JP6414412B2 - Exhaust system for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust system for an internal combustion engine including a supercharger (turbocharger).

  Generally, an exhaust passage of an internal combustion engine equipped with a turbocharger (hereinafter also referred to as an “engine”) has a wastegate passage (exhaust bypass passage) equipped with a wastegate valve for adjusting a supercharging pressure of the turbocharger. ) Is provided. By opening and closing the wastegate passage by this wastegate valve, for example, an excessive increase in the supercharging pressure is suppressed, the stability of the supercharging pressure is improved, and damage to the engine and the turbocharger itself is suppressed ( For example, see Patent Document 1).

JP 2004-44509 A

  Incidentally, an exhaust gas purification catalyst for purifying exhaust gas is provided in the exhaust passage of the engine. In an engine equipped with a turbocharger, the exhaust purification catalyst is generally provided downstream of the turbocharger (turbine) in the exhaust passage. In recent years, in order to improve the exhaust gas purification performance, an exhaust gas purification catalyst has been arranged close to the turbocharger.

  The amount of work of the turbocharger in such an engine exhaust system is such that the first region upstream of the turbocharger in the exhaust passage, and the second region upstream of the exhaust purification catalyst downstream of the turbocharger of the exhaust passage. Determined by the pressure ratio (differential pressure) with the area. Therefore, the greater the pressure in the first region, the greater the work of the turbocharger. That is, if the pressure difference between the first region and the second region of the exhaust passage increases, the engine output is easily improved.

  However, as described above, in an exhaust system of an engine including an exhaust purification catalyst on the downstream side of the turbocharger, the pressure in the second region of the exhaust passage may increase due to the exhaust resistance of the exhaust purification catalyst. In particular, when the exhaust purification catalyst is disposed close to the turbocharger, the pressure in the second region tends to increase. As the pressure rises, the pressure ratio between the first region and the second region of the exhaust passage is reduced regardless of the pressure in the first region, and the work of the turbocharger may be reduced. That is, there is a possibility that the output of the engine cannot be sufficiently increased.

  The present invention has been made in view of such circumstances, and the exhaust of the internal combustion engine that can appropriately increase the output of the internal combustion engine by adjusting the pressure ratio between the first region and the second region of the exhaust passage. The purpose is to provide a system.

A first aspect of the present invention that solves the above-described problems includes a supercharger that supercharges intake air of an internal combustion engine, an exhaust purification catalyst that is provided in an exhaust passage on the downstream side of the supercharger, and the exhaust passage. A first region upstream of the supercharger is connected to a second region downstream of the supercharger in the exhaust passage and upstream of the exhaust purification catalyst, and can be opened and closed by a first opening / closing valve. And a downstream end of the exhaust passage is connected to a third region downstream of the exhaust purification catalyst of the exhaust passage, and can be opened and closed by a second opening / closing valve. A catalyst bypass passage for adjusting a pressure ratio between the first region and the second region of the exhaust passage, and an upstream end portion of the catalyst bypass passage is connected to the second region of the exhaust passage. An exhaust system for an internal combustion engine Valve control means for controlling the operation of the first on-off valve and the second on-off valve according to the pressure state of the exhaust passage, wherein the valve control means includes the first on-off valve and the second on-off valve When the pressure ratio between the first region and the second region of the exhaust passage is smaller than a predetermined threshold value with the on-off valve closed, the second on-off valve is first opened. It is in the exhaust system of the internal combustion engine.

According to a second aspect of the present invention, there is provided an exhaust system for an internal combustion engine according to the first aspect, further comprising a downstream side exhaust purification catalyst provided downstream of the exhaust purification catalyst in the exhaust passage, and the valve control means. When the pressure ratio between the first region and the second region of the exhaust passage becomes smaller than a predetermined threshold value with the first on-off valve and the second on-off valve closed. However, the exhaust system of the internal combustion engine is characterized in that the closed state of the second on-off valve is maintained until the downstream side exhaust purification catalyst exceeds a predetermined temperature.

  In the present invention, the supercharging characteristic of the turbocharger can be improved by adjusting the pressure ratio between the first region and the second region of the exhaust passage. Therefore, the output of the internal combustion engine can be appropriately increased according to the traveling state of the vehicle, for example.

1 is a schematic view of an engine including an exhaust system according to Embodiment 1 of the present invention. It is a block diagram which shows schematic structure of the exhaust system which concerns on Embodiment 1 of this invention. It is the schematic which shows the principal part of the exhaust system which concerns on Embodiment 1 of this invention. It is the schematic which shows the principal part of the exhaust system which concerns on Embodiment 2 of this invention. It is the schematic which shows the principal part of the exhaust system which concerns on Embodiment 3 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
First, the overall configuration of the engine 10 including the exhaust system according to Embodiment 1 of the present invention will be described. As shown in FIG. 1, the engine body 11 constituting the engine 10 includes a cylinder head 12 and a cylinder block 13, and a piston 14 is accommodated in the cylinder block 13. The piston 14 is connected to the crankshaft 16 via a connecting rod 15. The piston 14, the cylinder head 12, and the cylinder block 13 form a combustion chamber 17.

  An intake port 18 is formed in the cylinder head 12, and an intake pipe (intake passage) 20 including an intake manifold 19 is connected to the intake port 18. The intake manifold 19 is provided with an intake pressure sensor (MAP sensor) 21 that detects intake pressure and an intake temperature sensor 22 that detects the temperature of intake air. An intake valve 23 is provided in the intake port 18, and the intake port 18 is opened and closed by the intake valve 23. Further, an exhaust port 24 is formed in the cylinder head 12, and an exhaust pipe (exhaust passage) 26 including an exhaust manifold 25 is connected to the exhaust port 24. An exhaust valve 27 is provided in the exhaust port 24. Like the intake port 18, the exhaust port 24 is opened and closed by the exhaust valve 27.

  The engine body 11 is provided with, for example, a fuel injection valve 28 that injects fuel into the combustion chamber 17 of each cylinder. Although not shown, the fuel in the fuel tank is supplied to the fuel injection valve 28 by a supply pump or the like. Furthermore, a spark plug 30 is attached to the cylinder head 12 for each cylinder.

  A turbocharger (supercharger) 31 is provided in the middle of the intake pipe 20 and the exhaust pipe 26. The turbocharger 31 includes a turbine 31a and a compressor 31b. The turbine 31a and the compressor 31b are connected by a turbine shaft 31c. When the exhaust gas flows into the turbocharger 31, the turbine 31a is rotated by the flow of the exhaust gas, and the compressor 31b is rotated along with the rotation of the turbine 31a. Air (intake air) pressurized by the rotation of the compressor 31 b is sent to the intake pipe 20 and supplied to each intake port 18.

  For example, an upstream side exhaust purification catalyst (FCC) 32 and a downstream side exhaust purification catalyst (UCC) 33 which are three-way catalysts are interposed in the exhaust pipe 26 on the downstream side of the turbocharger 31. An intercooler 34 is provided on the intake pipe 20 on the downstream side of the compressor 31b, and a throttle valve 35 is provided on the downstream side of the intercooler 34.

  Further, the first region 26a upstream of the turbocharger 31 (turbine 31a) of the exhaust pipe 26 and the second region 26b downstream of the turbocharger 31 of the exhaust pipe 26 and upstream of the upstream exhaust purification catalyst 32. Are connected by a wastegate passage 36. The wastegate passage 36 is provided with a wastegate valve (first on-off valve) 37. The wastegate valve 37 includes, for example, a valve body and an electric actuator (electric motor) that drives the valve body, and the amount of exhaust gas flowing through the wastegate passage 36 can be adjusted by the opening degree of the valve body. Yes. That is, the wastegate valve 37 is configured to control the supercharging pressure of the turbocharger 31 by adjusting the opening degree.

  Further, in the present embodiment, the first region 26 a of the exhaust pipe 26 and the third region 26 c on the downstream side of the upstream exhaust purification catalyst of the exhaust pipe 26 are connected by the catalyst bypass passage 38. A catalyst bypass valve (second on-off valve) 39 is provided in the catalyst bypass passage 38. The catalyst bypass passage 38 is configured to be opened and closed by the catalyst bypass valve 39.

  Then, by appropriately controlling the open / close state of the catalyst bypass valve 39, the pressure ratio between the first region 26a and the second region 26b of the exhaust pipe 26 connected by the catalyst bypass passage 38 is adjusted. Yes. The first region 26 a of the exhaust pipe 26 is provided with a first pressure sensor (first pressure detection means) 40 that detects the pressure (exhaust pressure) of the first region 26 a, and the second region of the exhaust pipe 26. 26b is provided with a second pressure sensor (second pressure detecting means) 41 for detecting the pressure in the second region 26b. Moreover, you may make it estimate the pressure of each area | region from an operating state, without providing the 1st pressure sensor 40 and the 2nd pressure sensor 41. FIG. That is, the first pressure detection means and the second pressure detection means acquire the operating state of the engine, for example, refer to a map or the like that defines the relationship between the engine operating conditions and the pressure of each area. The pressure may be estimated.

  Thus, in the exhaust system for an internal combustion engine according to the present invention, the exhaust pipe 26 is provided with the catalyst bypass passage 38 including the catalyst bypass valve 39 together with the waste gate passage 36 including the waste gate valve 37. The supercharging characteristic of the turbocharger 31 can be improved by adjusting the pressure ratio between the first region 26a and the second region 26b. Therefore, by adopting the exhaust system according to the present invention, the output of the engine 10 can be appropriately increased according to, for example, the traveling state of the vehicle.

  As shown in the block diagram of FIG. 2, the engine 10 includes an electronic control unit (ECU) 50. The ECU 50 includes an input / output device, a storage device that stores a control program, a control map, and the like, and a central processing unit. Devices, timers and counters are provided. In addition to the intake pressure sensor 21, the intake air temperature sensor 22, the first pressure sensor 40, and the second pressure sensor 41, the ECU 50 detects a rotation speed of the engine 10 (a rotation speed detection means). ) Etc., etc., based on information from various sensors, etc., comprehensive control of the engine 10 is performed. For example, the ECU 50 controls the operating states of the above-described waste gate valve 37 and the catalyst bypass valve 39 as appropriate. That is, the ECU 50 also functions as a part of the engine exhaust system.

  Hereinafter, control of the opening / closing operation of the waste gate valve 37 and the catalyst bypass valve 39 in the exhaust system of the internal combustion engine according to the present embodiment will be described.

  The ECU 50 includes valve control means 51 that controls opening and closing operations of the waste gate valve 37 and the catalyst bypass valve 39 in the exhaust system. In the present embodiment, the valve control means 51 appropriately controls the opening degrees of the waste gate valve 37 and the catalyst bypass valve 39 according to the operating state of the engine 10. Specifically, the valve control means 51 controls the open / closed states of the waste gate valve 37 and the catalyst bypass valve 39 according to the detection results of the first pressure sensor 40 and the second pressure sensor 41.

  For example, in the operation state of the engine 10 in which the pressure in the first region 26a is relatively low, both the waste gate valve 37 and the catalyst bypass valve 39 are closed as shown in FIG. In this state, for example, when high-speed and high-load operation is performed, the exhaust gas flow rate increases, and when the first pressure sensor 40 detects that the pressure in the first region 26a exceeds a predetermined threshold value, there is a margin in engine strength. Determine whether or not. For example, if the volumetric efficiency is lower than a predetermined value, it is determined that there is a surplus in engine strength, and the catalyst bypass valve 39 is maintained while the closed state of the waste gate valve 37 is maintained as shown in FIG. Open the valve. Thereby, the pressure of the 1st field 26a can be maintained high to such an extent that it does not exceed a predetermined threshold. That is, the pressure ratio between the first region 26a and the second region 26b can be kept relatively high. Therefore, the supercharging characteristic (work volume) of the turbocharger 31 can be improved as compared with the case where the wastegate valve 37 is opened, the amount of air fed into the engine body 11 is increased, and the performance (output) of the engine 10 is improved. can do.

  On the other hand, for example, when the volumetric efficiency is greater than or equal to a predetermined value, it is determined that there is no margin in engine strength, and the waste gate valve 37 is opened at a predetermined opening as shown in FIG. The workload of the turbocharger 31 is reduced. Further, when the pressure of the first region 26a exceeds a predetermined threshold value with the catalyst bypass valve 39 opened as described above, the waste gate valve 37 is opened and the work amount of the turbocharger 31 is increased. Reduce. Thereby, the excessive raise of a supercharging pressure can be prevented.

(Embodiment 2)
FIG. 4 is a diagram illustrating a main part of the exhaust system of the internal combustion engine according to the second embodiment. In addition, the same code | symbol is attached | subjected to the same member and the overlapping description is abbreviate | omitted.

  As shown in FIG. 4, in the present embodiment, the upstream end portion of the catalyst bypass passage 38 is connected to the second region 26 b of the exhaust pipe 26. That is, the second region 26 b and the third region 26 c of the exhaust pipe 26 are connected by the catalyst bypass passage 38. Other configurations are the same as those of the first embodiment.

  In such a configuration of the present embodiment, the valve control means 51 is in a state in which the wastegate valve 37 and the catalyst bypass valve 39 are closed (FIG. 4A) and the first region 26a of the exhaust pipe 26. When the pressure ratio with the second region 26b becomes smaller than a predetermined threshold, the catalyst bypass valve 39 is opened (FIG. 4B). As a result, as indicated by an arrow in FIG. 4B, a part of the exhaust in the second region 26 b flows into the third region 26 c through the upstream side exhaust purification catalyst 32, and the catalyst bypass passage 38. Into the third region 26c. Accordingly, the pressure in the second region 26b decreases, and the pressure ratio between the first region 26a and the second region 26b increases relatively. As a result, the workload of the turbocharger 31 can be increased.

  However, when the downstream side exhaust purification catalyst 33 is lower than a predetermined temperature at which the engine 10 is activated, such as when the engine 10 is cold-started, the valve control means 51 is connected to the first region 26a of the exhaust pipe 26 and the first region 26a. Even when the pressure ratio with respect to the second region 26b becomes smaller than a predetermined threshold value, it is preferable to maintain the closed state of the catalyst bypass valve 39 until the downstream side exhaust purification catalyst 33 exceeds a predetermined temperature.

Thereby, the performance (output) of the engine 10 can be improved while purifying the exhaust gas .

(Embodiment 3)
FIG. 5 is a diagram illustrating a main part of the exhaust system of the internal combustion engine according to the third embodiment. In addition, the same code | symbol is attached | subjected to the same member and the overlapping description is abbreviate | omitted.

  In the present embodiment, as shown in FIG. 5, the waste gate passage 36 also serves as a part of the catalyst bypass passage 38. Specifically, the upstream end of the catalyst bypass passage 38 is connected to the waste gate passage 36, and a catalyst bypass valve 39 </ b> A composed of a three-way valve is provided at the connection portion between the catalyst bypass passage 38 and the waste gate passage 36. It has been. Other configurations are the same as those of the above-described embodiment.

  In such a configuration of the present embodiment, the first region 26a and the second region 26b, the first region 26a and the third region 26 of the exhaust pipe 26 are controlled by appropriately controlling the open / closed states of the waste gate valve 37 and the catalyst bypass valve 39A. The region 26c, the second region 26b, and the third region 26c can be connected to each other. Therefore, it is possible to improve the performance of the engine 10 as in the above-described embodiment while reducing the size of the engine 10 in the exhaust system. In this embodiment, the flow rate of the waste gate passage 36 is adjusted by the waste gate valve 37, but the waste gate valve 37 is not provided and the flow rate of the waste gate passage 36 is adjusted by the catalyst bypass valve 39A. It can also be configured.

  As mentioned above, although embodiment of this invention was described, of course, this invention is not limited to the structure of these Embodiment 1-3. For example, in the above-described embodiment, only the configuration of the engine is illustrated, but the present invention can of course be applied to, for example, an engine of a hybrid vehicle including an electric motor.

10 Engine (Internal combustion engine)
11 Engine Body 12 Cylinder Head 13 Cylinder Block 14 Piston 15 Connecting Rod 16 Crankshaft 17 Combustion Chamber 18 Intake Port 19 Intake Manifold 20 Intake Pipe 21 Intake Pressure Sensor 22 Intake Temperature Sensor 23 Intake Valve 24 Exhaust Port 25 Exhaust Manifold 26 Exhaust Pipe 26a First 1 region 26b 2nd region 26c 3rd region 27 Exhaust valve 28 Fuel injection valve 30 Spark plug 31 Turbocharger 31a Turbine 31b Compressor 31c Turbine shaft 32 Upstream exhaust purification catalyst 33 Downstream exhaust purification catalyst 34 Intercooler 35 Throttle valve 36 West Gate passage 37 Waste gate valve 38 Catalyst bypass passage 39 Catalyst bypass valve 40 First pressure sensor 41 Second pressure sensor 42 Crank angle sensor 50 ECU

Claims (2)

A supercharger for supercharging the intake air of the internal combustion engine;
An exhaust purification catalyst provided in an exhaust passage downstream of the supercharger;
The first region of the exhaust passage upstream of the supercharger is connected to the second region of the exhaust passage downstream of the supercharger and upstream of the exhaust purification catalyst, and the first region A wastegate passage configured to be opened and closed by an opening and closing valve;
A downstream end is connected to a third region downstream of the exhaust purification catalyst in the exhaust passage, and is configured to be opened and closed by a second opening / closing valve, and the first region of the exhaust passage and the first region A catalyst bypass passage for adjusting a pressure ratio with the second region,
An exhaust system of an internal combustion engine in which an upstream end portion of the catalyst bypass passage is connected to the second region of the exhaust passage,
Valve control means for controlling the operation of the first on-off valve and the second on-off valve according to the pressure state of the exhaust passage;
The valve control means is configured such that a pressure ratio between the first region and the second region of the exhaust passage is lower than a predetermined threshold value in a state where the first on-off valve and the second on-off valve are closed. An exhaust system for an internal combustion engine characterized in that, when it becomes smaller, the second on-off valve is first opened. An exhaust system for an internal combustion engine according to claim 1,
Further comprising a downstream side exhaust purification catalyst provided downstream of the exhaust purification catalyst in the exhaust passage,
The valve control means is configured such that a pressure ratio between the first region and the second region of the exhaust passage is lower than a predetermined threshold value in a state where the first on-off valve and the second on-off valve are closed. An exhaust system for an internal combustion engine, characterized in that the closed state of the second on-off valve is maintained until the downstream side exhaust purification catalyst exceeds a predetermined temperature even when it becomes smaller.

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