JP2013019388A - 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 can properly determine timing when a fuel injection valve is opened, with an inexpensive configuration, without an exclusive current detection means.SOLUTION: The fuel injection control device for the internal combustion engine 3 includes: a capacitor 23 to which a boosted voltage is charged; a drive circuit 10 which applies the voltage charged in the capacitor 23 to a coil 6b for opening an electromagnetic fuel injection valve 4; and a voltmeter 30 which detects a voltage VC of the capacitor 23. The fuel injection control device obtains an inflection point PI in a waveform of the detected voltage VC of the capacitor 23, while the voltage is being applied to the coil 6b (ECU2, Steps 21 to 23); determines the timing when the inflection point PI appears as valve opening timing when a valve body 9 is seated on a yoke 6a (Steps 23 and 26); and controls operation of the fuel injection valve 4 according to the determined valve opening timing (Steps 10 and 13).

Description

  The present invention relates to a fuel injection control device for an internal combustion engine that injects fuel by opening an electromagnetic fuel injection valve.

  Conventionally, as this type of fuel injection control device, for example, one disclosed in Patent Document 1 is known. In this fuel injection control device, a voltage is applied to a coil of an electromagnetic fuel injection valve to operate the valve body and open the fuel injection valve to inject fuel. Further, by changing the coil application time (energization time), the valve opening time is controlled, and the fuel injection amount is controlled.

  Further, the current flowing through the coil during application is detected by the current detection circuit, and the drop point (singular point) of the detected current waveform is used as the operation end timing (valve opening timing) of the valve body of the fuel injector. Ask. The operation end timing obtained in this way is used to correct the coil application time, thereby compensating for variations in the responsiveness of the valve body of the fuel injection valve and obtaining a desired fuel injection amount. ing.

Japanese Examined Patent Publication No. 62-4543

  However, this conventional fuel injection control device requires a dedicated current detection circuit for detecting the current flowing through the coil of the fuel injection valve in order to obtain the operation end timing of the valve body of the fuel injection valve. As a result, the manufacturing cost increases and the amount of heat generated by the heat generation of the current detection circuit also increases.

  The present invention has been made to solve the above-described problems, and appropriately determines the timing at which the fuel injection valve is opened with an inexpensive configuration without requiring a dedicated current detection means. An object of the present invention is to provide a fuel injection control device for an internal combustion engine.

  In order to achieve the above object, the invention according to claim 1 includes a yoke 6a, a coil 6b wound around the yoke 6a, and a coil 6b of an electromagnetic fuel injection valve 4 having a valve body 9 integral with the armature 8. A fuel injection control device for the internal combustion engine 3 that opens the fuel injection valve 4 and injects fuel in a state where the valve element 9 is seated on the yoke 6a via the armature 8 by applying a voltage to A booster circuit 20 for boosting a voltage (battery voltage VB) of a power source (battery 25 in the embodiment (hereinafter the same in this section)), a capacitor 23 charged with the boosted voltage, and a fuel injection valve 4 Application means (driving circuit 10, ECU 2, step 5) for applying a voltage charged in the capacitor 23 to the coil 6b to open the valve, and a voltage for detecting the voltage VC of the capacitor 23 And an inflection point detection means (ECU 2, steps 21 to 23) for detecting an inflection point of the waveform of the voltage VC of the capacitor 23 detected during application of the voltage to the coil 6b. The valve opening timing determining means (ECU 2, steps 23 and 26) for determining the timing at which the detected inflection point appears as the valve opening timing at which the valve body 9 is seated on the yoke 6a, and the determined valve opening timing. Correspondingly, it is characterized by comprising injection valve control means (ECU 2, steps 10, 13) for controlling the operation of the fuel injection valve 4.

  According to this configuration, the voltage of the power supply is boosted by the booster circuit and charged to the capacitor. The voltage charged in the capacitor is applied to the coil of the fuel injection valve. As a result, the armature is attracted to the yoke by the generated magnetic flux, and the fuel injection valve is opened and fuel is injected with the valve body seated on the yoke via the armature.

  Further, according to the present invention, the inflection point of the detected capacitor voltage waveform is detected during application of the voltage to the coil, and the timing at which the detected inflection point appears is determined so that the valve body It is determined that the valve opening timing has been seated on. This determination method is based on the following principle.

  That is, when the voltage of the capacitor is applied to the coil of the fuel injection valve as described above, the capacitor voltage starts to decrease accordingly. On the other hand, in the fuel injection valve, as the armature moves to the yoke side and the distance between them decreases, the back electromotive force is generated as the magnetic flux passing through the gap between them decreases. For this reason, until the armature is seated on the yoke, the decrease in the capacitor voltage is slowed by this counter electromotive force.On the other hand, after the armature is seated on the yoke, the counter electromotive force does not act so that the capacitor voltage Decreases rapidly. As a result, an inflection point occurs in the waveform of the capacitor voltage before and after the armature is seated on the yoke, and the timing at which this inflection point appears coincides with the timing at which the armature sits on the yoke.

  Based on the above principle, according to the present invention, the inflection point of the voltage waveform of the capacitor detected during the application of the voltage to the coil is detected, and the timing at which the detected inflection point appears is determined by the valve body. Is determined to be the valve opening timing when it is seated on the yoke. Therefore, it is possible to appropriately determine the valve opening timing. Since the operation of the fuel injection valve is controlled according to the determined valve opening timing, the fuel injection valve can be appropriately controlled according to the actual valve opening timing of the fuel injection valve.

  In addition, the capacitor voltage represents the storage state of the capacitor, and is a parameter necessary for control of the fuel injection valve. Usually, a voltage detection means is provided for the detection, so that such existing voltage detection is performed. The means can be used as it is. On the other hand, the conventional current detection circuit used for grasping the valve opening timing of the fuel injection valve is no longer necessary, so that the manufacturing cost can be reduced and the heat generation in the current detection circuit is eliminated. Can be reduced.

1 is a diagram schematically showing a fuel injection control device according to an embodiment of the present invention together with an internal combustion engine to which the fuel injection control device is applied. FIG. It is a figure which shows a fuel injection valve roughly. It is a circuit diagram which shows the drive circuit for driving a fuel injection valve. It is a flowchart which shows a fuel-injection control process. It is a flowchart which shows the subroutine of the seating determination process of a fuel injection valve. It is a timing chart which shows the operation example of a fuel-injection control apparatus.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. An internal combustion engine (hereinafter referred to as “engine”) 3 shown in FIG. 1 is a gasoline engine for vehicles having, for example, four cylinders (not shown). Each cylinder has a fuel injection valve (hereinafter referred to as “injector”). 4 is provided, and fuel is directly injected from the injector 4 into a combustion chamber (not shown). The operation of the injector 4 is controlled by an ECU 2 described later.

  As shown in FIG. 2, the injector 4 is housed in a casing 5, an electromagnet 6 fixed to the upper end portion thereof, a spring 7, an armature 8 disposed below the electromagnet 6, and a lower part of the armature 8. It is comprised by the valve body 9 etc. which were integrally provided in the side. High pressure fuel is supplied to the injector 4 from a fuel supply device (not shown).

  The electromagnet 6 includes a yoke 6a and a coil 6b wound around the yoke 6a, and a drive circuit 10 shown in FIG. 3 is connected to the coil 6b. The spring 7 is disposed between the yoke 6a and the armature 8 and biases the valve body 9 toward the valve closing side.

  The drive circuit 10 drives the injector 4, and as shown in FIG. 3, the booster circuit 20, first to third switches 11 to 13 each formed of an N-channel FET, and a Zener diode 14 Etc.

  The booster circuit 20 includes a switch 21, a coil 22, and a capacitor 23. The switch 21 is composed of an N-channel FET, and the drain thereof is connected to the battery 25 via the coil 22 and is connected to the drain of the first switch 11 via the capacitor 23. The battery 25 is charged using a generator using the engine 3 as a power source. The source and gate of the switch 21 are connected to the ground and the ECU 2, respectively.

  In the booster circuit 20 having the above configuration, when the drive signal SD from the ECU 2 is input to the gate, the switch 21 is turned on, and the drain-source is energized, whereby the voltage from the battery 25 (hereinafter, “ VB) is boosted via the coil 22. The boosted voltage is applied to the capacitor 23 and charged. Such step-up control is performed so that the voltage of the capacitor 23 (hereinafter referred to as “capacitor voltage”) VC becomes the target value, and thereby the capacitor voltage VC is kept high.

  The drain, source, and gate of the first switch 11 are connected to the booster circuit 20, one end of the coil 6b of the electromagnet 6, and the ECU 2, respectively. When the first drive signal SD1 from the ECU 2 is input to the gate, the first switch 11 is turned on and the drain-source is energized.

  The drain, source and gate of the second switch 12 are connected to the battery 25, one end of the coil 6b and the ECU 2, respectively. When the second drive signal SD2 from the ECU 2 is input to the gate, the second switch 12 is turned on and the drain-source is energized.

  The drain, source, and gate of the third switch 13 are connected to the other end of the coil 6b, the ground, and the ECU 2, respectively. When the third drive signal SD3 from the ECU 2 is input to the gate, the third switch 13 is turned on, and the drain-source is energized.

  The Zener diode 14 has an anode side connected to the ground and a cathode side connected to the other end of the coil 6b.

  In the drive circuit 10 having the above configuration, the ON / OFF states of the first to third switches 11 to 13 are switched according to the first to third drive signals SD1 to SD3 from the ECU 2, and the coil 6b of the injector 4 is supplied to the coil 6b. By controlling the voltage application state, the operation of the injector 4 is controlled.

  Specifically, when the first to third switches 11 to 13 are in the OFF state, the coil 6b of the injector 4 is not applied, and the drive current IAC does not flow through the coil 6b, so that the valve body 9 of the injector 4 is The injector 4 is positioned at the valve closing position (FIG. 2A) by the urging force of the spring 7, and the injector 4 is held in the valve closing state.

  When the first and third switches 11 and 13 are turned on from this state, the boosted capacitor voltage VC is applied to the coil 6b of the injector 4, so that a large drive current IAC flows through the coil 6b and the electromagnet 6 is excessive. Excited. By this excitation, the armature 8 is attracted to the electromagnet 6 against the biasing force of the spring 7, and the injector 4 is opened (fully opened) in a state where the valve body 9 is seated on the yoke 6a via the armature 8. In FIG. 2 (b)), fuel is injected from the injector 4. Hereinafter, such control for applying the capacitor voltage VC to the coil 6b of the injector 4 is referred to as “overexcitation control”, and a large drive current IAC flowing through the coil 6b at this time is referred to as “overexcitation current”.

  Thereafter, when the first switch 11 is turned off and the application of the capacitor voltage VC is finished, and the second switch 12 is turned on, a battery voltage VB smaller than the capacitor voltage VC is applied to the coil 6b of the injector 4. As a result, a small drive current IAC flows through the coil 6b, whereby the injector 4 is held in the valve open state and fuel injection is continued. Hereinafter, such control for applying the battery voltage VB to the coil 6b of the injector 4 is referred to as “holding control”, and the small drive current IAC flowing through the coil 6b at this time is referred to as “holding current”. In this holding control, the battery voltage VB is intermittently applied, whereby the holding current is controlled to a small value within a predetermined range.

  When the second and third switches 12 and 13 are turned off from this state, the application of the battery voltage VB is completed, and the valve body 9 is returned to the valve closing position by the biasing force of the spring 7 accordingly. Closes and fuel injection ends. Further, the current remaining in the coil 6b flows to the ground via the Zener diode 14, so that the electromagnet 6 is in a non-excited state.

  As described above, when the injector 4 is opened, first, overexcitation control is executed, so that the boosted capacitor voltage VC is applied to the coil 6b and the electromagnet 6 is overexcited, so that the fuel is high. Sufficient magnetic force is secured to quickly open the injector 4 against the pressure. Further, subsequently, holding control is executed, and the battery voltage VB is applied to the coil 6b, whereby the valve opening state of the injector 4 is held in a state where power consumption is suppressed.

  Further, the booster circuit 20 is provided with a voltmeter 30. The voltmeter 30 detects a capacitor voltage VC and outputs a detection signal to the ECU 2.

  Furthermore, a crank angle sensor 31 is provided on the crankshaft (not shown) of the engine 3. The crank angle sensor 31 outputs a CRK signal and a TDC signal, which are pulse signals, to the ECU 2 as the crankshaft rotates.

  The CRK signal is output every predetermined crank angle (for example, 1 °). The ECU 2 calculates the engine speed (hereinafter referred to as “engine speed”) NE of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that a piston (not shown) in any cylinder is at a predetermined crank angle position slightly ahead of the top dead center at the start of the intake stroke. When the engine 3 is a 4-cylinder type as described above, it is output every crank angle of 180 °.

  The engine 3 is provided with a cylinder discrimination sensor (not shown). The cylinder discrimination sensor outputs to the ECU 2 a cylinder discrimination signal that is a pulse signal for discriminating the cylinder. The ECU 2 calculates the crank angle CA for each cylinder based on the cylinder discrimination signal, the CRK signal, and the TDC signal. Specifically, the crank angle CA is reset to a value of 0 when the TDC signal is generated, and is incremented every crank angle of 1 ° at which the CRK signal is generated.

  Further, the ECU 2 outputs a detection signal representing the depression amount (hereinafter referred to as “accelerator opening”) AP of an accelerator pedal (not shown) of the vehicle from the accelerator opening sensor 32.

  The ECU 2 is composed of a microcomputer including a CPU, a RAM, a ROM, an I / O interface (all not shown), and the like. The ECU 2 determines the operating state of the engine 3 according to the control program stored in the ROM in accordance with the detection signals of the voltmeter 30 and the sensors 31 to 32 described above, and the fuel from the injector 4 according to the determined operating state. A fuel injection control process for controlling injection is executed for each cylinder. In the embodiment, the ECU 2 corresponds to an application unit, an inflection point detection unit, a valve opening timing determination unit, and an injection valve control unit.

  FIG. 4 is a flowchart showing this fuel injection control process. This process is repeatedly executed in synchronization with the generation of the CRK signal described above. In this process, first, in step 1 (illustrated as “S1”, the same applies hereinafter), it is determined whether or not the calculated crank angle CA is equal to the fuel injection timing TINJ. This fuel injection timing TINJ corresponds to a timing at which the drive operation of the injector 4 should be started, and is represented by a crank angle CA. Calculated.

  When the answer to step 1 is YES and the crank angle CA is equal to the fuel injection timing TINJ, the following steps 2 to 5 are executed on the assumption that overexcitation control is started as drive control of the injector 4. First, the value TM of the up-count timer is reset to 0 (step 2), and then the capacitor voltage application flag F_VC is set to “1” to indicate that overexcitation control is in progress (step 1). 3). Next, in order to indicate that the injector 4 is being driven, the fuel injection flag F_INJ is set to “1” (step 4), and the capacitor voltage VC is applied to the injector 4 in step 5, thereby overexciting. Control is started and this process is terminated. Note that the capacitor voltage application flag F_VC, the fuel injection flag F_INJ, and various flags described later are all reset to “0” when the engine 3 is started.

  On the other hand, if the answer to step 1 is NO and the crank angle CA is not equal to the fuel injection timing TINJ, it is determined whether or not the fuel injection flag F_INJ is “1” (step 6). If the answer is YES and the injector 4 is being driven, it is determined whether or not the capacitor voltage application flag F_VC is “1” (step 7). If the answer is YES and overexcitation control is being performed, seating determination processing for the injector 4 is executed (step 8).

  This seating determination process determines whether or not the valve element 9 of the injector 4 is seated on the yoke 6a via the armature 8, that is, whether or not the injector 4 has reached the valve opening state, with the execution of overexcitation control. And is performed according to the subroutine shown in FIG. In this process, first, in step 21, the difference (= VC−VCZ) between the capacitor voltage VC detected by the voltmeter 30 and its previous value VCZ is calculated as a voltage change amount ΔVC. Next, the difference (= ΔVC−ΔVCZ) between the calculated voltage change amount ΔVC and the previous value ΔVCZ is calculated as a voltage change amount differential value ΔΔVC (step 22).

  Next, it is determined whether or not the calculated voltage change amount differential value ΔΔVC is a negative value (step 23). As described above, when the valve element 9 moves toward the yoke 6a when the injector 4 is opened, the rate of decrease of the capacitor voltage VC changes slowly until the valve element 9 is seated on the yoke 6a, and thereafter Since it changes rapidly, an inflection point appears in the waveform of the capacitor voltage VC at the timing when the valve body 9 is seated, and the voltage change differential value ΔΔVC changes from a positive value to a negative value at the inflection point.

  Therefore, when the answer to step 23 is NO and the voltage variation differential value ΔΔVC is not a negative value, the valve body 9 is not yet seated on the yoke 6a, and the seating flag F_OPEN is set to “0” to indicate that. (Step 24). Next, the current capacitor voltage VC and the voltage change amount ΔVC are shifted to the previous values VCZ and ΔVCZ, respectively (step 25), and this process ends.

  On the other hand, if the answer to step 23 is YES and the voltage variation differential value ΔΔVC becomes a negative value, the current timing corresponds to the inflection point PI (see FIG. 6) of the waveform of the capacitor voltage. Assuming that the body 9 is seated on the yoke 6a and the injector 4 has reached the valve open state, the seating flag F_OPEN is set to "1" (step 26), and this process is terminated.

  Returning to FIG. 4, in step 9 following step 8, it is determined whether or not the seating flag F_OPEN set in the seating determination process is “1”. If the answer is NO and the injector 4 has not yet reached the valve open state, the process proceeds to step 5 and the overexcitation control is continued.

  On the other hand, if the answer to step 9 is YES and the injector 4 reaches the valve open state, the application of the capacitor voltage VC to the injector 4 is terminated (step 10), thereby terminating the overexcitation control. In order to express this, the capacitor voltage application flag F_VC is reset to “0” (step 11).

  Next, the battery voltage application flag F_VB is set to “1” (step 12), and the battery voltage VB is applied to the injector 4 (step 13), thereby starting the holding control and ending this process. As described above, at the same time when it is determined that the injector 4 has reached the valve opening state, the overexcitation control is terminated and the holding control is started.

  In addition, as a result of execution of step 11, the answer to step 7 becomes NO (F_VC = 0). In this case, whether or not the timer value TM reset in step 2 has reached the predetermined time TMREF is determined. A determination is made (step 14). When the answer is NO, the process proceeds to step 13 and the holding control is continued.

  The predetermined time TMREF is calculated according to the pressure of the fuel supplied to the injector 4 and the fuel injection amount. The fuel pressure is detected by a sensor (not shown), and the fuel injection amount is It is calculated according to the engine speed NE and the required torque PMCMD. The required torque PMCMD is a torque required for the engine 3 and is calculated by searching a predetermined map (not shown) according to the engine speed NE and the detected accelerator opening AP.

  On the other hand, when the answer to step 14 is YES and the timer value TM reaches the predetermined time TMREF, that is, when the predetermined time TMREF has elapsed from the start of the driving operation of the injector 4, the fuel injection by the injector 4 is terminated. As an example, the application of the battery voltage VB is terminated (step 15). Next, in steps 16 and 17, the battery voltage application flag F_VB and the fuel injection flag F_INJ are each reset to “0”, and this process ends. By executing step 17, the answer to step 6 becomes NO (F_INJ = 0). In this case, the present process is terminated.

  FIG. 6 shows an operation example obtained by the fuel injection control process described above. First, when the crank angle CA becomes equal to the fuel injection timing TINJ (step 1: YES), the capacitor voltage VC is applied to the coil 6b of the injector 4 (step 5), and overexcitation control is started. As a result, the voltage VI of the injector 4 (hereinafter referred to as “injector voltage”) VI increases, and an overexcitation current flows through the coil 6b, whereby the valve body 9 of the injector 4 begins to move toward the yoke 6a. During this overexcitation control, both the capacitor voltage VC and the injector voltage VI decrease, and in parallel with this, the seating determination process of the valve body 9 is executed (step 8).

  Thereafter, when the valve body 9 is seated on the yoke 6a via the armature 8 and the injector 4 reaches the valve open state, an inflection point PI appears in the waveform of the capacitor voltage VC from the above-described principle. The occurrence of the inflection point PI is determined in the seating determination process as described above, and the timing TOPEN at this time is determined as the valve opening timing at which the valve body 9 is seated on the yoke 6a (F_OPEN = 1). ). Immediately after the determination is made, the overexcitation control is terminated (step 10), and simultaneously, the holding control is started (step 13).

  Thereafter, when the predetermined time TMREF has elapsed from the start of the drive operation of the injector 4 (timing TINJE), the holding control is ended, whereby the injector 4 is closed and the fuel injection is ended.

  As described above, according to the present embodiment, during the overexcitation control, it is determined whether or not the inflection point PI appears in the waveform of the capacitor voltage VC by the seating determination process, and the inflection point PI is determined. The appearing timing TOPEN is determined as the valve opening timing at which the valve body 9 of the injector 4 is seated on the yoke 6a. Therefore, it is possible to appropriately determine the valve opening timing of the injector 4.

  Further, since the holding control is started simultaneously with the end of the overexcitation control at the timing when it is determined that the injector 4 is opened, the overexcitation control is changed to the holding control according to the timing when the injector 4 is actually opened. The transition can be done properly.

  Further, in order to perform the above determination, the voltmeter 30 that is usually provided for detecting the capacitor voltage VC is used as it is, while the conventional current detection circuit becomes unnecessary, so that the manufacturing cost can be reduced. Since the heat generation in the current detection circuit is eliminated, the heat generation amount can be reduced.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, the embodiment is an example in which overexcitation control is performed by applying the capacitor voltage VC to the injector 4, but the present invention is not limited to this, and the boosted capacitor voltage is applied to the coil of the fuel injection valve. As long as the fuel injection valve is opened, the present invention can be applied.

  In the embodiment, the determined seating / opening timing of the valve body 9 of the injector 4 is used to determine the transition timing from overexcitation control to holding control. However, the present invention is not limited to this, and the injector 4 It may be used for determining the valve closing timing, correcting the application time, and the like. In the former case, for example, the valve closing timing of the injector 4 is defined as the timing when the set time has elapsed since the valve was opened, and the set time is determined from the determined seating / opening timing of the actual valve element 9. When the time has elapsed, the injector 4 may be closed. Furthermore, the method of detecting (determining) the inflection point of the waveform of the capacitor voltage VC shown in the embodiment is merely an example, and it is needless to say that other appropriate methods may be adopted.

  Further, the embodiment is an example in which the present invention is applied to a direct injection gasoline engine for a vehicle. However, the present invention is not limited to this, and a port injection engine, a diesel engine, and a crankshaft are arranged vertically. The present invention can be applied to various industrial internal combustion engines such as a marine vessel propulsion engine such as an outboard motor. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

2 ECU (application means, inflection point detection means, valve opening timing determination means, injection valve control means)
3 Engine (Internal combustion engine)
4 Injector (fuel injection valve)
6a Yoke 6b Coil 8 Armature 9 Valve body 10 Drive circuit (applying means)
20 Booster circuit 23 Capacitor 25 Battery (Power supply)
30 Voltmeter (voltage detection means)
VB battery voltage (power supply voltage)
VC capacitor voltage (capacitor voltage)
PI inflection point

Claims (1)

The valve body is seated on the yoke through the armature by applying a voltage to the coil of the electromagnetic fuel injection valve having a yoke, a coil wound around the yoke, and a valve body integral with the armature. A fuel injection control device for an internal combustion engine that opens the fuel injection valve and injects fuel in a state;
A booster circuit for boosting the voltage of the power supply;
A capacitor charged with the boosted voltage;
Applying means for applying a voltage charged in the capacitor to the coil in order to open the fuel injection valve;
Voltage detecting means for detecting the voltage of the capacitor;
An inflection point detecting means for detecting an inflection point of the waveform of the voltage of the capacitor detected during application of the voltage to the coil;
Valve opening timing determination means for determining the timing at which the detected inflection point appears as the valve opening timing at which the valve element is seated on the yoke;
Injection valve control means for controlling the operation of the fuel injection valve according to the determined valve opening timing;
A fuel injection control device for an internal combustion engine, comprising:

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