JP6548571B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine mounted on a vehicle or the like.

While reducing the emissions of the combustion temperature to reduce the by NO _x of the mixture in the cylinders, exhaust gas recirculation to reduce the pumping loss (Exhaust Gas Recirculation) is a device known. The EGR device is configured to recirculate the combustion gas generated in the cylinder, that is, the exhaust gas, to the intake passage via the EGR passage and mix it with the intake air.

  Recently, in order to further improve the fuel efficiency, a specific cylinder of the cylinders contained in the internal combustion engine is designated as an EGR dedicated cylinder, and the exhaust port of the cylinder and the intake passage are connected by the EGR passage. It has been attempted to recirculate the entire amount of exhaust gas discharged from the cylinder to the intake passage (see, for example, the following patent documents).

U.S. Pat. No. 8,291,891

  In a multi-cylinder, large displacement internal combustion engine, even if a specific cylinder is a cylinder dedicated to EGR, the exhaust turbocharger is operated using exhaust gas discharged from the other cylinders. Output can be obtained.

  However, for small displacement three-cylinder engines, etc., the exhaust turbocharger should function sufficiently during high load operation or wide open throttle operation by using a specific cylinder for EGR only. There is a concern that the required output performance can not be achieved.

  The present invention, which has been made for the first time focusing on the above points, aims to realize an internal combustion engine capable of obtaining a high output when necessary, while making a specific cylinder a cylinder dedicated to EGR.

In the present invention, an EGR passage can be connected to the exhaust passage of a specific cylinder or cylinders and the intake passage, and the entire exhaust gas discharged from the cylinder can be recirculated to the intake passage as EGR gas, and the EGR passage The EGR valve capable of opening and closing the valve, the exhaust port of a cylinder other than the specific cylinder and the exhaust turbine of the exhaust turbocharger can be connected to allow the exhaust gas discharged from the cylinder to flow into the exhaust turbine An exhaust passage, a communication passage connecting the EGR passage and the exhaust passage, and a control valve capable of opening and closing the communication passage, the length of the open period of the exhaust valve of the specific cylinder or valve lift amount, the rather smaller than the length or the valve lift amount of the valve opening period of the exhaust valves of the cylinders other than the specific cylinder, in the operating region of the middle load Fully close the control valve and open the EGR valve, reduce the opening degree of the EGR valve in the high load or full load operation area or close the open valve than the medium load operation area, and open the control valve. An internal combustion engine that opens the control valve and fully closes the EGR valve in the low load operating region .

  According to the present invention, it is possible to realize an internal combustion engine that can obtain a high output when necessary, while using a specific cylinder as a cylinder dedicated to EGR.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows typically the structure of the internal combustion engine of one Embodiment of this invention. FIG. 7 is a view showing transition of the opening degree of the exhaust valve of each cylinder in the internal combustion engine of the same embodiment. FIG. 3 is a view showing a cam profile of an exhaust cam that drives an exhaust valve of each cylinder in the internal combustion engine of the same embodiment.

  One embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of a vehicle internal combustion engine in the present embodiment. The internal combustion engine of the present embodiment is a spark-ignition four-stroke engine, and includes a plurality of cylinders 11, 12, 13. The internal combustion engine in the illustrated example is a three-cylinder engine. In the vicinity of the intake port of each of the cylinders 11, 12, 13, an injector (not shown) for injecting fuel is provided. Further, a spark plug (not shown) is attached to the ceiling of the combustion chamber of each of the cylinders 11, 12, 13. The spark plug is for inducing spark discharge between the center electrode and the ground electrode in response to application of an induction voltage generated in the ignition coil. The ignition coil is integrally incorporated in a coil case together with an igniter which is a semiconductor switching element.

  An intake passage 3 for supplying intake air takes in air from the outside and leads it to the intake port of each of the cylinders 11, 12, 13. An air cleaner 31, a compressor 51 of an exhaust turbocharger 5, an intercooler 35, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are disposed in this order from the upstream on the intake passage 3.

  The exhaust passage 4 for discharging the exhaust leads the exhaust generated as a result of burning the fuel in the cylinders 12 and 13 from the exhaust port of each of the cylinders 12 and 13 to the outside. An exhaust manifold 42, an exhaust turbine 52 of the exhaust turbocharger 5 and a three-way catalyst 41 for exhaust purification are disposed on the exhaust passage 4.

  The specific cylinder 11 of the cylinders 11, 12, 13 included in the internal combustion engine of the present embodiment is a cylinder dedicated to EGR that supplies EGR gas to be mixed with the intake air. The exhaust passage 4 is not connected to the cylinder 11, and instead, the EGR passage 2 is connected. The EGR passage 2 guides the exhaust generated as a result of burning the fuel in a specific cylinder 11 dedicated to EGR from the exhaust port of the cylinder 11 to the intake passage 3. The outlet of the EGR passage 2 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3, specifically to a surge tank 33. An EGR cooler 21 and an EGR valve 22 are provided on the EGR passage 2. It is preferable to take measures against acid and alkali in the EGR cooler 21. The EGR valve 22 opens and closes the EGR passage 2 to control the flow rate of the EGR gas flowing through the EGR passage 2.

  In addition, in the internal combustion engine of the present embodiment, the communication passage 6 connecting the EGR passage 2 and the exhaust passage 4 is provided, and the control valve 61 is provided on the communication passage 6. The control valve 61 opens and closes the communication passage 6 to control the flow rate of the exhaust gas flowing through the communication passage 6.

  The exhaust turbocharger 5 is configured such that the exhaust turbine 52 and the impeller of the compressor 51 are coaxially connected via a shaft 53 and interlocked. Then, the energy of the exhaust gas flowing into the exhaust turbine 52 from the exhaust passage 4 is used to rotationally drive the turbine 52 and the impeller of the compressor 51, and the compressor 51 exerts a pumping action with that rotational force to take intake air. Pressurize and compress (supercharge) and feed to cylinders 11, 12, 13.

  An ECU (Electronic Control Unit) 0 that controls the operation of the internal combustion engine according to the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface includes the vehicle speed signal a output from the vehicle speed sensor that detects the actual vehicle speed of the vehicle, the crank angle signal b output from the engine rotation sensor that detects the rotation angle of the crankshaft and the engine speed, and stepping on the accelerator pedal The accelerator opening signal c output from the sensor that detects the amount or the opening of the throttle valve 32 as the accelerator opening (in other words, the required engine load), and the brake depression output from the sensor that detects the depression amount of the brake pedal Amount signal d, intake temperature / intake pressure signal e output from an intake temperature / intake pressure sensor for detecting intake temperature and intake pressure (supercharging pressure) in the intake passage 3 (particularly, the surge tank 33); The coolant temperature signal f output from the coolant temperature sensor that detects the coolant temperature, and the cam angle sensor output at a plurality of cam angles of the intake camshaft A cam angle signal g that is, battery current / voltage signal h or the like which is output from the sensor for detecting the terminal current and / or the terminal voltage of the vehicle battery is input.

  From the output interface, the ignition signal i to the igniter of the ignition plug, the fuel injection signal j to the injector, the opening operation signal k to the throttle valve 32, the opening operation signal l to the EGR valve 22, control An opening operation signal m or the like is output to the valve 61.

  The processor of the ECU 0 interprets and executes a program stored in advance in the memory, calculates operating parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, h necessary for the operation control of the internal combustion engine through the input interface, and obtains the engine rotational speed, as well as the cylinders 11, 12, 13 Estimate the amount of intake air filled in the The required fuel injection amount, fuel injection timing (including the number of fuel injections per one combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR), based on the engine speed and intake amount etc. Determines various operation parameters such as The ECU 0 applies various control signals i, j, k, l, m corresponding to the operation parameters via the output interface.

  In the present embodiment, the air-fuel ratio of the air-fuel mixture supplied to the specific cylinder 11 dedicated to EGR is made richer than the stoichiometric air-fuel ratio. On the other hand, the air-fuel ratio of the air-fuel mixture supplied to the other cylinders 12 and 13 is controlled to the theoretical air-fuel ratio or its vicinity (leaner than the air-fuel ratio of the air-fuel mixture supplied to the EGR dedicated cylinder 11). . Therefore, the amount of fuel injected from the injector associated with the EGR dedicated cylinder 11 is made larger than the amount of fuel injected from the injectors associated with the other cylinders 12 and 13.

  Furthermore, as shown in FIG. 2, the opening period (represented by a broken line) of the exhaust valve of the EGR dedicated cylinder 11 is shorter than the opening period (represented by a solid line) of the exhaust valves of the other cylinders 12 and 13. Do. Therefore, as shown in FIG. 3, an exhaust cam for driving the exhaust valve of the other cylinders 12 and 13 is used for the cam operating angle θ of the exhaust cam (represented by a broken line) for driving the exhaust valve of the cylinder 11 exclusively for EGR. The angle is narrower than the cam operating angle θ ′ (represented by a solid line).

  As a result, the exhaust gas discharged from the EGR dedicated cylinder 11 to the EGR passage 2 becomes higher in temperature and pressure than the exhaust gas discharged from the other cylinders 12 and 13 to the exhaust passage 4. Therefore, when the control valve 61 is opened to open the communication passage 6, exhaust gas flows from the EGR passage 2 into the exhaust passage 4.

  The ECU 0 according to the present embodiment fully closes the control valve 61 and opens the EGR valve 22 in a situation where the EGR rate should be increased by mixing the EGR gas as much as possible into the intake air, for example, in a medium load operating region. The entire exhaust gas discharged from the cylinder 11 dedicated to EGR flows into the intake passage 3 via the EGR passage 2. This can reduce the fuel consumption and also reduce the pumping loss.

  On the other hand, in a situation where the EGR rate is to be reduced, for example, in a high load or full load operating range, the control valve 61 is opened, and if necessary, the opening degree of the EGR valve 22 is reduced or totally closed. A part or all of the exhaust gas discharged from the cylinder 11 of the engine 1 flows into the exhaust turbine 52 via the EGR passage 2, the communication passage 6 and the exhaust passage 4. This makes it possible to achieve the required engine power.

  Further, during the low load operation region or idle operation, the control valve 61 is opened and the EGR valve 22 is fully closed so that the EGR gas does not mix in the intake air flowing through the intake passage 3.

  In the present embodiment, the EGR passage 2 can connect the exhaust port of a specific cylinder 11 and the intake passage 3 and can recirculate the entire exhaust gas discharged from the cylinder 11 to the intake passage 3 as EGR gas, and Exhaust ports that connect exhaust ports of the cylinders 12 and 13 other than the specific cylinder 11 and the exhaust turbine 52 of the exhaust turbocharger 5 so that exhaust gas discharged from the cylinders 12 and 13 can flow into the exhaust turbine 52 A passage 4, a communication passage 6 connecting the EGR passage 2 and the exhaust passage 4, and a control valve 61 capable of opening and closing the communication passage 6, and the exhaust valve of the specific cylinder 11 The internal combustion engine was configured such that the length of the valve opening period is smaller than the length of the valve opening period of the exhaust valves of the cylinders 12 and 13 other than the specific cylinder 11.

  According to the present embodiment, it is possible to realize an internal combustion engine that can obtain a high output when necessary, while using a specific cylinder as a cylinder dedicated to EGR. The configuration of the internal combustion engine of the present embodiment is particularly suitable for a small displacement engine or a small number of cylinders.

  The present invention is not limited to the embodiments detailed above. For example, although the cylinder 11 dedicated to EGR is single in the above embodiment, two or more cylinders dedicated to EGR may exist. Also in this case, the exhaust ports of two or more cylinders dedicated to EGR and the intake passage are connected via the EGR passage, and the exhaust ports of the other cylinders and the exhaust turbine are connected via the exhaust passage, and The EGR passage and the exhaust passage are connected by the communication passage 6.

  As shown in FIG. 2, in place of or together with shortening the opening period of the exhaust valve of the cylinder 11 for EGR only than the opening period of the exhaust valves of the other cylinders 12, 13 as shown in FIG. The valve lift amount of the exhaust valve of the cylinder 11 (that is, the opening degree, represented by a chain line) may be smaller than the valve lift amount of the exhaust valves of the other cylinders 12 and 13 (represented by a solid line). For that purpose, as shown in FIG. 3, the cam lift L of the exhaust cam (represented by a chain line) for driving the exhaust valve of the EGR dedicated cylinder 11 and the exhaust cam for driving the exhaust valves of the other cylinders 12 and 13 It is smaller than the cam lift L of (represented by a solid line).

  The exhaust valve of the cylinder 11 exclusively for EGR and / or the exhaust valves of the other cylinders 12 and 13 are not necessarily driven to open and close by the exhaust cam. In the case of an internal combustion engine in which an electromagnetic solenoid valve is mounted as an exhaust valve, the valve opening period and / or the valve lift can be directly controlled by the ECU 0.

  The specific configurations of the other components can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to an internal combustion engine mounted on a vehicle or the like.

1 ... specific cylinder 1 ... cylinder other than specific cylinder 2 ... EGR passage 3 ... intake passage 4 ... exhaust passage 5 ... exhaust turbocharger 52 ... exhaust turbine 6 ... communication passage 61 ... control valve

Claims (1)

An EGR passage which connects an exhaust port of a specific one or more cylinders and an intake passage and can recirculate the entire exhaust gas discharged from the cylinder as an EGR gas to the intake passage;
An EGR valve capable of opening and closing the EGR passage;
An exhaust passage through which an exhaust port of a cylinder other than the specific cylinder and an exhaust turbine of an exhaust turbocharger are connected and exhaust gas discharged from the cylinder can flow into the exhaust turbine;
A communication passage connecting the EGR passage and the exhaust passage;
And a control valve capable of opening and closing the communication passage,
The length or the valve lift amount of the valve opening period of the exhaust valve of a particular cylinder, rather smaller than the length or the valve lift amount of the valve opening period of the exhaust valves of the cylinders other than the specific cylinder,
In the medium load operating range, fully close the control valve and open the EGR valve,
In the high load or full load operating range, the control valve is opened by reducing or closing the EGR valve opening than the medium load operating range.
An internal combustion engine that opens the control valve and fully closes the EGR valve in the low load operating region .

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