Internal combustion engine control device

Abstract

To stabilize an engine rotation speed after cold start at the time of using heavy fuel at an early stage while suppressing a total amount of emission of fine particle substance.SOLUTION: An engine ECU decides a final ignition timing on the basis of a catalyst warming-up delay angle amount for promoting warming up of a catalyst, and a rotation speed correction advance angle amount as an advance angle amount for raising an engine rotation speed after starting. Further, when at least one of a first condition that the final ignition timing is nearer to a delay angle side than a specified value after a compression upper dead point and a second condition that the rotation speed correction advance angle amount is a predetermined advance angle amount threshold value or more is satisfied, a cylinder injection valve is controlled so that a required fuel injection amount is injected while being divided into a plurality of times and also atomization formed by a latest final fuel injection of the fuel injection divided into a plurality of times is ignited by a spark of an ignition plug.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for a spray guide injection type direct injection internal combustion engine. [Background technology]

[0002] Conventionally, in order to stabilize combustion, a spray guide injection type direct injection internal combustion engine has been known in which the fuel to be injected during the compression stroke is injected in multiple divided injections, the penetration force of the spray formed by a single fuel injection is reduced, and the spray is ignited directly (see, for example, Patent Document 1).On the other hand, catalyst warm-up control of ignition timing is also known, which promotes catalyst warm-up by retarding the ignition timing after a cold start of the engine.

[0003] Incidentally, the last fuel injection (i.e., the final fuel injection) of the multiple divided fuel injections needs to be performed immediately before the ignition timing. However, if the final fuel injection is performed when the ignition timing is near the top dead center of the compression stroke due to catalyst warm-up control, the amount of injected fuel that adheres directly to the top surface of the piston increases, resulting in the generation of a large amount of particulate matter (PM).

[0004] Therefore, when performing catalyst warm-up control of the ignition timing, a conventional control device (hereinafter referred to as the "conventional device") does not perform final fuel injection as a spray guide injection before the ignition timing is retarded to a "predetermined value on the retard side by an appropriate crank angle from the compression top dead center," but instead performs final fuel injection as a spray guide injection after the ignition timing is retarded to the specified value. This allows the final fuel injection to be performed when the piston is at a position some distance from the compression top dead center position, thereby reducing the amount of injected fuel that directly adheres to the top surface of the piston. Therefore, the conventional device can prevent an increase in the amount of particulate matter emitted during catalyst warm-up control. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-24682 [Patent Document 2] Japanese Patent Publication No. 2023-22640 Summary of the Invention

[0006] However, when a fuel with poor volatility (hereinafter referred to as "heavy fuel") is used, combustion tends to become unstable immediately after engine start, resulting in a prolonged period during which the engine speed is lower than a predetermined speed. During the period during which the engine speed is lower than the predetermined speed, conventional devices execute rotational speed correction control to advance the ignition timing in order to increase the engine speed. Therefore, the ignition timing that would otherwise be retarded by catalyst warm-up control is advanced by the rotational speed correction control, resulting in a prolonged period during which the final ignition timing is more advanced than the above-mentioned specified value. As a result, the period during which spray guide injection cannot be performed becomes longer, resulting in a prolonged unstable combustion state. This results in a longer period during which the engine speed fluctuates significantly, resulting in a deterioration in drivability. The present invention has been made to address this problem.

[0007] One aspect of the control device for an internal combustion engine of the present invention is applied to a direct injection type internal combustion engine including: a direct injection valve (23); an ignition device (24) including an ignition plug disposed in a cylinder head (12) so as to be able to directly ignite a spray of fuel injected from the direct injection valve; and a catalyst (42) that purifies exhaust gas discharged from the combustion chamber, The fuel injection system further includes a controller (50) for controlling fuel injection by the in-cylinder injection valve and ignition by the ignition device.

[0008] Further, the controller A catalyst warm-up retard amount (SR) that is an amount of retardation of the ignition timing for accelerating the warm-up of the catalyst and a rotational speed correction advance amount (SISC) that is an amount of advance of the ignition timing for increasing the engine rotational speed after starting the internal combustion engine are calculated (S315, S325), a final ignition timing is determined based on the catalyst warm-up retard amount and the rotational speed correction advance amount (S330), and the ignition device is controlled so that the spark plug generates an ignition spark at the determined final ignition timing (S355), A first condition is that the final ignition timing is retarded from a predetermined crank angle after the compression top dead center; and a second condition that the rotational speed correction advance amount is equal to or greater than a predetermined advance amount threshold; If at least one of the following is true, a required fuel injection amount, which is the amount of fuel used for one combustion, is injected in multiple divided injections, and the in-cylinder injection valve is controlled so that the spray formed by the final fuel injection, which is the last fuel injection of the multiple divided fuel injections, is ignited by an ignition spark generated by the spark plug (S335, S340); It is structured as follows.

[0009] According to this, if the rotational speed correction advance amount becomes equal to or greater than a predetermined advance amount threshold due to the use of heavy fuel, final fuel injection is performed as a spray guide injection, stabilizing combustion and increasing the engine rotational speed. As a result, the rotational speed correction advance amount becomes smaller, and the ignition timing retarded by the catalyst warm-up retard amount reaches a value more retarded than the specified crank angle earlier, so final fuel injection is performed again as a spray guide injection. Therefore, the engine rotational speed after a cold start when using heavy fuel can be stabilized early while suppressing the total amount of particulate matter emissions. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic configuration diagram of an internal combustion engine to which a control device according to an embodiment of the present invention is applied; [Figure 2]1 is a time chart of various parameters showing the operation of a conventional device and a control device according to an embodiment of the present invention. [Figure 3] The routine executed by the CPU of the engine ECU shown in Figure 1 DETAILED DESCRIPTION OF THE INVENTION

[0011] A control device for an internal combustion engine according to an embodiment of the present invention (hereinafter referred to as "this device") is applied to a spray-guided direct-injection multi-cylinder internal combustion engine (hereinafter simply referred to as "engine") 10 shown in Fig. 1. The structure of engine 10 is disclosed in detail in Patent Documents 1 and 2 mentioned above, and will be briefly described below.

[0012] The engine 10 includes a combustion chamber R defined by a cylinder block 11, a cylinder head 12, and a piston 13. The piston 13 is reciprocally inserted into a cylindrical space formed in the cylinder block 11. The cylinder head 12 has a recess 15 facing the piston 13. The piston 13 is connected to a crankshaft 17 via a connecting rod 16. One end of an intake port 18 formed in the cylinder head 12 opens to the combustion chamber R, and the other end of the intake port 18 communicates with an intake passage 31. The portion (opening) connecting the intake port 18 and the combustion chamber R is opened and closed by an intake valve 21 disposed in the cylinder head 12 and driven by a "valve drive mechanism including an intake camshaft," not shown. One end of an exhaust port 19 formed in the cylinder head 12 opens to the combustion chamber R, and the other end of the exhaust port 19 communicates with an exhaust passage 41. The portion (opening) where the exhaust port 19 and the combustion chamber R are connected is opened and closed by an exhaust valve 22 that is disposed in the cylinder head 12 and driven by a "valve drive mechanism including an exhaust camshaft" (not shown).

[0013] An in-cylinder injection valve (fuel injection valve) 23 is disposed in the cylinder head 12 so as to inject fuel in a conical shape from the center and upper part of the combustion chamber R toward the top surface of the piston 13. An ignition device 24 including an ignition plug is disposed in the cylinder head 12 so as to generate an ignition spark from the tip of the ignition plug protruding above the combustion chamber R, and can directly ignite the fuel spray injected from the in-cylinder injection valve 23.

[0014] A throttle valve 33 driven by a throttle motor 32 is disposed in the intake passage 31. A three-way catalyst 42 is disposed in the exhaust passage 41. A particulate filter 43 with a three-way catalyst function is disposed downstream of the three-way catalyst 42 in the exhaust passage 41. This filter 43 is disclosed in, for example, Japanese Patent Laid-Open Publication No. 2024-11109, Japanese Patent No. 7254143, and Japanese Patent No. 7271610.

[0015] This system includes an engine ECU 50. The engine ECU 50 is an electronic control unit equipped with a microcomputer including a CPU, ROM, RAM, non-volatile memory, etc., and is also called a controller. The ROM stores constants, lookup tables, programs, etc. The engine ECU 50 controls the direct injection valve 23, the ignition device 24, and the throttle motor 32.

[0016] The engine ECU 50 acquires the detection values ​​or outputs of the following sensors. An air flow meter 51 is disposed upstream of the throttle valve 33 in the intake passage 31 and detects the intake air flow rate (weight) Ga. A crank position sensor 52 that generates a pulse each time the crankshaft 17 rotates a predetermined angle. A cam position sensor 53 that generates a pulse each time an intake camshaft (not shown) rotates a predetermined angle. A coolant temperature sensor 54 detects the coolant temperature THW of the engine 10.

[0017] The engine ECU 50 acquires the engine rotation speed NE based on the pulses generated by the crank position sensor 52. The engine ECU 50 acquires the crank angle based on the pulses generated by the crank position sensor 52 and the pulses generated by the cam position sensor 53.

[0018] (Overview of operation) In both the conventional device and this device, when performing spray guide injection that directly ignites the spray, the fuel injection is divided into multiple injections (typically two) to avoid deterioration of combustion, reducing the penetration power of the spray in each fuel injection. Hereinafter, the last fuel injection in the divided injections in which fuel injection is divided into multiple injections is referred to as the "final fuel injection."

[0019] Incidentally, in order to hasten the activation of the three-way catalyst 42 (i.e., to promote the warm-up of the three-way catalyst 42) after a cold start of the engine 10, the conventional device and the present device retard the ignition timing. As a result, the ignition timing may be near the top dead center of the compression stroke, and if the final fuel injection is performed at a timing corresponding to such an ignition timing, a large amount of fuel will adhere to the top surface of the piston 13, resulting in the generation of a large amount of particulate matter.

[0020] Therefore, as shown in Figure 2(A), in the conventional device and the present device, when the ignition timing SA is retarded to warm up the catalyst, final fuel injection as spray guide injection is prohibited until the ignition timing SA is more retarded than the "specified crank angle SAth, which is retarded by a specified crank angle from the top dead center of compression," and after the ignition timing SA becomes more retarded than the specified crank angle SAth, final fuel injection as spray guide injection is performed at "a specified timing between the specified crank angle SAth and the ignition timing SA (for example, the timing when the crank angle coincides with the specified crank angle SAth)."

[0021] However, when a so-called "heavy fuel" with poor volatility is used and the ignition timing SA is retarded to warm up the catalyst, the following problem occurs: Because the heavy fuel has poor volatility, combustion becomes unstable after a cold start of the engine 10, and as shown in FIG. 2B, the engine speed NE fluctuates greatly and the average engine speed NEave may become equal to or lower than a predetermined target engine speed NEtgt.

[0022] In this case, the conventional and present devices execute rotational speed correction control to increase the engine speed NE by advancing the ignition timing SA by the rotational speed correction advance amount SISC. Therefore, the ignition timing SA, which is intended to be retarded for catalyst warm-up, is advanced by the rotational speed correction advance amount SISC. This lengthens the period during which the ignition timing SA is not retarded from the specified crank angle SAth, thereby lengthening the period during which final fuel injection as spray guide injection cannot be performed. As a result, combustion becomes unstable for a longer period after a cold start of the engine 10, resulting in a problem of deterioration in drivability due to a prolonged period of large fluctuations in the engine speed NE.

[0023] Therefore, as shown in Figure 2(C), the present device executes final fuel injection as spray guide injection when the rotational speed-corrected advance amount SISC exceeds the advance amount threshold SISCth, even before the ignition timing SA becomes more retarded than the specified crank angle SAth. As a result, although particulate matter emissions increase momentarily, combustion is improved, fluctuations in the engine speed NE are suppressed, and the engine speed stabilizes early near the target rotational speed NEtgt. Accordingly, the rotational speed-corrected advance amount SISC decreases, so that the ignition timing SA, which is retarded for catalyst warm-up, quickly reaches the specified crank angle SAth, and final fuel injection as spray guide injection is resumed. This reduces the total amount of particulate matter emissions, shortens the period of large fluctuations in the engine speed NE, and improves drivability.

[0024] (Specific operation) 3 from step 300 (hereinafter, "step" will be abbreviated as "S") and proceeds to S305, where the CPU of the engine ECU 50 determines whether or not a post-start control condition is met every time a predetermined time has elapsed. The post-start control condition is met when the current time is between "the point in time when the engine speed NE after the start of cranking exceeds the full explosion speed NEst, which indicates a complete explosion" and "the point in time when a certain amount of time has elapsed since the point in time when the complete explosion occurs."

[0025] If the post-start control conditions are met, the CPU proceeds from S305 to S310, where it calculates the basic ignition timing SB by applying the engine load KL (= Ga / NE) and the engine speed NE to a look-up table MapSB(KL, NE). The ignition timing is expressed by the crank angle before the top dead center of the compression stroke.

[0026] Next, the CPU calculates the rotational speed-corrected advance amount SISC of the ignition timing at S315. More specifically, if the average value NEave of the engine rotational speed NE over a predetermined time period is lower than the target rotational speed NEtgt, the CPU increases the rotational speed-corrected advance amount SISC by a predetermined advance amount DA over the predetermined time period, and if the average value NEave is equal to or higher than the target rotational speed NEtgt, the CPU decreases the rotational speed-corrected advance amount SISC by a predetermined delay amount DB over the predetermined time period.

[0027] Next, the CPU proceeds to S320 to determine whether a catalyst warm-up condition is met. The catalyst warm-up condition is met when either the coolant temperature THW is lower than a threshold water temperature THWth or the integrated value SGa of the intake air amount Ga since the time of complete combustion is less than a predetermined integrated threshold SGath.

[0028] If the catalyst warm-up condition is met, the CPU proceeds from S320 to S325 to calculate the catalyst warm-up delay amount SR to promote warm-up of the three-way catalyst 42. For example, the CPU increases the catalyst warm-up delay amount SR by a fixed amount at a predetermined time interval during the period when the catalyst warm-up condition is met, and decreases the catalyst warm-up delay amount SR by a fixed amount until the catalyst warm-up delay amount SR becomes "0" during the period when the catalyst warm-up condition is not met.

[0029] Next, the CPU proceeds to S330, where it calculates the final ignition timing SA by retarding the basic ignition timing SB by the catalyst warm-up retard amount SR and advancing it by the rotational speed correction advance amount SISC.

[0030] Next, the CPU proceeds to S335, where it determines whether or not at least one of the following first and second conditions is met. (First condition) The final ignition timing SA is retarded from a specified crank angle SAth. The specified crank angle SAth is a crank angle that is retarded from the compression top dead center by a predetermined crank angle. (Second condition) The rotational speed correction advance amount SISC is greater than the advance amount threshold SISCth.

[0031] If at least one of the first and second conditions is satisfied, the CPU proceeds from S335 to S340, where it performs split injections for spray guide injection using the direct injection valve 23. For example, the CPU sets the number of split injections to two, sets the injection start timing of the first fuel injection to 160 degrees before top dead center of compression, and sets the amount of fuel injected by that first fuel injection to 97% of the required injection amount (the amount of fuel required for one explosion stroke). Furthermore, the CPU sets the amount of fuel injected by the final fuel injection to 3% of the required injection amount, and sets the injection start timing of the final fuel injection so that the injection end timing of the final fuel injection coincides with the ignition timing SA.

[0032] Next, the CPU proceeds from S340 to S345, where it controls the ignition device 24 so that an ignition spark is generated from the spark plug at the ignition timing SA. After that, the CPU proceeds to S395, where it temporarily ends this routine.

[0033] If the CPU determines in S335 that neither the first condition nor the second condition is met, it proceeds from S335 to S350 and performs normal fuel injection. More specifically, the CPU injects the required injection amount of fuel in a single fuel injection. The CPU sets the injection start timing of that fuel injection to 160 degrees before top dead center of compression. The CPU then executes ignition processing in S345, proceeds to S395, and temporarily ends this routine.

[0034] If the CPU determines in S320 that the catalyst warm-up condition is not satisfied, it proceeds from S320 to S355, where it calculates the final ignition timing SA by advancing the basic ignition timing SB by the rotational speed-corrected advance amount SISC. The CPU then performs normal injection using the direct injection valve 23 in S350, proceeds to S345 to execute ignition processing, and proceeds to S395 to temporarily end this routine. Furthermore, if the CPU determines "No" in S305, it proceeds directly to S395. In this case, ignition timing control and fuel injection control are executed either during startup or after completion of startup control.

[0035] As described above, when the rotational speed correction advance amount becomes equal to or greater than a predetermined advance amount threshold due to the use of heavy fuel, the device performs final fuel injection as a spray guide injection, stabilizing combustion and increasing the engine rotational speed. As a result, the rotational speed correction advance amount becomes smaller, the ignition timing retarded by the catalyst warm-up retard amount reaches a value more retarded than the specified crank angle earlier, and final fuel injection as a spray guide injection is performed again. As a result, the engine rotational speed after cold start when using heavy fuel can be stabilized early while suppressing total particulate matter emissions.

[0036] The present invention is not limited to the above embodiment, and various modifications can be adopted within the scope of the present invention. For example, the basic ignition timing calculated in S310 may be a fixed timing. [Explanation of symbols]

[0037] 10...internal combustion engine, 23...direct injection valve, 24...ignition device, 50...engine ECU

Claims

[Claim 1] The present invention is applied to a direct injection type internal combustion engine including: an in-cylinder injection valve disposed in a cylinder head so as to inject fuel directly into a combustion chamber; an ignition device including an ignition plug disposed in the cylinder head so as to be able to directly ignite the spray of fuel injected from the in-cylinder injection valve; and a catalyst for purifying exhaust gas discharged from the combustion chamber, A control device for an internal combustion engine, comprising: a controller for controlling fuel injection by the direct injection valve and an ignition operation by the ignition device, The controller calculating a catalyst warm-up delay amount, which is an amount of delay of the ignition timing for accelerating the warm-up of the catalyst, and a rotational speed correction advance amount, which is an amount of advance of the ignition timing for increasing the engine rotational speed after start-up of the internal combustion engine; determining a final ignition timing based on the catalyst warm-up delay amount and the rotational speed correction advance amount; and controlling the ignition device so that the spark plug generates an ignition spark at the determined final ignition timing; A first condition is that the final ignition timing is retarded from a predetermined crank angle after the compression top dead center; and a second condition that the rotational speed correction advance amount is equal to or greater than a predetermined advance amount threshold; If at least one of the following is true, a required fuel injection amount, which is the amount of fuel used for one combustion, is injected in a plurality of divided injections, and the in-cylinder injection valve is controlled so that a spray formed by a final fuel injection, which is the last fuel injection of the plurality of divided fuel injections, is ignited by an ignition spark generated by the spark plug; It was configured as follows: Control device for internal combustion engines.

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