JP2015031222A - Control device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably restrain knocking regardless of an operation condition such as an injection amount of fuel.SOLUTION: A control device of an engine comprises: one exhaust port 7 and one exhaust valve 6 provided each for one cylinder; plural intake ports 4 and intake valves 5 provided for one cylinder; a fuel injection device 8 for injecting fuel into the plural intake ports 4; and control means for controlling fuel injection by the fuel injection device 8 so that it is divided into first fuel injection a to be initially performed during opening the intake valves 5 and second fuel injection b to be performed after completion of the first fuel injection a during opening the intake valves 5. The fuel injection device 8 adopts a control device of an engine for directing to a face opposite to faces of the plural intake valves 5 faced to a combustion chamber 2 at least during the second fuel injection b.

Description

  The present invention relates to an engine control device having a fuel injection device at an intake port.

  In a gasoline engine, a port injection type engine is known in which fuel is injected from a fuel injection device (injector) provided in an intake port while an intake valve is open, and fuel and air are supplied into a cylinder.

  In a port injection type engine, when fuel injection is started after the intake valve is opened, for example, the amount of fuel injection is large during high-speed driving, so even after the piston passes the bottom dead center and enters the compression stroke. Fuel injection may continue.

  For example, Patent Document 1 discloses a technique in which fuel is injected even after a piston passes through a bottom dead center and then enters a compression stroke. In this technology, in order to improve the homogeneity of the air-fuel mixture and the charging efficiency of the intake air, the intake valve is opened from the time when the piston is near the top dead center until after the piston passes the bottom dead center. The injection is divided into main fuel injection performed from the first half of the intake stroke to the middle of the intake stroke and sub fuel injection performed from the second half of the intake stroke to the intake valve closing timing in the first half of the compression stroke.

  For example, during low-speed operation where knocking is likely to occur, in the intake process with the throttle fully open, the exhaust valve closes earlier and the intake valve opens later, reducing the overlap period when both the intake and exhaust valves are open. In addition, by suppressing the return of combustion gas into the intake port, the gas temperature in the combustion chamber is lowered to suppress knocking. In addition, in the compression process after the piston passes through the bottom dead center, the auxiliary fuel injection is performed until the intake valve closes, thereby suppressing the air-fuel mixture from being blown back, and the efficiency of fuel filling into the combustion chamber Is increasing.

  Note that the fuel injection performed immediately before closing the intake valve causes fuel droplets that do not vaporize to flow into the combustion chamber. It is said that the inflow of droplets promotes cooling of the end gas spontaneous ignition that is one of the causes of knocking, that is, cooling of the intake side end in the combustion chamber, and as a result, has the effect of suppressing knocking. Yes.

JP 2011-252451 A

  The split injection technique disclosed in Patent Document 1 is mainly for suppressing fuel blowback when the throttle is fully open. The auxiliary fuel injection is set to a minimum amount necessary for suppressing air-fuel mixture blowback in the compression stroke. For this reason, no particular attention has been paid to the suppression of knocking caused by flowing fuel droplets into the combustion chamber. Further, there is room for further improvement in that knocking is reliably suppressed under various operating conditions other than when the throttle is fully opened.

  In general, when the amount of fuel injection per cycle is small, such as at low speeds, there is a problem that fuel injection cannot be continued until just before the intake valve is closed. Therefore, when the fuel injection amount is small, it is not possible to expect the knocking suppression effect by letting fuel droplets flow into the combustion chamber.

  Accordingly, an object of the present invention is to reliably suppress knocking regardless of operating conditions such as the fuel injection amount.

  In order to solve the above-described problems, the present invention provides a plurality of intake ports provided per cylinder, an intake valve that opens and closes the intake port, and a fuel injection device that injects fuel into the plurality of intake ports. The first fuel injection performed by the fuel injection device first during the valve opening period of the intake valve and the second fuel performed after completion of the first fuel injection during the valve opening period of the intake valve Control means for performing control so as to be divided into injection, and at least in the second fuel injection, the fuel injection device is provided on a side opposite to a surface facing the combustion chamber side of the plurality of intake valves. The engine control system is oriented to the surface.

  Further, as the control means, it is possible to employ a configuration in which a swirl flow is generated in the combustion chamber by providing a phase difference between the valve opening timings of the plurality of intake valves.

  At this time, the control means includes a period from the opening timing of the intake valve that opens late to the bottom dead center of the piston in the intake stroke and a closing timing of the intake valve that is closed first from the bottom dead center of the piston in the intake stroke. Based on the ratio of the period until, the fuel injection can be divided into the first fuel injection and the second fuel injection.

  The control means may increase the ratio of the first fuel injection when the engine is operating in a low rotation and high load range, and decrease the ratio of the first fuel injection when the engine is in a high rotation and high negative operating range. Is desirable.

  Preferably, the first fuel injection ends before the piston reaches bottom dead center, and the second fuel injection starts after the piston passes through bottom dead center.

  According to the present invention, the fuel injection timing of the port injection engine is divided into the first fuel injection that is first performed during the opening period of the intake valve and the second fuel injection that is performed thereafter, thereby The fuel injection penetration force immediately after the valve is opened, that is, the initial velocity of the fuel injection is used to enhance the flow of the air-fuel mixture in the combustion chamber, and the fuel injection device is placed on the side opposite to the surface facing the combustion chamber side of the intake valve. By directing it toward the back of the umbrella, that is, immediately behind the umbrella valve, the fuel droplets are effectively allowed to flow in the vicinity of the end portion near the inner peripheral surface of the combustion chamber immediately before the intake valve is closed, thereby cooling the combustion chamber. Can do.

  Thus, knocking can be reliably suppressed regardless of operating conditions such as the fuel injection amount, and thermal efficiency can be improved by advancement of ignition. Further, if a swirl is formed in the combustion chamber, fuel droplets are supplied to the entire periphery of the end of the combustion chamber, and the knocking suppression effect can be further enhanced.

It is explanatory drawing showing the injection timing of the fuel of one Embodiment of this invention, and the opening / closing timing of an intake / exhaust valve. It is a principal part enlarged plan view which shows the same embodiment. It is a front view which shows the structure of the embodiment. It is a map figure used for control of this embodiment. It is explanatory drawing showing the injection timing of the fuel of other embodiment, and the opening / closing timing of an intake / exhaust valve. It is explanatory drawing which shows the injection timing of the fuel of a general engine, and the opening / closing timing of an intake / exhaust valve.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. This embodiment is a control device for a four-cycle gasoline engine for automobiles. FIG. 1 shows the fuel injection timing and the intake / exhaust valve opening / closing timing. 2 and 3 show the configuration of the main part of the combustion chamber 2 in one cylinder provided in the engine and the control device for the engine. In these drawings, only members and means directly related to the present invention are shown, and other members and the like are not shown.

  As shown in FIGS. 2 and 3, a piston 3 is accommodated in a cylinder 1 of the engine. A combustion chamber 2 is formed by the inner wall surface of the cylinder 1, the upper surface of the piston 3, and the like. Further, the cylinder 1 has two intake ports 4; 4a, 4b for guiding the air-fuel mixture to the combustion chamber 2, two exhaust ports 7; 7a, 7b for sending exhaust from the combustion chamber 2, and a cylinder from the cylinder head side. , That is, a spark plug 9 disposed downward along the cylinder axis direction of the cylinder.

  Although only one cylinder 1 is shown in the drawing, the engine may be a single cylinder or a multi-cylinder having a plurality of cylinders 1.

  The intake port 4 is provided with a fuel injection device (injector) 8 that injects fuel into the intake port 4. The fuel injection device 8 injects fuel into the intake air in the flow paths of the two intake ports 4a and 4b to form an air-fuel mixture. Here, the fuel injection device 8 may be provided separately for each intake port 4a, 4b.

  The two intake ports 4a and 4b are provided with intake valves 5a and 5b for opening and closing the opening to the combustion chamber 2, respectively. The two exhaust ports 7a and 7b are provided with exhaust valves 6a and 6b for opening and closing the opening to the combustion chamber 2, respectively. Hereinafter, the two intake valves 5 are referred to as a first intake valve 5a and a second intake valve 5b, respectively, and the two exhaust valves 6 are referred to as a first exhaust valve 6a and a second exhaust valve 6b, respectively.

  Since these intake valve 5 and exhaust valve 6 are connected to a camshaft provided on the cylinder head side via a valve lifter, the intake port 4 and the exhaust port 7 are opened and closed at a predetermined timing by the rotation of the camshaft. . Power is transmitted to the camshaft by connecting a sprocket provided on the camshaft side and a sprocket provided on the crankshaft side by a timing chain or the like.

  The first intake valve 5a, the second intake valve 5b, the first exhaust valve 6a, the second exhaust valve 6b, the spark plug 9, the fuel injection device 8, and other devices necessary for the operation of the engine are connected to the electronic control unit through cables. It is controlled by the control means provided in (Electronic Control Unit) 10. In this embodiment, a part of the computer of the electronic control unit is used as engine control means.

  The intake valve 5 has a camshaft, a valve lifter, and the electronic control so that the opening timing of the first intake valve 5a that is one intake valve 5 and the second intake valve 5b that is the other intake valve 5 are different from each other. A control device including the unit 10 and others is set.

  Further, the exhaust valve 6 has a camshaft and a valve lifter so that the opening timing of the first exhaust valve 6a which is one exhaust valve 6 and the second exhaust valve 6b which is the other exhaust valve 6 are the same. A control device including the electronic control unit 10 and others is set.

  An example of the operation of the intake valve 5 and the exhaust valve 6 is shown in FIG. The opening timing of the first intake valve 5a (see the intake valve A in the figure) is the time when the piston 3 is located at the top dead center, and the second intake valve 5b (see the intake valve B in the figure) is opened. It is set earlier than the valve timing. Further, the closing timing of the first intake valve 5a (see the intake valve A in the figure) is the midpoint of the compression stroke after the time when the piston 3 is located at the bottom dead center. It is set earlier than the closing timing of the intake valve 5b (see the intake valve B in the figure). The opening timing and closing timing of the two exhaust valves 6a and 6b are set simultaneously.

  In this embodiment, the opening timing of the first intake valve 5a is set at the same time as the closing timing of the two exhaust valves 6a and 6b, and the overlap period during which both the intake valve 5 and the exhaust valve 6 are opened is set. Not. However, it is also possible to set an overlap period in which both the first intake valve 5a and the second intake valve 5b and the two exhaust valves 6a and 6b are open. It is also possible to provide a phase difference between the two exhaust valves 6a and 6b in the valve opening timing and the valve closing timing.

  It is possible to set the opening / closing timing of each valve under the above conditions and operate the vehicle at a fixed valve timing, but a variable valve device is used for the opening timing and closing timing of each of these valves. Thus, it can be changed appropriately during driving according to the driving state of the vehicle.

  In the intake port 4, the fuel injection device 8 includes a surface opposite to the surface of the first intake valve 5 a and the second intake valve 5 b facing the combustion chamber 2, that is, the umbrella back of the intake valves 5 a and 5 b. Is oriented. In this embodiment, the fuel injection device 8 is arranged so as to face the umbrella back of each intake valve 5a, 5b at any position from the open state to the closed state of each intake valve 5a, 5b. However, at least in the state in which each intake valve 5a, 5b is immediately before the valve is closed, it suffices if it faces the back of the umbrella.

  Regarding the orientation of the intake valves 5a and 5b of the fuel injection device 8, in this embodiment, on the extended line of the center line of the fuel injection portion (nozzle) of the fuel injection device 8, the back of the umbrella of the intake valves 5a and 5b is provided. However, it is only necessary that the backs of the intake valves 5a and 5b be positioned in the fuel injection direction by fuel injection.

  The engine control apparatus and control method will be described.

  As described above, the control means provides a phase difference between the opening and closing valve timings of the first intake valve 5a of the first intake port 4a and the second intake valve 5b of the second intake port 4b. That is, as shown in FIG. 1, the opening timing and closing timing of the first intake valve 5a are advanced by the opening timing and closing timing of the second intake valve 5b, respectively. In addition, the control means simultaneously opens and closes the exhaust valves 6a and 6b of the two exhaust ports 7a and 7b.

  In the exhaust stroke, the exhaust valves 6a and 6b of the exhaust ports 7a and 7b are closed, and at the same time, the first intake valve 5a starts to open. Next, with a slight delay, the second intake valve 5b starts to open.

  Of the two intake valves 5a and 5b, after opening the first intake valve 5a, the second intake valve 5b was opened with a delay, so as shown in FIGS. 2 and 3, it was opened first. By the intake air from the first intake valve 5a, a stable swirl flow S in one direction is formed in the combustion chamber 2 along the inner peripheral surface of the combustion chamber 2. For this reason, even if the second intake valve 5 b is opened later, the swirl flow S is not easily inhibited, and a large swirl flow S is formed in the combustion chamber 2.

  Here, as shown in FIG. 1, the fuel injection by the fuel injection device 8 is performed first during the valve opening period of the intake valve 5 and after the first fuel injection a ends. The second fuel injection b is divided and performed.

  The first fuel injection a is a fixed period set between the start timing of the intake stroke and the piston 3 reaching the bottom dead center. The end timing of the first fuel injection a is determined according to the required fuel injection amount. However, the example of FIG. 1 shows the low-speed operation when the required fuel injection amount is small. The end time of the injection a is earlier than the time when the piston 3 at the end of the intake stroke is at the bottom dead center.

  Next, the second fuel injection b is performed. After the end of the first fuel injection a, the second fuel injection b has a period t during which no fuel injection is performed (hereinafter referred to as a non-injection period t), and then the first intake valve 5a and the second fuel injection b. This is performed immediately before the intake valve 5b is closed.

  The start timing of the second fuel injection b is after the non-injection period t and after the piston 3 which is the end of the intake stroke is at the bottom dead center, and the end timing is the closing timing of the first intake valve 5a. It is said. Note that the end timing of the second fuel injection b may be the closing timing of the second intake valve 5b.

  By performing the second fuel injection b, the fuel adhering to the back of the first intake valve 5a and the second intake valve 5b, that is, the surface opposite to the surface facing the combustion chamber side of the intake valve, Immediately before the valves 5a and 5b are closed, the droplets flow into the combustion chamber 2 from the back of the umbrella. By the inflow of the droplets, the intake side end portion in the combustion chamber 2 is cooled, and knocking can be reliably suppressed.

The reason why the fuel droplets can be effectively introduced into the combustion chamber 2 by the second fuel injection b is that the fuel injection device 8 is directed to the back of the intake valve 5 immediately before the valve is closed. The fuel adhering to the back of the umbrella is easily introduced into the combustion chamber 2 as droplets without being vaporized.
Further, the fuel injection is performed immediately before the intake valve 5 is closed, that is, when the valve opening degree is small, so that the amount of air flowing around the valve is small and the vaporization speed is slowed down. Further, since the time until combustion after the fuel is introduced into the combustion chamber 2 is short, much fuel is not vaporized.
On the other hand, since the first fuel injection a is performed while the degree of opening of the intake valve 5 is large, the amount of air flowing around the valve is large and droplets are not easily generated. In addition, since it takes a long time to reach combustion after the fuel is introduced into the combustion chamber 2, a large amount of fuel is vaporized during that period, and droplets are not easily generated.

  Since the intake side is more likely to knock than the exhaust side, the effect of suppressing knocking by cooling the intake side is high. If knocking can be suppressed, a high compression ratio can be easily achieved. Further, according to the present invention, knocking can be easily suppressed even when using low-octane fuel, at low speed and high load, during supercharging, etc., so that the thermal efficiency of the internal combustion engine can be increased, and the output and fuel consumption can be improved.

  Further, in this embodiment, as shown in FIG. 1, after the first intake valve 5 a is opened, the second intake valve 5 b is opened with a delay, so that the combustion chamber 2 is in the combustion chamber 2. A stable swirl flow S in one direction is formed along the inner peripheral surface. For this reason, the droplets of the fuel that flowed into the combustion chamber 2 by the second fuel injection b are carried along the swirl flow S to the entire circumference of the end portion in the combustion chamber 2, and the entire circumference of the end portion is conveyed. Cooling. For this reason, the temperature of the end gas is lowered over the entire circumference, and a higher knocking suppression effect can be expected.

  Here, as shown in FIG. 1, the first fuel injection a is performed within a period c from the opening timing of the second intake valve 5b that opens late to the bottom dead center of the piston 3 in the intake stroke. The second fuel injection b is performed within a period d from the bottom dead center of the piston 3 in the intake stroke to the closing timing of the first intake valve 5a that is closed first.

  The ratio of the injection amounts of the first fuel injection a and the second fuel injection b (the injection amount per unit time is constant, so that the injection amount ratio is equal to the injection time ratio) opens later. The period c from the opening timing of the two intake valves 5b to the bottom dead center of the piston 3 in the intake stroke and the period from the bottom dead center of the piston 3 in the intake stroke to the closing timing of the first intake valve 5a that is closed first. Based on the ratio of d, the fuel injection can be divided into a first fuel injection and a second fuel injection. For example, the period c from the opening timing of the second intake valve 5b that opens late to the bottom dead center of the piston 3 in the intake stroke, and the first intake valve 5a that closes first from the bottom dead center of the piston 3 in the intake stroke. When the ratio to the period d until the valve closing time is 7: 3, the ratio of the injection amount between the first fuel injection and the second fuel injection can be 7: 3. Further, when the ratio of the first fuel injection a is increased due to various factors, the ratio of the injection amount can be set to 8: 2, 9: 1, or the like.

  In particular, the ratio of the first fuel injection a may be increased in a low-speed and high-load operation region where knocking is likely to occur, and the ratio of the first fuel injection a may be decreased in a high-speed and high-negative operation region. For distinguishing the operation regions, for example, using a map as shown in FIG. 4, the electronic control unit 10 automatically recognizes the operation regions and controls the fuel injection. In FIG. 4, symbol a indicates a low-speed and high-load operation region, and symbol b indicates a high-speed and high-negative operation region. Moreover, the code | symbol c shows the low load operation area | region.

  Assuming an operation region (for example, a high load operation region) with a large amount of required fuel injection, the ratio of the first fuel injection a becomes high. For example, as shown in FIG. The end timing may be further extended, and may be the latest time when the piston 3 that is the end of the intake stroke is at the bottom dead center. In such a case, conversely, the start timing of the first fuel injection a may be advanced. The start timing of the first fuel injection a may be the earliest and may be the time when the piston 3 is at top dead center.

  Note that the total injection amount of the first fuel injection a and the second fuel injection b (the injection amount per unit time is constant, so the total injection amount is equal to the total injection time) is, for example, In the relationship with the conventional control shown in FIG. 6 in which the divided injection is not performed, if all other operating conditions are equal, the total injection amount and the injection time for each operating condition at the low speed and at the high speed are shown. It is desirable that the sum is set equal to each other.

  In the present invention, in the first fuel injection a in which fuel injection is started after the intake valve 5 is opened, the fuel flows into the combustion chamber 2 together with the intake air flow. For this reason, the penetration force of the fuel spray, that is, the momentum at the time of injection of the fuel injection is maintained thereafter, and the intake air flow in the combustion chamber 2 can be strengthened to promote combustion and increase the thermal efficiency.

  Further, in the second fuel injection b in which the injection is completed immediately before the intake valve 5 is closed, a part of the fuel flows into the combustion chamber 2 from behind the umbrella of the intake valve 5. For this reason, knocking can be suppressed by cooling the intake side end in the combustion chamber 2, and the engine performance and fuel consumption can be improved. At this time, if the swirl flow S is formed in the combustion chamber 2, the droplets are carried together with the swirl flow S to the entire periphery of the end portion in the combustion chamber 2, so that a high knocking suppression effect can be expected.

1 cylinder 2 combustion chamber 3 piston 4 intake port 4a first intake port 4b second intake port 5 intake valve 5a first intake valve 5b second intake valve 6 exhaust valve 6a first exhaust valve 6b second exhaust valve 7 exhaust port 8 Fuel injection device (port injection valve)
9 Spark plug 10 Electronic control unit (Electronic Control Unit)

Claims (5)

A plurality of intake ports per cylinder,
An intake valve for opening and closing the intake port;
A fuel injection device for injecting fuel into the plurality of intake ports;
First fuel injection performed by the fuel injection device first during the valve opening period of the intake valve, and second fuel injection performed after completion of the first fuel injection during the valve opening period of the intake valve And a control means for controlling to be divided into
The engine control device according to claim 1, wherein the fuel injection device is directed to a surface opposite to a surface facing the combustion chamber of the plurality of intake valves at least during the second fuel injection.   2. The engine control device according to claim 1, wherein the control unit generates a swirl flow in the combustion chamber by providing a phase difference between valve opening timings of the plurality of intake valves. 3.   The control means includes a period from the opening timing of the intake valve that opens late to the bottom dead center of the piston in the intake stroke and a period from the bottom dead center of the piston in the intake stroke to the closing timing of the intake valve that is closed first. 3. The engine control device according to claim 2, wherein the fuel injection is divided into the first fuel injection and the second fuel injection based on the ratio.   The control means increases the ratio of the first fuel injection when the engine is operating in a low rotation and high load range, and decreases the ratio of the first fuel injection when the engine is in a high rotation and high negative operating range. The engine control device according to claim 3.   The first fuel injection is finished before the piston reaches bottom dead center, and the second fuel injection is started after the piston passes bottom dead center. The engine control device according to claim 1.

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