JP7828269B2 - Engine control unit - Google Patents

Description

The present invention relates to an engine control device that controls a hydraulically driven variable valve mechanism and a variable displacement oil pump that supplies lubricating oil to an oil gallery.

In engines, for example, misfires, which occur when the fuel-air mixture does not ignite due to a malfunction in the ignition system, can lead to reduced idle stability and drivability. Taking into consideration the possibility of engine misfires, Japanese Patent Application Laid-Open No. 2012-225172 (Patent Document 1) proposes a technology that increases the oil pressure of the lubricating oil discharged from the oil pump when a misfire occurs, thereby increasing the flow rate of lubricating oil injected from the oil jet toward the piston, lowering the exhaust temperature and reducing the thermal impact on the catalytic converter.

JP 2012-225172 A

However, in the case of an oil pump that is mechanically driven by the engine, increasing the oil pressure of the lubricating oil discharged from the oil pump increases the load on the engine, which, combined with the occurrence of misfires and reduced idle stability and drivability, could make the engine more susceptible to stalling.

Therefore, the present invention aims to provide an engine control device that relates to a hydraulically driven variable valve mechanism and a variable displacement oil pump that supplies lubricating oil to an oil gallery, and that makes it less likely for the engine to stall even if a misfire occurs in the engine.

An engine control device that controls a hydraulically driven variable valve mechanism and a variable displacement oil pump that supplies lubricating oil to an oil gallery reduces a target oil pressure of the oil pump, which is set according to the engine operating state, when a misfire occurs in the engine, and controls the oil pressure of the lubricating oil discharged from the oil pump based on this target oil pressure. Furthermore, when the maximum number of misfires over a predetermined period of time reaches or exceeds a first threshold, the engine control device reduces the target oil pressure to the lower limit oil pressure for operating the variable valve mechanism.

According to the present invention, in an engine control device that controls a hydraulically driven variable valve mechanism and a variable displacement oil pump that supplies lubricating oil to an oil gallery, it is possible to make it less likely for the engine to stall even if a misfire occurs in the engine.

1 is a schematic diagram illustrating an example of an engine system mounted on a vehicle. FIG. 4 is an explanatory diagram showing an example of the characteristics of a variable displacement oil pump. 4 is a flowchart showing an example of control of a variable displacement oil pump. 4 is a flowchart showing an example of control of a variable displacement oil pump. 4 is a flowchart showing an example of control of a variable displacement oil pump. FIG. 10 is an explanatory diagram of a region T in which the catalytic converter temperature may exceed the allowable temperature. FIG. 10 is an explanatory diagram showing changes in the maximum number of misfire occurrences over a predetermined period of time. FIG. 4 is a diagram illustrating the control state of the oil pump over time. FIG. 4 is an explanatory diagram of a control state of an oil pump.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows an example of an engine system mounted on a vehicle to which an engine control device according to this embodiment can be applied.

The engine 10 mounted on a vehicle such as an automobile is, for example, an inline 3-cylinder, inline 4-cylinder, or V6 gasoline engine. An intake air flow sensor 14 is attached to a predetermined location in the intake pipe 12, which introduces intake air (intake air) into each cylinder. It detects the intake air flow rate Q, which is one example of the load on the engine 10. The intake air flow rate sensor 14 can be, for example, a hot-wire flow meter such as an air flow meter. The load on the engine 10 is not limited to the intake air flow rate Q; other state quantities closely related to torque, such as intake vacuum, boost pressure, throttle opening, and accelerator opening, can also be used.

An intake port 18, which introduces intake air into the combustion chamber 16 of each cylinder, is equipped with an intake valve 20 that opens and closes the end opening facing the combustion chamber 16. An electromagnetic fuel injection valve 22 is attached to a predetermined location in the intake pipe 12, located upstream of the intake valve 20. The electromagnetic fuel injection valve 22 injects fuel toward the back surface of the intake valve's head. When magnetic attraction is generated by energizing the electromagnetic coil, the valve element of the fuel injection valve 22, which is biased by a spring in the valve closing direction, lifts, opening the nozzle hole at the tip and injecting fuel. Fuel adjusted to a predetermined pressure is supplied to the fuel injection valve 22 so that the amount of fuel injected is approximately proportional to the duration the nozzle hole is open. The fuel injection valve 22 is not limited to a configuration that injects fuel toward the back surface of the intake valve's head, but may also be a configuration that injects fuel directly into the combustion chamber 16, or a configuration that combines both.

Fuel injected from the nozzle hole of the fuel injection valve 22 passes through the gap between the end opening of the intake port 18 and the intake valve 20 and is introduced into the combustion chamber 16 along with the intake air, where it is ignited and burned by spark from the spark plug 24. As a result, the combustion pressure pushes the piston 26 toward the crankshaft (not shown), driving it to rotate.

An exhaust port 28, which discharges exhaust gas from the combustion chamber 16, is equipped with an exhaust valve 30 that opens and closes the end opening facing the combustion chamber 16. When the exhaust valve 30 opens the end opening of the exhaust port 28, the exhaust gas passes through the gap between the end opening of the exhaust port 28 and the exhaust valve 30 and is discharged into the exhaust pipe 32. A catalytic converter 34 is attached to a predetermined location in the exhaust pipe 32. Harmful substances contained in the exhaust are purified into harmless components by the catalytic converter 34, and then released into the atmosphere from the end opening of the exhaust pipe 32. Here, the catalytic converter 34 can be, for example, a three-way catalyst that simultaneously purifies CO (carbon monoxide), HC (hydrocarbons), and NOx (nitrogen oxides) contained in the exhaust.

A hydraulically driven variable valve timing (VVT) mechanism 38 is attached to the end of the intake camshaft 36, which drives the intake valves 20 to open and close. This mechanism changes the valve timing (opening and closing timing) of the intake valves 20 by varying the phase angle of the intake camshaft 36 relative to the crankshaft. Hydraulically driven VVT mechanisms 38 are well known to those skilled in the art, so a detailed description thereof will be omitted. The VVT mechanism 38 is not limited to the intake valve 20, and may be provided on at least one of the intake valve 20 and exhaust valve 30. The VVT mechanism 38 is also an example of a variable valve mechanism.

In addition to the intake air flow rate sensor 14, an engine speed sensor 40, a crank angle sensor 42, a cam angle sensor 44, a water temperature sensor 46, and an air-fuel ratio sensor 48 are attached to predetermined locations in the engine system. The engine speed sensor 40 detects the rotation speed Ne of the engine 10. The crank angle sensor 42 detects the crank angle θ _CRK from a reference position of the crankshaft. The cam angle sensor 44 detects the cam angle θ _CAM from a reference position of the intake camshaft 36. The water temperature sensor 46 detects the coolant temperature (water temperature) Tw of the engine 10. The air-fuel ratio sensor 48 detects the air-fuel ratio ABF in the exhaust gas.

The output signals of the intake air flow sensor 14, engine speed sensor 40, crank angle sensor 42, cam angle sensor 44, water temperature sensor 46, and air-fuel ratio sensor 48 are each input to an engine control module (ECM) 100, which incorporates a microcomputer (not shown).

The engine control module 100 reads the intake air flow rate Q and the engine rotation speed Ne from the intake air flow rate sensor 14 and the engine rotation speed sensor 40, respectively, and calculates a basic fuel injection amount corresponding to the engine operating conditions based on these values. The engine control module 100 also reads the water temperature Tw from the water temperature sensor 46 and calculates a fuel injection amount by correcting the basic fuel injection amount based on the water temperature Tw or the like. The engine control module 100 then reads the crank angle θ _CRK and the cam angle θ _CAM from the crank angle sensor 42 and cam angle sensor 44, respectively, and outputs activation signals to the fuel injector 22 and the spark plug 24 at the timing corresponding to the engine operating conditions calculated from these values. As a result, fuel corresponding to the fuel injection amount is injected from the fuel injector 22, and the spark plug 24 ignites and burns the mixture of fuel and intake air. At this time, the engine control module 100 reads the air-fuel ratio ABF from the air-fuel ratio sensor 48 and feedback controls the fuel injector 22 so that the air-fuel ratio ABF in the exhaust gas approaches the target air-fuel ratio.

Also, a variable displacement oil pump 52 driven by the engine 10 is installed in a predetermined location in the engine system to supply lubricating oil to the hydraulically driven VVT mechanism 38 and the oil gallery 50 of the engine 10. The oil pump 52 incorporates or is attached to a solenoid valve 52A, which controls the amount of lubricating oil supplied to and discharged from the control chamber by axially moving a spool through duty control, thereby varying the oil pressure of the lubricating oil discharged from the oil pump 52. As shown in Figure 2, the oil pump 52 is fully open when the duty applied to the solenoid valve 52A is 0%. As the duty increases from 0%, the opening gradually decreases. The oil pressure of the lubricating oil discharged from the oil pump 52 increases linearly with the rotational speed of the engine 10 and is limited to a maximum oil pressure corresponding to the duty applied to the solenoid valve 52A. This eliminates the need for a relief valve to limit the maximum oil pressure of the oil pump 52. Variable displacement oil pumps 52 are well known to those skilled in the art, so further explanation will be omitted.

As an example of a lubrication system that supplies lubricating oil to the VVT mechanism 38 and oil gallery 50, in addition to the oil pump 52, the engine system is equipped with an oil pan 54 that stores a predetermined amount of lubricating oil, an oil strainer 56 that removes relatively large foreign matter from the lubricating oil, an oil filter 58 that removes relatively small foreign matter from the lubricating oil, an oil jet 60 that sprays lubricating oil toward the underside of the piston 26 to cool it, and a solenoid valve 62 that controls the supply and discharge of lubricating oil to the VVT mechanism 38 to change the valve timing.

When the oil pump 52 is activated, the lubricating oil stored in the oil pan 54 is drawn into the oil line L1 through the oil strainer 56 and supplied to the oil pump 52. The lubricating oil supplied to the oil pump 52 is pressurized to a pressure determined by the duty applied to the solenoid valve 52A and the rotational speed Ne of the engine 10, and is then supplied to the oil gallery 50 through the oil line L2, with the oil filter 58 located in the middle. The lubricating oil supplied to the oil gallery 50 to lubricate and cool various parts of the engine 10 is returned to the oil pan 54 through the oil line L3. In addition, the oil line L2, located between the oil filter 58 and the oil gallery 50, branches off from the oil line L4, and an oil jet 60 is attached to the tip of the oil line L4.

In addition, oil line L2, located between the oil filter 58 and the oil gallery 50, branches off into oil line L5, which has a solenoid valve 62 located in the middle, and its tip is connected to the VVT mechanism 38. Lubricating oil supplied to the VVT mechanism 38 through oil line L5 is returned to the oil pan 54 through oil line L6.

The engine system is equipped with such a lubrication system, which allows the lubrication and cooling of each part of the engine 10 and the driving of the VVT mechanism 38. Note that the lubrication system shown in Figure 1 is merely one example used to explain this embodiment, and those skilled in the art will easily understand that any modification can be made to the lubrication system as long as it allows the lubrication and cooling of each part of the engine 10 and the driving of the VVT mechanism 38.

In controlling the VVT mechanism 38, the engine control module 100 reads the intake air flow rate Q and the engine rotation speed Ne from the intake air flow rate sensor 14 and the engine rotation speed sensor 40, respectively, and determines a target angle of the VVT mechanism 38 according to the engine operating state. The engine control module 100 then reads the crank angle θ _CRK and the cam angle θ _CAM from the crank angle sensor 42 and cam angle sensor 44, respectively, and feedback controls the solenoid valve 62 so that the actual VVT angle determined from the crank angle θ _CRK and the cam angle θ _CAM approaches the target angle.

Figures 3 to 5 show an example of the control of the variable displacement oil pump 52 that is executed by the microcomputer of the engine control module 100 in accordance with an application program pre-stored in non-volatile memory when the engine control module 100 is started. Note that, for the sake of simplicity, the "microcomputer of the engine control module 100" will be abbreviated as "engine control module 100" below.

In step 10 (abbreviated as "S10" in Figure 3, and the same applies below), the engine control module 100 begins counting the number of times the mixture is ignited by the spark plug 24 in preparation for counting the maximum number of misfires over a predetermined period. Specifically, the engine control module 100 uses, for example, a counter (initial value = 0) to count the number of ignitions, and increments this counter each time an activation signal is output to the spark plug 24.

In step 11, the engine control module 100 sets a target oil pressure for the oil pump 52 according to the operating state of the engine 10. Specifically, the engine control module 100 reads the intake flow rate Q from the intake flow rate sensor 14 and the rotation speed Ne from the engine rotation speed sensor 40. The engine control module 100 then references a map in which target oil pressures suited to the intake flow rate and engine rotation speed are preset, and sets a target oil pressure according to the intake flow rate Q and the rotation speed Ne.

In step 12, the engine control module 100 starts a misfire counter that counts the number of misfires over a predetermined period. Specifically, the engine control module 100 reads, for example, the crank angle θ _CRK and the cam angle θ _CAM from the crank angle sensor 42 and the cam angle sensor 44, respectively, and determines whether a misfire has occurred based on fluctuations in the engine speed Ne output from the engine speed sensor 40 near top dead center, which are determined from these values. Then, every time the engine control module 100 determines that a misfire has occurred, it increments the misfire counter, which has an initial value of 0.

In step 13, the engine control module 100 determines whether the number of ignitions has reached a predetermined number or more. Here, the predetermined number is a parameter for defining a predetermined period for counting the maximum number of misfires, and can be set to, for example, 500 times. If the engine control module 100 determines that the number of ignitions has reached or exceeded the predetermined number (Yes), it proceeds to step 14. On the other hand, if the engine control module 100 determines that the number of ignitions is less than the predetermined number (No), it proceeds to step 18.

In step 14, the engine control module 100 has finished counting the number of ignitions over the specified period, so it resets the number of ignitions, in other words, sets the number of ignitions to 0, and prepares to count the number of ignitions over the next specified period.

In step 15, the engine control module 100 determines whether the misfire counter, which has counted over a predetermined period, is greater than a maximum value. Here, the maximum value is a parameter for counting the maximum number of misfires over a predetermined period from startup to shutdown of the engine control module 100, and is set to 0 as its initial value. If the engine control module 100 determines that the misfire counter is greater than the maximum value (Yes), it proceeds to step 16. On the other hand, if the engine control module 100 determines that the misfire counter is equal to or less than the maximum value (No), it proceeds to step 17.

In step 17, since counting the number of misfires over the specified period has finished, the engine control module 100 resets the misfire counter, i.e., sets the misfire counter to 0, and prepares to count the number of misfires over the next specified period.

In step 18, the engine control module 100 determines whether a fuel cut is in progress, in which fuel injection by the fuel injection valve 22 is temporarily suspended. Here, the engine control module 100 can determine that a fuel cut is in progress, for example, when the idle determination is ON and the engine speed is decelerating at or above a first predetermined value, or when the engine speed is at high speed and is at or above a second predetermined value that is greater than the first predetermined value. If the engine control module 100 determines that a fuel cut is in progress (Yes), it proceeds to step 19. On the other hand, if the engine control module 100 determines that a fuel cut is not in progress (No), it proceeds to step 24.

In step 19, the engine control module 100 determines whether the maximum value, which represents the maximum number of misfires over a predetermined period of time, is greater than threshold B. Here, threshold B is a parameter used to determine whether the maximum number of misfires over a predetermined period of time is high, making the engine highly susceptible to stalling, and can be determined appropriately, for example, taking into account the characteristics of the engine system. If the engine control module 100 determines that the maximum value is greater than threshold B (Yes), it proceeds to step 20. On the other hand, if the engine control module 100 determines that the maximum value is equal to or less than threshold B (No), it proceeds to step 22. Threshold B is an example of a second threshold.

In step 20, because the engine is highly susceptible to stalling, the engine control module 100 reduces the target oil pressure of the oil pump 52 to the minimum oil pressure that can protect the engine. The state in which the target oil pressure of the oil pump 52 has been reduced to the minimum oil pressure that can protect the engine corresponds to the second stage in which the target oil pressure has been reduced in stages. Note that simply reducing the target oil pressure of the oil pump 52 does not actually reduce the oil pressure of the lubricating oil discharged from the oil pump 52 (the same applies below).

In step 21, taking into account the possibility that the lubricating oil pressure will decrease in the future due to the reduction in the target oil pressure of the oil pump 52, the engine control module 100 controls the solenoid valve 62 to change the VVT mechanism 38 to the most retarded position. The engine control module 100 then proceeds to step 28.

In step 22, which executes processing to determine whether the maximum value representing the maximum number of misfire occurrences over a predetermined period is equal to or less than threshold B, the engine control module 100 determines whether this maximum value is greater than threshold A. Here, threshold A is a parameter used to determine whether the number of misfire occurrences over a predetermined period is relatively high, thereby making the engine prone to stall, and can be determined appropriately taking into account, for example, the characteristics of the engine system. If the engine control module 100 determines that the maximum value is greater than threshold A (Yes), it proceeds to step 23. On the other hand, if the engine control module 100 determines that the maximum value is equal to or less than threshold A (No), it proceeds to step 28. Threshold A is an example of a first threshold.

In step 23, because the engine is in a state where stalling is likely to occur, the engine control module 100 reduces the target oil pressure of the oil pump 52 to the lower limit oil pressure for operation of the VVT mechanism 38. The state in which the target oil pressure of the oil pump 52 has been reduced to the lower limit oil pressure for operation of the VVT mechanism 38 corresponds to the first stage of a stepwise reduction in the target oil pressure. The engine control module 100 then proceeds to step 28.

In step 24, when it is determined that fuel cut is not in progress, the engine control module 100 determines whether the catalytic converter 34 is in the T region, where the temperature may exceed the allowable temperature. Specifically, as shown in FIG. 6, the engine control module 100 references a map in which catalytic converter 34 temperatures appropriate for engine speed and intake air flow rate are preset, and determines whether the engine operating condition characterized by the rotation speed Ne and intake air flow rate Q is in the T region. In other words, the engine control module 100 determines whether the catalytic converter 34 temperature may exceed the allowable temperature, taking into account the possibility that the engine operating condition may become high speed and high load, causing the exhaust temperature to rise in the future. If the engine control module 100 determines that the engine operating condition is in the T region (Yes), it proceeds to step 25. On the other hand, if the engine control module 100 determines that the engine operating condition is not in the T region (No), it proceeds to step 28.

In step 25, the engine control module 100, for example, uses a timer function to determine whether a predetermined time has elapsed since the engine operating state entered the T region. The predetermined time is a parameter that ensures the time required for the temperature of the catalytic converter 34 to rise, because even if the engine operating state temporarily enters the T region, it cannot be determined that the catalytic converter 34 will reach or exceed the allowable temperature. If the engine control module 100 determines that the predetermined time has elapsed since the engine operating state entered the T region (Yes), the process proceeds to step 26. On the other hand, if the engine control module 100 determines that the predetermined time has not elapsed since the engine operating state entered the T region (No), the process proceeds to step 28.

In step 26, the engine control module 100 determines whether the maximum value, which represents the maximum number of misfires over a predetermined period of time, is equal to or greater than threshold C. Here, threshold C is a parameter used to determine whether a predetermined time has passed since the catalytic converter 34 exceeded its allowable temperature, potentially causing thermal damage to the catalytic converter 34. Threshold C can be determined appropriately, for example, taking into account the heat resistance characteristics of the catalytic converter 34. If the engine control module 100 determines that the maximum value is equal to or greater than threshold C (Yes), the process proceeds to step 27. On the other hand, if the engine control module 100 determines that the maximum value is less than threshold C (No), the process proceeds to step 28.

In step 27, the engine control module 100 reduces the duty cycle applied to the solenoid valve 52A of the oil pump 52 to 0% to fully open it, in order to increase the flow rate of lubricating oil injected from the oil jet 60 and reduce the exhaust temperature. The engine control module 100 then proceeds to step 29.

In step 28, the engine control module 100 applies a duty cycle to the solenoid valve 52A that corresponds to the target oil pressure of the oil pump 52, thereby controlling the oil pump 52 to approach the target oil pressure.

In step 29, the engine control module 100 determines whether the ignition switch (not shown) has changed from ON to OFF, in other words, whether to transition to self-shutdown processing. If the engine control module 100 determines that the ignition switch has changed from ON to OFF (Yes), it proceeds to step 30. On the other hand, if the engine control module 100 determines that the ignition switch remains ON (No), it returns to step 13.

In step 30, engine control module 100 clears a maximum value representing the maximum number of misfire occurrences over a predetermined period of time, i.e., sets the maximum value to zero.
In step 31, the engine control module 100 stops the control of the VVT mechanism 38 to the most retarded position, and changes the VVT mechanism 38 to an angle suitable for restarting the engine 10, for example.

According to this control, the engine control module 100 sets the target oil pressure for the oil pump 52 according to the engine operating state, and, as shown in FIG. 7, begins updating the maximum value, which represents the maximum number of misfires that can occur over a predetermined period of time. As is clear from FIG. 7, the maximum value is updated when the value of the misfire counter, counted over a predetermined period of time, exceeds the maximum value. Therefore, the maximum value can be considered a parameter that represents the maximum number of misfires that can occur over each predetermined period of time from startup to shutdown of the engine control module 100.

Then, if the maximum value indicating the maximum number of misfires over a specified period is greater than threshold B during fuel cut, the engine control module 100 reduces the target oil pressure of the oil pump 52 to the second stage and controls the VVT mechanism 38 to the most retarded position. On the other hand, if the maximum value is greater than threshold A during fuel cut, the engine control module 100 reduces the target oil pressure of the oil pump 52 to the first stage. Then, the engine control module 100 applies a duty cycle to the solenoid valve 52A of the oil pump 52 according to the target oil pressure, and controls the oil pressure of the lubricating oil discharged from the oil pump 52 to approach the target oil pressure.

Therefore, when the maximum number of misfires over a predetermined period exceeds threshold A, the engine control module 100 reduces the oil pressure of the lubricating oil discharged from the variable displacement oil pump 52 to the lower limit oil pressure (first stage) for operating the VVT mechanism 38, making the engine 10 less likely to stall. Then, if the maximum number of misfires over a predetermined period gradually increases through subsequent operation despite the oil pressure of the lubricating oil discharged from the oil pump 52 being reduced to the first stage and exceeds threshold B, the engine control module 100 further reduces the oil pressure of the lubricating oil discharged from the oil pump 52 to the lower limit oil pressure (second stage) that can protect the engine, making the engine 10 less likely to stall. As a result, the variable displacement oil pump 52 that supplies lubricating oil to the hydraulically driven VVT mechanism 38 and oil gallery 50 can make the engine less likely to stall even when a misfire occurs in the engine 10.

Furthermore, when fuel is not being cut and the engine operating state remains in the T region for a predetermined period of time, the engine control module 100 immediately sets the duty applied to the solenoid valve 52A of the oil pump 52 to 0% without changing the target oil pressure of the oil pump 52. As a result, the oil pressure of the lubricating oil discharged from the oil pump 52 reaches its maximum, increasing the flow rate of the lubricating oil injected from the oil jet 60 to the bottom of the piston 26. As the flow rate of the lubricating oil injected to the bottom of the piston 26 increases, the piston 26 is cooled by the lubricating oil, lowering the combustion temperature and thereby the exhaust temperature. This suppresses the temperature rise of the catalytic converter 34 located in the exhaust pipe 32, causing the engine operating state to move out of the T region, reducing the possibility of thermal effects on the catalytic converter 34.

To facilitate understanding of this embodiment, as shown in Figure 8, we will now explain the operation that occurs after the engine control module 100 is started and immediately before the maximum number of misfires over a predetermined period of time exceeds threshold A.

If fuel cut is performed after the maximum number of misfires over a specified period exceeds threshold A, the oil pressure of the lubricating oil discharged from the oil pump 52 is reduced to a first stage, i.e., as shown in FIG. 9, to a lower limit oil pressure at which lubricating oil cannot be injected from the oil jet 60 but the VVT mechanism 38 can be operated. As a result, as described above, engine stalls are less likely to occur. If fuel cut is performed after the maximum number of misfires over a specified period exceeds threshold B, which is greater than threshold A as the engine 10 operates, the oil pressure of the lubricating oil discharged from the oil pump 52 is reduced to a second stage, i.e., as shown in FIG. 9, to a lower limit oil pressure at which the engine can be protected. As a result, as described above, engine stalls are even less likely to occur.

Furthermore, as shown in FIG. 8 , when a T-zone determination is performed a predetermined time after the engine operating state has entered the T-zone, and the maximum number of misfires over the predetermined period exceeds threshold C, which is greater than threshold A but smaller than threshold B, the oil pressure of the lubricating oil discharged from the oil pump 52 reaches its maximum. As a result, as described above, the temperature rise of the catalytic converter 34 located in the exhaust pipe 32 is suppressed, making it less susceptible to thermal effects. When the oil pressure of the lubricating oil discharged from the oil pump 52 reaches its maximum, the load on the engine 10 that drives the oil pump 52 increases, making engine stall more likely. Therefore, as shown in FIG. 8 , as soon as the T-zone determination is canceled, the oil pressure of the lubricating oil discharged from the oil pump 52 is restored to its previous state to prevent engine stall. In short, by maximizing the oil pressure of the lubricating oil discharged from the oil pump 52 only when the T-zone determination is being performed, it is possible to both prevent engine stall and thermally protect the catalytic converter 34.

A person skilled in the art will readily understand that new embodiments can be created by omitting parts of the technical ideas of the above embodiments, combining parts as appropriate, or replacing parts with well-known technology.

As an example, the engine 10 installed in the vehicle is not limited to a gasoline engine, but may also be a diesel engine. Furthermore, the oil pump 52 is not limited to being controlled by the engine control module 100, but may also be controlled by a different control device.

10...Engine, 34...Catalytic converter, 38...VVT mechanism (variable valve timing mechanism), 50...Oil gallery, 52...Oil pump, 60...Oil jet, 100...Engine control module (control device)

Claims (3)

An engine control device that controls a hydraulically driven variable valve mechanism and a variable displacement oil pump that supplies lubricating oil to an oil gallery,
When a misfire occurs in the engine, a target oil pressure of the oil pump, which is set in accordance with an operating state of the engine, is reduced, and the oil pressure of the lubricating oil discharged from the oil pump is controlled based on the target oil pressure .
When the maximum number of misfire occurrences over a predetermined period of time becomes equal to or greater than a first threshold value, the target oil pressure is reduced to a lower limit oil pressure for operating the variable valve mechanism.
Engine control device . When the maximum occurrence number is equal to or greater than a second threshold value that is greater than the first threshold value, the target oil pressure is reduced to a lower limit oil pressure that allows engine protection.
The engine control device according to claim 1 . When the maximum occurrence number is equal to or greater than the second threshold value, the target oil pressure is reduced to a lower limit oil pressure that allows engine protection, and the variable valve mechanism is controlled to a most retarded position.
The engine control device according to claim 2 .