U.S. patent application number 14/193860 was filed with the patent office on 2014-09-04 for valve timing control system of internal combustion engine.
This patent application is currently assigned to HITACHI AUTOMOTIVE SYSTEMS, LTD.. The applicant listed for this patent is HITACHI AUTOMOTIVE SYSTEMS, LTD.. Invention is credited to Shinichi KAWADA, Hiroyuki NEMOTO, Ryo TADOKORO, Atsushi YAMANAKA.
Application Number | 20140245978 14/193860 |
Document ID | / |
Family ID | 51420285 |
Filed Date | 2014-09-04 |
United States Patent
Application |
20140245978 |
Kind Code |
A1 |
TADOKORO; Ryo ; et
al. |
September 4, 2014 |
VALVE TIMING CONTROL SYSTEM OF INTERNAL COMBUSTION ENGINE
Abstract
In a valve timing control system of an internal combustion
engine employing both an electric-motor-driven intake valve timing
control device (VTC) and an electric-motor-driven exhaust VTC
having similar fundamental configurations, a maximum
drive-efficiency motor-speed range of a first electric motor of the
intake VTC and a maximum drive-efficiency motor-speed range of a
second electric motor of the exhaust VTC are set to differ from
each other depending on two different working ranges respectively
suitable for the intake VTC and the exhaust VTC such that the
maximum drive-efficiency motor-speed range of the intake VTC is set
higher than that of the exhaust VTC. A reduction ratio of a first
speed reducer configured to reduce a rotational speed of the first
electric motor is set higher than that of a second speed reducer
configured to reduce a rotational speed of the second electric
motor.
Inventors: |
TADOKORO; Ryo; (Atsugi-shi,
JP) ; KAWADA; Shinichi; (Isehara-shi, JP) ;
YAMANAKA; Atsushi; (Atsugi-shi, JP) ; NEMOTO;
Hiroyuki; (Hitachi-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HITACHI AUTOMOTIVE SYSTEMS, LTD. |
Hitachinaka-shi |
|
JP |
|
|
Assignee: |
HITACHI AUTOMOTIVE SYSTEMS,
LTD.
Hitachinaka-shi
JP
|
Family ID: |
51420285 |
Appl. No.: |
14/193860 |
Filed: |
February 28, 2014 |
Current U.S.
Class: |
123/90.11 |
Current CPC
Class: |
F01L 2820/032 20130101;
F01L 2001/34433 20130101; F01L 2001/0537 20130101; F01L 2001/34496
20130101; F01L 2001/34479 20130101; F01L 1/344 20130101 |
Class at
Publication: |
123/90.11 |
International
Class: |
F01L 13/00 20060101
F01L013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2013 |
JP |
2013-040325 |
Claims
1. A valve timing control system of an internal combustion engine,
comprising: an electric-motor-driven intake valve timing control
device installed on an intake camshaft and having a first electric
motor provided to generate torque by energizing the first electric
motor; and an electric-motor-driven exhaust valve timing control
device installed on an exhaust camshaft and having a second
electric motor provided to generate torque by energizing the second
electric motor, wherein a maximum drive-efficiency motor-speed
range of the first electric motor of the electric-motor-driven
intake valve timing control device and a maximum drive-efficiency
motor-speed range of the second electric motor of the
electric-motor-driven exhaust valve timing control device are set
to differ from each other depending on a first working range
suitable for the electric-motor-driven intake valve timing control
device and a second working range suitable for the
electric-motor-driven exhaust valve timing control device.
2. The valve timing control system as recited in claim 1, wherein:
the maximum drive-efficiency motor-speed range of the first
electric motor of the electric-motor-driven intake valve timing
control device, whose working range is wider than the working range
of the electric-motor-driven exhaust valve timing control device,
is set higher than that of the second electric motor of the
electric-motor-driven exhaust valve timing control device.
3. The valve timing control system as recited in claim 1, wherein:
each of the first electric motor of the electric-motor-driven
intake valve timing control device and the second electric motor of
the electric-motor-driven exhaust valve timing control device is a
brush-equipped direct-current motor.
4. A valve timing control system of an internal combustion engine,
comprising: an electric-motor-driven intake valve timing control
device installed on an intake camshaft, the electric-motor-driven
intake valve timing control device comprising: a first electric
motor provided to generate torque by energizing the first electric
motor; and a first speed reducer configured to reduce a rotational
speed of the first electric motor, and transmit the reduced
rotational speed to the intake camshaft for changing intake valve
timing; and an electric-motor-driven exhaust valve timing control
device installed on an exhaust camshaft, the electric-motor-driven
exhaust valve timing control device comprising: a second electric
motor provided to generate torque by energizing the second electric
motor; and a second speed reducer configured to reduce a rotational
speed of the second electric motor, and transmit the reduced
rotational speed to the exhaust camshaft for changing exhaust valve
timing, wherein a reduction ratio of the first speed reducer for a
reduction in the rotational speed of the first electric motor and a
reduction ratio of the second speed reducer for a reduction in the
rotational speed of the second electric motor are set to differ
from each other.
5. The valve timing control system as recited in claim 4, wherein:
the reduction ratio of the first speed reducer of the
electric-motor-driven intake valve timing control device is set to
be greater than the reduction ratio of the second speed reducer of
the electric-motor-driven exhaust valve timing control device.
6. The valve timing control system as recited in claim 4, wherein:
each of the first speed reducer of the electric-motor-driven intake
valve timing control device and the second speed reducer of the
electric-motor-driven exhaust valve timing control device is a
cycloid speed reducer employing a plurality of rollers.
7. A valve timing control system of an internal combustion engine,
comprising: an electric-actuator equipped intake valve timing
control device installed on an intake camshaft, the
electric-actuator equipped intake valve timing control device
comprising: a first electric actuator provided to generate torque
by energizing the first electric actuator; and a first speed
reducer configured to reduce a rotational speed of the first
electric actuator, and transmit the reduced rotational speed to the
intake camshaft for changing intake valve timing; and an
electric-actuator equipped exhaust valve timing control device
installed on an exhaust camshaft, the electric-actuator equipped
exhaust valve timing control device comprising: a second electric
actuator provided to generate torque by energizing the second
electric actuator; and a second speed reducer configured to reduce
a rotational speed of the second electric actuator, and transmit
the reduced rotational speed to the exhaust camshaft for changing
exhaust valve timing, wherein a reduction ratio of the first speed
reducer for a reduction in the rotational speed of the first
electric actuator and a reduction ratio of the second speed reducer
for a reduction in the rotational speed of the second electric
actuator are set to differ from each other.
Description
TECHNICAL FIELD
[0001] The present invention relates to a valve timing control
system of an internal combustion engine for variably controlling
valve timings (i.e., valve open timing and valve closure timing) of
intake and exhaust valves.
BACKGROUND ART
[0002] A valve timing control system, which is configured to change
an angular phase of a camshaft relative to a timing sprocket by
virtue of hydraulic pressure, is generally known. In recent years,
there have been proposed and developed various valve timing control
systems in which an angular phase of a camshaft relative to a
timing sprocket that is configured to rotate in synchronism with
rotation of an engine crankshaft is changed by transmitting rotary
motion (torque) of an electric motor through a speed reducer to the
camshaft, so as to variably control intake-valve timing and
exhaust-valve timing.
[0003] One such valve timing control system has been disclosed in
Japanese Unexamined Patent Application Publication No. 2006-207398
(hereinafter is referred to as "JP2006-207398"), corresponding to
U.S. Pat. No. 7,603,223, issued on Oct. 13, 2009. In the valve
timing control system disclosed in JP2006-207398, two
electric-motor-driven valve timing control devices are mounted
respectively on the intake camshaft and the exhaust camshaft.
SUMMARY OF THE INVENTION
[0004] By the way, the working range of the intake valve timing
control (VTC) device and the working range of the exhaust valve
timing control (VTC) device generally differ from each other,
depending on engine operating conditions. Regarding the intake
electric-motor-driven VTC device, its electric motor tends to be
frequently driven over the entire engine operating range after the
engine has been started. In particular, under high engine-speed
conditions, the drive load on the motor of the intake VTC device
tends to increase. In contrast, regarding the exhaust
electric-motor-driven VTC device, its electric motor tends to be
frequently driven at middle engine speeds. Thus, in such a middle
engine-speed range, the drive load on the motor of the exhaust VTC
device tends to increase.
[0005] However, in the case of the valve timing control system
disclosed in JP2006-207398, the electric motors, respectively
applied to the intake VTC device and the exhaust VTC device, have
almost the same configuration. Additionally, the speed reducers are
the same in the intake VTC device and the exhaust VTC device. For
the reasons discussed above, assume that the drive efficiencies of
the electric motors of the intake VTC device and the exhaust VTC
device are both set to a drive efficiency which is predetermined to
be suitable for the drive load in a specific engine-speed range
within which the electric motor of one of the intake VTC device and
the exhaust VTC device frequently operates. In such a case, there
is an increased tendency for the drive efficiency of the electric
motor of the other VTC device, which is unsuitable for the specific
engine-speed range, to be undesirably decreased.
[0006] Accordingly, it is an object of the invention to provide a
valve timing control system of an internal combustion engine,
configured to efficiently drive each of electric motors of an
intake valve timing control device and an exhaust valve timing
control device.
[0007] In order to accomplish the aforementioned and other objects
of the present invention, a valve timing control system of an
internal combustion engine comprises an electric-motor-driven
intake valve timing control device installed on an intake camshaft
and having a first electric motor provided to generate torque by
energizing the first electric motor, and an electric-motor-driven
exhaust valve timing control device installed on an exhaust
camshaft and having a second electric motor provided to generate
torque by energizing the second electric motor, wherein a maximum
drive-efficiency motor-speed range of the first electric motor of
the electric-motor-driven intake valve timing control device and a
maximum drive-efficiency motor-speed range of the second electric
motor of the electric-motor-driven exhaust valve timing control
device are set to differ from each other depending on a first
working range suitable for the electric-motor-driven intake valve
timing control device and a second working range suitable for the
electric-motor-driven exhaust valve timing control device.
[0008] According to another aspect of the invention, a valve timing
control system of an internal combustion engine comprises an
electric-motor-driven intake valve timing control device installed
on an intake camshaft, the electric-motor-driven intake valve
timing control device comprising a first electric motor provided to
generate torque by energizing the first electric motor, and a first
speed reducer configured to reduce a rotational speed of the first
electric motor, and transmit the reduced rotational speed to the
intake camshaft for changing intake valve timing, and an
electric-motor-driven exhaust valve timing control device installed
on an exhaust camshaft, the electric-motor-driven exhaust valve
timing control device comprising a second electric motor provided
to generate torque by energizing the second electric motor, and a
second speed reducer configured to reduce a rotational speed of the
second electric motor, and transmit the reduced rotational speed to
the exhaust camshaft for changing exhaust valve timing, wherein a
reduction ratio of the first speed reducer for a reduction in the
rotational speed of the first electric motor and a reduction ratio
of the second speed reducer for a reduction in the rotational speed
of the second electric motor are set to differ from each other.
[0009] According to a further aspect of the invention, a valve
timing control system of an internal combustion engine, comprises
an electric-actuator equipped intake valve timing control device
installed on an intake camshaft, the electric-actuator equipped
intake valve timing control device comprising a first electric
actuator provided to generate torque by energizing the first
electric actuator, and a first speed reducer configured to reduce a
rotational speed of the first electric actuator, and transmit the
reduced rotational speed to the intake camshaft for changing intake
valve timing, and an electric-actuator equipped exhaust valve
timing control device installed on an exhaust camshaft, the
electric-actuator equipped exhaust valve timing control device
comprising a second electric actuator provided to generate torque
by energizing the second electric actuator, and a second speed
reducer configured to reduce a rotational speed of the second
electric actuator, and transmit the reduced rotational speed to the
exhaust camshaft for changing exhaust valve timing, wherein a
reduction ratio of the first speed reducer for a reduction in the
rotational speed of the first electric actuator and a reduction
ratio of the second speed reducer for a reduction in the rotational
speed of the second electric actuator are set to differ from each
other.
[0010] 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
[0011] FIG. 1 is a plane cross-sectional view illustrating the
essential part of the embodiment of a valve timing control
system.
[0012] FIG. 2 is a view taken in the direction of the arrow A of
FIG. 1.
[0013] FIG. 3 is a cross-sectional view taken along the line B-B of
FIG. 2 and illustrating the longitudinal cross section of an intake
valve timing control (VTC) device of the embodiment.
[0014] FIG. 4 is a perspective disassembled view illustrating major
component parts constructing the VTC device of the embodiment.
[0015] FIG. 5 is a lateral cross section taken along the line C-C
of FIG. 3.
[0016] FIG. 6 is a lateral cross section taken along the line D-D
of FIG. 3.
[0017] FIG. 7 is a lateral cross section taken along the line E-E
of FIG. 3.
[0018] FIG. 8 is a cross-sectional view taken along the line F-F of
FIG. 2 and illustrating the longitudinal cross section of an
exhaust VTC device of the embodiment.
[0019] FIG. 9 is a lateral cross section taken along the line G-G
of FIG. 8.
[0020] FIG. 10 is a lateral cross section taken along the line H-H
of FIG. 8.
[0021] FIG. 11 is a characteristic diagram illustrating the
relationship between a motor speed of each of the intake-VTC-side
electric motor and the exhaust-VTC-side electric motor and a drive
efficiency of each of the electric motors.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] Referring now to the drawings, particularly to FIGS. 1-2,
the valve timing control system of the embodiment includes an
intake camshaft 02 rotatably supported on the upper deck of a
cylinder head 01 through a frame-shape camshaft-journal bearing
member 06 fixedly connected onto the upper deck of cylinder head
01, an exhaust camshaft 03 rotatably supported on the cylinder head
01 through the camshaft-journal bearing member 06 and arranged
parallel to the intake camshaft 02, an electric-motor-driven intake
valve timing control device (hereinafter referred to as "intake
VTC") 04 installed on the front end of intake camshaft 02, and an
electric-motor-driven exhaust valve timing control device
(hereinafter referred to as "exhaust VTC") 05 installed on the
front end of exhaust camshaft 03.
[0023] Camshaft-journal bearing member 06 is made from aluminum
alloy. Both ends of intake camshaft 02, and the intermediate
sections of intake camshaft 02 are rotatably supported by means of
bearings, that is, rotatably sandwiched between half-round sections
formed on the upper deck of cylinder head 01 and upper bearing
halves of camshaft-journal bearing member 06 fit into the
respective half-round sections of cylinder head 01. In a similar
manner, both ends of exhaust camshaft 03, and the intermediate
sections of exhaust camshaft 03 are rotatably supported by means of
bearings, that is, rotatably sandwiched between half-round sections
formed on the upper deck of cylinder head 01 and upper bearing
halves of camshaft-journal bearing member 06 fit into the
respective half-round sections of cylinder head 01. The front end
of camshaft-journal bearing member 06 is formed integral with a
chain cover 07 configured to partially cover both the intake VTC 04
and the exhaust VTC 05. A VTC cover 3 is bolted to the front end of
chain cover 07 on the side of intake VTC 04 for hermetically
covering the front end of intake VTC 04. In a similar manner, a VTC
cover 3 is bolted to the front end of chain cover 07 on the side of
exhaust VTC 05 for hermetically covering the front end of exhaust
VTC 05.
[Intake VTC]
[0024] First, the above-mentioned intake VTC 04 is hereunder
explained in detail. As shown in FIGS. 3-4, intake VTC 04 is
comprised of a sprocket 1 (serving as a driving rotary member) that
rotates in synchronism with rotation of an engine crankshaft, and a
phase change mechanism (a phase converter) 2 installed between the
sprocket 1 and the intake camshaft 02 for changing a relative
angular phase between the sprocket 1 and the intake camshaft 02
depending on an engine operating condition.
[0025] Sprocket 1 is comprised of an annular sprocket body 1a, a
timing gear 1b formed integral with the outer periphery of sprocket
body 1a, and an internal-tooth structural member 19. Sprocket body
1a is made from iron-based metal material, and formed with a
stepped inner peripheral portion and formed integral with the
timing gear 1b. Timing gear 1b receives torque from the crankshaft
through a timing chain (not shown) wound on both a sprocket on the
crankshaft and the sprocket 1 on the intake camshaft side.
Internal-tooth structural member 19 is formed integral with the
front end of sprocket body 1a on the intake camshaft side.
[0026] Also, sprocket 1 is rotatably supported by a large-diameter
ball bearing 43 interleaved between the sprocket body 1a and a
driven rotary member, simply, a driven member 9 (described later)
fixedly connected to the front end of intake camshaft 02, so as to
permit rotary motion of intake camshaft 02 relative to sprocket
1.
[0027] Large-diameter ball bearing 43 is comprised of an outer ring
43a, an inner ring 43b, and balls 43c confined between outer and
inner rings 43a-43b. The outer ring 43a is fixed to the inner
periphery of sprocket body 1a, whereas the inner ring 43b is fixed
to the outer periphery of driven member 9 (described later).
[0028] Sprocket body 1a has an outer-ring retaining annular groove
60 formed and cut in its inner peripheral surface. Outer-ring
retaining annular groove 60 is formed as a shouldered annular
groove into which the outer ring 43a of large-diameter ball bearing
43 is axially press-fitted. The shouldered portion of outer-ring
retaining annular groove 60 serves to position one axial end face
(i.e., a forward end face, viewing FIG. 3) of the outer ring 43a in
place.
[0029] Internal-tooth structural member 19 is formed integral with
the circumference of the front end of sprocket body 1a, and formed
into a cylindrical shape extended toward an electric motor 12
(described later) of phase converter 2. Internal-tooth structural
member 19 is formed on its inner periphery with a plurality of
waveform internal teeth 19a. The annular rear end face of an
annular female screw-threaded member 6, formed integral with a
housing 5 (described later), and the annular front end face of
internal-tooth structural member 19 are arranged to be axially
opposed to each other.
[0030] An annular retainer plate 61 is located at the rear end of
sprocket body 1a, facing apart from the internal-tooth structural
member 19. Retainer plate 61 is made from a metal plate. As shown
in FIG. 3, the outside diameter of retainer plate 61 is dimensioned
to be approximately equal to that of the sprocket body 1a. The
inside diameter of retainer plate 61 is set or dimensioned to be
less than the inside diameter of the outer ring 43a of ball bearing
43 and also dimensioned to be approximately equal to the outside
diameter of the inner ring 43b of ball bearing 43.
[0031] Hence, the inner peripheral portion 61a (see FIG. 4) of
retainer plate 61 is arranged to be axially opposed to the rearward
end face 43e of the outer ring 43a of ball bearing 43 with a given
clearance space in such a manner as to cover the rearward end face
43e of the outer ring 43a. Also, the inner peripheral portion 61a
of annular retainer plate 61 has a radially-inward protruding
stopper 61b integrally formed at a given circumferential angular
position of the inner peripheral portion 61a.
[0032] As seen in FIG. 6, the radially-inward protruding stopper
61b is formed into a substantially sector. The innermost edge 61c
of stopper 61b is configured to be substantially conformable to a
shape of the circular-arc peripheral surface of a stopper groove
02b (described later) of the front end of intake camshaft 02. The
outer peripheral portion of retainer plate 61 is formed with
circumferentially equidistant-spaced, six bolt insertion holes 61d
(through holes) through which bolts 7 are inserted.
[0033] Furthermore, an annular pressing member 62 is interleaved
between the inside face (the left-hand side face) of retainer plate
61 and the rearward end face 43e of the outer ring 43a of ball
bearing 43. Pressing member 62 is provided for applying a slight
push from the inside face of retainer plate 61 to the rearward end
face 43e of the outer ring 43a, when the annular female
screw-threaded member 6 (housing 5), the sprocket 1, and the
retainer plate 61 are integrally connected to each other by
fastening them together with bolts 7.
[0034] In a similar manner to the six bolt insertion holes 61d
(through holes) formed in the retainer plate 61, the outer
peripheral portion of sprocket body 1a (internal-tooth structural
member 19) is formed with circumferentially equidistant-spaced, six
bolt insertion holes 1c (through holes). On the other hand, the
annular female screw-threaded member 6 is formed with six female
screw threads 6a configured to be conformable to respective
circumferential positions of bolt insertion holes 1c (bolt
insertion holes 61d). Hence, the annular female screw-threaded
member 6 (the housing 5), the sprocket 1, and the retainer plate 61
are integrally connected to each other by axially fastening them
together with bolts 7.
[0035] Outside diameters of the sprocket body 1a, the
internal-tooth structural member 19, the retainer plate 61, and the
female screw-threaded member 6 are dimensioned to be almost the
same.
[0036] As shown in FIGS. 1-3, chain cover 07 is laid out and bolted
to an engine body in a manner so as to vertically extend for
covering the timing chain (not shown) wound on the sprocket. Chain
cover 07 has a substantially circular opening 07a (see FIGS. 1 and
3) configured to be conformable to the contour of intake VTC 04 and
a substantially circular opening 07b (see FIG. 1) configured to be
conformable to the contour of exhaust VTC 05. The openings 07a-07b
are formed in respective annular walls of the front end of chain
cover 07. Each of the annular walls has four boss sections 07c
integrally formed on the inner periphery of the annular wall and
circumferentially spaced from each other. Four female screw-threads
07d are machined in respective boss sections 07c such that female
screw-threads 07d extend from the front end face of the annular
wall into the respective boss sections.
[0037] As shown in FIGS. 1 and 3, VTC cover 3 on the side of intake
VTC 04 is made from aluminum alloy and formed into a substantially
cup shape. The VTC cover 3 is comprised of a cup-shaped cover main
body 3a and an annular flange 3b formed integral with the
circumference of the right-hand side opening end (viewing FIG. 1)
of cover main body 3a. Cover main body 3a is configured to cover
the front end of phase converter 2. Cover main body 3a has a
slightly axially-extending cylindrical wall portion 3c integrally
formed at a given position deviated radially upward from the center
of the frontal flat wall portion of cover main body 3a. The
cylindrical wall portion 3c has a retaining through-hole 3d formed
therein.
[0038] Annular flange 3b is integrally formed with four tab-like
portions 3e, circumferentially spaced apart from each other at
intervals of approximately 90 degrees. Four bolt insertion holes 3f
(through holes) are bored in respective tab-like portions 3e of the
annular flange 3b. VTC cover 3 is fixedly connected to the chain
cover 07 by means of bolts 54 (see FIG. 3), which are inserted
through the respective bolt insertion holes 3f and screwed into the
female screw-threads 07d formed in the respective boss sections 07c
of chain cover 07.
[0039] Also, the inner periphery of the right-hand side opening end
(viewing FIG. 3) of cover main body 3a is formed as a shouldered
oil-seal retaining annular groove 3h. A large-diameter oil seal 50
is interleaved between the shouldered oil-seal retaining annular
groove 3h of cover main body 3a and the outer peripheral surface of
housing 5. Large-diameter oil seal 50 is formed into a
substantially C-shape in lateral cross section. Oil seal 50 is made
from synthetic rubber (a base material), and also a core metal is
buried in the base material. The cylindrical outer peripheral
surface of oil seal 50 is fitted to the shouldered oil-seal
retaining annular groove 3h of cover main body 3a of VTC cover 3 in
a fluid-tight fashion, whereas the inner periphery of oil seal 50
(that is, a spring-loaded single lip and a non-spring-loaded dust
lip) is fitted onto the outer periphery of housing 5 in a
fluid-tight fashion.
[0040] As shown in FIGS. 3-4, housing 5 is comprised of a housing
main body 5a made from iron-based metal material and formed into a
substantially cylindrical shape with a rear end face (a bottom
face) by pressing, and a seal plate 11 made from synthetic resin
(non-magnetic material) and provided for sealing the axially
forward opening (the left-hand side opening end, viewing FIG. 3) of
housing main body 5a.
[0041] Housing main body 5a has a bottom 5b formed at its rear end,
facing the internal-tooth structural member 19. Housing main body
5a is formed in a substantially center of the bottom 5b with a
large-diameter eccentric-shaft insertion hole into which an
eccentric shaft 39 (described later) is inserted. An
axially-leftward extending cylindrical portion 5c is formed
integral with the annular edge of the eccentric-shaft insertion
hole in a manner so as to somewhat extend in the axial direction of
intake camshaft 02. The previously-discussed annular female
screw-threaded member 6 is formed integral with the outer periphery
of the bottom 5b of housing 5.
[0042] Intake camshaft 02 has two rotary drive cams (per cylinder)
integrally formed on its outer periphery for operating the
associated two intake valves (not shown) per one engine cylinder.
Also, intake camshaft 02 has a flanged portion 02a integrally
formed at its front end. Driven member 9 is fixedly connected to
the front end of the flanged portion 02a by means of a cam bolt 10
under a condition where the front end face of the flanged portion
02a has been kept in abutted-engagement with the rear end face of a
fixed-end portion 9a of driven member 9. As seen in FIG. 3, the
outside diameter of flanged portion 02a is dimensioned to be
slightly greater than that of the fixed-end portion 9a of driven
member 9. Hence, after installation of all component parts, the
circumference of the front end face of the flanged portion 02a of
intake camshaft 02 is brought into abutted-engagement with the
rearward end face of the inner ring 43b of large-diameter ball
bearing 43.
[0043] As shown in FIG. 6, the outer periphery of the flanged
portion 02a of intake camshaft 02 is partially machined or cut as
the stopper groove 02b recessed along the circumferential
direction. The radially-inward protruding stopper 61b of retainer
plate 61 is circumferentially moveably installed in the stopper
groove 02b. Stopper groove 02b is formed into a circular-arc shape
having a specified circumferential length to permit a
circumferential movement of stopper 61b within a limited motion
range determined based on the specified circumferential length.
Hence, a maximum phase-advance position of intake camshaft 02
relative to sprocket 1 is restricted by abutment between the
counterclockwise edge of stopper 61b and the clockwise edge 02c of
stopper groove 02b. On the other hand, a maximum phase-retard
position of intake camshaft 02 relative to sprocket 1 is restricted
by abutment between the clockwise edge of stopper 61b and the
counterclockwise edge 02d of stopper groove 02b.
[0044] As appreciated from the longitudinal cross section of FIG.
3, stopper 61b is kept in a spaced, contact-free relationship with
the fixed-end portion 9a of driven member 9 in the axial direction,
thus adequately suppressing undesirable interference between the
stopper 61b and the fixed-end portion 9a.
[0045] As appreciated from the longitudinal cross section of FIG.
3, cam bolt 10 is comprised of a head 10a and a shank 10b formed
integral with each other, and an annular washer provided at the
boundary of head 10a and shank 10b. Shank 10b is formed on its
outer periphery with a male-screw-threaded portion, which is
screwed into a female-screw-threaded portion machined into the
front end of intake camshaft 02 along the axis of intake camshaft
02.
[0046] Driven member 9 is made from iron-based metal material. As
seen from the longitudinal cross section of FIG. 3, the driven
member 9 is comprised of the disk-shaped fixed-end portion 9a, an
axially-forward-extending cylindrical portion 9b formed integral
with the front end face of disk-shaped fixed-end portion 9a, and a
substantially cylindrical cage 41, which cage is formed integral
with the outer periphery of disk-shaped fixed-end portion 9a and
configured to serve as a roller holder for holding a plurality of
rollers 48 (rolling elements).
[0047] The rear end face of disk-shaped fixed-end portion 9a is
arranged to abut with the front end face of the flanged portion 02a
of intake camshaft 02, and fixedly connected to the flanged portion
02a by an axial force of cam bolt 10.
[0048] As shown in FIG. 3, cylindrical portion 9b is formed with a
central bore 9d into which the shank 10b of cam bolt 10 is
inserted. A needle bearing 38 is mounted on the outer periphery of
cylindrical portion 9b.
[0049] As shown in FIGS. 3-5, cage 41 (the roller holder) is
configured to further extend from the outer periphery of
disk-shaped fixed-end portion 9a, and bent into a substantially L
shape in longitudinal cross section and formed into a substantially
cylindrical shape extending in the same axial direction as the
cylindrical portion 9b and having an annular bottom axially opposed
to one sidewall of a ball-bearing outer ring 47b (described later).
More concretely, the substantially cylindrical portion 41a of cage
41 is configured to extend toward the bottom 5b of housing 5
through an annular internal space 44 defined between the annular
female screw-threaded member 6 and the axially-leftward extending
cylindrical portion 5c. Also, the substantially cylindrical portion
41a of cage 41 has a plurality of axially-protruding lugs. As a
whole, the axially-protruding lugs are shaped into a substantially
comb-tooth shape. That is, by virtue of the axially-protruding
lugs, each having a substantially rectangular cross-section, a
plurality of roller-holding holes 41b are configured to be
equidistant-spaced from each other with a given circumferential
interval in the circumferential direction of the outer periphery of
disk-shaped fixed-end portion 9a. Rollers 48 are rotatably held or
installed in respective roller-holding holes 41b. The substantially
cylindrical portion 41a of cage 41 has one fewer roller-holding
holes (in other words, one fewer rollers or one fewer
axially-protruding lugs) than the number of internal teeth 19a of
internal-tooth structural member 19.
[0050] An inner-ring retaining annular groove 63 is machined and
defined between the outer periphery of disk-shaped fixed-end
portion 9a and the annular bottom of cage 41 formed integral with
each other, for retaining the inner ring 43b of large-diameter ball
bearing 43.
[0051] Inner-ring retaining annular groove 63 is formed as a
shouldered annular groove configured to be radially opposed to the
outer-ring retaining annular groove 60 of sprocket body 1a.
Inner-ring retaining annular groove 63 is comprised of a
cylindrical outer peripheral surface extending in the axial
direction of intake camshaft 02 and a radially-extending shouldered
annular surface configured to extend radially outward from the
innermost end of the cylindrical outer peripheral surface. When
assembling, the inner ring 43b of ball bearing 43 is axially
press-fitted onto the cylindrical outer peripheral surface. At the
same time, the forward end face of the press-fitted inner ring 43b
is brought into abutted-engagement with the shouldered annular
surface of inner-ring retaining annular groove 63, to position one
axial end face (the forward end face) of the inner ring 43b in
place.
[0052] Phase converter 2 is mainly constructed by the electric
motor 12 coaxially located at the front end of intake camshaft 02,
and a roller speed reducer 8 provided for reducing the rotational
speed of the motor output shaft 13 of electric motor 12 and for
transmitting the reduced motor speed (in other words, the increased
motor torque) to the intake camshaft 02.
[0053] As seen in FIGS. 3-4, electric motor 12 is a brush-equipped
direct-current (DC) motor. Electric motor 12 is comprised of the
housing 5 serving as a yoke and rotating together with the sprocket
1, the motor output shaft 13 rotatably installed in the housing 5,
a pair of substantially semi-circular permanent magnets 14-15
fixedly connected onto the inner peripheral surface of housing 5,
and a stator 16 fixed to the seal plate 11.
[0054] Motor output shaft 13 is formed into a shouldered
cylindrical-hollow shape, and serves as an armature. Motor output
shaft 13 is constructed by a large-diameter portion 13a of the
intake-camshaft side and a small-diameter portion 13b of the
brush-holder side through a shouldered portion 13c formed
substantially at a midpoint of the axially-extending
cylindrical-hollow motor output shaft. An iron-core rotor 17,
having a plurality of magnetic poles, is fixedly connected onto the
outer periphery of large-diameter portion 13a. Eccentric shaft 39
is axially press-fitted into the large-diameter portion 13a, in a
manner so as to be axially positioned in place by the inside
annular face of shouldered portion 13c.
[0055] An annular member 20 is press-fitted onto the outer
periphery of small-diameter portion 13b. A commutator 21 is axially
press-fitted onto the outer peripheral surface of annular member
20, in a manner so as to be axially positioned in place by the
outside annular face of shouldered portion 13c.
[0056] Furthermore, a plug 53 is fixed or press-fitted to the inner
peripheral surface of small-diameter portion 13b, for preventing or
adequately suppressing undesirable leakage of lubricating oil,
which oil is supplied into the cylindrical-hollow motor output
shaft 13 and eccentric shaft 39 for lubrication of a ball bearing
37 (described later) as well as the previously-discussed needle
bearing 38, to the outside.
[0057] Iron-core rotor 17 is formed by a magnetic material having a
plurality of magnetic poles. The outer periphery of iron-core rotor
17 is constructed as a bobbin having slots on which coil windings
of an electromagnetic coil 18 is wound.
[0058] On the other hand, commutator 21 is formed as a
substantially annular shape and made from a conductive material.
Commutator 21 is divided into a plurality of segments whose number
is equal to the number of magnetic poles of iron-core rotor 17.
Terminals of the coil winding (not shown) drawn out from
electromagnetic coil 18 are electrically connected to each of
segments of commutator 21. That is, the terminals of the coil
winding are sandwiched and electrically connected to the hemmed
section formed on the periphery of commutator 21.
[0059] As a whole, the substantially semi-circular permanent
magnets 14-15 are formed into a cylindrical shape, and have a
plurality of magnetic poles in the circumferential direction. The
axial position of each of permanent magnets 14-15 is offset forward
from the fixed position of iron-core rotor 17.
[0060] As shown in FIG. 7, stator 16 is mainly comprised of a
disk-shaped synthetic-resin plate 22, a pair of synthetic-resin
brush holders 23a-23b, a pair of first brushes 25a-25b, a
radially-inside electricity-feeding slip ring 26a, a
radially-outside electricity-feeding slip ring 26b, and pig-tale
harnesses 27a-27b. Disk-shaped synthetic-resin plate 22 is
integrally connected to the inner periphery of seal plate 11. Brush
holders 23a-23b are attached onto the inside face of
synthetic-resin plate 22. The first brushes 25a-25b serve as
current-supply switching brushes and supported by respective
holders 23a-23b so as to be radially slidable. The radially-inward
ends of first brushes 25a-25b are kept in sliding-contact
(elastic-contact or electric-contact) with the outer peripheral
surface of commutator 21 by respective spring forces of coil
springs 24a-24b. The radially-inside electricity-feeding slip ring
26a and the radially-outside electricity-feeding slip ring 26b are
attached to the synthetic-resin plate 22, such that the outside
face (the left-hand side face, viewing FIG. 3) of each of
electricity-feeding slip rings 26a-26b is partially exposed and
that the inside face (the right-hand side face, viewing FIG. 3) of
each of slip rings 26a-26b is buried in the front end face of
synthetic-resin plate 22. The first brush 25a and the
electricity-feeding slip ring 26b are electrically connected to
each other via the pig-tale harness 27a, whereas the first brush
25b and the electricity-feeding slip ring 26a are electrically
connected to each other via the pig-tale harness 27b. The
radially-inside annular slip ring 26a and the radially-outside
annular slip ring 26b are laid out to be coaxial with each other
with a given aperture.
[0061] The previously-discussed seal plate 11 is fitted into an
annular groove cut in the inner periphery of the front end of the
cylindrical housing main body 5a of housing 5, and fixedly
connected to the front end of housing main body 5a in place by
caulking. Also, the subassembly (11, 22) of seal plate 11 and
disk-shaped synthetic-resin plate 22 is formed in its center with a
shaft insertion hole 11a into which one axial end (the left-hand
axial end, viewing FIG. 3) of motor output shaft 13 is partially
inserted.
[0062] Synthetic-resin plate 22 and synthetic-resin brush holders
23a-23b are made from heat-resistant synthetic-resin materials. For
instance, a PPS (polyphenylene sulfide) synthetic resin material is
used as a heat-resistant synthetic resin material.
[0063] A brush retainer 28, which is integrally molded of a
synthetic resin material (serving as an electrical insulating
material), is fixedly connected to the cover main body 3a. In a
similar manner to the synthetic-resin plate 22 and synthetic-resin
brush holders 23a-23b, brush retainer 28 is also made from a
heat-resistant synthetic-resin material, such as a PPS
(polyphenylene sulfide) synthetic resin material. As shown in FIGS.
3-4, brush retainer 28 is formed into a substantially L shape in
side view. Brush retainer 28 is comprised of a substantially
cylindrical brush-retaining portion 28a, a connector portion 28b, a
pair of laterally-extending tab-like brackets 28c, 28c (see FIG.
4), and a pair of terminal strips 31, 31. Brush-retaining portion
28a is inserted into the retaining through-hole 3d. Connector
portion 28b is formed integral with the upper end of
brush-retaining portion 28a. Tab-like brackets 28c, 28c are formed
integral with both sides of brush-retaining portion 28a. Most of
terminal strips 31, 31 are buried in the synthetic-resin brush
retainer 28.
[0064] Terminal strips 31, 31 are arranged parallel with each other
and partly cranked. One end (the downward terminal 31a) of each of
the crank-shaped terminal strips 31 is exposed to the bottom of
brush-retaining portion 28a. The other end (the upward terminal
31b) of each of terminal strips 31 is configured to protrude into a
female fitting groove 28d of connector portion 28b. The upward
terminals 31b, 31b of the two parallel terminal strips 31, 31 are
electrically connected to a control unit (not shown) via a male
socket (not shown) fitted to the female fitting groove 28d.
[0065] Brush-retaining portion 28a is configured to extend
horizontally (axially). An upper hollow sleeve 29b is press-fitted
into an upper cylindrical-hollow through hole bored in the
brush-retaining portion 28a. In a similar manner, a lower hollow
sleeve 29a is press-fitted into a lower cylindrical-hollow through
hole bored in the brush-retaining portion 28a. A pair of second
brushes 30a, 30a are supported by the respective hollow sleeves so
as to be axially slidable. The tips of second brushes 30a, 30a are
kept in sliding-contact (abutted-engagement or electric-contact)
with respective slip rings 26a and 26b.
[0066] For instance, as a preferable material for each of hollow
sleeves 29a-29b, brass such as 70/30 brass (JIS alloy C2600) is
used, thereby ensuring a favorable sliding performance of each of
second brushes 30a, 30a.
[0067] Each of second brushes 30a, 30a is formed into a
substantially rectangular parallelopiped shape. A second coil
spring 32a is disposed between the downward terminal exposed to the
bottom of the upper cylindrical-hollow through hole of
brush-retaining portion 28a and the associated second brush 30a
under preload. In a similar manner, a second coil spring 32a is
disposed between the downward terminal exposed to the bottom of the
lower cylindrical-hollow through hole of brush-retaining portion
28a and the associated second brush 30a under preload. Thus, the
tips of second brushes 30a, 30a are permanently forced or biased
toward respective slip rings 26a and 26b by the spring forces of
second coil springs 32a, 32a, so as to bring the tips of second
brushes 30a, 30a into elastic-contact with the respective outside
faces of slip rings 26a-26b.
[0068] Additionally, a flexible pig-tale harness 33 is connected
between the square base of second brush 30a and the downward
terminal 31a exposed to the bottom of the upper cylindrical-hollow
through hole of brush-retaining portion 28a by welding, to provide
electric connection. In a similar manner, a flexible pig-tale
harness 33 is electrically connected between the square base of
second brush 30a and the downward terminal 31a exposed to the
bottom of the lower cylindrical-hollow through hole of
brush-retaining portion 28a by welding, to provide electric
connection. The lengths of pig-tale harnesses 33, 33 are set to
appropriate lengths sufficient to restrict maximum sliding
movements (maximum axially-extended positions) of second brushes
30a, 30a relative to sleeves 29a-29b for preventing the second
brushes 30a, 30a from falling out of the respective sleeves 29a-29b
by the spring forces of coil springs 32a, 32a.
[0069] An annular seal member 34 is interleaved between the outer
periphery of the root (the basal end) of brush-retaining portion
28a and an annular groove formed in the opening end of the
cylindrical wall portion 3c of cover main body 3a.
[0070] As seen in FIG. 4, each of the diametrically-opposed
tab-like brackets 28c, 28c is formed into a substantially
triangular shape, and formed with a bolt insertion hole (a through
hole) 28e. Thus, brush retainer 28 is fixedly connected to the
cover main body 3a by means of bolts 4, 4 (see FIG. 2), which are
inserted through the respective bolt insertion holes 28e, 28e of
tab-like brackets 28c, 28c and screwed into respective female
screw-threads (not shown) formed in the cover main body 3a.
[0071] The previously-discussed motor output shaft 13 and eccentric
shaft 39 are rotatably supported by means of the small-diameter
ball bearing 37 and the needle bearing 38. Small-diameter ball
bearing 37 is installed on the outer peripheral surface of the root
of the shank 10b near the head 10a of cam bolt 10. On the other
hand, needle bearing 38 is mounted on the outer peripheral surface
of cylindrical portion 9b of driven member 9, and arranged in close
proximity to the right-hand side end (viewing FIG. 3) of
small-diameter ball bearing 37 such that these bearings 37-38 are
juxtaposed to each other.
[0072] Needle bearing 38 is comprised of a cylindrical retainer 38a
press-fitted into the inner peripheral surface of eccentric shaft
39 and a plurality of needle rollers 38b (rolling elements)
rotatably retained inside of the retainer 38a. Each of needle
rollers 38b is in rolling-contact with the outer peripheral surface
of cylindrical portion 9b of driven member 9.
[0073] The inner ring of small-diameter ball bearing 37 is retained
between the annular front end face of cylindrical portion 9b of
driven member 9 and the annular washer 10c of cam bolt 10. On the
other hand, the outer ring of small-diameter ball bearing 37 is
press-fitted to the stepped portion defined between the
small-inside-diameter section and the large-inside-diameter section
of eccentric shaft 39, in a manner so as to be axially positioned
in place by abutment with the inside annular face of the stepped
portion of eccentric shaft 39.
[0074] A small-diameter oil seal (a seal member) 46 is interleaved
between the outer peripheral surface of large-diameter portion 13a
of motor output shaft 13 (eccentric shaft 39) and the inner
peripheral surface of axially-leftward extending cylindrical
portion 5c of housing 5, for preventing leakage of lubricating oil
from the inside of speed reducer 8 toward the inside of electric
motor 12.
[0075] The control unit (not shown) includes an input/output
interface (I/O), memories (RAM, ROM), and a microprocessor or a
central processing unit (CPU). The input/output interface (I/O) of
the control unit receives input information from various
engine/vehicle sensors, namely, a crank angle sensor, a cam shaft
angle sensor, an airflow meter, an engine temperature sensor (an
engine coolant temperature sensor), an accelerator opening sensor,
and the like. Within the control unit, the CPU allows the access by
the I/O interface of input informational data signals from the
engine/vehicle sensors. The CPU is responsible for carrying the
engine control program (i.e., the
ignition-timing/throttle/fuel-injection/valve-timing control
program) stored in memories, and is capable of performing necessary
arithmetic and logic operations, depending on the current
engine/vehicle operating condition, determined based on latest
up-to-date informational data signals from the engine/vehicle
sensors. Computational results (arithmetic calculation results),
that is, calculated output signals are relayed through the output
interface circuitry of the control unit to output stages
(actuators), for electronic spark control, control of an
electronically-controlled throttle valve, control of the
fuel-injection system, and control of the VTC system. Concretely,
the control unit is configured to detect an actual relative phase
of intake camshaft 02 to sprocket 1 responsively to input
informational signals from the crank angle sensor and the cam angle
sensor and also configured to determine a desired relative phase of
intake camshaft 02 to sprocket 1 depending on the current
engine/vehicle operating condition. The control unit is further
configured to perform rotational speed control of motor output
shaft 13 by controlling electric-current supply to the
electromagnetic coil 18 of electric motor 12. The rotational speed
of motor output shaft 13 is reduced by means of the speed reducer
8. In this manner, the actual relative phase of intake camshaft 02
to sprocket 1 can be controlled and brought closer to the desired
value.
[0076] As seen from the cross sections of FIGS. 3 and 5, and the
perspective disassembled view of FIG. 4, speed reducer 8 is mainly
comprised of the eccentric shaft 39 (constructing a part of the
eccentric rotation member) that performs eccentric rotary motion, a
middle-diameter ball bearing 47 (constructing the remainder of the
eccentric rotation member) installed on the outer periphery of
eccentric shaft 39, a plurality of rollers (serving as rolling
elements) 48 rotatably installed on the outer periphery of
middle-diameter ball bearing 47 and circumferentially arranged
substantially at regular intervals, the cage 41 configured to
partition, retain and guide these rollers 48, kept in
rolling-contact with an outer ring 47b (described later) of
middle-diameter ball bearing 47, in the circumferential direction
by respective roller-holding holes 41b (in other words, respective
axially-protruding lugs), while permitting a slight radial
displacement (a slight oscillating motion) of each of rollers 48,
and the driven member 9 formed integral with the cage 41, and the
internal-tooth structural member 19 with the waveform internal
toothed portion 19a.
[0077] Eccentric shaft 39 is formed into a shouldered
cylindrical-hollow shape. Eccentric shaft 39 is constructed by a
small-diameter portion 39a (at the front end) and a large-diameter
portion 39b (at the rear end). The small-diameter portion 39a of
eccentric shaft 39 is press-fitted into the inner peripheral
surface of large-diameter portion 13a of motor output shaft 13. The
large-diameter portion 39b of eccentric shaft 39 is a substantially
cylindrical cam. The geometric center "Y" of the cam contour
surface of the outer periphery of large-diameter portion 39b of
eccentric shaft 39 is slightly displaced from the axis "X" (i.e.,
the rotation center "X" shown in FIGS. 3 and 5) of motor output
shaft 13 in the radial direction.
[0078] As viewed from the longitudinal cross section of FIG. 3,
middle-diameter ball bearing 47 is comprised of an inner ring 47a,
the outer ring 47b, and balls 47c rotatably disposed and confined
between them. The inner ring 47a of ball bearing 47 is press-fitted
onto the outer peripheral surface (i.e., the eccentric-cam contour
surface) of large-diameter portion 39b of eccentric shaft 39 in a
manner so as to be axially positioned in place. In contrast to the
inner ring 47a, the outer ring 47b is not securely fixed in the
axial direction. That is, the outer ring 47b is free and therefore
is able to move contact-free. Concretely, the left-hand sidewall
(viewing FIG. 3) of the outer ring 47b, facing the electric-motor
side, is kept out of contact with the housing 5 of electric motor
12, while the right-hand sidewall of the outer ring 47b, axially
opposed to the annular bottom of cage 41, is kept out of contact
with the inside wall surface of the annular bottom of cage 41. More
concretely, a very small axial clearance "Caxial" is defined
between the right-hand sidewall of the outer ring 47b and the
inside wall surface of the annular bottom of cage 41, axially
opposed to each other. Rollers 48, interleaved between the outer
periphery of outer ring 47b of middle-diameter ball bearing 47 and
the waveform internal toothed portion 19a of internal-tooth
structural member 19, are held in rolling-contact with the outer
peripheral surface of outer ring 47b. A crescent-shaped annular
clearance "Cannular" is defined between the outer peripheral
surface of outer ring 47b and the substantially comb-tooth shaped
protruding portion (the substantially cylindrical portion 41a) of
cage 41. Owing to eccentric rotary motion of eccentric shaft 39,
middle-diameter ball bearing 47 is radially moved or displaced by
virtue of the crescent-shaped annular clearance "Cannular". That
is, the crescent-shaped annular clearance "Cannular" permits a
slight radial displacement (a slight oscillating motion) of
middle-diameter ball bearing 47.
[0079] Each of rollers 48 is made from iron-based metal material,
and formed as a cylindrical solid roller. Owing to the eccentric
displacement (oscillating motion) of middle-diameter ball bearing
47, the radially-inward contact surface of each of rollers 48,
included within a given area, is brought into abutment
(rolling-contact) with the outer peripheral surface of the outer
ring 47b of middle-diameter ball bearing 47. On the other hand, the
radially-outward contact surfaces of some of rollers, associated
with the given area, are fitted into some troughs of internal teeth
19a of internal-tooth structural member 19 (serving as a toothed
wheel or a toothed gear). That is, in the eccentric position of the
eccentric rotation member (namely, the middle-diameter ball bearing
47 and eccentric shaft 39) shown in FIG. 5, roller 48, located at
the 12 o'clock position, is brought into completely
fitted-engagement (full tooth engagement) with the inner face of
the trough between the uppermost two adjacent internal teeth 19a,
19a. In contrast, roller 48, located at the 6 o'clock position, is
brought out of engagement. That is, owing to the eccentric
displacement (oscillating motion) of the eccentric rotation member
(i.e., the middle-diameter ball bearing 47 and eccentric shaft 39),
rollers 48 can radially oscillate, while being circumferentially
guided by respective axially-protruding lugs (respective
roller-holding holes 41b) of cage 41.
[0080] The phase converter 2 of intake VTC 04 is frequently
operated over the entire range of engine speed and load after
engine start-up by driving both the electric motor 12 and the speed
reducer 8, so as to change or convert the angular phase of intake
camshaft 02 relative to sprocket 1 (i.e., the engine crankshaft).
That is, when the engine is started from cold, the relative phase
of intake camshaft 02 is controlled to a given intermediate angular
phase between the maximum phase-advance position and the maximum
phase-retard position, thereby ensuring a better engine
startability. When the engine operating condition changes between
low-speed and low-load operation and high-speed and high-load
operation, a phase change of intake camshaft 02 between the maximum
phase-retard position and the maximum phase-advance position is
repeatedly executed, thereby reducing a pumping loss and
consequently ensuring improved fuel economy and enhanced engine
power output. Furthermore, it is possible to improve the exhaust
emission performance in combination with operation of exhaust VTC
05 (described later).
[0081] Therefore, as seen from the characteristic diagram of FIG.
11, an electric motor having a drive-efficiency characteristic such
that the motor drive efficiency (a positive efficiency .eta.) is
set to become higher in a comparatively high motor-speed range is
used for the intake-VTC-side electric motor 12.
[0082] Additionally, the intake-VTC-side speed reducer 8 is
constructed by a cycloid speed reducer that uses a plurality of
rollers 48. Note that, in the valve timing control system of the
embodiment, the reduction ratio of the intake-VTC-side speed
reducer 8 of intake VTC 04 is set to be greater than that of the
exhaust-VTC-side speed reducer 8 (described later) of exhaust VTC
05.
[0083] To ensure smooth operation of the electric-motor-driven
phase-converter equipped VTC apparatus, lubricating oil is supplied
into the internal space of speed reducer 8 by lubricating-oil
supply means. As shown in FIG. 3, the lubricating-oil supply means
is comprised of an annular oil supply passage (not numbered), which
is annularly grooved in the outer periphery of the journal of
intake camshaft 02 rotatably supported by camshaft-journal bearing
member 06 mounted on the cylinder head 01 and to which lubricating
oil is supplied from a main oil gallery (not shown), an axial oil
supply hole 51, a small-diameter axial oil hole 52, and
large-diameter oil drain holes (not shown). Axial oil supply hole
51 is formed in the front end of intake camshaft 02 to communicate
the annular oil supply passage via an oil groove, cut in the front
end face of intake camshaft 02 and configured to communicate the
downstream end of axial oil supply hole 51. Small-diameter axial
oil hole 52 is formed as a through hole in the driven member 9,
such that one end of small-diameter axial oil hole 52 is opened
into the axial oil supply hole 51 through the oil groove cut in the
camshaft end face and the other end of small-diameter axial oil
hole 52 is opened into the internal space defined near both the
needle bearing 38 and the middle-diameter ball bearing 47.
Large-diameter oil drain holes (not shown) are formed in the driven
member 9 as oil outlets.
[0084] During operation, lubricating oil is constantly fed from the
discharge port of an oil pump (not shown) into the oil supply hole
51 via the main oil gallery formed in the cylinder head. Hence, by
the previously-discussed lubricating-oil supply means, lubricating
oil can be fed via the oil supply hole 51 to the internal space 44
and stays in the internal space 44. Then, the lubricating oil is
supplied from the internal space 44 to moving parts, namely,
middle-diameter ball bearing 47 and rollers 48 for lubrication, and
further flows into the eccentric shaft 39 and the internal space of
motor output shaft 13, for lubrication of moving parts, such as
needle bearing 38 and small-diameter ball bearing 37. By the way,
undesirable leakage of lubricating oil, staying in the internal
space 44, to the inside of the electric-motor housing 5 can be
prevented or adequately suppressed by means of the small-diameter
oil seal 46.
[0085] The fundamental operation of intake VTC 04 incorporated in
the VTC system of the embodiment is hereunder described in
detail.
[0086] When the engine crankshaft rotates, sprocket 1 rotates in
synchronism with rotation of the crankshaft through the timing
chain (not shown). On one hand, torque flows from the sprocket 1
through the internal-tooth structural member 19 via the annular
female screw-threaded member 6 to the housing 5 of electric motor
12, and thus permanent magnets 14-15 and stator 16, all attached to
the inner periphery of housing 5, rotate together with the housing
5. On the other hand, torque flows from the sprocket 1 through the
internal-tooth structural member 19 via the rollers 48, cage 41,
and driven member 9 to the intake camshaft 02. Thus, intake
camshaft 02 is rotated to operate (open/close) the intake valves
against the spring forces of the valve springs by the intake-valve
cams.
[0087] During a given engine operating condition after the engine
start-up, an electric current is applied from the control unit
through the terminal strips 31, 31, pig-tale harnesses 33, 33,
second brushes 30a, 30a, and slip rings 26a-26b to the
electromagnetic coil 18 of electric motor 12. Hence, motor output
shaft 13 is driven. Then, the output rotation from the motor output
shaft 13 is reduced by means of the speed reducer 8, and thus the
reduced motor speed (in other words, the multiplied motor torque)
is transmitted to the intake camshaft 02.
[0088] That is, when eccentric shaft 39 rotates eccentrically
during rotation of motor output shaft 13, each of rollers 48 moves
(rolls) and relocates from one of two adjacent internal teeth 19a,
19a to the other with one-tooth displacement per one complete
revolution of motor output shaft 13, while being held in
rolling-contact with the outer ring 47b of middle-diameter ball
bearing 47 and simultaneously radially guided by the associated
axially-protruding lug (the associated roller-holding hole 41b) of
cage 41. By way of the repeated relocations of each of rollers 48
every revolutions of motor output shaft 13, rollers 48 move in the
circumferential direction with respect to the waveform internal
toothed portion 19a of internal-tooth structural member 19, while
being held in rolling-contact with the outer ring 47b of
middle-diameter ball bearing 47. In this manner, torque is
transmitted through the driven member 9 to the intake camshaft 02,
while the rotational speed of motor output shaft 13 is reduced.
[0089] As discussed above, by execution of rotational speed control
of motor output shaft 13, intake camshaft 02 is rotated in a
normal-rotational direction or in a reverse-rotational direction
with respect to the sprocket 1, and thus an angular phase of intake
camshaft 02 relative to sprocket 1 is changed, and as a result
intake valve open timing (IVO) and intake valve closure timing
(IVC) can be phase-advanced or phase-retarded.
[0090] The reduction ratio of this type of speed reducer 8 can be
determined by the number of rollers 48, in other words, the number
of roller-holding holes 41b (i.e., the number of axially-protruding
lugs of cage 41). The fewer the number of rollers 48, the lower the
reduction ratio. That is, the reduction ratio can be arbitrarily
set depending on the number of rollers 48.
[0091] As discussed above, the speed reducer 8, incorporated in the
intake VTC 04, is configured such that the rotational speed of
motor output shaft 13 of electric motor 12 can be reduced by virtue
of the repeated relocations of each of rollers 48 every revolutions
of motor output shaft 13, rollers 48 moving in the circumferential
direction with respect to the waveform internal toothed portion 19a
of internal-tooth structural member 19, while being held in
rolling-contact with the outer ring 47b of middle-diameter ball
bearing 47. Hence, a friction of intake VTC 04 during operation (in
other words, during speed-reduction of the speed reducer 8) becomes
adequately reduced. Thus, it is possible to enhance or improve the
phase-conversion responsiveness for the angular phase shift of
intake camshaft 02 relative to sprocket 1 in the phase-advance
direction or in the phase-retard direction.
[Exhaust VTC]
[0092] As shown in FIGS. 1 and 8-10, regarding the
electric-motor-driven exhaust VTC 05, its fundamental configuration
is identical to the electric-motor-driven intake VTC 04. Thus, in
explaining the exhaust VTC 05, for the purpose of simplification of
the disclosure, the same reference signs used to designate elements
in the intake VTC 04 will be applied to the corresponding elements
used in the exhaust VTC 05, while detailed description of the same
reference signs will be omitted because the above description
thereon seems to be self-explanatory.
[0093] The exhaust VTC 05 differs from the intake VTC 04 in that a
biasing mechanism 70 is provided between the exhaust camshaft 03
and the driven member 9, for biasing or forcing the exhaust
camshaft 03 in the phase-advance direction relatively to the
sprocket 1, and that a drive torque of electric motor 12 and a
reduction ratio of speed reducer 8 in the exhaust VTC 05 differ
from those in the intake VTC 04.
[0094] That is to say, as shown in FIG. 8, exhaust VTC 05 is
comprised of a sprocket 1 (serving as a driving rotary member) that
rotates in synchronism with rotation of the engine crankshaft, and
a phase change mechanism (a phase converter) 2 installed between
the sprocket 1 and the exhaust camshaft 03 for changing a relative
angular phase between the sprocket 1 and the exhaust camshaft 03
depending on an engine operating condition.
[0095] Sprocket 1 is comprised of a cylindrical sprocket body 1a, a
timing gear 1b formed integral with the outer periphery of sprocket
body 1a, and an internal-tooth structural member 19. Sprocket body
1a is made from iron-based metal material, and formed integral with
the timing gear 1b. Timing gear 1b receives torque from the
crankshaft through the common timing chain (not shown) wound on the
sprocket on the crankshaft, the sprocket 1 on the intake camshaft
side and the sprocket 1 on the exhaust camshaft side.
Internal-tooth structural member 19 is formed integral with the
front end of sprocket body 1a on the exhaust camshaft side.
[0096] The sprocket body 1a shown in FIG. 8 and partly constructing
the exhaust-VTC-side internal-tooth structural member 19 is
configured to be axially longer than the sprocket body 1a shown in
FIG. 3 and partly constructing the intake-VTC-side internal-tooth
structural member 19.
[0097] Biasing mechanism 70 is mainly comprised of a spring
retainer 71 and a torsion spring 72. Spring retainer 71 is
installed between the front end of exhaust camshaft 03 and the
fixed-end portion 9a of driven member 9. The driven member 9, the
spring retainer 71, and the front end of exhaust camshaft 03 are
integrally connected to each other by screwing the cam bolt 10 into
the axial end of exhaust camshaft 03. Torsion spring 72 is
installed on the outer periphery of spring retainer 71.
[0098] Spring retainer 71 is shaped into a substantially
cylindrical shape having a short axial length. Spring retainer 71
has a central bolt insertion hole (a through hole) 71a into which
the shank 10b of cam bolt 10 is inserted. On one hand, the central
portion of the front end of spring retainer 71 is formed with a
cylindrical fitted bore 71b into which a cylindrical-hollow
axially-protruding portion 9c extending backward from the central
portion of the disk-shaped fixed-end portion 9a of driven member 9
is fitted. On the other hand, the central portion of the rear end
of spring retainer 71, facing apart from the cylindrical fitted
bore 71b, is formed with a cylindrical-hollow axially-protruding
portion 71c is fitted into a cylindrical fitted bore 03a formed in
the center of the front end of exhaust camshaft 03.
[0099] Additionally, spring retainer 71 has a communication hole
(an axial through hole) 71d through which the axial oil supply hole
51 formed in the front end of exhaust camshaft 03 and the axial oil
hole 52 formed in the driven member 9 are communicated with each
other. Also, the outer periphery of the rear end of spring retainer
71, facing the front end of exhaust camshaft 03, is partly cut or
machined as a first spring-hook retaining slit 71e with which one
end (a first hook, described later) 72a of torsion spring 72 is
brought into engagement in the radial direction.
[0100] As best seen in FIG. 9, torsion spring 72 is loosely
assembled or fitted over the outer periphery of spring retainer 71,
in such a manner as to permit torsion spring 72 to diametrically
expand or contract without tightly fitting the inside diameter of
torsion spring 72 over the outer periphery of spring retainer 71.
When assembling, the one end (the first short torsion-spring hook)
72a, bent radially inward, is brought into engagement with the
first spring-hook retaining slit 71e of spring retainer 71. The
other end (a second short torsion-spring hook) 72b, bent radially
outward, is brought into engagement with a second spring-hook
retaining slit 1d, which slit is formed in the timing gear 1b of
sprocket body 1a, in the radial direction.
[0101] By virtue of the installed torsion spring 72, exhaust
camshaft 03 is permanently biased or forced in the phase-advance
direction indicated by the arrow in FIG. 9 relatively to the
sprocket 1. Hence, during the engine starting period, there is no
valve overlapping period where exhaust and intake valves are both
open. This contributes to the better combustibility and improved
startability.
[0102] By the way, a cylindrical pressing member 73 is installed on
the inner periphery of sprocket body 1a, for axially supporting the
outer ring 43a of large-diameter ball bearing 43 through the
retainer plate 61, while applying a slight push from the inside
face of retainer plate 61, caused by axial forces of bolts 7, to
the rearward end face 43e of the outer ring 43a.
[0103] As appreciated from the longitudinal cross section of FIG.
8, a locate pin 74 is provided or axially press-fitted, for the
purpose of radial positioning of exhaust camshaft 03 and spring
retainer 71. In a similar manner, a locate pin 75 is provided or
axially press-fitted, for the purpose of radial positioning of
spring retainer 71 and driven member 9.
[0104] In contrast to the intake VTC 04, in the case of the exhaust
VTC 05, a phase-change (a phase-conversion) in relative-rotation
phase of exhaust camshaft 03 with respect to sprocket 1 is not
frequently executed during operation of the engine. For instance,
during the engine starting period, the phase of exhaust camshaft 03
relative to sprocket 1 is forcibly changed or converted in the
phase-advance direction by the spring force of torsion spring 72
without driving the electric motor 12 of exhaust VTC 05. When the
engine operating condition changes between middle-speed operation
and high-speed operation, the phase of exhaust camshaft 03 relative
to sprocket 1 is held at a substantially intermediate phase-angle
position. Also, when the engine is running at low speeds, the
electric motor 12 of exhaust VTC 05 is often driven.
[0105] For the reasons discussed above, as appreciated from the
motor-efficiency diagram of FIG. 11, the motor drive efficiency
.eta. of the exhaust-VTC-side electric motor 12 is set to become
maximum in a low motor-speed range. As previously described, the
motor drive efficiency .eta. of the intake-VTC-side electric motor
12 is set to become maximum in a high motor-speed range. That is,
the maximum drive-efficiency range of the exhaust-VTC-side electric
motor 12 is set to be different from that of the intake-VTC-side
electric motor 12.
[0106] On the other hand, as appreciated from comparison between
the cross sections of FIGS. 5 and 10, the number of internal teeth
19a of internal-tooth structural member 19 of the exhaust-VTC-side
speed reducer 8 is set to be fewer than that of the intake-VTC-side
speed reducer 8. That is, depending on the fewer internal teeth 19a
of the exhaust-VTC-side speed reducer 8, the number of rollers 48
of the exhaust-VTC-side speed reducer 8 is decreased. Hence, the
reduction ratio of the exhaust-VTC-side speed reducer 8 is set to
be less than that of the intake-VTC-side speed reducer 8.
[0107] Additionally, regarding the electricity-feeding device of
exhaust VTC 05, synthetic-resin plate 22, synthetic-resin brush
holders 23a-23b, and brush retainer 28 are made from nylon resin
materials.
[0108] As will be appreciated from the above, the drive-efficiency
characteristics of the intake-VTC-side electric motor 12 and the
exhaust-VTC-side electric motor 12 are set independently of each
other, such that the respective motor drive efficiencies become
high depending on two different motor-speed ranges, namely a
frequently-used motor-speed range suitable for the intake-VTC-side
electric motor and a frequently-used motor-speed range suitable for
the exhaust-VTC-side electric motor. Thus, it is possible to more
efficiently drive each of intake-VTC-side electric motor and the
exhaust-VTC-side electric motor.
[0109] Accordingly, when switching, shifting, or changing an
angular phase (i.e., intake valve open timing and intake valve
closure timing) of intake camshaft 02 relative to the sprocket 1 on
the side of intake VTC 04 and an angular phase (i.e., exhaust valve
open timing and exhaust valve closure timing) of exhaust camshaft
03 relative to the sprocket 1 on the side of exhaust VTC 05, it is
possible to improve both the operational responsiveness of intake
VTC 04 for the phase shift of intake camshaft 02 relative to the
intake-side sprocket and the operational responsiveness of exhaust
VTC 05 for the phase shift of exhaust camshaft 03 relative to the
exhaust-side sprocket, thereby exhibiting a sufficient engine
performance.
[0110] Furthermore, as discussed above, it is possible to more
efficiently drive both the electric motor 12 on the side of intake
VTC 04 and the electric motor 12 on the side of exhaust VTC 05, and
hence it is possible to reduce the drive load on each of the
intake-VTC-side electric motor 12 and the exhaust-VTC-side electric
motor 12. This contributes to the enhanced durability of each of
the intake-VTC-side electric motor 12 and the exhaust-VTC-side
electric motor 12.
[0111] Moreover, in the valve timing control system of the
embodiment, the speed reducer 8 on the side of intake VTC 04 and
the speed reducer 8 on the side of exhaust VTC 05 are configured,
such that the reduction ratio of the intake-VTC-side speed reducer
8 and the reduction ratio of the exhaust-VTC-side speed reducer 8
differ from each other. That is, the reduction ratio of the
intake-VTC-side speed reducer 8 in the intake VTC 04, by means of
which intake-valve timing can be frequently switched or changed
over the entire engine operating range, is set to be greater than
the reduction ratio of the exhaust-VTC-side speed reducer 8 in the
exhaust VTC 05. Thus, it is possible to remarkably enhance the
operational responsiveness of intake VTC 04. Hence, in combination
with the previously-discussed appropriate setting of the drive
efficiency .eta. of the intake-VTC-side electric motor 12 in which
the motor drive efficiency .eta. becomes maximum in a high
motor-speed range, it is possible to further enhance the
operational responsiveness of intake VTC 04, and consequently more
greatly improve the intake-valve-timing control responsiveness.
[0112] As discussed previously, regarding the exhaust VTC 05, by
decreasing the number of internal teeth 19a of internal-tooth
structural member 19 of the exhaust-VTC-side speed reducer 8, in
other words, by decreasing the number of rollers 48 of the
exhaust-VTC-side speed reducer 8, the reduction ratio of the
exhaust-VTC-side speed reducer 8 is set to be less than that of the
intake-VTC-side speed reducer 8. In comparison with the
intake-VTC-side speed reducer 8, the decreased number of internal
teeth 19a (i.e., the decreased number of rollers 48) in the
exhaust-VTC-side speed reducer 8 contributes to the reduced
manufacturing costs and improved assembling efficiency.
[0113] Additionally, regarding the intake-VTC-side
electricity-feeding device that requires a very high heat
resistance owing to a comparatively long total operation time of
the intake-VTC-side electric motor 12, synthetic-resin plate 22,
synthetic-resin brush holders 23a-23b, and brush retainer 28 are
made from PPS (polyphenylene sulfide) synthetic resin materials
having a high heat-resisting property. In contrast, regarding the
exhaust-VTC-side electricity-feeding device that does not require a
very high heat resistance owing to a comparatively short total
operation time of the exhaust-VTC-side electric motor 12,
synthetic-resin plate 22, synthetic-resin brush holders 23a-23b,
and brush retainer 28 are made from inexpensive nylon resin
materials. This also contributes to the reduced manufacturing costs
in the exhaust VTC 05.
[0114] As will be appreciated from the above, the invention is not
limited to the particular embodiments shown and described herein,
but various changes and modifications may be made. For instance,
the drive-efficiency settings of the intake-VTC-side electric motor
12 and the exhaust-VTC-side electric motor 12 and the
reduction-ratio settings of the intake-VTC-side speed reducer 8 and
the exhaust-VTC-side speed reducer 8 may be appropriately modified
or arbitrarily set depending on the type of the internal combustion
engine and the specification and size of each of intake VTC 04 and
exhaust VTC 05.
[0115] As a matter of course, the type of electric motor 12 and the
type of speed reducer 8 are not limited to the particular
embodiment shown and described herein. In the shown embodiment, a
brush-equipped direct-current motor is used for the electric motor
12. In lieu thereof, a brushless motor may be used for the electric
motor 12. Also, in the shown embodiment, a roller-type cycloid
speed reducer employing a plurality of rollers 48 is used for the
speed reducer 8. In lieu thereof, the speed reducer 8 may be
constructed by a planetary-gear type cycloid speed reducer such as
disclosed in U.S. Pat. No. 7,959,537 issued Jun. 14, 2011, the
teachings of which are hereby incorporated by reference.
[0116] The entire contents of Japanese Patent Application No.
2013-040325 (filed Mar. 1, 2013) are incorporated herein by
reference.
[0117] While the foregoing is a description of the preferred
embodiments carried out the invention, it will be understood that
the invention is not limited to the particular embodiments shown
and described herein, but that various changes and modifications
may be made without departing from the scope or spirit of this
invention as defined by the following claims.
* * * * *