JP2004100592A - Fuel injection control unit of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control unit of an internal combustion engine for appropriately avoiding the sticking of a nozzle in an injector and for avoiding the generation of circuit heat generation. <P>SOLUTION: A CPU 31 provided in an injector drive circuit 30 boosts the drive voltage of the injector 10 through a boosting circuit 32 when an engine is started, and stops the boosting of the drive voltage based on a change in the pattern of a command signal outputted from an ECU 20 for driving the injector 10. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control device applied to an internal combustion engine that performs boost drive control of an injector when the engine is started.
[0002]
[Prior art]
In recent years, in response to environmental problems, the adoption of internal combustion engines using compressed natural gas (CNG), which emits less air pollutants, as fuels, instead of conventional fuels such as gasoline, as fuels, It is being pursued in various fields.
[0003]
Such a CNG engine can be constructed with a configuration substantially common to a gasoline engine except for a fuel supply system such as a fuel tank, a fuel pipe, and an injector. Therefore, CNG engines are widely developed at low cost by diverting many components of existing gasoline engines. In addition, many of the existing electronic control devices for gasoline engines that are used as bases have been diverted to CNG engines.
[0004]
Here, in the gasoline engine, an electronic control unit (ECU) for engine control generates a command signal for injector drive control according to the operating state of the internal combustion engine based on detection signals of various sensors, and outputs the command signal. Output to the injector drive circuit. Then, based on the command, the injector drive circuit energizes an electromagnetic solenoid of the injector to open a nozzle so that a required amount of fuel can be injected, thereby performing fuel injection control.
[0005]
When such a gasoline engine ECU is used for a CNG engine, it is necessary to perform CNG injection based on a command signal of the ECU assuming gasoline injection. Therefore, it is necessary to provide the injector drive circuit with a function for converting the fuel injection time so that CNG injection equivalent to gasoline injection indicated by the command signal can be performed.
[0006]
By the way, in a CNG engine, a needle component of an injector may be stuck at a low temperature due to a tar component contained in the CNG itself or contained in a mechanical oil of a compressor mixed in the CNG when filling a fuel tank with gas. is there. In addition, the needle valve may be fixed due to freezing of moisture contained in methane gas, which is a main component of CNG, or moisture generated by combustion of CNG.
[0007]
Therefore, conventionally, as a fuel injection control device for such a CNG engine, there is known a fuel injection control device for executing a boost drive control of an injector at the time of engine start in order to eliminate such sticking of the needle valve, that is, sticking of the nozzle (for example, Patent Document 1). reference). The boost drive control increases the needle valve opening drive force by applying a higher voltage than usual to the electromagnetic solenoid and driving the injector when the engine starts to be at a low temperature, thereby eliminating the sticking. It is intended. Since such a boost drive control is a control that is not performed in a gasoline engine, an ECU designed for a gasoline engine does not deal with it.
[0008]
However, if the boost drive control can be independently performed only by the injector drive circuit, the fuel injection control device of the CNG engine configured by diverting the ECU for the gasoline engine can also perform the control. For that purpose, it is necessary to incorporate a booster circuit for increasing the drive voltage of the injector into the injector drive circuit. Also, it is necessary to input the detection signals of the sensors necessary for the start determination to the injector drive circuit, and to make the injector drive circuit independently determine whether or not the engine is being started in order to determine the execution period of the boost drive control. is there.
[0009]
In the fuel injection control device configured as described above, the fuel injection control at the time of starting the engine is performed in the following manner.
When the engine start is started, the ECU performs start control corresponding to the engine start. At this time, the ECU generates a command signal to execute fuel injection corresponding to engine start, that is, start injection, and outputs the command signal to the injector drive circuit. Further, the injector drive circuit generates a drive signal based on the input command signal and outputs the drive signal to the injector. At this time, the drive signal output from the injector drive circuit has a drive voltage higher than usual by the booster circuit.
[0010]
The electronic control unit determines the start of the internal combustion engine based on the detection signals of the various sensors, and switches the fuel injection control from the start injection to the normal injection when it is determined that the engine has been started. As a result, the command signal output to the injector drive circuit is also switched from the command signal corresponding to the start-up injection to the command signal corresponding to the normal injection in which the injection amount and the like are set according to the operating condition of the internal combustion engine. On the other hand, also in the injector drive circuit, the start determination of the internal combustion engine is performed based on the detection signals of the various sensors, and when it is determined that the engine startup is completed, the boosting of the drive signal by the booster circuit is stopped, and the injector The boost drive control ends.
[0011]
[Patent Document 1]
JP-A-2000-282905
[0012]
[Problems to be solved by the invention]
In the above-described fuel injection control device, the ECU and the injector drive circuit independently determine the start of the internal combustion engine. However, in such a case, for example, if noise is mixed in the detection signals of the sensors or the signal transmission is delayed on the electric circuit, it is determined between the ECU and the injector drive circuit that the engine start is completed. At the same time. Such a shift in the determination timing may cause the following inconvenience.
[0013]
If the ECU drive has already determined that the engine has been started, but the injector drive circuit has not yet completed the determination, the injector drive circuit may receive a command signal corresponding to the normal injection. Regardless, the boost drive control is performed. In the normal injection, the injection amount or the like is set according to the engine operating condition, so that the fuel injection request period per injection may be longer than the start injection time. In that case, the boost driving of the injector is performed continuously for a longer period than originally expected, and unexpected circuit heat generation is caused in the boost circuit, the electromagnetic solenoid of the injector, and the like.
[0014]
In this regard, in the above-described conventional fuel injection device, the number of times of fuel injection for boosting the injector is set in advance based on the state of the coolant temperature and the fuel pressure at the time of engine start. In this way, even if the engine start is prolonged, it is possible to prevent the prolonged period of the step-up drive control from being prolonged accordingly. Is reduced.
[0015]
However, such a setting of the number of times alone cannot fundamentally solve the problem of the circuit heat generated due to the difference in the determination timing as described above. That is, even if the number of fuel injections for performing the boosting drive is set in advance as described above, before the set number of injections is completed, the ECU determines that the engine has been started, and switches to the normal injection. If this is done, circuit heating as described above will occur.
[0016]
However, if the number of times of the fuel injection for performing the boosting drive is set to be small so that the boosting drive control is surely terminated before the completion of the engine start, such generation of the circuit heat can be certainly avoided. However, in this case, the boost drive control is discontinued during the start of the engine before the temperature is sufficiently increased, so that even if the sticking of the nozzle can be removed once, the freezing occurs again and the nozzle is restarted. This causes another problem such as sticking.
[0017]
Incidentally, such a problem is not limited to the case of the CNG engine developed based on the gasoline engine as described above, and the fuel injection control device is configured so that the injector drive circuit independently performs the boosting operation of the injector at the time of starting the engine. If so, it may occur similarly regardless of the internal combustion engine.
[0018]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fuel injection control device for an internal combustion engine that can prevent generation of circuit heat while appropriately suppressing nozzle sticking of an injector. To provide.
[0019]
[Means for Solving the Problems]
Hereinafter, the means for achieving the above object and the effects thereof will be described.
The invention according to claim 1 includes an injection command unit that outputs a command signal related to drive control of an injector based on an engine operating state, and an injector drive circuit that drives the injector based on the command signal. A fuel injection control device for an internal combustion engine that controls fuel injection of a fuel cell. The booster circuit boosts a drive voltage of the injector when the engine is started, and boosts the drive voltage by the booster circuit based on a change in a pattern of the command signal. And step-up drive stopping means for stopping the operation.
[0020]
In the above configuration, the injection command means outputs a command signal related to the drive control of the injector based on the engine operating state. Such a command signal also reflects a difference in the engine operating state between the engine starting state and the normal operating state after the completion of the engine starting. Therefore, the pattern of the command signal changes according to the determination made by the injection command means that the engine start has been completed.
[0021]
Therefore, in the above configuration, the boosting of the drive voltage by the booster circuit is stopped based on such a change in the pattern of the command signal. Thus, the boosting of the drive voltage can be stopped in conjunction with the result of the start determination of the injection command means. Therefore, it is possible to prevent the generation of circuit heat while appropriately suppressing the nozzle sticking of the injector.
[0022]
In addition, circuit heat generated by the booster circuit or the electromagnetic solenoid of the injector drives the injector continuously with the boosted drive voltage for a long time, that is, the fuel injection period per injection is prolonged while the drive voltage is boosted. Occurs according to. On the other hand, in the above configuration, whether or not the boosting of the drive voltage is stopped is determined based on the pattern of the command signal indicating the fuel injection request period, so that it is possible to accurately avoid the generation of circuit heat.
[0023]
According to a second aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the first aspect, the step-up drive suspending unit is configured to output a command signal output from the injection command unit when the engine signal is started when the pattern of the command signal is started. The boosting of the drive voltage is stopped when the pattern changes to a pattern different from the above pattern.
[0024]
In the above configuration, when the pattern of the command signal output from the injection command unit changes to a pattern different from the pattern of the command signal output when starting the engine, the boosting of the drive voltage is stopped. Therefore, the boosting of the drive voltage can be more accurately stopped in accordance with the completion of the engine start.
[0025]
According to a third aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the first or second aspect, the step-up driving stop unit is configured to perform a step based on a change in a fuel injection request period indicated by the command signal. The boosting of the driving voltage is stopped.
[0026]
When the engine startup is completed and the engine is brought into the normal operation state, a different amount of fuel injection is required than during the previous engine startup, and a change may occur in the fuel injection request period indicated by the command signal. In the above configuration, the stop determination of the drive voltage boosting is performed by paying attention to the change in the fuel injection request period instructed by the command signal, so that the stop determination of the drive voltage is more easily and appropriately performed. be able to.
[0027]
According to a fourth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the third aspect, the boosting drive stopping means changes a fuel injection request period indicated by the command signal to a predetermined value or more. The boosting of the drive voltage is sometimes stopped.
[0028]
As described above, circuit heat generation of the booster circuit and the electromagnetic solenoid of the injector occurs as the fuel injection period per injection becomes longer while the drive voltage is being boosted. Therefore, as described above, if the boosting of the drive voltage is stopped on the condition that the fuel injection request period indicated by the command signal has changed to a predetermined value or more, the generation of circuit heat is more accurately avoided. can do.
[0029]
According to a fifth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to any one of the first to fourth aspects, the step-up drive stopping means further includes a detection signal from sensors for detecting an engine operating state. The start of the internal combustion engine is then determined, and the boosting of the drive voltage is also stopped when it is determined that the engine has been started.
[0030]
In the above-described configuration, the stop determination based on the change in the pattern of the command signal and the stop determination based on the start determination of the internal combustion engine are both determined to stop the drive voltage boosting. Therefore, it is possible to more easily and appropriately determine whether to stop the boosting of the drive voltage.
[0031]
According to a sixth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to any one of the first to fifth aspects, the injection command means supplies a fuel different from the fuel actually injected from the injector. Outputting a command signal for the injector to be injected, wherein the injector drive circuit drives the injector by converting the command signal for fuel actually injected from the injector; It is characterized by.
[0032]
When an internal combustion engine using a different fuel from the existing internal combustion engine is developed, the above configuration may be adopted. In such a configuration, the existing internal combustion engine serving as a base often does not support the boosting of the driving voltage of the injector, and circuit heat generation accompanying the boosting of the driving voltage is likely to occur. Therefore, by applying the fuel injection device for an internal combustion engine described in each of the above claims, more remarkable effects can be obtained. Further, in the above-described configuration, the drive voltage of the injector can be appropriately increased.
[0033]
According to a seventh aspect of the present invention, in the fuel injection control device for an internal combustion engine according to any one of the first to sixth aspects, the internal combustion engine uses a gaseous fuel as a fuel.
[0034]
In an internal combustion engine using a gaseous fuel, the nozzle of the injector is likely to be stuck due to cooling by the heat of vaporization of the fuel accompanying fuel injection from the injector. Therefore, the fuel injection control device for an internal combustion engine according to the above claims is applied. Thereby, a more remarkable effect can be obtained.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment in which the present invention is embodied as a fuel injection control device for a CNG engine will be described in detail with reference to FIG. The CNG engine to which the fuel injection control device according to the present embodiment is applied has been developed based on a gasoline engine, and many of the components of the CNG engine are those of the base gasoline engine.
[0036]
First, the structure of an injector 10 to be controlled by the fuel injection control device according to this embodiment will be described with reference to FIG.
The injector 10 includes a fuel chamber 11, an injection port 12, a needle valve 13, and an electromagnetic solenoid 15. The fuel chamber 11 is formed inside the injector 10 so that pressurized fuel flows from the outside. The fuel chamber 11 can communicate with an injection port 12 formed at the tip of the injector 10 via a nozzle 14.
[0037]
The communication between the fuel chamber 11 and the injection port 12 is allowed or blocked according to the drive of the needle valve 13. The needle valve 13 is urged by a spring 16 to a side that blocks communication between the fuel chamber 11 and the injection port 12. On the other hand, the electromagnetic solenoid 15 generates an electromagnetic attraction force that drives the needle valve 13 to a side that allows communication between the fuel chamber 11 and the injection port 12 against the urging force of the spring 16 in response to the application of the voltage. appear.
[0038]
Therefore, in the injector 10, when a voltage is applied to the electromagnetic solenoid 15, the needle valve 13 is driven, and the fuel flowing into the fuel chamber 11 is injected from the injection port 12 through the nozzle 14. Here, the voltage applied to the electromagnetic solenoid 15 when the injector 10 is driven to open the valve is referred to as “drive voltage”. Incidentally, the valve-opening driving force of the needle valve 13 increases as the driving voltage applied to the electromagnetic solenoid 15 increases.
[0039]
Next, a configuration of the fuel injection control device according to the present embodiment will be described with reference to FIG. As shown in FIG. 2, a fuel injection control device according to the present embodiment includes an electronic control unit (ECU) 20 for executing various controls of an internal combustion engine, and an injector 10 based on a command signal output from the ECU 20. And an injector drive circuit 30 for driving the power supply. Incidentally, in this fuel injection control device, the ECU 20 of the gasoline engine as the base is diverted.
[0040]
The ECU 20 receives, for example, detection signals of various sensors for detecting the operating state of the engine, such as a starter switch 21 for detecting whether or not the starter motor is operating and a rotation speed sensor 22 for detecting the engine rotation speed. Further, the ECU 20 generates an NE signal that outputs a pulse every time the engine output shaft rotates by a predetermined angle based on the detection signal of the rotation speed sensor 22. The ECU 20 uses this NE signal for its own engine control and also outputs it to the injector drive circuit 30. The detection signal of the starter switch 21, that is, the starter signal is also input to the injector drive circuit 30.
[0041]
The ECU 20 calculates the fuel injection start timing and the required injection amount according to the engine operating state based on the detection signals of the sensors. The ECU 20 generates a command signal based on the calculation result, and outputs the command signal to the injector drive circuit 30. Therefore, in the present embodiment, the ECU 20 is configured to correspond to the above-mentioned injection command means.
[0042]
This command signal is set to “ON” at the time when fuel injection is started from the injector, and thereafter, is set so as to be kept “ON” during a period in which the required amount of fuel can be injected from the injector. . That is, the period during which the command signal is “on” is a fuel injection request period set to satisfy the required injection amount.
[0043]
On the other hand, the injector drive circuit 30 includes a central processing unit (CPU) 31 that performs various processes related to driving of the injector 10, and a booster circuit 32 that boosts a drive voltage applied to the injector 10. I have. The injector drive circuit 30 is connected to the injector 10 of each cylinder via a power supply line.
[0044]
The CPU 31 of the injector drive circuit 30 generates a drive signal for the injector 10 based on a command signal input from the ECU 20. However, the command signal generated by the ECU 20 assumes a gasoline engine as a base. Therefore, when generating the drive signal, the CPU 31 adjusts the fuel injection request period in accordance with the amount of heat generated per unit mass of the injected fuel and the injectors 10 of the CNG engine having different injection characteristics. That is, when generating the drive signal for the injector 10, the CPU 31 adjusts the injection request period so that CNG injection equivalent to gasoline injection during the injection request period indicated by the command signal of the ECU 20 is possible.
[0045]
Here, the drive signal generated by the CPU 31 is maintained at the supply voltage E of the battery 40 during the period when the fuel is actually injected from the injector 10. This drive signal is output to the corresponding injector 10 through the booster circuit 32. The booster circuit 32 boosts the voltage level of the drive signal, that is, the drive voltage of the injector 10 as necessary.
[0046]
Through the processing of the ECU 20 and the injector drive circuit 30 as described above, a drive voltage is applied to the electromagnetic solenoid 15 of each injector 10 at a required time and for a required period, and fuel injection is performed.
[0047]
In the fuel injection control device according to the present embodiment, in order to eliminate the nozzle sticking as described above, the injector 10 is driven to increase the pressure when the engine is started. The boosting drive is performed by boosting the voltage level of the drive signal generated by the CPU 31 of the injector drive circuit 30 by a predetermined value Δ in the booster circuit 32 and outputting the boosted voltage to the injector 10.
[0048]
The drive signal to the injector 10 at the time of boost driving is formed through a process as illustrated in FIG. That is, for example, when a command signal as shown in FIG. 2A is input from the ECU 20, the CPU 31 of the injector drive circuit 30 adjusts the fuel injection request period indicated by the command signal for CNG injection. A drive signal (see FIG. 3B) is generated. In this example, the drive signal is set so that the injection request period is longer than the period instructed by the command signal from the ECU 20.
[0049]
The drive signal thus generated by the CPU 31 is input to the booster circuit 32, where the drive signal is boosted and then output to the injector 10. As a result, a drive signal having a higher drive voltage as shown in FIG. Therefore, the electromagnetic attraction generated by the electromagnetic solenoid 15 increases, and the driving force for opening the needle valve 13 during fuel injection increases.
[0050]
Note that, other than during the boost driving, the boost signal of the boost circuit 32 is not performed, and the drive signal generated by the CPU 31 as shown in FIG.
[0051]
On the other hand, at the time of starting the engine in which the boost driving of the injector 10 is performed, the ECU 20 performs a process related to fuel injection in the following manner. FIG. 4 shows a flow of a process related to fuel injection of the ECU 20 from the start of the engine start to the end thereof.
[0052]
After the starter switch 21 is turned on to start the engine and the engine is started, the ECU 20 starts the fuel injection in the “start mode” when the engine speed is higher than the predetermined value α (S100: YES) (S110). ). In the start mode, the required injection amount is basically calculated based only on the temperature of the engine cooling water. Specifically, the ECU 20 sets the required injection amount to be larger as the temperature of the engine cooling water is lower, and to set the required injection amount to be smaller as the temperature of the engine cooling water is higher.
[0053]
During execution of the fuel injection in such a start mode, the ECU 20 makes a start determination based on the starter signal and the engine speed (S120). Specifically, when both (condition A) and (condition B) below are satisfied, it is determined that the engine is being started, and at least one of the (condition A) and (condition B) is not satisfied. , It is determined that the engine start has been completed.
(Condition A) The starter switch 21 is turned on.
(Condition B) The engine rotation speed is lower than a predetermined rotation speed β (for example, 400 rpm).
[0054]
Note that the completion of the engine start here includes a case where the internal combustion engine shifts to a complete explosion state and becomes capable of autonomous operation, and a case where the engine start is interrupted before reaching the complete explosion state.
[0055]
The ECU 20 continues the fuel injection in the start mode as long as the start determination condition is satisfied and it is determined that the engine is being started (S120: YES). If the conditions for the start determination are no longer satisfied and it is determined that the engine is not being started (S120: NO), the ECU 20 stops fuel injection in the start mode and shifts to fuel injection in the "normal mode". (S130). In the normal mode, the required injection amount is calculated based on a number of parameters relating to the engine operating state, such as the engine speed and the amount of depression of the accelerator pedal. As described above, the ECU 20 ends the fuel injection control at the time of starting, and shifts to the normal fuel injection control.
[0056]
As described above, the ECU 20 executes the fuel injection in the start mode during the engine start and in the normal mode after the start is completed. In both of these modes, the calculation of the required injection amount is performed in a greatly different manner as described above. Therefore, the pattern of the command signal output from the ECU 20 changes between when the ECU 20 determines that the engine is still being started and after it is determined that the engine has been started.
[0057]
FIG. 5 shows an example of a command signal pattern in such a start mode and a normal mode. In the start mode, the required injection amount is calculated based only on the temperature of the engine cooling water, so that the change in the required injection amount is small. Further, since a large amount of fuel is not required for starting the engine, the required injection amount in the starting mode is set to be relatively small. On the other hand, after the start is completed, it is necessary to greatly change the required injection amount according to the operating condition. Therefore, a command signal having a shorter injection request period as shown in FIG. 6B is output as compared to a command signal in the start mode as exemplified in FIG. ) May be output as a command signal having a long injection request period.
[0058]
On the other hand, in parallel with the start-time fuel injection control of the ECU 20, the CPU 31 of the injector drive circuit 30 performs the boost drive control. This boost drive control is performed in the following manner.
[0059]
The CPU 31 drives the injector 10 to step-up from the start of the engine start. Then, the CPU 31 itself makes a start determination similar to that of the ECU 20 based on the starter signal and the engine rotation speed, and stops boosting drive when it is determined that the engine start is completed based on the determination result.
[0060]
Further, in the present embodiment, the CPU 31 continues or stops the boosting drive based on the change in the pattern of the command signal input from the ECU 20 during the engine start and after the completion of the engine start as described above. Is determined. More specifically, the CPU 31 stops the boost drive of the injector 10 even when a command signal indicating an injection request period that exceeds the upper limit of the set range of the fuel injection period in the start mode is input from the ECU 20.
[0061]
More specifically, the CPU 31 stops the boost driving of the injector 10 when the fuel injection request period indicated by the command signal input from the ECU 20 becomes equal to or longer than the limit period γ shown in FIG. I have. The limit period γ is longer than the upper limit of the setting range of the injection request period in the start mode, and is a period that does not cause the generation of circuit heat as described above, that is, the lower limit of the injection request period in which circuit heat generation may occur. It is set to a shorter period. Therefore, if the injection request period indicated by the command signal from the ECU 20 is equal to or longer than the limit period γ, the transition of the fuel injection control from the start mode to the normal mode has already been performed, and the ECU 20 has completed the engine start. It can be determined that the determination has been made.
[0062]
In the present embodiment, even if there is a discrepancy in the start determination result between the ECU 20 and the injector drive circuit 30, the injector drive circuit 30 determines the start determination result of the ECU 20 based on the command signal from the ECU 20. , The step-up drive can be stopped. Further, when a command signal for instructing a long injection request period that causes generation of circuit heat is input from the ECU 20, the boost driving is stopped. Therefore, generation of circuit heat is reliably avoided.
[0063]
FIG. 6 shows a flow of processing from the start of the engine start of the CPU 31 to the stop of the boosting drive. As shown in FIG. 6, the CPU 31 instructs the booster circuit 32 to boost the drive signal from the start of the engine start (S200), and drives the injector 10 to boost the pressure.
[0064]
During the execution of the boosting drive, the CPU 31 performs the same start determination as the ECU 20 based on the starter signal and the engine speed (S210). That is, if both (condition A) and (condition B) are satisfied, the CPU 31 determines that the engine is being started. Then, as a result, when it is determined that the engine start has been completed (S210: NO), the boost driving is stopped (S230).
[0065]
Further, when it is determined that the engine is being started (S210: YES), the CPU 31 determines whether the fuel injection request period indicated by the command signal input from the ECU 20 is equal to or longer than the limit period γ. Is performed (S220). Here, when it is determined that the injection request period is less than the limit period γ (S220: NO), the CPU 31 continues the boost driving as it is.
[0066]
On the other hand, as a result of the determination, when it is determined that the injection request period is equal to or longer than the limit period γ (S220: YES), the boost drive is forcibly stopped even if it is not determined that the engine start has been completed (S220). S230). Note that, in the present embodiment, each processing of steps S210 to S230 by the CPU 31 corresponds to the processing of the boost driving stop unit.
[0067]
According to the embodiment described above, the following effects can be obtained.
(1) In the present embodiment, the CPU 31 of the injector drive circuit 30 determines that the engine start has been completed when the fuel injection request period indicated by the command signal output from the ECU 20 has exceeded the limit period γ. The boost drive is stopped. Therefore, even if there is a time difference between when the ECU 20 and the CPU 31 determine the completion of the engine start, it is possible to preferably suppress the circuit heat generation. Therefore, it is possible to prevent the generation of circuit heat while appropriately suppressing the nozzle sticking of the injector.
[0068]
(2) In the present embodiment, the CPU 31 of the injector drive circuit 30 makes a start determination based on the starter signal and the engine speed, and performs boosting drive also when it is determined that the engine has been started based on the determination result. I have been canceled. Therefore, after the completion of the start of the engine, the boost driving can be stopped more accurately.
[0069]
(3) In the present embodiment, in the fuel injection control device for the CNG engine constructed by diverting the ECU 20 for the gasoline engine, the above-described determination of the stop of the boosting drive is performed. This makes it possible to realize a suitable fuel injection control device capable of avoiding generation of circuit heat even when the ECU 20 for a gasoline engine which is not adapted to the boosting drive of the injector 10 is used.
[0070]
The above embodiment can be modified as follows.
In the above embodiment, the ECU 20 and the CPU 31 determine the start based on the starter signal and the engine speed, but the mode of the start determination may be appropriately changed.
[0071]
In the above embodiment, the boost driving of the injector 10 is stopped on condition that the injection request period indicated by the command signal of the ECU 20 is equal to or longer than the limit period γ. May be changed as follows. For example, when the lower limit exists in the range of the injection request period specified in the start mode, even when the injection request period specified by the command signal from the ECU 20 becomes shorter than the lower limit, the ECU 20 completes the engine start. It can be determined that the determination has been made. Therefore, even in such a case, the step-up driving may be stopped. Also in this case, the boosting drive can be suitably stopped while avoiding circuit heat generation as in the above embodiment.
[0072]
In addition to the injection request period, if there is a change in the pattern of the command signal of the ECU 20 between when it is determined that the engine is starting and after it is determined that the engine has been completed, such an injection request period The step-up driving may be stopped according to a change in a pattern other than the above. For example, in some internal combustion engines, the injection pattern is changed between during the engine start and after the engine start is completed, such as performing split injection during the engine start and performing batch injection after the engine start is completed. In such a case, even if the stoppage of the boosting drive is determined based on a change in the injection pattern instructed by the command signal, the boosting drive is suitably stopped while avoiding circuit heat generation as in the above embodiment. Can be done.
[0073]
In the above-described embodiment, the CPU 31 performs the same start determination as the ECU 20, and when it is determined that the engine start is completed, the boost driving of the injector 10 is stopped. The judgment is arbitrary. That is, the boost driving of the injector 10 may be stopped based only on the pattern of the command signal output from the ECU 20 as described above. In this case as well, the ECU 20 determines that the engine has been started, and if there is a change in the pattern of the command signal, the boosting drive is stopped. Therefore, it is possible to sufficiently suppress circuit heat generation.
[0074]
In the above embodiment, the injector drive circuit 30 and the ECU 20 are configured separately, but the injector drive circuit 30 may be incorporated in the ECU 20.
[0075]
In the above-described embodiment, an example of application to a CNG engine developed based on a gasoline engine has been described. However, the present invention is not limited to a configuration in which the injector drive circuit independently performs an injector boosting drive at the time of engine start. Can be applied to the internal combustion engine. Incidentally, in an internal combustion engine using a gaseous fuel as a fuel, nozzle sticking of the injector tends to occur at a low temperature, and therefore, the present invention is particularly suitable for application to an internal combustion engine using such a gaseous fuel.
[Brief description of the drawings]
FIG. 1 is a sectional view of an injector used in one embodiment of the present invention.
FIG. 2 is a block diagram showing a schematic configuration of the embodiment.
FIG. 3 is a time chart showing an example of an output mode of various signals during boost driving according to the embodiment;
FIG. 4 is a flowchart of start-time fuel injection control of the embodiment.
FIG. 5 is a time chart showing an example of an output mode of a command signal according to the embodiment;
FIG. 6 is a flowchart of boost drive control according to the embodiment;
[Explanation of symbols]
Reference Signs List 10 injector, 11 fuel chamber, 12 injection port, 13 needle valve, 14 nozzle, 15 electromagnetic solenoid, 16 spring, 20 electronic control unit (ECU), 21 starter switch, 22 Rotation speed sensor, 30: injector drive circuit, 31: central processing unit (CPU), 32: boost circuit.

Claims (7)

Injection command means for outputting a command signal related to drive control of the injector based on the engine operating state, and an injector drive circuit for driving the injector based on the command signal, for controlling the fuel injection from the injector. In the fuel injection control device,
A booster circuit that boosts the drive voltage of the injector at the time of engine start;
Boost drive stopping means for stopping boosting of the drive voltage by the boost circuit based on a change in the pattern of the command signal;
A fuel injection control device for an internal combustion engine, comprising: 2. The boosting drive stopping means stops the boosting of the drive voltage when the pattern of the command signal changes to a pattern different from the pattern of the command signal output from the injection command means at engine start. A fuel injection control device for an internal combustion engine. 3. The fuel injection control device for an internal combustion engine according to claim 1, wherein the boost driving stop unit stops boosting the drive voltage based on a change in a fuel injection request period instructed by the command signal. 4. 4. The fuel injection control device for an internal combustion engine according to claim 3, wherein the boost drive stop unit stops boosting the drive voltage when a fuel injection request period indicated by the command signal changes to a predetermined value or more. 5. The boost drive stopping means further performs a start determination of the internal combustion engine based on a detection signal of a sensor that detects an engine operating state, and stops boosting the drive voltage also when it is determined that the engine start is completed. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 4, wherein: The injection command means outputs a command signal for an injector that injects a fuel different from the fuel actually injected from the injector, and the injector drive circuit outputs the command signal to the injector. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 5, wherein the injector is driven by converting the fuel into fuel actually injected from the engine. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 6, wherein the internal combustion engine uses a gaseous fuel as a fuel.

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