Oil dilution determination device

Abstract

The invention provides an oil dilution determination device which can distinguish and determine water dilution and fuel dilution of oil. An oil dilution determination device (100) is provided with: an oil temperature sensor (3) that acquires the temperature of oil; a state quantity acquisition unit (12) that acquires a state quantity relating to the operating state of the engine (1); and a determination unit (13) that, when the temperature of the oil belongs to a temperature region in which the water freezes, determines the water dilution of the oil and the fuel dilution of the oil on the basis of the difference between the rotational speed of the engine (1) and a predetermined reference rotational speed, the difference between the torque of the engine (1) and a predetermined reference torque, or the difference between the friction of the engine (1) and a predetermined reference friction torque.

Description

TECHNICAL FIELD

[0001] The present application relates to an engine oil dilution determination device. BACKGROUND

[0002] Conventionally, a control device of an internal combustion engine that performs braking of a vehicle while taking into account a change in engine friction caused by mixing of fuel into engine oil and the like is known (for example, refer to Patent Literature 1).

[0003] PRIOR ART DOCUMENT

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2008-303784 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In the above-described related art, as a change in engine friction, a case where friction of the internal combustion engine decreases when engine oil is diluted due to mixing of fuel is taken into account. However, dilution of engine oil is sometimes caused by mixing of water. Therefore, it is desirable to be able to determine dilution of engine oil caused by which kind of mixing.

[0008] MEANS FOR SOLVING THE PROBLEMS

[0009] One aspect of the present application is an engine oil dilution determination device that determines dilution of engine oil used in an internal combustion engine, wherein the engine oil dilution determination device includes an engine oil temperature acquisition section that acquires a temperature of the engine oil, a state quantity acquisition section that acquires a state quantity related to an operating state of the internal combustion engine, and a determination section that, in a case where the temperature of the engine oil belongs to a temperature region in which water freezes, distinguishes and determines water dilution of the engine oil and fuel dilution of the engine oil based on a difference between a rotational speed of the internal combustion engine and a predetermined reference rotation, a difference between a torque of the internal combustion engine and a predetermined reference torque, or a difference between friction of the internal combustion engine and a predetermined reference friction torque.

[0010] EFFECTS OF THE INVENTION

[0011] According to one embodiment of the present application, it is possible to distinguish and determine water dilution of engine oil and fuel dilution of engine oil. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a block diagram showing the structure of an engine oil dilution determination device of an embodiment.

[0013] Figure 2 is a graph for explaining the relationship of viscosity of engine oil with respect to temperature.

[0014] Figure 3 is a graph for explaining the relationship of friction torque with respect to temperature of engine oil.

[0015] Figure 4 is a flowchart showing an example of the process of the engine oil dilution determination device of Figure 1

[0016] Figure 5 is a flowchart showing another example of the process of the engine oil dilution determination device of Figure 1

[0017] Figure 6 is a flowchart showing another example of the process of the engine oil dilution determination device of Figure 1 DETAILED DESCRIPTION

[0018] Hereinafter, an embodiment of the present application will be described with reference to the accompanying drawings. In the following description, the same or corresponding elements are denoted by the same reference numerals, and repetitive description is omitted.

[0019] Figure 1 is a block diagram showing the structure of the engine oil dilution determination device of the embodiment. As shown in Figure 1

[0020] The engine oil dilution determination device 100 includes the engine 1 and an ECU [Electronic Control Unit] 10. The engine 1 is not particularly limited, and is, for example, a four-stroke reciprocating engine.

[0021] The engine 1 is mounted on a hybrid vehicle 50 that is an HEV or a PHEV, for example. In the hybrid vehicle 50, 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 are switchable.

[0022] The engine 1 is provided with a motor generator 2. The motor generator 2 is capable of regenerative power generation using the output torque of the engine 1. The motor generator 2 is capable of assisting the engine 1 by motoring torque in the state in which the output torque of the engine 1 is transmitted to the drive wheels. The motor generator 2 is capable of rotating the engine 1 by motoring in the state in which the output torque of the engine 1 is not transmitted to the drive wheels.

[0023] Dilution of the engine oil includes mixing of fuel into the engine oil and mixing of water into the engine oil. The mixing of fuel includes, for example, mixing of fuel that is increased when the engine 1 is in a cold state into the engine oil in an unburned state. The mixing of water includes, for example, mixing of water vapor that condenses inside the engine 1 when the engine 1 is in a cold state into the engine oil.

[0024] ​​​​In the hybrid vehicle 50, there is a tendency for the period during which the engine 1 is intermittently stopped to increase in accordance with recent increased requirements for travel opportunities in the EV state, and the like. There is a tendency for the operation time of the engine 1 to become short, and the case where the engine 1 reaches a full warm-up state becomes less. Therefore, the engine 1 easily becomes in an unwarmed-up state, and fuel mixing into the oil and water mixing into the oil easily occur. Therefore, the oil dilution determination device 100 is configured to distinguish and determine water dilution of the oil and fuel dilution of the oil.

[0025] The engine 1 is provided with an oil temperature sensor 3 (an oil temperature acquisition section). The oil temperature sensor 3 is a sensor that detects the temperature of the oil. The oil temperature sensor 3 can also be a publicly known sensor that, for example, is installed to an oil pan of the engine 1 and detects the temperature of the oil stored in the oil pan. The oil temperature sensor 3 transmits a detection signal of the detected temperature of the oil to the ECU 10. The oil temperature sensor 3 can also be provided at a position other than the oil pan as long as the temperature of the oil can be acquired.

[0026] The engine 1 is provided with an engine rotation speed sensor 4 that acquires the rotation speed of the engine 1. The engine rotation speed sensor 4 can also be a publicly known sensor that, for example, acquires the rotation speed of a crankshaft as the engine rotation speed. The engine rotation speed sensor 4 transmits a detection signal related to the engine rotation speed to the ECU 10.

[0027] 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, and the like. In the ECU 10, for example, a program stored in the ROM is loaded to the RAM, and the program loaded to the RAM is executed by the CPU, whereby various functions are realized. The ECU 10 implements comprehensive control for operating the engine 1. The ECU 10 can also be configured by a plurality of electronic units.

[0028] The ECU 10 is communicably connected to the engine 1, the motor generator 2, the oil temperature sensor 3, and the engine rotation speed sensor 4.

[0029] The ECU 10 has a drive source control section 11, a state quantity acquisition section 12, and a determination section 13 as functional structures.

[0030] The drive source control section 11 controls the operation of the engine 1 and the motor generator 2. The drive source control section 11 causes the engine 1 to be intermittently stopped in accordance with the operation state of the motor generator 2, the state of the travel storage battery, and the like.

[0031] The drive source control portion 11 can also implement the pre-stop autonomous operation of the engine 1 for a predetermined period before the engine 1 is stopped. The pre-stop autonomous operation is an idle operation in which neither output torque is transmitted to the motor generator 2 nor output torque is transmitted to the drive wheels, and refers to an operation in which the engine 1 is caused to operate by ignition in such a manner that a predetermined target rotational speed is attained. The drive source control portion 11 causes the engine 1 to operate in such a manner that an idle output torque is output, so as to cause the engine 1 to perform the pre-stop autonomous operation.

[0032] The drive source control portion 11 can rotate the engine 1 by electric drive operation in a state in which neither output torque is transmitted to the motor generator 2 nor output torque is transmitted to the drive wheels. The drive source control portion 11 can rotate the engine 1 in a stopped state by electric drive operation so as to start the engine 1. At the time of the start, the drive source control portion 11 drives the motor generator 2 with a feedforward torque value that targets a predetermined start-time target rotational speed, so as to rotate the engine 1.

[0033] The drive source control portion 11 causes the engine 1 to rotate by electric drive operation using the motor generator 2, for example, after the ignition of the engine 1 is stopped in the pre-stop autonomous operation before the engine 1 is stopped, or after the ignition of the engine 1 ends after a predetermined period has elapsed from the pre-stop autonomous operation before the engine 1 is stopped. The drive source control portion 11 can measure an electric drive operation torque that corresponds to the friction torque of the engine 1 when the engine 1 that is not ignited is rotated by electric drive operation.

[0034] The state quantity acquisition portion 12 acquires state quantities related to the operation state of the engine 1 on the basis of the detection results of various sensors. The state quantity acquisition portion 12 acquires the temperature of the oil stored in the oil pan on the basis of the detection result of the oil temperature sensor 3. The state quantity acquisition portion 12 acquires the engine rotational speed on the basis of the detection result of the engine rotational speed sensor 4.

[0035] The state quantity acquisition portion 12 acquires an idle output torque with which the engine 1 performs the pre-stop autonomous operation, a difference between the start-time target rotational speed at the time of the start of the motor generator 2 and the engine rotational speed, and an electric drive operation torque of the engine 1 that is not ignited.

[0036] The state quantity acquisition portion 12 acquires a predetermined reference friction torque. The predetermined reference friction torque is a value (a nominal value) of the friction torque of the engine 1 in a state in which water and fuel are sufficiently evaporated from the oil and dilution is eliminated. The reference friction torque can be acquired by actual machine testing. The reference friction torque can also be stored in the ECU 10 in advance.

[0037] Figure 2 is a graph for explaining the relationship of the viscosity of the oil with respect to the temperature. Figure 3 is a graph for explaining the relationship of the friction torque with respect to the temperature of the oil. In Figure 2In FIG. 6, the horizontal axis is the temperature of the engine oil (engine oil temperature), and the vertical axis is the viscosity of the engine oil. In FIG. 6, the horizontal axis is the temperature of the engine oil, and the vertical axis is the relative value of the torque with respect to the predetermined reference friction torque. Figure 3

[0038] Figure 2 The solid line L1 of FIG. 6 indicates the viscosity of the engine oil in a state in which dilution of the engine oil has not occurred. As shown in FIG. 6, the lower the temperature of the engine oil, the greater the viscosity of the engine oil. The friction torque in the state of the solid line L1 of FIG. 6, which is the nominal friction torque, corresponds to the solid line L4 of FIG. 6. Figure 2 Figure 2 Figure 3

[0039] Figure 2 The dashed line L2 of FIG. 6 indicates the viscosity of the engine oil in a state in which fuel dilution of the engine oil has occurred. In the state in which fuel dilution of the engine oil has occurred, the viscosity of the engine oil decreases. The lower the temperature of the engine oil, the greater the degree of decrease in the viscosity of the engine oil, and the greater the difference from the solid line L1. Figure 2 The friction torque in the state of the dashed line L2 of FIG. 6 corresponds to the dashed line L5 of FIG. 6. Figure 3

[0040] Figure 2 The one-dot chain line L3 of FIG. 6 indicates the viscosity of the engine oil in a state in which water dilution of the engine oil has occurred. In the state in which water dilution of the engine oil has occurred, the viscosity of the engine oil increases in the temperature range in which water freezes. This is because the water present in the engine oil partially becomes ice. The lower the temperature of the engine oil, the greater the degree of increase in the viscosity of the engine oil, and the greater the difference from the solid line L1. Figure 2 The friction torque in the state of the one-dot chain line L3 of FIG. 6 corresponds to the one-dot chain line L6 of FIG. 6. Figure 3

[0041] Therefore, in the case where the temperature of the engine oil belongs to the temperature region in which water freezes (for example, the temperature region T1, for example, the range of 0°C or lower), the friction torque (friction) of the engine 1 in the state in which fuel dilution of the engine oil has occurred has a smaller size relationship with respect to the reference friction torque according to the relationship of the solid line L4 and the dashed line L5 of FIG. 6. On the other hand, in the case where the temperature of the engine oil belongs to the temperature region in which water freezes, the friction torque of the engine 1 in the state in which water dilution of the engine oil has occurred has a larger size relationship with respect to the reference friction torque according to the relationship of the solid line L4 and the one-dot chain line L6 of FIG. 6. Figure 3 Figure 3

[0042] ​​​​​​​​In addition, in a case where the temperature of the engine oil belongs to the temperature region of the fully-warmed state (for example, the temperature region T3), the influence of the fuel dilution of the engine oil almost disappears, and the frictional torque of the engine 1 has a magnitude relationship equal to the reference frictional torque. On the other hand, in a case where the temperature of the engine oil belongs to the temperature region of the fully-warmed state, the influence of the water dilution of the engine oil almost disappears, and the frictional torque of the engine 1 has a magnitude relationship equal to the reference frictional torque. The fully-warmed state refers to a state in which the engine 1 is sufficiently warmed such that the temperature of the engine oil is high to the extent that water and fuel are evaporated.

[0043] In addition, in a case where the temperature of the engine oil belongs to the temperature region of the semi-warmed state (for example, the temperature region T2, for example, a range of 4°C or higher and 80°C or lower), the influence of the fuel dilution of the engine oil becomes an influence of an intermediate degree between the influence in the temperature region T1 and the influence in the temperature region T3. Therefore, the frictional torque of the engine 1 has a magnitude relationship in which the frictional torque is smaller than the reference frictional torque at a smaller decreasing rate than in the temperature region T1. On the other hand, in a case where the temperature of the engine oil belongs to the temperature region of the semi-warmed state, the influence of the water dilution of the engine oil is sufficiently small compared to the influence of the fuel dilution of the engine oil, and the frictional torque of the engine 1 has a magnitude relationship equal to the reference frictional torque.

[0044] When the magnitude relationship of the frictional torque of the engine 1 and the reference frictional torque is used Figure 3 When the magnitude relationship of the frictional torque of the engine 1 and the reference frictional torque is used

[0045] Therefore, the determination unit 13 distinguishes and determines the water dilution of the engine oil and the fuel dilution of the engine oil based on the difference between the rotational 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 frictional torque in a case where the temperature of the engine oil belongs to the temperature region T1 of the water freezing state.

[0046] The determination unit 13 will be described together with the processing example of the ECU 10. Figure 4 is a flowchart showing an example of the processing of the engine oil dilution determination device. Figure 1 is a flowchart showing an example of the processing of the engine oil dilution determination device. Figure 5 is a flowchart showing an example of the processing of the engine oil dilution determination device.Figure 1 The flowchart shows another example of the processing of the oil dilution determination device. Figure 6 It means Figure 1 The flowchart shows another example of the processing of the oil dilution determination device. Figures 4-6 The processes shown are executed repeatedly according to a predetermined calculation cycle, for example, during the operation of engine 1.

[0047] like Figure 4 As shown, the difference between the engine speed of engine 1 and a predetermined reference rotation speed is used to determine the difference between the engine speed of engine 1 and the target rotation speed (predetermined reference rotation speed) when engine 1 is started by rotating it electrically from a stopped state (startup requirement, S11). The drive source control unit 11 drives the electric generator 2 with a feedforward torque value (e.g., a fixed value) that targets the startup target rotation speed, thus rotating engine 1. Therefore, the engine speed of engine 1 is limited by the frictional torque of engine 1, which may result in a rotational difference relative to the startup target rotation speed. Furthermore, the startup requirement may also include starting engine 1 after intermittent stops. In S11, the fuel dilution count and water dilution count (described later) may also be reset to 0.

[0048] When the oil temperature is in the water freezing temperature range T1, the determination unit 13 determines whether the oil is diluted based on the relationship between the engine speed of the engine 1 before ignition and the target speed at startup.

[0049] When the engine oil temperature is within the water freezing temperature range T1, and the engine 1 is started by rotating it electrically, if the engine speed is higher than the target starting speed (S12: higher), it is presumed that the frictional torque of the engine 1 is small, and therefore the determination unit 13 determines that fuel dilution of the engine oil has occurred. Figure 4 In the example, the fuel dilution count, corresponding to the higher or lower probability of fuel dilution causing engine oil production, is incremented by 1 (S13). Figure 4 In the example, ECU10 increments the fuel dilution count by 1 based on the determination result of the size relationship of S12, thereby determining that fuel dilution of engine oil has occurred.

[0050] When the engine oil temperature is within the water freezing temperature range T1, if the engine 1 is started by rotating it electrically, and the engine speed is lower than the target starting speed (S12: lower), it is presumed that the frictional torque of the engine 1 is large, and therefore the determination unit 13 determines that water dilution of the engine oil has occurred. Figure 4 In the example, the water dilution count, corresponding to the higher or lower probability of water dilution from the generated engine oil, is incremented by 1 (S14). Figure 4In the example, ECU10 increments the water dilution count by 1 based on the determination result of the size relationship of S12, thereby determining that water dilution of engine oil has occurred.

[0051] When the engine oil temperature falls within the water freezing temperature range T1, and the engine 1 is started by rotating it electrically, if the engine speed is equal to the target speed at startup (S12: equal), it is presumed that the friction torque of the engine 1 is equal to the reference friction torque. Therefore, the determination unit 13 determines that no oil dilution has occurred. Here, "equal" is not limited to the friction torque being exactly the same as the reference friction torque; it also includes cases where the friction torque is within a predetermined range relative to the reference friction torque (in...). Figure 5 , Figure 6 (Same as above). Figure 4 In the example, maintain the fuel dilution count and water dilution count (S15). Figure 4 In the example, based on the determination result of the size relationship of S12, ECU10 keeps the fuel dilution count and water dilution count at 0, thus determining that no oil dilution has been generated.

[0052] As another example, such as Figure 5 As shown, the difference between the torque of engine 1 and a predetermined reference torque is used. In the case of autonomous operation of engine 1 before stopping for a predetermined period before stopping (S21, intermittent stop request), the determination unit 13 obtains the difference between the current idle output torque (torque) of engine 1 and the reference value of the idle output torque (predetermined reference torque). The reference value of the idle output torque is the value of the idle output torque in a state where no oil dilution occurs. The current idle output torque of engine 1 is the value of the idle output torque that includes a correction amount, such as ignition timing advance or retardation, for the output torque to converge to the predetermined target speed during operation where engine 1 is operated by ignition to reach the predetermined target speed. Therefore, the current idle output torque of engine 1 includes the correction amount of output torque required according to the change in the friction torque of engine 1. Furthermore, the stop request is not limited to intermittent stop requests, but may also include a stop request for engine 1 when the IG (ignition) switch is turned off. In S21, the fuel dilution count and water dilution count may also be reset to 0.

[0053] When the oil temperature is in the water freezing temperature range T1, the determination unit 13 determines whether the oil is diluted based on the relationship between the current idle output torque and the reference value of the idle output torque when the engine 1 is running autonomously before stopping (S22).

[0054] When the engine oil temperature is within the water freezing temperature range T1, if the engine 1 is automatically run before stopping, and the current idle output torque of the engine 1 is less than the reference value of the idle output torque (S22: small), it is presumed that the friction torque of the engine 1 is small, and therefore the determination unit 13 determines that fuel dilution of the engine oil has occurred. Figure 5 In the example, the fuel dilution count is incremented by 1 (S23). Figure 5 In the example, ECU10 increments the fuel dilution count by 1 based on the determination result of the size relationship of S22, thereby determining that fuel dilution of engine oil has occurred.

[0055] When the engine oil temperature is within the water freezing temperature range T1, if the engine 1 is automatically run before stopping, and the current idle output torque of the engine 1 is greater than the reference value of the idle output torque (S22: large), it is presumed that the friction torque of the engine 1 is large, and therefore the determination unit 13 determines that water dilution of the engine oil has occurred. Figure 5 In the example, the water dilution count is incremented by 1 (S24). Figure 5 In the example, ECU10 increments the water dilution count by 1 based on the determination result of the size relationship of S22, thereby determining that water dilution of engine oil has occurred.

[0056] When the engine oil temperature is within the water freezing temperature range T1, if the engine 1 is automatically run before stopping, and the current idle output torque of the engine 1 is equal to the reference value of the idle output torque (S22: equal), it is presumed that the friction torque of the engine 1 is equal to the reference friction torque, and therefore the determination unit 13 determines that no oil dilution has occurred. Figure 5 In the example, the fuel dilution count and water dilution count are maintained (S25). Figure 5 In the example, based on the determination result of the size relationship of S22, ECU10 keeps the fuel dilution count and water dilution count at 0, thus determining that no oil dilution has been generated.

[0057] As another example, such as Figure 6 As shown, the difference between the friction of engine 1 and the predetermined reference friction torque can be determined by comparing the electric operating torque of the unignited engine 1 with the reference friction torque, in cases where the engine 1 is rotated by electric operation via electric generator 2 (S31, intermittent stop requirement), after the ignition of engine 1 is stopped during autonomous operation before the engine 1 stops, or after the ignition of engine 1 ends after a predetermined period of autonomous operation before the engine 1 stops, in which case the engine 1 is rotated by electric operation via electric generator 2. In S31, the fuel dilution count and water dilution count can also be reset to 0.

[0058] When the oil temperature is in the water freezing temperature range T1, the determination unit 13 determines whether the oil is diluted based on the relationship between the electric operating torque of the unignited engine 1 and the reference friction torque (S32).

[0059] When the engine oil temperature is within the water freezing temperature range T1, if the unignited engine 1 is rotated by electric generator 2, and the electric operating torque is smaller than the reference friction torque (S32: smaller), it is presumed that the friction torque of engine 1 is small, and therefore the determination unit 13 determines that fuel dilution of the engine oil has occurred. Figure 6 In the example, the fuel dilution count is incremented by 1 (S33). Figure 6 In the example, ECU10 increments the fuel dilution count by 1 based on the determination result of the size relationship of S32, thereby determining that fuel dilution of engine oil has occurred.

[0060] When the engine oil temperature falls within the water freezing temperature range T1, and the unignited engine 1 is rotated electrically by the electric generator 2, if the electric operating torque is greater than the reference friction torque (S32: greater), it is presumed that the friction torque of the engine 1 is greater, and therefore the determination unit 13 determines that water dilution of the engine oil has occurred. Figure 6 In the example, the water dilution count is incremented by 1 (S34). Figure 6 In the example, ECU10 increments the water dilution count by 1 based on the determination result of the size relationship of S32, thereby determining that water dilution of engine oil has occurred.

[0061] When the engine oil temperature is within the water freezing temperature range T1, if the unignited engine 1 is rotated by electric generator 2, and the electric operating torque is equal to the reference friction torque (S32: equal), it is presumed that the friction torque of engine 1 is equal to the reference friction torque, and therefore the determination unit 13 determines that no oil dilution has occurred. Figure 6 In the example, maintain the fuel dilution count and water dilution count (S35). Figure 6 In the example, based on the determination result of the size relationship of S32, ECU10 keeps the fuel dilution count and water dilution count at 0, thus determining that no oil dilution has been generated.

[0062] [Functions and Effects]

[0063] As explained above, according to the oil dilution determination device 100, when the oil temperature is within the water freezing temperature range T1, the device distinguishes and determines whether the oil is diluted by water or by fuel, based on the difference between the engine speed and a predetermined reference rotation, the difference between the engine torque and a predetermined reference torque, or the difference between the friction and a predetermined reference friction torque of the engine. When using...Figure 3 When considering the relationship between the friction torque of engine 1 and the reference friction torque, at least within the water-freezing temperature range T1, it is possible to distinguish and determine whether the engine oil is diluted by water or diluted by fuel based on whether the friction torque of engine 1 is greater or less than the reference friction torque. Therefore, the engine oil dilution determination device 100 can distinguish and determine whether the engine oil is diluted by water or diluted by fuel.

[0064] [Variation Example]

[0065] The embodiments of the present invention have been described above, but the present invention is not limited to the embodiments described above.

[0066] In the above embodiments, Figures 4-6 In this system, the oil is distinguished and determined based on the following: the oil temperature is within the water freezing temperature range T1; the difference between the engine speed and the predetermined reference rotation speed; the difference between the engine torque and the predetermined reference torque; or the difference between the friction of the engine and the predetermined reference friction torque. However, it is also possible to add a determination based on the oil temperature being within temperature ranges T2 and T3, and to determine the oil dilution based on the fuel dilution count and water dilution count corresponding to the additional determination results.

[0067] For example, the treatment of S15, S25, and S35 in temperature zone T2, where the comparison result of the same magnitude relationship as S12, S22, and S32 is "equal", can be changed to "add the water dilution count". The treatment of S14, S24, and S34 in the case of "low" or "large" can be changed to "keep the fuel dilution count and water dilution count". The treatment of S13, S23, and S33 in the case of "high" or "small" can be kept as "add the fuel dilution count". This determines the condition when the temperature of the added oil is in temperature zone T2.

[0068] For example, the treatment of S15, S25, and S35 in temperature zone T3, where the comparison result of the same magnitude relationship as S12, S22, and S32 is "equal", can be changed to "add the fuel dilution count and water dilution count". The treatment of S13, S23, and S33 in the case of "high" or "low" can be changed to "maintain the fuel dilution count and water dilution count". The treatment of S14, S24, and S34 in the case of "low" or "high" can be changed to "maintain the fuel dilution count and water dilution count". This will help determine if the temperature of the added engine oil belongs to temperature zone T3.

[0069] Explanation of reference numerals in the attached figures

[0070] 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 region.

Claims

1. An engine oil dilution determination device that determines dilution of engine oil used in an internal combustion engine, wherein the engine oil dilution determination device includes: an engine oil temperature acquisition section that acquires a temperature of the engine oil; a state quantity acquisition section that acquires a state quantity related to an operating state of the internal combustion engine; and a determination section that, in a case where the temperature of the engine oil belongs to a temperature region in which water freezes, distinguishes and determines water dilution of the engine oil and fuel dilution of the engine oil based on a difference between a rotational speed of the internal combustion engine and a predetermined reference rotation, a difference between a torque of the internal combustion engine and a predetermined reference torque, or a difference between a friction of the internal combustion engine and a predetermined reference friction torque.

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