JP5262863B2 - Method and apparatus for controlling exhaust system of multi-cylinder engine - Google Patents

Description

  The present invention relates to a control method and apparatus for an exhaust system of a multi-cylinder engine.

  In an engine equipped with an exhaust turbocharger, exhaust gases from a plurality of cylinders are gathered in a collecting part via an exhaust manifold, and the exhaust turbocharger is disposed downstream of the collecting part. . In order to operate the exhaust turbocharger efficiently, the exhaust gas immediately after being discharged from the exhaust port, that is, blowdown gas, is supplied to the exhaust turbocharger without reducing the force as much as possible. Is preferable.

In Patent Document 1, an exhaust turbo-type supercharger is disposed downstream of a collecting portion where independent branch passages of the exhaust manifold are gathered. There has been proposed a nozzle valve that is deflected toward the exhaust gas so that exhaust gas is supplied to the exhaust turbocharger as vigorously as possible. In the racing engine, in order to maintain the exhaust turbocharger as high as possible, for example, fuel is injected into the exhaust passage during deceleration, and combustion is performed in the exhaust passage. Has been.
JP 2007-231791 A

  By the way, the exhaust passage on the upstream side of the exhaust turbocharger is branched into a plurality of independent branch passages connected to different cylinders, but the exhaust gas discharged to a certain independent branch passage becomes another independent branch passage. As a result, the momentum of the exhaust gas supplied to the exhaust turbocharger is reduced, making it difficult to operate the exhaust turbocharger efficiently. In the thing of patent document 1, although it has the effect | action which concentrates the exhaust gas supplied to a gathering part so that it may go to an exhaust turbo supercharger, the exhaust gas from a certain independent branch passage goes to another independent branch passage. It will be difficult to prevent it from flowing. In addition, fuel injection in the exhaust passage is a special engine for racing, and is difficult to use for general engines such as passenger cars and commercial vehicles. In order to perform injection, a structure will also become complicated.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to control an exhaust system of a multi-cylinder engine that can efficiently drive an exhaust turbocharger by a simple method. And providing an apparatus thereof.

In order to achieve the object, the following solution is adopted in the method of the present invention. That is, as described in claim 1 in the claims,
Three or more independent branch passages connected to different exhaust ports and independent of each other;
A collecting portion in which the downstream sides of each of the independent branch passages are gathered together;
An exhaust turbocharger disposed downstream of the collecting section;
A variable throttle valve for forming a throttle part by changing the opening area of each independent branch passage on the upstream side of the collecting part;
Between the overlap period in which the valve opening period of the intake / exhaust valve overlaps in the intake stroke and the cylinder in which the valve opening period of the exhaust valve overlaps in the exhaust stroke when the variable throttle valve is greater than the predetermined opening Communication between the independent branch passages, while the communication between the independent branch passages is blocked when the variable throttle valve is less than a predetermined opening,
A control method for an exhaust system of a multi-cylinder engine equipped with
A first step of detecting a value relating to oxygen concentration in the exhaust passage;
A second step of closing the communication passage by closing the variable throttle valve when a value relating to the oxygen concentration in the exhaust passage detected in the first step is less than a predetermined value in a predetermined operating region of the engine; ,
In the predetermined operating region, when the value related to the oxygen concentration in the exhaust passage detected in the first step is equal to or greater than the predetermined value, the variable throttle valve is set to be equal to or greater than the predetermined opening, A third step of performing post-combustion by mixing exhaust gas and scavenging gas;
It is supposed to be equipped with.

  According to the above solution, the exhaust ejector effect (suction effect) can be obtained by the throttle portion formed by closing the variable throttle valve. That is, the exhaust gas discharged to a certain independent branch passage has its flow velocity increased by passing through the throttle portion, and flows vigorously toward the exhaust turbocharger side. When the exhaust gas passes through the throttle portion, the suction effect of sucking in the other independent branch passage is exhibited, and the exhaust gas from one independent branch passage is exhausted without being expanded to the other independent branch passage. It will be supplied directly to the turbocharger. Particularly, the suction effect is enhanced by vigorous exhaust gas, that is, blowdown gas immediately after the exhaust port is opened. Also, due to the suction effect, the exhaust gas discharged from a certain cylinder improves the scavenging of the other cylinders and increases the charging efficiency of the other cylinders (improvement of charging efficiency by 10 to 20%). . Furthermore, when dynamic pressure supercharging utilizing exhaust pulsation is obtained, exhaust gas flowing through one independent branch passage is prevented from flowing (expanding) to another independent branch passage, so the exhaust passage volume is reduced. As a result, the effect of dynamic pressure supercharging can be enhanced (the instantaneous flow rate due to the strong blowdown gas can be effectively supplied to the exhaust turbocharger). In summary, the engine torque, particularly the engine torque at low speeds, can be greatly improved.

  In addition to the above, when the value related to the oxygen concentration in the exhaust passage is greater than or equal to a predetermined value, that is, when after-combustion can be expected in the exhaust passage by mixing the exhaust gas and the scavenging gas, the variable throttle valve is moved beyond the predetermined opening degree. As for the opening degree of the exhaust gas, after-burning is performed by mixing unburned components in the exhaust gas from one cylinder and scavenging gas (oxygen in the cylinder) from another cylinder, and the exhaust energy is obtained by the combustion energy of the after-burning The supercharger can be operated more efficiently (a rapid increase in the rotational speed can be obtained). Of course, since the post-combustion is performed by mixing the exhaust gas and the scavenging gas, the structure becomes very simple as compared with the case where fuel is separately injected into the exhaust passage.

A preferred mode based on the above solution is as described in claim 2 and the following claims. That is,
A fourth step of detecting a value related to the temperature of the exhaust gas;
A fifth step of setting the predetermined value to a smaller value as the value related to the exhaust gas temperature detected in the fourth step is higher;
In addition,
(Corresponding to claim 2). In this case, post-combustion with a lower oxygen concentration becomes possible as the exhaust gas temperature becomes higher, so that the exhaust combustion using post-combustion is performed by performing post-combustion with a relatively low oxygen concentration as the exhaust temperature becomes higher. Opportunities for driving the turbocharger can be expanded.

  In the third step, the variable throttle valve is set to a minimum opening required for opening the communication path (corresponding to claim 3). In this case, a sufficient suction effect can be obtained while performing post-combustion, which is more preferable for efficiently operating the exhaust turbocharger.

  The predetermined operation region is set to a low rotation region equal to or lower than the engine speed when the waste gate valve in the exhaust turbocharger is opened (corresponding to claim 4). In this case, it is possible to efficiently drive the exhaust turbocharger using post-combustion in the low rotation region before the wastegate valve is opened. In the high rotation region where the wastegate valve is opened, the exhaust turbocharger is sufficiently driven, so that driving assistance control using post-combustion is no longer necessary.

A sixth step of detecting a value related to the intake pressure;
In the third step, the variable throttle valve is set to be equal to or greater than the predetermined opening degree on condition that the value related to the intake pressure detected in the sixth step is equal to or greater than atmospheric pressure. 5 correspondence). In this case, supercharging by the exhaust turbocharger takes effect after the intake pressure rises to atmospheric pressure, so if the intake pressure is less than atmospheric pressure, the suction effect is maintained by closing the communication path. The exhaust turbo turbocharger is efficiently driven by drawing out the maximum amount of exhaust gas, and the exhaust turbo turbocharger is driven by post-combustion from the time when the intake pressure becomes atmospheric pressure. A rapid increase in the rotational speed of the feeder can be obtained.

In order to achieve the above object, the following solution is adopted in the device of the present invention. That is, as described in claim 6 in the claims,
Three or more independent branch passages connected to different exhaust ports and independent of each other;
A collecting portion in which the downstream sides of each of the independent branch passages are gathered together;
An exhaust turbocharger disposed downstream of the collecting section;
A variable throttle valve for forming a throttle part by changing the opening area of each independent branch passage on the upstream side of the collecting part;
Between the overlap period in which the valve opening period of the intake / exhaust valve overlaps in the intake stroke and the cylinder in which the valve opening period of the exhaust valve overlaps in the exhaust stroke when the variable throttle valve is greater than the predetermined opening Communication between the independent branch passages, while the communication between the independent branch passages is blocked when the variable throttle valve is less than a predetermined opening,
A control device for an exhaust system of a multi-cylinder engine equipped with
Oxygen concentration detecting means for detecting a value related to the oxygen concentration in the exhaust passage;
Control means for receiving an output from the oxygen concentration detection means and controlling the opening and closing of the variable throttle valve;
With
The control means closes the communication passage by closing the variable throttle valve when the value relating to the oxygen concentration detected by the oxygen concentration detection means is less than a predetermined value in a predetermined operating region of the engine, When the value related to the oxygen concentration in the exhaust passage detected by the oxygen concentration detecting means is equal to or greater than the predetermined value, the variable throttle valve is set to the predetermined opening or more to mix the exhaust gas and the scavenging gas through the communication passage. Is set to perform after-combustion,
It is like that. According to the said solution technique, the apparatus which performs the control method of Claim 1 is provided.

  According to the present invention, the exhaust turbo-supercharger can be efficiently operated by a simple method of using post-combustion by mixing exhaust gas and scavenging gas in addition to the suction effect by exhaust gas. .

  FIG. 1 is a schematic configuration diagram of an engine supercharging device according to a first embodiment of the present invention. 2 is a partial side sectional view of FIG. 1 and 2, the engine 1 is an in-line four-cylinder spark expansion type four-cycle engine. In the cylinder block 2, first to fourth cylinders 3a, 3b, 3c, 3d (referred to collectively as cylinders 3) are arranged on a straight line. The configuration of each cylinder 3 is common, and as shown in FIG. 2, an intake port 6 for sucking intake Wi and an exhaust port 8 for discharging exhaust We are provided above the combustion chamber 4. An intake valve 7 for opening and closing the intake port 6 and an exhaust valve 9 for opening and closing the exhaust port 8 are provided. Further, a spark plug 5 for generating a spark is provided at the top of the combustion chamber 4. In addition, an unillustrated fuel supply means (such as a fuel injection valve) is provided at an appropriate position.

  First to fourth exhaust passages 16a, 16b, 16c, and 16d are connected to the exhaust port 8 of each cylinder 3. As shown in FIG. 1, the second exhaust passage 16b and the third exhaust passage 16c are gathered on the downstream side to form an auxiliary collective exhaust passage 16bc. The first to fourth exhaust passages 16a to 16d and the auxiliary collective exhaust passage 16bc constitute an exhaust manifold 16 as a whole.

  That is, the exhaust manifold 16 has four independent exhaust passages (first to fourth cylinders 3a, 3b, 3c, 3d) on the upstream side, and three independent exhaust passages (first and fourth exhausts) on the downstream side. The passages 16a and 16d and the auxiliary collective exhaust passage 16bc) are provided. In the following description, unless otherwise specified, the independent exhaust passage refers to three downstream independent exhaust passages.

  A housing 31 is connected to the downstream side of the exhaust manifold 16. A variable throttle valve 30 is provided on the inner upstream side of the housing 31 (near the connection portion with the exhaust manifold 16). Further, the housing 31 forms a collective portion 31 c where the three independent exhaust passages gather on the downstream side of the variable throttle valve 30.

  The variable throttle valve 30 is a valve that changes the cross-sectional area of each of the three independent exhaust passages 16a, 16bc, and 16d while maintaining the independent state thereof, and includes a flap 35 as a valve body and an actuator that drives the flap 35 38 etc. The detailed structure will be described later with reference to FIG.

  As shown in FIG. 1, the housing 51 of the exhaust turbocharger 50, specifically the turbine nozzle thereof, is connected to the downstream side of the housing 31 (collecting portion 31 c). The exhaust turbo-type supercharger 50 is a well-known supercharger, in which a turbine 54 provided in an exhaust passage 60 and a compressor 52 provided in an intake passage are connected by a shaft 53. The compressor 52 is driven by rotating 54, and the intake air Wi is compressed to increase the intake pressure. The exhaust passage 60 is provided with a waist passage 61 that bypasses the turbine 54 and a waste gate valve 62 that opens and closes the waist passage 61.

  The exhaust turbocharger 50 of the present embodiment is a large turbo with a strong torque increasing action mainly in a high rotation region. Generally, A / R (ratio between the nozzle area A of the turbine section shown in FIG. 2 and the distance R from the turbine shaft to the nozzle center section) is relatively large, and the turbine diameter D is also relatively large. It is called turbo. The exhaust turbocharger 50 of the present embodiment is set to have a relatively small A / R, although the turbine diameter D is the same as that of a general large turbocharger.

  As shown in FIG. 1, the engine 1 is provided with a variable valve timing mechanism 12 (valve timing changing means). The variable valve timing mechanism 12 according to the present embodiment is a so-called VVT (Variable Valve Timing) in which the valve timing (valve opening / closing valve timing) is moved back and forth in parallel while maintaining the valve opening periods of the intake valve 7 and the exhaust valve 9. It is. As a VVT system, the valve timing may be continuously changed or may be changed in two or more steps.

  The variable valve timing mechanism 12 of the present embodiment includes an intake side intake VVT 12i (intake valve timing changing means) and an exhaust side exhaust VVT 12e (exhaust valve timing changing means), and both the intake valve 7 and the exhaust valve 9 are provided. The valve timing is changed at.

  As shown in FIG. 1, an ECU (Engine Control Unit) 20 that electrically controls the operation of the engine 1 is provided. The ECU 20 is a control unit composed of a microprocessor having a CPU, a memory, a counter timer group, an interface, a bus connecting these units, and the like. The ECU 20 performs drive control of the variable valve timing mechanism 12 and opening / closing control of the wastegate valve 62 in addition to general combustion control such as fuel supply amount, throttle opening, or ignition timing.

  Further, the ECU 20 also functions as a variable throttle valve control means for driving and controlling the variable throttle valve 30. Specifically, the ECU 20 controls the independent exhaust passages 16a and 16bc by the variable throttle valve 30 as will be described later in at least a predetermined low rotation region of the supercharging region (a rotation region lower than the intercept point at which the wastegate valve 62 starts to open). , 16d, the independent exhaust throttle control is performed to reduce the cross-sectional area of each passage more than the maximum area (the variable throttle valve 30 is open).

  Further, the engine 1 of this embodiment, like a general four-cylinder engine, shifts each stroke so that each cylinder 3 sequentially reaches the ignition timing at every crank angle of 180 degrees (hereinafter referred to as 180 degrees CA). Driving. The ignition order (also referred to as the exhaust stroke order) is so-called # 1 → # 3 → # 4 → # 2 (#x indicates the x-th cylinder). That is, for example, when the first cylinder 3a is in the expansion stroke, the second cylinder 3b is in the exhaust stroke, the third cylinder 3c is in the compression stroke, and the fourth cylinder 3d is in the intake stroke.

  In the state shown in FIG. 2, the first cylinder 3a is in the transition period (near the bottom dead center) from the expansion stroke to the exhaust stroke. At this time, the exhaust valve 9 is opened and the exhaust We begins to be discharged from the combustion chamber 4 to the exhaust port 8 (blowdown). At this time, the second cylinder 3b is in a transition period (near top dead center) from the exhaust stroke to the intake stroke. In this transition period, as shown in the figure, a period during which both the intake valve 7 and the exhaust valve 9 are open, that is, a so-called overlap period is provided. More specifically, in an operation state in which the exhaust passage is throttled or after-combustion described later, in each cylinder, the exhaust valve 8 is opened before the bottom dead center of the expansion stroke and closed after the top dead center of the intake stroke. The intake valve 7 is opened before the intake top dead center. The overlap period during which the intake valve 7 and the exhaust valve 9 are opened is set to the minimum in the low engine speed range, and is set to the maximum when the engine speed is higher than the predetermined speed. In the range between the maximum and the maximum engine speed, the engine speed is increased. In order to increase the overlap period, it is only necessary to advance the opening timing of the intake valve 7 and / or delay the closing timing of the exhaust valve 9.

  FIG. 3 is an external perspective view of the exhaust manifold 16 and the housing 31. 4 is a partial perspective view of the exhaust manifold 16 on the downstream side. FIG. 5 is a perspective view of a main part of the variable throttle valve 30. FIG. 6 is a longitudinal sectional view of the exhaust manifold 16 and the housing 31 and shows a state in which the variable throttle valve 30 is in an open state. FIG. 7 is a cross-sectional view similar to FIG. 6, and shows a state where the variable throttle valve 30 is in an open state. FIG. 8 is a cross-sectional view similar to FIG. 6, showing a state where the variable throttle valve 30 is at a minimum opening degree that opens a communication passage 41 described later. 9 is a cross-sectional view taken along line X9-X9 in FIG. Hereinafter, the exhaust manifold 16 and the housing 31, particularly the variable throttle valve 30 in the housing 31 will be described with reference to these drawings.

  As shown in FIG. 3, a flange 16 e is provided at the upstream end of the exhaust manifold 16 and is fixed to a cylinder head (not shown) of the engine 1. Four exhaust passages, that is, first, second, third and fourth exhaust passages 16a, 16b, 16c and 16d are connected to the flange 16e. In the flange 16e portion, each exhaust passage has a circular cross section of φ36 mm.

  The first exhaust passage 16a is connected to the exhaust port 8 of the first cylinder 3a disposed on one end side of the cylinders 3 arranged in a row. The fourth exhaust passage 16d is connected to the exhaust port 8 of the fourth cylinder 3d disposed on the other end side. The second exhaust passage 16b and the third exhaust passage 16c are connected to the exhaust ports 8 of the second cylinder 3b and the third cylinder 3c on the center side, respectively.

  As shown in FIG. 4, the first exhaust passage 16a and the fourth exhaust passage 16d maintain an independent state over their entire lengths, but the second exhaust passage 16b and the third exhaust passage 16c are located immediately before their downstream ends. So as to form an auxiliary collective exhaust passage 16bc. Accordingly, three independent exhaust passages (first exhaust passage 16a, auxiliary collective exhaust passage 16bc, and fourth exhaust passage 16d) are formed near the downstream end of the exhaust manifold 16. These are arranged in parallel at a shallow angle (preferably substantially parallel) so that the auxiliary exhaust passage 16bc is sandwiched between the first exhaust passage 16a and the fourth exhaust passage 16d.

The three independent exhaust passages are opened at a manifold outlet 17 which is a downstream end of the exhaust manifold 16. That is, the first opening 17a of the first exhaust passage 16a, the auxiliary collection opening 17bc of the auxiliary collection exhaust passage 16bc, and the fourth opening 17d of the fourth exhaust passage 16d are arranged in a straight line in this order. The opening areas of the openings 17a, 17bc, and 17d are configured to be substantially equal to each other within a range of about 380 to 616 mm ² . This area corresponds to a circular cross-sectional area of φ22 to φ28 mm. Moreover, this is 37 to 61% in area ratio with respect to the area (equivalent to φ36 mm) of the manifold inlet portion of each exhaust passage 16a, 16b, 16c, and 16d.

  The first exhaust passage 16a and the fourth exhaust passage 16d, and the second exhaust passage 16b and the third exhaust passage 16c are symmetrical to each other. Accordingly, the first exhaust passage length La and the fourth exhaust passage length Ld are substantially equal. In the present embodiment, the first exhaust passage length La is configured to be 200 mm or less.

  Further, the first passage volume Va and the fourth passage volume Vd are substantially equal to each other, and are also substantially equal to the auxiliary collective passage volume Vbc (including a part of the second exhaust passage 16b alone and a part of the third exhaust passage 16c alone). It is configured.

  In order to obtain dynamic pressure supercharging, the exhaust pulsation (the peak value thereof) may be increased, and the most effective means for obtaining a large exhaust pulsation is to reduce the volume of the exhaust manifold 16. For this purpose, the first passage volume Va (≈fourth passage volume Vd≈auxiliary collective passage volume Vbc) shown in FIG. 4 may be reduced. In view of the fact that reducing the cross-sectional area of the passage increases the exhaust resistance, which is undesirable, the first exhaust passage 16a can be made as short as possible to reduce the first passage volume Va. It will be. Specifically, it is desirable that the length La (shown in FIG. 4) of the first exhaust passage 16a be 6 times or less the passage diameter D1 (shown in FIG. 6) at the exhaust manifold inlet of the first exhaust passage 16a. In the present embodiment, since the diameter D1 = φ36 mm and the length La ≦ 200 mm as described above, this condition is satisfied. Therefore, effective dynamic pressure supercharging can be expected.

  Further, as described above, the passage volumes of the first passage volume Va, the fourth passage volume Vd, and the auxiliary collective passage volume Vbc of the exhaust manifold 16 are substantially equal to each other. If there is a large difference between the volumes of these independent exhaust passages, the scavenging promotion effect due to the ejector effect also varies greatly between the cylinders. As a result, there is a difference in the knocking performance depending on the scavenging performance. As a result, the setting corresponding to the cylinder 3 having the lowest knocking performance is forced, and even if the knocking performance is improved in the other cylinders 3, it is wasted. . In addition, the cylinder-to-cylinder variation also occurs in the intake amount increasing effect due to the ejector effect.

  According to the configuration of the present embodiment, the volumes of the first passage volume Va, the fourth passage volume Vd, and the auxiliary collective passage volume Vbc are substantially equal to each other, so there is no such problem, and the advantage of the suction effect (ejector effect) is further improved. Can be obtained effectively.

  As shown in FIG. 6, a housing 31 is connected to the manifold outlet 17 of the exhaust manifold 16. The housing 31 functions as a valve housing that supports and stores the flap 35 of the variable throttle valve 30 on the upstream side, and the exhausts We from the independent exhaust passages 16a, 16bc, and 16d merge on the downstream side. A collective portion 31c is formed.

The variable throttle valve 30 is provided in a direction crossing the flow of the exhaust We, and is provided with a flap shaft 37 supported by the housing 31, a flap 35 as a valve body that can be turned around the flap shaft 37, and the ECU 20. An actuator 38 (such as a motor) that rotates the flap shaft 37 based on a control signal (an opening command of the variable throttle valve 30) and a return spring 39 that biases the flap 35 in the valve opening direction are included. The flap 35 has a fan-shaped surface 36 having a fan-shaped cross section in which the flap shaft 37 is a key of the fan as viewed from the flap shaft 37. The inside of the fan-shaped surface 36 is a hollow to reduce the weight.

  As shown in FIG. 6, the housing 31 is formed with a bulging portion 31b that bulges upward, and the state in which the flap 35 is stored inside the bulging portion 31b (the state shown in FIG. 6) is a variable throttle. The valve 30 is open (fully open). When the variable throttle valve 30 is fully opened, as shown in FIG. 6, the exhaust We introduced into the housing 31 from the manifold outlet 17 is guided to the collecting portion 31 c without being throttled by the flap 35 (variable throttle valve 30).

  On the other hand, the state in which the flap 35 is driven to rotate about the flap shaft 37 and enters the innermost side than the bulging portion 31b (the state shown in FIG. 7) is the closed (fully closed) state of the variable throttle valve 30. The opening degree of the flap 35 is appropriately adjusted between the fully closed state and the fully open state by the actuator 38.

  When the variable throttle valve 30 is fully closed, as shown in FIG. 7, the fan-shaped surface 36 of the flap 35 blocks a part of the flow path, so that the exhaust passage cross-sectional area is reduced. Accordingly, the exhaust We introduced into the housing 31 from the manifold outlet 17 is throttled by the variable throttle valve 30, and then guided to the collecting portion 31c.

  As shown in FIGS. 6 to 8, a partition plate 32 is provided on the upstream side of the housing 31. Two partition plates 32 are erected along (in parallel with) the flow of the exhaust gas We, and are provided in two spaced apart in the direction of the flap shaft 37. One of the two partition plates 32 is erected so as to continue from the wall surface that partitions the first opening 17a and the auxiliary assembly opening 17bc at the mating portion with the manifold outlet 17, and partitions the inside of the housing 31. Is erected so as to continue from the wall surface that partitions the auxiliary assembly opening 17bc and the fourth opening 17d, and partitions the inside of the housing 31. In other words, in the section where the exhaust gas We flows along the partition plate 32, the independent state and the parallel state of the independent exhaust passages 16a, 16bc and 16d are maintained by the two partition plates 32.

  Each rear edge 32a of each partition plate 32 is formed along the fan-shaped surface 36 of the flap 35 when the variable throttle valve 30 is in the closed state. Therefore, when the exhaust gas We is throttled by the flap 35, the exhaust gas We is throttled while the independent state and the parallel state are maintained.

  The collecting portion 31 c is formed on the downstream side of the rear edge 32 a of the partition plate 32.

  A flange 31 a is provided on the downstream end side of the housing 31 and is joined to the housing 51 of the exhaust turbocharger 50. For convenience of the layout of the exhaust turbocharger 50, the housing 31 is bent downward halfway. Depending on the installation position of the exhaust turbocharger 50, such bending is not necessary. Different bending angles may also be used.

  As shown in FIGS. 6 to 9, a flow guide plate 33 is provided in the housing 31 along the bending direction of the housing 31. The flow guide plate 33 guides the exhaust gas We passed through the partition plate 32 so as to smoothly flow along the bend of the housing 31. In particular, as shown in FIG. 7, when the variable throttle valve 30 is closed, the flow guide plate 33 is disposed so that the housing 31 and the flow guide plate 33 surround the exhaust gas We that has passed through the partition plate 32. .

  Further, as shown in FIGS. 6 to 9, a rectifying guide 34 is provided in the collective portion 31 c in the housing 31 so as to stand inward from the bent outer wall surface of the housing 31. The two rectifying guides 34 are provided upright (in parallel) along the flow of the exhaust gas We, and are provided in two spaced apart in the direction of the flap shaft 37. Each rectifying guide 34 is provided on substantially the same plane as each partition plate 32. A gap is provided between the rectifying guide 34 and the flow guide plate 33 on the inner side in the bending direction of the housing 31. As will be described in detail later, the rectifying guide 34 is provided to restrict the swirling flow in the direction intersecting the exhaust direction (the direction not parallel to the paper surface of FIGS. 6 and 7).

  Here, when the exhaust pressure acts on the fan-shaped surface 36 of the flap 35, the exhaust pressure Pe acts perpendicularly to the fan-shaped surface 36, that is, in the radial direction of the flap shaft 37, so that no rotational moment is theoretically generated. (A radial load acts on the flap shaft 37 as a resultant force). Therefore, even if the exhaust pulsation is large, the flap 35 hardly flutters, and it is not necessary to increase the size of the actuator 38 and the return spring 39 to prevent this. As a result, the variable throttle valve 30 can be reduced in size while ensuring reliable operation.

  As shown in FIGS. 6 to 8, a communication passage 41 extending in the longitudinal direction of the flap 35, that is, the axis of the flap shaft 37 is formed on the upper surface side of the upstream end portion of the flow guide plate 33. The communication passage 41 is constituted by a passage-constituting projection 42 protruding from the upper surface of the flow guide plate 33. That is, the projecting portion 42 extends upward at one end and then extends toward the front (upstream side of the exhaust passage). And the communicating path 41 is opened by each independent exhaust passage 16a, 16bc, and 16d in the state which the front opening part was opened, and connects each independent exhaust passage 16a, 16bc, and 16d. In the state shown in FIG. 7 in which the flap 35 is in the valve-closed state, the front opening is closed, and the communication of the independent exhaust passages 16a, 16bc, and 16d via the communication passage 41 is blocked. Further, when the flap 35 is in the valve open state shown in FIG. 6, the front opening is opened, and the three independent exhaust passages 16 a, 16 bc, and 16 d are communicated with each other via the communication passage 41. Become. FIG. 8 shows a case where the flap 35 has a minimum opening degree that opens the communication passage 41. When the flap 35 has this minimum opening degree, the throttle action by the flap 35 and the independent exhaust passages 16a, 16bc, and 16d via the communication passage 41 are shown. Both communication states are secured. Then, as the opening degree of the flap 35 increases from the state of FIG. 8, the throttle action is reduced.

  As shown in FIG. 1, signals from various sensors S <b> 1 to S <b> 4 are input to the ECU 20 for drive control of the flap 35 (the actuator 38 for use). The sensor S1 detects the engine speed. The sensor S2 detects intake pressure (pressure in the intake passage on the downstream side of the compressor 52). The sensor S3 detects the oxygen concentration in the exhaust passage. The sensor S4 detects the temperature of the exhaust gas. The sensors S3 and S4 can be provided, for example, in the exhaust passage downstream of the collecting portion 31c and the turbine 54 and upstream of the exhaust gas purification catalyst (not shown).

  FIG. 10 is a time chart showing an example of control by the ECU 20, where (a) shows changes in the throttle opening, and (b) shows changes in the overlap period during which the intake valve 7 and the exhaust valve 9 are opened. (C) shows the change in opening of the variable throttle valve 30 (flap 35), (d) shows the change in intake pressure, and (e) shows the change in oxygen concentration. FIG. 11 is a flowchart for executing the control of FIG.

  In the control example shown in FIG. 10, a predetermined rotation speed N2, a predetermined oxygen concentration OB, and a predetermined intake pressure P1 are set as control threshold values. The predetermined rotation speed N2 is an engine rotation speed (intercept rotation speed, for example, 2000 rpm) at which the wastegate valve 62 is opened. When the actual engine speed is higher than the predetermined engine speed N2, the flap 35 is fully opened as shown in FIG. 6 in order to efficiently discharge a large amount of exhaust gas.

  In the low engine speed range where the actual engine speed is N2 or less, the oxygen concentration detected by the sensor S3 is greater than or equal to the predetermined oxygen concentration OB, and the intake pressure detected by the sensor S2 is the predetermined intake pressure P1. Assuming that it is possible to perform post-combustion at the time of (atmospheric pressure in the embodiment) or higher and that efficient driving of the exhaust turbocharger utilizing post-combustion can be obtained, the flap 35 is shown in FIG. The minimum opening degree that opens the communication path 41 shown is set to a state in which after combustion is obtained in addition to the suction effect. The predetermined oxygen concentration OB is set lower as the exhaust temperature detected by the sensor S4 is higher.

  Even when the actual engine speed is equal to or lower than the predetermined engine speed N2, the flap 35 is in the fully closed state shown in FIG. 7 when the intake pressure is lower than the predetermined intake pressure P1 or when the oxygen concentration is lower than the predetermined oxygen concentration OB. Therefore, it is controlled exclusively using the suction effect.

  When the flap 35 has the minimum opening degree that opens the communication passage 41, the exhaust valve 9 is opened from the end of the expansion stroke of a certain cylinder, and the exhaust gas is discharged into the independent passage in the exhaust stroke. The cylinder in which the intake valve 7 and the exhaust valve 9 are opened is scavenged by the suction effect of the exhaust gas, and the scavenging gas (oxygen) is discharged to the independent passage. The exhaust gas passes through the communication passage 41. Combustion caused by mixing with the scavenging gas in the scavenging cylinder is post-combustion. In addition, in the case of the embodiment, the cylinders that are related to the after combustion are as follows. That is, as shown in FIG. 17, the first cylinder # 1 (exhaust) and the second cylinder # 2 (intake), the third cylinder # 3 (exhaust), the first cylinder # 1 (intake), and the fourth cylinder # 4 (Exhaust), # 3 cylinder # 3 (intake), # 2 cylinder # 2 (exhaust), and # 4 cylinder # 4 (intake).

  Referring to FIG. 10 in detail, first, at the time t1 when the flap 35 is fully closed in the low rotation region, the throttle opening is greatly opened, and the engine speed is increased accordingly. As the engine speed increases, the overlap period during which the intake valve 7 and the exhaust valve 9 are opened is increased. As the engine speed increases, the rotational speed of the exhaust turbocharger 50 also increases. However, until the time t2, the intake pressure is less than atmospheric pressure, so the rotational speed increases in the natural intake (NA) state exclusively. It becomes.

  The time point t2 is a time point when the intake pressure becomes atmospheric pressure. In the state before the time point t2, the exhaust turbo supercharger is driven exclusively using the suction effect. Even after the time t2, when the oxygen concentration is less than the predetermined oxygen concentration OB, the flap 35 remains fully closed.

  The time point t3 is when the oxygen concentration becomes equal to or higher than the predetermined oxygen concentration OB. At this time, the flap 35 is set to the minimum opening degree that opens the communication passage 41, and the exhaust turbo-type excess due to the post-combustion and the suction effect. The feeder 50 is driven.

  The time point t4 is a time point when the engine speed becomes larger than the predetermined speed N2, and after this time t4, the flap 35 is fully opened (control giving priority to efficient exhaust of a large amount of exhaust gas).

  FIG. 11 is a flowchart specifically showing the control by the ECU 20 as described above. Hereinafter, this flowchart will be described. In the following description, Q indicates a step. First, in Q1 of FIG. 11, signals from the sensors S1 to S4 are read. That is, the read engine speed is N, the read oxygen concentration is OX, the read intake pressure is P, and the read exhaust temperature is T.

  Thereafter, at Q2, it is determined whether or not the actual engine speed N is equal to or less than a predetermined engine speed N2. If the determination at Q2 is NO, the flap 35 is fully opened at Q3 as shown in FIG. 6 (the exhaust of large amounts of exhaust gas is efficient, no post-combustion, no suction effect).

  If YES in Q2, the predetermined oxygen concentration OB is set in Q4 according to the exhaust gas temperature T. The predetermined oxygen concentration OB is set to a lower value as the exhaust gas temperature T is higher, but is set to a value in a range between a predetermined upper limit value and a lower limit value.

  After Q4, at Q5, it is determined whether or not the actual intake pressure P is equal to or higher than a predetermined intake pressure P1 (in the embodiment, atmospheric pressure). If YES in Q5, it is determined in Q6 whether or not the actual oxygen concentration OX is equal to or higher than the predetermined oxygen concentration OB. If the determination in Q6 is YES, in Q7, the flap 35 is set to the minimum opening degree that opens the communication passage 41 shown in FIG. 8 (with post-combustion + with suction effect).

  When NO is determined in Q5 or NO in Q6, the flap 35 is fully closed as shown in FIG. 7 at Q8 (no post-combustion + suction effect).

  FIGS. 12 and 13 show a second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and redundant description thereof will be omitted (this will be described below). The same applies to the third embodiment). 12 corresponds to FIG. 7, and FIG. 13 corresponds to FIG.

  In the present embodiment, the communication path 45 (corresponding to the communication path 41 in the above embodiment) is formed in the flap 35. In other words, the communication path 45 is configured by forming a recess opened in the fan-shaped surface of the flap 35. The communication path 45 extends in the axial direction of the flap shaft 37. As shown in FIG. 12, when the flap 35 is in a fully closed state, the communication passage 45 is blocked by the flow guide plate 33 (the individual exhaust passages 16a, 16bc, and 16d are connected to the communication passage 45). Are in a state of being blocked from each other).

  When the flap 35 is slightly rotated in the valve opening direction from the state of FIG. 12, the communication passage 45 is opened as shown in FIG. 13, and the independent exhaust passages 16a, 16bc, and 16d communicate with each other. (A state in which exhaust gas and scavenging gas are mixed). The fully open state of the flap 35 is not shown, but corresponds to FIG.

  FIGS. 14 to 16 show a third embodiment of the present invention, and are simplified cross-sectional views corresponding to FIGS. In FIGS. 14 to 16, the partition plate 32 is omitted, but the partition plate 32 is provided in the same manner as in FIGS. 6 to 8. In the present embodiment, the communication path 47 (corresponding to the communication path 41 or 45) is configured substantially at a portion immediately upstream of the flow guide plate 33. That is, of the exhaust passages downstream from the collecting portion 31 c, one passage defined by the flow guide plate 33 is shown as the first passage 71 and the other passage is shown as the second passage 72. The first passage 71 is opened and closed by the flap 35, while the second passage 72 is always open. An opening / closing valve 73 is disposed in the first passage 71 opened and closed by the flap 35.

  FIG. 14 shows a case where the first passage 71 is closed by the flap 35 (the on-off valve 73 is closed, but the same is true even if it is opened). FIG. 15 shows a state in which the flap 35 is driven slightly in the valve opening direction from the fully closed state. In this state, the first passage 71 and the second passage 72 are provided in the portion immediately upstream of the flow guide plate 33. Thus, a communication passage 47 is formed in which the upstream portions thereof are communicated with each other. FIG. 16 shows a state in which the flap 35 is fully opened.

  Although the embodiment has been described above, the present invention is not limited to the embodiment, and can be appropriately changed within the scope described in the scope of claims. For example, the invention includes the following cases. . The same applies to multi-cylinder engines other than four cylinders. For example, in the case of a three-cylinder engine, each branch pipe 16a, 16bc, 16d may be communicated with only one different cylinder. For example, in a 6-cylinder engine (in-line 6 cylinders, V-type 6 cylinders), one exhaust turbo supercharger 50 is provided for every three cylinders, and a total of two exhaust turbo superchargers 50 are provided. (2 sets of exhaust passage structures are configured for a three-cylinder engine). In an 8-cylinder engine, in particular, a V-type 8-cylinder engine, one exhaust turbo supercharger 50 is provided for each bank (4 cylinders), and a total of two exhaust turbo superchargers 50 are provided. (2 sets of exhaust passage structures are configured for a four-cylinder engine).

The variable throttle valve is not limited to the one having a fan-shaped surface, and an appropriate type of valve such as a swinging plate can be used. The engine is not limited to a spark ignition type engine, but may be a compression ignition type engine typified by a diesel engine, or a reciprocating type rotary engine.
The predetermined rotational speed N1 may be set to be slightly lower than the predetermined rotational speed N2 (N1 is, for example, 1700 rpm when N2 is 2000 rpm, for example). In this case, the engine rotational speeds are N1 and N2. The flap 35 may be gradually opened from the minimum opening state where the communication passage 41 (45, 47) is opened as the engine speed increases (after-combustion and So that the suction effect is balanced in accordance with the engine speed). The engine speed, oxygen concentration, intake pressure, and exhaust temperature may be detected directly, but may be detected (calculated) indirectly from values related to these. In the opening / closing control of the flap 35, the control using the oxygen concentration may be performed without performing the control based on the intake pressure (the control of shifting to Q6 after Q4 without the step of Q5 shown in FIG. 11). As well). Of course, the object of the present invention is not limited to what is explicitly stated, but also implicitly includes providing what is substantially preferred or expressed as an advantage.

1 is a schematic configuration diagram of an engine supercharging device according to a first embodiment of the present invention. It is a partial sectional side view of FIG. It is an external appearance perspective view of the housing of an exhaust manifold and a variable throttle valve. It is a downstream partial perspective view of an exhaust manifold. It is a principal part perspective view of a variable throttle valve. It is a longitudinal cross-sectional view of the exhaust manifold and the housing of the variable throttle valve, and shows the state where the variable throttle valve is fully open. It is sectional drawing similar to FIG. 6, Comprising: It is a figure which shows the state which has a variable throttle valve in a fully closed state. It is sectional drawing similar to FIG. 6, Comprising: It is a figure which shows the state which is in the minimum opening state which a variable throttle valve opens a communicating path. It is X9-X9 line equivalent sectional drawing of FIG. It is a time chart which shows the example of control of this invention. It is a flowchart for performing the control shown in FIG. FIG. 8 shows a second embodiment of the present invention and is a cross-sectional view corresponding to FIG. 7. FIG. 9 illustrates a second embodiment of the present invention and is a cross-sectional view corresponding to FIG. 8. FIG. 9 shows a third embodiment of the present invention and is a simplified cross-sectional view corresponding to FIG. 7. 9 shows a third embodiment of the present invention and is a simplified cross-sectional view corresponding to FIG. 7 shows a third embodiment of the present invention and is a simplified cross-sectional view corresponding to FIG. 6. FIG. The figure which shows the stroke order of each cylinder, and the overlap period when both the intake and exhaust valves open.

1: Engine 3: Cylinder 7: Intake valve 8: Exhaust port 9: Exhaust valve 16: Exhaust manifolds 16a, 16d: First and fourth exhaust passages (independent exhaust passages)
16bc: auxiliary collective exhaust passage (independent exhaust passage)
20: ECU (control means)
30: Variable throttle valve 31c: Collecting portion 35: Flap (valve element)
41: Communication path (FIGS. 6 to 8)
45: Communication path (FIGS. 14 and 15)
47: Communication path (Fig. 17)
73: On-off valve (FIGS. 16 to 18)
74: Communication path (FIGS. 16 to 18)
50: Exhaust turbocharger 62: Wastegate valve 71: First passage (FIGS. 16 to 18)
72: Second passage (FIGS. 16 to 18)
S1: Sensor (engine speed)
S2: Sensor (intake pressure)
S3: Sensor (oxygen concentration)
S4: Sensor (exhaust temperature)

Claims (6)

Three or more independent branch passages connected to different exhaust ports and independent of each other;
A collecting portion in which the downstream sides of each of the independent branch passages are gathered together;
An exhaust turbocharger disposed downstream of the collecting section;
A variable throttle valve for forming a throttle part by changing the opening area of each independent branch passage on the upstream side of the collecting part;
Between the overlap period in which the valve opening period of the intake / exhaust valve overlaps in the intake stroke and the cylinder in which the valve opening period of the exhaust valve overlaps in the exhaust stroke when the variable throttle valve is greater than the predetermined opening Communication between the independent branch passages, while the communication between the independent branch passages is blocked when the variable throttle valve is less than a predetermined opening,
A control method for an exhaust system of a multi-cylinder engine equipped with
A first step of detecting a value relating to oxygen concentration in the exhaust passage;
A second step of closing the communication passage by closing the variable throttle valve when a value relating to the oxygen concentration in the exhaust passage detected in the first step is less than a predetermined value in a predetermined operating region of the engine; ,
In the predetermined operating region, when the value related to the oxygen concentration in the exhaust passage detected in the first step is equal to or greater than the predetermined value, the variable throttle valve is set to be equal to or greater than the predetermined opening, A third step of performing post-combustion by mixing exhaust gas and scavenging gas;
An exhaust system control method for a multi-cylinder engine. In claim 1,
A fourth step of detecting a value related to the temperature of the exhaust gas;
A fifth step of setting the predetermined value to a smaller value as the value related to the exhaust gas temperature detected in the fourth step is higher;
In addition,
A control method for an exhaust system of a multi-cylinder engine. In claim 1 or claim 2,
In the third step, an exhaust system control method for a multi-cylinder engine, wherein the variable throttle valve has a minimum opening required for opening the communication passage. In any one of Claims 1 thru | or 3,
The predetermined operation region is a low rotation region equal to or lower than the engine speed when the waste gate valve in the exhaust turbocharger is opened.
A control method for an exhaust system of a multi-cylinder engine. In claim 4,
A sixth step of detecting a value related to the intake pressure;
The multi-cylinder characterized in that, in the third step, the variable throttle valve is set to be equal to or greater than the predetermined opening degree on condition that the value related to the intake pressure detected in the sixth step is equal to or greater than atmospheric pressure. Control method of engine exhaust system. Three or more independent branch passages connected to different exhaust ports and independent of each other;
A collecting portion in which the downstream sides of each of the independent branch passages are gathered together;
An exhaust turbocharger disposed downstream of the collecting section;
A variable throttle valve for forming a throttle part by changing the opening area of each independent branch passage on the upstream side of the collecting part;
Between the overlap period in which the valve opening period of the intake / exhaust valve overlaps in the intake stroke and the cylinder in which the valve opening period of the exhaust valve overlaps in the exhaust stroke when the variable throttle valve is greater than the predetermined opening Communication between the independent branch passages, while the communication between the independent branch passages is blocked when the variable throttle valve is less than a predetermined opening,
A control device for an exhaust system of a multi-cylinder engine equipped with
Oxygen concentration detecting means for detecting a value related to the oxygen concentration in the exhaust passage;
Control means for receiving an output from the oxygen concentration detection means and controlling the opening and closing of the variable throttle valve;
With
The control means closes the communication passage by closing the variable throttle valve when the value relating to the oxygen concentration detected by the oxygen concentration detection means is less than a predetermined value in a predetermined operating region of the engine, When the value related to the oxygen concentration in the exhaust passage detected by the oxygen concentration detecting means is equal to or greater than the predetermined value, the variable throttle valve is set to the predetermined opening or more to mix the exhaust gas and the scavenging gas through the communication passage. Is set to perform after-combustion,
A control device for an exhaust system of a multi-cylinder engine.

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