Lubrication control device for internal combustion engine

Abstract

To provide a lubrication control device for an internal combustion engine capable of improving efficiency of evaporating and separating moisture mixed into lubrication oil.SOLUTION: A lubrication control device for an internal combustion engine is configured to: determine a moisture percentage that is an amount of moisture mixed into lubrication oil relative to an oil amount of the lubrication oil (Step S4); determine a temperature of a piston (Step S7); and start injection of the lubrication oil from a nozzle (Step S10) when at least two specific conditions that are a condition where the determined moisture percentage is predetermined specific percentage or larger (affirmative determination in Step S5) and a condition where the piston temperature is a predetermined first specific temperature enabling evaporation of the moisture mixed into the lubrication oil (affirmative determination in Step S8) are satisfied.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a lubrication control device for an internal combustion engine that outputs power by burning a mixture of air and a fuel such as gasoline or hydrogen. [Background technology]

[0002] Patent Document 1 describes a device that prevents the lubricating performance of oil from deteriorating by separating water mixed in the oil for lubricating a rotary piston engine. Specifically, the device is configured so that the lubricating oil flows in the order of the rotor housing, turbine, storage tank, and oil pan. The storage tank is provided with a heater, and above the heater, a space is formed to trap gas containing water vapor formed by evaporation of water mixed in the high-temperature oil. Therefore, the oil is heated by the turbine or by the heater, and the oil and water are separated in the storage tank. The separated oil is discharged to the oil pan, and the water is mixed with the blow-by gas and returned to the intake passage.

[0003] Patent Document 2 describes a device that rotates together with the crankshaft of an engine and separates the lubricating oil from the moisture mixed in the lubricating oil by the centrifugal force accompanying the rotation. The separation device has a retention chamber to which oil pumped from an oil pan is supplied, and the outer periphery of the retention chamber is connected to the outside via a partition membrane having water permeability. Therefore, when lubricating oil containing moisture is supplied to the retention chamber, the moisture, which has a relatively large specific gravity, is retained on the outer periphery of the retention chamber by the centrifugal force accompanying the rotation of the retention chamber. The moisture separated from the lubricating oil in this way is discharged to the outside via the partition membrane.

[0004] Furthermore, Patent Document 3 describes a separation device configured to separate the lubricating oil and the moisture mixed in the lubricating oil by the difference in specific gravity in an oil pan or oil filter where the lubricating oil temporarily stays, and to discharge the separated moisture to the outside. Specifically, a separation membrane that allows moisture to pass through is provided below the oil pan or oil filter, and the moisture that permeates the separation membrane is discharged to the outside. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-109005 A [Patent Document 2] Japanese Patent Application Publication No. 2-267309 [Patent Document 3] Japanese Patent Application Publication No. 1-228511 Summary of the Invention [Problem to be solved by the invention]

[0006] The device described in Patent Document 1 is configured such that the lubricating oil receives heat from the turbine as it flows through the turbine, or is heated by a heater provided in a storage tank downstream of the turbine, and as a result, the moisture mixed in the lubricating oil evaporates, and the lubricating oil and the moisture are separated. On the other hand, the lubricating oil flowing through the turbine is a part of the lubricating oil stored in the oil pan, and the oil pan may contain lubricating oil that has dropped from the rotor housing. Therefore, the device described in Patent Document 1 is configured such that a part of the lubricating oil stored in the oil pan is supplied to the turbine to separate the lubricating oil and the moisture, and therefore only a part of the lubricating oil stored in the oil pan is separated from the moisture, and there is room for improvement in order to improve the efficiency of separating the lubricating oil and the moisture. In addition, it cannot be immediately applied to an engine that does not have a turbine, and there is room for technical improvement in order to separate the moisture from the lubricating oil.

[0007] The present invention has been made in consideration of the above-mentioned technical problems, and aims to provide a lubrication control device for an internal combustion engine that can improve the efficiency of evaporating and separating water that has become mixed into lubricating oil. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the present invention provides a lubrication control device for an internal combustion engine which has a cylinder bore and a piston which reciprocates inside the cylinder bore and generates power by burning a mixture of fuel and air supplied to one side of the piston, wherein the cylinder bore has a nozzle which injects lubricating oil onto the other side of the piston, and a controller which controls whether or not the lubricating oil is injected from the nozzle, and the controller is characterized in that it is composed of a moisture percentage calculation unit which calculates a moisture percentage which is the amount of moisture mixed in the lubricating oil relative to the amount of the lubricating oil, a piston temperature calculation unit which calculates the temperature of the piston, and an injection start determination unit which starts injection of the lubricating oil from the nozzle when at least two predetermined conditions are satisfied: the moisture percentage calculated by the moisture percentage calculation unit is equal to or greater than a predetermined percentage, and the temperature of the piston calculated by the piston temperature calculation unit is a first predetermined temperature at which the moisture mixed in the lubricating oil can evaporate.

[0009] In the present invention, the moisture percentage calculation unit may calculate the moisture percentage based on the amount of moisture mixed into the lubricating oil due to combustion of the mixture and the amount of moisture vaporized from the lubricating oil depending on the temperature of the lubricating oil.

[0010] In the present invention, the controller may set the amount of the lubricating oil to be injected from the nozzle to be greater as the moisture percentage calculated by the moisture percentage calculation unit becomes higher.

[0011] In the present invention, the piston temperature calculation section may determine the temperature of the piston based on the amount of supplied fuel.

[0012] In the present invention, the controller is configured to supply the lubricating oil from the nozzle to the piston when the temperature of the piston is higher than a second predetermined temperature predetermined for cooling the piston, and the first predetermined temperature may be lower than the second predetermined temperature. Effect of the Invention

[0013] According to the present invention, when at least two predetermined conditions are met, that is, the moisture rate, which is the amount of moisture mixed in the lubricating oil relative to the amount of the lubricating oil, is equal to or higher than a predetermined rate, and the temperature of the piston is at a first predetermined temperature, the injection of the lubricating oil from the nozzle to the piston is started. The lubricating oil thus injected spreads over the entire back surface of the piston and receives heat from the piston, so that the heat receiving area of ​​the lubricating oil can be increased, and the efficiency of evaporating the moisture from the lubricating oil can be improved. [Brief description of the drawings]

[0014] [Figure 1] 1 is a diagram illustrating a schematic configuration of an internal combustion engine according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a configuration of an ECU in the form of functional blocks. [Diagram 3] 4 is a flowchart illustrating an example of control executed by a lubrication control device according to an embodiment of the present invention. [Figure 4] 4 is an example of a map for determining the discharge amount of the oil jet. [Diagram 5] 4 is an example of a map for determining a piston temperature. [Figure 6] 1 is a map showing a relationship between an evaporation possible flag and a piston temperature. [Figure 7] 10 is a flowchart showing an example of control for setting an evaporation possible flag based on a measured moisture percentage. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will be described based on the embodiment shown in the drawings. Note that the embodiment described below is merely one example of a specific embodiment of the present invention, and is not intended to limit the present invention.

[0016] An internal combustion engine (hereinafter referred to as engine) 1 in an embodiment of the present invention can be configured in the same manner as a conventional gasoline engine or hydrogen engine that generates power by burning a mixture of air and a fuel such as gasoline or hydrogen. That is, as shown in Fig. 1, the engine 1 includes an engine block 3 in which a plurality of cylinder bores 2 are formed, a cylinder head 4 attached to the upper surface of the engine block 3, a crankcase 6 attached to the lower surface of the engine block 3 and accommodating a crankshaft 5, and an oil pan 7 attached to the lower end of the crankcase 6 and storing lubricating oil O.

[0017] A cylinder bore 2 is formed penetrating the engine block 3 in the up-down direction in the vertical direction, and a cylindrical water jacket 8 is attached to the inside of the cylinder bore 2. Like a conventional water jacket, this water jacket 8 has a cavity 8b formed in a wall 8a for allowing the flow of cooling water, and is configured so that the cooling water cooled by a radiator (not shown) flows through the cavity to cool the engine 1.

[0018] A piston 9 is provided to move up and down (reciprocate) in the hollow portion of the water jacket 8. The piston 9 is composed of a piston head 9a formed in a disk shape and a cylindrical portion 9b hanging down from the outer edge of the piston head 9a along the central axis of the piston 9. The upper surface of the piston head 9a (the upper surface in FIG. 1) is formed in a predetermined shape so that the flow of a mixture of air and fuel supplied from an intake port 12 described later becomes a predetermined flow, and the back surface of the piston head 9a (the lower surface in FIG. 1) is formed recessed on the upper surface side (the upper surface in FIG. 1) so as to have an arc-shaped cross section. A piston ring 9c is attached to the outer peripheral surface of the piston head 9a to seal the gap with the water jacket 8.

[0019] A combustion chamber 10 is formed in the cylinder head 4, which communicates with an opening on the upper side of the cylinder bore 2. This combustion chamber 10 is formed in a generally mountain shape, and an ignition plug 11 for igniting the mixture is provided on the ridge line, more specifically, at the position where it intersects with the central axis of the piston 9. An intake port 12 for taking in outside air and fuel into the combustion chamber 10 is formed in one inclined surface, and an exhaust port 13 for discharging exhaust gas generated in the combustion chamber 10 is formed in the other inclined surface.

[0020] The intake port 12 is connected to an intake passage 14 through which outside air taken in via an air cleaner (not shown) or the like flows. A fuel injection device 15 that injects fuel toward the intake port 12 is provided in the intake passage 14. Also, an intake valve 16 that opens and closes the intake port 12 is provided on the combustion chamber 10 side of the intake port 12.

[0021] An exhaust passage 17 for discharging exhaust gas outside the vehicle via a catalytic converter (not shown) or the like is connected to the exhaust port 13. An exhaust valve 18 for opening and closing the exhaust port 13 is provided on the combustion chamber 10 side of the exhaust port 13.

[0022] 1 is formed with an EGR passage 19 for recirculating a portion of the exhaust gas to the intake air. That is, one end of the EGR passage 19 is connected to the intake passage 14, and the other end is connected to the exhaust passage 17. The EGR passage 19 is provided with an EGR valve 20 for controlling the flow rate of the exhaust gas to be recirculated. Furthermore, a recirculation passage 21 that communicates with the space below the piston 9 and the intake passage 14 is connected to the intake passage 14.

[0023] The crankshaft 5 is freely accommodated in the crankcase 6 by a bearing (not shown). This crankshaft 5 can be configured in the same manner as a conventional crankshaft 5. That is, the crankshaft 5 includes an output section 5a that outputs the power of the engine 1, and a crankpin 5b that rotates around the rotational center axis of the output section 5a. A connecting rod 22 is fitted to the crankpin 5b. One end of the connecting rod 22 is fitted to the crankpin 5b so as to be relatively rotatable, and the other end is fitted to a piston pin 23, both ends of which are supported by the cylindrical section 9b of the piston 9 so as to be relatively rotatable. That is, the connecting rod 22 is configured to rotate (revolve) the crankpin 5b around the rotational center axis of the output section 5a as the piston 9 moves up and down. Also, one end of a return passage 21 is connected to the crankcase 6.

[0024] The oil pan 7 stores lubricating oil O for lubricating sliding parts between the piston 9 and the water jacket 8 and for cooling parts to be cooled such as the piston 9. By driving an oil pump (not shown), the lubricating oil O is pumped up from the oil pan 7 and pumped out, so that the lubricating oil O is supplied to each sliding part and part to be cooled.

[0025] As described above, the engine 1 generates power by burning a mixture of fuel and air. When the mixture is burned in this manner, water is inevitably produced. In particular, when hydrogen is used as fuel, a large amount of water is produced because hydrogen and oxygen mainly react with each other.

[0026] The moisture thus generated is mainly discharged to the outside together with the exhaust gas through the exhaust port 13 and the exhaust passage 17, but some of the generated moisture leaks to the crankcase 6 side through the gap between the piston 9 and the water jacket 8 and drips into the oil pan 7. In addition, since the exhaust gas recirculated to the intake passage 14 through the EGR passage 19 also contains moisture, the moisture becomes cold and liquefied, and is supplied to the combustion chamber 10 together with the intake air, and the moisture leaks to the crankcase 6 side and drips into the oil pan 7 in the same manner as above. Therefore, the moisture mixed into the lubricating oil O stored in the oil pan 7 may shorten the life of the lubricating oil O and may also deteriorate the lubricating performance of the lubricating oil O.

[0027] Therefore, the engine 1 in the embodiment of the present invention is configured to spray the lubricating oil O pumped up and pressure-fed from the oil pan 7 onto the back surface of the piston head 9a, thereby raising the temperature of the lubricating oil O and evaporating water mixed into the lubricating oil O. Specifically, an oil jet 24 connected to an oil pump (not shown) is attached to the lower end of the water jacket 8.

[0028] This oil jet 24 corresponds to the "nozzle" in the embodiment of the present invention, and can be configured similarly to the conventional oil jet 24 configured to spray the lubricating oil O onto the piston head 9a to cool the piston 9. That is, the discharge port 24a opens toward the upper side so that the lubricating oil O pumped by pressure from an oil pump (not shown) is sprayed toward the back surface of the piston head 9a. More specifically, the discharge port 24a opens toward a position where the lubricating oil O spreads over the entire back surface of the piston head 9a. In addition, a control valve for opening and closing the oil passage (not shown) is provided in an oil passage (not shown) that communicates with the oil jet 24 and the oil pump, and the lubricating oil O is sprayed from the oil jet 24 by opening the control valve.

[0029] 2 shows a block diagram for explaining the configuration of an electronic control unit (hereinafter, ECU) 25 that controls whether or not lubricating oil O is injected from the oil jet 24, i.e., the opening and closing operation of the control valve. This ECU 25 corresponds to the "controller" in the embodiment of the present invention, and is mainly composed of a microcomputer, similar to ECUs provided in conventional vehicles. This ECU 25 is configured to output signals for controlling the open / close state and opening degree of the control valve, based on input data and pre-stored maps and arithmetic expressions.

[0030] 2 shows an example of signals input to the ECU 25, and signals are input to the ECU 25 from a throttle opening sensor 26 that detects the opening of a throttle valve (not shown) provided in the intake passage 14, a rotation speed sensor 27 that detects the rotation speed of the crankshaft 5, an oil temperature sensor 28 that detects the temperature of the lubricating oil O stored in the oil pan 7, and a moisture percentage sensor 29 that detects the moisture percentage, which is the amount of moisture mixed into the lubricating oil O stored in the oil pan 7. Note that, in the case of determining the moisture percentage as described later, the moisture percentage sensor 29 does not have to be provided.

[0031] 2 includes a moisture percentage calculation unit 30, a piston temperature calculation unit 31, and an injection start determination unit 32. The moisture percentage calculation unit 30 is for calculating the moisture percentage when the moisture percentage sensor 29 is not provided. The moisture percentage calculation unit 30 stores a map for calculating the rate at which moisture is supplied to the lubricating oil O using the operating conditions of the engine 1 such as the torque and rotation speed as parameters, and a map for calculating the rate at which moisture evaporates from the lubricating oil O based on the temperature of the lubricating oil O, and is configured to calculate the moisture percentage from the supply rate and evaporation rate of the moisture.

[0032] The piston temperature calculation unit 31 is for obtaining the temperature of the piston 9, which is increased by burning the air-fuel mixture. In order to obtain the piston temperature using the fuel injection amount (fuel supply amount) per unit time as a parameter, a map constructed in advance by experiments, simulations, etc. is stored in the piston temperature calculation unit 31, and the piston temperature calculation unit 31 is configured to obtain the fuel injection amount per unit time based on signals detected by the throttle opening sensor 26 and the rotation speed sensor 27, and to obtain the piston temperature based on the fuel injection amount and the map.

[0033] The injection start determination unit 32 determines whether or not at least two conditions are met, that is, that the moisture mixed in the lubricating oil O needs to be evaporated and that the conditions are such that the moisture can be evaporated, and starts the injection of the lubricating oil O from the oil jet 24. Specifically, it is configured to output a signal to open the control valve when an evaporation possible flag is turned ON based on a control flow described later.

[0034] Fig. 3 is a flow chart for explaining the control example. The control example shown in Fig. 3 is configured to obtain the moisture percentage without providing a moisture percentage sensor 29. Therefore, first, the supply rate of moisture to the lubricating oil O (water supply rate) is calculated to obtain the moisture percentage (step S1). This step S1 is obtained based on a map stored in the moisture percentage calculation unit 30. That is, the operating conditions of the engine 1, such as the torque and rotation speed, are obtained based on the signals detected by the throttle opening sensor 26 and the rotation speed sensor 27, and the water supply rate is obtained from the operating conditions and the map.

[0035] Next, the evaporation rate of water from the lubricating oil O (water evaporation rate) is calculated (step S2). Like step S1, this step S2 is also calculated based on a map stored in the water percentage calculation unit 30. That is, the evaporation rate of water is calculated from the signal detected by the oil temperature sensor 26 and the map.

[0036] Next, the amount of water in the lubricant O is calculated (step S3). Specifically, the difference between the water supply rate calculated in step S1 and the water evaporation rate calculated in step S2 is calculated, and this difference is multiplied by the calculation cycle. That is, the amount of change in water in the lubricant O during the calculation cycle in which this control flow is executed is calculated. Then, this amount of change in water is added to the amount of water calculated in the previously executed control flow. That is, the amount of change in water in the lubricant O is accumulated each time the control flow is executed.

[0037] Then, the moisture percentage in the lubricant O is calculated (step S4). Specifically, the moisture percentage is calculated by dividing the amount of moisture calculated in step S3 by the amount of lubricant and multiplying it by 100. Note that the amount of lubricant in step S4 may be calculated by, for example, detecting the oil level of the lubricant O stored in the oil pan 7 and calculating the amount of lubricant stored in the oil pan 7 from the detected value, or a predetermined amount of lubricant may be used.

[0038] Next, it is determined whether the moisture content determined in step S4 is higher than a predetermined first threshold value (step S5). This step S5 determines whether the lubricating performance of the lubricating oil O has deteriorated. Therefore, the first threshold value in step S5 can be set to a moisture content at which the lubricating performance of the lubricating oil O deteriorates below an allowable value. The first threshold value corresponds to the "predetermined percentage" in the embodiment of the present invention.

[0039] If the moisture content is equal to or less than the first threshold value and thus the result of the negative determination in step S5 is negative, there is no need to evaporate moisture from the lubricant O, and this routine is terminated. On the other hand, if the moisture content is higher than the first threshold value and thus the result of the positive determination in step S5 is positive, the amount of lubricant (discharge amount) discharged from the oil jet 24 to evaporate moisture is calculated (step S6). Specifically, the discharge amount of the oil jet 24 is calculated based on the map shown in FIG. 4. That is, the higher the moisture content, the larger the discharge amount of the oil jet 24 is set. Note that even when there is a request to cool the piston 9, the lubricant O is discharged from the oil jet 24. Therefore, in step S6, the discharge amount of the lubricant O required to evaporate moisture and the discharge amount of the lubricant O required to cool the piston 9, whichever is larger, is adopted.

[0040] Then, it is determined whether or not it is possible to evaporate water from the lubricating oil O injected from the oil jet 24. Specifically, following step S6, the temperature of the piston 9 is calculated (step S7). This step S7 is calculated based on a map stored in the piston temperature calculation unit 31. FIG. 5 shows an example of the map, with the fuel injection amount per unit time taken on the horizontal axis and the piston temperature taken on the vertical axis. That is, the piston temperature can be calculated by calculating the fuel injection amount per unit time based on signals detected by the throttle opening sensor 26 and the rotation speed sensor 27.

[0041] Next, it is determined whether the piston temperature obtained in step S7 is higher than a second threshold value (step S8). This step S8 determines whether water can be evaporated from the lubricant O. Therefore, the second threshold value in step S8 can be set to a temperature higher than the temperature at which water can be evaporated from the lubricant O. The second threshold value is set to a temperature lower than the piston temperature at which the oil jet 24 starts to inject the lubricant O to cool the piston 9. This second threshold value corresponds to the "first predetermined temperature" in the embodiment of the present invention, and the piston temperature at which the oil jet 24 starts to inject the lubricant O to cool the piston 9 corresponds to the "second predetermined temperature" in the embodiment of the present invention.

[0042] If the piston temperature is higher than the second threshold and thus the answer is affirmative in step S8, the evaporation flag is set to ON (step S9), then the injection of the lubricating oil O from the oil jet 24 is started (step S10), and this routine is temporarily terminated. On the other hand, if the piston temperature is equal to or lower than the second threshold and thus the answer is negative in step S8, since water cannot be evaporated from the lubricating oil O, the evaporation flag is set to OFF (step S11), and this routine is temporarily terminated. The relationship between the evaporation flag and the piston temperature is shown in FIG. 6.

[0043] As described above, when the moisture content in the lubricating oil O is higher than the first threshold value and the piston temperature is higher than the second threshold value, the lubricating oil O is injected from the oil jet 24 toward the piston 9. The lubricating oil O injected from the oil jet 24 spreads over the entire back surface of the piston 9 as shown by the arrow in FIG. 1. The lubricating oil O injected toward the piston 9 spreads along the back surface of the piston 9 while heat is transferred from the piston 9, and as a result, the moisture mixed in the lubricating oil O evaporates. The lubricating oil O removed by the evaporation of the moisture drips from the back surface of the piston 9 into the oil pan 7. The moisture evaporated from the lubricating oil O flows through the return passage 21 as blow-by gas and returns to the intake passage 14.

[0044] As described above, when the moisture content in the lubricating oil O is higher than the first threshold value and the piston temperature is higher than the second threshold value, the lubricating oil O is sprayed from the oil jet 24 toward the piston 9. This allows the lubricating oil O to spread over the entire back surface of the piston 9 and receive heat from the piston 9, thereby increasing the heat receiving area of ​​the lubricating oil O and improving the efficiency of evaporating moisture from the lubricating oil O. In addition, since the moisture can be evaporated from the lubricating oil O using the existing oil jet 24 provided inside the engine block 3 or the crankcase 6, the engine 1 can be prevented from becoming larger. In other words, there is no need to provide a device such as a storage tank for the sole purpose of separating moisture, and the engine 1 can be prevented from becoming larger.

[0045] In the above-described control example, the moisture percentage in the lubricant O is calculated, but if a moisture percentage sensor 29 is provided, the moisture percentage in the lubricant O may be measured first (step S12) and then, based on the measured value, it may be determined in step S5 whether the moisture percentage is higher than the first threshold value, as in the control example shown in Fig. 7. Note that steps similar to those in the control example shown in Fig. 3 are denoted by the same reference numerals.

[0046] The conditions for stopping the injection of the lubricant O from the oil jet 24 may be appropriately determined, for example, by switching the above-mentioned evaporation possible flag off when the moisture content in the lubricant O falls below another threshold value that is equal to or lower than the above-mentioned first threshold value. In addition, in the above-mentioned control example, whether or not to start the injection of the lubricant O from the oil jet 24 is determined based only on two conditions, that is, that the moisture content is greater than the first threshold value and that the piston temperature is higher than the second threshold value, but the injection of the lubricant O from the oil jet 24 may be started when another condition is met in addition to the above two conditions. [Explanation of symbols]

[0047] 1 Engine 2 Cylinder bore 9 Piston 9a Piston head 9b Cylindrical part 9c Piston ring 15 Fuel injection system 24 Oil Jet 25 Electronic Control Unit (ECU) 30 Moisture percentage calculation section 31 Piston temperature calculation unit 32 Injection start judgment section O Lubricating oil

Claims

1. A cylinder bore and a piston that reciprocates within the cylinder bore. A lubrication control device for an internal combustion engine that generates power by burning a mixture of fuel and air supplied to one side of the piston, The cylinder bore includes a nozzle for injecting lubricating oil onto the other side surface of the piston; a controller for controlling whether or not the lubricating oil is sprayed from the nozzle; The controller: a moisture content calculation unit for calculating a moisture content, which is an amount of moisture mixed into the lubricating oil relative to an amount of the lubricating oil; a piston temperature calculation unit for calculating a temperature of the piston; and an injection start determination unit that starts injection of the lubricating oil from the nozzle when at least two predetermined conditions are satisfied: the moisture percentage calculated by the moisture percentage calculation unit is equal to or higher than a predetermined percentage, and the temperature of the piston calculated by the piston temperature calculation unit is equal to a first predetermined temperature at which the moisture mixed in the lubricating oil can evaporate. A lubrication control device for an internal combustion engine.

2. 2. The lubrication control device for an internal combustion engine according to claim 1, The moisture percentage calculation unit calculates the moisture percentage based on an amount of moisture mixed into the lubricating oil due to combustion of the air-fuel mixture and an amount of moisture vaporized from the lubricating oil depending on a temperature of the lubricating oil. A lubrication control device for an internal combustion engine.

3. 3. The lubrication control device for an internal combustion engine according to claim 1, The controller sets the amount of the lubricating oil to be injected from the nozzle to be larger as the moisture percentage calculated by the moisture percentage calculation unit is higher. A lubrication control device for an internal combustion engine.

4. The lubrication control device for an internal combustion engine according to any one of claims 1 to 3, The piston temperature calculation unit calculates the temperature of the piston based on the amount of fuel supplied. A lubrication control device for an internal combustion engine.

5. The lubrication control device for an internal combustion engine according to any one of claims 1 to 4, the controller is configured to cause the lubricating oil to be supplied from the nozzle to the piston when a temperature of the piston is higher than a second predetermined temperature that is predetermined for cooling the piston; The first predetermined temperature is lower than the second predetermined temperature. A lubrication control device for an internal combustion engine.

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