JP4775355B2 - Valve unit for silencer - Google Patents

Description

  The present invention relates to a silencer valve device for reducing noise generated from an exhaust system when the exhaust pressure becomes high.

Generally, in a vehicle, it is required to sufficiently secure an output in a high-speed rotation range of the engine. Further, in order to ensure quietness during idling or low-speed running, it is required to reduce exhaust noise in the low-speed rotation region of the engine.
Here, the exhaust noise is greatly influenced by the cross-sectional area of the exhaust passage. That is, if the cross-sectional area of the flow path is increased, it becomes easier to secure the output of the engine by reducing the exhaust resistance, but the exhaust noise is increased by reducing the exhaust resistance. On the other hand, if the cross-sectional area of the exhaust flow path is reduced, the exhaust noise can be reduced by increasing the exhaust resistance, but this increases the exhaust resistance and leads to a decrease in engine output.

In order to cope with this, a bypass flow path may be connected to an exhaust flow path in the silencer provided in the exhaust system via a silencer valve device.
As the silencer valve device, for example, there is a device described in Patent Document 1. This silencer valve device includes a plate valve that opens and closes a valve hole formed in the exhaust flow path, and a plate spring member that urges the plate valve in the valve closing direction.
When the exhaust pressure exceeds a predetermined pressure, the plate valve is displaced in the valve opening direction against the spring force of the leaf spring, so that the bypass passage communicates with the exhaust passage and the exhaust passage is disconnected. The area increases.
JP 2006-63937 A

In the silencer valve device having the above configuration, the plate-like valve gradually opens as the exhaust pressure increases. For this reason, the exhaust noise gradually increases as the exhaust pressure increases. Further, the plate valve opens as the exhaust pressure increases, but the urging force in the valve closing direction increases as the plate valve opens. For this reason, the valve body is less likely to be displaced in the opening direction as the exhaust pressure increases.
Here, when considering application to a vehicle, from the viewpoint of achieving both quietness and engine output, it is desired to set a small range of the engine speed at which the exhaust noise is switched off and the noise is increased. However, the above-described conventional device has a problem that it is difficult to reduce the width of the engine speed at which the exhaust noise is switched between silence and increase.
The present invention pays attention to the above points, and an object of the present invention is to provide a silencer valve device capable of reducing the width of the engine speed at which the exhaust noise is switched between silence and increase.

  In order to solve the above-described problems, the silencer valve device of the present invention closes the valve body by sliding the free end against the sliding contact surface provided on the back surface of the valve body that opens and closes the valve hole. A spring member that generates a spring force that biases in the direction is provided. The spring force can be increased by rotationally displacing the free end portion about a predetermined base end axis. Further, the sliding contact surface provided on the valve body includes a first sliding contact surface that is in sliding contact with the valve body in a closed state, and a sliding surface that is continuous with the first sliding contact surface and is displaced in the valve opening direction. And a second slidable contact surface. And the inclination with respect to the surface orthogonal to the pressing force in the valve opening direction of the second sliding contact surface is set larger than that of the first sliding contact surface. The base end shaft is disposed closer to the valve body than a straight line passing through the sliding contact boundary portion and the valve body rotation shaft when viewed from the axial direction of the valve body rotation shaft, and the second sliding contact surface Is arranged on the inner diameter side of the first virtual arc that constitutes a part of a circle passing through the sliding contact boundary centering on the valve body rotation axis as viewed from the axial direction of the valve body rotation shaft.

  According to the present invention, when the valve body is opened and the free end portion shifts from the first sliding contact surface to the second sliding contact surface, the spring force in the valve closing direction by the spring member can be set to be significantly small. Become. That is, when the exhaust pressure in the exhaust passage exceeds a predetermined value, the spring force in the valve closing direction by the spring member is significantly reduced, and the exhaust pressure in the exhaust passage can be rapidly reduced. . As a result, it is possible to reduce the width of the engine speed at which the exhaust noise is switched between silence and increase.

(First embodiment)
Next, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an example of a silencer (muffler) provided with the silencer valve device of the present embodiment.
(Constitution)
The silencer includes a casing 1 having a substantially elliptical cross section. A space in the casing 1 is divided into four chambers by three baffle plates 6, 7, and 8. The four chambers constitute a third expansion chamber 4, a second expansion chamber 3, a first expansion chamber 2, and a resonance chamber 18 from the right side in FIG.

Reference numeral 5 denotes an inlet tube that guides exhaust from the engine 30 into the casing 1. The inlet tube 5 sequentially passes through the second expansion chamber 3 and the first expansion chamber 2, and positions the downstream opening end in the first expansion chamber 2. That is, the inlet tube 5 guides exhaust from the engine 30 to the first expansion chamber 2.
The first expansion chamber 2 and the second expansion chamber 3 communicate with each other via a pass tube 9 that penetrates the baffle plate 6. Similarly, the first expansion chamber 2 and the resonance chamber 18 communicate with each other via neck tubes 16 and 17 penetrating the baffle plate 8.

Further, the tail tube 10 communicates the second expansion chamber 3 with the outside. That is, the tail tube 10 protrudes outside the casing 1 after sequentially passing through the second expansion chamber 3, the first expansion chamber 2, and the resonance chamber 18. The tail tube 10 has a predetermined diameter and length that emphasizes the reduction of exhaust noise in the low-speed rotation region of the engine 30.
The second expansion chamber 3 and the third expansion chamber 4 that are adjacent to each other via the baffle plate 7 have a predetermined capacity that emphasizes reduction of exhaust noise in the high-speed rotation region of the engine 30. A tail tube 11 communicating with the outside opens in the third expansion chamber 4, and the tail tube 11 protrudes outside the casing 1 in parallel with the tail tube 10.

  Here, in the two tail tubes 10 and 11, a portion where a section passing through the first expansion chamber 2 and the resonance chamber 18 is located forms a sound absorbing portion. In this sound absorbing portion, a porous portion 19 composed of a large number of through holes is formed on the inner periphery, and a sound absorbing material 20 for attenuating airflow sound is provided on the outer periphery of the tail tubes 10 and 11 in which these porous portions 19 are formed. Provide. Further, an outer cylinder 21 is disposed so as to cover the outer periphery of the sound absorbing material 20 to prevent leakage of exhaust gas from the tail tubes 10 and 11 to the first expansion chamber 2 and the resonance chamber 18.

On the other hand, the baffle plate 7 is provided with a valve hole 12 for communicating the second expansion chamber 3 and the third expansion chamber 4. The valve hole 12 is formed at a position substantially opposite to the pass tube 9 in the axial direction. Further, a valve body 31 for opening and closing the valve hole 12 is disposed on the baffle plate 7 on the third expansion chamber 4 side.
Here, the inlet tube 5, the neck tubes 16 and 17, the pass tube 9, the resonance chamber 18, the first expansion chamber 2, the second expansion chamber 3, and the tail tube 10 form an exhaust passage. Further, the third expansion chamber 4 and the tail tube 11 constitute a bypass flow path.

(Configuration of valve device)
As shown in FIG. 2, the valve device of the present embodiment includes a valve body 31 that opens and closes the valve hole 12, and a return spring 38 that generates a spring force that biases the valve body 31 in the valve closing direction.
The said valve body 31 is comprised from the flat plate-shaped member of the magnitude | size which can obstruct | occlude the opening of the said valve hole 12 like FIG.
Further, a valve body rotation axis P <b> 1 fixed to the baffle plate 7 by a bracket 40 is provided. The valve body rotation axis P <b> 1 is disposed in parallel and horizontally to the surface of the baffle plate 7. And the arm member 37 protrudes diagonally downward from the back surface of the said valve body 31, and the front-end | tip part of the arm member 37 is connected with the said valve body rotating shaft P1 so that rotation is possible. As a result, the valve element 31 is supported by the valve element rotation shaft P1 so as to be rotatable about the valve element rotation axis P1. Thereby, the valve body 31 can be brought into contact with and separated from the baffle plate 7 as a valve seat by rotating around the valve body rotation axis P1. That is, the valve body 31 rotates around the valve body rotation axis P1 to open and close the valve hole 12.

In addition, a return spring 38 that biases the valve body 31 toward the baffle plate 7 is provided. The return spring 38 of the present embodiment has a coil-shaped member as a main body, and the coil-shaped portion is wound around a proximal end shaft P2 supported by the baffle plate 7. Then, one end of the coiled return spring 38 is fixed and fixed. Further, the other end side of the return spring 38 is extended toward the back surface of the valve body 31 to form a sliding contact body 39. An end portion in the extending direction of the sliding contact body 39 is used as a free end portion 39 a, and the free end portion 39 a is in sliding contact with a sliding contact portion provided on the back surface of the valve body 31.
As a result, the return spring 38 applies a reaction force to the fixed end portion, and the sliding contact body 39 rotates and displaces around the base end axis P2, thereby closing the valve body 31 input from the free end portion 39a. The spring force biased in the valve direction increases.

Here, the base end axis P2 is arranged in parallel with the valve body rotation axis P1. Further, the base end shaft P2 is disposed at a position closer to the valve body 31 than a straight line passing through the sliding contact boundary portion 36 and the valve body rotation axis P1 when viewed from the axial direction of the valve body rotation axis P1.
As shown in FIGS. 2 and 3, a recessed portion 32 that is recessed toward the valve opening direction, that is, the second expansion chamber 3 side, is provided at a position overlapping the valve hole 12 on the back surface of the valve body 31. And the upper surface in the recessed part 32 and the back surface of the valve body 31 continuous with the upper surface become a sliding contact part. Here, a boundary portion between the upper surface in the recess 32 and the back surface of the valve body 31 is referred to as a sliding contact boundary portion 36.

  The upper surface in the concave portion 32 is a surface parallel to the valve body rotation axis P1 and extends from the sliding contact boundary portion 36 to the second expansion chamber 3 side. The lower surface in the recess 32 constitutes the second sliding contact surface 34. Further, the back surface portion of the valve element 31 that continues upward from the sliding contact boundary portion 36 constitutes the first sliding contact surface 35. The free spring end 39a of the return spring 38 is formed on the back surface of the valve body 31 at a position slightly higher than the sliding contact boundary 36 when the valve body 31 is closed. 35 is in sliding contact. The first sliding contact surface 35 is from the position where the free end 39a in contact with the valve contacts to the sliding contact boundary 36.

In the present embodiment, as shown in FIG. 2, the upper surface in the recess 32 is obliquely downward as viewed from the axial direction of the valve body rotation axis P <b> 1 toward the second expansion chamber 3 from the sliding contact boundary 36. It is extended.
Here, the exhaust pressure applies a pressing force perpendicular to the surface of the valve body 31. Therefore, the surface of the valve body 31 is a surface orthogonal to the pressing force in the valve opening direction due to the exhaust pressure. Therefore, the second slidable contact surface 34 is inclined more than the first slidable contact surface 35 with respect to the surface orthogonal to the pressing force in the valve opening direction when viewed from the axial direction of the valve body rotation shaft.

Further, when viewed from the axial direction of the valve body rotation axis P1, a virtual axis at a position symmetrical to the base end axis P2 is assumed around the straight line passing through the sliding contact boundary portion 36 and the valve body rotation axis P1. It is defined as axis P3.
The second slidable contact surface 34 is set so as to be positioned on the inner diameter side with respect to the first virtual arc S1 which is a part of a circle passing through the slidable contact boundary portion 36 around the valve body rotation axis P1. .

Furthermore, at least a part of the second sliding contact surface 34 is on the third virtual arc S3 that is a part of a circle passing through the sliding contact boundary portion 36 about the virtual axis P3 or the third virtual arc S3. It is set to be located on the outer diameter side.
Here, the second slidable contact surface 34 has a curved or linear shape in which the contour viewed from the axial direction of the valve body rotation axis P1 does not change its curvature suddenly in the extending direction. . In FIG. 2, the case where the outline of the 2nd sliding contact surface 34 is linear is illustrated.
The return spring 38 constitutes a spring member.

(Operation)
Exhaust gas from the engine 30 first flows into the first expansion chamber 2 through the inlet tube 5. The exhaust gas flowing into the first expansion chamber 2 is attenuated in the resonance chamber 18 communicated via the neck pipes 16 and 17, that is, after the pressure is attenuated, the second exhaust gas is further attenuated through the pass tube 9 while being attenuated. It flows into the expansion chamber 3.
Here, the case where the rotation speed of the engine 30 is in a low speed rotation range is considered.
When the engine 30 rotates at a low speed, the exhaust pressure in the exhaust passage is low. For this reason, the valve body 31 urged by a predetermined spring constant of the return spring 38 is superior to the pressing force due to the exhaust pressure and holds the valve closed state. For this reason, the exhaust of the second expansion chamber 3 is discharged to the outside through the tail tube 10. That is, since the exhaust gas in the second expansion chamber 3 does not flow into the tail tube 11, the cross-sectional area of the exhaust channel does not increase.

And the pulsation of the exhaust gas synchronized with the rotational speed of the engine 30 by the capacity of the first expansion chamber 2, the second expansion chamber 3 and the resonance chamber 18 having a predetermined exhaust capacity corresponding to the low speed rotation region of the engine 30. The component is attenuated when sequentially passing through the first expansion chamber 2 and the second expansion chamber 3. As a result, exhaust noise can be reduced when the engine 30 rotates at a low speed. Further, the exhaust noise is also attenuated in the porous portion 19 and the sound absorbing material 20 of the tail tube 10.
Next, consider a case where the rotational speed of the engine 30 changes from a low speed rotation range to a high speed rotation range.
When the rotational speed of the engine 30 shifts to the high speed rotation range, the exhaust pressure flowing through the inlet tube 5 increases. When the internal pressure of the second expansion chamber 3 exceeds a predetermined value, the valve element 31 is rotationally displaced in the valve opening direction against the spring force of the return spring 38.

  When the valve body 31 is opened, the exhaust gas flowing into the casing 1 is discharged from the tail tube 10 to the outside through the first expansion chamber 2 and the second expansion chamber 3 in the same manner as in the low-speed rotation region. At the same time, it is also discharged from the tail tube 11 through the third expansion chamber 4. That is, the pipe area of the exhaust discharged from the casing 1 is a state in which the cross-sectional area of the tail tube 11 is added to the cross-sectional area of the tail tube 10. That is, this is equivalent to increasing the diameter of the exhaust pipe. As a result, exhaust loss in a high-speed rotation region where the exhaust flow rate increases can be reduced to suppress a decrease in engine 30 output, and exhaust airflow noise can be reduced.

  Here, the second slidable contact surface 34 of the present embodiment is set to have a larger inclination with respect to the valve body 31 than the first slidable contact surface 35 when viewed from the axial direction of the valve body rotation axis P1. Therefore, the exhaust pressure in the second expansion chamber 3 exceeds a predetermined value, the free end portion 39a slides on the first sliding contact surface 35 to the sliding contact boundary portion 36, and the free end portion 39a is in the second sliding contact. As soon as the surface 34 is shifted, the urging force by the return spring 38 suddenly decreases. That is, the apparent spring constant of the return spring 38 is greatly reduced, and the valve body 31 opens at a stroke to the maximum opening position 34x, so that the pressure can be rapidly reduced.

This tendency becomes more prominent as the second sliding contact surface 34 is brought closer to the first virtual arc S1. This can be realized by setting at least a part of the second sliding contact surface 34 so as to be positioned between the first virtual arc S1 and the third virtual arc S3.
The exhaust pressure change characteristics of the valve device according to the embodiment when at least a part of the second slidable contact surface 34 is set to be located between the first virtual arc S1 and the third virtual arc S3. As shown in FIG.

  In FIG. 4, the free end 39 a moves to the second slidable contact surface 34 at the position indicated by the symbol A. As shown in FIG. 4, at the moment when the free end 39 a shifts to the second sliding contact surface 34, the spring force by the return spring 38 is suddenly and greatly reduced, so that the exhaust pressure suddenly decreases, The exhaust pressure is in an equilibrium state. At this time, even if the valve body 31 reaches the maximum opening position 34x, the spring force by the return spring 38 is significantly small, so that the exhaust pressure does not increase.

The sliding contact position of the free end 39a when the valve is closed may be arranged as close as possible to the sliding contact boundary portion 36 on the first sliding contact surface 35. In this way, when the exhaust pressure becomes equal to or higher than the predetermined pressure, the valve body 31 immediately opens to the maximum opening position 34x.
Here, the arrangement of the second sliding contact surface 34 between the first virtual arc S1 and the third virtual arc S3 means that the sliding between the second sliding contact surface 34 and the free end 39a when the valve is opened. It means that the contact position is located between the first virtual arc S1 and the second virtual arc S2. The second virtual arc S2 is a virtual arc that constitutes a part of a circle that passes through the sliding contact boundary portion 36 with the base end axis P2 as the center.

  Here, a case is considered in which the base end axis P2 is disposed at a position farther from the valve body 31 than a straight line passing through the sliding contact boundary portion 36 and the valve body rotation axis P1 when viewed from the axial direction of the valve body rotation axis P1. In this case, in order to set the spring force by the return spring 38 at a stroke and greatly reduced at the moment when the free end 39a moves to the second sliding contact surface 34, it is necessary to configure as shown in FIG. In other words, the second slidable contact surface 34 is processed so that the angle formed by the first slidable contact surface 35 and the second slidable contact surface 34 (the lower surface of the recess) is an acute angle, that is, an acutely inclined surface from the back surface of the valve element 31. There is a need.

On the other hand, in the present invention, as shown in FIG. 2, the angle formed by the first slidable contact surface 35 and the second slidable contact surface 34 (the lower surface of the recess) is an obtuse angle, that is, the obtuse angle from the back surface of the valve element 31. What is necessary is just to process the 2nd sliding contact surface 34 as a smooth inclined surface.
Further, in FIG. 5, in order to make the free end portion 39 a slidably contact the second slidable contact surface 34, it is necessary to bend the tip end portion (free end portion 39 a side) of the slidable contact body 39. On the other hand, in the embodiment of the present application, as shown in FIG. 2, the second sliding contact surface 34 faces the base end axis P <b> 2, so the distal end portion of the sliding contact body 39 is bent and the free end 39 a is formed. It is not necessary to design so as to be in sliding contact with the second sliding contact surface 34.

(Effect of this embodiment)
(1) When the rotational speed of the engine 30 is in a high-speed rotation range, the valve element 31 is opened, thereby reducing exhaust loss in the high-speed rotation range where the exhaust flow rate is increased to suppress a decrease in the output of the engine 30 and Noise can be reduced.
(2) At this time, when the second sliding contact surface 34 is viewed from the axial direction of the valve body rotation shaft S1, the inclination with respect to the surface orthogonal to the pressing force in the valve opening direction is set larger than that of the first sliding contact surface 35. Further, the second sliding contact surface 34 is arranged on the inner diameter side with respect to the first virtual arc S1. As a result, when the exhaust pressure exceeds a predetermined pressure value, the spring force of the return spring 38 becomes small, and the exhaust pressure can be reduced. As a result, when the engine speed changes from the low-speed engine speed range to the high-speed engine speed range, the range of the engine 30 speed at which the exhaust noise is switched off and the noise increase can be set small.

(3) Particularly, the second sliding contact surface 34 is disposed between the first virtual arc S1 and the third virtual arc S3. In this case, when the exhaust pressure exceeds a predetermined pressure value, the spring force of the return spring 38 is reduced at a stretch, and the valve body 31 is opened at a stretch, whereby the pressure can be rapidly reduced. As a result, when the engine speed changes from the low-speed engine speed range to the high-speed engine speed range, the range of the engine 30 speed at which the exhaust noise is switched off and the noise increase can be set more reliably. .

(4) Since the second sliding contact surface 34 is arranged on the inner diameter side of the first virtual arc S1, the return spring 38 can surely have a restoring force for returning the valve body that has been opened to the valve closing position. .
(5) Further, the base end shaft P2 is disposed at a position closer to the valve body 31 than a straight line passing through the sliding contact boundary portion 36 and the valve body rotation axis P1 when viewed from the axial direction of the valve body rotation axis P1. . Accordingly, even if the spring force of the return spring is set to be greatly increased when moving from the first sliding contact surface 35 to the second sliding contact surface 34, the first sliding contact surface 35 and the second sliding contact surface are set. The angle with 34 can be set to an obtuse angle. Since the obtuse angle can be set, processing of the recess 32 for forming the second sliding contact surface 34 is facilitated.
(6) Further, the base end shaft P2 is disposed at a position closer to the valve body 31 than a straight line passing through the sliding contact boundary portion 36 and the valve body rotation axis P1 when viewed from the axial direction of the valve body rotation axis P1. Therefore, it is not necessary to bend the front end portion of the sliding contact body 39.

(Modification)
(1) In the said embodiment, the return spring 38 which generate | occur | produces a spring force with a coil spring is illustrated as a spring member. Instead of this, the spring member may be constituted by a leaf spring in which the fixed end portion is fixed to the base end portion and the free end portion 39a is slidably contacted with the sliding contact surface.
(2) Moreover, in the said embodiment, the 1st sliding contact surface 35 is arrange | positioned in parallel with the back surface itself of the valve body 31, or its back surface. Instead of this, the first sliding contact surface 35 may be arranged on the surface of the valve body 31, that is, the surface inclined with respect to the surface orthogonal to the direction of the exhaust pressure. The inclination with respect to the surface orthogonal to the pressing direction due to the exhaust pressure is sufficient if the second sliding contact surface 34 is larger than the first sliding contact surface 35.

(4) Here, the contour shape of the second slidable contact surface 34 is smoothly changed with a curvature sufficient to restore the valve body 31 opened in the closing direction against the sliding resistance. design. For this reason, if a part of the second sliding contact surface 34 is set so as to satisfy the above-mentioned conditions, when the exhaust pressure increases and the valve body 31 opens, that is, the engine 30 rotates at a low speed. When changing from the rotational speed range to the high speed rotational pressure range, the exhaust pressure can be greatly reduced.

(Second Embodiment)
Next, a second embodiment will be described with reference to the drawings. In addition, about the components similar to said each embodiment, the same code | symbol is attached | subjected and demonstrated.
The basic configuration of this embodiment is the same as that of the first embodiment. However, as shown in FIG. 6, the contour shape of the second sliding contact surface 34 is different from the axial direction of the valve body rotation axis P1. Other configurations are the same as those in the first embodiment.
On the second slidable contact surface 34 of the present embodiment, the contour line viewed from the axial direction of the valve body rotation axis P1 is below the position near the slidable contact boundary 36 (on the side where the free end 39a is slidably contacted). A convex curved portion 34a is provided. The curvature of the curved portion 34a is set larger than the curvature of the first virtual arc S1.
Further, it is designed such that at least a part of the second sliding contact circle 34 is located between the first virtual arc S1 and the third virtual arc S3.
The contour line of the second sliding contact surface 34 viewed from the axial direction of the valve body rotation axis P1 has a shape in which the curvature changes smoothly.

(Operation)
As in the first embodiment, the free end 39a significantly reduces the spring force when slidingly contacting the second sliding contact surface 34, so that the exhaust pressure can be rapidly decreased by opening the valve body 31. I can do it.
At this time, by providing a convex curved portion 34a on the sliding contact boundary portion 36 side of the second sliding contact surface 34, a decrease in the spring force is suppressed accordingly. As a result, the biasing force generated by the spring force generated when the exhaust pressure in the second expansion chamber 3 exceeds a predetermined value and the free end 39a moves to the second sliding contact surface 34 is compared with the first embodiment. And gradually become smaller. That is, when the exhaust pressure rises and the free end 39a shifts to the second sliding contact surface 34, the valve body 31 opens at once, and the pressure does not decrease suddenly. The valve is displaced in the valve opening direction up to the maximum opening position 34x while maintaining a nearly constant state.

The characteristics are shown in FIG.
That is, when the exhaust pressure increases and the free end 39a moves to the second sliding contact surface 34, the spring force by the return spring 38 is significantly reduced. However, by forming the convex curved portion 34a on the sliding contact boundary 36 side, as shown in FIG. 4, the valve body 31 does not open at a stretch and the pressure is not rapidly reduced, as shown in FIG. Although the pressure slightly increases, the valve body 31 opens to the maximum opening position 34x while being maintained at the pressure when the opening is made to the maximum opening position 34x.
In FIG. 7, reference symbol B indicates characteristics when the second sliding contact surface 34 is the same plane as the first sliding contact surface 35, that is, when the spring force gradually increases as the valve is opened. In this case, the urging force by the return spring 38 increases as it approaches the maximum opening position 34x, so that the state does not shift to a small pressure state as in the present embodiment.

(Effect of embodiment)
(1) A convex curved portion 34 a is formed on the sliding contact boundary portion 36 side with respect to the second sliding contact surface 34. Thereby, even if the inclination between the first slidable contact surface 35 and the second slidable contact surface 34 is greatly changed and the spring force by the return spring 38 is greatly reduced, the pressure can be greatly reduced. When the free end 39a moves from the first slidable contact surface 35 to the second slidable contact surface 34, it is possible to suppress a rapid decrease in pressure due to the valve body 31 opening at a stretch.
For this reason, the increased exhaust pressure decreases, that is, the pressure characteristic of the valve device at the time of pressure reduction approaches the locus at the time of pressure increase, and a hysteresis characteristic can be avoided. That is, it is possible to suppress the occurrence of a temporary pressure drop during decompression.
As a result, even when the engine 30 is switched from the high-speed rotation region to the low-speed rotation region, it is possible to switch from exhaust sound increase to mute within a range where the engine rotation width is small.
(2) Other effects are the same as those of the first embodiment.

(Modification)
In the above embodiment, the convex curved portion 34 a is provided on the second sliding contact surface 34 on the sliding contact boundary 36 side. Instead, the shape of the contour of the entire second sliding contact surface 34 may be set to be a curved shape having a slightly larger curvature than the curvature of the first virtual arc S1.
Even in this case, it is possible to suppress a sudden pressure drop during the transition from the first sliding contact surface 35 to the second sliding contact surface 34.

(Third embodiment)
Next, a third embodiment will be described with reference to the drawings. In addition, about the components similar to said each embodiment, the same code | symbol is attached | subjected and demonstrated.
(Constitution)
The basic configuration of this embodiment is the same as that of the first embodiment. However, as shown in FIG. 8, the sliding contact surface is provided so as to protrude from the back surface of the valve body 31.
That is, the substantially rectangular box 40 for forming the sliding contact surface is fixed to the back surface of the valve body 31.
Of the surface of the box body 40, the lower surface is the second sliding contact surface 34, and the front surface parallel or substantially parallel to the rear surface of the valve body 31 is the first sliding contact surface 35. In this case, a corner portion formed by the lower surface and the front surface becomes the sliding contact boundary portion 36.

The second slidable contact surface 34 formed from the upper surface is located on the inner diameter side of the first virtual arc when viewed from the axial direction of the valve body rotation axis P1.
In FIG. 8, the second sliding contact surface is not located between the first virtual arc S1 and the third virtual arc S3 when viewed from the axial direction of the valve body rotation axis P1. However, when the free end portion moves from the first slidable contact surface 35 to the second slidable contact surface 34 by being disposed close to the third virtual arc S3, the spring force is greatly reduced.
Preferably, at least a part of the second sliding contact surface 34 is positioned between the first virtual arc S1 and the third virtual arc S3 when viewed from the axial direction of the valve body rotation axis P1.
Other configurations are the same as those in the first embodiment.

(Effect of embodiment)
(1) The same effects as those of the first embodiment are obtained.
That is, when the rotational speed of the engine 30 is in the high speed rotation range, the valve body 31 opens, thereby reducing exhaust loss in the high speed rotation range where the exhaust flow rate is increased and suppressing a decrease in the output of the engine 30, and exhaust airflow noise. Can be reduced.
At this time, the second slidable contact surface 34 is disposed close to the third virtual arc S3 when viewed from the axial direction of the valve body rotation axis P1. As a result, when the exhaust pressure exceeds a predetermined pressure value, the valve body 31 opens at a stretch, and the pressure can be rapidly reduced. As a result, it is possible to set the range of the rotational speed of the engine 30 at which the exhaust sound is silenced and increased.
In particular, when the second slidable contact surface 34 is positioned at a portion between the first virtual arc S1 and the third virtual arc S3, when the exhaust pressure exceeds a predetermined pressure value, the valve is immediately blown. The body 31 opens and the pressure can be rapidly reduced. That is, the range of the number of revolutions of the engine 30 at which the exhaust sound is silenced and increased can be set more reliably.

(2) The sliding surface was extended from the back surface of the valve body 31 to the back surface side. This eliminates the need to form the recess 32 that protrudes to the front side of the valve body 31 when forming the sliding contact surface. That is, the surface of the valve body 31 that receives the exhaust pressure can be made flat.
(3) Moreover, when forming a sliding contact surface, it is possible to form a sliding contact surface by fixing the box 40 to the back surface of the valve body 31. That is, production is facilitated by eliminating the need to open a part of the valve body 31 and fix the member constituting the recess 32.

(Application examples)
FIG. 9 shows a case where the configuration of the second embodiment is used in combination with the configuration of the third embodiment.
That is, a curved portion 34a having an upward convex arc portion having a larger curvature than the first virtual arc S1 is formed on the second sliding contact surface 34 formed from the upper surface of the box 40.
Even in this case, it is preferable that at least a part of the second sliding contact surface 34 is set to be positioned between the first virtual arc S1 and the third virtual arc S3.
The effect is the same as that of the second embodiment.

It is sectional drawing which shows the silencer which concerns on embodiment based on this invention. It is a schematic diagram which shows the valve apparatus which concerns on 1st Embodiment based on this invention. It is a front view which shows the valve body which concerns on 1st Embodiment based on this invention. It is a figure which shows the pressure characteristic by the valve apparatus which concerns on 1st Embodiment based on this invention. It is a schematic diagram which shows the example at the time of changing the relationship between a valve body rotating shaft and a base end axis | shaft. It is a schematic diagram which shows the valve apparatus which concerns on 2nd Embodiment based on this invention. It is a figure which shows the pressure characteristic by the valve apparatus which concerns on 2nd Embodiment based on this invention. It is a schematic diagram which shows the valve apparatus which concerns on 3rd Embodiment based on this invention. It is a schematic diagram which shows the valve apparatus of another example which concerns on 3rd Embodiment based on this invention.

Explanation of symbols

7 Baffle plate (valve seat)
12 Valve hole 31 Valve body 34 Second sliding contact surface 34a Bending portion 35 First sliding contact surface 36 Sliding contact boundary portion 38 Return spring 39 Sliding contact body 39a Free end portion 40 Box body P1 Valve body rotating shaft P2 Base end shaft P3 Virtual axis S1 First virtual arc S2 Second virtual arc S3 Third virtual arc

Claims (4)

A valve body that is supported rotatably about a predetermined valve body rotation shaft and opens and closes a valve hole formed in an exhaust passage in the silencer, and a spring force that urges the valve body in a valve closing direction. A valve member for a silencer that receives a pressing force in a valve opening direction due to an exhaust pressure in the exhaust flow path.
The spring member includes a sliding contact body having a free end portion that is in sliding contact with a sliding contact surface provided on a back surface of the valve body opposite to a surface receiving the exhaust pressure in the valve body, and the free contact of the sliding contact body The above-mentioned spring force can be increased by rotating and displacing the end portion in the valve opening direction around a predetermined base end axis,
The slidable contact surface provided on the valve body is slid when the valve body is displaced in the valve opening direction more than a predetermined distance from the first slidable contact surface that is slidably contacted in the closed state. And a boundary portion between the first sliding contact surface and the second sliding contact surface is defined as a sliding contact boundary portion.
The second slidable contact surface is set to have a larger inclination than the first slidable contact surface with respect to the surface orthogonal to the pressing force in the valve opening direction when viewed from the axial direction of the valve body rotation shaft.
The base end shaft is disposed closer to the valve body than a straight line passing through the sliding contact boundary portion and the valve body rotation shaft when viewed from the axial direction of the valve body rotation shaft,
The second slidable contact surface is viewed from the axial direction of the valve body rotation shaft and is located on the inner diameter side of the first virtual arc that forms a part of a circle that passes through the slidable contact boundary centered on the valve body rotation axis. A valve device for a silencer, characterized by being arranged. When a virtual axis that is symmetrical to the base end axis is defined as a virtual axis around a line passing through the sliding contact boundary and the valve body rotation axis,
When at least a part of the second slidable contact surface is viewed from the axial direction of the valve body rotation axis, outside the third virtual arc that forms a part of a circle that passes through the slidable contact boundary centered on the imaginary axis. The silencer valve device according to claim 1, wherein the silencer valve device is positioned on a radial side.   At least a part of the contour of the second sliding contact surface viewed from the axial direction of the valve body rotation shaft is a curved portion that is convexly curved toward the side where the free end slides, and the curvature of the curved portion is defined as the valve body. 3. The silencer valve device according to claim 1, wherein the silencer valve device is set to be larger than a curvature of a first virtual arc that constitutes a part of a circle that passes through the sliding contact boundary portion with the rotation axis as a center. .   The silencer valve device according to any one of claims 1 to 3, wherein the second slidable contact surface is formed so as to protrude to a valve body rear surface side.

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