Engine control device

Abstract

To provide an engine control device which can eliminate dilution of engine oil while suppressing an increase of cost.SOLUTION: An engine control device comprises a determination unit for determining whether or not a degree of dilution of engine lubrication oil is higher than a threshold, and an execution unit for executing measure processing for lowering the degree of dilution when an affirmative determination is given by the determination unit. The measure processing includes at least one of processing for increasing an idling rotation number of an engine compared to the case where a negative determination is given by the determination unit, processing for increasing a suction air quantity of the engine compared to the case where a negative determination is given by the determination unit, processing for increasing a discharge quantity of a variable capacity oil pump which controls a discharge quantity of the oil when a negative determination is given by the determination unit, and processing for delaying a valve-opening timing of an on-off valve which starts circulation of cooling water of the engine into an air-conditioning heater compared to the case where a negative determination is given by the determination unit.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] BACKGROUND ART There is known a technique for eliminating engine oil dilution by heating the engine oil with an oil heater to volatilize fuel and water in the engine oil (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4962625 Summary of the Invention [Problem to be solved by the invention]

[0004] The above technique requires the installation of an oil heater, which may increase costs.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an engine control device that can prevent engine oil dilution while suppressing increases in costs. [Means for solving the problem]

[0006] The above object can be achieved by an engine control device comprising: a judgment unit that judges whether the degree of dilution of engine oil used to lubricate the engine is greater than a threshold value; and an execution unit that executes countermeasure processing to reduce the degree of dilution when a positive judgment is made by the judgment unit, wherein the countermeasure processing includes at least one of a rotation speed processing that increases the idle rotation speed of the engine more than when a negative judgment is made by the judgment unit; an air volume processing that increases the amount of intake air of the engine more than when a negative judgment is made by the judgment unit; a discharge volume processing that increases the discharge volume of a variable displacement oil pump that controls the discharge volume of the engine oil more than when a negative judgment is made by the judgment unit; and a valve opening processing that delays the opening timing of an opening / closing valve that starts the flow of engine coolant to an air conditioning heater more than when a negative judgment is made by the judgment unit.

[0007] The countermeasure processing may include at least two of the rotation speed processing, the air amount processing, the discharge amount processing, and the valve opening processing.

[0008] In the discharge amount processing, the discharge amount of the variable displacement oil pump may be controlled to a maximum.

[0009] The countermeasure process may include an injection rate process for increasing a port injection rate of the engine to a value higher than that in the case where a negative determination is made by the determination unit.

[0010] In the injection rate control, the port injection rate may be controlled to a maximum. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an engine control device that can prevent engine oil dilution while suppressing increases in cost. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of the engine. [Figure 2]FIG. 2 is an explanatory diagram of the engine oil flow path. [Figure 3] FIG. 3 is an explanatory diagram of the cooling water flow path. [Figure 4] FIG. 4 is a flowchart showing an example of a countermeasure process executed by the ECU. [Figure 5] FIG. 5 is a timing chart for explaining the valve opening process. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Engine outline] FIG. 1 is a schematic diagram of an engine 10. The engine 10 is mounted as a drive source in an internal combustion engine vehicle, but is not limited to this and may also be applied to a hybrid vehicle equipped with an engine and a motor as a drive source. The engine 10 is a gasoline engine, but is not limited to this and may also be a diesel engine. The engine 10 includes a cylinder head 11a, a cylinder block 11b provided below the cylinder head 11a, and an oil pan 11c provided below the cylinder block 11b.

[0014] Each cylinder 12 of the cylinder block 11b is provided with a piston 13. The piston 13 is connected to a crankshaft 15, which is the output shaft of the engine 10, via a connecting rod 14. The reciprocating motion of the piston 13 is converted into the rotational motion of the crankshaft 15 by the connecting rod 14.

[0015] The cylinder block 11b is provided with an oil jet 26. The oil jet 26 injects a portion of the engine oil pumped up from the oil pan 11c by a variable displacement oil pump 52 (described later) toward the back surface of the piston 13, thereby cooling the piston 13. The oil jet 26 is provided with a control valve that switches the injection of engine oil on and off.

[0016] A combustion chamber 16 is formed in the cylinder head 11a above the piston 13, and a spark plug 18 that ignites a mixture of fuel and air is attached to this combustion chamber 16. The timing at which the spark plug 18 ignites the mixture is adjusted by an igniter 19 provided above the spark plug 18. Engine oil for lubrication is stored in the oil pan 11c.

[0017] The cylinder head 11a is provided with an intake valve 24 that opens and closes the intake passage 20 and the combustion chamber 16, and similarly, an exhaust valve 25 that opens and closes the exhaust passage 21 and the combustion chamber 16. The intake passage 20 is provided with a throttle valve 23 that adjusts the amount of air introduced into the combustion chamber 16.

[0018] Each intake port 20a constituting part of the intake passage 20 is provided with a port injection valve 22 for each cylinder 12, which injects fuel into the intake port 20a. The engine 10 is also provided with an in-cylinder injection valve 17 for injecting fuel into each combustion chamber 16. The ratio of the fuel injection amount from each in-cylinder injection valve 17 and each port injection valve 22 to the total fuel injection amount is controlled based on the in-cylinder injection rate and the port injection rate, respectively. The sum of the in-cylinder injection rate and the port injection rate is always calculated as 100%.

[0019] The exhaust passage 21 is provided with an air-fuel ratio sensor 35, a three-way catalyst 41, and a GPF (Gasoline Particulate Filter) 42, arranged in this order from the upstream side. The three-way catalyst 41 contains a catalytic metal such as platinum (Pt), palladium (Pd), or rhodium (Rh), has oxygen storage capacity, and purifies NOx, HC, and CO. The GPF 42 is a porous ceramic structure in which the front and rear ends of adjacent cells are alternately sealed. Exhaust gas flows into cells with open upstream ends of the GPF 42 and passes through the porous walls between adjacent cells, capturing PM (particulate matter) in the exhaust gas.

[0020] The ECU (Electronic Control Unit) 100 is an electronic control unit that performs control processing related to the engine 10. The ECU 100 is mainly composed of a computer including a CPU (Central Processing Unit) and volatile and non-volatile memories such as RAM (Random Access Memory) and ROM (Read Only Memory). The ECU 100 executes various control processes related to the engine 10 by running programs installed in the memory on the CPU. Various sensors are connected to the ECU 100, which will be described in detail later. The ECU 100 is an example of an engine control device, and functionally implements a determination unit and an execution unit, which will be described in detail later.

[0021] An ignition switch 31, a water temperature sensor 32, an air flow meter 33, a crank angle sensor 34, and an air-fuel ratio sensor 35 are connected to the ECU 100, and output signals from these various sensors are input. The ignition switch 31 detects the on / off state of the ignition. The water temperature sensor 32 detects the temperature of the coolant that cools the engine 10. The air flow meter 33 detects the amount of intake air. The crank angle sensor 34 detects the rotation angle of the crankshaft 15. The air-fuel ratio sensor 35 is provided in the exhaust passage 21 upstream of the three-way catalyst 41, and detects the air-fuel ratio of the exhaust gas flowing into the three-way catalyst 41.

[0022] The ECU 100 calculates the engine speed based on the detection value of the crank angle sensor 34, and calculates the engine load based on the engine speed and the intake air amount. The ECU 100 calculates the target engine speed and target load based on the accelerator opening, and controls the fuel injection amount, intake air amount, ignition timing, port injection rate, and in-cylinder injection rate so that the engine speed and load become the target engine speed and target load, respectively.

[0023] 2 is an explanatory diagram of the engine oil distribution path. Engine oil stored in the oil pan 11c is sucked from the oil pan 11c through the oil strainer 50 by the suction force of the variable displacement oil pump 52. The sucked engine oil passes through the oil filter 56, then passes through the main gallery 11d formed in the engine 10, and flows through the cylinder head 11a and cylinder block 11b. A portion of the engine oil that flows through the cylinder block 11b is supplied to the oil jet 26. The engine oil is then collected again in the oil pan 11c.

[0024] The variable displacement oil pump 52 is a known variable displacement type that can change the amount of oil discharged. The variable displacement oil pump 52 and the main gallery 11d are connected by an oil passage 60. An oil passage 61 branches off from the oil passage 60 between the oil filter 56 and the main gallery 11d. The oil passage 61 is connected to an oil inlet of an oil control valve (hereinafter referred to as OCV) 54, which is a linear solenoid valve. The oil outlet of the OCV 54 is connected to the variable displacement oil pump 52 via an oil passage 62. The OCV 54 opens and closes under the control of the ECU 100. The opening and closing of the OCV 54 changes the flow rate of engine oil introduced into the pressure chamber of the variable displacement oil pump 52, thereby changing the oil pressure in the pressure chamber. This changes the capacity of the variable displacement oil pump 52, thereby changing the amount of engine oil discharged.

[0025] 3 is an explanatory diagram of the coolant circulation paths. The coolant is circulated through a predetermined path by an electric water pump 70. The coolant that flows into the engine 10 branches into a path that flows from the engine 10 to an air conditioning heater 72, a path that flows from the engine 10 to an EGR cooler 75, and a path that flows to a radiator 74. An on-off valve 71 is provided in the path between the engine 10 and the air conditioning heater 72. The coolant that flows into the EGR cooler 75 branches into a path that flows to a thermostat 73 and a path that flows to an EGR valve 76 and the throttle valve 23. The path from the air conditioning heater 72 merges with the path between the EGR cooler 75 and the thermostat 73, and further merges with the path from the throttle valve 23.

[0026] Thermostat 73 has a first inlet communicating with a path from EGR cooler 75 and a second inlet communicating with a path from radiator 74. The path from thermostat 73 communicates with water pump 70. Thermostat 73 opens the first inlet and closes the second inlet when the coolant temperature is below a predetermined temperature, and opens both the first and second inlets when the coolant temperature reaches or exceeds the predetermined temperature. FIG. 3 shows thermostat 73 with the second inlet closed. Air conditioning heater 72 is a heat exchanger for air conditioning in the vehicle cabin, and heats the vehicle cabin using high-temperature coolant discharged from engine 10 as a heat source. The operation of water pump 70 and on-off valve 71 are controlled by ECU 100.

[0027] The ECU 100 that controls the engine 10 configured as described above executes a countermeasure process for reducing the degree of dilution of the engine oil based on the degree of dilution of the engine oil by fuel and water.

[0028] [Countermeasures] Next, a description will be given of the countermeasure processing executed by the ECU 100. Fig. 4 is a flowchart showing an example of the countermeasure processing executed by the ECU 100. This flowchart is repeatedly executed while the ignition is on.

[0029] First, the ECU 100 calculates the degree of dilution of the engine oil (step S1). The degree of dilution is calculated by, for example, calculating the degree of dilution per unit time based on the engine speed and the coolant temperature, and integrating this.

[0030] The dilution degree per unit time increases as the engine speed decreases and as the coolant temperature decreases. This is because the lower the engine speed, the lower the heat generation of the engine 10, which in turn reduces the engine oil temperature and suppresses the evaporation of fuel and water in the engine oil. Similarly, it is thought that the lower the coolant temperature, the lower the engine oil temperature. Furthermore, when the coolant temperature is above a predetermined temperature, the dilution degree per unit time becomes a negative value, and the dilution degree decreases over time. This is because when the coolant temperature rises above a predetermined temperature, the evaporation of fuel and water in the engine oil is promoted. The dilution degree is calculated with a minimum value of 0. Note that the method for calculating the dilution degree is not limited to this, and other known methods may be used, or it may be estimated based on a sensor value that detects the engine oil concentration.

[0031] Next, the ECU 100 determines whether the dilution degree is greater than a threshold value α (step S2). The threshold value α is set to the upper limit of the allowable range of the dilution degree that does not interfere with the operation of the engine 10. Step S2 is an example of processing executed by the determination unit. If the result in step S2 is No, it is considered that no countermeasure processing is necessary, and this control ends.

[0032] If the answer is Yes in step S2, the ECU 100 executes a countermeasure process (step S3). The countermeasure process is performed by executing all of the following processes: rotation speed process, air amount process, discharge amount process, injection rate process, and valve opening process, which will be described in detail later. The countermeasure process in this embodiment does not require an oil heater for heating the engine oil. This makes it possible to suppress an increase in engine manufacturing costs due to the provision of an oil heater. In addition, there is no need to secure space for installing an oil heater.

[0033] Next, the ECU 100 calculates the dilution degree again (step S4). The dilution degree is calculated by subtracting the amount of decrease in the dilution degree per unit time due to the execution of the countermeasure processing from the dilution degree per unit time calculated by the method of step S1 described above. The amount of decrease in the dilution degree per unit time due to the execution of the countermeasure processing is determined in advance based on experimental results, simulation results, etc. This makes it possible to calculate the dilution degree during the execution of the countermeasure control.

[0034] Next, the ECU 100 determines whether the dilution degree has fallen to or below a threshold value β (step S5). The threshold value β is a value smaller than the threshold value α. The threshold value β is set to, for example, 0, which indicates that no dilution of the engine oil by fuel or water has occurred. However, the threshold value β is not limited to 0, and may be less than the threshold value α and greater than or equal to 0.

[0035] If the answer is No in step S5, the ECU 100 continues the countermeasure processing, assuming that the dilution degree has not yet decreased sufficiently (step S3). If the answer is Yes in step S5, the ECU 100 stops the countermeasure processing, assuming that the dilution degree has decreased sufficiently (step S6). In this way, by providing a margin between the threshold value α for executing the countermeasure control and the threshold value β for stopping it, it is possible to prevent the countermeasure control from being frequently executed and stopped.

[0036] [Rotation speed processing] The rotation speed process is a process for increasing the idle rotation speed of the engine 10 more than when step S2 returns No. The idle rotation speed is the engine rotation speed during idle operation. Increasing the idle rotation speed increases the amount of heat generated by the engine 10, thereby promoting the evaporation of fuel and water in the engine oil. However, increasing the engine rotation speed during load operation may affect drivability. Therefore, by increasing the idle rotation speed instead of the engine rotation speed during load operation, it is possible to suppress engine oil dilution while also suppressing the impact on drivability.

[0037] [Air volume processing] The air amount processing is a process for increasing the intake air amount of the engine 10 more than when the determination in step S2 is No. Specifically, the target opening of the throttle valve 23 is increased more than when the determination in step S2 is No. By increasing the intake air amount, the heat generation amount of the engine 10 can be increased, thereby promoting the volatilization of fuel and water in the engine oil.

[0038] [Injection rate processing] The injection rate processing is a process for increasing the port injection rate compared to when step S2 is No. This reduces the in-cylinder injection rate, and the amount of fuel injected from the in-cylinder injection valve 17. This reduces the amount of fuel adhering to the inner wall surface of the bore of the cylinder 12, and suppresses engine oil dilution. Specifically, in this embodiment, the port injection rate is set to the maximum of 100% and the in-cylinder injection rate is set to 0%, but this is not limiting. For example, the injection rate obtained by adding a predetermined value to the port injection rate when step S2 is No may be set as the port injection rate during execution of the injection rate processing.

[0039] [Discharge volume processing] The discharge amount processing is a process for increasing the discharge amount of the variable displacement oil pump 52, which controls the amount of engine oil discharged, compared to when step S2 returns No. In this embodiment, the ECU 100 controls the OCV 54 so that the discharge amount of the variable displacement oil pump 52 is maximized. This increases the amount of engine oil flowing through the cylinder head 11a and the cylinder block 11b, and also increases the amount of engine oil injected from the oil jet 26 toward the piston 13. In this way, the heat of the engine 10 can be used to promote the evaporation of fuel and water from the engine oil.

[0040] [Valve opening process] The valve opening process is a process for delaying the opening timing of the on-off valve 71, which starts the flow of engine 10 coolant to the air conditioning heater 72, compared to when step S2 returns No. Fig. 5 is a timing chart for explaining the valve opening process. Fig. 5 shows the transitions in temperature and flow rate of coolant flowing into the engine 10. In Fig. 5, the solid line indicates a case where the valve opening process is not performed, and the dotted line indicates a case where the valve opening process is performed.

[0041] First, a case where the valve opening process is not executed will be described. When the ignition is turned on (time t1), the operation of water pump 70 is controlled so that the coolant flow rate is very low. As a result, the heat from engine 10 causes the coolant temperature to rise at a high rate. When the coolant temperature rises to temperature T1 sufficient to warm up air conditioning heater 72, water pump 70 is controlled to open open valve 71 and increase the coolant flow rate, causing the coolant to flow through air conditioning heater 72 (time t2). When the coolant temperature rises to thermostat 73 opening temperature T3, the second inlet of thermostat 73 opens, and water pump 70 is controlled to further increase the coolant flow rate, causing the coolant to flow to radiator 74 (time t3). The coolant flow rate after thermostat 73 opens is controlled by water pump 70 according to the operating state of engine 10.

[0042] When the valve opening process is executed, the coolant temperature T1 at which the on-off valve 71 opens is switched to a higher temperature T2, and the opening timing of the on-off valve 71 can be delayed. As a result, the coolant temperature reaches temperature T2 at time t2a, which is later than the above-mentioned time t2. As a result, the coolant temperature reaches the valve opening temperature T3 at time t3a, which is earlier than the above-mentioned time t3, and the thermostat 73 opens. In this way, the temperature rise of the coolant is accelerated, and the warm-up of the engine 10 can be accelerated. As a result, the temperature rise of the engine oil is accelerated, and the evaporation of fuel and water from the engine oil can be accelerated.

[0043] By performing multiple processes as countermeasures in this way, engine oil dilution can be quickly eliminated even if an oil heater for heating the engine oil is not provided. Note that at least one of the rotation speed process, air amount process, discharge amount process, injection rate process, and valve opening process can be performed as the countermeasures. This is because engine oil dilution can be eliminated while suppressing increases in costs.

[0044] In the above embodiment, the engine 10 is described as having both the in-cylinder injection valve 17 and the port injection valve 22, but is not limited to this. For example, the engine may be provided with only one of the in-cylinder injection valve 17 and the port injection valve 22. In this case, the injection rate processing described above is not performed as a countermeasure processing.

[0045] In the above embodiment, the ECU 100 that controls the engine 10 mounted on a vehicle has been described as an example of an engine control device, but the present invention is not limited to this. For example, the contents of the above embodiment can also be applied to engine control devices mounted on motorcycles, etc., and engine control devices mounted on things other than vehicles, such as ships and construction machinery. Furthermore, the vehicle on which such an ECU is mounted may be an engine vehicle equipped with only an engine as a power source for running, or may be a hybrid vehicle equipped with an engine and a motor as power sources for running.

[0046] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0047] 10 Engine 22-port injection valve 52 Variable displacement oil pump 71 On-off valve 72 Air conditioning heater 100 ECU (engine control unit, judgment unit, execution unit)

Claims

[Claim 1] A determination unit that determines whether the degree of dilution of engine oil used to lubricate an engine having a direct injection valve and a port injection valve is greater than a threshold value; an execution unit that executes a countermeasure process to reduce the dilution degree when a positive determination is made by the determination unit, The dilution degree is calculated by integrating the dilution degree of the engine oil per unit time calculated based on the engine rotation speed and the temperature of the engine cooling water, and the dilution degree of the engine oil per unit time is calculated so as to increase as the engine rotation speed is lower and as the temperature of the engine cooling water is lower, the countermeasure processing includes all of a rotation speed processing for increasing the idle rotation speed of the engine to a value greater than that in the case where a negative determination is made by the determination unit; an air volume processing for increasing the intake air volume of the engine to a value greater than that in the case where a negative determination is made by the determination unit; a discharge volume processing for increasing the discharge volume of a variable displacement oil pump that controls the discharge volume of the engine oil to a value greater than that in the case where a negative determination is made by the determination unit; a valve opening processing for delaying the opening timing of an opening / closing valve that starts the flow of engine cooling water to a heater to a value greater than that in the case where a negative determination is made by the determination unit; and an injection rate processing for increasing a port injection rate, which is the fuel injection rate from the port injection valve of the engine, to a value greater than that in the case where a negative determination is made by the determination unit. In the discharge amount processing, the discharge amount of the variable displacement oil pump is controlled to a maximum, In the injection rate processing, the port injection rate is controlled to a maximum.

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