U.S. patent application number 11/483603 was filed with the patent office on 2007-01-25 for air control device including air switching valve driven by motor.
This patent application is currently assigned to Denso Corporation. Invention is credited to Tadashi Komiyama, Takahiro Kouzu.
Application Number | 20070017217 11/483603 |
Document ID | / |
Family ID | 37650458 |
Filed Date | 2007-01-25 |
United States Patent
Application |
20070017217 |
Kind Code |
A1 |
Kouzu; Takahiro ; et
al. |
January 25, 2007 |
Air control device including air switching valve driven by
motor
Abstract
An air control device is advantageously used as a device for
supplying secondary air to a catalyzer contained in an exhaust pipe
of an internal combustion engine. The air control device includes
an electric motor, a speed reduction mechanism, a valve having a
valve shaft and a biasing spring. These components are all
contained in a housing that has a valve port formed therein. The
valve is driven to open the valve port by the electric motor
against a biasing force of the biasing spring. A rotational
movement of a final gear in the speed reduction mechanism is
converted into a linear movement of the valve shaft to thereby open
the valve port. Since the biasing spring such as a torsion spring
is wound around a flange connected to an axis of the final gear, a
length of the valve shaft is made short, and the device as a whole
is made compact.
Inventors: |
Kouzu; Takahiro;
(Kariya-city, JP) ; Komiyama; Tadashi;
(Chiryu-city, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
Denso Corporation
Kariya-city
JP
|
Family ID: |
37650458 |
Appl. No.: |
11/483603 |
Filed: |
July 11, 2006 |
Current U.S.
Class: |
60/289 ;
60/324 |
Current CPC
Class: |
F01N 3/206 20130101 |
Class at
Publication: |
060/289 ;
060/324 |
International
Class: |
F01N 3/00 20060101
F01N003/00; F01N 7/00 20060101 F01N007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 20, 2005 |
JP |
2005-209613 |
Claims
1. An air control device comprising: a housing having a valve port
formed therein; a valve disposed in the housing for opening or
closing the valve port, the valve having a valve shaft and a valve
head; a valve driving mechanism including an electric motor, a
speed reduction mechanism having a plurality of gears including a
final gear engaging with a rack formed on the valve shaft so that a
rotational movement of the final gear is converted to a linear
movement of the valve shaft for opening or closing the valve port;
and biasing means for biasing the valve in a direction to close the
valve port, wherein: the biasing means is disposed around an axis
of the final gear.
2. The air control device as in claim 1, wherein: the axis of the
final gear is disposed perpendicularly to the valve shaft.
3. The air control device as in claim 2, wherein: the biasing means
is a torsion spring wound around the axis of the final gear.
4. The air control device as in claim 3, wherein: a torsional
resilient force is accumulated in the torsion spring when the axis
of the final gear is driven in a direction to open the valve
port.
5. The air control valve as in claim 2, wherein: the rack is formed
on the valve shaft at its end portion opposite to an end where the
valve head is connected; and the rack engages with a pinion
connected to the axis of the final gear.
6. The air control valve as in claim 1, wherein: the valve driving
mechanism is contained in the housing together with the valve; and
the housing is fixed to an air passage communicating with the valve
port in a cantilever fashion.
7. The air control valve as in claim 1, wherein: the air control
device controls airflow of secondary air supplied from an air pump
to a calalyser in an exhaust pipe of an automotive vehicle.
8. The air control valve as in claim 7, further comprising a
one-way valve for preventing exhaust gas from flowing into the
valve port while permitting the secondary air to flow out through
the valve port.
9. An air control device comprising: a housing having a valve port
formed therein; a valve disposed in the housing for opening or
closing the valve port, the valve having a valve shaft and a valve
head; a valve driving mechanism including an electric motor, a
speed reduction mechanism having a plurality of gears including a
final gear engaging with a rack formed on the valve shaft so that a
rotational movement of the final gear is converted to a linear
movement of the valve shaft for opening or closing the valve port;
and biasing means for biasing the valve in a direction to open the
valve port, wherein: the biasing means is disposed around an axis
of the final gear.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims benefit of
priority of Japanese Patent Application No. 2005-209613 filed on
Jul. 20, 2005, the content of which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a valve for switching a
fluid flow such as airflow, the valve being driven by a driving
mechanism including a driving motor.
[0004] 2. Description of Related Art
[0005] An airflow control valve for controlling an amount of air
flowing through an air passage connected to an exhaust pipe of an
internal combustion engine has been known. The airflow control
valve is driven in an on-off fashion by a driving mechanism
including an electric motor and a speed reduction mechanism having
plural gears. A final gear in the speed reduction mechanism is
engaged with a rack formed on a valve shaft which is reciprocated
to open or close a valve port. Examples of this kind of airflow
control valve are disclosed in JP-A-6-173783 and JP-A-11-62724.
[0006] A coil spring for biasing the valve head toward an open
position or a closed position of the airflow control valve is
disposed around the valve shaft. Since the coil spring is disposed
around the valve shaft, it is unavoidable to make the valve shaft
longer by a length of the coil spring to secure a space for the
coil spring. Accordingly, the airflow control valve becomes large
in size, requiring a large mounting space.
[0007] Some of the airflow control valves such as EGR (Exhaust Gas
Recirculation) valves are connected in a cantilever fashion to an
air passage communicating with a combustion chamber of an internal
combustion engine. More particularly, a housing containing a motor,
a speed reduction mechanism and a valve therein is connected to the
air passage at a position opposite to the motor in a cantilever
fashion. If the valve shaft is long in its axial direction, a
distance from the mounting portion of the housing to the motor
becomes long, and the housing has to be made stronger to endure
vibration of the engine. When the speed reduction mechanism is
severely vibrated, a relative movement between a rack of the valve
shaft and a final gear of the speed reduction mechanism engaging
with the rack is generated, and thereby abrasion wear occurs in the
rack and the final gear.
SUMMARY OF THE INVENTION
[0008] The present invention has been made in view of the
above-mentioned problems, and an object of the present invention is
to provide an improved air control device including an air
switching valve, which is made compact in size by making the valve
shaft short. Another object of the present invention is to improve
its mechanical strength against vibration and to suppress the
abrasion wear of the rack and the final gear.
[0009] The air control device of the present invention is
advantageously used as a secondary air control device for an
internal combustion engine mounted in an automotive vehicle. The
air control device supplies secondary air sent from an air pump to
a catalyzer, such as three-way catalyzer, disposed in an exhaust
pipe for purifying exhaust gas. The secondary air is supplied to
the catalyzer to warm it up to thereby activate it when a
temperature of the catalyzer is low.
[0010] The air control device includes a housing having a valve
port formed therein, an electric motor, a speed reduction mechanism
having plural gears for transmitting a rotational torque of the
motor at a reduced speed, a valve for opening or closing a valve
port, and a biasing spring for biasing the valve in a direction to
close the valve port. The valve is composed of a valve head sitting
on a valve seat and a valve shaft connected to the valve head. The
valve shaft includes a rack engaging with a final gear of the speed
reduction mechanism. A rotational movement of the final gear is
converted to a linear movement of the valve shaft. The biasing
spring is disposed around an axis of the final gear. When the
electric motor is energized, the valve shaft of the valve is driven
in a direction to open the valve port against the biasing force of
the biasing spring, and thereby the valve port is open to supply
the secondary air to the catalyzer.
[0011] The housing containing components of the air control device
therein is connected to an air passage communicating with the valve
port in a cantilever fashion. The valve may be biased in a
direction to open the valve port so that the valve port is closed
when driven by the electric motor. The electric motor may be
replaced with other drivers such as an electromagnetic solenoid.
The air control device may be used for re-circulating exhaust gas
into an engine in a controlled manner. Preferably, the biasing
spring is a torsion spring wound around a flange connected to the
axis of the final gear.
[0012] Since the biasing spring is disposed around the axis of the
final gear, instead of disposing it around the valve shaft, a
length of the valve shaft can be made shorter. Accordingly, the air
control device can be made compact, and its mechanical strength
against engine vibration can be improved when the housing is
mounted on the air passage in a cantilever fashion. Other objects
and features of the present invention will become more readily
apparent from a better understanding of the preferred embodiment
described below with reference to the following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a perspective view showing a structure of a
valve-driving mechanism used in an air control device of the
present invention;
[0014] FIG. 2 is a cross-sectional view showing an entire structure
of a secondary air control device for an internal combustion
engine;
[0015] FIG. 3 is a cross-sectional view showing the valve-driving
mechanism; and
[0016] FIG. 4 is a plan view showing a speed reduction mechanism of
the secondary air control device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0017] A preferred embodiment of the present invention will be
described with reference to accompanying drawings. The present
invention is applied to a secondary air control device for an
internal combustion engine mounted on an automotive vehicle. The
secondary air control device is used in a system for supplying
secondary air to a three-way catalizer in an exhaust pipe to warm
up and quickly activate it when a temperature of the exhaust gas is
low at a starting up of the engine, for example. An air pump is
connected to the secondary air control device through a secondary
air passage.
[0018] Referring to FIG. 2, an entire structure of the secondary
air control device will be described. The secondary air control
device includes an air switching valve 1 for opening or closing an
air passage, a one-way valve 2 for permitting airflow only in one
direction and an electric motor 3 for driving the air switching
valve 1. A driving force of the electric motor 3 is transmitted
through a valve driving mechanism (shown in FIG. 1) to a poppet
valve 4 of the air switching valve 1. All of these components of
the secondary air control device are contained in a housing
composed of a valve case 11, an outlet case 13 and case cover 12
(shown in FIG. 3).
[0019] An air pump for supplying the secondary air to an inlet port
17 of the air switching valve 1 and the electric motor 3 are
controlled by an ECU (Electronic Control Unit) according to driving
conditions of the engine. The ECU is a known microcomputer
including a CPU (Central Processing Unit) and memories (ROM, RAM)
for storing programs and data. A temperature of the three-way
catalizer is detected and inputted to the ECU. When the catalizer
temperature is lower than a predetermined level, at a starting up
of the engine, the air pump and the electric motor 3 are driven to
supply the secondary air to the three-way catalizer.
[0020] The valve case 11 is made of a metallic material such as
die-cast aluminum having a high thermal conductivity. In the valve
case 11, a valve seat 14 having a valve port 15 which is closed or
opened by the poppet valve 4 and an inlet pipe 16 for introducing
air to the valve port 15 are integrally formed. The valve seat 14
may be formed separately from the valve case 11 and installed to
the valve case 11. The inlet pipe 16 is connected to the air pump
through the secondary air passage (not shown) and includes an inlet
passage 18 extending substantially straight from the inlet port 17
to the valve port 15 with an inclination. The inlet passage 18 is
connected to the valve port 15 through another inlet passage 19.
The one-way valve 2 having an air passage 21 is disposed downstream
of the valve port 15, and the valve port 15 is connected to the air
passage 21 through a passage 20.
[0021] The case cover 12 (shown in FIG. 3) is made of a resin
material and has a connector shell 22. The secondary air control
device is electrically connected to the ECU through a wire harness
that has female terminals to be coupled to male terminals 23 formed
in the connector shell 22. The outlet case 13 is made of a metallic
material such as die-cast aluminum and has an outlet port 28 for
delivering the secondary air therethrough. The valve case 11 and
the outlet case 13 are connected to each other by abutting
respective connecting flanges 24, 25. A circular seal rubber 27 for
sealing the connecting portion is disposed between both flanges 24,
25. A metal plate 35 of the one-way valve 2 is disposed in a
mounting portion 26 formed in the outlet case 13 and sandwiched
between the valve case 11 and the outlet case 13. The outlet port
28 and the passage 21 of the one-way valve 2 are connected through
an outlet passage 29.
[0022] The outlet case 13 forming the housing together with the
valve case 11 and case cover 12 includes a mounting stay 30 having
bolt holes 31. The outlet case 13 is fixedly connected to a
secondary air passage tube or an exhaust gas passage communicating
with the outlet port 28 with mounting bolts (not shown) inserted
into the bolt holes 31.
[0023] The air switching valve 1 includes a poppet valve 4 composed
of a valve head 5 and a valve shaft 6, both being integrally formed
by molding a resin material. The valve head 5 and the valve shaft 6
may be separately made and connected to each other. The poppet
valve 4 is reciprocally driven (in the vertical direction in FIG.
2) by the driving mechanism including the electric motor 3, and
thereby the valve port 15 is opened or closed by the valve head 5.
The valve head 5 includes a seal rubber 32 fixedly connected to an
outer peripheral portion of the valve head 5. The seal rubber 32
contacts the valve seat 14 to thereby seal the valve port 14 when
the valve port 15 is closed. The valve head 5 is separated from the
valve seat 14 and positioned in the passage 20 when the valve port
15 is opened. A lower part of the valve shaft 6 is formed in a
cylindrical shape, and an upper part in a solid rod having a rack
49 thereon, as shown in FIG. 2.
[0024] The one-way valve 2 is positioned downstream of the valve
port 15. The one-way valve 2 is composed of a metal plate 35 having
an air passage 21, a reed valve 33 for opening or closing the air
passage 21 and a stopper 34 for limiting movement of the reed valve
33. The metal plate 35 is fixedly held between the valve case 11
and the outlet case 13, and the reed valve 33 and the stopper 34
are fixed to the metal plate 35 at their one ends with a rivet or
the like. The reed valve 33 is made of a thin metallic plate such
as a spring plate and formed in a double- or triple-tongue shape so
that it resiliently moves to open or close the air passage 21. The
stopper 34 is made of a metallic plate and formed in a double- or
triple-tongue shape. The maximum movement of the reed valve 33 is
limited by the stopper 34 when the reed valve 33 opens the air
passage 21. The reed valve 33 opens the air passage 21 by a
pressure of the secondary air to be supplied to the three-way
catalyzer in the exhaust pipe. The reed valve 33 closes the air
passage 21 to prevent the exhaust gas from entering into the air
control device. The air passage 21 is formed in a mesh-like shape
having plural openings.
[0025] Now, referring FIGS. 1-4, how the poppet valve 4 is driven
will be described. As better seen in FIG. 1, the valve shaft 6 of
the poppet valve 4 is reciprocally driven in its axial direction by
a valve-driving mechanism composed of the electric motor 3 and a
speed reduction mechanism including plural gears. The poppet valve
4 is biased in a direction to close the valve port 15 by a torsion
spring 10 wound around a final gear 9. The poppet valve 4 opens the
valve port 15 when it is driven by the motor 3.
[0026] The electric motor 3 is a known brushless DC motor including
a rotor connected to a motor shaft 36 and a stator disposed outside
of the rotor. The rotor has permanent magnets, and the stator has
an armature winding disposed in a cylindrical yoke 37. Electric
power is supplied to the motor 3 from terminal 38 extending from a
motor housing and connected to the terminals 23 (refer to FIG. 3).
The motor 3 is driven under control of the ECU. The motor 3 is
contained and fixedly held in a motor hole 67 of the valve case 11
as shown in FIG. 3. A pinion gear 7 constituting part of the speed
reduction mechanism is connected to the motor shaft 36. In place of
the brushless DC motor 3, other motors such as a DC motor with
brushes or a three-phase induction motor may be used.
[0027] As shown in FIG. 1, the speed reduction mechanism is
composed of the pinion gear 7 connected to the motor shaft 36, an
intermediate gear 8 and a final gear 9. The pinion gear 7 engages
with a large gear 40 of the intermediate gear 8. The diameter of
the large gear 40 is much larger than the diameter of the pinion
gear 7. The intermediate gear 8 also has a small gear 42, and both
of the large gear 40 and the small gear 42 are commonly held by a
supporting shaft 41 which is rotatably supported in the housing.
The final gear 9 includes an axis 44, a pie-shaped gear portion 43
engaging with the small gear 42 of the intermediate gear 8 and a
pinion 46 (having teeth 47) engaging with the rack 49 of the valve
shaft 6. The final gear 9 further includes a flange 45 around which
the torsion spring 10 biasing the valve shaft in the direction of
closing the valve port 15 is wound. A first end 51 of the torsion
spring 10 is connected to first hook formed on the flange 45, and a
second end 53 of the torsion spring 10 is fixed to a second hook 54
held in the housing. Though the pinion 46 engaging with the rack 49
is formed all around the axis 44 in this embodiment, it may be
formed only at a portion corresponding to the rack 49.
[0028] As shown in FIGS. 1 and 3, the torsion spring 10 (a coil
spring) is disposed in a cylindrical space between the pinion 46
engaging with the rack 49 and the pie-shaped gear portion 43. When
the valve shaft 6 is driven in the direction to open the valve port
15, a resilient force is accumulated in the torsion spring 10. As
shown in FIGS. 2-4, a cylindrical spring guide 62 having a spring
space 61 therein, a cylindrical valve guide 64 having a hole 63
slidably containing the valve shaft 6 therein, a gear box 66
forming a gear chamber 65 therein, and a motor case 39 forming a
motor hole 67 therein are integrally formed in the valve case 11.
An inner bore of the spring guide 62 functions as a bore for
guiding an outer diameter of the torsion spring 10. As shown in
FIG. 2, a ring-shaped seal rubber 69 is disposed in the valve guide
64 to prevent leakage of the secondary air from the inlet passage
19. The gear box 66 contains the speed reduction mechanism
including the pinion gear 7, the intermediate gear 8 and the final
gear 9.
[0029] Operation of the secondary air control system described
above will be explained. The three-way catalyzer for converting
harmful components such as CO, HC and NOx in the exhaust gas to
harmless components is installed in the exhaust pipe. In
particular, HC (hydrocarbon) is oxidized in the three-way catalyzer
and converted into water and carbon-dioxides. However, the
three-way catalyzer does not function effectively if air-fuel
mixture supplied to the engine is not stoichiometric (15:1).
Further, the three-way catalyzer does not work properly when a
temperature of the exhaust gas is low.
[0030] In order to activate the three-way catalyzer, secondary air
generated by the air pump is supplied to the three-way catalyzer
through the secondary air control device. The exhaust gas
temperature is raised by oxidizing unburned components with the
secondary air, and thereby the three-way catalizer is activated.
Therefore, when the exhaust gas temperature is lower than a
predetermined level (under conditions such as starting up of the
engine), the secondary air is supplied to the three-way catalyzer.
The temperature may be detected by an exhaust gas temperature
sensor or a sensor for detecting the temperature of the three-way
catalyzer. The air pump and the secondary air control device are
operated under the control of the ECU to which the detected
temperature is fed.
[0031] When the electric motor 3 is driven, its rotational torque
is transmitted to the poppet valve 4 through the speed reduction
mechanism. More particularly, the motor torque is first transmitted
from the pinion gear 7 connected to the motor shaft 36 to the large
gear 40 of the intermediate gear 8. Then, the rotational torque is
further transmitted from the small gear 42 to the gear portion 43
of the final gear 9. Then, the rotating torque of the pinion 46 of
the final gear 9 is converted into a linear movement of the rack 49
engaging with the pinion 46. Thus, the valve shaft 6 is driven in
the direction to open the valve port 15. When power supply to the
motor 3 is terminated, the valve shaft 6 returns to its original
position by the biasing force of the torsion spring 10 to thereby
close the valve port 15.
[0032] Since the rotational torque of the motor 3 is transmitted,
through the speed reduction mechanism including the pinion gear 7,
the large gear 40, the small gear 42 and the gear portion 43, to
the pinion 46 of the final gear 9, the rotational speed is reduced
by an amount of the gear ratio in the speed reduction mechanism. An
amount of opening degree of the valve port 15 is also controlled by
the ECU.
[0033] The secondary air is supplied from the air pump to the
three-way catalyzer through the secondary air control device. More
particularly, the secondary air is supplied from the air pump
through: the inlet port 17 of the inlet pipe 16, the inlet passages
18, 19, the valve port 15, the passage 20, the air passage 21 in
the one-way valve 2, the outlet passage 29 in the outlet case 13,
and the outlet port 28. In this manner, the three-way catalyzer
temperature is raised by oxidation of unburned components by the
secondary air, and the three-way catalyzer is activated. Thus, the
harmful components in the exhaust gas are effectively converted
into harmless components.
[0034] Advantages attained in the embodiment described above will
be summarized. Since the torsion spring 10 is wound around the
flange 45 of the final gear 9, the length of the valve shaft 6 is
shortened (conventionally, a coil spring is disposed around the
valve shaft). Therefore, the secondary air control device can be
made compact, saving its mounting space in an engine compartment.
The housing containing the secondary air control device connected
to the secondary air passage pipe or the exhaust pipe in a
cantilever fashion has a higher strength against vibration because
a distance from the mounting stay 30 of the housing to the other
end of the device is made shorter. In other words, a cantilever
length of the housing is shortened.
[0035] Since the pinion 46 of the final gear 9 is firmly engaged
with the rack 49 of the valve shaft 6 by the biasing force of the
torsion spring 10 even when the motor 3 is not driven, abrasion
wear of the pinion 46 and the rack 49 due to vibration of the
engine can be minimized. Since the cylindrical space between the
pinion 46 and the gear portion 43 of the final gear 9 is utilized
for disposing the torsion spring 10, the size of the secondary air
control device is further reduced. Since the pinion 46 of the final
gear 9 is firmly engaged with the rack 49 by the biasing force of
the torsion spring 10, engaging wear of the pinion 46 and the rack
49 can be suppressed. Since the torsion spring 10 is positioned
closer to the motor 3 in this embodiment than in the conventional
device, a detent torque of the motor 3 for keeping an open position
of the poppet valve 4 can be effectively utilized.
[0036] The present invention is not limited to the embodiment
described above, but it may be variously modified. For example, the
present invention may be applied to devices other than the
secondary air control device, such as intake air control valves
(swirl control valves, tumble control valves) or valves for
controlling amount of intake air (throttle valves, idling speed
control valves). The present invention may be applied to an exhaust
gas recirculation control valve (EGR control valve). In this case,
the one-way valve may be eliminated. Further, the present invention
may be applied to valves for opening or closing a fluid passage,
valves for intercepting a fluid passage, valves for controlling an
amount of fluid, or valves for controlling a pressure of fluid. The
fluid is not limited to air, but it may be other gases such as
evaporated fuel, water, liquid fuel, oil or other liquids. Further,
the fluid may be a mixture of gaseous and liquid state fluids such
as refrigerant in an air-conditioner.
[0037] Though an electric motor is used for driving the poppet
valve 4, other drivers such as an electromagnetic actuator having a
solenoid coil may be used. In place of the poppet valve 4, other
valves, such as a rotary valve, a butterfly valve, a shutter valve
or a ball valve, may be used. A valve shaft and a valve body may be
separately formed and they may be connected thereafter. The one-way
valve may be eliminated in certain applications. The reed valve 33
and the stopper 34 may be riveted together at their one end,
fastened by a screw, or connected together by staking or the like.
The one-way valve 2 may be positioned at the outlet port 28. The
valve case 11 and the outlet case 13 may be combined into a single
body. An outlet pipe may be connected to the outlet port 28. The
torsion spring 10 may be replaced with a torsion bar or a leaf
spring, a double-coil spring, or a coil spring having an uneven
pitch.
[0038] While the present invention has been shown and described
with reference to the foregoing preferred embodiment, it will be
apparent to those skilled in the art that changes in form and
detail may be made therein without departing from the scope of the
invention as defined in the appended claims.
* * * * *