JP2018123692A - Sub-muffler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sub-muffler in a simple configuration, capable of actualizing a continuously variable distance to the opening end of an exhaust pipe.SOLUTION: A sub-muffler 1A has an exhaust pipe 11 which is connected to an engine and whose end is introduced into an expansion chamber 10 while opening in the expansion chamber 10, and an outer cylinder 111 slidably mounted on the outer peripheral face of an opening end 11o of the exhaust pipe 11 introduced into the expansion chamber 10. The outer cylinder 111 can be moved along the end outer peripheral face of the exhaust pipe 11 in the axial direction by a drive part 20, and so the projection amount of the outer cylinder 111 projecting from the opening end 11o of the exhaust pipe 11 can be varied. With the drive part 20 controlled by an opening end position control part 120, the travel of the outer cylinder 111 is set according to the operating condition of the engine.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a sub-muffler provided in an exhaust path for exhausting exhaust gas from an engine.

  A vehicle such as an automobile on which an engine is mounted generally includes an exhaust device that exhausts exhaust gas discharged from the engine. The exhaust device includes an exhaust pipe that constitutes an exhaust path, and the exhaust path (exhaust pipe) includes an exhaust gas purification device that contains a catalyst for purifying exhaust gas, a muffler that reduces exhaust noise (noise), and the like. Provided. Some mufflers perform noise reduction in two stages, and may include a sub-muffler in addition to the main muffler. Usually, the sub muffler is disposed on the upstream side (upstream side) of the main muffler.

  Patent Document 1 discloses an invention of a variable-length exhaust pipe for a two-cycle engine. In the exhaust pipe for a two-cycle engine including an exhaust pipe and an expansion pipe connected to the pipe, the length of the exhaust pipe is set to be the same as that of the engine. A technique for making it variable according to the rotational speed is described. In the exhaust pipe described in Patent Document 1, the exhaust pipe connected to the exhaust hole of the engine is cut in a predetermined section on the way, and a switching chamber is provided between the cut ends. The switching chamber is provided with a rotor, and the rotor is formed with two communication paths. By rotating the rotor, the end portions of the exhaust pipe communicate with each other via one communication path, It is possible to switch to a state of communicating with the auxiliary passage pipe via the communication passage. The former state is a state where the ends of the exhaust pipe are connected and short-circuited via one communication path, the length of the exhaust pipe is shortened, and the distance of the exhaust path from the exhaust hole to the expansion pipe is reduced. Shorter. On the other hand, the latter state is a state in which the auxiliary passage pipe is connected between the end portions of the exhaust pipe via two communication passages, the length of the exhaust pipe is extended, and the distance of the exhaust path is increased. In Patent Document 1, the length of the exhaust pipe is lengthened when the engine is rotating at a low speed and shortened when the engine is rotated at a high speed, thereby preventing the air-fuel mixture from blowing through in the two-cycle engine and improving the output performance of the engine. The purpose is that.

Japanese Patent Laid-Open No. 55-112823

  It is known that when the engine is operated, exhaust pulsation in which the exhaust pressure in the exhaust path (exhaust pipe) fluctuates occurs, and the exhaust pulsation changes depending on the operating state (rotation speed, etc.) of the engine. Further, since the exhaust pulsation is caused by a reflected wave at the open end of the exhaust pipe, it also varies depending on the length of the exhaust pipe (distance to the open end). During engine operation, this exhaust pulsation causes intake air blow-through (a phenomenon in which intake air sucked into the cylinder from the intake port flows out of the exhaust port) and exhaust blow-back (a phenomenon in which exhaust gas in the exhaust pipe flows back into the cylinder from the exhaust port). May occur and engine output performance may be reduced. Therefore, it is desired to optimize engine exhaust pulsation and improve output performance.

  FIG. 4 shows the relationship between the crank angle, exhaust pressure (solid line), and intake pressure (broken line) at a certain rotational speed (rotational speed) in a 4-cycle gasoline engine. In FIG. 4, the horizontal axis indicates the crank angle (° CA), the vertical axis indicates the pressure (kPa), and the exhaust top dead center is when the crank angle is 0 ° CA. Even in a 4-cycle engine, as shown in FIG. 4, when shifting from the exhaust process to the intake process, the exhaust period (EX) in which the exhaust valve opens and the intake period (IN) in which the intake valve opens may overlap. When the exhaust pulsation peak (Pe) is located in the overlap period (OL) where the intake period (IN) and the exhaust period (EX) overlap, the exhaust pressure becomes higher than the intake pressure, and exhaust blowback occurs. Sometimes. When blowback occurs, sufficient intake is not performed, and the output performance of the engine deteriorates. Normally, in order to improve the performance of the low rotation range, the exhaust pulsation peak position is shifted by adjusting the length of the exhaust pipe so that the exhaust pulsation peak is not located in the overlap period in the low rotation range. The exhaust pulsation at is set to be appropriate.

  However, even if the length of the exhaust pipe is set in accordance with a certain rotation speed so that the exhaust pulsation is appropriate in the low rotation range, the exhaust pulsation peak is located in the overlap period in the rotation range in the vicinity thereof. The exhaust pulsation may not be optimized. That is, even in the low rotation range, the output performance may be reduced in a rotation range that deviates from a certain rotation speed, and the output performance may not be improved in a wide rotation range. For example, when the accelerator opening (throttle valve opening) is fully opened in the low rotation range, sufficient output may not be obtained due to the influence of exhaust pulsation.

  The technique described in Patent Document 1 is a two-cycle engine exhaust pipe, which has a variable length structure including a switching chamber having a rotor and two communication passages formed in the rotor and a sub-passage pipe. Sometimes the length of the exhaust pipe (exhaust path) can be changed. With this technique, the exhaust pulsation cannot be optimized over the entire low speed range because the length of the exhaust pipe can be changed only in two stages at the time of low speed and high speed rotation of the engine. Moreover, it may be difficult to secure the installation space for the switching chamber and the auxiliary passage pipe, which is disadvantageous in terms of space efficiency.

  One of the objects of the present invention is to provide a sub-muffler capable of continuously varying the distance to the open end of the exhaust pipe with a simple configuration.

The sub-muffler according to one aspect of the present invention is
A sub-muffler provided in an exhaust path for exhausting exhaust gas from an engine,
An extension room,
An exhaust pipe having an open end in the expansion chamber;
An open end position variable mechanism that changes the length of the open end by changing the position of the open end in the expansion chamber;
An open end position control unit that controls the open end position variable mechanism according to the operating state of the engine.

  The sub-muffler includes an open end position variable mechanism that changes the position of the open end of the exhaust pipe in the expansion chamber, and the length of the open end is determined by the open end position control unit in accordance with the engine operating state (such as the number of revolutions). Can be changed. Therefore, by changing the length of the open end of the exhaust pipe, the length of the exhaust pipe (distance to the open end) can be made continuously variable, so that the optimum exhaust pulsation can be set in a wide rotation range. Therefore, output performance can be improved over the entire low rotation range. The sub-muffler is obtained by changing the structure of the conventional sub-muffler, and it is easy to secure an installation space, which is advantageous in terms of space efficiency. Therefore, the sub muffler can continuously vary the distance to the open end of the exhaust pipe with a simple configuration.

It is a schematic diagram which shows an example of the exhaust route in which the sub muffler which concerns on embodiment was provided. FIG. 3 is a schematic diagram illustrating a configuration example of a sub-muffler according to the first embodiment. 6 is a schematic diagram illustrating a configuration example of a sub-muffler according to a second embodiment. FIG. It is an image figure which shows the relationship between the crank angle and exhaust pulsation in a 4-cycle engine.

  A specific example of a sub-muffler according to an embodiment of the present invention will be described with reference to the drawings. The same reference numerals in the figure indicate the same names.

[Embodiment]
The sub-muffler 1 according to the embodiment will be described with reference to FIGS. As shown in FIG. 1, the sub muffler 1 is provided in an exhaust path 10 e that exhausts exhaust gas from the engine E. As shown in FIGS. 2 and 3, one of the features of the sub muffler 1 includes an expansion chamber 10 and an exhaust pipe 11 having an open end 12 in the expansion chamber 10. The position of the open end 12 can be freely changed. First, the configuration of the engine E and the exhaust path 10e will be briefly described with reference to FIG. 1, and then the configuration of the sub-muffler 1 of the embodiment will be described in detail with reference mainly to FIGS.

<Engine>
The engine E is an automobile engine, and in this example, is a four-cycle gasoline engine. As shown in FIG. 1, the engine E has a cylinder S formed therein, an intake port Pi that sucks air or a mixture of fuel and air into the cylinder S, and exhaust that discharges exhaust gas from the cylinder S. An intake valve Vi and an exhaust valve Ve that open and close the port Pe and the intake port Pi and the exhaust port Pe, respectively, are provided. An intake path Pi and an exhaust path Pe are connected to the intake port Pi and the exhaust port Pe of the engine E, respectively. Although only one cylinder S is shown in FIG. 1, the engine E may have a plurality of cylinders S. The engine E is electronically controlled by an electronic control unit (ECU) 200, and the ECU 200 collects information related to the operating state (engine speed, etc.) of the engine E by various sensors. The ECU 200 includes a microcomputer that includes a central processing unit (CPU) and a memory.

(Intake route)
The intake path 10i is composed of an intake pipe, and one end thereof is connected to the engine E (intake port Pi) via an intake manifold (not shown). The intake passage 10i is provided with a throttle valve Vs for adjusting the intake air amount. The opening degree of the throttle valve Vs is adjusted by operating an accelerator pedal (not shown). In this example, the throttle valve Vs is controlled by the ECU 200. Specifically, information on the accelerator opening is sent to the ECU 200, and the throttle valve opening is adjusted based on the accelerator opening.

(Exhaust route)
The exhaust path 10e is composed of an exhaust pipe 11, one end of which is connected to the engine E (exhaust port Pe) via an exhaust manifold (not shown). The exhaust path 10e (exhaust pipe 11) includes an engine The exhaust gas discharged from E circulates. In addition to the sub muffler 1, an exhaust gas purification device (catalytic converter) 2 and a main muffler 3 are provided in the exhaust path 10 e. In this example, the sub muffler 1 and the main muffler 3 are arranged on the rear stage side (downstream side) of the exhaust gas purification device 2, and the sub muffler 1 is arranged on the front stage side (upstream side) of the main muffler 3. These are connected by an exhaust pipe 11.

<Sub muffler>
The sub muffler 1 is attached in the middle of the exhaust path 10e (exhaust pipe 11). As shown in FIGS. 2 and 3, the exhaust pipe 11 connected to the engine E is connected to the expansion chamber 10, and the exhaust pipe is placed in the expansion chamber 10. 11 open ends 12 are provided. The expansion chamber 10 is silenced by expanding the exhaust gas from the exhaust pipe 11. As will be described later, the sub-muffler 1 includes an open end position variable mechanism 110 that changes the position of the open end portion 12 in the expansion chamber 10 and an open end that controls the open end position variable mechanism 110 according to the operating state of the engine E. A position control unit 120. Below, each embodiment of the sub muffler 1 which concerns on embodiment is described in detail based on FIG. 2, FIG. The sub-mufflers 1A and 1B of the embodiments shown in FIGS. 2 and 3 differ in the configuration of the open end position variable mechanism 110. In each of the following embodiments, the direction along the axial direction of the exhaust pipe 11 (the left-right direction in FIGS. 2 and 3) is the front-rear direction, and the engine E side (the left side in FIGS. 2 and 3) of the exhaust pipe 11 is the front. The other side (the right side in FIGS. 2 and 3) is the rear.

[Embodiment 1]
With reference to FIG. 2, the sub-muffler 1A of Embodiment 1 is demonstrated. In the first embodiment shown in FIG. 2, the open end position variable mechanism 110 is attached to the open end portion 11 o of the exhaust pipe 11 accommodated in the expansion chamber 10, and is movable in the axial direction of the exhaust pipe 11. And the drive part 20 which moves the outer cylinder 111 is an example comprised.

  As shown in FIG. 2, in the sub-muffler 1 </ b> A of the first embodiment, the end of the exhaust pipe 11 connected to the engine E is introduced into the expansion chamber 10, opened in the expansion chamber 10, and introduced into the expansion chamber 10. An outer cylinder 111 is slidably mounted on the outer peripheral surface of the open end portion 11o of the exhaust pipe 11 formed. In the sub-muffler 1 </ b> A, the open end 12 of the exhaust pipe 11 is constituted by the outer cylinder 111, and the position of the rear end of the outer cylinder 111 protruding from the open end 11 o of the exhaust pipe 11 is the open end of the exhaust pipe 11.

  The outer cylinder 111 can be moved in the axial direction (front-rear direction) along the outer peripheral surface of the end of the exhaust pipe 11 by the drive unit 20. In this example, the drive unit 20 includes an arm 21 and moves the outer cylinder 111 in the front-rear direction via the arm 21. One end of the arm 21 is connected to the front end surface of the outer cylinder 111, and the other end is pulled out of the expansion chamber 10 along the exhaust pipe 11. The drive unit 20 is disposed outside the expansion chamber 10 and moves the outer cylinder 111 in the front-rear direction by driving the arm 21 in the front-rear direction. For the drive unit 20, for example, a combination of a motor and a gear mechanism, a solenoid, or the like can be used. The drive unit 20 is controlled by an open end position control unit 120 described later. With this drive unit 20, the position of the outer cylinder 111 can be continuously changed with respect to the exhaust pipe 11, and the protruding amount of the outer cylinder 111 protruding from the open end portion 11 o of the exhaust pipe 11 can be changed. it can. That is, by changing the position of the open end 12 of the exhaust pipe 11 constituted by the outer cylinder 111, the length of the open end 12 in the expansion chamber 10 can be changed. The distance to the open end can be made continuously variable. In this example, as shown in FIG. 2, the outer cylinder 111 is movable in the front-rear direction around a reference position (a position indicated by “0” in FIG. 2). In FIG. 2, the outer cylinder 111 indicated by a one-dot chain line indicates a state positioned as far as possible in the rear, and the outer cylinder 111 indicated by a two-dot chain line indicates a state positioned as far as possible in the front. The length of the open end 12 of the exhaust pipe 11 can be increased by moving the outer cylinder 111 rearward (in the + direction in FIG. 2) with respect to the reference position. In this case, since the distance to the open end of the exhaust pipe 11 becomes long, the phase of the exhaust pulsation is delayed. Conversely, the length of the open end 12 of the exhaust pipe 11 can be shortened by moving the outer cylinder 111 forward (in the-direction in FIG. 2) with respect to the reference position. In this case, since the distance to the open end of the exhaust pipe 11 is shortened, the phase of exhaust pulsation advances. For example, the reference position may be set to a position where the exhaust pulsation is appropriate at the rotation speed of the engine E in a low rotation range.

  The open end position control unit 120 is incorporated in the ECU 200 (see FIG. 1) and controls the drive unit 20 according to the operating state of the engine E (see FIG. 1) determined by the ECU 200. Specifically, during operation of the engine E, when the exhaust pulsation peak (Pe) is located in the overlap period (OL) described with reference to FIG. The drive unit 20 is controlled to move the outer cylinder 111 from the reference position so as to be out of the period. For example, when the exhaust pulsation peak is located in the latter half (second half) of the overlap period, the outer cylinder 111 is moved rearward (in the + direction in FIG. 2) to increase the length of the open end 12. . As a result, the distance to the open end of the exhaust pipe 11 becomes longer, so the phase of the exhaust pulsation is delayed, and the peak of the exhaust pulsation is shifted to the delayed side (in the direction of the white arrow in FIG. 4). Is easily removed from the overlap period. On the other hand, when the exhaust pulsation peak is located in the first half (first half) of the overlap period, the outer cylinder 111 is moved forward (in the-direction in FIG. 2) to shorten the length of the open end 12. . As a result, the distance to the open end of the exhaust pipe 11 is shortened, so the phase of exhaust pulsation advances, and the peak of exhaust pulsation shifts to the leading side (in the direction of the black arrow in FIG. 4). Easy to remove from the overlap period.

  Examples of the operating state of the engine E include engine speed, throttle valve opening (accelerator opening), and the like. In this example, the relationship between the operating state (engine speed and throttle valve opening) and the corresponding exhaust pulsation is measured in advance, and the movement amount of the outer cylinder 111 corresponding to the operating state is mapped. It is stored in the open end position control unit 120. In the open end position control unit 120, the operating state is determined from the engine speed and the throttle valve opening, the movement amount of the outer cylinder 111 corresponding thereto is set, and the outer cylinder 111 is set by the drive unit 20 by the set movement amount. Move.

[Embodiment 2]
With reference to FIG. 3, the sub-muffler 1B of Embodiment 2 is demonstrated. In the second embodiment shown in FIG. 3, the open end position variable mechanism 110 is attached to a part of the exhaust pipe 11 accommodated in the expansion chamber 10 and is movable in the axial direction of the exhaust pipe 11. In this example, the through-hole 115 formed in the exhaust pipe 11 and the drive unit 20 that moves the outer cylinder 112 are shown. Below, it demonstrates centering around difference with Embodiment 1 shown in FIG. 2 mentioned above, The description is abbreviate | omitted about the same structure.

  As shown in FIG. 3, in the sub-muffler 1 </ b> B of the second embodiment, the exhaust pipe 11 connected to the engine E passes through the expansion chamber 10 and is accommodated in the expansion chamber 10, and is accommodated in the expansion chamber 10 of the exhaust pipe 11. A through hole 115 is formed in the portion, and an outer cylinder 112 is slidably mounted on the outer periphery thereof. In the sub-muffler 1B, the open end 12 of the exhaust pipe 11 is configured by an outer cylinder 112 and a through hole 115 formed in the exhaust pipe 11, and the through hole 115 exposed from the outer cylinder 112 and opening into the expansion chamber 10 is formed. Among these, the position of the through hole 115 located closest to the engine E (front side) is the open end of the exhaust pipe 11. In the case of the sub-muffler 1B shown in FIG. 3, among the through holes 115 exposed from the outer cylinder 112, the position of the through hole 115 (fourth from the right in FIG. 3) located on the foremost side of the exhaust pipe 11 is the open end. It becomes.

  In this example, the exhaust pipe 11 is provided with a plurality of through holes 115 at intervals along the axial direction of the exhaust pipe 11 (six in FIG. 3). The number, position, shape, and the like of the through holes 115 can be changed as appropriate. For example, as shown in FIG. 3, when the through holes 115 are provided at different positions in the axial direction of the exhaust pipe 11, the number of the through holes 115 is preferably 3 or more, and more preferably 4 or more and 8 or more. In this case, the larger the number of through holes 115, the more continuously the position of the open end of the exhaust pipe 11 can be changed. Further, in FIG. 3, one through hole 115 is provided at each different position in the axial direction of the exhaust pipe 11, but a plurality of through holes 115 may be provided in the circumferential direction of the exhaust pipe 11. Furthermore, it is preferable that the through-holes 115 are provided in a mesh shape so that the positions of the through-holes 115 are continuous in the axial direction of the exhaust pipe 11.

  The outer cylinder 112 is movable in the axial direction (front-rear direction) along the outer peripheral surface of the exhaust pipe 11 by the drive unit 20. Similarly to the first embodiment, the drive unit 20 includes an arm 21 and moves the outer cylinder 112 in the front-rear direction via the arm 21. With this drive unit 20, the position of the outer cylinder 112 can be continuously changed with respect to the exhaust pipe 11, and the position of the through-hole 115 exposed from the outer cylinder 112 and opening into the expansion chamber 10 is changed. be able to. In other words, the length of the open end 12 in the expansion chamber 10 can be changed by changing the position of the through hole 115 that becomes the open end 12 of the exhaust pipe 11 by the outer cylinder 112, and thereby the exhaust pipe The distance to the 11 open ends can be made continuously variable. In this example, as shown in FIG. 3, the outer cylinder 112 is movable in the front-rear direction around a reference position (a position indicated by “0” in FIG. 3). In FIG. 3, the outer cylinder 112 indicated by a one-dot chain line represents a state positioned as far as possible, and the outer cylinder 112 indicated by a two-dot chain line represents a state positioned as far as possible in the front. The length of the open end portion 12 of the exhaust pipe 11 can be increased by moving the outer cylinder 112 rearward (in the + direction in FIG. 3) with respect to the reference position. In this case, since the distance to the open end of the exhaust pipe 11 becomes long, the phase of the exhaust pulsation is delayed. On the contrary, the length of the open end 12 of the exhaust pipe 11 can be shortened by moving the outer cylinder 112 forward (in the − direction in FIG. 3) with respect to the reference position. In this case, since the distance to the open end of the exhaust pipe 11 is shortened, the phase of exhaust pulsation advances.

  The drive unit 20 is controlled by the open end position control unit 120. As described in the first embodiment, the open end position control unit 120 controls the drive unit 20 in accordance with the operating state of the engine E (see FIG. 1). Specifically, as in the first embodiment, when the operation state is such that the exhaust pulsation peak is located in the overlap period, the drive unit 20 is controlled so that the exhaust pulsation peak deviates from the overlap period. The outer cylinder 112 is moved from the reference position. For example, when the exhaust pulsation peak is located in the latter part of the overlap period, the outer cylinder 112 is moved rearward (in the + direction in FIG. 3) to increase the distance to the open end of the exhaust pipe 11. Thus, the phase of exhaust pulsation is delayed. On the other hand, when the exhaust pulsation peak is located in the first half of the overlap period, the outer cylinder 112 is moved forward (in the-direction in FIG. 3) to shorten the distance to the open end of the exhaust pipe 11. As a result, the phase of the exhaust pulsation is advanced. In the open end position control unit 120, the amount of movement of the outer cylinder 112 corresponding to the operating state (engine speed and throttle valve opening) is mapped and stored, and the amount of movement corresponding to the operating state is set, The outer cylinder 112 is moved by the drive unit 20.

[Function and effect]
The sub mufflers 1A and 1B of the first and second embodiments described above can change the position of the open end 12 of the exhaust pipe 11 in the expansion chamber 10 according to the operating state of the engine E. The distance to the open end can be made continuously variable. Therefore, since exhaust pulsation can be optimized in a wide rotation range, output performance can be improved over the entire low rotation range. For example, even when the accelerator opening (throttle valve opening) is fully opened in the low rotation range, it is possible to suppress a decrease in output performance due to exhaust pulsation and obtain a sufficient output.

  The present invention is not limited to these exemplifications, is shown by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

  The sub-muffler of the present invention can be suitably used for an exhaust system of an automobile engine.

10e Exhaust path 1, 1A, 1B Sub-muffler 10 Expansion chamber 11 Exhaust pipe 11o Open end 12 Open end 110 Open end position variable mechanism 111, 112 Outer cylinder 115 Through hole 20 Drive unit 21 Arm 120 Open end position control unit 2 Exhaust Gas purification device 3 Main muffler E Engine S Cylinder Pi Intake port Vi Intake valve Pe Exhaust port Ve Exhaust valve 10i Intake path Vs Throttle valve 200 ECU

Claims (1)

A sub-muffler provided in an exhaust path for exhausting exhaust gas from an engine,
An extension room,
An exhaust pipe having an open end in the expansion chamber;
An open end position variable mechanism that changes the length of the open end by changing the position of the open end in the expansion chamber;
A sub-muffler comprising: an open end position control unit that controls the open end position variable mechanism according to an operating state of the engine.

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