Engine oil dilution degree estimation device

Abstract

To provide an engine oil dilution degree estimation device which can accurately estimate a dilution degree after exchange of an engine oil.SOLUTION: An engine oil dilution degree estimation device estimates a dilution degree of an engine oil used for lubrication of an engine and includes: a calculation unit which calculates a rate of increase of an oil pressure which is a pressure in an oil passage of the engine in which the engine oil flows when the engine starts; a determination unit which determines whether or not the engine oil is exchanged based on a current value and a previous value of the rate of increase; and a reset unit which resets the dilution degree to an initial value when the determination by the determination unit is affirmative.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an engine oil dilution degree estimation device. [Background technology]

[0002] Engine oil is diluted by fuel and water mixed in. There is a technique for estimating the degree of dilution of engine oil (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-138538 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned technique, the dilution degree is estimated without taking into account engine oil changes, which may result in a decrease in the accuracy of the estimation of the dilution degree after engine oil changes.

[0005] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide an engine oil dilution degree estimating device that can accurately estimate the dilution degree even after engine oil has been changed. [Means for solving the problem]

[0006] The above object can be achieved by an engine oil dilution degree estimation device that estimates the dilution degree of engine oil used to lubricate an engine, the engine oil dilution degree estimation device comprising: a calculation unit that calculates a rate of increase of oil pressure, which is the pressure in the oil passage of the engine through which the engine oil flows, when the engine is started; a judgment unit that judges whether the engine oil has been replaced based on a current value and a previous value of the rate of increase; and a reset unit that resets the dilution degree to an initial value when a positive judgment is made by the judgment unit. Effect of the Invention

[0007] According to the present invention, it is possible to provide an engine oil dilution degree estimating device that can accurately estimate the dilution degree even after engine oil is changed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic configuration diagram of an engine system. [Diagram 2] FIG. 2 is a flowchart showing an example of the dilution degree reset control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Outline of engine system configuration] 1 is a schematic configuration diagram of an engine system 1. The engine system 1 includes an engine 10 and an ECU (Electronic Control Unit) 50 that controls the engine 10. The engine system 1 is mounted on, for example, a vehicle.

[0010] A circulation path is formed in the engine 10, through which engine oil used for lubricating the engine 10 circulates. The circulation path is provided with an oil pump 11, an oil strainer 14, an oil filter 15, an OCV (Oil Control Valve) 18, and an oil pressure sensor 36. The oil pump 11 draws engine oil from an oil pan 13 of the engine 10 and discharges it. The oil pump 11 is a mechanical pump that operates in response to the rotation of the crankshaft 12, i.e., the rotation of the engine 10. The oil strainer 14 is a filter that filters relatively large foreign matter contained in the engine oil sucked by the oil pump 11. The oil filter 15 is a filter that filters fine foreign matter contained in the engine oil discharged by the oil pump 11. The OCV 18 opens and closes under the control of the ECU 50. The amount of engine oil discharged from the oil pump 11 is changed by opening and closing the OCV 18.

[0011] The engine oil discharged from the oil pump 11 passes through an oil filter 15 and is then sent to a main gallery 16. The engine oil is distributed and supplied from the main gallery 16 to each lubrication part 17 of the engine 10. The main gallery 16 is an example of an oil passage. The oil pressure sensor 36 detects the oil pressure, which is the pressure of the engine oil passing through the main gallery 16.

[0012] The ECU 50 is mainly composed of a computer including a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and other volatile and non-volatile memories. The ECU 50 executes various control processes related to the engine 10 on the CPU, by executing programs installed in the memory. Various sensors are connected to the ECU 50, which will be described in detail later. The ECU 50 is an example of an engine oil dilution degree estimation device, and functionally realizes a calculation unit, a determination unit, and a reset unit, which will be described in detail later.

[0013] The ECU 50 is electrically connected to an ignition switch 31, an air flow meter 32, a crank angle sensor 33, a water temperature sensor 34, an oil temperature sensor 35, and an oil pressure sensor 36. The ignition switch 31 detects the on / off state of the ignition. The air flow meter 32 detects the amount of intake air. The crank angle sensor 33 detects the rotation angle of the crankshaft 12. The water temperature sensor 34 detects the temperature of the cooling water that cools the engine 10. The oil temperature sensor 35 detects the temperature of the engine oil. The oil pressure sensor 36 detects the oil pressure in the main gallery 16 as described above.

[0014] The ECU 50 calculates the engine speed based on the detection value of the crank angle sensor 33, and calculates the engine load factor based on the engine speed and the intake air amount. The ECU 50 controls the fuel injection amount, the intake air amount, and the ignition timing so that the engine speed and the load factor become the target speed and the target load factor, respectively.

[0015] The ECU 50 estimates the degree of dilution of the engine oil by fuel and water, and executes control according to the degree of dilution. For example, the ECU 50 executes control to suppress dilution of the engine oil according to the estimated degree of dilution. This control is a control to promote volatilization of the fuel and water in the engine oil by utilizing the heat generated by the engine 10, for example, by controlling the operating state of the engine 10 so that the amount of heat generated by the engine 10 increases.

[0016] The ECU 50 estimates the dilution degree of the engine oil as follows. The ECU 50 estimates the dilution degree by adding the following additional value to the initial value of the dilution degree and subtracting the subtraction value. The ECU 50 calculates the additional value based on the temperature of the cooling water at the start of the engine 10 and the integrated value of the load rate of the engine 10. The lower the temperature of the cooling water at the start and the larger the integrated value of the load rate of the engine 10, the larger the additional value is calculated and the larger the dilution degree is estimated. This is because the lower the temperature of the cooling water at the start, the less likely the water and fuel in the engine oil are to volatilize. Also, the larger the load rate of the engine 10, the larger the fuel injection amount is, and the more fuel is in the engine oil. The ECU 50 calculates the subtraction value based on the elapsed time during which the temperature of the engine oil is equal to or higher than a predetermined temperature (for example, 40 degrees). The longer the elapsed time, the larger the subtraction value is calculated. That is, the longer the elapsed time, the smaller the dilution degree is estimated to be.

[0017] [Dilution degree reset control] Next, a description will be given of the dilution degree reset control executed by the ECU 50. Fig. 2 is a flowchart showing an example of the dilution degree reset control. This flowchart is repeatedly executed while the ignition is on.

[0018] First, the ECU 50 determines whether the engine 10 has been started in a cold state (step S1). Specifically, it is determined whether the engine 10 has been started in a state in which the temperature of the cooling water is equal to or lower than a predetermined temperature. If the result in step S1 is No, this control ends.

[0019] If the answer is Yes in step S1, the ECU 50 calculates the oil pressure increase rate, which is the rate at which the oil pressure is increased by the engine oil (step S2). The ECU 50 calculates the oil pressure increase rate based on the detection value of the oil pressure sensor 36. The oil pressure increases to a desired pressure value by the oil pump 11, which is driven when the engine 10 starts. The method of calculating the oil pressure increase rate will be described in detail later. Step S2 is an example of a process executed by the calculation unit. Each time the ECU 50 calculates a calculated oil pressure increase rate, it updates the current value and previous value in the memory.

[0020] Next, the ECU 50 judges whether the engine oil has been replaced based on the current value and the previous value of the oil pressure increase rate (step S3). In detail, when the value obtained by subtracting the previous value of the oil pressure increase rate from the current value of the oil pressure increase rate is equal to or greater than a predetermined value, it is judged that the engine oil has been replaced. Here, the predetermined value is the minimum value assumed when subtracting the oil pressure increase rate immediately before the engine oil change from the oil pressure increase rate immediately after the engine oil change. The reason why the oil pressure increase rate increases after the engine oil change compared to before the change is that when the degree of dilution of the engine oil is large, the viscosity of the engine oil decreases and the oil pressure increase rate decreases. Therefore, when the value obtained by subtracting the previous value of the oil pressure increase rate from the current value of the oil pressure increase rate is less than the predetermined value, it is judged that the engine oil has not been replaced (No in step S3). In this case, this control ends. Step S3 is an example of a process executed by the judgment unit.

[0021] If the value obtained by subtracting the previous value from the current value of the hydraulic pressure rise rate is equal to or greater than a predetermined value, it is determined that the engine oil has been changed between the calculation of the previous value and the calculation of the current value (Yes in step S3). In this case, the ECU 50 resets the dilution degree estimated up to that point to an initial value (step S4). That is, the integrated value of the load factor of the engine 10 used to estimate the dilution degree is reset to zero. Step S4 is an example of a process executed by the reset unit.

[0022] In this way, if the current value of the oil pressure increase rate is greater than the previous value by a predetermined value or more, it is assumed that the engine oil has been changed and the dilution degree is reset. Therefore, the dilution degree after the engine oil change can be accurately estimated without being affected by the dilution degree estimated before the engine oil change.

[0023] A method for calculating the hydraulic pressure rise rate described above will now be described. For example, the hydraulic pressure rise rate may be calculated based on the time ΔT required for the hydraulic pressure to reach a certain amount of rise ΔP after the engine 10 is started. In this case, the longer the required time ΔT, the lower the hydraulic pressure rise rate is considered to be. Alternatively, the hydraulic pressure rise rate may be calculated based on the amount of rise ΔP of the hydraulic pressure from the start of the engine 10 until a certain amount of time ΔT has elapsed. In this case, the greater the amount of rise ΔP of the hydraulic pressure, the higher the hydraulic pressure rise rate is considered to be.

[0024] As described above, the reason why the oil pressure rise rate is calculated during cold start is that during cold start, the dilution has a large effect on the viscosity of the engine oil, and as a result, the dilution has a large effect on the oil pressure. Also, when the engine is not started cold, the fuel and water in the engine oil evaporate, making it difficult for the dilution degree to be reflected in the oil pressure rise rate.

[0025] In the above embodiment, the ECU 50 that controls the engine 10 mounted on a vehicle has been described as an example of an engine oil dilution degree estimation device, but the invention is not limited to this. For example, the contents of the above embodiment can be applied to an engine oil dilution degree estimation device mounted on a motorcycle or the like, or an engine oil dilution degree estimation device mounted on something other than a vehicle, such as a ship or construction machine. In addition, the vehicle on which such an ECU is mounted may be an engine vehicle equipped with only an engine as a power source for running, or may be a hybrid vehicle equipped with an engine and a motor as power sources for running.

[0026] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0027] 1 Engine System 10 Engine 16 Main gallery (oil passage) 36 Oil pressure sensor 50 ECU (engine oil dilution degree estimation device, calculation unit, judgment unit, reset unit)

Claims

[Claim 1] An engine oil dilution degree estimation device that estimates a dilution degree of engine oil used for lubricating an engine, comprising: a calculation unit that calculates a rate of increase in oil pressure, which is a pressure in an oil passage of the engine through which the engine oil flows, when the engine is started; a determination unit that determines whether the engine oil has been changed based on a current value and a previous value of the rate of increase; a reset unit that resets the dilution degree to an initial value when a positive determination is made by the determination unit.

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