Engine control unit

Abstract

The present invention provides an engine control device that can further reduce engine noise and vibration (NV) (i.e., improve the quietness of the engine). [Solution] The ECU 50 estimates the oil film thickness for each cylinder based on the crank angular velocity, engine load, and oil temperature corresponding to the expansion stroke of each cylinder, and corrects the ignition timing of cylinders whose estimated oil film thickness is thinner than a predetermined value.

Description

Technical Field

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[0001] The present invention relates to an engine control device.

Background Art

[0002] In a vehicle using an engine as a power source or the like, noise (Noise) and vibration (Vibration) (hereinafter also referred to as "NV") caused by the engine occur during the operation (operation) of the engine. On the other hand, the quietness (NV performance) of the vehicle is an important factor for the comfort (and thus the commerciality) of the vehicle.

[0003] Therefore, conventionally, in order to improve the quietness of the vehicle, for example, the quietness of the engine body has been improved by measures against piston knocking sound (for example, see Patent Document 1). [[ID=十七]]

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in recent years, the strengthening of vehicle exterior noise regulations (for example, R51-03 Phase 3, etc.) has been promoted. Therefore, in order to cope with such strengthened regulations and to further improve the above-described commerciality, it has been desired to further reduce the noise and vibration (NV) of the engine body (that is, to further improve the quietness of the engine body).

[0006] The present invention has been made to solve the above problems, and an object thereof is to provide an engine control device capable of further reducing the noise and vibration (NV) of the engine body (that is, further improving the quietness of the engine body).

Means for Solving the Problems

[0007] An engine control device according to one aspect of the present invention is characterized by comprising: an oil film thickness acquisition means for determining the thickness of the oil film on the inner surface of each of a plurality of cylinders formed in an engine; and a control unit for correcting the ignition timing of each cylinder according to the determined oil film thickness for each cylinder.

[0008] Incidentally, if there is a cylinder with an oil film thickness thinner than a predetermined value, and there is variation (large variation) in the oil film thickness of each cylinder, then variation occurs in the force pushing down the pistons between cylinders (i.e., the engine does not rotate smoothly), and there is a tendency for NV (Noise, Vibration, and Noise) to worsen. Therefore, according to one aspect of the present invention, the oil film thickness of each of the multiple cylinders is determined, and the ignition timing of each cylinder is corrected according to the oil film thickness of each cylinder, and the output torque of each cylinder is finely adjusted, thereby eliminating variation in the force pushing down the pistons between cylinders, and reducing noise and vibration (NV) of the engine body. [Effects of the Invention]

[0009] According to the present invention, it is possible to further reduce noise and vibration (NV) of the engine body (i.e., to further improve the quietness of the engine body). [Brief explanation of the drawing]

[0010] [Figure 1] This diagram shows an engine control device according to the first embodiment and the configuration of an engine to which the engine control device is applied. [Figure 2] This figure shows the relationship between oil film thickness and vibration level. [Figure 3] This flowchart shows the processing procedure for NV reduction control by the engine control device according to the first embodiment. [Figure 4] This figure shows the configuration of the engine control device according to the second embodiment, and the engine (main part) to which the engine control device is applied. [Figure 5]This flowchart shows the processing procedure for NV reduction control by the engine control device according to the second embodiment. [Figure 6] This flowchart shows the processing procedure for NV reduction control by the engine control device related to the modified example. [Modes for carrying out the invention]

[0011] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Unless otherwise necessary, the same reference numerals will be used for the same or corresponding parts in the drawings. Furthermore, in each drawing, the same reference numerals will be used for the same elements, and redundant descriptions will be omitted.

[0012] (First Embodiment) First, the configuration of the engine control device 1 according to the first embodiment will be described using Figure 1. Figure 1 is a diagram showing the configuration of the engine control device 1 and the engine 10 to which the engine control device 1 is applied.

[0013] The engine 10 can be of any type, but for example, it is a horizontally opposed 4-cylinder gasoline engine. The engine 10 is also an in-cylinder injection engine that directly injects fuel into the cylinders. In the engine 10, air drawn in from the air cleaner 16 is restricted by an electronically controlled throttle valve (hereinafter also simply called "throttle valve") 13 provided in the intake manifold 15, passes through the intake manifold 11, and is drawn into each cylinder formed in the engine 10. Here, the amount of air drawn in from the air cleaner 16 is detected by an airflow meter 14 placed between the air cleaner 16 and the throttle valve 13. In addition, a vacuum sensor 30 for detecting the pressure inside the intake manifold 11 (intake manifold pressure) is provided inside the collector section (surge tank) that constitutes the intake manifold 11. Furthermore, a throttle opening sensor 31 for detecting the opening degree of the throttle valve 13 is provided on the throttle valve 13.

[0014] The cylinder head has an intake port 22 and an exhaust port 23 for each cylinder (only one bank is shown in Figure 1). Each intake port 22 and exhaust port 23 is provided with an intake valve 24 and an exhaust valve 25 that open and close the intake port 22 and exhaust port 23, respectively. Between the intake camshaft and the intake cam pulley that drives the intake valve 24, a variable valve timing mechanism 26 is provided to advance or retard the valve timing (opening / closing timing) of the intake valve 24 by rotating the intake cam pulley and the intake camshaft relative to each other, thereby continuously changing the rotational phase (displacement angle) of the intake camshaft with respect to the crankshaft 10a. This variable valve timing mechanism 26 allows the opening and closing timing of the intake valve 24 to be variably set according to the engine operating conditions.

[0015] Similarly, a variable valve timing mechanism 27 is provided between the exhaust camshaft and the exhaust cam pulley. This mechanism rotates the exhaust cam pulley and the exhaust camshaft relative to each other, continuously changing the rotational phase (displacement angle) of the exhaust camshaft with respect to the crankshaft 10a, thereby advancing or retarding the valve timing (opening / closing timing) of the exhaust valve 25. This variable valve timing mechanism 27 allows the opening and closing timing of the exhaust valve 25 to be variably set according to the engine operating conditions.

[0016] Each cylinder of the engine 10 is fitted with an injector 12 that injects fuel into the cylinder. The injector 12 directly injects fuel pressurized by a high-pressure fuel pump (not shown) into the combustion chamber of each cylinder.

[0017] Furthermore, each cylinder head is fitted with a spark plug 17 for igniting the fuel-air mixture, and an igniter-integrated coil 21 for applying a high voltage to the spark plug 17. In each cylinder of the engine 10, the fuel-air mixture inhaled and injected by the injector 12 is ignited by the spark plug 17 and combusted. The exhaust gas after combustion is discharged through the exhaust pipe 18.

[0018] An air-fuel ratio sensor 19 is attached downstream of the collecting portion of the exhaust pipe 18 and upstream of the exhaust purification catalyst 20. As the air-fuel ratio sensor 19, a linear air-fuel ratio sensor (LAF sensor) that can output a signal corresponding to the oxygen concentration and unburned gas concentration in the exhaust gas (that is, a signal corresponding to the air-fuel ratio of the air-fuel mixture) and can detect the air-fuel ratio linearly is used.

[0019] An exhaust purification catalyst 20 is disposed downstream of the LAF sensor 19. The exhaust purification catalyst 20 is a three-way catalyst that simultaneously oxidizes hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas and reduces nitrogen oxides (NOx), and purifies harmful gas components in the exhaust gas into harmless carbon dioxide (CO2), water vapor (H2O), and nitrogen (N2). A muffler (silencer) 43 that reduces exhaust noise is attached to the downstream side of the exhaust purification catalyst 20.

[0020] An exhaust gas recirculation device (hereinafter referred to as "EGR (Exhaust Gas Recirculation) device") 40 for recirculating a part of the exhaust gas discharged from the engine 10 to the intake pipe 15 of the engine 10 is provided in the exhaust pipe 18. The EGR device 40 has an EGR pipe 41 that connects the exhaust pipe 18 and the intake pipe 15 of the engine 10, and an EGR valve 42 that is interposed on the EGR pipe 41 and adjusts the exhaust recirculation amount (EGR flow rate).

[0021] In addition, an EGR flow rate sensor 44 for detecting the exhaust recirculation amount (EGR flow rate) is attached to the EGR valve 42 or the EGR pipe 41. As the EGR flow rate sensor 44, for example, one that outputs an electrical signal (voltage, etc.) corresponding to the rotation angle (valve opening) of the EGR valve 42 (valve shaft), or a hot-wire type mass flow meter that detects the mass flow rate of the exhaust (EGR gas) flowing through the EGR pipe 41 can be preferably used.

[0022] The opening degree (EGRSTP) of the EGR valve 42 is controlled by the ECU 50, which will be described later, according to the operating conditions of the engine 10 (e.g., engine speed, intake air volume, etc.). More specifically, for example, the EEPROM of the ECU 50 has a target EGR valve opening degree map pre-stored, which defines the relationship between engine speed, intake air volume, and target EGR valve opening degree. The target EGR valve opening degree is determined by the real-time engine speed and intake air volume, and the EGR valve 42 is controlled (F / B control) so that the actual EGR valve opening degree matches the target EGR valve opening degree.

[0023] In addition to the aforementioned airflow meter 14, LAF sensor 19, vacuum sensor 30, throttle opening sensor 31, and EGR flow sensor 44, a cam angle sensor 32 for cylinder identification of the engine 10 is mounted near the camshaft of the engine 10. Furthermore, a crank angle sensor 33 for detecting the rotational position of the crankshaft 10a is mounted near the crankshaft 10a of the engine 10. Here, a timing rotor 33a is mounted on the end of the crankshaft 10a, for example, with 34 teeth (2 teeth missing) formed at 10° intervals. The crank angle sensor 33 detects the rotational position of the crankshaft 10a by detecting the presence or absence of the protrusions on the timing rotor 33a. For example, electromagnetic pickup type sensors are used for the cam angle sensor 32 and the crank angle sensor 33.

[0024] These sensors are connected to the ECU 50. In addition, the ECU 50 is also connected to various other sensors, including a water temperature sensor 34 that detects the temperature of the engine 10's coolant, an oil temperature sensor 35 that detects the temperature of the lubricating oil, an accelerator sensor 36 that detects the amount the accelerator pedal is pressed, i.e., the amount the accelerator pedal is operated, and a vehicle speed sensor 37 that detects the speed of the vehicle.

[0025] The ECU 50 is comprised of a microprocessor that performs calculations, an EEPROM that stores programs for the microprocessor to execute various processes, a RAM that stores various data such as calculation results, a backup RAM whose contents are maintained by a battery or the like, and an input / output interface. The ECU 50 also includes an injector driver that drives the injector 12, an output circuit that outputs an ignition signal, a motor driver that drives an electric motor 13a that opens and closes the electronically controlled throttle valve 13, and a driver circuit that drives the EGR valve 42.

[0026] In the ECU50, various information such as intake air volume, intake manifold negative pressure, accelerator pedal input, air-fuel ratio of the fuel mixture, and engine water temperature and oil temperature of the engine 10 is acquired based on detection signals input from the various sensors mentioned above. In addition, the ECU50 identifies the cylinder from the output of the camshaft angle sensor 32, and determines the rotational angular velocity and engine speed from the output of the crankshaft angle sensor 33. Furthermore, the ECU50 determines the crankshaft angular velocity corresponding to the expansion stroke of each cylinder (for example, the crankshaft angular velocity over 180 degrees (720 / 4) in the case of a 4-cylinder engine) (deg / s) from the output of the crankshaft angle sensor 33, and also determines the engine load (Nm) from the intake air volume (and engine speed).

[0027] The ECU 50 then comprehensively controls the engine 10 by controlling the fuel injection amount, ignition timing, and various devices such as the throttle valve 13 and the EGR valve 42 based on the acquired information. The ECU 50 functions as the control unit described in the claims.

[0028] In particular, the ECU50 has a function to further reduce noise and vibration (NV) from the engine 10 itself (i.e., to further improve the quietness of the engine 10). In the ECU50, this function is achieved by executing a program stored in an EEPROM or similar by a microprocessor.

[0029] Incidentally, there is a correlation between the thickness of the oil film on the inner surface of the cylinder (oil film thickness) and the NV level of engine 10. As shown in Figure 2, when the oil film thickness (oil film thickness) becomes thinner than a predetermined value (for example, about 4-6 μm), there is a tendency for the NV to rapidly worsen (increase). Also, if there is variation in the oil film thickness between cylinders (when it becomes large), there is a tendency for the NV to worsen. Figure 2 is a diagram showing the relationship between oil film thickness and vibration level. The horizontal axis of Figure 2 is oil film thickness (μm), and the vertical axis is vibration level.

[0030] Therefore, the ECU 50 first determines the thickness of the oil film on the inner surface of each of the multiple cylinders formed in the engine 10. In other words, the ECU 50 functions as an oil film thickness acquisition means as described in the claims.

[0031] More specifically, the ECU50 estimates the oil film thickness for each cylinder based, for example, on the crank angular velocity corresponding to the expansion stroke of each cylinder, engine load, and oil temperature.

[0032] Here, we will explain how to determine (estimate) the oil film thickness for each cylinder. For example, the EEPROM of the ECU50 stores an oil film thickness map (lookup table) that defines the relationship between the crank angular velocity corresponding to the expansion stroke, engine load, oil temperature, and oil film thickness. The oil film thickness for each cylinder is obtained by searching this oil film thickness map based on the crank angular velocity, engine load, and oil temperature corresponding to the expansion stroke for each cylinder.

[0033] In this oil film thickness map, the oil film thickness is assigned (set) for each combination (grid point) of crank angular velocity, engine load, and oil temperature, such that the oil film thickness decreases as the crank angular velocity increases, as the engine load increases, and as the oil temperature rises. The oil film thickness map data can be obtained, for example, through engine stand tests.

[0034] Therefore, the ECU50 estimates that the oil film thickness decreases as the crank angular velocity increases, as the engine load increases, and as the oil temperature rises.

[0035] The ECU50 then corrects the ignition timing for each cylinder according to the calculated oil film thickness for each cylinder. The basic ignition timing is set based on, for example, engine speed and intake air volume.

[0036] More specifically, the ECU 50 advances the ignition timing of cylinders where the oil film thickness is thinner than a predetermined value (e.g., 4-6 μm). In this case, it is preferable that the ECU 50 advances the ignition timing (increases the amount of correction) as the oil film thickness decreases. For cylinders where the oil film thickness is thicker than a predetermined value (preferably with hysteresis), the ignition timing may be retarded.

[0037] In this way, the ECU50 corrects the ignition timing of cylinders where the oil film thickness is thinner than a predetermined value to the advanced side, thereby increasing the torque of those cylinders and eliminating inter-cylinder variations in the force pushing down the piston, thereby reducing noise and vibration of the engine 10 itself.

[0038] Next, the operation of the engine control device 1 will be explained with reference to Figure 3. Figure 3 is a flowchart showing the processing procedure for NV reduction control by the engine control device 1. This process is repeatedly executed in the ECU 50 at predetermined timings.

[0039] First, in step S102, the crank angular velocity, engine load, and oil temperature for each cylinder are read.

[0040] Next, in step S104, the oil film thickness for each cylinder is estimated based on the read crank angular velocity, engine load, and oil temperature for each cylinder. The method for estimating the oil film thickness is as described above, so a detailed explanation is omitted here.

[0041] Next, in step S106, a determination is made as to whether or not there are any cylinders with an oil film thickness thinner than a predetermined value. If there are no cylinders with an oil film thickness less than the predetermined value, the process proceeds to step S110. On the other hand, if there are cylinders with an oil film thickness less than the predetermined value, the process proceeds to step S108.

[0042] In step S108, the ignition timing of cylinders with an oil film thickness below a predetermined value is advanced. After that, the process is temporarily exited.

[0043] In step S110, a determination is made as to whether or not there are any cylinders where the oil film thickness is thicker than a predetermined value (with hysteresis). If there are no cylinders where the oil film thickness is thicker than the predetermined value, the process is temporarily terminated. On the other hand, if there are cylinders where the oil film thickness is thicker than the predetermined value, the process proceeds to step S112.

[0044] In step S112, the ignition timing of cylinders with an oil film thickness greater than a predetermined value is retarded. After that, the process is temporarily exited.

[0045] As explained in detail above, according to this embodiment, the thickness of the oil film in each of the multiple cylinders is determined, and the ignition timing for each cylinder is corrected according to the thickness of the oil film in each cylinder, and the output torque for each cylinder is finely adjusted, thereby eliminating inter-cylinder variations in the force pushing down the piston (making rotation smoother), and reducing noise and vibration (NV) of the engine 10 itself.

[0046] As a result, it becomes possible to further reduce the noise and vibration (NV) of the engine 10 itself (i.e., to further improve the quietness of the engine 10 itself).

[0047] In particular, according to this embodiment, the ignition timing of cylinders with an oil film thickness thinner than a predetermined value is corrected to the advanced side (i.e., the force pushing down the piston of that cylinder is increased). As a result, inter-cylinder variations in the force pushing down the piston are eliminated quickly, and noise and vibration (NV) of the engine 10 can be reduced more rapidly (quietness can be improved more rapidly).

[0048] Furthermore, according to this embodiment, the thickness of the oil film for each cylinder is estimated based on the crank angular velocity, engine load, and oil temperature corresponding to the expansion stroke of each cylinder. Therefore, the thickness of the oil film for each cylinder can be accurately estimated.

[0049] More specifically, according to this embodiment, the oil film thickness is estimated to be thinner as the crank angular velocity increases, as the engine load increases, and as the oil temperature rises, so the oil film thickness for each cylinder can be estimated more accurately.

[0050] (Second Embodiment) In the first embodiment (engine control device 1) described above, the ignition timing of cylinders with an oil film thickness thinner than a predetermined value was advanced. However, instead of or in addition to correcting the ignition timing, the device may be configured to increase the oil pressure (increase the oil volume) of any cylinder or all cylinders if there is a cylinder with an oil film thickness thinner than a predetermined value.

[0051] Next, the engine control device 1B according to the second embodiment will be described with reference to Figure 4. Figure 4 is a diagram showing the configuration of the engine control device 1B and the engine 10B (main part) to which the engine control device 1B is applied. Note that only one of the four cylinders is shown in Figure 4. Also, in Figure 4, the same or equivalent components as in the first embodiment are denoted by the same reference numerals.

[0052] When increasing the oil pressure (oil volume) only in cylinders where the oil film thickness is thinner than a predetermined value, it is preferable to provide an oil jet circuit (cylinder-specific oil pressure circuit) 60 that supplies (injects) oil to each cylinder, as shown in Figure 4, and to control the on / off state of the oil jet.

[0053] More specifically, for example, the oil jet circuit (cylinder-specific hydraulic circuit) 60 pressurizes the oil stored in the oil pan 62 using an oil pump 61, pumps it through an oil passage (hydraulic circuit) 66 to a nozzle 65, and injects (supplies) the oil from the nozzle 65 towards the inner surface of the cylinder, etc. An on / off valve (solenoid valve) 64 is interposed in the oil passage (hydraulic circuit) 66 to start and stop (switch) the oil jet. The operation (opening and closing) of the on / off valve 64 is controlled by the ECU 50B.

[0054] For example, if the oil film thickness is thinner than a predetermined value, the ECU50B opens the on / off valve 64 for that cylinder and performs oil jetting (supplying oil to that cylinder). On the other hand, if the oil film thickness is thicker than a predetermined value, the ECU50B closes the on / off valve 64 for that cylinder and stops oil jetting (supplying oil to that cylinder).

[0055] On the other hand, when increasing the oil pressure (oil volume) of all cylinders, it is preferable to provide an electric oil pump (not shown) that is driven by an electric motor to pressurize and discharge the oil stored in the oil pan, and to increase the rotational speed (=discharge volume) of the electric oil pump according to the target oil pressure. The drive (rotational speed) of the electric oil pump is controlled by the ECU50B.

[0056] Alternatively, when increasing the oil pressure (oil volume) of all cylinders, a regulator valve (control valve) (not shown) may be provided to adjust (regulate) the oil pressure discharged from the oil pump (not shown), and the regulated pressure (target oil pressure) of the regulator valve (control valve) may be increased. As for the regulator valve (control valve), a known configuration may be used, for example, a configuration consisting of a linear solenoid that displaces the valve according to the current value applied from the ECU 50B (current value corresponding to the target oil pressure) to regulate the control pressure, and a spool valve that adjusts the oil pressure by sliding according to the balance between the pressing force due to the control pressure generated by the linear solenoid and the spring force of the spring.

[0057] The other components are the same as or similar to those of the engine control device 1 (first embodiment) described above, so a detailed explanation is omitted here.

[0058] Next, the operation of the engine control device 1B will be explained with reference to Figure 5. Figure 5 is a flowchart showing the processing procedure for NV reduction control by the engine control device 1B. This process is repeatedly executed in the ECU 50B at predetermined timings.

[0059] First, the processing content of steps S102 to S106 and S110 is the same as or similar to that of the first embodiment described above, so a detailed explanation will be omitted here.

[0060] In step S106, if it is determined that there is a cylinder with an oil film thickness thinner than a predetermined value, in step S208, instead of or in addition to correcting the ignition timing advance, the oil pressure of the cylinder or all cylinders with an oil film thickness thinner than a predetermined value is increased. The method of adjusting (increasing) the oil pressure is as described above, so a detailed explanation is omitted here.

[0061] Furthermore, if it is determined in step S110 that there is a cylinder with an oil film thickness greater than a predetermined value, in step S212, instead of or in addition to correcting the ignition timing retardation, the oil pressure of the cylinder with an oil film thickness greater than a predetermined value or all cylinders is reduced.

[0062] According to this embodiment, if there is a cylinder where the oil film thickness is thinner than a predetermined value, the oil pressure in that cylinder or all cylinders is increased (oil volume is increased) instead of or in addition to correcting the ignition timing advance. Therefore, by making the oil film thickness appropriate (for example, 4 to 6 μm or more) (increasing the oil film thickness), the noise and vibration (NV) of the engine 10 can be further reduced (quietness can be further improved).

[0063] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications are possible. For example, in the above embodiments, NV reduction control was performed in the entire operating range, but it may also be configured to be performed only during idling operation when particularly quietness is required.

[0064] In that case, in step S300 of Figure 6, a determination is made as to whether or not the engine 10 is in an idling state. If it is not in an idling state, the process is temporarily exited. On the other hand, if it is in an idling state, the process proceeds to step S102.

[0065] The processing steps from step S102 onward are the same as those in the first or second embodiment described above, so a detailed explanation is omitted here. Figure 6 is a flowchart showing the processing procedure for NV reduction control by the engine control device according to a modified example.

[0066] Furthermore, in the above embodiment, the thickness of the oil film was estimated from the crank angular velocity, engine load, and oil temperature. However, instead of the method described above, a configuration using a sensor that measures the thickness of the oil film (for example, a capacitive, electrical resistance, laser fluorescence, or optical interference sensor) may also be used.

[0067] Furthermore, although the above embodiments were described using a gasoline engine that uses gasoline as fuel as an example, the present invention can also be applied to, for example, a hydrogen engine that uses hydrogen as fuel, or a diesel engine that uses light oil as fuel. Also, although the above embodiments were described using a naturally aspirated (NA) engine as an example, the present invention can also be applied to an engine with a supercharger (for example, a turbo engine).

[0068] Furthermore, although the above embodiment was described using the case of application to a conventional gasoline engine vehicle as an example, the present invention can also be applied to engines such as those in hybrid electric vehicles (HEVs) that have an engine and an electric motor as driving power sources. [Explanation of Symbols]

[0069] 1. 1B Engine Control Unit 10, 10B engine 11 Intake Manifold 15 Intake pipe 17 Spark plugs 18 Exhaust pipe 19. Air-fuel ratio sensor 20 Exhaust purifying catalyst 40 Exhaust gas recirculation system 42 EGR valve 43. Silencer (muffler) 50, 50B ECU 60. Oil jet circuit (cylinder-specific hydraulic circuit) 61 Oil pump 64 On / Off Valve 65 nozzles

Claims

1. An oil film thickness acquisition means for determining the thickness of the oil film on the inner surface of each of the multiple cylinders formed in the engine, An engine control device characterized by comprising a control unit that corrects the ignition timing for each cylinder according to the required oil film thickness for each cylinder.

2. The engine control device according to claim 1, characterized in that the control unit corrects the ignition timing of cylinders in which the oil film thickness is thinner than a predetermined value to the advance side.

3. The engine control device according to claim 2, characterized in that, in lieu of or in addition to correcting the ignition timing, the control unit increases the oil pressure of a cylinder or all cylinders if there is a cylinder in which the oil film thickness is thinner than a predetermined value.

4. The engine control device according to claim 3, characterized in that the oil film thickness acquisition means estimates the thickness of the oil film for each cylinder based on the crank angular velocity, engine load, and oil temperature corresponding to the expansion stroke for each cylinder.

5. The engine control device according to claim 4, characterized in that the oil film thickness acquisition means estimates that the oil film thickness decreases as the crank angular velocity increases, estimates that the oil film thickness decreases as the engine load increases, and estimates that the oil film thickness decreases as the oil temperature rises.

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