U.S. patent application number 12/160708 was filed with the patent office on 2010-07-08 for variable valve timing apparatus.
This patent application is currently assigned to Toyota Jidosha Kabushiki Kaisha. Invention is credited to Tadao Hasegawa, Masayoshi Hattori, Yuji Itoh, Yoshihito Moriya, Akihiko Takenaka, Yuu Yokoyama.
Application Number | 20100170461 12/160708 |
Document ID | / |
Family ID | 37890849 |
Filed Date | 2010-07-08 |
United States Patent
Application |
20100170461 |
Kind Code |
A1 |
Yokoyama; Yuu ; et
al. |
July 8, 2010 |
VARIABLE VALVE TIMING APPARATUS
Abstract
An intake VVT mechanism includes: link mechanisms and connected
to an intake camshaft and operated to change a phase of an intake
valve; and a control pin sliding on a guide plate along a guide
groove to allow the link mechanism to operate; a control pin
sliding on the guide plate along a guide groove to allow the link
mechanism to operate. The control pin is detached from an end of
the guide groove when the control pins and are moved in a direction
allowing the phase to be retarded until the control pin abuts
against an end of the guide groove.
Inventors: |
Yokoyama; Yuu; (Okazaki-shi,
JP) ; Moriya; Yoshihito; (Nagoya-shi, JP) ;
Itoh; Yuji; (Okazaki-shi, JP) ; Hasegawa; Tadao;
(Toyota-shi, JP) ; Hattori; Masayoshi;
(Toyota-shi, JP) ; Takenaka; Akihiko; (Anjo-shi,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
Toyota Jidosha Kabushiki
Kaisha
Toyota-shi, Aichi-ken
JP
|
Family ID: |
37890849 |
Appl. No.: |
12/160708 |
Filed: |
January 11, 2007 |
PCT Filed: |
January 11, 2007 |
PCT NO: |
PCT/JP2007/050639 |
371 Date: |
July 11, 2008 |
Current U.S.
Class: |
123/90.17 |
Current CPC
Class: |
F01L 1/352 20130101 |
Class at
Publication: |
123/90.17 |
International
Class: |
F01L 1/34 20060101
F01L001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 13, 2006 |
JP |
2006-006172 |
Claims
1. A variable valve timing apparatus changing when at least one of
an intake valve and an exhaust valve should be opened/closed,
comprising a first operation unit provided to change when said at
least one of said intake and exhaust valves should be opened/closed
by an amount of variation depending on an amount of operation
thereof; a second operation unit provided to change when a valve
identical to said at least one of said intake and exhaust valves
controlled by said first operation unit should be opened/closed by
an amount of variation depending on an amount of operation thereof;
and a limiter unit limiting said first operation unit in operation
such that said first operation unit is operable only within a range
smaller than said second operation unit is operable, wherein said
first operation unit is smaller in strength than said second
operation unit.
2. (canceled)
3. The variable valve timing apparatus according to claim 1,
wherein: said valve is driven by a camshaft; said operation unit is
a link mechanism connected to said camshaft to rotate said camshaft
and actuated by an actuator; and when said at least one of said
intake and exhaust valves should be opened/closed is changed as
said camshaft is rotated by said actuator via said link
mechanism.
4. A variable valve timing apparatus changing when at least one of
an intake valve and an exhaust valve should be opened/closed,
comprising a first operation unit provided to change when said at
least one of said intake and exhaust valves should be opened/closed
by an amount of variation depending on an amount of operation
thereof; a second operation unit provided to change when a valve
identical to said at least one of said intake and exhaust valves
controlled by said first operation unit should be opened/closed by
an amount of variation depending on an amount of operation thereof;
and a first limiter unit limiting said first operation unit in
operation such that said first operation unit is operable only
within a range smaller than said second operation unit is operable
for a direction retarding when said at least one of said intake and
exhaust valves should be opened/closed; a second limiter unit
limiting said second operation unit in operation such that said
second operation unit is operable only within a range smaller than
said first operation unit is operable for a direction advancing
when said at least one of said intake and exhaust valves should be
opened/closed.
5. The variable valve timing apparatus according to claim 4,
wherein: said valve is driven by a camshaft; said operation unit is
a link mechanism connected to said camshaft to rotate said camshaft
and actuated by an actuator; and when said at least one of said
intake and exhaust valves should be opened/closed is changed as
said camshaft is rotated by said actuator via said link mechanism.
Description
TECHNICAL FIELD
[0001] The present invention relates to a variable valve timing
apparatus. In particular, the invention relates to a variable valve
timing apparatus that changes when a valve is should be
opened/closed by an amount of variation according to an amount of
operation of an operation unit (a link mechanism).
BACKGROUND ART
[0002] VVT (Variable Valve Timing) has conventionally been known
that changes the phase (crank angle) in (at) which an intake valve
or an exhaust valve is opened/closed, according to an operating
condition. Generally, the VVT changes the phase by rotating,
relative to a sprocket or the like, a camshaft that causes the
intake valve or exhaust valve to open/close. The camshaft is
rotated hydraulically or by an electric motor or the like. In the
case where the electric motor is used to rotate the camshaft, the
torque for rotating the camshaft is difficult to obtain, as
compared with the case where the camshaft is hydraulically rotated.
Therefore, in the case where the electric motor is used to rotate
the camshaft, the torque of the electric motor is transmitted via a
link mechanism or the like to the camshaft, thereby rotating the
camshaft.
[0003] Japanese Patent Laying-Open No. 2005-048706 discloses a
valve timing adjustment device employing a link (a link mechanism)
to transmit a torque to a driven shaft (a cam shaft) to adjust when
a valve should be opened/closed. The publication describes that the
valve timing adjustment device is provided in a transmission system
transmitting a driving torque of a driving shaft to a driven shaft
driving and thus opening and closing at least one of intake and
exhaust valves in an internal combustion engine to adjust when at
least one of the valves should be opened/closed. The valve timing
adjustment device includes a guide member forming a guide passage
of a generally constant width, a movable body with which the guide
member is engaged on both sides in the width direction of the guide
passage to be capable of relatively sliding to the guide member in
the direction in which the guide passage extends, a phase changing
mechanism formed of a plurality of links and composing a limiting
link with the guide member and such movable bodies as the movable
bodies are each engaged with an associated link to change the
rotation phase of the driven shaft to the drive shaft in accordance
with relative sliding of the movable bodies to the guide member,
and a torque transmission unit transmitting a control torque to the
guide member. The guide member forms the guide passage, which
extends with an inclination relative to a radial axis and has a
variable distance to a centerline of rotation, as seen in the
radial direction, and the guide member rotates relative to an
associated link as the control torque is transmitted.
[0004] As described in the publication, the valve timing adjustment
device includes a guide member that forms a guide passage extending
with an inclination relative to a radial axis and having a variable
distance to a centerline of rotation, as seen in the radial
direction and engages with a movable body on both sides in the
width direction of the guide passage. Thus from the torque
transmission unit to the guide member the control torque can be
transmitted to rotate the guide member relative to an associated
link. This can help to slide the movable body relative to the guide
member to change the phase of the rotation of the driven shaft and
as a result adjust when at least one of the intake and exhaust
valves should be opened/closed.
[0005] However, if, a valve timing adjustment device employs a
plurality of link mechanisms as described in the publication to
change when a valve should be opened/closed, however, it is
difficult to detect whether the link mechanisms have failure; if
one of the plurality of link mechanisms is damaged, the other link
mechanisms can change when the valve(s) should be opened/closed,
and the valve(s) can be opened/closed as controlled.
DISCLOSURE OF THE INVENTION
[0006] The present invention contemplates a variable valve timing
apparatus capable of detecting failure.
[0007] The present invention in an aspect provides a variable valve
timing apparatus changing when at least one of an intake valve and
an exhaust valve should be opened/closed. The variable valve timing
apparatus includes: a first operation unit provided to change when
at least one of the intake and exhaust valves should be
opened/closed by an amount of variation depending on an amount of
operation thereof; a second operation unit provided to change when
a valve identical to at least one of the intake and exhaust valves
controlled by the first mechanism should be opened/closed by an
amount of variation depending on an amount of operation thereof;
and a limiter unit limiting the first operation unit in operation
such that the first operation unit is operable only within a range
smaller than the second operation unit is operable.
[0008] In accordance with the present invention when at least one
of intake and exhaust valves should be opened/closed is changed by
an amount of variation depending on an amount of operation of a
first operation unit (e.g., a first link mechanism) and a second
operation unit (e.g., a second link mechanism). If one of the
operation units is damaged and cannot operate normally, the other
operation unit can change when at least one of the intake and
exhaust valves should be opened/closed. The first operation unit
can operate within a range limited by a limiter unit to be smaller
than the second operation unit can. If the first operation unit is
not damaged or the like and normally operates, when at least one of
the intake and exhaust valves should be opened/closed can be
changed until the first operation unit is limited in operation by
the limiter unit. In contrast, if the first operation unit is
damaged and cannot operate normally, the first operation unit is
not limited in operation by the limiter unit and when at least one
of the intake and exhaust valves should be opened/closed can
further be changed beyond the first operation unit's operable
range. As such, whether the first operation unit has failed or not
can be determined by detecting when at least one of the intake and
exhaust valves is opened/closed. A variable valve timing apparatus
capable of detecting failure can thus be provided.
[0009] Preferably the first operation unit is smaller in strength
than the second operation unit.
[0010] In accordance with the present invention the first operation
unit is provided to be smaller in strength than the second
operation unit. This allows a failure to be caused earlier in the
first operation unit capable of detection of failure than the
second operation unit. This can prevent the second operation unit
from having a failure while the first operation unit normally
operates and the failure cannot be detected.
[0011] Still preferably the valve is driven by a camshaft. The
first and second operation unit are link mechanisms connected to
the camshaft to rotate the camshaft and actuated by an actuator.
When at least one of the intake and exhaust valves should be
opened/closed is changed as the camshaft is rotated by the actuator
via the link mechanism.
[0012] In accordance with the present invention a failure can be
detected which arises in a link mechanism actuated by an actuator
to cause a camshaft to rotate to change when at least one of the
intake and exhaust valves should be opened/closed.
[0013] The present invention in another aspect provides a variable
valve timing apparatus changing when at least one of an intake
valve and an exhaust valve should be opened/closed. The variable
valve timing apparatus includes: a first operation unit provided to
change when at least one of the intake and exhaust valves should be
opened/closed by an amount of variation depending on an amount of
operation thereof; a second operation unit provided to change when
a valve identical to at least one of the intake and exhaust valves
controlled by the first mechanism should be opened/closed by an
amount of variation depending on an amount of operation thereof;
and a first limiter unit limiting the first operation unit in
operation such that the first operation unit is operable only
within a range smaller than the second operation unit is operable
for a direction retarding when at least one of the intake and
exhaust valves should be opened/closed; a second limiter unit
limiting the second operation unit in operation such that the
second operation unit is operable only within a range smaller than
the first operation unit is operable for a direction advancing when
at least one of the intake and exhaust valves should be
opened/closed.
[0014] In accordance with the present invention when at least one
of intake and exhaust valves should be opened/closed is changed by
an amount of variation depending on an amount of operation of a
first operation unit (e.g., a first link mechanism) and a second
operation unit (e.g., a second link mechanism). If one of the
operation units is damaged and cannot operate normally, the other
operation unit can change when at least one of the intake and
exhaust valves should be opened/closed. The first operation unit
can operate within a range limited by a first limiter unit to be
smaller than the second operation unit can for a direction
retarding when at least one of the intake and exhaust valves should
be opened/closed. The second operation unit can operate within a
range limited by a second limiter unit to be smaller than the first
operation unit can for a direction advancing when at least one of
the intake and exhaust valves should be opened/closed. If the first
operation unit is not damaged or the like and normally operates,
when at least one of the intake and exhaust valves should be
opened/closed can be retarded until the first operation unit is
limited in operation by the first limiter unit. In contrast, if the
first operation unit is damaged and cannot operate normally, the
first operation unit is not limited in operation by the limiter
unit and when at least one of the intake and exhaust valves should
be opened/closed can further be retarded beyond the first operation
unit's operable range. Similarly, if the second operation unit is
not damaged or the like and normally operates, when at least one of
the intake and exhaust valves should be opened/closed can be
advanced until the second operation unit is limited in operation by
the second limiter unit. In contrast, if the second operation unit
is damaged and cannot operate normally, the second operation unit
is not limited in operation by the second limiter unit and when at
least one of the intake and exhaust valves should be opened/closed
can further be advanced beyond the second operation unit's operable
range. As such, whether the first or second operation unit has
failed or not can be determined by detecting when at least one of
the intake and exhaust valves is opened/closed. A variable valve
timing apparatus capable of detecting failure can thus be
provided.
[0015] Preferably the valve is driven by a camshaft. The first and
second operation unit are link mechanisms connected to the camshaft
to rotate the camshaft and actuated by an actuator. When at least
one of the intake and exhaust valves should be opened/closed is
changed as the camshaft is rotated by the actuator via the link
mechanism.
[0016] In accordance with the present invention a failure can be
detected which arises in a link mechanism actuated by an actuator
to cause a camshaft to rotate to change when at least one of the
intake and exhaust valves should be opened/closed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is schematically shows a configuration of an engine
of a vehicle on which the present variable valve timing apparatus
in a first embodiment is mounted.
[0018] FIG. 2 shows a map defining the phase of an intake
camshaft.
[0019] FIG. 3 is a cross section showing an intake WT
mechanism.
[0020] FIG. 4 is a cross section along A-A in FIG. 3.
[0021] FIG. 5 is a (first) cross section along B-B in FIG. 3.
[0022] FIG. 6 is a (second) cross section along B-B in FIG. 3.
[0023] FIG. 7 is a cross section along C-C in FIG. 3.
[0024] FIG. 8 is a cross section along D-D in FIG. 3.
[0025] FIG. 9 is a flowchart representing a structure of a program
for control executed by an ECU controlling an intake VVT mechanism
of the present variable valve timing apparatus in the first
embodiment.
[0026] FIG. 10 is a (second) cross section along C-C in FIG. 3.
[0027] FIG. 11 is a (third) cross section along C-C in FIG. 3.
[0028] FIG. 12 is a (first) cross section of a link mechanism of
the present variable valve timing apparatus in a second
embodiment.
[0029] FIG. 13 is a (second) cross section of the link mechanism of
the present variable valve timing apparatus in the second
embodiment.
[0030] FIG. 14 is a (first) cross section of a guide plate of the
present variable valve timing apparatus in a third embodiment.
[0031] FIG. 15 is a flowchart representing a structure of a program
for control executed by the ECU controlling the intake VVT
mechanism of the present variable valve timing apparatus in the
third embodiment.
[0032] FIG. 16 is a (second) cross section of a guide plate of the
present variable valve timing apparatus in the third
embodiment.
[0033] FIG. 17 is a (third) cross section of the guide plate of the
present variable valve timing apparatus in the third
embodiment.
[0034] FIG. 18 is a cross section of a limiter pin limiting a range
within which a link mechanism is operable in the present variable
valve timing apparatus in another embodiment.
BEST MODES FOR CARRYING OUT THE INVENTION
[0035] With reference to the drawings, embodiments of the present
invention are hereinafter described. In the following description,
like components are denoted by like reference characters. They are
also named identically and function identically. Therefore, a
detailed description thereof is not repeated.
First Embodiment
[0036] Referring to FIG. 1, a description is given of an engine of
a vehicle on which a variable valve timing apparatus is mounted,
according to a first embodiment of the present invention.
[0037] An engine 1000 is a V-type 8-cylinder engine having an "A"
bank 1010 and a "B" bank 1012 each including a group of four
cylinders. Here, any engine other than the V8 engine may be
used.
[0038] Into engine 1000, air is sucked from an air cleaner 1020.
The quantity of sucked air is adjusted by a throttle valve 1030.
Throttle valve 1030 is an electronic throttle valve driven by a
motor.
[0039] The air is supplied through an intake manifold 1032 into a
cylinder 1040. The air is mixed with fuel in cylinder 1040
(combustion chamber). Into cylinder 1040, the fuel is directly
injected from an injector 1050. In other words, injection holes of
injector 1050 are provided within cylinder 1040.
[0040] The fuel is injected in the intake stroke. When the fuel is
injected is not limited to the intake stroke. Further, in the
present embodiment, engine 1000 is described as a direct-injection
engine having injection holes of injector 1050 that are disposed
within cylinder 1040. However, in addition to direct-injection
(in-cylinder) injector 1050, a port injector may be provided.
Moreover, only the port injector may be provided.
[0041] The air-fuel mixture in cylinder 1040 is ignited by a spark
plug 1060 and accordingly burned. The air-fuel mixture after
burned, namely exhaust gas, is cleaned by a three-way catalyst 1070
and thereafter discharged to the outside of the vehicle. The
air-fuel mixture is burned to press down a piston 1080 and thereby
rotate a crankshaft 1090.
[0042] At the top of cylinder 1040, an intake valve 1100 and an
exhaust valve 1110 are provided. Intake valve 1100 is driven by an
intake camshaft 1120. Exhaust valve 1110 is driven by an exhaust
camshaft 1130. Intake camshaft 1120 and exhaust camshaft 1130 are
coupled by such parts as a chain and gears to be rotated at the
same rotational speed.
[0043] Intake valve 1100 has its phase (or when it should be
opened/closed) controlled by an intake VVT mechanism 2000 provided
to intake camshaft 1120. Exhaust valve 1110 has its phase (or when
it should be opened/closed) controlled by an exhaust VVT mechanism
3000 provided to exhaust camshaft 1130.
[0044] In the present embodiment, intake camshaft 1120 and exhaust
camshaft 1130 are rotated by the VVT mechanisms to control
respective phases of intake valve 1100 and exhaust valve 1110.
Here, the phase control method is not limited to the aforementioned
one.
[0045] Intake VVT mechanism 2000 is operated by an electric motor
2060 (not shown in FIG. 1). Electric motor 2060 is controlled by an
ECU 4000. The current and voltage of electric motor 2060 are
detected by an ammeter (not shown) and a voltmeter (not shown) and
the measurements are input to ECU 4000.
[0046] Exhaust VVT mechanism 3000 is hydraulically operated. Here,
intake VVT mechanism 2000 may be hydraulically operated while
exhaust VVT mechanism 3000 may be operated by an electric
motor.
[0047] To ECU 4000, signals indicating the rotational speed and the
crank angle of crankshaft 1090 are input from a crank angle sensor
5000. Further, to ECU 4000, signals indicating respective phases of
intake camshaft 1120 and exhaust camshaft 1130 (phase: the camshaft
position in the rotational direction) are input from a cam position
sensor 5010.
[0048] Furthermore, to ECU 4000, a signal indicating the water
temperature (coolant temperature) of engine 1000 from a coolant
temperature sensor 5020 as well as a signal indicating the quantity
of intake air (quantity of air taken or sucked into engine 1000) of
engine 1000 from an airflow meter 5030 are input.
[0049] Based on these signals input from the sensors as well as a
map and a program stored in a memory (not shown), ECU 4000 controls
the throttle angle, the timing of ignition, the timing of injection
of fuel, the quantity of fuel injected, the phase of intake valve
1100, and the phase of exhaust valve 1110 for example, so that
engine 1000 is operated in a desired operating state.
[0050] In the present embodiment, ECU 4000 determines the phase of
intake valve 1100 based on the map as shown in FIG. 2 that uses the
engine speed NE and the intake air quantity KL as parameters. A
plurality of maps for respective coolant temperatures are stored
for determining the phase of intake valve 1100.
[0051] In the following, a further description is given of intake
VVT mechanism 2000. As shown in FIG. 3, intake VVT mechanism 2000
is comprised of a sprocket 2010, a cam plate 2020, a link mechanism
(A) 2030, a link mechanism (B) 2130, a guide plate 2040, a cycloid
speed reducer 2050, and electric motor 2060.
[0052] Sprocket 2010 is coupled via a chain or the like to
crankshaft 1090. The rotational speed of sprocket 2010 is half the
rotational speed of crankshaft 1090. Intake camshaft 1120 is
provided concentrically with the rotational axis of sprocket 2010
and rotatably relative to sprocket 2010.
[0053] Cam plate 2020 is coupled to intake camshaft 1120 with a pin
(1) 2070. Cam plate 2020 rotates, on the inside of sprocket 2010,
together with intake camshaft 1120. Here, cam plate 2020 and intake
camshaft 1120 may be integrated into one unit.
[0054] Link mechanism (A) 2030 is comprised of an arm (A1) 2031
(not shown in FIG. 3) and an arm (A2) 2032 (not shown in FIG. 3).
Link mechanism (B) 2130 is comprised of an arm (B1) 2131 and an arm
(B2) 2132.
[0055] As shown in FIG. 4 which is a cross section along A-A in
FIG. 3, arms (A1) 2031 and (B1) 2131 are provided within sprocket
2010 so that the arms are point symmetric to each other with
respect to the rotational axis of intake camshaft 1120. Arms (A1)
2031 and (B1) 2131 are coupled to sprocket 2010 so that the arms
can swing about a pin (2) 2072.
[0056] As shown in FIG. 5 which is a cross section along B-B in
FIG. 3 and as shown in FIG. 6 showing the state where the phase of
intake valve 1100 is advanced with respect to the state in FIG. 5,
arm (A1) 2031 and cam plate 2020 are coupled by arm (A2) 2032. Arm
(B1) 2131 and cam plate 2020 are coupled by arm (B2) 2132.
[0057] Arm (A2) 2032 is supported so that the arm can swing about a
pin (3) 2074 and with respect to arm (A1) 2031. Similarly, arm (B2)
2132 is supported so that the arm can swing about a pin (3) 2074
and with respect to arm (B1) 2131. Further, arms (A2) 2032 and (B2)
2132 are supported so that the arms can swing about a pin (4) 2076
and with respect to cam plate 2020.
[0058] Link mechanisms (A) 2030 and (B) 2130 cause intake camshaft
1120 to rotate relative to sprocket 2010 and thereby changes the
phase of intake valve 1100.
[0059] In the present embodiment a pair of link mechanisms (A) 2030
and (B) 2130 can be provided. As such, if one of link mechanisms
(A) 2030 and (B) 2130 is damaged or the like and thus broken, the
other link mechanism can operate to change the phase of intake
valve 1100.
[0060] Referring back to FIG. 3, at a surface of link mechanism (A)
2030 (arm (A2) 2032) that is a surface thereof facing guide plate
2040, a control pin (A) 2034 is provided. Similarly, at a surface
of link mechanism (B) 2130 (arm (B2) 2132) that is a surface
thereof facing guide plate 2040, a control pin (B) 2134 is
provided.
[0061] Control pins (A) 2034 and (B) 2134 are provided
concentrically with pin (3) 2074. Control pin (A) 2034 slides in a
guide groove (A) 2041 provided in guide plate 2040. Control pin (B)
2134 slides in a guide groove (B) 2042 provided in guide plate
2040.
[0062] Control pins (A) 2034 and (B) 2134 slide in guide grooves
(A) 2041 and (B) 2042 of guide plate 2040 to move in the radial
direction. Control pins (A) 2034 and (B) 2134 sliding in the radial
direction cause intake camshaft 1120 to rotate relative to sprocket
2010.
[0063] As shown in FIG. 7 which is a cross section along C-C in
FIG. 3, guide grooves (A) 2041 and (B) 2042 are formed to incline
at a predetermined angle to the radial direction so that rotation
of guide plate 2040 causes control pins (A) 2034 and (B) 2134 to
move in the radial direction. Here, guide grooves (A) 2041 and (B)
2042 may be formed to have a geometry other than described
above.
[0064] As control pins (A) 2034 and (B) 2134 are moved further in
the radial direction from the axial center of guide plate 2040, the
phase of intake valve 1100 is retarded to a greater extent. In
other words, the amount of variation of the phase has a value
corresponding to the amount of operation of link mechanisms (A)
2030 and (B) 2130 generated as control pins (A) 2034 and (B) 2134
positionally, radially move.
[0065] Note that the phase of intake valve 1100 may be advanced to
a greater extent as control pins (A) 2034 and (B) 2134 are moved
further in the radial direction from the axial center of guide
plate 2040.
[0066] Guide groove (A) 2041 is shorter than guide groove (B) 2042.
Guide grooves (A) 2041 and (B) 2042 are different only in length.
Other than that, they are provided in point symmetry with respect
to the axial center of guide plate 2040.
[0067] As shown in FIG. 7, control pin (B) 2134 is detached from an
end of guide groove (B) 2042 when control pins (A) 2034 and (B)
2134 are moved in a direction allowing the phase to be retarded
until control pin (A) 2034 abuts against an end of guide groove (A)
2041.
[0068] Note that control pin (B) 2134 may be detached from the end
of guide groove (B) 2042 when control pins (A) 2034 and (B) 2134
are moved in a direction allowing the phase to be advanced until
control pin (A) 2034 abuts against the end of guide groove (A)
2041.
[0069] When control pin (A) 2034 abuts against an end of guide
groove (A) 2041, link mechanism (A) 2030 is limited in operation in
the direction allowing the phase to be retarded. Therefore, if link
mechanism (A) 2030 normally operates, the phase for which control
pin (A) 2034 abuts against the end of guide groove (A) 2041 will be
the phase of the maximally retarded angle.
[0070] Furthermore, when control pins (A) 2034 and (B) 2134 are
moved in the direction allowing the phase to be advanced, the phase
for which control pin (A) 2034 abuts against the end of guide
groove (A) 2041 and control pin (B) 2134 abuts against the end of
guide groove (B) 2042 will be the phase of the maximally advanced
angle.
[0071] Referring back to FIG. 3, in guide plate 2040, a plurality
of depressed portions 2044 are provided in its surface facing
cycloid speed reducer 2050, for coupling guide plate 2040 and
cycloid speed reducer 2050 to each other.
[0072] Cycloid speed reducer 2050 is comprised of a ring gear 2052
and a planetary gear 2054. Ring gear 2052 is fixed with respect to
sprocket 2010 so that the gear rotates together with sprocket
2010.
[0073] Planetary gear 2054 has a plurality of protruded portions
2056 thereon that are received in depressed portions 2044 of guide
plate 2040. Planetary gear 2054 is supported rotatably about an
eccentric axis 2066 of a coupling 2062 formed eccentrically with
respect to an axial center 2064 of an output shaft of electric
motor 2060.
[0074] FIG. 8 shows a cross section along D-D in FIG. 3. Planetary
gear 2054 has teeth smaller in number than ring gear 2052 by one.
Planetary gear 2054 is provided so that a part of the teeth thereof
meshes with ring gear 2052.
[0075] When electric motor 2060 causes coupling 2062 to rotate
about axial center 2064 and relative to ring gear 2052, accordingly
planetary gear 2054 as a whole rotates about axial center 2064
while planetary gear 2054 rotates about eccentric axis 2066. The
rotational motion of planetary gear 2054 causes guide plate 2040 to
rotate relative to sprocket 2010 and thus the phase of intake valve
1100 is changed.
[0076] If the rotational speed of the output shaft of electric
motor 2060 is identical to the rotational speed of sprocket 2010,
coupling 2062 and planetary gear 2054 rotate at the same rotational
speed as that of ring gear 2052 (sprocket 2010). In this case,
guide plate 2040 rotates at the same rotational speed as that of
sprocket 2010 and accordingly the phase of intake valve 1100 is
maintained.
[0077] Reference will now be made to FIG. 9 to describe a structure
of a program for control that ECU 4000 controlling intake VVT
mechanism 2000 executes to determine whether intake VVT mechanism
2000 has failed. The program described hereinafter is executed at a
predetermined time, such as when an ignition switch (not shown) is
turned on to start engine 1000, the engine is idle, or the
like.
[0078] In step (S) 100 ECU 4000 controls intake VVT mechanism 2000
to maximally retard the phase of intake valve 1100 (or when the
valve is opened/closed). For example, electric motor 2060 is
operated in a direction allowing the phase to be retarded until the
drive current of electric motor 2060 rapidly increases (or a lock
current is detected).
[0079] In S110 ECU 4000 detects the phase of intake valve 1100 (or
that of intake camshaft 1120) as based on a signal transmitted from
crank angle sensor 5000 and cam position sensor 5010.
[0080] In S120 ECU 4000 determines whether a phase more retarded
than that for which control pin (A) 2034 abuts against an end of
guide groove (A) 2041 is detected. If so (YES in S120) the control
proceeds to S130. Otherwise (NO in S120), the control proceeds to
S140.
[0081] In S130 ECU 4000 determines that intake VVT mechanism 2000
has failed. At the time, a decision is made that link mechanism (A)
2030 has failed. In S140 ECU 4000 determines that intake VVT
mechanism 2000 has link mechanism (A) 2030 operating normally.
[0082] As based on the structure and flowchart as described above,
ECU 4000 operates to control the valuable valve timing apparatus in
the present embodiment, as will be described hereinafter.
[0083] Intake VVT mechanism 2000 is controlled to maximally retard
the phase of intake valve 1100 at a predetermined time (S100) and
the current phase is detected (S110).
[0084] If intake VVT mechanism 2000 has link mechanism (A) 2030
undamaged and hence in a condition allowing normal operation, then,
as shown in FIG. 10, control pin (A) 2034 abuts against an end of
guide groove (A) 2041 and control pin (B) 2134 is detached from an
end of guide groove (B) 2042.
[0085] In this condition, the phase will not further be retarded.
As such, the detected phase matches that for which control pin (A)
2034 abuts against the end of guide groove (A) 2041 (NO in
S120).
[0086] In that case, it can be said that link mechanism (A) 2030 is
normally operating. Accordingly a decision is made that intake VVT
mechanism 2000 has link mechanism (A) 2030 operating normally
(S140).
[0087] If intake VVT mechanism 2000 has link mechanism (A) 2030
damaged and thus broken or similarly failed, control pin (A) 2034
abutting against an end of guide groove (A) 2041 does not limit the
operation of link mechanism (A) 2030. Accordingly, the rotation of
intake camshaft 1120 relative to sprocket 2010 is not limited.
[0088] In that case, as shown in FIG. 11, until control pin (B)
2134 abuts against an end of guide groove (B) 2042 link mechanism
(B) 2130 operates and intake camshaft 1120 is rotated relative to
sprocket 2010.
[0089] If in that condition a phase is detected, it will be a phase
more retarded than that for which control pin (A) 2034 abuts
against the end of guide groove (A) 2041. As such, if a phase more
retarded than that for which control pin (A) 2034 abuts against the
end of guide groove (A) 2041 is detected (YES in S120) then a
decision is made that the VVT mechanism 2000 has failed at link
mechanism (A) 2030 (S130). A failure arising in intake VVT
mechanism 2000 at link mechanism (A) 2030 can thus be detected.
[0090] Thus the present embodiment provides a variable valve timing
apparatus implemented by an intake VVT mechanism in which a guide
groove (A) along which a control pin (A) of a link mechanism (A)
slides is shorter, for a direction allowing the intake valve's
phase to be retarded, than a guide groove (B) along which a control
pin (B) of a link mechanism (B) slides. If link mechanism (A) is
not damaged or the like and normally operates, the phase can be
retarded until control pin (A) of link mechanism (A) abuts against
an end of guide groove (A). If link mechanism (A) is damaged and
broken, then the phase can further be retarded until control pin
(B) of link mechanism (B) abuts against an end of guide groove (B).
Thus whether link mechanism (A) has failed or not can be determined
from a phase detected when the intake VVT mechanism is controlled
to allow the phase to be maximally retarded. As a result a failure
arising in the intake VVT mechanism can be detected.
Second Embodiment
[0091] A second embodiment of the present invention will be
described hereinafter. The present embodiment differs from the
first embodiment in that link mechanism (A) is formed to be smaller
in strength than link mechanism (B).
[0092] The remaining hardware and control structures are identical
to those described in the first embodiment. They are also identical
in function. Accordingly they will not be described repeatedly in
detail.
[0093] As shown in FIG. 12, link mechanism (A) 2030 has arm (A2)
2032 provided with a hole 2036 to be smaller in strength than arm
(B2) 2132 of link mechanism (B) 2130.
[0094] Note that in place of or in addition to hole 2036, link
mechanism (A) 2030 may have arm (A2) 2032 having a side surface
notched 2038, as shown in FIG. 13, to reduce arm (A2) 2032 in
strength.
[0095] Furthermore, in place of or in addition to arm (A2) 2032,
arm (A1) 2031 may be provided with a hole or notched to be smaller
in strength than arm (B1) 2131.
[0096] Furthermore, link mechanism (A) 2030 may have pins (2) 2072,
(3) 2074 and (4) 2076 smaller in strength than pins (2) 2072, (3)
2074 and (4) 2076 of link mechanism (B) 2130.
[0097] This allows a damage or a similar failure to be caused
earlier in link mechanism (A) 2030 capable of detecting that
failure has arisen than in link mechanism (B) 2130. This can
prevent link mechanism (B) 2130 having a failure while link
mechanism (A) 2030 normally operates and the failure cannot be
detected.
Third Embodiment
[0098] A third embodiment of the present invention will be
described hereinafter. The present embodiment differs from the
first embodiment in that control pin (A) is detached from an end of
guide groove (A) when control pins (A) and (B) are moved in a
direction allowing the phase to be advanced until control pin (B)
abuts against an end of guide groove (B).
[0099] The remaining hardware and control structures are identical
to those described in the first or second embodiment. They are also
identical in function. Accordingly they will not be described
repeatedly in detail.
[0100] As shown in FIG. 14, in the present embodiment, as well as
the first embodiment, control pin (B) 2134 is detached from an end
of guide groove (B) 2142 when control pins (A) 2034 and (B) 2134
are moved in a direction allowing the phase to be retarded until
control pin (A) 2034 abuts against an end of guide groove (A)
2141.
[0101] In the present embodiment, in contrast to the first
embodiment, guide groove (B) 2142 along which control pin (B) 2134
of link mechanism (B) 2130 slides is shorter, for a direction
allowing the phase of intake valve 1100 to be advanced, than guide
groove (A) 2141 along which control pin (A) 2034 of link mechanism
(A) 2030 slides.
[0102] As such, control pin (A) 2034 is detached from an end of
guide groove (A) 2141 when control pins (A) 2034 and (B) 2134 are
moved in a direction allowing the phase to be advanced until
control pin (B) 2134 abuts against an end of guide groove (B)
2142.
[0103] When control pin (B) 2134 abuts against the end of guide
groove (B) 2142, link mechanism (B) 2130 is limited in operation in
the direction allowing the phase to be advanced. Therefore, if link
mechanism (B) 2130 normally operates, the phase for which control
pin (B) 2134 abuts against the end of guide groove (B) 2142 will be
the phase of the maximally advanced angle.
[0104] Reference will now be made to FIG. 15 to describe a
structure of a program for control that ECU 4000 controlling intake
VVT mechanism 2000 executes to determine whether intake VVT
mechanism 2000 has failed. Note that the program described
hereinafter is executed before or after that in the first
embodiment is executed.
[0105] In S200 ECU 4000 controls intake VVT mechanism 2000 to
maximally advance the phase of intake valve 1100 (or when the valve
is opened/closed). For example, electric motor 2060 is operated in
a direction allowing the phase to be advanced until the drive
current of electric motor 2060 rapidly increases (or a lock current
is detected).
[0106] In S210 ECU 4000 detects the phase of intake valve 1100 (or
that of intake camshaft 1120) as based on a signal transmitted from
crank angle sensor 5000 and cam position sensor 5010.
[0107] In S220 ECU 4000 determines whether a phase more advanced
than that for which control pin (B) 2134 abuts against an end of
guide groove (B) 2142 is detected. If so (YES in S220) the control
proceeds to S230. Otherwise (NO in S220), the control proceeds to
S240.
[0108] In S230 ECU 4000 determines that intake VVT mechanism 2000
has failed. At the time, a decision is made that link mechanism (B)
2130 has failed. In S240 ECU 4000 determines that intake VVT
mechanism 2000 has link mechanism (B) 2130 operating normally.
[0109] As based on the structure and flowchart as described above,
ECU 4000 operates to control the valuable valve timing apparatus in
the present embodiment, as will be described hereinafter.
[0110] Intake VVT mechanism 2000 is controlled to maximally advance
the phase of intake valve 1100 (S200) and the current phase is
detected (S210).
[0111] If intake VVT mechanism 2000 has link mechanism (B) 2130
undamaged and hence in a condition allowing normal operation, then,
as shown in FIG. 16, control pin (B) 2134 abuts against an end of
guide groove (B) 2142 and control pin (A) 2034 is detached from an
end of guide groove (A) 2141.
[0112] In this condition, the phase will not further be advanced.
As such, the detected phase matches that for which control pin (B)
2134 abuts against the end of guide groove (B) 2142 (NO in
S220).
[0113] In that case, it can be said that link mechanism (B) 2130 is
normally operating. Accordingly a decision is made that intake VVT
mechanism 2000 has link mechanism (B) 2130 operating normally
(S240).
[0114] If intake VVT mechanism 2000 has link mechanism (B) 2130
damaged and thus broken or similarly failed, control pin (B) 2134
abutting against an end of guide groove (B) 2142 does not limit the
operation of link mechanism (B) 2130. Accordingly, the rotation of
intake camshaft 1120 relative to, sprocket 2010 is not limited.
[0115] In that case, as shown in FIG. 17, until control pin (A)
2034 abuts against an end of guide groove (A) 2141 link mechanism
(A) 2030 operates and intake camshaft 1120 is rotated relative to
sprocket 2010.
[0116] If in that condition a phase is detected, it will be a phase
more advanced than that for which control pin (B) 2134 abuts
against the end of guide groove (B) 2142. As such, if a phase more
retarded than that for which control pin (B) 2134 abuts against the
end of guide groove (B) 2142 is detected (YES in S220) then a
decision is made that the VVT mechanism 2000 has failed at link
mechanism (B) 2130 (S230).
[0117] Thus, similarly as has been described in the first
embodiment, a failure arising in intake VVT mechanism 2000 at link
mechanism (A) 2030 can be detected, and so can that arising at link
mechanism (B) 2130.
[0118] Thus the present embodiment provides a variable valve timing
apparatus implemented by an intake VVT mechanism in which a guide
groove (A) along which a control pin (A) of a link mechanism (A)
slides is shorter, for a direction allowing the intake valve's
phase to be retarded, than a guide groove (B) along which a control
pin (B) of a link mechanism (B) slides and guide groove (B) along
which control pin (B) of link mechanism (B) slides is shorter, for
a direction allowing the intake valve's phase to be advanced, than
guide groove (A) along which control pin (A) of link mechanism (A)
slides. If link mechanism (A) is not damaged or the like and
normally operates, the phase can be retarded until control pin (A)
of link mechanism (A) abuts against an end of guide groove (A). If
link mechanism (A) is damaged and broken, then the phase can
further be retarded until control pin (B) of link mechanism (B)
abuts against an end of guide groove (B). Similarly, if link
mechanism (B) is not damaged or the like and normally operates, the
phase can be advanced until control pin (B) of link mechanism (B)
abuts against an end, of guide groove (B). If link mechanism (B) is
damaged and broken, then the phase can further be advanced until
control pin (A) of link mechanism (A) abuts against an end of guide
groove (A). Thus whether link mechanism (A) or link mechanism (B)
has failed or not can be determined from a phase detected when the
intake VVT mechanism is controlled to allow the phase to be
maximally retarded or advanced. As a result a failure arising in
the intake VVT mechanism can be detected.
[0119] Note that while in the first to third embodiments intake VVT
mechanism 2000 has two link mechanisms, it may have three or more
link mechanisms.
[0120] Furthermore in exhaust VVT mechanism 3000 two or more link
mechanisms may be employed to change the phase of exhaust valve
1110 and detect a failure of a link mechanism in exhaust VVT
mechanism 3000.
[0121] Furthermore, in place of or in addition to a link mechanism,
a mechanism other than the link mechanism may be employed to change
a phase of intake valve 1100, exhaust valve 1100 or the like and
detect a failure arising in that mechanism.
Other Embodiment
[0122] In addition to guide grooves (A) 2041 and 2141 and (B) 2042
and 2142 provided in guide plate 2040, limiter pins (1) 2200, (2)
2202 and the like may be employed to limit the range within which
link mechanisms (A) 2030, (B) 2130 and the like are operable, as
shown in FIG. 18.
[0123] In FIG. 18 limiter pin (1) 2200 limits link mechanism (A)
2030 in operation so that, for a direction for retard, link
mechanism (A) 2030 is operable within a range smaller than link
mechanism (B) 2130 is.
[0124] Limiter pin (2) 2202 limits link mechanism (B) 2130 in
operation so that, for a direction for advance, link mechanism (B)
2130 is operable within a range smaller than link mechanism (A)
2030 is.
[0125] Although the present invention has been described and
illustrated in detail, it is clearly understood that the same is by
way of illustration and example only and is not to be taken by way
of limitation, the spirit and scope of the present invention being
limited only by the terms of the appended claims.
* * * * *