JP3725108B2 - Joint structure in engine exhaust system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a joint structure in an exhaust system of an engine, which mainly connects an exhaust manifold connected to an exhaust port of a vehicle engine and an exhaust pipe so as to be able to swing relative to each other.
[0002]
[Prior art]
In conventional exhaust systems for automobiles, the exhaust manifold connected to the exhaust pipe port of the engine and the exhaust pipe on the downstream side are connected via a spherical joint, and the exhaust manifold and the exhaust pipe swing relative to each other. It is known that the vibration caused by exhaust pulsation flowing through the exhaust system is attenuated by the spherical joint (for example, see Patent Document 1).
[0003]
[Patent Literature]
Japanese Patent No. 2847223 [0004]
Further, as shown in FIG. 9, in the joint structure in the exhaust system of the engine, the spherical gasket of the spherical joint is alternately layered with a metal mesh layer having a uniform density and a graphite layer in the radial direction. It is already known that it is configured to reduce the transmission of high-frequency vibration of the exhaust manifold caused by exhaust pulsation of exhaust flowing through the exhaust system to the downstream exhaust pipe and improve the sealing performance of the spherical joint Yes.
[0005]
[Problems to be solved by the invention]
By the way, the metal mesh layer of the spherical gasket can increase the damping effect of the surface vibration of the exhaust system due to the high-frequency vibration when the density is increased, but the sealing performance of the spherical gasket by the graphite layer is deteriorated, Conversely, if the density of the metal mesh layer is lowered, the sealing effect by the graphite layer can be enhanced, but there is a problem that the surface vibration of the exhaust pipe system due to the high frequency vibration by the metal mesh is lowered.
[0006]
The present invention has been made in view of such circumstances, and in a joint structure in an engine exhaust system, the effect of damping the surface vibration of the exhaust system by the metal mesh layer of the spherical gasket is enhanced and the sealing effect by the graphite layer of the spherical gasket is improved. It is an object of the present invention to provide a joint structure in an exhaust system of a new engine that can be improved.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, the downstream side of the exhaust manifold connected to the exhaust port of the engine and the upstream side of the exhaust pipe are connected so as to be capable of relative oscillation via a spherical joint. In the joint structure in the engine exhaust system,
The spherical joint includes a joint half on the exhaust manifold side and a spherical gasket interposed between the joint halves on the exhaust pipe side. The spherical gasket has an opening through which exhaust passes at the center thereof on the outer peripheral surface. It is formed in a short cylindrical shape having a spherical surface that makes spherical contact with one of the joint halves, and a metal mesh layer and a graphite layer in the radial direction are layered with the graphite layer facing the spherical surface. The density of the metal mesh layer on the radially inner side is higher than the density of the metal mesh layer on the radially outer side. According to such a feature, the spherical gasket of the spherical joint is mainly high in density. The transmission of high-frequency vibrations from the exhaust manifold to the downstream side can be reduced as much as possible by the metal mesh layer on the radially inner side. Since the surface area of the metal mesh layer exposed on the spherical surface of the spherical gasket can be reduced, not only can the sealing function by the expansion action of the graphite layer be improved, but also between the spherical gasket and the seating surface of the joint half. Therefore, the vibration absorption effect in the bending direction between the exhaust manifold and the exhaust pipe can be improved.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples of the present invention shown in the accompanying drawings.
[0009]
In this embodiment, the present invention is applied to an automobile equipped with a multi-cylinder engine. FIG. 1 is a side view of an engine exhaust system having the joint structure of the present invention, and FIG. 3 is an enlarged sectional view taken along line 3-3 in FIG. 2, FIG. 4 is a sectional view taken along line 4-4 in FIG. 3, and FIG. 6 is a partially enlarged cross-sectional view taken along line 6-6 of FIG. 5, FIG. 7 is a perspective view showing a state before the spherical gasket is molded, and FIG. 8 is an exhaust equipped with the joint structure of the present invention. It is a graph which shows the relationship between the frequency and sound pressure of a system and the conventional exhaust system.
[0010]
In FIGS. 1 and 2, a multi-cylinder engine E for running the automobile is placed horizontally on the subframe 1 constituting a part of the vehicle body of the automobile via front and rear engine mounts 2 and 3 (the crankshaft thereof). 4 is mounted in a direction perpendicular to the front-rear direction of the automobile. The engine E is a four-cycle serial type, and a cylinder block 5 in which a plurality of cylinders are arranged in parallel, a cylinder head 6 coupled thereon, a head cover 7 covering the upper surface of the cylinder head 6, An oil pan 8 coupled to the lower surface of the crankcase portion of the cylinder block 5 is provided.
[0011]
As shown in FIG. 1, the engine E has a vibration rotation axis that is parallel to the crankshaft 4 through the center of gravity G, that is, a rolling axis LL. When the vehicle V is traveling, the rolling axis LL is rolled. Rolling displacement back and forth as the center.
[0012]
A plurality of intake ports 11 are opened in parallel on the front side (left side in FIG. 1) of the engine E, and an intake system In is connected to the intake ports 11, and the rear side of the engine E (in FIG. 1). On the right side, a plurality of exhaust ports 12 are opened in parallel, and an exhaust system Ex having a joint structure according to the present invention is connected to these exhaust ports 12.
[0013]
The exhaust system Ex includes an exhaust manifold 14 whose upstream end is integrally connected to the exhaust port 12 and an exhaust pipe 15 connected to its downstream end. The exhaust pipe 15 includes an upstream side first exhaust pipe part 16 and a downstream side second exhaust pipe part 17, and the exhaust pipe 15 is disposed between the exhaust manifold 14 and the first exhaust pipe part 16. A spherical joint 18 according to the present invention is interposed, a flexible tube 19 is interposed between the first exhaust pipe portion 16 and the second exhaust pipe portion 17, and further, the second exhaust pipe portion 17 A catalytic converter 20 is interposed in the middle, and a silencer (not shown) is connected to the downstream side of the catalytic converter 20.
[0014]
By the way, the exhaust system Ex is provided with the spherical joint 18 and the flexible tube 19, and the engine E is greatly subjected to rolling vibration, that is, rolling displacement, due to traveling of the automobile, in particular, sudden start, sudden acceleration, sudden deceleration, and the like. In this case, the displacement is effectively absorbed, and the vehicle vibration caused by the rolling displacement of the engine E can be reduced as much as possible.
[0015]
In the following, the configuration of the exhaust system Ex will be described in more detail. As clearly shown in FIGS. 2 and 3, the plurality of distribution pipes 14a of the exhaust manifold 14 have their upstream ends at the exhaust ports of the engine E. 12 are respectively connected to 12 and curved in an elbow shape, gradually gathering toward the downstream side, and extending downward adjacent to the rear surface of the engine E, with their downstream ends open downwardly, The downstream end is integrally connected to one exhaust collecting portion 14b. As shown in FIGS. 1 and 2, the exhaust collecting portion 14 b is connected to the upstream end of the first exhaust pipe portion 16 via the spherical joint 18 near the rear surface of the engine E.
[0016]
As shown in FIGS. 2 to 6, the spherical joint 18 includes a first connection flange 22 constituting one joint half, a second connection flange 23 constituting the other joint half, and both flanges. The spherical gasket 24 is hermetically sandwiched between 22 and 23, and the spherical gasket 24 includes a graphite layer (expanded graphite layer in this embodiment) 37 and a metal mesh layer (in this embodiment, as will be described in detail later). In this embodiment, the stainless steel mesh layer) 35 is layered and formed into a flat short cylindrical shape with upper and lower end surfaces 24a and 24d, and has an opening 24a for exhaust circulation at the center thereof and its peripheral surface. In addition, a spherical surface portion 24b made of a spherical surface centering on a center point C (see FIG. 3) existing on the center line of the exhaust manifold 14 is provided. The spherical gasket 24 has a flat upper end surface 24 c in contact with the first connection flange 22, and the spherical portion 24 b is formed on a spherical seating surface 23 a formed on the second connection flange 23. It is slidably contacted. The outer peripheral portions of the first and second connection flanges 22 and 23 are elastically coupled via a compression coil spring 26 with a plurality of bolts and nuts 25.
[0017]
As clearly shown in FIG. 3, the downstream end of the exhaust manifold 14 is located at the center of the first connection flange 22 that constitutes one joint half of the spherical joint 18 (upper side in FIGS. 2 and 3). A first exhaust pipe is connected to the central portion of the second connection flange 23, which is integrally connected to the exhaust collecting portion 14b and constitutes the other half of the spherical joint 18 (the lower side in FIG. 3). An upstream end of the portion 16 that opens upward is integrally connected. Therefore, the exhaust gas flowing through the exhaust manifold 14 flows to the first exhaust pipe portion 16 through the spherical joint 18.
[0018]
As shown in FIG. 2, a stay 29 is fixed to one joint half on the side connected to the exhaust manifold 14 of the spherical joint 18, that is, to the first connection flange 22 by a plurality of bolts and nuts 28. Has been. The stay 29 extends forward toward the rear surface of the engine E, and a bent mounting portion at the tip thereof is fixed to the rear surface of the cylinder block 5 of the engine E with a plurality of connecting bolts 30. Therefore, when the engine E is rollingly displaced about the rolling axis LL, the other joint half 23 is rotationally displaced with respect to the one joint half 22 via the spherical gasket 24.
[0019]
As described above, the first exhaust pipe portion 16 whose upstream end is connected to the spherical joint 18 has a curved portion that curves convexly toward the engine E side as shown in FIG. The upstream half 16a extends downward with respect to the engine E, and the downstream half 16b extends rearward with respect to the engine E, and is formed in an elbow shape in a side view. The front end of the flexible tube 19 is connected to the downstream end of the first exhaust pipe portion 16 that is opened rearward. The flexible tube 19 is extended in the front-rear direction, can be expanded and contracted in the front-rear direction, and mainly absorbs the front-rear direction component of the rolling displacement of the engine E.
[0020]
In addition, since the said flexible tube 19 employ | adopts a conventionally well-known thing, the detailed description is abbreviate | omitted.
[0021]
The downstream end of the flexible tube 19 is integrally coupled to the upstream end of the second exhaust pipe portion 17 of the exhaust pipe 15, and the first exhaust pipe portion 16 and the second exhaust pipe portion 17 are: It communicates via the flexible tube 19.
[0022]
The second exhaust pipe portion 17 extends substantially horizontally in the front-rear direction of the automobile, and a catalytic converter 20 is connected to the middle of the second exhaust pipe portion 17. Further, a downstream end of the second exhaust pipe portion 17 is illustrated in the figure. A tail pipe that opens to the atmosphere is connected through a silencer that does not.
[0023]
As shown in FIG. 1, the second exhaust pipe portion 17 is supported by the subframe 1 of the vehicle body via the elastic support means S, and the vibration acting on the exhaust system Ex is also caused by the elastic support means S. Attenuated to reduce transmission to the car body.
[0024]
Next, the structure of the spherical gasket 24 according to the present invention of a spherical joint will be described with reference to FIGS.
[0025]
The spherical gasket 24 is formed by alternately layering a stainless steel mesh layer 35 as a metal mesh layer and an expanded graphite layer 37 as a graphite layer in the radial direction and laminating a surface layer 39 on the outer surface thereof. The multi-layered product L (see FIG. 7) to be molded is compression-molded into the above-mentioned shape by putting it into a mold, and particularly in this embodiment, the inner and outer expanded graphite layers 37i, 37o. The stainless mesh layer 35 interposed therebetween is characterized in that the density on the inner side in the radial direction of the spherical gasket 24 is higher than the density on the outer side.
[0026]
As shown in FIG. 7, a strip-shaped inner expanded graphite sheet constituting the inner expanded graphite layer 37i is wound around the inner peripheral surface of the multi-layered product L, and both free edges are mutually connected. Is superimposed.
[0027]
On the outer peripheral surface of the inner expanded graphite layer 37i, a stainless mesh layer 35 formed by winding a stainless mesh sheet formed in a belt shape by knitting stainless wire twice in a spiral shape is layered. The stainless mesh layer 35 has a multi-layered product L, that is, the inner density in the radial direction of the spherical gasket 24 is higher than the outer density. As a means for changing the density, for example, a belt-like stainless mesh sheet is used. Technical means such as changing the density of the mesh in the longitudinal direction of itself or changing the thickness of the belt-shaped stainless steel mesh sheet in the longitudinal direction is adopted.
[0028]
On the outer peripheral surface of the stainless steel mesh layer 35, an outer expanded graphite layer 37o configured by winding a strip-shaped outer expanded graphite sheet (thickness of about 0.5 mm) twice in a spiral shape is layered, and further the outer peripheral surface thereof In addition, the surface sheet constituting the belt-shaped surface layer 39 is wound around with the lubricant coating surface outward, and the free edges of the surface sheet are overlapped with each other. The surface layer 39 is made of a material having high hardness such as boron nitride.
[0029]
As described above, an inner expanded graphite layer 37i, a stainless mesh layer 35, an outer expanded graphite layer 37o, and a surface layer 39 are sequentially layered from the inner side to the outer side in the radial direction. The spherical gasket 24 having the above-described configuration is molded by putting it into a molding die and compressing it hot or cold with this molding die.
[0030]
In addition, since a conventionally well-known technical means is employ | adopted for the said shaping | molding die and its shaping | molding method, the description is abbreviate | omitted.
[0031]
By the way, as described above, the spherical gasket 24 is formed by layering the stainless mesh layer 35 and the inner and outer expanded graphite layers 37i and 37o, so that the stainless mesh layer 35 includes When the stainless steel fibers are brought into frictional contact with each other, the vibration applied to the spherical gasket 24 is damped, and the function of reducing high-frequency vibration transmitted from the exhaust manifold 14 to the exhaust pipe 15 is provided. The expanded graphite layers 37i and 37o are contracted by the elastic force of the compression coil spring 26 at a low temperature like when the operation of the engine E is stopped, but are heated as when the engine E is operated. When the temperature becomes high, the inner and outer expanded graphite layers 37i and 37o are hermetically pressed against the joint halves 22 and 23, and particularly the outer expanded graphite layer 3 o has a function of airtightly pressing the seating surface 23a of the joint half 23 through the surface layer 39 to improve the sealing performance of the spherical gasket 24. As a result, the spherical gasket 24 has a high frequency vibration damping function. And the sealing function, the transmission of high-frequency vibration (surface vibration) of the exhaust manifold 14 resulting from exhaust pulsation due to the operation of the engine E to the exhaust pipe 15 is reduced, and the sealing performance of the spherical joint 19 is further improved. Prevent leakage from the exhaust pipe to the outside.
[0032]
By the way, if the density of the stainless mesh layer 35 is increased in order to further enhance the damping function of the high-frequency vibration, the surface area of the stainless mesh exposed to the spherical portion 24b of the spherical gasket 24 increases, and the damping function is enhanced. On the other hand, not only the sealing function due to the expansion action of the expanded graphite layer 37 is lowered, but also the bending direction between the exhaust manifold 14 and the exhaust pipe 15 is increased due to an increase in the frictional resistance between the spherical gasket 24 and the seating surface 23a of the joint half 23. This causes a disadvantage that the vibration absorbing effect of the above is also reduced.
[0033]
Therefore, this embodiment is characterized in that the density on the inner side in the radial direction of the stainless steel mesh layer 35 of the spherical gasket 24 is made higher than the density on the outer side in order to eliminate such inconvenience. The height may be increased continuously from the inside to the outside of the plate, or may be increased stepwise.
[0034]
By the way, according to this embodiment, the stainless mesh layer 35 is exposed to the spherical portion 24b of the spherical gasket 24 by the radially outer side having a low density while enhancing the damping function of the high frequency vibration by the radially inner side having a high density. Since the surface area of the mesh can be reduced, the sealing function by the expansion action of the outer expanded graphite layers 37i and 37o can be enhanced as a whole while enhancing the high frequency vibration damping function by the stainless mesh layer 35. In addition, since the frictional resistance between the spherical gasket 24 and the seating surface 23a of the joint half 23 is reduced, the vibration absorbing effect in the bending direction between the exhaust manifold 14 and the exhaust pipe 15 can be improved.
[0035]
FIG. 8 shows a spherical surface when the spherical joint having the conventional spherical gasket shown in FIG. 9 (the density of the stainless mesh layer is uniform in the radial direction) and the spherical joint 18 having the spherical gasket 24 of this embodiment are used. The graph by the experimental result which showed the relationship between the frequency (Hz) which acts on the flexible tube 19 of the downstream of a coupling | joint, and the sound pressure (dB) of the radiated sound generated from there is shown, and a continuous line shows this Example The dotted line shows the conventional case. According to this graph, when the engine E is operated at 4000 rpm, in this embodiment, the frequency acting on the flexible tube 19 is 3000 to 8000 Hz, and the peak value of the sound pressure of the radiated sound of the flexible tube 19 is conventional. It can be seen that this is effective for reducing the radiated sound in this frequency region.
[0036]
Next, the operation of this embodiment will be described.
[0037]
Now, according to the operation of the engine E, the exhaust discharged from the exhaust port 12 is upstream of the exhaust manifold 14, the spherical joint 18, the first exhaust pipe portion 16, the flexible tube 19, and the second exhaust pipe portion 17. , The catalytic converter 20, the downstream part of the second exhaust pipe part 17 and a silencer (not shown), while harmful components such as HC and CO are purified, and the exhaust sound is silenced by the silencer to the atmosphere. Released.
[0038]
Further, in the process in which the exhaust flows from the exhaust port 12 to the exhaust manifold 14, the exhaust pulsation is transmitted from the engine E to the exhaust manifold 14, and the exhaust velocity energy and the pressure vibrate the inner surface of the exhaust manifold 14. As a result, surface vibration due to high-frequency vibration (1000 to 8000 Hz) is generated in the exhaust manifold, and this surface vibration becomes not only the axial direction of the exhaust system but also omnidirectional vibration. The exhaust pipe 16, the flexible tube 19, the downstream exhaust pipe 17, the catalytic converter 20, and the like are transmitted to the downstream side of the exhaust manifold 14, and for example, radiated sound is generated from the outer surface of the flexible tube 19 and the catalytic converter 20. , Spherical gas of the spherical joint 18 of this embodiment The transmission 24 can reduce the transmission of high-frequency vibrations from the exhaust manifold 14 to the downstream side as much as possible by the stainless steel mesh layer 35 having a high density in the radial direction. Since the surface area of the stainless steel mesh exposed to the spherical surface portion 24b of the spherical gasket 24 can be reduced by the stainless steel mesh layer 35, not only the sealing function by the expansion action of the expanded graphite layer 37 can be enhanced, but also the spherical surface Since the frictional resistance between the spherical portion 24a of the gasket 24 and the seating surface 23a of the joint half 23 is also reduced, the vibration absorbing effect in the bending direction between the exhaust manifold 14 and the exhaust pipe 15 can be improved.
[0039]
Although one embodiment of the present invention has been described above, the present invention is not limited to that embodiment, and various embodiments are possible within the scope of the present invention.
[0040]
For example, in the above-described embodiment, the case where the joint structure in the exhaust system of the engine according to the present invention is implemented in a multi-cylinder four-cycle engine has been described, but it is needless to say that this can be implemented in other types of engines. In the above embodiment, the case where a stainless steel mesh is used as the metal mesh of the spherical gasket and the expanded graphite is used as the graphite is described. However, the other effective metal mesh and graphite are used instead of the stainless steel mesh and the expanded graphite. May be.
[0041]
【The invention's effect】
As described above, according to the present invention, in the joint structure in the exhaust system of the engine, the spherical gasket of the spherical joint is mainly subjected to high-frequency vibration from the exhaust manifold to the downstream side by the metal mesh layer on the radially inner side having a high density. Since the transmission can be reduced as much as possible, and the surface area of the metal mesh exposed to the spherical surface of the spherical gasket can be reduced by the metal mesh layer on the radially outer side having a low density, the expansion of the graphite layer Not only can the sealing function by action be improved, but also the frictional resistance between the spherical gasket and the seating surface of the joint half is reduced, so that the vibration absorption effect in the bending direction between the exhaust manifold and the exhaust pipe can be improved. it can.
[Brief description of the drawings]
FIG. 1 is a side view of an engine exhaust system equipped with the joint structure of the present invention. FIG. 2 is an enlarged view of a portion surrounded by a virtual line in FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. 3. FIG. 5 is a perspective view of the spherical gasket. FIG. 6 is a partially enlarged cross-sectional view taken along line 6-6 in FIG. FIG. 8 is a perspective view showing a state before mold forming. FIG. 8 is a graph showing the relationship between the frequency and sound pressure of an exhaust system equipped with the joint structure of the present invention and a conventional exhaust system. (B) is an enlarged sectional view taken along line BB in (A).
14 ... Exhaust manifold 15 ... Exhaust pipe 18 ... Spherical joint 22 ... Half of joint ( on the other hand)
23 ・ ・ ・ ・ ・ ・ ・ ・ ・ Half joint (the other)
24 ... Spherical gasket 24a ... Opening (spherical gasket)
24b ... Spherical surface part (spherical gasket)
35 .... Metal mesh layer (stainless steel mesh layer)
37o ... Graphite layer (outside expanded graphite layer)
E ... Engine

Claims (1)

The downstream side of the exhaust manifold (14) connected to the exhaust port (12) of the engine (E) and the upstream side of the exhaust pipe (15) are connected via a spherical joint (18) so as to be capable of relative oscillation. In the joint structure in the exhaust system of the engine,
The spherical joint (18) includes a spherical gasket (24) interposed between a joint half (22) on the exhaust manifold (14) side and a joint half (23) on the exhaust pipe (15) side. The spherical gasket (24) has an opening (24a) through which exhaust passes at the center, and a spherical portion (24b) that makes spherical contact with one of the joint halves (22, 23) on the outer peripheral surface. The metal mesh layer (35) and the graphite layer (37o) are layered in the radial direction so that the graphite layer (37o) faces the spherical surface portion (24b) and is radially inner. A joint structure in an exhaust system of an engine, wherein the density of the metal mesh layer (35) is higher than the density of the metal mesh layer (35) on the radially outer side.

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