JP2017115811A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an internal combustion engine which can obtain a high output if necessary while making a specified cylinder act as an EGR-exclusive cylinder.SOLUTION: An internal combustion engine comprises: an EGR passage which connects an exhaust port and an intake port of a specified cylinder to each other, and can make an entire volume of an exhaust gas which is discharged from the cylinder flow back to an intake passage as an EGR gas; an exhaust passage which connects an exhaust port of a cylinder other than the specified cylinder and an exhaust turbine of a turbocharger, and can make the exhaust gas which is discharged from the cylinder flow into the exhaust turbine; a communication passage for connecting the EGR passage and the exhaust passage; and a control valve which can open and close the communication passage. A length of a valve-opening period or a valve lift amount of the exhaust valve of the specified cylinder is set shorter than or smaller than those of a valve-opening period of the exhaust valve of the cylinder other than the specified cylinder.SELECTED DRAWING: Figure 1

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. In the EGR device, combustion gas generated in a cylinder, that is, exhaust gas, is recirculated to an intake passage via an EGR passage and mixed with intake air.

  Recently, with the aim of further improving fuel efficiency, a specific cylinder of the cylinders included in the internal combustion engine is used as a dedicated EGR cylinder, and the exhaust port of the cylinder and the intake passage are connected by an EGR passage. Attempts have been made to recirculate the entire amount of exhaust gas discharged from the cylinders to the intake passage (see, for example, the following patent document).

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

  In a multi-cylinder and large-displacement internal combustion engine, even if a specific cylinder is a cylinder dedicated to EGR, the exhaust turbocharger is operated using exhaust gas exhausted from other cylinders. It is possible to obtain a simple output.

  However, in a three-cylinder engine with a small displacement and the like, a specific cylinder is a cylinder dedicated to EGR, so that the exhaust turbocharger can function sufficiently and sufficiently during a high load operation or a full load (Wide Open Throttle) operation. Therefore, there is a concern that the required output performance cannot be achieved.

  The present invention, which has been focused on for the first time, aims at realizing an internal combustion engine that can obtain a high output when necessary while a specific cylinder is a cylinder dedicated to EGR.

  In the present invention, an EGR passage that connects an exhaust port of one or more cylinders to an intake passage and can recirculate the entire amount of exhaust gas discharged from the cylinder as EGR gas to the intake passage; An exhaust passage that connects an exhaust port of a cylinder other than the cylinder and an exhaust turbine of the exhaust turbocharger and allows exhaust gas discharged from the cylinder to flow into the exhaust turbine, and the EGR passage and the exhaust passage A communication passage to be connected and a control valve capable of opening and closing the communication passage, and the length of the valve opening period or the valve lift amount of the specific cylinder is a cylinder other than the specific cylinder The internal combustion engine is configured to be smaller than the length of the exhaust valve opening period or the valve lift amount.

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

The figure which shows typically the structure of the internal combustion engine of one Embodiment of this invention. The figure which shows transition of the opening degree of the exhaust valve of each cylinder in the internal combustion engine of the embodiment. The figure which shows the cam profile of the exhaust cam which drives the exhaust valve of each cylinder in the internal combustion engine of the embodiment.

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

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

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

  A specific cylinder 11 among the cylinders 11, 12, and 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 intake air. The cylinder 11 is not connected to the exhaust passage 4 but is connected to the EGR passage 2 instead. The EGR passage 2 guides exhaust generated as a result of burning 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. The EGR cooler 21 is preferably provided with acid and alkali countermeasures. The EGR valve 22 opens and closes the EGR passage 2 and controls the flow rate of EGR gas flowing through the EGR passage 2.

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

  The exhaust turbo supercharger 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, by utilizing the energy of the exhaust gas flowing into the exhaust turbine 52 from the exhaust passage 4, the impeller of the turbine 52 and the compressor 51 is rotationally driven, and the compressor 51 is pumped with the rotational force to thereby reduce the intake air. Pressurize and compress (supercharge) and feed into cylinders 11, 12, and 13.

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

  The input interface includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from an engine rotation sensor that detects the rotation angle and engine speed of the crankshaft, and depression of an accelerator pedal. An accelerator opening signal c output from a sensor that detects the amount or the opening of the throttle valve 32 as an accelerator opening (in other words, a required engine load), and a brake pedal output from a sensor that detects the amount of depression of the brake pedal An amount signal d, an intake air temperature / intake pressure signal e output from an intake air temperature / intake pressure sensor for detecting intake air temperature and intake pressure (supercharging pressure) in the intake passage 3 (in particular, the surge tank 33), an internal combustion engine The coolant temperature signal f output from the coolant temperature sensor that detects the coolant temperature, and the cam angle sensor outputs the multiple 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, an ignition signal i for the ignition plug igniter, a fuel injection signal j for the injector, an opening operation signal k for the throttle valve 32, an opening operation signal l for the EGR valve 22, and 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 the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for controlling the operation of the internal combustion engine through the input interface, knows the engine speed, and cylinders 11, 12, 13. Estimate the amount of intake air to be filled. Based on the engine speed, the intake air amount, etc., the required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR rate) Various operating parameters such as volume). The ECU 0 applies various control signals i, j, k, l and 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 stoichiometric air-fuel ratio or in the vicinity thereof (lean compared to the air-fuel ratio of the air-fuel mixture supplied to the cylinder 11 dedicated to EGR). . Therefore, the amount of fuel injected from the injector attached to the cylinder 11 dedicated to EGR is made larger than the amount of fuel injected from the injector attached to the other cylinders 12 and 13.

  Further, as shown in FIG. 2, the opening period of the exhaust valve of the cylinder 11 dedicated for EGR (represented by a broken line) is shorter than the opening period of the exhaust valves of the other cylinders 12 and 13 (represented by the solid line). To do. Therefore, as shown in FIG. 3, the cam operating angle θ of the exhaust cam (represented by a broken line) that drives the exhaust valve of the cylinder 11 dedicated to EGR is set to the exhaust cam that drives the exhaust valves of the other cylinders 12 and 13. 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 of 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 as much amount of EGR gas as possible in the intake air, for example, in an intermediate load operation region. The exhaust gas exhausted from the cylinder 11 dedicated for EGR is entirely introduced into the intake passage 3 via the EGR passage 2. Thereby, fuel consumption can be reduced and a pumping loss is also reduced.

  On the other hand, in a situation where the EGR rate should be reduced, for example, in a high load or full load operation region, the control valve 61 is opened, and if necessary, the opening degree of the EGR valve 22 is reduced or fully closed. Part or all of the exhaust gas discharged from the cylinder 11 is caused to flow 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 output.

  Further, during the low-load operation region or idling operation, the control valve 61 is opened and the EGR valve 22 is fully closed so that EGR gas is not mixed into the intake air flowing through the intake passage 3.

  In the present embodiment, an EGR passage 2 that connects an exhaust port of a specific cylinder 11 and the intake passage 3 and can recirculate the entire amount of exhaust gas discharged from the cylinder 11 to the intake passage 3 as EGR gas; Exhaust gas that can 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 and allow exhaust gas discharged from the cylinders 12 and 13 to flow into the exhaust turbine 52. A passage 4, a communication passage 6 that connects the EGR passage 2 and the exhaust passage 4, and a control valve 61 that can open and close the communication passage 6. An internal combustion engine in which 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 is configured.

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

  The present invention is not limited to the embodiment described in detail above. For example, in the above embodiment, the EGR dedicated cylinder 11 is single, but there may be two or more EGR dedicated cylinders. In this case as well, the exhaust ports and intake passages of two or more cylinders dedicated to EGR are connected via the EGR passage, and the exhaust ports and exhaust turbines of the other cylinders are connected via the exhaust passage. The EGR passage and the exhaust passage are connected by a communication passage 6.

  As shown in FIG. 2, instead of or together with making the opening period of the exhaust valve of the cylinder 11 dedicated for EGR shorter than the opening period of the exhaust valves of the other cylinders 12 and 13, The valve lift amount of the exhaust valve of the cylinder 11 (that is, the opening degree, represented by a chain line) can be made smaller than the valve lift amount (represented by the solid line) of the other exhaust valves of the cylinders 12 and 13. For this purpose, as shown in FIG. 3, the cam lift L of the exhaust cam (represented by a chain line) that drives the exhaust valve of the cylinder 11 dedicated for EGR is replaced with the exhaust cam ( Smaller than the cam lift L (shown by a solid line).

  The exhaust valve of the cylinder 11 dedicated to EGR and / or the exhaust valves of the other cylinders 12 and 13 are not always opened and closed 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 amount can be directly controlled by the ECU 0.

  Other specific configurations of each part 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.

DESCRIPTION OF SYMBOLS 1 ... Specific cylinder 1 ... Cylinders other than a 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 one or more cylinders and an intake passage and can recirculate the entire amount of exhaust gas discharged from the cylinder as an EGR gas to the intake passage;
An exhaust passage for connecting an exhaust port of a cylinder other than the specific cylinder and an exhaust turbine of an exhaust turbocharger and allowing exhaust gas discharged from the cylinder to flow into the exhaust turbine;
A communication passage connecting the EGR passage and the exhaust passage;
A control valve capable of opening and closing the communication passage,
An internal combustion engine in which a length or valve lift amount of an exhaust valve of the specific cylinder is smaller than a length or valve lift amount of an exhaust valve of a cylinder other than the specific cylinder.

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