JP2012237274A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device for an internal combustion engine which is capable of stably carrying out suction port injection after an autonomous operation without depending on a pulsation damper while employing a dual injection system.SOLUTION: In the internal combustion engine 10, fuel is supplied to a fuel injection valves 11b-14b for the suction port injection through a low pressure fuel passage 30 and a low pressure fuel passage 50. High pressure fuel is supplied to fuel injection valves 11a-14a for a cylinder fuel injection through the low pressure fuel passage 30 and a high pressure fuel passage 40. An electronic controller 20 for controlling the drive of the fuel injection valves 11b-14b for the suction port injection and the fuel injection valves 11a-14a for the cylinder fuel injection corresponding to the operation condition of the internal combustion engine 10 corrects the amount of the fuel injection by the fuel injection valves 11b-14b for the suction port injection corresponding to the pressure fluctuation caused by the drive of a high pressure fuel pump 40P during engine start-up from the autonomous operation to the idling.

Description

  The present invention relates to a fuel injection control device for an internal combustion engine that controls a fuel injection amount in an internal combustion engine that includes a fuel injection valve for in-cylinder injection and a fuel injection valve for intake port injection.

  2. Description of the Related Art Fuel injection control for an internal combustion engine that employs a so-called dual injection system that includes an intake port injection fuel injection valve that injects fuel into an intake port and an in-cylinder injection fuel injection valve that directly injects fuel into a combustion chamber of a cylinder As an apparatus, for example, the apparatus described in Patent Document 1 is known.

  The fuel injection control device is provided with a fuel passage through which the fuel sucked up by the feed pump is pumped, and the passage is composed of a low pressure fuel passage and a high pressure fuel passage branched from the low pressure fuel passage. . In the high-pressure fuel passage, a high-pressure fuel pump that is intermittently driven by rotation of a cam provided on a crankshaft of the internal combustion engine is provided on the passage. However, although the internal combustion engine adopts such a dual injection system, only the intake port injection fuel valve is used at the time of starting. For this reason, when the engine is started, fuel is pumped to the low pressure fuel distribution pipe via the low pressure fuel passage and distributed to the fuel injection valve for intake port injection, but is intermittently driven as described above. As a result, pulsation may occur in the fuel pressure in the low-pressure fuel distribution pipe. Therefore, in the apparatus described in Patent Document 1, such a pressure pulsation is suppressed by providing a pulsation damper in the low-pressure fuel distribution pipe.

JP 2008-190508 A

  By the way, when the natural frequency of the pulsation damper coincides with the period of the pressure pulsation, a so-called resonance phenomenon occurs, so that the pulsation of the fuel pressure cannot be suppressed in the low-pressure fuel distribution pipe. Therefore, in order to suppress the occurrence of the resonance phenomenon during normal operation of the internal combustion engine, the natural frequency is designed to be lower than the frequency of pressure pulsation during idling. However, in this case, for example, as shown in FIG. 5, the resonance phenomenon occurs in the course from the start of the autonomous operation of the internal combustion engine to the idling. In other words, fuel injection by the fuel injection valve for intake port injection becomes unstable, and the startability of the internal combustion engine may be deteriorated. Although the pulsation of the fuel pressure can be suppressed by increasing the size of the pulsation damper, this impedes the downsizing of the engine and the engine room and may increase the cost.

  The present invention has been made in view of such circumstances, and its purpose is to stably perform intake port injection after autonomous operation without using a pulsation damper while adopting a dual injection method. An object of the present invention is to provide a fuel injection control device for an internal combustion engine.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
The invention described in claim 1 is an intake port injection fuel injection valve that injects fuel into an intake port of each cylinder of an internal combustion engine, and an in-cylinder injection fuel injection valve that directly injects fuel into the combustion chamber of each cylinder. A low-pressure fuel passage that pumps the fuel sucked by the feed pump to the fuel injection valve for intake port injection, and a high-pressure fuel pump that is driven in conjunction with the operation of the internal combustion engine, and is branched from the low-pressure fuel passage. A high pressure fuel passage for boosting the fuel in the passage, and pumping the boosted fuel to the in-cylinder injection fuel injection valve, and the intake port injection fuel injection valve and the in-cylinder injection according to the operating state of the engine A fuel injection control device for an internal combustion engine comprising a control device for controlling the drive of a fuel injection valve for an engine, and at the time of engine startup from autonomous operation to idling of the internal combustion engine, And summarized in that to correct the fuel injection amount by the intake port injection fuel injection valve according to the pressure pulsation generated in the low-pressure fuel passage by driving.

  According to such a configuration as a fuel injection control device for an internal combustion engine, even when pressure pulsation occurs in the low-pressure fuel passage according to the rotation cycle of the internal combustion engine at the time of engine start from autonomous operation to idling of the internal combustion engine, The fuel injection amount by the intake port injection fuel injection valve is corrected according to the pressure pulsation. As a result, it is possible to stably perform the intake port injection after the autonomous operation without suppressing the pressure pulsation itself by increasing the size of the pulsation damper. That is, the startability of the internal combustion engine is not deteriorated.

1 is a schematic diagram schematically showing a schematic configuration of an internal combustion engine and a fuel supply system of an embodiment of a fuel injection control device for an internal combustion engine according to the present invention. The time chart which shows an example in which the fuel pressure in a low pressure fuel passage fluctuates (pulsates). The map which shows an example of the correction value map for correct | amending the fuel injection quantity of the fuel injection valve for intake port injection prepared in the embodiment. The flowchart which shows the control procedure of the fuel injection control performed in the same embodiment. The graph which shows the example about the relationship between the fluctuation | variation of the fuel pressure in the low pressure fuel passage of the internal combustion engine which employs what is called a dual injection system, and an engine speed.

Hereinafter, an embodiment of a fuel injection control device for an internal combustion engine according to the present invention will be described in detail with reference to FIGS.
First, the configuration of an internal combustion engine and a fuel supply system to which the fuel injection control device of the present embodiment is applied will be described with reference to FIG.

  As shown in FIG. 1, an internal combustion engine (gasoline engine) 10 to be applied here includes a first cylinder 11, a second cylinder 12, a third cylinder 13, and a fourth cylinder 14 arranged in series in this order. This is an internal combustion engine consisting of four in-line cylinders. The cylinders 11 to 14 are respectively provided with in-cylinder injection fuel injection valves 11a to 14a for directly injecting fuel into the combustion chamber. The in-cylinder injection fuel injection valves 11a to 14a are respectively provided with high-pressure fuel distribution pipes. High pressure fuel is supplied from 10H. The cylinders 11 to 14 are respectively provided with intake port injection fuel injection valves 11b to 14b for injecting fuel into the intake ports. These intake port injection fuel injection valves 11b to 14b are respectively provided with a low-pressure fuel component. Low pressure fuel is supplied from the pipe 10L. Note that a pulsation damper (not shown) for suppressing pressure fluctuation in the low pressure fuel distribution pipe 10L is attached to the low pressure fuel distribution pipe 10L.

  Further, in the present embodiment, the electronic control unit 20 determines the fuel of the in-cylinder injection fuel injection valves 11a to 14a and the intake port injection fuel injection valves 11b to 14b according to data input from various sensors. This is a part that executes control such as injection control and ignition timing control of each cylinder. As described above, when the internal combustion engine 10 is started, the fuel injection is performed exclusively through the intake port injection fuel injection valves 11b to 14b. In this case, the electronic control unit 20 uses the built-in correction value map 20M. The fuel injection control is executed while correcting the injection amount based on this.

  On the other hand, the fuel supply system for supplying fuel to the internal combustion engine 10 includes a feed pump 30P for pumping fuel from the fuel tank TK, and a low-pressure fuel path for supplying the pumped fuel to the high-pressure fuel supply system and the low-pressure fuel supply system. 30. The fuel that has not been supplied to the high-pressure fuel supply system and the low-pressure fuel supply system is recirculated into the fuel tank TK via the relief valve 30V.

  Here, the high-pressure fuel system is pressurized to the high-pressure fuel distribution pipe 10H from the high-pressure fuel pump 40P via the check valve 40V and the high-pressure fuel pump 40P for increasing the pressure of the fuel supplied from the low-pressure fuel path 30. And a high-pressure fuel passage 40 for supplying fuel. Among them, the high-pressure fuel pump 40P has a cylinder 41 and a plunger 42 that reciprocates inside the cylinder 41, and in conjunction with the movement of the pump cam CM attached to the intake camshaft SF of the internal combustion engine 10, Pressurize. That is, in the intake stroke of the high-pressure fuel pump 40P, the electromagnetic on-off valve 43 is opened, the fuel inlet 40E of the pressurizing chamber 40R is opened, and the plunger 42 is lowered, so that the fuel is supplied to the low-pressure fuel path. 30 to the pressurizing chamber 40R. Then, in the pressurization stroke, the electromagnetic on-off valve 43 is closed to close the fuel introduction port 40E, and the volume of the pressurization chamber 40R is decreased as the plunger 42 is lifted, so that the pressurization is performed. The fuel pressure in the chamber 40R is increased. In this way, when the fuel pressure is increased, the check valve 40V receiving the pressure is opened, and the increased fuel is supplied to the high-pressure fuel distribution pipe 10H via the high-pressure fuel passage 40. The fuel that has not been injected from the cylinder injection fuel injection valves 11a to 14a is returned to the fuel tank TK via the relief valve 10V.

  The low-pressure fuel system includes a low-pressure fuel passage 50 branched from the low-pressure fuel passage 30, and the fuel supplied to the low-pressure fuel passage 50 is supplied as it is to the low-pressure fuel distribution pipe 10L.

  By the way, the electromagnetic on-off valve 43 provided in the high-pressure fuel pump 40P is driven by the electronic control unit 20 based on detection signals from an engine speed sensor, a cam position sensor, a high-pressure fuel pressure sensor (all not shown), and the like. Be controlled. However, as described above, since the cylinder injection fuel injection valves 11a to 14a are not used when the internal combustion engine 10 is started, the electromagnetic on-off valve 43 is maintained in the open state. Therefore, although the plunger 42 of the high-pressure fuel pump 40P moves up and down in conjunction with the movement of the pump cam CM, the fuel pressure in the pressurizing chamber 40R is not increased to a pressure that opens the check valve 40V. . As a result, the pressure pulsation generated in response to the vertical movement of the plunger 42 flows backward from the fuel introduction port 40E and propagates to the low pressure fuel path 30, and the propagated pressure pulsation is low pressure via the low pressure fuel path 50. It also propagates to the fuel distribution pipe 10L.

  FIG. 2 shows an example of such pressure pulsation with respect to the low pressure fuel passage 50 (low pressure fuel distribution pipe 10L). In FIG. 2, for the sake of convenience, pressure pulsation occurs in a predetermined cycle from the first cylinder 11 to the fourth cylinder 14 (line W1), and each time fuel injection is performed by the intake port injection fuel injection valves 11b to 14b, A state in which the fuel pressure fluctuates little by little (line W2) is shown. That is, when the pressure pulsation as illustrated in FIG. 2 occurs, for example, in the first cylinder 11 and the second cylinder 12, the fuel injection amount also varies due to the pulsation, and thus the internal combustion engine. This may cause deterioration of startability as 10.

  Therefore, in this embodiment, for example, an injection amount correction value map 20M illustrated in FIG. 3 is prepared in the electronic control unit 20, and the fuel injection for intake port injection is performed while referring to the correction value map 20M. By correcting the fuel injection amount by the valves 11b to 14b, the above-described variation in the fuel injection amount at the start due to the pressure pulsation is avoided.

  That is, as described above, in the example of FIG. 2, the fuel injection valves 11b and 13b for the intake port injection perform fuel injection when the peak of the pressure pulsation, that is, when the pressure in the low pressure fuel distribution pipe 10L is maximum. To do. Therefore, the fuel injection amount per unit time of the fuel injection valves 11b, 13b for intake port injection is larger than that in the case where there is no pressure pulsation. Therefore, the correction values KF1a to KF1g of the intake port injection fuel injection valve 11b and the correction values KF3a to KF3g of the intake port injection fuel injection valve 13b shown in FIG. 3 are both set to shorten the fuel injection period. Is set. Since the maximum pressure value of the pressure pulsation is substantially constant, the correction values KF1a to KF1g are set to be equal to the correction values KF3a to KF3g, respectively.

  Here, the pulsation damper is desired to be able to suppress the pressure pulsation during normal operation in which the engine speed ne of the internal combustion engine 10 is higher than idling. For this reason, the natural frequency of the pulsation damper is designed so as not to coincide with the frequency of the pressure pulsation during the normal operation, that is, not to be in a resonance state. In other words, the pulsation damper is designed to be in a resonance state when the engine speed ne is lower than idling. Incidentally, the map illustrated in FIG. 3 is a correction value map when the pulsation damper is designed to be in a resonance state when the engine speed ne is 700 rpm. In FIG. 3, when the engine speed ne is 400 rpm, the internal combustion engine 10 reaches the autonomous speed, and when the engine speed ne is 1000 rpm, the internal combustion engine 10 reaches the idling. The number of rotations just before.

  In the map of FIG. 3, the correction value KF1d (KF3d) when the engine speed ne is 700 rpm is set to be the minimum value among the correction values KF1a to KF1g (KF3a to KF3g). The correction values KF1a to KF1c (KF3a to KF3c) are set so as to increase from the correction value KF1d (KF3d) in reverse order to this order, and the correction values KF1e to KF1g (KF3e to KF3g) are In this order, the correction values KF1d (KF3d) are set so as to increase in order.

  On the other hand, the intake port injection fuel injection valves 12b and 14b inject fuel when the pressure in the bottom of the pressure pulsation, that is, the pressure in the low pressure fuel distribution pipe 10L is minimum in the example of FIG. Therefore, the fuel injection amount of the intake port injection fuel injection valves 12b and 14b is smaller than that in the case where there is no pressure pulsation. Therefore, the correction values KF2a to KF2g of the intake port injection fuel injection valve 12b and the correction values KF4a to KF4g of the intake port injection fuel injection valve 14b shown in FIG. 3 are both set to make the fuel injection period longer. Has been. Since the minimum pressure value of the pressure pulsation is substantially constant, the correction values KF2a to KF2g are set to be equal to the correction values KF4a to KF4g, respectively.

  As described above, since the resonance state is designed so that the engine speed ne is 700 rpm, the correction value KF2d (KF4d) when the engine speed ne is 700 rpm in the map of FIG. ) Is set to a maximum value among the correction values KF2a to KF2g (KF4a to KF4g). The correction values KF2a to KF2c (KF4a to KF4c) are set so as to be smaller in order from the correction value KF2d (KF4d) in the reverse order to this order. The correction values KF2e to KF2g (KF4e to KF4g) are In this order, the correction values KF2d (KF4d) are set to be smaller in order.

  Next, the operation of the fuel injection control apparatus of the present embodiment configured as described above will be described with reference to the flowchart shown in FIG. The process shown in FIG. 4 is repeatedly executed every time the internal combustion engine 10 is started through the electronic control unit 20. Further, in FIG. 4, illustration of the combustion control using the in-cylinder fuel injection valves 11 a to 14 a is omitted for convenience.

  As shown in FIG. 4, the electronic control unit 20 first determines whether or not the internal combustion engine 10 has reached autonomous operation (step S10). If the determination result is affirmative (S10 = YES), the processing is performed. To step S11.

  In the process of step S11, after starting the autonomous operation, that is, after starting, the post-startup fuel injection amount TAU of each intake port injection fuel injection valve 11b-14b is based on the intake air amount data input from the intake air amount sensor. To calculate. Thereby, the reference fuel injection time of each fuel injection valve 11b-14b for intake port injection is determined.

  Next, the electronic control unit 20 determines whether or not the engine speed ne calculated based on the data input from the engine speed sensor is equal to or lower than the idling speed NEH of the internal combustion engine 10 ( Step S12). If the determination result is affirmative (S12 = YES), the electronic control unit 20 proceeds to step S13.

  In the process of step S13, the electronic control unit 20 determines the correction values KF1 to KF4 of the intake port injection fuel injection valves 11b to 14b based on the engine speed ne and the correction value map 20M illustrated in FIG. To do. Specifically, for example, when the engine speed ne is 700 rpm, the correction value KF1 of the intake port injection fuel injection valve 11b is set to KF1d, the correction value KF2 of the intake port injection fuel injection valve 12b is set to KF2d, The correction value KF3 of the intake port injection fuel injection valve 13b is determined as KF3d, and the correction value KF4 of the intake port injection fuel injection valve 14b is determined as KF4d.

  Next, the electronic control unit 20 determines the fuel injection amount of each of the fuel injection valves 11b to 14b for intake port injection based on the post-startup fuel injection amount TAU and the correction values KF1 to KF4 (step S14). Specifically, for example, the fuel injection time of the fuel injection valves 11b and 13b for intake port injection is determined so as to be shorter than the reference fuel injection time by multiplying the reference fuel injection time by the correction values KF1 and KF3, respectively. . As a result, the fuel injection amount of the intake port injection fuel injection valves 11b, 13b, where the peak of the fuel pulsation peak is the fuel injection timing, can be reduced. On the other hand, the fuel injection time of the intake port injection fuel injection valves 12b and 14b is determined to be longer than the reference fuel injection time by multiplying the reference fuel injection time by the correction values KF2 and KF4, respectively. As a result, the fuel injection amount of the fuel injection valves 12b, 14b for intake port injection whose bottom of the valley of the pressure pulsation is the timing of fuel injection can be increased. That is, even if the pressure pulsation occurs, the fuel injection amount of the intake port injection fuel injection valves 11b to 14b after the autonomous operation can be stably performed. Therefore, the startability of the internal combustion engine 10 can be maintained well.

  On the other hand, when the determination result of step S12 is negative (S12 = NO), that is, when the internal combustion engine 10 is in a normal operation state in which no pressure pulsation exceeding the idling speed NEH occurs, the electronic control unit 20 The fuel injection amounts of the fuel injection valves 11b to 14b for injection are respectively determined as the post-startup fuel injection amount TAU (step S15).

As described above, according to the fuel injection control device for an internal combustion engine according to the present embodiment, the following effects can be obtained.
(1) Even when a pressure pulsation corresponding to the rotation cycle of the internal combustion engine 10 occurs in the low pressure fuel passage 50 (low pressure fuel distribution pipe 10L) at the time of engine start from the autonomous operation to idling of the internal combustion engine 10, the pressure pulsation Accordingly, the fuel injection amount by the intake port injection fuel injection valves 11b to 14b is corrected. As a result, the fuel injection amount of each intake port injection fuel injection valve 11b to 14b after autonomous operation can be stably performed without suppressing the pressure pulsation itself by increasing the size of the pulsation damper. Become. That is, the startability of the internal combustion engine 10 is not deteriorated.
(Modification)
In addition, the said embodiment can also be implemented with the following aspects.

  In the above embodiment, for convenience of explanation, the pressure pulsation illustrated in FIG. 2 occurs, and the fuel injection valves 11b and 13b for intake port injection inject fuel at the peak of the peak, and at the bottom of the valley of the pressure fluctuation. Although the fuel injection valves 12b and 14b for intake port injection inject fuel, this is merely an example. Actually, the fuel injection timing of the fuel injection valves 11b to 14b for intake port injection can be set at any location on the line W1, depending on the shape of the pump cam CM, the position of the piston in the cylinder when the internal combustion engine 10 is started, and the like. . That is, in the above embodiment, the correction values KF1 and KF3 are equivalent values, and the correction values KF2 and KF4 are equivalent values. However, the correction values are not always determined as such in practice. In short, if a pressure pulsation is obtained by experiment or the like, and a correction value that can equalize the fuel injection amount of each of the intake port injection fuel injection valves 11b to 14b can be set in the correction value map 20M according to the pressure pulsation. Good.

In the above embodiment, the fuel is burned sequentially from the first cylinder to the second cylinder, the third cylinder, and the fourth cylinder. However, the present invention is not limited to this. The order of combustion of the cylinders may be determined in any way.
・ The number of cylinders is not limited to four. Further, the arrangement of the cylinders is not limited to series. The present invention can be applied to any internal combustion engine that employs a dual injection system.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 10H ... High pressure fuel distribution pipe, 10L ... Low pressure fuel distribution pipe, 10V, 30V ... Relief valve, 11 ... 1st cylinder, 12 ... 2nd cylinder, 13 ... 3rd cylinder, 14 ... 4th cylinder, DESCRIPTION OF SYMBOLS 11a-14a ... Fuel injection valve for cylinder injection, 11b-14b ... Fuel injection valve for intake port injection, 20 ... Electronic control unit, 20M ... Correction value map, 30 ... Low pressure fuel path, 30P ... Feed pump, 40 ... High pressure Fuel passage, 40E ... Fuel inlet, 40P ... High pressure fuel pump, 40R ... Pressurization chamber, 40V ... Check valve, 41 ... Cylinder, 42 ... Plunger, 43 ... Electromagnetic on-off valve, 50 ... Low pressure fuel passage, CM ... Pump cam , SF: intake camshaft, TK: fuel tank.

Claims (1)

An intake port injection fuel injection valve that injects fuel into the intake port of each cylinder of the internal combustion engine, an in-cylinder injection fuel injection valve that directly injects fuel into the combustion chamber of each cylinder, and fuel sucked by a feed pump A low-pressure fuel passage that is pumped to the intake port injection fuel injection valve, and a high-pressure fuel pump that is driven in conjunction with the operation of the internal combustion engine to boost the pressure of the fuel in the passage branched from the low-pressure fuel passage; A high-pressure fuel passage for pumping the boosted fuel to the in-cylinder injection fuel injection valve, and driving of the intake port injection fuel injection valve and the in-cylinder injection fuel injection valve according to the operating state of the engine In a fuel injection control device for an internal combustion engine comprising a control device,
When starting the engine from the autonomous operation of the internal combustion engine to idling, the control device determines the fuel injection amount by the fuel injection valve for intake port injection according to the pressure pulsation generated in the low pressure fuel passage by driving the high pressure fuel pump. A fuel injection control device for an internal combustion engine characterized by correcting.

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