JP5076983B2 - Engine fuel injection control device - Google Patents

Description

  The present invention relates to fuel injection control of an engine, and more particularly to control of fuel injection amount accompanying change in valve timing in an engine having a variable valve mechanism.

  In the case of a so-called port injection type engine in which fuel is injected into the intake port, part of the fuel injected from the fuel injection valve adheres to the wall surface of the intake port and the intake valve and does not flow directly into the cylinder. In particular, when the opening / closing timing of the intake valve is changed by the variable valve mechanism, the amount of fuel adhering to the intake port wall surface or the like changes according to the change in the opening / closing timing. For this reason, if the fuel injection amount is not corrected in accordance with the change in the amount of fuel adhering to the intake port wall surface, the air-fuel ratio in the cylinder will be shifted.

Patent Document 1 discloses correction of fuel injection amount correction in accordance with a change in the valve opening overlap period in which the opening timings of the intake valve and the exhaust valve partially overlap.
JP 11-36936 A

  By the way, in a hybrid vehicle engine using an engine and an electric motor as a drive source, or an engine for a so-called idle stop vehicle that stops the engine when a signal is stopped, an intake valve is used as a measure for reducing the shock at the time of engine start. There is known a method of reducing the compression reaction force by retarding the closing timing to near the middle of the piston stroke from the intake bottom dead center to the compression top dead center. In a generally known variable valve mechanism that changes the phase of the camshaft and crankshaft, if the closing timing is retarded, the opening timing is also retarded by the same amount. When retarded, the intake valve opening timing is also retarded, and there is a period (minus overlap) in which both valves are closed after the exhaust valve is closed until the intake valve is opened.

  During the minus overlap period, the piston descends while the intake valve and the exhaust valve are closed, so the cylinder pressure decreases. That is, as the retard amount of the intake valve closing timing is increased and the minus overlap is increased, the piston lowering amount during the minus overlap period is increased, and the decrease in the cylinder pressure from the exhaust valve closing timing is increased. . As the cylinder pressure decreases, the pressure difference before and after the intake valve, that is, the pressure difference between the intake port and the cylinder increases, and the intake flow velocity when the intake valve is opened increases. Thus, when the amount of minus overlap changes, the amount of fuel adhering to the wall surface of the intake port also changes due to the change in the intake air flow velocity when the intake valve is opened.

  However, although the fuel injection amount correction described in Patent Document 1 corresponds to the overlap period in which both the intake valve and the exhaust valve are open, the minus overlap period is not considered at all.

  Therefore, an object of the present invention is to enable accurate air-fuel ratio control even when the minus overlap amount changes.

The engine fuel injection control device according to the present invention realizes a valve timing having a minus overlap period in which both the exhaust valve and the intake valve are closed between the exhaust valve closing timing and the intake valve opening timing. Possible variable valve mechanism, fuel injection means for injecting fuel into the intake passage, target torque setting means for setting a target torque according to the driver's request, and setting of a basic fuel injection amount according to the target torque A basic fuel injection amount setting means, an operating state detecting means for detecting the operating state of the engine, and a fuel injection amount correcting means for correcting the basic fuel injection amount in accordance with the operating state, the fuel injection amount correcting means The effective volume of the cylinder at the time of intake valve opening is calculated based on the minus overlap amount detected by the operating state detection means, and the effective volume of this cylinder is calculated. There calculates the pressure inside the cylinder in the intake valve opening time, using the amount of change in the cylinder pressure, is reduced and corrected when the minus overlap amount changes in a direction of increasing, negative valve overlap amount decreases When the direction changes, the amount of correction is corrected, and the amount of correction is increased as the rate of change of the minus overlap amount increases .

  According to the present invention, when the minus overlap amount changes, the fuel injection amount is corrected in accordance with the changing speed of the minus overlap amount, so that accurate air-fuel ratio control becomes possible.

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

  FIG. 1 is a configuration diagram of a system to which this embodiment is applied. DESCRIPTION OF SYMBOLS 1 is an engine, 2 is a cylinder provided in the engine 1, 3 is a piston that reciprocates in the cylinder 2, 4 is an intake passage for introducing intake air into the cylinder 2, and 5 is an exhaust of burned gas from the cylinder 2 6 is an intake valve for opening and closing the opening of the intake passage 4 in the cylinder 2, 7 is an exhaust valve for opening and closing the opening of the exhaust passage 5, and 8 is an intake camshaft for driving the intake valve 6. Is a variable valve mechanism that changes the opening and closing timing of the intake valve 6, 10 is an exhaust camshaft that drives the exhaust valve 7, 11 is an ignition plug that sparks the mixture in the cylinder 2, and 12 is directed toward the intake passage 4 A fuel injection valve for injecting fuel, 13 is a collector tank provided upstream of the fuel injection valve 12 in the intake passage 4, and 14 is an electronically controlled throttle bar provided upstream of the collector tank 13. , 15 is an air flow meter for detecting the intake air amount provided on the upstream side of the electronically controlled throttle valve 14, 16 is a cam angle sensor for detecting the rotation angle of the intake camshaft 6, and 17 is interposed in the exhaust passage 5. The exhaust purification catalyst 18 is provided, 18 is an air / fuel ratio sensor for detecting the air / fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 17, and 19 is a rotation of the crankshaft 21 connected to the piston 3 via the connecting rod 22. A crank angle sensor 20 for detecting the angle, 20 is a control unit for controlling the ignition timing, fuel injection timing, fuel injection amount, variable valve mechanism 9, electronically controlled throttle valve 14, etc. 23 is a pressure in the collector tank 13 A pressure sensor for detecting, a water temperature sensor for detecting a cooling water temperature, 25, a fuel temperature sensor for detecting the temperature of the fuel, and 26, a suction air It is an intake air temperature sensor for detecting the temperature.

  The control unit 20 sets a target torque based on detection values of a crank angle sensor 19 and an accelerator opening sensor (not shown), and the variable valve mechanism 9 and the electronically controlled throttle valve 14 are set so as to realize the target torque. The opening degree is controlled, and the fuel injection is controlled so as to maintain a predetermined air-fuel ratio with respect to the intake air amount detected by the air flow meter 15 at this time. Further, the phase difference between the intake camshaft 6 and the crankshaft 21 is calculated from the detection signals of the cam angle sensor 16 and the crank angle sensor 19, and the opening / closing timing of the intake valve 6 is detected based on this. In the fuel injection control, first, the basic fuel injection amount is set based on the target torque and the intake air amount, and this basic fuel injection amount is set according to the cooling water temperature, the intake air temperature, and a minus overlap period described later. The final fuel injection amount is set by correcting.

  FIG. 2 is an enlarged view around the intake valve 6 of FIG. A part of the injected fuel adheres to the wall surface of the intake passage 4 and the intake valve 6 as shown in FIG. These attached fuel flows into the cylinder 2 when the intake valve 6 is opened. The amount of the adhering fuel flowing into the cylinder 2 depends on the wall surface temperature of the intake passage 4, the intake air temperature, the fuel temperature, and the like. Increases and the amount of fuel remaining on the wall surface decreases. Furthermore, depending on the flow rate of the intake air, as the flow rate of the intake air increases, the amount of fuel sucked increases and the amount of fuel remaining on the wall surface decreases.

  FIG. 3 is a valve timing diagram showing an example of valve timing executed in the present embodiment. In FIG. 3, the closing timing (IVC) of the intake valve 6 is approximately halfway between the intake bottom dead center (BDC) and the compression top dead center (TDC). For this reason, the mixture of intake air and fuel once flowing into the cylinder 2 is pushed back to the intake passage 4 by the rise of the piston 3, and the effective compression ratio is lowered. For example, in a vehicle that performs a so-called idle stop in which the engine is stopped when the signal is stopped, such valve timing is reduced with respect to the compression ratio in the case of reducing the compression reaction force to reduce the shock at the start or in the steady operation state. This is effective for improving fuel efficiency by increasing the expansion ratio.

  Incidentally, at the valve timing shown in FIG. 3, both the intake valve 6 and the exhaust valve 7 are closed from the closing timing (EVC) of the exhaust valve 7 after top dead center to the opening timing (IVO) of the intake valve 6. It is a so-called minus overlap period.

  During the minus overlap period, the piston 3 descends in a state where there is no gas in and out of the cylinder 2, so that the internal pressure of the cylinder 2 is lowered according to the descending amount of the piston 3. That is, as shown in FIG. 4, the internal pressure of the cylinder 2 is reduced by an amount corresponding to the descending amount of the piston 3 from the closing timing EVC of the exhaust valve 7 to the opening timing IVO of the intake valve 6.

  As the internal pressure of the cylinder 2 decreases, the pressure difference between the intake passage 4 and the cylinder 2 increases, and the intake flow velocity when the intake valve 6 is opened increases.

  That is, as the intake valve 6 closing timing IVC is retarded and the minus overlap period becomes longer, the intake flow velocity when the intake valve 6 is opened becomes faster, and the amount of fuel flowing into the cylinder 2 increases.

  Therefore, the control unit 20 sets the final fuel injection amount by correcting the basic fuel injection amount according to the minus overlap period.

  FIG. 5 is a control block diagram showing a control logic for calculating the fuel injection amount correction rate corresponding to the minus overlap period, which is executed by the control unit 20. This control is repeatedly executed every certain minute time, for example, every 10 ms.

  The intake valve closing timing calculation unit B1 calculates the closing timing IVC [degATDC] of the intake valve 6 based on the detection values of the crank angle sensor 19 and the cam angle sensor 16. For example, the closing timing IVC [degATDC] of the intake valve 6 can be calculated based on the phase difference between the crankshaft 21 and the intake camshaft 8 calculated from the detection values of the crank angle sensor 19 and the cam angle sensor 16.

In the intake valve opening time cylinder volume calculation unit B2, the effective volume Vivo [m ³ of the cylinder 2 at the opening timing IVO [degATDC] of the intake valve 6 is calculated based on the opening timing IVO [degATDC] of the intake valve 6 according to the equation (1). ] Is calculated. The opening timing IVO [degATDC] can be calculated based on the closing timing IVC [degATDC] and the operating angle of the intake camshaft 8 to be used.

Vivo = Vcyl × (1-cos (IVO)) / 2 + Vcmb (1)
Vcyl: cylinder part volume [m ³ ], Vcmb: combustion chamber volume [m ³ ]
In the intake valve opening time cylinder internal pressure estimation unit B3, based on the cylinder effective volume Vivo [m ³ ], the internal pressure of the cylinder 2 (hereinafter referred to as cylinder internal pressure) at the opening timing IVO [degATDC] of the intake valve 6 according to the equation (2). ) Calculate Pivo [kPA].

Pivo = 101.3 × Vcmb / Vivo (2)
In the above formula (2), “101.3” indicates atmospheric pressure.

  In the intake valve front-rear differential pressure calculation unit B4, the front-rear differential pressure of the intake valve 6 is calculated from the cylinder internal pressure Pivo [kPA] and the collector pressure detected by the pressure sensor 23, that is, the intake manifold pressure Pmani [kPA] according to the equation (3) Pgap [kPA] is calculated.

Pgap = Pmani-Pivo (3)
The fuel injection amount correction factor calculation unit B5 calculates a fuel injection amount correction factor Kmor by a control logic, which will be described later, based on the front-rear differential pressure Pgap [kPa] of the intake valve 6.

  FIG. 6 is a flowchart of the control executed by the fuel injection amount correction rate calculation unit B6.

  In step S1, the presence or absence of a minus overlap is determined. If the closing timing IVC [degATDC] of the intake valve 6 is obtained, the opening timing IVO [degATDC] is also obtained from the specifications of the intake camshaft 8 to be used. Since the valve timing of the exhaust valve 7 is fixed, the closing timing EVC [degATDC] of the exhaust valve 7 can be read in advance. Therefore, the presence or absence of the minus overlap period is determined from the closing timing IVC [degATDC] of the intake valve 6 calculated by the intake valve closing timing calculation unit B1 and the closing timing [degATDC] of the exhaust valve 7 read in advance. be able to.

  When there is a minus overlap period, the process proceeds to step S2, and when there is no minus overlap period, it is not necessary to correct the fuel injection amount in accordance with the minus overlap period, so the process is ended as it is.

  In step S2, an intake valve front-rear differential pressure change amount ΔPgap, which is a change amount of the intake valve front-rear differential pressure Pgap, is calculated. Here, it may be the difference between the current value of the intake valve front-rear differential pressure Pgap and the value before a predetermined time, or may be the difference between the previous calculated value and the current calculated value.

  In step S3, the basic correction factor Kbase is calculated using the intake valve front-rear differential pressure change amount ΔPgap. Specifically, a basic correction rate table as shown in FIG. 7 is created in advance and searched.

  FIG. 7 is a table in which the vertical axis represents the basic correction rate Kbase and the horizontal axis represents the intake valve front-rear differential pressure change amount ΔPgap. As the intake valve front-rear differential pressure change amount ΔPgap increases, the basic correction rate Kbase increases to the second order. The curve is getting bigger. This is larger when the amount of change ΔPgap before and after the intake valve is large, that is, when the change rate of the minus overlap period is large, the change in the amount of fuel adhering to the wall surface of the intake passage 4 also increases. This is because it is necessary to correct.

  The basic correction factor Kbase may be calculated from the intake valve front-rear differential pressure Pgap without calculating the intake valve front-rear differential pressure change amount ΔPgap. In this case, the basic correction rate Kbase table is the same as that of FIG. 7 except that the horizontal axis is the intake valve front-rear differential pressure Pgap. This is because as the intake manifold pressure Pmani [kPa] is higher, the amount of fuel adhering to the wall surface of the intake passage 4 and the like is increased, and thus it is necessary to correct more.

  In step S4, the water temperature TW, the intake air temperature TA, and the fuel temperature TF are read, and the water temperature correction coefficient Ktw, the intake air temperature correction coefficient Kta, and the fuel temperature correction coefficient Ktf are calculated using these. Specifically, it is obtained by searching the tables shown in FIGS.

  8 is a water temperature correction coefficient table in which the vertical axis represents the water temperature correction coefficient Ktw and the horizontal axis represents the water temperature TW, and FIG. 9 is an intake air temperature correction coefficient table in which the vertical axis represents the intake air temperature correction coefficient Kta and the horizontal axis represents the intake air temperature TA. FIG. 10 is a fuel temperature correction coefficient table in which the vertical axis represents the fuel temperature correction coefficient Ktf and the horizontal axis represents the fuel temperature TF. In both tables, the correction coefficients Ktw, Kta, Ktf increase as the input values (water temperature TW, intake air temperature TA, fuel temperature TF) decrease, and the correction coefficients Ktw, Kta, Ktf approach 1 as the input values increase. . Note that “correction coefficient = 1” means no correction. This is because the lower the water temperature TW, the lower the wall surface temperature of the intake passage 4, and the lower the intake air temperature TA and the fuel temperature TF, the more difficult the fuel vaporizes. This is because it is necessary to correct.

  In step S5, the fuel injection amount correction rate Kmor is calculated by equation (4) using the basic correction rate Kbase calculated in step S3 and the correction coefficients Ktw, Kta, Ktf calculated in step S4.

Kmor = Kbase × Ktw × Kta × Ktf (4)
By multiplying the basic fuel injection amount by the fuel injection amount correction factor Kmor calculated in this way, the fuel injection amount can be corrected according to the minus overlap period.

  As the intake manifold pressure Pmani [kPa] increases, the amount of fuel adhering to the wall surface of the intake passage 4 increases. Therefore, in addition to the correction according to the water temperature TW, the intake air temperature TA, and the fuel temperature TF described above, the intake air is further increased. Correction according to the manifold pressure Pmani [kPa] may be performed. In this case, the higher the intake manifold pressure Pmani [kPa], the larger the correction.

  As described above, in the present embodiment, the following effects can be obtained.

  (1) A variable valve mechanism that can realize a valve timing that has a minus overlap period in which both the exhaust valve 7 and the intake valve 6 are closed between the exhaust valve closing timing and the intake valve opening timing. 9, a fuel injection valve 11 for injecting fuel into the intake passage 4, a control unit 20 for setting a target torque according to a driver's request and a basic fuel injection amount according to the target torque, A crank angle sensor 19, a cam angle sensor 16 and an air flow meter 15 for detecting the driving state, and a control unit 20 for correcting the basic fuel injection amount according to the driving state, and a change in the minus overlap amount. The basic fuel injection amount is corrected so that the fuel injection amount is increased or decreased according to the speed. If the timing is changed, and discharge the effects of changes in the amount of fuel adhering to the wall surface or the like of the intake passage 4, it is possible to maintain the air-fuel ratio of the mixture constant.

  (2) When the minus overlap amount changes in the increasing direction, the amount of decrease is corrected, and when the minus overlap amount changes in the decreasing direction, the amount of increase correction is corrected. Therefore, the intake air increases as the minus overlap amount increases. When the flow rate is increased and the amount of fuel adhering to the wall surface of the intake passage 4 is likely to evaporate, the fuel injection amount is decreased, and conversely, when the intake flow rate is decreased as the overlap amount decreases. Is increased. Therefore, the influence of the change in the amount of fuel adhering to the wall surface of the intake passage 4 can be eliminated, and the air-fuel ratio of the air-fuel mixture can be kept constant.

  (3) Since the correction amount is increased as the change rate of the minus overlap amount is larger, the correction according to the change rate of the intake air flow rate is possible.

  (4) Since the correction amount corresponding to the change rate of the minus overlap amount is calculated using the change rate of the differential pressure before and after the intake valve when the intake valve is opened, the amount of fuel adhering to the wall surface of the intake passage 4 is directly Since the correction amount is calculated using a parameter having a correlation, air-fuel ratio control with high accuracy becomes possible.

  (5) Since the correction amount is increased as the cooling water temperature is lower, highly accurate air-fuel ratio control is possible regardless of the wall surface temperature of the intake passage 4.

  (6) The correction amount is increased as the intake air temperature is lower. Therefore, when the amount of fuel adhering to the wall surface or the like of the intake passage 4 is large, the correction amount is corrected to be larger, and air-fuel ratio control with high accuracy is possible.

  (7) Since the correction amount is increased as the fuel temperature is lower, if the amount of fuel adhering to the wall surface or the like of the intake passage 4 is larger, the correction is made larger, and highly accurate air-fuel ratio control becomes possible.

  (8) The higher the intake manifold pressure, the larger the correction amount. Therefore, when there is a large amount of fuel adhering to the wall surface of the intake passage 4, etc., the correction is made larger and the air-fuel ratio control with high accuracy becomes possible.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

It is a block diagram of the system to which this embodiment is applied. FIG. 2 is an enlarged view of the vicinity of an intake valve in FIG. 1. It is a figure which shows an example of the valve timing which has a minus overlap period. It is a figure for demonstrating the fall of the cylinder internal pressure in a minus overlap period. It is a control block diagram for fuel injection amount correction | amendment during a minus overlap period. It is a flowchart which shows the control routine for fuel injection amount correction factor calculation. It is a basic correction factor table. It is a water temperature correction coefficient table. It is an intake air temperature correction coefficient table. It is a fuel temperature correction coefficient table.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Cylinder 3 Piston 4 Intake passage 5 Exhaust passage 6 Intake valve 7 Exhaust valve 8 Intake camshaft 9 Variable valve mechanism 10 Exhaust camshaft 11 Spark plug 12 Fuel injection valve 13 Collector tank 14 Electronically controlled throttle valve 15 Air flow meter 16 Cam angle sensor 17 Exhaust gas purification catalyst 18 Air-fuel ratio sensor 19 Crank angle sensor 20 Control unit 21 Crankshaft 22 Connecting rod

Claims (6)

A variable valve mechanism capable of realizing a valve timing having a minus overlap period in which both the exhaust valve and the intake valve are closed between the exhaust valve closing timing and the intake valve opening timing;
Fuel injection means for injecting fuel into the intake passage;
Target torque setting means for setting a target torque according to a driver's request;
Basic fuel injection amount setting means for setting a basic fuel injection amount in accordance with the target torque;
Driving state detection means for detecting the driving state of the engine;
Fuel injection amount correction means for correcting the basic fuel injection amount according to the operating state;
An engine fuel injection control device comprising:
The fuel injection amount correcting means calculates the effective volume of the cylinder at the intake valve opening time based on the minus overlap amount detected by the operating state detecting means, and uses the effective volume of the cylinder at the intake valve opening time. Calculate the cylinder pressure and use the rate of change of the cylinder pressure to correct the decrease when the minus overlap amount increases, and when the minus overlap amount decreases. A fuel injection control device for an engine , wherein the amount of correction is increased and the correction amount is increased as the rate of change of the minus overlap amount increases . Intake manifold internal pressure detection means for detecting the intake manifold internal pressure as the operating state detection means,
The fuel injection amount correction means uses a change rate of the differential pressure before and after the intake valve calculated from the cylinder internal pressure and the intake manifold internal pressure, and a correction amount corresponding to the change rate of the minus overlap amount. The fuel injection control device for an engine according to claim 1, wherein: A cooling water temperature detecting means for detecting an engine cooling water temperature as the operating state detecting means;
The engine fuel injection control device according to claim 1 or 2 , wherein the fuel injection amount correction means increases the correction amount as the cooling water temperature is lower. An intake air temperature detection means for detecting the intake air temperature as the operating state detection means;
The engine fuel injection control apparatus according to any one of claims 1 to 3 , wherein the fuel injection amount correction means increases the correction amount as the intake air temperature is lower. A fuel temperature detecting means for detecting a fuel temperature as the operating state detecting means;
The engine fuel injection control apparatus according to any one of claims 1 to 4 , wherein the fuel injection amount correction means increases the correction amount as the fuel temperature is lower. The fuel injection quantity correcting means, fuel injection control apparatus for an engine according to any one of claims 1 to 5, characterized in that to increase the correction amount as the intake manifold pressure is high.

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