JP2016118197A - Fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to accurately control an injection state by suppressing the temperature increase of a switching element.SOLUTION: A fuel injection control device switches over between a current-carrying state for carrying a current to a coil 14 of a fuel injection valve 10 and a cutoff state for cutting off current carrying. This fuel injection control device comprises a first MOSa1 provided in a low-potential line 20L; a second MOSa2 connected in parallel to the first MOSa1; and a microcomputer 21 which controls the operation of the first MOSa1 and the second MOSa2. The microcomputer 21 switches over between a first current-carrying state for turning the state into the current-carrying state by controlling the first MOSa1 to be turned on and the second MOSa2 to be turned off, and a second current-carrying state for turning the state into the current-carrying state by controlling the second MOSa2 to be turned on and the first MOSa1 to be turned off.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel injection control device that controls the energization state of a coil of a fuel injection valve.

  2. Description of the Related Art Conventionally, there has been known a fuel injection valve for injecting fuel by opening a valve body by electromagnetic attraction generated by energizing a coil. And the control apparatus which controls the electricity supply state to a coil is disclosed by patent document 1. FIG.

  Among the energization paths provided in the control device, switching elements are provided in each of the high-voltage side energization path connected to the high voltage side of the coil and the ground-side energization path connected to the ground side of the coil. When both of these switching elements are turned on, the coil is energized, the valve element is opened, and fuel is injected.

JP 2014-95325 A

  Now, the switching element generates heat when energized. When the temperature of the switching element rises due to this heat generation, the electrical resistance of the switching element increases, so the current flowing through the coil decreases and the rate of increase of the electromagnetic attractive force slows. As a result, the time from the start of energization until the valve element starts to open becomes longer, so the fuel injection start timing becomes later than the desired timing. In addition, since the injection start timing is delayed, the valve opening time (injection time) is shortened, and the injection amount becomes smaller than the desired amount.

  In short, when the switching element generates heat by energization and the temperature rises, the injection characteristics such as the injection start timing and the injection amount change. Therefore, it becomes impossible to control the injection state with high accuracy.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel injection control device that can control an injection state with high accuracy by suppressing a temperature rise of a switching element.

  The invention disclosed herein employs the following technical means to achieve the above object. Note that the reference numerals in parentheses described in the claims and in this section indicate the correspondence with the specific means described in the embodiments described later, and do not limit the technical scope of the invention. .

  One of the disclosed inventions is an energization path connected to a coil in a fuel injection control device that switches between an energized state for energizing the coil (14) of the fuel injection valve (10) and an interrupted state for deenergizing the coil. The first switching element (a1) provided in (20L), the second switching element (a2) connected in parallel to the first switching element, and the operation of the first switching element and the second switching element are controlled. Control means (21) for controlling the first switching element to turn on the second switching element while turning on the second switching element while turning on the first switching element, and to turn on the second switching element. It is characterized by switching to the 2nd electricity supply state made into an electricity supply state by turning off a 1st switching element, operating.

  According to the present invention, the first switching element and the second switching element connected in parallel are provided, and the first energized state using the first switching element and the second switching element are used to make the coil energized. Switch to the second energized state. Therefore, even if the temperature of the first switching element rises due to energization on in the first energization state, the temperature of the first switching element decreases during the energization off period in the subsequent second energization state. Similarly, the temperature of the second switching element is lowered during the energization off period in the first energization state.

  Therefore, temperature rise of the first switching element and the second switching element can be suppressed as compared with the case where one switching element is continuously used without switching. Therefore, it is possible to suppress a decrease in electromagnetic attraction force and to control the injection state with high accuracy.

1 is a circuit diagram showing a fuel injection valve control device according to a first embodiment of the present invention. The figure showing the time change of the various signals output with the control apparatus shown in FIG. 1, and the time change of the electric current which flows into the coil of a fuel injection valve. 5 is a flowchart illustrating a procedure in which a microcomputer controls a first MOS and a second MOS in the first embodiment. The figure which shows an example which switches an electricity supply state in 1st Embodiment at normal temperature. The figure which shows an example which switches an electricity supply state at the time of high temperature in 1st Embodiment. The figure which shows an example which switches an electricity supply state at the time of normal temperature and multistage injection in 1st Embodiment. The figure which shows an example which switches an electricity supply state at the time of high temperature and multistage injection in 1st Embodiment. FIG. 3 is a diagram illustrating an example of simultaneously turning on a first MOS and a second MOS in the first embodiment. The flowchart which shows the procedure in which a microcomputer controls 1st MOS and 2nd MOS in 2nd Embodiment of this invention. The flowchart which shows the procedure in which a microcomputer controls 1st MOS and 2nd MOS in 3rd Embodiment of this invention. The flowchart which shows the procedure in which a microcomputer controls 1st MOS and 2nd MOS in 4th Embodiment of this invention. The circuit diagram which shows the fuel injection valve control apparatus which concerns on 5th Embodiment of this invention.

  Hereinafter, a plurality of modes for carrying out the invention will be described with reference to the drawings. In each embodiment, portions corresponding to the matters described in the preceding embodiment may be denoted by the same reference numerals and redundant description may be omitted. In each embodiment, when only a part of the configuration is described, the other configurations described above can be applied to other portions of the configuration.

(First embodiment)
A fuel injection valve 10 shown in FIG. 1 is mounted on an internal combustion engine and injects fuel directly into a combustion chamber of the internal combustion engine. The fuel injection valve 10 includes a body 11 having a fuel passage and an injection hole 11a for injecting fuel. In the body 11, a valve body 12, a movable core (not shown), a fixed core 13 and the like are accommodated. The valve body 12 has a seat surface 12 a that is separated from and seated on the seating surface 11 b of the body 11. When the valve body 12 is closed so that the seat surface 12a is seated on the seating surface 11b, fuel injection from the nozzle hole 11a is stopped. When the valve body 12 is opened (lifted up) so as to separate the seat surface 12a from the seating surface 11b, fuel is injected from the injection hole 11a.

  The fixed core 13 is configured by winding a coil 14 around an iron core. When the coil 14 is energized, the fixed core 13 generates a magnetic attractive force, and the movable core is attracted to the fixed core 13 by this magnetic attractive force and lifts up. . The valve body 12 coupled to the movable core lifts up (valve opening operation) together with the movable core. On the other hand, when energization of the coil 14 is stopped, the valve body 12 is closed together with the movable core by the elastic force of a spring (not shown).

  The electronic control unit (ECU 20) is configured by accommodating a microcomputer (microcomputer 21), an integrated circuit (IC 22), a booster circuit 23, various switching elements, and the like in a case 20a. The microcomputer 21 includes a central processing unit, a nonvolatile memory (ROM), a volatile memory (RAM), and the like. The microcomputer 21 calculates the target injection amount of fuel, the target injection start timing, and the number of multistage injections based on the load of the internal combustion engine and the engine speed. Specifically, the ECU 20 controls the injection amount by controlling the energization time tQ (see FIG. 2A) to the coil 14, and controls the injection start timing by controlling the energization start timing.

  The IC 22 controls operations of a boosting SW 23c, a high potential SW 24, and a low potential SW 25, which will be described later, based on an injection command signal output from the microcomputer 21. The injection command signal is a signal for instructing the energization state of the coil 14 of the fuel injection valve 10, and is set by the microcomputer 21 based on the above-described target injection amount and target injection start timing and a coil current detection value described later. The The injection command signal includes a drive signal, a valve opening signal, and a hold signal shown in FIGS. 2 (a), 2 (b), and 2 (c).

  The booster circuit 23 includes a boosting coil 23a, a capacitor 23b, a boosting SW 23c, and a diode 23d. The boosting SW 23c is a switching element formed of a semiconductor. In the example of FIG. 1, a field effect transistor is used as the boosting SW 23c. When the IC 22 controls the boosting SW 23c so that the boosting SW 23c repeats the on operation and the off operation, the battery voltage applied from the battery terminal B is boosted by the boosting coil 23a. Further, the voltage fluctuation of the boosted power supply is suppressed by the capacitor 23b.

  Terminals 20b and 20c connected to the coil 14 of the fuel injection valve 10 are attached to the case 20a. A terminal 20b connected to the high potential side of the coil 14 is connected to a high potential wiring 20H accommodated in the case 20a. The high-potential wiring 20H is branched into two systems. The diode 24a and the high-potential SW 24 are connected to one high-potential wiring 20H, and the diode 25a and the low-potential SW 25 are connected to the other high-potential wiring 20H. Connected. That is, the high potential SW 24 and the low potential SW 25 are connected in parallel. The high potential SW 24 and the low potential SW 25 are switching elements formed of a semiconductor, and field effect transistors are used in the example of FIG.

  Signals from the IC 22 are input to the gate terminals of the high potential SW 24 and the low potential SW 25. The source terminals of the high potential SW 24 and the low potential SW 25 are connected to the anode sides of the diodes 24a and 25a. The cathode sides of the diodes 24a and 25a are connected to the terminal 20b. The booster circuit 23 is connected to the drain terminal of the high potential SW 24, and the battery terminal B is connected to the drain terminal of the low potential SW 25.

  A terminal 20c connected to the low potential side of the coil 14 is connected to a low potential wiring 20L accommodated in the case 20a. The low potential wiring 20L is branched into two systems. The first MOSa1 is connected to one low potential wiring 20L, and the second MOSa2 is connected to the other low potential wiring 20L. That is, the first MOSa1 and the second MOSa2 are connected in parallel. The first MOSa1 and the second MOSa2 are switching elements formed of a semiconductor, and a field effect transistor is used in the example of FIG.

  Signals from the first TRb1 and the second TRb2 are input to the gate terminals of the first MOSa1 and the second MOSa2. The first TRb1 and the second TRb2 are switching elements formed of a semiconductor, and bipolar transistors are used in the example of FIG. A signal from the microcomputer 21 is input to the base terminals of the first TRb1 and the second TRb2. Therefore, it can be said that the microcomputer 21 controls the operation of the first MOSa1 and the second MOSa2. The microcomputer 21 during this control corresponds to “control means”.

  The source terminals of the first MOSa1 and the second MOSa2 are connected to the ground side, and the drain terminals of the first MOSa1 and the second MOSa2 are connected to the terminal 20c. Accordingly, when at least one of the high potential SW 24 and the low potential SW 25 is turned on and at least one of the first MOSa1 and the first TRb1 is turned on, power is supplied (energized) to the coil 14 of the fuel injection valve 10. It becomes. In this case, the low potential wiring 20 </ b> L and the high potential wiring 20 </ b> H correspond to “energization paths” for supplying power to the coil 14.

  A shunt resistor 26 is connected to the ground side of the first MOSa1 and the second MOSa2. The microcomputer 21 calculates the current flowing through the first MOSa1 and the second MOSa2 based on the voltage drop amount generated in the shunt resistor 26. This current corresponds to a current (coil current) flowing through the coil 14 when the electric resistances of the first MOSa1 and the second MOSa2 are assumed to be zero.

  A temperature sensor 27 for detecting the temperature of the internal air is provided inside the case 20a. Specifically, the temperature sensor 27 is disposed in the vicinity of the first MOSa1 and the second MOSa2, and detects the ambient temperature of the first MOSa1 and the second MOSa2. The detected temperature signal output from the temperature sensor 27 is input to the microcomputer 21.

  The energization will be described in detail. When the high potential SW 24 is turned on while turning on at least one of the first MOSa1 and the second MOSa2, the boost voltage boosted by the booster circuit 23 is applied to the coil 14. On the other hand, when the high potential SW 24 is turned off and the low potential SW 25 is turned on while at least one of the first MOSa1 and the second MOSa2 is turned on, the battery voltage is applied to the coil 14. When the voltage application to the coil 14 is stopped, all of the high potential SW 24, the low potential SW 25, the first MOSa1, and the second MOSa2 are turned off.

  Each of FIGS. 2A, 2B, and 2C shows temporal changes in the drive signal, the valve opening signal, and the hold signal when the fuel injection is performed once. During an on period (energization time tQ) of the drive signal, at least one of the first MOSa1 and the second MOSa2 is turned on. Accordingly, when the high potential SW 24 or the low potential SW 25 is turned on, an energized state is established. During the ON period (t10 to t20) of the valve opening signal, the high potential SW 24 is turned on to apply the boost voltage to the coil 14. Further, the low potential SW 25 is turned on during the on period of the hold signal to apply the battery voltage to the coil 14.

  The microcomputer 21 turns on the valve opening signal at the driving signal on time t10, and turns off the valve opening signal at the time t20 when the coil current detected by the shunt resistor 26 reaches the peak threshold value TH1. Therefore, the coil current starts to rise by applying the boost voltage at the time when the drive signal instructs to start energization. Thereafter, when the coil current reaches the peak threshold value TH1, energization is turned off, and the coil current starts to decrease.

  Further, after the coil current reaches the peak threshold value TH1, the microcomputer 21 turns on the hold signal at time t30 when the coil current reaches the lower limit threshold value TH2. Thereafter, when the detected coil current value reaches the upper limit threshold TH3, the microcomputer 21 turns off the hold signal and switches on / off so that the coil current is held between the lower limit threshold TH2 and the upper limit threshold TH3. Therefore, feedback control is performed so that the coil current is held at a predetermined hold value by the battery voltage. Thereafter, the microcomputer 21 turns off the hold signal at the drive signal off timing t40.

  During the valve-opening control period by the valve-opening signal, the charge accumulated in the capacitor 23b is used in the booster circuit 23. Therefore, the voltage between terminals of the capacitor 23b (boost voltage) gradually decreases. The amount of charge supplied to the coil 14 during the valve opening control is determined by the peak current when the peak threshold value TH1 is reached and the valve opening control period (t10 to t20).

  The booster circuit 23 has a function of starting charging when the boost voltage becomes a certain value or less, and the decrease in the boost voltage is reduced. During the valve opening control, it is necessary to apply energy for overcoming the fuel pressure to the coil 14, and the energy is generated by the peak current. That is, as the fuel pressure increases, more energy is required to exert the electromagnetic attractive force, and therefore the peak threshold value TH1 needs to be increased. That is, the higher the fuel pressure, the higher the peak threshold value TH1.

  However, as the peak threshold value TH1 is set higher, a higher current flows through the coil 14. As a result, the amount of heat generated by energization in the high potential SW 24, the low potential SW 25, the first MOSa1, and the second MOSa2 increases. In particular, since the fuel injection valve 10 according to this embodiment is a direct injection type, the pressure of the fuel supplied to the fuel injection valve 10 is set higher than that of the port injection type fuel injection valve. Therefore, the calorific value tends to increase.

  The solid line in FIG. 2D shows the time change of the coil current, and FIG. 2E shows the time change of the lift amount of the valve body 12. The coil current rises to the peak threshold value TH1 during the on-command period t10 to t20 of the valve opening signal. Thereafter, the coil current is held at the hold value during the on-command period t30 to t40 of the hold signal.

  On the other hand, the electromagnetic attractive force generated by energizing the coil 14 gradually increases as the coil current increases. Then, at time t11 when the magnetic attraction force reaches the attraction force required for opening the valve (required valve opening force), the valve body 12 starts to lift up. Accordingly, a delay time td occurs from the energization start timing t10 to the valve opening start timing t11. Thereafter, the valve body 12 is lifted up to the maximum position until the coil current reaches the peak threshold value TH1.

  Here, as described above, in the case of a direct injection internal combustion engine, the amount of heat generated by energization of the first MOSa1 and the second MOSa2 tends to increase. When the first MOSa1 and the second MOSa2 rise in temperature due to this heat generation, the electrical resistance of the first MOSa1 and the second MOSa2 increases, so that the current flowing through the coil 14 decreases and the electromagnetic attractive force decreases. As a result, since the delay time td becomes longer, the valve opening start timing t11 (injection start timing) becomes later than the desired timing. Further, the valve opening start timing t11 is delayed, so that the valve opening time (t11 to t41) is shortened, and the injection amount becomes smaller than a desired amount.

  In this embodiment, the microcomputer 21 controls the first MOSa1 and the second MOSa2 according to the control procedure shown in FIG. 3 to switch to the first energization state and the second energization state described below. The first energized state is a state in which the coil 14 is energized using the first MOSa1 without using the second MOSa2 by turning off the second MOSa2 while turning on the first MOSa1. The second energized state is a state where the coil 14 is energized using the second MOSa2 without using the first MOSa1 by turning off the first MOSa1 while turning on the second MOSa2.

  After the injection in the first energized state is repeated a predetermined number of times or continuously for a predetermined time, the injection is switched to the injection in the second energized state (see FIGS. 4 and 5). Note that switching of the energization state during one energization time tQ is prohibited. The microcomputer 21 changes the switching frequency according to the temperature detected by the temperature sensor 27. The change procedure will be described with reference to FIG. FIG. 3 is a flowchart showing a process that is repeatedly executed by the microcomputer 21 at a predetermined cycle. This process is always executed when the internal combustion engine is operated.

  First, in step S10 of FIG. 3, the ambient temperature T of the first MOSa1 and the second MOSa2 is acquired. Specifically, the ambient temperature T is calculated based on the temperature signal detected by the temperature sensor 27. The microcomputer 21 when executing the processing of step S10 corresponds to “acquiring means” for acquiring a physical quantity (atmosphere temperature T) correlated with the temperature of the first MOSa1 and the temperature of the second MOSa2.

  In a subsequent step S11, it is determined whether or not the acquired ambient temperature T is lower than a predetermined upper limit temperature (first temperature Ta). When an affirmative determination is made that T <Ta, it is determined in subsequent step S12 whether or not the ambient temperature T is lower than the second temperature Tb. The second temperature Tb is set to a value lower than the first temperature Ta. When an affirmative determination is made that T <Tb, in the subsequent step S13, the first energization state and the second energization state are switched at a low frequency (see FIGS. 4 and 6). On the other hand, if a negative determination is made that T <Tb is not satisfied, in the subsequent step S14, the first energization state and the second energization state are switched frequently (see FIGS. 5 and 7). If a negative determination is made in step S11 that T <Ta, the first MOSa1 and the second MOSa2 are simultaneously turned on to prohibit switching between the first energized state and the second energized state (see FIG. 8).

  The upper part of FIGS. 4 to 8 shows the time change of the command signal for turning on the first MOSa1, that is, the command signal output from the microcomputer 21 to the first TRb1. The lower part of FIGS. 4 to 8 shows the time change of the command signal for turning on the second MOSa2, that is, the command signal output from the microcomputer 21 to the second TRb2. These command signals are the same as the drive signals shown in FIG. 2A, and coincide with the energization time tQ.

  In the example of FIG. 4, the first MOSa1 is turned on continuously for a predetermined number of times and then switched to use of the second MOSa1. Thereafter, the second MOSa2 is turned on continuously for a predetermined number of times, and then switched to use of the first MOSa1. The second MOSa2 is kept off during the use period of the first MOSa1, and the first MOSa1 is kept off during the use period of the second MOSa2. In short, every time it is used a predetermined number of times, the first energized state using the first MOSa1 and the second energized state using the second MOSa2 are switched.

  On the other hand, in the example of FIG. 5, every time it is used, the first energization state using the first MOSa1 and the second energization state using the second MOSa2 are switched. That is, in the case of FIG. 5, the switching frequency between the first energization state and the second energization state is higher than that in the case of FIG.

  In the examples of FIGS. 4 and 5, the single-stage injection in which the fuel is injected once during one combustion cycle, but in the examples of FIGS. 6 and 7, the multi-stage injection in which the fuel is injected a plurality of times during one combustion cycle. is there. In the example of FIG. 6, switching between the first energized state and the second energized state is prohibited during one combustion cycle (during multistage injection). Each time the multistage injection is performed a predetermined number of times, the first energized state and the second energized state are switched.

  On the other hand, in the example of FIG. 7, switching between the first energized state and the second energized state is performed during multistage injection. Specifically, the first stage injection is performed in the first energization state using the first MOSa1, and the second stage injection is performed in the second energization state using the second MOSa2. That is, in the case of FIG. 7, the switching frequency between the first energization state and the second energization state is higher than that in the case of FIG.

  As described above, according to the present embodiment, the first MOSa1 and the second MOSa2 connected in parallel are provided, and the first energization state using the first MOSa1 and the second energization state using the second MOSa2 are switched. Therefore, even if the temperature of the first MOSa1 rises due to energization on in the first energization state, the temperature of the first MOSa1 decreases during the energization off period in the subsequent second energization state. Similarly, the temperature of the second MOSa2 decreases during the energization-off period in the first energization state.

  Therefore, temperature rise of the first MOSa1 and the second MOSa2 can be suppressed as compared with the case where one switching element is continuously used without switching. Therefore, it is possible to suppress a decrease in the increasing speed of the electromagnetic attractive force. Therefore, it is possible to suppress problems such as a delay in the injection start timing due to an increase in the delay time td and a decrease in the injection amount due to a decrease in the injection time. It can be said that the fact that the temperature rise of the switching element can be suppressed as described above makes it possible to employ a switching element having low heat resistance.

  Here, when this inventor tested, it turned out that a temperature rise can be suppressed, so that switching frequency is made high. However, if switching is performed at a high frequency, the processing load of the control increases when the microcomputer 21 controls the operation of the first MOSa1 and the second MOSa2. In this embodiment in view of this point, the microcomputer 21 changes the frequency of switching between the first energized state and the second energized state based on the acquired ambient temperature T. Therefore, it is possible to promote temperature rise suppression by switching frequently at high temperatures when the atmospheric temperature T is equal to or higher than the predetermined temperature (second temperature Tb). Nevertheless, the processing load on the microcomputer 21 can be reduced by switching at a low frequency at room temperature below a predetermined temperature.

  Here, if the first MOSa1 and the second MOSa2 are simultaneously turned on, the current flowing through the first MOSa1 and the second MOSa2 decreases, and the amount of heat generation decreases. However, since there is no switching between the first energized state and the second energized state, the off-operation period contributing to heat dissipation is shortened. When this inventor tested about this point, when it turned ON simultaneously as mentioned above, it turned out that the effect of temperature rise suppression will become high compared with the case where it switches frequently, if it is short period (temporary). . In this embodiment in view of this point, when the temperature detected by the temperature sensor 27 exceeds the first temperature Ta (upper limit temperature) higher than the second temperature Tb and becomes a high temperature, the first MOSa1 and the second MOSa2 At the same time. Therefore, when it becomes high temperature exceeding upper limit temperature, the effect of temperature rise suppression can be improved temporarily and temperature reduction can be aimed at. Therefore, it is possible to take measures to temporarily lower the temperature.

(Second Embodiment)
In the first embodiment, the temperature in the case 20a (atmosphere temperature T) is acquired as a physical quantity correlated with the temperature of the first MOSa1 and the temperature of the second MOSa2 in step S10 of FIG. On the other hand, in the present embodiment, the aforementioned engine rotational speed, that is, the rotational speed per unit time of the output shaft of the internal combustion engine (engine rotational speed NE) is acquired as the physical quantity.

  The larger the engine speed NE, the shorter the fuel injection interval. That is, the interval from the energization end time indicated by reference numeral t40 in FIG. 2 to the energization start timing t10 related to the next injection is shortened. Then, the off-operation period of the first MOSa1 and the second MOSa2 is shortened, and the temperature rise is promoted. Thus, the engine speed NE is a physical quantity having a correlation with the temperature of the first MOSa1 and the temperature of the second MOSa2.

  Specifically, first, in step S20 shown in FIG. 9, the engine speed NE is acquired. The microcomputer 21 when executing the process of step S20 corresponds to “acquiring means” for acquiring the physical quantity (engine speed NE). In a succeeding step S21, it is determined whether or not the acquired engine rotational speed NE is less than a predetermined value (first rotational speed Na). If an affirmative determination is made that NE <Na, in the subsequent step S22, it is determined whether or not the engine speed NE is less than the second speed Nb. The second rotation speed Nb is set to a value smaller than the first rotation speed Na.

  When a positive determination is made that NE <Nb, in the subsequent step S23, the first energization state and the second energization state are switched at a low frequency (see FIGS. 4 and 6). On the other hand, if a negative determination is made that N <Nb is not satisfied, in the subsequent step S24, the first energization state and the second energization state are switched frequently (see FIGS. 5 and 7). If it is determined in step S21 that N <Na is not satisfied, the first MOSa1 and the second MOSa2 are simultaneously turned on to prohibit switching between the first energized state and the second energized state (see FIG. 8).

  As described above, also in the present embodiment, similarly to the first embodiment, the temperature increase of the first MOSa1 and the second MOSa2 can be suppressed by switching between the first energization state and the second energization state. Therefore, it is possible to suppress a decrease in electromagnetic attraction force and to control the injection state with high accuracy. Moreover, the temperature sensor 27 shown in FIG. 1 can be made unnecessary.

(Third embodiment)
In the first embodiment, the switching frequency between the first energized state and the second energized state is changed in two stages of high frequency and low frequency. On the other hand, in this embodiment, it changes in three steps.

  Specifically, the process shown in FIG. 10 is executed and changed in three stages of high frequency, medium frequency, and low frequency. The process of FIG. 10 is obtained by adding step S12A and step S13A to the process of FIG. In step S12A, it is determined whether or not the ambient temperature T is lower than the third temperature Tc. The third temperature Tc is set to a value lower than the second temperature Tb.

  When an affirmative determination is made that T <Tc, in the subsequent step S13, the first energization state and the second energization state are switched at a low frequency (see FIGS. 4 and 6). On the other hand, if a negative determination is made that T <Tc is not satisfied, in the subsequent step S13A, the first energization state and the second energization state are switched at a medium frequency. If it is determined in step S12 that T <Tb is not satisfied, the first energization state and the second energization state are frequently switched in step S14 (see FIGS. 5 and 7).

  For example, every time a predetermined number of times is used, when switching between a first energized state using the first MOSa1 and a second energized state using the second MOSa2, the predetermined number is decreased in the order of low frequency, medium frequency, and high frequency. Set.

  As described above, according to the present embodiment, the switching frequency between the first energization state and the second energization state is changed in three stages of high frequency and low frequency. Therefore, the change in consideration of the promotion of the temperature rise suppression and the reduction of the processing load of the microcomputer 21 can be performed more finely than the case of changing in two stages.

(Fourth embodiment)
In the first to third embodiments, the microcomputer 21 controls the frequency of use of the first MOSa1 in the first energized state to be the same as the frequency of use of the second MOSa2 in the second energized state. On the other hand, in the present embodiment, control is performed such that the usage frequency of the first MOSa1 in the first energization state is higher than the usage frequency of the second MOSa2 in the second energization state.

  That is, first, in step S30 in FIG. 11, the first energization state and the second energization state are switched while the first MOSa1 is frequently used. For example, after the first MOSa1 is turned on continuously for a predetermined first number of times, the second MOSa1 is switched to use. Thereafter, after the second MOSa2 is turned on continuously for a predetermined second number of times, the first MOSa1 is switched to use. Then, the first number is set to a value larger than the second number. In the present embodiment, the first MOSa1 and the second MOSa2 use the same components, and the heat-resistant temperature is the same. Therefore, the temperature of the first MOSa1 that is frequently used should be higher than that of the second MOSa2.

  In a succeeding step S31, it is determined whether or not an abnormality has occurred in the first MOSa1. For example, when the ambient temperature T acquired based on the detection value of the temperature sensor 27 becomes a value outside the normal range, it is determined that an abnormality has occurred in the first MOSa1. Alternatively, when the coil current acquired based on the detection value of the shunt resistor 26 becomes a value outside the normal range, it is determined that an abnormality has occurred in the first MOSa1.

  If it is determined in step S31 that an abnormality has occurred and an abnormality is detected, in the subsequent step S32, the use of the first MOSa1 is prohibited and the second MOSa2 is used. That is, the switching is prohibited and the second MOSa2 is turned on during the energization time tQ for all injections.

  In the subsequent step S33, the driver of the internal combustion engine is notified that an abnormality has occurred. For example, when the internal combustion engine is mounted on a vehicle, the vehicle driver is notified of the occurrence of an abnormality by means such as turning on a warning lamp. On the other hand, if no abnormality is detected in step S31, the process in step S30 is continued.

  As described above, also in the present embodiment, similarly to the first embodiment, the temperature increase of the first MOSa1 and the second MOSa2 can be suppressed by switching between the first energization state and the second energization state.

  Further, in the present embodiment, control is performed so that the usage frequency of the first MOSa1 is higher than the usage frequency of the second MOSa2. Therefore, there is a high probability that the deterioration of the second MOSa2 has not progressed greatly at the time when an abnormality has occurred in the first MOSa1 used frequently. Therefore, it is possible to ensure a long period during which fuel injection using the second MOSa2 can be performed after the first MOSa1 is abnormal. Therefore, it is possible to ensure a long period of time from when the abnormality occurs in the first MOSa1 until the abnormality occurs in the second MOSa2, that is, a fail-safe period until the failed first MOSa1 is repaired.

(Fifth embodiment)
The ECU 20 according to the first to fourth embodiments controls one fuel injection valve 10. That is, the fuel injection valve 10 provided in the internal combustion engine is a fuel injection control device applied to one single cylinder engine. In contrast, the ECU 200 according to the present embodiment controls a plurality of fuel injection valves 10 and is a fuel injection control device applied to a multi-cylinder engine.

  In the example of FIG. 12, there are four fuel injection valves 10, and a ground-side terminal 20 c is provided for each coil 14. Two terminals 20b on the high potential side are provided, and two coils 14 are connected to each terminal 20b. A high potential SW 24 and a low potential SW 25 are connected to each of the high potential wirings 20H connected to the terminals 20b. Each high potential SW 24 is connected to one booster circuit 23.

  A first MOSa1 and a second MOSa2 are connected in parallel to each of the low potential wirings 20L connected to the ground side terminal 20c. A first TRb1 and a second TRb2 are connected to each of the first MOSa1 and the second MOSa2. The shunt resistor 26 shown in FIG. 1 is not shown in FIG.

  In short, the ECU 200 includes two sets of the high potential SW 24 and the low potential SW 25, and four sets of the first MOSa 1 and the second MOSa 2 for the four coils 14. And the microcomputer 21 controls 1st MOSa1 and 2nd MOSa2 similarly to 1st Embodiment, and switches to a 1st electricity supply state and a 2nd electricity supply state. Therefore, the same effects as those of the first embodiment are also exhibited by this embodiment.

(Other embodiments)
The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made as illustrated below. Not only combinations of parts that clearly show that combinations are possible in each embodiment, but also combinations of the embodiments even if they are not explicitly stated unless there is a problem with the combination. Is also possible.

  In the fourth embodiment, the first MOSa1 and the second MOSa2 use the same components and have the same heat resistance temperature. On the other hand, a switching element having higher heat resistance than the second MOSa2 may be used as the first MOSa1. According to this, it is possible to suppress the occurrence of abnormality in the first MOSa1 used frequently, which is preferable.

  In step S14 of FIG. 3 and step S24 of FIG. 9, switching between the first energization state and the second energization state at a high frequency is performed each time the first MOSa1 and the second MOSa2 are used once. On the other hand, the present invention is not limited to switching every time it is used. For example, as long as switching is performed more frequently than infrequent switching in step S13 or step S23, the switching may be performed every time it is used a plurality of times.

  In each of the above embodiments, the ambient temperature T and the engine speed NE are used as physical quantities correlated with the temperature of the first MOSa1 and the temperature of the second MOSa2. On the other hand, the load of the internal combustion engine may be used as the physical quantity. In each of the above embodiments, field effect transistors are used as the first switching element and the second switching element, but bipolar transistors may be used.

  In each of the above embodiments, the first switching element and the second switching element are connected in parallel to the low-potential wiring 20L to switch between the first energization state and the second energization state. On the other hand, the first switching element and the second switching element may be connected in parallel to the high potential wiring 20H to switch between the first energization state and the second energization state. Alternatively, the first switching element and the second switching element according to the present invention may be applied to both the switching element connected to the low potential wiring 20L and the switching element connected to the high potential wiring 20H.

  In the above embodiments, the microcomputer 21 controls the first TRb1 and the second TRb2, thereby controlling the operations of the first MOSa1 and the second MOSa2. On the other hand, the first TRb1 and the second TRb2 may be eliminated and the IC 22 may control the operation of the first MOSa1 and the second MOSa2.

  In each of the embodiments described above, both the first MOSa1 and the second MOSa2 are simultaneously turned on when the ambient temperature T becomes higher than the upper limit temperature Ta. On the other hand, when the atmospheric temperature T is predicted to be higher than the upper limit temperature Ta, both of the above may be simultaneously turned on. For example, when the engine speed NE rises rapidly, even if the ambient temperature T is the upper limit temperature Ta at the current time, it is predicted that there is a high probability that the temperature will be higher than the upper limit temperature Ta immediately after the current time.

  The internal combustion engine described in each of the above embodiments may be a gasoline engine or a diesel engine.

  Means and / or functions provided by the ECUs 20 and 200 (control devices) may be provided by software recorded in a substantial storage medium and a computer that executes the software, software only, hardware only, or a combination thereof. it can. For example, if the controller is provided by a circuit that is hardware, it can be provided by a digital circuit including a number of logic circuits, or an analog circuit.

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve, 12 ... Valve body, 14 ... Coil, 20L ... Low potential wiring (energization path), 21 ... Microcomputer (control means), a1 ... 1st MOS (1st switching element), a2 ... 2nd MOS (1st 2 switching elements).

Claims (5)

In the fuel injection control device for switching between an energized state for energizing the coil (14) of the fuel injection valve (10) and an interrupted state for deenergizing the coil,
A first switching element (a1) provided in an energization path (20L) connected to the coil;
A second switching element (a2) connected in parallel to the first switching element;
Control means (21) for controlling the operation of the first switching element and the second switching element;
With
The control means includes
A first energization state in which the first switching element is turned on while the second switching element is turned off, and the first switching element is turned off while the second switching element is turned on. The fuel injection control device is switched to the second energized state that makes the energized state by causing the power to flow. Obtaining means (S10, S20) for obtaining a physical quantity correlated with the temperature of at least one of the first switching element and the second switching element;
2. The fuel injection control device according to claim 1, wherein the control unit changes a frequency of switching between the first energization state and the second energization state based on the physical quantity acquired by the acquisition unit. . The control means includes
The frequency of use of the first switching element in the first energized state is controlled to be higher than the frequency of use of the second switching element in the second energized state. Fuel injection control device.   The fuel injection control device according to claim 3, wherein a switching element having higher heat resistance than the second switching element is used as the first switching element. The control means includes
When at least one of the first switching element and the second switching element is higher than a predetermined upper limit temperature (Ta), or when it is predicted to be higher than the upper limit temperature,
5. The fuel injection control device according to claim 1, wherein both of the first switching element and the second switching element are turned on simultaneously so as to be in the energized state.

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