JP2005264781A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress that exhaust gases including emission flow out in starting an engine. <P>SOLUTION: This internal combustion engine comprises an exhaust gas recirculating passage 27 recirculating the exhaust gases in an exhaust gas passage 26 discharged from a combustion chamber 5 to intake passages 17 and 13 on the downstream side of the throttle valve 21 of the internal combustion engine and a recirculating exhaust gas control valve 29 capable of controlling the amount of the recirculation exhaust gases flowing in the exhaust gas recirculation passage. When the internal combustion engine is started, the throttle valve is closed and the recirculating exhaust gas control valve is opened. If the number of cycles (K) of the internal combustion engine exceeds a specified number of cycles after the start of the internal combustion engine, the throttle valve is opened and the recirculating exhaust gas control valve is closed. Also, the internal combustion engine may comprise a catalyst with oxidation function or a filter 24 carrying the catalyst installed in the exhaust passage and the exhaust gas recirculation passage may be extended from the downstream side of the catalyst or the filter to the intake passage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an internal combustion engine.

  2. Description of the Related Art In recent years, hybrid vehicles that are capable of traveling with engine output and / or motor output by adding an electric motor in addition to the engine have become known. Also, when the engine does not need to be operated (for example, when the vehicle is stopped while waiting for a signal, waiting for a train, or waiting for a person), the engine is stopped, and the engine is restarted when the engine needs to be operated. An auto-stop traveling mode vehicle (eco-run vehicle) that starts (restarts) the vehicle has also been developed. In such hybrid vehicles and eco-run vehicles, the engine is operated intermittently as necessary, and it is possible to operate by selecting a highly efficient operation region, so that it has excellent fuel efficiency and exhaust purification performance. Yes.

  Conventionally, in an internal combustion engine, for example, a diesel engine, an engine exhaust passage and an engine intake passage are connected by an exhaust gas recirculation (hereinafter referred to as EGR) passage in order to suppress generation of NOx, and the EGR passage is connected to the engine exhaust passage. Thus, exhaust gas, that is, EGR gas is recirculated in the engine intake passage. In this case, since the EGR gas has a relatively high specific heat and can absorb a large amount of heat, the EGR gas amount increases, that is, the EGR rate (EGR gas amount / (EGR gas amount + intake air amount)). As the value increases, the combustion temperature in the combustion chamber decreases. As the combustion temperature decreases, the amount of NOx generated decreases, and as the EGR rate increases, the amount of NOx generated decreases.

  However, if the EGR rate is made larger than the maximum allowable limit in the course of research on combustion of diesel engines, smoke increases rapidly as described above, but there is a peak in the amount of smoke generated, and the EGR rate exceeds this peak. If the value is further increased, the smoke starts to decrease sharply. When the EGR rate is increased to 70% or higher during idling operation, and when the EGR gas is strongly cooled, the smoke is almost reduced when the EGR rate is increased to approximately 55% or higher. It was found that it became zero, that is, almost no wrinkles occurred. At this time, it has been found that the amount of NOx generated is extremely small. After this, based on this knowledge, the reason why soot was not generated has been studied, and as a result, a new combustion (low temperature combustion) system capable of simultaneously reducing soot and NOx has been established. . Although this new combustion (low temperature combustion) system will be described in detail later, briefly speaking, hydrocarbon growth is stopped in the middle of the process until hydrocarbon (hereinafter referred to as “HC”) grows drastically. It is based on making it.

  That is, as a result of repeated experimental research, it has been found that when the temperature of the fuel during combustion in the combustion chamber and the surrounding gas is below a certain temperature, the growth of the hydrocarbon stops before it reaches the soot. And when the temperature of the gas around it exceeds a certain temperature, the hydrocarbon grows up to a soot. In this case, the endothermic effect of the gas around the fuel when the fuel burns greatly affects the temperature of the fuel and the surrounding gas, and the endothermic amount of the gas around the fuel is adjusted according to the amount of heat generated during fuel combustion. As a result, the temperature of the fuel and the surrounding gas can be controlled.

  Therefore, if the temperature of the fuel during combustion in the combustion chamber and the surrounding gas temperature is suppressed below the temperature at which hydrocarbon growth stops halfway, soot will not be generated, and the temperature of the fuel during combustion in the combustion chamber and the surrounding gas temperature It is possible to suppress the temperature below the temperature at which hydrocarbon growth stops halfway by adjusting the endothermic amount of the gas around the fuel. On the other hand, hydrocarbons that have stopped growing before reaching soot can be easily purified by post-treatment using an oxidation catalyst or the like. There is a basic idea of such a new low-temperature combustion system.

  By the way, in addition to a new low-temperature combustion system capable of simultaneously reducing soot and nitrogen oxides (hereinafter referred to as “NOx”), carbon monoxide (hereinafter referred to as “CO”), HC, NOx, etc. Other solutions that can reduce emissions in exhaust gases have also been proposed.

For example, it has been proposed to arrange zeolite in the exhaust passage of an internal combustion engine to trap emissions, particularly NOx, in the exhaust gas. However, even after NOx is trapped by zeolite, it has a property of desorbing from zeolite when the temperature becomes higher than that at the time of trapping. For this reason, Patent Document 1 and Patent Document 2 propose that the exhaust gas flowing downstream from the zeolite provided in the exhaust passage of the internal combustion engine is temporarily collected in the collection tank. In this case, the exhaust passage downstream of the zeolite and the collection tank are connected by the branch passage, and the collection tank is connected to the intake passage of the internal combustion engine by another passage. Therefore, once the trapped emission in the zeolite, especially when the conditions for desorbing NOx from the zeolite are satisfied, the exhaust gas is passed through the branch passage and collected in the collection tank, and when the predetermined condition is satisfied The exhaust gas in the collection tank is passed through the intake passage. By collecting the exhaust gas in the collection tank in this manner, it is possible to prevent the exhaust gas including the emission from flowing out of the internal combustion engine (see, for example, Patent Document 1 and Patent Document 2).
JP 2002-70539 A JP 2002-147227 A

  However, in the internal combustion engines as described in Patent Document 1 and Patent Document 2, it is necessary to separately provide a collection tank for collecting the exhaust gas and a pump for guiding the exhaust gas to the collection tank. . And since the capacity | capacitance of this collection tank needs to be sufficient capacity | capacitance to collect the whole quantity of temporary exhaust gas, a collection tank is comparatively large. Therefore, these collection tanks and pumps require a considerable space, and the vehicle mountability is extremely deteriorated.

  In order to achieve the above-described object, according to the first aspect of the invention, the exhaust gas recirculation for recirculating the exhaust gas in the exhaust passage discharged from the combustion chamber to the intake passage downstream of the throttle valve of the internal combustion engine. A recirculation exhaust gas control valve capable of controlling the amount of recirculation exhaust gas flowing through the exhaust gas recirculation passage, and closing the throttle valve and starting the recirculation exhaust gas when starting the internal combustion engine The control valve is opened, and when the number of cycles of the internal combustion engine exceeds a predetermined number of cycles after starting the internal combustion engine, the throttle valve is opened and the recirculation exhaust gas control valve is closed. An internal combustion engine is provided.

  That is, in the first invention, when the throttle valve is closed and the recirculation exhaust gas control valve is opened when the internal combustion engine is started, the intake passage downstream of the throttle valve, the engine body of the internal combustion engine, and the exhaust gas recirculation. A closed loop is formed by the exhaust passage to the passage and the exhaust gas recirculation passage, and the exhaust gas containing air or unburned components circulates in the closed loop. Exhaust gas when starting the engine contains a relatively large amount of emissions, but there is no need for a collection tank or the like by circulating the exhaust gas containing air and unburned components in the closed loop described above In addition, it is possible to suppress the exhaust gas including these emissions from flowing out of the internal combustion engine when the engine is started. Furthermore, since a combustible air-fuel mixture can be easily formed by circulating a relatively high temperature exhaust gas containing air or unburned components in a closed loop, the amount of fuel actually injected should be reduced compared to the conventional case. Also good.

According to a second invention, in the first invention, further provided is a catalyst having an oxidation function provided in the exhaust passage or a filter carrying the catalyst, wherein the exhaust gas recirculation passage is the catalyst or filter. From the downstream to the intake passage downstream from the throttle valve.
That is, in the second aspect of the invention, when the recirculated exhaust gas passes through the catalyst or the filter carrying the catalyst, the emission in the exhaust gas, particularly HC, CO, etc. is purified by oxidation, and these catalysts are warmed up. It is also possible. As the catalyst, an oxidation catalyst or a NOx catalyst can be adopted.

According to a third aspect, in the first or second aspect, the apparatus further comprises a turbocharger, and the exhaust gas recirculation passage is located downstream of the exhaust turbine of the turbocharger and upstream of the compressor of the turbocharger. And connected.
That is, in the third aspect of the invention, the above-described closed loop becomes larger by the amount of the turbocharger, and it is possible to suppress a larger amount of exhaust gas including emissions from flowing out from the internal combustion engine. In the third invention according to the second invention, the catalyst can be easily warmed up by a large amount of exhaust gas.

According to a fourth aspect, in any one of the first to third aspects, the internal combustion engine is stopped when a predetermined condition is satisfied, and is restarted when the predetermined condition is not satisfied. It was started.
That is, in the fourth aspect of the invention, exhaust gas can be prevented from flowing out from the internal combustion engine even in the case of a so-called eco-run vehicle or hybrid vehicle. Further, in the fourth invention according to the second invention, the catalyst warm-up by circulating the exhaust gas containing air and unburned components in the closed loop is compared with the internal combustion engine of the eco-run vehicle or the hybrid vehicle. This is particularly advantageous when the catalyst temperature is likely to decrease due to frequent stopping.

According to a fifth aspect, in the second aspect, when the number of cycles of the internal combustion engine exceeds another predetermined number of cycles after the start of the internal combustion engine, temperature increase control is performed to raise the temperature of the catalyst. I did it.
That is, in the fifth aspect of the invention, it is possible to remove the emissions adhering to the inner wall of the closed loop described above by performing predetermined catalyst temperature rise control.

  According to each invention, it is possible to achieve a common effect that exhaust gas including emissions can be prevented from flowing out from the internal combustion engine when the engine is started.

Furthermore, according to the second aspect of the invention, it is possible to produce an effect that the exhaust gas can be purified by oxidation and the catalyst can be warmed up.
Furthermore, according to the third aspect of the invention, it is possible to produce an effect that a larger amount of exhaust gas can be suppressed from flowing out from the internal combustion engine.
Further, according to the fourth aspect of the invention, it is possible to prevent the exhaust gas from flowing out from the internal combustion engine to the outside even in the case of a so-called eco-run vehicle or hybrid vehicle.
Furthermore, according to the fifth aspect, by performing predetermined catalyst temperature increase control, it is possible to achieve the effect that the emissions attached to the inner wall of the closed loop described above can be removed.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following drawings, the same members are denoted by the same reference numerals. In order to facilitate understanding, the scales of these drawings are appropriately changed.

  1 and 2 show the case where the present invention is applied to an in-cylinder injection compression ignition internal combustion engine, the present invention can also be applied to an in-cylinder injection spark ignition gasoline engine. 1 and 2, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is an electrically controlled fuel injection valve, 7 is an intake valve, and 8 is intake air. Port, 9 is an exhaust valve, and 10 is an exhaust port. The intake port 8 is connected to a surge tank 12 via a corresponding intake branch pipe 11, and the surge tank 12 is connected to an outlet of a compressor 16 of a supercharger, for example, an exhaust turbocharger 15, via an intake duct 13 and an intercooler 14. Connected. An inlet portion of the compressor 16 is connected to an air cleaner 19 via an intake duct 17 and an air flow meter 18, and a throttle valve 21 driven by a step motor 20 is disposed in the intake duct 17.

  On the other hand, the exhaust port 10 is connected to an inlet portion of an exhaust turbine 23 of an exhaust turbocharger 15 via an exhaust manifold 22, and an outlet portion of the exhaust turbine 23 is connected to a particulate filter (hereinafter referred to as “filter” as appropriate) via an exhaust pipe 26. It is connected to a casing 25 containing 24). The exhaust pipe 26 downstream of the filter 24 and the intake duct 17 downstream of the throttle valve 21 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 27, and are driven by a step motor 28 in the EGR passage 27. An EGR control valve 29 is arranged. An EGR cooler 30 for cooling the EGR gas flowing in the EGR passage 27 is disposed in the EGR passage 27. In the embodiment shown in FIG. 1, the engine cooling water is guided into the EGR cooler 30, and the EGR gas is cooled by the engine cooling water.

  On the other hand, the fuel injection valve 6 is connected to a fuel reservoir, so-called common rail 32, through a fuel supply pipe 31. Fuel is supplied into the common rail 32 from an electrically controlled fuel pump 33 with variable discharge amount, and the fuel supplied into the common rail 32 is supplied to the fuel injection valve 6 through each fuel supply pipe 31. A fuel pressure sensor 34 for detecting the fuel pressure in the common rail 32 is attached to the common rail 32, and a fuel pump 33 is set so that the fuel pressure in the common rail 32 becomes the target fuel pressure based on the output signal of the fuel pressure sensor 34. The discharge amount is controlled.

  On the other hand, in the embodiment shown in FIG. 1, a transmission 35 is connected to the output shaft of the engine, and an electric motor 37 is connected to the output shaft 36 of the transmission 35. In this case, as the transmission 35, a clutch operation and a shift operation are automatically performed in a normal automatic transmission having a torque converter, various continuously variable transmissions, or a manual transmission having a clutch. An automatic transmission or the like can be used.

  The electric motor 37 connected to the output shaft 36 of the transmission 35 constitutes a driving force generator that generates driving force separately from the driving force of the engine. In the embodiment shown in FIG. 1, the electric motor 37 is mounted on a rotor 38 mounted on the output shaft 36 of the transmission 35 and a plurality of permanent magnets mounted on the outer peripheral surface, and an exciting coil for forming a rotating magnetic field. And an AC synchronous motor provided with the stator 39. The excitation coil of the stator 39 is connected to a motor drive control circuit 40, and this motor drive control circuit 40 is connected to a battery 41 that generates a DC high voltage. For this reason, the illustrated internal combustion engine can be used as a hybrid engine.

  The electronic control unit 50 is composed of a digital computer, and is connected to each other by a bidirectional bus 51. It comprises. Output signals of the air flow meter 18 and the fuel pressure sensor 34 are input to the input port 55 via the corresponding AD converters 57. A temperature sensor 43 for detecting the temperature of the filter 24 is attached to the casing 25 containing the filter 24, and an output signal of the temperature sensor 43 is input to the input port 55 via the corresponding AD converter 57. Note that the temperature of the filter 24 can be estimated using a model indicating the relationship between the engine operating state and the temperature of the filter 24 without providing such a temperature sensor 43. The casing 25 is provided with a differential pressure sensor 61 for detecting a pressure difference between the upstream side and the downstream side of the filter 24. The output signal of the differential pressure sensor 61 is input to the input port 55 via the corresponding AD converter 57. In addition, various signals representing the gear ratio or gear position of the transmission 35, the rotation speed of the output shaft 36, and the like are input to the input port 55.

  On the other hand, a load sensor 45 that generates an output voltage proportional to the depression amount L of the accelerator pedal 44 is connected to the accelerator pedal 44, and the output voltage of the load sensor 45 is input to the input port 55 via the corresponding AD converter 57. Is done. Further, a crank angle sensor (so-called rotational speed sensor) 46 that generates an output pulse every time the crankshaft rotates, for example, 30 ° is connected to the input port 55. On the other hand, a hydrocarbon supply valve 42 for supplying hydrocarbon, for example, fuel, into the exhaust gas is disposed at the inlet of the casing 25 containing the filter 24, and the output port 56 is connected to the fuel via a corresponding drive circuit 58. The injector 6 is connected to the step motors 20 and 28, the fuel pump 33, the transmission 35, the motor drive control circuit 40, and the hydrocarbon feed valve 42.

  The supply of electric power to the exciting coil of the stator 39 of the electric motor 37 is normally stopped. At this time, the rotor 38 rotates together with the output shaft 36 of the transmission 37. On the other hand, when the electric motor 37 is driven, the DC high voltage of the battery 41 is converted into a three-phase alternating current having a frequency of fm and a current value of Im in the motor drive control circuit 40, and this three-phase alternating current is supplied to the exciting coil of the stator 39. Is done. This frequency fm is a frequency necessary for rotating the rotating magnetic field generated by the exciting coil in synchronization with the rotation of the rotor 38, and this frequency fm is calculated by the CPU 54 based on the rotational speed of the output shaft 36. In the motor drive control circuit 40, this frequency fm is a three-phase AC frequency.

  On the other hand, the output torque of the electric motor 37 is substantially proportional to the three-phase AC current value Im. The current value Im is calculated by the CPU 54 based on the required output torque of the electric motor 37, and the motor drive control circuit 40 sets the current value Im as a three-phase AC current value. Further, when the vehicle is decelerated, the electric motor 37 operates as a generator, and the electric power generated at this time is regenerated in the battery 41. The CPU 54 determines whether or not the electric motor 37 should be operated as a generator. When it is determined that the electric motor 37 should be operated as a generator, the electric power generated in the electric motor 37 by the motor control circuit 40 is stored in the battery. 41 is controlled to be regenerated.

  FIG. 3 shows another embodiment of the compression ignition type internal combustion engine. In this embodiment, an electric motor 37 is connected to the output shaft 47 of the engine, and a transmission 35 is connected to the output shaft of the electric motor 37. In this embodiment, the rotor 38 of the electric motor 37 is mounted on the output shaft 47 of the engine, so that the rotor 38 always rotates together with the output shaft 47 of the engine. Also in this embodiment, as the transmission 35, a clutch operation and a shift operation are automatically performed in a normal automatic transmission having a torque converter, various continuously variable transmissions, or a manual transmission having a clutch. An automatic transmission or the like of the type as described above can be used.

  In the embodiment according to the present invention, the target intake air amount GAO necessary for setting the air-fuel ratio to the target air-fuel ratio is previously shown in the form of a map as a function of the required torque TQ and the engine speed N as shown in FIG. It is stored in the ROM 52. The target opening ST of the throttle valve 21 is stored in advance in the ROM 52 in the form of a map as a function of the required torque TQ and the engine speed N as shown in FIG. On the other hand, the opening degree of the EGR control valve 29 is controlled so that the intake air amount detected by the air flow meter 18 becomes the target intake air amount GAO. Further, the expected reference opening degree SEO of the EGR control valve 29 that will be taken when normal, that is, when the filter 24 is not clogged, is a function of the required torque TQ and the engine speed N as shown in FIG. It is stored in the ROM 52 in advance in the form of a map.

  In the present invention, a NOx storage agent is supported on the filter 24. This NOx storage agent has, for example, alumina as a carrier, and on this carrier, for example, potassium K, sodium Na, lithium Li, alkali metal such as cesium Cs, alkaline earth such as barium Ba, calcium Ca, lanthanum La, yttrium Y, etc. At least one selected from rare earths such as, and a noble metal such as platinum Pt are supported. When the ratio of air and fuel (hydrocarbon) supplied to the engine intake passage, the combustion chamber 5 and the exhaust passage upstream of the filter 24 is referred to as the air-fuel ratio of the exhaust gas, this NOx occlusion agent has the lean air-fuel ratio of the exhaust gas. Sometimes NOx is occluded, and when the air-fuel ratio of the exhaust gas becomes the stoichiometric air-fuel ratio or rich, the NOx is absorbed and released.

  If the filter 24 carrying the NOx occluding agent is disposed in the engine exhaust passage, the NOx occluding agent actually performs the NOx absorbing / releasing action, but the detailed mechanism of the absorbing / releasing action is not clear. However, this absorption / release action is considered to be performed by the mechanism shown in FIG. Next, this mechanism will be described by taking as an example the case where platinum Pt and barium Ba are supported on the support, but the same mechanism can be obtained by using other noble metals, alkali metals, alkaline earths, and rare earths.

  The internal combustion engine shown in FIGS. 1 to 3 has a transmission 35, an electric motor 37, and a battery 41. Hereinafter, the operation of a general internal combustion engine that does not have these will be described. FIG. 6 is a flowchart showing the operation of the general internal combustion engine according to the present invention. In step 101 of FIG. 6, it is determined whether or not the ignition switch of the internal combustion engine has been turned on. If the ignition switch is ON, the process proceeds to step 102. In step 102, the EGR control valve 29 shown in FIG. 1 is opened. Next, the routine proceeds to step 103 where the throttle valve 21 shown in FIG. 1 is closed. Thereby, the EGR passage 27, the intake duct 17 located downstream of the throttle valve 21, the compressor 16, the intake duct 13, the surge tank 12, the engine body 1, the exhaust manifold 22, the exhaust turbine 23, A closed loop is formed by the exhaust pipe 26 to the EGR passage 27. Since the throttle valve 21 is closed, new air does not flow into the engine body 1, and only air remaining in the closed loop at the time of start-up or exhaust gas containing unburned components flows into the engine body 1. To come. Here, since the inflow amount into the engine body 1 and the outflow amount from the engine body 1 are the same, the exhaust gas flowing into the exhaust pipe 26 from the exhaust turbine 23 hardly flows out from the exhaust pipe 26. Since the engine body 1 is operating, air and exhaust gas circulate repeatedly in a closed loop.

  In the engine body 1, the exhaust gas formed when the internal combustion engine was started last time usually remains in the engine body 1, the exhaust manifold 22, the exhaust pipe 26, and the like, and when EGR control is performed, EGR Exhaust gas also remains in the passage 27 and the intake system of the engine. These exhaust gases contain emissions such as CO, CH, NOx and the like. When the engine of a normal internal combustion engine is started, the catalyst carried on the filter 24 has not reached the activation temperature inherent to the catalyst. Therefore, even if the exhaust gas that has passed through the engine body 1 passes through the filter 24, the emission does not decrease so much. The exhaust gas including the emission flows out from the exhaust pipe 26 to the outside. However, in the present invention, since the air or exhaust gas is circulated in the above-described closed loop, the exhaust gas including such an emission hardly flows out from the exhaust pipe 26 to the outside. Further, as can be seen from FIG. 1, since the filter 24 is also included in the above-described closed loop, the relatively high-temperature exhaust gas flowing out from the engine body 1 also passes through the filter 24. For this reason, the catalyst carried on the filter 24 reaches the activation temperature earlier than usual, and the emission in the exhaust gas can be reduced by oxidation.

  As described above, since the inflow amount to the engine body 1 and the outflow amount from the engine body 1 are the same, even if the exhaust pipe 26 downstream from the EGR passage 27 is opened as shown in the figure. Air or exhaust gas hardly flows out from the exhaust pipe 26 to the outside. However, in order to completely prevent air or exhaust gas from flowing out, an exhaust pipe opening / closing valve (not shown) is provided in the exhaust pipe 26 downstream of the EGR passage 27, and the exhaust gas circulates in the above-described closed loop. Sometimes, this exhaust pipe on-off valve may be closed.

  Incidentally, in an internal combustion engine as shown in FIG. 1 and the like, fuel is injected from the fuel injection valve 6 into the combustion chamber 5. The injected fuel is a constant amount when the internal combustion engine is operating stably. However, since the temperature of the combustion chamber 5 and the like is low when the engine is started, not all of the injected fuel becomes a combustible mixture and burns. For this reason, normally, in order to maintain the amount of combustible air-fuel mixture at the time of starting the engine, the amount of fuel injected at the time of starting the engine is made larger than the amount of fuel at the time of stable operation. In other words, the amount of fuel at the time of starting the engine is larger than that at the time of stable operation by the increased amount of starting. The fuel for the increased starting amount is discharged from the exhaust pipe 26 together with the exhaust gas as an unburned component without being completely burned in the engine body. In the case of a normal internal combustion engine, the emissions increase due to these unburned components. Similarly, in the case of a gasoline engine (not shown), when the engine is started, the fuel is injected into the intake port by an amount corresponding to the increased starting amount, which similarly leads to an increase in emissions.

  On the other hand, in the present invention, the exhaust gas containing a relatively large amount of unburned components discharged from the engine body 1 when the engine is started passes through the exhaust manifold 22, the exhaust turbine 23, the exhaust pipe 26, and the EGR passage 27 and is taken into the intake air. It flows into the system again. When exhaust gas containing a large amount of unburned components is repeatedly circulated to the engine body 1 through the closed loop, most of the unburned components become a combustible air-fuel mixture. A proper amount of combustible mixture can be obtained. It can be determined, for example, by the number of cycles K of the internal combustion engine whether or not most of the exhaust gas exhausted from the engine body 1 after starting the engine and containing many unburned components has become a combustible mixture.

  Referring again to FIG. 6, in step 104, the cycle number K of the internal combustion engine is obtained from the crank angle sensor 46 through the electronic control unit 50. The cycle number K is determined according to the engine speed N. For example, when the internal combustion engine is a four-cylinder internal combustion engine as shown in the figure, a value half the engine speed N corresponds to the cycle number K. Next, the routine proceeds to step 105, where it is determined whether or not the acquired cycle number K is larger than a predetermined cycle number KA. The cycle number KA is a cycle number corresponding to a time sufficient for the exhaust gas discharged from the engine body 1 after the engine start to circulate and become a combustible mixture. As shown in FIG. 7A, the cycle number KA is obtained in advance in the form of a map as a function of, for example, the required load L and the engine coolant temperature T, and is stored in the ROM 52 of the electronic control unit 50 or the like. . In FIG. 7A, the cycle number KA is obtained as a function of the required load L and the engine coolant temperature T, but other parameters, for example, the temperature of the filter 24 detected by the temperature sensor 43 and the previous engine. The elapsed time from the stop may be adopted as a parameter. Further, as the cycle number KA, if the starter is activated, a cycle number corresponding to a time sufficient for the explosion to continuously occur in the plurality of combustion chambers 5 of the engine body 1 can be adopted.

  If it is determined in step 105 that the cycle number K is not greater than the predetermined cycle number KA, the process proceeds to step 104 and the process is repeated. On the other hand, if it is determined that the cycle number K is greater than the predetermined cycle number KA, the routine proceeds to step 106. At this time, since it is determined that a sufficient amount of the combustible air-fuel mixture is formed in the cylinder, there is no need for the fuel for the starting increase amount. Therefore, in step 106, the fuel weak injection control is performed to inject the amount of fuel excluding the starting increase amount. Thereby, in the present invention, it is also possible to reduce the fuel injection amount corresponding to the startup increase amount.

  Furthermore, it progresses to step 107 and acquires the cycle number K again. Next, the routine proceeds to step 108, where it is determined whether or not this cycle number K is larger than a predetermined cycle number KB. The number of cycles KB is larger than the number of cycles KA described above. Like the number of cycles KA, the number of cycles KB is obtained in advance in the form of a map as a function of, for example, the required load L and the engine coolant temperature T. It is stored in the ROM 52 or the like (see FIG. 7B). The number of cycles KB is, for example, the number of cycles corresponding to the time during which the unburned components in the closed loop can be consumed. If it is determined in step 108 that the cycle number K is larger than the predetermined cycle number KB, the routine proceeds to step 109. On the other hand, if it is determined that the number of cycles is not greater than the predetermined number of cycles KB, the process proceeds to step 107 and the process is repeated. Next, in step 109, the throttle valve 21 is opened, and in step 110, the EGR control valve 29 is closed. As a result, the internal combustion engine operates under normal control.

  In FIG. 6, the throttle valve 21 is closed after opening the EGR control valve 29 (step 102 and step 103), and the EGR control valve 29 is closed after opening the throttle valve 21 (step 109 and step 103). 110), the order of closing and opening the throttle valve 21 and the EGR control valve 29 may be reversed. For example, the opening of the EGR control valve 29 and the closing of the throttle valve 21 may be performed simultaneously. .

  FIG. 8 is a flowchart for performing catalyst temperature rise control. The control shown in the flowchart of FIG. 8 is performed after all the steps of FIG. 6 are completed, but the control itself shown in FIG. 8 may not be performed. In step 111 of FIG. 8, the cycle number K is acquired again, and in step 112, it is determined whether or not this cycle number is larger than a predetermined cycle number KC. The cycle number KC is a larger value than the cycle number KB described above, and is obtained in advance in the form of a map as a function of, for example, the required load L and the engine coolant temperature T, similarly to the cycle number KA and the cycle number KB. It is stored in the ROM 52 of the electronic control unit 50 (see FIG. 7C). The cycle number KC is, for example, a cycle number corresponding to a time sufficient for a complete explosion of the internal combustion engine (a state in which explosion in the combustion chamber 5 occurs continuously even when the starter is in an OFF state). When the cycle number K is larger than the predetermined cycle number KC at step 112, the routine proceeds to step 113. If the cycle number K is not larger than the predetermined cycle number KC, the routine proceeds to step 111 and the process is repeated.

  The catalyst temperature increase control performed from step 113 to step 115 is, for example, low temperature combustion. Here, the low temperature combustion means that an extremely large amount of exhaust gas is recirculated from the exhaust side to the intake side of the internal combustion engine so that the amount of soot generated becomes a peak in the combustion chamber rather than the amount of recirculation gas (EGR gas). Combustion with a large amount of EGR gas and almost no soot. That is, for example, as shown in FIG. 1, low temperature combustion is performed by recirculating exhaust gas in the exhaust pipe 26 through the EGR passage 27 to the intake duct 17. In step 113, the target opening ST of the throttle valve 21 is calculated from the map shown in FIG. 4B, and the opening of the throttle valve 21 is set as this target opening. Next, at step 114, the target opening degree SEO of the EGR control valve 29 is calculated from the map shown in FIG. 5, and the opening degree of the EGR control valve 29 is made the target opening degree SEO. Next, in step 115, fuel injection control is performed so that the inside of the combustion chamber 5 is in a lean atmosphere, whereby low-temperature combustion is performed. The fuel injection amount is calculated from a map relating to the fuel injection amount similar to that shown in FIGS. Under low temperature combustion, the temperature of the filter 24 in the casing 25 can be raised from, for example, about 500 ° C. to about 600 ° C. by introducing EGR gas. Thereby, unburned components such as HC adhering to the above-described closed loop, in particular, the inner wall of the exhaust pipe 26 and the EGR passage 27 can be removed by combustion.

  Next, the routine proceeds to step 116 where auxiliary injection control is performed. The auxiliary injection control may not be performed when the unburned components are sufficiently removed by the processing from step 113 to step 115. Whether or not the auxiliary injection control shown in step 116 is to be performed may be determined from the pressure change detected by the differential pressure sensor 61. For example, when the pressure difference between the upstream side and the downstream side of the filter 24 detected by the differential pressure sensor 61 is larger than a predetermined value, it is determined that PM is accumulated in the filter 24, and the auxiliary injection control is performed. I do. Further, whether or not to perform the auxiliary injection control shown in step 116 may be determined from the temperature change detected by the temperature sensor 43. For example, when the temperature change detected by the temperature sensor 43 before and after step 115 is smaller than a predetermined value, it is determined that the temperature rise effect by the injection control in step 115 is small, and the auxiliary injection control is performed.

  In the auxiliary injection control performed in step 116, the main injection Qm of the fuel injection performed by the fuel injection valve 6 is slightly delayed from the compression top dead center (TDC), that is, the control performed on the retard side, after the main injection Qm. And post injection Qp performed in the expansion stroke immediately before the exhaust valve 9 is opened. Either the main injection Qm delay or the post injection Qp, or both the main injection Qm delay and the post injection Qp may be performed. In any case, the temperature of the filter 24 can be raised, and as a result, unburned components such as HC adhering to the inner wall of the closed loop can be removed by combustion. As a matter of course, other catalyst temperature increase control may be performed. When the internal combustion engine is a gasoline engine not shown in FIG. 1 or the like, the ignition timing may be shifted to the retard side.

  FIG. 9 and FIG. 10 are flowcharts showing the operation when the internal combustion engine having the function as the hybrid engine shown in FIG. The processes in the flowcharts shown in these drawings are repeatedly performed. In step 1020 of FIG. 9, the input signal is processed. Next, in step 1030, it is determined whether or not the eco-run is being performed, that is, whether or not the vehicle is being stopped. Eco-run means that the internal combustion engine is stopped and the vehicle equipped with the internal combustion engine is completely stopped, and that the internal combustion engine is stopped but the battery 35 is set through the transmission ratio setting of the transmission 35. 41, the vehicle itself includes both cases where the vehicle is traveling by driving from the electric motor 37. If it is determined in step 1030 that the eco-run is not being performed, the process proceeds to step 1040 to determine whether or not the eco-run condition is satisfied.

  The eco-run conditions in step 1040 are that the vehicle speed is not more than a predetermined value close to 0 (determined by the signal of the vehicle speed sensor), the foot brake is ON (determined by the signal of the foot brake sensor), and the accelerator is OFF. (Determined by the signal of the accelerator opening sensor), that the internal combustion engine water temperature is equal to or higher than a predetermined value (determined by the signal of the water temperature sensor), etc. are established in parallel.

  If it is determined in step 1040 that the eco-run condition is not satisfied, the process proceeds to step 1050 to continue driving the internal combustion engine. On the other hand, if an affirmative determination is made in step 1040, the routine proceeds to step 1070, where the internal combustion engine is stopped.

  On the other hand, if it is determined in step 1030 that the engine is in an eco-run, the process proceeds to step 1080 and it is determined whether or not an eco-run return condition, that is, a restart condition for the internal combustion engine is satisfied. If the eco-run return condition is not satisfied, the routine proceeds to step 1110, where the internal combustion engine is stopped. If it is determined in step 1080 that the eco-run return condition is satisfied, the routine proceeds to step 1090, where the internal combustion engine is started using the starter. Next, the process proceeds to step 1100.

  Details of the process X described in step 1100 are shown in FIG. A part of the steps shown in FIG. 10 is the same as the step shown in FIG. As described with reference to FIG. 6, the EGR control valve 29 is opened in step 1101 and the throttle valve 21 is closed in step 1102. Next, in step 1103, the speed ratio of the transmission 35 is adjusted, and the load of the internal combustion engine is set to a predetermined low load. In step 1104, the electric motor 37 is driven using the battery 41, and control for assisting the difference between the original load of the internal combustion engine and a predetermined low load is performed. For this reason, even when the engine is started, the vehicle equipped with the internal combustion engine can quickly reach the desired speed.

  Control from step 1105 to step 1109 is the same as step 104 to step 108 in FIG. In step 1110, the throttle valve 21 is opened, and in step 1111 the EGR control valve 29 is closed, so that the internal combustion engine is brought into normal control. Further, in step 1112, the transmission ratio of the transmission 35 is adjusted to increase the load of the internal combustion engine from a predetermined low load to the original load. At this time, since the desired speed can be maintained only by the internal combustion engine, control is then performed to charge the battery 41 as appropriate in step 1113, and the flow returns to the flow shown in FIG.

  As can be seen with reference to FIGS. 9 and 10, when the internal combustion engine is mounted on the eco-run vehicle, the internal combustion engine is frequently stopped (step 1070) and started (step 1090). For this reason, if it is a prior art internal combustion engine, exhaust gas with much emission will be discharged | emitted comparatively frequently. However, in the present invention, since the EGR control valve 29 is opened in step 1101 and the throttle valve 21 is closed in step 1102, the exhaust gas circulates in the above-described closed loop and is not discharged to the outside. Therefore, it is extremely advantageous to mount the internal combustion engine of the present invention on an eco-run vehicle.

  Further, as the engine is frequently stopped and started, the temperature of the catalyst carried on the particulate filter 24 also frequently increases and decreases. Therefore, although there are many states where the catalyst is below the specific activation temperature, the EGR control valve 29 is opened (step 1101) and the throttle valve 21 is closed (step 1102) when the engine is started. For the same reason as described with reference to FIG. 6, the catalyst reaches the activation temperature earlier than the normal case, and this also makes it possible to reduce the emission in the exhaust gas.

  FIG. 11 is an overall view of a compression ignition type internal combustion engine according to another embodiment. The reference numerals used in FIG. 1 and FIG. 2 and the members corresponding to the same reference numerals in FIG. 11 are the same as those in FIG. 1 and FIG. In the internal combustion engine shown in FIG. 11, the arrangement structure or the position of the EGR passage is different. In FIG. 11, an EGR passage 67 that connects the exhaust manifold 22 and the intake duct 13 downstream from the intercooler 14 is provided. An EGR control valve 69 provided in the EGR passage 67 is provided by a step motor 68. Operate. An intercooler 70 is provided in the EGR passage 67. As can be seen from FIG. 11, the exhaust gas flowing through the EGR passage 67 does not pass through the exhaust turbine 23 of the exhaust turbocharger 15. Therefore, the pressure in the EGR passage 67 shown in FIG. 11 is higher than the pressure in the EGR passage 27 shown in FIG.

  In the internal combustion engine having the EGR passage 67 as shown in FIG. 11, the EGR control valve 69 is opened and the throttle valve 21 is closed when the engine is started as described above with reference to FIG. Thus, a closed loop is formed by the engine body 1, the exhaust manifold 22, the EGR passage 67, and the intake duct 13 downstream from the throttle valve 21, and air or exhaust gas circulates in the closed loop. Therefore, as in the case of the above-described embodiment, exhaust gas containing a relatively large amount of emissions can be suppressed from being discharged from the exhaust pipe 26 to the outside.

  Since the closed loop described with reference to FIG. 1 passes through the exhaust turbocharger 15, it is longer than the closed loop of FIG. 11, and therefore the volume of the closed loop is larger in the case of FIG. For this reason, the amount of emissions in the closed loop is also larger in the case of FIG. Therefore, in the embodiment shown in FIG. 1, a larger amount of emission is prevented from flowing out from the internal combustion engine than in the embodiment shown in FIG. Also, as a matter of course, both the amount of residual oxygen and the amount of unburned components in the exhaust gas in the entire closed loop of FIG. 1 are larger than the amounts of oxygen and unburned components in the case of FIG. In this embodiment, it is preferable that the time for opening the EGR control valve 29 and closing the throttle valve 21 (corresponding to the number of cycles) is longer than that in the case of FIG.

  In the case where the exhaust turbocharger 15 shown in FIG. 11 does not exist, and in FIG. 11, a filter (not shown) equivalent to the filter 24 is separately provided in the EGR passage 67 upstream of the EGR control valve 69. Even so, it is clear that it falls within the scope of the present invention.

1 is an overall view of a compression ignition type internal combustion engine. It is a sectional side view of an engine body. It is a general view which shows another Example of a compression ignition type internal combustion engine. It is a figure which shows maps, such as target intake air amount. It is a figure which shows the map of the prediction reference | standard opening degree of an EGR control valve. It is a flowchart which shows the operation | movement based on this invention about a general internal combustion engine. It is a figure which shows the map of target cycle number. It is a flowchart for performing catalyst temperature rising control. It is a flowchart which shows the operation | movement based on this invention of an eco-run vehicle. It is a flowchart which shows the operation | movement based on this invention of an eco-run vehicle. It is a general view of the compression ignition type internal combustion engine of other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine main body 5 ... Combustion chamber 13 ... Intake duct 15 ... Turbocharger 16 ... Compressor 17 ... Intake passage 21 ... Throttle valve 23 ... Exhaust turbine 24 ... Particulate filter 26 ... Exhaust pipes 27, 67 ... EGR passage (exhaust gas re- Circulation passage)
29, 69 ... EGR control valve (recirculation exhaust gas control valve)

Claims (5)

An exhaust gas recirculation passage for recirculating exhaust gas in the exhaust passage discharged from the combustion chamber to an intake passage downstream of the throttle valve of the internal combustion engine;
A recirculation exhaust gas control valve capable of controlling the amount of recirculation exhaust gas flowing through the exhaust gas recirculation passage;
When the internal combustion engine is started, the throttle valve is closed and the recirculation exhaust gas control valve is opened. If the number of cycles of the internal combustion engine exceeds a predetermined number of cycles after the internal combustion engine is started, the throttle valve An internal combustion engine in which a valve is opened and the recirculation exhaust gas control valve is closed.   And a catalyst having an oxidation function provided in the exhaust passage or a filter carrying the catalyst, wherein the exhaust gas recirculation passage extends from downstream of the catalyst or filter to the intake passage downstream of the throttle valve. 2. An internal combustion engine according to claim 1, which extends.   The internal combustion engine according to claim 1, further comprising a turbocharger, wherein the exhaust gas recirculation passage connects a downstream side of the exhaust gas turbine of the turbocharger and an upstream side of the compressor of the turbocharger.   The internal combustion engine according to any one of claims 1 to 3, wherein the internal combustion engine is stopped when a predetermined condition is satisfied, and is restarted when the predetermined condition is not satisfied. organ.   3. The internal combustion engine according to claim 2, wherein when the number of cycles of the internal combustion engine exceeds another predetermined number of cycles after the start of the internal combustion engine, temperature increase control for increasing the temperature of the catalyst is performed.

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