Control device for internal combustion engine

Abstract

The invention relates to a control device for an internal combustion engine. An engine ECU (50) controls fuel injection from the in-cylinder injection valve (23) and ignition by the ignition device (24). An engine ECU determines a final ignition timing on the basis of a catalyst warm-up retardation amount (SR), which is the retardation amount of the ignition timing for promoting warm-up of a catalyst (42), and a rotational speed correction advance amount (SISC), which is the advance amount of the ignition timing for increasing the rotational speed of the internal combustion engine after starting of the internal combustion engine. When at least one of a first condition in which the final ignition timing is closer to the retard side than a predetermined crank angle after compression top dead center and a second condition in which the rotational speed correction advance is equal to or greater than a predetermined advance threshold value is satisfied, the engine ECU controls the in-cylinder injection valve in such a manner that the in-cylinder injection valve is in a state in which the rotational speed correction advance is greater than or equal to the predetermined advance threshold value. Fuel of a required fuel injection amount is divided into a plurality of times to be injected, and a spray formed by a final fuel injection, which is the last fuel injection among the divided fuel injections, is ignited by an ignition spark generated by an ignition plug.

Description

TECHNICAL FIELD

[0001] The present application relates to a control device for a cylinder injection internal combustion engine of a spray-guided injection type. BACKGROUND

[0002] In the past, a cylinder injection internal combustion engine of a spray-guided injection type is known in which, in order to stabilize combustion, fuel to be injected in a compression stroke is divided into a plurality of injections, the penetration force of spray formed by one fuel injection is reduced, and the spray is directly ignited (for example, refer to Patent Document 1). On the other hand, a catalyst warm-up control of ignition timing is known in which, after a cold start of an internal combustion engine, the ignition timing is delayed to promote catalyst warm-up.

[0003] However, the last fuel injection (i.e., final fuel injection) of fuel injection divided into a plurality of injections needs to be performed just before the ignition timing is reached, but if the final fuel injection is performed in a case where the ignition timing becomes near the compression top dead center by the catalyst warm-up control, the amount of fuel directly adhering to the upper surface of the piston among the injected fuel increases, and thus, particulate matter (particulate matter, PM) is generated in a large amount.

[0004] Therefore, the conventional control device (hereinafter referred to as "conventional device") does not perform the final fuel injection as spray-guided injection until the ignition timing is delayed to a "predetermined value of a crank angle amount that is appropriately delayed from the compression top dead center" when the catalyst warm-up control of the ignition timing is performed, and performs the final fuel injection as spray-guided injection after the ignition timing is delayed to the predetermined value. Thus, the final fuel injection is performed when the piston is at a position that is apart from the compression top dead center position by a certain degree, and thus, the amount of fuel directly adhering to the upper surface of the piston among the injected fuel decreases. Therefore, the conventional device can prevent the amount of particulate matter discharged in the catalyst warm-up control from increasing.

[0005] [Related Art Documents]

[0006] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2009-24682

[0008] [Patent Document 2] Japanese Patent Application Publication No. 2023-22640 SUMMARY

[0009] However, in the case of using a fuel having poor volatility (hereinafter referred to as "heavy fuel"), combustion becomes unstable immediately after the start of the internal combustion engine, and thus the period during which the engine speed is lower than a prescribed speed is prolonged. In the period during which the engine speed is lower than the prescribed speed, the prior art device performs speed correction control for advancing the ignition timing in order to increase the engine speed. Therefore, the ignition timing that is to be delayed by catalyst warm-up control is advanced by the speed correction control, and thus the period during which the final ignition timing is on the advance side from the prescribed value described above is prolonged. As a result, the period during which the spray-guided injection cannot be performed is lengthened, and thus the unstable combustion state continues, and thus the period during which the engine speed fluctuates greatly is lengthened, and thus the drivability deteriorates. The present application was made in order to address this problem.

[0010] One embodiment of the control device of the internal combustion engine of the present application is applied to an in-cylinder injection type internal combustion engine that includes an in-cylinder injection valve (23), an ignition device (24) including a spark plug that is disposed in a cylinder head (12) in a manner that enables direct ignition of a spray of fuel injected from the in-cylinder injection valve, and a catalyst (42) that purifies exhaust gas discharged from the combustion chamber, and has a controller (50) that controls fuel injection by the in-cylinder injection valve and ignition operation by the ignition device.

[0011] Furthermore, the controller is configured to calculate a delay amount of the ignition timing for promoting warm-up of the catalyst, i.e., a catalyst warm-up delay amount (SR), and an advance amount of the ignition timing for increasing the engine speed after the start of the internal combustion engine, i.e., a speed correction advance amount (SISC) (S315, S325), determine a final ignition timing based on the catalyst warm-up delay amount and the speed correction advance amount (S330), control the ignition device so that the spark plug generates an ignition spark at the determined final ignition timing (S355), in the case where at least one of a first condition in which the final ignition timing is on the delay side from a predetermined prescribed crank angle after the compression top dead center and a second condition in which the speed correction advance amount is equal to or greater than a predetermined advance amount threshold value is satisfied, control the in-cylinder injection valve in such a manner that the amount of fuel for one combustion, i.e., a required fuel injection amount, is divided into a plurality of fuel injections, and the spray formed by the last fuel injection, i.e., a final fuel injection, of the fuel injections divided into a plurality of fuel injections is ignited by the ignition spark generated by the spark plug (S335, S340).

[0012] Thus, if the rotation speed correction advance amount becomes equal to or more than the prescribed advance amount threshold value due to the use of the heavy fuel, the final fuel injection as the spray-guiding injection is performed, combustion is stabilized, and thus the engine rotation speed also rises and stabilizes. As a result, the rotation speed correction advance amount becomes small, the ignition timing delayed by the catalyst warm-up delay amount reaches a value on the prescribed crank angle delay side, and thus the final fuel injection as the spray-guiding injection is performed again. Thus, it is possible to stabilize the engine rotation speed after the cold start when the heavy fuel is used while suppressing the total emission amount of particulate matter. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a schematic configuration view of an engine to which a control device of an embodiment of the present application is applied.

[0014] Figure 2 is a timing chart showing various parameters indicating the operation of the control device of the related art and the control device of the embodiment of the present application.

[0015] Figure 3 is Figure 1 a routine executed by the CPU of the engine ECU shown in FIG. 1. DETAILED DESCRIPTION

[0016] The control device of the engine of the embodiment of the present application (hereinafter, referred to as "the present device") is applied to Figure 1 "the spray-guiding in-cylinder injection · multi-cylinder · engine (hereinafter, simply referred to as "the engine") 10" shown in FIG. 1. The configuration of the engine 10 is disclosed in detail in the above-described patent document 1 and patent document 2, and thus a brief description will be given below.

[0017] The engine 10 is provided with a combustion chamber R defined by a cylinder block 11, a cylinder head 12, and a piston 13. The piston 13 is inserted into a cylindrical space formed in the cylinder block 11 in a manner capable of reciprocating. The cylinder head 12 has a recess 15 facing the piston 13. The piston 13 is linked 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) of the intake port 18 linked to the combustion chamber R is opened and closed by an intake valve 21 provided to the cylinder head 12 and driven by an "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) of the exhaust port 19 linked to the combustion chamber R is opened and closed by an exhaust valve 22 provided to the cylinder head 12 and driven by an "valve drive mechanism including an exhaust camshaft" not shown.

[0018] An in-cylinder injection valve (fuel injection valve) 23 is provided to the cylinder head 12 in a manner that fuel is injected in a conical shape from the central and upper portions of the combustion chamber R toward the upper surface of the piston 13. An ignition device 24 including a spark plug is provided to the cylinder head 12 in a manner that an ignition spark is generated from the tip portion of the spark plug protruding toward the upper portion of the combustion chamber R, and is capable of directly igniting the spray of fuel injected from the in-cylinder injection valve 23.

[0019] A throttle valve 33 driven by a throttle valve motor 32 is provided to the intake passage 31. A three-way catalyst 42 is provided to the exhaust passage 41. A particulate filter 43 having a three-way catalyst function is provided to the exhaust passage 41 downstream of the three-way catalyst 42. This filter 43 is disclosed in, for example, Japanese Patent Application Publication No. 2024-11109, Japanese Patent No. 7254143, Japanese Patent No. 7271610, and the like.

[0020] The device has an engine ECU 50. The engine ECU 50 is an electronic control device provided with a microcomputer including a CPU, a ROM, a RAM, a nonvolatile memory, and the like, and is also referred to as a controller. The ROM stores constants, lookup tables, programs, and the like. The engine ECU 50 controls the in-cylinder injection valve 23, the ignition device 24, and the throttle valve motor 32.

[0021] The engine ECU 50 acquires the detection values or outputs of the sensors listed below.

[0022] • An air flow meter 51 is provided to the intake passage 31 upstream of the throttle valve 33, and detects the intake air flow (weight) Ga.

[0023] • A crankshaft position sensor 52 that generates a pulse every time the crankshaft 17 rotates a prescribed angle.

[0024] • A cam position sensor 53 that generates a pulse every time the intake camshaft, not shown, rotates a prescribed angle.

[0025] • A cooling water temperature sensor 54 that detects the cooling water temperature THW of the internal combustion engine 10.

[0026] Furthermore, the engine ECU 50 acquires the engine speed NE based on the pulses generated by the crankshaft position sensor 52. The engine ECU 50 acquires the crank angle based on the pulses generated by the crankshaft position sensor 52 and the pulses generated by the cam position sensor 53.

[0027] (Summary of Operation)

[0028] In existing devices and this device, when performing spray-guided injection for direct ignition of the spray, the fuel injection is divided into multiple injections (typically two) to avoid combustion degradation, thereby reducing the penetration force of the spray in a single fuel injection. Hereinafter, the last fuel injection in the multi-stage injection process is referred to as the "final fuel injection".

[0029] Furthermore, in order to accelerate the activation of the three-way catalyst 42 after a cold start of the internal combustion engine 10 (i.e., to promote the preheating of the three-way catalyst 42), conventional devices and this device delay the ignition timing. As a result, there is a situation where the ignition timing becomes the timing near the top dead center of the compression stroke. If the final fuel injection is performed at the timing corresponding to such an ignition timing, a large amount of fuel will adhere to the upper surface of the piston 13, thus generating a large amount of particulate matter.

[0030] Therefore, the conventional device and this device are as follows: Figure 2 As shown in (A), when the ignition timing SA is delayed for catalyst preheating, the final fuel injection as a spray-guided injection is prohibited before the ignition timing SA becomes a delay side of "the specified crankshaft angle SAth which is a delay side of the specified crankshaft angle from the top dead center of the compression stroke". After the ignition timing SA becomes a delay side of "the specified timing between the specified crankshaft angle SAth and the ignition timing SA (e.g., the timing when the crankshaft angle coincides with the specified crankshaft angle SAth)".

[0031] However, when using so-called "heavy fuels" with poor volatility and implementing a delay in ignition timing SA for catalyst preheating, the following problem arises: Because heavy fuels have poor volatility, combustion becomes unstable after a cold start of the internal combustion engine 10, such as... Figure 2 As shown in (B), sometimes the internal combustion engine speed NE varies greatly and the average value of the internal combustion engine speed NEave becomes below the predetermined target speed NEtgt.

[0032] In this situation, conventional devices and this device perform speed correction control by advancing the ignition timing SA by a speed correction advance amount SISC to increase the internal combustion engine speed NE. Therefore, because the speed correction advance amount SISC for advancing the ignition timing SA to preheat the catalyst is increased, the period during which the ignition timing SA is not further from the specified crankshaft angle SAth becomes longer, and the period during which final fuel injection, as a spray-guided injection, cannot be performed becomes longer. As a result, the following problems exist: the period of unstable combustion after a cold start of the internal combustion engine 10 becomes longer, and the period of large fluctuations in the internal combustion engine speed NE persists, leading to a deterioration in driving performance.

[0033] Therefore, as Figure 2that is, even before the ignition timing SA becomes the retard side of the prescribed crank angle SAth, when the speed correction advance amount SISC is larger than the advance amount threshold SISCth, the device executes the final fuel injection as the spray-guided injection. As a result, although the particulate matter emission amount increases only momentarily, the combustion is improved and the variation of the engine speed NE is suppressed, and the engine speed is stabilized at an earlier timing in the vicinity of the target engine speed NEtgt. Along with this, the speed correction advance amount SISC becomes smaller, and therefore, as a result, the ignition timing SA delayed for catalyst warm-up reaches the prescribed crank angle SAth quickly, and the final fuel injection as the spray-guided injection is started again. Therefore, the particulate matter emission amount is reduced overall, and the period during which the variation of the engine speed NE is large is shortened, and the drivability is improved.

[0034] (Detailed Operation)

[0035] The CPU of the engine ECU 50 starts the routine shown in FIG. 3 (hereinafter, "step" is marked as "S") every prescribed time from S300 Figure 3 The routine shown in FIG. 3 (hereinafter, "step" is marked as "S") every prescribed time from S300

[0036] In the case where the post-start control condition is established, the CPU proceeds from S305 to S310, and calculates the basic ignition timing SB by applying the engine load KL (= Ga / NE) and the engine speed NE to the lookup table MapSB(KL, NE). Further, the ignition timing is indicated by the crank angle before the compression top dead center.

[0037] Next, the CPU calculates the speed correction advance amount SISC of the ignition timing in S315. More specifically, in the case where the average value NEave of the engine speed NE over a predetermined time is lower than the target engine speed NEtgt, the speed correction advance amount SISC is increased by a predetermined advance amount DA each time over the predetermined time, and in the case where the average value NEave is equal to or higher than the target engine speed NEtgt, the speed correction advance amount SISC is decreased by a predetermined retard amount DB each time over the predetermined time.

[0038] Next, the CPU proceeds to S320, and determines whether the catalyst warm-up condition is established. The catalyst warm-up condition is established in either case where the cooling water temperature THW is lower than the threshold water temperature THWth and the cumulative value SGa of the intake air amount Ga from the time point of the complete combustion is smaller than a predetermined cumulative threshold SKath.

[0039] When the catalyst warm-up condition is established, the CPU proceeds from S320 to S325, and calculates a catalyst warm-up delay amount SR for promoting warm-up of the three-way catalyst 42. For example, the CPU increases the catalyst warm-up delay amount SR by a predetermined amount each time during the period when the catalyst warm-up condition is established, and decreases the catalyst warm-up delay amount SR by a predetermined amount each time during the period when the catalyst warm-up condition is not established, until the catalyst warm-up delay amount SR becomes "0".

[0040] Next, the CPU proceeds to S330, and calculates the final ignition timing SA by delaying the basic ignition timing SB by the catalyst warm-up delay amount SR and advancing the rotational speed correction advance amount SISC.

[0041] Next, the CPU proceeds to S335, and determines whether at least one of the following first condition and second condition is established.

[0042] (The first condition) The final ignition timing SA is on the delay side from a prescribed crank angle SAth. Further, the prescribed crank angle SAth is a crank angle that is delayed from the compression top dead center by a prescribed crank angle.

[0043] (The second condition) The rotational speed correction advance amount SISC is greater than an advance amount threshold SISCth.

[0044] When at least one of the first condition and the second condition is established, the CPU proceeds from S335 to S340, and performs split injection for spray guide injection using the in-cylinder injection valve 23. For example, the CPU sets the number of times of split injection to 2, sets the injection start timing of the first fuel injection to 160 degrees before the compression top dead center, and sets the fuel amount injected by the first fuel injection to 97% of the required injection amount (the amount of fuel required for one explosion stroke). Also, the CPU sets the fuel amount injected by the final fuel injection to 3% of the required injection amount, and sets the injection start timing of the final fuel injection in such a manner that the injection end timing of the final fuel injection coincides with the ignition timing SA.

[0045] Next, the CPU proceeds from S340 to S345, and controls the ignition device 24 in such a manner that an ignition spark is generated from the spark plug at the ignition timing SA. Thereafter, the CPU proceeds to S395, and temporarily ends the routine.

[0046] Note that in a case where the CPU determines in S335 that neither the first condition nor the second condition is established, the CPU proceeds from S335 to S350 to perform normal fuel injection. More specifically, the CPU injects fuel of the required injection amount by one-time fuel injection. The CPU sets the injection start timing of this fuel injection to 160 degrees before compression top dead center. Thereafter, the CPU performs the ignition processing of S345, proceeds to S395, and temporarily ends the routine.

[0047] Further, in a case where the CPU determines in S320 that the catalyst warm-up condition is not established, the CPU proceeds from S320 to S355 to advance the basic ignition timing SB by the advance amount SISC, thereby calculating the final ignition timing SA. Thereafter, the CPU performs normal injection using the in-cylinder injection valve 23 in S350, proceeds to S345 to perform the ignition processing, and proceeds to S395 to temporarily end the routine. Further, in a case where the CPU determines "No" in step S305, the CPU directly proceeds to step S395. In this case, the ignition timing control and the fuel injection control are performed at any point during startup and after completion of startup control.

[0048] As described above, the device performs the final fuel injection as the spray guide injection when the advance amount of the rotational speed correction becomes equal to or greater than the prescribed threshold value due to the use of heavy fuel, stabilizes combustion, and thus the engine rotational speed also rises and stabilizes. As a result, the advance amount of the rotational speed correction becomes small, the ignition timing delayed by the catalyst warm-up delay amount reaches a value on the delayed side from the prescribed crank angle, and the final fuel injection as the spray guide injection is performed again. As a result, it is possible to stabilize the engine rotational speed after cold start when heavy fuel is used while suppressing the total emission amount of particulate matter.

[0049] Further, the present application is not limited to the above-described embodiment, and various modifications can be employed within the scope of the present application. For example, the basic ignition timing calculated in S310 can be a prescribed timing.

[0050] [Legend of Reference Numerals]

[0051] 10... internal combustion engine, 23... in-cylinder injection valve, 24... ignition device, 50... engine ECU.

Claims

1. A control device for an internal combustion engine, applied to an in-cylinder injection internal combustion engine, the in-cylinder injection internal combustion engine comprising: an in-cylinder injection valve disposed on a cylinder head for directly injecting fuel into a combustion chamber; an ignition device including a spark plug disposed on the cylinder head for directly igniting a spray of fuel injected from the in-cylinder injection valve; and a catalyst for purifying exhaust gases discharged from the combustion chamber. The control device of the internal combustion engine includes a controller for controlling the fuel injection of the in-cylinder injection valve and the ignition action of the ignition device, wherein... The controller is configured to calculate a catalyst preheating delay and a speed correction advance. The catalyst preheating delay is an ignition timing delay used to promote catalyst preheating, and the speed correction advance is an ignition timing advance used to increase the engine speed after engine start-up. Based on the catalyst preheating delay and the speed correction advance, the controller determines the final ignition timing to control the ignition device so that the spark plug generates an ignition spark at the determined final ignition timing. The controller is configured to, when at least one of the following conditions is met—a first condition where the final ignition timing is on the delayed side of a predetermined crankshaft angle after compression top dead center and a second condition where the speed correction advance is above a predetermined advance threshold—control the in-cylinder injection valve in such a way that the amount of fuel for a single combustion, i.e., the required fuel injection amount, is divided into multiple injections, and the spray formed by the last fuel injection in these multiple fuel injections is ignited by the spark generated by the spark plug.

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