U.S. patent application number 13/490671 was filed with the patent office on 2012-12-13 for variable valve timing apparatus.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Motomasa Iizuka, Kenichi Nara, Kuniaki OKA, Taketsugu Sasaki, Junji Ute, Jun Yamada.
Application Number | 20120312261 13/490671 |
Document ID | / |
Family ID | 47292073 |
Filed Date | 2012-12-13 |
United States Patent
Application |
20120312261 |
Kind Code |
A1 |
OKA; Kuniaki ; et
al. |
December 13, 2012 |
VARIABLE VALVE TIMING APPARATUS
Abstract
A phase adjusting mechanism is engaged with a brake shaft, and
adjusts a rotation phase between a crankshaft and a camshaft
according to a braking torque acting on a rotor. The rotation phase
is adjusted in a predetermined direction when the braking torque is
increased. A torque input mechanism inputs a return torque into the
phase adjusting mechanism to return the rotation phase in an
opposite direction opposite from the predetermined direction. The
torque input mechanism increases the return torque corresponding to
the rotation phase as an environmental temperature of the variable
valve timing apparatus is lowered.
Inventors: |
OKA; Kuniaki; (Nishio-city,
JP) ; Sasaki; Taketsugu; (Nagoya-city, JP) ;
Iizuka; Motomasa; (Anjo-city, JP) ; Ute; Junji;
(Kariya-city, JP) ; Yamada; Jun; (Okazaki-city,
JP) ; Nara; Kenichi; (Nagoya-city, JP) |
Assignee: |
DENSO CORPORATION
Kariya-city
JP
NIPPON SOKEN, INC.
Nishio-city
JP
|
Family ID: |
47292073 |
Appl. No.: |
13/490671 |
Filed: |
June 7, 2012 |
Current U.S.
Class: |
123/90.15 |
Current CPC
Class: |
F01L 2001/0537 20130101;
F01L 1/352 20130101; F01L 2250/02 20130101; F01L 2301/00 20200501;
F01L 2001/34483 20130101; F01L 2820/00 20130101 |
Class at
Publication: |
123/90.15 |
International
Class: |
F01L 1/344 20060101
F01L001/344 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 10, 2011 |
JP |
2011-130492 |
Claims
1. A variable valve timing apparatus that controls valve timing of
a valve which is opened and closed by a camshaft driven by torque
transmission from a crankshaft in an internal combustion engine,
the apparatus comprising: a case defining a fluid chamber inside;
magnetic viscosity fluid kept in the fluid chamber, the magnetic
viscosity fluid having a viscosity variable in accordance with
magnetic flux passing through; a control device which carries out
variable control of the viscosity of the magnetic viscosity fluid
by varying the magnetic flux; a rotor having a brake shaft
penetrating the case to come into contact with the magnetic
viscosity fluid so that the rotor receives a braking torque
according to the viscosity of the magnetic viscosity fluid; a phase
adjusting mechanism engaged with the brake shaft at an outside of
the case, the phase adjusting mechanism adjusting a rotation phase
between the crankshaft and the camshaft according to the braking
torque acting on the rotor, the rotation phase being adjusted in a
predetermined direction when the braking torque is increased; and a
torque input mechanism inputting a return torque into the phase
adjusting mechanism to return the rotation phase in an opposite
direction opposite from the predetermined direction, wherein the
torque input mechanism increases the return torque corresponding to
the rotation phase as an environmental temperature of the variable
valve timing apparatus is lowered.
2. The variable valve timing apparatus according to claim 1,
wherein the torque input mechanism has an elastic member connected
to the phase adjusting mechanism in a state where the elastic
member has an elastic deformation, the elastic member inputting the
return torque corresponding to the rotation phase using a
recovering force of the elastic member from the elastic
deformation, and a deformation increasing portion connected to the
elastic member, the deformation increasing portion increasing the
return torque by increasing an amount of the elastic deformation of
the elastic member as the environmental temperature of the variable
valve timing apparatus is lowered.
3. The variable valve timing apparatus according to claim 2,
wherein the deformation increasing portion has a contraction part
that is contacted as the environmental temperature of the variable
valve timing apparatus is lowered, a contraction casing defining an
accommodation chamber that accommodates the contraction part, and a
displacement part penetrating the contraction casing, the
displacement part increasing the amount of the elastic deformation
of the elastic member at outside of the contraction casing by being
displaced by the contraction of the contraction part in the
accommodation chamber.
4. The variable valve timing apparatus according to claim 3,
wherein the deformation increasing portion further has a biasing
part that biases the displacement part toward the contraction part,
inside of the contraction casing.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on Japanese Patent Application No.
2011-130492 filed on Jun. 10, 2011, the disclosure of which is
incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] The present disclosure relates to a variable valve timing
apparatus.
BACKGROUND
[0003] A fluid brake device conducts variable control of viscosity
of magnetic viscosity fluid by causing a magnetic flux to pass
through the magnetic viscosity fluid. The magnetic viscosity fluid
is filled in a fluid chamber of a casing, and contacts a brake
rotor. Braking torque is provided to the brake rotor of the fluid
brake device with comparatively small electric power, so that the
fluid brake device is suitably used in a variable valve timing
apparatus that controls a relative engine phase between a
crankshaft and a camshaft of an engine in accordance with the
braking torque.
[0004] JP-A-2008-51093 describes a variable valve timing apparatus
having a casing, a brake shaft penetrating the casing, and a phase
adjusting mechanism engaged with the brake shaft. If the braking
torque acting on the brake rotor is increased, the phase adjusting
mechanism adjusts the engine phase in a direction advancing the
valve timing.
[0005] The variable valve timing apparatus further includes an
elastic member that inputs a return torque to the phase adjusting
mechanism to return the engine phase in a direction retarding the
valve timing. The intensity of the return torque corresponds to the
engine torque. If the braking torque input into the brake rotor is
decreased, the engine phase is returned to the retarding direction
by the return torque input from the elastic member. Thus, the
engine phase can be controlled in accordance with the braking
torque acting on the brake rotor by controlling the viscosity of
the magnetic viscosity fluid.
[0006] However, as a temperature of the magnetic viscosity fluid is
lowered, the viscosity of the magnetic viscosity fluid becomes
high. When the environmental temperature of the variable valve
timing apparatus is relatively low, for example, immediately after
the engine is started, the low-temperature magnetic viscosity fluid
has high viscosity, so that the braking torque is increased. Even
if the magnetic flux passing through the magnetic viscosity fluid
is weakened, it is difficult to retard the valve timing. Thus, at
the low-temperature time, it may be difficult to control the engine
phase by variably controlling the viscosity of the magnetic
viscosity fluid.
[0007] If the return torque is increased for the low-temperature
time, the return torque remains high when the environmental
temperature is raised by the continuous operation of the engine. On
the other hand, the braking torque input into the brake rotor is
decreased by the lowering in the viscosity of the magnetic
viscosity fluid when the environmental temperature is raised. In
this case, it is difficult to balance the return torque and the
braking torque, so that the engine phase may become unstable in the
ordinary temperature time.
SUMMARY
[0008] According to an example of the present disclosure, a
variable valve timing apparatus that controls valve timing of a
valve which is opened and closed by a camshaft driven by torque
transmission from a crankshaft in an internal combustion engine
includes a case, magnetic viscosity fluid, a control device, a
rotor, a phase adjusting mechanism, and a torque input mechanism.
The case defines a fluid chamber inside. The magnetic viscosity
fluid is kept in the fluid chamber, and has a viscosity variable in
accordance with magnetic flux passing through. The control device
carries out variable control of the viscosity of the magnetic
viscosity fluid by varying the magnetic flux. The rotor has a brake
shaft penetrating the case to come into contact with the magnetic
viscosity fluid so that the rotor receives a braking torque
according to the viscosity of the magnetic viscosity fluid. The
phase adjusting mechanism is engaged with the brake shaft at an
outside of the case, and adjusts a rotation phase between the
crankshaft and the camshaft according to the braking torque acting
on the rotor. The rotation phase is adjusted in a predetermined
direction when the braking torque is increased. The torque input
mechanism inputs a return torque into the phase adjusting mechanism
to return the rotation phase in an opposite direction opposite from
the predetermined direction. The torque input mechanism increases
the return torque corresponding to the rotation phase as an
environmental temperature of the variable valve timing apparatus is
lowered.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Additional objects and advantages of the present disclosure
will be more readily apparent from the following detailed
description when taken together with the accompanying drawings. In
which:
[0010] FIG. 1 is a schematic sectional view illustrating a variable
valve timing apparatus including a fluid brake device according to
a first embodiment of the present disclosure;
[0011] FIG. 2 is a sectional view taken along a line II-II of FIG.
1;
[0012] FIG. 3 is a sectional view taken along a line of FIG. 1;
[0013] FIG. 4 is a graph illustrating characteristics of magnetic
viscosity fluid of the fluid brake device;
[0014] FIG. 5 is a sectional view taken along a line V-V of FIG.
1;
[0015] FIG. 6A is a sectional view illustrating a return torque
input mechanism of the fluid brake device at a low-temperature
time, and FIG. 6B is a sectional view illustrating the return
torque input mechanism at an ordinary temperature time;
[0016] FIG. 7A is a sectional view illustrating a return torque
input mechanism of a fluid brake device according to a second
embodiment at a low-temperature time, and FIG. 7B is a sectional
view illustrating the return torque input mechanism of the second
embodiment at an ordinary temperature time; and
[0017] FIG. 8A is a sectional view illustrating a return torque
input mechanism of a fluid brake device according to a third
embodiment at a low-temperature time, and
[0018] FIG. 8B is a sectional view illustrating the return torque
input mechanism of the third embodiment at an ordinary temperature
time.
DETAILED DESCRIPTION
[0019] A plurality of embodiments of the present disclosure are
explained referring to drawings. Components and parts corresponding
to the components and parts described in the preceding description
may be indicated by the same reference number and may not be
described redundantly. In a case that only a part of component or
part is described, other descriptions for the remaining part of
component or part in the other description may be incorporated. The
embodiments can be partially combined or partially exchanged in
some forms which are clearly specified in the following
description. In addition, it should be understood that, unless
trouble arises, the embodiments can be partially combined or
partially exchanged each other in some forms which are not clearly
specified.
First Embodiment
[0020] FIG. 1 is a cross-sectional view taken along a line I-I of
FIG. 2 and shows a variable valve timing apparatus 1 having a fluid
brake device 100 according to a first embodiment. The variable
valve timing apparatus 1 is mounted on an engine of a vehicle. The
variable valve timing apparatus 1 is installed in a torque
transmission train which transmits engine torque to a camshaft 2
from a crankshaft (not shown). The camshaft 2 opens and closes an
intake valve (not shown) of the engine through the transmission of
the engine torque. The variable valve timing apparatus 1 controls a
valve timing of the intake valve.
[0021] The variable valve timing apparatus 1 has a control circuit
200 and a phase adjusting mechanism 300 in addition to the fluid
brake device 100. The control circuit 200 is a circuit supplying
energizing current. The variable valve timing apparatus 1 provides
appropriate valve timing for the engine by adjusting an engine
phase which is a relative angular phase between the camshaft 2 and
the crankshaft.
[0022] The fluid brake device 100 is provided with a case 110, a
brake rotor 130, a magnetic viscosity fluid 140, a sealing device
160 and a solenoid coil 150.
[0023] The case 110 is formed in a hollow shape as a whole. The
case 110 has a fixing member 111 and a cover member 112. The fixing
member 111 has a cylindrical shape in which outside diameter is
changed to form a step, and is made of magnetic materials. The
fixing member 111 is fixed to a member of the engine, such as a
chain cover (not shown). The cover member 112 has a round disc
shape, and is made of magnetic materials. The cover member 112 is
arranged to have the same axis as the fixing member 111, and
opposes the phase adjusting mechanism 300 through the fixing member
111. The fixing member 111 and the cover member 112 are
liquid-tightly tightened to form the case 110 and to define a fluid
chamber 114 therebetween.
[0024] The rotor 130 includes a shaft 131 and a plate 132 securely
fixed each other. The shaft 131 extends in an axis direction, and
is made of magnetic materials. The shaft 131 penetrates the fixing
member 111 of the case 110 between an inside and an outside of the
case 110. One end of the shaft 131 extends to the outside of the
case 110, and is engaged with the phase adjusting mechanism 300 at
the outside of the case 110. Intermediate part of the shaft 131 is
rotatably supported by a bearing 116 defined in the fixing member
111. Since the phase adjusting mechanism 300 receives the engine
torque from the crankshaft, the rotor 130 receives a rotating
torque in a counterclockwise direction in FIGS. 2 and 3 from the
phase adjusting mechanism 300.
[0025] As shown in FIG. 1, the annular plate 132 made of magnetic
materials is disposed on an outer surface of the shaft 131 and is
located on an end portion of the shaft 131 opposite from the phase
adjusting mechanism 300. The plate 132 spreads outward in the
radial direction, and is accommodated in the fluid chamber 114. In
the fluid chamber 114, the plate 132 and the fixing member 111
define a magnetic gap 114a in the axis direction. Similarly, the
plate 132 and the cover member 112 define a magnetic gap 114b in
the axis direction.
[0026] The magnetic viscosity fluid 140 is filled in the fluid
chamber 114 having the magnetic gaps 114a and 114b. The magnetic
viscosity fluid 140 is a kind of functional fluid. For example, the
magnetic viscosity fluid 140 contains magnetic particles which are
suspended in non-magnetic base liquid. For example, oil which is
the same kind of lubrication oil for the internal combustion engine
may be used as the base liquid. A powdered magnetic material such
as carbonyl iron etc. may be used as the magnetic particles for the
magnetic viscosity fluid 140.
[0027] Viscosity of the magnetic viscosity fluid 140 is varied
according to a magnetic field intensity applied. In other word,
viscosity of the magnetic viscosity fluid 140 is varied according
to a magnetic flux density. As shown in FIG. 4, viscosity of the
magnetic viscosity fluid 140 is raised according to increase in the
magnetic flux density. Therefore, the yield stress is increased in
proportion to the viscosity.
[0028] As shown in FIG. 1, the sealing device 160 is arranged
between the fluid chamber 114 and the bearing 116 in the axis
direction of the case 110. The sealing device 160 seals a space
between the fixing member 111 of the case 110 and the shaft 131 of
the brake rotor 130, thereby restricting the magnetic viscosity
fluid 140 from leaking outside of the case 110.
[0029] Specifically, the shaft 131 of the brake rotor 130 has a
guide rotor 134 continuously extending in the rotation direction. A
magnetism sealing sleeve 170 is arranged to surround the outer
circumference side of the shaft 131 in the rotation direction. The
sealing sleeve 170 has a permanent magnet 171 and a pair of guide
yokes 174, 175. A seal gap 180 is defined between the guide yoke
174 and the guide rotor 134 and a seal gap 181 is defined between
the guide yoke 175 and the guide rotor 134. The seal gap 180, 181
communicates with the fluid chamber 114.
[0030] A magnetic flux generated by the permanent magnet 171 is
guided from the guide yoke 174, 175 through the seal gap 180, 181
to the guide rotor 134. The magnetic flux having high density
passes through the seal gap 180, 181, and the viscosity of the
magnetic viscosity fluid 140 is raised by the high density magnetic
flux. Thereby, the magnetic viscosity fluid 140 is caught in a film
shape at the seal gap 180, 181, and works as a self-sealing film
that restricts the magnetic viscosity fluid 140 from leaking.
[0031] The solenoid coil 150 is produced by winding a metal wire on
a radial outside surface of a cylindrical bobbin 151. The solenoid
coil 150 is disposed on a radial outside part of the plate 132 in a
coaxial manner. The solenoid coil 150 is supported in the case 110,
and is interposed between the fixing member 111 and the cover
member 112 in the axis direction. The solenoid coil 150 is excited
by being supplied with electric current, and generates a magnetic
flux which passes through the fixing member 111, the magnetic gap
114a, the plate 132, the magnetic gap 114b, and the cover member
112.
[0032] When the solenoid coil 150 generates the magnetic flux
during counterclockwise rotation of the rotor 130 shown in FIGS. 2
and 3, the magnetic flux passes through the magnetic viscosity
fluid 140 of the magnetic gaps 114a and 114b of the fluid chamber
114. The viscosity of the magnetic viscosity fluid 140 is varied by
the magnetic flux, and a braking torque is generated between the
case 110 and the rotor 130 which come in contact with the magnetic
viscosity fluid 140. Therefore, the plate 132 of the rotor 130
receives the braking torque in the clockwise direction in FIGS. 2
and 3, due to the viscosity resistance. As a result, the braking
torque according to the viscosity of the magnetic viscosity fluid
140 is applied to the rotor 130 by supplying the magnetic flux from
the solenoid coil 150.
[0033] The control circuit 200 controls current supplied to the
solenoid coil 150. The control circuit 200 is mainly constructed by
a microcomputer. The control circuit 200 is disposed separately
from the fluid brake device 100. The control circuit 200 is
electrically connected with the solenoid coil 150 and a battery 4
arranged in the vehicle. During a stop of the engine, the control
circuit 200 turns off a current supply to the solenoid coil 150 in
response to a turning off an electric power supply from the battery
4. At this time, the solenoid coil 150 does not generate the
magnetic flux, and does not generate the braking torque on the
rotor 130.
[0034] On the other hand, during an operation of the engine, the
control circuit 200 is supplied with the electric power from the
battery 4, and controls an amount of current supply to the solenoid
coil 150. As a result, the solenoid coil 150 generates a regulated
amount of the magnetic flux which passes through the magnetic
viscosity fluid 140. At this time, variable control of the
viscosity of the magnetic viscosity fluid 140 is carried out. The
braking torque applied to the rotor 130 is adjusted by the amount
of the current supplied to the solenoid coil 150.
[0035] As shown in FIG. 1, the phase adjusting mechanism 300
includes a driving rotor 10, a driven rotor 20, a returning member
30, a planetary carrier 40, and a planetary gear 50.
[0036] The driving rotor 10 includes a gear member 12 and a chain
wheel 13 which are made of metal. The gear member 12 and the chain
wheel 13 are formed in cylindrical shapes and are fastened by
screws in a coaxial manner. As shown in FIG. 2, the gear member 12
has a radial inside surface where a driving inner gear 14 is
formed. A teeth tip circle has a diameter smaller than that of a
teeth bottom circle in the gear 14. As shown in FIG. 1, the chain
wheel 13 has a radial outside surface where a plurality of gear
teeth 16 is formed. The gear teeth 16 of the chain wheel 13 is
engaged with the crankshaft via a timing chain (not shown) and
rotated synchronously with the crankshaft. Therefore, the driving
rotor 10 is rotated in the counterclockwise direction in FIGS. 2
and 3 in response to the rotation of the crankshaft when the engine
torque is transmitted to the chain wheel 13 from the crankshaft
through the timing chain.
[0037] As shown in FIG. 1, the driven rotor 20 is formed in a
cylindrical shape and is arranged in a radial inside of the chain
wheel 13 in a coaxial manner. The driven rotor 20 has a connection
part 21 on the bottom wall and the connection part 21 is fitted and
connected to the camshaft 2 in a coaxial manner using screw. The
driven rotor 20 is able to rotate in response to the rotation of
the camshaft 2 and is able to have relative rotation relative to
the driving rotor 10. The rotation direction of the driven rotor 20
is set in the counterclockwise direction of FIGS. 2 and 3,
similarly to the driving rotor 10. The driven rotor 20 is
interlocked with the camshaft 2, and is supported to relatively
rotate with respect to the driving rotor 10.
[0038] As shown in FIG. 3, the driven rotor 20 has a radial inside
surface where a driven inner gear 22 is formed. A teeth tip circle
has a diameter smaller than that of a teeth bottom circle in the
gear 22. The inside diameter of the driven inner gear 22 is set
larger than that of the driving inner gear 14, and the number of
teeth of the driven inner gear 22 is set greater than the number of
teeth of the driving inner gear 14. The driven inner gear 22 is
positioned away from the driving inner gear 14 in the axis
direction, in a direction opposite from the fluid brake device
100.
[0039] As shown in FIG. 1, the returning member 30 consists of a
helical torsion metal spring. The returning member 30 is coaxially
arranged in an inside of the chain wheel 13. The returning member
30 has one end 31 which is engaged with the chain wheel 13 and the
other end 32 which is engaged with the connection part 21. The
returning member 30 generates assist torque when the returning
member 30 is twisted between the rotors 10 and 20. The assist
torque urges and pushes the driven rotor 20 in a retarding
direction with respect to the driving rotor 10.
[0040] As shown in FIGS. 1-3, the planetary carrier 40 is formed in
a cylindrical shape as a whole and is made of metal. The planetary
carrier 40 has a radial inside surface where a transfer part 41
which receives the braking torque from the rotor 130 is formed. The
transfer part 41 is coaxially arranged with the rotors 10 and 20.
The transfer part 41 has a pair of engaging grooves 42 and a
connector 43 fitted with the grooves 42. The transfer part 41 of
the planetary carrier 40 and the brake shaft 131 are engaged via
the connector 43. The planetary carrier 40 is capable of rotating
with the brake rotor 130, and is capable of having relative
rotation relative to the driving rotor 10. The rotation direction
of the planetary carrier 40 is set in the counterclockwise
direction in FIGS. 2 and 3 when the engine is active, similarly to
the brake rotor 130.
[0041] As shown in FIGS. 1-3, the planetary carrier 40 has a
supporting portion 46 which supports the planetary gear 50. The
supporting portion 46 is located eccentrically with respect to the
rotors 10 and 20 and the brake shaft 131, and is coaxially engaged
with a center hole 51 of the planetary gear 50 through a planetary
bearing 48. The planetary gear 50 is supported by the supporting
portion 46 in such a manner as to perform the planetary motion. The
planetary gear 50 rotates about an eccentric axis of the supporting
portion 46, and also the planetary gear 50 revolves relative to the
planetary carrier 40. Thus, when the planetary carrier 40 performs
relative rotation with respect to the driving rotor 10 in the
revolution direction of the planetary gear 50, the planetary gear
50 performs the planetary motion.
[0042] The planetary gear 50 has a radial outside surface formed in
a stepped cylindrical shape. The planetary gear 50 has a driving
outer gear 52 and a driven outer gear 54 on the radial outside. The
driving outer gear 52 is formed on a smaller diameter part of the
gear 50, and the driven outer gear 54 is formed on a larger
diameter part of the gear 50. The driving outer gear 52 and the
driven outer gear 54 are coaxially arranged. The driving outer gear
52 intermeshes with the driving inner gear 14 only at a position
where the planetary gear 50 is located by its orbiting motion. The
driven outer gear 54 also intermeshes with the driven inner gear 22
only at a position where the planetary gear 50 is located by its
orbiting motion. The outside diameter of the driven outer gear 54
is set larger than that of the driving outer gear 52, and the
number of teeth of the outer gear 52, 54 is set smaller than the
number of teeth of the inner gear 22, 14 by the same number.
[0043] The phase adjusting mechanism 300 adjusts the engine phase
according to a balance of torques among the braking torque input
into the rotor 130, the assist torque of the returning member 30
acting in the opposite direction of the braking torque, and
fluctuating torque acting on the camshaft 2 during the operation of
the engine.
[0044] In a case where the braking torque is adjusted in a constant
value in order to enable the rotor 130 to rotate with the drive
rotor 10 in the same rotating speed, the planetary carrier 40 does
not rotate relatively with respect to the driving inner gear 14.
Then, the planetary gear 50 orbits synchronously with both the
rotors 10 and 20 without performing relative rotation of the
sun-and-planet motion. Therefore, the engine phase is maintained in
a constant angular phase.
[0045] In a case where the braking torque is increased in order to
enable the rotor 130 to rotate at a rotating speed that is slower
than that of the drive rotor 10, the planetary carrier 40
relatively rotates in a retarding direction with respect to the
driving inner gear 14. Then, the planetary gear 50 itself rotates
by the sun-and-planet motion and orbits on the gears 14 and 22.
Therefore, the driven rotor 20 is relatively rotated in an
advancing direction with respect to the drive rotor 10. Therefore,
the engine phase is advanced.
[0046] In a case where the braking torque is decreased in order to
enable the rotor 130 to rotate at a rotating speed that is higher
than that of the drive rotor 10, the planetary carrier 40
relatively rotates in an advancing direction with respect to the
driving inner gear 14. Then, the planetary gear 50 itself rotates
by the sun-and-planet motion and orbits on the gears 14 and 22.
Therefore, the driven rotor 20 is relatively rotated in a retarding
direction with respect to the drive rotor 10. Therefore, the engine
phase is retarded.
[0047] As shown in FIG. 5, a return torque input mechanism 60 is
constructed by a thermo sensor element 70 and a holding member 80,
in addition to the returning member 30.
[0048] As shown in FIG. 1, the returning member 30 is constructed
by a wire spirally winded, as a main part 30a. The one end 31 of
the returning member 30 is received by the thermo sensor element 70
through a pillar-shaped connection component 31a made of metal
materials. The one end 31 of the returning member 30 is extended to
the outer circumference side from the main part 30a of the
returning member 30. The other end 32 of the returning member 30 is
received by a stationary portion 21 through a boss 32a embedded in
the stationary portion 21.
[0049] The returning member 30 is connected with the phase
adjusting mechanism 300. As the engine phase is adjusted in the
advancing direction advancing the valve timing, the returning
member 30 is twisted at the center axis, so that strong recovery
force is acted to the phase adjusting mechanism 300 from the
returning member 30. That is, the returning member 30 inputs a
return torque corresponding to the engine phase into the phase
adjusting mechanism 300, and the return torque causes the engine
phase to return in the retarding direction retarding the valve
timing.
[0050] The thermo sensor element 70 is arranged at periphery side
of the returning member 30, and is connected with the returning
member 30. The thermo sensor element 70 has a case part 71, a wax
74, a piston 76, and a diaphragm 75, as shown in FIG. 5.
[0051] The case part 71 has a cylindrical shape, and is made of
metallic material which is excellent in heat conduction, for
example. A wax chamber 72 is defined inside of the case part 71.
The wax 74 is accommodated in the wax chamber 72. An environmental
temperature of the variable valve timing apparatus 1 is transmitted
to the wax chamber 72 through the holding member 80 and the case
part 71.
[0052] The wax 74 is paraffin wax, for example, and is enclosed
within the wax chamber 72 of the case part 71. The volume of the
wax 74 is decreased, as the temperature of the wax 74 is lowered.
The volume of the wax 74 is increased, as the temperature of the
wax 74 is raised. The volume of the wax chamber 72 of the case part
71 is varied by the expansion/contraction of the wax 74.
[0053] The piston 76 penetrates the case part 71 between the inside
and the outside of the case part 71, and is movable relative to the
case part 71. The piston 76 has a holding part 78 and a pressure
receiving part 77. The holding part 78 is constructed by a portion
of the piston 76 located outside of the case part 71, and holds the
connection component 31a. Thereby, the piston 76 is connected with
the one end 31 of the returning member 30 through the connection
component 31a.
[0054] The pressure receiving part 77 has a board shape and defines
the wax chamber 72 inside of the case part 71. The pressure
receiving part 77 displaces the piston 76 in the axis direction of
the case part 71 by the pressure received from the wax 74 when the
wax 74 has the expansion/contraction. The piston 76 moves relative
to the case part 71 by being displaced by the expansion/contraction
of the wax 74, so that the piston 76 increases the amount of
elastic deformation of the returning member 30 outside of the case
part 71.
[0055] The diaphragm 75 has a ring shape and is made of rubber
material which can be expanded or contracted. The diaphragm 75 is
arranged between the outer circumference wall of the pressure
receiving part 77 of the piston 76 and the inner circumference wall
of the case part 71, and is joined with the outer circumference
wall and the inner circumference wall. The diaphragm 75 expands and
contracts in response to the displacement of the piston 76, so as
to maintain the definition of the wax chamber 72 inside of the case
part 71. That is, the diaphragm 75 works as a sealing device, so
that the wax 74 is restricted from leaking out of the wax chamber
72.
[0056] The holding member 80 has a disc shape and is made of
metallic material. The holding member 80 is fixed to the chain
wheel 13 by plural fastening components 82. A thermo sensor chamber
81 is defined in the holding member 80, and has a shape
corresponding to the thermo sensor element 70. The holding member
80 holds the thermo sensor element 70 in the thermo sensor chamber
81 in the state where the piston 76 can have the displacement.
[0057] If the variable valve timing apparatus 1 is left under
low-temperature environment in a state where the engine is stopped,
the environmental temperature of the variable valve timing
apparatus 1 is also lowered with progress of time. The temperature
of the magnetic viscosity fluid 140 accommodated in the variable
valve timing apparatus 1 is also lowered to the same degree as the
environmental temperature. Thereby, the viscosity of the oil, which
is the base liquid of the magnetic viscosity fluid 140, is raised
as shown in a broken line of FIG. 4.
[0058] Therefore, the braking torque which acts on the brake rotor
130 from the magnetic viscosity fluid 140 will increase. In
addition, in the inside of the phase adjusting mechanism 300, the
viscosity of the lubrication oil is also raised by the lowering in
the temperature of the lubrication oil. Therefore, as the
environmental temperature of the variable valve timing apparatus 1
is lowered, the torque required to adjust the engine phase in the
phase adjusting mechanism 300 is increased.
[0059] The return torque input mechanism 60 increases the return
torque input into the phase adjusting mechanism 300, as the
environmental temperature of the variable valve timing apparatus 1
is lowered. Details of operation of the return torque input
mechanism 60 will be explained with reference to FIGS. 6A and
6B.
[0060] In low-temperature environment (e.g., about -30.degree. C.)
immediately after start-up of the engine, as the environmental
temperature of the variable valve timing apparatus 1 is lowered,
the temperature of the thermo sensor element 70 is also lowered.
Therefore, as shown in FIG. 6A, the wax 74 accommodated in the wax
chamber 72 of the thermo sensor element 70 is contracted. At this
time, the piston 76 moves to follow the contracted wax 74, so that
the piston 76 is displaced in the counterclockwise direction shown
in FIG. 6A. The displacement of the piston 76 is transmitted to the
returning member 30 through the connection component 31a, therefore
the thermo sensor element 70 further increases the amount of
elastic deformation of the returning member 30.
[0061] Thus, the recovery force of the returning member 30 which
acts on the phase adjusting mechanism 300 becomes still stronger,
because a set load of the returning member 30 is increased.
Therefore, the return torque input into the phase adjusting
mechanism 300 is increased by the lowering in the environmental
temperature in all the range of the engine phase adjusted with the
phase adjusting mechanism 300. Accordingly, the return torque input
mechanism 60 increases the return torque input into the phase
adjusting mechanism 300, as the environmental temperature of the
variable valve timing apparatus 1 is lowered. In addition, the set
load of the returning member 30 mentioned above represents a power
elastically deforming the returning member 30 in a case where the
engine phase has the most retarded phase in the phase adjusting
mechanism 300.
[0062] When the environmental temperature of the variable valve
timing apparatus 1 is raised to an ordinary temperature (e.g.,
about 130.degree. C.) by continuous operation of the engine, the
temperature of the thermo sensor element 70 is also raised.
Therefore, the wax 74 accommodated in the wax chamber 72 of the
thermo sensor element 70 is expanded, as shown in FIG. 6B. The
piston 76 is displaced in the clockwise rotation shown in FIG. 6B
by the pressure of the expanding wax 74. The displacement of the
piston 76 is transmitted to the returning member 30 through the
connection component 31a, therefore the thermo sensor element 70
decreases the amount of elastic deformation of the returning member
30.
[0063] Then, because the set load of the returning member 30
decreases, the recovery force of the returning member 30 which acts
on the phase adjusting mechanism 300 becomes weak. Thus, the return
torque input into the phase adjusting mechanism 300 is decreased by
the raising in the environmental temperature in all the range of
the engine phase adjusted with the phase adjusting mechanism 300.
Accordingly, the return torque input mechanism 60 decreases the
return torque input into the phase adjusting mechanism 300, as the
environmental temperature of the variable valve timing apparatus 1
is raised.
[0064] In the first embodiment, the braking torque input into the
brake rotor 130 and the torque required for adjusting the engine
phase are assumed to increase due to the lowering in the
environmental temperature. At this time, the return torque input
mechanism 60 can cause the valve timing to return in the retarding
direction by increasing the return torque, while the engine phase
is advanced by the increase in the braking torque. That is, even in
the low-temperature time, the engine phase can be adjusted by the
phase adjusting mechanism 300 through the variable control of the
viscosity of the magnetic viscosity fluid 140.
[0065] When the environmental temperature of the variable valve
timing apparatus 1 becomes to have the ordinary temperature, the
braking torque input into the brake rotor 130 from the magnetic
viscosity fluid 140 is decreased due to the lowering in the
viscosity of the magnetic viscosity fluid 140 in response to the
rise in the temperature. At this time, the return torque input
mechanism 60 makes it easy to balance the return torque and the
braking torque input into the brake rotor 130 by decreasing the
return torque input into the phase adjusting mechanism 300. Thus,
in the ordinary temperature time, the engine phase can be
maintained as stable by the phase adjusting mechanism 300 through
the variable control of the viscosity of the magnetic viscosity
fluid 140.
[0066] According to the first embodiment, the engine phase can be
suitable adjusted at the low-temperature time, and the engine phase
can be maintained as stable at the ordinary temperature time, due
to the variable valve timing apparatus 1.
[0067] In addition, according to the first embodiment, the
construction of the return torque input mechanism 60 can be
simplified using the wax 74 that is contracted as the environmental
temperature is lowered and the piston 76 that is displaced by the
contraction of the wax 74. Further, the reliability of the return
torque input mechanism 60 is raised by the simplification of the
return torque input mechanism 60. Therefore, the return torque
input mechanism 60 can increase the return torque as the
environmental temperature of the variable valve timing apparatus 1
is lowered, with more reliability. Thus, the engine phase can be
suitable adjusted at the low-temperature time, and the engine phase
can be maintained as stable at the ordinary temperature time, with
more reliability.
[0068] In the first embodiment, the returning member 30 may
correspond to an elastic member. The return torque input mechanism
60 may correspond to a torque input mechanism. The thermo sensor
element 70 may correspond to a deformation increasing portion that
increases the deformation amount of the elastic member. The wax
chamber 72 may correspond to an accommodation chamber. The casing
part 71 may correspond to a contraction casing. The wax 74 may
correspond to a contraction part. The piston 76 may correspond to a
displacement part. The control circuit 200 and the solenoid coil
150 may correspond to a control device that controls the viscosity
of the magnetic viscosity fluid. The advancing direction of the
valve timing may correspond to a predetermined direction. The
retarding direction of the valve timing may correspond to an
opposite direction opposite from the predetermined direction.
Second Embodiment
[0069] A second embodiment, which is a modification of the first
embodiment, will be described with reference to FIGS. 7A and 7B.
The thermo sensor element 70 of the second embodiment further
includes a coil spring 279. The coil spring 279 is formed by a wire
spirally winded around the piston 76, and is made of metallic
materials. The coil spring 279 is accommodated in a space opposite
from the wax chamber 72 through the pressure receiving part 77 in
the state where the coil spring 279 is contracted in the axis
direction, in the case part 71. Hereinafter, the space is referred
as a spring chamber 273. In the inside of the case part 71, the
coil spring 279 biases the pressure receiving part 77 of the piston
76 toward the wax 74.
[0070] Operation of the return torque input mechanism 60 with the
coil spring 279 will be explained below.
[0071] As the environmental temperature of the variable valve
timing apparatus 1 is lowered, the wax 74 contracts, and the piston
76 moves to follow the contracted wax 74 so that the piston 76 is
displaced in the counterclockwise direction shown in FIG. 7A.
Because the coil spring 279 biases the piston 76 toward the wax 74,
the piston 76 suitably follows the contracted wax 74 and is
displaced with reliability. The displacement of the piston 76
further increases the amount of elastic deformation of the
returning member 30, so that the recovery force of the returning
member 30 which acts on the phase adjusting mechanism 300 becomes
still stronger. Thus, the return torque input mechanism 60 can
increase the return torque input into the phase adjusting mechanism
300 certainly, as the environmental temperature of the variable
valve timing apparatus 1 is lowered.
[0072] Moreover, as shown in FIG. 7B, as the temperature of the
variable valve timing apparatus 1 is raised to the ordinary
temperature, the wax 74 expands. Thereby, the pressure of the
expanding wax 74 displaces the piston 76 in the clockwise rotation
by resisting the biasing force of the coil spring 279. The
displacement of the piston 76 decreases the amount of elastic
deformation of the returning member 30, so that the recovery force
of the returning member 30 which acts on the phase adjusting
mechanism 300 becomes weak. Thus, as the environmental temperature
of the variable valve timing apparatus 1 is raised, the return
torque input mechanism 60 can decrease the return torque input into
the phase adjusting mechanism 300.
[0073] According to the second embodiment, the thermo sensor
element 70 has the coil spring 279. Therefore, as the environmental
temperature of the variable valve timing apparatus 1 is lowered,
the return torque input mechanism 60 increases the return torque
with reliability. Thus, the engine phase can be suitably adjusted
at the low-temperature time, and the engine phase can be maintained
as stable at the ordinary temperature time, due to the variable
valve timing apparatus 1.
[0074] The coil spring 279 of the second embodiment may correspond
to a biasing part.
Third Embodiment
[0075] A third embodiment, which is a modification of the second
embodiment, will be described with reference to FIGS. 8A and 8B. A
thermo sensor element 370 of the third embodiment is arranged at
the clockwise direction side of the connection component 31a. In
the thermo sensor element 370, arrangement of the wax chamber 72
and the spring chamber 273 is reverse in the axis direction of the
case part 71, compared with the thermo sensor element 70 of the
first and second embodiments. The wax chamber 72 defined in the
case part 71 is located between the holding part 78 and the
pressure receiving part 77. Moreover, the spring chamber 273
defined in the case part 71 is located on the clockwise direction
side of the pressure receiving part 77, that is separated from the
holding part 78. Operation of the return torque input mechanism 60
with the thermo sensor 370 of the third embodiment will be
explained below.
[0076] When the environmental temperature of the variable valve
timing apparatus 1 is lowered, the wax 74 is contracts, and the
piston 76 moves to follow the contacted wax 74 so that the piston
76 is displaced in the counterclockwise rotation shown in FIG. 8A,
due to the biasing force of the coil spring 279. The displacement
of the piston 76 further increases the amount of elastic
deformation of the returning member 30, so that the recovering
force of the returning member 30 which acts on the phase adjusting
mechanism 300 becomes still stronger. Thus, the return torque input
mechanism 60 can increase the return torque input into the phase
adjusting mechanism 300 certainly, as the environmental temperature
of the variable valve timing apparatus 1 is lowered.
[0077] Moreover, as shown in FIG. 8B, as the temperature of the
variable valve timing apparatus 1 is raised to the ordinary
temperature, the wax 74 expands. Thereby, the pressure of the
expanding wax 74 displaces the piston 76 in the clockwise rotation
by resisting the biasing force of the coil spring 279. The
displacement of the piston 76 decreases the amount of elastic
deformation of the returning member 30, so that the recovery force
of the returning member 30 which acts on the phase adjusting
mechanism 300 becomes weak. Thus, as the environmental temperature
of the variable valve timing apparatus 1 is raised, the return
torque input mechanism 60 can decrease the return torque input into
the phase adjusting mechanism 300.
[0078] According to the thermo sensor 370 of the third embodiment,
the return torque input mechanism 60 can increase or decrease the
return torque input into the phase adjusting mechanism 300 so as to
respond to the environmental temperature. Therefore, the variable
valve timing apparatus 1 of the third embodiment can suitably
adjust the engine phase at the low-temperature time, and can
maintain the engine phase as stable at the ordinary temperature
time.
Other Embodiments
[0079] The present disclosure should not be limited to the above
embodiments, but may be implemented in other ways without departing
from the spirit of the disclosure.
[0080] The deformation increasing portion is not limited to the
thermo sensor element 70. Alternatively, the deformation increasing
portion may be constructed by a temperature detector that detects
the environmental temperature of the variable valve timing
apparatus 1, and an actuator that is displaced to increase the
amount of elastic deformation of the returning member 30 as the
temperature detected by the detector is lowered. Furthermore, the
elastic member such as the returning member 30 may be omitted. In
this case, the variable valve timing apparatus 1 may be equipped
with an actuator that increases the return torque as the
temperature detected by the detector is lowered, as a torque input
mechanism.
[0081] Although the present disclosure is applied to the intake
valve, the present disclosure may be applied to an apparatus for
controlling valve timing of an exhaust valve. In this case, the
retarding direction may correspond to a predetermined direction,
and the advancing direction may correspond to an opposite direction
opposite from the predetermined direction.
[0082] The elastic member is not limited to the returning member
30. Alternatively, the elastic member may be a coil spring, plate
spring, etc., or may be made of rubber material.
[0083] The contraction part is not limited to the wax 74 in
semi-solid state. The contraction part may be other component that
is contracted as the environmental temperature of the variable
valve timing apparatus 1 is lowered. Further, the contraction part
may be in a solid state, a liquid state, or a gas state.
[0084] More specifically, the contraction part may be a spring made
of a shape memory alloy, and the shape of the spring is changed by
the temperature. The shape memory alloy may be an alloy of titanium
and nickel, for example. The spring made of the shape memory alloy
is contracted as the environmental temperature of the variable
valve timing apparatus 1 is lowered, and will be recovered into the
initial shape as the environmental temperature of the variable
valve timing apparatus 1 is raised. In this case, the thermo sensor
element corresponding to the deformation increasing portion further
increases the amount of elastic deformation of the returning member
30 under low-temperature environment, so that the return torque
input into the phase adjusting mechanism 300 from the returning
member 30 is made stronger.
[0085] Further, the thermo sensor element corresponding to the
deformation increasing portion decreases the amount of elastic
deformation of the returning member 30 under ordinary temperature
environment, so that the return torque input into the phase
adjusting mechanism 300 from the returning member 30 is made
weak.
[0086] In addition, the shape memory alloy may be an alloy using
iron as a principal component, and manganese and silicon are mixed
into the principal component. Moreover, the spring may have a coil
shape, a pan shape or a board shape.
[0087] The engine phase may be adjusted according to the braking
torque input into the brake rotor 130 due to the cooperation with
the brake shaft 131. Although the present disclosure is applied to
the intake valve, the present disclosure may be applied to an
apparatus for controlling valve timing of an exhaust valve or an
apparatus for controlling valve timing of an intake valve and an
exhaust valve. Further, the present disclosure may be applied to a
variety of apparatuses using the braking torque.
[0088] Although the present disclosure has been fully described in
connection with the preferred embodiments thereof with reference to
the accompanying drawings, it is to be noted that various changes
and modifications will become apparent to those skilled in the art.
Such changes and modifications are to be understood as being within
the scope of the present disclosure as defined by the appended
claims.
* * * * *