U.S. patent application number 13/158753 was filed with the patent office on 2011-12-15 for valve timing controller.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Kenichi Nara, Shuhei Oe, Kuniaki OKA, Masayoshi Sugino.
Application Number | 20110303171 13/158753 |
Document ID | / |
Family ID | 45020210 |
Filed Date | 2011-12-15 |
United States Patent
Application |
20110303171 |
Kind Code |
A1 |
OKA; Kuniaki ; et
al. |
December 15, 2011 |
VALVE TIMING CONTROLLER
Abstract
A valve timing controller has a case which defines a fluid
chamber therein. A magnetic viscosity fluid is enclosed in the
fluid chamber. The magnetic viscosity fluid including magnetic
particles and its viscosity varies according to a magnetic field
applied thereto. A coil and a control circuit applies magnetic
field to the magnetic viscosity fluid to variably control a
viscosity thereof. A brake rotor is rotatably accommodated in the
fluid chamber and receives a brake torque from the magnetic
viscosity fluid according to the viscosity thereof. A phase
adjusting mechanism is connected to the brake rotor for adjusting a
relative rotational phase between the crankshaft and the camshaft
according to the brake torque. When it is estimated that the engine
will be started, the coil is energized to generated heat in the
magnetic viscosity fluid.
Inventors: |
OKA; Kuniaki; (Nishio-city,
JP) ; Oe; Shuhei; (Kariya-city, JP) ; Sugino;
Masayoshi; (Anjo-city, JP) ; Nara; Kenichi;
(Nagoya-city, JP) |
Assignee: |
DENSO CORPORATION
Kariya-city
JP
NIPPON SOKEN, INC.
Nishio-city
JP
|
Family ID: |
45020210 |
Appl. No.: |
13/158753 |
Filed: |
June 13, 2011 |
Current U.S.
Class: |
123/90.17 |
Current CPC
Class: |
F01L 2001/0537 20130101;
F01L 2250/02 20130101; F01L 2820/032 20130101; F01L 2201/00
20130101; F01L 2001/34483 20130101; F01L 2800/01 20130101; F01L
1/352 20130101; F01L 2301/00 20200501 |
Class at
Publication: |
123/90.17 |
International
Class: |
F01L 1/34 20060101
F01L001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 11, 2010 |
JP |
2010-134431 |
Claims
1. A valve timing controller which adjusts a valve timing of a
valve opened/closed by a torque transmitted from a crankshaft to a
camshaft of an internal combustion engine, the valve timing
controller comprising: a case defining a fluid chamber therein; a
magnetic viscosity fluid enclosed in the fluid chamber, the
magnetic viscosity fluid including magnetic particles, the magnetic
viscosity fluid having a viscosity which varies according to a
magnetic field applied thereto; a viscosity control means for
variably controlling a viscosity of the magnetic viscosity fluid by
applying a magnetic field to the magnetic viscosity fluid; a brake
rotor rotatably accommodated in the fluid chamber and receiving a
brake torque from the magnetic viscosity fluid according to the
viscosity thereof; a phase adjusting mechanism connected to the
brake rotor for adjusting a relative rotational phase between the
crankshaft and the camshaft of the internal combustion engine
according to the brake torque which is inputted into the brake
rotor; and a heating control means for generating a heat in the
magnetic viscosity fluid when it is estimated that the internal
combustion engine will be started.
2. A valve timing controller according to claim 1, wherein the
heating control means starts a heating of the magnetic viscosity
fluid to generate heat therein when it is estimated that the
internal combustion engine will be started and it is detected that
a temperature of the magnetic viscosity fluid is lower than a
lower-limit temperature which is required to vary the relative
rotational phase.
3. A valve timing controller according to claim 1, wherein the
heating control means includes a coil disposed in the case, and
when the coil is energized, a magnetic field of which intensity is
variable is applied to the magnetic viscosity fluid, whereby the
magnetic viscosity fluid generates the heat therein.
4. A valve timing controller according to claim 1, wherein the
heating control means includes a coil disposed in the case, and
when the coil is energized, the coil generates heat which is
transmitted to the magnetic viscosity fluid, whereby the magnetic
viscosity fluid is heated.
5. A valve timing controller according to claim 3, wherein the
heating control means energizes the coil to generate a magnetic
field which is applied to the magnetic viscosity fluid, whereby the
viscosity of the magnetic viscosity fluid is variably
controlled.
6. A valve timing controller according to claim 5, wherein the
heating control means sets a first variable frequency of the
magnetic field when it is estimated that the engine will be
started, and the heating control means sets a second variable
frequency of the magnetic field which is higher than the first
variable frequency when the engine is started.
7. A valve timing controller according to claim 5, wherein the
heating control means sets a first electric power supplied to the
coil when it is estimated that the engine will be started, and the
heating control means sets a second electric power supplied to the
coil, which is lower than the first electric power, when the engine
is started.
8. A valve timing controller according to claim 3, wherein the
heating control means further includes a second coil, and the
viscosity control means energizes the second coil to generate a
magnetic field which is applied to the magnetic viscosity fluid,
whereby the viscosity of the magnetic viscosity fluid is variably
controlled.
9. A valve timing controller according to claim 8, wherein the
viscosity control means controls the viscosity of the magnetic
viscosity fluid in order to vary the relative rotational phase when
the engine is started, and the heating control means terminates
heating of the magnetic viscosity fluid when a variation in the
relative rotational phase is detected.
10. A valve timing controller according to claim 1, wherein the
heating control means terminates heating of the magnetic viscosity
fluid when it is detected that a temperature of the magnetic
viscosity fluid exceeds a lower-limit temperature which is required
to vary the relative rotational phase.
11. A valve timing controller according to claim 1, wherein the
heating control means terminates heating of the magnetic viscosity
fluid when a specified heating period has elapsed, which is
required to increase the temperature of the magnetic viscosity
fluid higher than a lower-limit temperature which is required to
vary the relative rotational phase.
12. A valve timing controller according to claim 1, wherein the
heating control means terminates heating of the magnetic viscosity
fluid when the internal combustion engine is started.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based on Japanese Patent Application
No.2010-134431 filed on Jun. 11, 2010, the disclosure of which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a valve timing controller
which adjusts valve timing of a valve that is opened/closed by a
camshaft driven by a torque transmitted from a crankshaft of an
internal combustion engine.
BACKGROUND OF THE INVENTION
[0003] Conventionally, it is known that a valve timing controller
adjusts a relative rotational phase between a crankshaft and a
camshaft according to a braking torque generated by an actuator. A
valve timing of an intake valve and/or an exhaust valve depends on
the above relative rotational phase, which is referred to as an
engine-phase. JP-2008-51093A shows such a valve timing controller
which adjusts an engine-phase by generating braking torque of a
fluid actuator.
[0004] Specifically, this valve timing controller has an actuator
in which magnetic viscosity fluid is enclosed in a casing. The
magnetic viscosity fluid is in contact with a braking rotor. A
magnetic field is applied to the magnetic viscosity fluid, whereby
a viscosity of the magnetic viscosity fluid is variably controlled.
The braking torque is generated on the braking rotor supported by
the casing according to the viscosity of the magnetic viscosity
fluid. Thus, the engine-phase is adjusted according to the braking
torque.
[0005] Generally, when temperature of the magnetic viscosity fluid
extremely falls, the magnetic viscosity fluid becomes the glass
transition condition (solid) in which its viscosity is unstable
relative to the magnetic field. Thus, if the magnetic viscosity
fluid is brought into the glass transition condition during an
engine stop, it is likely that necessary braking torque is not
generated at the time the engine is restarted. In such a case, an
optimum engine-phase is not obtained and a startability of the
engine is deteriorated. An accuracy of the valve timing controller
is less ensured.
SUMMARY OF THE INVENTION
[0006] The present invention is made in view of the above matters,
and it is an object of the present invention to provide a valve
timing controller of which reliability is ensured.
[0007] According to the present invention, a valve timing
controller adjusts a valve timing of a valve opened/closed by a
torque transmitted from a crankshaft to a camshaft of an internal
combustion engine. The valve timing controller includes: a case
defining a fluid chamber therein; and a magnetic viscosity fluid
enclosed in the fluid chamber. The magnetic viscosity fluid
includes magnetic particles and its viscosity varies according to a
magnetic field applied thereto.
[0008] The valve timing controller further includes: a viscosity
control means for variably controlling a viscosity of the magnetic
viscosity fluid by applying a magnetic field to the magnetic
viscosity fluid; a brake rotor rotatably accommodated in the fluid
chamber and receiving a brake torque from the magnetic viscosity
fluid according to the viscosity thereof; a phase adjusting
mechanism connected to the brake rotor for adjusting a relative
rotational phase between the crankshaft and the camshaft according
to the brake torque; and a heating control means for generating a
heat in the magnetic viscosity fluid when it is estimated that the
internal combustion engine will be started.
[0009] When it is estimated that the engine will be started, the
coil is energized to generate heat in the magnetic viscosity fluid.
Even if the magnetic viscosity fluid is in the glass transition
condition, the magnetic viscosity fluid is brought out from the
glass transition condition, whereby the variation in viscosity
becomes stable according to the applied magnetic field.
Consequently, when the engine is started, the viscosity of the
magnetic viscosity fluid can be controlled by applying the magnetic
field thereto, whereby desired brake torque is inputted into the
brake rotor so that the phase adjusting mechanism makes the
engine-phase optimal. Therefore, a high reliability of the valve
timing controller can be ensured.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Other objects, features and advantages of the present
invention will become more apparent from the following description
made with reference to the accompanying drawings, in which like
parts are designated by like reference numbers and in which:
[0011] FIG. 1 is a cross sectional view showing a valve timing
controller according to a first embodiment of the present
invention, taken along a line in FIG. 2;
[0012] FIG. 2 is a cross-sectional view taken along a line II-II in
FIG. 1;
[0013] FIG. 3 is a cross-sectional view taken along a line in FIG.
1;
[0014] FIG. 4 is a characteristics chart for explaining a magnetic
viscosity fluid;
[0015] FIG. 5 is another characteristics chart for explaining a
magnetic viscosity fluid;
[0016] FIG. 6A and FIG. 6B are time charts for explaining an
energization control according to the first embodiment;
[0017] FIG. 7 is a characteristics chart for explaining a heating
of the magnetic viscosity fluid according to the first
embodiment;
[0018] FIG. 8 is a flowchart showing a control flow of an
energization control circuit according to the first embodiment;
[0019] FIG. 9A and FIG. 9B are time charts for explaining an
energization control according to a second embodiment;
[0020] FIG. 10A and FIG. 10B are time charts for explaining an
energization control according to a third embodiment;
[0021] FIG. 11 is a flowchart showing a control flow of an
energization control circuit according to a fourth embodiment;
[0022] FIG. 12 is a flowchart showing a control flow of an
energization control circuit according to a fifth embodiment;
[0023] FIG. 13 is a cross sectional view showing a valve timing
controller according to a sixth embodiment;
[0024] FIG. 14 is a flowchart showing a control flow of an
energization control circuit according to a sixth embodiment;
and
[0025] FIG. 15 is a flowchart showing a control flow of an
energization control circuit according to a seventh embodiment;
DETAILED DESCRIPTION OF EMBODIMENTS
[0026] Multiple embodiments of the present invention will be
described with reference to accompanying drawings. In each
embodiment, the same parts and the components are indicated with
the same reference numeral and the same description will not be
reiterated. Further, each embodiment can be suitably combined.
First Embodiment
[0027] FIG. 1 shows a valve timing controller 1 according to a
first embodiment of the present invention. The valve timing
controller 1 is mounted on a vehicle, and more specifically, the
valve timing controller 1 is mounted on a transmission system that
transmits an engine torque from a crankshaft (not shown) to a
camshaft 2 of an internal combustion engine. In the present
embodiment, the camshaft 2 opens and closes an intake valve (not
shown) of the internal combustion engine through transmission of
the engine torque. The valve timing controller 1 adjusts a valve
timing of the intake valve.
[0028] As shown in FIGS. 1 to 3, the valve timing controller 1
includes an actuator 100, a current control circuit 200, a phase
adjusting mechanism 300 and the like. The valve timing controller 1
adjusts a relative rotational phase between the crankshaft and the
camshaft 2 to realize a desired valve timing.
(Actuator 100)
[0029] As shown in FIG. 1, the actuator 100 is an electromotive
fluid brake which is comprised of a case 110, a brake rotor 130 and
a coil 150.
[0030] The case 110 is comprised of a fixed member 111 and a cover
member 112. The fixed member 111 is annular-shaped and is made of
magnetic material. The fixed member is fixed on a chain case (not
shown) of the internal combustion engine. The cover member 112 is
also made of magnetic material. The cover member 112 and the fixed
member 111 define a fluid chamber 114 therebetween.
[0031] The brake rotor 130 is made of magnetic material and
includes a shaft portion 131 and a rotor portion 132. The shaft
portion 131 extends through the fixed member 111 to be connected
with the phase adjusting mechanism 300. The other end of the shaft
portion 131 is rotatably supported by the cover member 112 through
a bearing 115. A middle portion of the shaft portion 131 is
supported by the fixed member 111 through a bearing 116. When
receiving an engine torque from the phase adjusting mechanism 300,
the brake rotor 130 rotates counterclockwise in FIGS. 2 and 3.
[0032] The rotor portion 132 is disc-shaped and is accommodated in
the fluid chamber 114. A first magnetic gap 114a is defined between
the rotor portion 132 and the fixed member 111. A second magnetic
gap 114b is defined between the rotor portion 132 and the cover
member 112.
[0033] The magnetic viscosity fluid 140 is enclosed in the fluid
chamber 114. The magnetic viscosity fluid 140 is functional fluid
comprised of base-liquid and magnetic particles. The base-liquid is
nonmagnetic fluid such as oil. Preferably, the base-liquid is
lubrication oil for an engine. The magnetic particles are magnetic
powder of carbonyl iron.
[0034] As shown in FIG. 4, the magnetic viscosity fluid 140 has
characteristics in which its viscosity increases according to an
intensity of applied magnetic field. Further, in proportion to the
viscosity, its shear yield stress also increases. Further, in a
condition where no magnetic field is applied to the magnetic
viscosity fluid 140, the base viscosity of the magnetic viscosity
fluid 140 is increased along with a decrease in temperature
thereof. When the temperature is excessively decreased, the
magnetic viscosity fluid 140 becomes the glass transition condition
(solid) in which its viscosity is unstable relative to the magnetic
field. In the present embodiment, a lower limit temperature "Tl" of
the magnetic viscosity fluid 140 is set at "-20.degree. C.".
[0035] A coil 150 is winded around a resin bobbin coaxially to the
fixed member 111. When the coil 150 is energized, magnetic field is
generated in such a manner that magnetic flux passes through the
first magnetic gap 114a, the rotor portion 132, the second magnetic
gap 114b, the cover member 112 and the fixed member 111. The
generated magnetic field is applied to the magnetic viscosity fluid
140 in the magnetic gaps 114a, 114b, so that its viscosity is
varied. Thus, between the case 110 and the brake rotor 130, braking
torque is generated to brake the brake rotor 130 in clockwise
direction in FIGS. 2 and 3. As above, when the coil 150 is
energized to generate the magnetic field which is applied to the
magnetic viscosity fluid 140, the braking torque is inputted into
the brake rotor 130 according to the viscosity of the magnetic
viscosity fluid 140.
[0036] As shown in FIG. 1, the resin bobbin 151 is exposed to the
first magnetic gap 114a in the fluid chamber 114. The fixed member
111 is also exposed to the first magnetic gap 114a. Thus, even if
the coil 150 generates heat when energized, the heat is transferred
to the magnetic viscosity fluid 140 in the first magnetic gap 114a
through the resin bobbin 151 and the fixed member 111.
(Current Control Circuit 200)
[0037] The current control circuit 200 includes a microcomputer and
is electrically connected to the coil 150 and a battery 4 of a
vehicle. When a specified starting condition "Cw" is established
with the engine stopped, the current control circuit 200 receives
electricity from the battery 4, whereby the current control circuit
200 is changed from OFF-mode to ON-mode so that the coil 150 can be
energized. The starting condition "Cw" is established when a door
lock of a vehicle is released, a vehicle door is opened, or a
receiver receives a signal from a transmitter of a keyless entry
system. If the engine is not started even after a specified time
"ST" elapses from changing mode to the ON-mode, the ON-mode is
automatically changed to the OFF-mode.
[0038] During the On-mode, the current control circuit 200 controls
electric current "I" supplied to the coil 150 so that the magnetic
field applied to the magnetic viscosity fluid 140 is adjusted.
Consequently, according to the applied magnetic field, the
viscosity of the magnetic viscosity fluid 140 is variably
controlled so that the braking torque to the brake rotor 130 is
increased/decreased.
[0039] In the present embodiment, the electric current "I" is
controlled as shown in FIG. 6A, so that the magnetic flux density
"B" applied to the magnetic viscosity fluid 140 is varied before
and after the engine is started as shown in FIG. 6B. Specifically,
during a period ".alpha." in which the engine is not started, the
electric current "I" is controlled in such a manner that the
electric current "I" is varied like pulses having low frequency
"f.alpha." and an effective electric power in a specified period
"RT" is high effective electric power "W.alpha." around 5 Ws.
During a period ".beta." in which the engine is started, the
electric current "I" is controlled in such a manner that the
electric current "I" is varied like pulses having high frequency
"f.beta." and an effective electric power in a specified period
"RT" is low electric power "W.beta.".
[0040] According to the above energization control, during the
period ".alpha.", the magnetic particles in the magnetic viscosity
fluid 140 repeatedly perform a movement in which chain-shaped
cluster of the magnetic particles is composed and decomposed
according to a variation in magnetic flux density "B" as shown in
FIG. 6B. As the result, the magnetic viscosity fluid 140 generates
heat due to the above movement of the magnetic particles. As shown
in FIG. 7, in a case that the applied electric current has low
frequency "f.alpha.", such as 2-10 Hz, the magnetic viscosity fluid
140 effectively generates heat. Further, the magnetic viscosity
fluid 140 receives heat from the coil 150, so that the temperature
of the magnetic viscosity fluid 140 is effectively increased.
[0041] During the period ".beta.", the electric current "I" has
high frequency "f.beta." around 50 Hz to generate low electric
power "W.beta." around 3 Ws. Further, as shown in FIG. 6B, the
magnetic flux density "B" is varied according to the frequency
"f.beta.", the magnetic viscosity fluid 140 receives an agitation
action. Thus, the variation in viscosity of the fluid 140 becomes
stable with respect to the applied magnetic field, and the desired
braking torque can be obtained stably.
[0042] It should be noted that the current control circuit 200
controls the energization of other electrical components.
(Phase Adjusting Mechanism 300)
[0043] As shown in FIGS. 1 to 3, the phase adjusting mechanism 300
is provided with a driving rotor 10, a driven rotor 20, an assist
member 30, a planetary carrier 40 and a planetary gear 50.
[0044] The driving rotor 10 is comprised of a gear member 12 and a
sprocket member 13, which are coaxially connected with each other
by a bolt. The gear member 12 includes a first internal gear 14 on
its radially inner peripheral wall. The first internal gear 14
defines an addendum circle located radially inside of a root
circle. As shown in FIG. 1, the sprocket member 13 has a plurality
of gear tooth 16 on its outer periphery. A timing chain (not shown)
is wound around the gear teeth 16 of the sprocket member 13 and a
plurality of gear teeth of the crankshaft so that the sprocket
member 13 is linked to the crankshaft. When the engine torque is
transmitted from the crankshaft to the sprocket member 13 through
the timing chain, the driving rotor 10 rotates in accordance with
the crankshaft. A rotation direction of the driving rotor 10 is a
counterclockwise direction in FIGS. 2 and 3.
[0045] As shown in FIGS. 1 and 3, the driven rotor 20 is coaxially
arranged in the sprocket member 13. The driven rotor 20 has a
connection portion 21 on a bottom wall portion thereof. The
connection portion 21 is coaxially coupled with the camshaft 2.
This coupling enables the driven rotor 20 to rotate synchronously
with the camshaft 2 and to rotate relatively with respect to the
driving rotor 10. The rotational direction of the driven rotor 20
corresponds to the counterclockwise direction in FIGS. 2 and 3.
[0046] As shown in FIG. 1, the driven rotor 20 includes a second
internal gear 22 on its radially inner peripheral wall. The second
internal gear 22 defines an addendum circle located radially inside
of a root circle. The second internal gear 22 has an inner diameter
larger than an inner diameter of the first internal gear 14, and
the number of teeth of the second internal gear 22 is greater than
the number of teeth of the first internal gear 14. The second
internal gear 22 is positioned away from the first internal gear 14
in its axial direction.
[0047] The assist member 30 is a torsion coil springs and is
coaxially arranged inside of the sprocket member 13. One end 31 of
the assist member 30 is engaged with the sprocket member 13, and
the other end 32 is engaged with the connection portion 21. The
assist member 30 generates assist torque between the driving rotor
10 and the driven rotor 20 so that the driven rotor 20 is biased in
a retard direction relative to the driving rotor 10.
[0048] The cylindrical planetary carrier 40 has a torque-receiving
portion 41 to which the braking torque is transmitted from the
brake rotor 130. The torque-receiving portion 41 which is coaxial
to the shaft portion 131 includes a pair of grooves 42 with which a
joint 43 is engaged. Through the joint 43, the torque-receiving
portion 41 is connected to the shaft portion 131. The planetary
carrier 40 rotates along with the brake rotor 130 and performs a
relative rotation with respect to the driving rotor 10. It should
be noted that the planetary carrier 40 and the brake rotor 130
rotate in counterclockwise direction in FIGS. 2 and 3.
[0049] As shown in FIGS. 1 to 3, the planetary carrier 40 has a
supporting portion 46 which supports the planetary gear 50. The
supporting portion 46 is arranged eccentrically with respect to the
shaft portion 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.
[0050] The planetary gear 50 has a first external gear 52 and a
second external gear 54. The first external gear 52 engages with
the first internal gear 14. The second external gear 54 engages
with the second internal gear 22. The second external gear 54 has
an outer diameter larger than that of the first external gear 52.
The number of gear teeth of the second external gear 54 and the
first external gear 52 is smaller than the number of teeth of the
internal gears 22, 14 by the same number of gear teeth.
[0051] The above phase adjusting mechanism 300 adjusts the
engine-phase according to a balance between the braking torque of
the brake rotor 130, the assist torque of the assist member 30 and
the variable torque transmitted from the camshaft 2 to the brake
rotor 130.
[0052] Specifically, when the brake rotor 130 rotates at the same
speed as the driving rotor 10, the planetary carrier 40 does not
perform a relative rotation with respect to the driving rotor 10.
Thus, the planetary gear 50 rotates along with the rotors 10, 20
without performing the planetary motion, so that the engine-phase
is maintained.
[0053] Meanwhile, when the brake rotor 130 rotates at a lower speed
than the driving rotor 10 against the assist torque, the planetary
carrier 40 rotates in a retard direction relative to the driving
rotor 10. As the result, the planetary gear 50 performs the
planetary motion and the driven rotor 20 relatively rotates in the
advance direction with respect to the driving rotor 10, so that the
engine-phase is advanced.
[0054] Meanwhile, when the brake rotor 130 rotates at faster speed
than the driving rotor 10, the planetary carrier 40 rotates in the
advance direction relative to the driving rotor 10. As the result,
the planetary gear 50 performs the planetary motion and the driven
gear 20 rotates in the retard direction relative to the driving
rotor 10, so that the engine-phase is retarded.
(Control Flow)
[0055] Referring to FIG. 8, a control flow which the current
control circuit 200 executes will be described hereinafter.
[0056] In step S100, the computer determines whether a pre-starting
condition "Cs" is established with respect to the engine which is
stopped. The pre-starting condition "Cs" includes any event which
occurs prior to a starting of the engine.
[0057] When the answer is YES in step S100, the procedure proceeds
to step S101 in which the computer determines whether an interior
of the case 110 is in a low-temperature condition "Sl" in which the
temperature of the magnetic viscosity fluid 140 is lower than the
lower limit temperature "Tl".
[0058] When the answer is YES in step S101, the procedure proceeds
to step S102 in which the coil 150 is energized for the period
".alpha.". Consequently, the coil 150 receives electricity of low
frequency "f.alpha.", which generates the high electric power
"W.alpha.". The effective heating of the magnetic viscosity fluid
140 is started.
[0059] In step S103, the computer determines whether an engine
start command "Os", such as turning on of an ignition switch, is
detected. When the answer is YES in step S103, the procedure
proceeds to step S104 in which a cranking of the engine is started
and the coil is deenergized. Thus, until the engine is started, the
magnetic viscosity fluid 140 has been effectively heated.
[0060] In step S105, the coil 150 is started to be energized for
the period ".beta.". Consequently, the coil 150 receives
electricity of high frequency "f.beta.", which generates the low
electric power "W.beta.". In a condition where the magnetic
viscosity fluid 140 is agitated and is less heated, the braking
torque is generated to adjust the engine-phase.
[0061] In step S106, the computer determines whether a complete
combustion condition "Ss" of the engine is detected. When the
answer is YES in step S106, the present control flow is terminated.
Thus, when the engine is started, the magnetic viscosity fluid 140
stably generates the braking torque, so that the stable
engine-phase adjustment is achieved.
[0062] When the answer is NO in step S101, the procedure proceeds
to step S107 in which the computer determines whether the engine
start command "Os" is detected. When the answer is YES is step
S107, the procedure proceeds to steps S105 and 8106 in which the
coil 150 is energized for the period ".beta.".
[0063] According to the above embodiment, even if the magnetic
viscosity fluid 140 is in the low-temperature condition "Sl", the
magnetic viscosity fluid 140 is surely heated when it is estimated
that the engine will be started. As the result, the viscosity of
the magnetic viscosity fluid 140 depends on the applied magnetic
field. When the engine is started, the viscosity of the magnetic
viscosity fluid 140 less depends on its temperature, so that
desired braking torque can be stably inputted into the brake rotor
130. Therefore, since the phase adjusting mechanism 300 connected
to the brake rotor 130 optimizes the engine-phase for starting the
engine, high reliability of the valve timing controller 1 can be
ensured.
[0064] In the above first embodiment, the coil 150 and the current
control circuit 200 correspond to a viscosity control means of the
present invention. Also, the coil 150 and the current circuit 200
correspond to a heating control means of the present invention.
Second Embodiment
[0065] As shown in FIGS. 9A and 9B, the second embodiment is a
modification of the first embodiment. In an energization control
step during the period ".alpha.", which corresponds to step S102 in
FIG. 8, alternate electric current having low frequency "f.alpha."
is applied to the coil 150 as shown in FIG. 9A. The effective
electric power in a specified period "RT" is high effective
electric power "W.alpha.". As the result, as shown in FIG. 9B, the
magnetic flux density "B" which varies at low frequency "f.alpha."
is applied to the magnetic viscosity fluid 140. The magnetic
viscosity fluid 140 generates heat due to the movement of the
magnetic particles and receives heat from the coil 150 which
generates heat according to the high electric power "W.alpha.".
[0066] During the period ".beta.", alternate electric current
having high frequency "f.beta." is applied to the coil 150. The
effective electric power in a specified period "RT" is low
effective electric power "W.beta.". As the result, the magnetic
viscosity fluid less generates heat during the period ".beta.".
[0067] Thus, also in the second embodiment, even if the magnetic
viscosity fluid 140 is in the low-temperature condition "Sl", the
magnetic viscosity fluid 140 is surely heated when it is estimated
that the engine will be started. When the engine is started, the
viscosity of the magnetic viscosity fluid 140 depends on the
applied magnetic field. The variation in viscosity becomes stable.
Thus, the desired braking torque can be stably inputted into the
brake rotor 130. The engine phase which the phase adjusting
mechanism 300 adjusts is optimized. A high reliability of the valve
timing controller 1 can be ensured.
Third Embodiment
[0068] As shown in FIG. 10, a third embodiment is a modification of
the first embodiment, During the period ".alpha.", a constant
electric current "I.alpha." is applied to the coil 150, The
effective electric power in a specified period "RT" is high
effective electric power "W.alpha.". As the result, as shown in
FIG. 10B, the magnetic flux density "B" which is constant is
applied to the magnetic viscosity fluid 140. The magnetic viscosity
fluid 140 generates heat due to the movement of the magnetic
particles and receives heat from the coil 150 which generates heat
according to the high electric power "W.alpha.".
[0069] During the period ".beta.", a constant electric current
"I.beta." is applied to the coil 150. The effective electric power
in a specified period "RT" is low effective electric power
"W.beta.". Thus, the magnetic viscosity fluid 140 less generates
heat during the period ".beta.".
[0070] Thus, also in the third embodiment, even if the magnetic
viscosity fluid 140 is in the low-temperature condition "Sl", the
magnetic viscosity fluid 140 is surely heated when it is estimated
that the engine will be started. When the engine is started, the
viscosity of the magnetic viscosity fluid 140 depends on the
applied magnetic field. The variation in viscosity becomes stable.
Thus, the desired braking torque can be stably inputted into the
brake rotor 130. The engine-phase which the phase adjusting
mechanism 300 adjusts is optimized. A high reliability of the valve
timing controller 1 can be ensured.
Fourth Embodiment
[0071] As shown in FIG. 11, a fourth embodiment is a modification
of the first embodiment. In a control flow of the fourth
embodiment, step S400 and step S401 are included.
[0072] Specifically, in step S400, the computer determines whether
a temperature of the magnetic viscosity fluid is in a
normal-temperature condition "Sn" in which the temperature of the
magnetic viscosity fluid 140 is greater than the lower limit
temperature "Tl".
[0073] Until the normal-temperature condition "Sn" is detected, the
processes in steps S103 and S400 are repeatedly performed, so that
the magnetic viscosity fluid 140 effectively generates heat.
Meanwhile, when the answer is YES in step S400, the procedure
proceeds to step S401 in which the energization in the period
".alpha." is terminated with the engine stopped. Then, the
procedure proceeds to step S107 in which the computer determines
whether the engine start command "Os" is generated. It should be
noted that the specified time "ST" of the current control circuit
200 is suitably varied to avoid a situation where the temperature
of the magnetic viscosity fluid 140 becomes lower than the
lower-limit temperature "Tl".
[0074] According to the fourth embodiment, from the time when it is
estimated that the engine will be started until the time when the
temperature of the magnetic viscosity fluid exceeds "Tl", the
magnetic viscosity fluid generates heat therein. Thus, when the
engine is started, the viscosity of the magnetic viscosity fluid
depends on the applied magnetic field.
Fifth Embodiment
[0075] As shown in FIG. 12, a fifth embodiment is a modification of
the fourth embodiment. In a control flow of the fifth embodiment,
step S500 is included instead of step S400.
[0076] Specifically, in step S500, the computer determines whether
a specified heat-generating period "HT" has elapsed. It should be
noted that the specified heat-generating period "HT" is required
for the magnetic viscosity fluid 140 to be brought in the
normal-temperature condition "Sn". The heat-generating period "HT"
is previously determined based on the low-frequency "f.alpha." and
the high effective electric power "W.alpha.".
[0077] Until the heat-generating period "HT" has elapsed, the
processes in steps S103 and S500 are repeatedly performed, so that
the magnetic viscosity fluid 140 effectively generates heat.
Meanwhile, when the answer is YES in step S500, the procedure
proceeds to step S401 in which the energization in the period
".alpha." is terminated with the engine stopped. Then, the
procedure proceeds to step S107 in which the computer determines
whether the engine start command "Os" is generated.
[0078] According to the fifth embodiment, from the time when it is
estimated that the engine will be started until the heat-generating
period "HT" has passed, the magnetic viscosity fluid generates heat
therein. Thus, when the engine is started, the viscosity of the
magnetic viscosity fluid depends on the applied magnetic field.
Sixth Embodiment
[0079] As shown in FIG. 13, a sixth embodiment is a modification of
the first embodiment. An actuator 600 includes the coil 150 and a
second coil 650 for generating heat in the magnetic viscosity fluid
140.
[0080] Specifically, the second coil 150 is winded around a resin
bobbin 651 coaxially to the cover member 112. When the second coil
650 is energized, magnetic field is generated in such a manner that
magnetic flux passes through the cover member 112, the second
magnetic gap 114b, the rotor portion 132, the first magnetic gap
114a and the fixed member 111. The generated magnetic field is
applied to the magnetic viscosity fluid 140 in the magnetic gaps
114a, 114b.
[0081] The cover member 112 is exposed to the second magnetic gap
114b. Thus, if the second coil 650 generates heat when energized,
the heat is transferred to the magnetic viscosity fluid 140 in the
second magnetic gap 114b through the resin bobbin 651 and the cover
member 112. In the present embodiment, the cover member 112 is
comprised of two bodies 612a, 612b made from magnetic material.
[0082] The coil 150 and the second coil 650 are electrically
connected to a current control circuit 620. The current control
circuit 620 has the same configuration and function as the current
control circuit 200 in the first embodiment. Further, the current
control circuit 620 can control the energization of the second coil
650 independently from the coil 150.
[0083] In a control flow of the sixth embodiment, step S600 is
included instead of step S102, as shown in FIG. 14. In step S600,
the second coil 650 is energized during the period ".alpha.".
Consequently, the second coil 650 receives electricity of low
frequency "f.alpha.", which generates the high electric power
"W.alpha.". The effective heating of the magnetic viscosity fluid
140 is started in a similar way of the first embodiment. Until the
engine start command "Os" is generated, the magnetic viscosity
fluid 140 effectively generates the heat therein.
[0084] Thus, also in the sixth embodiment, even if the magnetic
viscosity fluid 140 is the glass transition condition, the second
coil 650 is energized when it is estimated that the engine will be
started, so that the magnetic viscosity fluid 140 surely generates
heat therein. When the engine is started, the second coil 650 is
surely deenergized. Thus, in step S105, the magnetic viscosity
fluid 140 less receives thermal influence. As above, the
heat-generation control and the viscosity control of the magnetic
viscosity fluid 140 can be suitably executed.
[0085] In the above sixth embodiment, the coil 150 and the current
control circuit 620 correspond to a viscosity control means of the
present invention. Also, the second coil 650 and the current
control circuit 620 correspond to a heating control means of the
present invention.
Seventh Embodiment
[0086] As shown in FIG. 15, a seventh embodiment is a modification
of the sixth embodiment. In a control flow of the seventh
embodiment, step S700 to step S703 are included.
[0087] Specifically, in step S700, the cranking of the engine is
started and the energization control of during the period ".alpha."
is continued even in the period ".beta.". Then, the procedure
proceeds to step S105.
[0088] In step S701, the computer determines whether the
engine-phase is changed after performing step S105. A variation in
the engine-phase is computed based on output signals from a crank
angle sensor (not shown) and a camshaft sensor (not shown). When
this variation exceeds the specified quantity ".DELTA..theta.", the
computer determines that the engine-phase is changed. When the
variation in the engine-phase is detected in step S701, the
procedure proceeds to step S702 in which the second coil 650 is
deenergized. Then, the procedure proceeds to step S106. Thus, until
the engine-phase is varied, the magnetic viscosity fluid 140
effectively generates heat therein.
[0089] When the engine start command "Os" is detected in step S107,
the procedure proceeds to step S703 and step 106. The coil 150 is
energized during the period ".beta.".
[0090] According to the seventh embodiment, from the time when it
is estimated that the engine will be started until the engine-phase
is completely changed, the magnetic viscosity fluid generates heat
therein. Thus, when the engine is started, the viscosity of the
magnetic viscosity fluid depends on the applied magnetic field.
Other Embodiment
[0091] The present invention should not be limited to the
disclosure embodiment, but may be implemented in other ways without
departing from the sprit of the invention.
[0092] Specifically, in the first, second, forth to seventh
embodiments, during the period ".beta.", the effective electric
power may be set greater than or equal to the electric power
"W.alpha." while the frequency is changed from "f.alpha." to
"f.beta.". Also, in the third embodiment, during the period
".beta.", the effective electric power may be set greater than or
equal to the electric power "W.alpha.".
[0093] In the first, second and fourth to seventh embodiments,
during the period ".alpha." and the period ".beta.", the frequency
"f.alpha.", "f.beta." may be varied directly or indirectly. In the
first second and fourth to seventh embodiments, during the period
".alpha." and the period ".beta.", the frequency of the electric
current "I" can be set smaller than or equal to the frequency
"f.alpha." while the effective electric power is changed from
"W.alpha." to "W.beta.". In the sixth and seventh embodiments, it
may be configured that the magnetic field generated by the second
coil 650 is less applied to the magnetic viscosity fluid. In such a
case, the frequency of the electric current "I" supplied to the
second coil 650 is not necessary to be controlled.
[0094] In the control flow of the second, third, sixth, and seventh
embodiments, between step S102 and S103 or between step S600 and
S103, the processes of steps S400 and S401 in the fourth embodiment
may be added. When the normal-temperature condition "Sn" is
detected in step S400, the procedure proceeds to step S401 and then
proceeds to step S107. Also, in the control flow of the second,
third, sixth, and seventh embodiments, between step S102 and S103
or between step S600 and S103, the processes of steps S500 and S401
in the fifth (fourth) embodiment may be added. When it is
determined that the heating period "HT" has elapsed in step S500,
the procedure proceeds to step S401 and then proceeds to step S107.
Furthermore, in the control flow of the sixth and seventh
embodiments, the energization control in step S102 of the second
embodiment or the third embodiment can be executed in step S600
with respect to the coil 650.
[0095] The configuration of the phase adjusting mechanism 300 is
suitably variable.
[0096] In the first to seventh embodiments, the directions of
"advance" and "retard" can be changed therebetween. The present
invention is applicable also to a controller which adjusts the
valve timing of the exhaust valve, and a controller which adjusts
the valve timings of the intake valve and the exhaust valve.
* * * * *