JPH04194319A - Exhaust device for supercharged engine - Google Patents

Abstract

PURPOSE:To reliably absorb the thermal deformation of pipe passage due to a temperature difference to suppress the thermal distortion of an exhaust mergence pipe to a small value, by providing a space portion between a pipe passage of the exhaust pipe through which an exhaust gas from a main turbo- charger flows and a pipe passage thereof through which an exhaust gas from a sub turbo-charger flows. CONSTITUTION:A bent pipe 51a is intended for causing a flowing therethrough of an exhaust gas G1 from a main turbo-charger. A bent pipe 51b is intended for causing a flowing therethrough of an exhaust gas G2 from a sub turbo- charger. A space portion 68 is provided between the bent pipes 51a and 51b of an exhaust mergence section 51. The space portion 68 is provided extending over the entire length of the bent pipe 51b. Namely, the bent pipes 51a, 51f and the bent pipe 51b are completely separately provided by the space portion 68 excepting their flange portions. The space portion 68 absorbs thermal deformation of each pipe 51a, 51b, 51f and concurrently functions as a heat insulation means. Accordingly, an excessive thermal stress does not act on the bent pipe 51b due to the thermal deformation of the bent pipe 51a, suppressing the thermal distortion to a small value.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides supercharging with only the main turbocharger in a low intake air amount range, and operates both the main and auxiliary turbochargers in a high intake air amount range. This invention relates to the structure of an exhaust manifold for a supercharged engine, a so-called two-stage twin turbo engine.

[Conventional technology]

Two turbochargers, a main and a sub-turbocharger, are arranged in parallel to the engine body, so that only the main turbocharger is operated in the low intake air volume range, forming a single turbocharger, and both turbochargers are operated in the high intake air volume range. I made it to
A supercharged engine employing a so-called two-stage turbo system is known.

The configuration of this type of supercharged engine is shown in FIG. 9, for example. A main turbocharger (T/C-1) 92 and a sub-turbocharger (T/C-2) 93 are provided in parallel to the engine main body 91. The intake and exhaust systems connected to the auxiliary turbocharger 93 are provided with an intake switching valve 94 and an exhaust switching valve 95, respectively, and an intake bypass passage 97 that bypasses the compressor of the auxiliary turbocharger 93 is provided with an intake bypass valve 96. It is provided. In a low intake air amount range, both the intake switching valve 94 and the exhaust switching valve 95 are fully closed, so that only the main turbocharger 92 is supercharged, and in a high intake air amount range, both switching valves 94 and 95 are fully opened. and intake bypass valve 96
By closing the auxiliary turbocharger 93, the supercharging operation is also performed, and two turbochargers can be operated.

When transitioning from a low intake air amount region to a high intake air amount region, the exhaust bypass valve 98 is controlled to be slightly opened while the intake switching valve 95 and the exhaust switching valve 94 are closed, and the intake bypass valve 96 is further closed. By doing so, it is possible to increase the run-up rotation speed of the sub-turbocharger 93 and to perform turbocharger switching more smoothly (with less shock at the time of switching).

FIG. 10 shows an example of an exhaust manifold pipe for merging exhaust gases from the main and auxiliary turbochargers 92 and 93. The exhaust manifold pipe 80 includes a pipe line 80a into which exhaust gas G1 from the main turbocharger 92 flows, and a pipe line 80a into which exhaust gas G1 from the sub-turbocharger 93 flows. The exhaust gas G flowing through the pipe 80b into which it flows and the exhaust bypass valve 98
, has a conduit 80C into which it flows. Each pipe 80a
, 80b, and 80c are formed in series.

[FF1 Problem to be Solved by the Invention] However, in the case of the exhaust manifold pipe 80 as shown in FIG. 10, since the pipe line 80a and the pipe line 80b are continuous, a problem with thermal deformation occurs. In other words, when a single turbocharger is used, exhaust gas flows only to the turbine side of the main turbocharger, so the exhaust gas flows through the pipe 80a.
The temperature difference between the pipe 80b and the pipe 80b through which exhaust gas does not flow becomes large, and the difference in the amount of expansion of each pipe leads to large thermal deformation and distortion.

As a prior art related to the exhaust passage structure, JP-A-2-1
In the device of the 0th publication of which the 25926 publication is known,
In order to prevent the turbine elbow from being deformed due to the temperature difference between the main turbocharger side and the auxiliary turbocharger side, the exhaust inlet section is curved. However, in this case, since the partition wall separating the exhaust passages on the main turbocharger side and the sub-turbocharger side is shared, it is insufficient to prevent deformation due to temperature difference. Therefore, excessive thermal strain occurs, and there is a risk of deformation and breakage due to this.

The present invention focuses on the above-mentioned problem, and even if there is a significant temperature difference between the pipe through which exhaust gas from the main turbocharger flows and the pipe through which exhaust gas flows from the sub-turbocharger, the present invention sufficiently prevents thermal deformation. An object of the present invention is to provide an exhaust system for a supercharged engine having an exhaust manifold that can absorb the exhaust gas.

[Means to solve the problem]

The exhaust system for a supercharged engine according to the present invention in accordance with this purpose includes a main turbocharger and a sub-turbocharger arranged in the engine body, and only the main turbocharger is operated for supercharging in a low intake air amount region. In an exhaust system for a supercharged engine, in which both the main and auxiliary turbochargers are operated for supercharging in a high intake air amount region, and the exhaust gas from the turbocharger is collected in an exhaust collecting pipe, the exhaust gas is It consists of a collecting pipe in which a gap is provided between a pipe through which exhaust gas from the main turbocharger flows and a pipe through which exhaust gas from the sub-turbocharger flows.

[Effect]

In the exhaust system of a supercharged engine configured in this way, the exhaust switching valve is closed when a single turbocharger is used, in which only the main turbocharger operates, so the pipe through which exhaust gas from the main turbocharger flows is closed. Exhaust gas flows only through the duct, and does not flow through the duct that carries exhaust gas from the auxiliary turbocharger. As a result, the temperature of the main turbocharger line is exceeded by the exhaust gas, and significant temperatures occur in both lines. Here, a gap is provided between the pipe through which exhaust gas from the main turbocharger flows and the pipe through which exhaust gas from the sub-turbocharger flows, so thermal deformation is absorbed by this void. .

〔Example〕

Below is the exhaust gas of the supercharged engine according to the present invention! aN
A preferred embodiment will be described with reference to the drawings.

Figures 1 to 8 show an engine with a filter feeder according to an embodiment of the present invention, in which two turbochargers are arranged in parallel to the engine body, and the intake and exhaust switching valves are opened and closed. The present invention is applied to a supercharged engine of a so-called two-stage twin-turbo system in which the number of operating turbochargers can be changed.

First, the entire system will be explained with reference to FIG. In the figure, 1 indicates a 6-cylinder engine main body, and for the engine main body, there are a main turbocharger 7 that is always active and a sub-turbocharger that operates in a high intake air amount region and stops in a low intake air amount region. 8 are arranged in parallel. 7a and 8a are turbines of each turbocharger;
7b and 8b indicate compressors.

Air is sucked into the compressor 7b, 8b side of each turbocharger 7.8 from the intake passage 15 via the air cleaner 23 and air flow meter 24, and after being pressurized, the air is passed through the intake passage 14, the intercooler 6, and the surge tank 2. Supercharged air is sent to the engine 1. In the exhaust manifold 3, each collection part is communicated with each other by a communication pipe 3a, and exhaust gas is sent from each collection part to the turbine 7a of each turbocharger 7.8.

Send to 8a and glue. The exhaust passages from each turbine 7a, 8a are gathered together by an exhaust manifold pipe 51, and the exhaust gas GI,
G x is exhausted through the front vibe 2° as an exhaust pipe. As shown in FIG. 7, the exhaust gas is equipped with a valve body 63 and an exhaust switching valve 17 provided in the exhaust passage from the auxiliary turbocharger 8 side in the valve body 63 on the upstream side of the exhaust gas confluence part. A switching valve assembly 65 is provided. The exhaust switching valve 17 is connected to the actuator 1
It is opened and closed by 6.

By closing both the exhaust switching valve 17 and the intake switching valve 18 provided on the intake passage side, the supercharging operation of the sub-turbocharger 8 is stopped, and only the main turbocharger 7 is operated. By opening the intake/exhaust switching valve 18.17,
Both turbochargers 7.8 are activated. Switching between one turbocharger and two turbochargers is performed depending on the amount of intake air, with both turbochargers operating in a high intake air amount region and one turbocharger operating in a low intake air amount region. .

In this embodiment, an intake bypass passage 13 is provided for returning pressurized air to the upstream side of the turbocharger so that the pressure on the outlet side of the compressor of the auxiliary turbocharger 8 does not rise too much when the intake switching valve 18 is closed. An intake bypass valve 33 is provided in the intake bypass passage 13 .

Also, before switching from one turbocharger to two turbochargers, some of the exhaust gas is transferred to the sub-turbocharger 8.
An exhaust bypass passage 40 is provided in order to increase the run-up rotation speed of the auxiliary turbocharger 8 by flowing the exhaust gas to the side, and an exhaust bypass passage 41 is provided in the exhaust bypass passage 40. 11, 10, and 42 indicate actuators for opening and closing the intake switching valve 18, the intake bypass valve 33, and the exhaust bypass valve 41, respectively, 31 is a waste gate valve, 9 is an actuator for the waste gate valve, and 4 is a throttle valve. , 30 indicate intake pipe pressure sensors, respectively. A front pipe 20 forming an exhaust passage is connected to an exhaust muffler via an exhaust gas catalyst 21.

In FIG. 7, 1 is an engine body, 71 is a cylinder head, 72 is a cylinder block, 73 is an oil pan, 74 is an oil return pipe, and 75 is an engine mount. Turbine housing 7c of main turbocharger 7, sub-turbocharger 8,
The exhaust gas inflow side of 8c is connected to the exhaust manifold 3.

The exhaust gas outflow side of the turbine housing 7C of the main turbocharger 7 has a curved pipe 51 as a conduit for the exhaust manifold pipe 51.
connected to a. The exhaust gas outflow side of the turbine housing 8c of the auxiliary turbocharger 8 is connected to a zero-bent pipe 51 that is connected to a bent pipe 51b as a pipe of the exhaust gas collecting section 51.
a, 51b are connected to a valve body 63 of an exhaust switching valve assembly 65, and the valve body 63 is connected to an exhaust merging pipe 66. The exhaust confluence pipe 66 is connected to the front vibe 2o as an exhaust pipe.

The bent pipe 51a receives exhaust gas G from the main turbocharger 7,
A single curved pipe 51a has a connecting flange 51c formed at the upstream end of the curved pipe 51a.
The zero-bent pipe 51b, which has a connecting flange 51d formed at its downstream end, is connected to the exhaust gas G! from the sub-turbocharger 8. A flange portion 5Le for connection is formed at the upstream end of the zero-bent pipe 51b for flowing the water, and a flange portion 51d is located at the downstream end of the bent pipe 51b. In other words, the flange 51d has a function of connecting the downstream ends of the curved pipes 51a and 51b to the valve body 63.

In this embodiment, the exhaust bypass passage 40 provided for the run-up of the sub-turbocharger 8 is configured by a bent pipe 51f formed in the exhaust collecting section 51.
The above-mentioned flange 51e is located at the upstream end of the curved pipe 51f.The downstream end of the zero-bent pipe 51f is connected to the middle of the curved pipe 51a, and the exhaust bypass passage 40 in the curved pipe 51a
The exhaust gas Gt that has passed through flows into the curved pipe 51a. Therefore, the flange ste is
It has a function of connecting the upstream ends of the curved pipes 51b and 51f to the turbine housing 8C of the sub-turbocharger 8.

Between the bent pipe 51a and the bent pipe 51b of the exhaust collecting part 51,
A cavity 68 is provided. The void part 6th is bent pipe 51
It is provided over the entire length of b. In other words, the curved pipe 5
1a, 51f and the bent pipe 51b are completely partitioned by a cavity 68 except for the flange portion. The cavity 68 is
It absorbs the thermal deformation of each tube 51a, 51b, 51r and also functions as a heat insulating means.

Next, the operation of the above-mentioned supercharged engine control device will be explained.

As described above, in the high intake air amount region of this supercharged engine, both the intake switching valve 18 and the exhaust switching valve 17 are opened, and the intake bypass valve 33 is closed. As a result, the two turbochargers 7.8 operate for supercharging, a sufficient amount of supercharging air is obtained, and the output is improved. At this time, the boost pressure is +
The waste gate valve 31 is controlled by a duty-controlled waste gate valve 31 so as not to exceed soo fill.

In a low speed range and under high load, both the intake switching valve 18 and the exhaust switching valve 17 are closed, and the intake bypass valve 33 is opened. As a result, only one turbocharger 7 is driven. The reason why one turbocharger is used in the low intake air amount range is that the supercharging characteristics of one turbocharger are superior to the supercharging characteristics of two turbochargers in the low intake air amount range. By using one turbocharger, boost pressure and torque rise quickly, and response is quick.

In a low speed range and under light load, the intake switching valve 18 is opened while the exhaust switching valve 17 is closed. As a result, the intake passages for two turbochargers are opened while one turbocharger remains driven, and an increase in intake resistance caused by one turbocharger can be eliminated. Therefore, the boost pressure rise characteristics and response at the initial stage of acceleration from a low load can be further improved.

When transitioning from a low intake air amount region to a high intake air amount region, that is, when switching from one turbocharger operation to two turbocharger operation, the exhaust bypass valve is closed while the intake switching valve 18 and the exhaust switching valve 17 are closed. 41 is controlled by the DEAT control, and by closing the intake bypass valve 33, the approach rotation speed of the auxiliary turbocharger 8 is increased, making it possible to switch the turbocharger more smoothly (reducing the shock at the time of switching). Become.

In the low intake air amount region, the exhaust gas switching valve 17 is closed, so that exhaust gas flows only into the turbine 7a of the main turbocharger 7. The exhaust gas flowing out from the turbine 7a flows into the curved pipe 51a of the exhaust manifold pipe 51, and the curved pipe 51a is heated by receiving heat from the exhaust gas. In this state, since exhaust gas is not flowing through the curved pipe 51b of the exhaust manifold pipe 51, the temperature difference between the curved pipe 51a and the curved pipe 51b becomes large, causing thermal deformation of the curved pipe 51a. However, since a gap 68 is provided between the curved pipe 51a and the curved pipe 51b,
Thermal deformation of the curved pipe 51a is sufficiently absorbed by the cavity 68. Therefore, due to the thermal deformation of the curved pipe 51a, the curved pipe 51
Excessive thermal stress is no longer applied to b, and thermal strain is suppressed to a small level.

Furthermore, since the void 68 has a heat insulating function, the amount of heat conducted from the curved pipe 51a to the curved pipe 51b is suppressed by the void 68 when one turbocharger is used. Therefore, it is possible to substantially reduce the heat capacity of the exhaust collector pipe 51 when one turbocharger is used, and the warm-up performance of the exhaust gas catalyst 21 is improved accordingly.

〔Effect of the invention〕

As explained above, when using the exhaust system for a supercharged engine according to the present invention, the exhaust manifold has a pipe through which exhaust gas from the main turbocharger flows and a pipe through which exhaust gas from the sub-turbocharger flows. Since a gap is provided between the main turbocharger and the sub-turbocharger, in the region where only the main turbocharger operates, the pipe where the exhaust gas from the main turbocharger flows and the pipe where the exhaust gas from the sub-turbocharger flows are separated. Even if there is a significant difference in temperature, thermal deformation of the pipe line due to the temperature difference can be reliably absorbed.

Thereby, thermal distortion of the exhaust manifold can be reduced.

In addition, by providing a gap between each pipe, in areas where only the main turbocharger operates, the pipe in which the exhaust gas from the main turbocharger flows is changed from the pipe in which the exhaust gas from the sub-turbocharger flows. The amount of heat conducted to the road can be suppressed.

Therefore, the heat capacity of the exhaust gas collecting section in this supercharging region can be substantially reduced, and the warm-up performance of the exhaust gas catalyst can be improved accordingly.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an exhaust manifold pipe in an exhaust system for a supercharged engine according to the present invention, FIG. 2 is a plan view of FIG. 1, FIG. 3 is a side view of FIG. 3, and FIG. 4 is a side view of FIG. 3 is a sectional view taken along line N-IV, FIG. 5 is a sectional view taken along line V-V in FIG. 3, and FIG. 6 is a sectional view taken along line V--V in FIG.
7 is a front view of the main part of the exhaust system in which the exhaust manifold pipe of FIG. 1 is provided; FIG. 8 is a system diagram of the supercharged engine according to the present invention; FIG. 9 is a schematic system diagram of a conventional supercharged engine, No. 10
The figure is a plan view showing an example of a conventional exhaust manifold pipe. l...Engine 7...Main turbocharger 7a...Main turbocharger turbine 8...
...Sub-turbocharger 8b...Sub-turbocharger turbine 13.
... Intake bypass passage 17 ... Exhaust switching valve 18 ... Intake switching valve 21 ... Exhaust gas catalyst 51 ... Exhaust manifold pipe 51a. ... Pipe 51b through which exhaust gas from the main turbocharger flows ... Pipe 68 through which exhaust gas from the sub-turbocharger flows ... Gap Patent Applicant: Toyota Motor Corporation Co., Ltd. Figure 4

Claims (1)

[Claims] 1. A main turbocharger and a sub-turbocharger are installed in the engine body, and only the main turbocharger is operated for supercharging in a low intake air amount region, and the main turbocharger is operated in a high intake air amount region.
In an exhaust system for a supercharged engine in which both sub-turbochargers are supercharged and exhaust gases from both turbochargers are collected in an exhaust manifold, the exhaust gas from the main turbocharger in the exhaust manifold is An exhaust system for a supercharged engine, characterized in that a gap is provided between a pipe through which gas flows and a pipe through which exhaust gas from a sub-turbocharger flows.