JPH05332133A - Exhaust device of horizontal opposed four cylinder engine - Google Patents

Abstract

PURPOSE:To improve exhaust ability, exhaust noise and catalysis ability by eliminating exhaust interference and equalizing and also shortening the length of pipe lines in the exhaust system from the right and left banks of a horizontal opposed four cylinder engine. CONSTITUTION:An exhaust manifold 20 is nearly horizontally arranged before the lower part of an engine body 1, which is connected to the exhaust ports 7a to 7d of right and left bank L and R through branch pipes 20a to 20d, the length of the pipe lines of which is equal. A catalysis converter 22 is floatedly mounted on the lower part of the right side of the engine body on a car body and connected to the collecting section 20e of the exhaust manifold 20 through a short flexible exhaust duct 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust system for a horizontally opposed four-cylinder engine mounted on a vehicle, and more particularly to a layout of exhaust pipes from left and right banks, a catalytic converter and the like.

[0002]

2. Description of the Related Art In a horizontally opposed four-cylinder engine, the engine body is constructed by horizontally connecting cylinder heads to the left and right banks of a crankcase, and the first and third cylinders are located in the right bank and the second cylinder is located in the left bank. A fourth cylinder is arranged, a transmission is connected to the rear part of the engine body, and is vertically installed in the longitudinal direction of the vehicle body. In the cylinder head, an intake port is provided in the upper part and an exhaust port is provided in the lower part. Therefore, the exhaust pipe needs to be routed below the engine body. Furthermore, an oil pan is attached to the lower part of the crankcase, and a cross member on the vehicle body side is installed immediately after the oil pan. Therefore, exhaust pipes and the like cannot be collected immediately after the engine body.

When the exhaust system is laid out due to such a peculiar shape of the engine body and the mounting state on the vehicle body, the catalytic converter is installed using a space on the right side of the transmission behind the engine body, for example. The exhaust pipe from the exhaust manifold of the right bank extends straight rearward and is linearly connected to the catalytic converter.The exhaust pipe from the exhaust manifold of the left bank extends rearward and then bends so as to traverse below the transmission. Connected to the catalytic converter.

By the way, the ignition sequence of this engine is # 1 →
According to the above exhaust system, since the left and right banks having the same ignition order are gathered together, exhaust interference occurs and the exhaust is not good, so that the exhaust pressure of each cylinder is not good. It produces a uniform and radiated sound due to high frequency pressure. Moreover, since the exhaust pipes of the left and right banks are gathered with unequal lengths, the discharge sound becomes discontinuous. Since the distance from the exhaust port to the catalytic converter is long, it is disadvantageous for activating the catalyst, and abnormal noise such as a shock wave is generated. Further, since the exhaust pipes are connected to the catalytic converter from two directions, it is easy to be oscillated by pressure fluctuation, and it is difficult to determine the mounting position of the O ₂ sensor. Therefore, also in this horizontally opposed four-cylinder engine, it is required that the exhaust device be laid out so as to eliminate exhaust interference and equalize and shorten the pipe length.

Conventionally, as an exhaust system for an engine having the above-mentioned left and right banks, there is a prior art disclosed in, for example, Japanese Patent Laid-Open No. 1-294911. Here, in an exhaust collecting device of a V-type 6-cylinder engine, branch pipes from each of the left and right banks are connected to a collecting pipe, and a branch pipe having a short pipe length is approximately L.
It is shown that a character-shaped interference tube is provided to reduce exhaust interference noise in the collecting tube.

[0006]

By the way, in the above-mentioned prior art, since it is premised that the exhaust pipes from the left and right banks have unequal lengths, a horizontally opposed four cylinder cylinder is used. It is similar to the conventional exhaust system of an engine and is not the solution of the present invention.

The present invention has been made in view of this point. In the exhaust system from the left and right banks of a horizontally opposed four-cylinder engine, exhaust interference is eliminated, and the pipe length is made equal and shortened, The purpose is to improve exhaust performance, exhaust noise, catalyst performance, and the like.

[0008]

In order to achieve the above object, the present invention has a first and third cylinders arranged in the right bank of the engine body, and second and fourth cylinders arranged in the left bank. An exhaust port is provided under the cylinder head of the bank,
In a horizontally-opposed 4-cylinder engine that is mounted vertically mounted in the longitudinal direction of the vehicle by connecting a transmission to the rear part of this engine body, an exhaust manifold is installed in front of the lower part of the engine body, and the pipe length is equal. A catalyst that is connected to the exhaust ports of the left and right banks with substantially four branch pipes and is disposed substantially horizontally. The catalyst is disposed in the lower part of one of the left and right of the engine body through the exhaust duct from the collection part of the exhaust manifold. It is connected to the converter.

[0009]

According to the above structure, when the engine is in operation, the exhaust gas is discharged from the exhaust ports of the left and right banks of the engine body into the branch pipes of the four equal lengths of the exhaust manifold based on the ignition sequence. As a result, exhaust interference due to the ignition sequence is eliminated, the exhaust pressure between the cylinders is equalized, and various exhaust noises are reduced. Exhaust gas from all cylinders is gathered in an exhaust manifold to have a constant pressure and exhaust gas concentration, and flows into a catalytic converter located on one of the left and right sides of the engine body through a short exhaust duct to efficiently purify the exhaust gas. To be done. Further, by disposing the exhaust manifold, the exhaust duct, and the catalytic converter in front of the lower part of the engine body, the exhaust air is positively cooled and the exhaust temperature is prevented from rising.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2, the structure of an exhaust system for a horizontally opposed four-cylinder engine will be described. Engine body 1
The left and right banks L and R of the crankcase 2 are horizontally connected to the cylinder heads 3 and 4, and the first and third cylinders are arranged in the right bank R and the second and fourth cylinders are arranged in the left bank L. The ignition sequence is # 1 → # 3 → # 2 → # 4. Further, the cylinder head 4 of the right bank R is offset from the cylinder head 3 of the left bank L toward the front of the vehicle body and is bank-offset, and an oil pan 12 for storing lubricating oil is projectingly provided at a lower portion of the center of the crankcase 2. .. The engine body 1 is connected to a rear portion of the transmission 5 and is vertically mounted in the vehicle front-rear direction.

In the cylinder heads 3 and 4, an intake port 6 is provided in the upper part, and exhaust ports 7a to 7d are provided in the lower part. Therefore, the intake manifold 8 of the intake system
The engine main body 1 is horizontally mounted between the left and right cylinder heads 3 and 4 and connected to an intake port 6, and a chamber 9 in the middle of the intake manifold 8 is provided with a throttle valve 11
Is connected to a throttle body 10 having

Explaining the exhaust system, the oil pan 12 under the center of the crankcase 2 is formed by partial deformation. Further, an exhaust manifold 20 having a predetermined pipeline length is routed from the lower portions of the cylinder heads 3 and 4 of the left and right banks L and R toward the front of the vehicle body. The oil pan 12 is deformed so as to have a recess 12a at the front right corner so as not to interfere with the routing of the exhaust manifold 20. In this case, the oil pan 12 can eliminate the problems caused by deformation by adding an oil return passage or improving the baffle plate.

The exhaust manifold 20 has two branch pipes 20a, 2 at one connection port 20f of the bifurcated collecting portion 20e.
0c and the coupling fitting 20i, and the other connection port 20g is also configured by integrally connecting the two branch pipes 20b and 20d and the coupling fitting 20j. Two branch pipes 20a, 20c on the right side
Is bent in a substantially L shape, and the two branch pipes 20 on the left side are formed.
b and 20d are bent in a substantially arcuate shape, and when the collecting portion 20e is located substantially in front of the center of the crankcase 2, the four branch pipes 20a to 20d have the same length and are from the same direction. The exhaust gas flows into the collecting portion 20e and collects.

In the exhaust manifold 20, the two branch pipes 20a, 20c on the right side are arranged with the collecting portion 20e arranged substantially immediately below the oil pan below the crankcase 2.
Passes near the recess 12a of the oil pan 12 and is routed to the right bank R, and the coupling fitting 20i is coupled to the cylinder head 4 and connected to the exhaust port 7a of the first cylinder and the exhaust port 7c of the third cylinder, respectively. It The two left branch pipes 20b and 20d pass through the left side of the oil pan 12 and are routed to the left bank L. Similarly, the coupling fitting 20j is coupled to the cylinder head 3 to form the exhaust port 7b of the second cylinder. It is connected to the exhaust port 7d of the fourth cylinder. In this way, the exhaust manifold 20 is provided in front of the lower part of the engine body 1.
It is arranged horizontally without being affected by the cross member on the vehicle body side.

On the other hand, on the further right side of the cylinder head 4 of the right bank R, a catalytic converter 22 is mounted by float mounting on the vehicle body side. Further, from the outlet 20h of the collecting portion 20e of the exhaust manifold 20, a short and flexible exhaust duct 23 is linearly taken out to the right of the lower front portion of the engine body 1, and the exhaust duct 23 is connected to the catalytic converter 22. To be done. An exhaust pipe 24 from the catalytic converter 22 is extended rearward along the transmission. In this way, the exhaust systems from the left and right banks L and R are once drawn out to the front of the lower part of the engine body 1 by the exhaust manifold 20 having the same pipe length, and then to the rear by bypassing the right catalytic converter 22. It is composed by turning. An O ₂ sensor 25 is attached to the exhaust duct 23 so as to detect harmful components in the exhaust gas.

Next, the operation of this embodiment will be described. First, when the engine is running, the # 1 cylinders of the cylinder heads 3 and 4 of the left and right banks L and R of the engine body 1
→ # 3 → # 2 → # 4 In the order of cylinders, the intake air is taken in through the throttle body 10 and the intake manifold 8 of the intake system, ignited and burned, and the exhaust gas is exhausted from the exhaust manifold 2
It is discharged to the four branch pipes 20a to 20d of No. 0 in the above-mentioned order. At this time, the four branch pipes 2 of the exhaust manifold 20
Since 0a to 20d have the same pipe length, the exhaust gas guided by each of the branch pipes 20a to 20d has a collecting portion 20.
The time to reach e is the same. As a result, the exhaust pressure between the four cylinders and the left and right banks L and R is equalized, the exhaust interference due to the ignition order of the left and right banks L and R is eliminated, and the exhaust performance is improved. Further, the pressure difference between the cylinders and the high-frequency pressure associated therewith are not generated, and the emission noise reduces the emission noise due to the high-frequency pressure and the abnormal noise of the shock wave, resulting in a continuous discharge sound.

In the collecting portion 20e of the exhaust manifold 20, the pressure fluctuations of the exhaust gases of all the cylinders are interfered with each other to reduce the pressure fluctuations, the peaks are attenuated when passing through the exhaust duct 23, and the exhaust gas concentration is always constant. Be constant. Then, this exhaust gas flows into the catalytic converter 22 at a high exhaust temperature state by the short exhaust duct 23, activates the catalyst and satisfactorily removes harmful components, and the exhaust gas purified in this way is further guided rearward by the exhaust pipe 24. Get burned.

The exhaust manifold 20, the exhaust duct 23,
By arranging the catalytic converter 22 in front of and below the lower part of the engine main body 1, the outside air A is immediately hit by the vehicle traveling to be positively cooled, thereby suppressing an increase in exhaust temperature. Further, during engine operation, fluctuations in vibration between the exhaust manifold 20 on the engine body side and the catalytic converter 22 are absorbed by the flexible exhaust duct 23.

Another embodiment of the present invention will be described with reference to FIG. In this embodiment, in the exhaust system of the horizontally opposed four-cylinder engine configured as described above, the engine body 1, the exhaust manifold 20, the exhaust duct 23,
An under cover 30 is horizontally installed below the catalytic converter 22. In the region of the exhaust manifold 20 and the exhaust duct 23, the radiator 31 in front of them is also provided.
For example, two upper and lower baffle plates 32 are installed so as to be opened and closed by a motor 33. A thermosensor 34 is attached to the catalytic converter 22.
The exhaust temperature signal of is input to the control unit 35 and processed.
The motor 33 is configured to control the opening degree of the baffle plate 32. The same parts as those of the embodiment shown in FIGS. 1 and 2 are designated by the same reference numerals and the description thereof will be omitted.

Therefore, in this embodiment, the control unit 35 determines the exhaust gas temperature of the thermo sensor 34 during the warm-up operation by starting the engine in the cold state, and closes the air guide plate 32 as shown by the solid line. Therefore, the exhaust manifold 20 and the exhaust duct 23 of the exhaust system are surrounded by the baffle plate 32 and the under cover 30, and a heat insulating layer is formed therebetween. As a result, the exhaust gas temperature of the exhaust manifold 20 and the like are prevented from being released and cooled, and conversely, the exhaust temperature rapidly rises due to highly efficient reflected heat. Therefore, the catalytic converter 22 is activated early, and the exhaust gas during the warm-up operation is satisfactorily purified. At this time, since the temperature and velocity gradient of the exhaust gas from the exhaust valve to the exhaust manifold 20 suddenly change, a shock wave is generated inside the exhaust manifold 20 and a radiating sound is generated from the exhaust duct 23. The sound is blocked by the wind guide plate 32 and the under cover 30, and the sound outside the vehicle is reduced.

After the warm-up, when the exhaust temperature becomes higher than the set value, the baffle plate 32 is opened as shown by the alternate long and short dash line. Therefore, particularly when the vehicle is traveling, the outside air A directly hits the exhaust manifold 20, the exhaust duct 23, and the catalytic converter 22 arranged in the lower front portion of the engine body 1 to be actively cooled,
Exhaust temperature rise is suppressed and high temperature deterioration of the catalyst is avoided. Further, since the rise of the exhaust gas temperature is suppressed, it is not necessary to lower the exhaust gas temperature by cooling the fuel with the rich air-fuel mixture, and therefore, it becomes possible to control the air-fuel ratio of the lean air-fuel mixture even under a high load.

Although the embodiment of the present invention has been described above, the layout of the exhaust manifold, the layout of the catalytic converter, and the like are not limited thereto.

[0023]

As described above, according to the present invention, since the exhaust manifold of the exhaust system of the horizontally opposed four-cylinder engine is configured to collect the branch pipes having the same pipe length, the exhaust gas is exhausted. Exhaust performance and engine performance are improved by eliminating interference. Further, the exhaust pressure between the cylinders is equalized, various exhaust noises are reduced, and the discharge sound quality is improved. Since the distance from the exhaust port to the catalytic converter is shortened, the purification performance of the catalytic converter is improved. The exhaust manifold, exhaust duct, and catalytic converter are located in front of the lower part of the engine body, so the exhaust layout is compact,
The cooling performance is also improved, and the rise in exhaust temperature can be suppressed.

According to another embodiment of the present invention, an undercover and a baffle which can be opened and closed are provided to keep the exhaust manifold and the like warm or cool according to the exhaust temperature. Both exhaust gas purification performance and cooling performance after warm-up can be improved. In particular, the increase in exhaust temperature can be suppressed by the cooling performance after warming up, so lean air-fuel ratio control can be performed, and fuel efficiency and engine output are improved.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of an exhaust system for a horizontally opposed four-cylinder engine according to the present invention.

FIG. 2 is a side view of the embodiment.

FIG. 3 is a side view showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine main body 3,4 Cylinder head 5 Transmission 7a-7d Exhaust port 20 Exhaust manifold 20a-20d Branch pipe 20e Assembly part 22 Catalytic converter 23 Exhaust duct

Claims (4)

[Claims] 1. A first bank and a third cylinder are arranged in a right bank of an engine body, a second cylinder and a fourth cylinder are arranged in a left bank, and an exhaust port is provided below a cylinder head of both banks.
In a horizontally-opposed 4-cylinder engine that is mounted vertically mounted in the longitudinal direction of the vehicle by connecting a transmission to the rear part of this engine body, an exhaust manifold is installed in front of the lower part of the engine body, and the pipe length is equal. A catalyst that is connected to the exhaust ports of the left and right banks with substantially four branch pipes and is disposed substantially horizontally. The catalyst is disposed in the lower part of one of the left and right of the engine body through the exhaust duct from the collection part of the exhaust manifold. An exhaust system for a horizontally opposed four-cylinder engine characterized by being connected to a converter. 2. The exhaust manifold is provided with a collecting portion in front of a lower portion of a substantial center of an engine body, and four branch pipes are bent from the collecting portion so that pipe lengths are equal to each other, and exhaust gases of the left and right banks are exhausted. The exhaust system for a horizontally opposed four-cylinder engine according to claim 1, wherein the exhaust system is connected to each of the ports. 3. The horizontal facing according to claim 1, wherein a recess is formed in a part of an oil pan connected to a lower portion of a center of the engine body so as not to interfere with a branch pipe of an exhaust manifold. Exhaust device for four-cylinder engine. 4. The engine body, exhaust manifold,
The undercover is installed under the exhaust duct and the catalytic converter, and a wind guide plate is provided in front of the exhaust manifold and the exhaust duct so as to open and close according to the exhaust temperature. Exhaust device for horizontally opposed 4-cylinder engine.