to said combustion chamber.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a valve system for an
engine, including a valve resting mechanism provided between an
engine valve and a valve lifter supported by a cylinder head so as
to be slidably driven by a valve system cam. The valve resting
mechanism is capable of switching an acting state and a non-acting
state of a pressing force applied from the valve lifter to the
engine valve in the valve opening direction and turning, in the
non-acting state of the pressing force, the engine valve into the
resting state irrespective of the sliding motion of the valve
lifter.
[0003] 2. Related Art
[0004] A valve system of this type has been known, for example,
from Japanese Utility Model Publication No. Hei 3-7526. In a valve
resting mechanism of the valve system disclosed in this document, a
slide pin having a containing hole capable of containing the
leading end of a valve stem of an engine valve is directly fitted
in a valve lifter supported in a cylinder head so as to be slidably
driven by a valve system cam. The rotation of the slide pin around
its axis is prevented by fitting the leading end of the valve stem
in a groove formed in a pin holder.
[0005] The above valve resting mechanism, however, has a
disadvantage: The rotation stop of the slide pin is achieved in a
state in which the valve resting mechanism is assembled in the
valve stem of the engine valve. In other words, the rotation stop
of the slide pin with respect to the valve lifter is not achieved
in the step of assembling the valve resting mechanism. As a result,
it is difficult to align the groove of the pin holder with the
leading end of the valve stem upon assembly of the valve lifter in
the cylinder head. This complicates the step of assembling the
valve resting mechanism.
[0006] In view of the foregoing, an object of the present invention
is to provide a valve system for an engine valve which facilitates
the work of assembling a valve resting mechanism.
SUMMARY OF THE INVENTION
[0007] To achieve the above object, there is provided a valve
system for an engine including an engine valve including a valve
body capable of opening/closing a valve port provided in a cylinder
head so as to be opened to a combustion chamber, and a valve stem
whose base end is integrated with the valve body, the engine valve
being openably/closably supported in the cylinder head so as to be
spring-biased in the direction of closing the valve port. A valve
lifter is supported in the cylinder head so as to be slidable in
the same axial direction as the axis of the valve stem. A valve
resting mechanism is provided between the valve lifter and the
engine valve, the valve resting mechanism being capable of
switching an acting state and a non-acting state of a pressing
force applied from the valve lifter to the engine valve in the
valve opening direction and turning, in the non-acting state of the
pressing force, the engine valve into the resting state
irrespective of the sliding motion of the valve lifter.
[0008] In this valve system, the valve resting mechanism includes a
pin holder slidably fitted in the valve lifter formed into a
bottomed cylinder shape with its end on the valve system cam
closed. The pin holder has a sliding hole having an axis
perpendicular to the axis of the valve lifter, and an insertion
hole opened in the inner surface of the sliding hole so as to allow
the valve stem to be movably inserted therethrough in the axial
direction. A slide pin is slidably fitted in the sliding hole with
its one end facing to an hydraulic chamber, the slide pin having a
containing hole coaxially connectable to the insertion hole. A
return spring is included for biasing the slide pin in the
direction of reducing the volume of the hydraulic chamber. A
rotation stopping means is provided between the pin holder and the
slide pin for stopping the rotation of the slide pin around its
axis. The slide pin is fitted in the sliding hole so as to be
slidable between a position wherein the containing hole is
coaxially aligned to the insertion hole for allowing the leading
end of the valve stem to be contained in the containing hole, and a
position wherein the leading end of the valve stem is brought into
contact with the outer side surface of the slide pin.
[0009] With this configuration, when the slide pin is moved to the
position wherein the containing hole is coaxially aligned to the
insertion hole of the pin holder, the pin holder and the slide pin
are moved, together with the valve lift, to the engine valve side
due to the sliding motion of the valve lifter by a pressing force
applied from the valve system cam. However, only the leading end of
the valve stem inserted in the insertion hole is contained in the
containing hole and the pressing force in the valve opening
direction is not applied from the valve lifter and the pin holder
to the engine valve. The result is that the engine valve remains
rested.
[0010] When the slide pin is moved to the position wherein the
outer side surface is brought into contact with the leading end of
the valve stem, the pressing force in the valve opening direction
is applied to the engine valve along with the movement of the pin
holder and the slide pin toward the engine valve due to the sliding
motion of the valve lifter by the pressing force applied from the
valve system cam. The result is that the engine valve is operated
to be opened/closed in accordance with the rotation of the valve
system cam. Also, since the rotation of the slide pin around its
axis in the pin holder is prevented by the rotation stopping means,
the valve resting mechanism can be easily assembled to the valve
stem by mounting the valve lifter to the cylinder head in a state
that the pin holder in which the slide pin has been fitted is
fitted in the valve lifter.
[0011] The rotation stopping means can be a stopper pin mounted in
the pin holder so as to pass through the slide pin, while
permitting the movement of the slide pin in the axial direction.
With this configuration, the rotation stopping means can be
simplified.
[0012] The pin holder can have an extension hole capable of
containing the leading end of the valve stem, the extension hole
being coaxial with the insertion hole with the sliding hole put
between the insertion hole and the extension hole. A shim for
blocking an end portion of the extension hole on the closed end
side of the valve lifter can be mounted on the pin holder so as to
be allowed to be brought into contact with the closed end of the
valve lifter.
[0013] Because the leading end of the valve stem is contained not
only in the containing hole but also in the extension hole in the
valve resting state, it is possible to reduce the length of the
containing hole, that is, the diameter of the slide pin, and hence
to miniaturize the pin holder and further miniaturize the valve
resting mechanism as a whole. Further, 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 to
the pin holder, and according to this invention, the end portion of
the extension hole is blocked with the shim brought into contact
with the closed end of the valve lifter Accordingly, it is possible
to simplify the structure of the pin holder, and to suitably adjust
a gap at the valve head of the engine valve by changing the
thickness of the shim.
[0014] A containing cylinder portion coaxial with the axis of the
extension hole can be integrally provided on the pin holder at a
position facing to the closed end of the valve lifter, and the shim
formed into a disk shape is partially fitted in the containing
cylinder portion. With this configuration, it is possible to simply
mount a relatively small shim on the pin holder.
[0015] A projecting portion to be in contact with the shim is
integrally provided on the inner surface of the closed end of the
valve lifter. With this configuration, the sliding motion of the
valve lifter with respect to the cylinder head can be reliably
performed along the axis of the valve stem so that the pressing
force is applied from the valve lifter to the pin holder on the
extension of the axis of the valve stem of the engine valve. As a
result, the sliding motion of the valve lifter can be
smoothened.
[0016] A coil spring for biasing the pin holder toward the closed
end of the valve lifter can be provided between the pin holder and
the cylinder head so as to surround the valve stem at a position
wherein the outer periphery of the coil spring is not in contact
with the inner surface of the valve lifter; and positioning
portions for positioning an end portion of the coil spring in the
direction perpendicular to the axis of the valve stem are provided
on the pin holder. With this configuration, it is possible to
reliably apply the spring force of the coil spring along the axis
of the valve stem, and to prevent the occurrence of a frictional
loss due to the slide-contact of the outer periphery of the coil
spring with the valve lifter.
[0017] Positioning portions are projections integrally provided on
the pin holder, and the projecting amount of each of the
projections is less than the diameter of the coil spring. The
positioning portions can be grooves provided in the pin holder, the
depth of each of the grooves being less than the diameter of the
coil spring. Even if the coil spring is contracted, it is not in
slide-contact with the pin holder. As a result, it is possible to
prevent the occurrence of the frictional loss due to the
slide-contact of the coil spring with the pin holder.
[0018] 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
[0019] 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.
[0020] FIG. 1 is a side view of a motorcycle according to a first
embodiment of the invention;
[0021] FIG. 2 is a plan view seen from arrow 2 of FIG. 1;
[0022] FIG. 3 is partial vertical sectional view, taken on line 3-3
of FIG. 5;
[0023] FIG. 4 is a transverse sectional view, taken on line 4-4 of
FIG. 5;
[0024] FIG. 5 is a bottom view, seen from arrows 5-5 of FIG. 3, of
a cylinder head;
[0025] FIG. 6 is a partial transverse sectional view of the
cylinder head near an intake port;
[0026] FIG. 7 is an enlarged vertical sectional view of a valve
resting mechanism;
[0027] FIG. 8 is a perspective view, seen from above, of a pin
holder;
[0028] FIG. 9 is a perspective view, seen from below, of the pin
holder;
[0029] FIG. 10 is a perspective view of a slide pin;
[0030] FIG. 11 is a plot of the valve opening lift amounts of
intake valves and exhaust valves,
[0031] FIG. 12 is a side view, seen from an arrow 12 of FIG. 5, of
the cylinder head;
[0032] FIG. 13 is a sectional view showing a configuration of a
hydraulic control valve;
[0033] FIG. 14 is a vertical sectional view showing a hydraulic
passage of the cylinder block and a crank case; and
[0034] FIG. 15 is a sectional view, similar to FIG. 7, showing a
second embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] Referring first to FIGS. 1 and 2, a body frame 21 of a
motorcycle according to the present invention 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, and a connection frame 24,
formed into an approximately U-shape opens downwardly, 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 WF is steerably supported by the head
pipe 23, and a steering handle 27 is connected to the front fork 26
A rear fork 28 for supporting a rear wheel WR is vertically
pivotably supported by a rear portion of one of the main frames 22,
and a pair of cushion units 29 are provided between the seat stay
25 and the rear wheel WR.
[0036] An engine E is supported by the main frames 22 and the
connecting frame 24, and power is transmitted to the rear wheel WR
via a transmission assembled in the engine E and a chain
transmission 30.
[0037] A fuel tank 31 is mounted on the right and left main frames
22 and the connection frame 24 so 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.
[0038] Referring to FIGS. 3 and 4, the engine E is a multi-cylinder
(for example, 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 so as to be arranged along the width direction
of the body frame 21. The cylinder bores 37 are tilted upwardly and
forwardly. To be more specific, cylinder liners 38 for forming the
cylinder bores 37 are fixed in the cylinder block 36 so 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.
[0039] A cylinder block 40 is connected to an upper portion of the
cylinder block 36. Recesses 41 individually corresponding 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.
[0040] Referring to FIG. 5, a plurality (for example, a pair) of
first and second intake valve ports 44.sub.1 and 44.sub.2 open to
the combustion chamber 43, and a plurality of (for example, a pair)
of first and second exhaust valve ports 45.sub.1, and 45.sub.2 open
to the combustion chamber 43. The intake and exhaust ports are
provided in the cylinder head 40. The first intake valve port
44.sub.1, and the first exhaust valve port 45.sub.1, are
substantially symmetrically disposed with respect to the center of
the combustion chamber 43, and the second intake valve port
44.sub.2 and the second exhaust valve port 45.sub.2 are
substantially symmetrically disposed with respect to the center of
the combustion chamber 43.
[0041] Referring to FIG. 6, a first intake passage 46.sub.1,
connected to the first intake valve port 44.sub.1, a second intake
passage 46.sub.2 connected to the second intake valve port
44.sub.2, and an intake port 47 commonly connected to the first and
second intake passages 46.sub.1 and 46.sub.2 and opened to one side
surface 40a of the cylinder head 40 are provided in the cylinder
head 40. The one side surface 40a of cylinder head 40, to which
each intake port 47 opens, is disposed on the back of the
motorcycle.
[0042] A first exhaust passage 48.sub.1 connected to the first
exhaust valve port 45.sub.1, a second exhaust passage 48.sub.2
connected to the second exhaust valve port 45.sub.2, and an intake
port 49 commonly connected to the first and second exhaust passages
48.sub.1 and 48.sub.2 are opened to the other side surface 40b of
the cylinder head 40. The exhaust passages and the intake port are
provided in the cylinder head 40 for each combustion chamber 43.
The other side surface 40b of the cylinder head 40 to which each
exhaust port 49 is opened is disposed on the front side of the
motorcycle.
[0043] 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 and forward of the rear wheel WR.
[0044] Referring to FIGS. 3 and 4, the communication and cutoff
between the first intake valve port 44.sub.1 and the first intake
passage 46.sub.1 is switched by a first intake valve 56.sub.1, as
an engine valve. The communication and cutoff between the second
intake valve port 44.sub.2 and the second intake passage 46.sub.2
is switched by a second intake valve 56.sub.2, as an engine valve.
Meanwhile, the communication and cutoff between the first exhaust
valve port 45.sub.1 and the first exhaust passage 48.sub.1 is
switched by a first exhaust valve 57.sub.1, as an engine valve. The
communication and cutoff between the second exhaust valve port
45.sub.2 and the second exhaust passage 48.sub.2 is switched by a
second exhaust valve 57.sub.2, as an engine valve.
[0045] Each of the first and second intake valves 56.sub.1 and
56.sub.2 includes a valve body 58 capable of closing the associated
one of the intake valve ports 44.sub.1 and 44.sub.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.sub.1 and
57.sub.2 includes a valve body 60 capable of closing the associated
one of the exhaust valve ports 45.sub.1 and 45.sub.2, and a valve
stem 61 having the base end integrally connected to the valve body
60.
[0046] The valve stem 59 of each of the first and second intake
valves 56.sub.1 and 56.sub.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.sub.1 and 57.sub.2 is
slidably fitted in a guide cylinder 63 provided in the cylinder
head 40.
[0047] 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.sub.1. A coil valve spring 65.sub.1 is provided between the
retainer 64 and the cylinder head 40, whereby the first intake
valve 56.sub.1 is biased in the direction of closing the first
intake port 44.sub.1 by the valve spring 65.sub.1.
[0048] 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.sub.2. A coil valve spring 65.sub.2 is provided between the
retainer 64 and the cylinder head 40, whereby the second intake
valve 56.sub.2 is biased in the direction of closing the second
intake port 44.sub.2 by the valve spring 65.sub.2.
[0049] 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.sub.1. A coil valve spring 67.sub.1 is provided between the
retainer 66 and the cylinder head 40, whereby the first exhaust
valve 57.sub.1 is biased in the direction of closing the first
exhaust port 45.sub.1 by the valve spring 67.sub.1.
[0050] 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.sub.2. A coil valve spring 67.sub.1 is provided between the
retainer 66 and the cylinder head 40, whereby the second exhaust
valve 57.sub.2 is biased in the direction of closing the second
exhaust port 45.sub.2 by the valve spring 67.sub.2.
[0051] An intake side valve system 68I for driving the first and
second intake valves 56, and 56.sub.2 of the combustion chambers 43
includes a cam shaft 70, bottomed cylindrical valve lifters
71.sub.1, and bottomed cylindrical valve lifters 71.sub.2. The cam
shaft 70 has first intake side valve system cams 69.sub.1
corresponding to the first intake valves 56.sub.1 and the second
intake side valve system cams 69.sub.2 corresponding to the second
intake valves 56.sub.2. The valve lifters 71.sub.1 are supported by
the cylinder head 40 so as to be slidably driven by the first
intake side valve system cams 69.sub.1. The valve lifters 71.sub.2
are supported by the cylinder head 40 so as to be slidably driven
by the second intake side valve system cams 69.sub.2.
[0052] The cam shaft 70 has an axis perpendicular to the extensions
of the axes of the valve stems 59 of the first and second intake
valves 56.sub.1 and 56.sub.2, and is rotatably supported between
the cylinder head 40 and a holder 55 connected to the cylinder head
40 The valve lifters 71.sub.1 are slidably fitted in the cylinder
head 40 so as to be slidably movable in the same axial direction as
the axes of the valve stems 59 of the first intake valves 56.sub.1.
The outer surface of the closed end of each valve lifter 71.sub.1
is in slide-contact with the associated one of the first intake
side valve system cams 69.sub.1. The valve lifters 71.sub.2 are
slidably fitted in the cylinder head 40 so as to be slidably
movable in the same axial direction as the axes of the valve stems
59 of the second intake valves 56.sub.2. The outer surface of the
closed end of each valve lifter 71.sub.2 is in slide-contact with
the associated one of the second intake side valve system cams
69.sub.2.
[0053] The leading end of the valve stem 59 of the second intake
valve 56.sub.2 is in contact with the inner surface of the closed
end of the valve lifter 71.sub.2 via a shim 72. The second intake
valve 56.sub.2 is, during operation of the engine E, usually
operated to be opened/closed by the second intake side valve system
cam 69.sub.2.
[0054] A valve resting mechanism 73I is provided between the valve
stem 59 of the first intake valve 56.sub.1 and the valve lifter
71.sub.1. The valve resting mechanism 73I can switch an acting
state and a non-acting state of a pressing force applied from the
valve lifter 71.sub.1 to the first intake valve 56.sub.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 73I creates the
non-acting state of the pressing force, thereby turning the first
intake valve 56.sub.1 into the resting state irrespective of the
sliding motion of the valve lifter 71.sub.1.
[0055] Referring to FIG. 7, the valve resting mechanism 73I
includes a pin holder 74 slidably fitted in the valve lifter
71.sub.1; a slide pin 76 slidably fitted in the pin holder 74 so as
to form a hydraulic chamber 75 between the inner surface of the
valve lifter 71.sub.1 and the slide pin 76; a return spring 77,
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; and a stopper pin 78 functioning as a
rotation stopping means, provided between the pin holder 74 and the
slide pin 76, for stopping the rotation of the slide pin 76 around
its axis.
[0056] Referring to FIGS. 8 and 9, the pin holder 74 includes a
ring portion 74a slidably fitted in the valve lifter 71.sub.1; and
a bridging portion 74b, integrated with the ring portion 74a, for
connecting, the opposed inner peripheral portions of the ring
portion 74a along one diameter line of the ring portion 74a. The
inner periphery of the ring portion 74a and both the side surface
portions of the bridging portion 74b 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 74a and the inner peripheral surface of the valve
lifter 71.sub.1 are subjected to carburization.
[0057] 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 74a. A bottomed sliding hole 80 is provided in
the bridging portion 74b of the pin holder 74. The sliding hole 80
has an axis along one diameter line of the ring portion 74a, that
is, an axis perpendicular to the axis of the valve lifter
71.sub.1.
[0058] 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.sub.1 to pass therethrough is formed at the center
of a lower portion of the bridging portion 74b so 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.sub.1
is provided at the center of an upper portion of the bridging
portion 74b so 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.
[0059] A containing cylinder portion 83 coaxial with the axis of
the extension hole 82 is integrally formed on a portion, facing to
the closed end of the valve lifter 71.sub.1, of the bridging
portion 74b 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.sub.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.sub.1.
[0060] 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.
[0061] 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.sub.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.
[0062] Referring to FIG. 10, a containing hole 87, which can be
coaxially communicated to the insertion hole 81 and the extension
hole 82 and can also contain the leading end of the valve stem 59,
is provided at the intermediate axial portion 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 so as to face to the
insertion hole 82. To be more specific, the contact plane 88 is
relatively longer along the axis 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.
[0063] Such a slide pin 76 is slid in the axial direction so that a
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 rightward 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 axes 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.
[0064] When the slide pin 76 is moved to the position wherein the
containing hole 87 is coaxial with the insertion hole 81 and the
extension hole 82, the first intake valve 56.sub.1 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.sub.1 side along with
the sliding motion of the valve lifter 71.sub.1 by the pressing
force acting from the first intake side valve system cam 69.sub.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.sub.1 and the pin
holder 74 to the first intake valve 56.sub.1 in the valve opening
direction.
[0065] When the slide pin 76 is moved to the position wherein the
leading end of the valve stem 59 is in contact with the contact
plane 88, the first intake valve 56.sub.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.sub.1 side along with the sliding motion of the valve lifter
71.sub.1 by the pressing force acting from the first intake side
valve system cam 69.sub.1, so that the pressing force is applied to
the first intake valve 56.sub.1 in the valve opening direction. In
this way, the first intake valve 56.sub.1 is operated to be
opened/closed in accordance with the rotation of the first intake
side valve system cam 69.sub.1.
[0066] If the slide pin 76 is rotated around its axis in the pin
holder 74, the axis 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 axis.
[0067] The stopper pin 78 is mounted in mounting holes 89 and 90
which are coaxially provided in the bridging portion 74b of the pin
holder 74 so as to put part of the sliding hole 80 on its one end
side therebetween. The stopper pin 78 passes through a slit 91
provided on the one end side of the slide pin 76 so 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 of the slide pin 76 toward the hydraulic chamber 75 side
is restricted.
[0068] 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.sub.1. To be more specific, the coil spring 92 is disposed
between the pin holder 74 and the cylinder head 40 so 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.sub.1. A pair of projections 93 and
94 are integrally provided on the bridging portion 74b of the pin
holder 74 The projections 93 and 94 function as positioning
portions for positioning the end of the coil spring 92 in the
direction perpendicular to the axis of the valve stem 59.
[0069] Each of the projections 93 and 94 are formed into a
circular-arc centered at the axis of the valve stem 59. They
project from the pin holder 74 by an amount less than the diameter
of the coil spring 92.
[0070] The projection 93 has a stepped portion 95 brought into
contact with the end portion, on the first intake valve 56.sub.1
side, of the stopper pin 78, thereby preventing the movement of the
stopper pin 78 on the first intake valve 56.sub.1 side.
[0071] 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.sub.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.
[0072] The cylinder head 40 has a supporting hole 98 for slidably
supporting the valve lifter 71.sub.1, and an annular recess 99 is
provided in the supporting hole 98 so as to surround the valve
lifter 71.sub.1. The valve lifter 71.sub.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.sub.1 in the supporting hole
98, and also has a release hole 101.
[0073] The release hole 101 is provided in the valve lifter
71.sub.1 so as to allow, when the valve lifter 71.sub.1 is moved at
the uppermost position in FIG. 7, communication between the annular
recess 99 to the inside of the valve lifter 71.sub.1 through the
lower portion of the release hole 101 positioned under the pin
holder 74. The release hole blocks communication between the
annular recess 88 and the inside of the valve lifter 71.sub.1 as
the valve lifter 71.sub.1 is moved downwardly from the uppermost
position in FIG. 7.
[0074] The cylinder head 40 also has working oil feed passages 103
communicated to the annular recesses 99 of the combustion chambers
43.
[0075] An exhaust side valve system 68E for driving the first and
second exhaust valves 57.sub.1 and 57.sub.2 of the combustion
chambers 43 includes a cam shaft 106, bottomed cylindrical valve
lifters 107.sub.1, and bottomed cylindrical valve lifters
107.sub.2. The cam shaft 106 has first exhaust side valve system
cams 105.sub.1 corresponding to the first exhaust valves 57.sub.1
and the second exhaust side valve system cams 105.sub.2
corresponding to the second exhaust valves 57.sub.2. The valve
lifters 107.sub.1 are supported by the cylinder head 40 so as to be
slidably driven by the first exhaust side valve system cams
105.sub.1.
[0076] The valve lifters 107.sub.2 are supported by the cylinder
head 40 so as to be slidably driven by the second exhaust side
valve system cams 105.sub.2.
[0077] The cam shaft 106 has an axis perpendicular to the
extensions of the axes of the valve stems 61 of the first and
second exhaust valves 57.sub.1 and 57.sub.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 68I. The valve lifters 107.sub.1 are slidably fitted
in the cylinder head 40 so as to be slidably movable in the same
axial direction as the axes of the valve stems 61 of the first
exhaust valves 57.sub.1. The outer surface of the closed end of
each valve lifter 107.sub.1 is in slide-contact with the associated
one of the first exhaust side valve system cams 105.sub.1. The
valve lifters 107.sub.2 are slidably fitted in the cylinder head 40
so as to be slidably movable in the same axial direction as the
axes of the valve stems 61 of the second exhaust valves 57.sub.2.
The outer surface of the closed end of each valve lifter 107.sub.2
is in slide-contact with the associated one of the second exhaust
side valve system cams 105.sub.2.
[0078] The leading end of the valve stem 61 of the second exhaust
valve 57.sub.2 is in contact with the inner surface of the closed
end of the valve lifter 107.sub.2 via a shim 108. The second
exhaust valve 57.sub.2 is, during operation of the engine E,
usually operated to be opened/closed by the second exhaust side
valve system cam 105.sub.2. A valve resting mechanism 73E is
provided between the valve stem 61 of the first exhaust valve
57.sub.1 and the valve lifter 107.sub.1. The valve resting
mechanism 73E can switch an acting state and a non-acting state of
a pressing force applied from the valve lifter 107.sub.1 to the
first exhaust valve 57.sub.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 73E creates the non-acting state of the pressing force,
thereby turning the first exhaust valve 57.sub.1 into the resting
state irrespective of the sliding motion of the valve lifter
107.sub.1. The valve resting mechanism 73E has the same
configuration as that of the valve resting mechanism 73I of the
intake side valve system 68I.
[0079] In the non-acting state of the valve resting mechanism 73I
and 73E, that is, in the state in which the first intake valve
56.sub.1 and the first exhaust valve 57.sub.1 are operated to be
opened/closed, as shown by broken curves in FIG. 11, the first
intake side valve system cam 69.sub.1 and the first exhaust side
valve system cam 105.sub.1 are operated so that the total opening
angle is made relatively large and the angle wherein the opening
state of the first intake valve 56.sub.1 is overlapped to that of
the first exhaust valve 57.sub.1 is made relatively large. However,
as shown by solid curves in FIG. 11, the second intake side valve
system cam 69.sub.1 and the second exhaust side valve system cam
105.sub.2 are operated so that the total opening angle is made
relatively small and the angle wherein the opening state of the
second intake valve 56.sub.2 is overlapped to that of the second
exhaust valve 57.sub.2 is made relatively small.
[0080] In accordance with such intake side and exhaust side valve
systems 68I and 68E, in a low speed operational region as a
specific operational region of the engine E, the first intake valve
56.sub.1 and the first exhaust valve 57.sub.1 are rested and only
the second intake valve 56.sub.2 and the second exhaust valve
57.sub.2 are operated to be opened/closed. At this time, since the
angle wherein the opening state of the second intake valve 56.sub.2
is overlapped to that of the second exhaust valve 57.sub.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.sub.2, the fuel consumption can be reduced
and the output torque is increased. In a high speed operational
region, since the valve resting mechanisms 73I and 73E are turned
into the acting state, not only the second intake valves 56.sub.2
and the second exhaust valves 57.sub.2 are usually operated to be
opened/closed, but also the first intake valve 56.sub.1 and the
first exhaust valve 57.sub.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 low
speed to high speed operation, it is possible to enhance output and
to reduce fuel consumption.
[0081] As described above, in a low speed operational region of the
engine E, the first intake valve 56.sub.1 is rested, and in such a
state, fuel remains in the intake passage corresponding to the
intake valve 56.sub.1, that is, the first intake passage 46.sub.1.
And, 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.sub.1 and 56.sub.2 are operated to be
opened/closed, the fuel thus remaining in the first intake passage
46.sub.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 occurrence of unburned hydrocarbon.
[0082] A solution to this condition is shown in FIG. 6. A
communication passage 109, which communicates the second intake
passage 46.sub.2 corresponding to the second intake valve 56.sub.2
(usually opened/closed upon operation of the engine E to the first
intake passage 46.sub.1, corresponding to the first intake valve
56.sub.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.sub.1, the fuel-air mixture in
the first intake passage 46.sub.1 flows in the second intake
passage 46.sub.2 through the communication passage 109 as shown by
arrow 110 in FIG. 6.
[0083] The communication passage 109 is formed in the cylinder head
40 obtained by casting, by cutting from the combustion chamber 43
side, so as to be tilted toward the combustion chamber 43 in the
direction from the second intake passage 46.sub.2 to the first
intake passage 46.sub.1. The opening end of the communication
passage 109 for communicating the first intake passage 46.sub.1 to
the second intake passage 46.sub.2 is disposed at a position as
close to the combustion chamber 43 as possible.
[0084] 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.sub.1 and
40.sub.2.
[0085] 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
68I and 68E is contained in the containing hole 112.
[0086] Referring additionally to FIG. 12, a hydraulic control valve
113 is mounted on the one side surface 40a 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.sub.1
side. The hydraulic control valve 113 is used for controlling a
hydraulic pressure of working oil fed to the valve resting
mechanism 43I and 43E of the intake side and exhaust side valve
systems 68I and 68E.
[0087] Referring to FIG. 13, the hydraulic control valve 113 is
mounted on the one side surface 40a 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 40a of
the cylinder head 40 and the opening end of a first working oil
discharge passage 115.sub.1 to the one side surface 40a 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.sub.1, and a spool valve body 119 slidably fitted in a housing
118 mounted on the side surface 40a of the cylinder head 40.
[0088] 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 so 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 biases 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.
[0089] In a state in which the housing 118 is mounted on the one
side surface 40a 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.
[0090] The housing 118 also has a bypass port 128 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.
[0091] 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 formed in the cap 120 so 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.
[0092] 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.
[0093] 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.
[0094] 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 135a, which projects upwardly from the upper
crank case 39, is provided on the mission case 135. A starter motor
140 having a rotational axis parallel to the crank shaft 137 is
mounted on the projecting portion 135a at a position over the upper
crank case 39.
[0095] 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.
[0096] The working oil intake passage 114 includes a connection
port 114a connected to the inlet 116 of the hydraulic control valve
113 and opened to the one side surface 40a of the cylinder head 40.
A first passage 114b is provided in the cylinder head 40 so as to
be connected to the connection port 114a and to extend in straight
line along the one side surface 40a. A second passage 114c is
provided in the cylinder block 36 so as to be coaxially connected
to the first passage 114b. A third passage 114d is provided in the
lower crank case 39 so as to be coaxially connected to the second
passage 114c and to extend in straight line. A fourth passage 114e
is provided in the lower crank case 136 so as to be connected to
the lower end of the third passage 114d and to extend in the
vertical direction. A fifth passage 114f is provided in the lower
crank case 136 so as to be connected to the lower end of the fourth
passage 114e and to extend substantially in the horizontal
direction. A sixth passage 114g is provided in the lower crank case
136 so as to extend substantially in parallel to the fifth passage
114f. A filter 141 interposed between the fifth and sixth passages
114f and 114g is mounted in the lower crank case 136, and the sixth
passage 114g is connected to a discharge port of the oil pump
139.
[0097] A strainer 142 disposed in the oil pan 138 is connected to
an intake port of the oil pump 139. Working oil sucked in the oil
pump 139 via the strainer 142 is discharged in the working oil
intake passage 141 in which the filter 141 is interposed. A relief
valve 143 for preventing excess of the hydraulic pressure of the
working oil is connected between the oil pump 139 and the filter
141. An oil gallery 144 for feeding oil to each portion of the
engine E to be lubricated is communicated to an intermediate
portion of the fifth passage 114f connected to the filter 141.
[0098] A water jacket 145 is provided in the cylinder block 36 and
the cylinder head 40. The first passage 114b and the second passage
114c, 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.
[0099] Referring to FIGS. 5 and 12, the first head portion 40, of
the cylinder head 40 has a first working oil discharge passage 115,
for feeding working oil to the valve resting mechanisms 73I and 73E
for each of the combustion chambers 43 disposed on the first head
portion 40.sub.1 side, and the second head portion 40.sub.2 has a
second working oil discharge passage 115.sub.2 for feeding working
oil to the valve resting mechanisms 73I and 73E for each of the
combustion chambers 43 on the second head portion 40.sub.2 side.
The working oil feed passages 103 provided in the cylinder head 40
for the valve resting mechanisms 73I and 73E (see FIG. 7) are
branched from the first and second working oil discharge passages
115.sub.1 and 115.sub.2.
[0100] A mounting seat 146 is mounted on the one side surface 40a
of the cylinder head 40 so as to cross between the first and second
head portions 40.sub.1 and 40.sub.2. The first and second working
oil discharge passages 115.sub.1 and 115.sub.2 are provided in the
cylinder head 40 so that one ends thereof are commonly opened to
the mounting seat 146 and the other ends thereof are closed at a
position near the containing hole 112.
[0101] A cover 147 is fastened to the mounting seat 146, and the
working oil discharge passage 115.sub.1 and 115.sub.2 are
communicated to each other via the cover 147.
[0102] The function of the first embodiment will not be
described.
[0103] The communication passage 109 for communicating the second
intake passage 46.sub.2 (corresponding to the second intake valve
56.sub.2 opened/closed even in a specific operational region to the
first intake passage 46.sub.1 corresponding to the first intake
valve 56.sub.1 rested in the specific operational region) is
provided in the cylinder head 40. Accordingly, when the first
intake valve 56.sub.1 is rested, a fuel-air mixture flows from the
first intake passage 46.sub.1 corresponding to the rested first
intake valve 56.sub.1, to the second intake passage 46.sub.2
corresponding to the opened/closed second intake valve 56.sub.2 via
the communication passage 109, so that it is possible to prevent
the fuel from remaining in the first intake passage 46.sub.1 in the
resting state of the first intake valve 56.sub.1. 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.sub.1 and 56.sub.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.
[0104] Since the phenomenon in which the fuel remains in the first
intake passage 46.sub.1 in the resting state of the first intake
valve 56.sub.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.sub.1 and 46.sub.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.sub.1 is rested is switched to the operation
for the operational region in which the intake valves 56.sub.1 and
56.sub.2 are both opened/closed.
[0105] 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.sub.2 to the first intake passage
46.sub.1, the opening end of the communication passage 109 for
communicating the first intake passage 46.sub.1, rested in a
specific operational region to the second intake passage 46.sub.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.sub.1 is rested in the specific operational region, the first
intake passage 46.sub.1, corresponding to the rested first intake
valve 56.sub.1 can be communicated to the second intake passage
46.sub.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.sub.1 can be made as small as
possible.
[0106] The hydraulic control valve 113 for controlling the
hydraulic pressure of working oil to the hydraulic valve resting
mechanism 73I and 73E for resting the first intake valve 56.sub.1
and the first exhaust valve 57.sub.1 in a specific operational
region are mounted on the side surface 40a 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 40a 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
excessive length of engine E along the direction of the cylinder
bores 37, 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
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 reduced.
[0107] Since the hydraulic control valve 113 is mounted on the side
surface 40a 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 make shorter the length of
the multi-cylinder engine E along the width direction of the body
frame 21.
[0108] 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 additional pipe line for introducing the working oil
from the oil pump 139 to the hydraulic control valve 113, which
simplifies the appearance of the multi-cylinder engine E.
[0109] 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.
[0110] The working oil intake passage 114 has at least the first
passage 114b provided in the cylinder head 40 so as to extend in
straight line along the side surface 40a between the one side
surface 40a of the cylinder head 40 and the water jacket 145. The
second passage 114c is provided in the cylinder block 36 so as to
be coaxial with the first passage 114b. The third passage 114d is
provided in the upper crank case 39 so as to be coaxial with the
second passage 114c 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 reduce the loss in hydraulic pressure in the working
oil intake passage 114.
[0111] 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.sub.1 and 40.sub.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.
[0112] The first working oil discharge passage 115.sub.1 for
supplying working oil to the valve resting mechanism 73I and 73E
for each of the combustion chambers 43 on the first head portion
40.sub.1 side is provided in the first head portion 40, so as to be
connected to the hydraulic control valve 113 mounted on the side
surface 40a of the cylinder head 40 between a pair of the intake
ports 47 disposed on the first head portion 40.sub.1 side.
[0113] The second working oil discharge passage 115.sub.2 for
supplying working oil to the valve resting mechanism 73I and 73E
for each of the combustion chambers 43 on the second head portion
40.sub.2 side is provided in the second head portion 402. The
one-ends of the first and second working oil discharge passages
115.sub.1 and 115.sub.2 are opened to the mounting seat 146 formed
on the side surface 40a of the cylinder head 40 so as to cross
between the first and second head portions 40.sub.1 and 40.sub.2.
The first and second working oil discharge passages 115.sub.1 and
115.sub.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.sub.1 and 115.sub.2 provided in the
cylinder head 40 on both 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 73I and 73E for
each of the combustion chambers 43.
[0114] In the valve resting mechanism 73I (or 73E), the pin holder
74 is slidably fitted in the valve lifter 71.sub.1 (or 107.sub.1)
driven by the valve system cam 59.sub.1 (or 105.sub.1).
[0115] The slide pin 76 slidably fitted in the pin holder 74 is
slidable between the position wherein the leading end of the valve
stem 59 (or 61) is contained in the containing hole 87 and the
position wherein 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.sub.1 (or the first exhaust valve 571) from each other.
[0116] Since the rotation of the slide pin 76 around its axis 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 73I (or 73E) can be easily assembled with the
stem 59 (or 61) of the first intake valve 56.sub.1 (or the first
exhaust valve 57.sub.1) by mounting the valve lifter 71.sub.1 (or
107.sub.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.sub.1 (or 107.sub.1).
[0117] 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.sub.1 (or the first exhaust valve 57.sub.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.sub.1 (or the first exhaust valve 57.sub.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 73I (or 73E).
[0118] The shim 84 for blocking the end portion of the extension
hole 82 on the closed end side of the valve lifter 71.sub.1 (or
107.sub.1) is mounted on the pin holder 74 so that it can be
brought into contact with the closed end of the valve lifter 71,
(107.sub.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.sub.1
(or 107.sub.1) to the pin holder 74, and in this embodiment, the
end portion of the extension hole 82 is blocked with the shim 84
brought into contact with the closed end of the valve lifter
71.sub.1 (or 107.sub.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.sub.1 (or first exhaust
valve 57.sub.1) by changing the thickness of the shim 84.
[0119] The containing cylinder portion 83 coaxial with the axis 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.sub.1
(or 107.sub.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.
[0120] 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.sub.1 (or 107.sub.1), and accordingly, the sliding
motion of the valve lifter 71.sub.1 (or 107.sub.1) with respect to
the cylinder head 40 can be reliably performed along the axis of
the valve stem 59 (or 61) so that the pressing force is applied
from the valve lifter 71.sub.1 (or 107.sub.1) to the pin holder 74
on the extension of the axis of the valve stem 59 (or 61) of the
first intake valve 56.sub.1 (or the first exhaust valve 57.sub.1).
As a result, the sliding motion of the valve lifter 71.sub.1 (or
107.sub.1) can be smoothened.
[0121] The coil spring 92 for biasing the pin holder 74 toward the
closed end side of the valve lifter 71.sub.1 (or 107.sub.1) is
provided between the pin holder 74 and the cylinder head 40. To be
more specific, the coil spring 92 is disposed so as to surround the
valve stem 59 (or 61) at a position wherein the outer periphery of
the coil spring 92 is not in contact with the inner surface of the
valve lifter 71.sub.1 (or 107.sub.1). The projections 93 and 94 for
positioning the end portion of the coil spring 92 in the direction
perpendicular to the axis 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 reliably applied along the
axis 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.sub.1 (or 107.sub.1).
[0122] 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.
[0123] A second embodiment of the present invention will be
described with reference to FIG. 15. The coil spring 92 provided
between the pin holder 74 and the cylinder head 40 is disposed so
as to surround the valve stem 59 at a position wherein the outer
periphery of the coil spring 92 is not in slide-contact with the
inner surface of the valve lifter 71.sub.1. At this time, grooves
149 and 150 for positioning the end portion of the coil spring 92
in the direction perpendicular to the axis of the valve stem 59 may
be provided in the pin holder 74. The depth of each of the grooves
149 and 150 is set to be less than the diameter of the coil spring
92.
[0124] Even in this second embodiment, as in the first embodiment,
it is possible to allow the spring force of the coil spring 92 to
be reliably applied along the axis of the valve stem 59, 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.sub.1. Further, even if the coil spring 92 is contracted, the
coil spring 92 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 slide-contact of the coil spring 92 with the pin holder
74.
[0125] As described above, according to the present invention,
since the rotation of the slide pin around its axis in the pin
holder is prevented by the rotation stopping means, the valve
resting mechanism can be easily assembled to the valve stem by
mounting the valve lifter to the cylinder head in a state that the
pin holder in which the slide pin has been fitted is fitted in the
valve lifter.
[0126] In addition, the rotation stopping means can be
simplified.
[0127] It is further possible to reduce the size of the containing
hole, that is, the diameter of the slide pin, and hence to
miniaturize the pin holder and further miniaturize the valve
resting mechanism as a whole. Further, it is possible to simplify
the structure of the pin holder, and to suitably adjust a gap at
the valve head of the engine valve by changing the thickness of the
shim.
[0128] It is further possible to simply mount a relatively small
shim on the pin holder.
[0129] It is also possible to more surely perform the sliding
motion of the valve lifter with respect to the cylinder head along
the axis of the valve stem, and hence to smoothen the sliding
motion of the valve lifter.
[0130] The spring force of the coil spring along the axis of the
valve stem can be reliably applied, and frictional loss due to the
slide-contact of the outer periphery of the coil spring with the
valve lifter can be reduced. Even if the coil spring is contracted,
it is not in slide-contact with the pin holder. As a result, it is
possible to prevent the occurrence of the frictional loss due to
the slide-contact of the coil spring with the pin holder.
[0131] 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.
* * * * *