JP2017066965A - Exhaust system of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust system of a cylinder rest engine capable of obtaining the output improvement while maintaining muffling action in all cylinder operation and increasing exhaust gas circulation resistance to enhance muffling action in cylinder deactivation operation.SOLUTION: An exhaust pipe of an engine is branched into a first branch pipe 15 and a second branch pipe 16. The exhaust system of an engine comprises: a first muffler 20 mounted on the first branch pipe 15 and having a comparatively small exhaust gas circulation resistance; a second muffler 25 mounted on the second branch pipe and having a comparatively large exhaust gas circulation resistance; and a selector valve 17 for selectively switching exhaust gas into the first branch pipe 15 and the second branch pipe 16. In all cylinder operation, exhaust gas is introduced into the first branch pipe 15 to be muffled by the first muffler 20 while the engine output is improved. In cylinder deactivation operation, the second branch pipe 16 is opened and exhaust gas is introduced into the second muffler 25 to mute the low-frequency exhaust gas sound due to the cylinder deactivation operation and muffle the muffed sound efficiently.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust system of an engine, and more particularly to an exhaust system of a cylinder deactivation engine.

  2. Description of the Related Art In recent years, multi-cylinder engines as vehicle engines include a cylinder deactivation engine including a cylinder that is always operated for the purpose of improving fuel efficiency and a cylinder that is deactivated during low-power operation.

  In such a cylinder deactivation engine, when a transition is made from full cylinder operation to cylinder deactivation operation in which some cylinders are deactivated, the explosion order of the engine decreases and low frequency exhaust noise, so-called humming noise increases.

  In this type of silencer for a cylinder deactivation engine, there is a proposal to extend an exhaust gas exhaust pipe protruding from the silencer body in order to reduce low-frequency exhaust noise by a resonance damping action. However, it is extremely difficult to arrange a long exhaust gas exhaust pipe that reduces the low-frequency exhaust sound by the resonance damping action, and the exhaust gas energy is attenuated by increasing the exhaust gas flow resistance in the silencer body. To mute the low-frequency exhaust sound. On the other hand, if the exhaust gas flow resistance in the silencer body is increased, there is a concern that the output will decrease during all cylinder operation.

  For example, in the exhaust silencer of Patent Document 1, as schematically shown in FIG. 7, the silencer main body 101 is partitioned into expansion chambers A and B by a partition wall 102 made of a porous plate, and the exhaust gas introduction pipe 103 is silenced. The downstream end of the container body 101 is opened to the outside. A peripheral wall portion of the exhaust gas introduction pipe 103 has a through hole 103a for introducing exhaust gas into the expansion chamber A, and an on-off valve 104 is provided at the downstream end. Further, an exhaust gas exhaust pipe 105 for exhausting the exhaust gas in the expansion chambers A and B to the outside is provided.

  In the cylinder deactivation operation, the on-off valve 104 is maintained in a closed state, and the exhaust gas introduced from the engine into the exhaust gas introduction pipe 103 flows from the through hole 103a to the expansion chamber A as indicated by the solid line arrow, and further the partition wall. The exhaust gas flows into the expansion chamber B through the through-hole 102a of 102, and the exhaust gas energy is attenuated and muffled by the repeated expansion in the expansion chambers A and B, and then discharged from the exhaust gas discharge pipe 105 to the outside.

  On the other hand, in the all-cylinder operation, the on-off valve 104 is opened, and the exhaust gas introduced from the engine into the exhaust gas introduction pipe 103 is discharged from the downstream end of the exhaust gas introduction pipe 103 to the outside as indicated by a two-dot chain line arrow. Discharge.

JP 2008-45495 A

  According to Patent Document 1, in the cylinder deactivation operation, exhaust gas is introduced into the expansion chambers A and B by closing the on-off valve 104 provided at the lower end of the exhaust gas introduction pipe 103, and the exhaust gas flow resistance. And the low-frequency exhaust noise is silenced, and in the all-cylinder operation, the on-off valve 104 of the exhaust gas introduction pipe 103 is opened, the exhaust gas flow resistance is reduced, and the engine output is improved.

  However, in all-cylinder operation, the exhaust gas introduced into the exhaust gas introduction pipe 103 is discharged to the outside without being silenced.

  Further, since the exhaust gas introduction pipe 103 has the on-off valve 104 at the downstream end penetrating the silencer body 101, when the on-off valve 104 is closed by switching from the full cylinder operation to the cylinder deactivation operation, There is concern about the generation of low-frequency exhaust noise, that is, humming noise due to the moderate flow switching.

  Furthermore, it is difficult to appropriately process high-frequency exhaust sounds and low-frequency exhaust sounds that have greatly different characteristics due to all-cylinder operation and cylinder operation in a single silencer main body 101.

  Accordingly, an object of the present invention made in view of such a point is to increase the exhaust noise flow resistance by increasing the exhaust gas flow resistance in the cylinder deactivation operation, and to improve the output while maintaining the silencing effect in the all cylinder operation. To provide a system.

  The exhaust system for an engine according to claim 1, which achieves the object, includes a cylinder that is always operated and a cylinder that is deactivated during low-power operation, wherein all cylinders are activated and the deactivated cylinder is deactivated. In the exhaust system of a cylinder deactivation engine that can be switched to a cylinder deactivation operation, a downstream side of the exhaust pipe of the engine is branched into a first branch pipe and a second branch pipe, and is relatively attached to the first branch pipe A first silencer having a small exhaust gas flow resistance, a second silencer mounted on the second branch pipe and having a relatively large exhaust gas flow resistance, and an exhaust gas provided in the exhaust pipe and flowing through the exhaust pipe. A switching valve that selectively switches between the first branch pipe and the second branch pipe, and the switching valve is controlled to be switched to the first branch pipe side during the all cylinder operation and to the second branch pipe side during the cylinder deactivation operation. Control device And said that there were pictures.

  According to this configuration, in all-cylinder operation, the exhaust gas flowing through the exhaust pipe is introduced into the first branch pipe by the switching valve, and is introduced into the first silencer having a relatively low exhaust gas flow resistance to mute and the engine output Will improve.

  On the other hand, in the cylinder deactivation operation, the exhaust gas flowing through the exhaust pipe is introduced into the second branch pipe, and is introduced into the second silencer having a relatively large exhaust gas flow resistance. The sound is muted and the muffled sound is effectively muted.

  Further, by arranging a switching valve for switching the exhaust gas between the first branch pipe and the second branch pipe on the upstream side of the first silencer and the second silencer, the exhaust gas flow is changed simultaneously with the switching of the switching valve. It is switched to the silencer side or the second silencer side and has excellent responsiveness.

  According to a second aspect of the present invention, in the engine exhaust system according to the first aspect, an exhaust gas exhaust pipe of the second silencer communicates with the first silencer.

  According to this configuration, the exhaust gas exhaust pipe of the second silencer communicates with the first silencer, so that the exhaust gas silenced by the second silencer during the cylinder deactivation operation is silenced in the exhaust gas exhaust pipe. The sound is muted with one silencer.

  According to a third aspect of the present invention, in the engine exhaust system according to the first or second aspect, the first silencer has a silencing action of a medium / high frequency exhaust sound, and the second silencer has a low frequency The present invention is characterized in that it has a silencing action of exhaust sound.

  According to this, the low-frequency exhaust sound in the cylinder deactivation operation is efficiently silenced by the second silencer, and the middle / high-frequency exhaust sound is silenced by the first silencer.

  According to the present invention, in all-cylinder operation, exhaust gas is introduced into the first silencer having a relatively small exhaust gas flow resistance, and is silenced and engine output is improved. On the other hand, in the cylinder deactivation operation, the exhaust gas is introduced into the second silencer having a relatively large exhaust gas flow resistance, so that the low-circulation exhaust sound is silenced and the booming noise is efficiently silenced.

  Further, the exhaust gas flow can be switched simultaneously with the switching of the switching valve, and the response is excellent.

It is a mimetic diagram showing a schematic structure of an exhaust system of an engine concerning a 1st embodiment. It is an action explanatory view, (a) shows an action at the time of all cylinder operation, and (b) shows an action at the time of cylinder deactivation operation. It is an operation | movement flowchart. It is an operation | movement flowchart. It is a schematic diagram which shows schematic structure of the exhaust system of the engine which concerns on 2nd Embodiment. It is an operation explanatory view, (a) shows the action at the time of all cylinder operation, and (b) shows the action at the time of cylinder deactivation operation. It is outline | summary explanatory drawing of the conventional silencer.

(First embodiment)
A first embodiment of an engine exhaust system according to the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic diagram showing a schematic configuration of an engine exhaust system 1, and FIG.

  In the present embodiment, the vehicle engine 10 includes two cylinders that are always operated and two cylinders that are deactivated during low-power operation, and the cylinders that are deactivated during all-cylinder operation and low-power operation are all deactivated. The cylinder deactivation engine can be switched to a cylinder deactivation operation, and exhaust gas is discharged from each cylinder to an unillustrated exhaust manifold.

  The exhaust manifold has a plurality of exhaust introduction parts connected to the exhaust ports of the cylinders, and a collecting pipe part that collects the exhaust introduction parts. The exhaust system 1 exhausts exhaust gas from the engine via the exhaust manifold. Has an exhaust pipe. The exhaust pipe has a front exhaust pipe 11 into which exhaust gas from the engine is introduced. A sub silencer 12 is connected to the front exhaust pipe 11, and a main exhaust pipe 13 is connected to the exhaust gas exhaust pipe of the sub silencer 12. Is connected. A first branch pipe 15 and a second branch pipe 16 branching left and right are connected to the rear end of the main exhaust pipe 13 via a switching valve 17 described later.

  The exhaust gas introduction pipe of the first silencer 20 is connected to the downstream end of the first branch pipe 15, and the exhaust gas introduction pipe of the second silencer 25 is connected to the second branch pipe 16. Further, the exhaust gas discharge pipe 27 of the second silencer 25 is connected to the exhaust gas introduction pipe of the first silencer 20. The first silencer 20 and the second silencer 25 are separated from each other on the left and right sides of the vehicle body and arranged in parallel to suppress the longitudinal length of the vehicle body and extend the exhaust gas discharge pipe 27. Depending on the length of the exhaust gas discharge pipe 27, the exhaust gas flow resistance in the exhaust gas discharge pipe 27 increases.

  The first silencer 20 has, for example, an expansion chamber formed in the silencer body 21 and is connected to the first branch pipe 15 to introduce exhaust gas into the silencer body 21 and the silencer body 21. It has an exhaust gas discharge pipe 22 for discharging the exhaust gas inside. The first silencer 20 is set to have a relatively low exhaust gas flow resistance and a low pressure loss so as to be mainly responsible for the silencing action of the medium / high frequency exhaust sound.

  On the other hand, the second silencer 25 is formed by, for example, a plurality of expansion chambers and glass wool accommodated in the expansion chamber main body 26 and connected to the second branch pipe 16 to exhaust gas in the silencer main body 26. And an exhaust gas exhaust pipe 27 for exhausting exhaust gas in the silencer body 26. The second silencer 25 is set to have a relatively large exhaust gas flow resistance so as to be mainly responsible for the silencing action of the low-frequency exhaust sound.

  The switching valve 17 disposed at the lower end of the main exhaust pipe 13 which becomes the branch point of the exhaust pipe opens the first branch pipe 15 side by the operation of the electric or hydraulic actuator 18 and opens the second branch pipe 16 side. It is configured to selectively switch between an all-cylinder operation position where the valve is closed and a cylinder deactivation operation position where the first branch pipe 15 side is closed and the second branch pipe 16 side is opened. The exhaust gas from the main exhaust pipe 13 is guided to the first branch pipe operation 15 side as indicated by the solid line arrow a at the all cylinder operation position, and the main exhaust pipe 13 is indicated at the cylinder deactivation operation position as indicated by the two-dot chain line arrow b. The exhaust gas from is guided to the second branch pipe 16.

  A controller 19 that operates the actuator 18 is connected to the actuator 18. The control device 19 controls the operation of the actuator 18 in accordance with, for example, a cylinder deactivation signal output from the engine control unit (ECU) during cylinder deactivation operation.

  Next, the operation of the exhaust system configured as described above will be described with reference to an operation explanatory diagram shown in FIG. 2 and an operation flowchart of FIG.

  As the engine 10 is operated, a cylinder deactivation signal is transmitted from the engine control unit (ECU) to the control unit 19 during cylinder deactivation operation, and transmission of the cylinder deactivation signal is interrupted during all cylinder operation.

  The control device 19 determines whether or not all cylinders are operated according to the presence or absence of a cylinder deactivation signal transmitted from the engine control unit (step S101).

  In step S101, Yes, that is, in the all cylinder operation, the switching valve 17 is switched to and maintained in the all cylinder operation position by the operation of the actuator 18 (step S102). As a result, the first branch pipe 15 side opens and the second branch pipe 16 side closes, and the exhaust gas from the main exhaust pipe 13 is guided to the first branch pipe 15 as shown in FIG. As a result, the exhaust gas from the engine 10 is introduced from the main exhaust pipe 13 through the first branch pipe 15 to the first silencer 20 in charge of the silencing action of the medium / high-frequency exhaust sound, and is silenced by the first silencer 20. Then, it is discharged from the exhaust gas discharge pipe 22 to the outside.

  On the other hand, in step S101, No, that is, in the cylinder deactivation operation, the switching valve 17 is switched to and maintained in the cylinder deactivation operation position by the operation of the actuator 18 (step S103).

  Thus, the first branch pipe 15 side is closed and the second branch pipe 16 side is opened, and the exhaust gas from the main exhaust pipe 13 is guided to the second branch pipe 16 as shown in FIG. As a result, the exhaust gas from the engine 10 is introduced from the main exhaust pipe 13 through the second branch pipe 16 into the second silencer 25 having a large exhaust gas flow resistance and mainly responsible for the silencing action of the low-frequency exhaust sound. The sound is silenced by the second silencer 25, further introduced into the first silencer 20 through the exhaust gas discharge pipe 27, silenced by the first silencer 20, and discharged from the exhaust gas discharge pipe 22 to the outside.

  Next, the operation will be described.

  During operation of the engine 10, exhaust gas is introduced from the exhaust manifold of the engine 10 into the main exhaust pipe 13 through the front exhaust pipe 11 and the sub silencer 12. In the all cylinder operation, the switching valve 17 is held at the all cylinder operation position, and the exhaust gas is introduced from the main exhaust pipe 13 to the first branch pipe 15 side as shown in FIG. The first branch pipe 15 is introduced into the first silencer 20 which is mainly responsible for the silencing action of the medium and high frequency exhaust sound and is set to a relatively small exhaust gas flow resistance, and is silenced by the first silencer 20 and exhaust gas. It is discharged from the discharge pipe 22 to the outside. Here, the first silencer 20 has a small exhaust gas flow resistance, a very low pressure loss, and an improved engine output.

  On the other hand, in the cylinder deactivation operation, the switching valve 17 is held at the cylinder deactivation operation position, and the exhaust gas is introduced from the main exhaust pipe 13 to the second branch pipe 16 side. It is introduced into the second silencer 25 which is excellent in the effect of silencing exhaust sound. The exhaust gas silenced by the second silencer 25 is silenced via the long exhaust gas discharge pipe 27 of the second silencer 25 and then introduced into the first silencer 20 to be further silenced by the first silencer. The sound is silenced at 20 and discharged from the exhaust gas discharge pipe 22 to the outside. In other words, the exhaust gas in the cylinder deactivation operation is continuously silenced by the second silencer 25, the exhaust gas exhaust pipe 27, and the first silencer 20, which have large exhaust gas flow resistance, and the muffled noise is efficiently silenced.

  In addition, a switching valve 17 is interposed between the upstream end of the first branch pipe 15 and the second branch pipe 16 on the upstream side of the first silencer 20 and the second silencer 25 and the downstream end of the main exhaust pipe 13. When the all-cylinder operation is switched to the cylinder deactivation operation, the switching valve 17 is switched from the all-cylinder operation position to the cylinder deactivation operation position, so that the first silencer 20 can be instantaneously switched to the second silencer 22, and A silencing effect is obtained by the second silencer 25.

  Thereby, when switching from the full cylinder operation to the cylinder deactivation operation, the exhaust gas does not stay in the main exhaust pipe 13, and the generation of the low frequency exhaust noise, that is, the booming noise is suppressed.

  Thus, by providing the switching valve 17 that switches the exhaust gas from the engine 10 to the first silencer 20 side in the all cylinder operation and to the second silencer 25 side in the cylinder deactivation operation, the engine 10 in the cylinder deactivation operation is provided. The exhaust gas from the exhaust gas is silenced by the silencing action of the second silencer 25 having a large exhaust gas flow resistance and excellent silencing action of the low-frequency exhaust sound, and further silenced by the silencing action of the first silencer 20 and the exhaust silencing effect. Is increased. On the other hand, in the all-cylinder operation region, the sound is silenced by the first silencer 20 having a relatively small exhaust gas flow resistance, and an engine output improvement effect is obtained.

  In the above description, the switching valve 17 is configured to be switched based on the cylinder deactivation signal from the engine ECU. However, only a part of the cylinders are operated with respect to the exhaust gas pressure of all cylinder operation in which all cylinders are operated. Since the exhaust gas pressure during cylinder deactivation operation is extremely small, all cylinder operation or cylinder deactivation operation can be detected by detecting the exhaust gas pressure in the exhaust system, for example, the front exhaust pipe 11.

  An example of switching control of the switching valve 17 based on the exhaust gas pressure signal from the exhaust gas pressure sensor will be described with reference to the flowcharts of FIGS.

  When the exhaust gas pressure exceeding the threshold of the exhaust system path is detected, the control device 19 has an exhaust gas pressure sensor that outputs an exhaust gas pressure signal, and the control device 19 controls the operation of the actuator according to the presence or absence of the exhaust gas pressure signal. . Other configurations are the same as those described above.

  As shown in the flowchart in FIG. 4, when the exhaust gas pressure sensor detects an exhaust gas pressure equal to or higher than a threshold value, an exhaust gas pressure signal is transmitted to the control device 19. The control device 19 determines whether or not all cylinder operation is performed according to the presence or absence of the all cylinder operation signal (step S105).

  In step S105, that is, in the all cylinder operation, the switching valve 17 is switched to the all cylinder operation position by the operation of the actuator 18, the second branch pipe 16 side is closed, and the first branch pipe 15 side is opened (step) S106). As a result, as shown in FIG. 2A, the exhaust gas from the engine 10 is supplied from the main exhaust pipe 13 through the first branch pipe 15 to the first silencer 20 having a small exhaust gas flow resistance. The sound is silenced by the vessel 20 and discharged from the exhaust gas discharge pipe 22 to the outside.

  On the other hand, in step S105, No, that is, in the cylinder deactivation operation, the operation of the actuator 18 switches the switching valve 17 to the cylinder deactivation operation position, closes the first branch pipe 15 side, and opens the second branch pipe 16 side. (Step S107).

  As a result, as shown in FIG. 2 (b), the exhaust gas from the engine 10 has a large exhaust gas flow resistance from the main exhaust pipe 13 through the second branch pipe 16, and is excellent in the low frequency exhaust noise reducing action. Exhaust gas supplied to the silencer 25, silenced by the second silencer 25, and silenced by the second silencer 25 passes through the exhaust gas discharge pipe 22 to the first silencer 20 having a small exhaust gas flow resistance. Then, the sound is silenced by the first silencer 20 and discharged from the exhaust gas discharge pipe 22 to the outside.

(Second Embodiment)
A second embodiment will be described with reference to FIGS. In addition, the detailed description of this part is abbreviate | omitted by attaching | subjecting the same code | symbol to the site | part corresponding to FIG. 1 in the said 1st Embodiment.

  FIG. 5 is a schematic diagram showing a schematic configuration of an engine exhaust system.

  The vehicle engine 10 is a cylinder deactivation engine having two cylinders that are always operated and two cylinders that are deactivated during a low-load output operation, and exhaust gas is discharged from each cylinder to an unillustrated exhaust manifold. The exhaust system 1 has a front exhaust pipe 11 into which exhaust gas from the engine is introduced via an exhaust manifold, and a sub silencer 12 is connected to the front exhaust pipe 11, and an exhaust gas exhaust pipe of the sub silencer 12. The main exhaust pipe 13 is connected to.

  A first branch pipe 15 and a second branch pipe 16 are connected to the rear end of the main exhaust pipe 13 via a switching valve 17. A first silencer 20 is connected to the downstream end of the first branch pipe 15, and a second silencer 25 is connected to the second branch pipe 16.

  The first silencer 20 has an exhaust gas introduction pipe and an exhaust gas discharge pipe 22 that are connected to the first branch pipe 15 and introduce exhaust gas into the silencer body 21. The first silencer 20 is set to have a relatively low exhaust gas flow resistance and a low pressure loss so as to mainly handle the silencing action of the high and medium frequency exhaust sound.

  On the other hand, the second silencer 25 has an exhaust gas introduction pipe and an exhaust gas discharge pipe 27 that are connected to the second branch pipe 16 and introduce exhaust gas into the silencer body 26. The second silencer 25 is set to have a relatively large exhaust gas flow resistance so as to be mainly responsible for the silencing action of the low-frequency exhaust sound.

  The switching valve 17 is operated by the actuator 18 to open the first branch pipe 15 side and close the second branch pipe 16 side, and to close the first branch pipe 15 side and the second branch pipe 16 side. It is configured to selectively switch to the cylinder deactivation operation position where the side is opened. The exhaust gas from the main exhaust pipe 13 is guided to the first branch pipe 15 as indicated by the solid line arrow a at the all cylinder operating position, and the exhaust gas from the main exhaust pipe 13 is indicated at the cylinder deactivation valve opening position as indicated by the chain line arrow b. The gas is guided to the second branch pipe 16.

  During operation of the engine 10, exhaust gas is introduced from the exhaust manifold of the engine 10 to the front exhaust pipe 11, the sub silencer 12, and the main exhaust pipe 13, and in the all cylinder operation, the switching valve 17 is held at the all cylinder operation position. As shown in FIG. 6A, the exhaust gas is introduced from the main exhaust pipe 13 to the first branch pipe 15 and is introduced into the first silencer 20 having a relatively small exhaust gas flow resistance. The sound is silenced by the first silencer 20 and discharged from the exhaust gas discharge pipe 22 to the outside. Here, the first silencer 20 has a small exhaust gas flow resistance, has no pressure loss, or is extremely small and suppresses a reduction in engine output.

  On the other hand, in the cylinder deactivation operation, the switching valve 17 is held at the cylinder deactivation operation position and is introduced from the main exhaust pipe 13 to the second branch pipe 16 side, so that the exhaust gas flow resistance is relatively large and low frequency exhaust noise is generated. It is introduced into the second silencer 25 which has an excellent silencing effect. The exhaust gas in the cylinder deactivation operation is silenced by the second silencer 25 having a large exhaust gas flow resistance, and the muffled noise is efficiently silenced.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of invention.

1 exhaust system 10 vehicle engine 13 main exhaust pipe 15 first branch pipe 16 second branch pipe 17 switching valve 19 control device 20 first silencer 21 silencer body 22 exhaust gas exhaust pipe 25 second silencer 26 silencer body 27 Exhaust gas exhaust pipe

Claims (3)

In an exhaust system of a cylinder deactivation engine comprising a cylinder that is normally operated and a cylinder that is deactivated during low-power operation, and that can be switched between all cylinder operation in which all of the cylinders are activated and cylinder deactivation operation in which the cylinder to be deactivated is deactivated.
Branching the downstream side of the exhaust pipe of the engine into a first branch pipe and a second branch pipe;
A first silencer mounted on the first branch pipe and having a relatively low exhaust gas flow resistance;
A second silencer attached to the second branch pipe and having a relatively large exhaust gas flow resistance;
A switching valve that is provided in the exhaust pipe and selectively switches the exhaust gas flowing through the exhaust pipe between the first branch pipe and the second branch pipe;
An exhaust system for an engine, comprising: a control device that controls to switch the switching valve to the first branch pipe side during the all-cylinder operation and to the second branch pipe side during the cylinder deactivation operation.   2. The engine exhaust system according to claim 1, wherein an exhaust gas discharge pipe of the second silencer communicates with the first silencer. The first silencer has a silencing action of mid / high frequency exhaust sound,
3. The engine exhaust system according to claim 1, wherein the second silencer has a silencing action of a low-frequency exhaust sound. 4.

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