JP2006207375A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device for an internal combustion engine, for reducing performance requirement of a fuel pressure sensor to prevent increase in cost of a system. <P>SOLUTION: The fuel injection control device comprises: a basic fuel injection amount calculation means 501 for calculating a basic fuel injection amount to be injected from a fuel injection valve 5; and a fuel pressure-feed period calculation means 506 calculating a period where pressure-feed by a fuel pump is needed based on detected fuel pressure. The fuel injection control device further comprises: a fuel pulse width calculation means 503 calculating a fuel injection pulse width of the fuel injection valve 5 based on the detected fuel pressure Pf, the basic fuel injection amount, and the fuel pressure-feed period; and a fuel injection valve control means 504 controlling the fuel injection valve 5 based on the fuel injection pulse width. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly, to a fuel injection control device for an internal combustion engine that directly injects fuel pumped from a fuel pump through a pressure accumulation pipe into a combustion chamber of each cylinder by a fuel injection valve. About.

  Conventionally, in a fuel injection control device for an internal combustion engine using gasoline as a fuel, it is common to use an electromagnetic fuel injection valve as a valve that directly injects fuel into each cylinder. The apparatus drives a fuel pump to pump fuel according to the operating conditions of the internal combustion engine, accumulates fuel at a predetermined pressure in a pressure accumulation pipe to which the fuel injection valve is connected, and further opens the fuel injection valve. By outputting a valve drive signal, fuel is injected and supplied to each cylinder of the internal combustion engine.

  In addition, a fuel pressure adjusting valve is further arranged in the accumulator piping to which the fuel is pumped by the fuel pump, and the fuel pressure adjusting valve opens when the fuel pressure exceeds a predetermined level, and the fuel in the accumulator piping It is possible to adjust the fuel pressure in the pressure accumulating pipe by discharging the gas. As described above, the fuel pressure in the pressure accumulating pipe is maintained almost constant by the fuel pressure adjusting valve. Therefore, by controlling the valve opening period (fuel injection pulse width) of the fuel injection valve, each cylinder of the internal combustion engine has a predetermined pressure. A required amount of fuel can be stably injected and supplied.

  However, in a low fuel pressure state where the fuel pressure regulating valve does not operate, the increase in the fuel pressure due to the pumping of the fuel pump becomes dominant with respect to the fuel pressure in the pressure accumulating pipe, It cannot be maintained at a constant fuel pressure. In order to inject and supply a necessary amount of necessary fuel to each cylinder of the internal combustion engine, it is necessary to correct the valve opening period of the fuel injection valve by the fuel pressure in the pressure accumulating pipe.

  In view of this, for example, a common rail pressure sensor is arranged on a common rail (accumulation piping) that accumulates high-pressure fuel pumped from a high-pressure supply pump, and an injector (fuel) is based on the pressure of the high-pressure fuel detected by the common rail pressure sensor. There has been proposed a fuel injection control device that calculates an injection time of an injection valve and controls an injection amount of fuel supplied to each internal combustion engine based on the calculated injection time of the injector (see Patent Document 1).

  According to such a fuel injection control device, for example, even when the pressure feeding period of the high-pressure supply pump and the valve opening period of the fuel injection valve are not synchronized and the fuel pressure in the common rail is not constant, the fuel pressure with this fluctuation This state is detected by the common rail pressure sensor, and the fuel injection amount is controlled based on this fuel pressure, so that a desired amount of fuel can be injected and supplied to each cylinder of the internal combustion engine.

JP-A-8-144826

  However, the fuel injection control apparatus described in Patent Document 1 calculates the valve opening time (injection time) of the fuel injection valve based on the fuel pressure and controls the amount of fuel to be injected. When the fuel pressure fluctuates during the calculated fuel injection valve opening period, the fuel injection amount is not controlled on the assumption of such fuel pressure fluctuation. During the period, there is a possibility that a desired amount of fuel cannot be injected and supplied to each cylinder.

  In order to cope with such a problem, in order to inject and supply a desired amount of fuel to each cylinder, the calculated valve opening period is shortened or extended according to the detected fuel pressure detected during the valve opening period. It is possible to perform correction processing. However, in such a case, since it is necessary to detect the fluctuation of the fuel pressure during the valve opening period in real time, the sensor for detecting the fuel pressure is required to have very high responsiveness and accuracy. . When a fuel pressure sensor having such high performance is used in a fuel injection device, the system cost will increase.

  The present invention has been made in view of such a problem, and an object of the present invention is to suppress an increase in system cost by suppressing required specifications of a fuel pressure sensor, and further to a variation in fuel pressure. An object of the present invention is to provide a fuel injection control device for an internal combustion engine that can stably supply a desired amount of fuel to each cylinder.

  In order to achieve the above object, a fuel injection control device for an internal combustion engine according to the present invention includes a fuel pump that pumps fuel according to operating conditions of the internal combustion engine, and a fuel injection valve that injects fuel pumped by the fuel pump. And a fuel pressure sensor for detecting a fuel pressure pumped by the fuel pump, the fuel injection control device for an internal combustion engine, wherein the device determines a basic fuel injection amount to be injected by the fuel injection valve. Basic fuel injection amount calculating means for calculating; fuel pumping period calculating means for calculating a period during which the fuel pump should pump fuel based on the detected fuel pressure; the detected fuel pressure; the basic fuel injection amount; A fuel injection pulse width calculating means for calculating a fuel injection pulse width of the fuel injection valve based on a fuel pumping period; and a fuel injection valve control for controlling the fuel injection valve based on the fuel injection pulse width. Characterized in that it comprises a means.

  The fuel injection control device for an internal combustion engine of the present invention configured as described above is based on a period during which fuel is to be pumped, that is, a pumping start time when the fuel pump pumps fuel and a time during which the fuel is pumped from that point. Thus, the fuel injection pulse width is calculated, so that even if a pressure rise occurs due to the fuel pumping of the pump during fuel injection, the fuel injection valve prevents the fuel from being injected excessively into the cylinder. Can do. Further, the fuel control device according to the present invention calculates the period during which the fuel pump should pump fuel and predicts the change in fuel pressure, so the change in fuel pressure in real time without improving the detection specifications of the fuel pressure sensor. Can be obtained and can be implemented at a lower cost.

  Preferably, in the fuel injection control device for an internal combustion engine according to the present invention, the fuel injection pulse width calculation means calculates the basic fuel injection pulse width based on the basic fuel injection amount and the detected fuel pressure. Fuel injection pulse calculating means; and fuel injection pulse width correcting means for correcting the basic fuel injection pulse width based on the fuel pumping period to obtain the fuel injection pulse width of the fuel injection valve. Yes.

  In this way, by correcting the basic fuel injection pulse width calculated based on the period during which fuel should be pumped, even if there is an increase in fuel pressure due to the fuel pump during fuel injection, this pressure fluctuation is predicted. Therefore, the fuel can be stably injected. In addition, since a slight pressure fluctuation that cannot be detected by the fuel pressure sensor is predicted and correction is performed based on this pressure fluctuation, the fuel injection amount can be controlled with high accuracy.

  In the fuel injection control device for an internal combustion engine according to the present invention, when the fuel injection pulse width correcting means injects fuel during the fuel pumping period, the fuel injection pulse during a period when the fuel pump is not pumping fuel. The fuel injection pulse width is corrected so that the fuel injection pulse width becomes smaller than the width. With this configuration, the fuel injection pulse width can be easily corrected, and the calculation load on the control device can be reduced.

  Preferably, the internal combustion engine fuel injection control apparatus according to the present invention includes a fuel pump that pumps fuel according to an operating condition of the internal combustion engine, a fuel injection valve that injects the fuel pumped by the fuel pump, A fuel pressure sensor for detecting a fuel pressure pumped by the fuel pump, the fuel injection control device for an internal combustion engine, wherein the fuel injection control device is a basic fuel injection amount to be injected by the fuel injection valve A basic fuel injection amount calculating means for calculating the fuel, a fuel pumping period calculating means for calculating a period during which the fuel pump should pump fuel based on the detected fuel pressure, and a detected fuel pressure based on the fuel pumping period. Fuel pressure correcting means for correcting, and fuel injection pulse width calculating means for calculating the fuel injection pulse width of the fuel injection valve based on the corrected detected fuel pressure and the basic fuel injection amount It is characterized by comprising a fuel injection valve control means for controlling the fuel injection valve based on the fuel injection pulse width.

  As described above, the detected fuel pressure is corrected based on the period during which the fuel should be pumped, and the fuel injection pulse width is calculated based on the corrected fuel pressure, thereby increasing the fuel pressure caused by the fuel pump during fuel injection. Even if there is, since the pressure fluctuation is predicted and corrected, the fuel can be stably injected. In addition, since a slight pressure fluctuation that cannot be detected by the fuel pressure sensor is predicted and correction is performed based on this pressure fluctuation, the fuel injection amount can be controlled with high accuracy.

  According to the fuel injection control device for an internal combustion engine of the present invention, even if the fuel pressure fluctuates due to the fuel supply of the fuel pump during the fuel injection of the fuel injection valve, the fuel injection control device can stably achieve the desired regardless of the fuel pressure fluctuation. An amount of fuel can be injected into each cylinder. Furthermore, the system cost can be reduced without increasing the required specifications of the fuel pressure sensor.

  Several embodiments of a fuel injection control device for an internal combustion engine according to the present invention will be described below with reference to the drawings. FIG. 1 shows an overall configuration of a control system of an internal combustion engine (cylinder injection engine) 2 according to the first embodiment. The internal combustion engine 2 has three cylinders, and the air introduced into each cylinder 25 is taken in from the inlet 64 of the air cleaner 65, passes through an air amount sensor (air flow sensor) 63, and controls the supply air amount (intake flow rate). A combustion chamber formed by the piston 26 and the cylinder 25 after being distributed to the intake pipes 66 connected to the cylinders 25 of the internal combustion engine 2 through the throttle body 61 in which the electric throttle valve 6 is accommodated. 21 is led.

  On the other hand, fuel such as gasoline is primarily pressurized from the fuel tank 42 by the low pressure fuel pump 41, and the primary pressurized fuel is adjusted to a constant pressure (eg, 0.3 MPa) by the fuel pressure regulator 43. Secondary pressurization is performed by a high-pressure fuel pump (fuel pump) 3 to be described later to obtain a higher pressure. The secondary pressurized fuel is injected into the combustion chamber 21 from the fuel injection valve (injector) 5 provided in each cylinder 25 via the pressure accumulation pipe 4. The fuel injected into the combustion chamber 21 is ignited by the spark plug 28 by an ignition signal that has been increased in voltage by the ignition coil 27.

An engine control device (control unit) 1 having a fuel injection control device for an internal combustion engine of the present embodiment is detected by a cam angle sensor (rotation sensor) 9 attached to the cam shaft of the exhaust valve 22 of the internal combustion engine 2. The signal of the rotational position of the cam shaft, the signal of the supply air amount detected by the airflow sensor 63, the signal of the accelerator position detected by the accelerator position sensor 8 attached to the accelerator pedal 81, and the throttle valve opening attached to the throttle body 61 The throttle valve opening signal detected by the degree sensor 62, the fuel pressure signal detected by the fuel pressure sensor 7 attached to the pressure accumulating pipe 4, and the cooling detected by the water temperature sensor 29 attached to the cooling water passage of the internal combustion engine 2 A water temperature signal, an oxygen concentration signal detected by the O ₂ concentration sensor 24 attached to the exhaust pipe 68, and the like are input.

  In the control unit 1, signals output from these various sensors are input, and based on the input signals, control signals are output to various actuators so as to achieve the driving state required by the driver or vehicle. . Specifically, the control unit 1 outputs a drive control signal to the electric throttle valve 6 in order to control a desired supply air amount, and pumps it to the high pressure fuel pump 3 to control the fuel pressure pumped to the pressure accumulating pipe 4. A control signal (driving signal) is output, a valve opening control signal (valve opening driving signal) is output to the fuel injection valve 5 to control the amount of fuel injected into the combustion chamber 21, and the fuel in the combustion chamber 21 is further output. Is ignited at a predetermined timing, an ignition control signal is output to the spark plug 28 via the ignition coil 27.

  FIG. 2 is an internal configuration diagram of the control unit 1. The control unit 1 includes an MPU 203, an EP-ROM 202, a RAM 204, an I / O LSI 201 including an A / D converter, and the like. The control unit 1 transmits signals from the various sensors described above to the I / O LSI 201. As a result, the control signal calculated as a result of the calculation is output to various actuators, and the amount of intake air taken into the internal combustion engine 2 is calculated. Control, control of the amount of fuel discharged from the high-pressure fuel pump 3 described later, control of the amount of fuel injected into the cylinder, control of the ignition timing ignited by the ignition coil 27, and the like are executed.

  FIG. 3 shows a configuration diagram of a fuel system including the high-pressure fuel pump 3, the fuel injection valve 5, and the control unit 1.

  The high-pressure fuel pump 3 is connected to a fuel suction passage 44 and a fuel discharge passage 48, and mainly includes a pump body 33 and an actuator 30. The pump body 33 has a plunger 37 that slides on a cylinder 33b. The plunger 37 is pressed against a pump drive cam 23 that rotates together with the cam shaft of the exhaust valve 22 of the internal combustion engine 2, and the pressure chamber 33a In order to change the volume, the cylinder 33b is disposed so as to be able to reciprocate.

  The high-pressure fuel pump 3 includes a suction valve 31 between the fuel suction passage 44 and the pressurization chamber 33a. The suction valve 31 is connected to the fuel suction passage from the pressurization chamber 33a side by a suction valve spring 32. It is a check valve that is urged in the valve closing direction toward the 44 side. The high-pressure fuel pump 3 includes a discharge valve 38 between the pressurizing chamber 33a and the fuel discharge passage 48. The discharge valve 38 is pressurized from the fuel discharge passage 48 by a discharge valve closing spring 39. It is a check valve that is urged in the valve closing direction toward the chamber 33a.

  The actuator 30 is of an electromagnetic drive type and includes a solenoid 36, a valve opening spring 35, and a plunger type intake valve engaging member 34. When the solenoid 36 is not energized (the solenoid control signal is OFF), the suction valve engaging member 34 is urged by the valve opening spring 35 to abut the suction valve 31 to open the suction valve 31. Has been. Since the biasing force of the valve opening spring 35 is larger than the biasing force of the suction valve spring 32, the suction valve 31 is opened when the solenoid 36 is not energized. Next, the operation of supplying fuel to the fuel injection valve 5 will be described below.

  The fuel is primarily pressurized from the fuel tank 42 by the low pressure fuel pump 41, and the primarily pressurized fuel is adjusted to a constant pressure state by the pressure regulator 43, and the high pressure fuel pump 3 is connected via the fuel intake passage 44. To the fuel inlet.

  As the plunger 37 of the high-pressure fuel pump 3 descends, the volume of the pressurizing chamber 33a increases, the pressure in the pressurizing chamber 33a decreases, and the intake valve 31 is opened while the solenoid 36 is not energized. The fuel led to the high-pressure fuel pump 3 is sucked into the pressurizing chamber 33a, but even if the intake valve 31 is closed by energization of the solenoid 36 (solenoid control signal is ON), the plunger 37 Even when the negative pressure of the pressurizing chamber 33a due to the lowering of the pressure is high, the negative pressure causes the suction valve 31 to open against the biasing force of the suction valve closing spring 32, and the fuel from the fuel suction passage 44 is discharged. And is sucked into the pressurizing chamber 33a.

  As the plunger 37 rises and the volume of the pressurizing chamber 33a decreases, the solenoid 36 is not energized even when the pressure of the fuel sucked into the pressurizing chamber 33a increases (the intake valve 31 is If the valve is open, the fuel in the pressurizing chamber 33 a returns to the fuel intake passage 44. On the other hand, if the suction valve 31 is closed by energization of the solenoid 36, when the pressure in the pressurizing chamber 33a increases, the discharge valve 38 is opened against the urging force of the discharge valve closing spring 39, and the pressurizing chamber The fuel in 33 a is pumped to the fuel discharge passage 48. The fuel pumped to the fuel discharge passage 48 is accumulated in the pressure accumulating pipe 4 and injected into the combustion chamber by opening the fuel injection valve 5 via the fuel injection valve 5 disposed in each cylinder of the internal combustion engine 2. Is done.

  Further, as described above, the control unit 1 outputs a drive control signal to the solenoid 36 based on the detection signals from the cam angle sensor 9 and the fuel pressure sensor 7 to thereby control the fuel pumping amount of the high pressure fuel pump 3. The fuel injection amount is controlled by outputting a valve opening control signal (valve opening drive signal) of the fuel injection valve 5.

  FIG. 4 is a timing chart showing the operation of the high-pressure fuel pump 3 and the fuel injection valve 5 and the state of the fuel pressure in the pressure accumulating pipe 4 associated with the operation of these devices. In the present embodiment, the high-pressure fuel pump 3 pumps fuel twice into the accumulator pipe 4 during one cycle stroke of the internal combustion engine 2, and the fuel injection valve 5 is once per cycle for each cylinder. Injection (3 injections in total because of 3 cylinders). The actual stroke (actual position) of the plunger 37 driven by the pump drive cam 23 is a curve, but is represented by a straight line for easy understanding of the positions of the top dead center and the bottom dead center.

  As shown in FIG. 4, when the plunger 37 is moving from the top dead center side to the bottom dead center side by the rotation of the pump drive cam 23, the suction stroke of the high-pressure fuel pump 3 is performed. In this suction stroke, the pressure in the pressurizing chamber 33a of the high-pressure pump 3 decreases with the movement of the plunger 37, the suction valve engaging member 34 presses the suction valve 31, and the suction valve 31 is moved in the valve opening direction. The fuel that has been moved and led from the fuel suction passage 44 flows into the pressurizing chamber 33a. At this time, since the pressure in the pressurizing chamber 33a is negative, the discharge valve 38 is closed due to the biasing force of the discharge valve closing spring 39, and the fuel is not pumped to the pressure accumulating pipe 4.

  Next, the plunger 37 starts moving from the bottom dead center side to the top dead center side by the rotation of the pump drive cam 23, and the compression stroke of the high pressure fuel pump 3 is performed. In this compression stroke, first, when the plunger 37 starts to move from the bottom dead center to the top dead center, when the solenoid 36 of the actuator 30 is not energized, the intake valve 31 is opened. The fuel that has flowed into the pressurizing chamber 33a during the intake stroke is returned to the fuel intake passage 44 via the intake valve 31.

  When a drive signal (ON signal) is output from the control unit 1 to the actuator 30, the solenoid 36 is energized (in an ON state), and the suction valve engaging member 34 is resisted against the biasing force of the valve opening spring 35. To move the suction valve 31 open. As a result, the pressure in the pressurizing chamber 33a increases. Further, if the pressure in the pressurizing chamber 33a continues to rise, the discharge valve 38 is pressed by the increased pressure against the urging force of the discharge valve closing spring 39 to open the pressurizing chamber 33a. The fuel is pumped (discharged) to the pressure accumulating pipe 4. In this state, even if the energization of the solenoid 36 is stopped (OFF state), the suction valve 31 is kept closed because the pressure in the pressurizing chamber 33a is high, and the fuel is fed to the pressure accumulating pipe 4. Will continue. By this fuel pumping, the fuel pressure in the pressure accumulating pipe 4 increases. When the plunger starts moving again from the top dead center side to the bottom dead center side, the suction stroke of the high-pressure fuel pump 3 starts, and the above operation is repeated thereafter.

  As described above, the control unit 1 changes the output timing of the drive signal to the solenoid 36 of the high-pressure fuel pump 3, so that the high-pressure fuel pump 3 can adjust the amount of fuel pumped to the pressure accumulation pipe 4. . Based on the signal to the fuel pressure sensor 7 arranged in the pressure accumulating pipe 4, the control unit 1 calculates the output timing of the drive signal to the solenoid 36 and appropriately drives the solenoid 36. It is possible to feedback-control the detected fuel pressure to a predetermined target value.

  On the other hand, the fuel injection valve 5 is opened for each cylinder by a valve opening drive signal from the control unit 1 to inject and supply fuel to the combustion chamber 21 of each cylinder. By this fuel injection, the fuel pressure in the pressure accumulating pipe 4 is lowered.

  As described above, the actual pressure change is as shown by the solid line in the figure. The fuel pressure (measured pressure) detected by the fuel pressure sensor 7 operates as shown by the dotted line in the figure because a slight detection delay occurs. In this embodiment, as shown in FIG. 4, the fuel pumping period (pressure increase) and the fuel injection period (pressure decrease) are not synchronized in one cycle, and the fuel injection valve 5 is # 2 While the fuel is injected into the cylinder, the fuel pressure in the pressure accumulating pipe 4 decreases. However, while the fuel is injected into the # 3 cylinder, the fuel is pumped into the pressure accumulating pipe 4 by the high pressure fuel pump 3. Therefore, the fuel pressure does not decrease as much as other cylinders.

  When the opening period of the fuel injection valve 5 is set in each cylinder based on the detected fuel pressure immediately before the start of injection, the # 3 cylinder is pumped by the high pressure fuel pump 3 while the fuel injection valve 5 is opened. Therefore, more fuel than the required amount of fuel is injected into the # 3 cylinder. That is, there are a cylinder (# 3) that is greatly affected by the increase in fuel pressure in the pressure accumulating pipe 4 due to the pumping of the high-pressure fuel pump 3, and a cylinder (# 2) that is not at all.

  In order to avoid excessive fuel injection into a specific cylinder in this way, the fuel pressure sampling task is shortened, and a change in fuel pressure is detected even during the opening period of the fuel injection valve 5, It is conceivable to correct the valve opening period of the fuel injection valve 5 based on the detected fuel pressure detected. However, as indicated by the dotted line in the figure, a slight delay occurs in the pressure detected by the fuel pressure sensor 7, which in turn causes an error in the injection period of other cylinders. Therefore, in such a case, an appropriate valve opening period of the fuel injection valve 5 is calculated in consideration of the period during which fuel is pumped from the high-pressure fuel pump 3 as shown in FIGS. It is desirable.

  FIG. 5 shows a control block diagram relating to fuel injection of the internal combustion engine of the control unit 1 in the first embodiment.

As shown in FIG. 5, the basic fuel supply amount calculation means (basic fuel injection amount calculation means) 501 supplies basic fuel to be injected by the fuel injection valve 5 based on the detected supply air amount Qa and the engine speed Ne. The amount (basic fuel injection amount) is calculated. The air-fuel ratio feedback correction coefficient calculating means 502 determines whether the air-fuel ratio is in a rich state or a lean state based on the oxygen concentration O ₂ detected by the O ₂ concentration sensor 24. On the other hand, if the lean state is determined, an air-fuel ratio feedback correction coefficient for correcting the basic fuel supply amount on the increase side is calculated.

  On the other hand, the target fuel pressure calculation means 505 calculates a target fuel pressure when fuel is injected from the fuel injection valve 5 based on the detected supply air amount Qa and the engine rotational speed Ne, and uses the target fuel pressure as the fuel. It outputs to the pumping period calculating means 506. The fuel pumping period calculation means 506 is a period during which the high pressure fuel pump 3 should pump fuel so that the detected fuel pressure detected by the fuel pressure sensor 7 becomes the target fuel pressure calculated by the target fuel pressure calculation means 505. (Fuel pumping period) is calculated. The fuel pump control unit 507 outputs a drive signal to the high-pressure fuel pump 3 based on the fuel pumping period calculated by the fuel pumping period calculating unit 506.

  The fuel injection pulse width calculation means 503 corrects the basic fuel supply amount calculated by the basic fuel supply amount calculation means 501 with the air-fuel ratio feedback correction coefficient calculated by the air-fuel ratio feedback correction coefficient calculation means 502, and this corrected fuel supply Based on the amount, the fuel pumping period calculated by the fuel pumping period calculator 506, and the detected fuel pressure Pf detected by the fuel pressure sensor 7, the fuel injection pulse width that is the valve opening time of the fuel injector 5 is calculated. Based on the calculated fuel injection pulse width, the fuel injection valve control means 504 outputs a valve opening drive signal to the fuel injection valve in accordance with the fuel injection pulse width.

  As described above, the fuel injection pulse width is calculated based on the fuel pumping period, that is, the pumping start time when the high-pressure fuel pump 3 pumps the fuel to the pressure accumulating pipe 4 and the time for pumping the fuel from that point. Even if the pressure rises due to the fuel pumping of the high pressure fuel pump 3 during the fuel injection, the fuel injection valve 5 can prevent the fuel from being excessively injected and supplied into the cylinder (combustion chamber 21). it can. Further, since the change in the fuel pressure can be predicted by calculating the period during which the high-pressure fuel pump 3 pumps the fuel, it can be implemented at low cost without improving the detection specification of the fuel pressure sensor 7. it can.

  FIG. 6 shows a control block diagram relating to fuel injection of the internal combustion engine of the control unit 1 in the second embodiment. In FIG. 6, the same components as those of the first embodiment of FIGS. 1 to 5 are denoted by the same reference numerals, and detailed description thereof is omitted. The second embodiment is different from the first embodiment in that a fuel pressure correction unit 508 is provided.

  The fuel pressure correcting unit 508 corrects the detected fuel pressure Pf detected based on the fuel pumping period (fuel pumping start timing and pumping time) calculated by the fuel pumping period calculating unit 506. Specifically, the cylinder-by-cylinder pumping period in the fuel injection region set for each cylinder is calculated, and the average fuel pressure increase dPf is calculated from the cylinder-by-cylinder pumping period calculated to predict the pressure fluctuation in the accumulator pipe. The corrected fuel pressure FPf is calculated by adding this fuel pressure average increase dPf to the detected fuel pressure Pf.

  Here, the average fuel pressure increase dPf can be calculated by calculation from the calculated cylinder-by-cylinder pumping period and the characteristics of the fuel pump, but the relationship between the cylinder-by-cylinder pumping period and the fuel pressure average increase dPf is stored in advance as a table. You may search for it.

  The fuel injection pulse width calculation means 503 corrects the basic fuel supply amount calculated by the basic fuel supply amount calculation means 501 by the air-fuel ratio feedback correction coefficient calculated by the air-fuel ratio feedback correction coefficient calculation means 502, and the corrected fuel supply amount Is converted into a fuel injection pulse width of the fuel injection valve according to the corrected fuel pressure FPf corrected by the fuel pressure correction means 508 (the fuel injection pulse width is calculated), and the fuel injection valve control means 504 sets the fuel injection pulse width to this fuel injection pulse width. In response, a valve opening drive signal is output to the fuel injection valve.

  FIG. 7 shows a control block diagram relating to fuel injection of the internal combustion engine of the control unit 1 in the third embodiment. 7, the same components as those in the first embodiment in FIGS. 1 to 5 are denoted by the same reference numerals, and detailed description thereof is omitted. The third embodiment differs from the first embodiment in that a basic fuel injection pulse width calculation means 509 and a fuel injection pulse width correction means 510 are provided instead of the fuel injection pulse width calculation means 503. Yes.

  The basic fuel injection pulse width calculation means 509 corrects the basic fuel supply amount calculated by the basic fuel supply amount calculation means 501 with the air-fuel ratio feedback correction coefficient calculated by the air-fuel ratio feedback correction coefficient calculation means 502. Then, the basic fuel injection pulse width is calculated based on the corrected basic fuel supply amount and the detected detected fuel pressure Pf.

  The fuel injection pulse width correcting means 510 predicts the pressure fluctuation in the pressure accumulating pipe based on the fuel pumping period calculated by the fuel pumping period calculating means 506 (in consideration of the fluctuation margin), and the basic fuel injection pulse width. The basic fuel injection pulse width calculated by the calculation means 509 is corrected. Based on the corrected basic fuel injection pulse width, the fuel injection valve control means 504 outputs a valve opening drive signal to the fuel injection valve 5.

  The fuel injection control apparatus configured as described above is configured to predict and correct the fluctuation even if the fuel pressure varies due to the fuel supply of the fuel pump during the fuel injection of the fuel injection valve. Without excessive fuel supply, a desired amount of fuel can be stably injected into each cylinder. Further, the system cost can be reduced as a result without increasing the required specifications of the fuel pressure sensor.

  Although the three embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention described in the claims. The design can be changed.

  In the third embodiment, the basic fuel injection pulse width is corrected by predicting the pressure fluctuation based on the fuel pumping period calculated by the fuel pumping period calculating means, but as a simple correction, the fuel pumping period When injecting fuel, correction may be made such that the fuel injection pulse width becomes smaller than the fuel injection pulse width during a period when the fuel pump is not pumping fuel.

  In the above embodiment, the fuel pump control means and the fuel injection control means are provided in the same control unit, but each may be controlled by separate control units. However, in that case, it is necessary to configure so that the control signal of the fuel pump control means provided in a certain control unit or a predetermined signal equivalent thereto is input to another control unit provided with the fuel injection control means. There is.

  In the present embodiment, the basic fuel supply amount calculation means calculates the basic fuel supply amount, and the fuel injection pulse width calculation means corrects the basic fuel supply amount with the air-fuel ratio feedback coefficient. The basic fuel supply calculation means may calculate in advance.

  The present invention is particularly effective because stable fuel injection can be performed for a combination in which the pumping period of the fuel high-pressure pump and the injection timing of the fuel injection valve are not synchronized.

1 is an overall configuration diagram of an internal combustion engine including a fuel injection control device for an internal combustion engine according to a first embodiment of the present invention. The internal block diagram of the fuel-injection control apparatus of the internal combustion engine of FIG. FIG. 2 is an overall configuration diagram of a fuel system including the fuel injection control device for the internal combustion engine of FIG. 1. The operation | movement timing chart of the high pressure fuel pump of FIG. The control block diagram regarding the fuel system of the fuel-injection control apparatus of FIG. The control block diagram regarding the fuel system of the fuel-injection control apparatus which concerns on 2nd embodiment of this invention. The control block diagram regarding the fuel system of the fuel-injection control apparatus which concerns on 3rd embodiment of this invention.

Explanation of symbols

1 Control unit (fuel injection control device for internal combustion engine)
2 Internal combustion engine 3 High-pressure fuel pump (fuel pump)
4 Accumulation piping 5 Fuel injection valve 6 Electric throttle valve 7 Fuel pressure sensor 8 Accelerator position sensor 9 Rotation sensor 501 Basic fuel supply amount calculation means (basic fuel injection amount calculation means)
503 Fuel injection pulse width calculation means 504 Fuel injection valve control means 505 Target fuel pressure calculation means 506 Fuel pumping period calculation means 508 Fuel pressure correction means 509 Basic fuel injection pulse width calculation means 510 Fuel injection pulse width correction means

Claims (4)

A fuel pump that pumps fuel according to operating conditions of the internal combustion engine, a fuel injection valve that injects fuel pumped by the fuel pump, and a fuel pressure sensor that detects fuel pressure pumped by the fuel pump; A fuel injection control device for an internal combustion engine comprising:
The fuel injection control device calculates basic fuel injection amount calculation means for calculating a basic fuel injection amount to be injected by the fuel injection valve, and calculates a period during which the fuel pump should pump fuel based on the detected fuel pressure. Fuel injection period calculating means; fuel injection pulse width calculating means for calculating a fuel injection pulse width of the fuel injection valve based on the detected fuel pressure, the basic fuel injection amount, and the fuel pumping period; and the fuel injection And a fuel injection control device for controlling the fuel injection valve based on the pulse width. A fuel pump that pumps fuel according to operating conditions of the internal combustion engine, a fuel injection valve that injects fuel pumped by the fuel pump, and a fuel pressure sensor that detects fuel pressure pumped by the fuel pump; A fuel injection control device for an internal combustion engine comprising:
The fuel injection control device calculates basic fuel injection amount calculation means for calculating a basic fuel injection amount to be injected by the fuel injection valve, and calculates a period during which the fuel pump should pump fuel based on the detected fuel pressure. Fuel pumping period calculating means; fuel pressure correcting means for correcting the detected fuel pressure based on the fuel pumping period; and fuel injection pulses of the fuel injection valve based on the corrected detected fuel pressure and the basic fuel injection amount A fuel injection control device for an internal combustion engine, comprising: a fuel injection pulse width calculation means for calculating a width; and a fuel injection valve control means for controlling a fuel injection valve based on the fuel injection pulse width.   The fuel injection pulse width calculation means includes basic fuel injection pulse calculation means for calculating the basic fuel injection pulse width based on the basic fuel injection amount and the detected fuel pressure, and the basic fuel injection pulse width for the fuel pumping period. The fuel injection control device for an internal combustion engine according to claim 1, further comprising: a fuel injection pulse width correcting unit that corrects the fuel injection pulse width to be the fuel injection pulse width of the fuel injection valve.   The fuel injection pulse width correcting means, when injecting fuel during the fuel pumping period, makes the fuel injection pulse width smaller than a fuel injection pulse width during a period when the fuel pump is not pumping fuel. The fuel injection control device for an internal combustion engine according to claim 3, wherein the fuel injection pulse width is corrected.

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