JP4298972B2 - Engine exhaust system and control method of engine exhaust system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine exhaust system in which a supercharger is arranged on the exhaust side, and a control method therefor.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an engine exhaust system for an automobile, for example, what is described in JP-A-10-47053 is known. According to this engine exhaust system, a supercharger is provided on the exhaust side of the engine, and a turbine of the supercharger is rotated by exhaust gas to supercharge engine intake.
[0003]
This supercharger is called a so-called twin scroll type supercharger, and is independently connected to a separate combustion chamber of the engine, and is connected to a first exhaust passage and a second exhaust passage that are independent from each other. . The supercharger has a first scroll chamber corresponding to the first exhaust passage and a second scroll chamber corresponding to the second exhaust passage independently, and the exhaust gas flowing through each exhaust passage is independent. The turbine is rotated.
[0004]
Here, the combustion chambers whose ignition timings are adjacent to each other are connected to different exhaust passages so that the pressure pulsation (pressure density wave) of the exhaust gas in each exhaust passage increases. For example, in a 4-cylinder engine, when the ignition timing is in the order of the first cylinder, the third cylinder, the second cylinder, and the fourth cylinder, the first cylinder and the second cylinder are connected to the first exhaust passage, and the third cylinder The cylinder and the fourth cylinder are connected to the second exhaust passage.
[0005]
As a result, exhaust gas having a large pressure pulsation flows into each scroll chamber of the supercharger. Therefore, in the engine exhaust system including the twin scroll supercharger, the turbine can be efficiently rotated using the peak of pressure pulsation even when the engine is running at a low speed.
[0006]
[Problems to be solved by the invention]
However, in the engine exhaust system, the turbine of the twin scroll turbocharger is greatly affected by the pressure pulsation of the exhaust gas even at high speed. As a result, at the time of peak pressure pulsation, the exhaust gas flowing into the scroll chamber exceeds the capacity of the turbine, causing a problem that the supercharging efficiency of the engine is reduced. Here, it is conceivable to use a large-capacity turbine corresponding to the peak of pressure pulsation, but this deteriorates the responsiveness at the time of low rotation.
[0007]
The present invention has been made in view of the above circumstances, and an object of the present invention is to use pressure pulsation of exhaust gas in an exhaust passage at a high speed while using supercharging by a twin scroll supercharger. It is an object to provide an engine exhaust system and a control method therefor that can reduce the amount of fuel, improve the supercharging efficiency, and make the engine in a good combustion state.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, there is provided an engine exhaust system having an engine having a plurality of combustion chambers and a supercharger disposed on the exhaust side of the engine, The exhaust gas of one combustion chamber circulates and has a first exhaust passage and a second exhaust passage that are independent of each other. The supercharger includes a first scroll chamber corresponding to the first exhaust passage, A twin scroll supercharger that independently includes a second scroll chamber corresponding to two exhaust passages, and the exhaust gas flowing through each of the exhaust passages independently rotates one turbine. A connection passage communicating the exhaust passage and the second exhaust passage; an openable / closable communication control valve provided in the connection passage; and opening the communication control valve when the engine is rotating at high speed. Sometimes and a communication valve control means for closing the communication control valve And a downstream side of the connection portion of the connection passage in the first exhaust passage, a catalyst disposed downstream of the supercharger, an activity determination means for determining whether the catalyst is in an active state or an inactive state, and And an openable / closable exhaust control valve provided in the engine, and when the activity determination means determines that the catalyst is in an inactive state, the exhaust control valve is closed and the communication control valve is opened, so that the catalyst is in an active state. An exhaust valve control means for opening the exhaust control valve when it is determined that It is characterized by that.
[0009]
According to the first aspect of the present invention, since the communication control valve is opened during high engine rotation, the first exhaust passage and the second exhaust passage are in communication with each other, and the pressure of the exhaust gas in the first exhaust passage. The pulsation and the pressure pulsation of the exhaust gas in the second exhaust passage are made uniform. Thereby, the amplitude of the pressure pulsation is reduced, and the influence of the pressure pulsation in the turbine is reduced.
Further, since the communication control valve is closed when the engine is running at a low speed, the first exhaust passage and the second exhaust passage become independent, the amplitude of the pressure pulsation in each exhaust passage increases, and the pressure pulsation in the turbine increases. The impact will increase.
[0010]
Therefore, at the time of high engine rotation, the effect of exhaust gas pressure pulsation is reduced, and excessive exhaust gas exceeding the capacity of the turbocharger turbine does not flow into each scroll chamber, improving engine supercharging efficiency. The combustion state of the engine can be improved. Further, at the time of low engine rotation, the pressure pulsation can be used to efficiently rotate the turbine, and the supercharging efficiency of the engine can be improved.
In other words, the pressure pulsation is reduced at high engine speeds to eliminate the drawbacks of the twin scroll turbocharger. At low engine speeds, the pressure pulsation is used to provide a unique action for the twin scroll turbocharger. An effect can be obtained.
[0012]
Claims 1 In the described invention , Touch When the medium is in an inactive state, the exhaust control valve is closed and the communication control valve is opened, so that the exhaust gas discharged to the first exhaust passage is prevented from flowing to the supercharger side by the exhaust control valve. Then, it circulates from the second exhaust passage to the supercharger side through the connection passage.
In addition, when the catalyst is in an active state, the exhaust control valve is opened, so that the exhaust gas also flows downstream of the first exhaust passage.
[0013]
Therefore, when the catalyst is in an inactive state, the surface area of the exhaust passage through which the exhaust gas flows is reduced to suppress the temperature drop of the exhaust gas, and the catalyst is activated early by the relatively high temperature exhaust gas. In addition, when the catalyst is in an active state, the turbocharger turbine can be rotated through both the first and second exhaust passages so that the turbocharger can exhibit its desired performance.
[0014]
Claim 2 In the described invention, the claims 1 The engine exhaust system according to claim 1, wherein the engine is a multi-cylinder engine having a variable valve timing mechanism, and the intake valve in the engine is determined when the activation determination unit determines that the catalyst is in an inactive state. And valve timing control means for reducing the overlap amount of each opening timing of the exhaust valve.
[0015]
Claim 2 According to the described invention, the claims 1 In addition to the operation described above, when the catalyst is in an inactive state, the amount of overlap between the intake valve and the exhaust valve is reduced, and the catalyst becomes less susceptible to the pressure fluctuation in the exhaust pipe. As a result, an increase in residual gas due to an increase in exhaust pressure during overlap caused by opening the connection passage can be suppressed, and a normal combustion state can be maintained.
[0016]
Claim 3 In the described invention, claim 1 is provided. Or claim 2 In the engine exhaust system described above, an air amount detection unit that detects an intake air amount is provided in the intake passage of the engine, and the activity determination means is the intake air detected by the air amount detection unit. Based on the amount of air, it is determined whether the catalyst is in an inactive state or not.
[0017]
Claim 3 According to the described invention, claim 1 Or 2 In addition to the operation, the active state of the catalyst can be determined using an air amount detection unit provided in an intake passage or the like for engine control. Further, the state of the catalyst can be accurately grasped by detecting the amount of air taken into the engine.
[0018]
Therefore, it is possible to accurately determine the state of the catalyst using the existing air amount detection unit without providing a sensor or the like for detecting the activity / inactivity of the catalyst, which is extremely advantageous in practical use.
[0019]
According to a fourth aspect of the present invention, there is provided an engine having a plurality of combustion chambers and at least two exhaust passages through which exhaust gases from separate combustion chambers of the engine flow, and the exhaust gases flowing through the exhaust passages are independent. A turbocharger, and a connecting passage that communicates at least two of the exhaust passages, and an openable / closable communication control valve provided in the connecting passage; A catalyst disposed on the downstream side of the supercharger, and an exhaust control valve that is openable and closable downstream of a connection portion of the connection passage in at least one of the exhaust passages. An engine exhaust system control method comprising: opening the communication control valve when the engine rotates at a high speed, and closing the communication control valve when the engine is at a low speed At the same time, it is determined whether the catalyst is in an active state or an inactive state, and when it is determined that the catalyst is in an inactive state, the exhaust control valve is closed and the communication control valve is opened so that the catalyst is activated. If it is determined that the engine is in a state, the exhaust control valve is opened. It is characterized by that.
[0020]
Claim 4 According to the described invention, the communication control valve is opened during high engine rotation, so that the exhaust passages connected to the connection passages are in communication with each other, and the exhaust gas pressure pulsations in the exhaust passages are made uniform. The Thereby, the amplitude of the pressure pulsation is reduced, and the influence of the pressure pulsation in the turbine is reduced.
Further, since the communication control valve is closed when the engine is running at a low speed, each exhaust passage is in an independent state, the amplitude of the pressure pulsation in each exhaust passage is increased, and the influence of the pressure pulsation in the turbine is increased.
[0021]
Therefore, at the time of high engine rotation, the effect of exhaust gas pressure pulsation is reduced, and excessive exhaust gas exceeding the turbocharger turbine capacity does not flow into the scroll chamber of the turbocharger. The combustion state of the engine can be improved. Further, at the time of low engine rotation, the pressure pulsation can be used to efficiently rotate the turbine, and the supercharging efficiency of the engine can be improved.
[0023]
Claim 4 According to the described invention , Touch When the medium is in an inactive state, the exhaust control valve is closed and the communication control valve is opened, so the exhaust gas discharged to the exhaust passage provided with the exhaust control valve is sent to the supercharger side by the exhaust control valve. Is prevented from flowing, and flows from the other exhaust passage to the supercharger through the connection passage.
Further, when the catalyst is in the active state, the exhaust control valve is opened, so that the exhaust gas also flows downstream of the exhaust passage provided with the exhaust control valve.
[0024]
Therefore, when the catalyst is in an inactive state, the surface area of the exhaust passage through which the exhaust gas flows is reduced to suppress the temperature drop of the exhaust gas, and the catalyst is activated early by the relatively high temperature exhaust gas. In addition, when the catalyst is in an active state, the turbocharger turbine can be rotated through the entire exhaust passage so that the turbocharger can exhibit its desired performance.
[0025]
Claim 5 In the described invention, the claims 4 In the engine exhaust system control method described above, when the engine is a multi-cylinder engine having a variable valve timing mechanism and it is determined that the catalyst is in an inactive state, the intake valve and the exhaust valve of the engine The overlap amount at each opening timing is reduced.
[0026]
Claim 5 According to the described invention, the claims 4 In addition to the above action, when the catalyst is in an inactive state, the amount of overlap between the intake valve and the exhaust valve is reduced, and it becomes difficult to be affected by pressure fluctuations in the exhaust pipe. As a result, an increase in residual gas due to an increase in exhaust pressure during overlap caused by opening the connection passage can be suppressed, and a normal combustion state can be maintained.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
1 to 5 show an embodiment of the present invention. FIG. 1 is a schematic configuration diagram of an engine exhaust system, FIG. 2 is a schematic configuration block diagram of the engine exhaust system, and FIG. 3 is an intake valve and an exhaust valve of the engine. FIG. 4 is a flowchart showing the control operation of the communication control valve and the like according to the engine speed, and FIG. 5 is a flowchart showing the control operation of the exhaust control valve and the like according to the active state of the catalyst. is there.
[0028]
As shown in FIG. 1, the engine exhaust system 1 includes a multi-cylinder engine 2 having a plurality of combustion chambers, and a supercharger 3 disposed on the exhaust side of the engine 2.
[0029]
In the present embodiment, the engine 2 is a so-called four-cylinder engine having a first cylinder 4, a second cylinder 5, a third cylinder 6, and a fourth cylinder 7. Further, in the present embodiment, the engine 2 is a horizontally opposed type, the third cylinder 6 is located behind the first cylinder 4, the second cylinder 5 is opposed to the first cylinder 4 and the third cylinder 6. And the 4th cylinder 7 is arranged. The cylinders 4 to 7 as combustion chambers are arranged to be staggered in a side view. The arrangement of the cylinders 4 to 7 is the same as that of conventionally known cylinders, and will not be described in detail here. Further, in FIG. 1, the cylinders 4 to 7 are shown in a horizontal row for explanation.
[0030]
Further, the engine 2 has a variable valve timing mechanism 2a, and is configured to change the opening / closing timings of the intake valves 4a, 5a, 6a, 7a of the respective cylinders 4-7 as shown in FIG. FIG. 3 shows a state in which the timings at which the intake valves 4a, 5a, 6a, and 7a and the exhaust valves 4b, 5b, 6b, and 7b are opened do not overlap with each other by solid lines. Is indicated by a broken line. In other words, the opening timing overlaps by advancing the opening / closing timing of each intake valve 4a, 5a, 6a, 7a. The opening timing of each intake valve 4a, 5a, 6a, 7a is variably controlled according to the driving state of the engine 2 and the like.
[0031]
In the present embodiment, the firing order of the cylinders 4 to 7 is the third cylinder 6, the second cylinder 5, and the fourth cylinder 7 in order from the first cylinder 4. Each cylinder 4-7 is connected to an exhaust passage through which exhaust gas flows. In the present embodiment, the first exhaust passage 8 and the second exhaust passage 9 that are independent from each other are connected to the engine 2. As shown in FIG. 1, the first exhaust passage 8 is connected to the first cylinder 4 and the second cylinder 5, collects the exhaust gas of each cylinder 4, 5 and guides it to the supercharger 3 side. Further, the second exhaust passage 9 is connected to the third cylinder 6 and the fourth cylinder 7 to collect the exhaust gases of the cylinders 6 and 7 and guide them to the supercharger 3 side.
[0032]
Here, as shown in FIG. 1, the first exhaust passage 8 and the second exhaust passage 9 communicate with each other through a connection passage 10. The connection passage 10 is provided with a communication control valve 11 that can be freely opened and closed. That is, when the communication control valve 11 is open, the first exhaust passage 8 and the second exhaust passage 9 are connected, and when the communication control valve 11 is closed, the first exhaust passage 8 and the second exhaust passage 9 are connected. It becomes a state independent of the passage 9.
[0033]
An openable and closable exhaust control valve 13 is provided on the downstream side of the connection portion of the first exhaust passage 8 with the connection passage 10. That is, in the state where the exhaust control valve 13 is closed, the flow of the first exhaust passage 8 to the supercharger 3 side is blocked.
[0034]
As shown in FIG. 1, the supercharger 3 is a so-called twin scroll supercharger, and includes a first scroll chamber 14 corresponding to the first exhaust passage 8 and a second scroll corresponding to the second exhaust passage 9. It has the chamber 15 separately and independently. The exhaust gas flowing through the scroll chambers 14 and 15 rotates one turbine 16 independently to supercharge air into the intake passage 17 of the engine 2. The exhaust gas flowing out from the supercharger 3 flows out from the one downstream exhaust passage 18.
[0035]
Further, as shown in FIG. 1, a catalyst 19 for purifying exhaust gas is disposed in the downstream exhaust passage 18. The catalyst 19 is a conventionally known catalyst that exhibits a purification action in a predetermined temperature range. The exhaust gas purified by the catalyst 19 is released to the outside of the vehicle.
[0036]
Further, as shown in FIG. 2, the engine exhaust system 1 has a control unit 100. The control unit 100 is disposed in the variable valve timing mechanism 2 a of the engine 2, the crank angle sensor 2 b that detects the rotational speed of the engine 2, the airflow sensor 20 provided on the upstream side of the intake passage 17, and the connection passage 10. The communication control valve 11 and the exhaust control valve 13 disposed in the first exhaust passage 8 are connected.
[0037]
The control unit 100 also includes a communication valve control program 101 that opens and closes the communication control valve 11 according to the number of revolutions of the engine 2 and an activity determination program that determines whether the catalyst 19 is in an active state or an inactive state based on the air intake amount. 102, an exhaust valve control program 103 that opens and closes the exhaust control valve 13 and the like according to the state of the catalyst 19, and a valve timing control program 104 that changes the valve timing of the engine 2 according to the state of the catalyst 19 are stored. Yes. In the present embodiment, the control unit 100 constitutes a communication valve control means, an activity determination means, an exhaust valve control means, and a valve timing control means.
[0038]
The communication valve control program 101 is a program that controls to open the communication control valve 11 when the engine 2 is rotating at high speed and to close the communication control valve 11 when the engine 2 is rotating at low speed. In the present embodiment, when the rotational speed of the engine 2 detected by the crank angle sensor 2a of the engine 2 exceeds a preset rotational speed, it is determined that the engine 2 is at a high speed, and this setting is made. When the engine speed is equal to or lower than the engine speed, it is determined that the engine 2 is rotating at a low speed.
[0039]
The activity determination program 102 is a program for determining whether the catalyst 19 is in an inactive state from an active state. In the present embodiment, the state of the catalyst 19 is determined by integrating the air intake amount obtained from the start of the engine acquired by the airflow sensor 20.
[0040]
The exhaust valve control program 103 closes the exhaust control valve 13 and opens the communication control valve 11 when the activation determination program 102 determines that the catalyst 19 is in an inactive state, and determines that the catalyst 19 is in an active state. In this case, the exhaust control valve 13 is opened.
[0041]
The valve timing control program 104, when it is determined by the activation determination program 102 that the catalyst 19 is inactive, the intake valves 4a, 5a, 6a, 7a and the exhaust valves 4b, 5b, 6b, 7b in the engine 2. Is a program for reducing the overlap amount of the release timing compared to the normal state.
[0042]
The operation based on the communication valve control program 101 of the control unit 100 of the engine exhaust system 1 configured as described above will be described with reference to the flowchart shown in FIG.
[0043]
First, the driving state of the vehicle is acquired from each sensor of the vehicle (step S1). At this time, the rotation speed of the engine 2 is acquired by the crank angle sensor 2a. Next, it is determined whether or not the rotational speed of the engine 2 is lower than the set rotational speed, that is, whether the engine 2 is at a low speed or a high speed (step S2). When the engine 2 is running at a low speed, the communication control valve 11 is closed (step S3), and the exhaust control valve 13 is opened (step S4). When the engine 2 is rotating at a high speed, the communication control valve 11 is opened (step S5), and the exhaust control valve 13 is closed (step S6).
[0044]
Thus, when the engine 2 is rotating at high speed, the communication control valve 11 is opened, so that the first exhaust passage 8 and the second exhaust passage 9 are in communication with each other, and the exhaust gas pressure pulsation in the first exhaust passage 8 is established. And the pressure pulsation of the exhaust gas in the second exhaust passage 9 is made uniform. Thereby, the amplitude of the pressure pulsation is reduced, and the influence of the pressure pulsation in the turbine is reduced.
[0045]
Further, since the communication control valve 11 is closed when the engine 2 is rotating at a low speed, the first exhaust passage 8 and the second exhaust passage 9 become independent, and the amplitude of the pressure pulsations in the exhaust passages 8 and 9 is large. Thus, the influence of pressure pulsation in the turbine is increased.
[0046]
Next, operations based on the activity determination program 102, the exhaust valve control program 103, and the valve timing control program 104 in the control unit 100 of the engine exhaust system 1 will be described with reference to the flowchart shown in FIG. FIG. 5 shows the operation when the engine 2 is running at a low speed.
[0047]
First, the driving state of the vehicle is acquired from each sensor of the vehicle (step S11). At this time, the air intake amount is continuously acquired by the airflow sensor 20, and the air intake amount from the start of the engine 2 is integrated by the control unit 100.
[0048]
Next, based on the integration of the air intake amount, the activity determination program 102 determines whether the catalyst 19 is in an active state or an inactive state (step S12). When it is determined that the catalyst 19 is in an active state, that is, activated, the communication control valve 11 is closed (step S13), and the exhaust control valve 13 is opened (step S14). Further, the opening timing of each intake valve 4a, 5a, 6a, 7a and each exhaust valve 4b, 5b, 6b, 7b of the engine 2 is controlled in a normal state (step S15).
[0049]
If it is determined that the catalyst 19 is in an inactive state, the communication control valve 11 is opened (step S16), and the exhaust control valve 13 is closed (step S17). Further, the opening timing of each intake valve 4a, 5a, 6a, 7a and each exhaust valve 4b, 5b, 6b, 7b of the engine 2 is controlled so as to reduce the overlap amount compared to the normal state (step S18). ).
[0050]
Thus, when the catalyst 19 is in an inactive state, the exhaust control valve 13 is closed and the communication control valve 11 is opened, so that the exhaust gas discharged to the first exhaust passage 8 is excessively discharged by the exhaust control valve 13. The distribution to the turbocharger 3 side is blocked, and the second exhaust path 9 flows from the second exhaust path 9 to the supercharger 3 side through the connection path 10. Further, the overlap amount of the opening timing of each intake valve 4a, 5a, 6a, 7a and each exhaust valve 4b, 5b, 6b, 7b is reduced, the amount of heat at the time of combustion of the engine 2 becomes relatively large, and the first exhaust Exhaust gas having a temperature higher than that in the normal state flows through the engine 2 side of the passage 8 and the second exhaust passage 9.
[0051]
Further, when the catalyst 19 is in an active state, the exhaust control valve 13 is opened, so that the exhaust gas also flows downstream of the first exhaust passage 8. At this time, the communication control valve 11 does not necessarily need to be closed. If the engine 2 is rotating at a high speed, the communication control valve 11 may remain open. Further, the overlap amount of the opening timing of each intake valve 4a, 5a, 6a, 7a and each exhaust valve 4b, 5b, 6b, 7b is suitable for the driving state of the engine 2 as usual.
[0052]
As described above, according to the engine exhaust system 1 and the control method thereof of the present embodiment, when the engine 2 is rotating at a high speed, the influence of the exhaust gas pressure pulsation is reduced, and the excess of the turbine capacity of the turbocharger 3 is exceeded. The exhaust gas does not flow into the scroll chambers 14 and 15, the supercharging efficiency of the engine 2 can be improved, and the combustion state of the engine 2 can be improved. Further, when the engine 2 is rotating at a low speed, the turbine can be efficiently rotated using pressure pulsation, and the supercharging efficiency of the engine 2 can be improved.
In other words, the pressure pulsation is reduced when the engine 2 is rotating at high speed to eliminate the disadvantages of the twin scroll turbocharger 3, and the pressure pulsation is used when the engine 2 is rotating at a low speed. A specific effect can be obtained.
[0053]
Further, according to the engine exhaust system 1 and its control method of the present embodiment, when the catalyst 19 is in an inactive state, the surface area of the exhaust passages 8 and 9 through which the exhaust gas flows is reduced to reduce the temperature of the exhaust gas. And the catalyst 19 is activated early by the relatively high temperature exhaust gas. In particular, in the present embodiment, the engine 2 is a horizontally opposed type, and the exhaust passages 8 and 9 are relatively long in view of the layout of the engine 2. It is extremely effective for conversion. Further, when the catalyst 19 is in an active state, the turbine of the supercharger 3 can be rotated through both the first and second exhaust passages 8 and 9 so that the supercharger 3 can exhibit the desired performance. .
[0054]
Further, according to the engine exhaust system 1 and its control method of the present embodiment, the active state of the catalyst 19 can be determined using the airflow sensor 20 provided in the intake passage 17 for engine control. Further, the state of the catalyst 19 can be accurately grasped by detecting the amount of air taken into the engine 2. Therefore, it is possible to accurately determine the state of the catalyst 19 using the existing airflow sensor 20 without newly providing a sensor or the like for detecting whether the catalyst 19 is active or inactive, which is extremely advantageous in practical use.
[0055]
In the above-described embodiment, the engine 2 is of the horizontally opposed type. However, as long as it has a plurality of combustion chambers, it may be of another type such as a series type or a V type. Of course. Further, the engine may be a rotary engine having a plurality of rotors. In the case of a rotary engine, the first exhaust passage and the second exhaust passage are separately connected to the combustion chamber of the housing of each rotor.
[0056]
In the above-described embodiment, the engine 2 is shown as having four cylinders, but it is needless to say that the engine may be of other cylinders such as six cylinders and eight cylinders.
[0057]
Moreover, in the said embodiment, although the thing using the twin scroll type supercharger was shown as the supercharger 3, if it has at least two exhaust passages independently, the number of exhaust passages is two. For example, a supercharger in which three exhaust passages are independently connected to separate combustion chambers of the engine may be used.
[0058]
In the above-described embodiment, the engine 2 has the variable valve timing mechanism 2a. However, even in an engine that does not have the variable valve timing mechanism, the engine 2 can be operated at a high speed by controlling the communication control valve and the exhaust control valve. The supercharging efficiency at the time can be improved, and the catalyst can be activated early. A flowchart in this case is shown in FIG. In the flowchart of FIG. 6, steps S15 and S18 in the flowchart of FIG. 5 are omitted.
[0059]
Moreover, in the said embodiment, although the variable valve timing mechanism 2a which can change the opening timing of each intake valve 4a, 5a, 6a, 7a was shown, you may change the opening timing of each exhaust valve. In addition, the opening timing of both valves may be changed.
[0060]
In the above embodiment, the air flow sensor 20 detects the air intake amount. However, the air amount detection unit may of course be other detection means such as a pressure sensor.
[0061]
Further, in the above-described embodiment, the determination of the active state of the catalyst 19 is performed using the integration of the intake air amount. However, for example, it may be determined by a water temperature sensor of the engine 2, Further, a temperature sensor that directly detects the temperature of the catalyst 19 may be provided, and the determination may be made by this.
[0062]
In the above embodiment, the exhaust control valve 13 is provided. However, even if the exhaust control valve 13 is omitted, the engine 2 may be provided as long as the connection passage 10 and the communication control valve 11 are provided. Of course, it is possible to improve the supercharging efficiency at the time of high rotation, and it is of course possible to appropriately change the specific detailed structure and the like.
[0063]
【The invention's effect】
As described above in detail, according to the present invention, the influence of exhaust gas pressure pulsation is reduced at the time of high engine rotation, so that excessive exhaust gas exceeding the capacity of the turbocharger turbine flows into each scroll chamber. Without improving the supercharging efficiency of the engine, the combustion state of the engine can be improved. Further, at the time of low engine rotation, the pressure pulsation can be used to efficiently rotate the turbine, and the supercharging efficiency of the engine can be improved.
In other words, the pressure pulsation is reduced at high engine speeds to eliminate the drawbacks of the twin scroll turbocharger. At low engine speeds, the pressure pulsation is used to provide a unique action for the twin scroll turbocharger. An effect can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an engine exhaust system according to an embodiment of the present invention.
FIG. 2 is a schematic block diagram of an engine exhaust system.
FIG. 3 is a timing chart showing an open state of an intake valve and an exhaust valve of the engine.
FIG. 4 is a flowchart showing a control operation of a communication control valve or the like according to the engine speed.
FIG. 5 is a flowchart showing a control operation of an exhaust control valve or the like in accordance with an active state of a catalyst.
FIG. 6 is a flowchart showing another embodiment of the present invention and showing a control operation of an exhaust control valve or the like according to an active state of a catalyst.
[Explanation of symbols]
1 Engine exhaust system
2 Engine
3 turbochargers
4 Cylinder 1
4a Intake valve
4b Exhaust valve
5 Cylinder 2
5a Intake valve
5b Exhaust valve
6 3rd cylinder
6a Intake valve
6b Exhaust valve
7 4th cylinder
7a Intake valve
7b Exhaust valve
8 First exhaust passage
9 Second exhaust passage
10 Connection passage
11 Communication control valve
13 Exhaust control valve
14 First scroll chamber
15 Second scroll chamber
16 Turbine
17 Air intake passage
18 Downstream exhaust passage
19 Catalyst
100 Control unit
101 Communication valve control program
102 Activity determination program
103 Exhaust valve control program
104 Valve timing control program

Claims (5)

An engine exhaust system having an engine having a plurality of combustion chambers and a supercharger disposed on the exhaust side of the engine,
The exhaust gas of at least one combustion chamber in the engine circulates, and has a first exhaust passage and a second exhaust passage independent of each other
The supercharger has a first scroll chamber corresponding to the first exhaust passage and a second scroll chamber corresponding to the second exhaust passage independently, and the exhaust gas flowing through each exhaust passage is A twin scroll supercharger that independently rotates one turbine,
A connection passage communicating the first exhaust passage and the second exhaust passage;
An open / close communication control valve provided in the connection passage;
A communication valve control means for opening the communication control valve when the engine is rotating at high speed and closing the communication control valve when the engine is rotating at a low speed;
A catalyst disposed downstream of the supercharger;
Activity determination means for determining whether the catalyst is in an active state or an inactive state;
An openable and closable exhaust control valve provided on the downstream side of the connection portion of the connection passage in the first exhaust passage;
The exhaust control valve is closed and the communication control valve is opened when the activation determination means determines that the catalyst is in an inactive state, and the exhaust control valve is determined when the catalyst is determined to be in an active state. And an exhaust valve control means for opening the engine. The engine is a multi-cylinder engine having a variable valve timing mechanism,
Characterized by comprising valve timing control means for reducing an overlap amount of each opening timing of the intake valve and the exhaust valve in the engine when the activation determination means determines that the catalyst is in an inactive state. The engine exhaust system according to claim 1. The intake passage of the engine is provided with an air amount detection unit for detecting the intake air amount,
3. The engine exhaust system according to claim 1, wherein the activity determination unit determines whether the catalyst is in an inactive state based on an intake air amount detected by the air amount detection unit. . An engine having a plurality of combustion chambers and at least two exhaust passages through which exhaust gases from separate combustion chambers of the engine circulate; A connection passage configured to rotate the turbine and communicating at least two of the exhaust passages; an openable / closable communication control valve provided in the connection passage; and a catalyst disposed downstream of the supercharger; A control method for an engine exhaust system comprising an exhaust control valve that is openable and closable downstream of a connection portion of the connection passage in at least one of the exhaust passages ,
Opening the communication control valve at the time of high engine rotation, closing the communication control valve at the time of low engine rotation ;
It is determined whether the catalyst is in an active state or an inactive state. When it is determined that the catalyst is in an inactive state, the exhaust control valve is closed and the communication control valve is opened, and the catalyst is in an active state. An engine exhaust system control method comprising: opening the exhaust control valve when it is determined that the exhaust control valve is present . The engine is a multi-cylinder engine having a variable valve timing mechanism, and when it is determined that the catalyst is in an inactive state, the overlap amount of each opening timing of the intake valve and the exhaust valve in the engine is decreased. The method of controlling an engine exhaust system according to claim 4 .

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