JPH09287446A - Exhaust manifold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the quick display of exhaust emission control capacity soon after the engine is started by quickening temperature rise of a catalyzer converter. SOLUTION: A reinforcement member 31 is welded on an inlet and an outlet flanges 25 and 26, while on the outlet frange 26, a stiffener 28 is welded and fixed so an engine 11 by a bolt 38. The stiffener 31 is born load in order to thin a pipe member 21. Thermal insulation plate which covers the pipe member 21 from its outside is fixed onto the reinforcement member 31 with a bolt 37. Compared with a conventional exhaust manifold which has thermal insulation plate directly fixed to the pipe member with a thick wall, temperature rise of a catalyzer converter is rapid, moreover compared with an exhaust pipe having dual-piped structure the saturating temperature of the catalyzer converter is low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust manifold mounted on an exhaust port of an engine and guiding exhaust gas to an exhaust passage communicating with a catalytic converter.

[0002]

2. Description of the Related Art A general exhaust manifold installed in an automobile has an inlet flange connected to an exhaust port of an engine, an outlet flange connected to an exhaust passage communicating with a catalytic converter, and an inlet flange and an outlet flange. And a pipe member that communicates with the exhaust gas and guides the exhaust gas to the exhaust path. Such an exhaust manifold is disclosed in JP-A-4-29.
No. 427 publication.

On the other hand, an exhaust manifold of an automobile is directly exposed to a high temperature of exhaust gas and is heated to a temperature close to 900 ° C., so that the exhaust manifold receives a load due to relative vibration between an engine side and an exhaust path side. It is thick and secures sufficient strength. The exhaust manifold shown in Japanese Utility Model Laid-Open No. 3-32117 reduces the load on the exhaust manifold by providing a reinforcing member that connects the outlet flange and the engine block (and the transmission case).

Since the exhaust manifold during operation becomes extremely hot as described above, the outside thereof is covered with a heat shield plate so that the adjacent parts in the bonnet and the vehicle body are not exposed to high temperatures. In the exhaust manifold shown in Japanese Utility Model Laid-Open No. 63-10220, a female screw is provided on the outer wall of the pipe member, and one heat shield plate that commonly covers the outside of a plurality of pipe members is fixed to the female screw. .

[0005]

Since the conventional exhaust manifold is formed thick and has a considerable mass, the temperature rises slowly after the engine is started, and heat is taken from the exhaust gas to raise the temperature of the catalytic converter. Was delayed.
Since the catalytic converter is normally heated to 400 ° C. or higher and activated, if the time to reach 400 ° C. is extended, more unpurified exhaust gas is discharged. This problem can be solved by providing a preheater in the catalytic converter to speed up the temperature rise, but there is a problem that a large current is consumed and the load on the battery becomes large.

Therefore, an attempt has been made to construct the exhaust manifold with a double pipe to form the inner pipe having a thin wall that directly contacts the exhaust gas. However, if the exhaust manifold is configured with a double pipe, the temperature of the catalytic converter rises quickly after the engine is started, but on the other hand, the heat insulation performance becomes excessive, and if the high speed operation is continued for a long time, the temperature of the catalytic converter becomes 800
The temperature rises beyond the limit, and the high temperature adversely affects the internal catalytic element, thereby reducing its life and performance.

It is an object of the present invention to provide an exhaust manifold in which the temperature of the catalytic converter rises quickly and the temperature of the catalytic converter does not become excessive even if high speed operation is continued for a long time.

[0008]

According to a first aspect of the present invention, an inlet flange connected to an exhaust port of an engine and an outlet flange connected to an exhaust passage communicating with a catalytic converter are provided.
In an exhaust manifold having a pipe member that connects an inlet flange and an outlet flange to guide exhaust gas to the exhaust path, a first reinforcing member that is arranged outside the pipe member and integrally connects the inlet flange and the outlet flange. And a heat shield plate arranged to cover the outside of the pipe member and fixed to the first reinforcing member.

According to a second aspect of the present invention, a second reinforcing member having one end fixed to the outlet flange and the other end fixed to the engine block is added to the structure of the first aspect.

[0010]

In the exhaust manifold according to the first aspect, the outer wall of the pipe member having the single pipe structure is in contact with the outside air, so that the heat insulation performance is low and the heat radiation through the pipe wall is large as compared with the double pipe structure. . The pipe member having the single-tube structure contacts the outside air in the space formed between the engine and the heat shield plate. Therefore, the saturation value of the temperature of the exhaust gas flowing into the catalytic converter is suppressed as compared with the case of the double pipe structure, and the limit value of the temperature rise of the catalytic converter due to the high speed operation becomes lower.

On the other hand, since the inlet flange and the outlet flange are integrally connected by the first reinforcing member, the load applied between the inlet flange and the outlet flange, that is, the relative vibration between the engine and the exhaust passage and the support of the exhaust passage. There is no need for the pipe member to bear the load associated with. Therefore, while the supporting rigidity of the outlet flange with respect to the inlet flange is ensured by the first reinforcing member, the pipe member can be thinned and the mass of the pipe member can be reduced, so that the rise of the pipe wall temperature after the engine is started can be set rapidly. it can.

Since the heat shield plate is fixed to the first reinforcing member, it is not necessary to add unnecessary mass such as an internal thread to the pipe member. Since heat is not directly conducted from the pipe member to the heat shield plate, the temperature rise of the pipe member is not hindered, and the mounting portion of the heat shield plate is not locally overheated.

In the exhaust manifold of the second aspect, the support rigidity of the outlet flange with respect to the inlet flange is secured by the engine block via the second reinforcing member in addition to the first reinforcing member. Therefore, the load on the first reinforcing member can be further reduced without impairing the overall rigidity.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exhaust manifold according to an embodiment will be described with reference to FIGS. FIG. 1 is an explanatory view of an attached state of an exhaust manifold, FIG. 2 is a front view of the exhaust manifold, and FIG. 3 is a diagram of rising temperature of a catalytic converter. As shown in FIG. 1, an exhaust manifold inlet port 25 is connected to an exhaust port 15 of an automobile engine 11. The pipe member 21 connects and communicates with the inlet flange 25 and the outlet flange 26 on the opposite side. The outlet flange 26 is connected to the flange 16 of the exhaust pipe 12.
The exhaust pipe 12 has a double pipe structure, and a catalytic converter 13 is attached by welding to the downstream side. In the double-pipe structure of the exhaust pipe 12, the pipe wall that comes into contact with the exhaust gas is formed thin, and since the mass that is directly overheated by the exhaust gas is small, the temperature of the inner wall surface rises quickly at startup, Does not hinder the temperature rise of flowing exhaust gas.

The catalytic converter 13 stores a catalytic element therein. The catalytic element activates in the state of being heated to 400 ° C. or higher to purify the exhaust gas, while
If it is kept at a high temperature exceeding 100 ° C for a long time, the life and performance will be reduced. The exhaust pipe 14 connected to the downstream side of the catalytic converter 13 communicates with the exhaust port at the rear of the vehicle body via a muffler or the like (not shown).

As shown in FIG. 2, the openings of the inlet flange 25 (corresponding to the four exhaust ports 15 of the engine 11) and the openings of the outlet flange 26 are connected by four pipe members 21. The pipe member 21 is a so-called inside-type pipe line in which a pair of parts obtained by press-molding a stainless steel plate having a thickness of 0.8 mm are butted and both edges thereof are welded. Two pipe members 21 on the outside and two pipe members 21 on the inside
Are merged on the way and are guided to the two openings of the outlet flange 26.

Reinforcing members 31 and 32 are welded by connecting the shoulder portions on both sides of the inlet flange 25 and the shoulder portions on both sides of the outlet flange 26 in a V shape. The reinforcing members 31 and 32 are
In cooperation with the pipe member 21, the positional relationship between the inlet flange 25 and the outlet flange 26 is fixed, and the rigidity required for the exhaust manifold is secured. Two female screws 33 are formed on the center line of the reinforcing member 31, and the heat shield plate 27 is fixed thereto by using bolts 37 as shown in FIG. Heat shield 27
Are similarly fixed to the reinforcing member 32. The heat shield plate 27 is the engine 1 of the bent pipe member 21.
It is formed in a shape in which the surface opposite to 1 is gently covered from the outside. As shown in FIG. 1, the pipe member 21 is in direct contact with the outside air in the space sandwiched between the outer wall of the engine 11 and the heat shield plate 27.

The outlet flange 26 has a reinforcing member 28 formed by bending a stainless plate having a bolt hole into an L shape.
Is welded. A bolt 38 is inserted into this bolt hole and fastened to the female screw of the female screw portion 17 provided on the outer wall of the engine 11. As a result, the reinforcing member 28 is firmly fixed to the engine 11.

According to the exhaust manifold of the embodiment, since the positional relationship and the attitude relationship between the inlet flange 25 and the outlet flange 26 are firmly held by the reinforcing members 31, 32, 28, the engine 11 and the exhaust pipe 12 are prevented from each other. The load due to the relative vibration is not applied to the pipe member 21. Therefore, the rigidity of the entire exhaust manifold is sufficiently ensured even if the pipe member 21 has a thin structure or a middle structure.

Since the pipe member 21 is thin and there is no direct heat conduction from the pipe member 21 to the heat shield plate 27, the inner wall temperature of the pipe member 21 rises quickly after the engine 11 is started, and the catalyst of the catalytic converter 13 is increased. Temperature is 40
The time to reach 0 degree C is also shortened. FIG. 3 shows the rise of the temperature of the catalytic converter 13. Curve R1 in the figure
Is the curve R2 in the case of the exhaust manifold shown in FIGS.
Indicates a case of a conventional exhaust manifold in which a heat shield plate is directly attached to a thick pipe member, and a curve R3 indicates a case of an exhaust manifold having a double pipe structure. When the engine 11 is started at time A, the catalyst temperature of the thick exhaust manifold R2 reaches 400 degrees C at time D, but the exhaust manifold R1 of the embodiment and the exhaust manifold R3 of the double pipe structure have thick catalyst. The catalyst temperature exceeds 400 ° C. at time B in a time less than ⅓ of the exhaust manifold R2.

Further, since the pipe member 21 comes into contact with the outside air and is cooled in the space between the engine 11 and the heat shield plate 27,
The inner wall temperature is saturated at a temperature lower than that of the exhaust manifold R3 having the double pipe structure, and the temperature of the exhaust gas flowing into the catalytic converter 13 does not become extremely high. Therefore, in the exhaust manifold R3 having the double pipe structure, the final catalyst temperature is 8
Although it exceeds 00 ° C, in the exhaust manifold R1 shown in FIGS. 1 and 2, the final catalyst temperature becomes 700 ° C or less, and there is no fear of impairing the life or performance of the catalyst.

Further, since the heat shield plate 27 is fixed to the reinforcing members 31 and 32 and is floated from the pipe member 21,
The heat is not directly absorbed from the pipe member 21 to the heat shield plate 27, and there is no concern that the temperature rise of the pipe member 21 after the engine is started is prevented by the heat dissipation of the heat shield plate 27. at the same time,
Since the temperature rise of the mounting portion of the heat shield plate 27 is small, the deformation and oxidation (peeling of coating or plating) of the heat shield plate 27 is suppressed as compared with the case where the heat shield plate is screwed to the pipe member. There is no concern that the heat shield plate 27 will become irreplaceable due to seizure of the bolt 37, and the heat shield plate 27 and the bolt 37 will not overheat and damage other parts in the bonnet.

[0023]

According to the invention of claim 1, since the load applied to the pipe member is borne by the first reinforcing member, it is possible to drastically reduce the thickness without being restricted by the strength of the pipe member. Since the inner wall temperature of the pipe member rises earlier due to the reduced wall thickness, the time until the catalytic converter begins to function can be shortened, and a large amount of unpurified exhaust gas does not have to be emitted after the engine is started. A heater for preheating the catalytic converter is not required, and even if a heater is installed, the amount of heat required is small and the burden on the battery is reduced. Further, since the pipe member comes into contact with the outside air in the space formed between the heat shield plate and the engine, the final inner wall temperature becomes lower than that of the double pipe structure,
Even if high-power operation is continued for a long time, there is no concern that excessively high-temperature exhaust gas will flow into the catalytic converter and reduce the life and performance of the catalyst. Further, since the heat shield plate is fixed to the first reinforcing member, the temperature of the inner wall of the pipe member rises faster than when it is fixed to the pipe member, and the heat shield plate and its mounting portion are not overheated. Therefore, the degree of freedom in arranging parts around the engine is increased, and a compact and lightweight automobile can be configured.

According to the invention of claim 2, since the second reinforcing member and the first reinforcing member cooperate to bear the load applied to the pipe member, it is possible to further reduce the thickness of the pipe member.
By further reducing the wall thickness, it becomes possible to further speed up the rise of the temperature of the catalytic converter.

[Brief description of drawings]

FIG. 1 is an explanatory view of a mounted state of an exhaust manifold.

FIG. 2 is a front view of an exhaust manifold.

FIG. 3 is a diagram of rising temperature of a catalytic converter.

[Explanation of symbols]

 11 Engine 12 Exhaust Pipe 13 Catalytic Converter 14 Exhaust Pipe 15 Exhaust Port 16 Flange 17 Female Thread 21 Pipe Member 25 Inlet Flange 26 Outlet Flange 27 Heat Shield 28 Reinforcement Member (Second Reinforcement Member) 31, 32 Reinforcement Member (First Reinforcement) Material) 37, 38 Bolt 33 Female thread

Claims (2)

[Claims] 1. An inlet flange (25) connected to an exhaust port of an engine, an outlet flange (26) connected to an exhaust passage communicating with a catalytic converter (13), an inlet flange (25) and an outlet flange ( 26) An exhaust manifold having a pipe member (21) for communicating exhaust gas and guiding the exhaust gas to the exhaust passage, the inlet flange (25) and the outlet flange (26) being arranged outside the pipe member (21). And a heat shield plate (27) arranged to cover the outside of the pipe member (21) and fixed to the first reinforcement member (31). A characteristic exhaust manifold. 2. A second end having one end fixed to the outlet flange (26) and the other end fixed to the engine block (11).
Reinforcement member (28) is added, 1 characterized by the above-mentioned.
Exhaust manifold described.