Vehicle control device

Abstract

To accurately determine whether cold friction of an engine is increased due to contamination of soot into engine oil.SOLUTION: An electronic control unit 20 calculates an increase amount of a soot concentration of engine oil based on the operation state of an engine 11, and calculates an increase amount of a low-temperature viscosity of the engine oil based on a state quantity indicating a combustion state of an air-fuel mixture and the increase amount of the soot concentration. The electronic control unit 20 determines whether or not cold friction of the engine 11 is increased based on the calculation result of the increase amount of the low-temperature viscosity.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vehicle control device that controls a vehicle equipped with an engine. [Background technology]

[0002] When engine oil deteriorates due to the inclusion of soot produced by combustion, the viscosity of the oil increases. As a result, friction during cold engine operation increases, which can worsen engine startability. Patent Document 1 describes a method for determining whether engine oil has deteriorated in the following manner. First, the amount of soot generated is calculated based on the engine speed and the end time of fuel injection. The integrated value of the amount of soot generated from the start of use of the engine oil is calculated as an index value for the concentration of soot in the oil. Then, whether engine oil has deteriorated is determined based on whether the integrated value of the amount of soot generated exceeds a certain value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-276327 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the properties of soot generated by the combustion of the air-fuel mixture change depending on the combustion conditions of the mixture. The tendency of the viscosity of engine oil to increase at low temperatures due to the inclusion of soot also changes depending on the properties of the soot. Therefore, it may not be possible to accurately estimate the amount of increase in the viscosity of engine oil at low temperatures just by looking at the concentration of soot in the oil. [Means for solving the problem]

[0005] A vehicle control device that solves the above problem is a device that controls a vehicle equipped with an engine, and performs an increase amount calculation process that calculates the amount of increase in soot concentration of engine oil based on the operating state of the engine, an increase amount calculation process that calculates the amount of increase in low-temperature viscosity of the engine oil based on a state quantity that indicates the combustion state of the mixture and the amount of increase in soot concentration, and a judgment process that judges whether or not the cold friction of the engine is in a state where it has increased based on the result of the increase amount calculation.

[0006] In an engine, the properties of soot generated by the combustion of an air-fuel mixture change depending on the combustion state of the air-fuel mixture. The vehicle control device calculates the increase in the viscosity of the engine oil at low temperatures based on the increase in the soot concentration of the engine oil and a state quantity indicating the combustion state of the air-fuel mixture. Therefore, the increase in the viscosity at low temperatures can be calculated in a manner that reflects the difference in the effect that the difference in soot properties has on the viscosity of the engine oil at low temperatures. Then, the vehicle control device determines whether or not the cold friction of the engine is in a state of increased based on the calculation result of the increase in the viscosity of the engine oil at low temperatures. Therefore, the vehicle control device can accurately determine whether or not the cold friction of the engine is in a state of increased due to the inclusion of soot in the engine oil. [Brief description of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating a schematic configuration of an embodiment of a vehicle control device; [Diagram 2] 4 is a graph showing the relationship between the soot concentration of engine oil and the viscosity at low temperatures when a diesel engine is operated under three conditions with different engine water temperatures and air-fuel ratios. [Diagram 3] 5 is a flowchart showing a procedure of a process for determining an increase in cold friction executed by the vehicle control device. [Figure 4] 1 is a graph showing a relationship between a viscosity increase rate and a product of an average rotation speed and an average air-fuel ratio in a calculation map used for determining an increase in cold friction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of a vehicle control device will be described in detail with reference to FIGS. <Configuration of the vehicle control device> First, the configuration of a vehicle control device of this embodiment will be described with reference to Fig. 1. The vehicle control device of this embodiment is applied to a vehicle 10 equipped with a diesel engine as an engine 11 serving as a drive source.

[0009] As shown in Fig. 1, engine 11 has a combustion chamber 12 in which an air-fuel mixture is burned. Engine 11 also has an intake passage 13 which is a passage through which intake air is introduced into combustion chamber 12, and an exhaust passage 14 which is a passage through which exhaust gas is discharged from combustion chamber 12. In intake passage 13, an air flow meter 15 which detects an intake air amount GA, and a throttle valve 16 which is a valve for adjusting the intake air amount GA are installed. In combustion chamber 12, a fuel injection valve 17 which injects fuel into the intake air introduced therein is installed. Engine 11 also has a crank angle sensor 19 which detects the rotation angle of crankshaft 18 which is an output shaft.

[0010] The vehicle 10 is equipped with an electronic control unit 20. The electronic control unit 20 controls the onboard devices of the vehicle 10, including the engine 11. Detection signals from various sensors that detect the state of the vehicle 10 are input to the electronic control unit 20. The sensors that input detection signals to the electronic control unit 20 include the air flow meter 15 and the crank angle sensor 19 described above. A signal indicating the state of an ignition switch 21 is also input to the electronic control unit 20. The electronic control unit 20 then executes various controls of the vehicle 10 based on the input detection signals. For example, the electronic control unit 20 controls the operating state of the engine 11 through control of the opening degree of the throttle valve 16, the fuel injection amount and fuel injection timing of the fuel injection valve 17, and the like. The electronic control unit 20 includes a processing device 22 that executes processing for controlling the vehicle 10, and a storage device 23 in which control programs and data are stored. In this embodiment, the electronic control unit 20 corresponds to a vehicle control device.

[0011] <Increase in engine oil viscosity at low temperatures> When the air-fuel mixture in the combustion chamber 12 of the engine 11 is burned, soot is generated. Some of the generated soot is mixed into the engine oil. When the concentration of soot in the engine oil increases, the viscosity of the engine oil at low temperatures increases. When the viscosity of the engine oil at low temperatures increases, the friction of the engine 11 during cold operation increases. Therefore, when the soot concentration in the engine oil increases, this can lead to a deterioration in the cold startability of the engine 11 and an increase in noise and vibration during low-temperature operation. In the following description, the friction of the engine 11 during cold operation is referred to as the cold friction of the engine 11.

[0012] The properties of the soot generated by the combustion of the air-fuel mixture change depending on the combustion state of the mixture. The inventors have confirmed that the tendency of the viscosity of engine oil to increase at low temperatures in response to an increase in soot concentration varies depending on the properties of the mixed soot.

[0013] FIG. 2 shows the relationship between the soot concentration and the viscosity at low temperature of the engine oil when the engine 11 is operated under three different conditions of engine water temperature and air-fuel ratio. The ratio of the increase in viscosity at low temperature relative to the increase in soot concentration is larger when the engine water temperature is high than when it is low. Also, the ratio of the increase in viscosity at low temperature relative to the increase in soot concentration is larger when the air-fuel ratio is lean than when it is rich. If the air-fuel ratio of the mixture is different, the amount of oxygen provided for combustion changes, and the combustion state of the mixture changes. On the other hand, when the engine water temperature is low, the wall temperature of the combustion chamber 12 in which the mixture is burned also decreases. When the wall temperature of the combustion chamber 12 is low, the amount of fuel that adheres to the wall surface of the combustion chamber 12 after injection from the fuel injection valve 17 increases, and the combustion state is likely to deteriorate. In this way, the engine water temperature and the air-fuel ratio are factors that affect the combustion state of the mixture, and in turn, the properties of the soot generated by the combustion of the mixture.

[0014] <Determining increase in cold friction> The vehicle control device of this embodiment determines whether or not the cold friction of the engine 11 has increased due to soot mixed into the engine oil. In this embodiment, the increase determination is performed in a manner that reflects the difference in the tendency of the engine oil to increase in viscosity at low temperatures due to the properties of soot as described above.

[0015] Fig. 3 shows a processing procedure of the electronic control unit 20 related to the determination of an increase in cold friction. In this embodiment, the electronic control unit 20 starts a series of processing shown in Fig. 3 as processing at the end of a trip of the vehicle 10 in response to an OFF operation of the ignition switch 21.

[0016] When the electronic control unit 20 starts the process of FIG. 3, first, in step S100, it acquires the amount of soot concentration increase during the trip S. The amount of soot concentration increase during the trip S represents the amount of increase in the soot concentration of the engine oil from the start to the end of the current trip. While the engine 11 is operating, the electronic control unit 20 calculates the amount of soot generated by the combustion of the air-fuel mixture based on the operating state of the engine 11 at each predetermined calculation cycle. Then, the electronic control unit 20 obtains the amount of soot concentration increase during the trip S from a value obtained by accumulating the calculated values ​​of the amount of soot generated during the trip. In this embodiment, the process of step S100 corresponds to an increase amount calculation process that calculates the amount of increase in the soot concentration of the engine oil.

[0017] Next, in step S110, the electronic control unit 20 acquires the average rotation speed MNE and the average air-fuel ratio MABF. During the operation of the engine 11, the electronic control unit 20 calculates the engine rotation speed NE from the detection result of the crank angle sensor 19. Then, the electronic control unit 20 obtains the average value of the engine rotation speed NE during the period from the start to the end of the trip as the value of the average rotation speed MNE. Also, during the operation of the engine 11, the electronic control unit 20 obtains the air-fuel ratio ABF of the mixture burned in the combustion chamber 12 based on the intake air amount GA detected by the air flow meter 15 and the fuel injection amount commanded to the fuel injection valve 17. Then, the electronic control unit 20 obtains the average value of the air-fuel ratio ABF during the period from the start to the end of the trip as the average air-fuel ratio MABF.

[0018] Next, in step S120, the electronic control unit 20 calculates the viscosity increase rate K from the average rotation speed MNE and the average air-fuel ratio MABF. The electronic control unit 20 calculates the viscosity increase rate K using a calculation map MAP pre-stored in the storage device 23. The viscosity increase rate K represents the ratio of the increase in viscosity at low temperatures to the increase in soot concentration of the engine oil. The calculation map MAP is configured as a map that uses the product of the average rotation speed MNE and the average air-fuel ratio MABF (MNE×MABF) as an argument and the viscosity increase rate K as a return value.

[0019] FIG. 4 shows the relationship between the product of the average revolution speed MNE and the average air-fuel ratio MABF and the viscosity increase rate K in the calculation map MAP. As shown in the figure, the calculation map MAP is set so that the larger the product of the average revolution speed MNE and the average air-fuel ratio MABF, the larger the value of the viscosity increase rate K is calculated. If the engine revolution speed NE continues to be high, the engine water temperature becomes high. Therefore, in a trip in which the average revolution speed MNE is large, the engine 11 is operated with a high engine water temperature. Also, in a trip in which the average air-fuel ratio MABF is large, combustion is often performed with the air-fuel ratio lean. Therefore, in a trip in which the product of the average revolution speed MNE and the average air-fuel ratio MABF is large, it is considered that a lot of soot, which easily increases the viscosity at low temperatures, is mixed into the engine oil. The calculation map MAP is set in a manner that reflects such a tendency.

[0020] After calculating the viscosity increase rate K in this way, the electronic control unit 20 calculates the product (K×S) of the increase in soot concentration during trip S multiplied by the viscosity increase rate K as the value of the viscosity increase amount ΔVS during trip. The viscosity increase amount ΔVS during trip represents the increase in viscosity of the engine oil at low temperatures during the period from the start to the end of the current trip. Then, in step S140, the electronic control unit 20 updates the value of the viscosity increase amount VS at low temperatures based on the viscosity increase amount ΔVS during trip. Specifically, in step S140, the electronic control unit 20 updates the value of the viscosity increase amount VS at low temperatures so that the sum of the value before the update and the viscosity increase amount ΔVS during trip is set to the updated value. The viscosity increase amount VS at low temperatures represents the increase in viscosity at low temperatures after the start of use of the engine oil. Incidentally, the value of the viscosity increase amount VS at low temperatures is reset to “0” when the engine oil is replaced. In this embodiment, the processes of steps S120 to S140 correspond to an increase amount calculation process that calculates an increase amount of the viscosity of the engine oil at low temperatures based on a state amount indicating the combustion state of the air-fuel mixture and an increase amount of the soot concentration.

[0021] In the next step S150, the electronic control unit 20 judges whether the vehicle 10 is in a low temperature environment. This judgment can be made based on, for example, the measurement results of the outside air temperature and the intake air temperature. If date information can be acquired, it is possible to judge whether the vehicle is in a low temperature environment by judging from the date whether the temperature is low. Furthermore, if weather information for the current position of the vehicle 10 can be acquired from the outside, it is possible to judge whether the vehicle is in a low temperature environment based on the weather information. If the electronic control unit 20 judges that the vehicle is not in a low temperature environment (NO), it ends the current process. On the other hand, if the electronic control unit 20 judges that the vehicle is in a low temperature environment (YES), it proceeds to step S160.

[0022] When the process proceeds to step S160, the electronic control unit 20 determines whether or not the viscosity increase amount VS at low temperature exceeds a predetermined determination value. In this embodiment, when the viscosity increase amount VS at low temperature exceeds the determination value, it is determined that the cold friction of the engine 11 is in an increased state. In this embodiment, the process of step S160 corresponds to a determination process of determining whether or not the cold friction of the engine 11 is in an increased state based on the calculation result of the viscosity increase amount at low temperature.

[0023] When the electronic control unit 20 determines that the cold friction is not increased (S170: NO), the electronic control unit 20 ends the current process. On the other hand, when the electronic control unit 20 determines that the cold friction is increased (S170: YES), the electronic control unit 20 executes the process when the cold friction is increased in step S180. The process when the cold friction is increased is a process for changing the control content of the vehicle 10 in response to the increase in the cold friction of the engine 11.

[0024] <Treatment when cold friction increases> The process when cold friction has increased includes, for example, the following process. The electronic control unit 20 records the mileage of the vehicle 10 from the start of use of engine oil. When the mileage reaches or exceeds the oil change judgment value, the electronic control unit 20 notifies the user of the vehicle 10 that the engine oil needs to be changed. When the electronic control unit 20 determines that cold friction has increased, it performs the process when cold friction has increased by setting the oil change judgment value to a smaller value compared to when it determines that cold friction has not increased.

[0025] In addition, in a vehicle equipped with an automatic transmission, the following processing may be included in the processing when cold friction increases. The automatic transmission is provided with a clutch that connects and disconnects the power transmission between the transmission input shaft and the transmission output shaft. This clutch is in a disengaged state in the neutral range and in an engaged state in the drive range. When the clutch is engaged when switching from the neutral range to the drive range, the number of rotating elements that rotate together with the transmission input shaft increases. As a result, the drag torque of the torque converter and the lockup clutch increases. When the drag torque increases, the rotation load of the engine 11 increases. Therefore, when switching from the neutral range to the drive range, the electronic control unit 20 increases the engine output to offset the increase in the rotation load due to the increase in the drag torque. However, it takes a certain amount of time to increase the engine output. Therefore, the electronic control unit 20 gradually engages the clutch over time. On the other hand, when the cold friction increases, it takes a longer time to increase the engine output when the vehicle is cold. Therefore, in a vehicle equipped with an automatic transmission, when cold friction increases, a process for making the time required for clutch engagement longer than normal may be performed as a cold friction increasing process.

[0026] Furthermore, in a hybrid vehicle equipped with an engine 11 and a generator motor, the following processing may be included in the cold friction increase processing. In a hybrid vehicle, the engine torque and the power running and regenerative torque of the generator motor are controlled to maintain the battery charge at a target value. Meanwhile, in a hybrid vehicle, the engine 11 is operated intermittently depending on the driving conditions and the battery charge state. The engine 11 is restarted during intermittent operation using the power of the generator motor. When cold friction increases, more power is required to restart the engine 11 when it is cold. Therefore, in such a hybrid vehicle, when cold friction increases, processing to increase the target value of the battery charge amount from normal should be performed as cold friction increase processing.

[0027] <Effects of the embodiment> The operation and effects of this embodiment will be described. The properties of soot generated by the combustion of the air-fuel mixture change depending on the combustion state of the air-fuel mixture. Depending on the properties of the soot, the viscosity at low temperatures may increase significantly even if the soot concentration of the engine oil is low. On the other hand, depending on the properties of the soot, the viscosity at low temperatures may not increase significantly even if the soot concentration of the engine oil is high. Therefore, it may not be possible to appropriately determine whether the cold friction of the engine 11 is increased based only on the soot concentration of the engine oil.

[0028] In contrast, in this embodiment, the low-temperature viscosity increase amount VS of the engine oil is calculated based on the increase in soot concentration in the engine oil and the average rotation speed MNE and the average air-fuel ratio MABF, which are state quantities indicating the combustion state of the mixture. Therefore, the low-temperature viscosity increase amount VS can be calculated in a form that reflects the difference in the effect that the difference in soot properties has on the low-temperature viscosity of the engine oil. Then, in this embodiment, based on the calculation result of the low-temperature viscosity increase amount VS, it is determined whether or not the cold friction of the engine 11 is in a state of increased. Therefore, it is possible to accurately determine whether or not the cold friction of the engine 11 is in a state of increased due to the inclusion of soot in the engine oil.

[0029] This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction. As the process for increasing cold friction, a process different from the process described above may be performed.

[0030] In the above embodiment, the calculation of the increase in soot concentration and the increase in viscosity at low temperatures, and the determination of the increase in cold friction are performed for each trip of the vehicle 10. These calculations and determinations may be performed at different intervals.

[0031] In the above embodiment, the viscosity increase amount at low temperatures VS is calculated using the average engine speed MNE and the average air-fuel ratio MABF as state quantities indicating the combustion state of the mixture. Other state quantities indicating the combustion state of the mixture, such as engine water temperature, may be used to calculate the viscosity increase amount at low temperatures VS.

[0032] The vehicle control device of the above embodiment can also be applied to engines other than diesel engines, such as gasoline engines, as long as the engine experiences increased cold friction due to soot mixed into the engine oil. [Explanation of symbols]

[0033] 10…Vehicle 11...Diesel engine 12…Combustion chamber 13…Intake passage 14...Exhaust passage 15...Air flow meter 16...Throttle valve 17...Fuel injector 18…Crankshaft 19...Crank angle sensor 20...Electronic control unit 21…Ignition switch 22... Processing equipment 23…Storage device

Claims

[Claim 1] A device for controlling a vehicle equipped with an engine, An increase amount calculation process for calculating an increase amount of soot concentration in engine oil based on an operating state of the engine; An increase amount calculation process for calculating an increase amount of viscosity of the engine oil at low temperature; a determination process for determining whether or not the cold friction of the engine is increased based on a calculation result of the increase amount; Do the following: In the increase amount calculation process, a viscosity increase rate is calculated so that the viscosity increase rate increases as the product of an average engine speed during a period from the start to the end of a trip of the vehicle and an average air-fuel ratio during a period from the start to the end of a trip of the vehicle increases, and a value obtained by multiplying the increase amount by the viscosity increase rate is calculated as the increase amount. Vehicle control device.

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