Title:
Exhaust valve device
Kind Code:
A1


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)
Application Number:
12/591009
Publication Date:
03/25/2010
Filing Date:
11/04/2009
Assignee:
MIKUNI CORPORATION (Tokyo, JP)
Primary Class:
International Classes:
F01L9/04
View Patent Images:



Primary Examiner:
CHAUDRY, ATIF H
Attorney, Agent or Firm:
STAAS & HALSEY LLP (SUITE 700 1201 NEW YORK AVENUE, N.W., WASHINGTON, DC, 20005, US)
Claims:
What is claimed is:

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 θ123 is established between an operating angle θ1 of said exhaust valve, an operating angle θ2 of said electric actuator, and a detection angle θ3 of said opening detection sensor.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation, filed under 35 U.S.C. §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

1. Field

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.

2. Description of the Related Art

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.

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.

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.

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.

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.

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

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.

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.

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.

In the exhaust valve device, the electric actuator and the opening detecting means may be disposed coaxially.

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.

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.

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.

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.

In the exhaust valve device, the electric actuator and the opening detecting means may be covered by a protective cover.

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.

In the exhaust valve device, at least one of the exhaust valve and the electric actuator may be fixed via thermal insulation packing.

In the exhaust valve device, a magnitude relationship of θ123 may be established between an operating angle θ1 of the exhaust valve, an operating angle θ2 of the electric actuator, and a detection angle θ3 of the opening detecting means.

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.

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.

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.

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.

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.

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.

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.

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.

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 θ1, whereas the electric actuator rotates beyond the operating angle θ1 of the exhaust valve. Hence, when the opening detecting means detect a larger rotation angle than θ1, the opening detecting means can determine that an abnormality has occurred in the device.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

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;

FIG. 2 is a perspective view of the exhaust valve device according to the embodiment;

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;

FIG. 4 is a side view showing the exhaust valve device according to the embodiment from an opening detection sensor side;

FIG. 5 is a perspective view showing the exhaust valve device according to the embodiment from the opening detection sensor side;

FIG. 6 is a side view showing the exhaust valve device according to the embodiment 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 according to the embodiment; and

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

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.

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.

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.

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.

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.

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.

Next, the exhaust valve device 1 will be described in detail on the basis of FIGS. 2 to 7.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

FIG. 8 shows a relationship between a position detection output (voltage) of the opening detection sensor 4 and an operating angle θ1 of the exhaust valve 2, an operating angle θ2 of the electric actuator 3, and a detection angle θ3 of the opening detection sensor 4. As shown in FIG. 8, a magnitude relationship of θ123 is established between θ1, θ2 and θ3. 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 θ1 of the exhaust valve 2, the operating angle θ2 of the electric actuator 3, and the detection angle θ3 of the opening detection sensor 4.

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 θ1, whereas the electric actuator 3 remains capable of rotating up to the operating angle θ2, which is larger than the operating angle θ1 of the exhaust valve 2. Hence, when the opening detection sensor 4 detects a larger rotation angle than θ1, the opening detection sensor 4 can determine that an abnormality has occurred in the exhaust valve device 1.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.