JP3503450B2 - Exhaust system support structure for internal combustion engine for vehicles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust system supporting structure for a vehicle internal combustion engine in which a pair of exhaust pipes is supported by a subframe, for example, a suspension member. 2. Description of the Related Art As a structure for supporting an exhaust system of an internal combustion engine having a pair of exhaust pipes, an "exhaust system mounting structure for automobiles" described in Japanese Utility Model Laid-Open Publication No. 3-73615 is known. I have. In this exhaust system mounting structure, both exhaust pipes (exhaust pipes) are brought close to each other and fixed to each other by a bracket, and each integrated exhaust pipe is elastically supported by a suspension member. Usually, since this suspension member is elastically supported by the vehicle body, by attaching the exhaust pipe to the suspension member as described above, the exhaust system is double-vibrated. Therefore, according to the exhaust system mounting structure, the magnitude of the vibration transmitted from the exhaust system to the vehicle body can be reduced. However, in this exhaust system mounting structure, the two exhaust pipes are fixed close to each other, so that the arrangement of these exhaust pipes is restricted. Become. Therefore, it is conceivable that these exhaust pipes are separately supported by subframes such as suspension members. With this configuration, the arrangement of each exhaust pipe can be set relatively freely. However, in the above configuration, since a plurality of support portions for supporting each exhaust pipe are provided on a subframe such as a suspension member, a vibration transmission path between both members is increased, and the vibration of the subframe is increased. Tend. For this reason, when the increased vibration of the sub-frame is transmitted to the body of the vehicle, there is a possibility that the body resonates with a specific frequency component of the vibration and generates a muffled sound from the body. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust system mounting structure for an internal combustion engine for a vehicle, which can suppress generation of a vehicle booming sound. [0006] The above-mentioned vehicle muffled sound is excited by the pulsation of the exhaust gas and the engine vibration to excite the sub-frame, and the vibration is transmitted to the vehicle body. This occurs when the body resonates. Therefore, in order to reduce such a vehicle muffled sound, a vibration mode in which a natural frequency exists in the frequency band (20 to 80 Hz) of the vehicle muffled sound among the respective vibration modes of the subframe is not excited. Is effective. As the vibration mode of the suspension having a natural frequency in the frequency band of the vehicle muffled sound as described above, rotational vibration around an axis extending in the front-rear direction of the vehicle, that is, rolling,
The present inventor has found that there is rotational vibration around an axis extending in the left-right direction of the vehicle, that is, pitching. Accordingly, in the present invention, a pair of exhaust pipes constituting an exhaust system of an internal combustion engine are supported by respective support portions of a subframe supported by the vehicle body, and the exhaust system support structure of the internal combustion engine for a vehicle. In the above, each support portion is arranged at an asymmetrical position with respect to both the rolling rotation axis and the pitching rotation axis in the subframe. Therefore, according to the above configuration, even if the vibrating force caused by the exhaust pulsation or the engine vibration is input from each exhaust pipe to the sub-frame, the rolling and pitching of the sub-frame are hardly excited. Among the vibrations transmitted from the subframe to the vehicle body, the frequency components in the frequency band of the vehicle booming sound are reduced. An embodiment of the present invention will be described below. FIG. 1 schematically shows an in-line four-cylinder engine 11 mounted in front of a vehicle 10, an exhaust system 20 extending in the front-rear direction of the vehicle 10, a rear suspension member 30 disposed behind the vehicle 10, and the like. . The exhaust system 20 includes an exhaust manifold 21 attached to the engine 11, an exhaust pipe 22 connected to the manifold 21, and a pair of mufflers 28L and 28R connected to the pipe 22. Further, the exhaust pipe 22 has an upstream end connected to the exhaust manifold 21, a downstream end bifurcated into a front pipe 23, and a pair of rear pipes 24 </ b> L, 24 </ b> R connected respectively to a branch portion of the front pipe 23. And is constituted by. A catalyst 25 for purifying exhaust gas is provided in the middle of the front pipe 23. FIG. 2 is an enlarged view of the rear suspension member 30, FIG. 3 is a cross section taken along line 3-3 in FIG. 2, FIG. 4 is a cross section taken along line 4-4 in FIG. Shows cross sections along line 5-5 in FIG. In FIGS. 3 and 4, illustration of a drive system described later is omitted. As shown in FIGS. 2 to 4, the rear suspension member 30 has a substantially rectangular frame shape, and mounting portions 31FL, 31FR, 31RL, 31RR are formed at each corner. Each of the mounting portions 31FL, 31FR, 31
The RL and 31RR are elastically supported by the body 13 of the vehicle 10 shown in FIG. 1 via a mount (not shown) or the like, so that the rear suspension member 30 is located at a lower rear portion of the body 13 and is attached to the body 13. Installed. As shown in FIG. 1, a pair of left and right steering wheels (front wheels) 14L and 14R are provided on the front side of the vehicle 10, and a pair of left and right driving wheels (rear wheels) 15L and 15R are provided on the rear side. Is provided. These drive wheels 15L, 15R
Is drivingly connected to a crankshaft (not shown) of the engine 11 via a drive system such as a pair of left and right drive shafts 16L and 16R, a differential gear (not shown) built in the gear case 17, a propeller shaft 18, a transmission 19, and the like. Have been. The gear case 17 is elastically supported by the rear suspension member 30 via a stay and a mount (both not shown). Next, the support structure of the exhaust system 20 will be described. A first stay 32 and a second stay 33 each having a substantially L-shape for supporting the rear pipes 24L and 24R protrude from the rear suspension member 30, respectively. As shown in FIG. 2, the first stay 32 is located near the mounting portion 31FL on the front left side of the vehicle 10, and the second stay 33 is located near the mounting portion 31RR on the rear right side of the vehicle 10. . Therefore, in the present embodiment, each of the stays 32 and 33 passes through the center of gravity of the rear suspension member 30 and extends in the front-rear direction of the vehicle 10 (hereinafter, abbreviated as “front-rear axis”) and the vehicle 10 also passes through the center of gravity. The axis C2 extending in the left-right direction of
(Abbreviated as “left-right axis”). On the other hand, each rear pipe 24L, 24R has
Each stay 32, 3 of the rear suspension member 30
Bar-shaped stays 26 and 27 are respectively provided at positions corresponding to 3. The stays 26, 2 of the rear pipes 24L, 24R and the rear suspension member 30 are provided.
7, 32, 33 are connected via rubber mounts 40, 41, respectively. As shown in FIG. 5, a pair of insertion holes 40a and 40b are formed in the rubber mount 40 at a predetermined distance. The stays 2 of the rear pipe 24L and the rear suspension member 30 are inserted into the insertion holes 40a and 40b.
Both stays 26, 32 are connected by inserting 6, 32. The stays 27 and 33 of the rear pipe 24R and the rear suspension member 30 are also connected by a rubber mount 41 in the same manner. As described above, the rear pipe 2 is inserted through the rubber mounts 40 and 41.
By connecting the stays 26, 27, 32, 33 of the 4L, 24R and the rear suspension member 30,
The rear pipes 24L and 24R are elastically supported by the rear suspension member 30. When the operation of the engine 11 is started, the exhaust gas discharged from each cylinder (not shown) of the engine 11 is introduced into an exhaust manifold 21, and further from the manifold 21, a front pipe 23, each rear pipe 24L,
It is discharged to the outside through 24R and mufflers 28L and 28R. Here, since the explosion of the air-fuel mixture in each cylinder occurs intermittently, the pressure of the exhaust pulsates at a predetermined frequency. When the pulsating exhaust collides with the inner wall of the exhaust system 20, the vibration of the exhaust system 20 is excited. Further, since the exhaust system 20 is connected to the engine 11, the vibration of the engine 11 is also excited by the direct transmission of the vibration. The frequency of the exhaust pulsation and the vibration of the engine 11 changes according to the engine speed. For example, in the case of the four-cylinder engine 11 as in the present embodiment, when the engine speed is in the range of 600 to 2400 rpm, the frequency (fundamental frequency) of the exhaust pulsation and the vibration of the engine 11 is the frequency band of the vehicle muffled sound. Will be present in a band of about 20 to 80 Hz, which substantially coincides with Further, there are the following two modes in which the natural frequency exists in the frequency band of 20 to 80 Hz among the main vibration modes of the exhaust system 20. That is, as shown in FIG. 6, a mode in which the downstream ends of the rear pipes 24L and 24R vibrate up and down in the same phase (hereinafter, referred to as a “first vibration mode”), and as shown in FIG. Rear pipe 24
This is a mode in which the downstream ends of the L and 24R vibrate vertically in opposite phases (hereinafter, referred to as “second vibration mode”). still,
FIGS. 6A, 6C, 7A, and 7C show side views of the rear pipes 24L and 24R, and FIGS.
FIGS. 7B and 7D show the rear surfaces of the pipes 24L and 24R. When the rear pipes 24L and 24R vibrate in the first vibration mode, the first stay 32 and the second stay 33 are applied to the rear suspension member 30 at the frequency in the frequency band and in the same phase. A vibrating force to be vibrated is input. In addition, when the rear pipes 24L and 24R vibrate in the second vibration mode, the rear suspension member 30 causes the stays 32 and 33 to vibrate at frequencies in the frequency band and in opposite phases. Is entered. On the other hand, among the main vibration modes of the rear suspension member 30, there are the following two modes in which the natural frequency exists in the frequency band of 20 to 80 Hz. That is, as shown in FIG. 8, rolling in which the rear suspension member 30 swings around the longitudinal axis C1;
As shown in FIG. 9, the pitch is such that the rear suspension member 30 swings around the left-right axis C2. As described above, the rear suspension member 30 also includes
Since there are two vibration modes in the frequency band of up to 80 Hz, when a vibrating force caused by the vibration of the rear pipes 24L and 24R is input, the vibrating force causes the rear suspension member 30 to cause the above-described vibration modes. May vibrate greatly. When such vibration occurs, the vibration of the rear suspension member 30 is
To increase the muffled sound of the vehicle. Here, unlike the present embodiment, the second stay 33 is disposed near the mounting portion 31FR on the front right side of the vehicle 10 as shown by the arrow in FIG. The comparative example will be described. In this comparative example, the stays 32 and 33 are arranged at symmetrical positions with respect to the longitudinal axis C1. Therefore, when the same phase vibrating force is input from the rear pipes 24L and 24R to the positions of the stays 32 and 33, the pitching of the rear suspension member 30 is greatly excited. Further, the vibrating force of the opposite phase is input from the rear pipes 24L, 24R to the positions of the stays 32, 33, so that the rear suspension member 30
Is greatly excited. As a result, in this comparative example, an increase in the muffled sound of the vehicle is caused. On the other hand, in the present embodiment, the stays 32 and 33 are arranged at positions asymmetrical with respect to both the longitudinal axis C1 and the lateral axis C2. For this reason, even if the same phase vibrating force is input from the rear pipes 24L, 24R to the positions of the stays 32, 33, rolling and pitching are not excited. In this case, a vibration mode (bounce) in which the entire rear suspension member 30 vibrates up and down as shown by an arrow B in FIG. 10 is excited, but this bounce has a lower frequency than rolling and pitching. Therefore, even if the vibration of the rear suspension member 30 due to the bounce is transmitted to the body 13, the vehicle booming sound will not be generated. On the other hand, when the oscillating forces of opposite phases are input from the rear pipes 24L, 24R to the positions of the stays 32, 33, the oscillating forces are applied to a pair of mounting portions 31F located diagonally.
A line C3 connecting R and 31RL is used as an axis, and an oscillation mode that swings around the axis C3 is to be excited. However,
This vibration mode has an extremely high natural frequency as compared with lower-order vibration modes such as rolling and pitching. Therefore, if the frequency of the vibrating force input to the rear suspension member 30 is within the frequency band of 20 to 80 Hz as described above, this vibration mode does not cause the resonance phenomenon of the rear suspension member 30 to occur. In addition, most of the vibration energy input from each of the rear pipes 24L and 24R to the rear suspension member 30 is consumed by trying to excite the vibration mode in which resonance is unlikely to occur, so that rolling and pitching are performed. Rarely occurs. If the frequency of the vibrating force input to the rear suspension member 30 increases due to an increase in the engine speed, this vibration mode may be excited. There is no increase in muffled sound. Body 1 from rear suspension member 30
This is because the frequency of the vibration transmitted to 3 becomes higher than the frequency band of the muffled sound. As described above, according to this embodiment, the rear pipes 24L, 24R vibrate in the first and second vibration modes, and the rear pipes 24L, 24R vibrate due to the vibrations.
Even if the vibrating force is input to the rear suspension member 30 from L and 24R, rolling and pitching of the rear suspension member 30 hardly occur. Therefore, it is possible to suppress an increase in vehicle muffled sound due to resonance of the rear suspension member 30. In the comparative example described above, the vibration generated in the rear suspension member 30 due to the rolling and pitching is increased and the vehicle booming noise is increased. For example, a dynamic damper is provided in each of the rear pipes 24L and 24R. It becomes necessary to reduce the vibrating force transmitted from the rear pipes 24L, 24R to the rear suspension member 30 by, for example, mounting. However, providing such a dynamic damper increases the cost and the weight of the exhaust system. In this regard, according to the present embodiment, the rear pipe 24 can be mounted without increasing the cost and weight.
It is possible to suppress an increase in vehicle muffled sound only by adjusting the support positions of the L and 24R. The above embodiment can be implemented by changing the configuration as follows. Even if the configuration is changed in this way, the same operation and effect as the above embodiment can be obtained. In the above embodiment, the stays 32, 33 of the rear suspension member 30 are arranged near the mounting portions 31FL, 31RR on the front left side and the rear right side of the vehicle 10. On the other hand, the stays 32 and 33 are connected to the vehicle 10.
In the vicinity of the mounting portion 31RR on the front left side and the rear right side. On the other hand, each stay 32,
33 may be disposed near the mounting portions 31FR and 31RL on the front right and rear left sides of the vehicle 10. In the above embodiment, the support structure of the exhaust pipe 22 branched in a bifurcated manner on the rear side of the vehicle 10 has been described. For example, an exhaust pipe independently provided corresponding to each bank of the V-type engine may be used. You may make it support with the rear suspension member 30 similarly to the said embodiment. In the above embodiment, the support structure of the exhaust system 20 in the four-cylinder engine 10 has been described. However, the engine may have three or less cylinders or five or more cylinders. In the above embodiment, a rear wheel drive type (FR type)
Although the rear pipes 24L and 24R are supported by the rear suspension member 30 of the vehicle 10, the respective pipes 24L and 24R may be supported by the rear suspension member of a front-wheel drive (FF) vehicle. . The embodiments of the present invention have been described above, but the technical ideas that can be grasped from the above embodiments will be described. -In the exhaust system supporting structure of the internal combustion engine for a vehicle, the pair of exhaust pipes constituting the exhaust system of the internal combustion engine are supported by the respective supporting portions of the subframe supported by the vehicle body, and the rolling in the subframe is performed. An exhaust system support structure for an internal combustion engine for a vehicle, wherein each of the support portions is arranged on a straight line inclined with respect to both the rotation axis and the pitching rotation axis. According to the present invention, each supporting portion of the sub-frame for supporting a pair of exhaust pipes is arranged at an asymmetrical position with respect to both the rolling rotation axis and the pitching rotation axis in the sub-frame. ing. Therefore, even if the vibrating force caused by the exhaust pulsation and the engine vibration is input to the subframe from each exhaust pipe, the rolling and pitching of the subframe are less likely to be excited, and are transmitted from the subframe to the vehicle body. Among the vibrations, the frequency components in the frequency band of the vehicle muffled sound decrease. as a result,
The resonance of the vehicle body can be suppressed to reduce the muffled sound of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing an exhaust system and a rear suspension member of an engine. FIG. 2 is a plan view showing a support structure for a rear pipe. FIG. 3 is a sectional view taken along line 3-3 of FIG. 2; FIG. 4 is a sectional view taken along the line 4-4 in FIG. 2; FIG. 5 is a sectional view taken along the line 5-5 in FIG. 2; FIG. 6 is an explanatory diagram showing a first vibration mode of the exhaust system. FIG. 7 is an explanatory diagram showing a second vibration mode of the exhaust system. FIG. 8 is an explanatory view showing rolling of a rear suspension member. FIG. 9 is an explanatory view showing pitching of a rear suspension member. FIG. 10 is a perspective view showing a rear suspension member. [Description of Signs] 10 ... vehicle, 11 ... engine, 13 ... body, 20 ... exhaust system, 21 ... exhaust manifold, 22 ... exhaust pipe, 23 ... front pipe, 24L, 24R ...
Rear pipe, 28L, 28R muffler, 30 rear suspension member, 32 first stay, 33 second stay, 26, 27 stay, 40, 41 rubber mount.

Continuation of front page (56) References JP-A-8-170527 (JP, A) JP-A-7-108951 (JP, A) JP-A-56-81214 (JP, A) JP-A-56-81215 (JP, A) , A) Fully open sho 63-168172 (JP, U) Really open sho 61-67024 (JP, U) Full open sho 53-84831 (JP, U) Real open flat 3-73615 (JP, U) 3-88925 (JP, U) JP-A 4-29429 (JP, U) JP-A 57-109002 (JP, U) JP-A 60-1888023 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) B60K 13/04 B62D 21/00 B62D 25/20

Claims (1)

(1) An internal combustion engine for a vehicle, wherein a pair of exhaust pipes constituting an exhaust system of an internal combustion engine are supported by respective support portions of a subframe supported by the vehicle body. An exhaust system support structure for an internal combustion engine for a vehicle, wherein each of the support portions is disposed at an asymmetric position with respect to both a rotation axis of rolling and a rotation axis of pitching in the subframe.