JP2014136989A - Catalyst early warming-up control device of spark ignition type engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst early warming-up control device of a spark ignition type engine capable of restraining exhaust noises while maintaining an early activation effect of a catalyst device during AWS execution.SOLUTION: An valve opening start timing of an exhaust valve is set so that the exhaust valve starts to be opened during an expansion stroke during which air-fuel mixture ignited in a spark timing retarded beyond a compression top dead point is combusted. In a cam profile of a cam for the exhaust valve, at an early stage of a normal acceleration zone except for a cushioning zone on a valve opening start side of the exhaust valve, a loose acceleration zone in which an increase ratio of lift acceleration to a crank angle is smaller than in an early stage of the normal acceleration zone of an intake valve is formed.

Description

  The present invention relates to a catalyst early warm-up control device for a spark ignition engine, and belongs to the technical field of emission countermeasures for internal combustion engines.

  Conventionally, in a spark ignition type engine, a technique called AWS (Accelerated Warm-up System) may be used to achieve early activation of a catalytic device provided in an exhaust passage. This AWS is, for example, immediately after the engine is cold started, and when the catalyst device is in an inactive state, the intake air amount is increased and ignition is performed in the same operating state (for example, idling operation) than in the active state. By retarding the timing beyond the compression top dead center, the air-fuel mixture is post-burned during the expansion stroke, thereby increasing the exhaust gas temperature and hence the exhaust heat quantity, thereby promoting the warm-up of the catalyst device ( For example, see Patent Document 1).

JP 2007-321590 A

  During execution of AWS, the ignition timing is retarded beyond the compression top dead center, so the air-fuel mixture burns during the expansion stroke, and the in-cylinder pressure rises in the latter half of the expansion stroke. Since this timing overlaps with the timing when the exhaust valve for opening and closing the exhaust port starts opening, the blowdown energy flowing from the cylinder to the exhaust port when the exhaust valve is opened increases. As a result, there is a problem that the amplitude of the exhaust pulsation in the exhaust passage increases, the emission sound of the exhaust system increases, and the exhaust noise increases.

  In order to cope with this problem, it is conceivable to reduce the amount of intake air to reduce the engine speed. However, if this is done, the amount of exhaust heat is reduced and the early activation effect of the catalyst device is diminished.

  Therefore, an object of the present invention is to provide an early catalyst warm-up control device for a spark ignition engine that can suppress exhaust noise while maintaining the early activation effect of the catalyst device during execution of AWS.

  In order to solve the above-mentioned problems, the present invention increases the amount of intake air when the catalyst device provided in the exhaust passage is in an inactive state and increases the amount of intake air compared with when the catalyst device is in the same operating state. A catalyst early warm-up control device for a spark ignition engine that retards the timing beyond the compression top dead center, and the exhaust valve opens during the expansion stroke in which the air-fuel mixture ignited at the retarded ignition timing burns. An exhaust valve opening start timing setting means for setting the valve opening start timing of the exhaust valve so as to start the exhaust valve, and in the cam profile of the cam for the exhaust valve, a buffer on the valve opening start side of the exhaust valve is provided. A spark-ignition engine characterized in that a slow acceleration zone in which the rate of increase in lift acceleration with respect to the crank angle is small is formed at the beginning of the positive acceleration zone excluding the zone compared to the initial time of the positive acceleration zone of the intake valve. A rapid catalyst warm-up control apparatus (claim 1).

  According to the present invention, the exhaust valve starts to open during the expansion stroke in which the air-fuel mixture ignited at the ignition timing retarded beyond the compression top dead center is burned. The blowdown energy that flows from the cylinder to the exhaust port when the valve is turned on increases, resulting in an increase in the amplitude of exhaust pulsation in the exhaust passage, an increase in the emission noise of the exhaust system, and an increase in exhaust noise. To do.

  In order to solve this problem, in the present invention, in the cam profile of the cam for the exhaust valve, the slow acceleration section as described above is formed. Therefore, the exhaust valve is opened relatively slowly by the slow acceleration section. Become. Therefore, even if the blowdown energy is high, the release or transmission of the blowdown energy to the exhaust system is slowed down. As a result, the amplitude of the exhaust pulsation in the exhaust passage is reduced, and the emission sound of the exhaust system is reduced. Exhaust noise is suppressed.

  On the other hand, with respect to the catalyst activity, since the air-fuel mixture ignited at the ignition timing retarded beyond the compression top dead center is burned after the expansion stroke, the exhaust gas temperature and the exhaust heat quantity are increased. The early activation effect of the device is sufficiently maintained. That is, both catalyst activity and exhaust noise can be achieved.

  As described above, according to the present invention, a catalyst early warm-up control device for a spark ignition engine capable of suppressing exhaust noise while maintaining the early activation effect of the catalyst device during execution of AWS is provided.

  In the present invention, preferably, a plurality of the exhaust valves are provided in one cylinder, and the exhaust valve opening start timing setting means starts the opening of the exhaust valves so that the valve opening start timings of the plurality of exhaust valves are different. Time is set (Claim 2).

  According to this configuration, since the plurality of exhaust valves start opening at different timings, the flow of the exhaust gas discharged to the exhaust port is disturbed, and the exhaust gas in the exhaust passage is agitated, and the exhaust gas is exhausted. Afterburning in the passage is promoted. Therefore, afterburning is achieved at a site closer to the catalyst device, which is further advantageous in terms of catalyst activity.

  In the present invention, preferably, the slow acceleration section is formed only in an exhaust valve whose opening start timing is earlier among the plurality of exhaust valves.

  According to this configuration, even when the plurality of exhaust valves start opening at different timings, the effect of releasing or transmitting blowdown energy to the exhaust system is ensured.

  In the present invention, preferably, the slow acceleration section of the exhaust valve whose opening start timing is earlier among the plurality of exhaust valves is formed longer on the valve opening start side than the slow acceleration section of the other exhaust valves. (Claim 4).

  According to this configuration, since a plurality of exhaust valves that start valve opening at different timings slowly release blowdown energy for a long period that continues as a whole, it is possible to cope well when blowdown energy is excessive. it can.

  The present invention relates to an early catalyst warm-up control device for a spark ignition engine capable of suppressing exhaust noise while maintaining the early activation effect of the catalyst device during execution of AWS. It can contribute to countermeasures.

1 is a schematic configuration diagram of a spark ignition engine according to an embodiment of the present invention. It is the perspective view which showed the detailed structure of the multi-hole type injector, piston, and spark plug. (A) is a top view of a piston crown surface, (b) is an AA arrow directional cross-sectional view of a piston. It is a side view which shows the fuel-injection state in a compression stroke. (A) is a schematic diagram for demonstrating the mode in the combustion chamber immediately after fuel injection, (b) is a schematic diagram for demonstrating the mode after that. It is a top view which shows the exhaust upstream part of the exhaust system of the said engine. It is an enlarged plan view of the exhaust upstream portion. It is a control system figure of the engine. 6 is a time chart of fuel injection timing, ignition timing, intake / exhaust valve opening timing, and valve closing timing during execution of AWS. 6 is a time chart of engine rotation and ignition timing during execution of AWS. (A) is a time chart of in-cylinder pressure during execution of AWS when the retard amount of the ignition timing is ATDC 16 ° CA, ATDC 26 ° CA and ATDC 36 ° CA, and (b) Among them, the latter half of the expansion stroke is enlarged. It is a cam profile of the cam for exhaust valves of the engine. It is a graph which shows the change of the lift acceleration with respect to the crank angle of the said exhaust valve cam. It is a graph which shows the change of the lift acceleration with respect to the crank angle of the intake valve cam of the engine.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(1) Overall Configuration As shown in FIG. 1, an engine E according to this embodiment is an in-line four-cylinder (see FIG. 6) spark ignition engine, and a cylinder block 2 that rotatably supports a crankshaft 1. The cylinder block 3 has a cylinder head 3 disposed on the top of the cylinder block 2, and the cylinder block 2 and the cylinder head 3 are provided with four cylinders 4.

  Each cylinder 4 accommodates a piston 6 connected to the crankshaft 1 via a connecting rod 5. A combustion chamber 7 is formed above the piston 6. A ceiling wall 8 of the combustion chamber 7 is formed for each cylinder 4 on the lower surface of the cylinder head 3. The ceiling wall portion 8 is a pent roof type in which an intake side inclined surface 8a and an exhaust side inclined surface 8b extending from the central portion to the lower end of the cylinder head 3 are opposed to each other. An intake port 9 is opened on the intake side inclined surface 8a, and an exhaust port 10 is opened on the exhaust side inclined surface 8b. The intake port 9 and the exhaust port 10 branch into two on the cylinder 4 side (see FIG. 6), and an intake valve 16 for opening and closing the intake port 9 and an exhaust valve 17 for opening and closing the exhaust port 10 are provided respectively. ing. That is, two intake valves 16 and two exhaust valves 17 are provided per cylinder 4.

  A multi-hole injector (fuel injection valve) 11 is disposed at a lower end portion of the intake side inclined surface 8a so as to be directed obliquely downward. The multi-hole injector 11 is connected to a fuel supply system 12, and when the fuel supply system 12 receives a pulse signal from an engine control unit (ECU) 13 (see FIG. 8), the reception timing corresponds to the pulse width. An amount of fuel is injected directly into the combustion chamber 7. The detailed structure of the multi-hole injector 11 will be described later.

  A spark plug 14 is provided at the center of the ceiling wall 8 of each cylinder 4. The spark plug 14 is fixed to the cylinder head 3 and faces the electrode 14 a (see FIG. 2) in the combustion chamber 7. The spark plug 14 is connected to an ignition circuit 15, and when the ignition circuit 15 receives a control signal from the ECU 13, a spark is discharged to the electrode 14a and ignited at the reception timing.

  Tappet units 18 and 19 are provided on the two intake valves 16 and the two exhaust valves 17 of each cylinder 4, respectively. The tappet units 18 and 19 are driven in conjunction with engine rotation by an intake valve cam 20 and an exhaust valve cam 21 of a valve mechanism (not shown) provided in the cylinder head 3.

  More specifically, the valve mechanism includes an intake camshaft and an exhaust camshaft (not shown) provided with the intake valve cam 20 and the exhaust valve cam 21, and an intake VVT120 and an exhaust VVT121 (see FIG. 8). ing. The intake camshaft and the exhaust camshaft are connected to the crankshaft 1 via a chain or the like and are driven to rotate.

  The intake VVT 120 and the exhaust VVT 121 are for changing the valve timing of the intake valve 16 and the exhaust valve 17 by changing the phase difference between the crankshaft 1 and the intake camshaft and the exhaust camshaft. The intake VVT 120 and the exhaust VVT 121 change the valve timing of the intake valve 16 and the exhaust valve 17 in accordance with a control signal from the ECU 13.

  In the present embodiment, the intake VVT 120 and the exhaust VVT 121 are the valve opening periods IVO of the intake valve 16 and the exhaust valve 17 while maintaining the valve opening period and the lift amount of the intake valve 16 and the exhaust valve 17, that is, the valve profile, respectively. , EVO and valve closing timings IVC, EVC (see FIG. 9) are changed.

  In this embodiment, the valve opening period of the intake valve 16 and the exhaust valve 17 is a portion (ramp part) where the gradient of the valve lift is gentle on the valve opening start side and valve closing completion side during the valve lift period. The excluded section is referred to, and the valve opening timing and the valve closing timing of the intake valve 16 and the exhaust valve 17 are the valve opening start timing and the valve closing completion timing of the valve opening period. For example, when the height of the ramp portion is 0.2 mm, the timing when the valve lift amount increases or decreases to 0.2 mm is the valve opening timing and the valve closing timing, respectively.

  An independent intake pipe 22 of an intake manifold is connected to each intake port 9. A throttle valve 28 (see FIG. 8) for adjusting the amount of intake air is provided on the intake upstream side of the independent intake pipe 22. The throttle valve 28 changes the opening according to a control signal from the ECU 13. An independent exhaust pipe 23 of the exhaust manifold is connected to each exhaust port 10.

  Next, the structure of the exhaust system of the engine E will be described with reference to FIG. As shown in FIG. 6, the engine E is placed horizontally at the front of the vehicle so that the intake system is located on the front side in the vehicle front-rear direction and the exhaust system is located on the rear side in the vehicle front-rear direction. A transmission T is coupled to one end of the engine E in the cylinder row direction, and the engine E and the transmission T constitute a power train. The transmission T is an automatic transmission (AT) having a torque converter and a transmission gear mechanism (not shown). That is, the vehicle according to the present embodiment is an AT vehicle. Here, since the torque converter is a heavy object connected to the crankshaft 1, it is an external load that serves as a rotational resistance for the engine E.

  In the four cylinders, the first cylinder 4a, the second cylinder 4b, the third cylinder 4c, and the fourth cylinder 4d are arranged from the non-transmission side, and the first cylinder 4a, the third cylinder 4c, the fourth cylinder 4d, and the fourth cylinder In the order of the two cylinders 4b, the intake, compression, expansion, and exhaust strokes are shifted by one stroke.

  The first independent exhaust pipe 23a and the fourth independent exhaust pipe 23d connected to the first cylinder 4a and the fourth cylinder 4d, whose exhaust strokes are not continuous with each other, extend to the rear of the vehicle, and then merge to form the first merge pipe. 24a is formed. Similarly, the second independent exhaust pipe 23b and the third independent exhaust pipe 23c, which are connected to the second cylinder 4b and the third cylinder 4c, which do not have an exhaust stroke continuous with each other, extend to the rear of the vehicle, and then merge. Two junction pipes 24b are formed. The first merging pipe 24a and the second merging pipe 24b merge while being curved to form a single collecting pipe 25. That is, the exhaust system of the engine E has a structure called 4-2-1 exhaust.

  As shown in FIG. 7, the catalyst device 26 is connected to the exhaust downstream side of the collecting pipe 25, and the single exhaust pipe 27 is connected to the exhaust downstream side of the catalyst device 26. Although not shown, the exhaust pipe 27 extends rearward of the vehicle, and a silencer or the like is disposed in the middle thereof. The catalyst device 26 is a three-way catalyst, and is intended to purify HC and CO particularly when the engine E is cold. Therefore, the catalyst device 26 is disposed relatively upstream of the exhaust system of the engine E.

  However, since the exhaust system of the engine E is intended to scavenge the cylinders 4a to 4d by exhaust pulsation, the distance from the cylinder side opening of the exhaust port 10 to the catalyst device 26 is set to a relatively long value. . Therefore, it is difficult for the catalyst device 26 to be warmed up by the exhaust gas temperature, and AWS for activating the catalyst device 26 is required.

  The independent exhaust pipes 23a to 23d, the joining pipes 24a and 24b, the collecting pipe 25, and the exhaust pipe 27 are each made of, for example, a thin steel pipe made of stainless steel in order to reduce the weight of the engine E. . Therefore, the exhaust system of the engine E is likely to emit radiated sound, and measures to suppress the exhaust noise are required.

  In addition, each said independent exhaust pipe 23a-23d (independent exhaust pipe 23), each joining pipe 24a, 24b, the collection pipe 25, and the exhaust pipe 27 are respectively corresponded to the exhaust passage of this invention.

  Next, the structure of the multi-hole injector 11 will be described with reference to FIG. As shown in FIG. 2, the injector 11 is disposed such that the injection surface 11a at the tip is directed obliquely downward, and a plurality (6 in the example) is directed toward the crown surface 30 of the piston 6 near the compression top dead center. The fuel sprays Ga to Gf are injected.

  As shown in the detailed view of the ejection surface, six ejection ports 40a to 40f are formed in the ejection surface 11a. Specifically, a first nozzle hole 40a at the center of the first stage of the ejection surface 11a, a second nozzle hole 40b and a third nozzle hole 40c on the left and right sides of the second stage, a fourth nozzle hole 40d and a fifth nozzle hole 40e at the left and right ends of the third stage, A sixth nozzle hole 40f is formed at the center of the fourth stage.

  The diameter of each nozzle 40 is as small as about 0.1 mm, for example. The fuel injection amount and fuel injection direction from each nozzle 40 are determined by the diameter and direction of this nozzle 40. Specifically, the first spray Ga from the first nozzle 40a is the uppermost in the central direction, the second spray Gb from the second nozzle 40b and the third spray Gc from the third nozzle 40c are below the first spray Ga. In the left-right direction, the fourth spray Gd from the fourth nozzle 40d and the fifth spray Ge from the fifth nozzle 40e are shifted from the sixth nozzle 40f in the left-right direction below the second spray Gb and the third spray Gc. Six sprays Gf are sprayed in the central direction at the lowest position. The first spray Ga is injected below the electrode 14a so that fuel does not adhere to the electrode 14a of the spark plug 14.

  With such a structure, the multi-hole injector 11 uniformly injects a plurality of fuel sprays Ga to Gf obliquely downward into the cylinder. Therefore, at the time of homogeneous combustion during normal operation, fuel spreads throughout the cylinder, and the air-fuel mixture can be burned efficiently. Further, as will be described later, during the execution of the AWS, a weakly stratified state can be generated in the cylinder by appropriately controlling the injection timing. Here, the weakly stratified state refers to a state in which the air-fuel mixture in the cylinder becomes relatively rich around the spark plug 14 (more specifically, around the electrode 14a) and becomes relatively lean around the circumference (in-cylinder). Weak stratification of mixture).

  Next, the structure of the piston 6 will be described with reference to FIG. As shown in FIG. 3, the piston 6 according to the present embodiment similarly includes a pent roof-shaped raised portion 31 on the piston crown surface 30 corresponding to the pent roof type ceiling wall portion 8 of the combustion chamber 7 described above. That is, the raised portion 31 has an intake side inclined surface 31a and an exhaust side inclined surface 31b formed to face each other along the crankshaft direction.

  An intake side horizontal plane portion 32 and an exhaust side horizontal plane portion 33 that are reference surfaces of the piston crown surface 30 are provided on the intake side and the exhaust side from the raised portion 31. An intake valve recess 32a and an exhaust valve recess 33a corresponding to the intake valve 16 and the exhaust valve 17 are formed in each horizontal plane portion 32, 33 (see FIG. 2).

  A substantially circular concave cavity 34 is formed in the center of the raised portion 31 in plan view. The concave cavity 34 has an inner peripheral surface 35 formed in a substantially hemispherical shape and a bottom surface 36 formed in a substantially horizontal surface. When the piston 6 is positioned near the top dead center, the spark plug 14 A substantially spherical combustion space centering on the electrode 14a is formed. This substantially spherical combustion space provides an engine with an extremely high compression ratio.

  As shown in FIG. 3A, a receiving surface 37 for receiving fuel spray is formed on the intake side inclined surface 31a. The receiving surface 37 is formed of a substantially oval concave portion in plan view. By forming the receiving surface 37, as shown in FIG. 3B, the intake-side upper end 34a of the concave cavity 34 is positioned below the exhaust-side upper end 34b. Therefore, the first spray Ga injected from the injector 11 easily enters the concave cavity 34 and is difficult to exit.

  As shown in FIG. 3A, upper surface portions 38, 38 are formed on the ridge line of the raised portion 31 between the intake side inclined surface 31a and the exhaust side inclined surface 31b, excluding the concave cavity 34. The upper surface portions 38 and 38 are formed of inclined surfaces having a low piston outer peripheral side. Even when the piston 6 is located at the top dead center, a communication space that connects the intake side and the exhaust side is formed in the upper portion of the combustion chamber 7.

(2) Basic Operation of AWS Next, the operation state when the engine E is cold will be described with reference to FIG. That is, for example, immediately after a cold start of the engine E, it is detected by the catalyst temperature sensor SW5 (see FIG. 8) that the catalyst device 26 is not warmed up. When the catalyst device 26 is in an inactive state, the ECU 13 Thus, AWS (Accelerated Warm-up System) is executed. The AWS increases the intake air amount and retards the ignition timing beyond the compression top dead center when the catalytic device 26 is in an inactive state, compared to when the catalytic device 26 is in an active state in the same operating state (for example, idle operation). Thus, the air-fuel mixture is burnt after the expansion stroke, thereby increasing the exhaust gas temperature and hence the exhaust heat quantity (heat flux), thereby promoting the warm-up of the catalyst device 26.

  During execution of the AWS, the multi-hole injector 11 is controlled by the ECU 13 so that fuel is divided into two parts and injected twice per cycle, once in the intake stroke and once in the compression stroke. The

  Specifically, as shown in FIG. 9, when the start of the intake stroke is set to 0 ° CA (“° CA” represents a crank angle), the injector 11 performs a predetermined timing T1 (for example, 150 to The first stage injection is started at 170 ° CA), and the second stage injection is started at a predetermined time T2 (for example, 300 to 320 ° CA) in the middle of the compression stroke. The fuel injection amount of each time is set so that the total of the two fuel injection amounts realizes the theoretical air-fuel ratio (A / F = 14.7).

  In this way, a weakly stratified state is generated in the cylinder by injecting the fuel into two parts at an appropriate timing. That is, the fuel is vaporized and atomized early in the cylinder by the first stage injection in the intake stroke, and then a rich mixture layer having a high fuel concentration is formed around the spark plug 14 by the second stage injection in the compression stroke. Is done.

  Further, during execution of the AWS, the spark plug 14 is controlled by the ECU 13 so as to ignite at a timing significantly exceeding the compression top dead center (TDC). That is, the ignition timing is retarded until the ignition timing exceeds the compression top dead center and shifts to the expansion stroke. As will be described later, the ignition timing is changed according to the magnitude (high or low) of the external load of the engine E. FIG. 9 shows a case where the ignition timing is set to a predetermined timing T3 (for example, 375 to 400 ° CA) in the initial stage of the expansion stroke.

  By retarding the ignition timing in this way, much of the combustion energy of the engine E is converted into heat energy (that is, the rate of conversion into work that pushes down the piston 6 decreases), and exhaust loss increases. As a result, the exhaust gas temperature and the exhaust heat quantity are increased, and warming up of the catalyst device 26 is promoted. Therefore, the catalyst device 26 is activated early, and the purification of the exhaust gas is started early. In addition, in the present embodiment, the ignition timing is retarded significantly beyond the compression top dead center (for example, 36 ° CA as illustrated by the solid line in FIG. 11), so that the air-fuel mixture is burned after the expansion stroke, and more Further, the exhaust gas temperature and the exhaust heat quantity are increased, and the early activation effect of the catalyst device 26 is increased.

  Further, during execution of the AWS, the throttle valve 28 is controlled by the ECU 13 so that the intake air amount is increased as compared with the case where the catalyst device 26 is in the active state in the same idle operation. Thereby, even if the ignition timing is retarded beyond the compression top dead center, the torque and the engine rotation can be maintained. Moreover, since the amount of exhaust gas increases, the amount of exhaust heat can be increased.

  If the ignition timing is retarded, the combustion state becomes unstable, and combustion may not occur reliably. However, in this embodiment, since the in-cylinder mixture is weakly stratified by appropriately controlling the fuel injection timing, a stable combustion state can be obtained even if the ignition timing is significantly retarded.

  Specifically, in the first stage injection in the intake stroke, the sixth spray Gf from the sixth injection port 40f, which is injected downward, does not reach the side wall surface (liner) in the cylinder, and the concave shape of the piston crown surface 30 is reached. It is set to enter the cavity 34. As described above, the sixth spray Gf that is injected to the bottom reaches the piston crown surface 30, so that it is possible to prevent the fuel from adhering to the lower portion of the side wall surface in the cylinder having the lowest temperature in the cylinder. Therefore, the vaporization of the fuel in the intake stroke is promoted, and the exhaust gas is suppressed from containing HC (Raw HC), which is an unburned component.

  On the other hand, in the second stage injection in the compression stroke, as shown in FIG. 4, the first spray Ga from the first injection port 40 a that is injected at the uppermost position enters the concave cavity 34 of the piston crown surface 30. Specifically, it is set so as to face the inner peripheral surface 35 of the concave cavity 34. Further, the second spray Gb and the third spray Gc from the second nozzle hole 40b and the third nozzle hole 40c are set so as to face the intake side inclined surface 31a, more specifically the receiving surface 37, in front of the concave cavity 34. . The second spray Gb and the third spray Gc that have collided with the receiving surface 37 and weakened momentum are drawn into the concave cavity 34 by the negative pressure generated after the first spray Ga passes.

  Next, the pulling phenomenon will be described with reference to FIG. As shown in FIG. 5A, the first spray Ga is jetted toward the substantially hemispherical inner peripheral surface 35 of the concave cavity 34. Therefore, as shown in FIG. 5 (b), the first spray Ga is guided smoothly by the arc-shaped inclined surface 35a of the inner peripheral surface 35 and smoothly smoothly turns upward, and the spark plug 14 (ceiling wall portion 8). Head for.

  On the other hand, as shown in FIG. 5A, the second spray Gb and the third spray Gc are injected toward the receiving surface 37. Therefore, the second spray Gb and the third spray Gc collide with the receiving surface 37 to weaken the momentum, and drift above the receiving surface 37. Here, since a negative pressure is drawn into the concave cavity 34 after the first spray Ga has passed, the second spray Gb and the third spray Gc are caused by this negative pressure, as shown in FIG. It is drawn into the concave cavity 34.

  In this way, the second spray Gb and the third spray Gc in addition to the first spray Ga are drawn into the concave cavity 34, so that more fuel is located around the spark plug 14, and as a result, the fuel concentration A rich rich air-fuel mixture is present around the spark plug 14.

  Since the second spray Gb and the third spray Gc are injected to the receiving surface 37 that is recessed by one step from the intake side inclined surface 31a, the leakage from the intake side inclined surface 31a is suppressed and surely entered into the concave cavity 34. Be drawn.

(3) Control System As shown in FIG. 8, the vehicle (AT vehicle) according to this embodiment includes an engine water temperature sensor SW1 for detecting the engine water temperature, and an engine speed sensor for detecting the engine speed. SW2, a crank angle sensor SW3 for detecting the rotation angle of the crankshaft 1, an accelerator for detecting the presence / absence of the accelerator operation (depressing the accelerator pedal) and the accelerator operation amount (depressing the accelerator pedal). A position sensor SW4 and a catalyst temperature sensor SW5 for detecting the temperature of the catalyst device 26 are provided. The ECU 13 is electrically connected to these various sensors SW1 to SW5.

  As is well known, the ECU 13 is a microprocessor including a CPU, a ROM, a RAM, and the like, and corresponds to the ignition timing setting means, the exhaust valve opening start timing setting means, the injection timing setting means, and the external load reduction means of the present invention. To do.

  The ECU 13 controls the normal operation (homogeneous combustion) of the engine E based on various information input from the various sensors SW1 to SW5 provided in the vehicle. When the catalyst device 26 is in an inactive state, AWS is executed to activate the catalyst device 26 at an early stage.

  For execution of AWS, the ECU 13 is electrically connected to the fuel supply system 12, the ignition circuit 15, the throttle valve 28, the air conditioner (more specifically, its compressor) 101, the alternator 102, the oil pump 103, the intake VVT 120, and the exhaust VVT 121. Connected and outputs control signals to these various devices. Here, since the auxiliary equipment such as the air conditioner 101, the alternator 102, and the oil pump 103 is connected to the crankshaft 1 through a belt or the like and driven, it is an external load that serves as a rotational resistance for the engine E. .

(4) Features of the present embodiment Next, features of the present embodiment will be described with reference to FIGS. FIG. 9 is a time chart of fuel injection timing, ignition timing, intake / exhaust valve opening timings IVO, EVO and valve closing timings IVC, EVC during execution of AWS, and FIG. 10 shows engine rotation and ignition timing during execution of AWS. FIG. 11A is a time chart of in-cylinder pressure during execution of AWS when the retard amount of the ignition timing is ATDC (after compression top dead center) 16 ° CA, 26 ° CA, and 36 ° CA. FIG. 11 (b) is an enlarged view of the latter half of the expansion stroke. 12 is a cam profile of the exhaust valve cam 21 of the engine E, FIG. 13 is a graph showing changes in lift acceleration with respect to the crank angle of the exhaust valve cam 21, and FIG. 6 is a graph showing a change in lift acceleration with respect to a crank angle of the valve cam 20.

  As described above, during execution of the AWS, the ECU 13 retards the ignition timing beyond the compression top dead center, so that the air-fuel mixture burns during the expansion stroke, and the in-cylinder pressure rises in the latter half of the expansion stroke and peaks. Welcome. Since this timing overlaps with the valve opening start timing EVO of the exhaust valve 17, the blowdown energy flowing out from the cylinder 4 to the exhaust port 10 when the exhaust valve 17 is opened becomes high. As a result, the amplitude of the exhaust pulsation in the independent exhaust pipes 23a to 23d, the merge pipes 24a and 24b, and the collecting pipe 25 increases, the emission sound of the exhaust system increases, and the exhaust noise increases. In order to cope with this problem, when the intake air amount is reduced to lower the engine speed, the exhaust heat amount is reduced and the early activation effect of the catalyst device 26 is reduced.

  Therefore, in the present embodiment, in order to suppress the exhaust noise while maintaining the early activation effect of the catalyst device 26, the ECU 13 burns the air-fuel mixture ignited at the retarded ignition timing during the execution of the AWS. In the cam profile of the cam for the exhaust valve 17 (exhaust valve cam 21), the valve opening start timing EVO of the exhaust valve 17 is set so that the exhaust valve 17 starts to open during the expansion stroke. In the initial stage of the positive acceleration section excluding the buffer section on the valve opening start side of the exhaust valve 17, a slow acceleration section is formed in which the increase rate of the lift acceleration with respect to the crank angle is small compared to the initial stage of the positive acceleration section of the intake valve 16. Yes.

  As shown in FIG. 10, when the engine E is started, the ECU 13 executes AWS for a predetermined time during the idle operation after the complete explosion. During the execution of the AWS, the ECU 13 retards the ignition timing beyond the compression top dead center (TDC). Therefore, if the intake air amount is not increased by controlling the throttle valve 28, the ECU 13 Compared to the case where the ignition timing is not retarded, the torque is reduced and the engine speed is reduced. Moreover, the ECU 13 sets the ignition timing so that the retard amount from the compression top dead center becomes larger as the external load of the engine E is lower, as indicated by the arrow in FIG. The lower the external load, the lower the engine speed. The broken line in the figure shows the case where the ignition timing retard amount is ATDC (after compression top dead center) 16 ° CA, and the solid line shows the case where the ignition timing retard amount is ATDC 36 ° CA.

  As shown in FIG. 9, in the present embodiment, the valve opening period of the intake valve 16 and the exhaust valve 17, that is, the period from the valve opening timings IVO, EVO of the intake valve 16 and the exhaust valve 17 to the valve closing timings IVC, EVC. It is set relatively large. In particular, during execution of the AWS, the intake VVT 120 and the exhaust VVT 121 are controlled by the ECU 13 to provide an overlap period in which both the intake valve 16 and the exhaust valve 17 are opened across the exhaust top dead center (720 ° CA). . In addition, in that case, the advance amount of the valve opening timing IVO of the intake valve 16 from the exhaust top dead center is set larger than the retard amount of the valve closing timing EVC of the exhaust valve 17 from the exhaust top dead center. . As a result, a large amount of exhaust gas, that is, internal EGR gas is discharged to the intake system, so that the opening degree of the throttle valve 28 is increased in order to secure a new air amount. Therefore, the pumping loss is reduced and the fuel consumption is improved.

  Specifically, as shown in FIG. 9, during the execution of the AWS, the valve opening timing IVO of the intake valve 16 is set to a substantially middle timing in the latter half of the exhaust stroke, and the valve closing timing IVC is substantially in the middle of the first half of the compression stroke. The timing is set. On the other hand, the valve opening timing EVO of the exhaust valve 17 is set to a predetermined timing T4 (for example, 470 to 490 ° CA) in the middle of the expansion stroke, and the valve closing timing EVC is a predetermined timing T5 (for example, 0 to 10 ° CA) in the initial stage of the intake stroke. Set to Thus, the valve opening timing EVO of the exhaust valve 17 is greatly advanced from the expansion bottom dead center (BDC).

  In the present embodiment, the external load of the engine E can be changed variously depending on the driving degree of the air conditioner 101, the alternator 102, and the oil pump 103, on / off, and the like. In this embodiment, the air conditioner 101 is on, the alternator 102 is in the maximum power generation state (the state where the current value of the field coil for generating a magnetic field in the alternator 102 is set to the maximum value), and the oil pump 103 is in the maximum drive state ( When the oil discharge pressure by the oil pump 103 is set to the maximum value), the external load is highest, the air conditioner 101 is off, and the alternator 102 is in the lowest power generation state (the current value of the field coil is set to the minimum value). The external load is lowest when the oil pump 103 is in the lowest drive state (the oil discharge pressure is set to the minimum value). When the external load is the highest, the ECU 13 controls the ignition circuit 15 to set the ignition timing retard amount to 16 ° CA (after compression top dead center) (see FIG. 11). The ignition circuit 15 is controlled to set the ignition timing retard amount to ATDC 36 ° CA (see FIG. 11).

  As shown in FIGS. 11 (a) and 11 (b), when the ignition timing retard amount is ATDC 16 ° CA (dashed line), the in-cylinder pressure peak reaches approximately ATDC 90 ° CA, and the ignition timing retarded. When the amount is ATDC 36 ° CA (solid line), the in-cylinder pressure peak reaches approximately ATDC 140 ° CA. The intake air amount and the fuel injection amount are adjusted to be substantially the same in the case of the solid line and the case of the chain line. As described above, the ECU 13 increases the retard amount of the ignition timing from the compression top dead center as the external load of the engine E is lower. That is, the lower the external load of the engine E (the solid line is compared to the chain line), the later the time when the in-cylinder pressure reaches its peak, the lower the peak value.

  In the present embodiment, the reference load refers to the timing at which the peak of in-cylinder pressure arrives when the external load is the highest (ATDC 90 ° CA), and the timing at which the peak of in-cylinder pressure arrives when the external load is the lowest (ATDC 90 ° CA). This is the external load at which the peak of the in-cylinder pressure arrives at the timing of the ATDC 140 ° CA). In this embodiment, as shown in FIG. 11, the ignition load is an external load with a retard amount of ATDC 26 ° CA (broken line). This external load (reference load) is an external load having a value between the above-described state where the external load is the highest and the state where the external load is the lowest, and the on / off state of the air conditioner 101, the power generation state of the alternator 102, and This is an external load achieved when the driving state of the oil pump 103 is a predetermined combination.

  As shown in FIGS. 11A and 11B, the ECU 13 starts opening the exhaust valve 17 when the ignition timing retard amount is ATDC 36 ° CA (solid line), that is, when the external load is the lowest. The timing EVO is set to ATDC 126 ° CA (BBDC 54 ° CA) before ATDC 140 ° CA at which the in-cylinder pressure reaches its peak.

  However, as will be described later, in this embodiment, the valve opening start timings EVO of the two exhaust valves 17 provided per cylinder 4 are slightly different from each other. Here, the valve opening start timing EVO is set to ATDC 126 ° CA (BBDC 54 ° CA) for the exhaust valve 17 whose valve opening start timing EVO is earlier (the same applies hereinafter).

  When the retard amount of the ignition timing is ATDC 16 ° CA (chain line), that is, when the external load is the highest, the ECU 13 sets the valve opening start timing EVO of the exhaust valve 17 to ATDC 126 ° CA (BBDC 54 ° CA). This valve opening start timing EVO (= ATDC 126 ° CA) is delayed from ATDC 90 ° CA at which the in-cylinder pressure reaches its peak.

  Further, when the retard amount of the ignition timing is ATDC 26 ° CA (broken line), that is, when the external load is the reference load between the lowest and the highest, the ECU 13 also opens the opening timing of the exhaust valve 17. EVO is set to ATDC 126 ° CA (BBDC 54 ° CA). This valve opening start timing EVO (= ATDC 126 ° CA) is a timing close to (substantially coincides with) ATDC 125 ° CA at which the in-cylinder pressure reaches its peak.

  In any case, since the exhaust valve 17 starts to open during the expansion stroke in which the air-fuel mixture ignited at the ignition timing retarded beyond the compression top dead center is opened, when the exhaust valve 17 is opened. The blowdown energy flowing out from the cylinder 4 to the exhaust port 10 is increased. As a result, the amplitude of exhaust pulsation in the independent exhaust pipes 23a to 23d, the merge pipes 24a and 24b, and the collecting pipe 25 is increased. There may be a problem that the emission noise increases and the exhaust noise increases.

  In order to cope with this problem, in this embodiment, as shown in FIGS. 12 and 13, in the cam profile of the exhaust valve cam 21, the positive acceleration section excluding the buffer section on the valve opening start side of the exhaust valve 17. Initially, a slow acceleration section is formed in which the rate of increase in lift acceleration with respect to the crank angle is small compared to the initial stage of the positive acceleration section of the intake valve 16 shown in FIG.

  However, in this embodiment, the ECU 13 makes the valve opening start timing EVO of the two exhaust valves 17 different per cylinder 4 and the exhaust valve 17 with the earlier valve opening start timing EVO of the two exhaust valves 17. The slow acceleration section is formed only in

  Specifically, of the two exhaust valves 17, the exhaust valve cam 21 that drives the exhaust valve 17 whose valve opening start timing EVO is earlier is the “P cam”, and the exhaust valve cam that drives the other exhaust valve 17. If 21 is an “S cam”, as shown in FIG. 13, only the P cam (solid line), a slow acceleration zone where the increase rate of the lift acceleration with respect to the crank angle is small at the beginning of the positive acceleration zone except the buffer zone. Is formed. On the other hand, in the S cam (broken line), a slow acceleration section in which the increase rate of the lift acceleration with respect to the crank angle is small is not formed at the initial stage of the positive acceleration section excluding the buffer section. Therefore, the lift acceleration characteristic (broken line) of the S cam shown in FIG. 13 is similar to the lift acceleration characteristic of the intake valve cam 20 shown in FIG.

  Here, the buffer section corresponds to a portion where the gradient of the valve lift described above is gentle (ramp part), and the section until the valve lift amount increases to 0.2 mm during the valve lift period, or the valve lift. This is the interval after the amount has decreased to 0.2 mm.

  In addition, the code | symbol "a" in a figure is the allocation angle of the cam which a slow acceleration area complete | finishes.

  As shown in an enlarged view in FIG. 12, the valve opening start timing of the P cam (referred to as “EVOP” in FIG. 11B) is greater than the valve opening start timing of the S cam (also referred to as “EVOS”). It is set early. Then, as shown in FIG. 11B, the valve opening start timing EVOP of the P cam is set to ATDC 126 ° CA (BBDC 54 ° CA) (Note that the valve opening start timing EVOS of the S cam is ATDC 128 °. CA (set to BBDC 52 ° CA)). Accordingly, when the P cam having the earlier valve opening start timing EVOP among the two exhaust valves 17 provided per cylinder 4 starts to open, the P cam is relatively moved by the slow acceleration section. The valve opens slowly, and the release or transmission of blowdown energy to the exhaust system slows down.

(5) Operation, etc. As described above, in this embodiment, when the catalyst device 26 provided between the collecting pipe 25 and the exhaust pipe 27 is in an inactive state, the catalyst device 26 is in an active state in the same idle operation. As compared with the above, the following characteristic configuration was adopted in the catalyst early warm-up control device of the spark ignition engine that increases the intake air amount and retards the ignition timing beyond the compression top dead center.

  That is, in the cam profile of the exhaust valve cam 21, the lift acceleration relative to the crank angle at the initial stage of the positive acceleration section excluding the buffer section on the valve opening start side of the exhaust valve 17 compared to the initial stage of the positive acceleration section of the intake valve 16. Therefore, the exhaust valve 17 is opened relatively slowly by the slow acceleration section. Therefore, even if the blowdown energy is high, the release or transmission of the blowdown energy to the exhaust system is slowed down. As a result, in the independent exhaust pipes 23a to 23d, in the merging pipes 24a and 24b, and in the collecting pipe 25 The amplitude of the exhaust pulsation is reduced, the emission sound of the exhaust system is reduced, and the exhaust noise is suppressed.

  On the other hand, with respect to the catalyst activity, since the air-fuel mixture ignited at the ignition timing retarded beyond the compression top dead center is burned after the expansion stroke, the exhaust gas temperature and the exhaust heat quantity are increased. The early activation effect of the device 26 is sufficiently maintained. That is, both catalyst activity and exhaust noise can be achieved.

  As described above, according to the present embodiment, there is provided a catalyst early warm-up control device for a spark ignition engine that can suppress exhaust noise while maintaining the early activation effect of the catalyst device 26 during execution of AWS. The

  In this embodiment, the ECU 13 injects the fuel into the cylinder directly so that the air-fuel mixture in the cylinder becomes relatively rich around the spark plug 14 at the set ignition timing. The timing is set (see “first stage injection” and “second stage injection” in FIG. 9).

  According to this configuration, even when the ignition timing is largely retarded during execution of the AWS, the combustion state does not become unstable, and the air-fuel mixture is stably and reliably burned.

  In this embodiment, two exhaust valves 17 are provided in one cylinder 4, and the ECU 13 opens the two exhaust valves 17 so that the two exhaust valves 17 have different valve opening start times EVO. Set EVO.

  According to this configuration, since the two exhaust valves 17 per cylinder 4 start to open at different timings, the flow of exhaust gas discharged to the exhaust port 10 is disturbed, and as a result, the independent exhaust pipes 23a to 23d. The exhaust gas in the merging pipes 24a and 24b and the collecting pipe 25 is agitated to promote afterburning in these pipes. Therefore, afterburning is achieved at a portion closer to the catalyst device 26, which is further advantageous in terms of catalyst activity.

  In the present embodiment, the slow acceleration section is formed only in the exhaust valve cam 21 (P cam) that drives the exhaust valve 17 whose valve opening start timing EVO is earlier among the two exhaust valves 17.

  According to this configuration, even if the two exhaust valves 17 start opening at different timings, the effect of releasing or transmitting blowdown energy to the exhaust system is ensured.

  A slow acceleration zone may also be formed in the exhaust valve cam 21 (S cam) that drives the exhaust valve 17 having the later valve opening start timing EVO of the two exhaust valves 17. In that case, it is preferable to form the slow acceleration section of the P cam longer than the slow acceleration section of the S cam on the valve opening start side. As a result, the two exhaust valves 17 that start opening at different timings release the blowdown energy slowly for a long period of time as a whole, and can cope well when the blowdown energy is excessive. is there.

  In the above embodiment, the valve opening start timing EVO of the exhaust valve 17 is set to ATDC 126 ° CA (BBDC 54 ° CA). However, the present invention is not limited to this. Can change.

  Moreover, in the said embodiment, although the vehicle was an AT vehicle, it is not restricted to this, The MT vehicle whose transmission T is a manual transmission (MT) may be sufficient. In that case, since the heavy torque converter is not connected to the crankshaft 1, the external load of the engine E is generally lower than that of the AT vehicle, and the retard amount of the ignition timing is further increased during execution of the AWS. be able to.

DESCRIPTION OF SYMBOLS 1 Crankshaft 4a-4d 1st-4th cylinder 6 Piston 7 Combustion chamber 9 Intake port 10 Exhaust port 11 Multi-hole injector (fuel injection valve)
12 Fuel supply system 13 Engine control unit (exhaust valve opening start timing setting means)
DESCRIPTION OF SYMBOLS 14 Spark plug 15 Ignition circuit 16 Intake valve 17 Exhaust valve 20 Intake valve cam 21 Exhaust valve cam 23 Independent exhaust pipe (exhaust passage)
23a-23d 1st-4th independent exhaust pipe (exhaust passage)
24a First junction pipe (exhaust passage)
24b Second junction pipe (exhaust passage)
25 Collecting pipe (exhaust passage)
26 Catalytic device 27 Exhaust pipe (exhaust passage)
28 Throttle valve 40a-40f 1st-4th nozzle 101 Air-conditioner 102 Alternator 103 Oil pump 120 Intake VVT
121 Exhaust VVT
E Engine SW1 Engine water temperature sensor SW2 Engine speed sensor SW3 Crank angle sensor SW4 Accelerator position sensor SW5 Catalyst temperature sensor T Transmission

Claims (4)

Spark ignition type that increases the intake air amount and retards the ignition timing beyond the compression top dead center when the catalyst device provided in the exhaust passage is in an inactive state than in the active state in the same operating state An engine early catalyst warm-up control device,
Exhaust valve opening start timing setting means is provided for setting the opening timing of the exhaust valve so that the exhaust valve starts opening during the expansion stroke in which the air-fuel mixture ignited at the retarded ignition timing burns. And
In the cam profile of the cam for the exhaust valve, the lift acceleration increases with respect to the crank angle at the beginning of the positive acceleration section excluding the buffer section on the valve opening start side of the exhaust valve compared to the initial stage of the positive acceleration section of the intake valve. A catalyst early warm-up control device for a spark ignition engine, characterized in that a slow acceleration section with a small ratio is formed. The catalyst early warm-up control device for a spark ignition type engine according to claim 1,
A plurality of the exhaust valves are provided in one cylinder,
The exhaust valve opening start timing setting means sets the exhaust valve opening start timing so that the opening timings of the plurality of exhaust valves are different from each other. apparatus. The catalyst early warm-up control device for a spark ignition type engine according to claim 2,
The catalyst early warm-up control device for a spark ignition engine, wherein the slow acceleration section is formed only in an exhaust valve whose opening start timing is earlier among the plurality of exhaust valves. The catalyst early warm-up control device for a spark ignition engine according to claim 2 or 3,
The spark ignition characterized in that the slow acceleration section of the exhaust valve whose opening start timing is earlier among the plurality of exhaust valves is formed longer on the valve opening start side than the slow acceleration section of the other exhaust valves. Type early catalyst warm-up controller

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