JP5794045B2 - Multi-cylinder engine - Google Patents

Description

  The present invention relates to a multi-cylinder engine having a plurality of cylinders.

  Conventionally, in order to realize compression self-ignition combustion in a low load region in a gasoline engine, and to quickly raise and activate the catalyst at the time of cold start, high-temperature exhaust in the cylinder in a low load region The technology (EGR technology) has been developed to reverse the flow (reflux) of the engine to increase the amount of high-temperature exhaust gas remaining in the cylinder, thereby increasing the temperature.

  In compression self-ignition combustion, the air-fuel mixture generated in the combustion chamber is compressed by a piston, and the air-fuel mixture is self-ignited in a high-temperature and high-pressure environment regardless of spark ignition. In this compression self-ignition combustion, it is said that high thermal efficiency can be obtained as compared with combustion by spark ignition because self-ignition occurs simultaneously and frequently in various places in the combustion chamber. However, in order to realize compression self-ignition combustion, it is necessary to raise the mixture to a temperature at which self-ignition is possible. Therefore, in order to realize the temperature rise of the air-fuel mixture, an EGR technique for returning high-temperature exhaust gas into the cylinder is used.

  For example, the engine disclosed in Patent Document 1 below is configured so that the exhaust valve can be opened not only during the exhaust stroke but also during the intake stroke, and in the low load region where the temperature in the cylinder is low, By performing exhaust double opening control that opens the valve in the exhaust stroke and the intake stroke, high-temperature exhaust is caused to flow back into the cylinder.

JP 2007-85241 A

  As described above, in the low-speed and low-load region, it is desired to increase the temperature of the air-fuel mixture by leaving a large amount of high-temperature exhaust gas in the cylinder. However, if there is a large amount of high-temperature exhaust in the cylinder in a high-load region, the temperature of the mixture will become excessively high and abnormal combustion will occur, or the amount of fresh air introduced will decrease and the engine torque will decrease. There's a problem.

  In view of such circumstances, the present invention allows a large amount of high-temperature exhaust to remain in a cylinder in a low-speed and low-load region, while reducing the residual amount of high-temperature exhaust in the cylinder in a low-speed and high-load region. The purpose is to provide a cylinder engine.

In order to solve the above problems, the present invention includes a combustion chamber, an intake port and an exhaust port, an intake valve capable of opening and closing the intake port, an exhaust valve capable of opening and closing the exhaust port, A multi-cylinder engine having a plurality of cylinders having independent exhaust passages connected to exhaust ports of one cylinder or a plurality of cylinders whose exhaust order is not continuous with each other, and downstream of the independent exhaust passages And an exhaust manifold including a common exhaust passage that collects exhaust gas that has passed through each of the independent exhaust passages inside, and a flow state of the exhaust gas in the exhaust manifold. The exhaust gases in the independent exhaust passages are close to each other so that negative pressure is generated in the other independent exhaust passages due to the ejector effect as they flow into the exhaust passages. A first state in which the passage area becomes smaller toward the downstream side and flows individually into the common exhaust passage, and a passage in which the exhaust in each independent exhaust passage has a larger passage area than in the first state Passage state changing means that can be changed to a second state that passes through the common exhaust passage, valve drive means that can drive the intake valve and the exhaust valve, and the intake valve and the exhaust valve Control means capable of controlling the operation, the operation of the passage state changing means, and the operation of the valve driving means, wherein the valve driving means opens the exhaust valve in the intake stroke in addition to the valve opening operation in the exhaust stroke. execution resume valve operation for opening again, it is possible to stop, wherein, in the high have first operating region than a predetermined reference load load of engine is set in advance, the by the valve drive means Resume valve action And the passage state changing means sets the exhaust flow state in the exhaust manifold to the first state, and the opening period of the intake valve and the opening period of the exhaust valve of each cylinder are over a predetermined amount. The valve driving means causes the overlap period of one cylinder to overlap with the timing when the exhaust valve of the other cylinder is opened between cylinders that overlap in the lap period and the exhaust order continues. while driving the intake and exhaust valves of the cylinders, in the second operating region have lower than the previous SL reference load is the load of the engine, along with executing the resume valve operated by said valve drive means, said passage state changing means The multi-cylinder engine is characterized in that the flow state of the exhaust gas in the exhaust manifold is changed to the second state.

According to the present invention, in the second operating region on the low load side, a large amount of hot exhaust gas flows back into the cylinder to ensure a large amount of hot exhaust gas remaining in the cylinder, that is, a residual gas amount. While increasing the temperature of the air-fuel mixture, high scavenging performance is realized in the first operating region on the high load side, and the residual gas amount in the cylinder is reduced to suppress an excessive increase in the temperature of the air-fuel mixture. Suppression and improvement of engine torque can be realized.

  Specifically, in the present invention, in the first operating region, the exhaust valve is opened only in the exhaust stroke, and the exhaust flow state in the exhaust manifold is the first state, that is, the exhaust in each independent exhaust passage is The exhaust in each independent exhaust passage is close to each other and the flow area becomes smaller toward the downstream side so that negative pressure is generated in the other independent exhaust passage due to the ejector effect as it flows into the common exhaust passage. Each passage individually enters the common exhaust passage and the intake valve opening period and the exhaust valve opening period of each cylinder overlap with each other by a predetermined overlap period, and the exhaust order In each cylinder, the overlap period of one cylinder (intake stroke cylinder) overlaps with the time when the exhaust valve of the other cylinder (exhaust stroke cylinder) is opened. Exhaust valve It is dynamic. Therefore, scavenging of the intake stroke cylinder can be promoted by applying a high negative pressure in the exhaust port of the intake stroke cylinder during the overlap period due to the ejector effect.

  On the other hand, in the present invention, in the second operation region, the exhaust valve is opened in the intake stroke in addition to the exhaust stroke in order to ensure the high-temperature exhaust amount remaining in the cylinder, and from the cylinder to the exhaust port once in the exhaust stroke. The discharged exhaust gas is controlled to flow back into the cylinder during the intake stroke. Here, the intake stroke of a predetermined cylinder and the exhaust stroke of other cylinders coincide. Therefore, in this second operation region, exhaust flows from the exhaust stroke cylinder into the common exhaust passage at a high speed as in the first operation region, thereby exerting a high ejector effect and generating a high negative pressure in the intake stroke cylinder. If so, the exhaust pressure in the intake stroke cylinder and the exhaust port of the intake stroke cylinder is sucked downstream by this negative pressure, and there is a possibility that the amount of exhaust gas flowing back to the intake stroke cylinder cannot be secured. On the other hand, in the present invention, in the second operation region, the exhaust flow state in the exhaust manifold is in the second state, that is, the exhaust in each independent exhaust passage has a larger flow area than the first state. The state of passing through the passage and flowing into the common exhaust passage is promoted, and the expansion of the exhaust, that is, the reduction in the exhaust speed is promoted before the passage into the common exhaust passage. As a result, in the second operating region, exhaust of the exhaust gas in the cylinder and in the exhaust port due to the ejector effect is suppressed, and a reverse flow rate to the exhaust gas cylinder is ensured.

  Examples of the combustion mode implemented in the second operation region include self-ignition combustion. That is, as one embodiment of the present invention, an auto-ignition is provided that includes an injector that injects fuel, at least part of which is made of gasoline, into the combustion chamber, and in the second operation region, the air-fuel mixture in the combustion chamber burns by auto-ignition A combustion mode is executed (Claim 2).

  As a specific configuration of the exhaust manifold and the passage state changing means, the exhaust manifold is interposed between a downstream end of each independent exhaust passage and the common exhaust passage, A plurality of gas passages into which exhaust gases discharged from the downstream end independently flow in each have a throttle portion formed inside, and the passage state changing means can change the flow passage area of each gas passage. By changing the flow passage area, the flow passage area of the passage through which the exhaust gas in each independent exhaust passage passes before flowing into the common exhaust passage is changed, and the flow state of the exhaust gas in the exhaust manifold is changed. Is changed to the first state and the second state (claim 3).

  In this configuration, each gas passage includes a first passage extending from a downstream end of each independent exhaust passage to the common exhaust passage and individually communicating with each independent exhaust passage, and the first passage and the common passage. A second passage communicating with the exhaust passage, and the passage state changing means changes a flow area of each gas passage by changing a communication amount between the first passage and the second passage. (Claim 4).

  According to this configuration, the first passage and the second passage are formed in the throttle portion, and the flow area of each gas passage is changed by simply changing the communication amount between the first passage and the second passage. As a result, the flow state of the exhaust gas in the exhaust manifold can be changed.

  Each gas passage includes a first passage extending from a downstream end of each independent exhaust passage to the common exhaust passage and individually communicating with each independent exhaust passage, and each first passage and the common exhaust passage. A second passage communicating with the second passage, and the passage state changing means may change the passage area of each gas passage by changing the passage area of the second passage. Item 5).

  According to this configuration, the first passage and the second passage are formed in the throttle portion and the flow passage area of the second passage is changed. The distribution state of can be changed.

  As a specific configuration of the exhaust manifold and the passage state change means, the exhaust manifold includes a throttle portion interposed between a downstream end of each independent exhaust passage and the common exhaust passage, and each independent exhaust. A communication passage that is provided in the middle of the passage and communicates with the plurality of independent exhaust passages, and a communication state changing means that can change the communication state of the independent exhaust passages via the communication passage, A plurality of gas passages having a shape in which the flow passage area decreases toward the downstream and arranged so that exhaust discharged from the downstream ends of the independent exhaust passages flows independently are formed inside. The passage state changing means does not cause the independent exhaust passages to communicate with each other by the communication state changing means, and the exhaust in each independent exhaust passage is individually By making the gas passage in the throttle part pass, the exhaust gas distribution state in the exhaust manifold is changed to the first state, and the independent exhaust passages are communicated with each other by the communication state changing means. An example is one in which the exhaust state in the exhaust manifold is changed to the second state by setting the exhaust in the passage to pass through the plurality of gas passages in the throttle portion (claim 6).

  As a specific configuration of the exhaust manifold and the passage state change means, the exhaust manifold includes a throttle portion interposed between a downstream end of each independent exhaust passage and the common exhaust passage, and each independent exhaust. A bypass passage for connecting the passage and the common exhaust passage to bypass the throttle portion, and a bypass passage opening / closing means capable of opening and closing the bypass passage. A plurality of gas passages having a shape to be reduced and arranged so that exhaust discharged from the downstream ends of the independent exhaust passages flows independently from each other are formed, and the passage state changing means includes The bypass passage is closed by a bypass passage opening / closing means, and the exhaust gas in each independent exhaust passage individually passes through the gas passage in the throttle portion. As a result, the exhaust flow state in the exhaust manifold is changed to the first state, while the bypass passage is opened by the bypass passage opening / closing means, so that the exhaust in each independent exhaust passage becomes the gas in the throttle portion. In addition to the passage, there is one that changes the flow state of the exhaust gas in the exhaust manifold to the second state by passing the bypass passage (Claim 7).

  As described above, according to the present invention, while realizing a back flow to a cylinder of a large amount of high-temperature exhaust in a low-speed and low-load region, scavenging performance is improved in a low-speed and high-load region, and the residual amount in the cylinder of high-temperature exhaust is reduced. By suppressing the amount to a small extent, it is possible to avoid abnormal combustion and improve engine torque.

1 is a diagram illustrating an overall configuration of a multi-cylinder engine according to an embodiment of the present invention. It is a figure which shows the structure of the exhaust system of the engine shown in FIG. It is a figure for demonstrating the valve timing of an intake valve and an exhaust valve. It is a block diagram for demonstrating the control system of the intake / exhaust apparatus of the multicylinder engine which concerns on 1st Embodiment of this invention. It is the VV sectional view taken on the line of FIG. FIG. 6 is a cross-sectional view of the periphery of the throttle portion in a state where the outer tube is at the position where the flow path area is minimum. (A) It is the figure of the cut surface which cut | disconnected FIG. 6 by the VII-VII line. (B) It is the figure which showed only the inner pipe | tube among the figures of (a). (C) It is the figure which showed only the outer tube | pipe among the figures of (a). (A) It is the figure of the cut surface which cut | disconnected FIG. 6 by the VIII-VIII line. (B) It is the figure which showed only the inner pipe | tube among the figures of (a). (C) It is the figure which showed only the outer tube | pipe among the figures of (a). It is the figure of the cut surface which cut | disconnected FIG. 6 by the IX-IX line. FIG. 6 is a cross-sectional view of the periphery of the throttle portion in a state where the outer tube is at the maximum position of the flow path area. It is the figure of the cut surface which cut | disconnected FIG. 10 by the XI-XI line. It is a schematic perspective view which shows a part of outer tube | pipe. It is the figure which showed the control map used with the multicylinder engine which concerns on 1st Embodiment of this invention. It is a time chart for demonstrating the control content of lean HCCI combustion mode. It is a figure for demonstrating the valve opening time and valve closing time of an intake valve and an exhaust valve. It is a time chart for demonstrating the control content of rapid SI retarded combustion mode. It is the figure which showed the control map used with the multicylinder engine which concerns on 1st Embodiment of this invention. It is the figure which looked at the throttle part of the multicylinder engine concerning a 3rd embodiment of the invention from the upper stream. (A) In the intake / exhaust device for a multi-cylinder engine according to the third embodiment of the present invention, it is a schematic perspective view of an inner tube in a state where a lid is in a fully closed position. (B) In the intake / exhaust device for a multi-cylinder engine according to the third embodiment of the present invention, it is a schematic perspective view of an inner pipe in a state where a lid is in a fully open position. (A) It is sectional drawing of the aperture | diaphragm | squeeze part corresponding to (a) of FIG. (B) It is sectional drawing of the aperture | diaphragm | squeeze part corresponding to (b) of FIG. It is the schematic of the exhaust manifold of the multicylinder engine which concerns on 4th Embodiment of invention. It is the schematic of the exhaust manifold of the multicylinder engine which concerns on 4th Embodiment of invention. It is a schematic side view of the exhaust manifold periphery of a multi-cylinder engine according to a fifth embodiment of the invention.

(1) Overall Configuration of Engine FIG. 1 is a diagram showing an overall configuration of a multi-cylinder engine according to an embodiment of the present invention. FIG. 2 is a view showing a part of this engine (mainly an exhaust manifold). The engine shown in FIG. 1 is a reciprocating piston type multi-cylinder engine mounted on a vehicle as a power source for driving driving. The engine body 1 of this engine can reciprocately slide in each cylinder 2 with a cylinder block 3 having four cylinders 2 (see FIG. 2) arranged in a predetermined direction, a cylinder head 4 provided on the upper surface of the cylinder block 3 And the piston 5 inserted into the. Specifically, a first cylinder 2a, a second cylinder 2b, a third cylinder 2c, and a fourth cylinder 2d are formed in order from the right in FIG. In the present embodiment, the engine is a gasoline engine, and the fuel supplied to the engine body 1 is mainly composed of gasoline. In addition, the fuel may be all gasoline, or gasoline containing ethanol (ethyl alcohol) or the like.

  The engine body 1 is a four-cycle engine, and is configured such that the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke are shifted by 180 ° C. in each of the cylinders 2a to 2d (see FIG. 3). In this embodiment, ignition is performed in the order of the first cylinder 2a → the third cylinder 2c → the fourth cylinder 2d → the second cylinder 2b, and the exhaust stroke and the like are performed in this order.

  The piston 5 is connected to the crankshaft 7 via a connecting rod 8, and the crankshaft 7 rotates around the central axis in accordance with the reciprocating motion of the piston 5. A concave cavity 40 is provided at the center of the crown surface of the piston 5. The cavity 40 has an upward opening facing the later-described injector 21 at the upper end, and the area (opening area) of this opening is the maximum cross-sectional area inside the cavity 40 (each height position of the cavity 40). Is set smaller than the maximum horizontal cross-sectional area). That is, the cavity 40 is formed in a constricted shape so that the inner diameter becomes narrower in the range from the opening to a predetermined depth.

  A combustion chamber 6 is formed above the piston 5. An intake port 9 and an exhaust port 10 are opened in the combustion chamber 6, and an intake valve 11 and an exhaust valve 12 that open and close the ports 9 and 10 are provided in the cylinder head 4. The illustrated engine is a so-called double overhead camshaft (DOHC) engine, and two intake ports 9 and two exhaust ports 10 are provided for each cylinder, and two intake valves 11 and two exhaust valves 12 are also provided. It has been.

  Here, the engine body 1 of the present embodiment is set so as to have a relatively high geometric compression ratio of 14 or more for the purpose of improving the theoretical thermal efficiency, stabilizing the compression auto-ignition combustion described later, and the like. Yes. Since the upper limit value of the geometric compression ratio is considered to be about 30 from a practical viewpoint, the geometric compression ratio of the engine body 1 is set to an appropriate value in the range of 14 to 30. Is done.

  Various sensors are attached to the engine. For example, a water temperature sensor SW1 for detecting the temperature of engine cooling water, a rotation angle (crank angle) of the crankshaft 7, and a crank angle sensor SW2 for detecting the rotation speed of the engine, and a camshaft angle are detected to detect the cylinder temperature. Cam angle sensor SW3 that outputs a signal for determination (determination of whether each cylinder is in intake, compression, expansion, or exhaust), an outside air temperature sensor for detecting the temperature of fresh air flowing into the combustion chamber The SW 4 is attached to the engine body 1.

  The intake valve 11 and the exhaust valve 12 are driven to open and close in conjunction with the rotation of the crankshaft 7 by valve mechanisms 13 and 14 including a pair of camshafts (not shown) disposed in the cylinder head 4. .

  A CVVL 15 and a VVT (valve driving means) 16 are respectively incorporated in the valve mechanism 13 for the intake valve 11. The CVVL 15 is called a continuously variable valve lift mechanism and continuously (steplessly) changes the lift amount of the intake valve 11. The intake VVT 16 is called a variable valve timing mechanism and variably sets the opening / closing timing (phase angle) of the intake valve 11. The intake CVVL15 and the intake VVT16 are provided so that the lift amount and the opening / closing timing of all the intake valves 11 of the engine can be changed. When both the intake CVVL15 and the intake VVT16 are driven, The lift amount and opening / closing timing of the intake valve 11 are changed simultaneously.

  The intake CVVL 15 having the above-described configuration is already known. As a specific example, a link mechanism that reciprocally swings the cam for driving the intake valve 11 in conjunction with the rotation of the camshaft, and the arrangement of the link mechanism (lever A control arm that variably sets the ratio), and a stepping motor that changes the cam swing amount (the amount by which the intake valve 11 is pushed down) by electrically driving the control arm. (For example, refer to JP 2007-85241 A). Also, various types of intake VVT 16 such as a hydraulic type, an electromagnetic type, and a mechanical type are already known, and an appropriate one can be adopted.

  The valve mechanism 14 for the exhaust valve 12 includes a VVL (valve drive means) which is an ON / OFF type variable valve lift mechanism (variable valve lift mechanism) that enables or disables the function of pushing down the exhaust valve 12 during the intake stroke. ) 17 is incorporated. The exhaust VVL 17 allows the exhaust valve 12 to be opened not only in the exhaust stroke but also in the intake stroke, and has a function of switching between performing and stopping the valve opening operation of the exhaust valve 12 during the intake stroke. The exhaust VVL 17 is provided corresponding to all the exhaust valves 12 of the engine, and can individually perform or stop the valve opening operation during the intake stroke with respect to the pair of exhaust valves 12 of each cylinder 2. .

  The exhaust VVL 17 having such a configuration is already known, and as a specific example thereof, the exhaust valve 12 is arranged during the intake stroke separately from a normal cam for driving the exhaust valve 12 (a cam that pushes down the exhaust valve 12 during the exhaust stroke). Examples include a sub cam that is pushed down and a so-called lost motion mechanism that enables or disables transmission of the driving force of the sub cam to the exhaust valve 12 (see, for example, JP-A-2007-85241).

  When the exhaust valve 12 is opened during the intake stroke by the action of the exhaust VVL 17, the high-temperature exhaust once discharged from the combustion chamber 6 to the exhaust port 10 in the exhaust stroke flows back into the cylinder 2, that is, the combustion chamber 6. While the temperature of the combustion chamber 6 is increased, the amount of air (fresh air) introduced into the combustion chamber 6 is reduced. In the following description, the backflow operation of the high-temperature exhaust gas by the resumption valve of the exhaust valve 12 (opening during the intake stroke) is distinguished from the exhaust gas recirculation operation (external EGR control) by the external EGR device 30 described later. This is called degree opening control. Further, the high temperature exhaust gas remaining in the combustion chamber 6 including the exhaust gas that has flowed back by the exhaust double opening control is referred to as internal EGR gas, and the exhaust gas (refrigerant exhaust gas) recirculated into the combustion chamber 6 by the external EGR control This is called gas.

  The cylinder head 4 of the engine body 1 is provided with one set of spark plugs 20 and injectors 21 for each cylinder 2.

  The injector 21 is provided so as to face the combustion chamber 6 from the ceiling surface (the lower surface of the cylinder head 4 covering the combustion chamber 6). A fuel supply pipe 23 is connected to the injector 21 of each cylinder 2, and fuel (fuel mainly composed of gasoline) supplied through each fuel supply pipe 23 is injected from the tip of the injector 21.

  More specifically, on the upstream side of the fuel supply pipe 23, a high pressure fuel pump comprising a plunger type pump or the like linked to the crankshaft 7 is connected, and the high pressure fuel pump and the fuel supply are connected. A common rail for pressure accumulation common to all the cylinders is provided between the pipe 23. Then, the fuel accumulated in the common rail is supplied to the injectors 21 of the respective cylinders 2, whereby high pressure fuel of 30 MPa or more is injected from the injectors 21. Since the upper limit value of the fuel injection pressure is considered to be about 120 MPa from a practical viewpoint, the injection pressure from the injector 21 is set to an appropriate value in the range of 30 MPa to 120 MPa.

  The injector 21 is a so-called multi-hole injector, and has twelve nozzle holes at the tip. The installation portions of these injection holes (tip portions of the injectors 21) are located in the center of the ceiling of the combustion chamber 6, and each injection hole is perforated so that the opening direction faces obliquely downward on the outer side in the bore radial direction. Yes. For this reason, the fuel is injected radially from each nozzle hole of the injector 21 so as to expand outward in the bore radial direction as it approaches the crown surface (upper surface) of the piston 5.

  The spark plug 20 is disposed adjacent to the injector 21 so as to face the combustion chamber 6 of each cylinder 2 from above. This spark plug 20 has an electrode exposed to the combustion chamber 6 at the tip, and discharges a spark from the electrode in response to power supply from an ignition circuit (not shown).

  An intake passage 28 and an exhaust manifold 50 are connected to the intake port 9 and the exhaust port 10 of the engine body 1, respectively. Intake air (fresh air) from the outside is supplied to the combustion chamber 6 through the intake passage 28, and exhaust gas (burned gas) generated in the combustion chamber 6 is discharged to the outside through the exhaust manifold 50. The detailed structure of the exhaust manifold 50 will be described later.

  The intake passage 28 includes a common passage portion 28c formed of a single passage, a surge tank 28b provided at a downstream end portion of the common passage portion 28c, and a branch formed for each cylinder 2, and the surge tank 28b. A branch passage portion 28a that connects the intake port 9 of each cylinder 2 is provided.

  An external EGR device 30 is provided between the intake passage 28 and the exhaust manifold 50 to recirculate part of the exhaust gas passing through the exhaust manifold 50 to the intake passage 28. Specifically, the external EGR device 30 is provided in an EGR passage 31 that connects each common passage portion 28 c of the intake passage 28 and an upstream end 61 of a casing 62 described later of the catalyst device 60, and in the middle of the EGR passage 31. The EGR valve 32 controls the flow rate of the exhaust gas passing through the interior, and the water-cooled EGR cooler 33 that cools the temperature of the exhaust gas passing through the EGR passage 31.

  In the common passage portion 28c of the intake passage 28, a throttle valve 25 is provided so as to be openable and closable. However, in the present embodiment, the lift amount of the intake valve 11 is adjusted by the CVVL 15, the amount of exhaust gas remaining and flowing back into the combustion chamber 6 is adjusted by the exhaust VVL 17, and the intake passage 28 is further adjusted by the external EGR device 30. The amount of exhaust gas recirculated is adjusted. Therefore, based on these operations, the amount of air (fresh air) introduced into the combustion chamber 6 can be adjusted without operating the throttle valve 25. For this reason, the throttle valve 25 is fully opened or maintained at a value close to it except when the engine is stopped.

(2) Configuration of Exhaust Manifold Details of the exhaust manifold 50 will be described next. The exhaust manifold 50 includes three independent exhaust passages 52, a movable portion 51, and a catalyst device 60 in order from the upstream side. Here, a portion of the exhaust manifold 50 downstream of the throttle portion 53 described later of the movable portion 51 constitutes a common exhaust passage 50a (see FIG. 2). Specifically, in this embodiment, the collective portion 58 of the movable portion 51 and the catalyst device 60 constitute a common exhaust passage 50a.

(2-1) Configuration of Independent Exhaust Passage 52 As shown in FIG. 2, each independent exhaust passage 52 is connected to the exhaust port 10 of each cylinder 2 formed in the cylinder head 4. Specifically, in the cylinder 2, the exhaust port 10 of the first cylinder 2a and the exhaust port 10 of the fourth cylinder 2d are individually connected to the independent exhaust passages 52 and 52, respectively. On the other hand, the exhaust ports 10 of the second cylinder 3b and the third cylinder 2c, whose exhaust strokes are not adjacent to each other and the exhaust order is not continuous, are not exhausted from these cylinders 2b, 2c at the same time, so the structure is simplified. From this point of view, it is connected to one independent exhaust passage 52 formed in a bifurcated shape. Specifically, the independent exhaust passage 52 connected to the exhaust ports 10 of the second cylinder 2b and the third cylinder 2c is separated into two passages on the upstream side thereof, and one of the second cylinders 2b is connected to one of them. The exhaust port 10 is connected, and the exhaust port 10 of the third cylinder 2c is connected to the other.

  In the present embodiment, the independent exhaust passage 52 corresponding to the exhaust port 10 of the second cylinder 2b and the third cylinder 2c is linearly opposed to the intermediate position between these cylinders 2b and 2c, that is, the substantially central portion of the engine body 1. The independent exhaust passages 52 that extend and correspond to the exhaust ports 10 of the other cylinders 2a and 2d are independent exhaust passages 52 that correspond to the second cylinder 2b and the third cylinder 2c from positions corresponding to the corresponding exhaust ports 10. It curves and extends toward.

  5 is a cross-sectional view taken along line VV in FIG. As shown in FIG. 5, the sectional shape of the downstream end 52a of the independent exhaust passage 52, that is, the opening shape of the downstream end 52a is circular, and the circular downstream end 52a is obliquely downward toward the rear of the vehicle. Are arranged at equal intervals on the circumference of a circle centered on a point O1 on an axis L (see FIG. 2) extending in the direction of.

(2-2) Configuration of Movable Part 51 As shown in FIG. 2 and the like, the movable part 51 has a double-pipe structure, and the throttle part 53 and the collecting part 58 are accommodated inside a cylindrical accommodating pipe 51a. Has a structured. The throttle part 53 and the collecting part 58 are accommodated in this order from the upstream. The housing pipe 51a extends rearward and obliquely downward with an axis L extending obliquely downward toward the rear of the vehicle as a central axis. Hereinafter, the axis L of the accommodating tube 51a may be simply referred to as the axis L.

(2-2-1) Configuration of Restriction Part 53 FIG. 6 shows a movable part in a state where an outer tube 55 (to be described later) of the restriction part 53 is at the most upstream position (hereinafter, this position is referred to as a minimum flow channel area position). It is sectional drawing which expanded and showed 51 vicinity. FIG. 7A is a diagram showing only the throttle portion 53 in the cross-sectional view taken along the line VII-VII in FIG. FIG. 7B is a diagram showing only an inner tube 54 described later of the throttle portion 53 in FIG. FIG.7 (c) is a figure which showed only the outer tube | pipe 55 among FIG.7 (b). FIG. 8A is a diagram showing only the narrowed portion 53 in the sectional view taken along the line VIII-VIII in FIG. FIG. 8B shows only the inner pipe 54 in FIG. 8A. FIG. 8C shows only the outer tube 55 in FIG. 8B. FIG. 9 is a diagram showing only the diaphragm 53 in the cross-sectional view taken along the line IX-IX in FIG.

  FIG. 10 is a diagram corresponding to FIG. 6, and shows an enlarged view of the vicinity of the movable portion 51 in a state where the outer tube 55 is slid to the maximum flow path area position set downstream of the minimum flow path area position. It is sectional drawing shown. FIG. 11 is a view corresponding to FIG. 9 and showing only the aperture 53 in the cross-sectional view taken along the line IX-IX of FIG.

  The throttle unit 53 includes an inner tube 54 and an outer tube 55.

  The inner tube 54 is a tubular member extending in the upstream / downstream direction. Three first passages 54 a extending in the upstream and downstream directions are formed inside the inner tube 54. The outer shape of the inner tube 54 has a substantially frustoconical shape whose upstream portion has a cylindrical shape with the axis L of the containing tube 51a as the central axis, and whose downstream portion has a diameter decreasing toward the downstream with the axis L as the center. It is comprised so that it may make. That is, the outer peripheral surface 54g of the inner tube 54 includes a cylindrical surface 54g_1 provided in the upstream portion thereof and extending in parallel with the axis L, and an inner tube provided in the downstream portion thereof and inclined toward the axis L as going downstream. It consists of a side inclined surface 54g_2 (inner tube side inclined portion). The diameter of the outer peripheral surface 54g at the downstream end of the inner tube 54 is set to, for example, about half of the diameter of the outer peripheral surface 54g at the upstream end of the inner tube 54.

  The first passages 54a are arranged at equal intervals on a cylindrical surface of a cylinder having the axis L as a central axis. Each first passage 54a has a portion on the axis L side of the inner peripheral surface thereof extending along the axis L, while a portion of the inner peripheral surface on the side radially spaced from the axis L is an inner tube 54. It has a shape extending along the outer peripheral surface 54g. With this shape, the flow path area of each first passage 54a becomes smaller toward the downstream side.

  Specifically, the upstream end 54b of each first passage 54a is circular as shown in FIGS. 7 (a) and 7 (b). On the other hand, as shown in FIGS. 8A and 8B, the downstream end 54c of each first passage 54a has a substantially fan shape obtained by dividing one circle into three parts, and the area thereof is upstream of the circular shape. The area is set smaller than the area of the end 54b. Each first passage 54a extends from the circular upstream end 54b to the downstream side by a predetermined amount with the same flow path area, and then gradually toward the downstream end 54c having a flow path area smaller than the upstream end 54b. It extends while being reduced in diameter. In the present embodiment, the diameter of the circle formed by the entire downstream end 54c of the first passage 54a and the diameter of the circle of the upstream end 54b of each first passage 54a are set to be approximately the same size.

  The inner pipe 54 is disposed such that the circular upstream end 54 b of each first passage 54 a coincides with the downstream end 52 a of each independent exhaust passage 52. Therefore, the exhaust discharged from the downstream end 52a of each independent exhaust passage 52 individually (independently) flows into the corresponding first passage 54a.

  A portion of the tube wall of the inner tube 54 corresponding to each first passage 54 a is formed with a communication port 54 d that communicates the first passage 54 a with the outside of the inner tube 54. Each communication port 54d opens to the inner tube side inclined surface 54g_2 of the outer peripheral surface 54g of the inner tube 54, and opens toward the downstream. In the present embodiment, each communication port 54d is substantially circular.

  On the tube wall of the inner tube 54, grooves 54e extending from the outer peripheral surface 54g of the inner tube 54 toward the axis L and extending in the upstream / downstream direction are formed at portions corresponding to the spaces between the first passages 54a. .

  The outer tube 55 is a tubular member extending in the upstream / downstream direction. One passage is formed inside the outer tube 55, and the inner tube 54 is accommodated in the passage. The inner peripheral surface 55g of the outer tube 55 extends along the outer peripheral surface 54g of the inner tube 54 in a state where the outer tube 55 is at the minimum flow path area position shown in FIG. That is, the inner peripheral surface 55g of the outer tube 55 is provided on the upstream side portion thereof and extends in parallel with the axis L, and is provided on the downstream side portion thereof and is inclined toward the axis L side toward the downstream side. The outer tube side inclined surface 55g_2 (outer tube side inclined portion). The outer tube-side inclined surface 55g_2 of the outer tube 55 extends so as to contact the inner tube-side inclined surface 54g_2 of the inner tube 54 in a state where the outer tube 55 is at the minimum flow path area position. The mouth 54d is configured to be closed.

  FIG. 12 shows a perspective view of a part of the outer tube 55. As shown in FIG. 12 and FIG. 7 (a), the outer tube 55 extends from the inner peripheral surface 55g toward the axis L in the upstream and downstream direction corresponding to each groove 54e of the inner tube 54. An extending partition wall 55e is formed. These partition walls 55e are inserted into the respective grooves 54e.

  The outer tube 55 is movable relative to the inner tube 54 on the downstream side. In the present embodiment, the inner tube 54 does not move, and the outer tube 55 slides in the upstream / downstream direction in parallel with the axis L. In the present embodiment, the outer tube 55 is formed integrally with the collective portion 58 and slides in the upstream and downstream direction together with the collective portion 58.

  Specifically, as shown in FIG. 2, a slide actuator (passage state changing means) 55 f is attached to the outer peripheral surface of the outer tube 55. The slide actuator 55f receives a command from the ECU 100, which will be described later, and is a diagram in which the outer pipe 55 is parallel to the axis L, and is a position on the downstream side of the flow path area minimum position shown in FIG. Slide between the maximum position of the channel area shown in FIG. At this time, each partition wall 55e of the outer tube 55 slides in each groove 54e of the inner tube 54.

  6, the outer pipe 55 extends from the upstream end to the downstream end of the inner pipe 54. As described above, in this state, the inner peripheral surface 55g of the outer tube 55 is in contact with the outer peripheral surface 54g of the inner tube 54 to block the communication port 54d. When the communication port 54d is closed, the exhaust discharged from each independent exhaust passage 52 flows through only the first passage 54a in the throttle portion 53. As described above, in the state where the outer pipe 55 is at the position where the flow path area is the minimum (first state), the gas passage formed in the throttle portion 53 and through which the exhaust discharged from each independent exhaust passage 52 can pass is It consists of only one passage 54a, and the flow passage area of the gas passage is the minimum area.

  On the other hand, when the outer tube 55 is slid from the minimum position of the flow path area to the maximum position of the flow path area shown in FIG. 10 (second state), the inner peripheral surface 55g of the outer pipe 55 is the outer peripheral surface 54g of the inner pipe 54. To the downstream side and radially outward (in the direction away from the axis L). Along with this separation, each communication port 54d is opened, and a second passage 55a appears between the inner peripheral surface 55g of the outer tube 55 and the outer peripheral surface 54g of the inner tube 54.

  As shown in FIG. 11, each partition wall 55e of the outer tube 55 is inserted into each groove 54e of the inner tube 54, so that the inner peripheral surface 55g of the outer tube 55 and the outer peripheral surface 54g of the inner tube 54 Between the two, three second passages 55a are partitioned by the partition wall 55e. Each second passage 55a is located on the radially outer side of each first passage 54a and communicates with the first passage 54a through each communication port 54d.

  Thus, in a state where the outer tube 55 is slid to the maximum position of the flow path area shown in FIG. 10, the gas passage formed in the throttle portion 53 is constituted by the first passage 54a and the second passage 55a. Then, after the exhaust discharged from each independent exhaust passage 52 flows into the first passage 54a, a part thereof also flows into the second passage 55a through the communication port 54d. Thus, in a state where the outer tube 55 is at the maximum position of the flow path area, the flow path area of each gas passage is larger than the minimum area.

  The flow passage area of the second passage 55a, and hence the flow passage area of the gas passage in the throttle 53, increases as the sliding amount of the outer pipe 55 to the downstream side increases. Specifically, as the outer tube 55 slides downstream, the distance between the inner peripheral surface 55g of the outer tube 55 and the outer peripheral surface 54g of the inner tube 54 increases, and the second passage 55a and the gas passage are accordingly increased. The flow path area becomes larger.

  Here, in the state where the flow path area is at the maximum position shown in FIG. 10, the outer cylinder 55 is located on the most downstream side, and the flow path areas of the second passage 55a and the gas passage are the maximum areas. In this state, the upstream end of the outer tube 55 is positioned at the downstream end of the cylindrical upstream portion of the inner tube 54, and the outer tube 55 extends downstream from this position.

  In the present embodiment, the slide actuator 55f switches the position of the outer tube 55 to either the minimum flow path area position or the maximum flow path area position. Thereby, the flow path area of the gas passage is switched between the minimum area and the maximum area.

(2-2-2) Configuration of Collecting Portion 58 The collecting portion 58 is a portion where the exhaust discharged from each independent exhaust passage 52 and passing through the throttle portion 53 joins. Regardless of the position of the outer tube 55, the exhaust gas discharged from each independent exhaust passage 52 and flowing into each gas passage of the throttle portion 53 flows into the collecting portion 58.

  As shown in FIG. 10, in a state where the outer pipe 55 is at the maximum flow path area position, the outer pipe 55 extends downstream from the inner pipe 54, and the exhaust gas that has passed through the first passage 54a After flowing into the inside of the pipe 55 and joining the exhaust gas that has passed through the second passage 55 a, it flows into the collecting portion 58.

  As shown in FIG. 6 and the like, the collecting portion 58 includes a nozzle portion 58a, a mixing portion 58b, and a diffuser portion 58c in order from the upstream side. In the present embodiment, as described above, the collecting portion 58 is slidably connected to the outer tube 55 so that the nozzle portion 58a is integrally connected to the downstream end of the outer tube 55, and is downstream from the downstream end. It extends to.

  As will be described later, the gasoline engine is configured to exhaust the exhaust gas from the throttle portion 53 into the nozzle portion 58a at a high speed in a predetermined operation region (first operation region A1) to exert an ejector effect. Therefore, the shape of the nozzle portion 58a is set to a shape in which the flow path area becomes smaller toward the downstream side so that the exhaust discharged from the throttle portion 53 flows down while maintaining a high speed. In the present embodiment, the nozzle portion 58a has a substantially truncated cone shape that decreases in diameter toward the downstream. Further, the inner peripheral surface of the nozzle portion 58a is formed on the inner peripheral surface of the downstream portion of the outer tube 55, that is, the outer tube-side inclined surface, so that the exhaust gas flowing out from the throttle portion 53 smoothly flows along the inner peripheral surface. Continuing from 55g_2, it is inclined in a direction approaching the axis L as it goes downstream. The inclination angle of the nozzle portion 58a with respect to the axis L is set to be substantially the same as the inclination angle of the outer tube side inclined surface 55g_2 of the outer tube 55.

  The mixing portion 58b has a cylindrical shape extending from the downstream end of the nozzle portion 58a to the downstream side, and has the same flow area as the opening at the downstream end of the nozzle portion 58a. The diffuser portion 58c has a substantially frustoconical shape in which the flow path area increases as it goes downstream from the downstream end of the mixing portion 58b.

  Thus, in the part comprised by the nozzle part 58a and the mixing part 58b, the flow path area of an upstream is larger than the downstream. Therefore, the exhaust gas passes through the nozzle part 58a and the mixing part 58b at high speed. During this passage, the pressure and temperature of the exhaust gas decrease. Accordingly, in the nozzle part 58a and the mixing part 58b, the amount of heat released to the outside of the exhaust gas can be reduced. The exhaust gas that has passed through the mixing portion 58b flows into the diffuser portion 58c whose flow path area increases as it goes downstream, so that its pressure and temperature are recovered and discharged to the downstream side while maintaining a high temperature. .

  Further, as described above, in the present embodiment, the collecting portion 58 and the throttle portion 53 are inserted into the hollow housing tube 51a. Therefore, heat radiation to the outside of the exhaust when passing through the collecting portion 58 and the throttle portion 53 is further suppressed, and high temperature exhaust is discharged from the collecting portion 58 to the downstream side.

(2-3) Configuration of Catalyst Device 60 As shown in FIG. 1, the catalyst device 60 is a device for purifying the exhaust discharged from the engine body 1. The catalyst device 60 includes a catalyst body (catalyst) 64 and a casing 62 that houses the catalyst body 64. The casing 62 has a substantially cylindrical shape extending in parallel with the exhaust flow direction. The catalyst body 64 is for purifying harmful components in the exhaust gas, and has a three-way catalyst function in an atmosphere having a theoretical air-fuel ratio. The catalyst body 64 contains, for example, a three-way catalyst.

  The catalyst main body 64 is accommodated in a central portion in the upstream / downstream direction of the casing 62, and a predetermined space is formed at the upstream end 61 of the casing 62. The downstream end of the collecting portion 58, specifically, the downstream end of the diffuser portion 58 c is connected to the upstream end 61 of the casing 62, and the exhaust discharged from the diffuser portion 58 c flows into the upstream end 61 of the casing 62. Then, the process proceeds to the catalyst body 64 side.

  As described above, the exhaust gas having a high temperature is discharged from the collecting portion 58 to the downstream side. Therefore, the catalyst device 60 is directly connected to the gathering portion 58 in this manner, so that high-temperature exhaust gas flows into the catalyst device 60, whereby the catalyst body 64 is activated early. The active state of the main body 64 is reliably maintained.

(3) Action of Exhaust Manifold 50 In the first state in which the outer pipe 55 is at the position where the flow path area is minimum, as described above, the gas passage in the throttle 53 has a shape in which the flow path area decreases toward the downstream. It consists of only one passage 54a, and its flow path area is minimized. Therefore, in this first state, the exhaust gas flowing into each first passage 54a from each independent exhaust passage 52 is increased in speed while passing through the first passage 54a, and flows into the nozzle portion 58a at a high speed. In particular, in the present embodiment, the nozzle portion 58a also has a shape in which the channel area becomes smaller toward the downstream. Therefore, the exhaust discharged from each independent exhaust passage 52 flows down while maintaining a high speed also in the nozzle portion 58a. In this first state, the exhaust gas discharged from the predetermined first passage 54a passes through the nozzle portion 58a in this way at a high speed. As a result, the adjacent first passage 54a and the adjacent first passage 54a communicate with each other by the ejector effect. A relatively high negative pressure amount is generated in the independent exhaust passage 52 and the exhaust port 10.

  On the other hand, in the second state in which the outer tube 55 is at the maximum position of the flow path area, the gas passage in the throttle portion 53 is composed of the first passage 54a and the second passage 55a, and the flow passage area is smaller than the minimum area. Is also enlarged. Therefore, in this second state, the exhaust gas flowing into each first passage 54a from each independent exhaust passage 52 expands in the gas passage and flows into the nozzle portion 58a in a state where its speed is kept low. As a result, in this second state, resistance in the gas passage in the throttle portion 53 is suppressed, and the amount of negative pressure due to the ejector effect is reduced.

  As described above, in the present embodiment, the position of the outer pipe 55 is changed, so that the exhaust gas distribution state in the exhaust manifold 50 is generated in the other independent exhaust passage 52 by the ejector effect. In addition, the exhaust in each independent exhaust passage 52 passes through a passage that is close to each other and has a smaller flow path area toward the downstream side, and individually passes through the common exhaust passage 50a (in this embodiment, of the common exhaust passages). The first state flowing into the collecting portion 58) and the second state where the exhaust in each independent exhaust passage 52 passes through a passage having a larger flow area than the first state and flows into the common exhaust passage, Thereby, the amount of negative pressure generated in the predetermined independent exhaust passage 52 by the ejector effect in each state is changed.

(4) Control System FIG. 4 is a block diagram showing an engine control system. The ECU (control means) 100 shown in FIG. 4 is a device for comprehensively controlling each part of the engine, and includes a well-known CPU, ROM, RAM, and the like.

  Various information is input to the ECU 100 from various sensors provided in the engine. The ECU 100 is electrically connected to a water temperature sensor SW1, a crank angle sensor SW2, a cam angle sensor SW3, an outside air temperature sensor SW4, and the like provided in the engine, and based on input signals from these sensors SW1 to SW4. Various information such as engine coolant temperature, crank angle, engine speed, cylinder discrimination information, and fresh air temperature are acquired.

  In addition, information from various sensors provided in the vehicle is also input to the ECU 100. For example, the vehicle is provided with an accelerator opening sensor SW5 that detects an opening degree of an accelerator pedal (accelerator opening degree) that is not shown in the figure that is depressed by the driver, and the accelerator opening degree sensor SW5 detects the accelerator opening degree sensor SW5. The accelerator opening is input to the ECU 100.

  More specific functions of the ECU 100 will be described. The ECU 100 includes, as main functional elements, a determination unit 101, an injector control unit 102, an intake control unit 103, an exhaust double opening control unit 104, an external EGR control unit 105, an ignition control unit 106, and an actuator control unit 107. ,have.

  The determination means 101 determines the engine based on the engine speed specified from the detected value of the crank angle sensor SW2 and the engine load (target torque) specified from the detected value of the accelerator opening sensor SW4. It is determined each time whether or not to control. In the following, it is assumed that the engine speed is Ne and the engine load is T.

  FIG. 13 is a setting diagram (control map) showing the types of control determined based on the engine speed Ne and the load T. During engine operation, the determination unit 101 determines the control content of the engine so as to follow the control map of FIG.

  In the control map of FIG. 13, the region where the load T is lower than the reference load T1 (low load region) includes the low engine speed range (region where the engine rotational speed is lower than the predetermined rotational speed) over the entire engine rotational speed range. Two operation areas A2 are set. A first operation region A1 and a third operation region A3 are set in the middle and high load region where the load T is higher than that in the second operation region A2. The third operation region A3 is a high-speed and high-load region in which the engine speed Ne is equal to or higher than the reference rotation number N1 in the medium and high load region, and the load T is near the full load. The first operation region A1 is a region excluding the third operation region A3 in the medium and high load region, and includes a low speed and high load region A1_1 and a medium load region A1_2.

  Referring back to FIG. 4 again, the injector control means 102 combusts from the injector 21 by electromagnetically opening and closing a needle valve (not shown) built in the injector 21 (a valve for opening and closing the nozzle at the tip of the injector 21). The injection amount and injection timing of the fuel injected into the chamber 6 are controlled.

  The intake / exhaust control means 103 drives the intake CVVL15 and the intake VVT16 to change the lift amount (opening amount) and the open / close timing of the intake valve 11, and drives the exhaust VVL17 to open / close the exhaust valve 12. Control to change.

  The exhaust double opening control means 104 operates to reverse the high temperature exhaust gas into the combustion chamber 6 by driving the exhaust VVL 17 and executing or stopping the opening of the exhaust valve 12 during the intake stroke (opening twice the exhaust). Control) execution / stop. In the present embodiment, since two exhaust valves 12 are provided per cylinder, the combustion chamber 6 is switched by switching the number of exhaust valves 12 that are opened during the intake stroke between 0, 1, and 2. It is possible to change the amount of exhaust gas flowing back to the exhaust gas stepwise.

  The external EGR control means 105 switches execution / stop of an operation (external EGR control) for returning the exhaust gas from the exhaust passage 29 to the intake passage 28 by adjusting the opening degree of the EGR valve 32 provided in the EGR passage 31. .

  The ignition control means 106 controls the timing of spark ignition (ignition timing) by the spark plug 20 and the like.

(5) Control contents in each operation region Next, based on the control of the ECU 100 having the above functions, what control is performed in each operation region (A1, A2, A3) shown in FIG. Explain what will be done. ECU 100 sequentially determines to which operating region the engine operating point (load T and rotational speed Ne) corresponds in the control map of FIG. 13 based on the detected values of crank angle sensor SW2 and accelerator opening sensor SW4. To do. Then, depending on whether the determined operation region is one of the first operation region A1, the second operation region A2, and the third operation region A3 in FIG.

(5-1) Second operation region A2
In the second operating region A2 composed of the low load region, the ignition of the air-fuel mixture by the spark plug 20 is stopped, and the lean HCCI combustion is performed in which the sufficiently mixed fuel and air mixture is self-ignited by the compression action of the piston 5. (Homogeneous-Charge Compression Ignition Combustion, premixed compression self-ignition combustion) mode is executed.

  FIG. 14 is a diagram showing the fuel injection timing, the lift characteristics of the intake and exhaust valves 12 and 12, and the heat generation rate (J / deg) generated by combustion based on the fuel injection timing when the lean HCCI combustion mode is executed. As shown in FIG. 14, in this lean HCCI combustion mode, fuel is injected at a timing sufficiently earlier than the compression top dead center (TDC between the compression stroke and the expansion stroke), and the fuel and air are sufficiently mixed. The air-fuel mixture is ignited by the compression action of the piston 5 in the vicinity of the mixed compression top dead center.

  Specifically, in this embodiment, when operating in this lean HCCI combustion mode, a relatively small amount of fuel is injected (P) from the injector 21 into the combustion chamber 6 at a predetermined time during the intake stroke. The homogeneous and lean air-fuel mixture formed based on a small amount of fuel collectively injected by the fuel injection P and air (new air) introduced from the intake passage 28 into the combustion chamber 6 is compressed by the piston 5. Due to the action, the temperature and pressure are increased, and self-ignition occurs near the compression top dead center. Then, based on such self-ignition, combustion accompanied by heat generation as shown by the waveform Qa occurs.

  In the lean HCCI combustion mode, G / F, which is the ratio of the weight G of the total gas in the combustion chamber 6 to the fuel weight F injected into the combustion chamber 6, is set to be 30 or more (for example, 35). . However, under such a lean and homogeneous air-fuel ratio, misfire may occur unless the temperature in the combustion chamber is intentionally increased. As described above, in this gasoline engine, the geometric compression ratio of the engine body 1 is set to a high value of 14 or more, and the temperature in the combustion chamber 6 can be raised to a certain extent by the compression action of the piston 5. However, in this engine, in order to realize more stable combustion in the low load region where the temperature in the combustion chamber 6 is low, the high-temperature exhaust gas remaining in the combustion chamber 6 (cylinder 2), that is, the high-temperature internal EGR gas amount is reduced. A large amount of control is performed.

  Specifically, in the second operation region A2, the exhaust double opening control is performed, and the high-temperature exhaust gas flowing out to the exhaust port 10 side is caused to flow back into the combustion chamber 6. That is, the exhaust VVL 17 is driven, and the exhaust valve 12 opens during the exhaust stroke (lift curve EX in FIG. 14) and also opens during the intake stroke (lift curve EX ′ in FIG. 14).

  As described above, the high-temperature exhaust gas flows back into the combustion chamber 6, so that a large amount of high-temperature exhaust gas remaining in the combustion chamber 6, that is, high-temperature internal EGR gas is secured. As a result, the temperature of the air-fuel mixture in the combustion chamber 6 is increased, and as a result, self-ignition of the air-fuel mixture is promoted. The amount of internal EGR gas is set to be larger on the low load side and smaller on the high load side. As a control for that, for example, in the low load region (region close to no load) in the second operation region A2, the number of the exhaust valves 12 opened during the intake stroke is two, and the load becomes higher than that, The number of valve openings is reduced to one.

  Further, in the second operation region A2, the position of the outer pipe 55 of the throttle portion 53 is set to the maximum flow path area position, and the exhaust gas distribution state in the exhaust manifold 50 is in the second state, that is, each of the throttle portions 53 in the throttle portion 53. The flow passage area of the gas passage is in the maximum area. Such control is performed for the following reason.

  As described above, in the second operation region A2, the exhaust valve 12 is restarted during the intake stroke in order to secure a larger amount of internal EGR gas. As shown in FIG. 3, the intake stroke of a predetermined cylinder (intake stroke cylinder) 2 and the exhaust stroke of a cylinder (exhaust stroke cylinder) 2 that has one exhaust stroke after this intake stroke cylinder 2 coincide with each other. Accordingly, during the period when the exhaust valve 12 is restarted in addition to the intake valve 11 in the intake stroke cylinder 2, the exhaust in the exhaust stroke cylinder 2 is discharged to the nozzle portion 58a through the throttle portion 53.

  As described above, when the position of the outer pipe 55 of the throttle portion 53 is the minimum flow path area position and the exhaust flow state in the exhaust manifold 50 is in the first state, the exhaust discharged from the predetermined cylinder 2 When passing through the first passage 54a, a high negative pressure is generated in the exhaust port 10 of the other cylinder 2 due to the ejector effect. Therefore, when the restart valve control of the exhaust valve 12 is performed, the position of the outer pipe 55 of the throttle portion 53 is set to the minimum flow path area position, and the exhaust gas circulation state of the exhaust manifold 50 is set to the first state. Then, a high negative pressure generated by the exhaust of the exhaust stroke cylinder 2 acts on the exhaust port 10 of the cylinder (intake stroke cylinder) 2 in which the exhaust valve 12 is restarted, and the exhaust port 10 of the intake stroke cylinder 2 The exhaust in the engine is sucked downstream, and the amount of exhaust flowing back into the intake stroke cylinder 2, that is, the amount of internal EGR gas cannot be secured sufficiently. On the other hand, as described above, if the position of the outer pipe 55 of the throttle 53 is the maximum flow path area position and the exhaust manifold 50 is in the second state, the amount of negative pressure due to the ejector effect can be reduced.

  Therefore, in this engine, in the second operation region A2, in order to secure a large amount of internal EGR gas, in order to suppress the suction of the exhaust in the cylinder 2 and the exhaust port 10 to the downstream side due to the negative pressure generated by the ejector effect. The position of the outer tube 55 of the throttle 53 is the maximum flow path area position, and the exhaust flow state in the exhaust manifold 50 is the second state.

  Further, in the second operation region A2, in order to avoid a decrease in the temperature in the combustion chamber 6 due to a large amount of recirculation of the low-temperature external EGR gas into the combustion chamber 6, near the boundary with the first operation region A1, that is, The external EGR control is stopped except for the high load side region in the second operation region A2. Specifically, in the high load side region of the second operation region A2, the EGR valve 32 provided in the EGR passage 31 is opened, and a relatively low temperature external portion from the exhaust passage 29 to the intake passage 28 is opened. The recirculation of the EGR gas is performed, and the opening degree of the EGR valve 32 is fully closed in the other region of the second operation region A2, and the recirculation of the external EGR gas is stopped.

  As described above, in the second operation region A2, a large amount of internal EGR gas is secured, and the G / F is increased to a temperature at which the lean air-fuel mixture can be surely self-ignited with certainty. And by this self-ignition combustion of the air-fuel mixture, the generation of NOx is suppressed, and the high thermal efficiency (fuel consumption) accompanying the reduction of the combustion temperature and thus the cooling loss is realized.

(5-2) First operation region A1 and third operation region A3
In the first operation region A1 and the third operation region A3 set in the high load region, a large amount of fuel is injected and the temperature in the combustion chamber 6 becomes high, so when trying to perform compression self-ignition combustion, There is a problem that combustion noise is remarkably increased and knocking occurs. Therefore, in the first operation region A1 and the third operation region A3, spark ignition combustion (SI combustion) is performed in which the air-fuel mixture is ignited and flame is propagated instead of compression self-ignition combustion.

  Here, also in SI combustion, when the temperature in the combustion chamber 6 is excessively high, knocking occurs. In particular, in this gasoline engine, the compression ratio is set to a very high value. Therefore, the temperature in the combustion chamber 6 tends to be high, and the problem of combustion noise and knocking becomes significant.

  Therefore, in this engine, in the first operation region A1 and the third operation region A3, control is performed to reduce the amount of high-temperature internal EGR gas remaining in the combustion chamber 6 in order to suppress the temperature increase in the combustion chamber 6. Is implemented.

  Specifically, in the first operation region A1 and the third operation region A3, the exhaust double opening control is stopped, and the backflow of the high-temperature exhaust gas flowing out to the exhaust port 10 side into the combustion chamber 6 is stopped. . Specifically, the exhaust VVL 17 is adjusted so that the exhaust valve 12 opens only during the exhaust stroke. In addition, as shown below, the flow state of the exhaust gas in the intake valve 11, the exhaust valve 12, and the exhaust manifold 50 is to reduce the internal EGR gas amount in the first operation region A1 and the third operation region A3, respectively. Is adjusted to an appropriate condition.

(I) Control method of intake valve 11 and the like in first operation region A1 In the first operation region A1, the position of the outer pipe 55 is set to the minimum flow path area position, and the flow state of the exhaust gas in the exhaust manifold 50 is the first. In other words, the flow passage area of each gas passage in the throttle 53 is minimized, and as shown in FIG. 3, the valve opening period of the exhaust valve 12 and the valve opening period of the intake valve 11. And the exhaust valve 12 are adjusted so as to start opening during the overlap period T_O / L of the other cylinders 2 with the intake top dead center (TDC) interposed therebetween. Specifically, the exhaust valve 12 of the third cylinder 2c is opened during the period in which the intake valve 11 and the exhaust valve 12 of the first cylinder 2a overlap, and the intake valve 11 and the exhaust valve of the third cylinder 2c are opened. The exhaust valve 12 of the fourth cylinder 2d is opened during the period in which the second cylinder 2d overlaps with the second cylinder 2b during the period in which the intake valve 11 and the exhaust valve 12 of the fourth cylinder 2d overlap. The exhaust valve 12 of the first cylinder 2a is opened, and the exhaust valve 12 of the first cylinder 2a is adjusted to open during the period in which the intake valve 11 and the exhaust valve 12 of the second cylinder 2b overlap. In the present engine, the valve opening timing and the valve closing timing of the intake valve 11 and the exhaust valve 12, respectively, are as follows. As shown in FIG. This is the time of lowering, for example, the time of 0.4 mm lift. Such control is performed for the following reason.

  As described above, when the position of the outer pipe 55 of the throttle portion 53 is the minimum flow path area position and the exhaust manifold 50 is in the first state, the exhaust discharged from the predetermined cylinder 2 passes through the first passage 54a. In doing so, a high negative pressure is generated in the exhaust port 10 of the other cylinder 2 due to the ejector effect. Therefore, the valve opening period of the exhaust valve 12 and the valve opening period of the intake valve 11 overlap with each other with the intake top dead center (TDC) interposed therebetween, and the exhaust valve 12 overlaps the other cylinder 2 with an overlap period T_O /. If the valve is adjusted so as to start opening during L, the exhaust valve 12 of the predetermined cylinder (exhaust stroke cylinder) 12 is opened and the exhaust gas is discharged from the exhaust stroke cylinder 2 at high speed. A high negative pressure can be generated in the exhaust port 10 of the cylinder during the intake stroke (intake stroke cylinder) during the overlap period. Then, the residual pressure in the intake stroke cylinder 2 can be sucked out to the exhaust port 10 side by this negative pressure. In particular, immediately after the exhaust valve 12 starts to open, exhaust (so-called blowdown gas) is discharged from the cylinder 2 at a very high speed. Therefore, immediately after the blowdown gas is discharged, the exhaust gas remaining in the intake stroke cylinder 2 remains. Most of the gas can be sucked out to the exhaust port 10 side.

  Therefore, in the present engine, in the first operation region A1, in order to suppress the amount of internal EGR gas, the suction of the exhaust gas in the cylinder 2 and the exhaust port 10 to the exhaust port 10 side is promoted by the negative pressure generated by the ejector effect. As described above, the position of the outer pipe 55 of the throttle portion 53 is set to the maximum flow path area position, the exhaust flow state in the exhaust manifold 50 is set to the second state, and the exhaust valve 12 and the intake valve 11 are overlapped. The exhaust valve 12 is opened during the overlap period T_O / L of the other cylinders 2.

  As described above, in the present engine, in the first operation region A1, the internal EGR gas amount is suppressed to a low level by stopping the exhaust double opening control and using the negative pressure generated by the ejector effect, and thus the air-fuel mixture in the combustion chamber 6 is reduced. Overheating is avoided. And in 1st driving | operation area | region A1, abnormal combustion and the deterioration of a combustion noise are avoided reliably, and appropriate combustion is implement | achieved.

  Here, in the low speed and high load region A1_1 in the first operation region A1, it is necessary to secure a large amount of fresh air in order to obtain a high engine torque. Therefore, the external EGR control is stopped in the low speed and high load region A1_1. Specifically, the EGR valve 32 is closed and the flow of the low-temperature external EGR gas into the intake passage 28 is stopped. As described above, in the first operation region A1, the internal EGR gas amount is suppressed to a low level due to the ejector effect or the like. Therefore, in the low-speed and high-load region A1_1, a large amount of intake air that does not contain external EGR gas, that is, fresh air, flows into the combustion chamber 6, and high engine torque is realized while avoiding abnormal combustion and deterioration of combustion noise. In the present embodiment, the ignition timing can be advanced as the abnormal combustion (knocking) is suppressed as described above, and a high engine torque can also be obtained by this advancement. .

  On the other hand, in the medium load region A1_2 in the first operation region A1, the required amount of fresh air is small. Therefore, in this medium load region A1_2, external EGR control is performed in order to obtain high thermal efficiency, that is, good fuel consumption performance, and to reduce NOx by reducing intake pumping loss and cooling loss. . Specifically, the EGR valve 32 is opened, and the exhaust gas (external EGR gas) cooled by the EGR cooler 33 is recirculated into the combustion chamber 6. In the middle load region A1_2, the overlap amount between the valve opening period of the intake valve 11 and the valve opening period of the exhaust valve 12 is adjusted so that the low speed side is smaller than the high speed side.

(Ii) Control method of the intake valve 11 and the like in the third operation region A3 In the third operation region A3 composed of the high speed and high load region, the overlap amount between the valve opening period of the intake valve 11 and the valve opening period of the exhaust valve 12 is The adjustment is made to be less than the first operation region A1. Further, in the third operation region A3, the position of the outer pipe 55 is set to the maximum flow area, the flow area of each gas passage in the throttle 53 is set to the maximum area, and the exhaust gas in the exhaust manifold 50 is circulated. The state is the second state.

  In the third operation region A3, the exhaust flow rate is large as the engine speed Ne and the engine load T are high. Therefore, as in the first operation region A1, the intake valve 11 and the exhaust valve 12 are overlapped, and the flow passage area of each gas passage in the throttle portion 53 is small with the position of the outer tube 55 as the minimum flow passage area position. If the area is set, the scavenging performance deteriorates due to the back pressure becoming higher than the scavenging performance improvement effect by the ejector effect, and it becomes difficult to sufficiently reduce the internal EGR gas amount. Therefore, in the gasoline engine, the control as described above is performed in the third operation region A3.

  By being controlled in this manner, in the third operation region A3, the exhaust discharged from each independent exhaust passage 52 flows down in a state where the exhaust resistance is kept small in the gas passage having the largest flow path area. Therefore, the back pressure of the engine can be kept small. As the back pressure is reduced, scavenging is promoted, and the amount of internal EGR gas is reduced. In addition, the pumping loss of the exhaust is suppressed to a small level, and the intake efficiency is increased, thereby realizing a high engine torque.

  In the third operation region A3, the external EGR control is stopped in order to secure a larger amount of fresh air in order to obtain a high engine torque, as in the low speed and high load region A1_1 of the first operation region A1.

(Iii) Combustion modes in the first operation region A1 and the third operation region A3 Here, in the present embodiment, in the first operation region A1 and the third operation region A3 in order to more reliably avoid abnormal combustion such as knocking. , Rather than normal SI combustion in which fuel is injected substantially before the compression top dead center (for example, during the intake stroke) and spark ignition is performed near the compression top dead center, as shown in FIG. 16, during the compression stroke Fuel is injected from the injector 21 (P1, P2), and after this fuel injection P1, P2, the spark plug 20 is ignited, and a short time from the timing when the compression top dead center is passed (the initial stage of the expansion stroke). A rapid retarded SI combustion mode is performed in which the air-fuel mixture is burned by flame propagation.

  FIG. 16 is a diagram showing the fuel injection timing, the lift characteristics of the intake / exhaust valves 11 and 12, and the heat generation rate (J / deg) generated by combustion based on the fuel injection timing when the rapid retarded SI combustion mode is executed. . In this specification, the term “late stage” or “initial stage” of a certain process refers to the latter period or the initial stage when the process is divided into three stages: initial, middle, and late. For example, in the later stage of the compression stroke, it refers to the range of 60 to 0 ° CA before compression top dead center (BTDC), and in the early stage of the expansion stroke, it is from 0 to 60 ° CA after compression top dead center (ATDC). Will point to the range.

  Specifically, as shown in FIG. 16, in the rapid retarded SI combustion mode, fuel is injected at a high pressure of 30 MPa or more from the injector 21 in two injection timings (P1, P2) set in the latter half of the compression stroke. Is injected. As the timing of each fuel injection P1, P2, for example, the period from the start timing of the first injection P1 to the completion timing of the second injection P2 is approximately 20 ° to 0 ° before compression top dead center (BTDC). It is set to be within a period of about CA.

  In the rapid retarded SI combustion mode in which such injection control is performed, the injection period can be shortened by injecting fuel at a very high injection pressure of 30 MPa or more (for example, 40 MPa) as described above. At the same time, the fuel spray can be atomized, and a large amount of fuel can be sufficiently vaporized and atomized in a short time to form a relatively homogeneous (or weakly stratified) mixture. In addition, since the injection pressure is high, large turbulent energy can be maintained until the combustion chamber 6 passes a certain amount of compression top dead center at which the temperature and pressure of the combustion chamber 6 are the highest. In particular, the fuel is injected in two portions, and ignition is performed after the second fuel injection. The fuel is atomized by the first fuel injection P1, and the second fuel injection is performed at the time of ignition. Turbulent energy can be increased. Further, in the present embodiment, the turbulent energy can be increased also by using the multi-hole injector 21 and injecting fuel from a number of nozzles. Further, in the present embodiment, the cavity 40 is formed in the piston 5 so that the fuel spray injected by the fuel injections P1 and P2 in the latter stage of the compression stroke can be quickly performed mainly in the cavity 40 by the turbulent energy. This can also reduce the combustion period.

  Therefore, in this rapid retarded SI combustion mode, combustion by spark ignition is started for a short time after fuel injection, and within a period when the attenuation of turbulent energy accompanying fuel injection is small (in a period when turbulent energy is large). The combustion period can be shortened by this relatively large turbulent energy. As the combustion period is shortened, the air-fuel mixture can be burned out by proper flame propagation after spark ignition. That is, high thermal efficiency and engine torque can be maintained while avoiding abnormal combustion such as knocking. Further, in the rapid retarded SI combustion mode, combustion is started at the timing when the compression top dead center is passed, so that the combustion temperature does not rise excessively, and combustion may be started with insufficient vaporization and atomization of fuel. Therefore, the increase in NOx and soot is avoided, and the emission property is also maintained well.

  In the rapid retarded SI combustion mode, fresh air is set so that the average air-fuel ratio of the entire combustion chamber 6 becomes the stoichiometric air-fuel ratio (excess air ratio λ = 1) with respect to the total injection amount by the fuel injections P1 and P2. The amount is controlled. Further, the ignition timing is set to the most advanced angle timing (for example, about 0 ° to 20 ° CA after compression top dead center (ATDC)) from the viewpoint of improving thermal efficiency and output torque. .

(6) Operational Effects As described above, in this engine, in the low speed and high load region A1_1, the flow state of the gas passage in the throttle 53 is set to the minimum area with the exhaust flow in the exhaust manifold 50 being the first state. Thus, the ejector effect is effectively exerted, thereby achieving high scavenging performance, in turn avoiding abnormal combustion and deterioration of combustion noise, and high engine torque, and in the low load region A2, the exhaust gas in the exhaust manifold 50 is exhausted. The flow state is set to the second state, the flow area of the gas passage in the throttle 53 is set to the maximum area, and the scavenging performance due to the ejector effect is suppressed, thereby ensuring the reverse flow rate of the exhaust gas in the restart valve of the exhaust valve 12. Thus, it is possible to achieve proper compression self-ignition combustion and thus high thermal efficiency. In addition, by properly utilizing the ejector effect, it is possible to avoid abnormal combustion and deterioration of combustion noise in the middle load region A1_2 and to realize high engine torque in the high speed and high load region A3.

  In particular, in the present embodiment, the throttle portion 53 is constituted by an inner tube 54 having a first passage 54 a formed inside and an outer tube 55 that accommodates the inner tube 54, and the outer tube 55 and the inner tube 54 are separated from each other. The flow passage area of each gas passage in the restricting portion 53 is changed with a simple configuration in which the second passage 55a is defined in between and the flow passage area of the second passage 55a is changed. Thus, the structure of the entire apparatus can be simplified. Moreover, it is only necessary to slide the outer tube 55 in the upstream and downstream directions, and the drive structure of the outer tube 55 can be simplified.

(7) Other Embodiments (7-1) Second Embodiment In the first embodiment, HCCI combustion is performed in the low-load second operation region A2 in which the exhaust double opening control is performed, while the exhaust double opening is performed. Although the case where the SI combustion is performed in the first operation region A1 and the third operation region A3 of medium and high load where the control is not performed has been shown, the combustion mode of each region is not limited thereto.

  For example, as shown in FIG. 17, HCCI combustion may be performed in the entire operation region. However, as described above, a large amount of fuel is injected in the medium and high load region (region including the first operation region A1 and the third operation region A3 set in the same region as the first embodiment). There is a problem that combustion noise increases due to the high temperature inside the combustion chamber 6 or knocking easily occurs. Therefore, also in the second embodiment in which HCCI combustion is performed in the entire operation region, similarly to the first embodiment, in the first operation region A1 and the third operation region A3, the temperature in the combustion chamber 6 is increased. In order to avoid this, control is performed to reduce the amount of internal EGR gas in the combustion chamber 6 to a low level.

  Specifically, in the first operation region A1 and the third operation region A3, as in the first embodiment, the exhaust double opening control is stopped to stop the reverse flow of the high-temperature internal EGR gas amount to the cylinder 2. To do. Further, in the first operation region A1 where the exhaust flow rate is relatively small, the intake valve 11 and the like are adjusted so that the scavenging performance by the ejector effect is exhibited. That is, the valve opening period of the exhaust valve 12 and the valve opening period of the intake valve 11 overlap with each other with the intake top dead center (TDC) interposed therebetween, and the exhaust valve 12 overlaps the other cylinder 2 with an overlap period T_O / L. The intake valve 11 and the exhaust valve 12 are controlled so that the valve opening is started, and the position of the outer pipe 55 is set to the minimum position of the flow path area, and the flow area of each gas passage in the throttle 53 is set to the minimum area. And the flow state of the exhaust gas in the exhaust manifold 50 is controlled to the first state. On the other hand, in the third operation region A3 in which the deterioration of the scavenging performance increases due to the large exhaust flow rate and the back pressure higher than the scavenging performance improvement effect by the ejector effect, the intake valve 11 and the like are adjusted so as to keep the exhaust pressure small . That is, the position of the outer pipe 55 is set near the maximum flow area, the flow area of each gas passage in the throttle 53 is set near the maximum area, and the flow state of the exhaust gas in the exhaust manifold 50 is controlled to the second state.

(7-2) Third Embodiment In the first embodiment, the configuration for changing the flow passage area of the gas passage has been described as the configuration for changing the flow passage area of the gas passage. The configuration for changing the road area is not limited to this.

  For example, the flow passage area of the gas passage may be changed by changing the amount of communication between the first passage and the second passage formed in the throttle portion. An example of a configuration in which the flow passage area of the gas passage is changed by changing the communication amount is shown in FIGS. 18, 19A, 19B, and 29A, 29B. FIG. 18 is a diagram corresponding to FIG. 7A of the first embodiment. 19A and 19B are perspective views of the throttle portion 153 in a state where the outer tube 155 is omitted. FIG. 19A shows a state in which the communication port 154d is fully closed, and FIG. 19B shows a state in which the communication port 154d is closed. It is in a fully open state. 20A and 20B are cross-sectional views of the narrowed portion 153, in which FIG. 20A corresponds to FIG. 19A, and FIG. 20B corresponds to FIG. 19B.

  The third embodiment shown in FIG. 18 to FIG. 20 has a throttle portion 153 having an inner tube 154 and an outer tube 155, as in the first embodiment. As in the first embodiment, the outer peripheral surface 154g of the inner tube 154 is provided with a cylindrical surface 154g_1 provided in the upstream portion thereof and extending in parallel with the central axis L, and provided in the downstream portion thereof and being throttled toward the downstream. The inner tube side inclined surface 154g_2 is inclined to the central axis L side of the portion 153. As in the first embodiment, a plurality of first passages 154a whose flow area decreases toward the downstream side are formed inside the inner tube 154.

  On the other hand, the outer tube 155 according to the third embodiment is fixed so as not to move relative to the inner tube 154. The outer tube 155 has an inner peripheral surface 155g spaced radially outward from the outer peripheral surface 154g of the inner tube 154, and the second passage 155a is defined between the inner peripheral surface 155g and the outer peripheral surface 154g. It is fixed with. The inner peripheral surface 155g of the outer tube 155 extends in parallel with the outer peripheral surface 154g of the inner tube 154. A partition wall 154e that protrudes radially outward and extends to a position that contacts the inner peripheral surface 155g of the outer tube 155 is provided at a position corresponding to the space between the first passages 155a in the outer peripheral surface 154g of the inner tube 154. A second passage 155a is formed between the inner peripheral surface 155g of the outer tube 155 and the outer peripheral surface 154g of the inner tube 154 at a position corresponding to the first passage 155a. In the third embodiment, three second passages 155a are formed corresponding to the three first passages 155a. In the tube wall of the inner tube 154, a communication port 154d that connects the first passage 154a and the second passage 155a is formed. Each communication port 154d is open to the cylindrical surface 154g_1 of the outer peripheral surface 154g of the inner tube 154.

  In addition, the throttle unit 153 according to the third embodiment is provided with a lid 159 that can open and close each communication port 154d and a rotation actuator (passage state changing means, not shown) that can drive the lid 159. ing.

  Each lid 159 extends along the outer peripheral surface 154 g of the inner tube 154. The rotating actuator moves each lid 159 in the circumferential direction along the outer peripheral surface 154g of the inner tube 154. That is, the rotation actuator rotates each lid 159 about the central axis L of the aperture 153. The rotating actuator includes a position where each communication port 154d shown in FIGS. 19 (a) and 20 (a) is fully closed, and each communication port 154d shown in FIGS. 19 (b) and 20 (b). Is moved to a position where is fully opened. By this movement, the opening amount of the communication port 154d changes, and the communication amount between the first passage 154a and the second passage 155a changes with the change in the opening amount. The flow passage area of the gas passage through which the exhaust passes in the throttle 153 changes. Here, the exhaust gas flowing into the first passage 154a flows into the second passage 155a by an amount corresponding to the communication amount. Therefore, the flow passage area of the gas passage through which the exhaust passes in the throttle portion 153 is defined by the communication amount and the flow passage area of the first passage 154a. That is, the total area of the flow passage area of the first passage 154a and the opening area of the communication port 154d is the flow passage area of the gas passage.

  Thus, in the third embodiment, the flow area of the gas passage in the throttle portion 153 is changed by changing the communication amount between the first passage 154a and the second passage 155a. And by this change, the distribution | circulation state of the exhaust gas in an exhaust manifold is changed into a 1st state and a 2nd state.

(7-3) Fourth Embodiment In the first and third embodiments, the flow state of the exhaust gas in the exhaust manifold is changed to the first by changing the flow passage area of the gas passage formed in the throttle portion. Although the case where the state is changed to the state and the second state is shown, the specific configuration for changing the flow state of the exhaust gas in the exhaust manifold is not limited to this.

  For example, it is good also as a structure as shown to FIG. 21 and FIG. In the engine according to the fourth embodiment shown in these drawings, as in the first embodiment, the exhaust manifold 450 is provided with an independent exhaust passage 452 and a throttle portion 453. These drawings are views in which a portion of the exhaust manifold 450 on the downstream side of the throttle portion 453 is omitted. On the other hand, in this engine, unlike the first embodiment, an independent exhaust passage 452 is provided for each cylinder 2 independently. Further, the flow passage area of the gas passage formed in the throttle portion 453 cannot be changed. In addition, the independent exhaust passage 452 is communicated with each other by a communication passage 455 in the middle thereof. The communication passage 455 is provided with a valve (communication state changing means, not shown) capable of changing the communication state of the independent exhaust passages 452 via the communication passage 455 by opening and closing the passage.

  Specifically, the throttle portion 453 is composed only of a cylindrical member in which a plurality of gas passages 453a whose flow area decreases toward the downstream side are formed inside. Each gas passage 453a is connected to each independent exhaust passage 452, and the exhaust discharged from each cylinder 2 individually flows into each gas passage 453a. In the example shown in FIGS. 21 and 22, four independent exhaust passages 452 and four gas passages 453 a are provided for four cylinders 2. Then, as shown in FIG. 22, these four gas passages 453a are arranged on the circumference so that the gas passages 453a are adjacent to each other.

  The communication passage 455 communicates the independent exhaust passages 452 corresponding to the cylinders 2 where the exhaust stroke is not continuous. The valve is fully opened and the independent exhaust passages 52 communicate with each other through the communication passage 455. Even in this state, the exhaust discharged from each cylinder 2 is configured not to interfere. Specifically, the independent exhaust passages 452 corresponding to the first cylinder 2a and the fourth cylinder 2d communicate with each other, and the independent exhaust passages 452 corresponding to the second cylinder 2b and the third cylinder 2c communicate with each other.

  In the fourth embodiment, the exhaust state in the exhaust manifold 450 is set to the first state by fully closing the valve. That is, when the valve is fully closed, the exhaust discharged from each cylinder 2 passes through only one independent exhaust passage 52 and only one gas passage 453a whose flow area is set smaller toward the downstream. It is assumed to pass through. And by setting it as this state, the speed | rate of the exhaust_gas | exhaustion discharged | emitted from each independent exhaust passage 452 is raised at the time of passage of the gas passage 453a, and the high ejector effect is exhibited.

  On the other hand, in the fourth embodiment, when the valve is fully opened, the exhaust flow state in the exhaust manifold 450 is set to the second state. That is, when the valve is fully opened, the exhaust discharged from each cylinder 2 flows into the corresponding independent exhaust passage 452, and then is branched to the other independent exhaust passage 452 via the communication passage 455. The exhaust gas includes two gas passages 453a corresponding to the two independent exhaust passages 452, passes through a passage having a larger flow path area than the first state, and flows into the nozzle portion 58a. And by setting it as this state, the speed of the exhaust_gas | exhaustion discharged | emitted from each independent exhaust passage 452 is weakened, and the ejector effect is weakened.

  Thus, in the fourth embodiment, the state of the exhaust manifold 450 is changed between the first state and the second state by opening and closing the valve and changing the communication state of the plurality of independent exhaust passages 452. The

(7-4) Fifth Embodiment Further, the configuration shown in FIG. 23 may be used as a configuration for changing the flow state of the exhaust gas in the exhaust manifold.

  In the engine according to the fifth embodiment shown in FIG. 23, as in the first embodiment, the exhaust manifold 550 is provided with the independent exhaust passage 52, the throttle portion 553, the nozzle portion 558a, the mixing portion 558b, and the diffuser portion 558c. It has been. On the other hand, in this engine, unlike the first embodiment, the flow passage area of each gas passage 553a formed in the throttle portion 553 cannot be changed. Further, each of the independent exhaust passages 52 extends from the middle of the independent exhaust passage 52 to the common exhaust passage 550a, which is a portion downstream of the throttle portion 553, connects the independent exhaust passage 52 and the common exhaust passage 550a, and bypasses the throttle portion 553. A bypass passage 555 is provided. Each bypass passage 555 is provided with a bypass valve (bypass passage opening / closing means) 555a for opening and closing these bypass passages 555. Here, in the fifth embodiment, each bypass passage 555 is connected to the upstream end of the casing 61 of the catalyst device 60 in the common exhaust passage 550a.

  Specifically, the throttle portion 553 is composed only of a cylindrical member in which a plurality of gas passages 553a whose flow area decreases toward the downstream side are formed inside. Each gas passage 553a is individually connected to each independent exhaust passage 52. In the present embodiment, as in the first embodiment, three independent exhaust passages 52 are provided, and three gas passages 553a are provided in the throttle portion corresponding to these. These three gas passages 553a are arranged on the circumference like the first gas passages of the first embodiment.

  In the fifth embodiment, the bypass valve 555a is fully closed, so that the exhaust circulation state in the exhaust manifold 550 is set to the first state. That is, when the bypass valve 555a is fully closed, all the exhaust discharged from each cylinder 2 flows into the gas passage 553a whose flow area is set smaller toward the downstream without being diverted to the bypass passage 555 side. Will do. And in this 5th Embodiment, by setting it as this state, the speed of the exhaust_gas | exhaustion discharged | emitted from each independent exhaust passage 52 is raised at the time of passage of the gas passage 553a, and a high ejector effect is exhibited. .

  On the other hand, in the fifth embodiment, the bypass valve 555a is fully opened, so that the exhaust circulation state in the exhaust manifold 550 is set to the second state. Specifically, when the bypass valve 555a is fully opened, the exhaust discharged from each cylinder 2 flows into the corresponding independent exhaust passage 52 and then into the gas passage 553a and the bypass passage 555 in the throttle portion 553. It flows separately and then merges at the upstream end of the casing 61 of the catalyst device 60. Therefore, the flow passage area of the passage through which the entire exhaust in each independent exhaust passage 52 flows into the common exhaust passage 550a, that is, the nozzle portion 558a and the casing 61, is the flow passage of the gas passage 553a in the throttle portion 553. The total area of the area and the flow passage area of the bypass passage 555, and the flow passage area of the passage passage is larger than that in the first state.

  In this way, in the fifth embodiment, the bypass valve 555a is opened and closed, and the bypass passage 555 is switched between closed and open, so that the exhaust circulation state in the exhaust manifold 50 is in the first state and the second state. And changed.

(7-5) Other Embodiments In the above embodiment, the case where the HCCI combustion mode is implemented in the entire first operation region A1 has been described. However, in the region where the engine speed is high, the endothermic time of the fuel is obtained. Therefore, proper compression self-ignition combustion may be difficult. Therefore, in such a case, the HCCI combustion mode is performed only in the low speed region of the first operation region A1, and other combustion modes (for example, SI combustion or self-ignition of the air-fuel mixture by spark ignition are performed in the high speed region. Combustion configured to be facilitated) may be performed.

  Further, spark ignition combustion may be performed in the second operation region A2. Here, at the time of cold start, in order to increase the combustion temperature to improve the heating performance and to activate the catalyst early, this second operation is performed even when spark ignition combustion is performed in the second operation region A2. It is preferable to perform control to ensure a large amount of internal EGR gas in the combustion chamber 6 in the region A2. Therefore, even when spark ignition combustion is performed in the second operation region A2, as in the first embodiment, in the second operation region A2, the exhaust double opening control is executed and the exhaust gas in the exhaust manifold 50 is circulated. Let the state be the second state. Thereby, a large amount of internal EGR gas in the combustion chamber 6 can be secured in the second operation region A2, and the combustion temperature can be increased.

  Further, in the above embodiment, the fuel injection timing and ignition timing in each operation region are illustrated using FIGS. 14 and 16, but these are only examples, and the fuel injection timing and ignition timing are those of the engine. It can be appropriately changed depending on the characteristics and the like.

  In the above embodiment, the G / F is controlled to 30 or more in the lean HCCI combustion mode. However, the theoretical air-fuel ratio λ is controlled instead of G / F, and this theoretical air-fuel ratio is set to λ = 2 or more. You may implement control to.

2 cylinders 10 exhaust ports 11 intake valves 12 exhaust valves 16 VVT (valve drive means)
17 VVL (Valve drive means)
50 Exhaust manifold 50a Common exhaust passage 52 Independent exhaust passage 53 Throttle portion 55f Slide actuator (passage state changing means)
100 ECU (control means)

Claims (7)

A multi-cylinder engine having a plurality of cylinders each having a combustion chamber, an intake port, and an exhaust port, each having an intake valve capable of opening and closing the intake port and an exhaust valve capable of opening and closing the exhaust port There,
Independent exhaust passages respectively connected to exhaust ports of one cylinder or a plurality of cylinders whose exhaust sequences are not continuous with each other, and exhaust gas that is provided downstream of each independent exhaust passage and passes through each independent exhaust passage is inside An exhaust manifold including a common exhaust passage gathering at
The exhaust gas in the exhaust manifold is circulated so that negative pressure is generated in the other independent exhaust passages due to the ejector effect as the exhaust gas in each independent exhaust passage flows into the common exhaust passage. A first state in which the exhaust in each independent exhaust passage flows into the common exhaust passage individually through passages that are close to each other and whose flow path area decreases toward the downstream side; and the exhaust in each independent exhaust passage Passage state changing means capable of changing to a second state that passes through a passage having a larger flow area than the first state and flows into the common exhaust passage;
Valve driving means capable of driving the intake valve and the exhaust valve;
Control means capable of controlling the operation of the intake valve and the exhaust valve, the operation of the passage state changing means, and the operation of the valve driving means,
The valve driving means is capable of executing and stopping a restart valve operation for opening the exhaust valve again in the intake stroke in addition to the valve opening operation in the exhaust stroke.
The control means includes
In the high not the first operation region than the predetermined reference load load engine is set in advance, said stopping the restarting valve operated by valve driving means, the flow of exhaust in the exhaust manifold by the passage state changing means One of the cylinders between the cylinders in which the opening state of the intake valve and the opening period of the exhaust valve of each cylinder overlap with each other with a predetermined overlap period and the exhaust sequence continues is set to the first state. While driving the intake valve and the exhaust valve of each cylinder by the valve driving means so that the overlap period overlaps with the timing when the exhaust valve of the other cylinder is opened,
At low There second operating region than the load of the engine is pre-Symbol reference load, with to execute the resuming valve operated by said valve drive means, the distribution state of the exhaust in the exhaust manifold by the passage state changing means A multi-cylinder engine characterized by being in a second state. The multi-cylinder engine according to claim 1,
An injector for injecting at least a portion of gasoline fuel into the combustion chamber;
A multi-cylinder engine in which a self-ignition combustion mode in which the air-fuel mixture in the combustion chamber burns by self-ignition is executed in the second operation region. The multi-cylinder engine according to claim 1 or 2,
The exhaust manifold is interposed between a downstream end of each independent exhaust passage and the common exhaust passage, and a plurality of gas passages into which exhaust exhausted from the downstream end of each independent exhaust passage flows independently. Has a throttle part formed inside,
The passage state changing means can change the flow passage area of each gas passage, and by changing the flow passage area, the exhaust gas in each independent exhaust passage passes before flowing into the common exhaust passage. The multi-cylinder engine is characterized in that the flow area of the passage to be changed is changed to change the flow state of the exhaust gas in the exhaust manifold between the first state and the second state. The multi-cylinder engine according to claim 3,
Each gas passage includes a first passage extending from a downstream end of each independent exhaust passage to the common exhaust passage and individually communicating with each independent exhaust passage, and each first passage and the common exhaust passage. A second passage that communicates,
The multi-cylinder engine characterized in that the passage state changing means changes the flow area of each gas passage by changing a communication amount between the first passage and the second passage. The multi-cylinder engine according to claim 3,
Each gas passage includes a first passage extending from a downstream end of each independent exhaust passage to the common exhaust passage and individually communicating with each independent exhaust passage, and each first passage and the common exhaust passage. A second passage that communicates,
The passage state changing means changes the flow passage area of each gas passage by changing the flow passage area of the second passage. The multi-cylinder engine according to claim 1 or 2,
The exhaust manifold is provided in the middle of each of the independent exhaust passages so as to communicate the plurality of independent exhaust passages with a throttle portion interposed between the downstream end of each of the independent exhaust passages and the common exhaust passage. A communication state changing means capable of changing a communication state between the independent exhaust passages through the passage and the communication passage;
A plurality of gas passages having a shape in which the flow passage area decreases toward the downstream side inside the throttle portion and exhaust gas discharged from the downstream ends of the independent exhaust passages flows independently. Is formed,
The passage state changing means does not cause the independent exhaust passages to communicate with each other by the communication state changing means, and the exhaust in each of the independent exhaust passages individually passes through the gas passage in the throttle portion. The exhaust gas distribution state in the exhaust manifold is changed to the first state, the independent exhaust passages are communicated with each other by the communication state changing means, and the exhaust in each independent exhaust passage passes through the plurality of gas passages in the throttle portion. The multi-cylinder engine is characterized in that the passage state of the exhaust gas in the exhaust manifold is changed to the second state by setting the passage state. The multi-cylinder engine according to claim 1 or 2,
The exhaust manifold includes a throttle portion interposed between a downstream end of each independent exhaust passage and the common exhaust passage, and a bypass that bypasses the throttle portion by connecting each independent exhaust passage and the common exhaust passage. A passage and a bypass passage opening and closing means capable of opening and closing the bypass passage,
A plurality of gas passages having a shape in which the flow passage area decreases toward the downstream side inside the throttle portion and exhaust gas discharged from the downstream ends of the independent exhaust passages flows independently. Is formed,
The passage state changing means closes the bypass passage by the bypass passage opening / closing means so that the exhaust in each independent exhaust passage individually passes through the gas passage in the throttle portion, thereby While the exhaust state in the manifold is changed to the first state, the bypass passage is opened by the bypass passage opening / closing means, and the exhaust in each independent exhaust passage is added to the gas passage in the throttle portion and the bypass. A multi-cylinder engine characterized in that the exhaust gas in the exhaust manifold is brought into the second state by passing through the passage.

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