JP2006037907A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine, stably realizing favorable combustion state regardless of a change in air-fuel ration in a combustion chamber in the cylinder injection type engine. <P>SOLUTION: In a catalytic rapid warm-up control, an engine ECU 2000 forms an overlap period in which at the cold time, the valve closing timing of the exhaust valve is retarded to form an overlap period when both of an intake valve and an exhaust valve are opened, and an internal EGR is increased to raise the temperature of exhaust gas. At that time, the engine ECU 200 detects the combustion state of an engine 1 on the basis of the magnitude of load of an auxiliary machinery such as an alternator 400 and an air conditioner 500 and catalytic warm-up control time lapse, and determines the retard amount of the valve closing timing of the exhaust valve according to the detected combustion state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an internal combustion engine, and more particularly, to an internal combustion engine configured with an in-cylinder injection engine that directly injects fuel into a combustion chamber.

  In an internal combustion engine (engine) mounted on an automobile or the like, it is required to reduce harmful substances in exhaust gas discharged from the engine into the atmosphere in consideration of the environment.

  As a method for reducing harmful exhaust gas, a method is generally adopted in which a catalyst is disposed in an engine exhaust system and the exhaust gas is purified by this catalyst.

  However, since the catalyst used in this method does not cause a reaction that renders harmful gases harmless unless a certain temperature is reached, in an engine, for example, even at the time of cold start, the temperature of the catalyst is increased quickly. It is regarded as an important issue.

  Therefore, in order to meet such a problem, many engines having a catalyst activation promoting device have been proposed (see, for example, Patent Documents 1 and 2). These engines mainly have a so-called variable valve timing mechanism that makes the opening and closing periods of the intake valves and exhaust valves variable, extending the overlap period during which both the intake and exhaust valves are open when cold. The catalyst activation is promoted.

  FIG. 6 is a block diagram showing an engine equipped with a valve timing control device described in Patent Document 1, for example.

  Referring to FIG. 6, intake air is supplied to engine 601 from intake pipe 604 via air cleaner 602 and airflow sensor 603.

  The air cleaner 602 purifies the intake air to the engine 601, and the air flow sensor 603 measures the intake air amount of the engine 601. Inside the intake pipe 604, a throttle valve 605, an idle speed control valve 606, and an injector 607 are provided.

  The throttle valve 605 controls the output of the engine 601 by adjusting the amount of intake air that passes through the intake pipe 604. The idle speed control valve 606 adjusts the intake air that passes by bypassing the throttle valve 605 to control the engine speed during idling. The injector 607 supplies fuel corresponding to the amount of intake air into the intake pipe 604.

  A spark plug 608 is provided in the combustion chamber of the engine 601. The spark plug 608 generates a spark for burning the air-fuel mixture in the combustion chamber. The ignition coil 609 supplies high voltage energy to the spark plug 608.

The exhaust pipe 610 discharges exhaust gas burned in the engine 601. An O ₂ sensor 611 and a catalyst 612 are provided in the exhaust pipe 610. The O ₂ sensor 611 detects the amount of residual oxygen in the exhaust gas. The catalyst 612 is made of a known three-way catalyst, and simultaneously purifies harmful gases (HC (unburned gas), CO, NOx) in the exhaust gas.

  The sensor plate 613 for detecting the crank angle rotates integrally with the crankshaft rotated by the engine 601 and has a protrusion at a predetermined crank angle position.

  The crank angle sensor 614 is disposed opposite to the sensor plate 613 and generates an electrical signal when a protrusion on the sensor plate 613 crosses the crank angle sensor 614 to detect the rotational position (crank angle) of the crankshaft. .

  The engine 601 is provided with a valve that determines communication timing to the intake pipe 604 and the exhaust pipe 610. The drive timing of each of the intake and exhaust valves is controlled by changing the rotational positions (phases) of the camshafts 615C and 616C relative to the crankshaft by a valve timing control device described below.

  The valve timing control device includes cam phase variable actuators 615 and 616, oil control valves (OCV) 619 and 620 for driving the actuators 615 and 616, and actuators 615 and 616, which are coupled to the camshafts 615C and 616C, respectively. And an electronic control unit (ECU) 621A for changing the relative phase of the camshafts 615C and 616C with respect to the crankshaft by controlling the hydraulic pressure supplied to the crankshaft.

  The actuators 615 and 616 have a retarded hydraulic chamber and an advanced hydraulic chamber that are separated from each other, and relatively change the rotational phase of the camshafts 615C and 616C with respect to the crankshaft.

  Similarly to the crank angle sensor 614, the cam angle sensors 617 and 618 generate a pulse signal by a protrusion on a cam angle detection sensor plate (not shown) to detect the cam angle.

  Oil control valves 619 and 620 switch the hydraulic pressure supplied to each actuator 615 and 616 to control the cam phase.

  The ECU 621A constitutes a control means of the engine 601, and controls the injector 607 and the spark plug 608 according to the operation state detected by the various sensors 603, 611, 614, 617, 618, and the camshaft 615C, The cam angle phase of 616C is controlled.

  FIG. 7 is a diagram showing the phase change range by the valve timing control device shown in FIG. 6 in relation to the valve lift amount with respect to the phase position of the crank angle.

  Referring to FIG. 7, the alternate long and short dash line indicates a change in the valve lift amount at the time of the most retarded mechanical stop, and the broken line indicates the valve lift amount (the valve opening amount) at the most advanced angle of mechanical stop. The solid line indicates the change in the valve lift amount at the lock position set by the lock mechanism. TDC indicates a compression top dead center in each cylinder.

  Centering on TDC, the peak position of the valve lift amount on the retard side corresponds to the fully open position of the intake valve, and the peak position of the valve lift amount on the advance side corresponds to the fully open position of the exhaust valve. Therefore, the fluctuation range of each peak position on the retard side and the advance side indicates the movable range of each valve timing.

  Here, retarding the valve timing means that the opening start timing of both valves is retarded (slower) with respect to the crank angle, and conversely, advancing the valve timing is both valves. This means that the opening start timing of the valve advances (becomes faster) with respect to the crank angle. The opening start timing of the intake valve and the exhaust valve is controlled by the actuators 615 and 616 to an arbitrary retard position or advance position within the movable range shown in FIG.

  FIG. 8 is a flowchart for explaining the control operation of the valve timing control device shown in FIG.

  Referring to FIG. 8, first, ECU 621A determines whether engine 601 is in a start state or an engine stall state (step S100).

  If it is determined in step S100 that the engine 601 is in the start state or the engine stall state, the supply current to the coils (not shown) of the oil control valves 619 and 620 is set to the minimum current value MIN, and the processing routine is ended. (Step S106). Note that, as the minimum current value MIN at this time, a non-energized value or a minute current value as a standby current is set.

  On the other hand, if it is determined in step S100 that the engine 601 is not in the start state or the engine stall state, it is subsequently determined whether or not the engine 601 is in an idle state (step S101).

  If it is determined in step S101 that the engine 601 is not in the idle state, the ECU 621A controls the retard position or the advance position corresponding to the operating state of the engine 601 and ends the processing routine (step S105). Specifically, the ECU 621A stores in advance the target position corresponding to each operating state as map data in advance, and performs feedback control so that the rotational position becomes the target position.

  On the other hand, if it is determined in step S101 that the engine 601 is in the idle state, it is subsequently determined whether or not the engine 601 is in the cold state (step S102).

  If it is determined in step S102 that the engine 601 is not in the cold state, the ECU 621A controls the actuators 615 and 616 to the lock position and ends the processing routine (step S104). The lock position is a position of a cam phase suitable for starting the engine 601 and immediately after starting, and a position suitable for idle stability.

  On the other hand, if it is determined in step S102 that the engine 601 is in the cold state, the ECU 621A controls the valve timing to the retard side (step S103).

Here, as shown in step S103, the valve closing timing of the intake and exhaust valves is delayed by controlling the valve timing to the retard side when the engine 601 is cold. In particular, the exhaust gas exhausted to the exhaust pipe 610 can be re-inhaled into the combustion chamber of the engine 601 by delaying the completion timing of closing the exhaust valve. As a result, the combustion in the combustion chamber can be slowed and the temperature rise of the exhaust gas can be promoted. As a result, the temperature of the catalyst 612 can be accelerated by the high-temperature exhaust gas and activated early. .
JP 2002-161722 A Japanese Patent Laid-Open No. 11-324746

  By the way, in a cylinder injection engine that directly injects high-pressure fuel into a cylinder, lean combustion control by stratified combustion is performed as means for improving fuel efficiency and early activation of the catalyst.

  According to this, by injecting fuel in the latter half of the compression process immediately after the cold start, a stratified mixture is formed in which a combustible mixture exists only around the spark plug, and the stratified mixture is ignited by the ignition plug in that state. Is burned. By forming an air-fuel mixture layer having different fuel concentrations in the combustion chamber, good combustion can be established under a situation where the fuel concentration of the air-fuel mixture is extremely low, and fuel efficiency can be improved. Further, by stratifying the air-fuel mixture and combusting it for a long time, the temperature of the exhaust gas can be increased, and the early warm-up of the catalyst can be promoted.

  Furthermore, when the piston reciprocates by executing stratified combustion, the reciprocating movement of the piston is converted into rotation of the crankshaft that is the output shaft of the engine. When the crankshaft rotates, the rotation is transmitted to the vehicle tire via a transmission that transmits power.

  In general, the crankshaft is connected to a transmission, and is also connected to an auxiliary machine such as an alternator, an oil pump, and a compressor of an air conditioner. That is, the output torque of the engine is divided into torque for driving the vehicle and torque for driving the auxiliary machine. For this reason, the engine speed varies in real time according to the load state of the auxiliary machine. Hereinafter, the torque for driving the auxiliary machine is also referred to as an external load.

  For example, when the load state of the auxiliary machine becomes a high load, the engine speed decreases. When the engine speed decreases, feedback control is performed so as to compensate for the decrease in the engine speed by ISC (Idle Speed Control) control by the ECU and to keep the engine speed constant.

  The ISC control is control for maintaining the engine idling speed at a constant speed. Specifically, an air passage that bypasses the throttle valve of the engine is provided, and the throttle amount of the passage is driven by an actuator. The idling speed is controlled by adjusting the air (air mixture) flow rate. Therefore, in this case, the air flow rate is increased in order to increase the decreased engine speed.

  At this time, in the combustion chamber of the engine, in addition to the increase in the air flow rate by the ISC control, the exhaust gas is re-inhaled by the above-described variable valve timing control, and the amount of air is remarkably increased. Further, in the combustion chamber, as the air amount increases, the fuel injection amount is remarkably increased in order to make the average air-fuel ratio substantially the stoichiometric air-fuel ratio. When stratified combustion is performed in this state, the fuel concentration in the air-fuel mixture around the spark plug becomes very high (= the air-fuel ratio becomes rich), so the combustion state deteriorates and a lot of fuel is unburned from the combustion chamber. Ingredients will be discharged. From the above, in the cylinder injection type engine, improvement of the combustion state during the stratified combustion operation has been a major issue.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an internal combustion engine that can stably realize a good combustion state regardless of fluctuations in the air-fuel ratio in the combustion chamber in an in-cylinder injection engine.

  According to the present invention, the engine includes an in-cylinder injection engine that directly injects fuel into a combustion chamber, and a control device that performs catalyst warm-up control of the engine. The engine includes an intake valve that communicates with the combustion chamber by an opening / closing operation and intakes air into the combustion chamber, and an exhaust valve that communicates with the combustion chamber by an opening / closing operation and exhausts the combustion chamber. The control device includes valve timing control means for retarding the valve closing timing of the exhaust valve by a retard amount corresponding to the combustion state of the engine.

  Preferably, the valve timing control means includes a detecting means for detecting the combustion state of the engine, a retard amount determining means for determining a retard amount based on the combustion state of the engine detected by the detecting means, and a closing of the exhaust valve. Retarding means for retarding the valve timing by the determined retard amount. The retard amount determining means determines the retard amount to a relatively small value when it is detected that the combustion state of the engine is unstable.

  Preferably, the detection means detects the combustion state of the engine based on the magnitude of the load of the engine auxiliary machine.

  Preferably, the detection means detects that the combustion state of the engine is more unstable as the load on the engine auxiliary machine is larger.

  Preferably, the retard amount determining means has a predetermined retard amount map so that the retard amount becomes relatively smaller as the load of the auxiliary engine of the engine increases, and the retard amount map From the above, one retard amount corresponding to the load of the engine auxiliary machine is selected.

  Preferably, the detection means detects the combustion state of the engine based on the elapsed time of the engine catalyst warm-up control.

  Preferably, the detection means detects that the combustion state of the engine is more unstable as the elapsed time is longer.

  Preferably, the retard amount determining means has a predetermined retard amount map so that the retard amount becomes relatively smaller as the elapsed time becomes longer, and the elapsed time is calculated from the retard amount map. One retard amount corresponding to the length is selected.

  Preferably, the detection means detects the combustion state of the engine based on the magnitude of the load of the engine auxiliary machine and the elapsed time of the engine catalyst warm-up control.

  Preferably, the detection means detects that the combustion state of the engine is unstable when the load on the engine auxiliary machine is relatively large and the elapsed time is relatively long.

  Preferably, the retard amount determining means has a predetermined retard amount map so that the retard amount becomes relatively smaller as the load on the engine auxiliary equipment becomes larger and the elapsed time becomes longer. Then, one retard amount corresponding to the magnitude of the load on the engine auxiliary machine and the length of the elapsed time is selected from the map of the retard amount.

  According to the present invention, in a direct injection engine, it is possible to stably realize good combustion by making the retard amount of the exhaust valve timing during catalyst warm-up control variable according to the combustion state of the engine. Can do.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

  FIG. 1 is a diagram showing an overall structure in which an internal combustion engine according to an embodiment of the present invention is mounted.

  Referring to FIG. 1, the internal combustion engine includes an engine 1, valve characteristic control devices 100 and 100 ′, an automatic transmission 300, and an engine ECU 200.

  The engine 1 is an in-cylinder injection engine that directly injects high-pressure fuel into a cylinder.

  Intake air is supplied to an intake port of the engine 1 via an intake pipe 2, a surge tank 3 and an intake manifold 4. An air cleaner 5, an air flow meter 211, and a throttle valve 251 are disposed in the intake pipe 2. A fuel injection valve 252 is attached to the intake manifold 4 for each cylinder.

  An exhaust manifold 6 is attached to the exhaust port of the engine 1. In accordance with the order of ignition of the engine 1 in the order of # 1 cylinder → # 3 cylinder → # 4 cylinder → # 2 cylinder, the exhaust manifold 6 includes the # 1 cylinder and the # 4 cylinder as the # 2 cylinder. And # 3 cylinders are once assembled so as to have substantially the same length, and are further assembled into one.

  A catalyst 8 is disposed in an exhaust pipe 7 connected downstream of the exhaust manifold 6. An air-fuel ratio sensor 215 is disposed upstream of the catalyst 8. Based on the detection signal of the air-fuel ratio sensor 215, the fuel injection amount of the fuel injection valve 252 is feedback-controlled so that the catalyst 8 optimally performs the purification action.

  An igniter integrated spark plug 253 is disposed for each cylinder of the engine 1.

  In the above configuration, the intake air metered by the throttle valve 251 is introduced into the combustion chamber of each cylinder as the intake valve is opened. The fuel directly injected from the fuel injection valve 252 into the combustion chamber is mixed with the introduced intake air and then ignited by the spark plug 253. The air-fuel mixture after combustion is discharged to the exhaust manifold 6 when the exhaust valve is opened.

  When performing stratified combustion, fuel is injected in the latter half of the compression process immediately after the cold start, thereby forming a stratified mixture in which a combustible mixture exists only around the spark plug 253. In this state, ignition is performed by the spark plug 253, and the stratified mixture is burned.

  An automatic transmission 300 is connected to a crankshaft (not shown) that is an output shaft of the engine 1. The output of the engine 1 is transmitted as traveling driving force to the wheels via the automatic transmission 300.

  An alternator 400 is further connected to the crankshaft. Alternator 400 transmits power generated in the crankshaft to auxiliary equipment such as a compressor of an air conditioner (A / C).

  The engine 1 is further provided with various sensors for detecting the engine operating state and the like.

  The air flow meter 211 detects an intake air amount GA as a load of the engine 1 and generates a signal voltage corresponding to the detected intake air amount.

  The crank position sensor 212 is provided with an electromagnetic pickup in the vicinity of a projection of a signal generating disk attached to the crankshaft, and generates a signal voltage every time the projection of the electromagnetic pickup passes.

  A rotational speed sensor (not shown) detects the engine rotational speed NE from the rotation of the crankshaft, and generates a signal corresponding to the detected engine rotational speed NE.

  The engine water temperature sensor 213 detects the cooling water temperature of the engine 1 and generates a signal corresponding to the detected cooling water temperature.

  The intake cam angle sensor 214 detects the phase difference of the intake camshaft with respect to the crankshaft. Specifically, a signal voltage is generated every time an electromagnetic pickup close to a signal generation protrusion provided at an appropriate location on the intake camshaft 50 passes through the protrusion.

  The exhaust cam angle sensor 215 detects the phase difference of the exhaust camshaft with respect to the crankshaft. Specifically, a signal voltage is generated each time an electromagnetic pickup adjacent to a signal generation protrusion provided at an appropriate location on the exhaust camshaft 50 'passes through the protrusion.

  The engine ECU 200 performs overall control of the internal combustion engine. Detection signals from various sensors are taken into the engine ECU 200. Based on these detection signals, engine ECU 200 drives an actuator such as a motor that drives fuel injection valve 252, spark plug 253, and throttle valve 251, thereby performing various control modes such as combustion mode switching control, air-fuel ratio control, and ISC control. Execute control.

  The engine ECU 200 executes a CPU (not shown) for executing these various controls, a memory (not shown) for storing programs related to the various controls, a function map necessary for the execution, and control results based thereon. Is provided.

  The engine ECU 200 further includes a counter 202 for measuring the elapsed time after the start of execution of the catalyst rapid warm-up control described later.

  The valve characteristic control device 100 is a part that controls the phase of the valve opening period of the intake valve, and is attached to the intake camshaft 50 as shown in FIG.

  The valve characteristic control device 100 ′ is a part that controls the phase of the valve opening period of the exhaust valve, and is attached to the exhaust camshaft 50 ′ as shown in FIG. 1.

  Although not shown in the drawings, the valve characteristic control devices 100 and 100 ′ have the same structure. Each of the valve characteristic control devices 100 and 100 ′ is driven by a crankshaft through a chain, and the advance oil chamber and the retarding gear cooperate with the gear. It includes a housing that forms a square oil chamber, and an oil control valve that controls the supply of hydraulic oil to each oil chamber.

  Control of supply and discharge of hydraulic oil in the oil control valve is performed in accordance with a signal from engine ECU 200. Specifically, when the electromagnetic solenoid of the oil control valve is excited according to the duty ratio indicated by the signal from engine ECU 200, the spool valve is moved by the plunger and spring of the electromagnetic solenoid, and the advance oil chamber and retard oil are moved. Switch the direction of hydraulic oil flow in the chamber. For example, in order to retard the phase of the exhaust camshaft 50 ′ most, the hydraulic oil introduced from the oil control valve fills the retardation chamber while discharging all the hydraulic fluid in the advance oil chamber.

  Next, the rapid catalyst warm-up control executed in the internal combustion engine according to the present embodiment having the above configuration will be described.

  As described above, the catalyst rapid warm-up control is a control that accelerates the activation of the catalyst by rapidly raising the temperature of the catalyst at the time of cold start. FIG. 2 is a diagram schematically showing the rapid catalyst warm-up control according to the present embodiment.

  As shown in FIG. 2, an overlap period in which both the intake valve and the exhaust valve are open is formed by retarding the closing timing of the exhaust valve when cold. By extending this overlap period, the exhaust gas is recirculated into the combustion chamber and the internal EGR increases. Internal EGR refers to exhaust gas remaining in the combustion chamber during fuel combustion. By increasing the internal EGR, the combustion speed is delayed to increase the temperature of the exhaust gas.

  Here, consider a case where an external load by an auxiliary machine such as the air conditioner 500 shown in FIG. When the engine speed decreases as the external load increases, the engine ECU 200 performs ISC control for keeping the engine speed constant. Specifically, the engine ECU 200 corrects the decreased engine speed by increasing the amount of intake air that passes through the throttle valve.

  Thereby, in the combustion chamber, as shown in FIG. 2, the amount of air increases due to the exhaust gas recirculated from the exhaust valve and the fresh air introduced from the intake valve. The engine ECU 200 supplies fuel commensurate with the increased air amount from the fuel injection valve 252 through the intake port into the combustion chamber so that the average air-fuel ratio in the combustion chamber becomes substantially the stoichiometric air-fuel ratio.

  If the fuel injection amount is increased, in stratified combustion, as described above, the air-fuel ratio of the air-fuel mixture existing around the spark plug 253 becomes extremely rich, and the combustion state deteriorates. As a result, the exhaust gas cannot obtain the effect of purification by the catalyst and contains harmful components such as HC.

  Therefore, in the present embodiment, the delay amount of the closing timing of the exhaust valve is changed according to the combustion state of the engine 1. Specifically, as described above, the combustion state of the engine 1 deteriorates as the external load increases. Therefore, the retard amount of the exhaust valve closing timing is set according to the magnitude of the external load. Change the configuration. According to this, when the intake air amount increases due to the ISC control accompanying the increase in the external load, the exhaust valve closing timing of the exhaust valve is compensated so as to compensate for the increased intake air amount by the decreased exhaust gas recirculation amount. The amount of retardation will be reduced. Thereby, since the increase in the air amount is suppressed, the fuel injection amount is also suppressed, and the combustion state can be improved by making the air-fuel ratio of the air-fuel mixture around the spark plug lean.

  Further, the combustion state of the engine 1 varies depending on the elapsed time of the catalyst rapid warm-up control. This indicates that the air-fuel ratio of the air-fuel mixture in the combustion chamber varies depending on the elapsed time of the catalyst warm-up control. More specifically, in a direct injection engine, fuel is directly injected into the combustion chamber, so that atomization of the injected fuel is accelerated when the temperature of the combustion chamber is low, such as during cold start or immediately thereafter. It tends to be difficult. However, as the temperature of the combustion chamber increases as the rapid catalyst warm-up control is continued for a predetermined period, the atomization of the injected fuel proceeds and the air-fuel ratio of the combustion chamber starts to increase. Even in this case, since the air-fuel ratio of the air-fuel mixture around the spark plug becomes rich, the combustion state is deteriorated.

  Therefore, in the present embodiment, as a second configuration, the retard amount of the valve closing timing of the exhaust valve is changed according to the elapsed time of the catalyst rapid warm-up control. Specifically, when the combustion chamber temperature rises after the catalyst warm-up control is executed, the retard amount of the exhaust valve closing timing is reduced so as to reduce the exhaust gas recirculation amount. Thereby, since the increase in the air amount is suppressed, the fuel injection amount is also suppressed, and the combustion state can be improved by making the air-fuel ratio of the air-fuel mixture around the spark plug lean.

  In this embodiment, since the variation in the combustion chamber temperature is approximately proportional to the elapsed time after the catalyst warm-up control is executed, the combustion chamber temperature is simply estimated from the catalyst rapid warm-up control elapsed time.

  In the present embodiment, furthermore, as a third configuration, the combustion state of the engine 1 is determined based on a configuration in which the above first and second configurations are combined, that is, the magnitude of the external load and the elapsed time of the catalyst rapid warm-up control. A configuration is also proposed in which the amount of retardation of the valve closing timing of the exhaust valve is changed according to the detected combustion state. According to this, it is possible to adjust the retard amount that reflects the combustion state of the engine 1 with higher accuracy, and it is possible to establish a better combustion.

  FIG. 3 is a diagram showing a relationship between the combustion state of the engine 1 and the retard amount of the exhaust valve closing timing in the catalyst rapid warm-up control according to the present embodiment. In this figure, the retard amount is expressed as a ratio of the retard amount corresponding to the change in the combustion state of the engine 1.

  Referring to FIG. 3 in the right direction, the retard amount of the exhaust valve closing timing is set so as to become relatively smaller as the external load becomes larger. Further, referring to FIG. 3 in the downward direction, the retard amount of the closing timing of the exhaust valve is set so as to become relatively smaller as the elapsed time becomes longer.

  The relationship shown in this figure is stored in advance in a memory (not shown) of engine ECU 200 as a control map for determining the retard amount. Engine ECU 200 selects a desired retard amount from the control map based on the detection result of at least one of the external load and the catalyst warm-up control elapsed time, and the selected retard amount is provided on exhaust camshaft 50 '. This is transmitted to the valve characteristic control device 100 ′. For example, in the first configuration described above, engine ECU 200 selects and selects one retard amount corresponding to the detection result of the external load (the elapsed time is not considered (= 0 [ms])). The retard amount is output to the valve characteristic control device 100 ′. In the second configuration, engine ECU 200 selects and selects one retardation amount corresponding to the detection result of elapsed time (external load is not considered (= 0 [N · m])). The retard amount is output to the valve characteristic control device 100 ′. Further, in the third configuration, engine ECU 200 selects one retardation amount determined by the detection result of the external load and the detection result of the elapsed time, and selects the selected retardation amount as valve characteristic control device 100 ′. Output to.

  The valve characteristic control device 100 ′ controls the supply and discharge of hydraulic oil from the oil control valve so that the closing timing of the exhaust valve becomes the instructed retardation amount.

  FIG. 4 is a flowchart for illustrating catalyst rapid warm-up control according to the present embodiment. In the catalyst rapid warm-up control, first, it is determined whether or not the control is necessary according to the flow shown in FIG.

  Specifically, first, engine ECU 200 reads each parameter based on detection signals from various sensors (step S01).

  Specifically, first, it is determined whether or not the engine 1 is in a cold state by comparing the coolant temperature TW of the engine 1 with a predetermined determination value TWa (step S02). At this time, if the coolant temperature TW of the engine 1 is lower than the determination value TWa, it is determined that the engine 1 is in the cold state, and the process proceeds to step S03.

  On the other hand, in step S02, if the coolant temperature TW of the engine 1 is higher than the determination value TWa, it is determined that the engine 1 is not in a cold state, and the flag FCC that indicates that catalyst warm-up is unnecessary is set to “0”. Then, the process ends (step S06).

  Next, also in the engine speed NE, it is determined whether or not the engine 1 is in an idle state as compared with a predetermined determination value NEa (step S03). At this time, if the engine speed NE is lower than the determination value NEa, it is determined that the engine 1 is in an idle state.

  On the other hand, if the engine speed NE is higher than the determination value NEa in step S03, it is determined that the engine 1 is not in an idling state, and the flag FCC that indicates that catalyst warm-up is not required is set to “0”. The process ends (step S06).

  If it is determined in steps S02 and S03 that the engine 1 has not been warmed up and is in an idle state, the intake air amount GA as the engine load is subsequently compared with a predetermined determination value GAa (step S04). ). At this time, if the intake air amount GA is lower than the determination value GAa, it is determined that the engine 1 is in a low load operation, and the flag FCC instructing execution of the catalyst warm-up control is set to “1” (step S05).

  On the other hand, if the intake air amount GA is higher than the determination value GAa in step S04, it is determined that the engine 1 is not operating at a low load, and the flag FCC that indicates that catalyst warm-up is unnecessary is set to “0”. Is finished (step S06).

  If it is determined that the catalyst warm-up control is required for the engine 1 according to the flow of steps S01 to S05 described above, the catalyst warm-up control is subsequently executed according to the flow shown in FIG.

  FIG. 5 is a flowchart for explaining the catalyst warm-up control according to the present embodiment. In addition, the flowchart shown below respond | corresponds to the 3rd structure which detects the combustion state of the engine 1 based on external load and the elapsed time of catalyst rapid warm-up control among said three structures.

  Referring to FIG. 5, it is first determined whether or not the catalyst warm-up control should be executed based on whether or not flag FCC is “1” (step S10). At this time, if the flag FCC is “1” instructing execution of the catalyst warm-up control, the engine ECU 200 starts executing the catalyst warm-up control (step S11). On the other hand, if the flag FCC is not “1”, it is determined that the catalyst warm-up control is unnecessary, and the process is terminated.

  When executing the catalyst warm-up control, the engine ECU 200 counts the elapsed time of the catalyst warm-up control with the internal counter 202 as the start timing (step S12). This is because, as described above, the temperature in the combustion chamber is estimated based on the length of the catalyst warm-up control elapsed time. That is, engine ECU 200 estimates that the longer the catalyst warm-up control time, the higher the combustion chamber temperature, and thus the rich air-fuel ratio in the combustion chamber.

  Further, the combustion state of the engine 1 is estimated by the magnitude of an external load for operating an auxiliary machine such as a compressor of the air conditioner 500. Specifically, the external load is calculated as torque in engine ECU 200 based on the alternator duty and engine speed NE (step S13). As described above, the greater the calculated torque value, the greater the external load, and hence the greater the correction amount (increase amount) of the engine speed in ISC control. Therefore, as the air amount and fuel injection amount increase. It is estimated that the air-fuel ratio in the combustion chamber is rich.

  Next, the engine ECU 200 determines the retard amount of the exhaust valve closing timing based on the catalyst rapid warm-up control elapsed time counted by the counter 202 and the calculated external load (step S14). Specifically, the engine ECU 200 stores map data shown in FIG. 3 in advance, and a retard angle uniquely given by the catalyst rapid warm-up control elapsed time and the external load obtained from the map data. Read the amount.

  Finally, the engine ECU 200 controls the valve characteristic control device 100 'so as to delay the exhaust valve closing timing by the determined delay amount (step S15). The valve characteristic control device 100 ′ adjusts the hydraulic oil applied to the exhaust valve port by the oil control valve so as to make the delay amount of the closing timing of the exhaust valve coincide with the determined delay amount.

  Thus, according to steps S10 to S15, the retard amount of the exhaust valve closing timing is adjusted according to the combustion state of the engine 1. As a result, the air-fuel ratio around the spark plug in the combustion chamber is always kept lean, and a stable combustion state is ensured.

  In addition, the flow which abbreviate | omitted step S12 of FIG.5 S10-S15 is applied about the 1st structure which detects the combustion state of the engine 1 from the magnitude | size of an external load. Further, for the second configuration for detecting the combustion state of the engine 1 from the catalyst rapid warm-up control elapsed time, a flow in which step S13 of steps S10 to S15 in FIG. 5 is omitted is applied.

  As described above, according to the embodiment of the present invention, in an in-cylinder injection type engine, the retard amount of the exhaust valve timing at the time of catalyst warm-up control is made variable according to the combustion state, which is good. Combustion can be realized stably.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows the whole structure carrying the internal combustion engine according to embodiment of this invention. It is a schematic diagram which shows the catalyst rapid warm-up control which concerns on embodiment of this invention. It is the schematic of the control map of the retard amount of the valve closing timing of the exhaust valve in the catalyst rapid warm-up control according to the present embodiment. It is a flowchart for demonstrating catalyst rapid warm-up control according to embodiment of this invention. It is a flowchart for demonstrating the catalyst warm-up control which concerns on this Embodiment. It is a block diagram which shows the engine which mounts the valve timing control apparatus described in patent document 1, for example. It is a figure which shows the phase change range by the valve timing control apparatus shown in FIG. 6 by the relationship of the valve lift amount with respect to the phase position of a crank angle. It is a flowchart for demonstrating control operation | movement of the valve timing control apparatus shown in FIG.

Explanation of symbols

1,601 engine, 2,604 intake pipe, 3 surge tank, 4 intake manifold, 5 air cleaner, 6 exhaust manifold, 7,610 exhaust pipe, 8,612 catalyst, 50 intake camshaft, 50 'exhaust camshaft, 100, 100 'valve characteristic control device, 200 engine ECU, 202 counter, 211 air flow meter, 212 crank position sensor, 213 cooling water temperature sensor, 214, 214', 617, 618 cam angle sensor, 215 air-fuel ratio sensor, 251 throttle valve, 252 fuel injection valve, 253,608 spark plug 300 automatic transmission, 400 alternator, 500 air conditioner, 603 air flow sensor, 607 an injector, 609 spark plug 611 _{O 2} sensor, 614 a crank angle sensor, 615 616 actuator, 615C, 616 C camshaft, 619 and 620 the oil control valve, 621A ECU.

Claims (11)

An in-cylinder injection engine that directly injects fuel into the combustion chamber;
A control device for performing catalyst warm-up control of the engine,
The engine is
An intake valve that communicates with the combustion chamber by an opening and closing operation to intake air into the combustion chamber;
An exhaust valve communicating with the combustion chamber by an opening and closing operation and exhausting from the combustion chamber;
The controller is
An internal combustion engine comprising valve timing control means for retarding the valve closing timing of the exhaust valve by a retard amount corresponding to a combustion state of the engine. The valve timing control means includes
Detecting means for detecting a combustion state of the engine;
Retard amount determining means for determining the retard amount based on the combustion state of the engine detected by the detecting means;
A retard means for retarding the valve closing timing of the exhaust valve by the retard amount determined;
The internal combustion engine according to claim 1, wherein the retard amount determining means determines the retard amount to a relatively small value when it is detected that the combustion state of the engine is unstable.   The internal combustion engine according to claim 2, wherein the detection unit detects a combustion state of the engine based on a load size of an auxiliary machine of the engine.   The internal combustion engine according to claim 3, wherein the detection unit detects that the combustion state of the engine is more unstable as the load on an auxiliary machine of the engine is larger.   The retard amount determining means has a map of a retard amount that is determined in advance so that the retard amount becomes relatively smaller as the load of the auxiliary equipment of the engine becomes larger. The internal combustion engine according to claim 4, wherein one retard amount corresponding to the magnitude of the load on the engine auxiliary machine is selected from the map.   The internal combustion engine according to claim 2, wherein the detection unit detects a combustion state of the engine based on an elapsed time of catalyst warm-up control of the engine.   The internal combustion engine according to claim 6, wherein the detection means detects that the combustion state of the engine is more unstable as the elapsed time is longer.   The retard amount determination means has a map of a retard amount that is set in advance so that the retard amount becomes relatively smaller as the elapsed time becomes longer, and the progress amount is determined from the map of the retard amount. The internal combustion engine according to claim 7, wherein one retard amount corresponding to the length of time is selected.   The internal combustion engine according to claim 2, wherein the detection unit detects a combustion state of the engine based on a load size of an auxiliary machine of the engine and an elapsed time of catalyst warm-up control of the engine.   The internal combustion engine according to claim 9, wherein the detection unit detects that the combustion state of the engine is unstable when a load of an auxiliary machine of the engine is relatively large and the elapsed time is relatively long. organ.   The retard amount determining means provides a map of a retard amount determined in advance so that the retard amount becomes relatively smaller as the load on the auxiliary equipment of the engine becomes larger and the elapsed time becomes longer. 11. The internal combustion engine according to claim 10, further comprising: selecting one retard amount corresponding to a magnitude of a load of an auxiliary machine of the engine and a length of the elapsed time from the retard amount map.

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