U.S. patent application number 09/969662 was filed with the patent office on 2002-05-02 for valve timing control system for internal combustion engine.
Invention is credited to Watanabe, Kotaro.
Application Number | 20020050257 09/969662 |
Document ID | / |
Family ID | 18798766 |
Filed Date | 2002-05-02 |
United States Patent
Application |
20020050257 |
Kind Code |
A1 |
Watanabe, Kotaro |
May 2, 2002 |
Valve timing control system for internal combustion engine
Abstract
A valve timing control system for an internal combustion engine.
The valve timing control system comprises a rotation control
mechanism including a housing, and a vane rotor rotatably disposed
inside the housing and having at least one vane section. The vane
section defines a first chamber and a second chamber which are
located on opposite sides of the vane section, hydraulic pressure
being selectively supplied to and released from the first chamber
and the second chamber so as to controllably accomplish a relative
rotation of the vane rotor to the housing. The vane rotor is formed
at its axially end section with a depression. A first camshaft is
connected to the vane rotor by a cam bolt piercing the vane rotor
along an axis of the vane rotor. A second camshaft is disposed
parallel with the first camshaft. A first driving force
transmission member is installed to the housing and connected to
one of a crankshaft and the second camshaft. Additionally, a second
driving force transmission member is installed to an end section of
the first camshaft together with the vane rotor by the cam bolt and
connected to the other of the crankshaft and the second camshaft.
The second driving force transmission member includes a generally
cup-shaped section having a cylindrical wall portion fitted on the
end section of the first camshaft and fitted in the depression of
the vane rotor.
Inventors: |
Watanabe, Kotaro;
(Farmington Hills, MI) |
Correspondence
Address: |
Richard L. Schwaab
FOLEY & LARDNER
Washington Harbour
3000 K Street, N.W., Suite 500
Washington
DC
20007-5109
US
|
Family ID: |
18798766 |
Appl. No.: |
09/969662 |
Filed: |
October 4, 2001 |
Current U.S.
Class: |
123/90.17 ;
123/90.15 |
Current CPC
Class: |
F01L 1/3442 20130101;
F01L 2001/0537 20130101; F02B 2275/18 20130101 |
Class at
Publication: |
123/90.17 ;
123/90.15 |
International
Class: |
F01L 001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 20, 2000 |
JP |
2000-320488 |
Claims
What is claimed is:
1. A valve timing control system for an internal combustion engine,
comprising: a rotation control mechanism comprising a housing, and
a vane rotor which is rotatably disposed inside the housing and has
at least one vane section, the vane section defining a first
chamber and a second chamber which are located on opposite sides of
the vane section, a hydraulic pressure being selectively supplied
to and released from the first chamber and the second chamber to
controllably accomplish a relative rotation of the vane rotor to
the housing, the vane rotor being formed at its axially end section
with a depression; a first camshaft connected to the vane rotor by
a cam bolt piercing the vane rotor along an axis of the vane rotor;
a second camshaft disposed parallel with said first camshaft; a
first driving force transmission member connected to one of a
crankshaft and said second camshaft, the housing of said rotation
control mechanism having said first driving force transmission
member; and a second driving force transmission member installed to
an end section of said first camshaft together with the vane rotor
by the cam bolt and connected to the other of the crankshaft and
said second camshaft, said second driving force transmission member
comprising a generally cup-shaped section which has a cylindrical
wall portion fitted on the end section of said first camshaft and
fitted in the depression of the vane rotor, wherein the vane rotor
of said rotation control mechanism and the generally cup-shaped
section of said second driving force transmission member are fixed
together to the end section of said first camshaft upon tightening
the cam bolt.
2. A valve timing control system as claimed in claim 1, further
comprising a locating member disposed between the vane rotor and
said second driving force transmission member and between said
second driving force transmission member and said first
camshaft.
3. A valve timing control system as claimed in claim 2, wherein
said locating member is fixed to one of the vane rotor, said second
driving force transmission member and said first camshaft, wherein
two of the vane rotor, said second driving force transmission
member and said first camshaft are formed respectively with first
and second engaged sections to which said locating member engages,
the two being other than the one.
4. A valve timing control system as claimed in claim 3, wherein
said locating member is fixed to the generally cup-shaped section
of said second driving force transmission member, wherein the vane
rotor and said first camshaft are formed respectively with first
and second engaged sections to which said locating member
engages.
5. A valve timing control system as claimed in claim 4, wherein
said locating member is an axially extending locating pin, wherein
each of said engaged sections has a radially extending groove to
which said locating pin engages.
6. A valve timing control system as claimed in claim 5, wherein
each of said engaged sections has a radially extending surface
defining the radially extending groove, said axially extending
locating pin being axially separate from the radially extending
surface with a clearance.
7. A valve timing control system as claimed in claim 1, wherein
said first camshaft is an exhaust valve-side camshaft for driving
exhaust valves, and said second camshaft is an intake valve-side
camshaft for driving intake valves.
8. A valve timing control system as claimed in claim 1, wherein
said first camshaft has a cylindrical end section inside which a
tube is fixed, the tube having opposite end sections which are
enlarged in diameter, the tube being located radially outside of
the cam bolt to define a first passage in communication with the
first chamber of said rotation control mechanism and a second
passage in communication with the second chamber of said rotation
control mechanism.
9. A valve timing control system as claimed in claim 8, wherein the
generally cup-shaped section of said second driving force
transmission member has a portion defining a through-hole in
communication with the first passage defined between the tube and
an inner peripheral surface of the cylindrical end section of said
first camshaft, the first passage being in communication with one
of the first and second chambers of said rotation control
mechanism.
10. A valve timing control system as claimed in claim 9, wherein
the first passage defined between the tube and the inner peripheral
surface of the cylindrical end section of said first camshaft is in
communication with the first chamber of said rotation control
mechanism, the first chamber being a timing-advancing chamber which
is to be supplied with hydraulic pressure to advance a valve
timing.
11. A valve timing control system as claimed in claim 8, wherein
the cam bolt is fixed in a condition of being inserted in a central
bore formed in the vane rotor and a bolt insertion hole formed at a
bottom wall portion of the generally cup-shaped section of said
second driving force transmission member, wherein a first clearance
is formed between an inner peripheral surface of the vane rotor
defining the central bore and an outer peripheral surface of the
cam bolt, and a second clearance is formed between an inner
peripheral surface of the bottom wall portion defining the bolt
insertion hole and the outer peripheral surface of the cam bolt,
the second passage defined by an inner peripheral surface of the
tube being communicated through the first and second clearances
with one of the first and second chambers of said rotation control
mechanism.
12. A valve timing control system as claimed in claim 11, wherein
the second passage defined by the inner peripheral surface of the
tube is in communication with the second chamber of said rotation
control mechanism, the second chamber being a timing-retarding
chamber which is supplied with hydraulic pressure to retard a valve
timing.
13. A valve timing control system as claimed in claim 1, wherein
the depression is defined by a cylindrical inner wall surface of
the vane rotor, the cylindrical inner wall surface being coaxial
with the vane rotor, wherein the cylindrical inner wall surface is
in fitting contact with the cylindrical wall portion of the
generally cup-shaped section of said second driving force
transmission member.
14. A valve timing control system for an internal combustion
engine, comprising: a rotation control mechanism comprising a
casing, and a vane rotor which is rotatably disposed inside the
housing and comprises a generally cylindrical body section, and at
least one vane section integral with and radially extending from
the cylindrical body section, the vane section defining a
timing-advancing chamber and a timing-retarding chamber which are
located on opposite sides of the vane section, the vane rotor
making a relative rotation to the housing in a first direction for
advancing a valve timing upon supply of hydraulic pressure into the
timing-advancing chamber, the vane rotor making a relative rotation
to the housing in a second direction for retarding the valve timing
upon supply of hydraulic pressure into the timing-retarding
chamber, the second direction being opposite to the first
direction, the vane rotor being formed at its axially end section
with a depression generally coaxial with the cylindrical body
section; a change-over valve through which hydraulic pressure is
selectively supplied to the timing-advancing chamber and the
timing-retarding chamber in accordance with an engine operating
condition; a first camshaft coaxially connected to the body section
of the vane rotor by a cam bolt piercing the body section of the
vane rotor along an axis of the vane rotor; a second camshaft
disposed parallel with said first camshaft; a first driving force
transmission member connected to one of a crankshaft and said
second camshaft, the housing of said rotation control mechanism
coaxially having said first driving force transmission member; and
a second driving force transmission member coaxially installed to
an end section of the first camshaft together with the vane rotor
by the cam bolt and connected to the other of the crankshaft and
said second camshaft, said second driving force transmission member
comprising a generally cup-shaped section which comprises a
cylindrical wall portion coaxial with the cylindrical body section
of the vane rotor, the cylindrical wall portion being coaxially
fitted on the end section of said first camshaft and having an end
part fitted in the depression of the vane rotor of said rotation
control mechanism, wherein the vane rotor of said rotation control
mechanism and the generally cup-shaped section of said second
driving force transmission member are fixed together to the end
section of said first camshaft upon tightening the cam bolt.
15. A V-type internal combustion engine having first and second
banks of cylinders, comprising: a first exhaust valve-side camshaft
for driving exhaust valves, disposed in the first bank; a second
exhaust valve-side camshaft for driving exhaust valves, disposed in
the second bank; a first intake valve-side camshaft for driving
intake valves, disposed in the first bank and located inside
relative to said first exhaust valve-side camshaft, said first
intake valve-side camshaft being parallel with said first exhaust
valve-side camshaft; a second intake valve-side camshaft for
driving intake valves, disposed in the second bank and located
inside relative to said second exhaust-side camshaft, said second
intake valve-side camshaft being parallel with said second exhaust
valve-side camshaft; a first rotation control mechanism comprising
a housing, and a vane rotor which is rotatably disposed inside the
housing and has at least one vane section, the vane section
defining a first chamber and a second chamber which are located on
opposite sides of the vane section, hydraulic pressure being
selectively supplied to and released from the first chamber and the
second chamber to controllably accomplish a relative rotation of
the vane rotor to the housing, the vane rotor being formed at its
axially end section with a depression, the vane rotor being
connected to said first exhaust valve-side camshaft by a cam bolt
piercing the vane rotor along an axis of the vane rotor; a first
driving force transmission member connected to one of a crankshaft
and said first intake valve-side camshaft, the housing of said
first rotation control mechanism having said first driving force
transmission member; a second driving force transmission member
installed to an end section of said first exhaust valve-side
camshaft together with the vane rotor by the cam bolt and connected
to the other of the crankshaft and said first intake valve-side
camshaft, said second driving force transmission member comprising
a generally cup-shaped section which has a cylindrical wall portion
fitted on the end section of said first exhaust valve-side camshaft
and fitted in the depression of the vane rotor, wherein the vane
rotor of said first rotation control mechanism and the generally
cup-shaped section of said second driving force transmission member
are fixed together to the end section of said first exhaust
valve-side camshaft upon tightening the cam bolt; a second rotation
control mechanism comprising a housing, and a vane rotor which is
rotatably disposed inside the housing and has at least one vane
section, the vane section defining a first chamber and a second
chamber which are located on opposite sides of the vane section,
hydraulic pressure being selectively supplied to and released from
the first chamber and the second chamber to controllably accomplish
a relative rotation of the vane rotor to the housing, the vane
rotor being formed at its axially end section with a depression,
the vane rotor being connected to said second exhaust valve-side
camshaft by a cam bolt piercing the vane rotor along an axis of the
vane rotor; a third driving force transmission member connected to
one of the crankshaft and said second intake valve-side camshaft,
the housing of said second rotation control mechanism having said
third driving force transmission member; and a fourth driving force
transmission member installed to an end section of said second
exhaust valve-side camshaft together with the vane rotor by the cam
bolt and connected to the other of the crankshaft and said second
intake valve-side camshaft, said fourth driving force transmission
member comprising a generally cup-shaped section which has a
cylindrical wall portion fitted on the end section of said second
exhaust valve-side camshaft and fitted in the depression of the
vane rotor, wherein the vane rotor of said second rotation control
mechanism and the generally cup-shaped section of said fourth
driving force transmission member are fixed together to the end
section of said second exhaust valve-side camshaft upon tightening
the cam bolt.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to improvements in a valve timing
control system for hydraulically operating the opening and closing
timings of intake and exhaust valves of an internal combustion
engine, and more particularly to the valve timing control system of
the type wherein a driving force is transmitted from a first
camshaft to a second camshaft in the engine.
[0002] In recent years, a valve timing control system for an
internal combustion engine of the type having two camshafts (first
and second camshafts) on a cylinder head has been developed and
disclosed in Japanese Patent Provisional Publication No. 9-280020.
In this valve control system, the two camshafts are connected
through a rotation control mechanism in a manner to be operated in
timed relation to each other.
[0003] The valve timing control system disclosed in the Publication
No. 9-280020 is arranged as follows: A vane rotor of the rotation
control mechanism is installed together with a first driving force
transmission member (sprocket or the like) to an end section of the
first camshaft. A second driving force transmission member (gear or
the like) is integrally fixed to a housing of the rotation control
mechanism. The first driving force transmission member is driveably
connected to a crankshaft, while the second driving force
transmission member is drivingly connected to the second camshaft.
Accordingly, the driving force input from the crankshaft to the
first driving force transmission member is directly input to the
first camshaft and further transmitted to the second camshaft
through the rotation control mechanism and the second driving force
transmission member.
[0004] In case of this valve timing control system, the vane rotor
and the first driving force transmission member are formed with a
central through-hole, and fitted on the first camshaft in such a
manner that the first camshaft pierces the central through-hole, in
which they are thrust against an engagement flange formed on the
first camshaft. In other words, the engagement flange has been
previously formed on the first camshaft at a position close to the
end section of the first camshaft. A cam bolt is screwed into the
first camshaft under a condition where the vane rotor and the first
driving force transmission member are fitted on the end section of
the first camshaft, so that the vane rotor and the first driving
force transmission member are fastened and fixed between the head
section of the cam bolt and the engagement flange.
[0005] However, drawbacks have been encountered in the conventional
valve timing control system disclosed in the Publication No.
9-280020, in which the first camshaft must be integrally formed
with the engagement flange against which the vane rotor and the
first driving force transmission member are thrust to be fastened
and fixed in position. This increases a production cost for the
first camshaft.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to provide an
improved valve timing control system for an internal combustion
engine, which can overcome drawbacks encountered in conventional
valve timing control systems.
[0007] Another object of the present invention is to provide an
improved valve timing control system for an internal combustion
engine, in which a vane rotor of a rotation control mechanism and a
driving force transmission member can be securely installed to a
camshaft without inviting a rise in production cost and deformation
of a cam bolt for fixing the vane rotor and the driving force
transmission member to the camshaft.
[0008] A further object of the present invention is to provide an
improved valve timing control system for an internal combustion
engine, in which load applied to a vane rotor of a rotation control
mechanism and a driving force transmission member is supported on
the end section of a camshaft thereby preventing the load from
being applied to a cam bolt.
[0009] An aspect of the present invention resides in a valve timing
control system for an internal combustion engine. The valve timing
control system comprises a rotation control mechanism comprising a
housing, and a vane rotor which is rotatably disposed inside the
housing and has at least one vane section. The vane section defines
a first chamber and a second chamber which are located on opposite
sides of the vane section, a hydraulic pressure being selectively
supplied to and released from the first chamber and the second
chamber so as to controllably accomplish a relative rotation of the
vane rotor to the housing. The vane rotor is formed at its axially
end section with a depression. A first camshaft is connected to the
vane rotor by a cam bolt piercing the vane rotor along an axis of
the vane rotor. A second camshaft is disposed parallel with the
first camshaft. A first driving force transmission member is
installed to the housing and connected to one of a crankshaft and
the second camshaft. The housing of the rotation control mechanism
has the first driving force transmission member. Additionally, a
second driving force transmission member is installed to an end
section of the first camshaft together with the vane rotor by the
cam bolt and connected to the other of the crankshaft and the
second camshaft. The second driving force transmission member
comprises a generally cup-shaped section which has a cylindrical
wall portion fitted on the end section of the first camshaft and
fitted in the depression of the vane rotor. In the above
arrangement, the vane rotor of the rotation control mechanism and
the generally cup-shaped section of the second driving force
transmission member are fixed together to the end section of the
first camshaft upon tightening the cam bolt.
[0010] Another aspect of the present invention resides in a valve
timing control system for an internal combustion engine. The valve
timing control system comprises a rotation control mechanism
comprising a casing, and a vane rotor which is rotatably disposed
inside the housing. The vane rotor comprises a generally
cylindrical body section, and at least one vane section integral
with and radially extending from the cylindrical body section. The
vane section defines a timing-advancing chamber and a
timing-retarding chamber which are located on opposite sides of the
vane section, the vane rotor making a relative rotation to the
housing in a first direction for advancing a valve timing upon
supply of hydraulic pressure into the timing-advancing chamber, the
vane rotor making a relative rotation to the housing in a second
direction for retarding the valve timing upon supply of hydraulic
pressure into the timing-retarding chamber, the second direction
being opposite to the first direction. The vane rotor is formed at
its axially end section with a depression generally coaxial with
the cylindrical body section. A change-over valve is provided and
arranged such that a hydraulic pressure is selectively supplied
through the change-over valve to the timing-advancing chamber and
the timing-retarding chamber in accordance with an engine operating
condition. A first camshaft is coaxially connected to the body
section of the vane rotor by a cam bolt piercing the body section
of the vane rotor along an axis of the vane rotor. A second
camshaft is disposed parallel with the first camshaft. A first
driving force transmission member is coaxially installed to the
housing and connected to one of a crankshaft and the second
camshaft. The housing of the rotation control mechanism has the
first driving force transmission member. Additionally, a second
driving force transmission member is coaxially installed to an end
section of the first camshaft together with the vane rotor by the
cam bolt and connected to the other of the crankshaft and the
second camshaft. The second driving force transmission member
comprises a generally cup-shaped section which comprises a
cylindrical wall portion coaxial with the cylindrical body section
of the vane rotor. The cylindrical wall portion is coaxially fitted
on the end section of the first camshaft and has an end part fitted
in the depression of the vane rotor of the rotation control
mechanism. In the above arrangement, the vane rotor of the rotation
control mechanism and the generally cup-shaped section of the
second driving force transmission member are fixed together to the
end section of the first camshaft upon tightening the cam bolt.
[0011] In the above valve timing control system according to the
present invention, the second driving force transmission member is
fitted and supported at its cup-shaped section on the end section
of the camshaft. Additionally, the vane rotor is fitted and
supported through the cup-shaped section of the second driving
force transmission member on the end section of the camshaft.
Accordingly, load applied to the vane rotor and the second driving
force transmission member is supported on a fitting section at the
end section of the camshaft though the vane rotor and the second
driving force transmission member are fixed to the end section of
the cam bolt under fastening of the cam bolt.
[0012] A further aspect of the present invention resides in a
V-type internal combustion engine having first and second banks of
cylinders. The engine comprises a first exhaust valve-side camshaft
for driving exhaust valves, disposed in the first bank. A second
exhaust valve-side camshaft is provided for driving exhaust valves,
disposed in the second bank. A first intake valve-side camshaft is
provided for driving intake valves, and is disposed in the first
bank and located inside relative to the first exhaust valve-side
camshaft, the first intake valve-side camshaft being parallel with
the first exhaust valve-side camshaft. A second intake valve-side
camshaft is provided for driving intake valves and disposed in the
second bank and located inside relative to the second exhaust-side
camshaft, the second intake valve-side camshaft being parallel with
the second exhaust valve-side camshaft. A first rotation control
mechanism is provided comprising a housing, and a vane rotor which
is rotatably disposed inside the housing and has at least one vane
section. The vane section defines a first chamber and a second
chamber which are located on opposite sides of the vane section,
hydraulic pressure being selectively supplied to and released from
the first chamber and the second chamber so as to controllably
accomplish a relative rotation of the vane rotor to the housing.
The vane rotor is formed at its axially end section with a
depression. The vane rotor is connected to the first exhaust
valve-side camshaft by a cam bolt piercing the vane rotor along an
axis of the vane rotor. A first driving force transmission member
is connected to one of a crankshaft and the first intake valve-side
camshaft. The housing of the first rotation control mechanism has
the first driving force transmission member. A second driving force
transmission member is installed to an end section of the first
exhaust valve-side camshaft together with the vane rotor by the cam
bolt and connected to the other of the crankshaft and the first
intake valve-side camshaft. The second driving force transmission
member comprises a generally cup-shaped section which has a
cylindrical wall portion fitted on the end section of the first
exhaust valve-side camshaft and fitted in the depression of the
vane rotor, wherein the vane rotor of the first rotation control
mechanism and the generally cup-shaped section of the second
driving force transmission member are fixed together to the end
section of the first exhaust valve-side camshaft upon tightening
the cam bolt.
[0013] Additionally, the V-type internal combustion engine
comprises a second rotation control mechanism which comprises a
housing, and a vane rotor which is rotatably disposed inside the
housing and has at least one vane section. The vane section defines
a first chamber and a second chamber which are located on opposite
sides of the vane section, hydraulic pressure being selectively
supplied to and released from the first chamber and the second
chamber so as to controllably accomplish a relative rotation of the
vane rotor to the housing. The vane rotor is formed at its axially
end section with a depression. The vane rotor is connected to the
second exhaust valve-side camshaft by a cam bolt piercing the vane
rotor along an axis of the vane rotor. A third driving force
transmission member is connected to one of the crankshaft and the
second intake valve-side camshaft. The housing of the second
rotation control mechanism has the third driving force transmission
member. Additionally, a fourth driving force transmission member is
installed to an end section of the second exhaust valve-side
camshaft together with the vane rotor by the cam bolt and connected
to the other of the crankshaft and the second intake valve-side
camshaft. The fourth driving force transmission member comprises a
generally cup-shaped section which has a cylindrical wall portion
fitted on the end section of the second exhaust valve-side camshaft
and fitted in the depression of the vane rotor, wherein the vane
rotor of the second rotation control mechanism and the generally
cup-shaped section of the fourth driving force transmission member
are fixed together to the end section of the second exhaust
valve-side camshaft upon tightening the cam bolt.
[0014] The other objects and features of this invention will become
understood from the following description with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a longitudinal sectional view of an embodiment of
a valve timing control system according to the present invention,
taken in the direction of the arrows substantially along the line
A-A of FIG. 3;
[0016] FIG. 2 is a schematic plan view of an internal combustion
engine provided with the valve timing control system of FIG. 1;
[0017] FIG. 3 is a vertical section view taken in the direction of
the arrows substantially along the line B-B of FIG. 1;
[0018] FIG. 4 is a front view of a second driving force
transmission member (secondary sprocket) used in the valve timing
control system of FIG. 1; and
[0019] FIG. 5 is a back-side view of the second driving force
transmission member of FIG. 4.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Referring now to FIG. 2 of the drawings, an internal
combustion engine is illustrated incorporating an embodiment of a
valve timing control system according to the present invention. The
engine is of a so-called V-type and includes a two banks of
cylinders. The two banks respectively have cylinder heads 1A, 1B. A
crankshaft 2 is provided to be driven by pistons (not shown)
disposed in the two banks. Cylinder heads 1A, 1B are respectively
provided with exhaust valve-side camshafts 3A, 3B serving as first
camshafts, and respectively provided with intake valve-side
camshafts 4A, 4B serving as second camshafts. Exhaust and intake
valve-side camshafts 3A, 4A are disposed parallel with each other,
and exhaust and intake-side camshafts 3B, 4B are disposed parallel
with each other.
[0021] Rotation control mechanisms 5A, 5B are respectively provided
to end sections of exhaust valve-side camshaft 3A, 4A in banks 1A,
1B. Each rotation control mechanism 5A, 5B includes a housing 6A,
6B which is integrally formed with a primary sprocket (first
driving force transmission member) 7A, 7B. Primary sprocket 7A, 7B
is connected through a timing chain 8A, 8B to a crank sprocket 9
mounted on a crankshaft 2 in such a manner as to be driven by crank
sprocket 9. Additionally, secondary sprockets (second driving force
transmission members) 10A, 10B are respectively provided to the end
sections of exhaust valve-side camshafts 3A, 3B. Secondary
sprockets 10A, 10B are respectively drivingly connected through
chains 11A, 11B to cam sprockets 12A, 12B which are respectively
provided to end sections of intake valve-side camshafts 4A, 4B.
Accordingly, in the internal combustion engine, rotation of
crankshaft 2 is input to the exhaust valve-side camshafts 3A, 3B
through primary sprockets 7A, 7B and the rotation control
mechanisms 5A, 5B. Rotations of exhaust valve-side camshafts 3A, 3B
are input to intake valve-side camshafts 4A, 4B through secondary
sprockets 10A, 10B.
[0022] Hereinafter, the valve timing control system will be
discussed in detail with reference to FIGS. 1 and 3. Banks 1A, 1B
are basically the same in construction as each other, and therefore
explanation will be made only on the side of one bank 1A located on
the above-side of FIG. 2.
[0023] Rotation control mechanism 5A of the valve timing control
system includes housing 6A which is integrally formed with primary
sprocket 7A. A vane rotor 13 is fixedly fitted on the end section
of exhaust valve-side camshaft 3A and rotatably accommodated inside
housing 6A. A hydraulic pressure supply-release means or device 14
is provided to rotate vane rotor 13 in right and reverse directions
relative to housing 6A in accordance with operating conditions of
the engine. A lock mechanism 15 is provided to restrict a
rotational fluctuation of vane rotor 13 due to torque reaction
applied from exhaust valves (not shown) to exhaust valve-side
camshaft 3A.
[0024] Housing 6A includes a generally cylindrical housing main
body 16. Generally disc-shaped front and rear covers 17, 18 are
respectively fixedly connected to the front and rear end faces of
housing main body 16. As shown in FIG. 3, housing main body 16 is
formed at its inner peripheral surface with four partition walls 19
each of which is generally trapezoidal in section. Each partition
wall 19 projects radially inwardly from the inner peripheral
surface of housing main body 16. Primary sprocket 7A is formed
integral with the outer periphery of rear cover 18. Otherwise,
primary sprocket 7A may be formed integral with housing main body
16.
[0025] Vane rotor 13 has a generally cylindrical body section 20
which is integrally provided with four vane sections 21 which
project radially outwardly from the outer peripheral surface of
cylindrical body section 20. Cylindrical body section 20 is
disposed coaxial in housing 6A and rotatable around the axis of
housing 6A. Each vane section 21 is movably disposed between
adjacent partition walls 19, 19. A timing-advancing chamber (first
chamber) 22 is formed between one side surface of each vane section
21 of vane rotor 13 and the side surface of partition wall 19
facing the one side surface of vane section 21, while a
timing-retarding chamber (second chamber) 23 is formed between the
other side surface of the vane section and the side surface of the
other partition wall 19 facing the other side surface of the vane
section. Timing-advancing chamber 22 and timing-retarding chamber
23 are separate from each other, maintaining a liquid-tight
seal.
[0026] Cylindrical body section 20 of vane rotor 13 is formed with
a central bore 25 whose axis is aligned with the axis of housing
6A. A cam bolt 24 is disposed in central bore 25 in such a manner
that its axis is aligned with the axis of housing 6A. Cylindrical
body section 20 is formed at its rear surface with a circular
depression 26 which is coaxial with central bore 25. Depression 26
is defined by an axially extending cylindrical inner wall surface
(not identified) of cylindrical body section 20 which surface is
coaxial with central bore 25. Cylindrical body section 20 is formed
with first radial (radially extending) holes 27 and second radial
(radially extending) holes 28. Each first radial hole 27
establishes communication between each timing-advancing chamber 22
and depression 26. Each second radial hole 28 establishes
communication between each timing-retarding chamber 23 and central
bore 25. In a condition in which vane rotor 13 is installed to the
end section of exhaust valve-side camshaft 3A, each first radial
hole 27 and each second radial hole 28 are respectively brought
into communication with a first supply-release hole or passage 29
and a second supply-release hole or passage 30 (discussed in detail
after) formed in camshaft 3A.
[0027] Hydraulic pressure supply-release device 14 has a first
hydraulic pressure passage 32 and a second hydraulic pressure
passage 31. The first hydraulic pressure passage 32 is connected to
first supply-release hole 29 so as to supply hydraulic pressure to
or release hydraulic pressure from timing-advancing chamber 22. The
second hydraulic pressure passage 31 is connected to second
supply-release hole 30 so as to supply hydraulic pressure or
release hydraulic pressure from timing-retarding chamber 23. First
and second hydraulic pressure passages 31, 32 are respectively
connected to a supply passage 33 and a drain passage 34 through an
electromagnetic change-over valve 35. Supply passage 33 is provided
with an oil pump 37 which pressurizes oil or hydraulic fluid inside
an oil pan 36. An end section of drain passage 34 is connected to
the inside of oil pan 36. Electromagnetic change-over valve 35 is
controlled by a controller (electronic control unit) 38 which is
adapted to generate a variety of signals to be input to the valve
35, in accordance with engine speed, engine load, coolant
temperature and the like of the engine.
[0028] Lock mechanism 15 includes a lock pin 40 which is axially
movably accommodated in a cylindrical hole 39 which is axially
formed in one vane section 21 of vane rotor 13. A spring 41 is
accommodated in the cylindrical hole 39 so as to bias lock pin 40
in a direction of front cover 17, in which one (front) end of
spring 41 is in contact with lock pin. The other (rear) end of
spring 41 is in contact with a spring supporting pin 42 disposed in
cylindrical hole 39. A lock hole 43 is formed at the inside surface
of front cover 17. The tip end section of lock pin 40 is brought
into fit with lock hole 43 when vane rotor 13 is displaced to the
maximum onto a timing-advancing side (where the valve timing is
advanced) relative to housing 6A.
[0029] Cylindrical hole 39 of vane rotor 13 includes a
small-diameter section in which the main body (front-side) section
of rock pin 40 is slidably disposed, and a large-diameter section
in which an annular flange portion 45 of rock pin 40 is slidably
disposed. The small-diameter section is located close to the side
of front cover 17. The annular flange portion 45 is formed at the
outer periphery of the base (rear) section of rock pin 40, and
faces an radially extending annular wall surface (of vane section
21) connecting a wall surface defining the large-diameter section
and a wall surface defining the small-diameter section, so that an
annular space 44 is defined between annular flange portion 45 and
the annular wall surface. Annular space 44 is communicated with
timing-advancing chamber 22 through a communication passage 46 (See
FIG. 3) formed in vane section 21 as shown in FIG. 3. A lock
release passage 47 is connected to the bottom portion of the lock
hole 43 on the side of front cover 17, and is in communication with
timing-retarding chamber 23, so that hydraulic pressure within
timing-retarding chamber 23 acts on the tip end portion of lock pin
40 when rock pin 40 is in fit with lock hole 43. In this
embodiment, the pressure-receiving area of flange section 45 to
which hydraulic pressure within timing-advancing chamber 22 acts is
set to be equal to the pressure-receiving area of the tip end
portion of lock pin 40 on which hydraulic pressure within
timing-retarding chamber 23 acts. It will be understood that a
chamber (not identified) located at the rear side of the lock pin
40 and forming part of cylindrical hole 39 is maintained at the
atmospheric pressure through a passage (not shown).
[0030] This lock mechanism 15 is adapted to mechanically lock a
relative rotation of vane rotor 13 to housing 6A in a condition in
which vane rotator is rotated to the maximum onto the
timing-advancing side when the pressure of hydraulic fluid applied
to vane sections 21 of vane rotor 13 has not sufficiently risen,
for example, at engine starting. When the pressure of hydraulic
fluid rises from the above condition so as to introduce high
pressure hydraulic fluid into lock hole 43, lock pin 40 disengages
from lock hole 43 thereby allowing rotation of vane rotor 13.
[0031] When vane rotor 13 is controllably rotated from a
timing-retarding side (where the valve timing is retarded) to the
timing-advancing side, a high pressure of hydraulic fluid cannot
act on the tip end section of lock pin 40 because the pressure
within timing-retarding chamber 23 is low, so that the tip end
section of lock pin 40 is to be pressed on front cover 17 under the
biasing force of spring 41. However, at this time, a high pressure
of hydraulic fluid within timing-advancing chamber 22 acts on
flange portion 45 of lock pin 40, and therefore lock pin 40 is kept
at its rearward-most position under this high pressure.
Accordingly, the rotation of vane rotor 13 onto the
timing-advancing side cannot be impeded by lock pin 40.
[0032] As shown in FIGS. 1, 4 and 5, secondary sprocket 10A is not
simply disc-shaped and includes an annular main body section 48 and
a generally cup-shaped section 49 integral with main body section
48. Main body section 48 is formed at its outer peripheral portion
with sprocket teeth. Cup-shaped section 49 includes a cylindrical
wall portion 49a whose rear end part is integral with an inner
peripheral portion of main body section 48 in such a manner that
the inner peripheral surface of cylindrical wall portion 49a is
flush with the inner peripheral surface of main body section 48. A
bottom wall portion 49b is integral with the front end part of
cylindrical wall portion 49a. The end section of exhaust valve-side
camshaft 3A is fitted within cylindrical wall portion 49a of
cup-shaped section 49. The front end section of cylindrical wall
portion 49b and the outer peripheral portion of bottom wall portion
49b of cup-shaped section 49 are fitted in depression 26 of vane
rotor 13 in such a manner as to be in fitting contact with the
cylindrical inner wall surface of cylindrical body section 20 of
vane rotor 13. Bottom wall portion 49b is formed at its central
part with a bolt insertion hole 50 in which the cam bolt 24 is to
be disposed. Additionally, bottom wall portion 49b is formed with a
locating pin hole (no numeral) located radially outward of bolt
insertion hole 50, in which a locating pin 51 is press-fitted in
the locating pin hole in such a manner that the locating pin
projects forward and rearward of bottom wall portion 49b thereby to
form front and rear projected end portions 51a,51b.
[0033] Exhaust valve-side camshaft 3A is formed at its front end
face with a radial (radially extending) groove 52 serving as an
engaged portion. Another radial groove 53 serving as another
engaged portion is formed at a surface of vane rotor 13 which
surface defines the bottom of depression 26. Front and rear
projected end portions 51a, 51b of locating pin 51 are respectively
fitted in radial grooves 53, 52. Radial grooves 52, 53 are formed
to radially extend, thereby allowing errors of locating pin 51 in
radial installation position and angle. Additionally, each radial
groove 52, 53 is formed in such a manner that locating pin 51 is
axially loosely fitted in radial groove 52, 53 with a clearance,
thereby allowing an error of locating pin 51 in an axial
direction.
[0034] Secondary sprocket 10A is fitted on exhaust valve-side
camshaft 3A and to vane rotor 13 upon being positioned by locating
pin 51. Further, second sprocket 10A is fixed to exhaust valve-side
camshaft 3A together with vane rotor 13 by fastening cam bolt 24.
Cam bolt 24 is screwed in exhaust valve-side camshaft 3A through
the central hole 25 of vane rotor 13 and bolt insertion hole 50 of
secondary sprocket 10A, in which an annular clearance is formed
between the peripheral surface of cam bolt 24 and each of the inner
peripheral surface of cylindrical body section 20 of vane rotor 13
and the inner peripheral surface of bottom wall portion 49b of
secondary sprocket 10A. This annular clearance serves as a passage
for establishing communication between the second radial holes 28
of vane rotor 13 and second supply-release hole 30 of exhaust
valve-side camshaft 3A.
[0035] Furthermore, the end section of exhaust valve-side camshaft
3A is formed with through-holes 54. Cylindrical wall section 49a of
secondary sprocket 10A is formed with through-holes 55 which are in
communication with through-hole 54 of camshaft 3A. Each first
radial hole 27 of vane rotor 13 is communicated with the first
supply-release hole 29 of exhaust valve-side camshaft 3A through
through-holes 54, 55. The end section of exhaust valve-side
camshaft 3A is formed cylindrical thereby forming a cylindrical end
section. A tube 56 whose opposite end sections are enlarged in
diameter is fixed inside the cylindrical end section of camshaft
3A. The tube 56 divides an annular space formed between the inner
peripheral surface of the cylindrical end section of camshaft 3A
and the outer peripheral surface of the cam bolt 24 into an outer
annular space corresponding to first supply-release hole 29 and an
inner annular space corresponding to second supply-release hole
30.
[0036] Next, operation of the above valve timing control system
will be discussed hereinafter.
[0037] At engine starting of the internal combustion engine, lock
mechanism 15 mechanically locks vane rotor 13 of rotation control
mechanism 5A and housing 6A under a condition where vane rotor 13
has rotated onto the timing-advancing side relative to housing 6A.
In this condition, rotational force of crankshaft 2 is transmitted
to exhaust valve-side camshaft 3A through primary sprocket 7A and
rotation control mechanism 5A. Accordingly, at this time, exhaust
valve-side camshaft 3A drives exhaust valves (not shown) to open
and close at advanced timings which are advanced relative to a
standard timing. Further, rotation of exhaust valve-side camshaft
3A is transmitted to intake valve-side camshaft 4A through
secondary sprocket 10A. It will be understood that, at this time,
intake valve-side camshaft 4A is rotated in the same phase as or in
timed relation to exhaust valve-side camshaft 3A.
[0038] After the engine is started under the above condition, when
timing-retarding chambers 23 are brought into communication with
supply passage 33 while timing-advancing chambers 22 are
simultaneously brought into communication with drain passage 34,
high pressure of hydraulic oil to be introduced into
timing-retarding chamber 23 is applied to the tip (front) end of
lock pin 40, and therefore lock pin 40 is moved rearward under the
high pressure of hydraulic oil. This releases the mechanical lock
between housing 6A and vane rotor 13 under the action of lock
mechanism 15, so that vane rotor 13 is rotated onto the
timing-retarding side relative to housing 6A upon vane rotor
receiving a pressure within timing-retarding chambers 23. As a
result, exhaust-valve side camshaft 3A drives exhaust valves (not
shown) to open and close at retarded timings which are retarded
relative to the standard timing. Thus, rotation of exhaust
valve-side camshaft 3A is transmitted to intake valve-side camshaft
4A through secondary sprocket 10A.
[0039] As discussed above, in the valve timing control system,
rotation of exhaust valve-side camshaft 3A is transmitted to intake
valve-side camshaft 4A through secondary sprocket 10A.
Additionally, cylindrical wall portion 49a of secondary sprocket
10A is fitted on the end section of exhaust valve-side camshaft 3A
and fitted in depression 26 of vane rotor 13. Hence, the mass of
secondary sprocket 10A and the rotation control mechanism 5A and
other loads and the like to be applied thereto hardly act onto cam
bolt 24, and therefore they are directly supported on the outer
peripheral surface of exhaust valve-side camshaft 3A. Thus,
according to the valve timing control system, there is no fear of
deformation of cam bolt 24 even upon a long time use, thereby
preventing occurrence of problems of increased inertia force of
rotation control mechanism 5A due to deformation of cam bolt 24 and
of generation of vibrational noises due to the increased inertia
force.
[0040] In case of this valve timing control system, causing vane
rotor 13 and secondary sprocket 10A to be fitted and supported on
exhaust valve-side camshaft 3A is accomplished only by forming
cup-shaped section 49 integral with secondary sprocket 10A which is
inherently plate-shaped, without using a measure of forming an
engagement flange and the like on the outer peripheral surface of
axially lengthy exhaust valve-side camshaft 3A. This reduces
production cost of the valve timing control system.
[0041] Locating secondary sprocket 10A relative to exhaust
valve-side camshaft 3A and vane rotor 13 is accomplished by
incorporating a locating member such as locating pin 51 shown in
FIG. 1 or a key. This makes unnecessary special jigs or the like
for locating the three members 10A, 3A, 13, thereby improving a
production efficiency of the valve timing control system. During
such locating, particularly by fixing the locating member (locating
pin) to one of the three members as shown and described in this
embodiment, it is sufficient for the purpose of assembly of the
valve timing control system, that the locating member is inserted
into the engaged sections of the other two members, thereby
improving the production efficiency of the valve timing control
system.
[0042] In this embodiment, locating pin 51 is fixed to bottom wall
portion 49b of cup-shaped section 49 of secondary sprocket 10A. In
this case, locating pin 51 is supported at its axially central part
on secondary sprocket 10 and therefore is prevented from taking an
overhung type structure, so that the installation position and
angle of locating pin 51 cannot easily shift during assembly of the
valve timing control system. Accordingly, assembly operation for
the above three members can be achieved more easily and more
accurately.
[0043] Each engaged section with which projected end portion 51a,
51b of locating pin 51 engages may have a cross-sectional shape of
complete round corresponding to the cross-sectional shape of
locating pin 51. However, in this embodiment, radial (radially
extending) grooves 52, 53 are employed as the engaged sections. In
this case, the errors of locating pin 51 in radial installation
position and angle can be absorbed, thereby making it unnecessary a
severe dimensional control in radial direction during installation
of locating pin 51 and/or formation of the engaged section. This
makes it possible to produce the valve timing control system at a
low production cost. Additionally, in the embodiment, radial
grooves 52, 53 have such a depth (or axial dimension) that locating
pin 51 is engaged in the radial grooves with a clearance. In other
words, each of the radial grooves 52, 53 have a radially extending
surface (not identified) defining radial groove 52, 53, in which
axially extending locating pin 51 (or projected end portion 51a,
51b) is axially separate from the radially extending surface with
the clearance. This makes unnecessary a severe dimensional control
also in axial direction, thereby achieving a further lowing in
production cost.
[0044] While sprockets 7A, 10A have been shown and described as
being used respectively as the first driving force transmission
member to be installed to housing 6A and the second driving force
transmission member to be installed to camshaft 3A in the
embodiment, it will be understood that the first and second driving
force transmission members are not limited to sprockets and
therefore may be pulleys for transmitting a driving force in
cooperation with belts, or gears for transmitting the driving force
upon direct engagement with other gears.
[0045] Although the first driving force transmission member
(sprocket 7A) and the second driving force transmission member
(sprocket 10A) have been shown and described as being respectively
connected to crankshaft 2 and second camshaft 4A, it will be
understood that the first driving force transmission member
(sprocket 7A) to be installed to housing 6A may be conversely
connected to the second camshaft 4A, while the second driving force
transmission member (sprocket 10A) to be installed to first
camshaft 3A may be conversely connected to crankshaft 2.
[0046] Turning back to the conventional valve timing control system
disclosed in the Publication No. 9-280020 discussed in "Background
of the Invention", in which the drawback of increasing the
production cost for the first camshaft has been encountered. As a
measure for the above drawback, it may be proposed to fix the vane
rotor an the driving force transmission member to the camshaft by
the cam bolt under a condition where the end face of the vane rotor
or the driving force transmission member is brought into contact
with the end face of the cam the camshaft. However, in this case,
the cam bolt must support whole the rotation control mechanism
including the housing, and therefore a high load is applied to the
cam bolt thereby deforming the cam bolt. In the event that the cam
bolt is deformed, an inertia force of the rotation control
mechanism applied to the camshaft becomes high thereby causing
generation of vibrational noise and lowering of durability of a
bearing section for the camshaft. Such a problem may be solved to a
certain extent by thickening the cam bolt. However, there is a
limit for thickening the cam bolt. If the cam bolt is made too
thick, passages for hydraulic pressure cannot be formed in the
first camshaft and in the vane rotor. Thus, such a measure is
insufficient to prevent deformation of the cam bolt, and therefore
further improvements have been desired. It will be understood that
such further improvements can be achieved by the present
invention.
[0047] As appreciated from the above, according to the present
invention, the cylindrical wall portion of the generally cup-shaped
section of the second driving force transmission member is fitted
on the end section of the camshaft and in the depression of the
vane rotor, and therefore both the vane rotor and the second
driving force transmission member can be fitted and supported on
the end section of the first camshaft. Consequently, both the vane
rotor and the second driving force transmission member can be
securely installed to the first camshaft under a condition where
the load of the vane rotor and the second driving force
transmission member is hardly applied to the cam bolt. This can
effectively avoid difficulties such as generation of vibrational
noise due to deformation of the cam bolt, lowering in durability of
a bearing section for the camshaft, and the like. Additionally, the
first camshaft is not required to be provided at its outer
periphery with an engagement flange or the like, thereby preventing
a rise in production cost of the first camshaft.
[0048] The entire contents of Japanese Patent Application No.
2000-320488, filed Oct. 20, 2000, are incorporated herein by
reference.
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