JP2017180154A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten as much as possible the length of a low pressure loop EGR passage at the time of assembling a low pressure loop EGR device into a second stage turbo engine.SOLUTION: An internal combustion engine comprises: an exhaust turbine 62 of a first turbocharger 6 for rotating in the response of the inflow of an exhaust gas; a compressor 61 of a first turbocharger driven by the exhaust turbine of the first turbocharger; an exhaust turbine 52 of a second turbocharger 5 disposed downstream of and below the exhaust turbine of the first turbo supercharger; a compressor 51 of the second supercharger driven by the exhaust turbine of the second turbocharger disposed upstream of and below the compressor of the first turbo supercharger in an intake passage 3 and compressing intake air; and a low-pressure loop EGR passage connecting a predetermined portion downstream of the exhaust turbine of the second turbo supercharger and a predetermined portion upstream of the compressor of the second turbo supercharger.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an internal combustion engine accompanied by an exhaust turbocharger and a low pressure loop EGR (Exhaust Gas Recirculation) device.

  As an internal combustion engine for vehicles, a turbo engine provided with an exhaust turbocharger is known. The turbocharger is configured such that a drive turbine disposed on the exhaust passage side of the internal combustion engine and a compressor disposed on the intake passage side are coaxially connected and interlocked. The remaining energy of the exhaust is used to rotate the turbine, and thus the compressor impeller (compressor wheel), and pump the compressor so that the intake air is compressed (supercharged) and sent to the cylinder. Can do.

  Recently, a two-stage turbo (sequential turbo) engine using two turbochargers with different capacities has been developed (see, for example, Patent Document 1 below). In an in-line two-stage turbo system, a turbocharger with a relatively large capacity and a turbocharger with a relatively small capacity are connected in series, and the former is used in the operating region where the engine speed is high to In the operating region where the engine speed is low, the latter is used to supercharge the intake air.

Further, while reducing the emissions of the combustion temperature is lowered by NO _x in the gas mixture in the cylinder, a EGR device known to reduce the pumping loss. In the EGR device, an exhaust path and an intake path are communicated with each other via an EGR passage, and a part of combustion gas generated in the cylinder is returned to the intake path via the EGR passage and mixed into the intake air.

  A low-pressure loop EGR is one that recirculates exhaust gas after passing through an exhaust turbine and an exhaust purification device of a turbocharger to an intake passage (see, for example, Patent Document 2 below). The low-pressure loop EGR is advantageous in that a relatively low temperature and a large amount of EGR gas can be mixed into the intake air.

International Publication WO2012 / 081062 Pamphlet JP 2014-087882 A

  When a low pressure loop EGR device is incorporated into a two-stage turbo engine, the low pressure loop EGR passage connecting the exhaust passage and the intake passage is inevitably long. As a specific example, the turbine and compressor of the first turbocharger are arranged in the vicinity of the cylinder head where the exhaust port and the intake port of each cylinder exist, and the turbine and compressor of the second turbocharger are arranged in the first turbocharger. Consider positioning it above the turbocharger. When the exhaust gas purification device for purifying the exhaust gas exiting the turbine of the second turbocharger is positioned at the height of the cylinder block or crankcase of the internal combustion engine, the outlet of the exhaust gas purification device is the second turbocharger Will be well below. For this reason, the piping of the low-pressure loop EGR passage must be routed from the downstream side of the exhaust purification device in the exhaust passage to the upstream side of the compressor of the second turbocharger in the intake passage. A long EGR path length leads to a decrease in the responsiveness and responsiveness of control of the EGR rate (the ratio of EGR gas to the intake air) of the intake air filled in the cylinder.

  Alternatively, even if the first turbocharger and the second turbocharger are positioned at the same height, the piping of the intake passage connecting the compressors of both turbochargers becomes longer, and only that much Since the EGR path length becomes long, the control of the intake EGR rate is also delayed.

  The present invention, which has been made paying attention to the above problems, aims to shorten the length of the low-pressure loop EGR passage as much as possible when the low-pressure loop EGR device is incorporated into the two-stage turbo engine.

  In the present invention, the exhaust turbine of the first turbocharger that rotates in response to the inflow of exhaust gas discharged from the cylinder, and the intake air that is driven by the exhaust turbine of the first turbocharger to fill the cylinder A compressor of the first turbocharger for compressing the first turbocharger, and located downstream of the exhaust turbine of the first turbocharger in the exhaust passage and below the exhaust turbine of the first turbocharger And an exhaust turbine of the second turbocharger that rotates in response to the inflow of exhaust gas, and an upstream of the compressor of the first turbocharger in the intake passage, and the first turbocharger A compressor of the second turbocharger, which is positioned below the compressor and driven by the exhaust turbine of the second turbocharger to compress the intake air, and the exhaust of the second turbocharger in the exhaust passage Of the turbine is constituted an internal combustion engine; and a low-pressure loop EGR passage which connects the predetermined portion of the upstream of the compressor of the second turbocharger downstream of the predetermined position and the intake passage.

  According to the present invention, it is possible to shorten the length of the low-pressure loop EGR passage when the low-pressure loop EGR device is incorporated into the two-stage turbo engine.

The figure which shows typically the structure of the internal combustion engine for vehicles of one Embodiment of this invention. The front view which shows the positional relationship of the exhaust gas turbocharger and exhaust gas purification device of the internal combustion engine of the embodiment. The side view which shows the positional relationship of the exhaust gas turbocharger and exhaust gas purification device of the internal combustion engine of the embodiment.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically 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 compression ignition type four-stroke engine such as a diesel engine or a HCCI (homogeneous-charge compression ignition) engine, and a plurality of cylinders 1 (one of which is shown in FIG. 1). Are shown). An injector 11 that directly injects fuel into the combustion chamber of the cylinder 1 is installed on the ceiling of the combustion chamber of each cylinder 1. Further, a glow plug (residual heat plug) 12 and a swirl control valve 13 are provided in the vicinity of the intake port of each cylinder 1.

  The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, a compressor 51 of the second turbocharger 5, a compressor 61 of the first turbocharger 6, a water-cooled 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 cylinder 1 from the exhaust port of each cylinder 1 to the outside. On this exhaust passage 4, an exhaust manifold 42, an exhaust turbine 62 of the first turbocharger 6, an exhaust turbine 52 of the second turbocharger 5, and an exhaust purification device 41 are arranged in this order from the upstream. doing. The exhaust emission control device 41 is a known device that includes a filter that removes particulate matter contained in the exhaust gas (Particulate Material) and a catalyst that promotes oxidation or reduction of harmful substances.

  The exhaust turbochargers 5 and 6 are configured such that the exhaust turbines 52 and 62 and the impellers of the compressors 51 and 61 are coaxially connected via a shaft and interlocked with each other. Then, the impellers of the turbines 52 and 62 and the compressors 51 and 61 are rotationally driven using the energy of the exhaust, and the compressor is pumped with the rotational force to compress and compress (supercharge) the intake air. Into cylinder 1.

  The internal combustion engine of the present embodiment is a so-called two-stage turbo (sequential turbo) engine including two turbochargers 5 and 6. The first turbocharger 6 is a low-speed turbocharger that works in an operation region where the engine speed is relatively low. On the other hand, the second turbocharger 5 is a high-speed turbocharger that works in an operation region where the engine speed is relatively high. The capacity of the low-speed turbocharger 6 is smaller than the capacity of the high-speed turbocharger 5.

  In the intake passage 3, an intake bypass passage 36 that bypasses the compressor 61 of the low-speed turbocharger 6 is provided, and a valve 37 that opens and closes the outlet of the intake bypass passage 36 is provided. The valve 37 controls the flow rate of intake air flowing through the intake bypass passage 36. There is no intake bypass passage that bypasses the compressor 51 of the high-speed turbocharger 5.

  Further, the exhaust passage 4 also includes an exhaust bypass passage 43 that bypasses the turbine 62 of the low-speed turbocharger 6, and an exhaust bypass passage 44 that bypasses the turbine 52 of the high-speed turbocharger 5, and Exhaust bypass valves 45 and 46 for opening and closing the respective inlets of the exhaust bypass passages 43 and 44 are provided. The valve 45 controls the flow rate of exhaust flowing through the exhaust bypass passage 43, and the valve 46 controls the flow rate of exhaust flowing through the exhaust bypass passage 44. The exhaust bypass valves 45 and 46 may be referred to as WGV (Waste Gate Valve).

  Valves 37 and 46 are VSV (Vaccum Switching Valve) using negative pressure actuators 371 and 461. The negative pressure actuators 371 and 461 are diaphragm actuators, and negative pressure and an elastic biasing force by a built-in spring are applied to one surface of the diaphragm, and atmospheric pressure is applied to the other surface. The negative pressure is supplied from the vacuum pump 91. The vacuum pump 91 generates a negative pressure having a certain magnitude. Electromagnetic solenoid valves 372 and 462 are installed on pipes connecting the diaphragm actuators 371 and 461 and the vacuum pump 91, respectively. The magnitude of the negative pressure that actually acts on one surface of the diaphragms of the diaphragm actuators 371 and 461 varies depending on the opening degree of the electromagnetic solenoid valves 372 and 462. The opening degrees of the valves 37 and 46 change according to the difference between the differential pressure between the negative pressure and the atmospheric pressure acting on both surfaces of the diaphragm and the elastic biasing force of the spring that elastically biases the diaphragm. That is, the opening degree of the valves 37 and 46 can be operated through the operation of the opening degree of the electromagnetic solenoid valves 372 and 462.

  On the other hand, the valve 45 is an EVRV (Electric Vacuum Regulating Valve) which is an electromagnetic valve.

  The external EGR devices 2 and 7 return a part of the exhaust gas flowing through the exhaust passage 4 to the intake passage 3 to be mixed with the intake air. The internal combustion engine of this embodiment includes two EGR devices 2 and 7. The EGR device 2 realizes a so-called low pressure loop EGR, and communicates the downstream side of the exhaust purification device 41 in the exhaust passage 4 to the upstream side of the compressor 51 of the high-speed turbocharger 5 in the intake passage 3. 21 and an EGR valve 22 that opens and closes the EGR passage 21 are included as elements. The EGR valve 22 controls the flow rate of the low-pressure loop EGR gas that flows through the EGR passage 21.

  The EGR device 7 realizes a so-called high-pressure loop EGR, and an EGR passage 71 that communicates the upstream side of the turbine 62 of the low-speed turbocharger 6 in the exhaust passage 4 to the downstream side of the intercooler 35 in the intake passage 3. An EGR valve 72 that opens and closes the EGR passage 71 is included as an element. The EGR valve 72 controls the flow rate of the high-pressure loop EGR gas that flows through the EGR passage 71.

  In addition, an exhaust throttle valve 47 is installed in the exhaust passage 4 at a location downstream of the connection location of the low-pressure loop EGR passage 21. The pressure on the upstream side of the compressor 51 in the intake passage to which the low-pressure loop EGR passage 21 is connected varies depending on the degree of supercharging by the compressor 51. As a result, the flow rate of EGR gas flowing through the low pressure loop EGR passage 21 changes. The exhaust throttle valve 47, together with the EGR valve 22, functions to converge the flow rate of the low-pressure loop EGR gas, and thus the EGR rate, which is the ratio of EGR gas in the intake air charged in the cylinder 1, to the target value.

  An ECU (Electronic Control Unit) 0 which is a control device for controlling the internal combustion engine of the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface of the ECU 0 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 of the crankshaft and the engine speed, and an accelerator pedal. The accelerator opening signal c output from a sensor that detects the amount of depression of the engine or the opening of the throttle valve 32 as an accelerator opening (in other words, a required engine torque or load), and in the surge tank 33 of the intake passage 3 (that is, The intake air temperature / intake pressure signal d output from the intake air temperature / intake pressure sensor for detecting the temperature and pressure (supercharging pressure) of the intake air (flowing into the cylinder 1), and output from the atmospheric pressure sensor for detecting the atmospheric pressure. At the atmospheric pressure signal e, the most upstream of the intake passage 3, that is, downstream of the air cleaner 31 and upstream of the connection point of the low pressure loop EGR passage 21. An air flow meter for detecting the flow rate and temperature of fresh air, a fresh air flow rate / temperature signal f output from a fresh air temperature sensor, an intake pressure downstream of the compressor 51 and upstream of the compressor 61 in the intake passage 3 (high-speed turbocharger) An intake pressure signal g output from an intake pressure sensor that detects a supercharging pressure by the machine 5, a cooling water temperature signal h output from a water temperature sensor that detects a cooling water temperature that indicates the temperature of the internal combustion engine, and the like are input.

  From the output interface of the ECU 0, the fuel injection signal i for the injector 11, the opening operation signal j for the throttle valve 32, the opening operation signal k for the EGR valve 22, and the opening operation signal for the EGR valve 72. Opening operation signal m for the electromagnetic solenoid valve 372 that controls the opening / closing drive of the signal l, VSV 37, opening operation signal n for the EVRV 45, and opening operation signal o for the electromagnetic solenoid valve 462 that controls the opening / closing drive of the VSV 46. The opening operation signal p and the like are output to the exhaust throttle valve 47.

  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 operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the fuel injection amount commensurate with the amount of intake air (fresh air). At the same time, the fuel injection timing (including the number of fuel injections for one combustion), the fuel injection pressure, the required EGR rate (or EGR amount), and the target supercharging pressure for supercharging by the turbochargers 5 and 6 Etc. to determine various operating parameters. The ECU 0 applies various control signals i, j, k, l, m, n, o, and p corresponding to the operation parameters via the output interface.

  2 and 3, in the internal combustion engine of the present embodiment, the turbine 62 and the compressor 61 of the low-speed turbocharger that is the first turbocharger are connected to the exhaust port of each cylinder 1 and The turbine 52 and the compressor 51 of the high-speed turbocharger 5 that is the second turbocharger are arranged near the cylinder head where the intake port exists, and the turbine 62 and the compressor 51 of the low-speed turbocharger are more It is arranged below.

Exhaust gas exiting the exhaust port of the cylinder 1 flows from the exhaust manifold 42 into the turbine 62 of the turbocharger 6 for low speed. The exhaust gas exiting from the turbine 62 then flows into the turbine 52 of the high-speed turbocharger 5 and further flows into the exhaust gas purification device 41. The exhaust gas purification device 41 is located below the turbine 52, at the height position of the cylinder block or crankcase of the internal combustion engine, and the upper inlet thereof is connected to the outlet of the turbine 52, and exhausts from the upper side to the lower side. Circulate. In the process, PM mixed in the exhaust gas is removed and harmful substances are made harmless, particularly NO _x is reduced. The exhaust gas after the purification treatment is discharged from an outlet below the exhaust gas purification device 41, and then a part thereof recirculates as an EGR gas via the low-pressure loop EGR passage 21. The low-pressure loop EGR gas reaches the upstream side of the compressor 51 of the high-speed turbocharger 5 in the intake passage 3.

  Since the turbine 52 and the compressor 51 of the high-speed turbocharger 5 are lower than the turbine 62 and the compressor 61 of the low-speed turbocharger 6, respectively, they are downstream of the exhaust purification device 41 in the exhaust passage 4. The distance between the inlet of the low pressure loop EGR passage 21 and the outlet of the low pressure loop EGR passage 21 upstream of the compressor 51 in the intake passage 3 is reduced. As a result, the length of the low-pressure loop EGR passage 21 is shortened.

  As shown in FIG. 3, the flow path from the exhaust manifold 42 to the turbine 62 of the low-speed turbocharger 6 is curved upward, and the inlet of the turbine 62 is connected to the exhaust manifold 42 (or The exhaust port of the cylinder 1). Further, as indicated by arrows in FIG. 3, in this embodiment, the rotational direction of the turbine 62 of the low-speed turbocharger 6 and the rotational direction of the turbine 52 of the high-speed turbocharger 5 are mutually set. The setting is reversed. As a result, the exhaust discharged from the cylinder 1 flows smoothly and smoothly through the former turbine 62 and the latter turbine 52.

  In this embodiment, it is driven by the exhaust turbine 62 of the first turbocharger 6 that rotates in response to the inflow of exhaust discharged from the cylinder 1 and the exhaust turbine 62 of the first turbocharger 6. The compressor 61 of the first turbocharger 6 that compresses the intake air to be charged into the cylinder 1, the downstream of the exhaust turbine 62 of the first turbocharger 6 in the exhaust passage 4, and the first An exhaust turbine 52 of the second turbocharger 5 that is positioned below the exhaust turbine 62 of the turbocharger 6 and rotates in response to the inflow of exhaust gas, and the first turbocharger in the intake passage 3 The first compressor 61 is located upstream of the compressor 61 of the sixth turbocharger and below the compressor 61 of the first turbocharger 6 and is driven by the exhaust turbine 52 of the second turbocharger 5 to compress the intake air. Second turbo More than the compressor 51 of the second turbocharger 5 in the intake passage 3 and the compressor 51 of the second turbocharger 5 in the exhaust passage 4 and the predetermined location downstream of the exhaust turbine 52 of the second turbocharger 5 in the exhaust passage 4. An internal combustion engine having a low-pressure loop EGR passage 21 connecting to a predetermined upstream location was configured.

  According to the present embodiment, the length of the low-pressure loop EGR passage 21 when the low-pressure loop EGR device 2 is incorporated into the two-stage turbo engine is shortened, and the delay in the control of the intake EGR rate can be reduced or avoided.

  The present invention is not limited to the embodiment described in detail above. The specific configuration 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 ... Cylinder 21 ... Low pressure loop EGR passage 3 ... Intake passage 4 ... Exhaust passage 5 ... High speed turbocharger 51 ... Compressor 52 ... Turbine 6 ... Low speed turbocharger 61 ... Compressor 62 ... Turbine

Claims (1)

An exhaust turbine of a first turbocharger that rotates in response to an inflow of exhaust discharged from a cylinder;
A compressor of a first turbocharger that is driven by an exhaust turbine of the first turbocharger and compresses intake air to be charged into a cylinder;
A second turbo that is downstream of the exhaust turbine of the first turbocharger in the exhaust passage and is positioned below the exhaust turbine of the first turbocharger, and rotates in response to inflow of exhaust gas A turbocharger exhaust turbine;
Located upstream of the compressor of the first turbocharger in the intake passage and below the compressor of the first turbocharger and driven by the exhaust turbine of the second turbocharger A second turbocharger compressor that compresses the intake air;
A low pressure loop EGR passage connecting a predetermined location downstream of the exhaust turbine of the second turbocharger in the exhaust passage and a predetermined location upstream of the compressor of the second turbocharger in the intake passage; An internal combustion engine provided.

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