Exhaust flow control valve

Abstract

To provide an exhaust flow control valve capable of suppressing falling-off of a linkage.SOLUTION: An exhaust flow control valve (20) comprises a valve seat (30) having a valve hole (31) opened therein, a valve element (40) supported swingably so as to open and close the valve hole (31), a valve spring (25) urging the valve element (40) in a valve closing direction, and a linkage (50) which has one end abutting the valve seat (30) and the other end abutting the valve spring (25) and which can swing around a second fulcrum portion (P2) on the valve seat (30) in accordance with the position of the valve spring (25). The valve seat (30) includes a bent portion (33) that bends towards the linkage (50). A bent portion abutment portion (52) formed at the other end of the linkage (50) is shaped so as to abut only against the tip of the bent portion (33) in the fully closed state of the valve element (40), and to abut two places of the tip and the distal end of the bent portion (33) in the fully open state of the valve element (40).SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to an exhaust flow control valve. [Background technology]

[0002] Exhaust gas generated by an engine is sent to a muffler to reduce heat and sound energy. However, the flow rate of exhaust gas discharged from an engine is not constant and may suddenly increase. In such cases, an exhaust flow control valve is opened to allow a portion of the exhaust gas to escape outside the muffler. Patent Document 1 discloses a conventional technique related to an exhaust flow control valve used in this way.

[0003] The exhaust flow control valve as shown in Patent Document 1 has a valve seat with a valve hole that connects an upstream chamber and a downstream chamber in the muffler, a valve body that is arranged to be able to open and close the valve hole, a valve spring having one end that abuts against the valve body and urges the valve body in the closing direction, and a link that extends from the valve seat to the valve spring and swings in accordance with the swing of the valve body.

[0004] The other end of the valve spring is supported on the valve seat via a link, which allows the valve spring to swing together with the valve body. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5689837 Summary of the Invention [Problem to be solved by the invention]

[0006] When the present inventors studied the exhaust flow rate control valve disclosed in Patent Document 1, they found that there was a risk that the link would fall off when the valve body was opened.

[0007] An object of the present invention is to provide an exhaust flow control valve that can suppress the detachment of a link. [Means for solving the problem]

[0008] According to the present disclosure, there is provided a valve seat having a valve hole communicating between an upstream chamber and a downstream chamber in an exhaust system of an engine; a valve body that is swingably supported by a first fulcrum portion on the valve seat so as to open and close the valve hole, and receives the upstream pressure in a valve opening direction; a valve spring that biases the valve body in a valve closing direction and allows the valve body to open when the upstream pressure increases to or exceeds a predetermined value; a link having one end in contact with the valve seat and the other end in contact with the valve spring, the link being swingable about a second fulcrum portion on the valve seat in accordance with the position of the valve spring, the valve seat includes a bent portion bent toward the link, A tip of the bent portion serves as the second fulcrum portion, The other end of the link is a bent portion abutting portion formed so that the bent portion can abut against the other end of the link, An exhaust flow control valve is provided, characterized in that the bent portion abutment portion is shaped so as to abut only against the tip of the bent portion when the valve body is in a fully closed state, and to abut at two points, the tip and the end, of the bent portion when the valve body is in a fully open state. Effect of the Invention

[0009] The present invention can provide an exhaust flow control valve that can suppress the link from falling off. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a main portion of an exhaust muffler equipped with an exhaust flow control valve according to a first embodiment. [Diagram 2] FIG. 2 is a perspective view of the exhaust flow control valve shown in FIG. 1. [Diagram 3] FIG. 2 is an enlarged view of part 3 of FIG. [Figure 4] FIG. 3 is an exploded perspective view of the exhaust flow control valve shown in FIG. 2. [Diagram 5] FIG. 5 is a perspective view of the valve body shown in FIG. [Figure 6] FIG. 5 is a front view of the link shown in FIG. 4. [Figure 7] 2 is a diagram for explaining the operation of the exhaust muffler shown in FIG. 1. [Figure 8] FIG. 8 is an enlarged view of part 8 in FIG. [Figure 9] FIG. 9 is an enlarged view of part 9 in FIG. 8. [Figure 10] FIG. 11 is a perspective view of an exhaust flow control valve according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] An embodiment of the present invention will be described below with reference to the attached drawings. In the description, left and right refer to left and right based on the occupant of the vehicle on which the muffler is installed, and front and rear refer to front and rear based on the traveling direction of the vehicle. In the drawings, Fr indicates front, Rr indicates rear, Le indicates left as seen by the occupant, Ri indicates right as seen by the occupant, Up indicates up, and Dn indicates down.

[0012] <Example 1> Referring to Fig. 1, an exhaust muffler 10 constituting a part of the exhaust system of an engine E has an elliptical cylindrical muffler outer cylinder 11, an upstream lid portion 12 closing the upstream end of the muffler outer cylinder 11, a downstream lid portion 13 closing the downstream end of the muffler outer cylinder 11, and a first partition portion 30 and a second partition portion 15 which are two partitions fixed inside the muffler outer cylinder 11.

[0013] The interior of the muffler outer tube 11 is divided into a first chamber R1 separated by the upstream lid portion 12 and the first partition portion 30, a second chamber R2 separated by the first partition portion 30 and the second partition portion 15, and a third chamber R3 separated by the second partition portion 15 and the downstream lid portion 13.

[0014] The exhaust muffler 10 has a first pipe member 17 which is a pipe-shaped member that guides exhaust gas generated by the engine E from the upstream lid portion 12 to the first chamber R1, a second pipe member 18 which is a pipe-shaped member that penetrates the first partition portion 30 and the second partition portion 15 and guides the exhaust gas in the first chamber R1 to the third chamber R3, and a third pipe member 19 which is a pipe-shaped member that penetrates the second partition portion 15 and discharges the exhaust gas in the second chamber R2 from the downstream lid portion 13.

[0015] The first partition portion 30 has a valve hole 31 that communicates with the first chamber R1 and the second chamber R2, and the exhaust flow control valve 20 is provided to be able to open and close the valve hole 31. That is, the first partition portion 30 also serves as a valve seat for the exhaust flow control valve 20. Hereinafter, the first partition portion 30 may be referred to as the valve seat 30. It can also be said that the valve seat 30 is formed integrally with the first partition portion 30.

[0016] The second partition wall portion 15 is provided with a number of second partition wall holes 15a that allow exhaust gas to flow from the third chamber R3 to the second chamber R2.

[0017] Under normal conditions, exhaust gas generated by the engine E flows through the inside of the first pipe member 17 and is guided to the first chamber R1, passes through the inside of the second pipe member 18 and is guided from the first chamber R1 to the third chamber R3. The exhaust gas that reaches the third chamber R3 passes through the second partition hole 15a and reaches the second chamber R2, passes through the third pipe member 19 and is discharged from the second chamber R2 to the outside of the exhaust muffler 10.

[0018] The exhaust gas loses energy while passing through the inside of the exhaust muffler 10, so that its temperature drops and the sound produced when it is discharged into the atmosphere becomes quieter.

[0019] Any shape may be adopted for the shape of the muffler outer cylinder 11, and it may be a cylindrical shape or an elliptical shape. Also, the inside of the muffler outer cylinder 11 may be divided into two chambers, or may be divided into four or more chambers.

[0020] 2 to 4. The exhaust flow control valve 20 has a valve seat 30 in which a valve hole 31 is formed, a valve element 40 that opens and closes the valve hole 31, a support shaft 24 that is pressed against the valve element 40 by a valve spring 25, the valve spring 25 through which the support shaft 24 passes and which is supported by the support shaft 24, a link 50 that reduces and controls the valve-closing torque in accordance with an increase in the opening of the valve element 40, a buffer material 27 that is fixed to the valve seat 30 and that buffers the impact when the valve element 40 comes into contact with the valve seat 30, and a weight 28 that is attached to the valve element 40 and that adjusts the vibration characteristics.

[0021] Refer to Fig. 3. A fulcrum groove 32 is formed in the valve seat 30, protruding in a groove shape toward the first chamber R1. The groove bottom of the fulcrum groove 32 serves as a first fulcrum P1, which is the swing axis of the valve body 40. A bent portion 33 is formed in the valve seat 30 between the first fulcrum P1 and the valve hole 31, which is bent toward the link 50. The tip of the bent portion 33 serves as a second fulcrum P2, which is the swing axis of the link 50. A bulge 34 is formed in the valve seat 30 to bulge in order to accommodate the cushioning material 27, at a position opposite the bent portion 33 across the valve hole 31.

[0022] Please refer to Fig. 4. The valve body 40 is composed of a metal plate formed into a substantially rectangular shape, and one end of the valve body 40 is formed with a protrusion 41 that is bent so that its tip abuts against the first fulcrum portion P1, and a pair of stopper pieces 42 that are arranged on either side of the protrusion 41. Please refer to Fig. 3. The stopper pieces 42 are spaced apart from the valve seat 30 until the valve body 40 is fully open. The stopper pieces 42 abut against the valve seat 30 when the valve body 40 is fully open.

[0023] The valve element 40 can swing about the first fulcrum portion P1 from a fully closed position where the valve hole 31 is closed to a fully open position where the stopper piece 42 abuts against the valve seat 30 to fully open the valve hole 31.

[0024] A protrusion 43 is formed in the center of the valve body 40, which protrudes from the valve hole 31 in the closed state. The protrusion 43 has a trapezoidal cross section. The opposing surfaces of the protrusion 43 are inclined surfaces 43a formed in a tapered shape that widens toward the opening of the protrusion 43.

[0025] Please refer to Fig. 4. Valve spring 25 is made of a torsion coil spring and has coil portion 25a wound in a coil shape and through which support shaft 24 passes, rod-shaped first arm 25b extending linearly from one end of coil portion 25a, and second arm 25c extending from the other end, which is the center of coil portion 25a. A biasing force acts on valve spring 25 in a direction that increases the angle between first arm 25b and second arm 25c.

[0026] Two coil portions 25a are formed and are adjacent to each other on the same axis. One end of the coil portion 25a refers to the ends located at both ends of the two adjacent coil portions 25a. On the other hand, the other end of the coil portion 25a refers to the end of the two adjacent coil portions 25a that is adjacent to each other. The first arm 25b extends from one end of each coil portion 25a. The second arm portion 25c extends from the other end of each coil portion 25a and is connected to each other to form a substantially U-shape.

[0027] It is also possible to use a valve spring 25 having one each of the coil portion 25a, the first arm 25b, and the second arm 25c. In other words, the valve spring 25 is not limited to having two each of the coil portion 25a, the first arm 25b, and the second arm 25c.

[0028] Also refer to Fig. 3. The outer peripheral surface of coil portion 25a is disposed close to inclined surface portions 43a, 43a. Thus, a portion of coil portion 25a is housed in protrusion 43. The tip portions of the pair of first arms 25b are engaged with a pair of engagement claws 45 provided at the free end of valve body 40, and the tip portion of U-shaped second arm 25c passes through valve body hole 46. The tip of second arm 25c abuts against second fulcrum portion P2 via link 50 so as to be relatively swingable.

[0029] 3 and 5. The valve body 40 has a valve body hole 46 through which the second arm 25c passes. The valve body hole 46 has a substantially U-shape. The valve body hole 46 includes a clearance portion 46a that prevents contact with the second arm 25c when the second arm 25c is displaced relative to the valve body 40.

[0030] Referring only to Fig. 3, the support shaft 24 is generally formed in a U-shape and passes through the coil portion 25a. It is fixed to the valve body 40 so as to cross the opening of the protrusion 43 of the valve body 40. The arc surface of the support shaft 24 supports a part of the inner peripheral surface of the coil portion 25a, so that the outer peripheral surface of the coil portion 25a is raised above the inner peripheral surface of the protrusion 43.

[0031] By supporting a portion of the inner surface of coil portion 25a by spindle 24 fixed to valve body 40, and by raising the outer surface of coil portion 25a above the inner surface of convex portion 43, the friction area between coil portion 25a and its support portion is limited to one location. When the clamping angle between first arm 25b and second arm 25c changes in accordance with a change in the opening degree of valve body 40, the friction generated between coil portion 25a and spindle 24 can be kept small, and the valve body 40 can be opened and closed more smoothly.

[0032] Please refer to Figures 3 and 6. Link 50 is formed by bending a single, substantially rectangular metal plate into a substantially U-shape. Link 50 has a substantially rectangular shape when viewed from the front, and is provided with U-shaped spring contact portion 51 and bent portion contact portion 52 at both ends. Spring contact portion 51 and bent portion contact portion 52 are provided at opposing portions of the metal plate that is bent into a substantially U-shape. In other words, when link 50 is opened into a flat plate shape, the opened plate is line-symmetrical about the bent portion.

[0033] Refer only to FIG. 3. The U-shaped bent portion of the second arm 25c abuts against the spring abutment portion 51 so as to be able to swing freely. The bent portion 33 abuts against the bent portion abutment portion 52. One side of the bent portion abutment portion 52 extends along the longitudinal direction of the link 50 having a substantially rectangular shape (extending perpendicularly to the width direction), and the other side opposite to the one side extends obliquely to the longitudinal direction, so that the bent portion abutment portion 52 has a substantially U-shape that gradually opens toward the tip. The shape of the bent portion abutment portion 52 is such that it can abut against two points, the tip and the end, of the bent portion 33 when the valve body 40 is fully opened. In other words, the shape of the bent portion abutment portion 52 is such that it abuts against two points when fully opened, in accordance with the length, plate thickness, and extension angle of the bent portion 33.

[0034] A groove 53 recessed toward the center is formed in part of the side surface between the tip and the other end of the link 50. Also, corners 54 of the link 50 that face the valve body 40 are chamfered so as not to come into contact with the valve body. These grooves 53 and corners 54 are also formed in opposing positions.

[0035] The link 50 is not limited to a bent shape having a substantially U-shape in side view. The link 50 may be formed of a single plate. The shapes of the spring contact portion 51 and the bent portion contact portion 52 are not limited to a substantially U-shape. Any shape, such as a C-shape or a J-shape, may be adopted. In particular, it is important that the bent portion contact portion 52 contacts two points, the tip and the end of the bent portion 33, when the valve body 40 is fully open, and any shape may be adopted as long as this is satisfied.

[0036] A metal mesh can be used for the cushioning material 27. The cushioning material 27 is fixed to the bulging portion 34 by, for example, spot welding.

[0037] Weight 28 is fixed to the back surface of valve body 40 at a portion thereof that abuts against buffer material 27. Weight 28 is made of metal, for example, and is fixed to the back surface of valve body 40 by welding.

[0038] Next, the operation of the exhaust flow control valve 20 will be described.

[0039] When the valve spring 25 is attached, the coil portion 25a is supported on both inclined portions 43a, 43a of the convex portion 43 of the valve body 40 opposite the valve hole 31, and the first arm 25b is engaged with the locking claw 45 at the free end of the valve body 40 against the elastic repulsive force tending to widen the clamping angle between the first and second arms 25b, 25c, while the second arm 25c is supported on the second fulcrum portion P2 of the valve seat 30 via the link 50. As a result, the elastic repulsive force tending to widen the clamping angle between the first and second arms 25b, 25c urges the valve body 40 in the valve closing direction via the coil portion 25a.

[0040] Refer to FIG. 7. When the engine E shifts to a high-speed, high-load operating state, the flow rate of exhaust gas increases, and the pressure in the first chamber R1 rises. When the valve-opening torque of the valve element 40 caused by that pressure exceeds the valve-closing torque of the valve element 40 caused by the valve spring 25, the valve element 40 swings toward the fully open position, increasing the opening of the valve hole 31. Then, according to the opening of the valve hole 31, the exhaust gas that has left the first pipe member 17 and entered the first chamber R1 is short-circuited to the valve hole 31, and while being guided by the inclined valve element 40, it passes through the second chamber R2 and the third pipe member 19 and is released into the atmosphere. This reduces the back pressure and improves engine output.

[0041] Here, the valve closing torque applied to the valve body 40 by the valve spring 25 will be considered.

[0042] In FIG. 3, the elastic repulsive force acting on the second fulcrum P2 from the second arm 25c of the valve spring 25 via the link 50 is divided into a first component perpendicular to the line connecting the first and second fulcrum P1, P2, and a second component parallel to the line. The product of the first component and the distance between the first and second fulcrum P1, P2 is the valve-closing torque acting on the valve body 40.

[0043] 3 and 8, when the valve element 40 opens from the fully closed position, the second fulcrum P2 supporting the link 50 is offset toward the valve hole 31 from the first fulcrum P1 supporting the valve element 40, so that the angle at which the link 50 tilts about the second fulcrum P2 toward the valve seat 30 in response to the opening of the valve element 40 becomes larger than the opening angle of the valve element 40. Accordingly, the angle between the elastic repulsive force acting from the second arm 25c to the second fulcrum P2 and the first component force increases in response to the opening of the valve element 40, so that the first component force decreases. As a result, the closing torque of the valve element 40 due to the first component force decreases in response to the increase in the opening degree of the valve element 40, as shown in FIG. 8. Furthermore, the change in the angle between the first and second arms 25b, 25c as the opening of the valve body 40 changes is small, and therefore the friction generated between the coil portion 25a and the inclined surfaces 43a, 43a of the protrusion 43 is also extremely small.

[0044] Thus, when the valve body 40 starts to open due to the pressure in the first chamber R1, it automatically and smoothly swings to the fully open position, reliably reducing back pressure and airflow noise. Also, when the exhaust gas moves from the exhaust muffler 10 through the valve hole 31 to the second chamber R2, the inclined valve body 40 smoothly guides the flow of the exhaust gas, further reducing back pressure and airflow noise.

[0045] Please refer to Fig. 9. When the valve body 40 is in a fully open state, the bent portion abutment portion 52 abuts against two points, the leading end and the trailing end of the bent portion 33 (see P2 and P3).

[0046] 1 and 7. When the engine E returns to a low-speed, low-load operating state, the valve-opening torque of the valve element 40 due to the pressure in the first chamber R1 becomes smaller than the valve-closing torque of the valve spring 25, and the valve element 40 returns to the fully closed position.

[0047] Please refer to Fig. 3. In such an exhaust flow control valve 20, a part of the coil portion 25a of the valve spring 25 is housed in the protruding portion 43 of the valve body 40, thereby reducing the amount by which the coil portion 25a protrudes from the valve body 40, and the exhaust flow control valve 20 can be made more compact.

[0048] The valve spring 25 comprises a coil portion 25a, a pair of first arms 25b extending from both ends of the coil portion 25a, and a second arm 25c extending from the center of the coil portion 25a. The coil portion 25a is supported on the valve body 40, the tip portions of the pair of first arms 25b are engaged with a pair of locking claws 45 of the valve body 40, and the tip of the second arm 25c is abutted against the spring abutment portion 51. As a result, a closing torque is applied to the entire valve body 40 by the single valve spring 25, and the opening and closing positions of the valve body 40 can be stabilized.

[0049] <Example 2> Next, a second embodiment of the present invention will be described with reference to the drawings. An exhaust flow control valve 20A of the second embodiment is shown in Fig. 10. The same reference numerals are used for the parts common to the first embodiment, and detailed description thereof will be omitted.

[0050] The exhaust flow control valve 20A has a valve seat 30A that is formed of a separate member from the first partition portion 30 (see FIG. 2). The exhaust flow control valve 20A is, for example, welded to the first partition portion 30. The exhaust flow control valve 20A is provided so as to close a hole formed in the first partition portion 30.

[0051] The exhaust flow control valves 20, 20A described above will be summarized below.

[0052] Referring to Fig. 1, first, the exhaust flow control valve 20 has a valve seat 30 in which a valve hole 31 is formed, which communicates between an upstream chamber (first chamber R1) and a downstream chamber (second chamber R2) in the exhaust system of the engine E.

[0053] Refer to Fig. 8. The exhaust flow control valve 20 further includes a valve element 40 that is swingably supported at a first fulcrum P1 on the valve seat 30 so as to open and close the valve hole 31 and that receives upstream pressure in a valve opening direction, a valve spring 25 that urges the valve element 40 in a valve closing direction and allows the valve element 40 to open when the upstream pressure rises to or exceeds a predetermined value, and a link 50 that has one end abutting the valve seat 30 and the other end abutting the valve spring 25 and is swingable about a second fulcrum P2 on the valve seat 30 in accordance with the position of the valve spring 25.

[0054] The valve seat 30 includes a bent portion 33 that is bent toward the link 50. The tip of this bent portion 33 is the second fulcrum portion P2, and the other end of the link 50 is the bent portion abutment portion 52 that is formed so that the bent portion 33 can abut against it. The bent portion abutment portion 52 is shaped so that it abuts only against the tip of the bent portion 33 when the valve body 40 is in the fully closed state (see FIG. 3), and abuts against two points, the tip and the end of the bent portion 33, when the valve body 40 is in the fully open state.

[0055] See Fig. 9. When the valve body 40 is in a fully open state, the bent portion abutment portion 52 abuts at two points, the tip and end of the bent portion 33 (particularly preferably the underside of the end) (see P2 and P3). This makes it possible to prevent the link 50 from falling off, compared to when the bent portion abuts at one point. It is possible to provide an exhaust flow control valve 20 that can prevent the link 50 from falling off. The same applies to the exhaust flow control valve 20A (see Fig. 10).

[0056] See Fig. 8. Secondly, in the first exhaust flow control valve 20, the corners 54 of the link 50 are chamfered so as not to come into contact with the valve body 40. This makes it possible to prevent the link 50 from coming into contact with the valve body 40 and falling off. The same applies to the exhaust flow control valve 20A (see Fig. 10).

[0057] Thirdly, in the first or second exhaust flow control valve 20, the link 50 has a substantially rectangular shape, and a groove 53 recessed toward the center is formed in a portion of the side surface between the front end and the other end. This makes it possible to identify the direction during assembly, and prevents incorrect assembly. The same applies to the exhaust flow control valve 20A (see FIG. 10).

[0058] Fourth, in any one of the first to third exhaust flow control valves 20, the valve spring 25 includes a coil portion 25a wound in a coil shape, a rod-shaped first arm 25b extending linearly from one end of the coil portion 25a, and a second arm 25c extending from the other end of the coil portion 25a. A biasing force acts in a direction in which the angle formed by the first arm 25b and the second arm 25c widens.

[0059] Also see Fig. 5. The valve body 40 has a valve body hole 46 through which the second arm 25c passes. The valve body hole 46 includes a clearance portion 46a that prevents contact with the second arm 25c when the second arm 25c is displaced relative to the valve body 40.

[0060] This prevents contact between the second arm 25c and the valve body 40, and allows smooth operation of the valve body 40 and the link 50. The same applies to the exhaust flow control valve 20A (see FIG. 10).

[0061] See Fig. 3. Fifth, in any of the first to fourth exhaust flow control valves 20, a cushioning material 27 is provided at the portion of the valve seat 30 where the valve body 40 sits. This can suppress the generation of noise and can also suppress the leakage of exhaust gas when the valve is closed. The same applies to the exhaust flow control valve 20A (see Fig. 10).

[0062] Sixth, in the fifth exhaust flow control valve 20, a weight 28 for adjusting vibration characteristics is provided on the back side of the portion of the valve body 40 that abuts against the buffer material 27. This improves the vibration characteristics and suppresses the generation of noise. The same applies to the exhaust flow control valve 20A (see FIG. 10).

[0063] As long as the functions and effects of the present invention are achieved, the present invention is not limited to the examples. [Industrial Applicability]

[0064] The exhaust flow control valve of the present invention is suitable for use in a muffler of a four-wheeled vehicle. [Explanation of symbols]

[0065] E…Engine 10...Exhaust muffler 20, 20A…Exhaust flow control valve 25... valve spring, 25a... coil portion, 25b... first arm, 25c... second arm 27…Cushioning material 28... Weight 30, 30A…valve seat 31...Valve hole 40…Valve body 46: valve body hole portion, 46a: relief portion 50…Link 52...Bending portion contact portion 53…Groove 54…Corner P1: First support P2…Second fulcrum part R1: Room 1 (upstream room) R2: Room 2 (downstream room)

Claims

1. a valve seat having a valve hole communicating between an upstream chamber and a downstream chamber in an exhaust system of the engine; a valve body that is swingably supported by a first fulcrum portion on the valve seat so as to open and close the valve hole, and receives the upstream pressure in a valve opening direction; a valve spring that biases the valve body in a valve closing direction and allows the valve body to open when the upstream pressure increases to or exceeds a predetermined value; a link having one end in contact with the valve seat and the other end in contact with the valve spring, the link being swingable about a second fulcrum portion on the valve seat in accordance with the position of the valve spring, the valve seat includes a bent portion bent toward the link, A tip of the bent portion serves as the second fulcrum portion, The other end of the link is a bent portion abutting portion formed so that the bent portion can abut against the other end of the link, an exhaust flow control valve, characterized in that the bent portion abutment portion is shaped to abut only against the tip of the bent portion when the valve body is in a fully closed state, and to abut against two points, the tip and the end, of the bent portion when the valve body is in a fully open state.

2. 2. The exhaust flow control valve according to claim 1, wherein corners of the link are chamfered so as not to come into contact with the valve body.

3. 2. The exhaust flow control valve according to claim 1, wherein the link has a generally rectangular shape, and a groove recessed toward a center is formed in a portion of a side surface between the front end and the other end.

4. the valve spring includes a coil portion wound in a coil shape, a rod-shaped first arm extending linearly from one end of the coil portion, and a second arm extending from the other end of the coil portion, A biasing force acts in a direction in which the angle between the first arm and the second arm increases, The valve body has a valve body hole through which the second arm passes, 2. The exhaust flow control valve according to claim 1, wherein the valve body hole includes a relief portion that prevents contact with the second arm when the second arm is displaced relative to the valve body.

5. 2. The exhaust flow control valve according to claim 1, wherein a cushioning material is provided at a portion of the valve seat where the valve body sits.

6. 6. The exhaust flow control valve according to claim 5, further comprising a weight for adjusting vibration characteristics, provided on a rear surface of the valve body at a portion where the valve body abuts against the cushioning material.

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