Vehicle control device

Abstract

To suppress water generated by combustion from mixing into engine oil.SOLUTION: An electronic control unit 30 estimates a water residual amount in a combustion chamber 20, and, if the estimated water residual amount is equal to or more than a predetermined value, sets, as a target air-fuel ratio of a hydrogen gas engine 10, an air-fuel ratio leaner than that in a case less than the predetermined value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device. [Background technology]

[0002] Patent Document 1 describes driving the engine of a hybrid vehicle at an optimum operating point for improving fuel economy. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5522266 Summary of the Invention [Problem to be solved by the invention]

[0004] In a hydrogen engine that uses hydrogen gas as fuel, water is produced by the combustion of hydrogen gas in the combustion chamber. The water produced by the combustion is discharged from the combustion chamber along with the exhaust. However, when the engine displacement is small, some of the water may remain in the combustion chamber. This water may then be mixed into the engine oil, potentially reducing the lubricating performance of the engine oil. [Means for solving the problem]

[0005] A vehicle control device that solves the above problem controls a vehicle equipped with a hydrogen engine and a transmission connected to the hydrogen engine, and executes the following steps: a calculation process to calculate the required output of the hydrogen engine, a setting process to set a target air-fuel ratio for the hydrogen engine, a control process to control the hydrogen engine and the transmission so that the hydrogen engine operates at an operating point where an engine output equal to the required output and an air-fuel ratio equal to the target air-fuel ratio are obtained, and an estimation process to estimate the amount of remaining water, which is the amount of water that remains in the combustion chamber of the hydrogen engine without being discharged into the exhaust passage. When the amount of remaining water is equal to or greater than a predetermined value, the setting process in the control device sets the target air-fuel ratio to a leaner value than when the amount of remaining water is less than the predetermined value.

[0006] When the remaining water amount is equal to or greater than a predetermined value, the vehicle control device controls the hydrogen engine and the transmission so that the air-fuel ratio is leaner than when the remaining water amount is less than the predetermined value. The amount of water produced in the combustion chamber of a hydrogen engine is proportional to the amount of hydrogen gas burned in the combustion chamber. Meanwhile, the greater the amount of exhaust gas discharged from the combustion chamber, the more likely the water in the combustion chamber is to be discharged from the combustion chamber into the exhaust passage along with the exhaust. When the air-fuel ratio shifts to the lean side, the ratio of the amount of exhaust gas discharged from the combustion chamber to the amount of water produced in the combustion chamber increases. Therefore, when the target air-fuel ratio is shifted to the lean side, the ratio of the amount of water discharged into the exhaust passage to the amount of water produced in the combustion chamber increases. This reduces the amount of water remaining in the combustion chamber without being discharged into the exhaust passage, and therefore reduces the amount of water mixed into the engine oil. Therefore, the vehicle control device achieves the effect of suppressing water contamination into engine oil. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating a configuration of an embodiment of a vehicle control device; [Figure 2] 4 is a graph showing the relationship between the rotation speed and torque of a hydrogen engine and the target air-fuel ratio. [Figure 3] 2 is a flowchart of a drive control routine executed by the vehicle control device of FIG. [Figure 4]3 is a diagram showing a setting manner of a target operating point of the vehicle control device. FIG. [Figure 5] FIG. 10 is a diagram illustrating a setting mode of a target operating point in another embodiment of a vehicle control device. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a vehicle control device will be described in detail below with reference to FIGS. <Configuration of vehicle control device> First, the configuration of the vehicle control device of this embodiment will be described with reference to Fig. 1. As shown in Fig. 1, a vehicle C to be controlled by the vehicle control device of this embodiment is equipped with a hydrogen engine 10 and two generator motors. In the following description, the two generator motors will be referred to as MG1 and MG2, respectively. MG1 is connected to the hydrogen engine 10. MG2 is connected to wheels 12 via a transmission 11. MG1 and MG2 are connected to a battery 15 via inverters 13 and 14, respectively.

[0009] The hydrogen engine 10 is an internal combustion engine that uses hydrogen gas as fuel. The hydrogen engine 10 has multiple combustion chambers 20, intake passages 21 that are passages through which intake air is introduced into each combustion chamber 20, and exhaust passages 22 that are passages through which exhaust gas is discharged from each combustion chamber 20. A throttle valve 23 that is a valve that changes the flow area of the intake air is provided in the intake passage 21. A catalyst 24 for purifying exhaust gas is provided in the exhaust passage 22. The catalyst 24 is, for example, an NSR (NOx storage reduction) catalyst. Furthermore, the hydrogen engine 10 has an individual injector 25 for each combustion chamber 20. The injector 25 injects hydrogen gas into the intake air that is introduced into the combustion chamber 20 through the intake passage 21.

[0010] The vehicle C is also equipped with an electronic control unit 30 as a vehicle control device. The electronic control unit 30 includes a processing unit 31 and a storage device 32. The storage device 32 stores programs and data for vehicle control. The processing unit 31 reads and executes the programs from the storage device 32 to perform various processes for vehicle control. The electronic control unit 30 controls the operating state of the hydrogen engine 10 by controlling the opening of the throttle valve 23 and the amount of hydrogen gas injected by the injector 25. The electronic control unit 30 also controls the regeneration / powering torque of MG1 and MG2 by controlling the drive of the inverters 13 and 14.

[0011] The electronic control unit 30 is connected to sensors installed in various parts of the vehicle C, such as a crank angle sensor 33, a water temperature sensor 34, an outside air temperature sensor 35, an accelerator pedal sensor 36, and a vehicle speed sensor 37. The crank angle sensor 33 detects the rotation angle of the crankshaft, which is the output shaft of the hydrogen engine 10. The water temperature sensor 34 detects the engine water temperature THW, which is the temperature of the cooling water of the hydrogen engine 10. The outside air temperature sensor 35 detects the outside air temperature THA of the vehicle C. The accelerator pedal sensor 36 detects the accelerator pedal operation amount ACC, which is the amount of depression of the accelerator pedal by the driver of the vehicle C. The vehicle speed sensor 37 detects the vehicle speed SPD, which is the traveling speed of the vehicle C. The electronic control unit 30 calculates the engine speed NE, which is the rotation speed of the crankshaft of the hydrogen engine 10, from the detection result of the crank angle sensor 33.

[0012] <Control of hydrogen engine 10> The electronic control unit 30 sets a target air-fuel ratio based on the engine speed NE and engine torque TE. The electronic control unit 30 then controls the opening of the throttle valve 23 and the amount of hydrogen gas injected by the injector 25 so that the air-fuel ratio of the mixture burned in the combustion chamber 20 matches the target air-fuel ratio. Therefore, in this embodiment, once the operating point of the hydrogen engine 10, which is determined by the engine speed NE and engine torque TE, is determined, the value of the target air-fuel ratio is also determined.

[0013] Fig. 2 shows how the target air-fuel ratio is set. The four curves shown in the graph in Fig. 2 indicate operating lines of the hydrogen engine 10 where the target air-fuel ratios are λ1 to λ4. The values of λ1 to λ4 increase in the order of λ1, λ2, λ3, and λ4, in other words, they indicate air-fuel ratios on the lean side.

[0014] <Vehicle drive control> Next, the drive control of the vehicle C executed by the electronic control unit 30 will be described with reference to Figures 3 and 4. Figure 3 shows a flowchart of a drive control routine executed by the electronic control unit 30 to control the drive of the vehicle C. The electronic control unit 30 repeatedly executes this routine at predetermined control intervals while the hydrogen engine 10 is operating.

[0015] When this routine starts, the electronic control unit 30 first calculates the required output of the hydrogen engine 10 in step S100 based on the accelerator pedal depression amount ACC, vehicle speed SPD, etc. The required output represents the engine output necessary to generate the driving force of the vehicle C requested by the driver by depressing the accelerator pedal.

[0016] In step S110, the electronic control unit 30 also estimates the amount of remaining water in the combustion chamber 20 of the hydrogen engine 10. When hydrogen gas is burned in the combustion chamber 20, water is produced. Some of the produced water may cool and condense on the walls of the combustion chamber 20, etc. The condensed liquid water may remain in the combustion chamber 20 without being discharged with the exhaust. The remaining water may then mix with the engine oil and reduce the lubrication performance of the oil. The amount of remaining water estimated by the electronic control unit 30 in step S110 represents the amount of water remaining in the combustion chamber 20. The amount of water produced by combustion is determined by the amount of hydrogen gas burned in the combustion chamber 20, i.e., the amount of hydrogen gas injected by the injector 25. The proportion of water condensing in the combustion chamber 20 increases as the temperature of the combustion chamber 20 decreases. Note that some of the condensed water is discharged from the combustion chamber 20 along with the exhaust flow. The amount of condensed water discharged increases as the exhaust flow rate increases. The flow rate of the exhaust gas is calculated based on the amount of intake air introduced into the combustion chamber 20 and the amount of hydrogen gas injected by the injector 25. Therefore, the electronic control unit 30 calculates an estimated value of the remaining water amount based on the amount of intake air, the amount of injected hydrogen gas, the engine water temperature THW, the outside air temperature THA, etc.

[0017] In the following step S120, the electronic control unit 30 determines whether the remaining water amount estimated in step S110 is equal to or greater than a predetermined value. If the remaining water amount is less than the predetermined value (NO), the electronic control unit 30 determines a target operating point for the hydrogen engine 10 using the first map M1 in step S130. On the other hand, if the remaining water amount is equal to or greater than the predetermined value (YES), the electronic control unit 30 determines a target operating point for the hydrogen engine 10 using the second map M2 in step S140. The target operating point indicates the target values for the engine speed NE and the engine torque TE.

[0018] After processing step S130 or step S140, the electronic control unit 30 controls the hydrogen engine 10 and MG1 in step S150 so that the hydrogen engine 10 operates at the target operating point. The electronic control unit 30 then ends the processing of this routine for the current control cycle. As mentioned above, the target air-fuel ratio of the hydrogen engine 10 is determined by the operating point. Therefore, the electronic control unit 30 indirectly sets the target air-fuel ratio by setting the target operating point.

[0019] Next, referring to FIG. 4, the manner in which the target operating point is set in the first map M1 and the second map M2 will be described. The first map M1, which is used when the remaining water amount is less than a predetermined value, is set to calculate, as the target operating point, an operating point on the curve L1 in FIG. 4 at which an engine output equal to the required output is obtained. On the other hand, the second map M2, which is used when the remaining water amount is equal to or greater than a predetermined value, is set to calculate, as the target operating point, an operating point on the curve L2 in FIG. 4 at which an engine output equal to the required output is obtained. For example, assume that the equal-power line L0 shown in FIG. 4 is the equal-power line corresponding to the current required output. In this case, in the first map M1, the operating point corresponding to the intersection P1 between the equal-power line L0 and the curve L1 is calculated as the target operating point. In addition, in the second map M2, the operating point corresponding to the intersection P2 between the equal-power line L0 and the curve L2 is calculated as the target operating point. As shown in FIG. 4, the curve L2 is located on the high-speed side and the low-torque side relative to the curve L1. Therefore, in the drive control routine, when the remaining amount of water is equal to or greater than a predetermined value, the electronic control unit 30 sets the target air-fuel ratio so that it is leaner than when the remaining amount of water is less than the predetermined value.

[0020] <Actions and Effects of the Embodiment> The operation and effects of this embodiment will be described. 3, the electronic control unit 30 performs a calculation process to calculate the required output of the hydrogen engine 10. In addition, in steps S120 and S130 of the same routine, the electronic control unit 30 sets a target operating point for the hydrogen engine 10. Then, in step S150 of the same routine, the electronic control unit 30 controls the hydrogen engine 10 and MG1 so that the hydrogen engine 10 operates at the target operating point.

[0021] Furthermore, in step S110 of the drive control routine, the electronic control unit 30 performs an estimation process to estimate the amount of remaining water in the combustion chamber 20 of the hydrogen engine 10. Then, in steps S130 and S140, if the estimated amount of remaining water is equal to or greater than a predetermined value, the electronic control unit 30 sets, as the target operating point, an operating point at which the target air-fuel ratio is set to a leaner value than when the amount of remaining water is less than the predetermined value. In this case, the target air-fuel ratio is determined along with the target operating point. Therefore, the processes in steps S130 and S140 for setting the target operating point are equivalent to setting the target air-fuel ratio of the hydrogen engine 10. In steps S130 and S140, the electronic control unit 30 sets, as the target operating point, an operating point at which an engine output equal to the required output is obtained. Therefore, in step S150 of FIG. 3, a control process is performed to control the hydrogen engine 10 and MG1 so that the hydrogen engine 10 operates at an operating point at which an engine output equal to the required output and an air-fuel ratio equal to the target air-fuel ratio are obtained.

[0022] The amount of water produced by the combustion of hydrogen gas in the combustion chamber 20 is proportional to the amount of hydrogen gas burned in the combustion chamber 20. Meanwhile, the greater the amount of exhaust gas discharged from the combustion chamber 20, the more likely the water in the combustion chamber 20 is to be discharged from the combustion chamber 20 into the exhaust passage 22 along with the exhaust. When the air-fuel ratio shifts to the lean side, the ratio of the amount of water produced in the combustion chamber 20 to the amount of exhaust gas discharged from the combustion chamber 20 decreases. This reduces the amount of residual water, which is the amount of water remaining in the combustion chamber 20 of the hydrogen engine 10 without being discharged into the exhaust passage 22. Therefore, shifting the target air-fuel ratio to the lean side reduces the amount of residual water. Furthermore, reducing the amount of residual water in the combustion chamber 20 also reduces the amount of water mixed into the engine oil. As a result, the degradation of the lubrication performance of the engine oil due to water contamination is suppressed.

[0023] Note that changing the air-fuel ratio by changing the opening of the throttle valve 23 changes the engine output. In contrast, in this embodiment, the air-fuel ratio is changed by changing the operating point of the hydrogen engine 10 while keeping the engine output constant. Therefore, the air-fuel ratio can be changed to reduce the amount of remaining water without changing the engine output.

[0024] <Other embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0025] (Changing the target air-fuel ratio depending on the driving mode) Some vehicles C have multiple driving modes. The driving modes include a driving mode that improves fuel efficiency and a driving mode that improves driving performance. The driving mode can be switched manually by the driver or automatically depending on the driving conditions of the vehicle C. The deterioration of engine oil circulation performance due to water generated by combustion in the hydrogen engine 10 can also be suppressed by changing the target air-fuel ratio depending on the driving mode.

[0026] An example of an embodiment of changing the target air-fuel ratio depending on the driving mode will be described. Here, it is assumed that three driving modes, namely, a fuel economy driving mode, a normal driving mode, and a power driving mode, are set for the vehicle C. The fuel economy driving mode is a driving mode that improves the fuel economy performance of the hydrogen engine 10 compared to the normal driving mode. The power driving mode is a driving mode that improves the driving performance of the vehicle C compared to the normal driving mode. Note that, in general, the fuel economy performance of the hydrogen engine 10 and the driving performance of the vehicle C are in a mutually exclusive relationship. Therefore, it can be said that the normal driving mode is a driving mode that improves the fuel economy performance of the hydrogen engine 10 compared to the power driving mode.

[0027] FIG. 5 shows an example of how the target operating point is set in each driving mode. In the normal driving mode, among the operating points on the curve L3 in FIG. 5, an operating point at which an engine output equal to the required output is obtained is set as the target operating point. In the fuel economy driving mode, among the operating points on the curve L4 in FIG. 5, an operating point at which an engine output equal to the required output is obtained is set as the target operating point. Furthermore, in the power driving mode, among the operating points on the curve L5 in FIG. 5, an operating point at which an engine output equal to the required output is obtained is set as the target operating point. Therefore, in the normal driving mode, an air-fuel ratio that is leaner than in the fuel economy driving mode is set as the target air-fuel ratio value. In the power driving mode, an air-fuel ratio that is leaner than in the normal driving mode is set as the target air-fuel ratio value.

[0028] In the power driving mode, the hydrogen engine 10 tends to operate at a high load more frequently. During high-load operation, the amount of water remaining in the combustion chamber 20 increases. Therefore, when the power driving mode is selected, the target air-fuel ratio is shifted to the lean side, which prevents deterioration of the lubrication performance of the engine oil due to water contamination. In contrast, in the fuel economy driving mode, the hydrogen engine 10 tends to operate at a high load less frequently. Therefore, even if the amount of water remaining in the combustion chamber 20 increases slightly, it is unlikely that water will be mixed into the engine oil to the extent that its lubrication performance deteriorates. Therefore, when the fuel economy driving mode is selected, the fuel economy performance of the hydrogen engine 10 can be further improved by shifting the target air-fuel ratio to the rich side.

[0029] Here, two of the three driving modes are selected. Of the two selected driving modes, the one that improves the fuel efficiency of the hydrogen engine 10 is designated as the second driving mode, and the other is designated as the first driving mode. In this case, in the example of Fig. 5, the target operating point is set so that the target air-fuel ratio in the first driving mode is leaner than in the second driving mode.

[0030] (Changing the target air-fuel ratio according to the rate of change in accelerator pedal operation amount) Changing the target air-fuel ratio of the hydrogen engine 10 according to the rate of change of the accelerator pedal depression amount ACC can also suppress deterioration of the lubrication performance of the engine oil due to water contamination. Specifically, when the rate of change of the accelerator pedal depression amount ACC is large, it is advisable to set the target air-fuel ratio so that it is leaner than when the rate of change is small. For example, when the rate of change of the accelerator pedal depression amount ACC is less than a predetermined value, an operating point on curve L3 in Figure 5 that obtains an engine output equal to the required output is set as the target operating point. Then, when the rate of change is equal to or greater than the predetermined value, an operating point on curve L5 in Figure 5 that obtains an engine output equal to the required output is set as the target operating point for a certain period thereafter.

[0031] When the driver requests rapid acceleration, the rate of change in the accelerator pedal depression amount ACC increases. In such a case, there is a high possibility that the hydrogen engine 10 will subsequently be operated at high power. This tends to increase the amount of water produced by combustion. Therefore, when the rate of change in the accelerator pedal depression amount ACC is large, it is desirable to change the target air-fuel ratio to the lean side to reduce the amount of water remaining in the combustion chamber 20.

[0032] (Vehicle drivetrain) Although the vehicle C shown in FIG. 1 is a series hybrid vehicle, the vehicle control device of the above embodiment can be similarly applied to a parallel hybrid vehicle equipped with a hydrogen engine 10. In a parallel hybrid vehicle, a generator motor is also included in the transmission connected to the engine. Through torque control of the generator motor, the operating point of the engine can be changed while keeping the engine output constant. Therefore, the drive control of the above embodiment can also be performed in a parallel hybrid vehicle equipped with a hydrogen engine 10.

[0033] Furthermore, in a vehicle equipped with an automatic transmission, the operating point of the engine can be changed while keeping the engine output constant by changing the gear ratio of the automatic transmission. Therefore, the drive control of the above embodiment can also be applied to a vehicle equipped with a hydrogen engine 10 and an automatic transmission. In this case, the automatic transmission corresponds to the power transmission connected to the hydrogen engine 10.

[0034] (Change in target air-fuel ratio) In the above embodiment, the hydrogen engine 10 is operated at a target air-fuel ratio by operating at a target operating point. After the target air-fuel ratio is set, the hydrogen engine 10 may be operated at the target air-fuel ratio only by engine control such as controlling the opening of the throttle valve 23 and the amount of hydrogen gas injected by the injector 25. [Explanation of symbols]

[0035] C...Vehicle MG1: First generator motor MG2: Second generator motor 10...Hydrogen engine 11...Gearbox 12...Wheel 13, 14...Inverter 15...Battery 20...Combustion chamber 21...Intake passage 22...Exhaust passage 23...Throttle valve 24...Catalyst 25...Injector 30...Electronic control unit 31...Processing equipment 32…Storage device 33...Crank angle sensor 34...Water temperature sensor 35...Outside air temperature sensor 36...Accelerator pedal sensor 37...Vehicle speed sensor

Claims

1. A control device for a vehicle equipped with a hydrogen engine and a transmission device connected to the hydrogen engine, comprising: A calculation process for calculating a required output of the hydrogen engine; a setting process for setting a target air-fuel ratio for the hydrogen engine; a control process for controlling the hydrogen engine and the transmission so that the hydrogen engine operates at an operating point where an engine output equal to the required output and an air-fuel ratio equal to the target air-fuel ratio are obtained; an estimation process for estimating a remaining water amount, which is the amount of water remaining in the combustion chamber of the hydrogen engine without being discharged into an exhaust passage; Run In addition, when the remaining amount of water is equal to or greater than a predetermined value, the setting process sets the target air-fuel ratio so that the air-fuel ratio is leaner than when the remaining amount of water is less than the predetermined value. Vehicle control device.

2. the vehicle has a first driving mode and a second driving mode that improves fuel economy of the hydrogen engine more than in the first driving mode, The setting process sets the target air-fuel ratio in the first running mode so that the air-fuel ratio is leaner than in the second running mode. The vehicle control device according to claim 1 .

3. 2. The vehicle control device according to claim 1, wherein the setting process sets the target air-fuel ratio so that, when a rate of change in accelerator pedal depression amount is large, the air-fuel ratio is leaner than when the rate of change is small.

4. 4. The vehicle control device according to claim 1, wherein the vehicle is a hybrid vehicle having a generator motor in the transmission device.

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