JP2015200208A - Internal combustion engine fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine fuel injection control device capable of appropriately suppressing heat generation of a control circuit controlling a fuel injection valve to be driven and appropriately injecting a fuel a plurality of times in a case of injecting the fuel a plurality of times per combustion cycle.SOLUTION: An internal combustion engine fuel injection control device according to the present invention sets an upper limit value of the number of times of injection NFLMT for limiting the number of times of injection of a fuel of a fuel injection valve 4 per combustion cycle to a smaller value if the number of revolutions of an engine NE is higher based on a result of comparison of the detected number of revolutions of the engine NE to a predetermined reference number of revolutions NEREF (FIGS. 4 and 5). Furthermore, the fuel injection control device increases a reduction in the reference number of revolutions NEREF if a detected ECU temperature TECU is higher and sets a higher degree of the reduction in the reference number of revolutions NEREF if the number of revolutions of the engine NE is higher (FIG. 5).

Description

  The present invention provides a fuel injection control for an internal combustion engine that directly injects fuel multiple times per combustion cycle from a fuel injection valve into a cylinder by boosting the voltage of a battery with a control circuit and applying it to the fuel injection valve. Relates to the device.

  Conventionally, in a direct injection type internal combustion engine in which fuel is directly injected into a cylinder from a fuel injection valve, the fuel is injected in a plurality of times per combustion cycle in order to improve exhaust gas characteristics and suppress combustion noise. A technique for performing multiple injections is known. A drive circuit for driving the fuel injection valve is usually provided in a control circuit for controlling the internal combustion engine, and has a capacitor, a plurality of transistors, and the like for boosting the voltage of the battery and applying it to the fuel injection valve. These elements act as heating elements. For this reason, when the number of fuel injections per combustion cycle increases, the amount of heat generated by these heating elements increases, and as a result, the temperature of the control circuit including the drive circuit rises excessively, resulting in malfunction of the control circuit. There is a risk of reducing the service life.

  For example, Patent Document 1 discloses a conventional fuel injection control device for avoiding such a problem. In this fuel injection control device, the temperature of the drive circuit that drives the fuel injection valve is detected, and when the detected temperature of the drive circuit exceeds a predetermined temperature and the temperature of the drive circuit is increased, the fuel injection control device performs a plurality of times. The injection amount of a part of the injections is reduced. As a result, the amount of heat generated by the drive circuit is suppressed, and the above-mentioned problems are avoided.

JP 2005-201091 A

  In the above-described conventional fuel injection control apparatus, when the temperature of the drive circuit that drives the fuel injection valve is high, a part of the injection quantity among the multiple injections is reduced. For this reason, although the effect of suppressing the heat_generation | fever of a control circuit is acquired, depending on the driving | running state of an internal combustion engine, there exists a problem that multiple injection cannot necessarily be performed favorably.

  For example, when the internal combustion engine is a direct injection type, unlike the case of port injection in which fuel is injected into the intake port, the period during which fuel can be effectively injected in one combustion cycle is originally limited to the compression stroke or the like. Further, in the high speed region of the internal combustion engine, the effective injection time becomes shorter because the time of one combustion cycle becomes shorter as the rotational speed becomes higher. For this reason, when multiple injections are performed in the high rotation region, boosting and application of the battery voltage for driving the fuel injection valve is repeated a number of times equal to the number of injections within such a limited short time. Need to do.

  On the other hand, in the conventional fuel injection control device, since only a part of the injection quantity of the multiple injections is reduced according to the temperature of the drive circuit, the multiple injections are favorably performed within a limited short time. There are things you can't do. In that case, the required output torque of the internal combustion engine cannot be obtained due to a shortage of fuel injection amount or a delay in fuel injection timing, etc., while improving the exhaust gas characteristics and suppressing combustion noise, which are the original purposes of multiple injections Etc. cannot be achieved sufficiently.

  The present invention has been made to solve such a problem, and in the case of injecting the fuel a plurality of times per combustion cycle, the heat generation of the control circuit that controls the drive of the fuel injection valve can be appropriately suppressed. In addition, an object of the present invention is to provide a fuel injection control device for an internal combustion engine that can perform injections a plurality of times.

  In order to achieve the above object, according to the first aspect of the present invention, the voltage VBAT of the battery 5 is boosted by the control circuit (ECU 2 in the embodiment (hereinafter the same in this section)) and applied to the fuel injection valve 4. The fuel injection control device for the internal combustion engine 3 in which fuel is directly injected into the cylinder 3a from the fuel injection valve 4 and the fuel injection is performed a plurality of times per combustion cycle. Rotational speed detection means (crank angle sensor 21) for detecting the number NE (engine rotational speed NE), temperature acquisition means (ECU temperature sensor 24) for acquiring the temperature of the control circuit (ECU temperature TECU), and detected internal combustion The number of injections for limiting the number of fuel injections of the fuel injection valve 4 per combustion cycle based on the comparison result between the rotational speed NE of the engine 3 and a predetermined reference rotational speed NEREF The injection number upper limit value setting means (ECU 2, step 1 in FIG. 3, FIG. 4) for setting the limit value NFLMT to a smaller value as the rotational speed NE of the internal combustion engine 3 is higher, and the acquired temperature of the control circuit The reference speed setting means (ECU2, FIG. 2) sets the reference speed NEREF so that the higher the speed, the lower the reference speed NEREF and the greater the degree of reduction of the reference speed NEREF, the higher the speed NE of the internal combustion engine 3. 4 to 7).

  This internal combustion engine is a so-called direct injection type in which fuel is directly injected into a cylinder from a fuel injection valve, and a plurality of injections in which fuel is injected a plurality of times per combustion cycle are executed. In this fuel injection control device, the rotational speed of the internal combustion engine is detected, and the temperature of the control circuit that boosts and applies the voltage of the battery to drive the fuel injection valve is acquired. Then, based on the comparison result between the detected rotational speed of the internal combustion engine and a predetermined reference rotational speed, the upper limit of the number of injections for limiting the number of fuel injections per combustion cycle is set to a higher rotational speed of the internal combustion engine. The smaller the value is set.

  As a result, when the rotational speed of the internal combustion engine is high, the upper limit value of the number of injections is set to a smaller value, so that the number of fuel injections is limited to a smaller number. As the time becomes longer, the battery voltage for each injection can be boosted and applied with a time margin. As a result, by ensuring an appropriate fuel injection amount and fuel injection timing in each injection, a plurality of injections can be performed satisfactorily. Therefore, required output torque of the internal combustion engine can be ensured, and effects such as improvement of exhaust gas characteristics and suppression of combustion noise by multiple injections can be effectively obtained.

  Further, according to this fuel injection control device, the reference rotational speed to be compared with the rotational speed of the internal combustion engine is further reduced as the acquired temperature of the control circuit is higher, and the degree of reduction of the reference rotational speed is reduced. The higher the number of revolutions of the internal combustion engine, the greater the setting. Thereby, when the temperature of the control circuit is high, the number of injections is further limited as the reference rotational speed is set to a smaller value. Accordingly, the number of times of boosting and applying the battery voltage by the control circuit is reduced, so that the heat generation of the control circuit can be appropriately suppressed, and malfunction and life reduction due to overheating of the control circuit can be avoided.

  The invention according to claim 2 is the fuel injection control device for the internal combustion engine 3 according to claim 1, further comprising voltage detection means (battery voltage sensor 23) for detecting the voltage VBAT of the battery 5, and reference rotational speed setting means. Is such that the lower the detected voltage VBAT of the battery 5, the lower the reference rotational speed NEREF, and the higher the rotational speed NE of the internal combustion engine 3, the greater the degree of reduction of the reference rotational speed NEREF. It is characterized by setting (FIG. 6).

  When the voltage of the battery decreases, it becomes difficult to boost the voltage sufficiently in a short time, so the operation of the fuel injection valve tends to become unstable. This tendency increases because the application is repeated many times within a short time. According to this configuration, the lower the detected battery voltage, the lower the reference rotational speed, and the lower the rotational speed of the internal combustion engine, the higher the rotational speed of the internal combustion engine. .

  As a result, when the battery voltage is low, the number of injections is further limited as the reference rotational speed is set to a smaller value. Accordingly, the time allotted for one injection becomes longer, and the time necessary for boosting the battery voltage is secured in each injection, whereby the battery voltage can be sufficiently boosted. As a result, the operation of the fuel injection valve can be stabilized, and multiple injections can be performed more satisfactorily.

  According to a third aspect of the present invention, in the fuel injection control device for the internal combustion engine 3 according to the second aspect, the reference rotational speed setting means is configured such that the voltage VBAT of the battery 5 is a predetermined voltage (minimum voltage) indicating a state where the battery 5 has deteriorated The reference rotational speed NEREF is set to a predetermined minimum rotational speed (predetermined values N45 to N12) regardless of the temperature of the control circuit (FIG. 7).

  According to this configuration, when the battery voltage drops to a predetermined voltage representing a state where the battery has deteriorated, the reference rotational speed is set to a predetermined minimum rotational speed. As a result, the number of times of fuel injection is most severely limited, so that the operation of the fuel injection valve can be stabilized as much as possible, and a deteriorated battery can be protected appropriately.

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. It is a circuit diagram which shows the structure of the drive circuit of ECU which drives a fuel injection valve. It is a flowchart which shows a fuel-injection control process. It is an example of the map for calculating the injection frequency upper limit. It is a figure which shows the reference | standard rotation speed set when a battery voltage is the maximum voltage. It is a figure which shows the reference | standard rotation speed set when a battery voltage is an intermediate | middle predetermined voltage. It is a figure which shows the reference | standard rotation speed set when a battery voltage is the minimum voltage.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, an internal combustion engine (hereinafter referred to as “engine”) 3 to which the present invention is applied is a diesel engine that is mounted on, for example, a vehicle (not shown) and has four cylinders 3a. Each cylinder 3a is provided with a fuel injection valve (hereinafter referred to as “injector”) 4 so as to face a combustion chamber (not shown), and the injector 4 directly injects fuel into the combustion chamber.

  Each injector 4 is electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 2 and is driven by a drive signal from the ECU 2 as will be described later. The fuel injection amount is determined by the valve opening time and valve opening timing. And the fuel injection timing are respectively controlled.

  A battery 5 is connected to the ECU 2, and electric power for operating the ECU 2 and electric power for driving the injector 4 are supplied from the battery 5.

  FIG. 2 shows a drive circuit 6 for driving the injector 4 in the ECU 2. In this figure, solenoids L1 to L4 correspond to the solenoids of four injectors 4 provided for each cylinder 3a. Moreover, in the same figure, the same code | symbol is attached | subjected to the component which has the same function except L1-L4.

  The drive circuit 6 has a booster circuit 6a for boosting the voltage of the battery 5 (hereinafter referred to as “battery voltage”) VBAT. The booster circuit 6a includes a solenoid L0, a diode D0, a field effect transistor (hereinafter referred to as “FET”) Q0 as a switching element, a resistor R0, and a capacitor C0.

  The drain of the FET Q0 is connected to the output side of the solenoid L connected to the output terminal PVBAT of the battery 5, and the source is connected to the resistor R0. The diode D0 is connected between the solenoid L0 and the drain of the FET Q0 and is connected to the input side of the capacitor C0.

  In the booster circuit 6a configured as described above, when a switching signal is supplied from the CPU (not shown) of the ECU 2 to the gate of the FET Q0, the FET Q0 is turned on, whereby the battery voltage VBAT is applied to the solenoid L0, Energy is stored. When the FET Q0 is turned off from this state, the electric energy stored in the solenoid L0 is supplied to and stored in the capacitor C0 via the diode D0, thereby boosting the voltage. The voltage across the capacitor C0 at this time becomes the boosted voltage VBST which is the output voltage of the booster circuit 6a.

  The output terminal PVBST of the booster circuit 6a is connected to one end of each of the solenoids L1 to L4 via the FET Q1. An output terminal PVBAT of the battery 5 is further connected to one end of these solenoids L1 to L4 via an FET Q2 and a diode D1, respectively.

  An FET Q3 for controlling valve opening / closing of the injector 4 is connected between the other ends of the solenoids L1 to L4 and the ground. A Zener diode D3 is connected between the gate and drain of the FET Q3, and a resistor R3 is connected between the gate and source.

  From the above configuration, when the injector 4 is opened, the corresponding FET Q1 and FET Q3 are turned on by a switching signal from the CPU. As a result, the boosted voltage VBST is applied to the corresponding one of the solenoids L1 to L4 from the output terminal PVBST of the booster circuit 6a, and the injector 4 is opened by supplying a large drive current IDD to the solenoid. .

  Thereafter, the FET Q1 is turned off and the FET Q2 is turned on from this state. Thereby, the battery voltage VBAT is applied to the solenoid from the output terminal PVBAT of the battery 5, and the small drive current IDD is supplied to the solenoid, whereby the injector 4 is held in the valve open state.

  Further, when the FET Q2 and the FET Q3 are turned OFF from this state, the supply of the drive current IDD to the solenoid is stopped, and the injector 4 is closed.

  As shown in FIG. 1, a CRK signal and a TDC signal, which are pulse signals, are input from the crank angle sensor 21 to the ECU 2. The CRK signal is input 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.

  Further, the TDC signal is a signal indicating that in any one of the cylinders 3a, the piston (not shown) of the engine 3 is at a predetermined crank angle position slightly before the top dead center at the start of the intake stroke. is there. Therefore, when the engine 3 has four cylinders as in the present embodiment, a TDC signal is output at every crank angle of 180 °.

  Further, the ECU 2 receives from the accelerator opening sensor 22 a detection signal representing an operation amount (hereinafter referred to as “accelerator opening”) AP of an accelerator pedal (not shown) of the vehicle from the battery voltage sensor 23 to the battery voltage VBAT. A detection signal indicating the temperature of the ECU 2 near the drive circuit 6 (hereinafter referred to as “ECU temperature”) TECU is input from the ECU temperature sensor 24.

  The ECU 2 includes a microcomputer having a RAM, a ROM, an I / O interface (all not shown) and the like in addition to the CPU and the drive circuit 6 described above. The ECU 2 calculates the number of times of fuel injection by the injector 4, the fuel injection amount, and the fuel injection timing in accordance with the detection signals of the various sensors 21 to 24 described above, and outputs a drive signal based on the calculation results to the FETs Q0 to Q3. To control the operation of the injector 4. In the present embodiment, the ECU 2 corresponds to an injection number upper limit setting unit and a reference rotation number setting unit.

  FIG. 3 shows an injection frequency limiting process for limiting the injection frequency of the injector 4, which is executed by the ECU 2. This process is executed for each injector 4 in synchronization with the input of the TDC signal. In this process, first, in step 1 (illustrated as “S1”, the same applies hereinafter), a predetermined map is searched according to the detected ECU temperature TECU, battery voltage VBAT, and engine speed NE, whereby the injection frequency upper limit value is set. NFLMT is calculated. This injection number upper limit value NFLMT limits the number of injections of the injector 4 per combustion cycle.

  The above maps are respectively set for a plurality of (four in this example) predetermined values T1 to T4 (T1 <T2 <T3 <T4) of the ECU temperature TECU. FIG. A map used when = T4 is shown as a representative. As shown in the figure, in this map, the higher the engine speed NE, and the smaller the injection number upper limit value NFLMT is, in the vicinity of the predetermined minimum voltage VMIN that indicates the deterioration state of the battery 5, as the battery voltage VBAT is higher. In other words, the number of injections of the injector 4 is more strictly limited.

  The tendency of the injection number upper limit value NFLMT with respect to the engine speed NE and the battery voltage VBAT is basically the same in other maps. When the detected ECU temperature TECU does not match any of the four predetermined values T1 to T4, the injection number upper limit value NFLMT is calculated by interpolation calculation.

  Next, the process proceeds to step 2 where the number of injections of the injector 4 is set within the range of the injection number upper limit value NFLMT determined in step 1 according to the engine speed NE, the accelerator pedal opening AP, and the like. The injection control parameters such as the fuel injection amount and the fuel injection timing are calculated, and this process is terminated. More specifically, the number of times of fuel post-injection, main injection, and after-injection is determined based on the set number of injections, and the fuel injection amount and fuel injection timing are calculated for each injection.

  Next, the relationship between the above-described three parameters (ECU temperature TECCU, battery voltage VBAT, and engine speed NE) and the injection number upper limit value NFLMT will be described in detail with reference to FIGS. FIGS. 5 to 7 show the above relationships set by the four maps including the map of FIG. 4 described above using the reference rotation speed NEREF for three different battery voltages VBAT. .

  This reference rotational speed NEREF corresponds to a line that divides the region of the injection number upper limit value NFLMT in the map of FIG. 4 or the like, that is, the engine speed serving as a reference (threshold value) when increasing or decreasing the injection number upper limit value NFLMT. 5 to 7, each of the ECU temperatures TECU is depicted by a plurality of vertical lines connecting the upper and lower two injection count upper limit values NFLMT.

  For example, a line indicated by an arrow X in FIG. 5 shows a case where the injection number upper limit value NFLMT is switched between “4” and “5” under the conditions of battery voltage VBAT = maximum voltage VMAX and ECU temperature TECU = predetermined value T1. Represents the reference rotational speed NEREF. That is, under these conditions of the battery voltage VBAT and the ECU temperature TECU, when the engine speed NE crosses the reference speed NEREF from the lower side and exceeds this, the injection number upper limit value NFLMT is changed from “5” to “4”. The number of injections is limited from 5 to 4 times.

  As shown in FIG. 5, when battery voltage VBAT = maximum voltage VMAX, at each stage of injection number upper limit value NFLMT, reference rotation speed NEREF is determined by ECU temperature TECU from predetermined value T1 on the low temperature side to predetermined value T4 on the high temperature side. Is set to decrease, that is, the number of injections of the injector 4 is more strictly limited. Further, the reduction width A corresponding to the ECU temperature TECU in this case is set to be larger as the engine rotational speed NE is higher as shown in the reduction width A1 and the reduction width A2, for example. Yes.

  FIG. 6 shows the reference rotational speed NEREF when the battery voltage VBAT is a predetermined voltage VM between the maximum voltage VMAX and the minimum voltage VMIN. In this case, when the engine speed NEREF is relatively small and the injection number upper limit value NFLMT is switched between 3-4 and 4-5, the reference speed NEREF is set to the battery voltage VBAT = VMAX. Almost the same as the case, the higher the ECU temperature TECU, the lower the temperature is set.

  On the other hand, when the engine speed NE is relatively large and the injection number upper limit value NFLMT is switched between 1-2 and 2-3, the reference engine speed NEREF is simply set regardless of the ECU temperature TECU. One predetermined value N12 and N23 is set. These predetermined values N12 and N23 are substantially equal to the minimum reference rotational speed NEREF set when the ECU temperature TECU = T4 when the battery voltage VBAT = maximum VMAX shown in FIG.

  Further, in FIG. 6, the reference rotational speed NEREF when the battery voltage VBAT = maximum voltage VMAX and the ECU temperature TECU = T1 shown in FIG. 5 is indicated by a dotted line. As is apparent from the comparison between the reference rotational speed NEREF and the corresponding reference rotational speed NEREF in FIG. 6, the reference rotational speed NEREF is further reduced as the battery voltage VBAT is lower under the same ECU temperature TECU. Is set to

  Further, the reduction width B corresponding to the battery voltage VBAT in this case is set to be larger as the engine speed NE is higher as shown in the reduction width B1 and the reduction width B2, for example. Yes.

  FIG. 7 shows the reference rotational speed NEREF when the battery voltage VBAT is the minimum voltage VMIN. This minimum voltage VMIN represents a state in which the battery 5 has deteriorated. In this case, the reference rotational speed NEREF is set to a single predetermined value N12, N23, N34 and N45, respectively, at each switching stage of the injection number upper limit value NFLMT, regardless of the ECU temperature TECU. These predetermined values N12 to N45 are substantially equal to the minimum reference rotational speed NEREF set when the ECU temperature TECU = T4 when the battery voltage VBAT = maximum VMAX shown in FIG.

  As described above, according to this embodiment, the higher the engine speed NE, the lower the injection speed upper limit value NFLMT by setting the reference speed NEREF to a smaller value, thereby reducing the amount of fuel per combustion cycle. Limit the number of injections. As a result, when the engine speed NE is high, the battery voltage VBAT for each injection can be boosted and applied with a time margin in accordance with the limited number of injections. . As a result, by ensuring an appropriate fuel injection amount and fuel injection timing in each injection, a plurality of injections can be performed satisfactorily. Therefore, the required output torque of the engine 3 can be ensured, and effects such as improvement of exhaust gas characteristics and suppression of combustion noise by multiple injections can be effectively obtained.

  Further, the reference rotational speed NEREF is further reduced as the ECU temperature TECU is higher, and the reduction width A is set to be larger as the engine rotational speed NE is higher. As a result, when the ECU temperature TECU is high, the number of injections is further limited as the reference rotational speed NEREF is set to a smaller value. Along with this, the number of times of boosting and applying the battery voltage VBAT by the ECU 2 is reduced, so that the heat generation of the ECU 2 can be appropriately suppressed, and the malfunction and the life reduction due to the overheating of the ECU 2 can be avoided.

  Furthermore, the reference speed NEREF is further reduced as the battery voltage VBAT is lower, and the reduction width B is set to be larger as the engine speed NE is higher. As a result, when the battery voltage VBAT is low, the number of injections is further limited as the reference rotational speed is set to a smaller value. Accordingly, the time required for boosting the battery voltage VBAT is secured in each injection, so that the battery voltage VBAT can be boosted sufficiently. As a result, the operation of the injector 4 can be stabilized and a plurality of injections can be performed more satisfactorily.

  Further, when the battery voltage VBAT decreases to the minimum voltage VMIN representing the state where the battery 5 has deteriorated, the reference rotational speed NEREF is set to the minimum predetermined values N12 to N45. As a result, the number of fuel injections is most severely limited, so that the operation of the injector 4 can be stabilized as much as possible and the deteriorated battery 5 can be protected appropriately.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, in the embodiment, the reference rotational speed NEREF is set in advance in a map as shown in FIG. 4 according to the ECU temperature TECU and the battery voltage VBAT. The present invention is not limited to this, and without using a map, according to the detected ECU temperature TECU and battery voltage VBAT, a plurality of reference rotation speeds corresponding to each switching stage of the injection number upper limit value NFLMT are calculated, The injection number upper limit value NFLMT may be calculated based on the comparison result between the reference rotational speed and the engine rotational speed NE.

  In the embodiment, the ECU temperature TECU is detected by the ECU temperature sensor 24, but may be estimated from an appropriate parameter, for example, the number of injections of the injector 4 or the fuel injection amount.

  Further, the embodiment is an example in which the present invention is applied to a diesel engine mounted on a vehicle. However, the present invention is not limited to this, and may be applied to a direct injection type gasoline engine. The present invention can also be applied to engines other than those for use, for example, engines for marine propulsion devices such as outboard motors in which a crankshaft is arranged vertically. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

2 ECU (control circuit, injection frequency upper limit setting means, reference rotation speed setting means)
3 Engine (Internal combustion engine)
3a cylinder 4 injector (fuel injection valve)
5 Battery 21 Crank angle sensor (rotational speed detection means)
23 Battery voltage sensor (voltage detection means)
24 ECU temperature sensor (temperature acquisition means)
VBAT battery voltage (battery voltage)
TECU ECU temperature (control circuit temperature)
NE engine speed (speed of internal combustion engine)
NEREF reference speed NFLMT Upper limit of number of injections
A Reduction range of reference speed according to ECU temperature (degree of reduction)
B Reduction width of reference rotation speed according to battery voltage (degree of reduction)
VMIN minimum voltage (predetermined voltage)
N12 to N45 Predetermined value (minimum speed)

Claims (3)

By boosting the voltage of the battery by the control circuit and applying it to the fuel injection valve, the fuel is directly injected into the cylinder from the fuel injection valve, and the fuel injection is executed a plurality of times per combustion cycle. A fuel injection control device for an internal combustion engine,
A rotational speed detection means for detecting the rotational speed of the internal combustion engine;
Temperature acquisition means for acquiring the temperature of the control circuit;
Based on the comparison result between the detected rotational speed of the internal combustion engine and a predetermined reference rotational speed, an upper limit value of the number of injections for limiting the number of fuel injections of the fuel injection valve per combustion cycle is determined as the internal combustion engine. The higher the number of revolutions, the lower the number of injections upper limit setting means for setting a smaller value;
The reference is set such that the higher the temperature of the acquired control circuit is, the more the reference rotational speed is reduced, and the degree of reduction of the reference rotational speed is set to be larger as the rotational speed of the internal combustion engine is higher. Rotational speed setting means;
A fuel injection control device for an internal combustion engine, comprising: Voltage detection means for detecting the voltage of the battery,
The reference rotation speed setting means reduces the reference rotation speed as the detected battery voltage is lower, and the degree of reduction of the reference rotation speed is higher as the rotation speed of the internal combustion engine is higher. 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the fuel injection control device is set to be large.   The reference rotation speed setting means sets the reference rotation speed to a predetermined minimum rotation speed regardless of the temperature of the control circuit when the voltage of the battery decreases to a predetermined voltage indicating a state in which the battery has deteriorated. The fuel injection control device for an internal combustion engine according to claim 2, wherein the fuel injection control device is set.

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