JP2015129473A - Hybrid electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an increase in NOx emission at a time of regenerating a NOx storage reduction catalyst.SOLUTION: A hybrid electric vehicle 1 comprises: an engine 10; a motor generator 20; a three-way catalyst 81 and a NOx storage reduction catalyst 82; and a control unit 100 controlling the engine 10 and the motor generator 20. The control unit 100 is configured to execute a catalyst regeneration operation for reducing NOx stored in the NOx storage reduction catalyst 82 and regenerating the NOx storage reduction catalyst 82 by operating the engine 10 in a state in which an air-fuel ratio is rich with respect to a stoichiometric air-fuel ratio. The control unit 100 temporarily stops supplying a fuel and restarts supplying the fuel in an operation state corresponding to an air-fuel ratio after transition during transition from a lean operation for operating the engine 10 in a state in which the air-fuel ratio is lean with respect to that during the catalyst regeneration operation to the catalyst regeneration operation or during transition from the catalyst regeneration operation to the lean operation.

Description

  The technology disclosed here relates to a hybrid vehicle including a NOx storage reduction catalyst.

  Conventionally, a hybrid vehicle in which an NOx storage reduction catalyst is provided in an exhaust passage is known. For example, in the hybrid vehicle according to Patent Document 1, when the NOx occlusion amount of the NOx occlusion reduction catalyst increases, the NOx occlusion reduction catalyst is regenerated. In regeneration of the NOx storage reduction catalyst, a rich operation is performed in which the air-fuel ratio of the engine is richer than the stoichiometric air-fuel ratio, and the stored NOx is reduced by the fuel.

JP 2008-68802 A

  However, when shifting from an operation in which the air-fuel ratio of the engine is leaner than that at the time of regeneration of the NOx storage reduction catalyst to a rich operation at the time of regeneration of the NOx storage reduction catalyst, the NOx emission amount may temporarily increase. The regeneration of the NOx occlusion reduction catalyst is performed when there is not much room for NOx occlusion by the NOx occlusion reduction catalyst, so it is not preferable that the NOx emission amount increase at this timing.

  The technique disclosed here reduces the amount of NOx emissions when the NOx storage reduction catalyst is regenerated.

  The hybrid vehicle disclosed herein includes an engine, a motor generator that is driven by the engine to generate electric power, a three-way catalyst and a NOx occlusion reduction catalyst provided in an exhaust system of the engine, the engine and the motor generator. A control unit that controls, and the control unit is configured to perform a catalyst regeneration operation for regenerating the NOx storage reduction catalyst by operating the engine in a state where the air-fuel ratio is richer than the stoichiometric air-fuel ratio. And when the engine is shifted from the lean operation in which the engine is operated in a leaner state than the catalyst regeneration operation to the catalyst regeneration operation, or when the catalyst regeneration operation is shifted to the lean operation. When the operation is shifted, the fuel supply to the engine is temporarily stopped and the engine is operated in the operation state corresponding to the air-fuel ratio after the shift. It is intended to resume the fuel supply.

  According to the above configuration, the three-way catalyst and the NOx storage reduction catalyst are provided in the exhaust passage. The three-way catalyst has different NOx purification characteristics depending on the air-fuel ratio. For example, a three-way catalyst exhibits high purification performance at a stoichiometric air-fuel ratio, and has a low NOx purification capacity in an environment where the air-fuel ratio is lean. Therefore, by providing the NOx storage reduction catalyst, it is possible to purify NOx in various operating states including lean operation.

  As the NOx storage amount increases, the NOx storage reduction catalyst eventually needs to perform a catalyst regeneration operation. In the catalyst regeneration operation, the air-fuel ratio of the engine is made rich, and NOx stored in the NOx storage reduction catalyst is reduced by the fuel.

  By the way, the NOx discharged from the combustion chamber of the engine increases in a slightly lean operating state near the stoichiometric air-fuel ratio. On the other hand, the purification performance of the three-way catalyst in such an operating state is slightly lower than the maximum performance, and as a result, the NOx emission amount downstream of the three-way catalyst cannot be sufficiently reduced. In other words, due to the relationship between the NOx emission amount from the combustion chamber with respect to the air-fuel ratio of the engine and the NOx purification performance of the three-way catalyst with respect to the air-fuel ratio of the engine, the NOx emission amount downstream of the three-way catalyst depends on the air-fuel ratio of the engine. There are cases where it cannot be reduced sufficiently.

  In the catalyst regeneration operation, since the air-fuel ratio of the engine is rich, the amount of NOx discharged from the combustion chamber is small, and the amount of NOx discharged downstream of the three-way catalyst is also small. However, when shifting to the catalyst regeneration operation, or when shifting from the catalyst regeneration operation, if the operation state after the transition is a lean operation state, the engine In some cases, the air-fuel ratio of the air-fuel ratio temporarily becomes an air-fuel ratio (ie, a lean air-fuel ratio near the stoichiometric air-fuel ratio) at which the amount of NOx emission downstream of the three-way catalyst increases. As a result, the NOx emission amount downstream of the three-way catalyst may increase.

  On the other hand, in the above configuration, when shifting from the lean operation to the catalyst regeneration operation, or when shifting from the catalyst regeneration operation to the lean operation, the fuel supply to the engine is temporarily stopped to correspond to the air-fuel ratio after the transition. The fuel supply to the engine is resumed in the operating state. In other words, while continuously changing the fuel supply amount, the air-fuel ratio corresponding to the operation state after transition (catalyst regeneration operation or lean operation) from the air-fuel ratio corresponding to the operation state before transition (lean operation or catalyst regeneration operation). The fuel supply is temporarily stopped (that is, the combustion is temporarily stopped), the operation state is changed to the operation state corresponding to the air-fuel ratio after the transition, and the fuel supply is performed in the operation state. To resume. In this way, the engine air-fuel ratio becomes the air-fuel ratio that increases the NOx emission downstream of the three-way catalyst when shifting from lean operation to catalyst regeneration operation or when shifting from catalyst regeneration operation to lean operation. Can be prevented. As a result, it is possible to suppress an increase in NOx emission when the NOx storage reduction catalyst is regenerated.

  Further, the control unit is configured to perform the lean operation during a power generation operation in which the motor generator is driven by the engine to generate power, and in the catalyst regeneration operation, the throttle valve is compared with during the power generation operation. May be closed.

  According to the above configuration, during the catalyst regeneration operation, the throttle valve is closed, so that the amount of fresh air is less than that during the power generation operation, and the load is low. Therefore, since the exhaust gas discharged from the combustion chamber is reduced, the NOx emission amount itself is also reduced.

  Furthermore, the control unit adjusts the throttle valve to an opening corresponding to the air-fuel ratio after the transition when restarting the fuel supply to the engine at the time of the transition to the operation, and then the fuel is passed through a time delay. The supply may be resumed.

  According to the above configuration, the throttle valve is closed during the catalyst regeneration operation. Therefore, in order to realize the air-fuel ratio corresponding to the catalyst regeneration operation, the fuel amount is also taken into account in consideration of the throttle valve opening (that is, the air amount). Is set. However, even if the throttle valve is changed, the air taken into the fuel chamber does not react immediately and has a slight response delay. In other words, if the fuel supply is restarted substantially simultaneously with the change of the throttle valve or before the change of the throttle valve, or if the fuel supply is restarted immediately after the change of the throttle valve, the air filling amount becomes the desired value. Therefore, combustion cannot be resumed at a desired air-fuel ratio. On the other hand, when the fuel injection is resumed by changing the throttle valve and then restarting the fuel injection after a time delay, the air filling amount approaches the value corresponding to the opening of the throttle valve, and the desired value is reached. Combustion can be resumed at an air-fuel ratio or an air-fuel ratio close to the desired air-fuel ratio.

  The time delay is preferably set to be equal to or longer than the time from when the throttle valve is changed until the air charge amount changes to a value corresponding to the opening of the throttle valve.

  The controller may operate the motor generator so as to maintain the rotational speed of the engine when the operation after the transition is resumed when the operation after the transition is resumed.

  Since the engine load changes at the time of operation transition, the engine speed may vary accordingly. On the other hand, according to the above configuration, the motor generator is operated to maintain the engine speed. By doing so, it is possible to reduce a sense of discomfort given to the occupant due to fluctuations in engine speed.

  The control unit may increase the rotational speed of the engine before stopping the fuel supply to the engine when shifting from the lean operation to the catalyst regeneration operation.

  In the case of the above configuration, when the fuel supply is stopped, combustion is stopped, so that the temperature of the NOx storage reduction catalyst is lowered. Therefore, when the fuel supply is stopped, the engine speed is increased in advance, and the temperature of the NOx storage reduction catalyst is increased. By doing so, it is possible to suppress a decrease in the activity of the NOx storage reduction catalyst due to the stop of the fuel supply, and it is possible to efficiently regenerate the NOx storage reduction catalyst.

  In addition, the period from when the fuel supply to the engine is stopped to when the fuel regeneration is resumed when shifting from the lean operation to the catalyst regeneration operation is limited to when the engine regeneration is shifted from the catalyst regeneration operation to the lean operation. The period from when the fuel supply is stopped to when it is restarted may be shorter.

  As described above, when the fuel supply is stopped, the temperature of the NOx storage reduction catalyst is lowered. Therefore, the fuel supply stop period at the time of transition from the lean operation to the catalyst regeneration operation is shortened. By doing so, it is possible to suppress a decrease in the activity of the NOx storage reduction catalyst due to the stop of the fuel supply, and it is possible to efficiently regenerate the NOx storage reduction catalyst.

  According to the hybrid vehicle, it is possible to suppress an increase in NOx emission when the NOx storage reduction catalyst is regenerated.

1 is a schematic diagram of a hybrid vehicle according to Embodiment 1. FIG. It is a figure which shows the engine and control system of a hybrid vehicle. It is the first half part of the flowchart of a catalyst regeneration operation. It is the second half part of the flowchart of a catalyst regeneration operation. (A) is the fuel injection amount, (B) is the throttle valve opening, (C) is the air charge, (D) is the air-fuel ratio, and (E) is the time chart of the catalyst regeneration operation. The operating state of the motor generator, (F) indicates the engine speed. 6 is a first half of a flowchart of a catalyst regeneration operation according to Embodiment 2. 4 is a time chart of a catalyst regeneration operation according to Embodiment 2, wherein (A) shows the fuel injection amount, (B) shows the opening of the throttle valve, (C) shows the air filling amount, and (D) shows the air-fuel ratio. , (E) shows the operating state of the motor generator, and (F) shows the engine speed.

  Hereinafter, exemplary embodiments will be described in detail with reference to the drawings.

Embodiment 1 of the Invention
FIG. 1 is a schematic diagram of a hybrid vehicle 1 (hereinafter referred to as “vehicle 1”), and FIG. 2 is a diagram showing an engine and a control system of the hybrid vehicle. This vehicle 1 is a so-called series-type hybrid vehicle, in which an engine 10 and a rotating shaft are connected to an output shaft (an eccentric shaft 13 described later) of the engine 10 to drive and start the engine 10 and A motor generator 20 that is driven by the engine 10 after starting to generate electric power, a high-voltage / large-capacity battery 30 that stores (charges) the electric power generated by the motor generator 20, and the engine 10 is driven. And a traveling motor 40 driven by at least one of the electric power generated by the motor generator 20 and the stored electric power (discharge power) of the battery 30.

  An inverter 50 is provided between the motor generator 20, the battery 30, and the traveling motor 40. Via the inverter 50, the power generated by the motor generator 20 is supplied to the battery 30 and / or the traveling motor 40, and the discharged power from the battery 30 is supplied to the motor generator 20 and / or the traveling motor 40. Is done.

  The traveling motor 40 is driven by being supplied with at least one of the generated power of the motor generator 20 and the discharged power from the battery 30. The driving force of the traveling motor 40 is transmitted to the left and right front wheels 61 as driving wheels via the differential device 60, whereby the vehicle 1 travels. The traveling motor 40 is capable of generating regenerative generated power, and operates as a generator when the vehicle 1 is decelerated, and the generated power (regenerative generated power) is charged in the battery 30. The battery 30 can be externally charged by a power source external to the vehicle 1.

  Engine 10 is used only for power generation by motor generator 20. In this embodiment, the engine 10 is a hydrogen engine in which hydrogen gas stored in the hydrogen tank 70 is supplied as fuel.

  As shown in FIG. 2, the engine 10 is a twin-rotor (two-cylinder) rotary piston engine, and is roughly arranged in a rotor housing chamber 11 a formed in two saddle-shaped rotor housings 11 (inside cylinders). Each of the triangular rotors 12 is accommodated. The two rotor housings 11 are integrated with the side housings so as to be sandwiched between three side housings (not shown), and each rotor housing chamber 11a is composed of each rotor housing 11 and the side housings on both sides thereof. Is formed. In FIG. 2, the two rotor housings 11 (two cylinders) are shown in an unfolded state, and the eccentric shafts 13 respectively drawn in the central portions in the two rotor housings 11 are the same.

  Each of the rotors 12 has apex seals (not shown) at the apexes of the triangles, and these apex seals are in sliding contact with the inner surface of the trochoid of the rotor housing 11. Three working chambers (corresponding to combustion chambers) are defined in 11a (in each cylinder). Each rotor 12 rotates around the eccentric shaft 13 in a state where the three apex seals of the rotor 12 are in contact with the inner peripheral surface of the trochoid of the rotor housing 11, and around the axis of the eccentric shaft 13. To revolve around. While the rotor 12 makes one revolution, the working chambers formed between the tops of the rotor 12 move in the circumferential direction, and the intake, compression, expansion (combustion), and exhaust strokes are performed. The rotating force is output from the eccentric shaft 13 as the output shaft through the rotor 12.

  Each rotor accommodating chamber 11a communicates with an intake passage 14 so as to communicate with the working chamber in the intake stroke, and an exhaust passage 15 communicates with the working chamber in the exhaust stroke. There is one intake passage 14 on the upstream side, but on the downstream side, the intake passage 14 branches into two branch passages and communicates with each of the rotor accommodating chambers 11a. A throttle valve 16 that is driven by a throttle valve actuator 90 such as a stepping motor to adjust the cross-sectional area (valve opening) of the intake passage 14 is disposed upstream of the branch portion of the intake passage 14. A premixing injector 17 (fuel injection valve) for injecting hydrogen (fuel) supplied from the hydrogen tank 70 into the intake passage 14 is disposed in each branch passage downstream of the branch portion of the intake passage 14. It is installed. The hydrogen injected by the premixing injector 17 is supplied to the working chamber in the intake stroke in a state of being mixed with air (premixed state).

  Two exhaust passages 15 are provided on the upstream side so as to communicate with the respective rotor accommodating chambers 11a, but are joined together on the downstream side. A three-way catalyst 81 and a NOx occlusion reduction catalyst (hereinafter referred to as “NOx catalyst”) 82 for purifying exhaust gas are disposed downstream of the merging portion of the exhaust passage 15. In FIG. 2, arrows shown in the intake passage 14 and the exhaust passage 15 indicate the flow of intake and exhaust.

  In each rotor housing 11 (each cylinder), a direct injection injector 18 (fuel injection valve) that directly injects hydrogen (fuel) supplied from the hydrogen tank 70 into the rotor accommodating chamber 11a (inside the cylinder); Two spark plugs 19 for igniting the hydrogen injected from the premixing injector 17 or the direct injection injector 18 are provided.

  The premixing injector 17 and the direct injection injector 18 are switched in accordance with the engine coolant temperature (engine coolant temperature) detected by an engine coolant temperature sensor 106 described later.

  In the present embodiment, only one premixing injector 17 is provided in each branch path, but the direct injection injector 18 is provided in each rotor housing 11 in the axial direction of the eccentric shaft 13 (the surface of FIG. 2). Are arranged side by side (in FIG. 2, only one is visible).

  The vehicle 1 includes a battery current / voltage sensor 101 that detects a current flowing into and out of the battery 30 and a voltage of the battery 30, and an accelerator that detects an amount of depression of an accelerator pedal by a driver of the vehicle 1 (accelerator opening by a driver's operation). The opening sensor 102, the vehicle speed sensor 103 for detecting the vehicle speed of the vehicle 1, the rotation angle sensor 104 provided on the eccentric shaft 13 for detecting the rotation angle position of the eccentric shaft 13, and the air-fuel ratio of the exhaust gas of the engine 10 are determined. An air-fuel ratio sensor 105 for detecting, an engine water temperature sensor 106 for detecting a temperature (engine water temperature) of engine cooling water flowing in the water jacket facing a water jacket (not shown) formed in the rotor housing 11; , The pressure in the hydrogen tank 70 (that is, the hydrogen tank A tank pressure sensor 107 for detecting the remaining amount of hydrogen in the air), an air flow sensor 108 for detecting the intake flow rate drawn into the intake passage 14, a battery temperature sensor 109 for detecting the temperature of the battery 30, and the engine 10 A control unit 100 that performs operation control, operation control of the inverter 50 (that is, operation control of the motor generator 20 and the traveling motor 40), and the like is provided.

  The intake flow rate detected by the air flow sensor 108 corresponds to the amount of air filled into each cylinder of the engine 10. The rotation angle sensor 104 also serves as an engine speed sensor that detects the speed of the engine 10 (hereinafter referred to as engine speed). Further, the air-fuel ratio of the exhaust gas detected by the air-fuel ratio sensor 105 corresponds to the actual air-fuel ratio of the engine 10.

  The control unit 100 is a controller based on a well-known microcomputer, and includes a central processing unit (CPU) that executes a program, a memory that is configured by, for example, a RAM or ROM, and stores a program and data, and an electrical signal An input / output (I / O) bus. The control unit 100 includes a battery current / voltage sensor 101, an accelerator opening sensor 102, a vehicle speed sensor 103, a rotation angle sensor 104, an air-fuel ratio sensor 105, an engine water temperature sensor 106, a tank pressure sensor 107, an air flow sensor 108, a battery temperature sensor. Various signals from 109 and the like are input. The control unit 100 is an example of a control unit.

  Based on the input signal, the control unit 100 outputs a control signal to the throttle valve actuator 90, the port injection injector 17, the direct injection injector 18, and the spark plug 19 to control the engine 10, A control signal is output to the inverter 50 to control the motor generator 20 and the traveling motor 40.

  The inverter 50 generates an operating state of the motor generator 20 by driving the engine 10 by generating driving torque by supplying electric power from the battery 30, and generating electric power by driving the engine 10 to generate the generated electric power in the battery 30 or the traveling state. It has the function to switch to the power generation state supplied to the motor 40. Then, the control unit 100 controls the inverter 50 to start the engine 10 with the operating state of the motor generator 20 as the driving state when the engine 10 is started. After the engine 10 is started, the control unit 100 switches to the power generation state. When the motor generator 20 is in the power generation state, the power generated by the motor generator 20 can be changed by changing the absorption torque of the motor generator 20 under the control of the inverter 50. The inverter 50 can also make the motor generator 20 in an idle state where the engine 10 is not driven and does not generate electricity (a state where the absorption torque of the motor generator 20 is zero). When the motor generator 20 is idled by controlling the engine, the engine 10 enters a no-load operation state where no load is applied. On the other hand, when the motor generator 20 is in the power generation state, the engine 10 enters a loaded operation state in which a load due to the power generation operation of the motor generator 20 is applied.

  Inverter 50 further includes a first mode in which driving motor 40 is driven only with the discharged power from battery 30, a second mode in which only the generated power from motor generator 20 is driven, and battery 30 and motor generator. 20 has a function capable of switching to the third mode performed with the power from both.

  The control unit 100 detects the remaining capacity (SOC) of the battery 30 based on the current flowing into and out of the battery 30 and the voltage of the battery 30 detected by the battery current / voltage sensor 101. The control unit 100 preferentially uses the first aspect when the SOC of the battery 30 is high, and preferentially uses the second aspect or the third aspect when the SOC is low. Here, the second mode includes a case where all of the generated power is consumed by the traveling motor 40 and a case where the generated power is used for both the consumption of the traveling motor 40 and the charging of the battery 30. In the former case, the traveling motor 40 is driven while maintaining the SOC, and in the latter case, the traveling motor 40 is driven while increasing the SOC (while charging). The situation of the third aspect includes a scene where the driver's acceleration request is large based on input information from the accelerator opening sensor 102 or the like, or a case where the dischargeable power of the battery 30 is low. The first mode is selected when the remaining amount of hydrogen in the hydrogen tank 70 by the tank pressure sensor 107 becomes a predetermined value or less, or when the engine 10 is overheated.

  Based on the power generation request, the control unit 100 causes the engine 10 to drive the motor generator 20 to generate power (this operation is hereinafter referred to as “power generation operation”). The power generation request is issued, for example, when the battery dischargeable power is low or when the driver acceleration request is large. Further, the required amount of power generation varies according to the amount of battery dischargeable power or the acceleration demand of the driver.

  During power generation operation, the control unit 100 operates the engine 10 at a lean air-fuel ratio (for example, an excess air ratio λ = 2.3) that is leaner than the stoichiometric air-fuel ratio in order to improve fuel efficiency. At this time, the engine 10 is operated at a constant rotational speed at a predetermined rotational speed (for example, 2000 rpm) that is most efficient for improving fuel efficiency. However, when the power generation request is large, the engine 10 is operated at an engine speed higher than a predetermined speed corresponding to the power generation request.

  Further, the control unit 100 causes the engine 10 to perform a catalyst regeneration operation when the NOx occlusion amount in the NOx catalyst 82 becomes a predetermined amount or more. Specifically, the control unit 100 estimates the NOx occlusion amount. When the NOx occlusion amount obtained by the estimation becomes a predetermined amount or more, the control unit 100 causes the engine 10 to perform the catalyst regeneration operation. In the catalyst regeneration operation, the engine 10 is operated at a rich air-fuel ratio in which the air-fuel ratio is richer than the stoichiometric air-fuel ratio (for example, the excess air ratio λ = 0.8). By operating the engine 10 at a rich air-fuel ratio, the fuel that has reached the NOx catalyst 82 functions as a reducing agent, and NOx occluded in the NOx catalyst 82 is reduced. The catalyst regeneration operation is continued until the NOx occlusion amount is sufficiently reduced (for example, until the NOx occlusion amount becomes 0). For example, the catalyst regeneration operation may be performed for a predetermined time (for example, 10 seconds) in which the NOx occlusion amount is sufficiently reduced.

  The catalyst regeneration operation is a constant speed operation at the same engine speed as that during the power generation operation. Further, during the catalyst regeneration operation, the motor generator 20 is made idle, and the engine 10 is made idle. The idle operation state is basically a no-load operation state, but may be a light load operation state in which the engine 10 is subjected to a light load equal to or less than a predetermined load (a light load similar to an engine auxiliary machine).

  Hereinafter, the catalyst regeneration operation by the control unit 100 will be described in detail. FIG. 3 is the first half of a flowchart of the catalyst regeneration operation. FIG. 4 is the latter half of the flowchart of the catalyst regeneration operation.

  First, in step S101, the control unit 100 reads output signals from the various sensors.

  In step S102, the control unit 100 reads the NOx occlusion amount from the memory. The control unit 100 calculates the NOx supplement amount supplemented by the NOx catalyst 82 during operation of the engine 10, accumulates the NOx supplement amount, and stores the NOx occlusion amount in the memory.

  Specifically, the NOx supplement amount changes according to the engine operating state including the state of the NOx catalyst 82. The supplemental amount of NOx includes the maximum storage amount that can be stored by the NOx catalyst 82 in the current engine operation state, the NOx storage amount accumulated up to the previous engine operation, and the NOx amount flowing into the NOx catalyst 82 in the current engine operation state. Based on the above.

  The maximum storage amount that can be stored by the NOx catalyst 82 varies depending on the state of the exhaust gas and the state of the NOx catalyst 82. Therefore, the control unit 100 obtains the maximum occlusion amount that can be occluded by the NOx catalyst 82 by comparing the engine speed, the engine load (output), the exhaust gas temperature, the NOx catalyst temperature, and the like with a preset map.

  The NOx occlusion amount accumulated up to the previous engine operation is read from the memory.

  The amount of NOx flowing into the NOx catalyst 82 changes according to the engine speed and the engine load. Therefore, the control unit obtains the NOx amount flowing into the NOx catalyst 82 by comparing the engine speed and the engine load with a preset map.

  The control unit 100 flows into the NOx catalyst 82 in the current engine operation state, the maximum storage amount that can be stored in the NOx catalyst 82, the NOx storage amount accumulated up to the previous engine operation, and the current engine operation state. Based on the NOx amount to be calculated, the NOx supplement amount in the current engine operating state is calculated. Then, the control unit 100 adds the obtained NOx supplement amount to the previous NOx occlusion amount and stores it in the memory as the NOx occlusion amount.

  In step S102, the control unit 100 reads the NOx occlusion amount thus stored in the memory.

  In step S103, the control unit 100 determines whether the power generation operation is being performed. If the power generation operation is not being performed, the control unit 100 returns to step S101. If the power generation operation is being performed, the control unit 100 proceeds to step S104. During the power generation operation, the vehicle is in an operation state with a predetermined load, and the air-fuel ratio at that time is A1 leaner than the stoichiometric air-fuel ratio. The power generation operation is an example of a lean operation in which the air-fuel ratio is leaner than that in the catalyst regeneration operation.

  In step S104, the control unit 100 determines whether or not the NOx occlusion amount has increased to the extent that the regeneration of the NOx catalyst 82 is necessary. Specifically, the control unit 100 determines whether or not the NOx occlusion amount is greater than or equal to a predetermined first occlusion amount. The first storage amount is a value smaller than the maximum storage amount of the NOx catalyst 82 and close to the maximum storage amount, and is a value for determining the necessity of regeneration of the NOx catalyst 82. When the NOx storage amount is greater than or equal to the first storage amount, the control unit 100 proceeds to step S107, while when the NOx storage amount is less than the first storage amount, the control unit 100 proceeds to step S105.

  In step S105, the control unit 100 determines whether or not the NOx occlusion amount is greater than or equal to 90% of the first occlusion amount. When the NOx occlusion amount is equal to or greater than 90% of the first occlusion amount, the control unit 100 proceeds to step S106, while when the NOx occlusion amount is less than 90% of the first occlusion amount, the control unit 100 Return to step S101.

  In step S106, the control unit 100 determines whether or not the SOC of the battery is equal to or less than a predetermined first capacity (for example, 30%). When the SOC is less than or equal to the first capacity, the control unit 100 proceeds to step S107, while when the SOC is greater than the first capacity, the control unit 100 returns to step S101.

  In other words, even if it is determined in step S104 that the NOx occlusion amount has not increased to the extent that regeneration of the NOx catalyst 82 is necessary, the process does not always return to step S101, and the NOx occlusion amount is immediately increased. If the amount of reproduction 82 has reached a necessary level and the SOC is low to some extent, the process proceeds to step S107 without returning to step S101.

  In step S107, the control unit 100 stops the power generation by the engine 10. That is, the control unit 100 puts the motor generator 20 in the idling state and stops driving the motor generator 20 by the engine 10.

  In subsequent step S108, the control unit 100 performs transition control from the power generation operation to the catalyst regeneration operation. This transition control is to reduce the NOx emission amount from the combustion chamber at the time of operation transition, and is referred to as NOx suppression transition control.

  In the NOx suppression transition control, first, in step S108, the control unit 100 stops the fuel supply by the premixing injector 17 and the direct injection injector 18 (step S109), and opens the throttle valve 16 corresponding to the idling operation. (Step S110). At this time, the operation of the spark plug 19 is also stopped.

  The fuel supply is stopped and the throttle valve 16 is changed almost simultaneously. As shown in FIGS. 5A and 5B, when the fuel supply is stopped, the air-fuel ratio in the cylinder largely fluctuates to the lean side as shown in FIG. 5D. While the fuel supply is stopped, the air-fuel ratio is very lean.

  Thereafter, the control unit 100 operates the motor generator 20 and feedback-controls the motor generator 20 so that the engine speed becomes the target speed. The target rotational speed is the same rotational speed as the engine rotational speed in the power generation operation.

  In step S111, the control unit 100 starts changing the opening of the throttle valve 16 to the idle opening, and then waits for a predetermined first waiting time. As shown in FIGS. 5B and 5C, when the opening degree of the throttle valve 16 is changed, the air amount changes with a slight delay from the change in the opening degree. When the first standby time has elapsed, the air amount is an air amount corresponding to the idle opening. That is, the first waiting time includes a response delay of the air filling amount with respect to the throttle valve 16, and after the change of the throttle valve 16 is started, the air filling amount becomes the filling amount according to the idle opening. It's time.

  Then, when the first standby time has elapsed, the control unit 100 proceeds to step S112.

  In step S112, the control unit 100 restarts the fuel supply and executes the catalyst regeneration operation. Specifically, the control unit 100 restarts the fuel supply with the fuel amount corresponding to the air-fuel ratio A2 that is richer than the stoichiometric air-fuel ratio (step S113). Note that the fuel amount at the time of resumption of fuel supply is a predicted value that is set to be the air-fuel ratio A2 in consideration of the opening degree of the throttle valve 16 being an idle opening degree or the like. After resuming the fuel supply, the control unit 100 feedback-controls the fuel supply amount so that the actual air-fuel ratio detected by the air-fuel ratio sensor 105 matches the air-fuel ratio A2.

  In this way, the fuel supply is not resumed as soon as the throttle valve 16 opens to the idle opening, but after the throttle valve 16 opens to the idle opening, The fuel supply is resumed after a time delay corresponding to the response delay of the air amount. By doing so, the engine 10 is not operated at an air-fuel ratio with an excess air ratio λ of approximately 1.2, and the operation of the engine 10 is resumed at the air-fuel ratio A2. As a result, it is possible to reduce the NOx emission amount when shifting from the power generation operation to the catalyst regeneration operation.

  Thereafter, in step S113, the control unit 100 ends the feedback control of the motor generator 20.

  As shown in FIG. 5E, the motor generator 20 starts feedback control substantially simultaneously with the stop of fuel supply and the change of the throttle valve 16. The feedback control of the motor generator 20 is continued from when the fuel supply is stopped until after the fuel supply is restarted. Thereby, the fluctuation | variation of an engine speed when restarting fuel supply and restarting engine operation can be reduced. That is, when the catalyst regeneration operation is started, the engine operation is resumed under conditions where the air charge amount and the fuel amount are different from those in the power generation operation. For this reason, the engine speed tends to fluctuate when the engine operation is resumed. Specifically, the catalyst regeneration operation has a much smaller load than the power generation operation, and therefore the engine speed tends to drop when the engine operation is resumed. On the other hand, by performing feedback control of the motor generator 20 when the engine operation is resumed, fluctuations in the engine speed can be reduced by the motor generator 20. As a result, as shown in FIG. 5F, the engine speed is kept constant throughout the power generation operation, the operation transition time, and the catalyst regeneration operation.

  Thus, when the power generation operation is shifted to the catalyst regeneration operation, the control unit 100 executes the catalyst regeneration operation for a predetermined execution time (step S114). This execution time is a time sufficient for the first storage amount of NOx to be reduced, and is obtained in advance by experiments or the like. Then, when the execution time has elapsed, the control unit 100 proceeds to step S115 to end the catalyst regeneration operation.

  In step S115, the control unit 100 determines whether there is a power generation request. If there is a power generation request, the control unit 100 proceeds to step S116, whereas if there is no power generation request, the control unit 100 proceeds to step S121.

  In step S116, the control unit 100 operates the motor generator 20, and feedback-controls the motor generator 20 so that the engine speed becomes the target speed. The target rotational speed is the same rotational speed as the engine rotational speed in the power generation operation.

  Further, the control unit 100 stops the fuel supply by the premixing injector 17 and the direct injection injector 18 (step S117), and the opening corresponding to the power generation operation of the throttle valve 16 (hereinafter referred to as “power generation opening”). (Step S118).

  In step S119, the control unit 100 starts changing the opening of the throttle valve 16 to the power generation opening, and then waits for a predetermined second waiting time. The second standby time is a time from when the change of the throttle valve 16 is started until the air filling amount becomes a filling amount corresponding to the power generation opening. That is, the second waiting time includes a response delay of the air filling amount with respect to the throttle valve 16. The second waiting time is set longer than the first waiting time. The second waiting time may be the same as the first waiting time or may be shorter than the first waiting time.

  When the second standby time has elapsed, the control unit 100 proceeds to step S120, resumes fuel supply, and resumes power generation operation.

  In step S120, the control unit 100 resumes fuel supply with a fuel amount corresponding to the air-fuel ratio A1. Note that the fuel amount at the time of resumption of fuel supply is a predicted value that is set to be the air-fuel ratio A1 in consideration of the opening degree of the throttle valve 16 being the power generation opening degree. After resuming the fuel supply, the control unit 100 feedback-controls the fuel supply amount so that the actual air-fuel ratio detected by the air-fuel ratio sensor 105 matches the air-fuel ratio corresponding to the air-fuel ratio A1. Thereafter, the control unit 100 proceeds to step S123.

  When it is determined in step S115 that there is no power generation request, the control unit 100 stops the operation of the engine 10 in step S121. Thereafter, the control unit 100 proceeds to step S122.

  In step S122, the control unit 100 resets the NOx occlusion amount stored in the memory. Thereafter, the control unit 100 returns. In the NOx suppression transition control during the transition from the catalyst regeneration operation to the power generation operation, as shown in FIGS. 5 (A) and 5 (B), as in the transition from the power generation operation to the catalyst regeneration operation, The change of the throttle valve 16 is performed substantially simultaneously. When the fuel supply is stopped, the air-fuel ratio in the cylinder largely fluctuates to the lean side as shown in FIG. While the fuel supply is stopped, the air-fuel ratio is very lean.

  Further, when the opening degree of the throttle valve 16 is changed, the air amount changes with a slight delay from the change of the opening degree. When the second standby time has elapsed, the air amount is an air amount corresponding to the power generation opening.

  Then, the fuel supply is resumed after the air amount becomes the air amount corresponding to the power generation opening. By doing so, the operation of the engine 10 is resumed in the state of the air-fuel ratio A1 without the engine 10 being operated at an air-fuel ratio with an excess air ratio λ of approximately 1.2. As a result, it is possible to reduce the NOx emission amount when shifting from the catalyst regeneration operation to the power generation operation.

  Further, as shown in FIG. 5E, the feedback control of the motor generator 20 is started substantially simultaneously with the stop of the fuel supply and the change of the throttle valve 16. The feedback control of the motor generator 20 is continued from when the fuel supply is stopped until after the fuel supply is restarted. Thereby, the fluctuation | variation of an engine speed when restarting fuel supply and restarting engine operation can be reduced. That is, when the catalyst regeneration operation is started, the engine operation is resumed under conditions where the air charge amount and the fuel amount are different from those in the power generation operation. For this reason, the engine speed tends to fluctuate when the engine operation is resumed. Specifically, since the power generation operation has a larger load than the catalyst regeneration operation, the engine speed is likely to increase when the engine operation is resumed. On the other hand, by performing feedback control of the motor generator 20 when the engine operation is resumed, fluctuations in the engine speed can be reduced by the motor generator 20. As a result, as shown in FIG. 5F, the engine speed is kept constant throughout the power generation operation, the operation transition time, and the catalyst regeneration operation.

  Therefore, the hybrid vehicle 1 includes an engine 10, a motor generator 20 that is driven by the engine 10 to generate power, a three-way catalyst 81 and a NOx storage reduction catalyst 82 that are provided in the exhaust system of the engine 10, and the engine 10. And the control unit 100 for controlling the motor generator 20, and the control unit 100 stores the NOx storage reduction catalyst 82 by operating the engine 10 in a state where the air-fuel ratio is richer than the stoichiometric air-fuel ratio. The catalyst regeneration operation for regenerating the NOx occlusion reduction catalyst 82 is performed by reducing the generated NOx, and the engine 10 is operated with the air-fuel ratio being leaner than that during the catalyst regeneration operation. When shifting from the lean operation to the catalyst regeneration operation, or The During the is driving migration when lean shift to operation, by temporarily stopping the fuel supply to the engine 10 resumes the fuel supply to the engine 10 in the operating state corresponding to the air-fuel ratio after the migration.

  According to the above configuration, the air-fuel ratio changes when shifting from the lean operation to the catalyst regeneration operation or when shifting from the catalyst regeneration operation to the lean operation. At this time, even if the air filling amount and the fuel amount are changed from the amount corresponding to the air-fuel ratio of the operation before the transition to the amount corresponding to the air-fuel ratio of the operation after the transition, the air-fuel ratio does not change instantaneously. For example, the time delay from when the control signal is output to the throttle valve 16 until the intake air amount into the cylinder is changed, or after the control signal is output to the premixing injector 17 or the direct injection injector 18 The air-fuel ratio is changed from the air-fuel ratio of the operation before the transition to the time after the transition because of the time delay until the injection amount to the engine is changed or the responsiveness when performing feedback control based on the output of the air-fuel ratio sensor 105. It changes gradually or continuously to the air-fuel ratio of operation.

  The air-fuel ratio in the lean operation and the catalyst regeneration operation is normally set to an air-fuel ratio that reduces the NOx emission amount downstream of the three-way catalyst 81 in consideration of the NOx emission amount from the combustion chamber, the characteristics of the three-way catalyst 81, and the like. .

  However, if the air-fuel ratio changes gradually or continuously between the air-fuel ratio in the lean operation and the air-fuel ratio in the catalyst regeneration operation, the air-fuel ratio of the engine is temporarily, but the NOx emission downstream of the three-way catalyst 81 is reduced. The amount of air-fuel ratio increases.

  On the other hand, in the above configuration, when shifting from the lean operation to the catalyst regeneration operation, or when shifting from the catalyst regeneration operation to the lean operation, the fuel supply is stopped, and the operation state corresponding to the air-fuel ratio after the transition Then restart the fuel supply. As a result, it is possible to avoid operating the engine 10 at an air-fuel ratio between the air-fuel ratio in lean operation and the air-fuel ratio in catalyst regeneration operation in which the NOx emission amount downstream of the three-way catalyst 81 increases. The NOx emission amount at the time of transition to the regeneration operation or at the time of transition from the catalyst regeneration operation can be reduced.

  Further, since the unburned gas in the cylinder can be scavenged while the fuel supply is stopped, it is possible to accurately adjust the air-fuel ratio when the operation is resumed after the transition.

  Further, the control unit 100 is configured to perform the lean operation during the power generation operation in which the motor generator 20 is driven by the engine 10 to generate power, and during the catalyst regeneration operation, compared to during the power generation operation. The throttle valve 16 is closed.

  According to the above configuration, during the catalyst regeneration operation, the amount of fresh air is less than that during the power generation operation, and the load is low, so that NOx discharged from the combustion chamber can be reduced.

  Further, when the control unit 100 resumes fuel supply to the engine 10 at the time of the operation transition, the control unit 100 adjusts the throttle valve 16 to an opening corresponding to the air-fuel ratio of the operation after the transition. The fuel supply is resumed after a delay.

  The air filling amount does not react immediately even when the throttle valve 16 is changed, and has a response delay. Therefore, if the fuel supply is started immediately after the throttle valve 16 is set to the desired opening, the fuel supply may be started before the air filling amount reaches an amount corresponding to the desired opening. Therefore, by adjusting the throttle valve 16 to an opening corresponding to the air-fuel ratio of the operation after the transition, the fuel supply is resumed after a time delay, so that the engine 10 is appropriately operated at the air-fuel ratio of the operation after the transition. You can resume.

  Further, the control unit 100 operates the motor generator 20 so as to maintain the rotational speed of the engine 10 when restarting the operation after the transition at the time of the transition.

  According to the above configuration, since the load is different between the catalyst regeneration operation and the power generation operation, the engine speed is likely to fluctuate when restarting the operation after the transition. Therefore, when the operation after the transition is resumed, the fluctuation in the engine speed can be suppressed by operating the motor generator 20 so as to maintain the engine speed. As a result, a sense of incongruity to the occupant can be reduced.

  Furthermore, the first waiting time from when the fuel supply to the engine 10 is stopped to when it is restarted when shifting from the lean operation to the catalyst regeneration operation is when the transition from the catalyst regeneration operation to the lean operation is performed. It is shorter than the second waiting time from when the fuel supply to the engine 10 is stopped to when it is restarted.

  When shifting to the catalyst regeneration operation, it is preferable to raise the temperature of the NOx catalyst 82 in order to efficiently reduce NOx. Therefore, the period during which the combustion of the engine 10 is stopped is shortened by making the first standby time shorter than the second standby time. Thereby, the temperature fall of the NOx catalyst 82 at the time of shifting to the catalyst regeneration operation is suppressed as much as possible.

<< Embodiment 2 of the Invention >>
Next, Embodiment 2 will be described. The second embodiment is different from the first embodiment in the control for stopping the fuel supply when shifting to the catalyst regeneration operation. Therefore, the second embodiment will be described focusing on portions different from the first embodiment. FIG. 6 shows a part of a flowchart of the catalyst regeneration operation according to the second embodiment, and FIG. 7 shows a timing chart of the catalyst regeneration operation. In FIG. 7, (A) shows the fuel injection amount, (B) shows the throttle valve opening, (C) shows the air filling amount, (D) shows the air-fuel ratio, and (E) shows the operation of the motor generator. , (F) indicates the engine speed.

  In the flowchart of the catalyst regeneration operation, the control from step S101 to S107 is the same as in the first embodiment.

  Then, after stopping the power generation in step S107, the control unit 100 opens the throttle valve 16 by a predetermined opening and operates the engine 10 for a predetermined time in step S201. Thereafter, the control unit 100 proceeds to step S108. The control after step S108 is the same as in the first embodiment.

  That is, as shown in FIG. 7B, the throttle valve 16 is opened by a predetermined opening before stopping the fuel supply at the time of shifting to the catalyst regeneration operation. As a result, the air amount increases as shown in FIG. 7C, and the engine speed increases as shown in FIG. 7F. As a result, the temperature of the exhaust gas increases and the temperature of the NOx catalyst 82 increases.

  After the engine speed is increased and the operation is executed for a predetermined time, the fuel supply is stopped, the throttle valve 16 is changed to the idle opening, and the feedback control of the motor generator 20 is executed.

  Therefore, in the second embodiment, when the control unit 100 shifts from the lean operation to the catalyst regeneration operation, the control unit 100 increases the rotational speed of the engine 10 before stopping the fuel supply to the engine 10.

  Thereby, even if the temperature of the NOx catalyst 82 is lowered by stopping the fuel supply by increasing the temperature of the NOx catalyst 82 in advance before the combustion supply is stopped, the temperature of the NOx catalyst 82 during the catalyst regeneration operation is reduced. Can be secured. As a result, the regeneration of the NOx catalyst 82 can be performed efficiently.

<< Other Embodiments >>
As described above, the embodiment has been described as an example of the technique disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can also be applied to an embodiment in which changes, replacements, additions, omissions, and the like are appropriately performed. Moreover, it is also possible to combine each component demonstrated by the said embodiment and it can also be set as a new embodiment. In addition, among the components described in the attached drawings and the detailed description, not only the components essential for solving the problem, but also the components not essential for solving the problem in order to illustrate the technology. May also be included. Therefore, it should not be immediately recognized that these non-essential components are essential as those non-essential components are described in the accompanying drawings and detailed description.

  About the said embodiment, it is good also as following structures.

  In the said embodiment, although the engine 10 is a rotary piston engine, it is not restricted to this. The engine 10 may be a reciprocating engine. The fuel is not limited to hydrogen, and may be gasoline or light oil.

  In the embodiment described above, the fuel supply is stopped, the throttle valve 16 is changed, and the motor generator 20 is operated in this order at the time of transition to the catalyst regeneration operation or at the transition from the catalyst regeneration operation. However, the order of these is not limited to this. These controls may be performed in different orders or simultaneously. However, wasteful fuel supply can be prevented by first stopping the fuel supply.

  Further, the fuel supply is stopped after the throttle valve 16 is changed and before the actual air-fuel ratio detected by the air-fuel ratio sensor 105 reaches the air-fuel ratio at which the NOx emission amount downstream of the three-way catalyst 81 increases. It may be executed when a predetermined air-fuel ratio is reached. For example, when shifting from the power generation operation (λ = 2.3) to the catalyst regeneration operation (λ = 0.8), the fuel is changed when the actual air-fuel ratio becomes 2.0 by changing the throttle valve 16 in the closing direction. Supply may be stopped. Further, when the catalyst regeneration operation (λ = 0.8) shifts to the power generation operation (λ = 2.3), the fuel is changed when the actual air-fuel ratio becomes 1.0 by changing the throttle valve 16 in the opening direction. Supply may be stopped. As described above, in the configuration in which the fuel supply is continued until the actual air-fuel ratio becomes the predetermined air-fuel ratio, the feedback control of the fuel amount is stopped when the change of the throttle valve 16 is started, and the change of the throttle valve 16 is started. The fuel supply may be continued with the amount of fuel.

  In the embodiment, the fuel supply is resumed after the first standby time or the second standby time has elapsed since the fuel supply was stopped. However, the configuration in which the fuel supply is restarted after a time delay after the throttle valve 16 is adjusted to the opening corresponding to the air-fuel ratio after the transition is not limited to this. For example, after the throttle valve 16 is adjusted to an opening corresponding to the air-fuel ratio after the transition, the fuel supply may be resumed when the fluctuation in the output of the air flow sensor 108 falls below a predetermined value.

  In the above-described embodiment, the power generation operation is described as an example of the lean operation in which the air-fuel ratio is leaner than that of the catalyst regeneration operation. However, the lean operation is not limited to the power generation operation. If the air-fuel ratio is leaner than the catalyst regeneration operation, any operation state can be the lean operation.

  As described above, the technology disclosed herein is useful for a hybrid vehicle including a NOx storage reduction catalyst.

DESCRIPTION OF SYMBOLS 1 Hybrid vehicle 10 Engine 16 Throttle valve 20 Motor generator 81 Three way catalyst 82 NOx storage reduction catalyst 100 Control unit (control part)

Claims (6)

Engine,
A motor generator driven by the engine to generate electricity;
A three-way catalyst and a NOx storage reduction catalyst provided in the exhaust system of the engine;
A control unit for controlling the engine and the motor generator;
The controller is
It is configured to perform a catalyst regeneration operation for regenerating the NOx storage reduction catalyst by operating the engine in a state where the air-fuel ratio is richer than the stoichiometric air-fuel ratio,
An operation that is performed when the catalyst regeneration operation is shifted from the lean operation in which the engine is operated in a state where the air-fuel ratio is leaner than that during the catalyst regeneration operation, or when the catalyst regeneration operation is shifted to the lean operation. A hybrid vehicle that temporarily stops fuel supply to the engine at the time of transition and resumes fuel supply to the engine in an operating state corresponding to the air-fuel ratio after the transition. The hybrid vehicle according to claim 1,
The control unit is configured to perform the lean operation during power generation operation in which the motor generator is driven by the engine to generate power,
A hybrid vehicle in which the throttle valve is closed during the catalyst regeneration operation compared to during the power generation operation. The hybrid vehicle according to claim 2,
The control unit adjusts the throttle valve to an opening corresponding to the air-fuel ratio of the operation after the transition when restarting the fuel supply to the engine at the time of the operation transition, and then passes the fuel after a time delay. A hybrid vehicle that resumes supply. The hybrid vehicle according to any one of claims 1 to 3,
The control unit is a hybrid vehicle that operates the motor generator so as to maintain the rotational speed of the engine when the operation after the transition is resumed at the time of the transition to the operation. In the hybrid vehicle according to any one of claims 1 to 4,
When the control unit shifts from the lean operation to the catalyst regeneration operation, the hybrid vehicle increases the engine speed before stopping the fuel supply to the engine. The hybrid vehicle according to any one of claims 1 to 5,
During the transition from the lean operation to the catalyst regeneration operation, the period from when the fuel supply to the engine is stopped to when it is restarted is the fuel supply to the engine when the catalyst regeneration operation is shifted to the lean operation. A hybrid vehicle that is shorter than the period from when the vehicle is stopped to when it is restarted.

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