Injection control device

Abstract

An injection control device is provided with an injection valve, a drive circuit, and a control unit that controls the drive circuit. The control unit has: an injection setting unit that sets a target number of injections and a target injection period for each combustion cycle of the internal combustion engine in accordance with operating conditions of the internal combustion engine; and an interval determination unit that determines the interval when continuous injections in which the number of injections in a single combustion cycle or the total number of injections in two continuous combustion cycles is at least three are defined as a first injection, a second injection, and a third injection. Determining whether a first interval from a valve opening period of the first injection to a valve opening period of the second injection is equal to or greater than a first threshold value according to the target number of injections and the target injection period, and determining whether a second interval from the valve opening period of the second injection to a valve opening period of the third injection is equal to or greater than a second threshold value; when it is determined that the first interval is smaller than the first threshold value and the second interval is smaller than the second threshold value, the injection number correction unit corrects the injection number per combustion cycle to be smaller than the target injection number.

Description

Technical Field

[0001] The present invention relates to an injection control device for controlling fuel injection of a direct injection type internal combustion engine performing multi-stage injection. Background Art

[0002] In recent years, in order to ensure that everyone has access to appropriate, reliable, sustainable and modern energy, research and development on multi-stage injection of internal combustion engines that contribute to energy efficiency is being carried out. As such technology, there is a device that adjusts the number of injections and the injection interval of multi-stage injection. For example, in the device described in Patent Document 1, the number of injections is set to ensure the charging time of the boost capacitor of the high voltage generating circuit that generates the high voltage applied to the electromagnetic solenoid of the fuel injection valve, and the injection is prohibited in the period later than the injection period.

[0003] However, when the number of injections is set to ensure charging time for the boost capacitor as in the device described in Patent Document 1, the number of injections of the multi-stage injection is limited, which may impair the effect of the multi-stage injection.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent document 1: JP2011-106350A. Summary of the invention

[0007] An injection control device according to one technical solution of the present invention comprises: an injection valve that injects fuel into a combustion chamber of an internal combustion engine; a drive circuit that has a battery, a boost circuit that boosts electricity from the battery, and a current supply circuit that supplies a drive current to the injection valve using the electricity boosted by the boost circuit; and a control unit that controls the drive circuit. The control unit includes: an injection setting unit, which sets a target number of injections and a target injection period for each combustion cycle of the internal combustion engine according to the operating conditions of the internal combustion engine; an interval determination unit, which determines whether a first interval from a valve opening period of a first injection to a valve opening period of a second injection is greater than a first threshold value, and determines whether a second interval from a valve opening period of the second injection to a valve opening period of the third injection is greater than a second threshold value, when the number of injections in a single combustion cycle or the total number of injections in two consecutive combustion cycles is defined as a first injection, a second injection, and a third injection, according to the target number of injections and the target injection period set by the injection setting unit; and an injection number correction unit, which corrects the number of injections in each combustion cycle to be less than the target number of injections set by the injection setting unit when the interval determination unit determines that the first interval is less than the first threshold value and the second interval is less than the second threshold value. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The objects, features and advantages of the present invention will be further clarified through the following description of the embodiments in conjunction with the accompanying drawings.

[0009] Figure 1 This is a diagram schematically showing a main part configuration of an engine to which an injection control device according to an embodiment of the present invention is applied.

[0010] Figure 2 The drive is schematically shown Figure 1 Diagram of the main part structure of the injector drive circuit.

[0011] Figure 3 1 is a block diagram showing a main part configuration of an injection control device according to an embodiment of the present invention.

[0012] Figure 4 It is used to illustrate Figure 1 Graph showing the temperature rise of the piston crown surface.

[0013] Figure 5 This is a diagram showing an example of an injection characteristic map corresponding to the deposition reduction mode.

[0014] Figure 6 It is a diagram for explaining the injection interval in the deposition reduction mode.

[0015] Figure 7 This is a diagram for explaining the injection interval in the knock suppression mode.

[0016] Figure 8 It is used to illustrate Figure 1 A diagram of the boost recovery time of a capacitor.

[0017] Fig. 9 This is a diagram for explaining a case where the boosted state of the capacitor has not been restored.

[0018] Fig.10 It is a diagram for explaining how the boosted state of the capacitor is restored.

[0019] Fig.11 It is a diagram for explaining a modified example of the first injection, the second injection, and the third injection.

[0020] Fig.12 This is a flowchart showing an example of processing executed by the injection control device according to the embodiment of the present invention. DETAILED DESCRIPTION

[0021] The following reference Figures 1 to 12 An embodiment of the present invention will be described. The injection control device according to the embodiment of the present invention is applied to a direct injection internal combustion engine that performs multi-stage injection. In particular, an example in which the device is applied to a direct injection gasoline engine mounted on a vehicle will be described below.

[0022] Figure 1 1 is a diagram schematically showing the main structure of an engine 1 to which an injection control device according to an embodiment of the present invention is applied. The engine 1 is a spark ignition internal combustion engine, and is a four-stroke engine that undergoes four strokes, namely, an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke, in one combustion cycle. The engine 1 has a plurality of cylinders, such as four cylinders, but Figure 1 The structure of a single cylinder is shown in FIG. It should be noted that the structures of the cylinders are identical to each other.

[0023] like Figure 1 As shown, the engine 1 has a cylinder 2a formed in a cylinder block 2, a piston 3 slidably arranged inside the cylinder 2a, and a combustion chamber 5 formed between a crown surface (piston crown surface) 3a of the piston 3 and a cylinder head 4. A recess 3b is formed on the piston crown surface 3a, for example, along a tumble flow in the cylinder. The piston 3 is connected to the crankshaft 7 via a connecting rod 6, and the piston 3 reciprocates along the inner wall of the cylinder 2a, thereby rotating the crankshaft 7.

[0024] An intake port 8 and an exhaust port 9 are provided in the cylinder head 4. The combustion chamber 5 is connected to an intake passage 10 via the intake port 8, and is connected to an exhaust passage 11 via the exhaust port 9. The intake port 8 is opened and closed by an intake valve 12, and the exhaust port 9 is opened and closed by an exhaust valve 13. A throttle valve 14 is provided in the intake passage 10 on the upstream side of the intake valve 12. The throttle valve 14 is composed of, for example, a butterfly valve, and the amount of intake air to the combustion chamber 5 is adjusted by the throttle valve 14. The intake valve 12 and the exhaust valve 13 are driven to open and close by a valve mechanism 15.

[0025] The cylinder head 4 is provided with a spark plug 16 and a direct injection injector 17 facing the combustion chamber 5. The spark plug 16 is disposed between the intake port 8 and the exhaust port 9, and generates sparks by electrical energy to ignite the mixture of fuel and air in the combustion chamber 5.

[0026] The injector 17 is arranged near the intake valve 12, and is driven by electric energy to inject fuel. More specifically, high-pressure fuel is supplied from a fuel tank to the injector 17 via a fuel pump. The injector 17 atomizes the fuel and injects it obliquely downward into the combustion chamber 5 at a predetermined timing. It should be noted that the arrangement of the injector 17 is not limited to this, and it can also be arranged near the spark plug 16, for example.

[0027] The valve mechanism 15 includes an intake camshaft 18 and an exhaust camshaft 19. The intake camshaft 18 integrally includes an intake cam 18a corresponding to each cylinder (cylinder 2a), and the exhaust camshaft 19 integrally includes an exhaust cam 19a corresponding to each cylinder. The intake camshaft 18 and the exhaust camshaft 19 are connected to the crankshaft 7 via a timing belt (not shown), and the intake camshaft 18 and the exhaust camshaft 19 each rotate once for every two rotations of the crankshaft 7.

[0028] The intake valve 12 is opened and closed at a predetermined timing corresponding to the profile of the intake cam 18a by means of an intake rocker arm (not shown) due to the rotation of the intake camshaft 18. The exhaust valve 13 is opened and closed at a predetermined timing corresponding to the profile of the exhaust cam 19a by means of an exhaust rocker arm (not shown) due to the rotation of the exhaust camshaft 19.

[0029] Figure 2 1 is a diagram schematically showing a main part configuration of a drive circuit 20 that drives the injector 17 . Figure 2 , an example of a case where the engine 1 is an inline four-cylinder engine is shown. In the engine 1, ignition is performed every time the crank angle increases by 180° in the order of the first cylinder #1→the third cylinder #3→the fourth cylinder #4→the second cylinder #2. In the following, it is assumed that the injector 17a injects fuel into the combustion chamber 5a of the first cylinder #1, the injector 17b injects fuel into the combustion chamber 5b of the third cylinder #3, the injector 17c injects fuel into the combustion chamber 5c of the fourth cylinder #4, and the injector 17d injects fuel into the combustion chamber 5d of the second cylinder #2.

[0030] like Figure 2 As shown in FIG. 1 , the drive circuit 20 includes a single boost circuit 22 for boosting the power (voltage) from the vehicle-mounted battery 21 and a current supply circuit 23 for supplying drive current to the injectors 17a to 17d using the power boosted by the boost circuit 22. The boost circuit 22 includes a single capacitor 22a. By sharing the single boost circuit 22 including the single capacitor 22a with the four injectors 17a to 17d, the number of parts can be reduced, the cost can be suppressed, and the structure can be simplified.

[0031] The boost circuit 22 includes a boost coil 22b, a FET 22c as a switching element, a diode as a rectifying element, a resistor, etc., in addition to a capacitor 22a. One end of the boost coil 22b is connected to the vehicle battery 21, and the other end of the boost coil 22b is connected to the drain of the FET 22c and connected to the capacitor 22a via a diode. The source of the FET 22c is connected to the resistor.

[0032] When a switching signal is input to the gate of FET22c and FET22c is turned on, the battery voltage is applied to the booster coil 22b to store electric energy. When a switching signal is input to the gate of FET22c and FET22c is turned off, the electric energy stored in the booster coil 22b is supplied to the capacitor 22a and stored. By repeatedly turning on and off FET22c, the battery voltage is boosted to a predetermined boost voltage corresponding to the capacitance of the capacitor 22a.

[0033] The current supply circuit 23 has FET23a, 23b, and 23c as switching elements, a diode as a rectifying element, a resistor, and the like. The source of FET23a is connected to the output side of the boost circuit 22, and the drain of FET23a is connected to one end of the solenoid actuator of each injector 17a to 17d. The source of FET23b is directly connected to the vehicle battery 21, and the drain of FET23b is connected to one end of the solenoid actuator of each injector 17a to 17d via a diode. The other end of the solenoid actuator of each injector 17a to 17d is connected to the drain of FET23c. A diode is interposed between the gate and drain of FET23c, and a resistor is interposed between the gate and source of FET23c.

[0034] When each injector 17a to 17d is opened from a closed state, a switching signal is input to the gate of the FET 23a and FET 23c corresponding to each injector 17a to 17d, and the FET 23a and FET 23c are turned on. As a result, the capacitor 22a of the booster circuit 22 is discharged, and the boosted voltage is applied to the solenoid actuator of each injector 17a to 17d, and each injector 17a to 17d is opened from a closed state.

[0035] After each injector 17a to 17d is opened, in the case of maintaining the valve open state, a switching signal is input to the gates of the FETs 23a and 23b corresponding to each injector 17a to 17d, and the FET 23a is turned off, while the FET 23b is turned on. As a result, the battery voltage from the vehicle battery 21 is applied to the solenoid actuator of each injector 17a to 17d instead of the boosted voltage from the boost circuit 22, and the valve open state of each injector 17a to 17d is maintained.

[0036] When each injector 17a to 17d is closed from an open state, a switching signal is input to the gate of the FET 23b and FET 23c corresponding to each injector 17a to 17d, and the FET 23b and FET 23c are turned off. As a result, the supply of the driving current to the solenoid actuator of each injector 17a to 17d is stopped, and each injector 17a to 17d is closed from an open state.

[0037] Figure 3 1 is a block diagram showing the main structure of an injection control device (hereinafter referred to as a device) 100 according to an embodiment of the present invention. Figure 3 As shown, the device 100 is constructed around a controller 30. The controller 30 is connected to a crank angle sensor 31, an accelerator opening sensor 32, a water temperature sensor 33, an intake air amount sensor 34, an AF sensor 35, a fuel pressure sensor 36, a fuel temperature sensor 37, and a drive circuit 20.

[0038] The crank angle sensor 31 is arranged on the crankshaft 7 ( Figure 1), and is configured to output a pulse signal as the crankshaft 7 rotates. The controller 30 determines the rotation angle (crankshaft angle) of the crankshaft 7 based on the position of the top dead center TDC of the piston 3 at the beginning of the intake stroke, and calculates the engine speed, based on the pulse signal from the crankshaft angle sensor 31.

[0039] The accelerator opening sensor 32 is provided on the accelerator pedal of the vehicle equipped with the engine 1, and detects the operation amount of the accelerator pedal (accelerator opening). The target torque of the engine 1 is indicated based on the detection value of the accelerator opening sensor 32. The water temperature sensor 33 is provided on the path for the flow of engine cooling water for cooling the engine 1, and detects the temperature of the engine cooling water (cooling water temperature). The intake air amount sensor 34 is a sensor for detecting the intake air amount, for example, including an air flow meter arranged in the intake passage 10 (specifically, upstream of the throttle valve 14). The AF sensor 35 is provided in the exhaust passage 11, and detects the air-fuel ratio of the exhaust gas in the exhaust passage 11.

[0040] The fuel pressure sensor 36 is a sensor for detecting the pressure of the high-pressure fuel supplied to the injector 17 by the fuel pump and is provided in, for example, a fuel pipe. The fuel temperature sensor 37 is a sensor for detecting the temperature of the fuel supplied to the injector 17 and is provided in, for example, a fuel pipe.

[0041] The controller 30 performs a predetermined process based on the signals from the sensors 31 to 37, and outputs a switch signal to the FETs 22c, 23a to 23c, thereby controlling the drive circuit 20. More specifically, the drive circuit 20 is controlled so that after the injector 17a injects fuel into the combustion chamber 5a, the injector 17b injects fuel into the combustion chamber 5b, after the injector 17b injects fuel into the combustion chamber 5b, the injector 17c injects fuel into the combustion chamber 5c, after the injector 17c injects fuel into the combustion chamber 5c, the injector 17d injects fuel into the combustion chamber 5d, and after the injector 17d injects fuel into the combustion chamber 5d, the injector 17a injects fuel into the combustion chamber 5a.

[0042] The controller 30 includes an electronic control unit (ECU), which is composed of a computer having a processor such as a CPU (central processing unit), a memory such as a ROM (read only memory), a RAM (random access memory), and other peripheral circuits. The controller 30 has a temperature range determination unit 301, an injection setting unit 302, an interval determination unit 303, and an injection number correction unit 304 as functional structures, and functions as the temperature range determination unit 301, the injection setting unit 302, the interval determination unit 303, and the injection number correction unit 304.

[0043] The temperature range determination unit 301 determines whether the engine 1 is in the state of the piston crown surface 3a ( Figure 1) is in a low cylinder temperature state where the temperature Tp is lower than the specified temperature Tp0 (for example, 100°C), or in a high cylinder temperature state where the temperature is higher than the specified temperature Tp0. In the case of a gasoline engine, the output (power) of the engine 1 is correlated with the intake air amount G, and the work done (total work done) of the engine 1 is correlated with the cumulative amount ΣG of the intake air amount G. The cylinder 2a and the piston 3 constituting the combustion chamber 5 have heat capacities corresponding to their respective materials and masses, so in order to heat up these structural members, a certain amount of heat corresponding to their respective heat capacities is required, that is, a certain amount of work is required.

[0044] Figure 4 This is a diagram for explaining the temperature rise of the piston crown surface 3a, and shows an example of the time change of the soot emission amount measured by a measuring device when the engine 1 is warmed up from a cold state. Figure 4 The temperature Tp of the piston crown surface 3a shown is an estimated value, and the cooling water temperature Tw is a detected value of the water temperature sensor 33. In addition, the integrated amount ΣG of the intake air amount G is a calculated value calculated based on the intake air amount G detected by the intake air amount sensor 34.

[0045] like Figure 4 As shown, in the cold state of the engine 1, the temperature of the entire engine 1 including the piston crown surface 3a and the engine cooling water is uniform, and the cold state of the engine 1 can be detected by the water temperature sensor 33 as the cooling water temperature Tw when the engine 1 is started. During the warm-up process of the engine 1, the cumulative amount ΣG of the intake air volume G (heat and work generated by combustion) increases, and the temperature Tp of the piston crown surface 3a rises. When the temperature Tp of the piston crown surface 3a rises, the entire engine 1 including the piston crown surface 3a is gradually warmed up from the combustion chamber 5 side, and the cooling water temperature Tw rises. When the engine 1 is warmed up, the engine cooling water passes through the radiator not shown in the figure, thereby maintaining the cooling water temperature Tw below the specified temperature Tw0 (for example, 90°C), and the engine 1 is cooled by the engine cooling water.

[0046] like Figure 4 As shown in FIG. 1 , the soot emission is approximately constant until time t0, and then drops sharply at time t0 and falls below the target emission. Figure 1 As shown, the fuel injected from the injector 17 adheres to the piston crown surface 3a (recess 3b). At this time, when the temperature Tp of the piston crown surface 3a reaches the predetermined temperature Tp0 (e.g., 100°C), the adhered fuel evaporates immediately, so it is difficult to generate soot. On the other hand, when the temperature Tp of the piston crown surface 3a does not reach the predetermined temperature Tp0, the adhered fuel is not completely burned, so it is easy to generate soot.

[0047] By conducting Figure 4The soot emission confirmation test shown in the figure can pre-understand the cumulative amount (threshold) ΣG0 of the intake air volume G required for the temperature Tp of the piston crown surface 3a to reach the specified temperature Tp0 from the cooling water temperature Tw when the engine 1 is started. The temperature range determination unit 301 determines that the engine 1 is in a low cylinder temperature state when the cumulative amount ΣG of the intake air volume G is less than the threshold ΣG0, and determines that the engine 1 is in a high cylinder temperature state when it is greater than the threshold ΣG0. Thus, it is possible to determine whether the temperature Tp of the piston crown surface 3a has reached the specified temperature Tp0 without directly detecting the temperature Tp of the piston crown surface 3a that is reciprocating in the cylinder 2a facing the high-temperature combustion chamber 5 by a sensor.

[0048] It should be noted that if Figure 4 The threshold value ΣG0 shown varies depending on the cold state of the engine 1, that is, the cooling water temperature Tw at the start. That is, the lower the cooling water temperature Tw at the start of the engine 1, the larger the threshold value ΣG0 of the cumulative amount ΣG of the intake air amount G required until the engine 1 reaches the high cylinder temperature state, and the higher the cooling water temperature Tw at the start, the smaller the threshold value ΣG0 of the cumulative amount ΣG of the intake air amount G required until the engine 1 reaches the high cylinder temperature state. The characteristics of this threshold value ΣG0 with respect to the cooling water temperature Tw at the start of the engine 1 are pre-stored in the memory.

[0049] Figure 3 The injection setting unit 302 sets a target injection number and a target injection timing per combustion cycle of the engine 1 based on characteristics predetermined according to the operating conditions of the engine 1 .

[0050] <Attachment reduction mode>

[0051] When the temperature range determination unit 301 determines that the engine 1 is in a low cylinder temperature state, the injection setting unit 302 sets the target injection number and target injection period (adhesion reduction mode) to suppress the adhesion of fuel to the piston crown surface 3a, the inner wall surface of the cylinder 2a, etc. In the adhesion reduction mode, the fuel is injected to generate a mixed gas in an area other than the prescribed injection prohibition area near the intake top dead center TDC at the beginning of the intake stroke and the compression top dead center TDC at the end of the compression stroke, that is, the area (injectable area) where the piston crown surface 3a is away from the injector 17. At this time, the fuel is injected in multiple stages to suppress the amount of fuel injected each time. As a result, the adhesion of fuel to the piston crown surface 3a and the wall surface of the cylinder 2a can be suppressed, and the generation of soot can be suppressed. The injection prohibition area is set, for example, to a part or substantially the entire area of ​​the first half of the intake stroke and a part or substantially the entire area of ​​the second half of the compression stroke.

[0052] In more detail, the injection prohibition region is set according to the engine speed. The higher the engine speed, the faster the speed at which the piston crown surface 3a retreats from the injector 17 in the intake stroke and the speed at which the piston crown surface 3a approaches the injector 17 in the compression stroke. Therefore, the higher the engine speed, the narrower the injection prohibition region in the intake stroke becomes (the end of the injection prohibition region moves toward the advance angle side), and the wider the injection prohibition region in the compression stroke becomes (the start of the injection prohibition region moves toward the advance angle side).

[0053] The target number of injections and the target injection period in the injectable area are based on an injection specification map pre-stored in the memory, such as Figure 5 That is, Figure 5 As shown in FIG. 1 , it is determined based on a characteristic diagram predetermined in accordance with the characteristic f of the maximum output torque corresponding to the engine speed Ne and the target injection amount Q. When the number of injections is multiple, the injection amounts of each injection are equal to each other. It should be noted that the target injection amount Q is calculated so that the actual air-fuel ratio becomes the target air-fuel ratio, and is determined based on the intake air amount G. Therefore, Figure 5 The injection characteristic map can also be rewritten as a map of the engine speed Ne and the intake air amount G.

[0054] It should be noted that in Figure 5 In the figure, the crank angle of the interval from the start of the intake stroke (intake top dead center TDC) to the end of the compression stroke (compression top dead center TDC) is shown by the angle of a clockwise circle with the intake top dead center TDC as the starting point, and the timing of fuel injection is shown by the fan-shaped shadow extending radially from the center of the circle. The intake stroke is the range of the crank angle of 0° to 180°, and the compression stroke is the range of the crank angle of 180° to 360°. Sometimes, the range of the crank angle of 0° to 90° is called the first half of the intake stroke, the range of 90° to 180° is called the second half of the intake stroke, the range of 180° to 270° is called the first half of the compression stroke, and the range of 270° to 360° is called the second half of the compression stroke.

[0055] In order to suppress the attachment of fuel to the piston crown surface 3a, it is preferred to set the number of injections to multiple times and reduce the injection amount per injection. However, the minimum injection amount Qmin of the injector 17 per injection is specified according to the specifications of the injector 17, and the injector 17 cannot perform injections of an amount less than the minimum injection amount Qmin (minimum injection time limit). Therefore, the smaller the target injection amount Q is, the smaller the target number of injections is set.

[0056] In addition, the minimum rest time (minimum rest time limit) of the injector 17 from valve closing to valve opening is stipulated according to the specification of the injector 17. The minimum rest time is set for each injector 17a to 17d ( Figure 2) is set so that the change in injection amount (flow rate) caused by the residual magnetism of the solenoid actuator is within the allowable range.

[0057] On the other hand, in order to increase the number of injections, the injector 17 needs to be driven at a high speed, and the drive circuit 20 ( Figure 2 ) is charged and discharged by the capacitor 22a in the control circuit 20. In this case, the higher the engine speed Ne is, the faster the driving speed of the injector 17 needs to be, the greater the electrical load of the controller 30 that outputs the switch signal to the FET 22c of the drive circuit 20 is, and the greater the heat generated by the controller 30 is. As a result, the number of injections (maximum injection number limit) is limited due to the thermal limit of the controller 30. Therefore, the higher the engine speed Ne is, the smaller the target number of injections is set.

[0058] <Deflagration Suppression Mode>

[0059] When the temperature range determination unit 301 determines that the engine 1 is in a high cylinder temperature state, the injection setting unit 302 sets the target injection number and the target injection period so that when a predetermined knock suppression condition is satisfied, the occurrence of knock is suppressed (knock suppression mode). The knock suppression condition is satisfied when the retard angle corresponding to the optimal ignition timing of the ignition timing required to suppress the occurrence of knock at low speed and high load is greater than a predetermined value.

[0060] In the knock suppression mode, the retarded ignition timing is returned to the optimal ignition timing side, and fuel is injected once in the intake stroke (for example, the first half of the intake stroke) and once in the compression stroke (for example, the first half of the compression stroke) (intake compression two-stage injection). In this case, the injection amount in the compression stroke is the minimum injection amount Qmin, and the amount obtained by subtracting the minimum injection amount Qmin from the target injection amount Q is injected in the intake stroke. By injecting fuel in the compression stroke, the exhaust gas temperature of the combustion chamber 5 is reduced by the latent heat of vaporization. In this way, the occurrence of knock can be suppressed while suppressing the retarded angle of the ignition timing. Therefore, compared with the case where the ignition timing is retarded and fuel injection is performed only in the intake stroke, the combustion efficiency can be improved.

[0061] Figure 6 This is a diagram for explaining the injection interval Δt in the adhesion reduction mode, showing the injection interval Δt when the injector 17a injects fuel into the combustion chamber 5a of the first cylinder #1, and then the injector 17b injects fuel into the combustion chamber 5b of the third cylinder #3. The injection interval Δt is the time between two consecutive injections in a single combustion cycle or two consecutive combustion cycles, and is the time from the valve opening timing (target injection timing) of the previous injection to the valve opening timing of the next fuel injection.

[0062] like Figure 6As shown, in the adhesion reduction mode in which multi-stage injection is performed, the injection interval Δt1 from the last (the fourth in the example shown) injection of the first cylinder #1 (in the example shown, injection in the compression stroke) to the first injection of the third cylinder #3 (in the example shown, injection in the intake stroke) is sometimes shorter than the injection interval Δt2 from the first injection to the second injection of the third cylinder #3. That is, in the adhesion reduction mode, the injection intervals in a single combustion cycle in the same cylinder are equal to each other, but the injection interval from the last injection of the previous combustion cycle to the first injection of the next combustion cycle in two consecutive combustion cycles between cylinders is sometimes shorter than the injection interval in the same cylinder.

[0063] Figure 7 : is a diagram for explaining the injection interval Δt in the knock suppression mode. Figure 7 As shown, even in the knock suppression mode in which injection is performed in both the intake stroke and the compression stroke, the injection interval Δt1 from the last injection of the first cylinder #1 (for example, the first half of the compression stroke) to the first injection of the third cylinder #3 (for example, the first half of the intake stroke) is sometimes shorter than the injection interval Δt2 from the first injection to the second injection of the third cylinder #3. That is, even in the knock suppression mode, the injection interval from the last injection of the previous combustion cycle to the first injection of the next combustion cycle in two consecutive combustion cycles between cylinders is sometimes shorter than the injection interval in the same cylinder.

[0064] Figure 8 It is used to illustrate the capacitor 22a ( Figure 2 ) of the boost recovery time. Figure 8 As shown, after the capacitor 22a is discharged, a predetermined boost recovery time is required until the boost state in which the voltage is boosted to the boost voltage is restored. More specifically, a predetermined first recovery time Δta is required from the opening (discharging) of an injector 17 (solenoid actuator) in the boost state until the boost state is restored. The first recovery time Δta is specified by the specifications of the injector 17 and the drive circuit 20. After the previous discharge, a predetermined second recovery time Δtb longer than the first recovery time Δta is required from the next discharge until the boost state is restored in a state where the boost state has not been restored. The second recovery time Δtb is longest when the previous discharge and the next discharge are performed simultaneously. In this case, the second recovery time Δtb is about twice the first recovery time Δta.

[0065] like Figure 6 and Figure 7As shown, when the injection interval Δt1 is shortened, especially at high rotation and high load, the injection interval Δt1 is less than the first recovery time Δta, and the capacitor 22a is insufficiently charged, which sometimes causes the valve opening of the injector 17 to be delayed or insufficient. In such a case, when the number of injections is reduced in such a way that all the injection intervals Δt become longer than the first recovery time Δta, the effects of reducing the adhesion of fuel to the piston crown surface 3a, the inner wall surface of the cylinder 2a, etc., and suppressing knocking brought about by the multi-stage injection may be impaired. Therefore, in the present embodiment, the device 100 is configured as follows so that the number of injections of the multi-stage injection can be suppressed from being limited.

[0066] Fig. 9 2 is a diagram for explaining a case where the boosted state of the capacitor 22a is not restored, and shows the injection interval Δt of the first injection, the second injection, and the third injection of the injector 17 and the charging state of the capacitor 22a. Fig. 9 As shown, when the injection interval Δt1 from the first injection to the second injection is less than the first recovery time Δta, and the injection interval Δt2 from the second injection to the third injection is less than the second recovery time Δtb, the voltage of the accumulative capacitor 22a decreases. This is not allowed because the accumulation of the voltage drop of the capacitor 22a leads to a significant decrease in the injection amount (flow rate) of the injector 17. Therefore, it is necessary to reduce the number of injections per combustion cycle to ensure the appropriate injection amount of the injector 17. In this case, it is necessary to reduce the number of injections by, for example, prohibiting the last injection in each combustion cycle, and reconsider the injection amount of each injection to ensure the target injection amount Q.

[0067] Fig.10 2 is a diagram for explaining the situation where the boosted state of the capacitor 22a is restored. Fig.10 As shown, even if the injection interval Δt1 from the first injection to the second injection is less than the first recovery time Δta, if the injection interval Δt2 from the second injection to the third injection is greater than the second recovery time Δtb, the voltage drop of the capacitor 22a is not accumulated, and the boost state is restored. In such a temporary voltage drop of the capacitor 22a, since the drop in the injection amount of the injector 17 is limited, even if the number of injections is maintained, the reduction in combustion performance and emission performance due to the reduction in injection amount may be within the allowable range. For example, in the case where the previous discharge and the next discharge are performed simultaneously, the operating conditions under which the reduction in combustion performance and emission performance due to the reduction in injection amount is within the allowable range can be determined in advance through experiments.

[0068] Fig.11 1 is a diagram for explaining a modified example of the first injection, the second injection, and the third injection, and shows an injection interval Δt when performing a two-stage injection. Fig.11As shown, the first and second (last) injections of the previous combustion cycle of two consecutive combustion cycles can be set as the first injection and the second injection, and the first injection of the next combustion cycle can be set as the third injection. In this case, the previous combustion cycle and the next combustion cycle can be two consecutive combustion cycles in the same cylinder, or two consecutive combustion cycles between different cylinders.

[0069] Figure 3 The interval determination unit 303 determines whether the injection interval Δt1 from the first injection to the second injection is greater than the first recovery time Δta based on the target injection number and the target injection period set by the injection setting unit 302. Furthermore, when it is determined that the injection interval Δt1 is less than the first recovery time Δta, it is further determined whether the injection interval Δt2 from the second injection to the third injection is greater than the second recovery time Δtb. The second recovery time Δtb can be predetermined, for example, to be a value about twice the first recovery time Δta, or can be calculated based on the injection interval Δt1 from the first injection to the second injection.

[0070] When the interval determination unit 303 determines that the injection interval Δt2 from the second injection to the third injection is less than the second recovery time Δtb, the injection number correction unit 304 corrects the injection number per combustion cycle to be less than the target injection number. That is, even if the injection interval Δt1 from the first injection to the second injection is less than the first recovery time Δta, as long as the injection interval Δt2 from the second injection to the third injection is greater than the second recovery time Δtb, the target injection number is maintained. Thus, the injection number of multi-stage injection can be suppressed from being limited, and the emission performance and combustion performance can be improved even in the case of relatively high rotation and high load.

[0071] The controller 30 performs feedback control so that the actual air-fuel ratio detected by the AF sensor 35 becomes the target air-fuel ratio (for example, the theoretical air-fuel ratio), and calculates the target injection amount Q for each combustion cycle based on the intake air amount detected by the intake air amount sensor 34. In addition, the target injection amount (unit target injection amount) for each injection by the injector 17 is calculated based on the target injection number set by the injection setting unit 302. More specifically, in the adhesion reduction mode, the value obtained by dividing the target injection amount Q by the target injection number is calculated as the unit target injection amount, and in the knock suppression mode, the minimum injection amount Qmin (compression stroke) and the amount obtained by subtracting the minimum injection amount Qmin from the target injection amount Q are calculated as the target injection amount. The controller 30 controls the drive circuit 20 in accordance with the crank angle θ detected by the crank angle sensor 31 so that the injector 17 injects the unit target injection amount of fuel at the target injection period. That is, the drive circuit 20 is controlled by outputting a switch signal to the FETs 22c, 23a to 23c of the drive circuit 20.

[0072] Fig.12 1 is a flowchart showing an example of processing performed by the device 100, and shows an example of processing executed by the controller 30 according to a program pre-stored in the memory. The processing shown in the flowchart starts when the engine 1 starts to operate, for example, and is repeatedly performed at a predetermined cycle.

[0073] like Fig.12 As shown, first, in step S1, the signals from the sensors 31 to 37 are read. Next, in step S2, the target injection number and target injection period of each combustion cycle of the injector 17 are set according to the signals read in step S1. Next, in step S3, it is determined whether the target injection number set in step S2 is multiple, that is, whether it is multi-stage injection. When step S3 is affirmative (S3: Yes), the process proceeds to step S4, and when it is negative (S3: No), the process proceeds to step S8.

[0074] In step S4, it is determined whether the injection interval Δt1 from the first injection to the second injection is longer than the first recovery time Δta based on the target injection number and target injection period set in step S2. When step S4 is negative (S4: No), the process proceeds to step S5, and when it is positive (S4: Yes), the process proceeds to step S8. In step S5, it is determined whether the injection interval Δt2 from the second injection to the third injection is longer than the second recovery time Δtb based on the target injection number and target injection period set in step S2. When step S5 is positive (S5: Yes), the process proceeds to step S6, and when it is negative (S5: No), the process proceeds to step S7.

[0075] In step S6, based on the signal read in step S1, it is determined whether the current operating condition of the engine 1 is an operating condition in which the decrease in combustion performance and emission performance caused by the decrease in injection amount is within the allowable range. When step S6 is affirmative (S6: Yes), the process proceeds to step S8, and when it is negative (S6: No), the process proceeds to step S7. In step S7, the number of injections is reduced by one, and the process returns to step S3. In step S8, based on the signal read in step S1 and the number of injections set and corrected in steps S2 to S7, the target injection amount and the unit target injection amount are calculated, and a switch signal is output to the FETs 22c, 23a to 23c of the drive circuit 20, so that the injector 17 injects the fuel of the unit target injection amount during the target injection period.

[0076] The present embodiment can achieve the following effects.

[0077] (1) The device 100 comprises: an injector 17 that injects fuel into a combustion chamber 5 of an engine 1; a drive circuit 20 that has an onboard battery 21, a boost circuit 22 that boosts the power from the onboard battery 21, and a current supply circuit 23 that supplies a drive current to the injector 17 using the power boosted by the boost circuit 22; and a controller 30 that controls the drive circuit 20 ( Figure 1 to Figure 3 ).

[0078] The controller 30 comprises: an injection setting unit 302, which sets a target injection number and a target injection period for each combustion cycle of the engine 1 according to the operating conditions of the engine 1; an interval determination unit 303, which determines whether an injection interval Δt1 from the valve opening period of the first injection to the valve opening period of the second injection is longer than a first recovery time Δta, and determines whether an injection interval Δt2 from the valve opening period of the second injection to the valve opening period of the third injection is longer than a second recovery time Δtb, when the number of injections in a single combustion cycle or the total number of injections in two consecutive combustion cycles is at least three or more, according to the target injection number and the target injection period set by the injection setting unit 302; and an injection number correction unit 304, which corrects the number of injections per combustion cycle to be less than the target injection number set by the injection setting unit 302 (Δt1 is shorter than the first recovery time Δta, and the injection interval Δt2 is shorter than the second recovery time Δtb). Figure 3 , Fig.12 ).

[0079] That is, even if the injection interval Δt1 from the first injection to the second injection is less than the first recovery time Δta, as long as the injection interval Δt2 from the second injection to the third injection is greater than the second recovery time Δtb, the target injection number ( Fig.10 ). Thus, it is possible to suppress the number of injections of the multi-stage injection from being limited, and it is possible to improve emission performance and combustion performance even at relatively high speed and high load.

[0080] (2) The combustion chamber 5 includes combustion chambers 5a and 5b, and the injector 17 includes injectors 17a and 17b for injecting fuel into the combustion chambers 5a and 5b, respectively. Figure 2 ). The current supply circuit 23 supplies driving current to the injectors 17a and 17b respectively, and the controller 30 controls the driving circuit 20 in such a manner that after the injector 17a injects fuel into the combustion chamber 5a, the injector 17b injects fuel into the combustion chamber 5b. The first injection is the last injection of the injector 17a in the combustion cycle, the second injection is the first injection of the injector 17b in the combustion cycle, and the third injection is the second injection of the injector 17b in the combustion cycle ( Figure 6 to Figure 10 ).

[0081] That is, when a multi-stage injection is performed by a multi-cylinder engine, especially at high speed and high load, the injection interval between the last injection of the previous combustion cycle and the first injection of the next combustion cycle in two consecutive combustion cycles between cylinders is sometimes shortened to be less than the prescribed boost recovery time. In such a case, as long as the injection interval between the first injection and the second injection of the next combustion cycle is long enough, the number of injections is maintained, thereby improving emission performance and combustion performance even at relatively high speed and high load.

[0082] (3) The controller 30 further includes a temperature range determination unit 301, which determines whether the engine 1 is in a low cylinder temperature state where the temperature Tp of the piston crown surface 3a is lower than a predetermined temperature Tp0 or in a high cylinder temperature state where the temperature Tp of the piston crown surface 3a is higher than the predetermined temperature Tp0. Figure 3 When the temperature range determination unit 301 determines that the engine 1 is in a low cylinder temperature state, the injection setting unit 302 sets the target injection number and target injection period by injecting fuel multiple times from the intake stroke to the compression stroke of the combustion cycle ( Figure 6 That is, in the adhesion reduction mode, the adhesion of fuel to the piston crown surface 3a, the inner wall surface of the cylinder 2a, etc. is suppressed by performing multi-stage injection, thereby suppressing the generation of soot and improving emission performance.

[0083] (4) The controller 30 further includes a temperature range determination unit 301, which determines whether the engine 1 is in a low cylinder temperature state where the temperature Tp of the piston crown surface 3a is lower than a predetermined temperature Tp0 or in a high cylinder temperature state where the temperature Tp of the piston crown surface 3a is higher than the predetermined temperature Tp0. Figure 3 When the temperature range determination unit 301 determines that the engine 1 is in a high cylinder temperature state, the injection setting unit 302 sets the target injection number and target injection period in such a way that fuel is injected once in the intake stroke and the compression stroke of the combustion cycle when the prescribed knock suppression condition is satisfied ( Figure 7 That is, in the knock suppression mode, by performing intake and compression two-stage injection, the exhaust gas temperature of the combustion chamber 5 is reduced by the vaporization latent heat of the fuel injected in the compression stroke, thereby suppressing the retardation angle of the ignition timing and suppressing the occurrence of knock, thereby improving the combustion performance.

[0084] (5) The boost circuit 22 has a single capacitor 22a ( Figure 2 ) The single booster circuit 22 having the single capacitor 22a is shared by the plurality of injectors 17a to 17d, thereby reducing the number of parts, suppressing costs, and simplifying the structure.

[0085] In the above-mentioned embodiment, an example in which the present invention is applied to a gasoline engine mounted on a vehicle is described, but the present invention can also be applied to internal combustion engines other than those mounted on a vehicle and internal combustion engines other than gasoline engines. Figure 1 The specific structure of the injector 17 is exemplified and described in the examples, but the structure of the injection valve that injects fuel into the combustion chamber is not limited to the illustrated example.

[0086] In the above embodiment, Figure 5 In the above, the target injection number and the target injection timing in the adhesion reduction mode are determined according to the characteristic diagram showing the relationship between the engine speed and the target injection amount determined based on the intake air amount detected by the intake air amount sensor 34. That is, the engine output torque is detected based on the signal from the intake air amount sensor 34. However, the injection setting unit that sets the target injection number and the target injection timing for each combustion cycle based on the operating conditions of the internal combustion engine may be configured to use other physical quantities that have a correlation with the engine output torque.

[0087] In the above embodiment, the temperature domain determination unit 301 uses the cumulative amount of intake air as the work done by the engine 1 to determine whether the engine 1 is in a low cylinder temperature state or a high cylinder temperature state, but the temperature domain determination unit that determines whether the temperature of the combustion chamber is above a predetermined temperature is not limited to this. For example, the cumulative amount of fuel injection can also be used as the work done by the internal combustion engine. In addition, the temperature of the piston crown surface 3a is estimated as the cylinder temperature, but the temperature of the cylinder wall surface, the rotor surface of the rotary engine, etc. can also be estimated.

[0088] In the above embodiment, the interval determination unit 303 is described as follows. Fig.12 In step S4, it is determined whether the injection interval Δt1 from the first injection to the second injection is longer than the first recovery time Δta, and when it is negative, it proceeds to step S5 to determine whether the injection interval Δt2 from the second injection to the third injection is longer than the second recovery time Δtb, but the interval determination unit that determines whether the first interval is longer than the first threshold value and determines whether the second interval is longer than the second threshold value is not limited to this. For example, it is also possible to simultaneously determine whether the injection interval Δt1 is longer than the first recovery time Δta and determine whether the injection interval Δt2 is longer than the second recovery time Δtb, and it is also possible to determine whether the injection interval Δt1 is longer than the first recovery time Δta after determining whether the injection interval Δt2 is longer than the second recovery time Δtb.

[0089] One or more of the above-described embodiments and modifications may be arbitrarily combined, and modifications may be combined with each other.

[0090] According to the present invention, it is possible to suppress the number of injections of the multi-stage injection from being limited.

[0091] The present invention has been described above in conjunction with preferred embodiments, but it should be understood by those skilled in the art that various modifications and changes can be made without departing from the scope of the claims.

Claims

1. An injection control device (100), characterized in that: have: an injection valve (17) for injecting fuel into a combustion chamber (5) of the internal combustion engine (1); A drive circuit (20) comprising a battery (21), a boost circuit (22) for boosting the power from the battery (21), and a current supply circuit (23) for supplying a drive current to the injection valve (17) using the power boosted by the boost circuit (22); and a control unit (30) for controlling the drive circuit (20), The control unit (30) comprises: an injection setting unit (302) which sets a target injection number and a target injection period for each combustion cycle of the internal combustion engine (1) according to an operating condition of the internal combustion engine (1); an interval determination unit (303) for determining whether a first interval from a valve opening timing of the first injection to a valve opening timing of the second injection is greater than a first threshold value, and determining whether a second interval from a valve opening timing of the second injection to a valve opening timing of the third injection is greater than a second threshold value, based on the target number of injections and the target injection timing set by the injection setting unit (302), when the number of injections in a single combustion cycle or the total number of injections in two consecutive combustion cycles is at least three or more, is defined as a first injection, a second injection, and a third injection; as well as An injection number correction unit (304) corrects the injection number of each combustion cycle to be smaller than the target injection number set by the injection setting unit (302) when the interval determination unit (303) determines that the first interval is smaller than the first threshold value and the second interval is smaller than the second threshold value.

2. The injection control device (100) according to claim 1, characterized in that: The combustion chamber (5) comprises a first combustion chamber (5a) and a second combustion chamber (5b), The injection valve (17) includes a first injection valve (17a) for injecting fuel into the first combustion chamber (5a) and a second injection valve (17b) for injecting fuel into the second combustion chamber (5b). The current supply circuit (23) supplies driving current to the first injection valve (17a) and the second injection valve (17b), respectively. The control unit (30) controls the drive circuit (20) so that the second injection valve (17b) injects fuel into the second combustion chamber (5b) after the first injection valve (17a) injects fuel into the first combustion chamber (5a). The first injection is the last injection of a combustion cycle performed by the first injection valve (17a), The second injection is the first injection of a combustion cycle performed by the second injection valve (17b), The third injection is the second injection of the combustion cycle performed by the second injection valve (17b).

3. The injection control device (100) according to claim 2, characterized in that: The first injection is an injection performed by the first injection valve (17a) during a compression stroke of a combustion cycle. The second injection is the first injection performed by the second injection valve (17b) during the intake stroke of the combustion cycle.

4. The injection control device (100) according to claim 1 or 2, characterized in that: The control unit (30) further comprises a temperature range determination unit (301) for determining whether the temperature of the combustion chamber (5) is above a predetermined temperature. When the temperature range determination unit (301) determines that the temperature of the combustion chamber (5) is lower than the specified temperature, the injection setting unit (302) sets the target number of injections and the target injection period in a manner that injects fuel multiple times from the intake stroke to the compression stroke of the combustion cycle.

5. The injection control device (100) according to claim 1 or 2, characterized in that: The control unit (30) further comprises a temperature range determination unit (301) for determining whether the temperature of the combustion chamber (5) is above a predetermined temperature. When the temperature range determination unit (301) determines that the temperature of the combustion chamber (5) is above the specified temperature, the injection setting unit (302) sets the target number of injections and the target injection period in such a manner that fuel is injected once during the intake stroke and the compression stroke of the combustion cycle respectively when the specified conditions are met.

6. The injection control device (100) according to claim 1 or 2, characterized in that: The voltage boost circuit (22) has a single capacitor (22a).

7. The injection control device (100) according to claim 1, characterized in that: The second threshold is twice the first threshold.

8. The injection control device (100) according to claim 1, characterized in that: The second threshold is calculated according to the first interval.

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