JP2009103014A - Internal combustion engine control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine control system suppressing an increase of discharged PM in number, which is caused by direct contact of fuel sprays to an intake valve when the temperature of the valve is low. <P>SOLUTION: In the control system, when temperature Tv of the intake valve is higher than predetermined temperature A, the internal combustion engine is normally operated. A water pump e.g. is subjected to a normal control at a rotational speed (i.e., discharge volume of engine-cooling water) determined on the basis of operation of the internal combustion engine. When the temperature Tv of the intake valve is at prescribed temperature A or lower, "control for a temperature rise in the intake-valve " is excuted. For example, an operation of the water pump is stopped to reduce the degree of cooling the internal combustion engine by engine-cooling water as compared with that in the normal control time, and temperature of the intake-valve thereby becomes higher than the prescribed temperature A. As a result, in the case where a temperature of the intake-valve is low, the increase in the number of discharged PM, which is caused by direct contact of fuel spray to the intake valve, is suppressed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that is applied to a direct injection internal combustion engine (in particular, a spark ignition internal combustion engine) that includes a fuel injection valve that directly injects fuel into a combustion chamber of the internal combustion engine. Hereinafter, “the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber of the internal combustion engine” may be simply referred to as “air-fuel ratio”, and “the internal combustion engine” may be simply referred to as “engine”.

2. Description of the Related Art Conventionally, an in-cylinder injection type (spark ignition type) internal combustion engine is widely known (see, for example, Patent Document 1). In an in-cylinder injection type internal combustion engine, when an amount of fuel determined so that the air-fuel ratio matches a target air-fuel ratio (for example, the stoichiometric air-fuel ratio) is injected in the intake stroke, the fuel is injected into the intake port Compared to the case of a conventional port injection type internal combustion engine, the temperature of the air-fuel mixture in the combustion chamber (before combustion) can be lowered by the influence of the vaporization heat of the spray fuel. As a result, the combustion efficiency can be increased for reasons such as an increased compression ratio.
Japanese Patent Laid-Open No. 10-176562

  In a direct injection internal combustion engine, depending on the fuel injection timing, the fuel spray that moves in the combustion chamber by injection may directly contact the top surface of the piston or the back surface of the intake valve. The fuel that has come into contact with the top surface of the piston tends to adhere and remain on the top surface of the piston as it is, and the fuel that has come into contact with the back surface of the intake valve is reflected on the back surface and tends to adhere and remain on the top surface of the combustion chamber. As described above, when the amount of fuel adhering to or remaining on the top surface of the piston or the combustion chamber is large, the number of exhaust particles of PM (particulate matter, particulate matter) tends to increase. Here, the number of PM exhaust particles is, for example, the total number of PM exhaust particles when the engine is operated in a predetermined pattern.

  In recent years, there has been an increasing demand for reducing the number of PM exhaust particles for automobile internal combustion engines. Under such circumstances, there is an increasing need to reduce the number of PM exhaust particles even in a cylinder injection internal combustion engine.

  Recent research by the inventor has shown that the number of PM exhaust particles has a very strong correlation with the temperature of the intake valve, and that the lower the intake valve temperature, the greater the tendency for the number of PM exhaust particles to increase. Yes. This is considered to be based on the fact that the lower the intake valve temperature, the larger the amount of fuel that is reflected and adhered to the top surface of the combustion chamber by the back of the intake valve. Therefore, in order to suppress the increase in the number of PM exhaust particles, some special control (hereinafter referred to as “PM reduction control”) for reducing the number of PM exhaust particles when the intake valve temperature is low is performed. There is a need.

  In view of this, an object of the present invention is to provide an apparatus capable of suppressing an increase in the number of PM exhaust particles caused by direct contact of fuel spray with an intake valve when the intake valve temperature is low.

  The fuel injection control device according to the present invention is applied to a cylinder injection type (spark ignition type) internal combustion engine provided with a fuel injection valve that directly injects fuel into a combustion chamber of the internal combustion engine. The fuel injection valve is arranged so that the injected fuel directly contacts the intake valve (without contacting other members while moving in the combustion chamber) depending on the injection timing.

  The control apparatus for an internal combustion engine according to the present invention includes an intake valve temperature acquisition means for acquiring the temperature of the intake valve, and an intake valve for increasing the temperature of the intake valve when the temperature of the intake valve falls below a predetermined temperature. Intake valve temperature rise control means for performing temperature rise control.

  In this case, the intake valve temperature rise control means, in particular, when the injection timing is controlled to a timing at which the injected fuel is in direct contact with the intake valve while moving in the combustion chamber (that is, intake of fuel spray) When the temperature of the intake valve becomes equal to or lower than the predetermined temperature in the case where PM can be discharged due to direct contact with the valve), the intake valve temperature increase control is performed. Further, the “predetermined temperature” is set to a temperature at which the increase in the number of PM exhaust particles due to the direct contact of the fuel spray to the intake valve becomes significant when the temperature of the intake valve becomes equal to or lower than that temperature.

  According to the above configuration, the intake valve temperature can be increased when the intake valve temperature is low. As a result, the amount of fuel reflected on the back surface of the intake valve and adhering to and remaining on the top surface of the combustion chamber is reduced. As a result, an increase in the number of PM exhaust particles caused by direct contact of fuel spray with the intake valve can be suppressed. . That is, the “intake valve temperature rise control” can be the “PM reduction control” described above.

  As the intake valve temperature increase control, for example, control for reducing the degree of cooling of the internal combustion engine by the coolant for cooling the internal combustion engine can be executed. Specifically, as such control, for example, control such as reducing the discharge flow rate of a pump that circulates the coolant or stopping the pump can be executed. Thereby, the intake valve temperature can be increased.

  Further, as the intake valve temperature increase control, for example, a control for bringing the closing timing of the intake valve closer to the intake bottom dead center can be executed. Specifically, for example, when the intake valve temperature is higher than a predetermined temperature, the intake valve closing timing set after the intake bottom dead center is advanced (the intake valve opening / closing timing (intake VVT) is advanced). ) The valve closing timing of the intake valve is brought closer to the intake bottom dead center by speeding up. Thereby, the compression end temperature (cylinder gas temperature at the compression top dead center) can be increased, and as a result, the intake valve temperature can be increased.

  Further, as the intake valve temperature increase control, for example, control for reducing the degree of cooling of the EGR gas by an EGR cooler that cools the EGR gas returned to the intake system by an EGR device that returns a part of the exhaust gas to the intake system. Can be executed. Specifically, as such control, for example, control such as reducing the flow rate of the coolant flowing in the EGR cooler (accordingly, the discharge flow rate of the pump that circulates the coolant) or stopping the pump can be executed. Thereby, EGR gas temperature can be raised and, as a result, intake valve temperature can be raised.

  In addition, as the intake valve temperature increase control, for example, control for increasing the ratio (corresponding to the EGR rate) of the flow rate of EGR gas returned to the intake system by the EGR device to the flow rate of fresh air sucked into the intake system. Can be executed. As a result, the amount of hot EGR gas flowing into the combustion chamber can be increased, and as a result, the intake valve temperature can be increased.

  Further, as the intake valve temperature increase control, for example, a control for reducing the degree of cooling of the compressed fresh air by an intercooler that cools the fresh air sucked into the intake system and compressed by the supercharger can be executed. .

  Specifically, as such control, for example, control such as decreasing the flow rate of the coolant flowing in the intercooler (accordingly, the discharge flow rate of the pump that circulates the coolant) or stopping the pump can be executed. In addition, a first passage that passes through the intercooler and a second passage that bypasses the intercooler are provided in parallel in the intake passage downstream of the turbocharger (compressor), and flows through the first and second passages. When an adjustment valve that adjusts the flow rate of fresh air is provided, the control valve is controlled to increase the flow rate on the second passage side. Thereby, the temperature of the intake fresh air can be increased, and as a result, the intake valve temperature can be increased.

  Further, when the temperature of the intake valve becomes equal to or lower than the predetermined temperature in the lean operation state in which the air-fuel ratio of the air-fuel mixture is controlled to coincide with the lean air-fuel ratio rather than the stoichiometric air-fuel ratio, the intake valve temperature increase control is performed. Then, a control for switching the operation state of the internal combustion engine from the lean operation state to a stoichiometric operation state in which the air-fuel ratio of the air-fuel mixture is controlled to coincide with the stoichiometric air-fuel ratio can be executed. As a result, when the intake valve temperature becomes a predetermined temperature or lower in the lean operation state where the combustion temperature is relatively low, the operation is switched to the stoichiometric operation state where the combustion temperature is higher than the lean operation state, and as a result, the intake valve temperature is increased. Can do.

  By the way, in the case of the above-described in-cylinder spark ignition internal combustion engine, the idling rotational speed is set to a larger value between the time after the cold start and the time when the warm-up is completed. During the first idle control), fuel injection is performed in the latter half of the compression stroke, and the ignition timing is significantly retarded to a timing later than the compression top dead center, so that the exhaust system is utilized while utilizing so-called stratified combustion. A control (hereinafter, referred to as “catalyst warm-up control A”) that greatly accelerates warm-up of the disposed catalyst is known.

  Thus, performing fuel injection in the latter half of the compression stroke means that fuel injection is performed while the piston is moving up near the top dead center. In this case, the fuel spray tends to come into direct contact with the piston top surface. Therefore, the increase in the number of PM exhaust particles due to the direct contact of the fuel spray to the piston top surface is likely to occur.

  Here, it has also been found that the lower the temperature of the piston top surface, the greater the tendency for the number of PM discharged particles to increase. This is considered to be based on the fact that the lower the temperature of the piston top surface, the larger the amount of fuel adhering to and remaining on the piston top surface. As described above, when the temperature of the piston top surface is low during the execution of the above-described “catalyst warm-up control A”, the number of PM exhaust particles is likely to increase due to the direct contact of the fuel spray with the piston top surface. Become.

  On the basis of such a viewpoint, in the control device according to the present invention, the fuel injection valve causes the fuel injected depending on the injection timing (in addition to the intake valve) also to the top surface of the piston (while moving in the combustion chamber). Between the cold start and the completion of warm-up (for example, during the above-mentioned first idle control), the intake stroke In addition, fuel is injected from the fuel injection valve in the second half of the compression stroke or only in the second half of the compression stroke, and the ignition timing is retarded to a timing after the compression top dead center to warm the catalyst disposed in the exhaust system. When the catalyst warm-up control means for performing the “catalyst warm-up control A” for accelerating the engine is provided, the piston top surface temperature obtaining means for obtaining the temperature of the top surface of the piston, and the “catalyst warm-up control” A "middle When the top surface temperature of the piston is equal to or lower than the first temperature, fuel injection in the latter half of the compression stroke is prohibited and fuel injection is performed only in the intake stroke to suppress fuel adhesion to the top surface of the piston. It is preferable to provide a piston top surface fuel adhesion suppressing means for controlling the catalyst warm-up control means.

  Thereby, when the temperature of the piston top surface is low during the execution of “catalyst warm-up control A”, fuel injection in the latter half of the compression stroke is prohibited. As a result, it is possible to suppress an increase in the number of PM exhaust particles caused by direct contact of the fuel spray injected in the latter half of the compression stroke with the piston top surface. If fuel injection is not performed in the latter half of the compression stroke, so-called stratified combustion cannot be used. Therefore, if the ignition timing is significantly retarded to a timing after the compression top dead center, misfire is likely to occur. Therefore, in this case, the ignition timing needs to be advanced from the timing controlled based on the “catalyst warm-up control A”. As a result, the catalyst warm-up speed becomes slower than during the execution of “catalyst warm-up control A”. Hereinafter, the catalyst warm-up control executed in this way is also referred to as “catalyst warm-up control B”.

  In addition, as described above, when the “catalyst warm-up control A” is executed instead of the “catalyst warm-up control A” when the temperature of the piston top surface is equal to or lower than the first temperature, the piston top fuel In the “catalyst warm-up control A”, the adhesion suppressing means has a temperature of the top surface of the piston that is higher than the first temperature and lower than or equal to a second temperature that is higher than the first temperature. When the surface temperature is lower than the temperature of the intake valve, the ratio of the fuel injection amount in the latter half of the compression stroke to the fuel injection amount in the intake stroke (= compression stroke injection ratio (> 0)) is decreased to It is more preferable that the catalyst warm-up control unit is configured to control the fuel adhesion to the top surface. Hereinafter, the catalyst warm-up control in which the compression stroke injection ratio (> 0) is set smaller than the “catalyst warm-up control A” as described above is also referred to as “catalyst warm-up control C”.

  According to this, when the temperature of the piston top surface is slightly low, “catalyst warm-up control C” is executed instead of “catalyst warm-up control A”. Accordingly, since the fuel injection amount in the latter half of the compression stroke is set to be smaller, it is caused by the direct contact of the fuel spray injected in the latter half of the compression stroke with the top surface of the piston as compared with the time when “catalyst warm-up control A” is executed. The increase in the number of PM exhaust particles to be suppressed can be suppressed. In addition, since fuel injection is ensured in the latter half of the compression stroke, the ignition timing is greatly retarded to a time later than the compression top dead center, and so-called stratified combustion is used, and the catalyst is warmed up significantly. Can be promoted. That is, “catalyst warm-up control B” and “catalyst warm-up control C” can be the above-mentioned “PM reduction control”.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a control device for an internal combustion engine according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of a system in which a control device for an internal combustion engine according to an embodiment of the present invention is applied to an in-cylinder spark-ignition multi-cylinder (four-cylinder) internal combustion engine 10. The internal combustion engine 10 includes a cylinder block unit 20 including a cylinder block, a cylinder block lower case, an oil pan, and the like, a cylinder head unit 30 fixed on the cylinder block unit 20, and a gasoline mixture in the cylinder block unit 20. And an exhaust system 50 for releasing exhaust gas from the cylinder block 20 to the outside.

  The cylinder block unit 20 includes a cylinder 21, a piston 22, a connecting rod 23, and a crankshaft 24. The piston 22 reciprocates in the cylinder 21, and the reciprocating motion of the piston 22 is transmitted to the crankshaft 24 via the connecting rod 23, whereby the crankshaft 24 rotates. The heads of the cylinder 21 and the piston 22 form a combustion chamber 25 together with the cylinder head portion 30.

  The cylinder head portion 30 includes an intake port 31 communicating with the combustion chamber 25, an intake valve 32 that opens and closes the intake port 31, an intake camshaft that drives the intake valve 32, and a phase angle of the intake camshaft (therefore, the intake valve 32). (Hereinafter referred to as “intake VVT”), a variable intake timing device 33 that continuously changes, an actuator 33a of the variable intake timing device 33, an exhaust port 34 that communicates with the combustion chamber 25, and an exhaust port 34. An exhaust valve 35 that opens and closes, an exhaust camshaft 36 that drives the exhaust valve 35, an ignition plug 37, an igniter 38 that includes an ignition coil that generates a high voltage applied to the ignition plug 37, and fuel are directly injected into the combustion chamber 25. An injector (fuel injection valve) 39 is provided.

  The intake system 40 includes an intake manifold 41 including an intake manifold that communicates with the intake port 31 and forms an intake passage together with the intake port 31, an air filter 42 provided at an end of the intake pipe 41, and an intake pipe 41. A throttle valve 43 and a throttle valve actuator 43a that can change the opening cross-sectional area of the passage are provided.

  The exhaust system 50 includes an exhaust manifold 51 that communicates with the exhaust port 34, and an exhaust pipe (exhaust pipe) that is connected to the exhaust manifold 51 (actually, a collection portion of the exhaust manifolds 51 that communicate with each exhaust port 34). ) 52, the upstream three-way catalyst 53 (hereinafter referred to as “first catalyst 53”) disposed (interposed) in the exhaust pipe 52, and the exhaust pipe 52 downstream of the first catalyst 53. A downstream three-way catalyst 54 (hereinafter referred to as “second catalyst 54”) provided (interposed) is provided. The exhaust port 34, the exhaust manifold 51, and the exhaust pipe 52 constitute an exhaust passage.

  On the other hand, this system includes a hot-wire air flow meter 61, a throttle position sensor 62, a cam position sensor 63, a crank position sensor 64, a water temperature sensor 65, an exhaust passage upstream of the first catalyst 53 (in this example, each of the above exhaust manifolds). The air-fuel ratio sensor 66 (hereinafter referred to as “upstream air-fuel ratio sensor 66”) disposed in the collecting portion 51), the exhaust downstream of the first catalyst 53 and upstream of the second catalyst 54. An air-fuel ratio sensor 67 (hereinafter referred to as “downstream air-fuel ratio sensor 67”) disposed in the passage and an accelerator opening sensor 68 are provided.

  The hot-wire air flow meter 61 detects a mass flow rate per unit time of intake air flowing through the intake pipe 41 and outputs a signal representing a mass flow rate (intake air flow rate) Ga. The throttle position sensor 62 detects the opening of the throttle valve 43 and outputs a signal representing the throttle valve opening TA. The cam position sensor 63 generates a signal (G2 signal) indicating the rotational phase angle of the intake camshaft. The crank position sensor 64 generates a signal indicating the rotational phase angle of the crankshaft 24. This signal represents the operating speed NE. The water temperature sensor 65 detects the temperature of the cooling water of the internal combustion engine 10 circulated by the operation of the electric water pump 69, and outputs a signal representing the cooling water temperature THW.

  The upstream air-fuel ratio sensor 66 and the downstream air-fuel ratio sensor 67 are a limit current type oxygen concentration sensor and an electromotive force type (concentration cell type) oxygen concentration sensor, respectively, and output according to the air-fuel ratio of exhaust gas. It is supposed to occur. The accelerator opening sensor 68 detects the operation amount of the accelerator pedal 81 operated by the driver, and outputs a signal representing the operation amount Accp of the accelerator pedal 81.

  The electric control device 70 includes a CPU 71 connected by a bus, a routine (program) executed by the CPU 71, a ROM 72 that stores a table (lookup table, map), and the like, a RAM 73, a backup RAM 74, and an interface 75 including an AD converter. It is the microcomputer which consists of. The interface 75 is connected to the sensors 61 to 68, supplies signals from the sensors 61 to 68 to the CPU 71, and in response to instructions from the CPU 71, the actuator 33a, the igniter 38, the injector 39, and the throttle valve of the variable intake timing device 33. Drive signals are sent to the actuator 43a and the electric water pump 69.

(Increase in the number of PM exhaust particles due to direct contact of fuel spray with intake valve)
In the control apparatus (hereinafter referred to as “this apparatus”) according to the embodiment configured as described above, fuel is usually directly injected into the combustion chamber 25 from the injector 39 during the intake stroke (after complete warm-up). Is done. The fuel injection timing in the intake stroke is determined based on, for example, the engine speed NE, the intake air flow rate Ga, the coolant temperature THW, and the like.

  Depending on the fuel injection timing, as shown in FIG. 2, fuel is injected from the injector 39 in the intake stroke with the intake valve 32 sufficiently lowered (ie, the lift amount is large). As a result, the fuel spray tends to come into direct contact with the back surface of the intake valve 32, and the fuel that has contacted the back surface of the intake valve 32 is reflected as shown by the arrows in the figure and adheres and remains near the top surface of the combustion chamber 25. Easy to do. Due to the adhesion / residue of fuel on the top surface of the combustion chamber 25, the number of PM exhaust particles can be increased.

  Here, as described above, the lower the temperature of the intake valve 32, the stronger the tendency that the number of PM exhaust particles resulting from the direct contact of fuel spray with the intake valve 32 increases. Therefore, when the temperature of the intake valve 32 is low, it is necessary to increase the temperature of the intake valve 32 in order to suppress an increase in the number of PM exhaust particles caused by direct contact of fuel spray with the intake valve 32.

(Actual operation)
Based on the above knowledge, the CPU 71 of the present apparatus repeatedly executes the routine shown in the flowchart of FIG. 3 every elapse of a predetermined time. In this embodiment, the fuel injection timing is normally set during the intake stroke as described above (after complete warm-up), and the ignition timing is set near the compression top dead center (normally after complete warm-up) ( More specifically, it is set slightly before the compression top dead center. The ignition timing is determined based on, for example, the engine speed NE, the intake air flow rate Ga, the coolant temperature THW, and the like.

  That is, first, at step 305, the temperature of the intake valve 32 (intake valve temperature Tv) is calculated. The intake valve temperature Tv is based on one of well-known methods using, for example, the coolant temperature THW, the integrated value of the fuel injection amount Fi, the outputs of the upstream air-fuel ratio sensor 66, the downstream air-fuel ratio sensor 67, and the like. Can be estimated. Alternatively, the temperature of the intake valve 32 may be directly detected by a temperature sensor that can detect the temperature of the intake valve 32.

  In step 310, it is determined whether or not the calculated intake valve temperature Tv is equal to or lower than a predetermined temperature A. The predetermined temperature A is set to a temperature at which the increase in the number of PM exhaust particles due to the direct contact of the fuel spray with the intake valve 32 becomes significant when the temperature of the intake valve 32 becomes lower than that temperature. In step 310, the condition that “the fuel injection timing is controlled to the timing at which the injected fuel directly contacts the intake valve 32” may be added.

  If “No” is determined in step 310, normal control is performed on the water pump 69 in step 315. In this normal control, the rotation speed of the water pump 69 (that is, the discharge flow rate of engine cooling water) is determined based on, for example, the engine rotation speed NE, the intake air flow rate Ga, the cooling water temperature THW, and the like. On the other hand, if “Yes” is determined in step 310, the water pump 69 is stopped in step 320.

  As described above, according to the control device according to the above-described embodiment, when the temperature of the intake valve 32 is higher than the predetermined temperature A, the water pump 69 is rotated based on the operating state of the internal combustion engine. (I.e., the engine cooling water discharge flow rate) is normally controlled. On the other hand, when the temperature of the intake valve 32 is equal to or lower than the predetermined temperature A, the water pump 69 is stopped. Accordingly, the degree of cooling of the internal combustion engine 10 by the cooling water is lower than that during normal control. Thereby, the temperature of the intake valve 32 can be raised and become higher than the predetermined temperature A. As a result, when the temperature of the intake valve 32 is low, an increase in the number of PM exhaust particles due to direct contact of fuel spray with the intake valve 32 can be suppressed.

  The present invention is not limited to the above embodiment, and various modifications can be employed within the scope of the present invention. For example, in the above embodiment, the control for stopping the water pump 69 is executed as the “intake valve temperature rise control”, but the rotational speed of the water pump 69 (that is, the discharge flow rate of engine cooling water) is normally controlled. Control that is set smaller than the time may be executed.

  Further, instead of the routine shown in FIG. 3, the routine shown by the flowchart in FIG. 4 may be repeatedly executed every elapse of a predetermined time. In the routine of FIG. 4, the same steps as those of the routine of FIG. 3 are denoted by the same step numbers as those of FIG. 3 to replace these descriptions (the same applies to the later routines).

  In the routine shown in FIG. 4, when it is determined “No” in step 310, that is, when the intake valve temperature Tv is higher than the predetermined temperature A, in step 405, the variable intake timing device 33 (accordingly, intake air). Normal control is performed on VVT). In this normal control, the intake VVT is determined based on, for example, the engine rotational speed NE, the intake air flow rate Ga, the coolant temperature THW, and the like, and the valve closing timing of the intake valve 32 is set after the intake bottom dead center. On the other hand, if “Yes” is determined in step 310, that is, if the intake valve temperature Tv is equal to or lower than the predetermined temperature A, in step 410, the intake VVT is set to a more advanced side than during normal control. .

  Thus, according to the control apparatus according to this modification, when the temperature of the intake valve 32 is higher than the predetermined temperature A, the intake VVT is normally controlled based on the operating state of the internal combustion engine. On the other hand, when the temperature of the intake valve 32 is equal to or lower than the predetermined temperature A, the intake VVT is set to a more advanced side than during normal control, and the closing timing of the intake valve 32 is brought closer to the intake bottom dead center. As a result, the compression end temperature (in-cylinder gas temperature at the compression top dead center) can be increased, so that the temperature of the intake valve 32 can be increased to be higher than the predetermined temperature A. As a result, as in the above embodiment, when the temperature of the intake valve 32 is low, an increase in the number of PM exhaust particles due to direct contact of fuel spray with the intake valve 32 can be suppressed.

  Further, consider a case where an EGR device is provided as shown in FIG. The EGR device includes an EGR pipe 44 that connects the exhaust manifold 51 and the intake pipe 41, an EGR control valve 45 that controls the flow rate of EGR gas that flows through the EGR pipe 44, an EGR cooler 46 that cools the EGR gas, and an EGR cooler 46 A water pump 47 for controlling the flow rate of the cooling water is provided.

  When this EGR device is provided, the routine shown by the flowchart in FIG. 6 may be repeatedly executed every elapse of a predetermined time instead of the routine shown in FIG. In the routine shown in FIG. 6, when “No” is determined at step 310, that is, when the intake valve temperature Tv is higher than the predetermined temperature A, the normal control is performed on the water pump 47 at step 605. Done. In this normal control, the rotational speed of the water pump 47 (that is, the cooling water discharge flow rate of the EGR cooler 46) is determined based on, for example, the engine rotational speed NE, the intake air flow rate Ga, the cooling water temperature THW, and the like. On the other hand, if “Yes” is determined in step 310, that is, if the intake valve temperature Tv is equal to or lower than the predetermined temperature A, in step 610, the rotational speed of the water pump 47 (that is, the cooling water of the EGR cooler 46). The discharge flow rate) is set to be smaller than that during normal control. Alternatively, the water pump 47 may be stopped.

  As described above, according to the control device according to this modification, when the temperature of the intake valve 32 is higher than the predetermined temperature A, the water pump 47 rotates at a rotational speed (that is, EGR) determined based on the operating state of the internal combustion engine. The cooling water discharge flow rate of the cooler 46 is normally controlled. On the other hand, when the temperature of the intake valve 32 is equal to or lower than the predetermined temperature A, the rotational speed of the water pump 47 (that is, the discharge flow rate of the cooling water of the EGR cooler 46) is set to be lower than that during normal control, and the EGR by the EGR cooler 46 The degree of gas cooling is reduced as compared with normal control. Thereby, EGR gas temperature can be raised and the temperature of the intake valve 32 can be raised. As a result, as in the above embodiment, when the temperature of the intake valve 32 is low, an increase in the number of PM exhaust particles due to direct contact of fuel spray with the intake valve 32 can be suppressed.

  Further, when the above-described EGR device is provided, the routine shown in the flowchart of FIG. 7 may be repeatedly executed every elapse of a predetermined time instead of the routine shown in FIG. In the routine shown in FIG. 7, if “No” is determined in step 310, that is, if the intake valve temperature Tv is higher than the predetermined temperature A, in step 705, the EGR control valve 45 (that is, the EGR rate) is determined. ) Is normally controlled. In this normal control, the EGR rate is determined based on, for example, the engine speed NE, the intake air flow rate Ga, the coolant temperature THW, and the like. On the other hand, if “Yes” is determined in step 310, that is, if the intake valve temperature Tv is equal to or lower than the predetermined temperature A, in step 710, the EGR rate is set larger than that in normal control.

  Thus, according to the control device according to this modification, when the temperature of the intake valve 32 is higher than the predetermined temperature A, the EGR rate is normally controlled based on the operating state of the internal combustion engine. On the other hand, when the temperature of the intake valve 32 is equal to or lower than the predetermined temperature A, the EGR rate is set larger than that during normal control. Thereby, the amount of high-temperature EGR gas flowing into the combustion chamber 25 can be increased, and the temperature of the intake valve 32 can be increased. As a result, as in the above embodiment, when the temperature of the intake valve 32 is low, an increase in the number of PM exhaust particles due to direct contact of fuel spray with the intake valve 32 can be suppressed.

  Further, consider a case where a supercharging system is provided as shown in FIG. In this supercharging system, a compressor TCa of a supercharger (turbocharger) TC is interposed in an intake pipe 41, and an intercooler 48 for cooling air compressed by the compressor TCa is provided in an intake pipe 41 downstream of the compressor TCa. It is intervened. A bypass pipe 41b that bypasses the intercooler 48 is provided. Hereinafter, the compressed air passing through the intercooler 48 is referred to as “cooling fresh air”, and the compressed air passing through the bypass pipe 41b is referred to as “bypass fresh air”. In addition, a control valve 49a that can adjust the flow rate of the cooling fresh air and a control valve 49b that can adjust the flow rate of the bypass fresh air are provided, respectively. By controlling the control valves 49a and 49b, the total fresh air is controlled. The ratio (bypass fresh air ratio) of the bypass fresh air flow rate to the flow rate (cooling fresh air flow rate + bypass fresh air flow rate) can be adjusted.

  When this supercharging system is provided, the routine shown by the flowchart in FIG. 9 may be repeatedly executed every elapse of a predetermined time instead of the routine shown in FIG. In the routine shown in FIG. 9, if “No” is determined in step 310, that is, if the intake valve temperature Tv is higher than the predetermined temperature A, in step 905, the control valves 49 a and 49 b (accordingly, bypassing is performed). Normal control is performed on the fresh air ratio). In this normal control, the bypass fresh air ratio is determined based on, for example, the engine speed NE, the intake air flow rate Ga, the coolant temperature THW, and the like. On the other hand, if “Yes” is determined in step 310, that is, if the intake valve temperature Tv is equal to or lower than the predetermined temperature A, in step 910, the bypass fresh air ratio is set to be larger than that during normal control. (In other words, the bypass fresh air flow rate is set larger than that during normal control). Alternatively, the discharge flow rate of the water pump that circulates the cooling water circulating in the intercooler 48 may be reduced, and the water pump may be stopped.

  Thus, according to the control device according to this modification, when the temperature of the intake valve 32 is higher than the predetermined temperature A, the bypass fresh air ratio is normally controlled based on the operating state of the internal combustion engine. On the other hand, when the temperature of the intake valve 32 is equal to or lower than the predetermined temperature A, the bypass fresh air ratio is set to be larger than that during normal control, and the degree of fresh air cooling by the intercooler 48 is reduced as compared with that during normal control. As a result, the temperature of the intake fresh air can be increased and the temperature of the intake valve 32 can be increased. As a result, as in the above embodiment, when the temperature of the intake valve 32 is low, an increase in the number of PM exhaust particles due to direct contact of fuel spray with the intake valve 32 can be suppressed.

  When such a supercharging system is provided, the routine shown by the flowchart in FIG. 10 may be repeatedly executed every elapse of a predetermined time. In the routine shown in FIG. 10, when “No” is determined in step 310, that is, when the intake valve temperature Tv is higher than the predetermined temperature A, in step 1005, the boost pressure of the supercharger TC is set. On the other hand, normal control is performed. In this normal control, the supercharging pressure is determined based on, for example, the engine speed NE, the intake air flow rate Ga, the coolant temperature THW, and the like.

  On the other hand, if “Yes” is determined in step 310, that is, if the intake valve temperature Tv is equal to or lower than the predetermined temperature A, it is determined in step 1010 whether or not the injection period is longer than the predetermined period. When it is determined “No”, the normal control for the above-described supercharging pressure is performed in Step 1005. On the other hand, if “Yes” is determined, the supercharging pressure is limited to a predetermined value or less in step 1015. Here, the “predetermined value” is a value smaller than a normal relief pressure (upper limit value) for the supercharging pressure.

  Thus, in this example (reference example), when the temperature of the intake valve 32 is higher than the predetermined temperature A, the supercharging pressure is normally controlled based on the operating state of the internal combustion engine. On the other hand, when the temperature of the intake valve 32 is equal to or lower than the predetermined temperature A and the injection period is longer than the predetermined period, that is, the injected fuel has many opportunities to directly contact the intake valve 32 (and the piston top surface) and has come into contact. Is likely to adhere and remain on the combustion chamber top surface (and piston top surface), the supercharging pressure is limited to the predetermined value or less. Thereby, the fuel injection amount is limited and the injection period is limited. As a result, the chance that the injected fuel directly contacts the intake valve 32 (and the piston top surface) can be suppressed, and the number of PM exhaust particles due to the direct contact of the fuel spray to the intake valve 32 (and piston top surface) increases. Can be suppressed.

  In addition, a “lean operation state” in which the air-fuel ratio of the air-fuel mixture is controlled to match the lean air-fuel ratio rather than the stoichiometric air-fuel ratio, and a “stoichiometric operation” in which the air-fuel ratio of the air-fuel mixture is controlled to match the stoichiometric air-fuel ratio. Consider a case where “state” and “state” are configured to be switchable according to the driving state. The “lean operation state” can be selected, for example, at a predetermined low rotation and low load.

  In this case, instead of the routine shown in FIG. 3, the routine shown in the flowchart in FIG. 11 may be repeatedly executed every elapse of a predetermined time. In the routine shown in FIG. 11, it is determined in step 1105 whether or not the engine is in the “lean operation state”, and if “Yes” is determined, the process proceeds to step 310 and “No” is determined (ie, When the intake valve temperature Tv is higher than the predetermined temperature A), at step 1110, the “lean operation state” is continued. On the other hand, if “Yes” is determined in step 310 (that is, if the intake valve temperature Tv is equal to or lower than the predetermined temperature A), the “lean operation state” is switched to the “stoichiometric operation state” in step 1115. .

  Thus, according to the control device according to this modification, when the temperature of the intake valve 32 is higher than the predetermined temperature A in the “lean operation state”, the “lean operation state” is continued. On the other hand, when the temperature of the intake valve 32 is equal to or lower than the predetermined temperature A in the “lean operation state”, the “lean operation state” is switched to the “stoichiometric operation state”. That is, when the temperature of the intake valve 32 is low in the “lean operation state” where the combustion temperature is relatively low, the state is switched to the “stoichiometric operation state” where the combustion temperature is higher than the “lean operation state”. As a result, the temperature of the intake valve 32 can be increased. As a result, as in the above embodiment, when the temperature of the intake valve 32 is low, an increase in the number of PM exhaust particles due to direct contact of fuel spray with the intake valve 32 can be suppressed.

  Further, in this apparatus, during the period from the cold start to the completion of warm-up (and during so-called fast idle control), the above-mentioned “catalyst warm-up control A” (compression stroke second half injection + ignition timing significant delay) Consider a case in which control for greatly promoting catalyst warm-up is performed.

  Thus, performing fuel injection in the latter half of the compression stroke means that fuel injection is performed while the piston 22 is moving up near the top dead center, as shown in FIG. In this case, the fuel spray tends to come into direct contact with the top surface of the piston 22. Therefore, the increase in the number of PM exhaust particles due to the direct contact of the fuel spray to the piston top surface is likely to occur.

  Here, as described above, the lower the temperature of the piston top surface, the higher the number of PM exhaust particles resulting from the direct contact of the fuel spray with the piston top surface. Therefore, when the “catalyst warm-up control A” is performed, it is necessary to suppress the increase in the number of PM exhaust particles due to the direct contact of the fuel spray with the piston top surface as the temperature of the piston top surface is lower.

  Based on the above viewpoint, in this apparatus, it is preferable that the routine shown by the flowchart in FIG. 13 (in addition to the routine shown in FIG. 3) is repeatedly executed every elapse of a predetermined time. In the routine shown in FIG. 13, it is determined in step 1305 whether or not the fast idle control is being performed (that is, whether or not the warm-up is completed after the cold start). If it is determined, the intake valve temperature Tv is calculated at step 1310 as in step 305 described above.

  Subsequently, at step 1315, the piston top surface temperature Tp is calculated. This piston top surface temperature Tp is one of known methods using, for example, the coolant temperature THW, the integrated value of the fuel injection amount Fi, the outputs of the upstream air-fuel ratio sensor 66, the downstream air-fuel ratio sensor 67, and the like. Can be estimated based on.

  Next, it is determined in step 1320 whether or not “catalyst warm-up control A” is necessary. If “No” is determined, normal control of injection timing and ignition timing is performed in step 1325. In this normal control, the injection timing is set during the intake stroke, and the ignition timing is set near the compression top dead center (specifically, slightly before the compression top dead center). In this step 1320, for example, when the temperature (for example, average temperature) of the first and second catalysts 53 and 54 is equal to or lower than a predetermined temperature, “Yes” is determined.

  If “Yes” is determined in step 1320, it is determined in step 1330 whether or not the cooling water temperature THW is equal to or lower than the predetermined temperature B. If “No” is determined, in step 1335, the above-described operation is performed. The “catalyst warm-up control A” is executed as it is. This is because when the cooling water temperature THW is sufficiently high, it can be estimated that the piston top surface temperature is also sufficiently high. Therefore, even if the second half of the compression stroke injection is performed by the “catalyst warm-up control A”, the above-described fuel spray piston top temperature is increased. This is based on the fact that the increase in the number of PM emission particles due to direct contact with the surface hardly occurs. In this example, in the “catalyst warm-up control A”, both the intake stroke injection and the second compression stroke injection may be performed, or only the second compression stroke injection may be performed.

  On the other hand, if “Yes” is determined in step 1330, it is determined in step 1340 whether or not the piston top surface temperature Tp is equal to or lower than the predetermined temperature C. If it is determined “No”, step 1345 is determined. Thus, it is determined whether or not the piston top surface temperature Tp is equal to or lower than the predetermined temperature D and the piston top surface temperature Tp <the intake valve temperature Tv. Here, the predetermined temperature D> the predetermined temperature C. If “No” is determined in step 1345, the above-described “catalyst warm-up control A” is executed as it is in step 1335 because the piston top surface temperature is sufficiently high.

  On the other hand, if “Yes” is determined in step 1345, the compression stroke injection ratio (compression stroke relative to the total injection amount) is compared with the above-described “catalyst warm-up control C” (catalyst warm-up control A) in step 1350. The control in which the ratio of the injection amount in the second half) is set to a smaller value (> 0) is performed. In this way, when the piston top surface temperature is slightly low, “catalyst warm-up control C” is executed instead of “catalyst warm-up control A”. Accordingly, since the fuel injection amount in the latter half of the compression stroke is set to be smaller, it is caused by the direct contact of the fuel spray injected in the latter half of the compression stroke with the top surface of the piston as compared with the time when “catalyst warm-up control A” is executed. The increase in the number of PM exhaust particles to be suppressed can be suppressed. In addition, since fuel injection is ensured in the latter half of the compression stroke, the catalyst warm-up can be greatly promoted as in the “catalyst warm-up control A” using the ignition timing greatly retarded and stratified combustion. .

  On the other hand, if “Yes” is determined in step 1340, in step 1355, the above-described “catalyst warm-up control B” (intake stroke injection ratio (ratio of the injection amount in the intake stroke to the total injection amount)) is 100. % (Injection in the latter half of the compression stroke is prohibited) and the ignition timing is slightly advanced as compared with the catalyst warm-up control A). Thus, when the temperature of the piston top surface is sufficiently low, fuel injection in the latter half of the compression stroke is prohibited. As a result, it is possible to suppress an increase in the number of PM exhaust particles caused by direct contact of the fuel spray injected in the latter half of the compression stroke with the piston top surface. In this case, so-called stratified combustion cannot be used because fuel injection is not performed in the latter half of the compression stroke. Therefore, in order to suppress the occurrence of misfire, the ignition timing is set to a timing advanced from the timing controlled based on the “catalyst warm-up control A” (timing after the compression top dead center).

  As mentioned above, the control which concerns on each modification mentioned above may be performed independently, and may be performed in combination with a some modification.

1 is a schematic view of a direct injection internal combustion engine to which a control device for an internal combustion engine according to an embodiment of the present invention is applied. It is the figure which showed a mode that fuel spray contacted directly the back surface of an intake valve when fuel injection was carried out at the intake stroke. It is the flowchart which showed the routine which CPU shown in FIG. 1 performs. It is the flowchart which showed the routine corresponding to FIG. 3 which CPU of the control apparatus which concerns on the 1st modification of embodiment of this invention performs. It is the figure which showed the circumference | surroundings of the EGR apparatus. It is the flowchart which showed the routine corresponding to FIG. 3 which CPU of the control apparatus which concerns on the 2nd modification of embodiment of this invention performs. It is the flowchart which showed the routine corresponding to FIG. 3 which CPU of the control apparatus which concerns on the 3rd modification of embodiment of this invention performs. It is the figure which showed the surroundings of the supercharging system. It is the flowchart which showed the routine corresponding to FIG. 3 which CPU of the control apparatus which concerns on the 4th modification of embodiment of this invention performs. It is the flowchart which showed the routine which CPU of the control apparatus which concerns on the example relevant to this invention performs. It is the flowchart which showed the routine corresponding to FIG. 3 which CPU of the control apparatus which concerns on the 5th modification of embodiment of this invention performs. It is the figure which showed a mode that fuel spray contacted a piston top surface directly when fuel injection was carried out in the compression stroke latter half. It is the flowchart which showed the routine which CPU of the control apparatus which concerns on the 6th modification of embodiment of this invention performs.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 21 ... Cylinder, 22 ... Piston, 25 ... Combustion chamber, 32 ... Intake valve, 33 ... Variable intake timing device, 39 ... Injector, 45 ... EGR control valve, 46 ... EGR cooler, 48 ... Intercooler, 69 ... Water pump, 70 ... Electric control device, 71 ... CPU

Claims (9)

The present invention is applied to a direct injection internal combustion engine having a fuel injection valve that directly injects fuel into a combustion chamber of an internal combustion engine and is arranged so that the injected fuel directly contacts an intake valve depending on the injection timing. A control device for an internal combustion engine,
An intake valve temperature acquisition means for acquiring the temperature of the intake valve;
An intake valve temperature increase control means for performing an intake valve temperature increase control for increasing the temperature of the intake valve when the temperature of the intake valve is equal to or lower than a predetermined temperature;
The control apparatus of the internal combustion engine provided with. The control apparatus for an internal combustion engine according to claim 1,
The intake valve temperature increase control means, as the intake valve temperature increase control,
A control apparatus for an internal combustion engine configured to perform control for reducing a degree of cooling of the internal combustion engine by a coolant for cooling the internal combustion engine. The control apparatus for an internal combustion engine according to claim 1,
The intake valve temperature increase control means, as the intake valve temperature increase control,
A control device for an internal combustion engine configured to perform control to bring the closing timing of the intake valve closer to an intake bottom dead center. The control apparatus for an internal combustion engine according to claim 1,
The intake valve temperature increase control means, as the intake valve temperature increase control,
A control apparatus for an internal combustion engine configured to perform control to reduce a degree of cooling of the EGR gas by an EGR cooler that cools EGR gas that is returned to the intake system by an EGR apparatus that returns a part of the exhaust gas to the intake system. The control apparatus for an internal combustion engine according to claim 1,
The intake valve temperature increase control means, as the intake valve temperature increase control,
An internal combustion engine configured to perform control to increase the ratio of the flow rate of EGR gas returned to the intake system to the flow rate of fresh air sucked into the intake system by an EGR device that returns a part of the exhaust gas to the intake system. Control device. The control apparatus for an internal combustion engine according to claim 1,
The intake valve temperature increase control means, as the intake valve temperature increase control,
A control device for an internal combustion engine configured to perform control to reduce the degree of cooling of the compressed fresh air by an intercooler that cools the fresh air that has been sucked into the intake system and compressed by the supercharger. The control apparatus for an internal combustion engine according to claim 1,
The intake valve temperature rise control means includes:
In a lean operation state in which the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber is controlled to match the air-fuel ratio that is leaner than the stoichiometric air-fuel ratio, when the temperature of the intake valve falls below the predetermined temperature, the intake air An internal combustion engine configured to perform control for switching the operation state of the internal combustion engine from the lean operation state to a stoichiometric operation state for controlling the air-fuel ratio of the air-fuel mixture to match the stoichiometric air-fuel ratio as valve temperature increase control Control device. A control device for an internal combustion engine according to claim 1,
The fuel injection valve is arranged so that the injected fuel also directly contacts the top surface of the piston depending on the injection timing,
From the cold start to the completion of warm-up, fuel is injected from the fuel injection valve only in the latter half of the intake stroke and the compression stroke, or only in the latter half of the compression stroke, and the ignition timing is a timing after the compression top dead center. Catalyst warm-up control means for performing catalyst warm-up control for accelerating the warm-up of the catalyst disposed in the exhaust system at a retarded angle,
Piston top surface temperature acquisition means for acquiring the temperature of the top surface of the piston;
When the temperature of the top surface of the piston is equal to or lower than the first temperature during the catalyst warm-up control, fuel injection is prohibited in the latter half of the compression stroke, and fuel injection is performed only in the intake stroke to the top surface of the piston. Piston top surface fuel adhesion suppressing means for controlling the catalyst warm-up control means so as to suppress the fuel adhesion of
The control apparatus of the internal combustion engine provided with. The control apparatus for an internal combustion engine according to claim 8,
The piston top surface fuel adhesion suppressing means includes:
During the catalyst warm-up control, the temperature of the top surface of the piston is higher than the first temperature and equal to or lower than a second temperature higher than the first temperature, and the temperature of the top surface of the piston is lower than that of the intake valve. When the temperature is lower than the temperature, the catalyst warm-up control means is controlled to reduce the ratio of the fuel injection amount in the latter half of the compression stroke to the fuel injection amount in the intake stroke to suppress the fuel adhesion to the top surface of the piston. A control device for an internal combustion engine configured to

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