Control device for fuel injection 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

Fuel injection device control device

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

[0002] In recent years, with the tightening of exhaust emission regulations, internal combustion engines are required to reduce the total amount and number of unburned particles (PM), the unburned particle number (PN), hydrocarbons (HC), and nitrogen oxides (NOx) emitted during driving modes stipulated by fuel economy standards such as WLTC. PN and HC are generated when fuel injected from a fuel injector adheres to the piston and cylinder walls. Reducing fuel adhesion is an effective way to suppress PN and HC. PN tends to increase when the equivalence ratio (air-to-fuel ratio) is high immediately before ignition, i.e., when a rich (fuel-rich) mixture exists in the cylinder. Large amounts of HC are emitted during startup of an internal combustion engine when the catalyst is not activated. One known technique for accelerating catalyst activation is ignition retardation, which retards ignition timing relative to idle after the catalyst has warmed up, thereby increasing exhaust loss and raising exhaust temperature, thereby quickly raising the catalyst temperature. An internal combustion engine operating mode in which the catalyst is warmed up by ignition retard is also called a "catalyst warm-up mode."

[0003] Ignition retard is the process of retarding the ignition timing from the optimal ignition timing that maximizes fuel economy. Specifically, ignition retard is performed by retarding the ignition timing until the expansion stroke, which is the period from the end of the compression stroke until the piston reaches bottom dead center from top dead center. However, ignition retard can easily lead to unstable combustion. To ensure reliable ignition and improve combustion stability, it is necessary to form a rich mixture around the spark plug, which is necessary for ignition.

[0004] One effective technique for forming a rich mixture around the spark plug at the ignition timing is to form a cavity on the piston crown and inject fuel during the compression stroke to swirl up the mixture that has entered the cavity, thereby collecting the mixture around the spark plug.Another effective technique for forming a rich mixture around the spark plug at the ignition timing is to position a fuel injection device near the spark plug (hereinafter also referred to as a "center injection type") and inject fuel just before the ignition timing.

[0005] Patent Document 1 discloses a technique for ensuring combustion stability in which the more the ignition timing during the expansion stroke is retarded, the shorter the period from the end timing of fuel injection during the expansion stroke to the ignition timing is.

[0006] International Publication No. 2016 / 194184

[0007] The penetration (reaching distance) of the fuel spray injected from the fuel injector is likely to change due to changes in the pressure inside the cylinder. The more the ignition timing during the expansion stroke is retarded, the lower the pressure inside the cylinder becomes, and the longer the spray penetration tends to be. When the spray penetration is longer, the spray is more likely to diffuse inside the cylinder, making it difficult to maintain the air-fuel mixture around the spark plug at the ignition timing. In particular, in the case of a center injection type in which the fuel injector is located near the spark plug, the spark plug and the fuel injection position are close to each other, so in order to maintain the air-fuel mixture around the spark plug at the ignition timing, fuel must be injected immediately before the ignition timing.

[0008] If the period from the end of fuel injection to the ignition timing during the expansion stroke is shortened as the ignition timing during the expansion stroke is delayed, the end of fuel injection approaches the ignition timing. In this case, the time available for fuel spray to vaporize is shortened, making it more likely that fuel will adhere to the piston and cylinder walls at the ignition timing, which can increase PN. The technology disclosed in Patent Document 1 does not take such problems into consideration and leaves room for improvement.

[0009] The present invention has been made in view of the above, and has an object to ensure both combustion stability and PN suppression in an internal combustion engine when operating in a catalyst warm-up mode accompanied by ignition retard.

[0010] In order to solve the above problem, the control device of the fuel injection device of the present invention is a control device of the fuel injection device that directly injects fuel into the cylinders of an internal combustion engine operating in a catalyst warm-up mode in which the catalyst is warmed up by ignition retarding, which retards the ignition timing until the expansion stroke, and is characterized in that when operating in the catalyst warm-up mode, of the multiple fuel injections performed during one combustion cycle, the fuel injection immediately before the ignition timing is performed in the expansion stroke, and the fuel injection device is controlled so that the more the ignition timing is retarded, the smaller the injection amount of the fuel injection immediately before the ignition timing.

[0011] According to the present invention, it is possible to ensure combustion stability and suppress PN in an internal combustion engine when operating in a catalyst warm-up mode with ignition retard. Other problems, configurations, and effects will become clear from the description of the following embodiments.

[0012] 1 is a diagram showing a schematic configuration of an internal combustion engine having a fuel injection device. FIG. 2 is a diagram showing a schematic configuration of an internal combustion engine system including the internal combustion engine shown in FIG. 1. FIG. 3 is a longitudinal sectional view of the fuel injection device shown in FIG. 1 and a diagram showing a schematic configuration of a control device. FIG. 4 is an enlarged view of the vicinity of the moving element and the valve element in FIG. 3. FIG. 5 is a diagram showing 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 element and the moving element. FIG. 6 is a diagram explaining fuel injection control performed during operation in a catalyst warm-up mode. FIG. 7 is a projection view of a spray injected from the fuel injection device. FIG. 8 is a diagram showing the relationship between the penetration of the spray injected from the fuel injection device and the pressure inside the cylinder. FIG. 9 is a diagram explaining a first embodiment of fuel injection control performed immediately before ignition timing during operation in a catalyst warm-up mode. FIG. 10 is a diagram explaining a second embodiment of fuel injection control performed immediately before ignition timing during operation in a catalyst warm-up mode. FIG. 11 is a diagram showing 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 element in a second embodiment. 1 is a graph showing the relationship between the injection pulse width and the injection amount of the fuel injection device, and the relationship between the ignition retard amount, the fuel pressure, the injection amount, and the rotation speed of the internal combustion engine, and the elapsed time from the start of the internal combustion engine.

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

[0014] 1 to 9, a control device 150 for a fuel injection device 101 according to the first embodiment will be described. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine 10 having a fuel injection device 101.

[0015] The internal combustion engine 10 is a direct injection type internal combustion engine that directly injects fuel into a cylinder 615. The internal combustion engine 10 includes a fuel injection device 101, an ignition 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] Spark plug 604 is disposed at the top center of cylinder 614. Spark plug 604 has a negative electrode 612 and a positive electrode 613 exposed inside cylinder 615. Fuel injection device 101 is a center injection type fuel injection device that is disposed near spark plug 604 and injects fuel into cylinder 615. Note that fuel injection device 101 may also be a port injection type fuel injection device that is disposed in intake port 607 and injects fuel into intake port 607.

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

[0018] 1 illustrates an intake valve 605 and an exhaust valve 610 for convenience of explanation. However, in a typical direct-injection internal combustion engine 10 that is equipped with two intake valves 605 and two exhaust valves 610, the intake valve 605 and the exhaust valve 610 are not illustrated in a cross-sectional view passing through the central axis of a cylinder 614. Also, FIG. 1 illustrates the state (D1 to D8) of the spray in cylinder 615 immediately after fuel is injected from fuel injection device 101.

[0019] FIG. 2 is a diagram showing a schematic configuration of an internal combustion engine system 1 including the internal combustion engine 10 shown in FIG.

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

[0021] Turbines 702 are provided on the intake and exhaust sides of supercharging chamber 704, and are connected by shaft 707, so that turbines 702 rotate according to the flow speed of exhaust gas, increasing the amount of air flowing into cylinder 615 and improving output. The air that passes through supercharging chamber 704 is cooled by intercooler 705, as its temperature increases due to supercharging by turbine 702. The cooled air passes through throttle valve 706, which adjusts the amount of air, and intake port 607, before flowing into cylinder 615.

[0022] The air that has flowed into cylinder 615 mixes with fuel injected from fuel injector 101 to form an air-fuel mixture that is ignited and burned by spark plug 604. This combustion pushes piston 609 down, and the driving force of piston 609 is transmitted to crankshaft 710, after which exhaust valve 610 opens. Exhaust gas in cylinder 615 passes through exhaust port 608, rotates turbine 702 at the flow velocity of the exhaust gas, and passes through catalytic device 703.

[0023] The exhaust gas passes through the catalytic device 703, whereby HC, NOx, and CO are reduced and the exhaust gas is discharged outside the vehicle. The catalytic device 703 is configured, for example, with a three-way catalyst. The catalytic device 703 removes the HC, NOx, and CO contained in the exhaust gas by causing reduction and oxidation reactions with a catalyst using palladium, rhodium, platinum, or the like. However, the catalytic device 703 has low reduction ability when the catalyst temperature is low. In particular, under low temperature conditions, such as when the internal combustion engine 10 is started, combustion is required to quickly warm up the catalyst.

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

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

[0026] The ECU 104 communicates with the drive circuit 103 via a communication line 111. The ECU 104 can switch the drive current waveform determined by the drive circuit 103 and change the set values ​​of current and time depending on the fuel pressure supplied to the fuel injection device 101 and the operating conditions or operating mode of the internal combustion engine 10. The drive circuit 103 may be implemented as a component or a board integrated 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 injection device 101 is a normally closed solenoid valve (electromagnetic fuel injection device). As shown in FIG. 3 , the fuel injection device 101 has a valve element 214 that closes or opens a fuel injection hole 219 through which fuel is injected. When the solenoid 205 is not energized, the valve element 214 is biased in a valve closing direction (downward in FIG. 3 ) by a spring 210 (a first spring) and is in close contact with a valve seat 218, thereby maintaining a closed valve state. In the valve closed state, a force is applied to the armature 202 by a return spring 212 (a second spring) in a valve opening direction (upward in FIG. 3 ). At this time, the force of the spring 210 acting on the valve element 214 is greater than the force of the return spring 212. Therefore, as shown in FIG. 4 , an end face 302 of the armature 202 contacts the valve element 214, and the armature 202 is stationary. Valve element 214 and movable element 202 are configured to be relatively displaceable and are contained within nozzle holder 201. Nozzle holder 201 has an end surface 303 that serves as a spring seat for return spring 212. The force of spring 212 is adjusted during assembly by the amount of pressure applied to spring retainer 224 that is fixed to the inner surface of stator (core) 207.

[0028] The fuel injection device 101 also includes a magnetic circuit formed by a stator 207, a moving element 202, a nozzle holder 201, and a housing 203. A gap 301 is provided between the moving element 202 and the stator 207. A magnetic restriction 211 is formed in a portion of the nozzle holder 201 corresponding to the gap 301 between the moving element 202 and the stator 207. The solenoid 205 is wound around a bobbin 204 and attached to the outer periphery of the nozzle holder 201. A rod guide 215 is provided near the tip of the valve element 214 on the valve seat 218 side so as to be fixed to the nozzle holder 201. The movement of the valve element 214 in the valve axis direction (the up and down direction in FIG. 3 ) is guided by two sliding points: the stator 207, which contacts a spring seat 304 of the valve element 214, and the rod guide 215. An orifice 216 having 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) formed between the movable element 202 and the valve body 214 from the outside.

[0029] Fuel supplied to the fuel injection device 101 is supplied from a rail pipe provided upstream of the fuel injection device 101, flows through a fuel passage hole 231 to the tip of the valve element 214, and the fuel is sealed by the tip of the valve element 214 on the valve seat 218 side and the valve seat 218. In the valve closed state, a pressure difference is generated between the top and bottom of the valve element 214 due to fuel pressure, and the valve element 214 is pushed in the valve closing direction by the pressure difference calculated 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 in the valve closed state, a magnetic field is generated in the magnetic circuit, and magnetic flux passes between the stator 207 and the movable element 202, exerting a magnetic attraction force on the movable element 202. At the moment when the magnetic attractive force acting on the mover 202 exceeds the differential pressure and the force of the spring 210, the mover 202 starts to displace in the direction of the stator 207 (upward in FIG. 3).

[0030] After the valve element 214 starts its valve-opening operation, the movable element 202 moves to the position of the stator 207 and collides with the stator 207. After colliding with the stator 207, the movable element 202 bounces back (bounds) due to the reaction force from the stator 207, but the magnetic attraction force acting on the movable element 202 causes the movable element 202 to be attracted to the stator 207 and eventually stops. At this time, a force is applied to the movable element 202 in the direction of the stator 207 by the return spring 212, so the time until the bounding converges can be shortened. Because the bounding is small, the time during which the gap 301 between the movable element 202 and the stator 207 becomes large is shortened, and stable operation can be performed even with a smaller injection pulse width.

[0031] After completing the valve-opening operation in this manner, the moving element 202 and the valve element 214 remain stationary in the open state. In the open state, a gap is formed between the valve element 214 and the valve seat 218, and fuel is injected from the fuel injection holes 219. The fuel flows downstream through a central hole in the stator 207 and a fuel passage hole 305 in the moving element 202.

[0032] When the solenoid 205 is de-energized, the magnetic flux generated in the magnetic circuit disappears, and the magnetic attractive force also disappears. As the magnetic attractive force acting on the armature 202 disappears, the armature 202 and the valve element 214 are pushed back toward the valve-closed position in which they contact the valve seat 218 by the force of the spring 210 and the differential pressure.

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

[0034] At the moment when the valve disc 214 collides with the valve seat 218 and completes valve closing, the movable element 202 moves away from the valve disc 214. This allows the fuel injection device 101 to reduce the mass of the movable member at the moment when the valve disc 214 collides with the valve seat 218 by the mass of the movable element 202. Therefore, the fuel injection device 101 can reduce the collision energy when the valve disc 214 collides with the valve seat 218, and can suppress bounding of the valve disc 214 caused by the collision of the valve disc 214 with the valve seat 218.

[0035] In the fuel injection device 101, relative displacement occurs between the valve element 214 and the moving element 202 at the moment when the moving element 202 and the stator 207 collide when the valve is opened, and at the moment when the valve element 214 and the valve seat 218 collide when the valve is closed. This allows the fuel injection device 101 to suppress bounding of the moving element 202 against the stator 207 and bounding of the valve element 214 against the valve seat 218.

[0036] FIG. 5 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 injection device 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 is boosted to a voltage higher than the battery voltage VB, to the solenoid 205, thereby starting to supply a drive current to the solenoid 205. The drive circuit 103 stops applying the high voltage 401 when the current value of the drive current reaches a peak current value Ipeak set in advance by the ECU 104. Then, due to the back electromotive force caused by the inductance of the solenoid 205, the drive current supplied to the solenoid 205 is fed back to the voltage source VH side, and rapidly decreases from the peak current value Ipeak as shown by current 402. When the current value of the drive current becomes smaller than a predetermined current value 404, the drive circuit 103 applies the battery voltage VB to the solenoid 205, controlling it so that a predetermined current 403 is maintained.

[0038] When the fuel pressure supplied to the fuel injection device 101 increases, the differential pressure acting on the valve element 214 increases, and it takes longer for the valve element 214 to reach the target opening. As a result, the timing at which the target opening is reached may be delayed relative to the time it takes for the peak current value Ipeak to reach the target opening. If the drive current is rapidly reduced to the current 402, the magnetic attraction force acting on the moving element 202 also rapidly decreases, making the behavior of the valve element 214 unstable. In some cases, the valve element 214 may start to close even while current is still flowing.

[0039] During the transition period from peak current value Ipeak to current 403, drive circuit 103 causes the current generated by the back electromotive force to flow to the ground potential, thereby regenerating the current within the circuit, causing the voltage applied to solenoid 205 to become approximately 0 V, and enabling current 402 to gradually decrease. This allows drive circuit 103 to gradually decrease the magnetic attractive force acting on moving element 202, thereby stabilizing the behavior of valve element 214 at high fuel pressures. Therefore, drive circuit 103 can suppress variations in injection amount.

[0040] The fuel injection device 101 is driven by this driving current profile. Between the application of the high voltage 401 and the peak current value Ipeak, the armature 202 and the valve disc 214 begin to displace at timing t41. The armature 202 and the valve disc 214 then reach a predetermined maximum height position. At timing t42, when the armature 202 reaches the maximum height position, the armature 202 collides with the stator 207 and bounds. Because the valve disc 214 is configured to be displaceable relative to the armature 202, it separates from the armature 202, and the displacement of the valve disc 214 overshoots beyond the maximum height position. The magnetic attraction force generated by the current 403 and the force of the return spring 212 in the valve-opening direction then displace the armature 202 in the valve-opening direction, stopping at the maximum height position at timing t44. At timing t43, the valve element 214 seats on the moving element 202 and displaces in the valve opening direction, and at timing t44, it comes to rest at the maximum height position and enters the valve open state. In the case of a fuel injection device in which the valve element 214 and the moving element 202 are integrally formed, the displacement amount of the valve element 214 does not become larger than the maximum height position, and the displacement amounts of the moving element 202 and the valve element 214 after reaching the maximum height position (after timing t42) are equal.

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

[0042] FIG. 6 is a diagram illustrating the fuel injection control performed during operation in the catalyst warm-up mode.

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

[0044] During operation in the 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 of FIG. 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 of FIG. 6 , the control device 150 performs ignition retard, delaying the ignition timing to timing t86 during the expansion stroke 804. Note that the ignition timing t86 varies depending on the timing of the catalyst temperature increase request and environmental conditions and is set in advance. The control device 150 must control the fuel injector 101 to perform appropriate fuel injection for the desired ignition timing t86.

[0045] Specifically, at timing t81 when piston 609 reaches TDC, immediately before or simultaneously with the closing of exhaust valve 610, control device 150 starts opening intake valve 605 to allow air to flow into cylinder 615. At timing t82, between the start of intake valve 605 opening and the time when maximum lift is reached, control device 150 starts first fuel injection 805. Thereafter, at timing t83, until piston 609 reaches BDC, control device 150 starts second fuel injection 806. After piston 609 reaches BDC and enters compression stroke 803, and then piston 609 reaches TDC, control device 150 starts third fuel injection 807 at timing t84, immediately before ignition timing t86. 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 forms a rich mixture around the spark plug 604 that is richer in fuel than the theoretical air-fuel ratio (stoichiometry). The control device 150 sets the fuel split ratio between the intake stroke 802 and the expansion stroke 804 so that more fuel is split during the intake stroke 802. For example, the control device 150 may set the intake stroke 802:expansion stroke 804 ratio 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 performs ignition to ignite the mixture. In order to maintain the air-fuel mixture around the spark plug 604 at this ignition timing t86, it is preferable to bring the end timing t85 of the fuel injection immediately before the ignition timing t86 closer to the ignition timing t86. In other words, the control device 150 controls the fuel injection device 101 so that the more the ignition timing t86 is delayed, the shorter the period from the end timing t85 of the fuel injection immediately before the ignition timing t86 to the ignition timing t86 becomes.

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

[0048] Fuel injection device 101 is a multi-hole type fuel injection device in which fuel injection holes 219 are formed by a plurality of holes. The spray injected from fuel injection device 101 is made up of eight sprays, for example: sprays D1 and D2 injected toward spark plug 604, sprays D3 and D4 injected toward piston 609, and sprays D5 to D8 injected toward intake valve 605 relative to sprays D3 and D4.

[0049] The concept of this embodiment is that, in the fuel injection immediately before ignition timing, the sprays D1 and D2 form an air-fuel mixture between and around the negative electrode 612 and positive electrode 613 of the spark plug 604. The fuel injection device 101 injects the sprays D1 and D2 so that the sprays D1 and D2 are positioned on either side of the negative electrode 612 and the positive electrode 613. This allows the fuel injection device 101 to form an air-fuel mixture that is richer than stoichiometric between and around the negative electrode 612 and positive electrode 613, thereby ensuring combustion stability.

[0050] FIG. 8 is a diagram showing the relationship between the penetration of the spray injected from the fuel injection device 101 and the pressure inside the cylinder 615.

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

[0052] 9A and 9B are diagrams illustrating a first embodiment of fuel injection control immediately before ignition timing performed during operation in catalyst warm-up mode. FIG. 9A shows a case where the ignition retard amount is small, and FIG. 9B shows a case where the ignition retard amount is large. The dashed line in FIG. 9 represents the pressure inside the cylinder 615. In both FIG. 9A and FIG. 9B, the load on the internal combustion engine 10 during operation in the catalyst warm-up mode is the same.

[0053] The ignition retard amount is the amount by which the ignition timing is retarded from the optimum ignition timing that provides the best fuel economy. The greater the ignition retard amount, the more the ignition timing is retarded.

[0054] As shown in Figure 9A, when the ignition retard amount is small, the fuel injection start timing t91 is close to TDC, so the pressure inside cylinder 615 is high. In this case, the spray penetration is unlikely to be long, so the air-fuel mixture is unlikely to diffuse inside cylinder 615. In this case, control device 150 lengthens fuel injection period 901, that is, increases the injection amount, thereby increasing the spray penetration force and making it easier for the spray to diffuse inside cylinder 615. This makes it easier for control device 150 to maintain the air-fuel mixture around spark plug 604 at ignition timing t93.

[0055] As shown in FIG. 9B, when the ignition retard amount is large, the pressure inside cylinder 615 at fuel injection start timing t94 is lower than in the case of FIG. 9A. In this case, the spray penetration tends to be longer, making it easier for the mixture to diffuse into cylinder 615. In this case, control device 150 shortens fuel injection period 902, i.e., reduces the injection amount, thereby reducing the spray penetration force and suppressing the diffusion of the spray. This makes it easier for control device 150 to maintain the mixture around spark plug 604 at ignition timing t96. As a result, control device 150 can stably ignite the mixture, thereby ensuring combustion stability.

[0056] 9B, the penetration of the spray tends to be long, which makes it easier for fuel to adhere to the piston 609 and wall surfaces inside the cylinder 615, and increases PN. However, because the control device 150 reduces the injection amount, it is possible to prevent fuel from adhering to the piston 609 and the like, thereby suppressing PN.

[0057] In this way, the control device 150 controls the fuel injection device 101 so that the amount of fuel injected immediately before the ignition timing decreases as the ignition timing is retarded. This allows the control device 150 to maintain the air-fuel mixture around the spark plug 604 at the ignition timing and to suppress fuel adhesion to the piston 609, etc. Therefore, the control device 150 can ensure combustion stability and suppress PN at the same time.

[0058] 9A and 9B, when the amount of fuel injected immediately before the ignition timing during the expansion stroke varies depending on the ignition retard amount, the control device 150 may control the air-fuel ratio to be stoichiometric or constant by adjusting the amount of fuel injected during the intake stroke. Specifically, when the amount of fuel injected immediately before the ignition timing during the expansion stroke is reduced due to a large ignition retard amount, the control device 150 controls the fuel injection device 101 to increase the amount of fuel injected during the intake stroke in accordance with the reduction in the amount of fuel injected. In this way, the control device 150 can maintain the air-fuel ratio at a stoichiometric or constant level while suppressing PN, thereby reliably ensuring combustion stability.

[0059] Furthermore, when two or more fuel injections are performed during the intake stroke, the control device 150 may control the fuel injection device 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 increase the injection pulse width so that the injection amount of the second and subsequent fuel injections during the intake stroke (e.g., fuel injection 806 in FIG. 6) increases by the amount that the injection amount immediately before the ignition timing during the expansion stroke decreases.

[0060] Compared to the first fuel injection during the intake stroke (e.g., fuel injection 805 in FIG. 6 ), the fuel injection during the second intake stroke (e.g., fuel injection 806 in FIG. 6 ) is less likely to diffuse the air-fuel mixture. Therefore, increasing the injection amount of the fuel injection during the second intake stroke can further enhance the effect of forming a rich air-fuel mixture over a wide area in cylinder 615 and ensuring combustion stability. Furthermore, compared to the first fuel injection during the intake stroke, the injection timing of the fuel injection during the second intake stroke is later, so the time for mixing air and fuel is longer, making it more difficult for the air and fuel to mix. Therefore, increasing the injection amount of the fuel injection during the second intake stroke can more easily form a rich air-fuel mixture over a wide area around spark plug 604, thereby further enhancing the effect of ensuring combustion stability.

[0061] 10 to 12, a control device 150 for a fuel injection device 101 according to a second embodiment will be described. In the control device 150 for a fuel injection device 101 according to the second embodiment, the same configuration and operation as those of the first embodiment will not be described.

[0062] 10A and 10B are diagrams illustrating a second embodiment of fuel injection control immediately before ignition timing performed during operation in catalyst warm-up mode. Fig. 10A shows a case where the ignition retard amount is small, and Fig. 10B shows a case where the ignition retard amount is large. The dashed line in Fig. 10 represents the pressure inside the cylinder 615. In Fig. 10A and Fig. 10B, the load on the internal combustion engine 10 during operation in catalyst warm-up mode is the same.

[0063] The control device 150 according to the second embodiment performs the following fuel injection control in addition to the fuel injection control according to the first embodiment, which controls the fuel injection device 101 so that the injection amount of fuel injected immediately before the ignition timing decreases as the ignition retard amount increases. That is, the control device 150 according to the second embodiment controls the fuel injection device 101 so that the period from the end timing of the fuel injection immediately before the ignition timing to the ignition timing decreases as the ignition retard amount increases, i.e., as the ignition timing is delayed. Specifically, the control device 150 controls the fuel injection device 101 so that the period 1202 from the end timing t23 of the fuel injection immediately before the ignition timing to the ignition timing decreases when the ignition retard amount is large, compared to the period 1201 from the end timing t23 of the fuel injection to the ignition timing t93 when the ignition retard amount is small.

[0064] When the ignition retard amount is large, the pressure inside cylinder 615 at fuel injection start timing t24 is lower than when the ignition retard amount is small, so the spray penetration is longer and the air-fuel mixture is more likely to diffuse inside cylinder 615. As a result, it is difficult to maintain a rich air-fuel mixture around spark plug 604 at ignition timing t96.

[0065] The control device 150 according to the second embodiment shortens the period 1202 from the fuel injection end timing t25 to the ignition timing t96 as the ignition retard amount increases, thereby forming a stably rich mixture around the spark plug 604 and ensuring combustion stability. However, if the period 1202 is shortened too much, the fuel injection end timing t25 approaches the ignition timing t96, shortening the time available for the spray to vaporize and potentially causing the mixture to ignite before the spray has completely vaporized. However, the control device 150 according to the second embodiment reduces the injection amount to shorten the time required for the spray to vaporize, thereby suppressing fuel adhesion to the piston 609 and other components at the ignition timing t96 and ensuring combustion stability while suppressing PN. Furthermore, by suppressing an extremely rich mixture, for example, one with an equivalence ratio of 2 or greater, PN can be further suppressed.

[0066] Fig. 11 is a diagram showing the relationship among the injection pulse output from the ECU 104, the drive voltage applied to the solenoid 205 of the fuel injection device 101, the drive current supplied to the solenoid 205, and the displacement of the valve body 214 in the second embodiment. Fig. 11 is a diagram corresponding to Fig. 5. The dashed lines in Fig. 11 indicate the waveforms according to the first embodiment shown in Fig. 5, and the solid lines in Fig. 11 indicate the waveforms according to the second embodiment.

[0067] The control device 150 according to the second embodiment controls the valve element 214 during fuel injection immediately before the ignition timing so that the valve element 214 operates according to the change in displacement amount 1301 shown in Fig. 11. That is, the control device 150 controls the valve element 214 during fuel injection immediately before the ignition timing so that the valve element 214 is displaced within a range of height positions lower than the maximum height position. In other words, the control device 150 according to the second embodiment controls the lift amount of the valve element 214 during fuel injection immediately before the ignition timing within a range smaller than a predetermined maximum lift amount.

[0068] The control device 150 controls the fuel injection device 101 so that the lift amount of the valve element 214 decreases as the ignition retard amount increases, i.e., as the ignition timing is retarded. A smaller lift amount of the valve element 214 increases the pressure loss of the fuel flowing between the valve element 214 and the valve seat 218, slowing the flow velocity of the spray. Therefore, even if the ignition timing is retarded and the pressure inside the cylinder 615 is low at the timing of fuel injection, it is possible to make it easier to form an air-fuel mixture near the spark plug 604, ensuring combustion stability.

[0069] Note that the control device 150 reduces the lift amount of the valve element 214 as the ignition retard amount increases, but may control the valve element 214 to reach the maximum height position when the ignition retard amount is small. As a result, the upper limit of the lift amount of the valve element 214 can be changed significantly depending on the ignition retard amount, making it easier to maintain the air-fuel mixture around the spark plug 604 despite changes in the pressure inside the cylinder 615 that change depending on the ignition retard amount.

[0070] Fig. 12 is a diagram showing the relationship between the injection pulse width Ti and the injection amount of the fuel injection device 101. Fig. 12 shows the injection amount characteristic Q141 when each waveform shown in Fig. 11 is used.

[0071] When the injection pulse width Ti does not reach the predetermined time, if the force in the valve opening direction, which is the resultant force of the magnetic attractive force acting on the armature 202 and the return spring 212, does not exceed the force of the spring 210, the valve disc 214 does not start opening, and fuel is not injected. Alternatively, even if the armature 202 starts to displace, if the magnetic attractive force required for sliding through the gap 301 is not secured and the armature 202 does not contact the valve disc 214, the valve disc 214 does not start opening, and fuel is not injected. Also, if the injection pulse width Ti is short, for example, at point 1401 in Figure 12, the armature 202 collides with the valve disc 214, and the valve disc 214 separates from the valve seat 218 and starts to displace. However, because the valve disc 214 starts closing before reaching the maximum height position, the injection amount is less than the dashed-dotted line 1420 extrapolated from the linear region 1430 in which the relationship between the injection pulse width Ti and the injection amount is approximately linear.

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

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

[0074] At the injection pulse width Ti of point 1403, the valve starts to close at the timing when the amount of bounding of the valve element 214 caused by the moving element 202 colliding with the stator 207 is maximized. As a result, the repulsive force generated when the moving element 202 and the stator 207 collide acts on the moving element 202, shortening the valve closing delay time from when the injection pulse is turned off until the valve element 214 closes. As a result, the injection amount is smaller than that indicated by the dashed dotted line 1420.

[0075] The injection pulse width Ti at point 1404 indicates that the valve closure begins immediately after the valve element 214 has ceased to bounce. For injection pulse widths Ti greater than point 1404, the injection quantity increases substantially linearly with increasing injection pulse width Ti. From the start of fuel injection to the injection pulse width Ti at point 1404, the valve element 214 does not reach its maximum height position, or even if it does reach its maximum height position, the valve element 214's bounce is unstable, resulting in fluctuations in the injection quantity. Fuel injection immediately before the ignition timing during the expansion stroke significantly affects combustion stability if the injection quantity fluctuates. Therefore, the control device 150 may adjust the injection pulse width Ti so that the valve element 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] 13 and 14, a control device 150 for a fuel injection device 101 according to a third embodiment will be described. In the control device 150 for a fuel injection device 101 according to the third embodiment, the description of the same configuration and operation as those of the first and second embodiments will be omitted.

[0077] Fig. 13 is a diagram showing the relationship between the ignition retard amount, fuel pressure, injection amount, and rotation speed of the internal combustion engine 10, and the elapsed time from start of the internal combustion engine 10. In Fig. 13, when the ignition retard amount is 0, this indicates a case where the ignition timing is set to the TDC timing of the compression stroke. In Fig. 13, when the ignition retard amount is retarded, this indicates a case where the ignition timing is set to the retard side of the TDC of the compression stroke. In Fig. 13, when the ignition retard amount is advanced, this indicates a case where the ignition timing is set to the advance side of the TDC of the compression stroke.

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

[0079] Furthermore, during the cranking period 1501, the transition period 1502 until the ignition retard amount shifts to the retard side, and the catalyst warm-up mode operation period 1503 after the ignition retard amount shifts to the retard side, there is a transient period 1504 during which the fuel pressure (hereinafter also referred to as "fuel pressure") supplied to the fuel injection device 101 changes (increases). A fuel pump that supplies high-pressure fuel to the fuel injection device 101 supplies high-pressure fuel to a fuel pipe communicating with the fuel injection device 101 by compressing a plunger in synchronization with the camshaft of the internal combustion engine 10. Therefore, when the rotation 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. That is, the transient period 1504 during which the fuel pressure changes occurs between the start timing t51 of the internal combustion engine 10 and the timing t56 at which the catalyst warm-up ends. In particular, in hybrid vehicles (HEVs, SHEVs, PHEVs) equipped with an internal combustion engine 10 and an electric motor, the internal combustion engine 10 starts and stops more frequently than in vehicles equipped with only the internal combustion engine 10, so the fuel pressure when the internal combustion engine 10 starts changes frequently.

[0080] 14A and 14B are diagrams illustrating a third embodiment of fuel injection control immediately before ignition timing performed during operation in the catalyst warm-up mode. Fig. 14A shows a case where the fuel pressure is low, and Fig. 14B shows a case where the fuel pressure is high. The ignition retard amount is assumed to be the same in Fig. 14A and Fig. 14B.

[0081] When the fuel pressure is low, the spray penetration power is small, and the spray is less likely to diffuse within cylinder 615. When the fuel pressure is high, the spray penetration power is large, and the spray is more likely to diffuse within cylinder 615. Therefore, when the fuel pressure changes, it is desirable to adjust at least one of the injection amount and the end timing of the fuel injection immediately before the ignition timing.

[0082] The control device 150 according to the third embodiment controls the fuel injection device 101 so that the period from the end timing of the fuel injection immediately before the ignition timing to the ignition timing becomes longer as the fuel pressure supplied to the fuel injection device 101 at the start timing of the fuel injection immediately before the ignition timing becomes lower. Furthermore, the control device 150 controls the fuel injection device 101 so that the injection amount of the fuel injection immediately before the ignition timing becomes larger as the fuel pressure becomes lower.

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

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

[0085] Specifically, when the fuel pressure is high, the control device 150 controls the fuel injection period 907 so that it is shorter than the fuel injection period 906 when the fuel pressure is low. As a result, the control device 150 can reduce the penetration force of the spray and suppress diffusion of the spray, thereby suppressing fuel adhesion to the piston 609 and other components, and suppressing PN while ensuring combustion stability. Furthermore, when the fuel pressure is high, the control device 150 controls the period 1602 so that it is shorter than the period 1601 from the end timing t62 of the fuel injection to the ignition timing t63 when the fuel pressure is low. As a result, the control device 150 can make it difficult for the spray to diffuse within 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, thereby achieving both ensuring combustion stability and suppressing PN to a high degree.

[0086] In this way, control device 150 can adjust at least one of the injection amount and the end timing of fuel injection immediately before ignition timing in accordance with changes in fuel pressure, so that an air-fuel mixture can be formed around spark plug 604 even when fuel pressure changes, thereby ensuring combustion stability. Although adjusting the end timing and injection amount of fuel injection immediately before ignition timing individually is effective, adjusting both can greatly control the diffusion state of the spray in cylinder 615, thereby further ensuring combustion stability and enhancing the effects of PN suppression.

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

[0088] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace 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. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0089] Furthermore, the above-described configurations, functions, processing units, or processing means may be partially or entirely implemented in hardware, for example, by designing them as integrated circuits. The above-described configurations or functions may also be implemented in software, with a processor interpreting and executing a program that implements each function. Information such as the program, table, or file that implements each function can be stored in a storage device such as a memory, a hard disk, or an SSD (solid state drive), or in a storage medium such as an IC card, an SD card, or a DVD.

[0090] In addition, the control lines and information lines shown are those that are considered necessary for the explanation, and do not necessarily show all the control lines and information lines in the product. In reality, it can be assumed that almost all components are interconnected.

[0091] 10... internal combustion engine, 101... fuel injection device, 150... control device, 214... valve body, 219... fuel injection hole, 615... in-cylinder

Claims

1. A control device for a fuel injection device that directly injects fuel into a cylinder of an internal combustion engine operating in a catalyst warm-up mode in which a catalyst is warmed up by retarding ignition timing until the expansion stroke, wherein, when operating in the catalyst warm-up mode, the fuel injection immediately prior to the ignition timing of multiple fuel injections performed during one combustion cycle is performed during the expansion stroke, and the fuel injection device is controlled so that the more the ignition timing is retarded, the smaller the injection amount of the fuel injection immediately prior to the ignition timing becomes.

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

3. A control device for a fuel injection device as described in claim 1, characterized in that the fuel injection device is controlled so that fuel is injected two or more times during the intake stroke, and the injection amount of the fuel injection performed from the second injection onwards during the intake stroke is increased in response to a decrease in the injection amount of the fuel injection immediately before the ignition timing.

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

5. A control device for a fuel injection device that directly injects fuel into a cylinder of an internal combustion engine operating in a catalyst warm-up mode in which a catalyst is warmed up by retarding ignition timing until the expansion stroke, wherein, when operating in the catalyst warm-up mode, the fuel injection immediately before the ignition timing of multiple fuel injections performed during one combustion cycle is performed in the expansion stroke, and the fuel injection device is controlled so that the higher the fuel pressure supplied to the fuel injection device at the start timing of the fuel injection immediately before the ignition timing, the shorter the period from the end timing of the fuel injection immediately before the ignition timing to the ignition timing.

6. The control device for a fuel injection device according to claim 5, characterized in that the fuel injection device is controlled so that the injection amount of the fuel injection immediately before the ignition timing becomes smaller as the fuel pressure at the start timing of the fuel injection immediately before the ignition timing becomes higher.

Images