Fuel injection system control device

Abstract

The purpose of the present invention is to achieve both the assurance of combustion stability in an internal combustion engine and the suppression of PN during operation in a catalyst warm-up mode accompanied by an ignition retard. A control device 150 is fora fuel injection device 101 which directly injects a fuel into a cylinder 615 of an internal combustion engine 10 operating in a catalyst warm-up mode for warming up a catalyst by using an ignition retard for retarding an ignition timing until an expansion stroke. The control device 150 performs the fuel injection immediately before the ignition timing in an expansion stroke among a plurality of fuel injections performed during one combustion cycle during the operation in the catalyst warm-up mode, and controls the fuel injection device 101 so that the injection amount of the fuel injection immediately before the ignition timing becomes smaller as the ignition timing is retarded.

Description

Technical Field

[0001] The present invention relates to a control device for controlling a fuel injection device of an internal combustion engine.

Background Art

[0002] In recent years, with the strengthening of exhaust regulations, in internal combustion engines, it is required to reduce the total amount of unburned particles (PM: Particulate Matter) and the number of unburned particles (PN: Particulate Number), which is the number of the unburned particles, HC (hydrocarbons), and NOx (nitrogen oxides) discharged in a driving mode defined by a fuel consumption standard such as WLTC. PN and HC are generated when the fuel injected from the fuel injection device adheres to the piston and the wall surface in the cylinder. To suppress PN and HC, it is effective to reduce fuel adhesion. PN tends to increase when there is a region where the equivalence ratio, which is the ratio of air to fuel immediately before ignition, is large, that is, where a rich mixture of fuel exists in the cylinder. HC is mostly discharged at the start of an internal combustion engine when the catalyst is not activated. As a technique for early activation of the catalyst, there is known a technique of ignition retard in which the ignition timing is retarded from the idle after the catalyst has completed warm-up, increasing the exhaust loss and raising the exhaust temperature to warm up the catalyst early. The operation mode of an internal combustion engine that warms up the catalyst by ignition retard is also referred to as the "catalyst warm-up mode".

[0003] Ignition retard is to retard the ignition timing from the optimum ignition timing at which the fuel consumption is the best. Specifically, ignition retard retards the ignition timing until the expansion stroke, which is the stroke from the end of the compression stroke until the piston reaches the bottom dead center from the top dead center. However, ignition retard tends to make combustion unstable. In order to surely ignite and enhance combustion stability, it is necessary to form a rich mixture necessary for ignition around the spark plug.

[0004] One effective technique for creating a rich air-fuel mixture around the spark plug at ignition timing is to form a cavity on the piston crown and inject fuel during the compression stroke to swirl the mixture into the cavity, thereby concentrating the mixture around the spark plug. Another effective technique for creating a rich air-fuel mixture around the spark plug at ignition timing is to position the fuel injector near the spark plug (hereinafter also referred to as "center injection type") and inject fuel just before ignition timing.

[0005] Patent Document 1 discloses a technique for ensuring combustion stability in which the period from the end of fuel injection in the expansion stroke to the ignition timing is shortened as the ignition timing in the expansion stroke is retarded. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2016 / 194184 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The fuel spray injected from a fuel injector is susceptible to changes in spray penetration (reach) due to changes in cylinder pressure. The more retarded the ignition timing during the expansion stroke, the lower the cylinder pressure becomes, and the longer the spray penetration tends to be. When the spray penetration is longer, the spray tends to diffuse within the cylinder, making it difficult to maintain the air-fuel mixture around the spark plug at ignition timing. In particular, in the case of a center injection system where the fuel injector is positioned near the spark plug, the spark plug and the fuel injection position are close together, so in order to maintain the air-fuel mixture around the spark plug at ignition timing, fuel injection must be performed just before ignition timing.

[0008] The retarded ignition timing during the expansion stroke shortens the time between the end of fuel injection during the expansion stroke and the ignition timing, bringing the end of fuel injection closer to the ignition timing. In this case, the time available for the atom to vaporize is reduced, making it easier for fuel to adhere to the piston and cylinder walls at ignition timing, which can increase the PN (Percentage-to-Noise Ratio). The technology disclosed in Patent Document 1 does not consider these problems at all and has room for improvement.

[0009] The present invention has been made in view of the above, and aims to achieve both ensuring combustion stability of an internal combustion engine and suppressing PN during operation in a catalytic warm-up mode accompanied by ignition retardation. [Means for solving the problem]

[0010] To solve the above problems, the fuel injection device control device according to the present invention is a fuel injection device control device that directly injects fuel into the cylinder of an internal combustion engine operating in a catalyst warm-up mode in which the catalyst is warmed up by ignition retardation which retards the ignition timing until the expansion stroke, and is characterized in that, when operating in the catalyst warm-up mode, the fuel injection immediately before the ignition timing among the multiple fuel injections performed in one combustion cycle is performed in the expansion stroke, and the fuel injection device is controlled such that the amount of fuel injected immediately before the ignition timing decreases as the ignition timing is retarded. [Effects of the Invention]

[0011] According to the present invention, it is possible to achieve both combustion stability of the internal combustion engine and suppression of PN (Percentile Neutralization) during operation in a catalytic warm-up mode accompanied by ignition retardation. Other issues, configurations, and effects will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0012] [Figure 1] A diagram showing the schematic configuration of an internal combustion engine with a fuel injection system. [Figure 2]Figure 1 shows a schematic diagram illustrating the general configuration of an internal combustion engine system, including the internal combustion engine shown in Figure 1. [Figure 3] Figure 1 shows a longitudinal cross-sectional view of the fuel injection system and a schematic diagram of the control device. [Figure 4] Figure 3 shows a magnified view of the vicinity of the movable element and valve body. [Figure 5] This diagram shows the relationship between the injection pulse output from the ECU, the drive voltage applied to the solenoid of the fuel injection system, the drive current supplied to the solenoid, and the displacement of the valve body and movable element. [Figure 6] This diagram illustrates the fuel injection control performed during operation in catalytic converter warm-up mode. [Figure 7] A projection view of the spray ejected from the fuel injection system. [Figure 8] A diagram showing the relationship between the penetration of the fuel spray injected from the fuel injector and the pressure inside the cylinder. [Figure 9] This figure illustrates a first embodiment of fuel injection control immediately before ignition timing, which is performed during operation in catalytic converter warm-up mode. [Figure 10] This figure illustrates a second embodiment of fuel injection control immediately before ignition timing, which is performed during operation in catalyst warm-up mode. [Figure 11] This figure shows the relationship between the injection pulse output from the ECU, the drive voltage applied to the solenoid of the fuel injection device, the drive current supplied to the solenoid, and the displacement of the valve body in Embodiment 2. [Figure 12] A diagram showing the relationship between injection pulse width and fuel injection volume. [Figure 13] A diagram showing the relationship between ignition retard amount, fuel pressure, injection amount, engine speed, and elapsed time since engine startup. [Figure 14] This figure illustrates a third embodiment of fuel injection control immediately before ignition timing, which is performed during operation in catalytic converter warm-up mode. [Modes for carrying out the invention]

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For components or functions denoted by the same reference numerals in each embodiment, unless otherwise specified, they have the same components or functions in each embodiment, and the description thereof will be omitted.

[0014] [Embodiment 1] The control device 150 of the fuel injection device 101 according to Embodiment 1 will be described with reference to FIGS. 1 to 9. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine 10 having the fuel injection device 101.

[0015] The internal combustion engine 10 is a direct injection type internal combustion engine that directly injects fuel into the cylinder 615. The internal combustion engine 10 includes a fuel injection device 101, a spark plug 604, an intake port 607, an exhaust port 608, a cylinder 614, a piston 609, an intake valve 605, and an exhaust valve 610.

[0016] The spark plug 604 is disposed at the upper center of the cylinder 614. The spark plug 604 has a negative electrode 612 and a positive electrode 613 exposed in the cylinder 615. The fuel injection device 101 is a center injection type fuel injection device that is disposed near the spark plug 604 and injects fuel into the cylinder 615. Note that the fuel injection device 101 may be a port injection type fuel injection device that is disposed in the intake port 607 and injects fuel into the intake port 607.

[0017] The crown surface 606 of the piston 609 on the side of the spark plug 604 has a flat surface. A partition wall 602 that blocks the flow between the upper portion 620 and the lower portion 611 of the intake port 607 is attached to the intake port 607. A valve 601 is provided upstream of the partition wall 602, and the valve 601 is configured to be controlled to open and close by the control device 150. FIG. 1 shows a state in which the valve 601 is closed.

[0018] Note that in Figure 1, the intake valve 605 and exhaust valve 610 are shown for illustrative purposes. However, in a typical direct-injection internal combustion engine 10, which has two intake valves 605 and two exhaust valves 610, the intake valves 605 and exhaust valves 610 are not shown in the cross-sectional view passing through the central axis of the cylinder 614. Also, Figure 1 shows the state of the spray in the cylinder 615 (D1~D8) immediately after fuel is injected from the fuel injector 101.

[0019] Figure 2 shows a schematic configuration of the internal combustion engine system 1, including the internal combustion engine 10 shown in Figure 1.

[0020] The air flowing into the cylinder 615 of the internal combustion engine 10 passes through the air cleaner 701, the supercharger chamber 704 which is equipped with the turbine 702 of the supercharger, the intercooler 705, the throttle valve 706, and the intake port 607. The air cleaner 701 has the function of removing dust from the air and preventing it from being drawn into the cylinder 615, thereby suppressing wear on the cylinder 614 and the piston 609.

[0021] The supercharging chamber 704 is equipped with turbines 702 on the intake and exhaust sides, connected by a shaft 707. The turbines 702 rotate in accordance with the exhaust gas flow velocity, increasing the amount of air flowing into the cylinder 615 and improving power output. The air that has passed through the supercharging chamber 704 is heated by the supercharging by the turbines 702 and is cooled by the intercooler 705. The cooled air then flows into the cylinder 615 through a throttle valve 706 that adjusts the amount of air and an intake port 607.

[0022] The air flowing into cylinder 615 mixes with fuel injected from fuel injector 101 to form a fuel-air mixture, which is ignited by spark plug 604 and burns. This combustion pushes down piston 609, and after the driving force of piston 609 is transmitted to crankshaft 710, exhaust valve 610 opens. The exhaust gas from cylinder 615 passes through exhaust port 608, and the velocity of the exhaust gas rotates turbine 702, while also passing through catalytic converter 703.

[0023] The exhaust gas is discharged outside the vehicle after its HC, NOx, and CO content is reduced by passing through the catalytic converter 703. The catalytic converter 703 is composed of, for example, a three-way catalytic converter. The catalytic converter 703 removes HC, NOx, and CO contained in the exhaust gas by causing reduction and oxidation reactions using a catalyst made of palladium, rhodium, and platinum, etc. However, the catalytic converter 703 has low reduction capacity when the catalyst temperature is low. In particular, under low temperature conditions such as when starting the internal combustion engine 10, combustion is required to warm up the catalyst quickly.

[0024] Figure 3 is a diagram showing a longitudinal cross-sectional view of the fuel injection system 101 shown in Figure 1 and a schematic configuration of the control device 150. Figure 4 is an enlarged view of the vicinity of the movable element 202 and valve body 214 in Figure 3.

[0025] The fuel injection of the fuel injector 101 is controlled by injection pulses output from the engine control unit (ECU) 104. The ECU 104 is equipped with an A / D converter and I / O ports for receiving signals from various sensors. The ECU 104 receives signals from various sensors indicating the state of the internal combustion engine 10 and calculates the pulse width of the injection pulse (injection pulse width) for controlling the amount of fuel injected, as well as the start and end timings of fuel injection, according to the operating conditions or operating mode of the internal combustion engine 10. The injection pulses output from the ECU 104 are input to the drive circuit 103 through the signal line 110. The drive circuit 103 determines the drive current waveform supplied to the solenoid 205 of the fuel injector 101 based on the command from the ECU 104 and supplies the drive current waveform to the solenoid 205 of the fuel injector 101 for a time based on the injection pulse.

[0026] The ECU 104 communicates with the drive circuit 103 via the communication line 111. The ECU 104 can switch the drive current waveform determined by the drive circuit 103, or change the current and time settings, depending on the fuel pressure supplied to the fuel injector 101, the operating conditions of the internal combustion engine 10, or the operating mode. The drive circuit 103 may be mounted as an integrated component or on a circuit board with the ECU 104. In this embodiment, the drive circuit 103 and the ECU 104 are collectively referred to as the "control device 150".

[0027] The fuel injector 101 is a normally closed solenoid valve (electromagnetic fuel injector). As shown in Figure 3, the fuel injector 101 has a valve body 214 that closes or opens the fuel injection hole 219 through which fuel is injected. When the solenoid 205 is not energized, the valve body 214 is biased in the closing direction (downward in Figure 3) by the first spring 210 and is in close contact with the valve seat 218, resulting in a closed valve state. In the closed valve state, a force from the second spring, the return spring 212, acts on the movable element 202 in the opening direction (upward in Figure 3). At this time, the force from the spring 210 acting on the valve body 214 is greater than the force from the return spring 212, so as shown in Figure 4, the end face 302 of the movable element 202 is in contact with the valve body 214, and the movable element 202 is stationary. The valve body 214 and the movable element 202 are configured to be displaceable relative to each other and are enclosed within the nozzle holder 201. The nozzle holder 201 has an end face 303 that serves as a spring seat for the return spring 212. The force exerted by the spring 210 is adjusted during assembly by the amount of pressure applied to the spring retainer 224, which is fixed to the inner surface of the stator (core) 207.

[0028] Furthermore, the fuel injection device 101 has a magnetic circuit formed by a stator 207, a movable element 202, a nozzle holder 201, and a housing 203. A gap 301 is provided between the movable element 202 and the stator 207. A magnetic thrombus 211 is formed in the part of the nozzle holder 201 corresponding to the gap 301 between the movable element 202 and the stator 207. The solenoid 205 is attached to the outer circumference of the nozzle holder 201 while wound around a bobbin 204. A rod guide 215 is provided near the tip of the valve body 214 on the valve seat 218 side, so as to be fixed to the nozzle holder 201. The movement of the valve body 214 in the valve axis direction (vertical direction in Figure 3) is guided by two sliding points: the stator 207, which contacts the spring base 304 of the valve body 214, and the rod guide 215. An orifice 216, which has a valve seat 218 and a fuel injection hole 219, is fixed to the tip of the nozzle holder 201, sealing the internal space (fuel passage) between the movable element 202 and the valve body 214 from the outside.

[0029] Fuel supplied to the fuel injector 101 is supplied from rail piping located upstream of the fuel injector 101, flows through the fuel passage hole 231 to the tip of the valve body 214, and seals the fuel between the tip of the valve body 214 on the valve seat 218 side and the valve seat 218. In the closed state, the fuel pressure creates a differential pressure between the upper and lower parts of the valve body 214, and the valve body 214 is pushed in the closing direction by the differential pressure obtained by multiplying the fuel pressure by the pressure-receiving area of ​​the inner diameter at the position of the valve seat 218, and the force of the spring 210. When a drive current is supplied to the solenoid 205 from the closed state, a magnetic field is generated in the magnetic circuit, a magnetic flux passes between the stator 207 and the movable element 202, and a magnetic attractive force acts on the movable element 202. When the magnetic attractive force acting on the movable element 202 exceeds the differential pressure and the force of the spring 210, the movable element 202 begins to displace in the direction of the stator 207 (upwards in Figure 3).

[0030] After the valve body 214 begins its opening operation, the movable element 202 moves to the position of the stator 207 and collides with it. After the movable element 202 collides with the stator 207, it bounces back due to the reaction force from the stator 207, but is attracted to the stator 207 by the magnetic attractive force acting on it and eventually stops. At this time, a force is acting on the movable element 202 in the direction of the stator 207 by the return spring 212, so the time it takes for the bounce to subside can be shortened. Because the bounce is small, the time during which the gap 301 between the movable element 202 and the stator 207 is large is shortened, and stable operation can be performed even with smaller injection pulse widths.

[0031] Having completed the valve opening operation in this manner, the movable element 202 and valve body 214 remain stationary in the open valve state. In the open valve state, a gap is created between the valve body 214 and the valve seat 218, and fuel is injected from the fuel injection port 219. The fuel flows downstream through the central hole provided in the stator 207 and the fuel passage hole 305 provided in the movable element 202.

[0032] When the power to the solenoid 205 is cut off, the magnetic flux generated in the magnetic circuit disappears, and the magnetic attractive force also disappears. With the magnetic attractive force acting on the movable element 202 disappearing, the movable element 202 and the valve body 214 are pushed back toward the closed valve position toward contact with the valve seat 218 by the force of the spring 210 and the differential pressure.

[0033] When the valve body 214 closes from the open state, after the valve body 214 contacts the valve seat 218, the movable element 202 moves away from the valve body 214 and the stator 207 in the closing direction, moves for a certain period of time, and then is returned to the initial position of the closed state by the return spring 212.

[0034] At the moment the valve body 214 collides with the valve seat 218 and the valve closes, the movable element 202 separates from the valve body 214. This allows the fuel injector 101 to reduce the mass of the movable member at the moment the valve body 214 collides with the valve seat 218 by the mass of the movable element 202. Therefore, the fuel injector 101 can reduce the collision energy when it collides with the valve seat 218 and suppress the bouncing of the valve body 214 caused by the collision with the valve seat 218.

[0035] In the fuel injection system 101, relative displacement occurs between the valve body 214 and the movable element 202 at the moment of collision between the movable element 202 and the stator 207 when the valve is open, and at the moment of collision between the valve body 214 and the valve seat 218 when the valve is closed. As a result, the fuel injection system 101 can suppress the bouncing of the movable element 202 against the stator 207 and the bouncing of the valve body 214 against the valve seat 218.

[0036] Figure 5 shows the relationship between the injection pulse output from the ECU 104, the drive voltage applied to the solenoid 205 of the fuel injector 101, the drive current supplied to the solenoid 205, and the displacement of the valve body 214 and the movable element 202.

[0037] When an injection pulse is input to the drive circuit 103, the drive circuit 103 applies a high voltage 401 from a voltage source VH, which has been boosted to a voltage higher than the battery voltage VB, to the solenoid 205 and begins supplying drive current to the solenoid 205. When the current value of the drive current reaches a peak current value Ipeak that has been set in advance by the ECU 104, the drive circuit 103 stops applying the high voltage 401. Then, due to the back electromotive force caused by the inductance of the solenoid 205, the drive current that was supplied to the solenoid 205 is fed back to the voltage source VH side and rapidly decreases from the peak current value Ipeak, as in current 402. When the current value of the drive current becomes less than a predetermined current value 404, the drive circuit 103 applies the battery voltage VB to the solenoid 205 and controls it so that the predetermined current 403 is maintained.

[0038] When the fuel pressure supplied to the fuel injector 101 increases, the differential pressure acting on the valve body 214 increases, and the time it takes for the valve body 214 to reach the target opening increases. As a result, the timing of reaching the target opening may be delayed relative to the time it takes to reach the peak current value Ipeak. If the drive current is rapidly reduced, such as to current 402, the magnetic attractive force acting on the movable element 202 also decreases rapidly, causing the behavior of the valve body 214 to become unstable, and in some cases, it may start to close even while energized.

[0039] During the transition period from the peak current value Ipeak to current 403, the drive circuit 103 regenerates current within the circuit by allowing the current due to the back electromotive force to flow towards the ground potential. This causes the applied voltage to the solenoid 205 to become approximately 0V, and the current 402 can be gradually reduced. As a result, the drive circuit 103 can gradually reduce the magnetic attractive force acting on the movable element 202, stabilizing the behavior of the valve body 214 at high fuel pressures. Therefore, the drive circuit 103 can suppress variations in the injection amount.

[0040] The fuel injector 101 is driven by this drive current profile. From the application of the high voltage 401 until the peak current value Ipeak is reached, the movable element 202 and valve body 214 begin to displace at timing t41. Thereafter, the movable element 202 and valve body 214 reach a predetermined maximum height position. The movable element 202 collides with the stator 207 and bounces at timing t42 when it reaches the maximum height position. Since the valve body 214 is configured to be displaceable relative to the movable element 202, it moves away from the movable element 202, and the displacement of the valve body 214 overshoots beyond the maximum height position. Thereafter, due to the magnetic attraction force generated by the current 403 and the valve-opening force of the return spring 212, the movable element 202 is displaced in the valve-opening direction and comes to rest at the maximum height position at timing t44. The valve body 214 seats on the movable element 202 at timing t43 and is displaced in the opening direction, and at timing t44 it comes to rest at the maximum height position and enters the open state. In the case of a fuel injection system in which the valve body 214 and the movable element 202 are integrally formed, the amount of displacement of the valve body 214 does not exceed the maximum height position, and the amount of displacement of the movable element 202 and the valve body 214 after reaching the maximum height position (after timing t42) is equal.

[0041] The height position of the valve body 214 and the movable element 202 refers to the position of the valve body 214 and the movable element 202 in the opening direction from the reference position, with the position of the valve body 214 and the movable element 202 in the closed state when the valve body 214 is seated on the valve seat 218 as the reference position. In other words, the displacement amount of the valve body 214 and the movable element 202 is the amount of displacement of the valve body 214 and the movable element 202 from the reference position. The maximum height position of the valve body 214 and the movable element 202 is predetermined by the position of the stator 207 into which the movable element 202 collides. The displacement amount of the valve body 214 is also referred to as the lift amount of the valve body 214. In this embodiment, the displacement amount of the valve body 214 when the valve body 214 reaches the maximum height position is also referred to as the maximum lift amount.

[0042] Figure 6 illustrates the fuel injection control performed during operation in catalyst warm-up mode.

[0043] The horizontal axis in Figure 6 represents the angle of the crankshaft 710. In Figure 6, the angle of the crankshaft 710 at top dead center (TDC) of piston 609 during the intake stroke is -360 degrees, the angle of the crankshaft 710 at bottom dead center (BDC) of piston 609 is -180 degrees, and the angle of the crankshaft 710 at TDC of piston 609 during the compression stroke is 0 degrees. The dotted line in Figure 6 represents the lift amount of the intake valve 605. The dashed line in Figure 6 represents the average value of the turbulence velocity of 615 in the cylinder. The solid line in Figure 6 represents the tumble of 615 in the cylinder. The shaded area in Figure 6 represents the period during which fuel injection occurs.

[0044] During operation in catalyst warm-up mode, the control device 150 controls the fuel injector 101 to perform multiple fuel injections during one combustion cycle. In this case, the control device 150 may control the fuel injector 101 to perform two or more fuel injections during the intake stroke 802 and one or more fuel injections during the expansion stroke 804. In the example in Figure 6, the control device 150 controls the fuel injector 101 to perform two fuel injections during the intake stroke 802 and one fuel injection during the expansion stroke 804. In the example in Figure 6, the control device 150 performs ignition retardation, delaying the ignition timing to timing t86 within the expansion stroke 804. The ignition timing t86 is preset and changes according to the timing of the catalyst temperature rise requirement and environmental conditions. The control device 150 needs to control the fuel injector 101 so that appropriate fuel injection is performed at the desired ignition timing t86.

[0045] Specifically, at the timing t81 when the piston 609 reaches TDC, immediately before or simultaneously with the closing of the exhaust valve 610, the control device 150 starts opening the intake valve 605, allowing air to flow into the cylinder 615. At the timing t82 between the start of intake valve 605 opening and reaching maximum lift, the control device 150 starts the first fuel injection 805. Subsequently, at the timing t83 when the piston 609 reaches BDC, the control device 150 starts the second fuel injection 806. After the piston 609 reaches BDC and enters the compression stroke 803, and then the piston 609 reaches TDC, at the timing t84 just before the ignition timing t86, the control device 150 starts the third fuel injection 807. In this third fuel injection 807, the control device 150 controls the start timing t84 and end timing t85 of the fuel injection so that the spray injected from the fuel injector 101 around the spark plug 604 forms a rich mixture with a higher fuel content than the stoichiometric ratio. The control device 150 sets the fuel distribution ratio between the intake stroke 802 and the expansion stroke 804 so that the intake stroke 802 receives more fuel. For example, the control device 150 may set the ratio of intake stroke 802:expansion stroke 804 to approximately 6:4, 7:3, 8:2, or 9:1.

[0046] At timing t86, when a rich air-fuel mixture is formed between and around the negative electrode 612 and positive electrode 613 of the spark plug 604, the control device 150 ignites the mixture. To maintain the air-fuel mixture around the spark plug 604 at this ignition timing t86, it is desirable to bring the fuel injection termination timing t85, which is immediately before the ignition timing t86, closer to the ignition timing t86. In other words, the control device 150 controls the fuel injector 101 so that the more retarded the ignition timing t86 is, the shorter the period from the fuel injection termination timing t85 immediately before the ignition timing t86 to the ignition timing t86 becomes.

[0047] Figure 7 is a projection view of the spray injected from the fuel injector 101. Figure 7 shows the projection view of the spray when the A-A' cross-section of the spray shown in Figure 1 is viewed in the direction toward the fuel injector 101.

[0048] The fuel injector 101 is a multi-hole type fuel injector in which the fuel injection holes 219 are composed of multiple holes. The spray injected from the fuel injector 101 consists of eight sprays, for example, sprays D1 and D2 injected toward the spark plug 604, sprays D3 and D4 injected toward the piston 609, and sprays D5 to D8 injected toward the intake valve 605 side than sprays D3 and D4.

[0049] The concept of this embodiment is to form a fuel-air mixture by sprays D1 and D2 between and around the negative electrode 612 and positive electrode 613 of the spark plug 604 during fuel injection immediately before ignition timing. The fuel injector 101 injects sprays D1 and D2 so that they are positioned sandwiching the negative electrode 612 and positive electrode 613. As a result, the fuel injector 101 can form a fuel-air mixture richer than stoichiometric between and around the negative electrode 612 and positive electrode 613, thereby ensuring combustion stability.

[0050] Figure 8 shows the relationship between the penetration of the spray injected from the fuel injector 101 and the pressure inside the cylinder 615.

[0051] The spray injected from the fuel injector 101 is susceptible to changes in spray penetration due to changes in the pressure inside the cylinder 615. As shown in Figure 8, the lower the pressure inside the cylinder 615, the longer the spray penetration. When the spray penetration is longer, the spray is more likely to diffuse inside the cylinder 615, making it difficult to maintain the air-fuel mixture around the spark plug 604 at the ignition timing.

[0052] Figure 9 illustrates a first embodiment of fuel injection control immediately before ignition timing performed during operation in catalytic converter warm-up mode. Figure 9(a) shows the case where the ignition retard amount is small, and Figure 9(b) shows the case where the ignition retard amount is large. The dashed line in Figure 9 represents the pressure in the cylinder 615. In Figures 9(a) and 9(b), the load on the internal combustion engine 10 during operation in catalytic converter warm-up mode is assumed to be the same.

[0053] Ignition retardation refers to the amount by which the ignition timing is retarded from the optimal timing that results in the best fuel efficiency. The greater the ignition retardation, the greater the retardation of the ignition timing.

[0054] As shown in Figure 9(a), when the ignition retardation amount is small, the fuel injection start timing t91 is close to TDC, so the pressure in the cylinder 615 is high. In this case, the spray penetration is not long, so the air-fuel mixture does not diffuse easily in the cylinder 615. In this case, the control device 150 increases the penetration force of the spray by lengthening the fuel injection period 901, that is, by increasing the injection amount, thereby making it easier for the spray to diffuse in the cylinder 615. This makes it easier for the control device 150 to maintain the air-fuel mixture around the spark plug 604 at the ignition timing t93.

[0055] As shown in Figure 9(b), when the ignition retardation amount is large, the pressure in the cylinder 615 at the start timing of fuel injection t94 is lower than in the case of Figure 9(a). In this case, the spray penetration tends to be longer, so the air-fuel mixture tends to diffuse into the cylinder 615. In this case, the control device 150 shortens the fuel injection period 902, that is, reduces the injection amount, thereby reducing the penetration force of the spray and suppressing the diffusion of the spray. As a result, the control device 150 can more easily maintain the air-fuel mixture around the spark plug 604 at the ignition timing t96. As a result, the control device 150 can ignite the air-fuel mixture stably, thus ensuring combustion stability.

[0056] Furthermore, in the case shown in Figure 9(b), the spray penetration tends to be long, making it easier for fuel to adhere to the piston 609 and the wall surface inside the cylinder 615, thus increasing PN. However, the control device 150 reduces the injection amount, which can suppress fuel adhesion to the piston 609 and other parts, thereby suppressing PN.

[0057] Thus, the control device 150 controls the fuel injector 101 so that the amount of fuel injected just before ignition timing decreases as the ignition timing is retarded. As a result, the control device 150 can maintain the air-fuel mixture around the spark plug 604 at ignition timing and suppress fuel adhesion to the piston 609 and other components. Therefore, the control device 150 can achieve both combustion stability and PN suppression.

[0058] Furthermore, as shown in Figures 9(a) and 9(b), when the amount of fuel injected just before the ignition timing in the expansion stroke changes according to the amount of ignition retardation, the control device 150 may adjust the amount of fuel injected in the intake stroke to maintain the air-fuel ratio at stoichiometric or constant. Specifically, if the amount of fuel injected just before the ignition timing in the expansion stroke is reduced due to a large amount of ignition retardation, the control device 150 controls the fuel injector 101 so that the amount of fuel injected in the intake stroke increases in accordance with the decrease in the amount of fuel injected. As a result, the control device 150 can reliably ensure combustion stability by suppressing PN while maintaining the air-fuel ratio at stoichiometric or constant.

[0059] Furthermore, if two or more fuel injections are performed during the intake stroke, the control device 150 may control the fuel injector 101 so that the injection amount of the second and subsequent fuel injections during the intake stroke increases. For example, the control device 150 may lengthen the fuel injection period or widen the injection pulse width so that the injection amount of the second and subsequent fuel injections during the intake stroke (for example, fuel injection 806 in Figure 6) increases by the amount of the injection immediately before the ignition timing during the expansion stroke.

[0060] Compared to the first fuel injection in the intake stroke (for example, fuel injection 805 in Figure 6), the fuel mixture is less likely to diffuse during the second fuel injection in the intake stroke (for example, fuel injection 806 in Figure 6). Therefore, increasing the amount of fuel injected during the second intake stroke can further enhance the effect of forming a rich fuel mixture over a wide area within the cylinder 615, thereby ensuring combustion stability. Also, since the timing of the fuel injection during the second intake stroke is later than that of the first intake stroke, the time for mixing air and fuel is longer, making it more difficult for air and fuel to mix. Therefore, increasing the amount of fuel injected during the second intake stroke makes it easier to form a rich fuel mixture over a wide area around the spark plug 604, further enhancing the effect of ensuring combustion stability.

[0061] [Embodiment 2] The control device 150 of the fuel injection device 101 according to Embodiment 2 will be described using Figures 10 to 12. In the control device 150 of the fuel injection device 101 according to Embodiment 2, the same configuration and operation as in Embodiment 1 will not be described.

[0062] Figure 10 illustrates a second embodiment of fuel injection control immediately before ignition timing during operation in catalytic converter warm-up mode. Figure 10(a) shows the case where the ignition retard amount is small, and Figure 10(b) shows the case where the ignition retard amount is large. The dashed line in Figure 10 represents the pressure in the cylinder 615. In Figures 10(a) and 10(b), the load on the internal combustion engine 10 during operation in catalytic converter warm-up mode is assumed to be the same.

[0063] The control device 150 according to Embodiment 2 performs the following fuel injection control in addition to the fuel injection control according to Embodiment 1, which controls the fuel injector 101 so that the amount of fuel injected immediately before the ignition timing decreases as the amount of ignition retardation increases. Specifically, the control device 150 according to Embodiment 2 controls the fuel injector 101 so that the period from the end timing of the fuel injection immediately before the ignition timing to the ignition timing becomes shorter as the amount of ignition retardation increases, i.e., as the ignition timing is retarded. Specifically, the control device 150 controls the period 1202 to be shorter when the amount of ignition retardation is large compared to the period 1201 from the end timing t23 of the fuel injection to the ignition timing t93 when the amount of ignition retardation is small.

[0064] When the ignition retard amount is large, the pressure in cylinder 615 at the start timing t24 of fuel injection is lower compared to when it is small. As a result, the spray penetration is longer, and the air-fuel mixture diffuses more easily into cylinder 615. Consequently, it becomes difficult to maintain a rich air-fuel mixture around the spark plug 604 at the ignition timing t96.

[0065] The control device 150 according to Embodiment 2 can ensure combustion stability by stably forming a rich mixture around the spark plug 604, thereby shortening the period 1202 from the end of fuel injection timing t25 to the ignition timing t96 as the ignition retard amount increases. However, if the period 1202 is shortened too much, the end of fuel injection timing t25 approaches the ignition timing t96, reducing the time available for the spray to vaporize, and sometimes causing the mixture to ignite before the spray has finished vaporizing. However, the control device 150 according to Embodiment 2 can shorten the time required for the spray to vaporize by reducing the injection amount, thereby suppressing fuel adhesion to the piston 609, etc., at the ignition timing t96, and suppressing PN while ensuring combustion stability. Furthermore, by suppressing extremely rich mixtures with an equivalent ratio of 2 or more, for example, PN can be suppressed even further.

[0066] Figure 11 is a diagram showing the relationship between the injection pulse output from the ECU 104, the drive voltage applied to the solenoid 205 of the fuel injector 101, the drive current supplied to the solenoid 205, and the displacement of the valve body 214 in Embodiment 2. Figure 11 corresponds to Figure 5. The dashed lines in Figure 11 represent the waveforms according to Embodiment 1 shown in Figure 5, and the solid lines in Figure 11 represent the waveforms according to the Second Embodiment.

[0067] The control device 150 according to Embodiment 2 controls the valve body 214 so that it operates with a displacement change 1301 as shown in Figure 11 during fuel injection immediately before ignition timing. In other words, the control device 150 controls the valve body 214 so that it is displaced within a range of heights lower than the maximum height position during fuel injection immediately before ignition timing. To put it another way, the control device 150 according to Embodiment 2 controls the lift amount of the valve body 214 during fuel injection immediately before ignition timing within a range smaller than a predetermined maximum lift amount.

[0068] The control device 150 then controls the fuel injector 101 so that the lift amount of the valve body 214 decreases as the ignition retardation amount increases, that is, as the ignition timing is retarded. As the lift amount of the valve body 214 decreases, the pressure loss of the fuel flowing between the valve body 214 and the valve seat 218 increases, and the spray velocity decreases. Therefore, even when the ignition timing is retarded and the pressure inside the cylinder 615 is low at the timing of fuel injection, it is possible to easily form the air-fuel mixture near the spark plug 604, thereby ensuring combustion stability.

[0069] Furthermore, the control device 150 reduces the lift amount of the valve body 214 as the ignition retard amount increases, but when the ignition retard amount is small, it may be controlled so that the valve body 214 reaches its maximum height position. As a result, the upper limit of the lift amount of the valve body 214 can be greatly changed according to the ignition retard amount, making it easier to maintain the air-fuel mixture around the spark plug 604 in response to changes in the pressure inside the cylinder 615 that change according to the ignition retard amount.

[0070] Figure 12 shows the relationship between the injection pulse width Ti and the injection amount of the fuel injector 101. Figure 12 shows the injection amount characteristics Q141 when using each waveform shown in Figure 11.

[0071] If the injection pulse width Ti does not reach a predetermined time, and the force in the valve-opening direction, which is the resultant force of the magnetic attraction force acting on the movable element 202 and the return spring 212, does not exceed the force of the spring 210, the valve body 214 will not start to open and no fuel will be injected. Alternatively, even if the movable element 202 starts to displace, if the magnetic attraction force necessary for it to slide through the gap 301 cannot be secured and the movable element 202 does not come into contact with the valve body 214, the valve body 214 will not start to open and no fuel will be injected. Furthermore, in the case of a short injection pulse width Ti, for example, point 1401 in Figure 12, the movable element 202 collides with the valve body 214, causing the valve body 214 to separate from the valve seat 218 and begin to displace. However, since the valve body 214 starts to close before reaching its maximum height position, the injection amount is less than that of the dashed line 1420 extrapolated from the linear region 1430 where the relationship between the injection pulse width Ti and the injection amount is approximately a straight line.

[0072] Furthermore, in the case of the injection pulse width Ti at point 1402, the valve body 214 begins to close immediately after reaching its maximum height position, and the trajectory of the valve body 214 becomes parabolic. In this case, the kinetic energy of the valve body 214 in the opening direction is large, and the magnetic attractive force acting on the movable element 202 is large, so the proportion of time required for closing the valve increases, and the injection amount becomes larger than that of the dashed line 1420.

[0073] In this embodiment, in the injection volume characteristic Q141, the region 1440 in which the movable element 202 does not collide with the stator 207, that is, the region in which the valve body 214 does not reach its maximum height position and the trajectory of the valve body 214 becomes parabolic motion, is also referred to as the "half-lift region 1440". In this embodiment, in the injection volume characteristic Q141, the region 1441 in which the movable element 202 collides with the stator 207, that is, the region in which the valve body 214 reaches its maximum height position, is also referred to as the "full-lift region 1441". The solid line in Figure 11 shows the case in which the valve body 214 is displaced in the half-lift region 1440.

[0074] At point 1403, the injection pulse width Ti is such that the valve closing starts at the timing when the amount of bounce of the valve body 214 caused by the collision of the movable element 202 with the stator 207 is at its maximum. As a result, the repulsive force when the movable element 202 and the stator 207 collide acts on the movable element 202, reducing the valve closing delay time from when the injection pulse is turned OFF until the valve body 214 closes. Consequently, the injection amount is less than that shown by the dashed line 1420.

[0075] The injection pulse width Ti at point 1404 is the timing when the valve starts closing immediately after the bounce of the valve body 214 converges. For injection pulse widths Ti greater than that at point 1404, the injection amount increases approximately linearly with increasing injection pulse width Ti. In the region from the start of fuel injection up to the injection pulse width Ti at point 1404, the valve body 214 does not reach its maximum height position, or even if the valve body 214 reaches its maximum height position, the bounce of the valve body 214 is not stable, causing the injection amount to fluctuate. Fuel injection immediately before ignition timing, which occurs during the expansion stroke, has a significant impact on combustion stability if the injection amount fluctuates. Therefore, the control device 150 should adjust the injection pulse width Ti so that the valve body 214 is displaced in the half-lift region 1440 or the linear region 1430. As a result, the control device 150 can more easily ensure combustion stability.

[0076] [Embodiment 3] The control device 150 of the fuel injection device 101 according to Embodiment 3 will be described using Figures 13 and 14. In the control device 150 of the fuel injection device 101 according to Embodiment 3, the same configuration and operation as in Embodiments 1 and 2 will not be described.

[0077] Figure 13 shows the relationship between the ignition retard amount, fuel pressure, injection amount, and rotational speed of the internal combustion engine 10, and the elapsed time from the start of the internal combustion engine 10. In Figure 13, when the ignition retard amount is 0, it indicates that the ignition timing is set to the TDC of the compression stroke. In Figure 13, when the ignition retard amount is retarded, it indicates that the ignition timing is set to a retarded position compared to the TDC of the compression stroke. In Figure 13, when the ignition retard amount is advanced, it indicates that the ignition timing is set to a advanced position compared to the TDC of the compression stroke.

[0078] During the cranking period 1501 from the start timing t51 of the internal combustion engine 10 until combustion stabilizes, the control device 150 sets the ignition retard amount to the advanced side (ignition timing advanced beyond TDC of the compression stroke) to achieve stable combustion and raise the temperature inside the cylinder 615. After the cranking ends at timing t52, the control device 150 shifts the ignition retard amount to the retard side (ignition timing retarded beyond TDC of the compression stroke) to increase exhaust loss and raise the temperature of the exhaust gas discharged from inside the cylinder 615 to the exhaust port 608. As a result, the control device 150 can activate the catalyst of the catalytic converter 703 earlier and reduce HC.

[0079] Furthermore, during the cranking period 1501, the transition period 1502 until the ignition retard amount shifts to the retarded side, and the operating period 1503 in catalyst warm-up mode, which is the period after the ignition retard amount shifts to the retarded side, there is a transient period 1504 in which the fuel pressure supplied to the fuel injector 101 (hereinafter also referred to as "fuel pressure") changes (increases). The fuel pump that supplies high-pressure fuel to the fuel injector 101 supplies high-pressure fuel to the fuel piping communicating with the fuel injector 101 by the compression operation of a plunger synchronized with the camshaft of the internal combustion engine 10. Therefore, when the rotational speed of the internal combustion engine 10 is low, a certain amount of time is required for the fuel pressure to reach the target pressure 1505. In other words, between the start timing t51 of the internal combustion engine 10 and the timing t56 when the catalyst warm-up is completed, a transient period 1504 occurs in which the fuel pressure changes. In particular, in hybrid vehicles (HEV, SHEV, PHEV) equipped with an internal combustion engine 10 and an electric motor, the frequency of starting and stopping of the internal combustion engine 10 increases compared to vehicles equipped with only the internal combustion engine 10, so the fuel pressure when starting the internal combustion engine 10 changes frequently.

[0080] Figure 14 illustrates a third embodiment of fuel injection control immediately before ignition timing during operation in catalyst warm-up mode. Figure 14(a) shows the case where the fuel pressure is low, and Figure 14(b) shows the case where the fuel pressure is high. In Figures 14(a) and 14(b), the ignition retard amount is assumed to be the same.

[0081] When fuel pressure is low, the penetration force of the spray is reduced, making it difficult for the spray to diffuse within the cylinder 615. When fuel pressure is high, the penetration force of the spray is increased, making it easier for the spray to diffuse within the cylinder 615. Therefore, when fuel pressure changes, it is desirable to adjust at least one of the fuel injection termination timing and injection amount immediately before ignition timing.

[0082] The control device 150 according to Embodiment 3 controls the fuel injector 101 such that the lower the fuel pressure supplied to the fuel injector 101 at the start timing of fuel injection immediately before ignition timing, the longer the period from the end timing of fuel injection immediately before ignition timing to the ignition timing. Furthermore, the control device 150 controls the fuel injector 101 such that the lower the fuel pressure, the greater the amount of fuel injected immediately before ignition timing.

[0083] Specifically, the control device 150 controls the period 1601 from the end timing t65 of the fuel injection to the ignition timing t66 to be longer when the fuel pressure is low, compared to the period 1602 when the fuel pressure is high. This allows the control device 150 to make it easier for the spray to diffuse in the cylinder 615, thus making it easier for the air-fuel mixture to reach the spark plug 604 and ensuring combustion stability. Furthermore, the control device 150 controls the period 906 to be longer when the fuel pressure is low, compared to the period 907 when the fuel pressure is high. This allows the control device 150 to increase the penetration force of the spray and make it easier for it to diffuse, thus making it easier for the air-fuel mixture to reach the spark plug 604 and further ensuring combustion stability.

[0084] On the other hand, the control device 150 according to Embodiment 3 controls the fuel injector 101 such that the amount of fuel injected immediately before ignition timing decreases as the fuel pressure supplied to the fuel injector 101 at the start timing of fuel injection immediately before ignition timing increases. Furthermore, the control device 150 controls the fuel injector 101 such that the period from the end timing of fuel injection immediately before ignition timing to the ignition timing decreases as the fuel pressure increases.

[0085] Specifically, the control device 150 controls the fuel injection period 907 to be shorter when the fuel pressure is high compared to the fuel injection period 906 when the fuel pressure is low. This allows the control device 150 to reduce the penetration force of the spray and suppress the diffusion of the spray, thereby suppressing fuel adhesion to the piston 609 and other components, and suppressing PN while ensuring combustion stability. Furthermore, the control device 150 controls the period 1602 to be shorter when the fuel pressure is high compared to the period 1601 from the end timing t62 of the fuel injection to the ignition timing t63 when the fuel pressure is low. This allows the control device 150 to make it difficult for the spray to diffuse in the cylinder 615, making it easier to maintain the air-fuel mixture around the spark plug 604, and suppressing fuel adhesion to the piston 609 and other components, thus achieving a high degree of balance between ensuring combustion stability and suppressing PN.

[0086] Thus, the control device 150 can adjust at least one of the fuel injection termination timing and injection amount immediately before ignition timing in response to changes in fuel pressure. This allows a fuel-air mixture to form around the spark plug 604 even when fuel pressure changes, ensuring combustion stability. While adjusting the fuel injection termination timing and injection amount immediately before ignition timing individually is effective, adjusting both allows for greater control over the diffusion of the spray within the cylinder 615, thereby further enhancing combustion stability and PN suppression.

[0087] Furthermore, in hybrid vehicles (HEV, SHEV, PHEV) equipped with an internal combustion engine 10 and an electric motor, the fuel pressure at startup of the internal combustion engine 10 changes frequently, as described above. Therefore, the control device 150 according to Embodiment 3 is particularly effective when applied to hybrid vehicles, and can further enhance the effect of ensuring combustion stability and suppressing PN in hybrid vehicles.

[0088] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0089] Furthermore, each of the above configurations, functions, processing units, or processing means may be implemented in hardware, in whole or in part, for example, by designing them as integrated circuits. Alternatively, each of the above configurations or functions may be implemented in software by having the processor interpret and execute programs that implement each function. Information such as programs, tables, or files that implement each function can be stored in a recording device such as memory, a hard disk, or an SSD (solid state drive), or in a recording medium such as an IC card, SD card, or DVD.

[0090] Furthermore, the control lines and information lines shown are those deemed necessary for explanatory purposes, and not all control lines and information lines are necessarily shown in the actual product. In reality, it is safe to assume that almost all components are interconnected. [Explanation of Symbols]

[0091] 10...Internal combustion engine, 101...Fuel injection system, 150...Control device, 214...Valve body, 219...Fuel injection port, 615...Inside cylinder

Claims

1. A control device for a fuel injection system that directly injects fuel into the cylinders of an internal combustion engine operating in a catalyst warm-up mode, which warms up the catalyst by retarding the ignition timing until the expansion stroke, During operation in the catalyst warm-up mode, the fuel injection device is controlled such that the fuel injection immediately preceding the ignition timing, one of the multiple fuel injections performed during one combustion cycle, is performed during the expansion stroke, and the amount of fuel injected immediately preceding the ignition timing decreases as the ignition timing is retarded. A control device for a fuel injection system, characterized by the following features.

2. The fuel injection device is controlled such that the more the ignition timing is retarded, the shorter the period from the end of the fuel injection immediately before the ignition timing to the ignition timing. A control device for a fuel injection device according to claim 1.

3. The fuel injection system is controlled to perform two or more fuel injections during the intake stroke, and to increase the injection amount of the second and subsequent fuel injections during the intake stroke in accordance with the decrease in the injection amount of the fuel injection immediately before the ignition timing. A control device for a fuel injection device according to claim 1.

4. The fuel injection device has a valve body that closes or opens the fuel injection hole through which the fuel is injected. The control device controls the valve lift amount in the fuel injection immediately before the ignition timing to be within a range smaller than a predetermined maximum lift amount, and controls the valve so that the lift amount decreases as the ignition timing is retarded. A control device for a fuel injection device according to claim 1.

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