JPH07317539A - Exhaust manifold of internal combustion engine - Google Patents

Abstract

PURPOSE:To provide an exhaust manifold which can quickly eliminate drop in the temp, of exhaust gas when an internal combustion engine is in cold starting and can shorten the time required to attain the catalyst activation temp. CONSTITUTION:An exhaust manifold has a wall 3 where a curved exhaust passage 1 is formed, and a metal plate 4 thinner than this wall 3 and a heat insulating material 5 arranged between the metal plate 4 and the wall 3 in such a way as enclosing the back surface of metal plate 4 excluding its peripheral part are installed in the curving part of the wall 3 where the exhaust gas from the inlet to the exhaust passage 1 make collision.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust manifold for an internal combustion engine mounted on an automobile or the like.

[0002]

2. Description of the Related Art Conventionally, an exhaust manifold having an exhaust passage having one end connected to an exhaust port of a cylinder of the internal combustion engine and the other end connected to an exhaust pipe is disposed on the exhaust side of an internal combustion engine mounted in an automobile or the like. Has been done. In this exhaust manifold, the exhaust passage is formed in a curved state due to the structure for guiding the exhaust gas to the exhaust pipe, and the entire exhaust passage forming wall forming the exhaust passage is formed by casting.

[0003]

By the way, in an internal combustion engine mounted on an automobile or the like, there is widely used a post-treatment system in which a catalyst device is installed downstream of an exhaust manifold in order to purify exhaust gas discharged from the internal combustion engine. Has been adopted. In this case, immediately after the internal combustion engine is started (cold start), since the exhaust manifold and other exhaust system members are at ambient temperature, the high temperature exhaust gas discharged from the internal combustion engine may reach the catalytic device. The heat is absorbed and the temperature drops. Therefore, there is a problem that an effective purifying action by the catalyst device cannot be obtained while the exhaust gas passing through the catalyst device does not reach the activation temperature of the catalyst.

The present invention has been devised in view of the above problems, and provides an exhaust manifold capable of quickly eliminating the temperature decrease of exhaust gas at the cold start of an internal combustion engine and shortening the time required to reach the catalyst activation temperature. Providing is a problem to be solved.

[0005]

SUMMARY OF THE INVENTION The present invention, which solves the above problems, provides an exhaust passage forming wall forming a curved exhaust passage having one end communicating with an exhaust port of a cylinder of an internal combustion engine and the other end communicating with an exhaust pipe. In an exhaust manifold of an internal combustion engine that is formed by casting, a portion of the curved portion of the exhaust passage forming wall where exhaust gas flowing through the exhaust passage collides is thinner than the exhaust passage forming wall and has a heat insulating portion on its back surface. The metal plate has is provided.

The metal plate according to the present invention can be attached by casting when the exhaust manifold is cast, or can be attached by welding after casting. In a preferred aspect of the present invention, the thickness of the metal plate is 0.2 to 0.5 times the thickness of the exhaust passage forming wall. If it is smaller than 0.2 times, a strength problem occurs, and if it is larger than 0.5 times, the effect of providing the metal plate is weakened.

As another preferred mode, the heat insulating portion is made of a heat insulating material or a space portion.

[0008]

When the internal combustion engine equipped with the exhaust manifold of the present invention is started (cold start), the high temperature exhaust gas discharged from the internal combustion engine and flowing through the exhaust passage is placed on the curved portion of the exhaust passage forming wall. The heat is absorbed by the collision with the plate, and the metal plate is intensively heated. At this time,
The metal plate, which is thinner than the exhaust passage forming wall, has a small heat capacity and is kept warm by the heat insulating part on the back surface of the metal plate, so that its temperature rises rapidly and the temperature of the exhaust gas colliding with the metal plate rapidly decreases. Will be resolved. As a result, the timing at which the exhaust gas passing through the catalyst device installed on the downstream side of the exhaust manifold reaches the catalyst activation temperature is accelerated, and the effective purification action start time by the catalyst device is accelerated.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a front view of an exhaust manifold according to this embodiment, and FIG. 2 is a sectional view taken along the line AA of FIG.

In the exhaust manifold of this embodiment, four exhaust passages 1 communicating with the exhaust ports of each cylinder formed in a cylinder head (not shown) of a four-cylinder internal combustion engine, and each exhaust passage 1 are assembled. And a collective exhaust passage 2 communicating with an exhaust pipe (not shown) connected downstream.
Also, the exhaust passage forming wall 3 forming the collective exhaust passage 2 is mainly formed by casting. The exhaust passages 1 and the collective exhaust passages 2 are connected to the inlet of each exhaust passage 1 and the collective exhaust passage 2 respectively.
It is formed so as to be curved in an arc shape in a state in which the direction with respect to the outlet of is changed by about 90 °.

A portion of the curved portion of the exhaust passage forming wall 3 where the exhaust gas flowing from the inlet of each exhaust passage 1 collides is covered with the metal plate 4 and the rear surface of the metal plate 4 excluding the peripheral end portion. Further, the heat insulating material 5 arranged between the metal plate 4 and the exhaust passage forming wall 3 is arranged. The metal plate 4 is formed of a stainless steel plate having a thickness of about 1.5 mm, and the thickness of the exhaust passage forming wall 3 at the portion where the metal plate 4 is arranged is about 4 m.
Although it is m, it is thin. The heat insulating material 5 is made of ceramic wool.

The metal plate 4 and the heat insulating material 5 are attached by wrapping when the exhaust manifold is cast. That is, as shown in FIG. 3, a metal plate 4 having a back surface to which a heat insulating material 5 is bonded is placed in a cavity 8 formed by a mold 6 and a core 7, and is formed by pouring the metal into the cavity 8. The exhaust passage forming wall 3 is attached by being wrapped in the entire peripheral end portion of the metal plate 4.

The exhaust manifold of the present embodiment constructed as described above is attached so that the inlet of each exhaust passage 1 communicates with the exhaust port of each cylinder of the internal combustion engine, and the catalyst is provided at the outlet of the collective exhaust passage 2. The exhaust pipe connected to the device is connected and used. When the internal combustion engine is started (cold start), the high-temperature exhaust gas discharged from the internal combustion engine and flowing into the exhaust passage 1 collides with the metal plate 4 arranged on the curved portion of the exhaust passage forming wall 3. Heat is absorbed by
The metal plate 4 is intensively heated. At this time, the metal plate 4 formed thinner than the exhaust passage forming wall 3 has a small heat capacity, and heat transfer to the exhaust passage forming wall 3 is prevented by the heat insulating material 5 arranged on the back surface thereof. The temperature rises rapidly, and the temperature drop of the exhaust gas that collides with the metal plate 4 is quickly eliminated. As a result, the timing at which the exhaust gas passing through the catalyst device installed on the downstream side of the exhaust manifold reaches the catalyst activation temperature is accelerated, and the effective purification action start time by the catalyst device is accelerated.

As described above, according to the exhaust manifold of the present embodiment, the portion of the curved portion of the exhaust passage forming wall 3 where the exhaust gas flowing through the exhaust passage 1 collides is made of a metal thinner than the exhaust passage forming wall 3. A heat insulating material 5 for keeping the plate 4 and its metal plate 4 warm
Is provided, the temperature drop of the exhaust gas at the cold start of the internal combustion engine can be quickly eliminated, and the time required to reach the catalyst activation temperature can be shortened.

Further, in the exhaust manifold of this embodiment, since the heat insulating material 5 arranged between the mold 6 and the metal plate 4 plays a role of a core during casting, the casting can be easily performed. Thus, it is possible to avoid the occurrence of defective casting due to the gas generated from the core as in the case of using the core. In addition, since the metal plate 4 and the heat insulating material 5 in this embodiment are disposed in a part of the exhaust manifold, even if the metal plate 4 and the heat insulating material 5 are cast in when the exhaust manifold is cast, the molten metal does not flow well. The risk of occurrence of is reduced.

(Modification 1) FIG. 4 shows a modification of this embodiment.
Further, as shown in FIG. 5, the metal plate 14 and the heat insulating material 15 arranged on the curved portion of the exhaust passage forming wall 13 may be arranged over a wide range by using those larger than those in the above embodiment. By doing so, it becomes possible to eliminate the temperature drop of the exhaust gas more quickly and further shorten the time required to reach the catalyst activation temperature.

(Second Embodiment) FIG. 6 is a sectional view of an exhaust manifold according to the present embodiment. The exhaust manifold of this embodiment has the same basic structure as that of the first embodiment,
Four exhaust passages 21 (only one is shown in FIG. 6) and a collective exhaust passage 22 formed by assembling each exhaust passage 21 are provided, and each exhaust passage 21 and the collective exhaust passage 22 are connected to each other. The exhaust passage forming wall 23 to be formed is mainly formed by casting. Each exhaust passage 21 and collective exhaust passage 22
Are formed so as to be curved in an arc shape as in the case of the above embodiment.

In the exhaust manifold of this embodiment, an opening is formed in the curved portion of the exhaust passage forming wall 23 where the exhaust gas flowing from the inlet of each exhaust passage 21 collides, and the opening is formed. A metal plate 24 is arranged so as to close the portion. The metal plate 24 is formed of a self-fluxing alloy plate having a thickness of about 1.5 mm, which is thinner than the thickness of the exhaust passage forming wall 23 around the metal plate 24. The peripheral end portion is attached to the inner surface of the exhaust passage forming wall 23 while being in close contact with the molten metal by diffusion bonding. The back surface of the metal plate 24 is in contact with the atmosphere space, and the atmosphere space having a smaller heat transfer than the exhaust passage forming wall 23 is used as the heat insulating portion 25.

The exhaust manifold of the present embodiment constructed as described above is attached to an internal combustion engine for use as in the case of the first embodiment. Then, when the internal combustion engine is started (cold start), the internal combustion engine moves to the exhaust passage 2
The high temperature exhaust gas flowing into 1 absorbs heat by colliding with the metal plate 24, and the metal plate 24 is intensively heated while being kept warm by the heat insulating portion 25, and the temperature thereof rapidly rises. As a result, the temperature drop of the exhaust gas that collides with the metal plate 24 is quickly eliminated, and the timing of reaching the catalyst activation temperature of the exhaust gas that passes through the catalyst device installed on the downstream side of the exhaust manifold becomes faster.

As described above, according to the exhaust manifold of this embodiment, the exhaust passage 21 is formed by the curved portion of the exhaust passage forming wall 23.
A metal plate 24 thinner than the exhaust passage forming wall 23 having a heat insulating portion 25 on its back surface at a portion where the exhaust gas flowing through the vehicle collides.
Is provided, the temperature drop of the exhaust gas at the cold start of the internal combustion engine can be quickly eliminated, and the time required to reach the catalyst activation temperature can be shortened.

Since the exhaust manifold of the present embodiment is constructed without using a heat insulating material or the like as the heat insulating portion 25, the structure can be simplified and the castability can be improved. Excel. Also, the metal plate 2
Since the exhaust passage forming wall 23 in the portion provided with 4 is omitted, the weight of the exhaust manifold can be reduced.

(Modification 2) In the exhaust manifold of this modification, as shown in FIG. 7, in comparison with the exhaust manifold of the above embodiment, a heat insulating material 25 having a higher heat insulating property than the atmosphere is provided on the back surface of the metal plate 24. The metal plate 24 is attached by an adhesive, which enhances the heat retaining property of the metal plate 24. In this case, it is possible to easily provide the heat insulating material 25 that can obtain a more effective heat retaining effect without impairing the castability.

(Modification 3) In the exhaust manifold of this modification, as shown in FIG. 8, the metal plate 34 is formed in a shallow vessel shape with its entire peripheral end portion bent to the back side. A closed space 35 as a heat insulating portion is formed on the back surface side of the metal plate 34 by the lid plate 36 that is overlapped and joined to the entire circumference end portion. The metal plate 34 and the cover plate 36 are attached to the outer surface of the exhaust passage forming wall 33 in a state of being in close contact with each other by diffusion bonding of the entire peripheral end portion of the metal plate 34 arranged in the mold during casting with the molten metal. . When the closed space 35 is formed on the back surface of the metal plate 34 in this manner, the heat retaining property of the metal plate 34 becomes better than that in the case where the atmospheric space is used as the heat insulating portion.

The metal plate 34 and the cover plate 36 may be attached by welding after casting the exhaust manifold. (Test) A test for comparing the temperature change of the exhaust gas immediately after the start of the internal combustion engine, using the exhaust manifold of the first embodiment according to the present invention and the conventional exhaust manifold in which the metal plate and the heat insulating material are not arranged. I went. In this test,
The operating conditions of the internal combustion engine were set to the following five patterns, and the temperature of the exhaust gas was measured at a 150 mm descending portion from the outlet of each exhaust manifold.

In the first pattern, soaking is performed at room temperature, the internal combustion engine is started with no idling (800 rpm, intake pressure −560 mmHg), and measurement is started. The second pattern is to perform a motoring operation of the internal combustion engine in advance with no idling load (ignition switch OF
F) Then, when the exhaust gas temperature is constant (about 90 ° C.), idling no-load operation (ignition switch ON) is performed and measurement is started.

In the third pattern, the internal combustion engine is operated in a motoring operation (ignition switch is OFF) without idling in advance and the exhaust gas temperature is constant (about 90 ° C.). Barometric pressure-
Set to 360 mmHg and turn on the ignition switch to start measurement. In the fourth pattern, the internal combustion engine is operated in a motoring mode (ignition switch OFF) with no idling in advance and the exhaust gas temperature is constant (about 90 ° C), the internal combustion engine is operated at 2000 rpm, and the intake pressure is -360 mmHg. Then, turn on the ignition switch to start the measurement.

In the fifth pattern, the internal combustion engine is fully opened (3550 rpm, while the exhaust gas temperature is constant (about 90 ° C.) by performing the motoring operation (ignition switch OFF) of the internal combustion engine with no idling in advance. Set the intake pressure to -10 mmHg) and turn on the ignition switch to start measurement. As a result of measuring the exhaust gas temperature of the product of the present invention and the conventional product by the above respective patterns,
In all of the fifth patterns, it was found that the exhaust gas temperature of the product of the present invention rises faster than that of the conventional product, and reaches the high temperature region in a short time. FIG. 9 shows the measurement results of both in the third pattern as a representative thereof. By the way, the temperature difference between the two after 1 minute from the start of measurement is 4 ° C. in the first pattern and 20 ° C. in the second pattern.
It was 30 ° C. in the third pattern, 20 ° C. in the fourth pattern, and 25 ° C. in the fifth pattern.

At the same time as the measurement of the exhaust gas temperature,
When the surface temperature distributions of the product of the present invention and the conventional product were examined by thermo-video photography, it was confirmed that the surface temperature of the portion of the product of the present invention where the metal plate and the heat insulating material were disposed was lower than that of the conventional product. . From this, it can be seen that in the case of the product of the present invention, the metal plate heated by the impinging exhaust gas is kept warm by the heat insulating material and rapidly rises in temperature.

[0029]

According to the exhaust manifold of an internal combustion engine of the present invention, a portion of the curved portion of the exhaust passage forming wall where the exhaust gas flowing through the exhaust passage collides is thinner than the exhaust passage forming wall and has a heat insulating portion on its back surface. Since the metal plate having is disposed, it is possible to quickly eliminate the temperature decrease of the exhaust gas at the cold start of the internal combustion engine and shorten the time required to reach the catalyst activation temperature.

[Brief description of drawings]

FIG. 1 is a front view of an exhaust manifold according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is an explanatory diagram during casting of the exhaust manifold according to the first embodiment of the present invention.

FIG. 4 is a front view of an exhaust manifold according to a first modification of the first embodiment of the present invention.

5 is a sectional view taken along line BB of FIG.

FIG. 6 is a sectional view of an exhaust manifold according to a second embodiment of the present invention.

FIG. 7 is a cross-sectional view of an exhaust manifold according to a second modification of the second embodiment of the present invention.

FIG. 8 is a cross-sectional view of an exhaust manifold according to Modification 3 of Embodiment 2 of the present invention.

FIG. 9 is a graph showing changes in exhaust gas temperature in a test.

[Explanation of symbols]

1, 21 ... Exhaust passage 2, 22 ... Collecting exhaust passage 3, 13, 23 ... Exhaust passage forming walls 4, 14, 24,
34 ... Metal plate 5, 15 ... Heat insulating material (heat insulating part) 6 ... Mold 7 ... Core 25 ... Heat insulating part 35 ... Sealed space (heat insulating part)

Claims (3)

[Claims] 1. An exhaust manifold for an internal combustion engine, which is formed by casting and has an exhaust passage forming wall forming a curved exhaust passage having one end communicating with an exhaust port of a cylinder of the internal combustion engine and the other end communicating with an exhaust pipe. A metal plate that is thinner than the exhaust passage forming wall and has a heat insulating portion on its back surface is disposed in a portion of the curved portion of the exhaust passage forming wall where exhaust gas flowing through the exhaust passage collides. Exhaust manifold for internal combustion engine. 2. The exhaust manifold for an internal combustion engine according to claim 1, wherein the thickness of the metal plate is 0.2 to 0.5 times the thickness of the exhaust passage forming wall. 3. The exhaust manifold for an internal combustion engine according to claim 1, wherein the heat insulating portion is made of a heat insulating material or a space portion.