JP6031431B2 - Intake control device for internal combustion engine - Google Patents

Description

  The present invention relates to an apparatus for controlling intake air into a combustion chamber of an internal combustion engine, and more specifically, sucks gaseous fuel into a combustion chamber of an internal combustion engine configured to perform compression auto-ignition combustion of fuel directly injected into the combustion chamber. The present invention relates to an intake control device for an internal combustion engine.

  Conventionally, in an internal combustion engine (compression self-ignition type internal combustion engine) configured to perform compression auto-ignition combustion of fuel directly injected into the combustion chamber, in order to increase combustion energy (heat generation amount), direct injection into the combustion chamber In addition to the fuel to be used, a technique for sucking gaseous fuel is known (see Patent Document 1).

  For example, the invention of Patent Document 1 includes a reformer that reforms the properties of the fuel on the catalyst so that the combustion energy output from the fuel per unit amount increases. Then, the reformed fuel (gaseous fuel) reformed by the reformer is injected into the exhaust port and is annularly formed along the inner peripheral surface of the combustion chamber together with the exhaust gas from the exhaust port, that is, in the outer peripheral region of the combustion chamber. Inhale. Further, unreformed non-reformed fuel is directly injected into the central region of the combustion chamber. The non-reformed fuel is compressed and ignited and combusted, and the reformed fuel is ignited and combusted using the non-reformed fuel as a fire. According to this, when reforming the fuel, the problem of reduction in self-ignitability is solved, and heat loss, that is, cooling loss due to combustion heat escaping from the cylinder wall surface can be reduced.

JP2013-104364A

  However, in the configuration of Patent Document 1, high-temperature combustion by the non-reformed fuel occurs in a central region away from the outer peripheral region of the combustion chamber, so that the cooling loss can be reduced as compared with the case of high-temperature combustion in the outer peripheral region. Since the temperature of the region is high, there is a problem that the effect of reducing the cooling loss is still insufficient.

  The present invention has been made in view of the above problems, and injects gaseous fuel into a combustion chamber of an internal combustion engine configured to inject fuel directly into the combustion chamber and cause the fuel to undergo compression auto-ignition combustion. It is an object of the present invention to provide an intake control device for an internal combustion engine that can sufficiently reduce the cooling loss.

In order to solve the above-mentioned problems, the present invention provides a combustion chamber and an outer peripheral region of the combustion chamber of an internal combustion engine configured to inject fuel directly into the combustion chamber and to perform compression auto-ignition combustion of the fuel. An intake control device for an internal combustion engine that sucks the first gas into the central region inside the outer peripheral region,
The first gas is an EGR lean gas in which the concentration of EGR gas, which is exhaust gas recirculated from the exhaust system of the internal combustion engine to the intake system, is leaner than that of the second gas,
The second gas may be a gas containing an EGR rich gas, which is air having a higher concentration of the EGR gas than the first gas, and a gaseous fuel.

  According to the present invention, similarly to Patent Document 1, gas is stratified between the outer peripheral region and the central region of the combustion chamber, but each gas (first gas, second gas) sucked into the outer peripheral region and the central region is used. ) Is different between the present invention and Patent Document 1. Specifically, in the present invention, EGR lean gas (first gas) in which EGR gas (exhaust gas) is lean air is sucked into the outer peripheral region of the combustion chamber, and EGR gas in which EGR gas is rich in the central region. A gas (second gas) containing rich gas and gaseous fuel is sucked. As a result, the oxygen concentration in the central region, which becomes high when compressed auto-ignition combustion is performed, can be made lower than that in the outer peripheral region. Compared to the case where EGR rich gas is sucked into the outer peripheral region and EGR lean gas is sucked into the central region, The combustion temperature can be lowered. Further, in the present invention, since the gaseous fuel is sucked into the central region, the ignitability of the gaseous fuel can be improved as compared with the case of sucking into the outer peripheral region, and the ignited gaseous fuel flame escapes from the outer peripheral wall of the combustion chamber. Can be reduced. Therefore, the present invention can sufficiently reduce the cooling loss. Note that the EGR lean gas in the present specification includes the case where the concentration of the EGR gas is zero, that is, the case of only fresh air.

1 is a configuration diagram of an engine system 1. FIG. 2 is a sectional view of a cylinder 11. FIG. FIG. 3 is a diagram showing a schematic configuration of a reformer 73. It is a block diagram of the engine system 2 which concerns on a modification. FIG. 3 is a diagram in which a part of an EGR lean gas passage 22 and a part of an EGR rich gas passage 25 are extracted. It is the figure which showed the change of the lift amount of an intake valve (FIG. 6 (A)), and the intake flow rate of EGR lean gas, the intake flow rate of EGR rich gas, and gaseous fuel (FIG. 6 (B)). FIG. 3 is a diagram schematically showing the flow of gas (swirl flow, tumble flow) sucked into a combustion chamber 110. FIG. 3 is a diagram showing a gas stratification distribution in a cross-sectional plan view of a combustion chamber 110. It is the figure which showed the mode of the combustion chamber at the time of completion | finish of a compression stroke, and represented the exhaust concentration in each part of a combustion chamber by the color shading. It is the figure which showed the combustion temperature at the time of carrying out stratified distribution of EGR lean gas in the outer peripheral area | region of a combustion chamber, and EGR rich gas and gaseous fuel in the center area | region. It is the figure which showed the combustion temperature at the time of carrying out stratified distribution of EGR rich gas in the outer peripheral area | region of a combustion chamber, and EGR lean gas and gaseous fuel in the center area | region. It is the figure which showed the reduction rate of the cooling loss compared with the unstratified layer.

  Embodiments of an intake air control apparatus for an internal combustion engine according to the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration diagram of an engine system 1 mounted on a vehicle. The engine system 1 is configured to include a diesel engine 10 (hereinafter simply referred to as an engine) as an internal combustion engine and various configurations necessary for the operation of the engine 10. In the present embodiment, the engine 10 is a four-cylinder engine having four cylinders 11 (cylinders). The engine 10 is a four-stroke engine that generates power in each cylinder 11 through four strokes of intake, compression, combustion, and exhaust. A combustion cycle (“720 ° CA” cycle) of four strokes of intake, compression, combustion, and exhaust is sequentially executed with a shift of “180 ° CA” between the cylinders 11, for example. When numbers 1 to 4 are assigned in order from the cylinder 11 on the right side of FIG. 1, for example, the combustion cycles are executed in order of the cylinders 1, 3, 4, and 2.

  FIG. 2 shows a cross-sectional view of the cylinder 11. As shown in FIG. 2, the cylinder 11 includes a cylinder block 111 that constitutes a side wall of the cylinder 11 and a cylinder head 112 that is disposed on the cylinder block 111. A water jacket 113 is formed in the cylinder block 111, and cooling water discharged from a water pump (not shown) circulates in the water jacket 113 to cool the cylinder block 111. Further, a piston 16 is accommodated in the cylinder 11, and a crankshaft (not shown) that is an output shaft of the engine 10 is rotated by the reciprocating motion of the piston 16.

  Then, an area 110 surrounded by the cylinder block 111, the cylinder head 112 and the piston 16 is used as a combustion chamber, and compression self-ignition combustion is performed in the combustion chamber 110. That is, an injector 18 that injects fuel (for example, light oil) into the combustion chamber 110 is provided at the center of the cylinder head 112 (immediately above the central region 110b of the combustion chamber 110), and the fuel injected from the injector 18 burns. In the chamber 110, compression self-ignition combustion occurs.

  In each cylinder 11, two intake ports, a swirl generation port 12 and a tumble generation port 13, are formed as intake ports that serve as inlets for intake air (gas) sucked into the combustion chamber 110. These intake ports 12 and 13 are formed in the cylinder head 112. The swirl generation port 12 is an intake port that generates a swirl flow (lateral vortex) in the gas sucked into the combustion chamber 110 from the swirl generation port 12. The tumble generation port 13 is an intake port that generates a tumble flow (longitudinal vortex) in the gas sucked into the combustion chamber 110 from the tumble generation port 13.

  In addition, an intake valve 14 that opens and closes the opening is provided at an opening connecting each intake port 12, 13 and the combustion chamber 110. In the cylinder head 112, an exhaust port 17 for discharging the gas after combustion in the combustion chamber 110 from the combustion chamber 110 is formed. An exhaust valve 15 for opening and closing the opening is provided at an opening connecting the exhaust port 17 and the combustion chamber 110.

  As shown in FIG. 1, the engine system 1 is provided with an intake passage 21 through which fresh air drawn into the combustion chamber 110 flows. The intake passage 21 is provided with a supercharger 31 that compresses fresh air and an intercooler 32 that cools the fresh air compressed by the supercharger 31 from the upstream side. A throttle 33 for adjusting a new amount is provided in the intake passage 21 downstream of the intercooler 32. From the intake passage 21 downstream of the throttle 33, a passage 22 (an intake manifold passage, hereinafter referred to as an EGR lean gas passage) connected to each cylinder 11 is branched. Each EGR lean gas passage 22 is connected to the swirl generation port 12 of each cylinder 11. In the EGR lean gas passage 22 and the intake passage 21, only fresh air or fresh air is mixed with an EGR gas corresponding to the opening of the EGR valve 41 or an EGR gas flowing from a connection passage 29 described later (hereinafter referred to as EGR lean gas). ) Flows.

  Each cylinder 11 is connected to an exhaust manifold 23 for collectively passing exhaust gas discharged from each cylinder 11 to the exhaust passage 27. The exhaust passage 27 includes a turbocharger turbine 37 (variable nozzle turbo (VNT)) for recovering energy from the exhaust gas, a post-processing device 38 for performing a predetermined process on the exhaust gas, and an exhaust gas. An exhaust throttle valve 39 for adjusting the gas flow rate is arranged in this order. The post-processing device 38 is an oxidation catalyst that oxidizes and removes CO, HC, and the like in the exhaust gas, and a DPF that removes PM in the exhaust gas.

  A low pressure EGR passage 28 having one end connected to the exhaust passage 27 downstream from the post-processing device 38 and the other end connected to the intake passage 21 upstream from the supercharger 31 is provided. A part of the exhaust gas after passing through the VNT 37 is recirculated to the intake passage 21 through the low pressure EGR passage 28. The low pressure EGR passage 28 is provided with a low pressure EGR cooler 40 that cools the EGR gas flowing through the low pressure EGR passage 28 and a low pressure EGR valve 41 that adjusts the flow rate of the EGR gas. The low pressure EGR system including the low pressure EGR passage 28, the low pressure EGR cooler 40, and the low pressure EGR valve 41 may not be provided. In this case, only fresh air flows through the intake passage 21.

  The exhaust manifold 23 is connected to a high pressure EGR passage 24 for returning a part of the exhaust gas to the intake system as EGR gas. The high pressure EGR passage 24 is provided with a high pressure EGR cooler 34 that cools the EGR gas flowing through the high pressure EGR passage 24, and a high pressure EGR valve 35 that adjusts the flow rate of the EGR gas downstream from the high pressure EGR cooler 34. . From the high pressure EGR passage 24 downstream of the high pressure EGR valve 35, a passage 25 (hereinafter referred to as an EGR rich gas passage) connected to each cylinder 11 is branched. Each EGR rich gas passage 25 is connected to the tumble generation port 13 of each cylinder 11. In the EGR rich gas passage 25, a gas (hereinafter referred to as an EGR rich gas) having a higher concentration of EGR gas (a higher exhaust concentration and a lower oxygen concentration) than the EGR lean gas flowing through the EGR lean gas passage 22 flows.

  Further, the engine system 1 is provided with a connection passage 29 that connects the intake passage 21 and the high-pressure EGR passage 24. The connection passage 29 connects the intake passage 21 before branching to the EGR lean gas passage 22 and the high-pressure EGR passage 24 before branching to the EGR rich gas passage 25. With the connection passage 29, the pressure of the gas flowing through the intake passage 21 and the downstream EGR lean gas passage 22 can be made equal to the pressure of the gas flowing through the high pressure EGR passage 24 and the downstream EGR rich gas passage 25. As a result, the stratified distribution of the EGR lean gas and the EGR rich gas in the combustion chamber can be suppressed from being disturbed.

  Further, when the EGR rate target value (target EGR rate) cannot be achieved only by the EGR gas recirculated from the low pressure EGR passage 28 or the EGR rich gas (exhaust gas) flowing through the EGR rich gas passage 25, the connection passage 29 is used. The target EGR rate can be achieved by flowing EGR gas from the high pressure EGR passage 24 to the intake passage 21 or flowing fresh air from the intake passage 21 to the high pressure EGR passage 24. That is, when the target EGR rate is high, the EGR gas flows from the high pressure EGR passage 24 to the intake passage 21 via the connection passage 29 to increase the EGR concentration of the EGR lean gas flowing through the intake passage 21 and the EGR lean gas passage 22. Thus, the EGR rate can be increased. On the other hand, when the target EGR rate is low, fresh air flows from the intake passage 21 to the high pressure EGR passage 24 via the connection passage 29 to lower the EGR concentration of the EGR rich gas flowing through the high pressure EGR passage 24 and the EGR rich gas passage 25. As a result, the EGR rate can be lowered. The EGR rate is defined as the amount of EGR gas (exhaust gas) sucked into the combustion chamber, the total amount of gas sucked into the combustion chamber (fresh air intake amount + EGR gas intake amount + gaseous fuel intake amount). ) Divided by.

  The engine system 1 also includes a system for sucking gaseous fuel (fuel gas) separately from the fuel directly injected from the injector 18 into the combustion chamber in order to increase the combustion energy in the combustion chamber (hereinafter referred to as gaseous fuel suction system). Is provided). Similar to Patent Document 1, the gaseous fuel suction system uses liquid fuel (alcohol fuel) such as methanol (CH 3 —OH) such as hydrogen (H 2) so that the calorific value output from the fuel per unit amount increases. ) And carbon monoxide (CO), and the reformed fuel (reformed fuel, gaseous fuel) is sucked into the combustion chamber.

  Specifically, the gaseous fuel suction system includes a storage unit 71 that stores fuel before reforming (for example, methanol), a passage 72 that connects the storage unit 71 and the reformer 73, and a reformer 73. And a passage 74 through which the reformed fuel (gas fuel) reformed by the reformer 73 flows. Although not shown in FIG. 1, the gaseous fuel suction system is configured to pump the fuel stored in the storage unit 71 to the reformer 73 side via the passage 72, or to adjust the flow rate of the fuel flowing through the passage 72. It also has a valve to adjust.

  The fuel discharged from the storage unit 71 by the pump is supplied to the reformer 73 through the passage 72. The reformer 73 reforms the properties of the fuel supplied from the storage unit 71 on the catalyst so that the calorific value output from the fuel per unit amount increases. Here, FIG. 3 shows a schematic configuration of the reformer 73. The reformer 73 has the same configuration as the reformer disclosed in Patent Document 1. That is, the reformer 73 includes a catalyst 701 that promotes a chemical reaction for converting a fuel such as methanol into a reformed fuel such as H 2 or CO, and a heat exchanger 702 disposed around the catalyst 701. ing. Further, the reformer 73 is supplied with exhaust gas flowing through the exhaust passage 27 (see FIG. 1), and the reformer 73 supplies the supplied exhaust gas through the reformer 73. An exhaust passage 703 is provided. The exhaust passage 703 is disposed around the heat exchanger 702 so as to exchange heat between the exhaust gas flowing through the exhaust passage 703 and the heat exchanger 702. The reformer 73 has a fuel passage 704 through which the fuel supplied from the storage unit 71 flows in the reformer 73. The fuel passage 704 is disposed so as to pass over the catalyst 701.

  The operation of the reformer 73 will be described. Since the exhaust gas flowing through the exhaust passage 703 has a high temperature (several hundred degrees Celsius), heat exchange is performed between the exhaust gas and the catalyst 701 through the heat exchanger 702. Done. That is, the catalyst 701 is warmed by the exhaust gas and activated. The exhaust gas after heat exchange is discharged out of the reformer 73. The fuel supplied to the reformer 73 is supplied to the catalyst 701 heated by the exhaust gas through the fuel passage 704, and reacts with H2O (water) on the catalyst 701 to become gaseous fuel such as H2 or CO. Modified (converted). For example, H2O contained in the exhaust gas may be used as H2O for reacting with the fuel on the catalyst 701. The gaseous fuel is discharged from the reformer 73 through the fuel passage 704 after passing through the catalyst 701. The gaseous fuel (H2, CO) is a fuel having an increased calorific value per unit amount, although the self-ignitability is lower than that of the fuel (CH3-OH) before reforming.

  As shown in FIG. 1, the gaseous fuel reformed by the reformer 73 is supplied to the high-pressure EGR passage 241 before branching to each EGR rich gas passage 25 via the passage 74 and downstream of the connection passage 29. It has come to be. Therefore, the gas containing EGR rich gas and gaseous fuel flows through each EGR rich gas passage 25 downstream from the high pressure EGR passage 241. Further, by supplying the gaseous fuel downstream from the connection passage 29, it is possible to suppress the gaseous fuel from being supplied to the EGR lean gas passage 22 through the connection passage 29.

  Each EGR rich gas passage 25 is provided with a valve 42 (hereinafter referred to as an intake control valve) for adjusting the flow rate of the gas flowing through the EGR rich gas passage 25. For example, a butterfly valve is used as the intake control valve 42. The installation position of the intake control valve 42 should be as close to the intake valve 14 as possible. This is because the volume from the intake valve 14 to the intake control valve 42 is reduced, and the controllability of the intake flow rate is improved.

  However, as in the engine system 2 of FIG. 4, the intake control valve 42 may be provided in the passage 241 before branching to each EGR rich gas passage 25. The passage 241 is a passage through which gaseous fuel is supplied. In FIG. 4, the intake control valve 42 is provided downstream of the gaseous fuel supply port. The engine system 2 in FIG. 4 is different from the engine system 1 in FIG. 1 in the installation position and the number of intake control valves 42, and is otherwise the same as the engine system 1 in FIG. By providing the intake control valve 42 at the position shown in FIG. 2, the number of intake control valves 42 can be reduced to one.

  Returning to FIG. 1, the engine system 1 is provided with an actuator 43 that is connected to the intake control valve 42 and operates the intake control valve 42. The actuator 43 is, for example, a motor or an actuator that operates with hydraulic pressure or negative pressure. The actuator 43 may be provided for each intake control valve 42, or may be a common actuator among the four intake control valves 42.

  In the engine system 1, the valves including the intake control valve 42 (throttle 33, EGR valves 35, 41, etc.) are opened and closed (opening / closing timing, opening degree, etc.), fuel is supplied by the injector 18 (see FIG. 2), and the gas to be sucked An ECU 50 that controls the operation of the engine 10 by controlling the amount of fuel and the like is provided. The ECU 50 is mainly configured by a computer including a CPU, a ROM, a RAM, and the like.

  The ECU 50 is configured so that the EGR lean gas, the EGR rich gas, and the gaseous fuel are stratified and distributed in the combustion chamber in order to suppress emissions discharged from the engine 10, increase combustion energy, and reduce cooling loss. In addition, these gases are sucked into the combustion chamber. FIG. 5 is a view in which a part of the EGR lean gas passage 22 and a part of the EGR rich gas passage 25 are extracted and the passages 22 and 25 are shown side by side. FIG. 6 is a diagram for explaining how the EGR lean gas, the EGR rich gas, and the gaseous fuel are sucked in the intake stroke. Specifically, FIG. 6 shows a change in the lift amount of the intake valve 14 with respect to the crank angle (FIG. 6A), a change in the intake flow rate of EGR lean gas, the intake flow rate of EGR rich gas and gaseous fuel (FIG. 6B). Is shown. In FIG. 6B, a line 201 indicates the intake flow rate of the gas sucked from the swirl generation port 12, that is, the EGR lean gas. A line 202 indicates the intake flow rates of the gas sucked from the tumble generation port 13, that is, EGR rich gas and gaseous fuel.

  As shown in FIG. 5, since no intake control valve is provided in the EGR lean gas passage 22, the EGR lean gas is lifted by the intake valve 14 as shown by the line 201 in FIG. 6B (FIG. 6). Intake into the combustion chamber at an intake air flow rate according to (A). On the other hand, regarding the intake of EGR rich gas and gaseous fuel, as shown in FIG. 5, the ECU 50 opens the intake control valve 42 smaller than fully open during the intake stroke, as shown in FIG. 5. As a result, as indicated by the line 202 in FIG. 6B, the intake flow rates of the EGR rich gas and the gaseous fuel are made smaller than the intake flow rate of the EGR lean gas (line 201). During the intake stroke, the intake control valve 42 is not fully opened but is opened at a low opening, so that EGR rich gas and gaseous fuel are sucked into the combustion chamber in conjunction with the lift of the intake valve 14, that is, It will be inhaled from the first half of the intake stroke. As described above, as a result of restricting the intake flow rates of the EGR rich gas and the gaseous fuel, the EGR rich gas and the gaseous fuel are sucked weaker than the EGR lean gas.

  Note that the intake flow rates of the EGR rich gas and the gaseous fuel are reduced so that the ratio of the intake amount of the EGR rich gas and the gaseous fuel to the total intake amount of the gas sucked into the combustion chamber in one intake stroke is about 30%. Is preferred. That is, it is preferable that EGR lean gas: EGR rich gas and gaseous fuel = about 7: 3. The present inventors have obtained the knowledge that the degree of EGR stratification can be increased by using this ratio. The degree of EGR stratification refers to the portion with the highest exhaust concentration (the portion with the lowest oxygen concentration) and the portion with the lowest exhaust concentration (the portion with the highest exhaust concentration) at the stage where the compression stroke is completed after the intake stroke. ) Means the difference. And the inventor has obtained the knowledge that the emission (NOx, smoke) can be reduced when the degree of EGR stratification increases.

  FIG. 7 schematically shows the flow of gas sucked from the swirl generation port 12 into the combustion chamber 110 (swirl flow) and the flow of gas sucked from the tumble generation port 13 (tumble flow). As shown in FIG. 7, the swirl flow (EGR lean gas) is sucked near the outer periphery of the combustion chamber 110, while the tumble flow (EGR rich gas and gaseous fuel) is sucked near the center of the combustion chamber 110.

  As shown in FIG. 6B, the intake flow rates of the EGR rich gas and the gaseous fuel are reduced, and the EGR lean gas, the EGR rich gas, and the gaseous fuel are sucked as shown in FIG. ), The gas can be stratified in the combustion chamber 110 as shown in FIGS. 8 is a diagram (cross-sectional view in plan view of the combustion chamber 110) when the combustion chamber 110 is cut along the line VIII-VIII in FIG. That is, EGR lean gas is disposed in the lower part (piston 16 side) of the combustion chamber 110, and EGR rich gas and gaseous fuel are disposed in the central area 110b in the upper part (injector 18 side). An EGR lean gas is disposed in a ring shape along the peripheral surface.

  Thereafter, at the end of the compression stroke, as shown in FIG. 9, EGR rich gas containing gaseous fuel in the central region 161 of the combustion chamber (a region directly below the injector 18), that is, the exhaust concentration is high (the oxygen concentration is low). Gas can be arranged. Further, a squish area around the central region 161 (a gap between the outer periphery of the upper surface of the piston and the cylinder head) and a cavity area (an area indicated by reference numeral “162” in FIG. 9) formed on the upper surface (top) of the piston. EGR lean gas, that is, gas having a low exhaust concentration (high oxygen concentration) can be disposed in the squish and cavity areas). FIG. 9 shows the state of the combustion chamber at the end of the compression stroke, and shows the difference in exhaust concentration in each part of the combustion chamber by the difference in color shade. FIG. 9 shows that the exhaust concentration is higher as the color is darker.

  The central region 161 is a region where the amount of oxygen is likely to increase and the combustion temperature is likely to be high, and is a region where nitrogen and oxygen are combined and NOx is likely to be generated. On the other hand, the squish and cavity area 162 (outer peripheral region of the combustion chamber) is a region where the amount of oxygen tends to decrease and smoke (soot) tends to occur. Therefore, the EGR rich gas and gas fuel layer disposed in the central region 161 contributes to the reduction of NOx, and the EGR lean gas layer disposed in the squish and cavity area 162 is smoked. Contributes to reduction. That is, emission (NOx, smoke) can be reduced by stratification as shown in FIG.

  Further, since gaseous fuel is sucked into the combustion chamber, the combustion energy can be increased as compared with the case where gaseous fuel is not sucked. Further, since the gaseous fuel (H2, CO) that is difficult to ignite is sucked together with the EGR rich gas so as to be disposed in the central region 161 (see FIG. 9) of the combustion chamber, the compressed self-ignition combustion of the fuel injected from the injector 18 It is possible to easily ignite and burn the gaseous fuel using as a fire type. That is, the ignitability of the gaseous fuel can be improved and the combustion energy of the ignited gaseous fuel escapes from the outer peripheral wall (cylinder block 111) of the combustion chamber as compared with the case where the gaseous fuel is arranged in the squish and cavity area 162. Can be reduced.

  Further, since the EGR rich gas is sucked into the central region 161, the oxygen concentration in the central region 161 can be lowered, and as a result, the combustion temperature of the central region 161 (the combustion temperature of the fuel and gaseous fuel from the injector 18) is lowered. be able to.

  Here, FIG. 10 shows the combustion temperature in the case where the EGR lean gas is distributed in the outer peripheral region of the combustion chamber and the EGR rich gas and the gaseous fuel are stratified in the central region. Specifically, the upper part of FIG. 10 shows a state in which EGR lean gas is distributed in the outer peripheral region of the combustion chamber and EGR rich gas and gaseous fuel are stratified and distributed in the central region in the sectional view in plan view of the combustion chamber. The lower part of FIG. 10 shows the distribution of the combustion temperature from the center O of the combustion chamber to the outer periphery X in the plan view of the upper part of FIG. In the lower diagram of FIG. 10, the difference in the combustion temperature is shown by the difference in the shade of the color, and the color becomes darker as the combustion temperature approaches 3000K. FIG. 11 is a view of a comparative example with respect to FIG. 10, showing the combustion temperature when stratified distribution of EGR rich gas in the outer peripheral region of the combustion chamber and EGR lean gas and gaseous fuel in the central region. As in FIG. 10, the upper section shows a cross-sectional view of the combustion chamber in plan view, and the lower section shows the distribution of combustion temperature.

  In both the stratified distributions of FIGS. 10 and 11, the combustion temperature is higher in the vicinity of the center O (center region) of the combustion chamber than in the vicinity of the outer periphery X (outer periphery region). On the other hand, it can be seen that the stratified distribution of the present invention (FIG. 10) has a lower combustion temperature (color is lighter) near the center O than the stratified distribution of the comparative example (FIG. 11). Moreover, it turns out that the combustion temperature of the outer periphery X vicinity does not have so much difference between the stratification distribution of FIG. 10, FIG. From this, it can be said that the stratification distribution of FIG. 10 can reduce the cooling loss more than the stratification distribution of FIG.

  FIG. 12 is a diagram showing that cooling loss can be reduced by stratified distribution as in the present invention. Specifically, FIG. 12 shows the stratification distribution of the present invention and the stratification distribution of the comparative example when the cooling loss (cooling loss) when the gas containing the gaseous fuel is sucked in the unstratified layer is set as a reference (100%). The reduction rate of cooling loss is shown. The result on the left of FIG. 12 shows the cooling loss (100%) when fresh air, EGR gas, and gaseous fuel are sucked so as to be mixed in the combustion chamber, that is, sucked in the unstratified layer. The result in the middle of FIG. 12 shows the cooling loss when stratified distribution is performed in the same manner as in FIG. 11, that is, when EGR rich gas is distributed in the outer peripheral region of the combustion chamber and EGR lean gas and gaseous fuel are stratified in the central region. Yes. The result on the right side of FIG. 12 shows the cooling loss when stratified distribution is performed as in FIG. 10, that is, when EGR lean gas is distributed in the outer peripheral region of the combustion chamber and EGR rich gas and gaseous fuel are stratified in the central region. Yes.

  As shown in FIG. 12, it can be seen that if the gaseous fuel is stratified and distributed in the central region of the combustion chamber, the cooling loss can be reduced as compared with the case where the stratified distribution is not provided. Specifically, when EGR rich gas is stratified in the outer peripheral area of the firing chamber and EGR lean gas and gaseous fuel are stratified in the central area (result in the middle of FIG. 12), the cooling loss is lower than when stratified distribution is not achieved. Reduce by 10%. Further, when stratified distribution of EGR lean gas in the outer peripheral region of the combustion chamber and EGR rich gas and gaseous fuel in the central region (result on the right in FIG. 12), the cooling loss is reduced by 28% compared to the case where stratified distribution is not performed. To do. This is because when the gaseous fuel is stratified and distributed in the central region of the combustion chamber, the escape of the combustion of the gaseous fuel from the outer peripheral wall of the combustion chamber can be reduced.

  Further, comparing the result in the middle of FIG. 12 with the result on the right, it can be seen that the cooling loss can be reduced by stratifying the EGR rich gas in the central region of the combustion chamber as compared with the stratified distribution in the outer peripheral region. This is because, as described with reference to FIGS. 10 and 11, the combustion temperature in the central region of the combustion chamber can be reduced by stratified distribution of the EGR rich gas in the central region of the combustion chamber.

  As described above, according to the present embodiment, since the EGR lean gas is distributed in the outer peripheral region of the combustion chamber and the EGR rich gas and the gaseous fuel are stratified in the central region, the emission can be reduced and the calorific value can be increased. , Cooling loss can be reduced, that is, thermal efficiency can be improved.

  In addition, this invention is not limited to the said embodiment, A various change is possible to the limit which does not deviate from description of a claim. For example, in the above-described embodiment, an example in which the present invention is applied to an engine system having four cylinders has been described. However, the present invention may be applied to intake of a multi-cylinder engine other than a single-cylinder engine or a four-cylinder engine. . Moreover, although the example which inhales reformed fuel was demonstrated in the said embodiment, you may inhale directly, without reforming gaseous fuel, such as CNG.

  Also, the intake control valve may be closed during the first half of the intake stroke to stop the intake of EGR rich gas and gaseous fuel, and the intake control valve may be opened from the second half to start the intake of EGR rich gas and gaseous fuel. This also allows stratified distribution of EGR lean gas in the outer peripheral region of the combustion chamber and EGR rich gas and gaseous fuel in the central region. Further, the intake control valve may be omitted, and the stratified distribution may be realized by suppressing the lift amount of the intake valve provided in the tumble generation port to be lower than the lift amount of the intake valve provided in the swirl generation port. . In the above embodiment, light oil is supplied from the injector to the combustion chamber. However, the present invention may be applied to a system that supplies non-reformed fuel from the injector before reforming by the reformer.

  In the above embodiment, the engine systems 1 and 2 correspond to an “intake control device for an internal combustion engine” according to the present invention. The passages 21 and 22 correspond to the “first passage” of the present invention. The passages 24 and 25 correspond to the “second passage” of the present invention. The intake control valve 42 corresponds to the “flow rate adjusting means” of the present invention. The passage 74 corresponds to the “supplying means” of the present invention.

1, 2 Engine system (intake control system for internal combustion engine)
10 Diesel engine 10 (internal combustion engine)
110 Combustion chamber 110a Outer peripheral region of combustion chamber 110b Central region of combustion chamber

Claims (5)

The combustion chamber (110) has a first combustion chamber (110a) in the outer peripheral region (110a) of the internal combustion engine (10) configured to inject fuel directly into the combustion chamber and combust the compressed ignition fuel. An intake control device (1, 2) for an internal combustion engine that sucks gas and sucks a second gas into a central region (110b) inside the outer peripheral region,
The first gas is an EGR lean gas in which the concentration of EGR gas, which is exhaust gas recirculated from the exhaust system of the internal combustion engine to the intake system, is leaner than that of the second gas,
An intake control device for an internal combustion engine, wherein the second gas is a gas containing an EGR rich gas, which is a richer air of the EGR gas than the first gas, and a gaseous fuel. The internal combustion engine includes a swirl generation port (12) that generates a swirl flow in the gas sucked as an intake port for sucking gas into the combustion chamber, and a tumble generation port (13) that generates a tumble flow.
A passage through which the first gas flows and a first passage (21, 22) connected to the swirl generation port;
The intake control device for an internal combustion engine according to claim 1, further comprising a second passage (24, 25) that is a passage through which the second gas flows and is connected to the tumble generation port.   Flow rate adjusting means (42) for adjusting a flow rate of the second gas sucked into the combustion chamber from the tumble generation port so as to be smaller than a flow rate of the first gas sucked into the combustion chamber from the swirl generation port. The intake control device for an internal combustion engine according to claim 2, further comprising: A connection passage (29) for connecting the first passage and the second passage upstream of the swirl generation port and the tumble generation port;
The intake control device for an internal combustion engine according to claim 2 or 3, further comprising supply means (74) for supplying the gaseous fuel into the second passage at a position closer to the tumble generation port than the connection passage. . A reformer (73) for reforming the properties of the fuel on the catalyst so that the calorific value output from the fuel per unit amount is increased;
The intake control apparatus for an internal combustion engine according to any one of claims 1 to 4, wherein the gaseous fuel is a reformed fuel whose property is reformed by the reformer.