JP2586354Y2 - Exhaust system for turbocharged engine - Google Patents

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 turbocharged engine that operates in a sequential turbo type by equipping a vehicle engine with a plurality of turbochargers.
More specifically, it relates to exhaust gas purification measures including a catalytic converter.

[0002]

2. Description of the Related Art In recent years, as a turbocharged engine for a vehicle, a multi-cylinder exhaust system is equipped with a primary and secondary turbocharger in parallel, and the turbocharger is operated in a sequential turbo type. Something to do is suggested.
In this sequential turbo system, the primary turbocharger is configured to always operate, and the secondary turbocharger is provided with an intake control valve, a relief valve, an exhaust control valve, and the like. In the single turbo mode in the low and medium speed range, only the primary turbocharger is operated, and in the twin turbo mode in the high speed range, both the primary turbocharger and the secondary turbocharger are operated.

[0003] Therefore, in such a sequential turbo system, since the exhaust system has two systems, when purifying exhaust gas with a catalyst, it is required to take into consideration that purification is properly performed in each turbo mode. In particular, in the single turbo mode, the temperature of the exhaust gas that has operated the primary turbocharger has a large temperature drop. Therefore, it is necessary to consider quickly activating the catalyst and purifying the catalyst efficiently.

Conventionally, exhaust gas purification of the above-described engine with a sequential turbocharger has been described in, for example,
There is a prior art in JP-A-3-49545. Here, the two exhaust passages downstream of the turbines of the low-load turbocharger and the high-load turbocharger are assembled, and a first catalyst is installed downstream of the gathering portion. Indicates that a second catalyst having a smaller capacity than the first catalyst is installed.

[0005]

However, in the above-mentioned prior art, two catalysts for low load and high load are installed, so that the number of catalysts is increased, and the arrangement space, cost, and catalyst are increased. It is disadvantageous in terms of measures against heat damage. The interior of the engine chamber is very complicated because various accessories, two turbochargers, intake and exhaust passages for the turbochargers, and the like are arranged in addition to the engine body. It is very difficult to provide heat damage countermeasures.

The present invention has been made in view of this point, and aims to simplify exhaust gas purifying means including a catalytic converter in a sequential turbocharged engine with a turbocharger so as to always appropriately purify exhaust gas. And

[0007]

According to the present invention, a primary turbocharger and a secondary turbocharger are arranged in parallel in an intake and exhaust system of an engine body having left and right banks. Then, in an engine with a turbocharger that operates in a sequential turbo type, a primary turbocharger provided downstream of an exhaust pipe of one of the banks and a downstream pipe of an exhaust pipe of one of the other banks are provided. The exhaust pipes from the secondary turbocharger were assembled, a single catalytic converter was installed downstream of the collecting section, and the communication pipe connecting the upstream of the primary turbocharger and the secondary turbocharger was engine-connected. And at least part of the exhaust path from the engine body to the catalytic converter when only the primary turbocharger operates is insulated. It is characterized in that the.

[0008]

According to the above construction, only the primary turbocharger operates in, for example, a low-to-medium-speed region during engine operation. At this time, the exhaust from the engine main body is kept warm by the heat-insulated exhaust passage to form a single turbocharger. Guided to the catalytic converter, the catalyst is activated and the exhaust gas is purified even in this operating state. Also, when the primary turbocharger and the secondary turbocharger operate in the high-speed range, the exhaust gas from both turbochargers quickly flows into a single catalytic converter, and the exhaust gas is similarly purified. .

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. 1 and 2, a case where a horizontally opposed four-cylinder engine is equipped with a sequential turbocharger will be described. In an engine body 1 of a horizontally opposed four-cylinder engine, banks 3 and 4 are horizontally arranged on right and left sides of a crankcase 2, and first and third cylinders are arranged on a right bank 4, and second and third cylinders are arranged on a left bank 3. Four cylinders are arranged, and # 1 → # 3 → # 2 →
Operate in the ignition sequence of # 4. Therefore, the left and right banks 3, 4
The two cylinders are connected to each other in an ignition order. A transmission 5 is connected to a rear portion of the engine main body 1 and mounted vertically in the vehicle longitudinal direction.

The arrangement of the turbocharger and the exhaust system will be described. First, a secondary turbocharger 10 is disposed immediately after the right bank 4 of the engine body 1, and a primary turbocharger 20 is disposed immediately after the left bank 3. The exhaust ports 11 of the first and third cylinders of the right bank 4 communicate with an exhaust pipe 13 having both ends opened through an exhaust manifold 12, and a rear end of the exhaust pipe 13 has an exhaust control valve 15. The turbine of the secondary turbocharger 10 communicates with the turbine.
Also, the exhaust ports 21 of the second and fourth cylinders of the left bank 3
Similarly, the exhaust pipe 23 is communicated with an exhaust pipe 23 having both ends opened via an exhaust manifold 22, and the rear end of the exhaust pipe 23 is directly communicated with the turbine of the primary turbocharger 20.

Each of the left and right exhaust manifolds 12, 22 is formed to be curved toward the turbocharger side, and the exhaust from the left and right banks 3, 4 is supplied to each of the turbochargers 10, 20 with a small passage resistance. It is configured to be introduced into.
A communication pipe 16 is connected between the exhaust pipes 13 and 23 by being routed to the lower front part of the engine body 1. When the exhaust control valve 15 is closed in the single turbo mode, the exhaust of the right bank 4 is also changed to the primary turbo. It can be introduced into the supercharger 20.

The exhaust system downstream of the turbochargers 10, 20 and the exhaust gas purifying means will be described. First, the exhaust pipes 14 and 24 from both the turbochargers 10 and 20 are both extended rearward along the transmission 5, and are continuously provided so as to gather into one exhaust pipe 17 behind the transmission 5. . One catalytic converter 18 is provided in an exhaust pipe 17 downstream of the collecting section, and exhaust gas is introduced and purified in any turbo mode. Further, in order to promote the activation of the catalyst in the single turbo mode in the low-to-medium speed region, the region in which the exhaust gas flows in the turbo mode, that is, from the exhaust pipe 13 on the secondary side to the communication pipe 16 and the exhaust pipe 23 on the primary side, is used. Part or all of the passage leading to the catalytic converter 18 has a heat insulating structure.

Referring to FIG. 3, the heat insulation structure will be described. For example, the entire circumference of the exhaust pipe 24 is covered with a cover 30.
A heat insulating material 31 such as glass wool is filled between the two.

Next, the operation of this embodiment will be described. First, in a low-medium speed range during engine operation, a single turbo mode is set and the exhaust control valve 15 is closed. Therefore, the secondary turbocharger 10 arranged in the right bank 4 in the engine main body 1 becomes inoperative when the exhaust gas is cut by the exhaust control valve 15. Therefore, the exhaust gas discharged from the exhaust port 11 of the right bank 4 is guided to the communication pipe 16 side, merges with the exhaust gas discharged from the exhaust port 21 of the left bank 3 and is introduced into the primary turbocharger 20. I do. Thus, under the condition of low exhaust energy, only the primary turbocharger 20 operates efficiently with the exhaust of the left and right banks 3 and 4 to perform a supercharging action, and the output in this operating range is increased.

At this time, the exhaust from the left and right banks 3, 4 is:
After operating the primary turbocharger 20, all is guided to the catalytic converter 18 by the exhaust pipe 24. Here, since the region through which these exhausts pass has an adiabatic structure, even if the temperature of the exhausts slightly decreases due to the operation of the primary turbocharger 20, the temperature of the exhausts is kept at a relatively high temperature by the heat insulating material 31 so that the catalyst can be heated. The current flows into the converter 18. Therefore, the catalytic converter 18 is activated early even in this operation state, whereby exhaust gas passing through the catalyst is sufficiently purified.

Next, under conditions of high exhaust gas energy in the high-speed range, control is performed so as to enter the twin turbo mode and open the exhaust control valve 15. For this reason, the exhaust of the right bank 4 of the engine body 1 is separately introduced into the secondary turbocharger 10 through the exhaust pipe 13, and the exhaust of the left bank 3 is introduced into the primary turbocharger 20 through the exhaust pipe 23. As a result, the turbochargers 10 and 20 operate efficiently independently of each other, so that the overall supercharging pressure of the intake system is increased, resulting in higher output characteristics.

In this case, a large amount of exhaust gas from both turbochargers 10 and 20 flows into the catalytic converter 18 through exhaust pipes 14 and 24, respectively. At this time, the catalytic converter 18 has already been activated and the exhaust pipe 1 on the secondary side has been activated.
4 is not kept warm, but because it is short, it flows into the catalytic converter 18 in a high temperature state, and the exhaust gases of both the turbochargers 10, 20 are sufficiently purified together.

As shown in FIG. 4 (a), the heat insulating structure of the exhaust system is such that another exhaust pipe 32 is double covered around the exhaust pipe 24, and a heat insulating layer 33 of air or the like is provided between the two. May be provided.
In addition, as shown in FIG.
A heat insulating material 31 and an air heat insulating layer 33 may be provided between them.

Although the embodiment of the present invention has been described above, the present invention can be similarly applied to a horizontally opposed engine.

[0020]

[Effects of the Invention] As described above, according to the present invention,
In the case of a sequential turbocharged engine, when only the primary turbocharger operates in the low to medium speed range,
Since the path through which the exhaust gas flows is constituted by an adiabatic structure, the exhaust gas temperature is kept warm, and the exhaust gas can be sufficiently purified even by a catalytic converter arranged away from the engine body. Since only one catalytic converter is provided at the rear of the transmission, it is advantageous in terms of arrangement space and cost. In addition, since it is outside the engine chamber, installation becomes easy, and there is no fear of heat damage to peripheral accessories. Since the catalytic converter is located behind and behind the turbochargers, the exhaust flow is smooth, the engine back pressure is reduced and the output is improved, and the noise of the converter is also reduced. The heat insulating structure of the exhaust path can sufficiently maintain the exhaust temperature by the heat insulating material and the heat insulating layer.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of an exhaust device of an engine with a turbocharger according to the present invention.

FIG. 2 is a side view of the embodiment.

FIG. 3 is a sectional view showing a sectional structure of an exhaust path.

FIG. 4 is a sectional view showing another embodiment of the sectional structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine main body 10 Secondary turbocharger 20 Primary turbocharger 11 and 21 Exhaust port 12,22 Exhaust manifold 13,14,17,23,24 Exhaust pipe 16 Communication pipe 18 Catalytic converter 31 Thermal insulation

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-115735 (JP, A) JP-A-3-222810 (JP, A) JP-A 4-19642 (JP, U) JP-A 52-19752 129058 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01N 3/24 F02B 37/00

Claims (3)

(57) [Scope of request for utility model registration] An engine with a turbocharger that operates in a sequential turbo-type by arranging a primary turbocharger and a secondary turbocharger in parallel in an intake and exhaust system of an engine body having left and right banks. And a primary turbocharger provided downstream of the exhaust pipe of one of the banks and a downstream of the exhaust pipe of the other of the banks.
The exhaust pipes from the secondary turbocharger provided in the central turbocharger are assembled, a single catalytic converter is installed downstream of the collecting section, and the upstream and the secondary turbocharger of the primary turbocharger are installed.
Bypass the communication pipe connecting the upstream of the turbocharger to the front of the engine
Only the primary turbocharger with placing Te exhaust system of a turbocharged engine, characterized in that the insulating structure is at least a portion of the exhaust path from the engine body to the catalytic converter when operating. 2. The turbocharger according to claim 1, wherein the catalytic converters are arranged at the rear of the transmission by collecting exhaust pipes from both turbochargers behind the transmission. Engine exhaust system with 3. The exhaust device for a turbocharged engine according to claim 1, wherein the heat insulating structure is configured by providing one or both of a heat insulating material and a heat insulating layer around an exhaust pipe.