Exhaust valve and muffler for automobile

Abstract

An exhaust valve 1 opens and closes an exhaust passage with a valve body 3 in accordance with exhaust pressure. The valve body 3 is swingably supported with respect to a valve seat 2 having an opening 22 via a support shaft 4. The valve body 3 is biased in a closing direction by a coil spring 5 externally inserted in the support shaft 4. An elastic cylinder part 73 having an outer diameter larger than an inner diameter of the coil spring 5 in an open state of the valve body 3 to be reduced by the valve body opening operation is externally inserted in the vicinity of both ends of the support shaft 4 and inserted in both end parts of the coil spring 5. The present invention is capable of easily and reliably adjusting and setting a biasing force in the closing direction of the valve body to an appropriate range, and ensuring a high level of durability.

Description

Exhaust valves and automotive mufflers

[0001] The present invention relates to an exhaust valve that is installed in an exhaust passage through which exhaust from an automobile or the like flows, and whose valve body opens and closes in response to exhaust pressure to adjust the amount of exhaust gas flowing through, and a muffler equipped with the exhaust valve.

[0002] Conventionally, an exhaust valve installed in an exhaust passage of an automobile is disclosed in Patent Document 1. In the exhaust valve of Patent Document 1, a valve element is supported via a support shaft so as to be able to swing relative to a valve seat having an opening, a coil spring fitted onto the support shaft biases the valve element in a closing direction, valve seat hooks are provided to circumferentially embrace both ends of the support shaft, and a valve element wrap-around portion is provided to circumferentially embrace the coil spring from the opposite direction to the valve seat hook and also to circumferentially embrace the coil spring over the entire length of the coil spring.

[0003] Furthermore, in this exhaust valve, the cylindrical cushioning material, which is composed of a cylindrical portion and a flange portion, is made of a metal mesh material, and the cylindrical cushioning material is fixed by fitting the cylindrical portions into both ends of the valve disc winding portion with the support shaft and coil spring inserted into the valve disc winding portion. Both ends of the support shaft are inserted into the cylindrical cushioning material fitted into the valve disc winding portion, and the pair of cylindrical cushioning materials serve as bearings for the support shaft.

[0004] Japanese Patent Application Laid-Open No. 2021-188516

[0005] In an exhaust valve such as that disclosed in Patent Document 1, in which a coil spring biases the valve disc in the closing direction and the valve disc opens and closes in response to exhaust pressure, if the biasing force in the closing direction of the valve disc is too strong, the valve disc will not open, and if the biasing force in the closing direction of the valve disc is too weak, the valve disc will flutter excessively, resulting in significant surging. Therefore, it is necessary to adjust the biasing force in the closing direction of the valve disc within an appropriate range so that the valve disc opens and closes appropriately in response to exhaust pressure.

[0006] The biasing force of the valve disc in the closing direction can be adjusted by adjusting the wire diameter and number of turns of the coil spring, but adjusting the biasing force to an appropriate range by solely adjusting the wire diameter and number of turns of the coil spring requires a great deal of trial and error effort. Also, while attaching a weight to the valve disc is one way to adjust the biasing force of the valve disc in the closing direction to suppress surging, the increased weight of the valve disc that opens and closes with the weight attached creates another problem: reduced durability of exhaust valve components such as the coil spring. Therefore, there is a need for an exhaust valve that can easily and reliably adjust and set the biasing force of the valve disc in the closing direction to an appropriate range while also ensuring high durability.

[0007] The present invention has been proposed in light of the above-mentioned problems, and aims to provide an exhaust valve in which the valve body is biased in the closing direction by a coil spring and opens and closes in response to exhaust pressure, in which the biasing force in the closing direction of the valve body can be easily and reliably adjusted and set within an appropriate range, and which can ensure high durability, and an automotive muffler equipped with this exhaust valve.

[0008] The exhaust valve of the present invention is an exhaust valve that opens and closes an exhaust passage with a valve element in response to exhaust pressure, the valve element being supported via a support shaft so as to be able to swing against a valve seat having an opening, the valve element being urged in the closing direction by a coil spring fitted around the support shaft, and elastic cylindrical portions having an outer diameter larger than the inner diameter of the coil spring when the valve element is in an open state, which contracts as the valve element opens, are fitted around both ends of the support shaft and inserted into both ends of the coil spring, respectively. According to this, when the inner diameter of the coil spring contracts as the valve element opens, the opening movement of the valve element is suppressed by the resistance of the elastic cylindrical portions, thereby eliminating the need to adjust the urging force of the valve element in the closing direction by trial and error, which requires a great deal of effort, by simply adjusting the wire diameter or number of turns of the coil spring. For example, adjusting the wire diameter or number of turns of the coil spring to increase the spring rate and increase the frictional resistance between the coil spring windings in order to suppress surging, which is the tendency of the valve disc to flutter significantly, can result in insufficient valve disc opening. However, with the exhaust valve of the present invention, even if the spring rate of the coil spring is lowered to make the valve disc easier to open, surging can be suppressed by suppressing the opening movement of the valve disc due to the resistance of the elastic cylindrical portion. Therefore, the biasing force of the valve disc in the closing direction can be easily and reliably adjusted and set within an appropriate range so that the valve disc opens and closes appropriately according to the expected exhaust pressure. Furthermore, since there is no need to attach a weight to the valve disc to suppress surging and there is no increase in the weight of the valve disc that opens and closes, high durability of the exhaust valve components, such as the coil spring, and the exhaust valve itself can be ensured. Furthermore, since there is no need to use expensive coil springs with excessively high spring rates or weights attached to the valve disc, the manufacturing costs and parts costs of the exhaust valve can be reduced.

[0009] The exhaust valve of the present invention is characterized in that the elastic tubular portion is press-fitted into the coil spring, which has an inner diameter larger when the valve disc is in a closed state than when the valve disc is in an open state. With this, from the start of the opening movement of the valve disc, the surging energy that is transmitted to the coil spring and causes the valve disc to flutter can be consumed by the elastic tubular portion, and surging can be suppressed throughout the entire opening and closing movement of the valve disc.

[0010] The exhaust valve of the present invention is characterized in that the valve disc is provided with a valve disc winding portion that circumferentially embraces the coil spring over the entire length of the coil spring, the base tubular portion of a cylindrical cushioning material consisting of a base tubular portion and a flange portion is internally fitted to both ends of the valve disc winding portion, the elastic tubular portion is integrally formed with the cylindrical cushioning material, and the pair of cylindrical cushioning materials serve as bearings for the spindle. By integrally forming the elastic tubular portion with the cylindrical cushioning material that serves as a bearing for the spindle, the number of parts can be reduced, further reducing the manufacturing cost of the exhaust valve. Furthermore, by using a pair of cylindrical cushioning materials with integral elastic tubular portions as bearings for the spindle, the strength and impact resistance of the bearing for the spindle can be increased. Furthermore, since the elastic tubular portion can be inserted externally onto the spindle and then inserted internally into the coil spring in conjunction with the internal fitting of the cylindrical cushioning material into the valve disc winding portion, the manufacturing process of the exhaust valve can be made more efficient.

[0011] The exhaust valve of the present invention is characterized in that valve seat hooks are provided on the valve seat to circumferentially embrace both ends of the support shaft and are fixed to the support shaft, and the valve disc wrapping portions are provided to circumferentially embrace the coil spring from the opposite direction to the valve seat hooks. According to this, by providing the valve seat hooks of the valve seat to circumferentially embrace both ends of the support shaft and fixing them to the support shaft, and by providing the valve disc wrapping portions to circumferentially embrace the coil spring from the opposite direction to the valve seat hooks and to wrap around the coil spring circumferentially over the entire length of the coil spring, it is possible to prevent or minimize axial misalignment of the coil spring, which is inserted coaxially with the support shaft for opening and closing the valve disc. Furthermore, by eliminating or minimizing axial misalignment between the coil spring and the support shaft, the biasing force of the coil spring, into which the elastic cylindrical portion is inserted, in the valve disc closing direction can be more accurately adjusted and set within an optimal range.

[0012] The automotive muffler of the present invention is characterized in that the valve seat base plate of the valve seat in the exhaust valve of the present invention is fixed to the periphery of the opening of a separator that divides the interior of the muffler installed in the exhaust path. By installing the exhaust valve of the present invention in the separator of an automotive muffler, the exhaust valve can be closed when the engine speed is low to prevent the passage of pressure waves that cause noise, and can be opened when the engine speed is high to allow the exhaust to pass, thereby ensuring engine output. In other words, by installing an exhaust valve in an automotive muffler with an appropriate biasing force of the valve disc in the closing direction adjusted and set within an appropriate range, it is possible to reliably achieve both quietness during regular city driving and sufficient engine output during high-speed driving.

[0013] According to the present invention, in an exhaust valve in which a coil spring biases a valve body in the closing direction and the valve body opens and closes in response to exhaust pressure, the biasing force of the valve body in the closing direction can be easily and reliably adjusted and set within an appropriate range, and a high degree of durability can be ensured.

[0014] 1 is a perspective view showing an exhaust valve according to an embodiment of the present invention in a closed state; 2 is a perspective view showing an exhaust valve according to an embodiment in an open state; 3 is an exploded perspective view of an exhaust valve according to an embodiment; 4 is a perspective explanatory view showing a coil spring and a cylindrical cushioning material in an exhaust valve according to an embodiment; 5 is an explanatory view showing a coil spring, a cylindrical cushioning material, and a support shaft in an exhaust valve according to an embodiment; 6 is an explanatory view of an automotive muffler in which an exhaust valve according to an embodiment is attached to a separator; 7 is a front view of an exhaust valve according to an embodiment attached to a separator;

[0015] [Exhaust Valve of an Embodiment] An exhaust valve 1 of an embodiment according to the present invention is installed in, for example, a muffler in an exhaust passage of an automobile, and opens and closes the exhaust passage in response to the exhaust pressure of the engine, and is preferably attached to a separator that divides the interior of the muffler. As shown in Figures 1 to 3, the exhaust valve 1 comprises a valve seat 2, a valve element 3 that opens and closes, a support shaft 4, a coil spring 5, a ring buffer 6, and a cylindrical buffer 7. The valve element 3 is supported via the support shaft 4 so as to be able to swing relative to the valve seat 2, and is biased in the closing direction by the coil spring 5 that is fitted around the support shaft 4.

[0016] The valve seat 2 has a valve seat substrate 21 formed in a generally flat ring shape that is arranged, for example, along the separator, and an opening 22 that forms an exhaust path that is opened and closed is provided in the center of the valve seat substrate 21. The valve seat 2 is provided with a pair of valve seat hooks 23, 23 spaced apart on both sides of the width of the valve seat substrate 21. The valve seat hook 23 rises obliquely upward from the upper end portion of the valve seat substrate 21 in the figure, and is curved in an arc on the back side of the valve seat substrate 21, and is formed integrally with the valve seat substrate 21.

[0017] A pair of valve seat hooks 23, 23 are provided near both ends of the support shaft 4. The valve seat hooks 23 in the illustrated example are engaged with the support shaft 4 by circumferentially embracing both ends of the support shaft 4 from the valve body 3 side, and are fixed to the support shaft 4 by welded portions 41 formed on both ends of the support shaft 4. The shape and size of the inner peripheral surface of the tip of the valve seat hook 23 are formed to approximately match the shape and size of the outer peripheral surface of the support shaft 4 with which it engages.

[0018] The valve seat base plate 21 of the valve seat 2 is provided with a welding area 241 on the spindle 4 side that protrudes outward from the outer periphery of the valve body base plate 31 of the valve body 3 in a closed state, which will be described later, and a tongue-shaped welding area 242 located on the opposite side from the spindle 4. The welding areas 241, 242 are used as welding locations when, for example, attaching the exhaust valve 1 to a separator of a muffler by welding.

[0019] A ring buffer material 6 having a substantially flat ring shape is fixed by welding or the like to the valve seat substrate 21 on the valve disc 3 side, and is provided at a position substantially corresponding to a flat edge 32 of the valve disc 3 described below, so as to buffer the impact of the closing operation of the valve disc 3. The ring buffer material 6 can be any suitable buffer material that has a buffering function due to elasticity or the like and is heat resistant, and a metal mesh material is preferable, for example.

[0020] The valve 3 has a valve substrate 31, which is formed in the shape of a flat dish with a flat edge 32. The front surface of the valve substrate 31 is provided with a recess 33 that is generally circular in plan view and recessed so as to protrude toward the valve seat 2, and the flat edge 32 is formed in a ring shape around the periphery of the recess 33 or around the protruding portion of the recess 33.

[0021] The valve 3 has a valve body winding portion 34 that protrudes from the support shaft 4 side of the valve body substrate 31 and curves in a hook shape so as to fold back from the valve body substrate 31. The valve body winding portion 34 protrudes from the valve body substrate 31 in the opposite direction to the valve seat 2 in the closed state and is formed integrally with the valve body substrate 31. The shape and size of the inner circumferential surface of the valve body winding portion 34 are formed so as to roughly follow the shape and size of the outer circumferential surface of the coil body 51 of the coil spring 5, and the size of the inner circumferential surface of the valve body winding portion 34 is slightly larger than the size of the outer circumferential surface of the coil body 51.

[0022] In a cross-sectional view, the valve body winding portion 34 is formed to be curved in an arc shape that exceeds a semicircle, preferably an arc shape that exceeds a ¾ circle or is approximately a ¾ circle, and is arranged to circumferentially embrace the coil spring 5 that is extrapolated onto the support shaft 4 from the opposite direction to the direction in which the valve seat hook portion 23 circumferentially embraces the support shaft 4, and in this embodiment, the valve body winding portion 34 is arranged to circumferentially embrace the coil spring 5 from the valve seat side over the entire length of the coil spring 5.

[0023] The valve element wrapping portion 34 is formed to extend in the width direction at approximately the center of the valve element base plate 31 in the width direction, and is formed as a continuous, elongated portion having a length that fits between the pair of valve seat hooks 23, 23 of the valve seat 2. The continuous, elongated valve element wrapping portion 34 is provided so as to embrace the coil spring 5, which is inserted around the support shaft 4, in the circumferential direction over the entire length of the coil spring 5.

[0024] Cylinder cushioning materials 7, 7 are provided on both ends of the valve body wrapping portion 34. The cylinder cushioning material 7 is composed of a base cylinder portion 71, a flange portion 72 that protrudes outward from one axial end of the base cylinder portion 71, and an elastic cylinder portion 73 that protrudes from the outer end side of the axial direction of the base cylinder portion 71, and the base cylinder portion 71, flange portion 72, and elastic cylinder portion 73 are integrally formed.

[0025] With the support shaft 4 and coil spring 5 inserted into the valve disc winding portion 34, the tubular cushioning materials 7, 7 are fixed by fitting the base tubular portions 71, 71 respectively onto both ends of the valve disc winding portion 34, and the flange portions 72 are fitted into the base tubular portions 71 so as to abut against the widthwise end faces of the valve disc winding portion 34. The flange portions 72 are respectively arranged between the widthwise end faces of the valve disc winding portion 34 and the inner end faces of the valve seat hook portions 23 of the valve seat 2, and are arranged close to the inner end faces of the valve seat hook portions 23.

[0026] The valve body winding portion 34 is engaged with the support shaft 4, which is inserted through the tubular cushioning materials 7, 7, via the tubular cushioning materials 7, 7; in other words, the pair of tubular cushioning materials 7, 7 fitted into the valve body winding portion 34 serve as bearings for the support shaft 4 of the valve body 3. For the tubular cushioning material 7, any appropriate cushioning material that has a cushioning function due to elasticity or the like and is heat resistant can be used; for example, a metal mesh material is preferable.

[0027] An elastic cylindrical portion 73 made of a metal mesh material or the like that is provided integrally with the cylindrical cushioning material 7 has an outer diameter that is larger than the inner diameter of the coil spring 5 in the open state of the valve disc 3, which contracts when the valve disc 3 is in an opening state, in other words, the inner diameter of the coil body 51 of the coil spring 5. The elastic cylindrical portion 73 is fitted externally around both ends of the support shaft 4, and is also fitted internally into both ends of the coil spring 5, in other words, both ends of the coil body 51 of the coil spring 5. In this embodiment, the elastic cylindrical portion 73 is press-fitted into the coil spring 5 or the coil body 51 in the closed state of the valve disc 3, whose inner diameter is larger than the inner diameter when the valve disc 3 is in an open state (see FIGS. 4 and 5 ).

[0028] The wound coil body 51 of the coil spring 5 is disposed within the valve body winding portion 34 over its entire length and is fitted onto the support shaft 4. One arm 52 of the coil spring 5 is disposed to extend to the front side of the valve body base plate 31 of the valve body 3 near the base of the valve body winding portion 34, that is, to the front side of the flat edge 32 in the illustrated example, and the other arm 53 of the coil spring 5 is disposed to extend to the rear side of the rising portion of the valve seat hook 23 near the base of the valve seat hook 23, and is biased and pressed in the direction of closing the valve body 3 by the one arm 52 of the coil spring 5.

[0029] A notch 35 is formed on one side in the width direction of the valve body base plate 31 near the rising portion of the valve body wrapping portion 34 of the valve body 3, and the other arm 53 of the coil spring 5 is led out from the notch 35 to the back side of the valve body base plate 31. The other arm 53 of the coil spring 5 is led out to the back side near the base of the valve seat hook 23 through the space between the notch 35 and the valve seat hooks 23, 23, and presses and urges the rising portion of the valve seat hook 23 from the back side.

[0030] Between the valve seat hooks 23 of the valve seat 2, there is formed a rising portion 25 that rises at the same angle as the rising portion of the valve seat hook 23 at a height lower than the rising portion of the valve seat hook 23. The other arm 53 of the coil spring 5 passes through the notch 35 and the tip surface side of the rising portion 25 and is led out to the back side near the base of the valve seat hook 23.

[0031] The exhaust valve 1 of this embodiment is preferably used by attaching it to the separator 102 of a muffler 100 shown in Figures 6 and 7. The muffler 100 has a housing 101 whose interior is divided by a flat first separator 102 and a flat second separator 103, and is provided with an expansion chamber 104, a resonance chamber 105, and an expansion chamber 106. The second separator 103, which separates the expansion chamber 104 and the resonance chamber 105, has a large number of small holes (not shown) formed over its entire surface.

[0032] The muffler 100 includes an exhaust inlet pipe 107 that communicates with the engine's exhaust pipe and introduces exhaust into the housing 101, and an exhaust outlet pipe 108 that discharges exhaust from the housing 101. The exhaust inlet pipe 107 is provided so as to pass through the first separator 102 from the outer wall on the expansion chamber 106 side, crossing the expansion chamber 106, with the expansion chamber 104 serving as the outlet for the exhaust inlet pipe 107. The exhaust outlet pipe 108 is provided so as to pass through the second separator 103 and the first separator 102, crossing the resonance chamber 105 and the expansion chamber 104, with the expansion chamber 106 serving as the intake for the exhaust outlet pipe 108.

[0033] An exhaust circulation pipe 109 that is bent in a roughly σ shape is provided inside the housing 101, and is formed with a smaller diameter than the exhaust introduction pipe 107 and the exhaust discharge pipe 108. The exhaust circulation pipe 109 has an intake opening in the expansion chamber 104, penetrates the second separator 103 at two locations, on the introduction side and the discharge side, and is arranged to cross the resonance chamber 105 in a roughly arc shape, and is further arranged to cross the expansion chamber 104 and penetrate the first separator 102, and is curved so as to turn back inside the expansion chamber 106, with an outlet located near the inlet of the exhaust discharge pipe 108.

[0034] The exhaust valve 1 is provided on the expansion chamber 106 side of the first separator 102, and is arranged at a position corresponding to an opening that serves as an exhaust path in the first separator 102 so as to close the opening. The exhaust valve 1 has a valve seat substrate 21 that is substantially flat and ring-shaped arranged to correspond to the periphery of the opening in the first separator 102, and is welded to the periphery of the opening in welding regions 241, 242 of the valve seat substrate 21 with welds 110 such as spot welding, so that the valve seat substrate 21 is fixed to the periphery of the opening in the first separator 102.

[0035] In the muffler 100, when the engine exhaust pressure is below a predetermined pressure, the exhaust flows as shown by the thick solid arrows in Figure 6, from the exhaust inlet pipe 107 to the expansion chamber 104, the exhaust circulation pipe 109 in the expansion chamber 104, the exhaust circulation pipe 109 in the resonance chamber 105, the exhaust circulation pipe 109 in the expansion chamber 104, the exhaust circulation pipe 109 in the expansion chamber 106, and finally the exhaust lead-out pipe 108. At this time, the valve element 3 of the exhaust valve 1 is continuously biased in the closing direction by the coil spring 5, and the valve element 3 is maintained in a closed state, thereby providing a high noise reduction effect.

[0036] When the engine exhaust pressure in the muffler 100 exceeds a predetermined pressure, the exhaust pressure opens the valve element 3 of the exhaust valve 1 against the closing bias of the coil spring 5, creating an exhaust flow indicated by a thick, two-dot chain arrow in addition to the exhaust flow indicated by the thick, solid arrow in Figure 6. That is, the exhaust flow is added in this order from the exhaust inlet pipe 107 to the expansion chamber 104, through the exhaust path of the open exhaust valve 1, through the expansion chamber 106, through the gap between the exhaust circulation pipe 109 and the exhaust lead-out pipe 108, and back through the exhaust lead-out pipe 108, reducing the engine exhaust back pressure. Thereafter, when the engine exhaust pressure drops below the predetermined pressure, the valve element 3 closes while being cushioned by the ring cushion 6, and abuts against the ring cushion 6 or the valve seat substrate 21.

[0037] According to the exhaust valve 1 of this embodiment, when the inner diameter of the coil spring 5 decreases during the opening movement of the valve disc 3, the resistance of the elastic tubular portion 73 suppresses the opening movement of the valve disc 3, eliminating the need to laboriously adjust the biasing force of the valve disc 3 in the closing direction by trial and error, relying solely on adjusting the wire diameter or number of turns of the coil spring 5. For example, if the wire diameter or number of turns of the coil spring 5 is adjusted to increase the spring rate and increase the frictional resistance between the windings of the coil spring 5 in order to suppress surging, which is the tendency of the valve disc 3 to flutter significantly, this can result in insufficient opening of the valve disc 3. However, with the exhaust valve 1 of this embodiment, even if the spring rate of the coil spring 5 is reduced to make the valve disc 3 easier to open, surging can be suppressed by suppressing the opening movement of the valve disc due to the resistance of the elastic tubular portion 73. Therefore, the biasing force of the valve disc 3 in the closing direction can be easily and reliably adjusted and set within an appropriate range so that the valve disc 3 opens and closes appropriately according to the expected exhaust pressure.

[0038] Furthermore, since there is no need to attach a weight to the valve element 3 to suppress surging and there is no increase in the weight of the valve element 3 that opens and closes, it is possible to ensure high durability of the components of the exhaust valve 1, such as the coil spring 5, and of the exhaust valve 1. Furthermore, since there is no need to use an expensive coil spring with an excessively high spring rate or a weight attached to the valve element 3, the manufacturing costs and parts costs of the exhaust valve 1 can be reduced.

[0039] Furthermore, by press-fitting the elastic cylindrical portion 73 into the coil spring 5 when the valve body 3 is in the closed state, which has an inner diameter larger than that of the valve body 3 in the open state, the surging energy that is transmitted to the coil spring 5 and causes the valve body 3 to flutter can be consumed by the elastic cylindrical portion 73 from the start of the opening operation of the valve body 3, and surging can be suppressed throughout the entire opening and closing operation of the valve body 3.

[0040] Furthermore, by integrally providing the elastic cylindrical portion 73 with the cylindrical buffer material 7, which serves as a bearing for the spindle 4, the number of parts can be reduced, further reducing the manufacturing cost of the exhaust valve 1. Furthermore, by using a pair of cylindrical buffer materials 7, 7 with the elastic cylindrical portion 73 integrally provided therewith as a bearing for the spindle, the strength and impact resistance of the bearing for the spindle can be increased. Furthermore, since the elastic cylindrical portion 73 can be inserted externally onto the spindle 4 and internally into the coil spring 5 in conjunction with the internal fitting of the cylindrical buffer material 7 into the valve body wrapping portion 34, the manufacturing process for the exhaust valve 1 can be made more efficient.

[0041] Furthermore, by providing the valve seat hook 23 of the valve seat 2 so as to circumferentially embrace both ends of the support shaft 4 and fix it to the support shaft 4, and providing the valve disc wrapping portion 34 so as to circumferentially embrace the coil spring 5 from the opposite direction to the valve seat hook 23 and circumferentially embrace the coil spring 5 over the entire length of the coil spring 5, it is possible to prevent or minimize as much as possible any axial misalignment of the coil spring 5 that is inserted coaxially with the support shaft 4 for opening and closing the valve disc. Furthermore, by eliminating or minimizing as much as possible any axial misalignment between the coil spring 5 and the support shaft 4, the biasing force of the coil spring 5, into which the elastic cylindrical portion 73 is inserted, in the valve disc closing direction can be more accurately adjusted and set within an optimal range.

[0042] Furthermore, by installing the exhaust valve 1 in the first separator 102 of the muffler 100 for an automobile, the exhaust valve 1 can be closed when the engine speed is low to prevent the passage of pressure waves that are a source of noise, and can be opened when the engine speed is high to allow the exhaust to pass, thereby ensuring engine output. In other words, by installing the exhaust valve 1 in the muffler 100 for an automobile, with the biasing force of the valve body 3 in the closing direction adjusted and set within an appropriate range, it is possible to reliably achieve both quietness during regular city driving and sufficient engine output during high-speed driving.

[0043] [Scope of the invention disclosed herein] The invention disclosed herein includes, in addition to the individual inventions and embodiments listed as inventions, those specified by modifying partial contents of these with other contents disclosed in the present specification, those specified by adding other contents disclosed in the present specification to these contents, or those specified by deleting partial contents of these to the extent that partial effects are obtained and creating a generic concept. The invention disclosed herein also includes the following modifications and additions.

[0044] For example, the exhaust valve of the present invention also includes a configuration in which the elastic tubular portion is loosely inserted into the coil spring without being press-fitted when the valve disc is in a closed state, which has an inner diameter larger than that of the valve disc in the open state. The elastic tubular portion in the exhaust valve of the present invention may be any appropriate portion within the spirit and scope of the present invention, and is not limited to the elastic tubular portion 73 formed integrally with the tubular cushioning material 7 in the above embodiment. The valve disc wrapping portion in the exhaust valve of the present invention may be any appropriate valve disc wrapping portion formed on the valve disc so as to embrace the coil spring in the circumferential direction over the entire length of the coil spring, and is not limited to the valve disc wrapping portion 34 in the above embodiment.

[0045] For example, in the exhaust valve 1 of the above embodiment, the ring cushioning material 6 having a substantially flat ring shape is fixed to the valve seat substrate 21, but the ring cushioning material 6 having a substantially flat ring shape may be fixed to the valve seat 2 side of the flat edge 32 of the valve body substrate 31. Furthermore, the fixing structure for fixing the valve seat substrate 21 of the exhaust valve 1 to the periphery of the opening of the separator of the muffler 100 can be any suitable fixing structure within the spirit and scope of the present invention, other than welding at the welded joints 110 of the welding regions 241, 242.

[0046] Furthermore, the exhaust valve of the present invention is preferably an exhaust valve that is attached to a separator that divides the inside of an automobile muffler, but it can also be attached to the end of an exhaust pipe that is installed in an automobile muffler, for example, and can be installed at an appropriate location in an automobile exhaust duct within the applicable range, and further, can be installed at an appropriate location in an exhaust duct other than an automobile within the applicable range.

[0047] The present invention can be used, for example, as an exhaust valve attached to a separator that divides the inside of a muffler in an exhaust passage of an automobile.

[0048] DESCRIPTION OF SYMBOLS 1...Exhaust valve 2...Valve seat 21...Valve seat base plate 22...Opening 23...Valve seat hook portion 241, 242...Welding area 25...Upright portion 3...Valve body 31...Valve body base plate 32...Flat edge 33...Recess 34...Valve body winding portion 35...Notch 4...Support shaft 41...Welded portion 5...Coil spring 51...Coil body 52...One arm 53...Other arm 6...Ring cushioning material 7...Cylinder cushioning material 71...Base cylinder portion 72...Flange portion 73...Elastic cylinder portion 100...Muffler 101...Housing 102...First separator 103...Second separator 104...Expansion chamber 105...Resonance chamber 106...Expansion chamber 107...Exhaust inlet pipe 108...Exhaust outlet pipe 109...Exhaust circulation pipe 110...welded section

Claims

1. An exhaust valve which opens and closes an exhaust passage with a valve body in response to exhaust pressure, wherein the valve body is supported via a support shaft so that it can swing against a valve seat having an opening, the valve body is urged in the closing direction by a coil spring fitted onto the support shaft, and an elastic cylindrical portion having an outer diameter larger than the inner diameter of the coil spring in the open state of the valve body which contracts as the valve body opens is fitted onto the outside near both ends of the support shaft and fitted into both ends of the coil spring.

2. An exhaust valve as claimed in claim 1, characterized in that the elastic cylindrical portion is press-fitted into the coil spring, the inside diameter of which is larger when the valve body is in a closed state than when the valve body is in an open state.

3. An exhaust valve as claimed in claim 1 or 2, characterized in that the valve body is provided with a valve body wrapping portion that is arranged to circumferentially embrace the coil spring over the entire length of the coil spring, the base tube portion of a tubular cushioning material consisting of a base tube portion and a flange portion is fitted into both ends of the valve body wrapping portion, the elastic tubular portion is integrally formed with the tubular cushioning material, and the pair of tubular cushioning materials serve as bearings for the support shaft.

4. An exhaust valve as described in claim 3, characterized in that a valve seat hook portion is provided on the valve seat so as to circumferentially embrace both ends of the support shaft and is fixed to the support shaft, and the valve body winding portion is provided so as to circumferentially embrace the coil spring from the opposite direction to the valve seat hook portion.

5. An automotive muffler, characterized in that the valve seat base plate of the valve seat in the exhaust valve according to claim 1 or 2 is fixed to the periphery of the opening of a separator which divides the inside of the muffler to be installed in the exhaust passage.

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