Oil dilution determination device

Abstract

To provide an oil dilution determination device capable of distinctively determining dilution of engine oil by water and dilution of engine oil by fuel.SOLUTION: The oil dilution determination device 100 includes the oil temperature sensor 3 that acquires the temperature of the engine oil, the state quantity acquisition unit 12 that acquires the state quantity relating to the operation state of the engine 1, and the determination unit 13 that distinguishes and determines the dilution of the engine oil by water and the dilution of the engine oil by fuel based on the difference between the rotation speed of the engine 1 and the predetermined reference rotation, the difference between the torque of the engine 1 and the predetermined reference torque, or the difference between the friction of the engine 1 and the predetermined reference friction torque when the temperature of the engine oil belongs to the temperature range in which water freezes.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an oil dilution determination device. [Background technology]

[0002] BACKGROUND ART Conventionally, there is known a control device for an internal combustion engine that performs vehicle braking in consideration of changes in engine friction due to fuel mixing into engine oil, etc. (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-303784 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned conventional technology, it is considered that the change in engine friction is caused by the dilution of engine oil due to the inclusion of fuel, which reduces the friction of the internal combustion engine. However, engine oil dilution can also occur due to the inclusion of water. Therefore, it is desirable to be able to determine which type of inclusion is causing the dilution of engine oil. [Means for solving the problem]

[0005] One aspect of the present invention is an oil dilution determination device that determines the dilution of engine oil used in an internal combustion engine, and includes an oil temperature acquisition unit that acquires the temperature of the engine oil, a state quantity acquisition unit that acquires state quantities related to the operating state of the internal combustion engine, and a determination unit that, when the temperature of the engine oil falls within a temperature range at which water freezes, distinguishes between dilution of the engine oil with water and dilution with fuel based on the difference in the rotational speed of the internal combustion engine from a predetermined reference rotation, the difference in the torque of the internal combustion engine from a predetermined reference torque, or the difference in the friction of the internal combustion engine from a predetermined reference friction torque. [Effects of the Invention]

[0006] According to one aspect of the present invention, it is possible to distinguish between dilution of engine oil with water and dilution of engine oil with fuel and to determine the dilution. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a block diagram showing a configuration of an oil dilution determination device according to an embodiment; [Figure 2] FIG. 4 is a diagram for explaining the relationship between the viscosity and the temperature of engine oil. [Figure 3] FIG. 4 is a diagram for explaining the relationship between the temperature of engine oil and friction torque. [Figure 4] 2 is a flowchart showing an example of processing performed by the oil dilution determination device of FIG. 1. [Figure 5] 10 is a flowchart showing another example of the process of the oil dilution determination device of FIG. [Figure 6] 10 is a flowchart showing another example of the process of the oil dilution determination device of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same or equivalent elements will be designated by the same reference numerals, and redundant description will be omitted.

[0009] 1 is a block diagram showing the configuration of an oil dilution determination device according to an embodiment of the present invention, and FIG. 1 is a block diagram showing the configuration of an oil dilution determination device 100 according to an embodiment of the present invention. As shown in FIG.

[0010] The oil dilution determination device 100 includes an engine 1 and an ECU (Electronic Control Unit) 10. The engine 1 is not particularly limited, but is, for example, a four-stroke reciprocating engine.

[0011] The engine 1 is mounted on a hybrid vehicle 50, which may be, for example, an HEV or a PHEV. The hybrid vehicle 50 can switch between a state in which the output torque of the engine 1 is transmitted to the drive wheels and a state in which the output torque of the engine 1 is not transmitted to the drive wheels.

[0012] The engine 1 is provided with a motor generator 2. The motor generator 2 is capable of generating electricity regeneratively using the output torque of the engine 1. The motor generator 2 is capable of assisting the engine 1 with traction torque when the output torque of the engine 1 is being transmitted to the drive wheels. The motor generator 2 is capable of rotating the engine 1 by motoring using the traction torque when the output torque of the engine 1 is not being transmitted to the drive wheels.

[0013] Dilution of engine oil includes the mixing of fuel into engine oil and the mixing of water into engine oil. The mixing of fuel includes, for example, the mixing of an increased amount of unburned fuel into engine oil when engine 1 is not yet warmed up. The mixing of water includes, for example, the condensation of water vapor inside engine 1 when engine 1 is not yet warmed up and the mixing of water vapor into engine oil.

[0014] In hybrid vehicles 50, due to recent demands for increased opportunities to drive in EV mode, the engine 1 tends to be stopped intermittently for longer periods of time. The operating time of the engine 1 tends to be shorter, and the engine 1 rarely reaches a full warm-up state. As a result, the engine 1 is more likely to be in an under-warmed state, which makes it more likely for fuel and water to be mixed into the engine oil. Therefore, the oil dilution determination device 100 is configured to distinguish between engine oil dilution by water and engine oil dilution by fuel and to determine this.

[0015] The engine 1 is provided with an oil temperature sensor 3 (oil temperature acquisition unit). The oil temperature sensor 3 is a sensor that detects the temperature of the engine oil. The oil temperature sensor 3 may be a known sensor, and is attached to the oil pan of the engine 1, for example, to detect the temperature of the engine oil stored in the oil pan. The oil temperature sensor 3 transmits a detection signal of the detected engine oil temperature to the ECU 10. The oil temperature sensor 3 may be provided in a location other than the oil pan, as long as it can acquire the temperature of the engine oil.

[0016] The engine 1 is provided with an engine speed sensor 4 that acquires the rotation speed of the engine 1. The engine speed sensor 4 may be a known sensor, and acquires, for example, the rotation speed of a crankshaft as the engine speed. The engine speed sensor 4 transmits a detection signal related to the engine speed to the ECU 10.

[0017] The ECU 10 is an electronic control unit having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a CAN (Controller Area Network) communication circuit, etc. The ECU 10 realizes various functions by, for example, loading a program stored in the ROM into the RAM and executing the program loaded into the RAM with the CPU. The ECU 10 performs comprehensive control for operating the engine 1. The ECU 10 may be composed of multiple electronic units.

[0018] The ECU 10 is connected to the engine 1, the motor generator 2, the oil temperature sensor 3, and the engine rotation speed sensor 4 so as to be able to communicate with each other.

[0019] The ECU 10 has a drive source control unit 11, a state quantity acquisition unit 12, and a determination unit 13 as functional components.

[0020] The drive source control unit 11 controls the operation of the engine 1 and the motor generator 2. The drive source control unit 11 intermittently stops the engine 1 depending on the operating status of the motor generator 2, the status of the driving battery, and the like.

[0021] The drive source control unit 11 may perform pre-stop autonomous operation of the engine 1 for a predetermined period of time before stopping the engine 1. Pre-stop autonomous operation is idling operation in which output torque is not transmitted to the motor generator 2 or the drive wheels, and refers to operation in which the engine 1 is operated by firing so as to achieve a predetermined target rotation speed. The drive source control unit 11 operates the engine 1 so as to output idling output torque so that the engine 1 performs pre-stop autonomous operation.

[0022] The drive source control unit 11 can rotate the engine 1 by motoring without transmitting output torque to either the motor generator 2 or the drive wheels. The drive source control unit 11 can rotate the stopped engine 1 by motoring, thereby starting the engine 1. During this start-up, the drive source control unit 11 drives the motor generator 2 with a feedforward torque value aimed at a predetermined target rotation speed at start-up, thereby rotating the engine 1.

[0023] For example, the driving source control unit 11 causes the motor generator 2 to rotate the engine 1 by motoring after stopping firing of the engine 1 during pre-stop autonomous operation before stopping the engine 1, or after firing of the engine 1 has ended after a predetermined period of pre-stop autonomous operation before stopping the engine 1. When rotating the engine 1 by motoring while not firing, the driving source control unit 11 can measure the motoring torque equivalent to the friction torque of the engine 1.

[0024] The state quantity acquisition unit 12 acquires state quantities related to the operating state of the engine 1 based on the detection results of various sensors. The state quantity acquisition unit 12 acquires the temperature of the engine oil stored in the oil pan based on the detection result of the oil temperature sensor 3. The state quantity acquisition unit 12 acquires the engine rotation speed based on the detection result of the engine rotation speed sensor 4.

[0025] The state quantity acquisition unit 12 acquires the idling output torque for the engine 1 to operate autonomously before stopping, the difference between the target rotation speed at start-up and the engine rotation speed when started by the motor generator 2, and the motoring torque of the engine 1 when not firing.

[0026] The state quantity acquisition unit 12 acquires a predetermined reference friction torque. The predetermined reference friction torque is a value (nominal value) of the friction torque of the engine 1 in a state where water and fuel have sufficiently evaporated from the engine oil and dilution has been eliminated. The reference friction torque can be acquired by an actual machine test. The reference friction torque may be stored in the ECU 10 in advance.

[0027] Fig. 2 is a diagram illustrating the relationship between engine oil temperature and viscosity. Fig. 3 is a diagram illustrating the relationship between engine oil temperature and friction torque. In Fig. 2, the horizontal axis represents engine oil temperature (oil temperature), and the vertical axis represents engine oil viscosity. In Fig. 3, the horizontal axis represents engine oil temperature, and the vertical axis represents torque relative to a predetermined reference friction torque.

[0028] The solid line L1 in Figure 2 represents the viscosity of engine oil when there is no engine oil dilution. As shown in Figure 2, the viscosity of engine oil increases as the engine oil temperature decreases. The friction torque in Figure 2, where the "state where there is no engine oil dilution" represented by the solid line L1 is the nominal value, corresponds to the solid line L4 in Figure 3. The friction torque represented by the solid line L4 corresponds to a predetermined reference friction torque.

[0029] The dashed line L2 in Figure 2 represents the viscosity of engine oil when it is diluted by fuel. When engine oil is diluted by fuel, the viscosity of the engine oil decreases. The lower the engine oil temperature, the greater the degree of decrease in viscosity of the engine oil, and the greater the difference from the solid line L1. The friction torque in the state of dashed line L2 in Figure 2 corresponds to dashed line L5 in Figure 3.

[0030] The dashed-dotted line L3 in Figure 2 represents the viscosity of engine oil when it is diluted with water. When engine oil is diluted with water, the viscosity of the engine oil increases in the temperature range where water freezes. This is because the water in the engine oil partially turns to ice. The lower the engine oil temperature, the greater the increase in viscosity of the engine oil, and the greater the difference from the solid line L1. The friction torque in the state of the dashed-dotted line L3 in Figure 2 corresponds to the dashed-dotted line L6 in Figure 3.

[0031] Therefore, when the temperature of the engine oil falls within the temperature range at which water freezes (for example, temperature range T1, for example, a range below 0°C), the friction torque (friction) of the engine 1 in a state where the engine oil is diluted by fuel has a magnitude relationship in which it is smaller than the reference friction torque, as shown in the relationship between the solid line L4 and the dashed line L5 in Figure 3. On the other hand, when the temperature of the engine oil falls within the temperature range at which water freezes, the friction torque of the engine 1 in a state where the engine oil is diluted by water has a magnitude relationship in which it is larger than the reference friction torque, as shown in the relationship between the solid line L4 and the dashed line L6 in Figure 3.

[0032] Furthermore, when the engine oil temperature falls within the temperature range of the fully warmed-up state (for example, temperature range T3), the influence of engine oil dilution by fuel is almost eliminated, and the friction torque of engine 1 has a magnitude relationship that is equal to the reference friction torque. On the other hand, when the engine oil temperature falls within the temperature range of the fully warmed-up state, the influence of engine oil dilution by water is almost eliminated, and the friction torque of engine 1 has a magnitude relationship that is equal to the reference friction torque. The fully warmed-up state means a state in which engine 1 is sufficiently warmed up so that the engine oil temperature is high enough to evaporate water and fuel.

[0033] Furthermore, when the engine oil temperature falls within the temperature range of the semi-warmed state (for example, temperature range T2, e.g., a range of 4°C to 80°C), the influence of engine oil dilution by fuel is intermediate between the influence in temperature range T1 and the influence in temperature range T3. Therefore, the friction torque of the engine 1 has a magnitude relationship in which it decreases relative to the reference friction torque by a smaller amount than the decrease in temperature range T1. On the other hand, when the engine oil temperature falls within the temperature range of the semi-warmed state, the influence of engine oil dilution by water is sufficiently smaller than the influence of engine oil dilution by fuel, and the friction torque of the engine 1 has a magnitude relationship in which it is equal to the reference friction torque.

[0034] By using the magnitude relationship between the friction torque of the engine 1 and the reference friction torque as shown in Figure 3, it is possible to distinguish between dilution of the engine oil by water and dilution by fuel depending on whether the friction torque of the engine 1 is greater than the reference friction torque or whether the friction torque of the engine 1 is smaller than the reference friction torque, at least in the water freezing temperature range T1. That is, when the friction torque of the engine 1 is greater than the reference friction torque in the water freezing temperature range T1, it can be estimated that dilution of the engine oil by water is occurring. When the friction torque of the engine 1 is smaller than the reference friction torque in the water freezing temperature range T1, it can be estimated that dilution of the engine oil by fuel is occurring. Note that the accuracy of determining engine oil dilution may be improved by using the magnitude relationship between the friction torque of the engine 1 and the reference friction torque in the temperature ranges T2 and T3.

[0035] Therefore, when the temperature of the engine oil falls within the temperature range T1 at which water freezes, the judgment unit 13 distinguishes between dilution of the engine oil with water and dilution with fuel based on the difference in the engine 1 rotation speed from a predetermined reference rotation, the difference in the engine 1 torque from a predetermined reference torque, or the difference in the engine 1 friction from a predetermined reference friction torque.

[0036] The determination unit 13 will be described together with an example of processing by the ECU 10. Fig. 4 is a flowchart showing an example of processing by the oil dilution determination device of Fig. 1. Fig. 5 is a flowchart showing another example of processing by the oil dilution determination device of Fig. 1. Fig. 6 is a flowchart showing another example of processing by the oil dilution determination device of Fig. 1. The processing shown in Figs. 4 to 6 is each repeatedly executed at predetermined calculation intervals while the engine 1 is operating, for example.

[0037] As shown in FIG. 4, in a situation where the stopped engine 1 is rotated by motoring to start the engine 1 (start request, S11), the determination unit 13 obtains the difference in the engine 1 rotation speed from the target rotation speed at startup (predetermined reference rotation speed) as the difference in the engine 1 rotation speed from a predetermined reference rotation speed. The drive source control unit 11 described above drives the motor generator 2 with a feedforward torque value (e.g., a constant value) aimed at the target rotation speed at startup to rotate the engine 1. Therefore, the friction torque of the engine 1 determines the rotation speed of the engine 1, and a difference in rotation from the target rotation speed at startup may occur. Note that the start request may also include starting the engine 1 after an intermittent stop. In S11, a fuel dilution count and a water dilution count, which will be described later, may be reset to 0.

[0038] When the temperature of the engine oil falls within the temperature range T1 at which water freezes, the judgment unit 13 motors the engine 1 and judges whether the engine oil is diluted based on the magnitude relationship between the engine speed of the engine 1 before firing and the target speed at startup (S12).

[0039] When the engine oil temperature falls within the temperature range T1 at which water freezes, if the rotation speed of the engine 1 is higher than the target rotation speed at start-up (S12: High), when the stopped engine 1 is started by motoring, the determination unit 13 determines that engine oil is being diluted by fuel because the friction torque of the engine 1 is estimated to be small. In the example of FIG. 4, the fuel dilution count corresponding to the likelihood that engine oil dilution by fuel is occurring is counted up by one (S13). In the example of FIG. 4, the ECU 10 counts up the fuel dilution count by one in accordance with the magnitude relationship determination result of S12, thereby determining that engine oil is being diluted by fuel.

[0040] When the engine oil temperature is within the water freezing temperature range T1, if the engine 1 is started by motoring the stopped engine 1 and the engine speed is lower than the target engine speed at start (S12: low), the determination unit 13 determines that the engine oil is being diluted by water because it estimates that the friction torque of the engine 1 is large. In the example of FIG. 4, the water dilution count, which corresponds to the likelihood that the engine oil is being diluted by water, is counted up by one (S14). In the example of FIG. 4, the ECU 10 counts up the water dilution count by one in accordance with the magnitude relationship determination result of S12, thereby determining that the engine oil is being diluted by water.

[0041] When the engine oil temperature is within the water freezing temperature range T1, if the engine 1 is started by motoring the stopped engine 1, and the engine speed is equal to the target engine speed at start-up (S12: equal), the determination unit 13 determines that engine oil dilution is not occurring because the friction torque of the engine 1 is estimated to be equal to the reference friction torque. Here, "equal" does not necessarily mean that the friction torque and the reference friction torque are exactly the same value, but also includes the case where the friction torque is within a predetermined range relative to the reference friction torque (the same applies to FIGS. 5 and 6). In the example of FIG. 4, the fuel dilution count and the water dilution count are maintained (S15). In the example of FIG. 4, the ECU 10 maintains the fuel dilution count and the water dilution count at 0 in accordance with the magnitude relationship determination result of S12, thereby determining that engine oil dilution is not occurring.

[0042] As another example, as shown in FIG. 5, in a situation where the engine 1 is operating in a pre-stop autonomous mode for a predetermined period before being stopped (S21, stop request for intermittent stop), the determination unit 13 obtains the difference between the current idling output torque (torque) of the engine 1 and the reference value (predetermined reference torque) of the idling output torque. The reference value of the idling output torque is the value of the idling output torque in a state where engine oil dilution does not occur. The current idling output torque of the engine 1 is the value of the idling output torque that includes an output torque correction amount, such as an ignition timing advance or retard, to converge the engine 1 to a predetermined target rotation speed when the engine 1 is operated by firing to achieve the predetermined target rotation speed. Therefore, the current idling output torque of the engine 1 includes an output torque correction amount that becomes necessary in response to a change in the friction torque of the engine 1. Note that the stop request is not limited to a stop request for intermittent stop and may include a stop request for the engine 1 when the IG switch is turned off. In S21, the fuel dilution count and the water dilution count may be reset to zero.

[0043] When the temperature of the engine oil falls within the temperature range T1 at which water freezes, the judgment unit 13 judges whether the engine oil is diluted based on the magnitude relationship between the current idling output torque when the engine 1 is operating autonomously before being stopped and the reference value of the idling output torque (S22).

[0044] When the engine oil temperature is within the temperature range T1 at which water freezes, if the current idling output torque of the engine 1 is smaller than the reference value of the idling output torque (S22: smaller) when the engine 1 is operating in pre-stop autonomous mode before being stopped, the determination unit 13 determines that the engine oil is being diluted by fuel because it estimates that the friction torque of the engine 1 is small. In the example of FIG. 5, the fuel dilution count is incremented by one (S23). In the example of FIG. 5, the ECU 10 increments the fuel dilution count by one in accordance with the magnitude relationship determination result of S22, thereby determining that the engine oil is being diluted by fuel.

[0045] When the engine oil temperature is within the water freezing temperature range T1, if the current idling output torque of the engine 1 is greater than the reference value of the idling output torque (S22: greater) when the engine 1 is operating in pre-shutdown self-sustaining mode before being stopped, the determination unit 13 determines that the engine oil is being diluted with water because the friction torque of the engine 1 is estimated to be large. In the example of FIG. 5, the water dilution count is incremented by one (S24). In the example of FIG. 5, the ECU 10 increments the water dilution count by one in accordance with the magnitude relationship determination result of S22, thereby determining that the engine oil is being diluted with water.

[0046] When the engine oil temperature is within the water freezing temperature range T1, if the current idling output torque of the engine 1 is equal to the reference value of the idling output torque when the engine 1 is operating in pre-shutdown self-sustained mode before being stopped (S22: equal), the determination unit 13 determines that engine oil dilution is not occurring because the friction torque of the engine 1 is estimated to be equal to the reference friction torque. In the example of FIG. 5, the fuel dilution count and the water dilution count are maintained (S25). In the example of FIG. 5, the ECU 10 maintains the fuel dilution count and the water dilution count at 0 in accordance with the magnitude relationship determination result of S22, thereby determining that engine oil dilution is not occurring.

[0047] 6, as another example, the difference between the friction of engine 1 and a predetermined reference friction torque may be determined by comparing the motoring torque when motoring engine 1 that is not firing with the reference friction torque when motoring engine 1 using motor generator 2 after stopping firing of engine 1 during pre-stop autonomous operation before engine 1 is stopped or after firing of engine 1 has ended after a predetermined period of pre-stop autonomous operation before engine 1 is stopped (S31, stop request for intermittent stop). In S31, the fuel dilution count and the water dilution count may be reset to 0.

[0048] When the temperature of the engine oil falls within the temperature range T1 at which water freezes, the judgment unit 13 judges whether the engine oil is diluted based on the magnitude relationship between the motoring torque of the engine 1 that is not firing and the reference friction torque (S32).

[0049] When the temperature of the engine oil falls within the temperature range T1 at which water freezes, if the motoring torque of the engine 1 that is not firing and the motor generator 2 is motoring the engine 1 is smaller than the reference friction torque (S32: smaller), the determination unit 13 determines that the engine oil is being diluted by fuel because the friction torque of the engine 1 is estimated to be small. In the example of FIG. 6, the fuel dilution count is counted up by one (S33). In the example of FIG. 6, the ECU 10 counts up the fuel dilution count by one in accordance with the magnitude relationship determination result of S32, thereby determining that the engine oil is being diluted by fuel.

[0050] When the engine oil temperature is within the water freezing temperature range T1, if the motoring torque of the engine 1 that is not firing and is rotated by the motor generator 2 through motoring is greater than the reference friction torque (S32: greater), the determination unit 13 determines that the engine oil is being diluted with water because it estimates that the friction torque of the engine 1 is large. In the example of FIG. 6, the water dilution count is incremented by one (S34). In the example of FIG. 6, the ECU 10 increments the water dilution count by one in accordance with the magnitude relationship determination result of S32, thereby determining that the engine oil is being diluted with water.

[0051] When the engine oil temperature is within the water freezing temperature range T1, if the motoring torque of the engine 1 that is not firing and is rotated by the motor generator 2 through motoring is equivalent to the reference friction torque (S32: equivalent), the determination unit 13 determines that engine oil dilution is not occurring because it is estimated that the friction torque of the engine 1 is equivalent to the reference friction torque. In the example of FIG. 6, the fuel dilution count and the water dilution count are maintained (S35). In the example of FIG. 6, the ECU 10 maintains the fuel dilution count and the water dilution count at 0 in accordance with the magnitude relationship determination result of S32, thereby determining that engine oil dilution is not occurring.

[0052] [Action and effect] As described above, when the temperature of the engine oil falls within the water-freezing temperature range T1, the oil dilution determination device 100 distinguishes between dilution of the engine oil with water and dilution of the engine oil with fuel based on the difference in the engine 1 rotation speed from a predetermined reference rotation speed, the difference in the engine 1 torque from a predetermined reference torque, or the difference in the engine 1 friction from a predetermined reference friction torque. Using the magnitude relationship between the friction torque of the engine 1 and the reference friction torque as shown in FIG. 3 , it is possible to distinguish between dilution of the engine oil with water and dilution of the engine oil with fuel based on whether the friction torque of the engine 1 is greater than the reference friction torque or whether the friction torque of the engine 1 is smaller than the reference friction torque, at least within the water-freezing temperature range T1. This allows the oil dilution determination device 100 to distinguish between dilution of the engine oil with water and dilution of the engine oil with fuel.

[0053] [Variations] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments.

[0054] In the above embodiment, in Figures 4 to 6, when the temperature of the engine oil falls within the temperature range T1 at which water freezes, the determination is made to distinguish between dilution of the engine oil with water and dilution with fuel based on the difference in the engine 1 rotation speed from a predetermined reference rotation, the difference in the engine 1 torque from a predetermined reference torque, or the difference in the engine 1 friction from a predetermined reference friction torque.However, it is also possible to add a determination for when the engine oil temperature falls within the temperature ranges T2 and T3, and determine whether the engine oil is diluted based on the fuel dilution count and water dilution count corresponding to the added determination result.

[0055] For example, if the comparison result of the magnitude relationship similar to S12, S22, and S32 in temperature range T2 is "equivalent," the processing of S15, S25, and S35 can be changed to "add the water dilution count," and if the comparison result is "low" or "large," the processing of S14, S24, and S34 can be changed to "keep the fuel dilution count and the water dilution count," and if the comparison result is "high" or "small," the processing of S13, S23, and S33 can remain "add the fuel dilution count," thereby adding a judgment for when the engine oil temperature falls within temperature range T2.

[0056] For example, if the comparison result of the magnitude relationship similar to S12, S22, and S32 in temperature range T3 is "equivalent," the processing of S15, S25, and S35 can be changed to "add the fuel dilution count and the water dilution count," if the comparison result is "high" or "small," the processing of S13, S23, and S33 can be changed to "save the fuel dilution count and the water dilution count," and if the comparison result is "low" or "large," the processing of S14, S24, and S34 can be changed to "save the fuel dilution count and the water dilution count." In this way, a determination can be added for when the engine oil temperature falls within temperature range T3. [Explanation of symbols]

[0057] 1...engine (internal combustion engine), 3...oil temperature sensor (oil temperature acquisition unit), 12...state quantity acquisition unit, 13...determination unit, 100...oil dilution determination device, T1...temperature range.

Claims

[Claim 1] An oil dilution determination device for determining dilution of engine oil used in an internal combustion engine, an oil temperature acquisition unit that acquires the temperature of the engine oil; a state quantity acquisition unit that acquires a state quantity related to an operating state of the internal combustion engine; An oil dilution determination device comprising: a determination unit that, when the temperature of the engine oil falls within the temperature range at which water freezes, distinguishes between dilution of the engine oil with water and dilution with fuel based on the difference in the rotational speed of the internal combustion engine from a predetermined reference rotational speed, the difference in the torque of the internal combustion engine from a predetermined reference torque, or the difference in the friction of the internal combustion engine from a predetermined reference friction torque.

Images