JP2013002371A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine capable of stabilizing the combustion in the transient period where the engine rotation or the vehicle speed decelerates.SOLUTION: A curved section 35 is formed upstream of a compressor 51 in a suction passage 3, and an outlet from a low-pressure loop EGR passage 2 is connected with a part directly after the curved section 35 and facing the inside portion of the curved flow passage. The new gas flowing in the suction passage 3 undergoes exfoliation when it passes the curved section 35. Directly after the curved section 35, the inner peripheral portion of the flow passage becomes at negative pressure. Through utilization thereof, circulation of the EGR gas back to the suction passage 3 is promoted.

Description

  The present invention relates to an internal combustion engine with an exhaust gas recirculation device.

While reducing the emissions of the combustion temperature to reduce the by NO _x cylinders, a EGR device known to reduce the pumping loss. The EGR device connects an exhaust path and an intake path via an EGR passage, and part of combustion gas generated in the cylinder is recirculated to the intake path via the EGR path and mixed into the intake air.

  A low-pressure loop EGR recirculates exhaust gas that has passed through a turbine of an exhaust turbocharger and an exhaust gas purification catalyst to the intake passage (see, for example, Patent Document 1 below). The low pressure loop EGR is advantageous in that a large amount of EGR gas can be mixed into the intake air. On the other hand, the low-pressure loop EGR gas is a low-pressure and low-temperature gas close to the atmospheric pressure, and it is difficult to recirculate the EGR gas when the pressure of fresh air in the intake passage is high.

  Conventionally, an intake throttle valve is provided upstream of the outlet of the EGR passage in the intake passage, and the intake throttle valve is throttled to create a negative pressure around the outlet of the EGR passage to recirculate the EGR gas. It was.

JP 2011-089470 A

  An object of the present invention is to recirculate EGR gas more smoothly to an intake passage in a low-pressure loop EGR system.

  In the present invention, an EGR passage that communicates a turbine provided in the exhaust passage, a compressor provided in the intake passage and driven by the turbine, and a downstream side of the turbine in the exhaust passage and an upstream side of the compressor in the intake passage. And an exhaust gas recirculation device provided with an EGR valve provided in the EGR passage, wherein a curved portion is formed on the upstream side of the compressor in the intake passage, and immediately after the curved portion. The internal combustion engine is characterized in that the outlet of the EGR passage is connected to a portion facing the inner peripheral side (in other words, the corner of entry) of the curved flow path.

  Immediately after the curved portion of the intake passage, a separation vortex is generated in the fresh air, and the inner peripheral side of the curved flow path becomes a lower pressure than the outer peripheral side (outside corner side). In the present invention, the outlet of the EGR passage is connected to a portion where the negative pressure is generated immediately after the curved portion of the intake passage to promote the recirculation of the EGR gas.

  According to the present invention, in the low-pressure loop EGR system, EGR gas can be more smoothly recirculated to the intake passage.

The figure which shows the whole structure of the internal combustion engine in one Embodiment of this invention. The figure which expands and shows the inlet passage of the internal combustion engine of the embodiment, its bending part, and the exit of an EGR passage. The figure which shows one of the modifications of this invention. The figure which shows the modification. The figure which shows one of the modifications of this invention. The figure which shows the modification. The figure which shows one of the modifications of this invention. The figure which shows the modification. The figure which shows one of the modifications of this invention.

  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 supplies a plurality of cylinders 1 (one of which is shown in FIG. 1), an injector 11 that injects fuel into each cylinder 1, and intake air to each cylinder 1. An intake passage 3 for exhausting exhaust from each cylinder 1, an exhaust turbocharger 5 for supercharging intake air flowing through the intake passage 3, and from the exhaust passage 4 toward the intake passage 3. And an external EGR device 2 for refluxing the EGR gas.

  The internal combustion engine in the present embodiment is a two-cylinder four-cycle engine, and there is a phase difference of 360 ° CA (crank angle) between the stroke of the first cylinder 1 and the stroke of the second cylinder 1. That is, the piston 12 of the first cylinder 1 and the piston 12 of the second cylinder 1 are simultaneously raised and simultaneously lowered.

  The intake passage 3 takes in air from the outside and guides it to the intake port of the cylinder 1. On the intake passage 3, an air cleaner 31, a compressor 51 of the supercharger 5, an intercooler 32, an electronic throttle valve 33, a surge tank 34, and an intake manifold 36 are arranged in this order from the upstream side.

  The exhaust passage 4 guides exhaust generated as a result of burning fuel in the cylinder 1 from the exhaust port of the cylinder 1 to the outside. An exhaust manifold 42, a drive turbine 52 for the supercharger 5, and a three-way catalyst 41 are disposed on the exhaust passage 4. In addition, an exhaust bypass passage 43 that bypasses the turbine 52 and a waste gate valve 44 that is a bypass valve that opens and closes the inlet of the bypass passage 43 are provided. The waste gate valve 44 is an electric waste gate valve that can be opened and closed by inputting a control signal l to the actuator, and a DC servo motor is used as the actuator.

  The exhaust turbocharger 5 is configured such that the drive turbine 52 and the compressor 51 are connected and linked in a coaxial manner. Then, the driving turbine 52 is rotationally driven by using the energy of the exhaust gas, and the compressor 51 is pumped by using the rotational force, whereby the intake air is pressurized and compressed (supercharged) and sent to the cylinder 1.

  The external EGR passage 2 realizes a so-called low pressure loop EGR. In the low-pressure loop EGR, low-pressure exhaust gas close to atmospheric pressure is recirculated to the intake passage 3 through the EGR passage 2. The pressure loss in the low-pressure loop EGR passage 2 is as small as several hundred Pa. An EGR cooler 21 and an EGR valve 22 are provided on the external EGR passage 2. The inlet of the external EGR passage 2 is connected to a predetermined location downstream of the three-way catalyst 41 in the exhaust passage 4.

  The outlet of the external EGR passage 2 is connected to a predetermined location downstream of the air cleaner 31 and upstream of the compressor 51 in the intake passage 3. As shown in FIG. 1 and FIG. 2 (illustration of the EGR valve 22 is omitted in FIG. 2 and thereafter), in this embodiment, a curved portion 35 is formed in the region of the intake passage 3. Immediately after the curved portion 35, the outlet of the EGR passage 2 is connected.

  The fresh air flowing through the intake passage 3 causes separation when passing through the curved portion 35. In the figure, the portion where the air flow is separated is indicated by halftone dots. Immediately after the curved portion 35, a separation vortex is generated on the inner circumference (inner circumference, entry corner) side of the curved flow path, so that the inner circumference side of the flow path is larger than the outer circumference side (that is, more than atmospheric pressure). ) Low pressure. By utilizing this, in the present embodiment, the outlet of the EGR passage 2 is connected to a portion that becomes negative pressure due to separation of the air flow immediately after the bending portion 35, that is, a portion that faces the inner peripheral side of the curved flow path, The return of EGR gas to the intake passage 3 is promoted. The degree of negative pressure resulting from the separation of the airflow increases as the curvature radius of the curved portion 35 decreases.

  An ECU (electronic control unit) 0 that controls operation of the internal combustion engine is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like. The input interface outputs a vehicle speed signal a output from a vehicle speed sensor that detects the vehicle speed, a rotation speed signal b output from a rotation speed sensor that detects the engine rotation speed, and an accelerator sensor that detects the amount of depression of the accelerator pedal. An accelerator opening signal c, a temperature / pressure signal d output from a temperature / pressure sensor that detects intake air temperature and intake pressure (supercharging pressure) in the intake passage 3 (particularly, the surge tank 34), and cooling of the internal combustion engine A coolant temperature signal e output from a water temperature sensor for detecting the water temperature, a crank angle signal and cylinder discrimination signal f output from a timing sensor at the end of the intake camshaft, and a timing sensor at the end of the exhaust camshaft An exhaust cam signal g or the like output every rotation of a predetermined crank angle is input. From the output interface, the fuel injection signal h for the injector 11, the ignition signal i for the ignition plug (ignition coil thereof), the opening operation signal j for the EGR valve 22, and the opening operation for the throttle valve 33. An opening operation signal l and the like are output to the signal k and the waste gate valve 44. The amount of depression of the accelerator pedal can be considered as a required load (engine output) commanded by the driver.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, and g necessary for operation control of the internal combustion engine via the input interface, and based on them, the intake air amount, the required fuel injection amount, the ignition timing, A required EGR rate (or EGR amount) or the like is calculated. Then, various control signals h, i, j, k, and l corresponding to the calculation result are applied through the output interface. Since the calculation method of the control inputs h, i, j, k, and l can be the same as the operation control of a known internal combustion engine, a detailed description is omitted.

  In the present embodiment, a turbine 52 provided in the exhaust passage 4, a compressor 51 provided in the intake passage 3 and driven by the turbine 52, a downstream side of the turbine 52 in the exhaust passage 4, and the compressor in the intake passage 3. 51 is an internal combustion engine attached with an EGR device including an EGR passage 2 communicating with the upstream side of 51 and an EGR valve 22 provided in the EGR passage 2, and in the intake passage 3 upstream of the compressor 51. An internal combustion engine characterized in that a curved portion 35 is formed, and an outlet of the EGR passage 2 is connected to a portion facing the inner peripheral side of the curved flow path immediately after the curved portion 35.

  According to this embodiment, the low pressure EGR gas close to the atmospheric pressure is recirculated to the intake passage 3 at a low cost with a simple structure using the negative pressure resulting from the separation of fresh air passing through the curved portion 35. Can do. The fresh air separation phenomenon becomes particularly noticeable in an internal combustion engine having a small number of cylinders (two cylinders or a single cylinder) having a large intake pulsation and its maximum flow velocity, and a larger amount of EGR gas can be mixed into the intake air. Contributes to improvement of exhaust gas and purification of exhaust gas. Furthermore, it is not necessary to install an intake throttle valve in the intake passage 3 upstream of the outlet of the EGR passage 2.

  The present invention is not limited to the embodiment described in detail above. In the above embodiment, the portion of the intake passage 3 downstream from the curved portion 35 and the EGR passage 2 connected to the portion are substantially orthogonal to each other, but FIG. 3 and FIG. 4 (FIG. 3 is a front view, FIG. Is a plan view), or FIG. 5 and FIG. 6 (FIG. 5 is a front view, FIG. 6 is a plan view), the intake passage 3 and the EGR passage 2 are not orthogonally crossed and the fresh air flowing through the intake passage 3 The angle formed by the flow direction and the flow direction of the EGR gas flowing through the EGR passage 2 may be made smaller than a right angle.

  Further, as shown in FIGS. 7 and 8 (FIG. 7 is a perspective view and FIG. 8 is a plan view), the cross section of the intake passage 3 in the curved portion 35 and the portion 37 immediately before and the portion 38 immediately after the curved portion 35 is replaced with other portions. You may shape | mold in the flat shape of an unusual shape from a cross section, for example, an ellipse, an ellipse, a rectangle. That is, for the portion 37 immediately before the curved portion 35, the inner dimension L1 along the extending direction of the flow path of the immediately subsequent portion 38 is made longer than the inner dimension L2 in the direction orthogonal to the direction. And about the site | part 38 immediately after the curved part 35, the internal dimension L3 along the extending direction of the flow path of the front site | part 37 is made longer than the internal dimension L4 of the direction orthogonal to the said direction. Thereby, the fresh air peeling phenomenon in the part immediately after the bending part 35 can be strengthened.

  In addition, as shown in FIG. 9 (FIG. 9 is a plan view), the vicinity of the outlet of the EGR passage 2 is once branched and then joined again, and connected to a portion 38 immediately after the curved portion 35 of the intake passage 3. It doesn't matter.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

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

2 ... EGR passage 22 ... EGR valve 3 ... Intake passage 35 ... Curved portion 4 ... Exhaust passage 51 ... Compressor 52 ... Turbine

Claims (1)

A turbine provided in the exhaust passage;
A compressor provided in the intake passage and driven by the turbine;
An EGR passage communicating the downstream side of the turbine in the exhaust passage and the upstream side of the compressor in the intake passage;
An internal combustion engine attached with an exhaust gas recirculation device comprising an EGR valve provided in the EGR passage,
An internal combustion engine characterized in that a curved portion is formed on the upstream side of the compressor in the intake passage, and an outlet of the EGR passage is connected to a portion facing the inner peripheral side of the curved flow path immediately after the curved portion. organ.

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