Hybrid vehicle control device

Abstract

To suppress emission of ammonia to outside air.SOLUTION: An electronic control unit 30 executes stoichiometric combustion in a prescribed period, and then starts rich combustion, when switching to the rich combustion is required during lean combustion of an internal combustion engine 10. The electronic control unit 30 compensates decrease of a torque of the internal combustion engine 10 caused by execution of the stoichiometric combustion instead of the rich combustion by increase of a torque of an electric motor 11, during the execution of the stoichiometric combustion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Devices for purifying exhaust gas from internal combustion engines include exhaust gas purification catalysts such as three-way catalysts, oxidation catalysts, and NOx storage reduction catalysts. Exhaust gas purification catalysts generate hydrogen through catalytic action when exhaust gas containing hydrocarbons, carbon monoxide, and water flows into them. Furthermore, when this hydrogen reacts with nitrogen oxides in the exhaust gas, ammonia is generated. The generation of ammonia in such exhaust gas purification catalysts is likely to occur immediately after the air-fuel ratio of an internal combustion engine changes from a lean air-fuel ratio to a rich air-fuel ratio.

[0003] A control device for an internal combustion engine described in Patent Document 1 is known as a technology for suppressing the release of ammonia generated in an exhaust gas purification catalyst into the outside air. The internal combustion engine controlled by the control device described in this document is equipped with an exhaust gas recirculation device that recirculates into the intake air a portion of the exhaust gas flowing in the portion of the exhaust passage downstream of the exhaust gas purification catalyst. In such an internal combustion engine, a portion of the ammonia generated in the exhaust gas purification catalyst is recirculated into the intake air together with the exhaust gas and burned in the combustion chamber. The control device for an internal combustion engine described in Patent Document 1 suppresses the release of ammonia into the outside air by increasing the amount of exhaust gas recirculated when switching from a lean air-fuel ratio to a rich air-fuel ratio, thereby increasing the amount of ammonia recirculated into the intake air together with the exhaust gas. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-100067 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a limit to how much recirculated exhaust gas can be increased, which would cause deterioration of combustion. Therefore, in the internal combustion engine described in Patent Document 1, when a large amount of ammonia is generated in the exhaust purification catalyst, it may not be possible to sufficiently suppress the release of ammonia into the outside air. [Means for solving the problem]

[0006] A hybrid vehicle control device that solves the above problem controls a hybrid vehicle that has, as drive sources, an internal combustion engine with an exhaust purification catalyst installed in the exhaust passage and an electric motor. When a switch to rich combustion is requested during lean combustion of the internal combustion engine, the hybrid vehicle control device performs a first process that controls the air-fuel ratio of the internal combustion engine so that rich combustion begins after stoichiometric combustion has been performed for a predetermined period. Furthermore, the control device performs a second process that increases the torque of the electric motor while stoichiometric combustion is being performed for the predetermined period by the first process.

[0007] During lean combustion, the concentration of nitrogen oxides in the exhaust gas increases. Therefore, a large amount of nitrogen oxides remains in the exhaust gas purification catalyst immediately after switching from lean combustion to stoichiometric combustion or rich combustion. On the other hand, during rich combustion, the concentrations of carbon monoxide and hydrocarbons in the exhaust gas increase. Therefore, if rich combustion is requested during lean combustion and the combustion is immediately switched to rich combustion, the amount of ammonia produced in the exhaust gas purification catalyst is likely to increase.

[0008] In contrast, in the above-mentioned control device, when rich combustion is requested during lean combustion, stoichiometric combustion is performed for a predetermined period before rich combustion is started. That is, in the above-mentioned control device, stoichiometric combustion is performed during the period when nitrogen oxides remain in the exhaust purification catalyst immediately after the end of lean combustion. During stoichiometric combustion, the concentrations of carbon monoxide and hydrocarbons in the exhaust are low, so even if nitrogen oxides remain in the exhaust purification catalyst, ammonia is unlikely to be generated. Then, in the above-mentioned control device, rich combustion is started after the nitrogen oxides remaining in the exhaust purification catalyst have decreased. Therefore, the generation of ammonia in the exhaust purification catalyst is suppressed. Therefore, the above-mentioned control device for an internal combustion engine has the effect of suppressing the release of ammonia into the outside air.

[0009] However, when transitioning from lean combustion to rich combustion via stoichiometric combustion, the torque of the internal combustion engine rises more slowly than when transitioning directly from lean combustion to rich combustion. Therefore, simply performing stoichiometric combustion for the predetermined period as described above may temporarily result in a shortage of drive torque for the hybrid vehicle. In response to this, the control device increases the torque of the electric motor while stoichiometric combustion is being performed. This increased torque of the electric motor reduces the shortage of drive torque that would otherwise occur when performing stoichiometric combustion to suppress the release of ammonia into the atmosphere. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating a schematic configuration of an embodiment of a control device for a hybrid vehicle; [Figure 2] 4 is a flowchart of a combustion switching control routine executed by the control device of the embodiment. [Figure 3] 10 is a flowchart of a second combustion switching control routine executed by a modified example of the control device for a hybrid vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of a control device for a hybrid vehicle will be described in detail below with reference to FIGS. <Configuration of a control device for a hybrid vehicle> First, the configuration of the drive system of a hybrid vehicle C to which the vehicle control device of this embodiment is applied will be described with reference to Fig. 1. As shown in Fig. 1, the hybrid vehicle C includes an internal combustion engine 10 and an electric motor 11 as drive sources for traveling.

[0012] The internal combustion engine 10 has multiple combustion chambers 12, an intake passage 13, and an exhaust passage 14. The intake passage 13 is a passage through which intake air is introduced into each combustion chamber 12. The exhaust passage 14 is a passage through which exhaust gas is discharged from each combustion chamber 12. A throttle valve 15, which is a valve that changes the flow area of ​​the intake air, is provided in the intake passage 13. An exhaust purification catalyst 16 is provided in the exhaust passage 14. Examples of the exhaust purification catalyst 16 include a three-way catalyst, an oxidation catalyst, and a NOx storage reduction catalyst. An ignition device 17 that ignites the air-fuel mixture by spark discharge is provided in each combustion chamber 12. Furthermore, the internal combustion engine 10 has an individual injector 18 for each combustion chamber 12. The injector 18 injects fuel such as gasoline or diesel into the intake air introduced into the combustion chamber 12 through the intake passage 13.

[0013] A crankshaft 19, which is the output shaft of the internal combustion engine 10, is mechanically connected to a rotating shaft 21 of the electric motor 11 via a clutch 20. Furthermore, the rotating shaft 21 of the electric motor 11 is mechanically connected to wheels 24 via a transmission 22 and a differential 23. Furthermore, the electric motor 11 is electrically connected to a battery 26 via an inverter 25.

[0014] The control device for the hybrid vehicle C includes an electronic control unit 30. The electronic control unit 30 includes a processing unit 31 and a storage unit 32. The storage unit 32 stores programs and data for vehicle control. The processing unit 31 reads and executes programs from the storage unit 32 to perform various processes for controlling the hybrid vehicle C. The electronic control unit 30 receives detection signals from sensors installed in various parts of the hybrid vehicle C. These sensors include an air flow meter 33, a crank angle sensor 34, a water temperature sensor 35, an accelerator pedal sensor 36, and a vehicle speed sensor 37. The air flow meter 33 detects an intake air amount GA, which is the flow rate of intake air flowing through the intake passage 13. The crank angle sensor 34 detects a rotation angle of the crankshaft 19. The water temperature sensor 35 detects an engine water temperature THW, which is the temperature of the coolant for the internal combustion engine 10. The accelerator pedal sensor 36 detects an accelerator pedal depression amount ACC, which is the amount of accelerator pedal depression by the driver. The vehicle speed sensor 37 is a sensor that detects the vehicle speed SPD, which is the traveling speed of the hybrid vehicle C. The electronic control unit 30 obtains the engine speed NE, which is the rotation speed of the crankshaft 19, from the detection result of the crank angle sensor .

[0015] The electronic control unit 30 controls the internal combustion engine 10, the electric motor 11, the clutch 20, and the transmission 22 based on the detection results of these sensors, thereby controlling the hybrid vehicle C. The electronic control unit 30 controls the internal combustion engine 10 by manipulating the opening of the throttle valve 15, the ignition timing of the ignition device 17, the fuel injection amount of the injector 18, etc. The electronic control unit 30 also controls the torque of the electric motor 11 through the operation of the inverter 25. The electronic control unit 30 also controls the gear ratio of the transmission 22 based on the accelerator pedal operation amount ACC and the vehicle speed SPD.

[0016] <Drive control of hybrid vehicle C> Next, the drive control of the hybrid vehicle C executed by the electronic control unit 30 will be described. When controlling the drive of the hybrid vehicle C, the electronic control unit 30 first calculates a required drive torque based on the accelerator pedal operation amount ACC and the vehicle speed SPD. The required drive torque is a required value of torque input from the rotating shaft 21 of the electric motor 11 to the transmission 22. Next, the electronic control unit 30 distributes the required drive torque into a target engine torque TE* and a target motor torque TM*. The target engine torque TE* is a target value of torque to be generated in the internal combustion engine 10. The target motor torque TM* is a target value of torque to be generated in the electric motor 11. The electronic control unit 30 operates the inverter 25 so that the electric motor 11 generates a torque equal to the target motor torque TM*. The electronic control unit 30 also calculates operation amounts of the internal combustion engine 10, such as the opening of the throttle valve 15, the ignition timing of the ignition device 17, and the fuel injection amount of the injector 18, required to generate a torque equal to the target engine torque TE*. The electronic control unit 30 then operates the throttle valve 15, the ignition device 17, the injector 18, etc. in accordance with the calculated operation amount.

[0017] The electronic control unit 30 adjusts the air-fuel ratio of the mixture burned in the combustion chamber 12 according to the operating conditions of the internal combustion engine 10. For example, when the hybrid vehicle C accelerates, the electronic control unit 30 adjusts the air-fuel ratio to a rich air-fuel ratio that is richer than the stoichiometric air-fuel ratio. Furthermore, when the hybrid vehicle C is operating under a light load, the electronic control unit 30 adjusts the air-fuel ratio to a lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratio. The electronic control unit 30 also adjusts the air-fuel ratio based on the warm-up conditions of the internal combustion engine 10 and the exhaust purification catalyst 16. The electronic control unit 30 adjusts the air-fuel ratio by controlling the opening of the throttle valve 15 and the amount of fuel injected by the injector 18. In the following description, combustion of a mixture with a stoichiometric air-fuel ratio will be referred to as stoichiometric combustion, combustion of a mixture with a rich air-fuel ratio will be referred to as rich combustion, and combustion of a mixture with a lean air-fuel ratio will be referred to as lean combustion.

[0018] <Control when switching combustion> The electronic control unit 30 switches the combustion of the internal combustion engine 10 from lean combustion to rich combustion, for example, when accelerating the hybrid vehicle C. Next, the control when switching combustion from lean combustion to rich combustion will be described.

[0019] 2 shows a flowchart of a combustion switching control routine executed by the electronic control unit 30. The electronic control unit 30 repeatedly executes this routine at predetermined control intervals while the internal combustion engine 10 is in operation.

[0020] When this routine starts, the electronic control unit 30 first updates the value of the integrated intake air amount IGA, which is the integrated value of the intake air amount GA, in step S100. Specifically, the electronic control unit 30 updates the value of the integrated intake air amount IGA by setting the updated value to the sum of the value before the update and the current intake air amount GA.

[0021] Next, in step S110, the electronic control unit 30 determines whether the internal combustion engine 10 is in lean combustion. If the internal combustion engine 10 is in lean combustion (YES), the electronic control unit 30 resets the value of the integrated intake air amount IGA to "0" in step S120 and then proceeds to step S130. On the other hand, if the internal combustion engine 10 is not in lean combustion (NO), that is, if the internal combustion engine 10 is in stoichiometric combustion or rich combustion, the electronic control unit 30 skips step S120 and proceeds to step S130. In this way, the value of the integrated intake air amount IGA is reset to "0" during lean combustion. Therefore, the value of the integrated intake air amount IGA represents the integrated value of the intake air amount GA from the time when the combustion of the internal combustion engine 10 was switched from lean combustion to stoichiometric combustion or rich combustion.

[0022] In step S130, the electronic control unit 30 determines whether the cumulative intake air amount IGA is equal to or greater than a predetermined value X. If the cumulative intake air amount IGA is equal to or greater than the predetermined value X (YES), the electronic control unit 30 ends the processing of this routine for the current control cycle. On the other hand, if the cumulative intake air amount IGA is less than the predetermined value X (NO), the electronic control unit 30 proceeds to step S140.

[0023] In step S140, the electronic control unit 30 prohibits rich combustion. Subsequently, in step S150, the electronic control unit 30 determines whether rich combustion is requested. If rich combustion is not requested (NO), the electronic control unit 30 ends the processing of this routine for the current control cycle. On the other hand, if rich combustion is requested (YES), the electronic control unit 30 proceeds to step S160.

[0024] Note that when the process proceeds to step S160, rich combustion is prohibited (S150). Therefore, at this time, the electronic control unit 30 controls the air-fuel ratio so that the combustion in the internal combustion engine 10 is stoichiometric combustion. When stoichiometric combustion is performed in this manner, the torque of the internal combustion engine 10 is lower than when rich combustion is performed as requested. In response to this, the electronic control unit 30 calculates the torque decrease amount ΔTE of the internal combustion engine 10 in step S160. Then, in the next step S170, the electronic control unit 30 adds the calculated torque decrease amount ΔTE of the internal combustion engine 10 to the target motor torque TM*. Thereafter, the electronic control unit 30 ends the processing of this routine for the current control cycle.

[0025] In this embodiment, the processes of steps S100 to S140 in Fig. 2 correspond to the first process, and the processes of steps S150 to S170 in Fig. 2 correspond to the second process.

[0026] <Actions and Effects of the Embodiment> The operation and effects of the present embodiment configured as above will be described. During lean combustion, the concentration of nitrogen oxides in the exhaust gas increases. Therefore, a large amount of nitrogen oxides remains in the exhaust gas purification catalyst 16 immediately after switching from lean combustion to stoichiometric combustion or rich combustion. On the other hand, during rich combustion, the concentrations of carbon monoxide and hydrocarbons in the exhaust gas increase. Immediately after switching the combustion of the internal combustion engine 10 from lean combustion to rich combustion, nitrogen oxides are present in the exhaust gas purification catalyst 16. When rich combustion is started in this state and exhaust gas with high concentrations of carbon monoxide and hydrocarbons flows into the exhaust gas purification catalyst 16, ammonia is likely to be produced.

[0027] In response to this, the electronic control unit 30 prohibits rich combustion when the cumulative intake air amount IGA is less than the predetermined value X. In other words, even when rich combustion is requested during lean combustion, the electronic control unit 30 performs stoichiometric combustion until the cumulative intake air amount IGA becomes equal to or greater than the predetermined value X. During stoichiometric combustion, the concentrations of carbon monoxide and hydrocarbons in the exhaust are low, so even if nitrogen oxides remain in the exhaust purification catalyst 16, ammonia is unlikely to be generated. The amount of nitrogen oxides remaining in the exhaust purification catalyst 16 decreases during stoichiometric combustion. In this way, the electronic control unit 30 starts rich combustion after the amount of nitrogen oxides remaining in the exhaust purification catalyst 16 has decreased. Therefore, the generation of ammonia in the exhaust purification catalyst 16 is suppressed. As a result, the release of ammonia into the outside air is suppressed.

[0028] As described above, during stoichiometric combustion, the nitrogen oxides remaining in the exhaust purification catalyst 16 gradually decrease. At this time, the decrease in the nitrogen oxides remaining in the exhaust purification catalyst 16 becomes faster as the exhaust flow rate increases. Meanwhile, the exhaust flow rate is roughly proportional to the intake air amount GA. Therefore, based on the integrated value of the intake air amount GA after the start of stoichiometric combustion, it is possible to determine the time when the nitrogen oxides remaining in the exhaust purification catalyst 16 will have sufficiently decreased. Therefore, the electronic control unit 30 starts rich combustion when the integrated intake air amount IGA after the start of stoichiometric combustion becomes equal to or greater than a predetermined value X.

[0029] However, when transitioning from lean combustion to rich combustion via stoichiometric combustion, the torque of the internal combustion engine 10 rises more slowly than when transitioning directly from lean combustion to rich combustion. In response to this, the electronic control unit 30 calculates the torque reduction ΔTE of the internal combustion engine 10 caused by implementing stoichiometric combustion instead of the required rich combustion. The electronic control unit 30 then increases the torque of the electric motor 11 by a value equal to the torque reduction ΔTE. This prevents a shortage of drive torque for the hybrid vehicle C caused by implementing stoichiometric combustion instead of rich combustion.

[0030] <Other embodiments> (Switching from rich combustion to lean combustion) When switching from rich combustion to lean combustion, ammonia may be generated due to a mixture of carbon monoxide, hydrocarbons, and nitrogen oxides inside the exhaust purification catalyst 16. Therefore, even when switching to lean combustion is requested during rich combustion, the electronic control unit 30 may be configured to start lean combustion after performing stoichiometric combustion for a predetermined period.

[0031] 3 shows a flowchart of a second combustion switching control routine executed by the electronic control unit 30. The electronic control unit 30 repeatedly executes this routine at predetermined control intervals while the internal combustion engine 10 is in operation.

[0032] When this routine starts, the electronic control unit 30 first updates the value of the integrated intake air amount IGA in step S200, similar to step S100 in FIG. 2. Next, in step S210, the electronic control unit 30 determines whether the internal combustion engine 10 is performing rich combustion. If the internal combustion engine 10 is performing rich combustion (YES), the electronic control unit 30 resets the integrated intake air amount IGA to "0" in step S220 and then proceeds to step S230. If the electronic control unit 30 is not performing rich combustion (NO), the electronic control unit 30 skips step S220 and proceeds to step S230. In step S230, the electronic control unit 30 determines whether the integrated intake air amount IGA is equal to or greater than a predetermined value X. If the integrated intake air amount IGA is equal to or greater than the predetermined value X (YES), the electronic control unit 30 immediately ends the processing of this routine for the current control cycle. On the other hand, if the cumulative intake air amount IGA is less than the predetermined value X (NO), the electronic control unit 30 proceeds to step S240.

[0033] In step S240, the electronic control unit 30 prohibits lean combustion. Subsequently, in step S250, the electronic control unit 30 determines whether lean combustion is requested. If lean combustion is not requested (NO), the electronic control unit 30 ends the processing of this routine for the current control cycle. On the other hand, if lean combustion is requested (YES), the electronic control unit 30 proceeds to step S260. In this case, since lean combustion is prohibited, the electronic control unit 30 controls the air-fuel ratio of the internal combustion engine 10 to perform stoichiometric combustion.

[0034] When stoichiometric combustion is performed instead of lean combustion, the torque of the internal combustion engine 10 increases. In step S260, the electronic control unit 30 calculates the torque increase amount ΔTE1 of the internal combustion engine 10. Then, in the next step S270, the electronic control unit 30 subtracts the calculated torque increase amount ΔTE1 of the internal combustion engine 10 from the target motor torque TM*. Thereafter, the electronic control unit 30 ends the processing of this routine for the current control cycle.

[0035] In this case, when switching from rich combustion to lean combustion, the amount of ammonia generated in the exhaust purification catalyst 16 decreases. As a result, the release of ammonia into the outside air is suppressed. Furthermore, the electronic control unit 30 reduces the torque of the electric motor 11 by the amount that the torque of the internal combustion engine 10 has increased by performing stoichiometric combustion instead of lean combustion. Therefore, it is possible to appropriately generate drive torque for the hybrid vehicle C even while performing stoichiometric combustion.

[0036] The processes of steps S200 to S240 in Fig. 3 correspond to the third process, and the processes of steps S250 to S270 in Fig. 3 correspond to the fourth process. Furthermore, the above-described embodiment can be modified and implemented as follows: The above-described embodiment and the following modifications can be implemented in combination with each other within the scope of technical compatibility.

[0037] The predetermined period during which stoichiometric combustion is performed instead of rich or lean combustion may be determined by a parameter other than the cumulative intake air amount IGA. For example, the predetermined period during which stoichiometric combustion is performed may be determined by the cumulative value of the fuel injection amount after the start of stoichiometric combustion or the elapsed time after the start of stoichiometric combustion.

[0038] The control device of the above embodiment can also be applied to hybrid vehicles with a configuration different from that shown in FIG. 1, such as a hybrid vehicle equipped with a plurality of electric motors. [Explanation of symbols]

[0039] 10...internal combustion engine, 11...electric motor, 12...combustion chamber, 13...intake passage, 14...exhaust passage, 15...throttle valve, 16...exhaust purification catalyst, 17...ignition device, 18...injector, 19...crankshaft, 20...clutch, 21...rotating shaft, 22...transmission, 23...differential, 24...wheel, 25...inverter, 26...battery, 30...electronic control unit, 31...processing device, 32...storage device, 33...air flow meter, 34...crank angle sensor, 35...water temperature sensor, 36...accelerator pedal sensor, 37...vehicle speed sensor

Claims

1. A device for controlling a hybrid vehicle having an internal combustion engine with an exhaust purification catalyst installed in an exhaust passage and an electric motor as drive sources, a first process for controlling the air-fuel ratio of the internal combustion engine so that, when a switch to rich combustion is requested during lean combustion of the internal combustion engine, rich combustion is started after stoichiometric combustion is performed for a predetermined period of time; a second process for increasing the torque of the electric motor during the execution of stoichiometric combustion for the predetermined period by the first process; A control device for a hybrid vehicle that performs the above.

2. 2. The control device for a hybrid vehicle according to claim 1, wherein the predetermined period is a period from the start of stoichiometric combustion until an integrated intake air amount of the internal combustion engine reaches or exceeds a predetermined value.

3. a third process for controlling the air-fuel ratio of the internal combustion engine so that, when a switch to lean combustion is requested during rich combustion of the internal combustion engine, lean combustion is started after stoichiometric combustion is performed for a predetermined period of time; a fourth process of reducing the torque of the electric motor during the execution of stoichiometric combustion for the predetermined period by the third process; 2. The control device for a hybrid vehicle according to claim 1, wherein the control device performs the following.

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