U.S. patent application number 12/591009 was filed with the patent office on 2010-03-25 for exhaust valve device.
This patent application is currently assigned to MIKUNI CORPORATION. Invention is credited to Kenji Kubota.
Application Number | 20100071642 12/591009 |
Document ID | / |
Family ID | 40002067 |
Filed Date | 2010-03-25 |
United States Patent
Application |
20100071642 |
Kind Code |
A1 |
Kubota; Kenji |
March 25, 2010 |
Exhaust valve device
Abstract
An exhaust valve device includes an exhaust valve formed by a
valve body, a valve stem and a valve element, which opens and
closes an exhaust passage provided in the valve body, mounted on
the valve stem that is inserted into and supported rotatably by the
valve body; and an actuator that drives the exhaust valve to open
and close. The actuator includes an electric actuator, and an
opening detection sensor to detect an opening of the exhaust valve.
Further, the electric actuator and the opening detection sensor are
disposed coaxially, a connecting shaft that connects the two is
disposed parallel to and offset from the valve stem of the exhaust
valve, and the connecting shaft and valve stem are connected by a
link mechanism.
Inventors: |
Kubota; Kenji; (Odawara-shi,
JP) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700, 1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
MIKUNI CORPORATION
Tokyo
JP
|
Family ID: |
40002067 |
Appl. No.: |
12/591009 |
Filed: |
November 4, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/JP2008/057723 |
Apr 22, 2008 |
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12591009 |
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Current U.S.
Class: |
123/90.11 |
Current CPC
Class: |
F02D 9/04 20130101 |
Class at
Publication: |
123/90.11 |
International
Class: |
F01L 9/04 20060101
F01L009/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 7, 2007 |
JP |
2007-122019 |
Claims
1. An exhaust valve device comprising: an exhaust valve formed by a
valve body, a valve stem and a valve element, which opens and
closes an exhaust passage provided in the valve body, mounted on
the valve stem that is inserted into and supported rotatably by the
valve body; and an actuator that drives the exhaust valve to open
and close, the actuator comprising an electric actuator, and an
opening detection sensor to detect an opening of the exhaust
valve.
2. The exhaust valve device according to claim 1, wherein the
electric actuator and the opening detection sensor are disposed
coaxially.
3. The exhaust valve device according to claim 2, further
comprising: a connecting shaft to connect the electric actuator to
the opening detection sensor, the connecting shaft being disposed
parallel to and offset from the valve stem of the exhaust valve;
and a rotation transmitter to connect the connecting shaft and the
valve stem.
4. The exhaust valve device according to claim 3, wherein the
rotation transmitter comprises: a link mechanism including levers
attached respectively to the connecting shaft and the valve stem;
and a rod to connect the levers.
5. The exhaust valve device according to claim 4, wherein the lever
attached to the connecting shaft is disposed between the electric
actuator and the opening detection sensor in an axial
direction.
6. The exhaust valve device according to claim 3, further
comprising a return spring to bias the exhaust valve in an opening
direction at all times provided on the connecting shaft.
7. The exhaust valve device according to claim 1, further
comprising a protective cover to cover the electric actuator and
the opening detection sensor.
8. The exhaust valve device according to claim 7, wherein the
protective cover includes a slit or an opening portion to release
air that is formed in a ceiling portion of the protective
cover.
9. The exhaust valve device according to claim 1, wherein at least
one of the exhaust valve and said electric actuator is fixed via
thermal insulation packing.
10. The exhaust valve device according to claim 1, wherein a
magnitude relationship of .theta.1<.theta.2<.theta.3 is
established between an operating angle .theta.1 of said exhaust
valve, an operating angle .theta.2 of said electric actuator, and a
detection angle .theta.3 of said opening detection sensor.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation, filed under 35 U.S.C.
.sctn.111(a), of PCT international application No.
PCT/JP2008/057723, filed Apr. 22, 2008, which application claims
the priority benefit of Japanese patent application No.
2007-122019, filed May 7, 2007, the disclosures of which are
incorporated herein by reference.
BACKGROUND
[0002] 1. Field
[0003] The present invention relates to an exhaust valve that opens
and closes an exhaust passage of a vehicle engine, for example, and
an exhaust valve device including an actuator that drives the
exhaust valve to open and close.
[0004] 2. Description of the Related Art
[0005] An exhaust valve device including a butterfly type exhaust
valve that functions as an exhaust brake valve and a warm-up valve
and an actuator that drives the exhaust valve is provided in an
exhaust pipe of a vehicle such as a motorcycle or an
automobile.
[0006] With regard to this exhaust valve device, Japanese Patent
Application Laid-open No. H11-108207 proposes a device provided
with a duty ratio control change-over valve that is subjected to
duty ratio control by a controller in order to adjust a valve
opening thereof and an ON-OFF change-over valve that switches a
warm-up valve from an operative state to an inoperative state by
performing a simple ON-OFF operation, wherein a large diameter
passage having a large flow passage area is used on the ON-OFF
change-over valve side to reduce pressure loss and a small diameter
passage is used on the duty ratio control change-over valve side to
prevent the controller from hunting, and by connecting the duty
ratio control change-over valve and the ON-OFF change-over valve in
parallel to an operating pressure chamber, the responsiveness of
the warm-up valve to a rapid accelerator depression operation is
increased, thereby suppressing the generation of black smoke from
an engine.
[0007] Further, Japanese Patent Application Laid-open No.
2002-047949 proposes a constitution for accurately and reliably
detecting an opening/closing position of a valve over an entire
operating region of a valve main body, in which an angle sensor
serving as valve element rotation position detecting means is fixed
in a position removed from an end portion of a valve stem via a
bracket, rotation transmitting means is formed from an input rubber
fixed to an input shaft of the angle sensor and a pin, and a lever
connected to an output rod of an actuator and the input shaft of
the angle sensor are mechanically connected via the rotation
transmitting means.
[0008] However, in the constitution proposed in Japanese Patent
Application Laid-open No. H11-108207, a rod for transmitting a
position of a valve element that rotates within an exhaust pipe to
position detecting means is not connected to the position detecting
means at all times, and therefore the position of the valve element
cannot be detected over the entire operation region of the valve
element.
[0009] Further, in the constitution proposed in Japanese Patent
Application Laid-open No. 2002-047949, the valve stem is disposed
coaxially with the actuator and the angle sensor, leading to an
increase in the size of the device.
[0010] Furthermore, in the constitutions proposed in Japanese
Patent Application Laid-open No. H11-108207 and Japanese Patent
Application Laid-open No. 2002-047949, a negative pressure actuator
is used, and therefore a negative pressure tank for storing
negative pressure, which serves as a power supply, a solenoid valve
for controlling the negative pressure that is supplied to the
negative pressure actuator, and so on are required, leading to
increases in the complexity, size and cost of the system. Moreover,
with a negative pressure actuator, it is difficult to
open/close-control the exhaust valve with a high degree of
responsiveness.
SUMMARY
[0011] With the foregoing in view, it is an aspect of the present
invention to provide an exhaust valve device with which a reduction
in size, an increase in compactness, and an increase in
responsiveness can be realized.
[0012] Additional aspects and/or advantages will be set forth in
part in the description which follows and, in part, will be
apparent from the description, or may be learned by practice of the
invention.
[0013] The foregoing and/or other aspects of the present invention
are achieved by an exhaust valve device including: an exhaust valve
formed by mounting a valve element, which opens and closes an
exhaust passage provided in a valve body, on a valve stem that is
inserted into and supported rotatably by the valve body; and an
actuator that drives the exhaust valve to open and close, wherein
the actuator is constituted by an electric actuator, and opening
detecting means is provided to detect an opening of the exhaust
valve.
[0014] In the exhaust valve device, the electric actuator and the
opening detecting means may be disposed coaxially.
[0015] In the exhaust valve device, a connecting shaft that
connects the electric actuator to the opening detecting means may
be disposed parallel to and offset from the valve stem of the
exhaust valve, and the connecting shaft and the valve stem may be
connected by rotation transmitting means.
[0016] In the exhaust valve device, the rotation transmitting means
may be constituted by a link mechanism including levers attached
respectively to the connecting shaft and the valve stem, and a rod
connecting the levers.
[0017] In the exhaust valve device, the lever attached to the
connecting shaft may be disposed between the electric actuator and
the opening detecting means in an axial direction.
[0018] In the exhaust valve device, biasing means to bias the
exhaust valve in an opening direction at all times may be provided
on the connecting shaft.
[0019] In the exhaust valve device, the electric actuator and the
opening detecting means may be covered by a protective cover.
[0020] In the exhaust valve device, a slit or an opening portion to
release air may be formed in a ceiling portion of the protective
cover.
[0021] In the exhaust valve device, at least one of the exhaust
valve and the electric actuator may be fixed via thermal insulation
packing.
[0022] In the exhaust valve device, a magnitude relationship of
.theta.1<.theta.2<.theta.3 may be established between an
operating angle .theta.1 of the exhaust valve, an operating angle
.theta.2 of the electric actuator, and a detection angle .theta.3
of the opening detecting means.
[0023] In the exhaust valve device, the actuator to drive the
exhaust valve to open and close may be constituted by an electric
actuator, and therefore the exhaust value can be
open/close-controlled with a high degree of responsiveness and
driven to open and close even when the engine is stopped. Moreover,
the opening of the exhaust valve can be detected by the opening
detecting means.
[0024] In the exhaust valve device, the electric actuator and the
opening detecting means may be disposed coaxially, and the shaft
that connects the electric actuator and the opening detecting means
may be disposed parallel to and offset from the valve stem of the
exhaust valve, and therefore the entire device can be reduced in
size and increased in compactness. Moreover, the electric actuator
and opening detecting means are removed from the valve stem (a
high-temperature portion), and therefore an air layer exhibiting
high heat resistance is formed between the valve stem and the
electric actuator and opening detecting means, thereby preventing
the electric actuator and opening detecting means from receiving an
adverse thermal effect generated by radiation heat from the
high-temperature exhaust pipe. As a result, the operating stability
of the electric actuator and opening detecting means can be
improved, and a cost reduction can be achieved by using a
reasonably priced, lightweight resin material as the material
thereof.
[0025] In the exhaust valve device, the rotation transmitting means
to connect the connecting shaft that connects the electric actuator
and the opening detecting means to the valve stem may be
constituted by the structurally simple link mechanism, and
therefore the flow rate and pressure of exhaust gas flowing through
an exhaust passage can be adjusted as desired by transmitting the
rotation of the electric actuator to the valve stem via the link
mechanism such that the valve stem and a valve element mounted
thereon rotate.
[0026] In the exhaust valve device, the lever attached to the
connecting shaft that connects the electric actuator to the opening
detecting means may be disposed between the electric actuator and
the opening detecting means in the axial direction, and therefore
the electric actuator and opening detecting means can be provided
on either side of the connecting shaft after the lever is attached
to a central portion thereof, thus improving ease of assembly.
[0027] In the exhaust valve device, the exhaust valve may be biased
in the opening direction at all times by the biasing means, and
therefore the exhaust valve may remain open even when an
abnormality occurs in the electric actuator. As a result, a
defective situation in which the exhaust passage is closed, thereby
choking the flow of exhaust gas, is prevented and a favorable
failsafe property is secured. Furthermore, backlash from the
exhaust valve is absorbed by the biasing means, leading to an
improvement in the responsiveness of the exhaust valve.
[0028] In the exhaust valve device, the electric actuator and
opening detecting means may be covered by the protective cover, and
therefore the electric actuator and opening detecting means of the
exhaust valve device, which is often disposed on a lower surface of
a vehicle, can be protected from flying stones and the like such
that damage thereto is prevented.
[0029] In the exhaust valve device, the slit or opening portion to
release air may be formed in the ceiling portion of the protective
cover, and therefore air warmed by the exhaust gas is not held
inside the protective cover. As a result, temperature increases in
the electric actuator and opening detecting means covered by the
protective cover are suppressed, and a high degree of operational
stability is secured therein.
[0030] In the exhaust valve device, at least one of the exhaust
valve and the electric actuator may be fixed via the thermal
insulation packing, and therefore thermal conduction from a
high-temperature exhaust pipe to the electric actuator is blocked
effectively by the thermal insulation packing. As a result, adverse
thermal effects on the electric actuator are eliminated, and the
operational stability of the electric actuator is improved.
[0031] In the exhaust valve device, when a transmission mechanism
is constituted by the link mechanism, for example, and a rod of the
link mechanism breaks, the exhaust valve enters a fully open state
and does not rotate beyond the operating angle .theta.1, whereas
the electric actuator rotates beyond the operating angle .theta.1
of the exhaust valve. Hence, when the opening detecting means
detect a larger rotation angle than .theta.1, the opening detecting
means can determine that an abnormality has occurred in the
device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] These and/or other aspects and advantages will become
apparent and more readily appreciated from the following
description of the embodiments, taken in conjunction with the
accompanying drawings of which:
[0033] FIG. 1 is a block diagram showing a system constitution of
an exhaust system for a vehicle engine, which includes an exhaust
valve device according to an embodiment;
[0034] FIG. 2 is a perspective view of the exhaust valve device
according to the embodiment;
[0035] FIG. 3 is a cutaway front view showing a state in which a
protective cover is removed from the exhaust valve device according
to the embodiment;
[0036] FIG. 4 is a side view showing the exhaust valve device
according to the embodiment from an opening detection sensor
side;
[0037] FIG. 5 is a perspective view showing the exhaust valve
device according to the embodiment from the opening detection
sensor side;
[0038] FIG. 6 is a side view showing the exhaust valve device
according to the embodiment from an electric actuator side;
[0039] FIG. 7 is an exploded perspective view showing a connection
structure for connecting the electric actuator and the opening
detection sensor of the exhaust valve device according to the
embodiment; and
[0040] FIG. 8 is a view showing a relationship between a position
detection output of the opening detection sensor of the exhaust
valve device according to the embodiment and an operating angle of
an exhaust valve, an operating angle of the electric actuator, and
a detection angle of the opening detection sensor.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0041] Reference will now be made in detail to the embodiments,
examples of which are illustrated in the accompanying drawings,
wherein like reference numerals refer to the like elements
throughout. The embodiments are described below to explain the
present invention by referring to the figures.
[0042] FIG. 1 is a block diagram showing a system constitution of
an exhaust system for a vehicle engine, which includes an exhaust
valve device according to an embodiment of the present
invention.
[0043] An intake manifold 51 is connected to an intake side of a
vehicle engine 50 according to this embodiment, and an exhaust
manifold 52 is connected to an exhaust side. Although not shown in
the drawing, an air cleaner is connected to the intake manifold 51
via a throttle body and a surge tank.
[0044] A catalytic converter 53, an exhaust valve device 1, a
filter 54, and a muffler 55 are connected in sequence to an exhaust
pipe extending from the exhaust manifold 52.
[0045] The exhaust valve device 1 is drive-controlled by a control
device (ECU) 60. An engine rotation speed detected by an engine
rotation sensor 61, a cooling water temperature detected by a water
temperature sensor 62, an accelerator opening (throttle opening)
detected by an accelerator opening sensor 63, and an engine load
detected by a load sensor 64 are input into the control device 60,
and the control device 60 drive-controls the exhaust valve device 1
on the basis of these values.
[0046] When intake air (fresh air) is supplied to respective
cylinders of the engine 50 from the intake manifold 51, fuel is
injected into the intake air to form an air-fuel mixture, and the
air-fuel mixture is burned in a combustion chamber of each
cylinder. High-temperature exhaust gas generated upon combustion of
the air-fuel mixture is discharged to the exhaust manifold 52 from
the engine 50 and purified while flowing through the catalytic
converter 53 from the exhaust manifold 52. The exhaust valve device
1, which is drive-controlled by the control device 60 as described
above, then adjusts the flow rate and pressure of the exhaust gas,
whereupon the exhaust gas is muffled while passing through the
muffler 54. Finally, the exhaust gas is discharged to the
atmosphere.
[0047] Next, the exhaust valve device 1 will be described in detail
on the basis of FIGS. 2 to 7.
[0048] FIG. 2 is a perspective view of the exhaust valve device.
FIG. 3 is a cutaway front view showing a state in which a
protective cover is removed from the exhaust valve device. FIG. 4
is a side view showing the exhaust valve device from an opening
detection sensor side. FIG. 5 is a perspective view of the same.
FIG. 6 is a side view showing the exhaust valve device from an
electric actuator side. FIG. 7 is an exploded perspective view
showing a connection structure for connecting the electric actuator
and the opening detection sensor of the exhaust valve device.
[0049] As shown in FIG. 3, the exhaust valve device 1 is
constituted by an exhaust valve 2, an electric actuator 3 that
drives the exhaust valve 2 to open and close, and an opening
detection sensor 4 that detects an opening of the exhaust valve 2.
As shown in FIG. 2, the electric actuator 3 and the opening
detection sensor 4 are covered by a rectangular box-shaped
protective cover 5. Here, the protective cover 5 is formed from a
metallic material exhibiting high corrosion resistance and high
heat resistance, and a plurality of air releasing slits 5a are
formed in a ceiling portion thereof. Note that a simple opening
portion may be formed in the ceiling portion of the protective
cover 5 instead of the slits 5a.
[0050] As shown in FIG. 3, the exhaust valve 2 is formed by
mounting a disc-shaped valve element 9 that opens and closes an
exhaust passage 8 provided in a circular pipe-shaped valve body (an
exhaust pipe in this embodiment) 6 on a valve stem 7 that is
inserted into and supported rotatably by the valve body 6 using two
hinges 10.
[0051] Here, as shown in FIG. 3, a mounting bracket 11 having a
U-shaped transverse section is attached to one side portion of the
valve body 6, and the valve body 6 is mounted on a base plate 14 by
a plurality of bolts 12 inserted into the mounting bracket 11 and
nuts 13 screwed to the bolts 12. Note that in this embodiment,
thermal insulation packing 15 is interposed between the mounting
bracket 11 and the base plate 14.
[0052] Further, respective axial ends of the valve stem 7 are
supported rotatably by bearings, not shown in the drawings, one end
portion thereof (the right end portion in FIG. 3) extends
horizontally through the base plate 14, and a lever 16 is attached
to this end portion by a nut 17. Here, as shown in FIGS. 4 and 5,
two engagement projections 16a, 16b are formed integrally with the
lever 16 so as to project from predetermined angular positions on
an outer periphery thereof, and by engaging the engagement
projections 16a, 16b with a stopper 14a formed on the base plate
14, a rotation angle of the valve element 9 (in other words, the
opening of the exhaust valve 2) is restricted. When one of the
engagement projections 16a is engaged with the stopper 14a, as
shown in FIGS. 4 and 5, the valve element 9 (the exhaust valve 2)
is in a fully open state, as shown in FIG. 3, and when the other
engagement projection 16b is engaged with the stopper 14a, the
valve element 9 (the exhaust valve 2) is in a fully closed
state.
[0053] Further, a return spring 18 serving as biasing means is
wound between the base plate 14 of the valve stem 7 and the lever
16. One end of the return spring 18 is latched to the valve stem 7
and the other end is latched to the base plate 14 such that the
valve stem 7 and the valve element 9 (exhaust valve 2) mounted
thereon are constantly biased in an opening direction by the return
spring 18.
[0054] Meanwhile, a connecting shaft 19 is disposed rotatably on an
upper portion of the base plate 14 so as to be parallel to and
upwardly offset from the valve stem 7 of the exhaust valve 2, and
the electric actuator 3 and opening detection sensor 4 are mounted
on respective axial ends of the connecting shaft 19. In other
words, the electric actuator 3 and the opening detection sensor 4
are disposed coaxially and connected by the connecting shaft
19.
[0055] Here, the electric actuator 3 is constituted by a DC motor
and drive-controlled by the control device 60 shown in FIG. 1. As
shown in FIGS. 3 and 6, the electric actuator 3 is mounted on the
upper portion of the base plate 14 by two bolts 20, and as shown in
FIG. 7, a sector gear 21 is attached to an output shaft of the
electric actuator 3. Note that thermal insulation packing may be
interposed between the electric actuator 3 and the base plate
14.
[0056] Further, as shown in FIGS. 3 to 5 and FIG. 7, a mounting
flange 22 and a mounting bracket 23 are mounted on a surface of the
base plate 14 on which the electric actuator 3 is mounted and an
opposite surface thereto by two bolts 24 and nuts 25 screwed to the
bolts 24. Here, the mounting flange 22 is a flat plate-shaped
member with a circular hole 22a formed in a central portion
thereof. The mounting bracket 23, meanwhile, takes a
three-dimensional shape in which two leg portions 23B extend
integrally from either end of a flange-shaped mounting portion 23A
and a circular hole 23a is formed in a central portion of the
mounting portion 23A (see FIG. 7).
[0057] The opening detection sensor 4 is mounted on the mounting
portion 23A of the mounting bracket 23 by two bolts 26, and as
described above, the opening detection sensor 4 is connected to the
electric actuator 3 by the connecting shaft 19. The opening
detection sensor 4 is a variable resistance type sensor which
outputs an electric resistance variation generated by rotation of
the connecting shaft 19 as an output voltage variation and
transmits a corresponding output signal to the control device 60
shown in FIG. 1.
[0058] As shown in FIG. 7, a lever 27 is attached to an axial
intermediate position of the connecting shaft 19, or in other words
a site of the connecting shaft 19 located between the electric
actuator 3 and the opening detection sensor 4 in an axial
direction, by left and right nuts 28, 29. As shown in FIGS. 4 and
5, the lever 27 and the lever 16 attached to the end portion of the
valve stem 7 are connected by a rod 30, and together the levers 16,
27 and the rod 30 constitute a link mechanism 31 that serves as
rotation transmitting means for transmitting the rotation of the
electric actuator 3 to the valve stem 7 of the exhaust valve 2.
Note that another desired transmission mechanism such as a belt
transmission mechanism or a gear transmission mechanism may be used
as the rotation transmitting means.
[0059] In the exhaust valve device 1 constituted as described
above, when the electric actuator 3 is driven by the control device
shown in FIG. 1, rotation of the electric actuator 3 is transmitted
to the valve stem 7 of the exhaust valve 2 from the connecting
shaft 19 via the link mechanism 31, whereupon the valve stem 7 and
the valve element 9 mounted thereon rotate in an identical
direction and by an identical angle. By rotating the valve element
9 within the valve body (exhaust pipe) 6 in this manner, the flow
rate and pressure of the exhaust gas flowing through the exhaust
passage 8 in the valve body 6 are adjusted. Meanwhile, the rotation
angle of the electric actuator 3, or in other words the opening of
the exhaust valve 2, is detected by the opening detection sensor 4,
and as described above, a corresponding detection signal (voltage
signal) is fed back to the control device 60 shown in FIG. 1. The
control device 60 then determines the opening of the exhaust valve
2 from the detection signal input from the opening detection sensor
4, and feedback-controls the electric actuator 3 such that the
opening thereof equals a set value.
[0060] FIG. 8 shows a relationship between a position detection
output (voltage) of the opening detection sensor 4 and an operating
angle .theta.1 of the exhaust valve 2, an operating angle .theta.2
of the electric actuator 3, and a detection angle .theta.3 of the
opening detection sensor 4. As shown in FIG. 8, a magnitude
relationship of .theta.1<.theta.2<.theta.3 is established
between .theta.1, .theta.2 and .theta.3. Note that position
detection outputs V1, V2, V3 shown on the ordinate of FIG. 8 denote
output voltage values corresponding respectively to the operating
angle .theta.1 of the exhaust valve 2, the operating angle .theta.2
of the electric actuator 3, and the detection angle .theta.3 of the
opening detection sensor 4.
[0061] Therefore, in cases such as when the rod 30 of the link
mechanism 31 breaks, for example, the exhaust valve 2 enters the
fully open state and does not rotate beyond the operating angle
.theta.1, whereas the electric actuator 3 remains capable of
rotating up to the operating angle .theta.2, which is larger than
the operating angle .theta.1 of the exhaust valve 2. Hence, when
the opening detection sensor 4 detects a larger rotation angle than
.theta.1, the opening detection sensor 4 can determine that an
abnormality has occurred in the exhaust valve device 1.
[0062] When feedback control is performed, as in this embodiment,
the opening detection sensor 4 cannot detect an abnormality such as
breakage of the rod 30 of the link mechanism 31 during the feedback
control. However, an abnormality can be detected by issuing a
maximum operation command unrelated to position control to the
electric actuator 3 immediately after an ignition switch of the
engine is switched ON or OFF such that the electric actuator 3
rotates at a maximum limit. Note that when feedback control is not
performed, an abnormality in the exhaust valve device 1 can be
detected at any time without performing the operation described
above.
[0063] In the embodiment described above, the actuator for driving
the exhaust valve 2 to open and close is constituted by the
electric actuator 3, and therefore the exhaust valve 2 can be
open/close-controlled with a high degree of responsiveness and
driven to open and close even when the engine is stopped. Moreover,
the opening of the exhaust valve 2 can be detected by the opening
detection sensor 4.
[0064] Further, in this embodiment, the electric actuator 3 and the
opening detection sensor 4 are disposed coaxially while the
connecting shaft 19 that connects the two is disposed parallel to
and upwardly offset from the valve stem 7 of the exhaust valve 2,
and therefore the entire exhaust valve device 1 can be reduced in
size and increased in compactness. Moreover, the electric actuator
3 and opening detection sensor 4 are removed from the valve stem 7
(a high-temperature portion), and therefore an air layer exhibiting
high heat resistance is formed between the valve stem 7 and the
electric actuator 3 and opening detection sensor 4, thereby
preventing the electric actuator 3 and opening detection sensor 4
from receiving an adverse thermal effect generated by radiation
heat from the high-temperature exhaust pipe. As a result, the
operating stability of the electric actuator 3 and opening
detection sensor 4 can be improved, and a cost reduction can be
achieved by using a reasonably priced, lightweight resin material
as the material thereof.
[0065] Furthermore, according to this embodiment, the rotation
transmitting means to transmit the rotation of the electric
actuator 3 to the valve stem 7 of the exhaust valve 2 can be
constituted by the structurally simple link mechanism 31, and
therefore the flow rate and pressure of the exhaust gas flowing
through the exhaust passage 8 can be adjusted as desired by
transmitting the rotation of the electric actuator 3 to the valve
stem 7 via the link mechanism 31 such that the valve stem 7 and the
valve element 9 mounted thereon rotate.
[0066] Further, in this embodiment, the lever 27 attached to the
connecting shaft 19 that connects the electric actuator 3 to the
opening detection sensor 4 is disposed between the electric
actuator 3 and the opening detection sensor 4 in the axial
direction, and therefore the electric actuator 3 and opening
detection sensor 4 can be provided on either side of the connecting
shaft 19 after the lever 27 is attached to the central portion
thereof, thus improving ease of assembly.
[0067] Moreover, in this embodiment, the exhaust valve 2 is biased
in the opening direction at all times by the return spring 18, and
therefore the exhaust valve 2 remains open even when an abnormality
occurs in the electric actuator 3. As a result, a defective
situation in which the exhaust passage 8 is closed, thereby choking
the flow of exhaust gas, is prevented and a favorable failsafe
property is secured. Furthermore, backlash from the exhaust valve 2
is absorbed by the return spring 18, leading to an improvement in
the responsiveness of the exhaust valve 2.
[0068] Further, in this embodiment, the electric actuator 3 and
opening detection sensor 4 are covered by the protective cover 5,
and therefore the electric actuator 3 and opening detection sensor
4 of the exhaust valve device 1, which is often disposed on a lower
surface of the vehicle, can be protected from flying stones and the
like such that damage thereto is prevented. Moreover, the air
releasing slits 5a are formed in the ceiling portion of the
protective cover 5, and therefore air warmed by the exhaust gas is
not held inside the protective cover 5. As a result, temperature
increases in the electric actuator 3 and opening detection sensor 4
covered by the protective cover 5 are suppressed, and a high degree
of operational stability is secured therein.
[0069] Moreover, in this embodiment, the thermal insulation packing
15 is interposed between the mounting bracket 11 for mounting the
high-temperature valve body 6 on the base plate 14 and the base
plate 14, and therefore thermal conduction from the
high-temperature exhaust pipe to the electric actuator 3 is blocked
effectively by the thermal insulation packing 15. As a result,
adverse thermal effects on the electric actuator 3 are eliminated,
and the operational stability of the electric actuator 3 is
improved.
[0070] The present invention may be applied to another valve device
such as an EGR cooler passage change-over valve device or an EGR
introduction amount control valve device.
[0071] Although a few embodiments have been shown and described, it
would be appreciated by those skilled in the art that changes may
be made in these embodiments without departing from the principles
and spirit of the invention, the scope of which is defined in the
claims and their equivalents.
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