JP4715804B2 - Exhaust gas recirculation device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine in which a part of exhaust gas taken out from an exhaust passage is introduced as EGR gas into an intake device that guides air to a cylinder of the internal combustion engine.

  As an exhaust gas recirculation device for an internal combustion engine, an exhaust gas recirculation passage for introducing EGR gas is opened in the vicinity of the intake valve of the internal combustion engine and at the center side of the cylinder, and EGR gas is introduced in synchronization with the opening timing of the intake valve, One in which EGR gas flows in a layered manner in the center of a cylinder is known (Patent Document 1). In addition, Patent Documents 2 to 4 exist as prior art documents related to the present invention.

Japanese Patent Laid-Open No. 7-180616 JP-A-5-248249 JP 2002-106419 A JP 2004-257305 A

  Since the exhaust gas recirculation device of Patent Document 1 introduces EGR gas in a layered manner into the center of the cylinder without uniformly introducing it into the cylinder, the fuel injected into the cylinder is unevenly distributed in the center of the cylinder. By passing the EGR gas, the increase in combustion temperature can be suppressed to some extent. However, since this exhaust gas recirculation device cannot change the uneven distribution position of the EGR gas in accordance with the operating state of the internal combustion engine, there is a possibility that the increase in the combustion temperature cannot be sufficiently suppressed only by adjusting the absolute amount of the EGR gas. is there.

  Accordingly, an object of the present invention is to provide an exhaust gas recirculation device for an internal combustion engine that can change the position where EGR gas is unevenly distributed in accordance with the operating state of the internal combustion engine.

  An exhaust gas recirculation device for an internal combustion engine according to the present invention is an exhaust gas recirculation device for an internal combustion engine that introduces, as EGR gas, part of exhaust gas extracted from an exhaust passage of the internal combustion engine into an intake device that guides air to a cylinder of the internal combustion engine. The intake device includes a tangential flow generating section that generates a tangential flow directed in a tangential direction of an inner circumferential surface of the cylinder in a process of guiding air to the cylinder, and a center line of the cylinder in the process of guiding air to the cylinder. A swirl flow generation unit that generates a swirl flow that moves in the direction of the center line while swirling in a plane to be able to introduce EGR gas into each of the tangential flow generation unit and the swirl flow generation unit, and Introducing means capable of changing each of the amount of EGR gas introduced into the tangential flow generator and the amount of EGR gas introduced into the swirl flow generator, and depending on the operating state of the internal combustion engine By operating the introduction means, an introduction control means for controlling an introduction amount of EGR gas into the tangential flow generation section and an introduction amount of EGR gas into the swirling flow generation section, and the introduction means Distributing the EGR gas introduced into the tangential flow generation unit with respect to the horizontal direction of the tangential flow generation unit, the distribution adjustment means can be changed to solve the above-described problem.

  The intake device generates a tangential flow and a swirl flow in the process of guiding air to the cylinder. By introducing the tangential flow into the cylinder, a swirl flowing in the direction along the inner peripheral surface of the cylinder is generated in the cylinder. The swirling flow flows inside the swirl and functions to promote the generation of the swirl while ensuring a sufficient air flow rate. These flows create a non-uniform flow field in the cylinder. The EGR gas is introduced into the tangential flow generation unit and the swirl flow generation unit by the introduction means, and is introduced into the cylinder along the tangential flow and the swirl flow. The EGR gas riding on the tangential flow is mainly led to the outside in the radial direction of the cylinder, and the EGR gas riding on the swirling flow is mainly led to the center of the cylinder. The introduction means is operated in accordance with the operating state of the internal combustion engine to control the amount of EGR gas introduced into the tangential flow generator and the amount of EGR gas introduced into the swirl flow generator. Thereby, the position where the EGR gas is unevenly distributed in the cylinder can be changed according to the operating state of the internal combustion engine. Furthermore, since the distribution of the EGR gas introduced into the tangential flow generation unit can be changed in the left-right direction by the distribution adjusting means, the concentration distribution of the EGR gas unevenly distributed in the cylinder can be changed.

  The intake device can adopt various modes as long as the above-described tangential flow and swirl flow can be generated. For example, an intake device may be configured by providing an intake port having a tangential flow generation unit capable of generating a tangential flow and an intake port having a swirl flow generation unit capable of generating a swirl flow for one cylinder. Good. As another aspect, the intake device is provided with a swirl that is open in the cylinder and provided in the same port so that the tangential flow generation unit and the swirl flow generation unit are adjacent in the vertical direction. You may have a port (Claim 2). In the case of this aspect, since the tangential flow and the swirl flow can be generated by one intake port, both the generation of the swirl and the securing of a sufficient air flow rate can be achieved by the swirl generation port.

  Various modes can be adopted for the distribution adjusting means. For example, the distribution adjusting means is a rotation in which the introduction means is disposed downstream of the introduction position for introducing the EGR gas into the tangential flow generation section, and extends in the vertical direction and is located at the downstream end. You may have the distribution adjustment member which can rotate the periphery of an axis line, and the drive device which rotationally drives the said distribution adjustment member (Claim 3). In this case, by changing the rotation angle of the distribution adjusting member, the left and right distribution of the EGR gas guided to the tangential flow generation unit can be changed.

  In one aspect of the present invention, it further comprises distribution control means for controlling the distribution of the EGR gas introduced into the tangential flow generating section by operating the distribution adjusting means in accordance with the operating state of the internal combustion engine. (Claim 4). In this case, the concentration distribution of EGR gas unevenly distributed in the cylinder can be changed according to the operating state of the internal combustion engine, so that the state of EGR gas unevenly distributed in the cylinder can be controlled more finely. .

  For example, the internal combustion engine has a fuel injection valve that injects fuel into the cylinder, and the introduction control means is configured so that EGR gas is unevenly distributed in a region where combustion of fuel injected by the fuel injection valve is performed. In addition, the amount of EGR gas introduced into the tangential flow generator and the amount of EGR gas introduced into the swirl flow generator are respectively controlled, and the distribution control means is configured such that the lower the temperature in the cylinder, The distribution of the EGR gas introduced into the tangential flow generation unit may be controlled so that EGR gas guided to the side closer to the inner peripheral surface is reduced (Claim 5).

  The region where the injected fuel is burned is hotter than the other regions. According to this aspect, since EGR gas can be unevenly distributed in such a high temperature field, the combustion temperature reduction effect by EGR gas can be obtained efficiently. That is, since the EGR gas can be unevenly distributed at a position where the effect of introducing the EGR gas is easily obtained, the total amount of the EGR gas introduced into the cylinder can be reduced. Thereby, the bad effect by introduce | transducing EGR gas in large quantities can be avoided. Since the combustion of the injected fuel proceeds from the most advanced part toward the center of the cylinder, when the temperature in the cylinder is low, the ignitability of the most advanced part of the injected fuel is ensured and the rapid combustion is suppressed. It is preferable to suppress emission of fuel. According to this aspect, as the temperature in the cylinder is lower, the EGR gas guided to the side closer to the inner peripheral surface of the cylinder is reduced, so that the concentration of EGR gas in the most advanced portion of the injected fuel is reduced. Thereby, rapid combustion can be suppressed, ensuring the ignitability of the most advanced part of the injected fuel which combustion starts. This makes it possible to effectively suppress the discharge of unburned fuel when the temperature in the cylinder is low.

  In one aspect of the present invention, the introduction means opens to the side of the tangential flow generation unit and introduces EGR gas, and opens to the side of the swirl flow generation unit and supplies EGR gas. A second introduction passage to be introduced; a first adjustment valve for adjusting an introduction amount of EGR gas through the first introduction passage; and a second adjustment for adjusting an introduction amount of EGR gas through the second introduction passage. The introduction amount control means operates the respective opening degrees of the first adjustment valve and the second adjustment valve, thereby introducing the EGR gas introduction amount into the tangential flow generation unit. And the amount of EGR gas introduced into the swirling flow generating section may be controlled respectively. According to this aspect, since one introduction passage and one adjustment valve are provided on each side of the tangential flow generation unit and the swirl flow generation unit, by operating the opening of the two adjustment valves, The amount of EGR gas introduced into the flow generation unit and the amount of EGR gas introduced into the swirl flow generation unit can be accurately controlled.

  In the present invention, the left-right direction of the tangential flow generation unit means a direction parallel to a plane that crosses the tangential flow generation unit and is orthogonal to the center line of the cylinder. The vertical direction means a direction parallel to the center line of the cylinder.

  As described above, according to the present invention, the introduction means for introducing the EGR gas into the intake device is operated according to the operating state of the internal combustion engine, and the EGR gas to the tangential flow generating unit that guides the tangential flow into the cylinder. The amount of EGR gas introduced into the cylinder and the amount of EGR gas introduced into the swirling flow generator that guides the swirling flow into the cylinder are controlled, so that the position where the EGR gas is unevenly distributed in the cylinder can be changed according to the operating state of the internal combustion engine. it can. Furthermore, since the distribution of the EGR gas introduced into the tangential flow generation unit can be changed in the left-right direction, the concentration distribution of EGR gas unevenly distributed in the cylinder can be changed.

  FIG. 1 is an overall view showing a main part of an internal combustion engine to which an exhaust gas recirculation apparatus according to an embodiment of the present invention is applied, and FIG. 2 is an enlarged perspective view showing a part of the internal combustion engine of FIG. is there. The internal combustion engine 1 is mounted on a vehicle (not shown) as a driving power source, and is configured as an in-line four-cylinder diesel engine in which four (one in the figure) cylinders 2 are arranged in a row. Each cylinder 2 is formed in a cylinder block 3, and the upper part of each cylinder 2 is closed by a cylinder head 4. Each cylinder 2 is provided with a piston 5 that can reciprocate. The piston 5 is connected to a crankshaft 6 via a connecting rod 7. On the ceiling surface of each cylinder 2, a fuel injection valve 8 is provided at the center of the cylinder 2 so that its tip faces the cylinder 2. The fuel injection valve 8 is connected to a common rail (not shown) and is supplied with fuel of a predetermined fuel pressure.

  An intake passage 10 and an exhaust passage 11 are connected to each cylinder 2. The intake passage 10 is formed in the cylinder head 4 so as to open to the cylinder 2, and is connected to the intake ports 12, 13 provided for each cylinder 2, and the intake ports 12, 13. And an intake manifold 14. The intake passage 10 including these corresponds to the intake device according to the present invention. The opening on the cylinder 2 side of each intake port 12, 13 is opened and closed by an intake valve 15. As shown in FIG. 2, the intake ports 12 and 13 have different structures, and one intake port 12 corresponds to a swirl generation port according to the present invention. The intake port 12 generates a tangential flow St in the direction of tangential to the inner peripheral surface of the cylinder 2 in the process of guiding air to the cylinder 2 and swivels in a plane intersecting the center line CL of the cylinder 2. It is comprised so that the swirl | vortex flow Sr which goes to a direction can be produced | generated. On the other hand, the intake port 13 arranged next to the intake port 12 is configured as a known helical port, and generates a swirling flow Sr similar to the above to ensure the flow rate of air mainly led to the cylinder 2. The intake port 13 may be configured as a well-known straight port that can guide air toward the center line CL. In the following description, the intake port 12 may be displayed as a swirl generation port to be distinguished from the intake port 13.

  FIG. 3 shows details of the swirl generation port 12, and a plan view seen from above the cylinder 2 and sectional views a to d are shown. The swirl generation port 12 includes an opening 16 that opens to the cylinder 2, a helical portion 17 that continues along the opening 16 while being curved around the stem portion of the intake valve 15, and an upstream side (from the cylinder 2) of the helical portion 17. And an introduction portion 18 connected to the remote side. The introduction portion 18 includes an upper layer portion 18a positioned on the upper side and a lower layer portion 18b positioned on the lower side in the vertical direction of the cylinder 2, as shown in the respective sectional views taken along the lines aa and bb in FIG. The upper layer portion 18a and the lower layer portion 18b are provided in the swirl generation port 12 so as to be adjacent in the vertical direction. The introduction portion 18 is configured such that the lateral width W1 of the upper layer portion 18a is narrower than the lateral width W2 of the lower layer portion 18b, and the lateral width difference between these regions gradually increases as the helical portion 17 is approached. That is, the upper layer portion 18 a is configured to be gradually narrowed as it approaches the helical portion 17.

  The helical portion 17 is configured such that the height h in the vertical direction of the cylinder 2 gradually decreases in the process of bending toward the opening 16 as shown in the respective cross-sectional views of cc and dd in FIG. Has been. According to the swirl generation port 12, the air guided thereto passes through the lower layer portion 18 b of the introduction portion 18, thereby forming a tangential flow St, and the air is introduced into the upper layer portion 18 a of the introduction portion 18 and the helical portion 17 subsequent thereto. , A swirl flow Sr is formed. As a result, as shown in FIG. 2, a swirl Fsw is generated in the cylinder 2 along the circumferential direction of its inner peripheral surface while ensuring a desired intake flow rate. That is, the lower layer portion 18b in the illustrated form corresponds to the tangential flow generation portion according to the present invention, and the upper layer portion 18a and the helical portion 17 correspond to the swirl flow generation portion according to the present invention.

  As shown in FIG. 1, the exhaust passage 11 includes a plurality of exhaust ports 20 formed in the cylinder head 4 so as to open to the cylinder 2 and an exhaust manifold 21 connected to the exhaust port 20. Although not shown, two exhaust ports 20 are provided for each cylinder 2. The opening on the cylinder 2 side of each exhaust port 20 is opened and closed by an exhaust valve 22. The intake valve 15 and the exhaust valve 22 are driven by the valve gear 23 such that the opening / closing timing thereof is synchronized with the rotation of the crankshaft 6. The intake passage 10 is provided with an air filter 25 for air filtration, an air flow meter 26 for detecting an air flow rate, a compressor 27 a of a turbocharger 27, and an intercooler 28 for cooling air pressurized by the turbocharger 27. Yes. The exhaust passage 11 is provided with a turbine 27b of the turbocharger 27 and an exhaust purification device 29 for purifying the exhaust. The turbocharger 27 is a known type in which a compressor 27a and a turbine 27b rotate integrally.

  The internal combustion engine 1 is provided with an exhaust gas recirculation device 30 that extracts part of the exhaust gas as EGR gas and introduces it into the intake passage 10. The exhaust gas recirculation device 30 includes an exhaust gas recirculation passage 31 that guides the EGR gas extracted from the exhaust passage 11, a cooling device 32 that cools the EGR gas, and an introduction device that introduces the EGR gas guided by the exhaust gas recirculation passage 31 into the intake passage 10. 33. The inlet side of the exhaust gas recirculation passage 31 is connected to the exhaust manifold 21. That is, the EGR gas extraction position 31a of the exhaust gas recirculation device 30 is set on the upstream side of the turbine 27b. As shown in FIG. 2, the outlet side of the exhaust gas recirculation passage 31 is branched into two branch passages 41 and 42. The branch passage 41 corresponds to a first introduction passage according to the present invention, and the branch passage 42 corresponds to a second introduction passage according to the present invention. Hereinafter, in order to distinguish these from each other, they may be referred to as a lower branch passage 41 and an upper branch passage 42. The two branch passages 41 and 42 are connected to a cylindrical spacer 43 interposed between the swirl generation port 12 and the intake manifold 14. Specifically, the lower branch passage 41 is connected to a lower opening 45 formed in the spacer 43, and the upper branch passage 42 is connected to an upper opening 46 formed in the spacer 43. As shown in FIG. 1, the intake passage 10 also includes a spacer 43 as a part thereof, so that the two branch passages 41 and 42 open at different positions in the intake passage 10. In the form shown in the figure, the branch passages 41 and 42 open on the upper and lower inner walls of the intake passage 10, respectively. The lower branch passage 41 is provided with an adjustment valve 51, and the upper branch passage 42 is provided with an adjustment valve 52. Each of the regulating valves 51 and 52 can change the introduction amount of the EGR gas by freely changing the opening degree. The regulating valve 51 corresponds to the first regulating valve according to the present invention, and the regulating valve 52 corresponds to the second regulating valve according to the present invention. The regulating valve 51 is driven by the driving device 53 and the regulating valve 52 is driven by the driving device 54, respectively.

  FIG. 4 shows a state seen from the direction of arrow IV in FIG. As is clear from this figure, the lower branch passage 41 introduces EGR gas indicated by a broken line to the lower side of the swirl generation port 12, that is, the lower layer portion 18b side, and the upper branch passage 42 sends EGR gas to the swirl generation port 12. Is introduced to the upper side, that is, the upper layer portion 18a side (see also FIG. 3). As described above, the swirl generation port 12 generates a tangential flow St and a swirl flow Sr in the course of introducing air to the cylinder 2, and these flows are introduced into the cylinder 2. As a result, a non-uniform flow field is formed in the cylinder 2. That is, the swirl Fsw along the inner peripheral surface of the cylinder 2 is formed, and a flow having a slower flow rate than the swirl Fsw is formed at the center of the cylinder 2. The EGR gas is introduced to the lower layer 18b side in the lower branch passage 41 and to the upper layer portion 18a side in the upper branch passage 42, so that the EGR gas is tangential flow St generated by the swirl generation port 12 and Each of the swirl flows Sr is introduced into the cylinder 2. The EGR gas riding on the tangential flow St is mainly guided radially outward by the swirl Fsw of the cylinder 2. On the other hand, the EGR gas riding on the swirling flow Sr is mainly guided to the center of the cylinder 2. That is, layered EGR gas can be introduced into the cylinder 2. In other words, a concentration distribution in which the concentration of EGR gas changes in the radial direction in the cylinder 2 can be created. Since the concentration distribution changes depending on the introduction position of the EGR gas, the position where the EGR gas is unevenly distributed can be changed by operating the opening degree of the two regulating valves 51 and 52. In the present embodiment, by utilizing such properties of the swirl generation port 12, the amount of EGR gas introduced by the lower branch passage 41 and the amount of EGR gas introduced by the upper branch passage 42 are determined as the operating state of the internal combustion engine 1. The position where the EGR gas is unevenly distributed in the cylinder 2 is changed by changing each of them according to.

  FIG. 5 shows a state viewed from the direction of arrow V in FIG. As shown in FIGS. 2, 4, and 5, the exhaust gas recirculation device 30 further includes a distribution adjustment mechanism 60 as a distribution adjustment unit in order to adjust the distribution of EGR gas in the horizontal direction of the lower layer portion 18 b of the swirl generation port 12. I have. The distribution adjustment mechanism 60 extends in the flow direction of air or EGR gas, and distributes as a distribution adjustment member 61 that can rotate around the rotation axis Ax1 positioned at the downstream end 61a. And a drive device 62 (see FIG. 2). The rotation axis Ax1 is positioned substantially at the center of the spacer 43 and extends in the vertical direction. As shown in FIG. 5, the distribution adjustment valve 61 divides the lower region 43a of the spacer 43 following the lower layer portion 18b into right and left. That is, the lower area 43a is divided by the distribution adjustment valve 61 into a right area 43aR and a left area 43aL. The drive device 62 can drive the distribution adjusting valve 61 from the position a to the position b in FIG. 5 and can hold it at any position between them. For example, when the distribution adjustment valve 61 is held at the intermediate position c in FIG. 5, the EGR gas that has flowed from the opening 45 is evenly distributed to the right region 43aR and the left region 43aL. Further, when the distribution adjustment valve 61 is held at a position deviated to the position a side with respect to the intermediate position c, the inlet of the right region 43aR becomes larger than the inlet of the left region 43aL, so that EGR gas is more than the left region 43aL. Are also distributed to the right region 43aR. Conversely, when the distribution adjustment valve 61 is held at a position that is biased toward the position b with respect to the intermediate position c, more EGR gas is distributed to the left region 43aL than to the right region 43aR. Thus, by changing the position of the distribution adjustment valve 61, the distribution of the EGR gas guided to the lower layer portion 18b in the left-right direction can be changed. When the distribution changes, the EGR gas that rides on the tangential flow St can be made nonuniform in the left-right direction, so that the concentration distribution of the EGR gas unevenly distributed at a predetermined position in the cylinder 2 can be changed.

  As shown in FIG. 1, the opening control of the two adjusting valves 51 and 52 and the position control of the distribution adjusting valve 61 are performed by an engine control unit (ECU) 70 that controls the operating state of the internal combustion engine 1. , 62 by controlling the operations. The ECU 70 is a computer provided with a microprocessor (not shown) and peripheral devices such as RAM and ROM necessary for its operation, and various types of operation parameters such as the fuel injection amount, fuel injection timing, and fuel injection rate of the internal combustion engine 1 are mainly used. Control is performed with reference to an input signal from the sensor. As various sensors, in addition to the air flow meter 26 described above, a crank angle sensor 71 that can output a signal corresponding to the rotational speed (rotational speed) of the internal combustion engine 1, and a cooling water temperature used as a physical quantity representative of the engine temperature. There is a water temperature sensor 72 that can output a signal. In addition to these, signals from an accelerator opening sensor, a supercharging pressure sensor, and the like are input to the ECU 70, but illustration thereof is omitted.

  FIG. 6 is a flowchart showing an example of a control routine of exhaust gas recirculation control executed by the ECU 70 in relation to the present invention. The program for this routine is held in the ROM of the ECU 70, read out in a timely manner, and repeatedly executed at a predetermined calculation interval. The ECU 70 first acquires, for example, the engine speed Ne and the fuel injection amount Q as the operation state of the internal combustion engine 1 in step S1. The engine speed Ne is acquired based on a signal from the crank angle sensor 61. As the fuel injection amount Q, a calculation result of fuel injection control (not shown) executed in parallel with FIG. 6 is used. Next, in step S2, the opening ratio between the regulating valve 51 and the regulating valve 52 shown in FIG. 2 is set. This opening ratio has the same significance as the ratio (lower side: upper side) between the amount of EGR gas introduced by the lower branch passage 41 and the amount of EGR gas introduced by the upper branch passage 42. The opening ratio is set according to the engine speed Ne and the fuel injection amount Q. FIG. 7 shows an example of a map that the ECU 60 refers to in order to set the opening ratio. As is clear from this figure, the opening ratio between the regulating valve 51 and the regulating valve 52 depends on the lower branch passage 41 with respect to the introduction amount of EGR gas introduced into the swirl generation port 12 as the fuel injection amount Q increases. The ratio of the amount of EGR gas introduced is set to be high. The specific numerical values shown in the figure are only examples. It is also possible to provide an opening ratio such that EGR gas is introduced only from the upper branch passage 42 with this ratio being 0% or only from the lower branch passage 41 with this ratio being 100%. That is, the case where the opening ratio is set to 0:10 or 10: 0 can be included in the set values of the illustrated map.

  Here, the reason why the opening ratio is set as shown in FIG. 7 will be described with reference to FIGS. 9 shows the relationship between EGR gas and fuel spray when the fuel injection amount is small, FIG. 11 shows the relationship between EGR gas and fuel spray when the fuel injection amount is large, and FIG. 10 shows the fuel injection amount as shown in FIG. It is explanatory drawing which each showed the relationship between EGR gas and fuel spray in the case of the middle grade of FIG. As shown in these drawings, in the internal combustion engine 1, the fuel injection valve 8 injects fuel radially from the center of the cylinder 2. The injected fuel (fuel spray) F thus injected starts to burn from its tip and forms a high-temperature combustion field. As apparent from a comparison between FIG. 9 and FIG. 11, the position of the tip of the fuel spray F is more distant from the center of the cylinder 2 as the fuel injection amount is larger, in other words, the cylinder is more as the fuel injection amount is larger. 2 changes to a position radially outside. That is, the position where the injected fuel burns is further away from the center of the cylinder 2 as the fuel injection amount increases.

  On the other hand, the higher the ratio of the amount of EGR gas introduced by the lower branch passage 41, the higher the ratio of the EGR gas introduced to the lower layer portion 18b of the swirl generation port 12. For this reason, the amount of EGR gas riding on the tangential flow St generated by the swirl generation port 12, that is, the amount of EGR gas accompanying the tangential flow St increases as the ratio increases. Thereby, the higher the ratio, the higher the concentration of EGR gas can be unevenly distributed in a position closer to the inner peripheral surface of the cylinder 2. That is, as shown in FIG. 9, when the fuel injection amount is small, the opening ratio is set so that the ratio becomes low. Therefore, the EGR gas G is unevenly distributed in the center of the cylinder 2, thereby fuel spraying. The region where F burns is efficiently cooled by the EGR gas G. Also, as shown in FIG. 11, when the fuel injection amount is large, the opening ratio is set so that the ratio becomes high, so that the EGR gas G is unevenly distributed in a region near the inner peripheral surface of the cylinder 2. Thus, the region where the fuel spray F burns is efficiently cooled by the EGR gas G. Further, even in the intermediate fuel injection amount shown in FIG. 10, the region where the EGR gas G is unevenly distributed is changed to the center side of the cylinder 2 as compared with the case of FIG. 11, so the region where the fuel spray F burns is changed to the EGR gas G. And efficiently cooled. Therefore, as the fuel injection amount increases, the ratio of the amount of EGR gas introduced by the lower branch passage 41 is increased, so that the EGR gas can be unevenly distributed at the position of the tip of the fuel spray. Based on this idea, the opening ratio in FIG. 7 is set so that the EGR gas is disposed in an appropriate region (in the region where the injected fuel burns).

  Returning to FIG. 6, after setting the opening ratio in step S <b> 2, the process proceeds to step S <b> 3 to determine whether or not the fuel injection timing is within a predetermined range. The extension of fuel spray strongly depends on the atmospheric pressure (in-cylinder pressure) when fuel is injected from the fuel injection valve 8. That is, when the fuel is injected earlier than the compression top dead center, the extension of the fuel spray proceeds excessively to form a so-called premixed gas. FIG. 12 shows the relationship between fuel spray and EGR gas when such a premixed gas is formed. As is clear from FIG. 12, in contrast to the forms shown in FIGS. 9 to 11, radial traces of the fuel spray disappear and exist as a mixture H. Thus, since the region where combustion is performed changes according to the injection timing, the injection timing is determined in step S3 for the purpose of determining the necessity of correcting the opening ratio in accordance with the change. The predetermined range is set based on whether or not the opening ratio needs to be corrected. When the injection timing is within the predetermined range, no correction is necessary, and when it is out of the predetermined range, correction is necessary. If the injection timing is out of the predetermined range, the process proceeds to step S4 to correct the opening ratio. If the fuel injection timing is within the predetermined range, the process proceeds to step S5.

  FIG. 8 is an explanatory diagram for explaining a method of correcting the opening ratio. As shown in this figure, the correction ratio is set to 1 during the period from the timing A on the retard side to the timing B on the advance side of the top dead center TDC. That is, the range from time A to time B corresponds to the above-described predetermined range, indicating that the opening ratio is not corrected. When the injection timing is earlier than the timing A, the earlier, the earlier the injection timing, the more the mixture mixture described above tends to be generated. Therefore, the opening ratio is corrected in the direction in which EGR gas is unevenly distributed in the center of the cylinder 2, that is, in the direction in which the uneven distribution of EGR gas to the outside in the radial direction of the cylinder 2 is mitigated. In other words, the ratio of the amount of EGR gas introduced by the lower branch passage 41 is corrected so as to decrease. As shown in the parentheses in the figure, for example, when the opening ratio is set to 8: 2 (lower side: upper side) in step S2, the opening ratio is set in a state where the correction ratio is 0.25 which is corrected most. Is corrected to 2: 8. On the other hand, when the time is later than time B, the in-cylinder pressure decreases, so that the mixing of the injected fuel is promoted, and the situation is the same as the situation earlier than time A. Therefore, as the injection timing is later than the timing B, the ratio of the amount of EGR gas introduced by the lower branch passage 41 is corrected so as to decrease. As described above, by correcting the opening ratio, it is possible to introduce the EGR gas in accordance with the change in the combustion mode accompanying the change in the fuel injection timing.

  Returning to FIG. 6, in step S <b> 5, the final opening amount to be given to each of the adjustment valves 51 and 52 is set while maintaining the opening ratio described above. The opening amount is set based on the EGR gas amount calculated according to the engine speed and the fuel injection amount (load). The EGR gas amount is acquired by referring to a map (not shown), and the final opening amount to be given to each of the adjustment valves 51 and 52 is set so that the EGR gas of the EGR gas amount is introduced. The setting of the opening amount can be realized by referring to a map that gives the opening amount of the adjusting valve 51 and the opening amount of the adjusting valve 52 using the EGR gas amount and the opening ratio as variables.

  Next, in step S6, the temperature in the cylinder 2 is acquired. Since the temperature in the cylinder 2 changes in correlation with the cooling water temperature, the cooling water temperature can be acquired by referring to the output signal of the water temperature sensor 72, and the temperature in the cylinder 2 can be acquired by estimation based on the cooling water temperature. it can. However, it is also possible to provide a temperature sensor that outputs a signal corresponding to the temperature in the cylinder 2 and acquire the temperature in the cylinder 2 based on the output signal of the temperature sensor.

  Next, in step S7, the position (rotation angle) of the distribution adjustment valve 61 is set. In this embodiment, the setting is performed based on the temperature in the cylinder 2 acquired in step S6, and the EGR gas guided to the side closer to the inner peripheral surface of the cylinder is reduced as the temperature in the cylinder 2 is lower. The position of the regulating valve 61 is set. FIG. 13 is an explanatory diagram for explaining the relationship between the position of the distribution adjustment valve 61 and the concentration distribution of the EGR gas. This figure shows the position r1 in the radial direction of the cylinder 2 of the EGR gas G unevenly distributed in the cylinder 2 when the temperature in the cylinder 2 at high load is high (at high temperature) and low (at low temperature). The density distribution from to r2 is shown.

  As is clear from this figure, the position of the distribution adjustment valve 61 is set closer to the position a when the temperature is high (see also FIG. 5). Thereby, when the temperature is high, more EGR gas is guided to the side closer to the inner peripheral surface of the cylinder 2 than when the temperature is low. As a result, the peak of the EGR gas concentration distribution is located on the side closer to the inner peripheral surface of the cylinder 2. Since such a concentration distribution is formed at a high temperature, high concentration EGR gas is supplied to the most advanced portion where the combustion of the fuel spray F starts, and the combustion temperature at the high temperature is lowered to reduce the nitrogen oxide ( NOx) can be suppressed. On the other hand, at the time of low temperature, the position of the distribution adjustment valve 61 is set closer to the position b side (see also FIG. 5). Thereby, the EGR gas guided to the side closer to the inner peripheral surface of the cylinder 2 is less at the low temperature than at the high temperature. As a result, the peak of the EGR gas concentration distribution recedes toward the center of the cylinder 2 as compared to when the temperature is high, so that the EGR gas concentration at the most distal portion of the fuel spray F is reduced and overcooling at the most distal portion can be prevented. . Thereby, rapid combustion after the start of combustion can be suppressed while ensuring the ignitability of the most advanced portion of the fuel spray F at low temperatures. Therefore, it becomes possible to suppress discharge of unburned fuel at low temperatures. Such setting of the position of the distribution adjusting valve 61 can be realized, for example, by holding a map in which the position and the temperature in the cylinder 2 are associated with each other in the ROM of the ECU 70 and referring to the map. . If correction of the position of the distribution adjustment valve 61 is necessary due to environmental conditions such as outside air temperature and atmospheric pressure, a correction coefficient for multiplying the value obtained from the map is calculated, and the environmental condition is reflected in the operation amount of the drive device 62. May be.

  Returning to FIG. 6, in step S8, the opening degree of the regulating valve 51 and the regulating valve 52 is respectively manipulated by operating the driving device 53 and the driving device 54 so that the opening amount set in step S5 is obtained. In the subsequent step S9, the drive device 62 is operated so that the distribution adjustment valve 61 is held at the position set in step S7. Thereafter, the current routine is terminated.

  In the above embodiment, the ECU 70 functions as an introduction control unit and a distribution control unit according to the present invention by executing the control routine of FIG.

  In the embodiment described above, the swirl generation port in which the tangential flow generation unit and the swirl flow generation unit are provided in one port is exemplified as the intake device, but the configuration of the intake device according to the present invention is not limited to this. FIG. 14 shows an example of an exhaust gas recirculation device in which the intake device is implemented in another form. In the form of FIG. 14, a straight port 141 that generates a tangential flow St and a helical port 142 that generates a swirl flow Sr are provided for one cylinder 2 in the process of introducing air, and EGR gas is supplied to these ports. 2 is connected to the straight port 141 via the spacer 43, the branch passage 42 is connected to the helical port 142 via the spacer 43, and the spacer on the straight port 141 side is further connected. 43 is provided with the distribution adjusting mechanism 60 described above. In the form of FIG. 14, the straight port 141 corresponds to the tangential flow generation unit according to the present invention, the helical port 142 corresponds to the swirl flow generation unit according to the present invention, and the combination of the straight port 141 and the helical port 142 is the present invention. This corresponds to the intake device according to. As is apparent from the above, even when the intake device of the above-described form is replaced with the form of FIG. 14, the amount of EGR gas introduced into the straight port 141 and the amount of EGR gas introduced into the helical port 142 are controlled. Thus, the position where the EGR gas is unevenly distributed in the cylinder 2 can be controlled, and the concentration distribution of the unevenly distributed EGR gas can be changed by operating the distribution adjusting mechanism 60.

  The distribution adjustment unit according to the present invention is not limited to the distribution adjustment mechanism 60 described above. FIG. 15 shows another form of the distribution adjusting means. In this embodiment, the lower branch passage 41 shown in FIG. 2 is further branched into two branch passages 41A and 41B, and these passages 41A and 41B are connected to two openings 45A and 45B formed in the spacer 43. It is a thing. These opening portions 45A and 45B have different opening positions in the left-right direction. The adjustment valve 51A is connected to the branch passage 41A, and the adjustment valve 51B is connected to the branch passage 41B. The regulating valve 51A is driven by the driving device 53A, and the regulating valve 51B is driven by the driving device 53B. The distribution of the EGR gas flowing from the two openings 45A and 45B can be changed by changing the respective opening degrees of the regulating valves 51A and 51B. Since the two openings 45A and 45B open at different positions in the left-right direction, the distribution of the EGR gas in the left-right direction introduced into the lower layer 18b of the swirl generation port 12 by the adjusting valves 51A, 51B is changed. Can do. That is, the adjusting valve 51A and the adjusting valve 51B shown in FIG. 15 function as distribution adjusting means according to the present invention. The opening degree of each regulating valve 51A, 51B is operated by the ECU 70. The operation is performed according to a control routine similar to that for the distribution adjustment mechanism 60. That is, when the EGR gas guided to the side closer to the inner peripheral surface of the cylinder 2 is increased and the concentration distribution peak is biased toward the inner peripheral surface, the opening of the adjusting valve 51B is opened. Set larger than degree. Conversely, when the concentration distribution is biased toward the center side of the cylinder 2, the opening of the adjustment valve 51A is set larger than the opening of the adjustment valve 51B. Thus, ECU70 functions as the distribution control means which concerns on this invention, when each opening degree of adjustment valve 51A, 51B is operated. Note that the opening control of each of the regulating valves 51 and 52 may be the same as the processing of FIG. 6, and the ECU 70 functions as the introduction control means according to the present invention also in the form of FIG. Further, the present invention can also be implemented by applying the configuration shown in FIG. 15 to the intake device shown in FIG.

1 is an overall view showing a main part of an internal combustion engine to which an exhaust gas recirculation apparatus according to an embodiment of the present invention is applied. The perspective view which expanded and showed a part of internal combustion engine of FIG. The figure which showed the detail of the swirl production | generation port. The figure which showed the state seen from the direction of arrow IV of FIG. The figure which showed the state seen from the direction of the arrow V of FIG. The flowchart which showed an example of the control routine of exhaust gas recirculation | reflux control. The figure which showed an example of the map referred in order to set an opening ratio. Explanatory drawing explaining the correction method of opening ratio. Explanatory drawing which showed the relationship between EGR gas and fuel spray when fuel injection amount is small. Explanatory drawing which showed the relationship between EGR gas and fuel spray in case a fuel injection quantity is a middle grade. Explanatory drawing which showed the relationship between EGR gas and fuel spray when fuel injection amount is large. Explanatory drawing which showed the relationship between fuel spray and EGR gas in case premixed gas is formed. Explanatory drawing explaining the relationship between the position of a distribution adjustment valve, and the density | concentration distribution of EGR gas. The figure which showed an example of the exhaust gas recirculation apparatus which implemented the intake device with the other form. The figure which showed an example of the exhaust gas recirculation apparatus which implemented the distribution adjustment means with the other form.

Explanation of symbols

1 Internal combustion engine 2 Cylinder 8 Fuel injection valve 11 Exhaust passage 12 Swirl generation port (intake device)
18a Upper layer (swirl flow generator)
18b Lower layer (tangential flow generator)
30 Exhaust gas recirculation device 33 Introduction device (introduction means)
41 Branch passage (first introduction passage)
42 Branch passage (second introduction passage)
51 Regulating valve (first regulating valve)
52 Regulating valve (second regulating valve)
60 Distribution adjustment mechanism (distribution adjustment means)
61 Distribution adjustment member (distribution adjustment valve)
62 Drive device 70 ECU (introduction control means, distribution control means)
141 Straight port (tangential flow generator)
142 Helical port (Swirl flow generator)
Ax1 Rotating axis CL Centerline St of cylinder St Tangent flow Sr Swirl flow Fsw Swirl

Claims (6)

In an exhaust gas recirculation device for an internal combustion engine, a part of exhaust gas taken out from an exhaust passage of the internal combustion engine is introduced as EGR gas into an intake device that guides air to a cylinder of the internal combustion engine.
The intake device includes a tangential flow generating section that generates a tangential flow directed in a tangential direction of an inner circumferential surface of the cylinder in a process of guiding air to the cylinder, and a center line of the cylinder in the process of guiding air to the cylinder. A swirl flow generating unit that generates a swirl flow toward the direction of the center line while swirling in a plane to be
EGR gas can be introduced into each of the tangential flow generator and the swirl flow generator, and the amount of EGR gas introduced into the tangential flow generator and the amount of EGR gas introduced into the swirl flow generator can be changed. And introducing the EGR gas into the tangential flow generation unit and introducing the EGR gas into the swirl flow generation unit by operating the introduction unit according to the operating state of the internal combustion engine. Introduction control means for controlling the amount respectively, and distribution adjustment means capable of changing the distribution of the EGR gas introduced into the tangential flow generation section in the horizontal direction of the tangential flow generation section by the introduction means. An exhaust gas recirculation device for an internal combustion engine, comprising:   The intake device has a swirl generation port that is open in the cylinder and provided in the same port so that the tangential flow generation unit and the swirl flow generation unit are adjacent in the vertical direction. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein the exhaust gas recirculation device is an internal combustion engine.   The distribution adjusting means is arranged around a rotation axis that is arranged on the downstream side of the introduction position for introducing the EGR gas into the tangential flow generating section and that extends in the vertical direction and is located at the downstream end. The exhaust gas recirculation apparatus for an internal combustion engine according to claim 1, further comprising: a distribution adjusting member that can rotate in a straight line; and a drive device that rotationally drives the distribution adjusting member.   The distribution control means for controlling the distribution of the EGR gas introduced into the tangential flow generating section by operating the distribution adjusting means according to the operating state of the internal combustion engine. Or an exhaust gas recirculation device for an internal combustion engine according to 2; The internal combustion engine has a fuel injection valve for injecting fuel into the cylinder;
The introduction control means introduces the amount of EGR gas into the tangential flow generation unit and the swirl flow generation unit so that EGR gas is unevenly distributed in a region where the fuel injected by the fuel injection valve is burned. Control the amount of EGR gas introduced,
The distribution control means distributes the EGR gas introduced into the tangential flow generation unit so that the EGR gas guided to the side closer to the inner peripheral surface of the cylinder decreases as the temperature in the cylinder decreases. The exhaust gas recirculation device for an internal combustion engine according to claim 4, wherein the exhaust gas recirculation device is controlled. The introduction means includes a first introduction passage that opens to the tangential flow generation unit and introduces EGR gas, and a second introduction passage that opens to the swirl flow generation unit and introduces EGR gas. A first regulating valve that regulates the amount of EGR gas introduced by the first introduction passage, and a second regulating valve that regulates the amount of EGR gas introduced by the second introduction passage,
The introduction control means operates the opening degree of each of the first adjustment valve and the second adjustment valve to thereby introduce the amount of EGR gas introduced into the tangential flow generation unit and the swirl flow generation unit. The exhaust gas recirculation device for an internal combustion engine according to claim 1 or 2, wherein the amount of EGR gas introduced is controlled.

Images