Controller of internal combustion engine

Abstract

To suppress deterioration of drivability and NV of a vehicle while suppressing deterioration of an internal combustion engine due to low-speed preignition, even when inferior fuel is used.SOLUTION: A controller of an internal combustion engine disclosed herein is a controller of an internal combustion engine comprising a turbocharger and a variable valve mechanism, where, when the number of occurrences of low-speed preignition is equal to or less than a predetermined upper limit and is equal to or larger than a predetermined number that is smaller than the upper limit, valve timing in a predetermined low-speed, high-load range is changed so that the low-speed preignition does not occur, and when the number of occurrences of low-speed preignition exceeds the upper limit, a load factor of the internal combustion engine is limited to a small value.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a control device for an internal combustion engine that has a turbocharger and a variable valve mechanism and is mounted on a vehicle. [Background technology]

[0002] Conventionally, there is known an internal combustion engine including an in-cylinder injection valve, a port injection valve, a first cooling water passage for cooling a peripheral wall of a cylinder, and a second cooling water passage for cooling an intake port or a peripheral wall of the cylinder closer to the combustion chamber than a part cooled by the first cooling water passage with a second cooling water having a lower temperature than the first cooling water flowing through the first cooling water passage (for example, see Patent Document 1). A control device for this internal combustion engine derives an index value (number of occurrences of LSPI) indicating a degree of deterioration of the internal combustion engine due to LSPI (Low Speed ​​Pre Ignition). Furthermore, when the calculated index value exceeds a first threshold value, the water temperature of the second cooling water cooling the peripheral wall of the cylinder closer to the combustion chamber is lower than a threshold temperature, and the internal combustion engine is operated in a low rotation and high load range, the control device reduces the ratio of fuel injection by the in-cylinder injection valve and increases the ratio of fuel injection by the port injection valve compared to before the index value exceeds the first threshold value, thereby suppressing the occurrence of LSPI. In addition, when the index value exceeds a second threshold value that is greater than the first threshold value and the internal combustion engine is operated in the low rotation, high load range, the control device increases the temperature of the second cooling water compared to before the index value exceeded the second threshold value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-2781 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in an internal combustion engine equipped with a turbocharger, when poor quality fuel containing a large amount of manganese is used as fuel, LSPI may occur when a small amount of fuel (manganese) adheres to the cylinder wall or the like in the low speed, high load range of the internal combustion engine, even if the fuel injection rate by the port injection valve is increased according to the number of occurrences of LSPI. On the other hand, when the number of occurrences of LSPI reaches a predetermined upper limit, it is preferable to limit the intake air amount (load factor) of the internal combustion engine in order to suppress deterioration of parts due to LSPI. However, if the upper limit is reduced by prioritizing the protection of parts, the operation of the internal combustion engine in the low speed, high load range is restricted due to the restriction of the intake air amount, and the drivability and NV (noise and vibration) of the vehicle are deteriorated.

[0005] Therefore, a primary object of the present disclosure is to suppress deterioration of an internal combustion engine due to low-speed pre-ignition, while suppressing deterioration of vehicle drivability and NV, even when inferior fuel is used. [Means for solving the problem]

[0006] The control device for an internal combustion engine disclosed herein is a control device for an internal combustion engine that has a turbocharger and a variable valve mechanism and is mounted on a vehicle, and when the number of occurrences of low-speed early ignition is equal to or less than a predetermined upper limit and is equal to or greater than a predetermined number that is smaller than the upper limit, changes the valve timing in a predetermined low-speed, high-load range so that the low-speed early ignition does not occur, and when the number of occurrences exceeds the upper limit, limits the load rate of the internal combustion engine to a low value.

[0007] The control device for an internal combustion engine disclosed herein changes the valve timing in a predetermined low-speed, high-load range so that low-speed pre-ignition does not occur when the number of occurrences of low-speed pre-ignition is equal to or less than a predetermined upper limit number and equal to or more than a predetermined number smaller than the upper limit number. As a result, even if inferior fuel is used, it is possible to suppress the occurrence of low-speed pre-ignition by changing the valve timing, thereby protecting the internal combustion engine and suppressing deterioration of the drivability and NV of the vehicle. In addition, the control device limits the load factor of the internal combustion engine to a low value when the number of occurrences of low-speed pre-ignition exceeds the upper limit number. As a result, it is possible to limit the operation of the internal combustion engine in the low-speed, high-load range after the number of occurrences of low-speed pre-ignition exceeds the upper limit number, and suppress the occurrence of LSPI and the deterioration of the internal combustion engine due to the LSPI.

[0008] Furthermore, the control device of the present disclosure may reduce the amount of valve overlap between the exhaust valve and the intake valve in the low rotation, high load range by advancing the exhaust valve closing timing when the number of occurrences of low speed early ignition is equal to or less than an upper limit number and is equal to or greater than a predetermined number that is smaller than the upper limit number, compared to when the number of occurrences of low speed early ignition is less than the predetermined number. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram showing an internal combustion engine controlled by a control device of the present disclosure. [Diagram 2] FIG. 2 is a control block diagram showing a control device of the present disclosure. [Diagram 3] 4 is a flowchart illustrating a routine executed by the control device of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Next, an embodiment of the present disclosure will be described with reference to the drawings.

[0011] 1 is a schematic diagram showing an engine 10, which is an internal combustion engine controlled by a control device of the present disclosure. The engine 10 shown in the figure is mounted on a vehicle 1, which is a vehicle using the engine 10 as the only power source, or a hybrid vehicle including a motor generator in addition to the engine 10. In this embodiment, the engine 10 is a multi-cylinder gasoline engine (for example, an in-line 4-cylinder engine or a V-type 6-cylinder engine) that converts the reciprocating motion of pistons 13, which accompanies the combustion of a mixture of hydrocarbon fuel and air in a plurality of combustion chambers (cylinders) 12 formed in an engine block 11, into the rotational motion of a crankshaft (output shaft) 14.

[0012] As shown in Fig. 1, the engine 10 includes an engine block 11, a plurality of combustion chambers 12, pistons 13, and a crankshaft 14, as well as an air cleaner 15, an intake pipe 16, an electronically controlled throttle valve 17, an intake manifold 18, a plurality of intake valves 19i, a plurality of exhaust valves 19e, a variable valve mechanism (variable valve timing mechanism) 190, a plurality of port injection valves 20p, a plurality of in-cylinder injection valves 20d, a plurality of spark plugs 21, and an exhaust pipe 22 forming an exhaust passage. The intake manifold 18 has a surge tank and a plurality of intake ports. The plurality of intake valves 19i open and close the corresponding intake ports, and the plurality of exhaust valves 19e open and close the corresponding exhaust ports. The variable valve mechanism 190 changes the opening timing and lift amount of the intake valves 19i and the exhaust valves 19e. The plurality of port injection valves 20p inject fuel into the corresponding intake ports, and the plurality of in-cylinder injection valves 20d inject fuel directly into the corresponding combustion chambers 12.

[0013] The engine 10 also includes an upstream purification device 23 and a downstream purification device 24, each of which is incorporated in the exhaust pipe 22. The upstream purification device 23 includes a NOx storage type exhaust gas purification catalyst (three-way catalyst) that purifies harmful components such as CO (carbon monoxide), HC, and NOx in the exhaust gas from each combustion chamber 12 of the engine 10. The downstream purification device 24 includes a particulate filter (GPF) that collects particulate matter (fine particles) in the exhaust gas, and is disposed downstream of the upstream purification device 23.

[0014] In addition, the engine 10 includes a supercharger 28 that compresses intake air by utilizing the energy of exhaust gas from each combustion chamber 12, and a liquid-cooled intercooler 29 that cools the air compressed by the supercharger 28. The supercharger 28 is a turbocharger and includes a turbine wheel 28t, a compressor wheel 28c, a turbine shaft 28s that integrally connects the turbine wheel 28t and the compressor wheel 28c, a wastegate valve 28w, and an air bypass valve (blow-off valve) 28b. The turbine wheel 28t is rotatably disposed in a turbine housing formed in the exhaust pipe 22 so as to be located upstream of the upstream purification device 23. The compressor wheel 28c is rotatably disposed in a compressor housing formed in the intake pipe 16 so as to be located between the air cleaner 15 and the throttle valve 17.

[0015] The engine 10 configured as described above is controlled by an engine electronic control unit (hereinafter referred to as "engine ECU") 100, which is a control device of the present disclosure including a microcomputer having a CPU, ROM, RAM, input / output interfaces, etc. (not shown), various drive circuits, various logic ICs, etc. As shown in Fig. 2, the engine ECU 100 obtains detection values ​​of the crank angle sensor 14a, the air flow meter 16a, the intake pressure sensor 16p, the boost pressure sensor 16c, the intake air temperature sensor 16t, the throttle opening sensor 17o, the surge pressure sensor 18p, the temperature sensor 18t, the upstream air-fuel ratio sensor 22f, the downstream air-fuel ratio sensor 22r, the exhaust gas temperature sensor 22t, the water temperature sensor 25t, the knock sensor 26, etc., via an input port (not shown).

[0016] The crank angle sensor 14a detects the rotational position (crank position) of the crankshaft 14. The air flow meter 16a detects the intake air amount Qa upstream of the compressor wheel 28c of the intake pipe 16. The intake pressure sensor 16p detects the intake pressure Pin upstream of the compressor wheel 28c of the intake pipe 16. The boost pressure sensor 16c detects the boost pressure Pc, which is the pressure of air compressed by the compressor wheel 28c between the compressor housing of the intake pipe 16 and the intercooler 29. The intake air temperature sensor 16t detects the intake temperature Tin upstream of the compressor wheel 28c of the intake pipe 16.

[0017] The throttle opening sensor 17o detects the opening TH of the throttle valve 17. The surge pressure sensor 18p detects the surge pressure Ps, which is the pressure of the air in the surge tank, and the temperature sensor 18t detects the surge temperature Ts, which is the temperature of the air in the surge tank. The upstream air-fuel ratio sensor 22f detects the upstream air-fuel ratio AFf, which is the air-fuel ratio of the exhaust gas flowing into the upstream purification device 23 on the upstream side of the upstream purification device 23, and the downstream air-fuel ratio sensor 22r detects the downstream air-fuel ratio AFr, which is the air-fuel ratio of the exhaust gas flowing into the downstream purification device 24 on the downstream side of the upstream purification device 23. The exhaust gas temperature sensor 22t detects the temperature Teg of the exhaust gas flowing through the portion of the exhaust pipe 22 between the upstream purification device 23 and the downstream purification device 24. The water temperature sensor 25t detects the water temperature Tw (the temperature of the engine 10) of the cooling water that has absorbed heat from (flowed out of) the engine block 11. The knock sensor 26 is attached to the engine block 11 (cylinder block) and detects knocking that occurs in the engine 10 (vibration of the cylinder block caused by knocking).

[0018] The engine ECU 100 calculates the rotation speed Ne of the engine 10 (crankshaft 14) based on the crank position from the crank angle sensor 14a. Furthermore, the engine ECU 100 calculates a load factor KL based on the intake air amount Qa from the air flow meter 16a and the rotation speed Ne of the engine 10. The load factor KL is a ratio of the volume of air actually taken in during one cycle to the stroke volume per cycle of the engine 10. The engine ECU 100 controls the throttle valve 17, the variable valve mechanism 190, the multiple port injection valves 20p and the multiple in-cylinder injection valves 20d, the multiple ignition plugs 21, and the like based on the rotation speed Ne, the load factor KL, and the like. The engine ECU 100 also controls an electric pump (not shown) that pumps the cooling water, and a wastegate valve 28w and an air bypass valve 28b of the supercharger 28.

[0019] Furthermore, the engine ECU 100 determines whether or not low speed early ignition (hereinafter referred to as "LSPI") has occurred based on the detection value of the knock sensor 26 and the crank position (crank angle), and increments a counter for counting the number of occurrences (accumulated number of occurrences) Nlspi of LSPI every time it is determined that LSPI has occurred. However, the engine ECU 100 may determine whether or not LSPI has occurred based on the combustion pressure in the combustion chamber 12 detected by an internal cylinder pressure sensor (not shown). In order to suppress deterioration of the engine 10 (engine block 11 and various components) due to LSPI, the engine ECU 100 repeatedly executes the routine of FIG. 3 at predetermined time intervals (micro time) while the engine 10 is operating.

[0020] When the timing for executing the routine of FIG. 3 arrives, the engine ECU 100 acquires the number of occurrences Nlspi of LSPI, which is the value of the counter (step S100), and determines whether the acquired number of occurrences Nlspi is less than a predetermined upper limit value Nlim (step S110). The upper limit value Nlim is a relatively large positive integer that is determined in advance based on an expected number of occurrences of LSPI that will occur in the engine 10 before the useful life of the vehicle 1 has elapsed through experiments and analysis. If the number of occurrences Nlspi is less than the upper limit value Nlim (step S110: YES), the engine ECU 100 determines whether the number of occurrences Nlspi acquired in step S100 is equal to or greater than a predetermined value Nref (step S120). The predetermined value Nref is a predetermined positive integer that is sufficiently smaller than the upper limit value Nlim (for example, a value approximately a fraction of the upper limit value Nlim).

[0021] If the occurrence count Nlspi is less than the predetermined value Nref (step S120: NO), the engine ECU 100 does not execute the subsequent processes and temporarily ends the routine of Fig. 3. On the other hand, if the occurrence count Nlspi is equal to or greater than the predetermined value Nref (step S120: YES), the engine ECU 100 sets a map that is pre-adapted to suppress the occurrence of LSPI as a map that defines the valve timing of the engine 10 (step S130), and temporarily ends the routine of Fig. 3.

[0022] The map that specifies the valve timing for suppressing the occurrence of LSPI is created so that, for example, the valve overlap amount between the exhaust valve 19e and the intake valve 19i in a low-speed, high-load region where the engine speed Ne of the engine 10 is equal to or lower than a predetermined speed (e.g., a value of about 2500-3000 rpm) and the torque required for the engine 10 is equal to or higher than a predetermined torque (e.g., a value of about 100-150 Nm) is smaller than when the occurrence count Nlspi is less than a predetermined value Nref. In this embodiment, when the occurrence count Nlspi of LSPI becomes equal to or higher than the predetermined value Nref, the valve overlap amount between the exhaust valve 19e and the intake valve 19i in the low-speed, high-load region is set to zero.

[0023] On the other hand, if the number of occurrences of LSPI Nlspi is equal to or greater than the upper limit value Nlim (step S110: NO), the engine ECU 100 limits the load factor KL (upper limit value) of the engine 10 to a value smaller than the value when the number of occurrences Nlspi is less than the upper limit value Nlim (step S140), and temporarily ends the routine of Fig. 3. In this embodiment, when the number of occurrences of LSPI Nlspi is equal to or greater than the upper limit value Nlim, the load factor KL is set to a predetermined limit value that is, for example, about 60-70% of the value when the number of occurrences Nlspi is less than the upper limit value Nlim.

[0024] 3 is executed, in the vehicle 1, when the number of occurrences of LSPI in the engine 10 Nlspi is equal to or less than a predetermined upper limit number Nlim and equal to or more than a predetermined number Nref smaller than the upper limit number Nlim (step S110: YES, S120: YES), the valve timing in a predetermined low speed, high load range of the engine 10 is changed so as not to cause LSPI (step S130). That is, when the process of step S130 is executed, the valve overlap amount between the exhaust valve 19e and the intake valve 19i in the low speed, high load range is set to zero by advancing the closing timing of the exhaust valve 19e, compared to when the number of occurrences of LSPI Nlspi is less than the predetermined number Nref.

[0025] This makes it possible to increase the amount of air in the combustion chamber 12 by changing the valve timing, thereby reducing the penetration force of the injected fuel, and effectively suppress adhesion of the fuel (manganese) to the wall surface, etc., of the combustion chamber 12. Therefore, when the number of occurrences of LSPI Nlspi is equal to or less than the upper limit number Nlim and equal to or greater than the predetermined number Nref, it is possible to ensure the output torque of the engine 10 in the low rotation, high load range while suppressing the occurrence of LSPI and protecting the engine 10, thereby effectively suppressing the deterioration of the drivability of the vehicle 1 in the low rotation, high load range and the deterioration of NV due to an increase in the rotation speed Ne of the engine 10.

[0026] When the number of occurrences of LSPI Nlspi exceeds the upper limit number Nlim (step S110: NO), the engine ECU 100 limits the load factor KL of the engine 10 to a small value (step S140). This limits the operation of the engine 10 in the low rotation, high load range after the number of occurrences of LSPI Nlspi exceeds the upper limit number Nlim, and effectively suppresses the occurrence of LSPI and the deterioration of the engine 10 due to the LSPI.

[0027] In the above embodiment, when the number of occurrences of LSPI Nlspi is equal to or less than the upper limit number Nlim and equal to or more than the predetermined number Nref, the valve overlap amount between the exhaust valve 19e and the intake valve 19i in the low rotation, high load range is set to zero, but this is not limited to this. That is, when the number of occurrences of LSPI Nlspi is equal to or less than the upper limit number Nlim and equal to or more than the predetermined number Nref, the valve overlap amount between the exhaust valve 19e and the intake valve 19i in the low rotation, high load range may be reduced to a value other than zero by advancing the closing timing of the exhaust valve to reduce the amount of scavenging, compared to when the number of occurrences Nlspi is less than the predetermined number Nef.

[0028] In addition, the invention of the present disclosure is not limited to the above embodiment, and various modifications can be made within the scope of the present disclosure. Furthermore, the above embodiment is merely a specific form of the invention described in the Summary of the Invention, and does not limit the elements of the invention described in the Summary of the Invention. [Industrial Applicability]

[0029] The invention of the present disclosure can be used in the internal combustion engine manufacturing industry and the like. [Explanation of symbols]

[0030] 1 vehicle, 10 engine, 12 combustion chamber, 19e exhaust valve, 19i intake valve, 26 knock sensor, 28 turbocharger, 190 variable valve mechanism, 100 engine ECU (control device).

Claims

[Claim 1] A control device for an internal combustion engine having a turbocharger and a variable valve mechanism and mounted on a vehicle, A control device for an internal combustion engine that changes valve timing in a predetermined low-speed, high-load range so that low-speed early ignition does not occur when the number of occurrences of low-speed early ignition is equal to or less than a predetermined upper limit and is equal to or greater than a predetermined number that is smaller than the upper limit, and that limits the load factor of the internal combustion engine to a low value when the number of occurrences exceeds the upper limit.

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