JP2008184934A - Exhaust device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust system of an internal combustion engine, which prevents the occurrence of the sound having half order, generated during exhaust, and becoming more distinct due to unequal length of a plurality of exhaust pipes, and improves tone of the sound. <P>SOLUTION: This exhaust system of the internal combustion engine is provided with: an exhaust pipe 21 on one side; and an exhaust pipe 22 having larger length than that of the exhaust pipe 21 on the other side, which introduce exhaust gas from the engine 11 into them, respectively, to join the exhaust gases introduced into both exhaust pipes 21, 22 at a predetermined joining point A and exhaust the gases. This exhaust system is provided with an exhaust gas temperature adjusting means 40 for adjusting the temperature of the exhaust gas flowing from the exhaust pipe 21 on the one side to the joining point A to the temperature being lower than the temperature of the exhaust gas flowing from the exhaust pipe 22 on the other side to the joining point A by adjusting temperature of at least either of the exhaust gases flowing in the exhaust pipes 21, 22 on the upstream side more than the joining point A. Preferably, the exhaust gas temperature adjusting means 40 cools the exhaust gas passing through the exhaust pipe 21 on the one side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust system for an internal combustion engine, and more particularly, to an exhaust system for an internal combustion engine that is mounted on a vehicle and reduces exhaust noise due to interference by introducing exhaust gas into one and the other exhaust pipes.

  An exhaust device of an internal combustion engine (hereinafter also referred to as an engine) mounted on a vehicle such as an automobile generally joins exhaust gases from a plurality of cylinders of a multi-cylinder internal combustion engine together with an exhaust manifold while suppressing exhaust interference, and a silencer After the sound is silenced, the air is exhausted to the atmosphere, and various exhaust sound reduction techniques have been proposed.

  As a conventional internal combustion engine exhaust system, for example, an actuator that mechanically varies the pipe length is provided in a part of a plurality of exhaust pipes constituting an exhaust manifold, and a plurality of exhaust pipes are assembled at a predetermined collection point. By providing a phase difference to the 1st to 3rd order exhaust sounds (having frequencies of 1, 2 and 3 times the engine speed) from the plurality of exhaust pipes at the collection point, The first to third order exhaust sounds cancel each other out due to mutual interference (for example, see Patent Document 1).

  Further, even in an exhaust system of an internal combustion engine having a plurality of banks such as a V-type engine, after exhaust gas is introduced into one exhaust pipe and the other exhaust pipe from exhaust manifolds arranged on both sides of the engine, When the exhaust gas passing through is silenced with a silencer and merged in the vicinity of the silencer and then exhausted into the atmosphere, one of the exhaust pipe and the other exhaust pipe attenuates the exhaust sound from the other There is known one in which the collection positions of both exhaust pipes are set so as to make a resonator that performs the same (for example, see Patent Document 2).

Furthermore, for example, an exhaust cooler is provided on the downstream side of the catalytic converter in the exhaust passage, and the exhaust cooler is allowed to flow from the circulation circuit of the engine cooling water to reduce the flow rate of the exhaust gas passing through the silencer. Some exhaust noise reduction (see, for example, Patent Document 3).
Japanese Utility Model Publication No. 3-20490 JP 2005-106052 A JP 2004-245128 A

  However, in the exhaust system of the conventional internal combustion engine as described above, two exhaust paths from the limitation of the space under the floor of the vehicle to the silencer (so-called main muffler), particularly as in the exhaust system of the V-type engine. When the unequal lengths are set, the exhaust sound pressure level of the integer order is reduced by interfering exhaust sound (sound wave) when the exhaust gas from the two exhaust pipes merges by setting an appropriate exhaust pipe assembly position. On the other hand, exhaust sound components having a so-called half order other than the basic order (integer order) due to the explosion of the internal combustion engine (for example, 0.5 times (0.5 order) and 1.5 times (1.5 times the engine speed)) Next), 2.5 times (2.5th order) and the like) interference was noticeable, and an unpleasant exhaust sound such as a so-called “battered” sound was generated. For this reason, there has been an unsolved problem in sensory performance, such as improvement of unpleasant exhaust noise.

  That is, when one exhaust pipe and the other exhaust pipe have the same length, as shown in FIG. 4 (a), the resonance frequencies determined by the pipe length are equal, so that the integer orders from the left and right banks are equal. FIG. 4B shows a case where the exhaust sound strengthens due to interference and the combined wave after merging has a high sound pressure level, whereas one exhaust pipe and the other exhaust pipe are unequal in length. As described above, although the exhaust sounds of integer orders from the left and right banks have the advantage that they tend to weaken due to interference and the combined wave after joining tends to have a low sound pressure level, the exhaust sounds of half orders are equal in length. Compared to the case, the exhaust sound pressure level becomes relatively high due to interference at the time of exhaust merging (see FIG. 5), and as a result, when the synthesized sound is heard, it becomes an unpleasant exhausted exhaust tone. The sensual exhaust sound performance was degraded.

  Therefore, an object of the present invention is to provide an exhaust system for an internal combustion engine that suppresses interference of exhaust noise of a half order due to unequal lengths of a plurality of exhaust pipes and improves the exhaust tone.

  In order to achieve the above object, the present invention includes (1) one exhaust pipe for introducing exhaust gas from an internal combustion engine and the other exhaust pipe having a longer length than the exhaust pipe, and the one exhaust pipe and the other exhaust pipe. In the exhaust system for an internal combustion engine that exhausts the exhaust gas introduced into the exhaust pipe by joining at a predetermined junction, at least one of the one exhaust pipe or the other exhaust pipe is located upstream from the junction. By adjusting the temperature of one exhaust gas, the temperature of the exhaust gas flowing from the one exhaust pipe to the junction is adjusted to be lower than the temperature of the exhaust gas flowing from the other exhaust pipe to the junction. Means is provided.

  With this configuration, the speed of sound in one exhaust pipe with a short pipe length is relatively smaller than the speed of sound in the other exhaust pipe, so that the difference in pipe length between one exhaust pipe and the other exhaust pipe is somewhat reduced. It is possible to produce an equivalent effect and prevent the exhaust sound pressure of the half order other than the basic order due to the explosion of the internal combustion engine from being increased by interference when the exhaust gas from one and the other exhaust pipes merges. Even when the lengths of one exhaust pipe and the other exhaust pipe must be different from the layout surface under the floor, it is possible to reduce the sound pressure level of an unpleasant exhaust sound such as a so-called “tattered sound”.

  In the exhaust system for an internal combustion engine of the present invention having the configuration (1), preferably, (2) the exhaust temperature adjusting means cools the exhaust gas passing through the one exhaust pipe.

  In this case, the exhaust gas temperature in one exhaust pipe decreases, so the exhaust sound speed in one exhaust pipe decreases, and the air column resonance frequency of one exhaust pipe also decreases. Thereby, if there is a silencer in the downstream of one exhaust pipe, the silencing effect can be enhanced, and the exhaust temperature released into the atmosphere can be lowered.

  In the exhaust device for an internal combustion engine having the configuration of (2), (3) the exhaust temperature adjusting means exchanges heat between the cooling water for cooling the internal combustion engine and the exhaust gas passing through the one exhaust pipe. It is preferable to have an exhaust heat recirculator.

  With this configuration, heat is exchanged between the cooling water of the internal combustion engine and the exhaust gas passing through one of the exhaust pipes, so that the exhaust heat can be recirculated to the engine side. This can contribute to the early warming up of the engine immediately after starting and the improvement of the heating performance. In addition, a hybrid vehicle having a traveling drive motor separately from the engine can further contribute to improvement in fuel consumption by shortening the engine operation time.

  An exhaust system for an internal combustion engine having any one of the configurations (1) to (3) includes: (4) a silencer that introduces and silences exhaust gases from the one exhaust pipe and the other exhaust pipe, respectively. And the merging point may be located in the silencer.

  With this configuration, since the junction is located in the silencer, one of the exhaust pipes can be made relatively long, and the degree of freedom of arrangement of the exhaust temperature adjusting means can be increased.

  The internal combustion engine exhaust system having any one of the above configurations (1) to (3) includes (5) an assembly in which the one exhaust pipe and the other exhaust pipe are assembled at the downstream ends of both exhaust pipes. A pipe may be provided, and the junction may be located in the collecting pipe.

  With this configuration, since the confluence is located in the collecting pipe, the one exhaust pipe and the other exhaust pipe can be gathered at an arbitrary position regardless of the installation position of the silencer, etc. The length of the other exhaust pipe can be set and the degree of layout can be increased.

  An exhaust system for an internal combustion engine having any one of the configurations (1) to (5) includes (6) a silencer that silences the exhaust gas introduced from the one exhaust pipe and the other exhaust pipe. The junction is preferably located outside the silencer.

  Thereby, a silencer can be arrange | positioned without being restrained by the position of a collecting pipe, and the freedom degree of the layout can be raised. In this case, the collecting pipe can be arranged upstream of the silencer, and the gas passing through the one exhaust pipe and the other exhaust pipe can be merged and then introduced into the silencer. It is also possible to attach a silencer to each of the other exhaust pipes and to collect one exhaust pipe and the other exhaust pipe downstream from the silencer.

  The exhaust system for an internal combustion engine of the present invention having the configuration of any one of (1) to (3) includes (7) an exhaust gas purifying catalyst device mounted on the one exhaust pipe, and the exhaust temperature. The adjusting means may include a cooling unit attached to the one exhaust pipe on the downstream side of the catalyst device.

  In this case, since the exhaust gas after passing through the catalyst device is cooled, there is no adverse effect on the warm-up property at the start of the catalyst device.

  The exhaust system for an internal combustion engine according to the present invention having the above-described configuration (1) or (2) includes (8) the other exhaust gas purification catalyst device mounted on the other exhaust pipe, and the exhaust gas The temperature adjusting means may include a heating unit that heats the exhaust gas in the other catalyst device or upstream of the other catalyst device.

  With this configuration, the exhaust gas temperature in the other exhaust pipe having the longer pipe length rises and the exhaust sound speed in the other exhaust pipe increases, so that the sound speed in the one exhaust pipe having the shorter pipe length is relatively reduced. It becomes smaller than the sound speed inside. Therefore, the effect of increasing the sound speed of the exhaust in the other exhaust pipe and substantially shortening the pipe length of the other exhaust pipe, that is, the pipe length difference between one exhaust pipe and the other exhaust pipe is slightly reduced. It is possible to produce an effect equivalent to the above, and to prevent the exhaust sound pressure of the half order other than the basic order due to the explosion of the internal combustion engine from being strengthened by interference when the exhaust gas from one and the other exhaust pipes merges. .

  In addition, an exhaust system for an internal combustion engine according to the present invention having any one of the configurations (1) to (8) described above is (9) the internal combustion engine has a pair of banks each having a plurality of cylinders, It is preferable that one exhaust pipe and the other exhaust pipe are respectively connected to the pair of banks.

  With this configuration, even if the two exhaust pipes corresponding to the pair of banks of the V-type engine have unequal lengths, the half-order exhaust sound component can be effectively reduced.

  According to the present invention, the speed of sound in one exhaust pipe is relatively lowered than the speed of sound in the other exhaust pipe to produce the same effect as reducing the pipe length difference between the two exhaust pipes. It is possible to prevent the exhaust sound pressure of the half order other than the basic order due to the explosion of the internal combustion engine from being increased due to interference when the exhaust gas from the engine is merged, and one exhaust pipe and the other exhaust pipe from the layout surface under the vehicle floor Even when the pipe lengths of the pipes are inevitably different, an unpleasant exhaust sound pressure level such as so-called “tattered sound” can be reduced. As a result, an exhaust system for an internal combustion engine with improved exhaust tone can be provided.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[First embodiment]
1 and 2 are views showing an exhaust device for an internal combustion engine according to a first embodiment of the present invention.

  First, the configuration will be described.

  In FIG. 1, a V-type 8-cylinder engine 11 which is a multi-cylinder internal combustion engine has a plurality of banks 11a and 11b, and exhaust manifolds 12 and 13 arranged on both sides of the engine 11 have upstream ends. The exhaust gas is discharged from the banks 11a and 11b of the engine 11 into the exhaust passages in the exhaust manifolds 12 and 13, respectively.

  Specifically, the exhaust manifold 12 is, for example, a first cylinder to a fourth cylinder formed in one bank 11a of the engine 11 (a plurality indicated by reference numerals # 1, # 2, # 3, and # 4 in FIG. 1). The exhaust manifold 13 is connected to an exhaust port of each of the cylinders), and a collecting pipe portion 12b that collects the exhaust introduction portions 12a. The exhaust manifold 13 is formed in the other bank 11b of the engine 11, for example. A plurality of exhaust introduction portions 13a connected to the exhaust ports of the cylinders to the eighth cylinder (a plurality of cylinders indicated by symbols # 5, # 6, # 7, and # 8 in FIG. 1) and a collecting pipe portion for collecting them 13b. The engine 11 explodes in a predetermined explosion order, for example, the first cylinder, the eighth cylinder, the fourth cylinder, the third cylinder, the sixth cylinder, the fifth cylinder, the second cylinder, and the seventh cylinder. During operation of the engine 11, exhaust is sequentially performed into the exhaust manifolds 12 and 13 from the engine 11 that is in the exhaust stroke in that order.

  The exhaust system for an internal combustion engine according to the present embodiment has a first exhaust pipe 21 (one exhaust pipe) and a second exhaust pipe having different pipe lengths for introducing exhaust gases from the engine 11 through the exhaust manifolds 12 and 13, respectively. An exhaust pipe 22 (the other exhaust pipe) is provided. The first exhaust pipe 21 has a shorter length than the second exhaust pipe 22 and is connected to the collecting pipe portion 12 b of the exhaust manifold 12. In addition, the second exhaust pipe 22 that is longer than the first exhaust pipe 21 is connected to the collecting pipe portion 13 b of the exhaust manifold 13.

  The exhaust gas passing through the first exhaust pipe 21 and the second exhaust pipe 22 is exhausted after joining at a predetermined joining point A.

  That is, the first exhaust pipe 21 and the second exhaust pipe 22 have upstream ends 21a and 22a connected to the exhaust manifolds 12 and 13, respectively, and downstream ends 21b and 22b connected to the silencer 24. The downstream ends 21 b and 22 b of the exhaust pipes 21 and 22 are inserted into the silencer 24 and open in the silencer 24. In this case, the exhaust gas passing through the first exhaust pipe 21 and the second exhaust pipe 22 merges in the silencer 24, and the predetermined junction A is located in the silencer 24.

  Since the lengths of the exhaust passages in the exhaust manifolds 12 and 13 are equal to each other, the pipe length L1 of the first exhaust pipe 21 is from a plurality of exhaust ports of one bank 11a of the engine 11 to the junction A. Corresponding to the average exhaust passage length, the pipe length L2 of the second exhaust pipe 22 corresponds to the average exhaust passage length from the plurality of exhaust ports of the other bank 11b of the engine 11 to the junction A. .

  In FIG. 1, the first exhaust pipe 21 includes an upstream exhaust pipe portion 21c equipped with catalyst devices 31a and 31b, respectively, and a downstream exhaust pipe portion 21d fixed to the silencer 24 by welding or the like. Thus, the upstream exhaust pipe portion 21c and the downstream exhaust pipe portion 21d are flange-coupled by a flange joint portion 21e. Similarly, the second exhaust pipe 22 also includes an upstream exhaust pipe portion 22c equipped with the catalyst devices 32a and 32b, and a downstream exhaust pipe portion 22d fixed to the silencer 24 by welding or the like. The upstream side exhaust pipe part 22c and the downstream side exhaust pipe part 22d are flange-connected by a flange joint part 22e. Further, the muffler 24 is connected to the rearmost exhaust pipe portion 26 having an exhaust port 26a. In addition, since the silencer 24 itself is a well-known thing, description of the detailed internal structure of the silencer 24 is abbreviate | omitted.

  On the other hand, of the first exhaust pipe 21 and the second exhaust pipe 22, the first exhaust pipe 21 having a short pipe length is located upstream from the joining point A and is moved from the first exhaust pipe 21 to the joining point A. An exhaust heat recirculator 40 is mounted as exhaust temperature adjusting means for adjusting the temperature of the flowing exhaust gas to a temperature lower than the temperature of the exhaust gas flowing from the second exhaust pipe 22 to the junction A.

  The exhaust heat recirculator 40 is a known heat exchanger for exchanging heat between the cooling water of the engine 11 and the exhaust gas passing through the first exhaust pipe 21. For example, as shown in FIG. An exhaust cooler 42 is provided in a case 41 surrounding the entire circumference of a part of the exhaust pipe 21. The exhaust cooler 42 includes a cooling water introduction part 42a and a cooling water discharge part 42b that penetrate the case 41, and a cooler main body part 42c connected to the cooling water introduction part 42a and the cooling water discharge part 42b. The cooler main body 42c has a cooling water passage (not shown) therein and an exhaust cooling surface that contacts the exhaust gas in the case 41 over a wide area. Note that the configuration of the exhaust heat recirculator 40 as such a heat exchanger itself is the same as the configuration of other known various heat exchangers (for example, the one shown in FIG. 6 of Patent Document 3). can do.

  The exhaust cooler 42 of the exhaust heat recirculator 40 is connected to a water pump (not shown) mounted on the engine 11 by piping, and the cooling water passing through the water jacket in the engine 11 and the radiator 45 disposed in front of the water jacket. For example, the cooling water after cooling the engine 11 is introduced into the cooling water introduction part 42a, and the cooling water discharge part 42b is connected to the engine 11 side (from the radiator 45 to the engine 11). The cooling water after exhaust cooling is recirculated to the cooling water supply passage). That is, the exhaust cooler 42 can recirculate the exhaust heat of the engine 11 to the engine 11 side by returning the cooling water whose temperature has been increased by exhaust cooling to the engine 11 side.

  The exhaust heat recirculator 40 further includes a flow rate adjusting valve 47 that adjusts the flow rate of the cooling water passing through the exhaust cooler 42. The flow rate adjusting valve 47 is connected to the engine 11 or the radiator 45, for example. While being supported, the engine 11 is controlled by an engine control computer (not shown) that electronically controls the engine 11. In other words, the exhaust heat recirculator 40 functions as the exhaust temperature adjusting means in cooperation with the flow rate adjusting valve 47 and the engine control computer.

  The exhaust heat recirculator 40 is located on the downstream side of the exhaust gas purification catalyst devices 31a and 31b attached to the first exhaust pipe 21, and after passing through the catalyst devices 31a and 31b. Exhaust gas passes through the case 41 of the exhaust heat recirculator 40.

  Next, the operation will be described.

  During operation of the engine 11, exhaust gas is introduced into the first exhaust pipe 21 and the second exhaust pipe 22 from the exhaust manifolds 12 and 13 on both sides of the engine 11, and the exhaust gas passing through both the exhaust pipes 21 and 22 is In the silencer 24, they merge and are silenced, and are exhausted to the atmosphere through the exhaust pipe part 26 at the end.

  In this state, the first exhaust pipe 21 and the second exhaust pipe 22 are sequentially exhausted at a high temperature from the engine 11 in accordance with a predetermined explosion order of the engine 11, and the first exhaust pipe 21 and the second exhaust pipe. The exhaust pressure in 22 fluctuates according to the rotation of the engine 11.

At this time, the length of the exhaust passage from the exhaust port of the engine 11 to the junction A is L, the diameter of the passage (exhaust pipe) is d, and the frequency of the exhaust sound (sound wave) that fluctuates according to the rotation of the engine 11 is set. If the mode order is m and the sound speed is C, the Helmholtz resonance frequency (natural frequency) of the exhaust pipes 21 and 22 due to the exhaust sound in the exhaust pipes 21 and 22 is expressed by the following equation (1). Is done.

In the present embodiment, the exhaust heat recirculator 40 exchanges heat between the cooling water of the engine 11 and the exhaust gas passing through the first exhaust pipe 21, and the exhaust passing through the first exhaust pipe 21. Since the temperature of the gas is adjusted to be lower than the temperature of the exhaust gas passing through the second exhaust pipe 22, the speed of sound in the first exhaust pipe 21 is reduced, and the air column resonance frequency f of the first exhaust pipe 21 is reduced. As a result, the same effect as that obtained by increasing the tube length L1 of the first exhaust pipe 21 is produced. Therefore, when the exhaust gas from the first exhaust pipe 21 and the second exhaust pipe 22 joins at the junction A, the exhaust sound pressure of the half order other than the basic order (integer order) due to the explosion of the engine 11 is strengthened by interference. It is prevented from matching, and the exhaust sound of the half order is out of the range where it can be heard as an unpleasant exhaust sound. That is, even when the two exhaust gas passages corresponding to the first exhaust pipe 21 and the second exhaust pipe 22 are likely to be unequal in the V-type engine as in the present embodiment, the exhaust sound component of the half order. As a result, even when the first exhaust pipe 21 and the second exhaust pipe 22 have to be unequal in length from the layout surface under the floor of the vehicle, so-called “tattered sound” The sound pressure level of such an unpleasant exhaust noise can be reduced.

  Incidentally, if the first exhaust pipe 21 has a pipe length of 2 m and the exhaust heat recirculator 40 reduces the exhaust temperature within a range of, for example, 800 degrees Celsius to 400 degrees Celsius, The adjustment range of the air column resonance frequency f by the heat recirculator 40 is about 17 Hz. This is an adjustment range corresponding to a rotational difference of 255 rpm in the case of a V-type 8-cylinder engine. It can be seen that this can contribute to the reduction of

  Further, in this embodiment, the exhaust heat recirculator 40 as the exhaust temperature adjusting means performs heat exchange between the cooling water of the engine 11 and the exhaust gas passing through the first exhaust pipe 21, thereby Since it is recirculated, in a normal gasoline vehicle or diesel vehicle, it can contribute to the early warming up of the engine 11 immediately after starting and the improvement of the heating performance of the vehicle. Further, if the vehicle is a hybrid vehicle equipped with an electric motor for driving along with the engine 11, it can further contribute to improving fuel efficiency by shortening the engine operation time.

  In the present embodiment, since the junction A is located in the silencer 24, the first exhaust pipe 21 can be made relatively long, and the arrangement position of the exhaust heat recirculator 40 is not so limited. It will be over.

  Furthermore, since the exhaust heat recirculator 40 located downstream of the catalyst devices 31a and 31b cools the exhaust gas after passing through the catalyst devices 31a and 31b, when the catalyst devices 31a and 31b are started. There is no adverse effect on warm-up.

  As described above, according to the exhaust system for an internal combustion engine of the present embodiment, the sound velocity in the first exhaust pipe 21 is lowered to lower the air column resonance frequency f of the first exhaust pipe 21, and substantially this Other than the basic order due to the explosion of the engine 11 when the exhaust gas from the first exhaust pipe 21 and the second exhaust pipe 22 merges, producing an effect equivalent to that of increasing the pipe length L1 of the first exhaust pipe 21 Therefore, the first exhaust pipe 21 and the second exhaust pipe 22 have to be different in length from the layout surface under the vehicle floor. Even in such a case, an unpleasant exhaust sound pressure level such as a so-called “tattered sound” can be reduced, and an exhaust device for an internal combustion engine with improved exhaust tone can be provided.

  In the above-described embodiment, the confluence point A of the exhaust gas passing through the first exhaust pipe 21 and the second exhaust pipe 22 is located in the silencer 24, but the confluence point is outside the silencer 24. Needless to say, the downstream ends of the first exhaust pipe 21 and the second exhaust pipe 22 may be gathered outside the silencer 24 to set the above. That is, the collecting pipe is disposed upstream of the silencer 24, and the gas passing through the first exhaust pipe 21 and the second exhaust pipe 22 can be merged and then introduced into the silencer 24. Each of the exhaust pipe 21 and the second exhaust pipe 22 is equipped with a silencer that can mute as much as the silencer 24, and the first exhaust pipe 21 and the second exhaust pipe 22 on the downstream side of the silencer. The gas that has passed through can also be merged by the collecting pipe. Next, such an embodiment will be described.

[Second Embodiment]
FIG. 3 is a diagram showing an exhaust device for an internal combustion engine according to the second embodiment of the present invention.

  This embodiment is similar to the above-described first embodiment, and the first method is different from the above-described case in that the exhaust gas passing through the first exhaust pipe and the second exhaust pipe is merged. Except for the point that the length and shape of the exhaust pipe and the second exhaust pipe are different, other configurations are the same as those of the first embodiment. Therefore, in FIG. 3, the same components as those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals as the corresponding components in FIG. 1, and the differences will be described below. .

  As shown in FIG. 3, the exhaust device for the internal combustion engine according to the present embodiment has a first exhaust pipe 51 (one exhaust pipe) and a second exhaust pipe 52 (the other exhaust pipe) arranged outside the silencer 54. And a confluence B of exhaust gas passing through the first exhaust pipe 51 and the second exhaust pipe 52 is located in the collective pipe 53. The collecting pipe 53 has a substantially Y-shaped collecting pipe structure itself that is similar to a known one, and a pair of upstream portions 53 a and 53 b that constitute the downstream ends of the first exhaust pipe 51 and the second exhaust pipe 52. And a downstream portion 53c connected to the silencer 54. The upstream exhaust pipe portions 51c and 52c of the first exhaust pipe 51 and the second exhaust pipe 52 are substantially the same as the upstream exhaust pipe portions 21c and 22c of the exhaust pipes 21 and 22 of the first embodiment described above. The same is connected to the exhaust manifolds 12 and 13.

  Also in the present embodiment, the air column resonance frequency f in the pipe line of the first exhaust pipe 51 is lowered, and an effect equivalent to that of substantially increasing the pipe length L1 of the first exhaust pipe 51 is produced. Thus, the exhaust sound pressure of the half order other than the basic order due to the explosion of the engine 11 is prevented from being increased by interference when the exhaust gas passing through the first exhaust pipe 51 and the second exhaust pipe 52 at the junction B is joined. The same effect as the first embodiment can be expected.

  Furthermore, in this embodiment, since the junction B is located in the collecting pipe 53, the pipes in the first exhaust pipe 51 and the second exhaust pipe 52 can be arbitrarily set regardless of the installation position of the silencer 54 or the like. Can be merged at the position. Accordingly, the length of the first exhaust pipe 51 and the second exhaust pipe 52 can be set and the degree of freedom in layout can be increased.

  In each of the above-described embodiments, the exhaust heat recirculator 40 is provided on the side of the first exhaust pipe having the short pipe length of the first exhaust pipe and the second exhaust pipe. The adjusting means is not limited to a heat exchanger that uses cooling water, and is not limited to one that cools the exhaust gas passing through the first exhaust pipe.

  For example, the first exhaust pipe 51 and the second exhaust pipe 52 shown in FIG. 3 are connected to the second exhaust pipe 52 having a long pipe length by using the electric heaters h1, h2 (exhaust gas as shown by phantom lines in FIG. If the exhaust gas temperature passing through the second exhaust pipe 52 is increased by attaching a temperature adjusting means), the length of the second exhaust pipe 52 is increased by increasing the exhaust sound speed in the second exhaust pipe 52. An effect equivalent to that of a slightly shortened state can be produced, and the exhaust sound pressure of a half order other than the basic order due to the explosion of the engine 11 interferes when the exhaust gas from both exhaust pipes 51 and 52 joins at the junction B. Can be prevented from being strengthened. In this case, the electric heaters h1 and h2 are mounted on one or both of the catalyst devices 32a and 32b, or are positioned upstream of the downstream catalyst device 32b, thereby warming up the catalyst. It can also function as a heater.

  In the case shown in FIG. 3, since the exhaust temperature adjusting means includes the exhaust heat recirculator 40 mounted on the first exhaust pipe 51 together with the electric heaters h1 and h2, the exhaust heat recirculator 40 alone is used. Compared with the second embodiment, the adjustment range for reducing the exhaust noise of the half order at the junction B can be expanded. Further, the exhaust tone color adjusting effect can be expected only by mounting the electric heaters h1 and h2 on the second exhaust pipe 52 without mounting the exhaust heat recirculator 40 on the first exhaust pipe 51.

  As described above, according to the present invention, by adjusting the exhaust temperature of at least one of the one exhaust pipe and the other exhaust pipe, the sound velocity in the first exhaust pipe is made to be relative to that in the second exhaust pipe. The exhaust gas from both the exhaust pipes at the junction of the first and second exhaust pipes is produced with the same effect as reducing the difference in length between the first exhaust pipe and the second exhaust pipe. It is possible to suppress the exhaust sound pressure of the half order other than the basic order due to the explosion of the internal combustion engine at the time of gas merging from interfering with each other, and from the layout surface under the vehicle floor, the first exhaust pipe and the second exhaust pipe Even when the pipe length must be different, an unpleasant exhaust sound pressure level such as so-called “tattering noise” can be reduced, and an exhaust system for an internal combustion engine with improved exhaust tone can be provided. The internal combustion machine Exhaust system, in particular mounted on a vehicle, is useful for exhaust devices in general for an internal combustion engine to reduce exhaust noise reduction by interference by introducing joins the exhaust pipe of the one and the other of the exhaust gas of a multi-cylinder internal combustion engine.

1 is a plan view showing a schematic overall configuration of a first embodiment of an exhaust device for an internal combustion engine according to the present invention. It is a typical sectional view of an important section of an exhaust system of an internal-combustion engine concerning a 1st embodiment. It is a top view which shows the general | schematic whole structure of 2nd Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention. The graph which shows the change of the sound pressure level by the interference of the exhaust sound of an integer order about each of the case where two exhaust pipes in the exhaust apparatus of the conventional internal combustion engine are equal length (a), and the case where it is unequal length (b) The vertical axis represents the exhaust sound pressure level, and the horizontal axis represents the frequency. FIG. 5 is a graph for explaining the problem that half-order exhaust interference appears prominently when two exhaust pipes in an exhaust system of a conventional internal combustion engine are of unequal length, where the vertical axis represents the exhaust sound pressure level and the horizontal axis represents the frequency. Indicates.

Explanation of symbols

11 Engine 11a, 11b Bank 12, 13 Exhaust manifold 21, 51 First exhaust pipe (one exhaust pipe)
21a, 22a, 51a, 52a Upstream end portion 21b, 22b, 51b, 52b Downstream end portion 21c, 22c Upstream exhaust pipe portion 21d, 22d Downstream exhaust pipe portion 21e, 22e Flange joint portion 22, 52 Second exhaust pipe (The other exhaust pipe)
24, 54 Silencer 26 Last exhaust pipe portion 31a, 31b Catalytic device 32a, 32b Catalytic device (the other catalytic device)
40 Exhaust heat recirculator (exhaust temperature control means)
41 Case 42 Exhaust cooler 42a Cooling water introduction part 42b Cooling water discharge part 42c Cooler body part 45 Radiator 47 Flow rate adjustment valve 53 Collecting pipe 53a, 53b Upstream part 53c Downstream part A, B Junction point h1, h2 Electric heater (exhaust temperature adjustment) means)
L1, L2 pipe length

Claims (9)

One exhaust pipe for introducing the exhaust gas from the internal combustion engine and the other exhaust pipe having a longer length than the exhaust pipe, and the exhaust gas introduced into the one exhaust pipe and the other exhaust pipe are supplied to the predetermined exhaust pipe. In an exhaust system of an internal combustion engine that exhausts by merging at a junction,
By adjusting the exhaust temperature of at least one of the one exhaust pipe or the other exhaust pipe upstream from the junction, the temperature of the exhaust gas flowing from the one exhaust pipe to the junction is adjusted. An exhaust system for an internal combustion engine, characterized in that exhaust temperature adjusting means for adjusting the temperature to be lower than the temperature of the exhaust gas flowing from the exhaust pipe to the confluence is provided.   The exhaust system for an internal combustion engine according to claim 1, wherein the exhaust temperature adjusting means cools the exhaust gas passing through the one exhaust pipe.   3. The exhaust heat recirculator according to claim 1, wherein the exhaust temperature adjusting means includes an exhaust heat recirculator for exchanging heat between cooling water for cooling the internal combustion engine and exhaust gas passing through the one exhaust pipe. An exhaust system for an internal combustion engine as described.   4. A silencer for silencing by introducing exhaust gases from the one exhaust pipe and the other exhaust pipe, respectively, wherein the junction is located in the silencer. An exhaust system for an internal combustion engine according to claim 1.   4. The apparatus according to claim 1, further comprising a collecting pipe that collects the one exhaust pipe and the other exhaust pipe at the downstream ends of the two exhaust pipes, wherein the junction is located in the collecting pipe. 2. An exhaust system for an internal combustion engine according to item 1.   6. A silencer that silences by introducing exhaust gas from the one exhaust pipe and the other exhaust pipe, and the junction is located outside the silencer. 2. An exhaust system for an internal combustion engine according to item 1. An exhaust gas purifying catalyst device mounted on the one exhaust pipe;
The exhaust of the internal combustion engine according to any one of claims 1 to 3, wherein the exhaust temperature adjusting means includes a cooling unit mounted on the one exhaust pipe at a downstream side of the catalyst device. apparatus. Comprising the other catalyst device for purifying exhaust gas mounted on the other exhaust pipe;
3. The internal combustion engine according to claim 1, wherein the exhaust gas temperature adjusting means includes a heating unit that heats the exhaust gas in the other catalyst device or upstream of the other catalyst device. Exhaust system. The internal combustion engine has a pair of banks each having a plurality of cylinders;
9. The exhaust system for an internal combustion engine according to claim 1, wherein the one exhaust pipe and the other exhaust pipe are connected to the pair of banks, respectively.