JP2009243360A - Engine combustion control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for improving the mixing of fuel and air by sufficiently gasifying or atomizing fuel in all cycles at the start of an engine. <P>SOLUTION: At the start of the engine E in which valve timing varying mechanisms 15, 18 are provided for an intake valve 12 and an exhaust valve 13, an opening/closing timing for the intake valve 12 is set in the first cycle so that a valve opening timing for the intake valve 12 is at a delay side beyond an intake top dead center and valve opening periods for the intake valve 12 and the exhaust valve 13 are not overlapped with each other. In this case, a fuel injection timing is set at a delay side beyond the valve opening timing for the intake valve 12. Meanwhile, after the second starting cycle, an opening/closing timing for the exhaust valve 13 is delayed so that the valve opening periods for the exhaust valve 13 and the intake valve 12 are overlapped with each other, and the fuel injection timing is set to be normal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an engine combustion control device provided with a variable valve timing mechanism.

  Generally, in an automobile engine, fuel is injected into air in an intake port or a combustion chamber to be vaporized or atomized, and thermal energy generated by burning the vaporized or atomized fuel and air mixture. Is converted into rotational energy of the crankshaft through a piston and a connecting mechanism such as a connecting rod. However, when the engine is started, particularly during a cold start, the combustion chamber is at a low temperature, so that the fuel is not easily vaporized, and air and fuel are not sufficiently mixed. For this reason, there exists a problem that the combustibility of air-fuel mixture is bad and the emission amount of HC (hydrocarbon) increases. In view of this, various engines have been proposed that improve the combustibility of the fuel or reduce the amount of HC emission by changing the opening and closing timing of the intake valve or the exhaust valve when starting the engine (for example, Patent Document 1). reference.).

For example, when the engine is cold started, by changing the opening and closing timing of the intake valve or exhaust valve, the overlap period of the intake valve opening period and the exhaust valve opening period is expanded and discharged into the exhaust passage An engine has been proposed in which exhaust gas is recirculated into the combustion chamber (that is, internal exhaust gas recirculation) to increase the temperature of the air in the combustion chamber by using exhaust heat to promote fuel vaporization. . Note that in the engine disclosed in Patent Document 1, unburned HC is burned by supplying secondary air to the exhaust passage upstream of the catalyst when the engine is started to reduce the HC emission amount.
JP 2007-113469 A (paragraph [0027], FIG. 2)

  However, in the conventional engine in which the temperature of the air in the combustion chamber is increased by, for example, internal exhaust gas recirculation, since the exhaust gas is not yet present in the first cycle when the engine is started, the temperature of the air in the combustion chamber is increased. It is not possible. For this reason, in the first cycle, the fuel is not sufficiently vaporized or atomized, and there is a problem that although it is temporary, the amount of HC (hydrocarbon) generated increases and the engine output decreases.

  The present invention has been made to solve the above-described conventional problems, and at the time of starting the engine, the fuel and air are sufficiently vaporized or atomized in all cycles including the first cycle. It is an object to be solved to provide means that can improve the mixing of the engine and, in turn, improve engine output and emission performance.

  An engine combustion control apparatus according to the present invention, which has been made to solve the above problems, includes valve timing control means for controlling the opening / closing timing (valve timing) of the intake valve and the exhaust valve. In the first cycle at the time of engine start (hereinafter referred to as “starting first cycle”), the valve timing control means is such that the opening timing of the intake valve is retarded from the intake top dead center, and the intake valve Control is performed so that the valve opening period and the exhaust valve opening period do not overlap. On the other hand, in the second and subsequent cycles when starting the engine (hereinafter referred to as “starting second cycle and thereafter”), control is performed so that the valve opening period of the intake valve and the valve opening period of the exhaust valve overlap.

  In the engine combustion control apparatus according to the present invention, the engine includes a fuel injection valve that injects fuel into the combustion chamber (inside the cylinder), and a fuel injection control unit that controls fuel injection timing of the fuel injection valve. In this case, in the first cycle of starting, the fuel injection control means starts fuel injection during a period from when the exhaust valve is closed until the intake valve starts to open (hereinafter referred to as “non-overlap period”). It is preferable to control the fuel injection valve.

  In this case, the fuel injection control means controls the fuel injection valve to perform fuel injection divided into at least two periods including a non-overlap period and a period after the intake valve starts to open. More preferred.

  In the combustion control apparatus for an engine according to the present invention, the valve timing control means delays the valve closing timing of the exhaust valve after the second cycle of starting, thereby opening the intake valve opening period and the exhaust valve opening period. Are preferably overlapped with each other.

  According to the combustion control apparatus for an engine according to the present invention, in the first cycle of starting, both the intake valve and the exhaust valve are closed at the beginning of the intake stroke. The pressure is reduced to near vacuum. Then, when the intake valve is subsequently opened, air flows from the intake port into the combustion chamber at a very high speed. For this reason, the turbulence of the air becomes very strong in the combustion chamber, and the strong turbulence of the air promotes the vaporization or atomization of the fuel, thereby improving the mixing of the fuel and the air in the combustion chamber.

  Further, in the second and subsequent cycles of the start, the valve opening period of the intake valve and the valve opening period of the exhaust valve overlap, so that the temperature of the air in the combustion chamber is increased by the internal exhaust gas recirculation, and the fuel is vaporized or atomized. This improves the mixing of fuel and air in the combustion chamber. Therefore, at the time of engine start, fuel can be sufficiently vaporized or atomized in all cycles including the first start cycle to improve fuel and air mixing, thereby improving engine output and emission performance. Can do.

  In the engine combustion control apparatus according to the present invention, when the fuel injection is started in the non-overlap period in the first cycle of the start, the combustion chamber (inside the cylinder) is moved along with the lowering of the piston at the beginning of the intake stroke. When in a state close to a vacuum, fuel is injected into the combustion chamber. In this case, since the fuel injected into the combustion chamber is rapidly vaporized by boiling under reduced pressure in the first start cycle, the fuel can be vaporized more effectively to improve the mixing of the fuel and the air.

  Further, in the first cycle of starting, when fuel injection is performed by dividing into at least two periods including a non-overlap period and a period after the intake valve starts to open, the pressure is reduced in the non-overlap period. Fuel can be vaporized by boiling to improve mixing of fuel and air. On the other hand, during the period after the intake valve starts to open, the turbulent air flowing at high speed into the combustion chamber in a state close to a vacuum promotes the vaporization or atomization of the fuel, and the fuel in the combustion chamber Air mixing can be improved. Together, the fuel and air mixing at the time of engine start can be further improved.

  In the engine combustion control apparatus according to the present invention, when the valve opening period of the intake valve overlaps the valve opening period of the exhaust valve by delaying the valve closing timing of the exhaust valve after the second cycle of starting. Since the overlap between the valve opening period of the intake valve and the valve opening period of the exhaust valve occurs in the intake stroke in which the piston descends, more exhaust gas in the exhaust passage can be recirculated into the combustion chamber. For this reason, the temperature in the combustion chamber can be increased after the second cycle of the start, and the fuel can be vaporized or atomized more effectively to improve the mixing of fuel and air.

  Embodiments 1 and 2 of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1 shows a system configuration of an in-cylinder injection type spark ignition engine E (hereinafter abbreviated as “engine E”) provided with a combustion control device according to the present invention. Although the engine E is a four-cylinder engine, only one cylinder is shown in FIG. 1, and the other cylinders are not shown. The present invention is not limited to a four-cylinder engine, and can be applied to multi-cylinder engines other than four-cylinder engines (for example, a six-cylinder engine, an eight-cylinder engine, etc.). Further, the engine E is an in-cylinder injection type engine, but the present invention can also be applied to a port injection type engine in which fuel is injected into an intake port in its basic mode.

(Embodiment 1)
As shown in FIG. 1, the main body of the engine E is composed of a cylinder head 1 and a cylinder block 2. The engine E is a four-cylinder four-cycle engine and includes four cylinders 3. In the engine E, each cylinder 3 repeats a cycle composed of expansion, exhaust, intake, and compression strokes with a predetermined phase difference. These cycles include the first cylinder, the third cylinder, It is repeated with a phase difference of 180 ° (180 ° CA) in the crank angle in the order of the 4th cylinder and the 2nd cylinder.

  A piston 4 is fitted in each cylinder 3, and a combustion chamber 5 is formed above the piston 4. The piston 4 is connected to the crankshaft 7 via a connecting mechanism having a connecting rod 6 and the like. A spark plug 8 is provided at the top of the combustion chamber 5 of each cylinder 3, and the plug tip end faces the combustion chamber 5. A fuel injection valve 9 that directly injects fuel into the combustion chamber 5 is provided on the side of the combustion chamber 5. Although not shown in detail, the fuel injection valve 9 incorporates a needle valve and a solenoid, receives a pulse signal, is driven for a time corresponding to the pulse width at the pulse input timing, and opens the valve. The amount of fuel is injected according to the time. The fuel injection valve 9 is arranged so as to inject fuel toward the vicinity of the spark plug 8. Although not shown, the fuel injection valve 9 is supplied with fuel through a fuel supply passage or the like by a fuel pump, and injects the fuel at a pressure higher than the pressure in the combustion chamber in the compression stroke. It has become.

  An intake port 10 and an exhaust port 11 are opened to the combustion chamber 5 of each cylinder 3, and an intake valve 12 and an exhaust valve 13 are provided in both the ports 10 and 11, respectively. The opening / closing timings of the intake valve 12 and the exhaust valve 13 of each cylinder 3 are set so that each cylinder 3 performs each cycle consisting of four strokes of expansion, exhaust, intake, and compression with a predetermined phase difference.

  Here, the intake valve 12 is opened and closed by the intake valve cam 14 at a predetermined timing in synchronization with the crankshaft 7. An electric intake valve timing variable mechanism 15 (VVT) is provided for the intake valve cam 14. The intake valve timing variable mechanism 15 can advance or retard the opening / closing timing of the intake valve 12 via the intake valve cam 14 in accordance with a control signal from the intake valve controller 16.

  On the other hand, the exhaust valve 13 is opened and closed at a predetermined timing by the exhaust valve cam 17. An electric exhaust valve timing variable mechanism 18 (VVT) is provided for the exhaust valve cam 17. The exhaust valve timing variable mechanism 18 can advance or retard the opening / closing timing of the exhaust valve 13 via the exhaust valve cam 17 in accordance with a control signal from the exhaust valve controller 19. The electric intake valve timing variable mechanism 15 and the exhaust valve timing variable mechanism 18 can operate immediately after the engine is started, and the opening / closing timing is linear (linear) compared to the hydraulic valve timing variable mechanism. Can be changed. The specific structures of the intake valve timing variable mechanism 15 and the exhaust valve timing variable mechanism 18 will be described later with reference to FIG.

  An intake passage 20 that supplies fuel combustion air to the combustion chamber 5 is connected to the intake port 10. Although not shown in detail, the intake passage 20 is a single passage (common intake passage) on the upstream side in the flow direction of air sucked into the combustion chamber 5 (hereinafter referred to as “intake air”). Although there is a branch on the downstream side, each passage (branch intake passage) is connected to an intake port 10 of the corresponding cylinder 3. An upstream portion (common intake passage) of the intake passage 20 has an air cleaner (not shown) for removing dust and the like in the intake air in order from the upstream side in the direction of the intake air flow. An air flow sensor 41 (see FIG. 3) for detecting the flow rate, a throttle body 22 having a throttle valve 21, a surge tank (not shown) for stabilizing the flow of intake air, and the like are provided.

  Further, an individual tumble swirl control valve 23 (TSCV) is provided for each cylinder in the downstream portion (branch intake passage) of the intake passage 20 from the surge tank. Although the tumble swirl control valve 23 is not shown in detail, the strength of the tumble (vertical vortex) and swirl (lateral vortex) generated in the combustion chamber 5 of the corresponding cylinder 3 is changed by changing the opening degree. Adjust or control.

  On the other hand, the exhaust port 11 is provided with an exhaust passage 25 for exhausting combustion gas generated in the combustion chamber 5, that is, exhaust gas, outside the engine (in the atmosphere). The exhaust passage 25 branches from each cylinder 3 in the vicinity of the upstream end (exhaust manifold) and is connected to each exhaust port 11 in the flow direction of the exhaust gas, but is common to each cylinder 3 on the downstream side. It is a single passage (common exhaust passage). Although not shown, the exhaust passage 25 (common exhaust passage) is an oxidation catalyst (for example, a catalyst made of platinum, rhodium, palladium, or the like) that oxidizes and purifies HC and CO to purify the exhaust gas. ) And a reduction catalyst (a catalyst made of platinum, barium, or the like) that reduces and purifies NOx. This exhaust gas purification device exhibits a catalytic action or an exhaust gas purification action effectively when the catalyst temperature is equal to or higher than the activation temperature (for example, 200 to 250 ° C.).

  As shown in FIG. 2, the electric intake valve timing varying mechanism 15 is attached to the front end portion (front end portion) of the camshaft 30 to which the intake valve cam 14 of each cylinder 3 is attached. The variable intake valve timing mechanism 15 includes a sprocket portion 31 driven by the crankshaft 7, a link mechanism 32 fixed to the camshaft 30 and rotating integrally with the camshaft 30, an electric VVT motor 33, a sprocket A chain case 34 disposed between the portion 31 and the link mechanism 32 and the VVT motor 33 is provided.

  Here, the intake valve timing variable mechanism 15 drives the VVT motor 33 to change the rotational phase difference between the sprocket unit 31, the link mechanism 32, and the camshaft 30, that is, the rotational phase of the camshaft 30. be able to. In this way, by changing the rotational phase of the camshaft 30 in the forward direction or the reverse direction of the camshaft 30, the rotational phase of the intake valve cam 14 and thus the opening / closing timing (valve timing) of the intake valve 12 is predetermined. Can be advanced or retarded within an angle range (for example, within a range of −60 ° to + 60 ° in crank angle). The electric exhaust valve timing varying mechanism 18 is basically of the same structure as the intake valve timing varying mechanism 15, and the opening / closing timing of the exhaust valve 13 is set within a predetermined angular range (for example, crank The angle can be advanced or retarded within a range of −60 ° to + 60 °.

Hereinafter, the control system of the engine E will be described.
As shown in FIG. 3, the engine E is provided with various sensors for collecting various information related to the operating state. For example, an air flow sensor 41 that detects the flow rate of intake air, an engine speed sensor 42 that detects the rotational speed of the crankshaft 7, that is, an engine speed, a crank angle sensor 43 that detects the crank angle, and an opening degree of the throttle valve 21 are detected. A throttle opening sensor 44 for detecting the engine temperature, a water temperature sensor 45 for detecting the engine water temperature (engine temperature), and the like are provided. The detection signals of these sensors 41 to 45 are input to the control unit C as control information for the engine E.

  The control unit C is a comprehensive control means of the engine E including “valve timing control means” and “fuel injection control means” described in the section for solving the problems. Although not shown in detail, the control unit C includes an input / output unit (interface) that inputs and outputs control signals, a storage unit (ROM, RAM, and the like) that stores data and control information, and a central unit that performs various arithmetic processes. A computer including a processing unit (CPU), a timer, a counter, and the like.

  And the control unit C is based on the various data detected by each said sensors 41-45, the spark plug 8, the fuel injection valve 9, the intake valve timing variable mechanism 15 (intake valve controller 16), the exhaust valve timing variable mechanism. 18 (exhaust valve controller 19), throttle valve 21 and the like are controlled or driven to perform normal engine control such as ignition timing control, fuel injection control, and normal opening / closing timing control of intake valve 12 and exhaust valve 13. At the time of engine start, control according to the present invention (hereinafter referred to as “engine start control”) for improving mixing of fuel and intake air is performed. However, the control method for ordinary engine control is well known to those skilled in the art, and since such ordinary engine control is not the gist of the present invention, the description thereof is omitted.

  Hereinafter, the control procedure of the engine start control according to the present invention, which is executed by the control unit C, will be specifically described with reference to the flowchart shown in FIG. As shown in FIG. 4, the engine start control is started when cranking (start) of the engine E is started based on an output signal of the starter switch 46 (see FIG. 3).

  When engine start control is started in this manner, it is first determined in step S1 whether or not engine start has been completed, that is, whether or not engine E has reached a complete explosion state after cranking has started. Here, if it is determined that the engine start has not been completed (NO), it is determined in step S2 whether or not the current cycle is the first start cycle (the first cycle at the time of engine start). The

  If it is determined in step S2 that the current cycle is the first start cycle (YES), the opening / closing timing of the intake valve 12 and the opening timing of the intake valve 12 are the intake top dead center (exhaust stroke) in step S3. And the top dead center between the intake stroke) and the intake valve 12 is set so that the valve opening period of the intake valve 12 and the valve opening period of the exhaust valve 13 do not overlap. Subsequently, in step S4, the fuel injection timing of the fuel injection valve 5 is set to the retard side with respect to the opening timing of the intake valve 12, and thereafter, the process returns to step S1 (return).

That is, as shown in FIG. 6, in the engine E, during normal operation, the opening and closing timing of the exhaust valve 13 is set to a normal timing L _1, opening and closing timing of the intake valve 12 is set to a normal timing L _2. In this case, the valve opening period of the exhaust valve 13 and the valve opening period of the intake valve 12 hardly overlap each other or slightly overlap in the vicinity of the intake top dead center.

In contrast, when the step S3~S4 is performed, the opening and closing timing of the exhaust valve 13 remains normally timing L _1, in particular is not changed. On the other hand, the opening / closing timing of the intake valve 12 is retarded by a predetermined crank angle (for example, 20 to 60 ° in crank angle) from the normal timing L ₂ (broken line), and at the timing L ₃ (solid line) for the first cycle. Be changed. Then, fuel injection, as indicated by I, is set to point approximately simultaneous or this somewhat more retarded angle side, the opening timing of the intake valve 12 is opened at the timing L ₃ for the first cycle.

  In this case, the intake stroke is started with both the intake valve 12 and the exhaust valve 13 being closed, and the piston 4 is lowered from the intake top dead center position. As the piston 4 descends, the inside of the combustion chamber 5 is suddenly depressurized, and a state close to a vacuum is obtained. Then, when the intake valve 12 is subsequently opened, air flows from the intake port 10 into the combustion chamber 5 at a very high speed. For this reason, air turbulence becomes very strong in the intake port 10 or the combustion chamber 5. Since the fuel is injected into this very strong turbulent air, the vaporization or atomization of the fuel is promoted, and the mixing of the fuel and air in the combustion chamber 5 becomes very good.

In FIG. 9, the opening / closing timing of the exhaust valve 13 is set to the normal timing (Exh lift), and the intake valve 12 opening / closing timing (Int lift) is normal pressure (see FIG. 6), the pressure in the combustion chamber 5 when the crank angle is retarded by 20 ° (20 ° CA), 40 ° (40 ° CA), or 60 ° (60 ° CA). The results of measuring (in-cylinder pressure) (respectively IO-20 ° CA, IO-40 ° CA, IO-60 ° CA) are shown. As apparent from FIG. 9, in the range of the opening / closing timing retardation amount of the intake valve 12, the pressure in the combustion chamber 5 becomes lower as the retardation amount of the opening / closing timing of the intake valve 12 becomes larger.

  In FIG. 10, the opening / closing timing of the exhaust valve 13 is set in the same manner as in FIG. 9, and the opening / closing timing of the intake valve 12 is changed in the same manner as in FIG. The result of measuring the flow velocity is shown (IO-20 ° CA, IO-40 ° CA, IO-60 ° CA, respectively). This flow velocity is a flow velocity in the space between the intake valve 12 and the intake port 10. As is apparent from FIG. 10, in the range of the opening / closing timing retardation amount of the intake valve 12, the air flow rate increases as the retardation amount of the opening / closing timing of the intake valve 12 increases.

  On the other hand, if it is determined in step S2 that the current cycle is not the first start cycle (NO), that is, if it is determined that the current cycle is the second cycle or later (the second and subsequent cycles when starting the engine). In step S5, the opening / closing timing or closing timing of the exhaust valve 13 is retarded by a predetermined amount, so that the opening period of the exhaust valve 13 and the opening period of the intake valve 12 are overlapped. Subsequently, in step S6, the fuel injection timing of the fuel injection valve 5 is set to the normal fuel injection timing, that is, the vicinity of the intake top dead center, and thereafter returns to step S1 (return).

That is, as shown in FIG. 8, the opening / closing timing of the exhaust valve 13 is retarded by a predetermined crank angle (for example, 20 to 40 ° in crank angle) from the normal timing N ₁ (broken line) and for the second and subsequent cycles. The timing is changed to N ₂ (solid line). The opening / closing timing of the intake valve 12 is set to the normal timing N ₄ (broken line). The fuel injection timing is set near the intake top dead center, as indicated by K.

  In this case, as is apparent from FIG. 8, the overlap between the valve opening period of the exhaust valve 13 and the valve opening period of the intake valve 12 occurs in the intake stroke in which the piston 4 descends. Therefore, more exhaust gas in the exhaust port 11 or the exhaust passage 25 can be recirculated into the combustion chamber 5. Therefore, the temperature in the combustion chamber 5 can be further increased after the second start cycle, and the fuel can be effectively vaporized or atomized to improve the mixing of fuel and air.

Incidentally, the opening and closing timing, fix the normal timing N _1, the opening and closing timing of the intake valve 12, typically a timing N _{4 (dashed} line) from a predetermined crank angle of the exhaust valve 13 (e.g., 20 to 40 ° in crank angle) The opening period of the exhaust valve 13 and the opening period of the intake valve 12 can also be overlapped by changing to the timing N ₃ (solid line) that is advanced only by the angle. However, in this case, since the overlap between the valve opening period of the exhaust valve 13 and the valve opening period of the intake valve 12 occurs in the exhaust stroke in which the piston 4 rises, the above-described case where the opening / closing timing of the exhaust valve 13 is retarded. Compared to the above, the recirculation amount of the exhaust gas is reduced.

  By the way, when it is determined in step S1 that the engine start is completed (YES), the engine E is already in a complete explosion state, and the control routine (steps S2 to S6) unique to the engine start is executed. Therefore, normal operation control of the engine E is performed in step S7. Thereafter, the process returns to step S1 (return).

  As described above, according to the engine start control according to Embodiment 1 of the present invention, at the time of engine start, fuel is sufficiently vaporized or atomized to mix fuel and air in all cycles including the first start cycle. This can improve the engine output and the emission performance.

(Embodiment 2)
The second embodiment of the present invention will be described below. However, the configuration of the engine according to the second embodiment is the same as that of the engine according to the first embodiment, and the second embodiment is different from the first embodiment only in the control mode of engine start control. The engine start control according to the second embodiment is different only in that step S14 is provided instead of step S4 of the engine start control according to the first embodiment, and the contents of the other steps are the same. . In order to avoid duplication of explanation, only the points different from the engine start control according to the first embodiment will be described below. In the flowchart shown in FIG. 5, steps having the same contents as those in the flowchart shown in FIG.

  As shown in FIG. 5, in the engine start control according to the second embodiment, if it is determined in step S2 that the current cycle of the engine E is the first start cycle (YES), the embodiment is performed in step S3. As in the case of 1, the opening / closing timing of the intake valve 12 is retarded, and then step S14 is executed. In step S14, two periods, a period from when the exhaust valve 13 is closed to when the intake valve 12 starts to open, that is, a non-overlap period and a period after the intake valve 12 starts to open are shown. Fuel injection is performed divided into periods.

That is, as shown in FIG. 7, the opening and closing timing of the exhaust valve 13 is set to a normal timing M _1. On the other hand, the opening / closing timing of the intake valve 12 is retarded by a predetermined crank angle (for example, 20 to 60 ° in crank angle) from the normal timing M ₂ (broken line), and reaches the timing M ₃ (solid line) for the first cycle. Be changed.

In the first fuel injection, as indicated by J ₁ , both the exhaust valve 13 and the intake valve 12 are closed after the intake top dead center, and the inside of the combustion chamber 5 is close to a vacuum as the piston 4 descends. It is done when in a state. In this case, since the fuel injected into the combustion chamber 5 is rapidly vaporized by boiling under reduced pressure, the fuel can be effectively vaporized to improve the mixing of fuel and air.

On the other hand, the second fuel injection, as indicated by J _2, is set to a slightly retard side point than the valve opening timing of the intake valve 12 is opened at the timing M ₃ for the first cycle. In this case, as in the case of the first embodiment (step S4), the fuel is injected into the extremely turbulent air in the combustion chamber 5, so that vaporization or atomization of the fuel is promoted, and the combustion chamber The mixing of fuel and air in 5 is very good.

  The other points are the same as in the first embodiment. Thus, according to the second embodiment, in the non-overlap period, fuel can be vaporized by boiling under reduced pressure to improve the mixing of fuel and air, while in the period after the intake valve 12 starts to open. The highly turbulent air flowing into the combustion chamber 5 in a state close to a vacuum at a high speed can promote the vaporization or atomization of the fuel and improve the mixing of the fuel and air in the combustion chamber 5. For this reason, as compared with the first embodiment, the mixing of fuel and air at the time of starting the engine can be further improved.

It is a partial cross section front view which shows the system configuration | structure of the engine which concerns on Embodiment 1 or Embodiment 2 of this invention. It is a partial cross section side view of the valve timing variable mechanism of the engine shown in FIG. It is a block diagram which shows the structure of the control system of the engine shown in FIG. It is a flowchart which shows the control procedure of the engine starting control which concerns on Embodiment 1 of this invention. It is a flowchart which shows the control procedure of the engine starting control which concerns on Embodiment 2 of this invention. It is a figure which shows the opening / closing timing and fuel injection timing of the intake valve and the exhaust valve in the first start cycle of the engine according to Embodiment 1 of the present invention. It is a figure which shows the opening / closing timing of the intake valve and the exhaust valve, and the fuel injection timing in the first start cycle of the engine according to Embodiment 2 of the present invention. It is a figure which shows the opening-and-closing timing and fuel injection timing of an intake valve and an exhaust valve after the engine start 2nd cycle after Embodiment 1 and Embodiment 2 of this invention. It is a graph which shows the change characteristic with respect to the crank angle of the pressure (cylinder pressure) in a combustion chamber. It is a graph which shows the change characteristic with respect to the crank angle of the flow velocity of the intake air which flows in into a combustion chamber.

Explanation of symbols

  E engine, C control unit, 1 cylinder head, 2 cylinder block, 3 cylinder, 4 piston, 5 combustion chamber, 6 connecting rod, 7 crankshaft, 8 spark plug, 9 fuel injection valve, 10 intake port, 11 exhaust port, 12 intake valve, 13 exhaust valve, 14 intake valve cam, 15 intake valve timing variable mechanism, 16 intake valve controller, 17 exhaust valve cam, 18 exhaust valve timing variable mechanism, 19 exhaust valve controller, 20 intake passage, 21 throttle valve, 22 throttle Body, 23 Tumble swirl control valve, 25 Exhaust passage, 30 Camshaft, 31 Cam sprocket, 32 Link mechanism, 33 VVT motor, 34 Chain case, 41 Air flow center 42, engine speed sensor, 43 crank angle sensor, 44 throttle opening sensor, 45 engine water temperature sensor, 46 starter switch.

Claims (4)

  In the first cycle when the engine is started, the opening and closing timing of the intake valve and exhaust valve is delayed from the intake top dead center, and the intake valve opening period and the exhaust valve opening While controlling the valve period so as not to overlap, the valve timing control means for controlling the valve opening period of the intake valve and the valve opening period of the exhaust valve to overlap in the second and subsequent cycles at the time of engine start. An engine combustion control device comprising: The engine includes a fuel injection valve for injecting fuel into the combustion chamber, and fuel injection control means for controlling fuel injection timing of the fuel injection valve,
In the first cycle, the fuel injection control means controls the fuel injection valve to start fuel injection in a period from when the exhaust valve is closed until the intake valve starts to open. The engine combustion control apparatus according to claim 1, wherein   The fuel injection control means is divided into at least two periods including a period from when the exhaust valve is closed until the intake valve starts to open, and a period after the intake valve starts to open. The engine combustion control apparatus according to claim 2, wherein the fuel injection valve is controlled to perform fuel injection.   The valve timing control means overlaps the valve opening period of the intake valve and the valve opening period of the exhaust valve by retarding the valve closing timing of the exhaust valve in the second and subsequent cycles. The engine combustion control device according to any one of claims 1 to 3.

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