JP2013104378A - Exhaust manifold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust manifold configured to improve cylinder filling efficiency from low- to high-speed rotation with a simple structure, and to prevent a backflow pulse from affecting a cylinder inner pressure.SOLUTION: The exhaust manifold 1 arranged between an exhaust port 20 of an engine 2 and a muffler 3 includes: an inlet A having an opening larger in area than the exhaust port 20 and extended in an exhaust direction; an outlet C connected to the muffler 3 and having an opening nearly as large in area as the exhaust port 20; and an intermediate part B for connecting the inlet A to the outlet C, and gradually decreasing in cross sectional area from the opening of the inlet A to that of the outlet C.

Description

  The present invention relates to an exhaust manifold disposed between an exhaust side of an engine and a muffler.

  Patent Document 1 provides an exhaust manifold that can suppress the generation of radiated sound from an outer pipe due to vibration of a flat portion of an inner pipe in an exhaust manifold having a double pipe structure. The exhaust manifold disclosed in Patent Document 1 forms two outer stainless steel plate materials, welds the mating surfaces to form an outer tube, fixes the inner tube and the outer tube to the flange, and flats the inner tube. An arc-shaped shielding plate is extended from the flange inward of the portion, and the shielding plate prevents the pressure wave of the exhaust gas from directly vibrating the flat portion of the inner tube.

  Patent Document 2 can effectively suppress the generation of noise due to a pressure wave generated by an exhaust gas collision, and can increase the temperature of a downstream exhaust gas purification catalyst quickly without increasing the cost. An exhaust manifold that can be used is provided. The exhaust manifold disclosed in Patent Document 2 is configured by integrally joining two sheet metal molded products, and has an attachment flange with respect to the exhaust port arrangement surface of the cylinder head and an outlet flange through which exhaust gas flows. A linear boundary area that divides the part facing the exhaust port and the part including the outlet flange continuously or intermittently with respect to the other parts is set, and the boundary area is configured with a thinned part and a leaf spring part It is a thing.

JP-A-11-107745 JP 2009-127557 A JP 2009-180184 A

  The current intake manifold is designed based on fluid dynamics and flow dynamics such as laminar flow because the pressure is not so high even with a turbo. The exhaust pipe is similarly designed based on the flow dynamics, but the exhaust gas is very hot and high in pressure, so the flow dynamics cannot cope with it, and there is a problem that the filling efficiency is lowered. Moreover, if the exhaust pipe is basically designed around changes in temperature and pressure, high efficiency can be obtained even if the engine is used as it is.

  In a multi-cylinder engine, the exhaust pipes are assembled before entering the catalyst. However, there is a problem that the exhaust pipe pulses flow backward in the adjacent exhaust pipes, increasing the cylinder internal pressure and inducing knocking. Further, as described in Patent Documents 1 and 2, this pulse causes high-frequency abnormal noise. Furthermore, in some types of automobiles, the exhaust pipe assembly is moved away from the engine to change the timing of the backflow pulse to suppress the increase in cylinder internal pressure, but only a specific rotational speed is effective, and the backflow pulse is delivered. For example, there is no change in the pulse entering the cylinder, and the exhaust gas is cooled to hinder the function of the catalyst. Therefore, there is a problem that complicated control is required to control it.

  Furthermore, in the conventional muffler, the exhaust pipe inner diameter is the same as the exhaust port diameter, so the exhaust gas enters the silencer while maintaining a high pressure and expands to a low pressure. Since the pressure of the exhaust gas remains high, the exhaust gas remaining in the cylinder is difficult to be discharged, and there is a problem that the efficiency is lowered because new air (air mixture) is not sufficiently filled. Further, when the pressure in the cylinder is high, not only the charging efficiency is lowered, but also knocking is likely to occur, so that the ignition timing must be delayed or the compression ratio must be lowered, resulting in a low efficiency. For this reason, in high-performance engines, the exhaust port, exhaust pipe, and silencer are expanded in inner diameter, and the overall pressure is lowered to lower the pressure in the cylinder and increase the charging efficiency. However, this is effective only at high speeds. On the other hand, when the engine is running at a low speed, the slipping out is too good, resulting in a problem that the torque is reduced.

  Therefore, the present invention provides an exhaust manifold that can improve the filling efficiency of the cylinder from a low rotation speed to a high rotation speed with a simple structure, and can suppress the influence of the backflow pulse on the cylinder internal pressure. There is to do.

  Accordingly, the present invention relates to an exhaust manifold disposed between an exhaust port of an engine and a muffler, an inlet portion having an opening area larger than an opening area of the exhaust port and extending in an exhaust direction, and the muffler And an outlet portion having an opening area substantially equal to the opening area of the exhaust port, the inlet portion and the outlet portion are connected, and a gradual cross-sectional area extends from the opening area of the inlet portion to the opening area of the outlet portion. It is characterized by comprising an intermediate part to be reduced.

  Further, a step is formed between the inlet portion and the exhaust port.

  Furthermore, it is desirable that the inlet portion has an elliptical or oval shape. Furthermore, it is preferable that the inlet portion is fitted on a holding extension portion formed on a peripheral edge of the exhaust port.

  According to the present invention, since the opening area on the inlet side of the exhaust manifold is made larger than the opening area of the exhaust port, the pressure can be lowered to the inlet portion of the exhaust manifold. Since it can be pulled out without difficulty, the pressure in the cylinder of the engine can be lowered efficiently, and the charging efficiency at high rotation can be increased.

  In addition, since a step is formed between the exhaust port and the exhaust manifold, this step can reflect the backflow pulse that flows back from the muffler side into the exhaust manifold, greatly reducing the backflow pulse that enters the cylinder. Is something that can be done.

FIG. 1 is a schematic configuration diagram showing the present invention. FIG. 2 is an explanatory diagram showing the state of the exhaust pulse in the exhaust manifold of the present invention. FIG. 3 is an explanatory view showing another embodiment of the inlet portion of the exhaust manifold of the present invention. FIG. 4 is an explanatory view showing another embodiment of the exhaust manifold of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, the exhaust manifold 1 according to the present invention is disposed between the exhaust port 20 of the engine 2 and the muffler 3, and has an inlet portion A communicating with the exhaust port 20 and an intermediate portion B. And an outlet C that communicates with the muffler 3. D is a fresh air mixture in the intake port 23 of the engine 2.

  A flange portion 10 for fixing the exhaust manifold 1 to the housing 21 is provided at an end portion of the inlet portion A, and is fixed to the housing 21 by a bolt 11. The inlet portion A has an opening area larger than the opening area of the exhaust port 20, and a step 22 is formed between the exhaust port 20 and the inlet portion A.

  The inlet portion A has an opening area larger than the opening area of the exhaust port 20 and extends a predetermined length in the exhaust direction from the exhaust port 20 to define a diffusion space 12. The subsequent intermediate portion B has a shape in which the sectional area is gradually reduced from the sectional area similar to the opening area of the inlet portion A to the sectional area substantially equal to the opening area of the exhaust port 20, and the throttle space 13 is defined. Made. The outlet portion C defines a connection space 14 that extends to the connection portion 15 with the muffler 3 with the reduced cross-sectional area.

  With the above configuration, in the exhaust manifold 1 according to the present invention, the exhaust gas discharged from the exhaust port 20 is discharged and diffused into the diffusion space 12 of the inlet portion A of the exhaust manifold 1 to generate the low pressure portion H. For this reason, since the exhaust gas existing in the high-pressure portion G can be drawn out without difficulty, the pressure F in the cylinder can be lowered, so that the charging efficiency at the time of high rotation can be greatly increased.

  Further, the exhaust gas in the low pressure portion H is throttled to an intermediate pressure when passing through the intermediate portion B, and is discharged to the muffler 3 (I to J, K). As described above, the exhaust manifold 1 can be prevented from being excessively exhausted by restricting the exhaust manifold 1 at the intermediate portion B, so that the torque in the low and medium speed range can be improved.

  Further, the step 22 between the inlet portion A and the exhaust port 20 is, for example, as shown in FIG. 2, the backflow pulse BP of the exhaust gas reflected and returned from the muffler side passes through the intermediate portion B. When the diffusion space 12 reaches the diffusion space 12, it diffuses and weakens, and since the peripheral portion of the backflow pulse that has spread through the diffusion space 12 collides with the step 22 and is reflected, the backflow pulse entering the exhaust port 20 is greatly reduced. It can be reduced. Thus, according to the exhaust manifold 1 of the present invention, since the back flow pulse can be reduced in the entire region (from low to high rotation), high compression can be achieved, knocking can be suppressed, and high efficiency can be achieved. It can be achieved.

  As described above, in Embodiment 1, the cross-sectional shape of the inlet portion A is substantially circular. On the other hand, in the exhaust manifold 1 ′ according to the second embodiment of the present invention shown in FIG. 3, it is desirable that the shape of the inlet portion A of the exhaust manifold 1 is an ellipse or an ellipse. This is a shape that makes it possible to avoid the fixing bolt 11 in the flange portion 10. By adopting this shape, it can be adopted in almost all current engines. As described above, it is desirable that the cross-sectional shape is circular, but the same effect can be obtained if the structure has an opening area larger than the opening area of the exhaust port 20 and the step 22.

  In the third embodiment shown in FIG. 4, the exhaust manifold 1 ″ of the present invention may be mounted so as to be fitted on the outer peripheral side surface of the flange portion 10 ′ formed on the periphery of the exhaust port of the engine. In this case, the holding portion 16 is provided on the flange portion 10 'so as to extend in the mounting direction, and the inlet portion A of the exhaust manifold 1 "is externally fitted to the holding portion 16 and fixed with a spring or the like. Is also good.

  In addition, about Example 2 shown by FIG. 3 and Example 3 shown by FIG. 4, the same number is attached | subjected to the part which has the same part and the same effect, and the description is abbreviate | omitted.

1, 1 ', 1 "Exhaust Manifold 2 Engine 3 Muffler 10, 10' Flange 11 Bolt 12 Diffusion Space 13 Restricted Space 14 Connection Space 15 Connection 20 Exhaust Port 21 Housing 22 Step 23 Intake Port A Inlet B Intermediate Exit

Claims (4)

In the exhaust manifold placed between the exhaust port of the engine and the muffler,
An inlet portion having an opening area larger than the opening area of the exhaust port and extending in the exhaust direction;
An outlet connected to the muffler and having an opening area substantially equal to the opening area of the exhaust port;
An exhaust manifold comprising: an intermediate portion that connects the inlet portion and the outlet portion, and that gradually decreases in cross-sectional area from the opening area of the inlet portion to the opening area of the outlet portion.   The exhaust manifold according to claim 1, wherein a step is formed between the inlet portion and the exhaust port.   The exhaust manifold according to claim 1 or 2, wherein the inlet portion has an elliptical or oval shape.   The exhaust manifold according to claim 1 or 2, wherein the inlet portion is fitted on a holding extension portion formed on a peripheral edge of the exhaust port.

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