Hybrid vehicle control device and hybrid vehicle control method

Abstract

Provided are a control device and a control method for a hybrid vehicle, which can suppress NOx emission to the outside of the vehicle and ensure good drivability even when an abnormality occurs in an LNT system. A hybrid vehicle has an engine and an electric motor as power sources, can perform series hybrid travel and engine direct travel, and has a NOx purification system using an SCR catalyst and an LNT catalyst in an engine exhaust passage. The control device includes: an abnormality detection unit that detects an abnormality in the NOx purification system using the LNT catalyst; and a travel state control unit that, when an abnormality is detected, restricts the travel mode of the vehicle to series hybrid travel and prohibits engine-direct travel, and causes the engine to operate in a steady state so that the output becomes an output that is equal to or greater than a predetermined value within the following output range. The output range is a range in which the NOx emission amount of the engine does not exceed the NOx cleanable amount of the NOx purification system using the SCR catalyst.

Description

Technical Field

[0001] This disclosure relates to a control device for hybrid vehicles and a control method for hybrid vehicles. Background Technology

[0002] In recent years, due to the need to improve energy efficiency and reduce exhaust emissions (NOx), the structure of hybrid vehicles has become increasingly diversified.

[0003] For example, among hybrid vehicles in recent years, there are series-parallel hybrid vehicles that can switch between series driving and parallel driving.

[0004] Generally, series hybrid vehicles are driven by an electric motor. The engine is only used to generate electricity, which is then used to power a generator to charge the battery or to supply the electric motor.

[0005] Series hybrid vehicles have two driving modes: "EV (Electric Vehicle) mode" and "series driving mode." In EV mode, the hybrid vehicle is driven by an electric motor powered by the battery. The engine is not driven. In series driving mode, the hybrid vehicle is driven by an electric motor, which is powered by a combination of electricity from the battery and a generator, or solely by electricity from the generator. In this mode, the engine is driven to generate electricity in the generator. The advantage of series driving mode is that it allows the engine to operate steadily near its optimal fuel efficiency point.

[0006] Parallel hybrid vehicles operate using the driving force of either an electric motor or an engine, or both. The mode in which a parallel hybrid vehicle operates solely on the engine's power is specifically called "engine driving mode." The mode in which a parallel hybrid vehicle operates using both the engine and the electric motor is called "parallel driving mode." Both engine driving mode and parallel driving mode offer advantages in suppressing battery charging and discharging losses, as well as various resistance losses that occur when the electric motor and / or generator are operating.

[0007] Series / parallel hybrid vehicles employ a structure that combines the advantages of both series and parallel configurations. Specifically, in this configuration, the drive force transmission system is switched between series and parallel modes by disengaging or engaging (disengaging) the clutch according to the vehicle's driving conditions. The advantage of series / parallel hybrid vehicles is that they can enjoy the advantages of both series and parallel hybrid vehicles.

[0008] It should be noted that in order to improve exhaust emissions (NOx) in such hybrid vehicles, it is necessary to optimize the operation of the entire vehicle, including the control of both the engine and the electric motor (see, for example, Patent Document 1 and Patent Document 2).

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent document 1: Japanese Patent Application Publication No. 2020-050009.

[0012] Patent document 2: Japanese Patent Application Publication No. 2019-166943. Summary of the Invention

[0013] The problem the invention aims to solve

[0014] In addition, in the past, such vehicles were usually equipped with a NOx purification system (hereinafter referred to as "LNT system") that uses LNT (Lean NOx Trap) catalyst (also known as "adsorption NOx catalyst") as the exhaust purification device for the engine.

[0015] Typically, from the perspective of preventing exhaust emissions (NOx), such vehicles are equipped with an ECU (Electric Control Unit) with fault diagnosis function. This function monitors abnormalities in the temperature of the LNT catalyst, abnormalities in the NOx sensor located upstream of the LNT catalyst, and other conditions to confirm whether the LNT system is functioning properly.

[0016] Previously, when this type of ECU detected an abnormality in the LNT system, it would limit the engine output (i.e., the amount of fuel injected) in order to suppress the engine's NOx emissions.

[0017] Figure 1 This diagram illustrates the engine control methods used in conventional technologies when the LNT system malfunctions.

[0018] like Figure 1As shown, by limiting engine output, the amount of NOx emitted by the engine can still be suppressed even when the LNT catalyst cannot properly purify NOx. However, while such engine output ensures a minimum level of power to reach a repair shop on its own, the vehicle may struggle to keep up with traffic flow when carrying cargo or towing, where more engine output is required for driving compared to an unloaded state.

[0019] The present invention was made in view of the above-mentioned problems, and its object is to provide a control device and control method for a hybrid vehicle that can suppress NOx emissions to the outside of the vehicle even in the event of an LNT system malfunction, while ensuring good driving performance.

[0020] Solution to the problem

[0021] The main content of the present invention, which solves the above-mentioned technical problems, is a control device for a hybrid vehicle. The hybrid vehicle has an engine and an electric motor as power sources, enabling it to perform series hybrid driving and direct-drive driving using these power sources. Furthermore, the exhaust passage of the engine includes a NOx purification system using an SCR catalyst and an LNT catalyst. The control device comprises:

[0022] An anomaly detection unit detects anomalies in the NOx purification system related to the LNT catalyst; and

[0023] When the driving status control unit detects the abnormality, it restricts the vehicle's driving mode to the series hybrid driving mode and prohibits the engine from driving directly. It also enables the engine to operate in a steady state by making the output above a predetermined value within an output range, wherein the output range is the output range that ensures the NOx emissions of the engine do not exceed the NOx purifiable amount of the NOx purification system using the SCR catalyst.

[0024] Furthermore, in other respects, it is a control method for a hybrid vehicle having an engine and an electric motor as power sources, capable of using these power sources for series hybrid driving and engine direct drive, and having a NOx purification system using SCR and LNT catalysts in the exhaust passage of the engine. The control method includes:

[0025] Handling of anomalies in the NOx purification system associated with the LNT catalyst; and

[0026] In the event of the detected anomaly, the vehicle's driving mode is restricted to the series hybrid mode, and direct engine operation is prohibited. The engine is then operated in a steady state such that its output is above a specified value within a range where the NOx emissions from the engine do not exceed the NOx purifiable range of the NOx purification system using the SCR catalyst.

[0027] According to the hybrid vehicle control device of the present invention, even if the LNT system malfunctions, it can ensure good driving performance while suppressing NOx emissions to the outside of the vehicle. Attached Figure Description

[0028] Figure 1 This diagram illustrates the engine control method in conventional technology when the LNT system malfunctions.

[0029] Figure 2 This is a schematic diagram illustrating the overall structure of a vehicle according to one embodiment of the present invention.

[0030] Figure 3 This is a diagram illustrating an example of the structure of an exhaust purification device according to an embodiment of the present invention.

[0031] Figure 4 This is a diagram illustrating an example of the functional structure of an ECU according to an embodiment of the present invention.

[0032] Figure 5 This diagram illustrates the engine control method performed by the ECU in an LNT system malfunction according to an embodiment of the present invention.

[0033] Figure 6 This diagram illustrates an example of a control mapping used by an ECU to control the valve opening of an EGR device according to an embodiment of the present invention.

[0034] Figure 7 This is a flowchart illustrating an example of the operation of the LNT system anomaly detection function of an ECU according to an embodiment of the present invention.

[0035] Explanation of reference numerals in the attached figures

[0036] 1 vehicle

[0037] 1R Drive wheel

[0038] 10 batteries

[0039] 20 Electric motors

[0040] 30 Engine

[0041] 30E EGR unit

[0042] 40 generators

[0043] 50 Clutch

[0044] 60 Gear Mechanism

[0045] 70 Exhaust Purification Device

[0046] 71 LNT catalyst

[0047] 72 PM filter

[0048] 73 SCR catalyst

[0049] 74 ASC catalyst

[0050] 75 Urea Water Supply Device

[0051] 80 Various Sensors

[0052] 80a Flow Sensor

[0053] 80b First NOx Sensor

[0054] 80c Second NOx Sensor

[0055] 80d Third NOx Sensor

[0056] 80e First Temperature Sensor

[0057] 80f Second Temperature Sensor

[0058] 100 ECU

[0059] 101 Anomaly Detection Department

[0060] 102 Driving Status Control Unit

[0061] 103 Fuel-Rich Pulse Execution Control Unit Detailed Implementation

[0062] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that in this specification and the accompanying drawings, constituent elements having substantially the same function are labeled with the same reference numerals, and repeated descriptions are omitted.

[0063] <Vehicle Overall Structure>

[0064] Hereinafter, an example of the structure of a hybrid vehicle (hereinafter referred to as "vehicle 1") according to an embodiment of the present invention will be described. The vehicle 1 according to this embodiment is a hybrid vehicle with a series / parallel configuration that combines series and parallel configurations.

[0065] Figure 2This is a schematic diagram representing the overall structure of vehicle 1.

[0066] Vehicle 1 includes battery 10, electric motor 20, engine 30, generator 40, clutch 50, gear mechanism 60, exhaust purification device 70, various sensors 80 and ECU 100.

[0067] Battery 10 is, for example, a lithium-ion battery that can provide a high voltage of 200-350V. Battery 10 is connected to motor 20 via a line, enabling it to supply the motor 20 with the electrical energy stored in battery 10. In addition, battery 10 is also connected to generator 40 in parallel with motor 20 via a line, enabling it to charge the battery 10 with the electrical energy generated by generator 40.

[0068] The electric motor 20 utilizes the electrical energy stored in the battery 10 and / or the electrical energy generated by the generator 40 (i.e., the electrical energy generated by the engine 30) to produce the power required for the vehicle 1 to move. The output torque generated by the electric motor 20 is transmitted to the drive wheels 1R of the vehicle 1 through the gear mechanism 60. It should be noted that the rotor of the electric motor 20 is directly connected to the gear mechanism 60. In addition, during regenerative braking, the electric motor 20 operates as a generator, and the electrical energy generated by the electric motor 20 is charged to the battery 10.

[0069] It should be noted that the motor 20 has an inverter (not shown) that can convert the DC power obtained from the battery 10 or the DC power sent by the generator 40 (in this embodiment, the generator 40 converts the AC power generated by its own power generation inverter into DC power and then sends it to the motor 20 or the battery 10) into AC voltage for use.

[0070] Engine 30 is directly connected to the rotor of generator 40. When clutch 50 is disengaged and vehicle 1 is traveling in series, engine 30 is used only to generate electricity for generator 40. However, when clutch 50 is engaged, the output of engine 30 is directly transmitted to the drive wheel 1R of vehicle 1 through generator 40, clutch 50 and gear mechanism 60 as the mechanical energy required for vehicle 1 to move.

[0071] From the perspective of reducing NOx emissions, engine 30 is equipped with an EGR (Exhaust Gas Recirculation) device 30E (see...). Figure 3 In addition, an exhaust purification device 70 is installed on the exhaust passage 30T of the engine 30.

[0072] The generator 40 uses the power of the engine 30 to generate electrical energy. The electrical energy generated by the generator 40 is used to charge the battery 10 or directly supplied to the motor 20. It should be noted that the generator 40 has an inverter (not shown) that can convert the AC voltage it generates into DC voltage and supply it to the battery 10 or to the motor 20.

[0073] According to the instructions of ECU100, clutch 50 disconnects the power transmission path from engine 30 to drive wheel 1R of vehicle 1.

[0074] The gear mechanism 60 converts the driving force from the engine 30 via the generator 40 or the driving force from the electric motor 20 into a specified speed and output torque, and transmits it to the drive wheels 1R of the vehicle 1.

[0075] Various sensors 80 are used to detect the status of various parts of the vehicle 1 and the driver's operating operations, etc. For example, the various sensors 80 include: a vehicle speed sensor to detect the vehicle 1's speed, a throttle opening sensor to detect the driver's throttle operation, a speed sensor to detect the engine 30's rotational speed, a speed sensor to detect the generator 40's rotor rotational speed, a speed sensor to detect the electric motor 20's rotor rotational speed, a voltage sensor to detect the battery 10's charge status, and sensors to detect the status of various parts of the exhaust purification device 70 (which will be referred to later). Figure 3 (Explanation), etc. Signals detected by various sensors 80 are transmitted to ECU 100.

[0076] The ECU 100 communicates with various parts of the vehicle 1 to uniformly control the actions of each part of the vehicle 1. For example, the ECU 100 performs the following controls: switching the drive force transmission system to the drive wheels 1R; controls related to the disengagement of the clutch 50; operation control of the engine 30; operation control of the generator 40; operation control of the electric motor 20; charging and discharging control of the battery 10; and operation control of the exhaust purification device 70, etc.

[0077] It should be noted that the ECU100 obtains sensor information from various sensors 80 installed on the vehicle 1 and detects the status of various parts of the vehicle 1.

[0078] ECU100 may be configured to include, for example, a Central Processing Unit (CPU), Read Only Memory (ROM), Random Access Memory (RAM), input ports, and output ports. The various functions of ECU100 are implemented by the CPU calling control programs and various types of data stored in ROM, RAM, etc. However, some or all of these functions may also be implemented in place of CPU processing by a Digital Signal Processor (DSP) or dedicated hardware circuitry (e.g., an Application Specific Integrated Circuit (ASIC) or a Field Programmable Gate Array (FPGA)), or in cooperation with CPU processing.

[0079] Vehicle 1 has, for example, the following driving modes: (a) EV driving mode, (b) series driving mode, (c) engine driving mode, and (d) parallel driving mode.

[0080] In EV driving mode, clutch 50 is disengaged and engine 30 stops. Vehicle 1 is driven by electric motor 20 powered by battery 10.

[0081] In series driving mode, clutch 50 is disengaged, and engine 30 operates to supply electrical energy that enables electric motor 20 to output the required driving force according to throttle opening, vehicle speed, etc. Vehicle 1 travels by the driving force of electric motor 20, which is powered by generator 40. In addition, auxiliary power from battery 10 can also be supplied to electric motor 20 at this time.

[0082] In engine driving mode, clutch 50 is engaged, and vehicle 1 moves solely by the driving force of engine 30. When driving in engine driving mode, the rotors of electric motor 20 and generator 40 rotate together with the engine 30.

[0083] In parallel driving mode, clutch 50 is engaged, and vehicle 1 moves using the driving forces of both engine 30 and electric motor 20. When driving in parallel driving mode, the rotor of generator 40 rotates together with the engine 30.

[0084] ECU100 switches between these driving modes to optimize, for example, energy efficiency (e.g., fuel efficiency). Since this control is a well-known technology, a description is omitted here.

[0085] It should be noted that driving in engine mode and parallel mode will be referred to as "engine direct driving" in the following text, while driving in series mode will be referred to as "series hybrid driving".

[0086] <Structure of Exhaust Purification Device 70>

[0087] Figure 3 This is a diagram showing an example of the structure of the exhaust purification device 70.

[0088] The exhaust purification device 70 includes an LNT catalyst 71, a PM filter 72, an SCR catalyst 73, an ASC catalyst 74, and a urea water supply device 75. It should be noted that these catalysts, etc., are arranged in the exhaust passage 30T of the engine 30 in the order of LNT catalyst 71, PM filter 72, SCR catalyst 73, and ASC catalyst 74, from the upstream side to the downstream side.

[0089] When there is excess oxygen in the exhaust gas, the LNT catalyst 71 adsorbs NOx from the exhaust gas. In a reducing atmosphere, the adsorbed NOx reacts with hydrocarbons in the exhaust gas to reduce it to harmless gases such as nitrogen before being released. For example, the LNT catalyst 71 can be a catalyst made by supporting a catalyst carrier such as alumina with catalysts such as platinum or rhodium for NOx reduction and NOx adsorption materials such as calcium or barium.

[0090] It should be noted that the NOx adsorption efficiency of the LNT catalyst 71 decreases when it approaches saturation. Therefore, the ECU 100 monitors the NOx adsorption status of the LNT catalyst 71. That is, when the NOx adsorption amount of the LNT catalyst 71 increases and approaches NOx saturation, the ECU 100 causes the engine 30 to operate at an air-fuel rich ratio (called a "rich spike"), thereby forcibly generating a reducing atmosphere in the exhaust gas to remove NOx from the LNT catalyst 71.

[0091] PM filter 72 captures particulate matter (PM) contained in exhaust gas. PM filter 72 may be made of porous ceramics such as cordierite or silicon carbide.

[0092] The SCR (Selective Catalytic Reduction) catalyst 73 (also known as a "NOx selective reduction catalyst") adsorbs ammonia produced by the hydrolysis of urea water supplied by the urea water supply device 75, and selectively reduces and purifies NOx in the exhaust gas using the adsorbed ammonia. For example, the SCR catalyst 73 can be a catalyst made by supporting NOx reduction catalysts such as Fe zeolite, Cu zeolite, or vanadium on a ceramic support surface.

[0093] ASC catalyst 74 (also known as "Ammonia Slip Suppression Catalyst") suppresses the emission of ammonia leaking from SCR catalyst 73 to the outside. ASC catalyst 74 suppresses ammonia leakage from SCR catalyst 73 by oxidizing the ammonia that has passed through SCR catalyst 73 and decomposing it into water and nitrogen.

[0094] The urea water supply device 75 injects urea water upstream of the SCR catalyst 73 within the exhaust passage 30T. The urea water supply device 75 includes, for example, a urea water addition valve, a urea water tank, and a supply pump. Specifically, in the urea water supply device 75, urea water pressurized and supplied from the urea water tank by the supply pump is injected into the exhaust passage 30T through the urea water addition valve.

[0095] The injection quantity of urea water from the urea water supply device 75 to the exhaust passage 30T is adjusted by adjusting the opening of the urea water addition valve. It should be noted that the opening of the urea water addition valve is controlled by a control signal output from the ECU 100.

[0096] Since the control of urea water injection by ECU 100 is the same as that of conventionally known methods, the description is omitted here. However, ECU 100 sets a target value for the ammonia storage in SCR catalyst 73, for example, based on the catalyst temperature of SCR catalyst 73 displayed by the first temperature sensor 80e. Then, ECU 100 calculates the ammonia consumption in SCR catalyst 73 sequentially, for example, based on the sensor values ​​displayed by the second NOx sensor 80c and the flow sensor 80a (i.e., the amount of NOx flowing into SCR catalyst 73). Then, ECU 100 controls the urea water injection rate of urea water supply device 75 to maintain the ammonia storage in SCR catalyst 73 at the target value.

[0097] Thus, in the exhaust gas purification device 70 of this embodiment, both SCR catalyst 73 and LNT catalyst 71 are used in order to minimize exhaust gas emissions (NOx).

[0098] Generally, SCR catalyst 73 has high NOx purification performance, but it is inactive at low exhaust temperatures (e.g., below 200°C). In this regard, by placing both SCR catalyst 73 and LNT catalyst 71 in the exhaust passage 30T, when the exhaust temperature is low and SCR catalyst 73 is inactive during engine start-up, NOx emitted by engine 30 can be purified by LNT catalyst 71.

[0099] Moreover, thanks to this structure, even if the NOx purification system using LNT catalyst 71 malfunctions, NOx purification can still be performed using SCR catalyst 73.

[0100] It should be noted that the exhaust purification device 70 includes various sensors 80, such as a flow sensor 80a for detecting the flow rate of the intake air flowing into the engine 30, a first NOx sensor 80b for detecting the amount of NOx emitted by the engine 30, a second NOx sensor 80c for detecting the amount of NOx flowing into the SCR catalyst 73, a third NOx sensor 80d for detecting the amount of NOx flowing out of the vehicle 1, a first temperature sensor 80e for detecting the temperature of the SCR catalyst 73, and a second temperature sensor 80f for detecting the temperature of the LNT catalyst 71. These various sensors 80 sequentially send the sensor information obtained through detection to the ECU 100.

[0101] [Detailed Structure of ECU100]

[0102] Figure 4 This is a diagram illustrating an example of the functional structure of ECU100.

[0103] The ECU100 functions as an abnormality detection unit 101, a driving status control unit 102, and a fuel-rich pulse execution control unit 103.

[0104] <Anomaly Detection Department 101>

[0105] The anomaly detection unit 101 detects anomalies related to the NOx purification system (hereinafter referred to as the "LNT system") that uses the LNT catalyst 71 installed in the exhaust passage 30T of the engine 30.

[0106] Here, the anomaly related to the LNT system refers to an anomaly that causes the LNT catalyst 71 to be unable to adequately purify NOx in the exhaust gas (i.e., a failure mode that is judged to be unable to ensure the purification performance of the LNT catalyst 71).

[0107] Such abnormalities include, for example, abnormal temperatures in the LNT catalyst 71, as well as abnormal sensor values ​​and malfunctions in the first NOx sensor 80b located upstream of the LNT catalyst 71.

[0108] It should be noted that an abnormal temperature of the LNT catalyst 71 refers to a state where the temperature of the LNT catalyst 71 drops due to the influence of condensate from the engine 30 or from the upstream pipe. In this case, the NOx purification performance of the LNT catalyst 71 decreases. Furthermore, if the first NOx sensor 80b installed upstream of the LNT catalyst 71 malfunctions, the NOx adsorption capacity of the LNT catalyst 71 cannot be accurately determined. Therefore, in this situation, the fuel-rich pulse execution control unit 103 (described later) will stop executing the fuel-rich pulse. In other words, in this situation, the LNT catalyst 71 may be saturated, and its NOx purification performance may decrease.

[0109] The anomaly detection unit 101 can detect temperature anomalies in the LNT catalyst 71, for example, based on the sensor value displayed by the second temperature sensor 80f. Furthermore, the anomaly detection unit 101 can determine that the first NOx sensor 80b is malfunctioning, for example, if the sensor value of the first NOx sensor 80b displays an abnormal value or the detection signal of the first NOx sensor 80b is interrupted. When the anomaly detection unit 101 detects such an anomaly related to the LNT system, it sets an anomaly occurrence flag in the storage unit (e.g., RAM) to switch the operating state of the vehicle 1.

[0110] It should be noted that in the exhaust passage 30T, an oxygen concentration sensor (not shown) is sometimes installed upstream of the LNT catalyst 71. Since the purification performance of the LNT catalyst 71 may be compromised if this oxygen concentration sensor malfunctions, the malfunction detection unit 101 can also set an malfunction indicator when the oxygen concentration sensor malfunctions.

[0111] It should be noted that, in addition to this, the anomaly detection unit 101 can also set an anomaly flag in cases such as malfunction of the flow sensor 80a. This is because the NOx storage level of the LNT catalyst 71 is uncertain in such situations.

[0112] <Driving Status Control Unit 102>

[0113] The driving status control unit 102 controls the driving mode of vehicle 1.

[0114] As described above, under normal circumstances (referring to when the LNT system is working properly, the same below), the driving state control unit 102 switches the driving mode of the vehicle 1 between EV driving mode, series driving mode, engine driving mode and parallel driving mode in order to maximize energy efficiency (i.e., fuel efficiency).

[0115] However, if the anomaly detection unit 101 detects an anomaly in the LNT system, the driving state control unit 102 restricts the driving mode of the vehicle 1 to series hybrid driving and prohibits direct engine driving. Furthermore, during this series hybrid driving, the driving state control unit 102 ensures that the engine 30 operates in a steady state with the output being above a predetermined value within an output range, where the output range ensures that the NOx emissions of the engine 30 do not exceed the NOx purification capacity of the NOx purification system using the SCR catalyst 73.

[0116] This will be explained in detail below.

[0117] Figure 5 This diagram illustrates the engine control methods employed by ECU100 when the LNT system malfunctions.

[0118] As described above, in conventional engine control, when the LNT system malfunctions, the output (fuel injection quantity) of engine 30 is limited to suppress the amount of NOx emitted by engine 30 to the outside. However, in this case, when the vehicle 1 is carrying cargo or towing, and requires more engine output compared to an empty vehicle, it may be difficult for the vehicle 1 to follow traffic flow and drive itself.

[0119] In this respect, the driving state control unit 102 of this embodiment restricts the driving mode of the vehicle 1 to series hybrid driving, and makes the engine 30 operate in a steady state such that the output is above a predetermined value within the output range, wherein the output range is the output range in which the NOx emission of the engine 30 does not exceed the NOx purification capacity of the NOx purification system using the SCR catalyst 73.

[0120] It should be noted that the engine output at this point is preferably close to its maximum value within the aforementioned output range. However, considering factors such as the change in the purification performance of the SCR catalyst 73 over time, it is preferable to ensure a specified margin relative to the maximum value within the aforementioned output range. Furthermore, the engine output at this point does not need to be completely constant during steady-state operation; it can vary smoothly according to changes in the required driving force in real time.

[0121] Therefore, even if the LNT system malfunctions, the required driving force for vehicle 1 can be ensured without output limitation, thus maintaining good driving performance.

[0122] At this point, the structure becomes such that the output of the electric motor 20 satisfies the required driving force for the vehicle 1, and the engine 30 performs power generation. It should be noted that the required driving force for the vehicle 1 is set, for example, based on the vehicle 1's speed and the driver's throttle operation (i.e., throttle opening), and the electric motor 20 is controlled to output this required driving force. At this time, the electrical energy required for the electric motor 20 to drive is directly supplied from the engine 30 (i.e., generator 40), and any shortfall in the electrical energy generated by the engine 30 (i.e., generator 40) is supplemented by the battery 10. Furthermore, any surplus electrical energy generated by the engine 30 (i.e., generator 40) is charged to the battery 10.

[0123] Generally, during direct-drive (i.e., engine-driven or parallel-driven) operation, the instantaneous NOx emissions increase because the operating state of the engine 30 needs to be changed according to the acceleration requirements of vehicle 1. Consequently, the NOx emissions emitted by vehicle 1 to the outside also tend to increase. In this respect, as mentioned above, during the steady-state operation of the engine 30 using series hybrid powertrain, the fluctuations in exhaust temperature, flow rate, and NOx emissions are smaller, thereby suppressing instantaneous NOx emissions caused by rapid acceleration, etc.

[0124] Furthermore, in the vehicle 1 of this embodiment, in principle all NOx emitted by the engine 30 is purified by the SCR catalyst 73. Therefore, even if the LNT catalyst 71 does not fully function, the amount of NOx emitted by the vehicle 1 to the outside can be suppressed to an extremely small amount.

[0125] Here, "the output range of engine 30 during steady-state operation" (i.e., the output range of NOx emissions of engine 30 not exceeding the NOx purification capacity of the NOx purification system using SCR catalyst 73) can be set to a range predetermined by experiment or simulation, taking into account, for example, the NOx purification performance of SCR catalyst 73 under normal conditions.

[0126] However, the NOx purification performance of the SCR catalyst 73 fluctuates significantly depending on the circumstances. Therefore, the "output range of the engine 30 during steady-state operation" should ideally be set to a more accurate range based on the current conditions. By doing so, steady-state operation of the engine 30 can be implemented with the engine output set as close as possible. Specifically, the current NOx purification capacity of the SCR catalyst 73 can be calculated, for example, based on the current temperature of the SCR catalyst 73 and the ammonia storage capacity of the SCR catalyst 73. Moreover, based on this NOx purification capacity, using a pre-set control mapping (e.g., a mapping that pre-determines the correspondence between the NOx purification capacity and the maximum engine output through experiments or simulations), the output range of the engine 30 where the NOx emissions do not exceed this NOx purification capacity can be accurately calculated.

[0127] Here, the driving state control unit 102 preferably operates the engine 30 in NOx reduction mode instead of fuel efficiency priority mode when the LNT system malfunctions. That is, in fuel efficiency priority mode, the operating state of the engine 30 is generally set from the perspective of improving fuel efficiency (e.g., engine speed, output torque, fuel injection timing, EGR rate, and turbocharger boost pressure, etc.), but from the perspective of reducing NOx emissions, this fuel efficiency priority mode may not be optimal.

[0128] From this perspective, in NOx reduction mode, the driving state control unit 102, for example, increases the opening of the valve of the EGR device 30E to a level greater than the opening set in fuel efficiency priority mode. This reduces NOx emissions from the engine 30.

[0129] Figure 6 This is a diagram illustrating an example of a control mapping used to control the valve opening of the EGR device 30E. Figure 6 (A) represents the control mapping used in fuel efficiency priority mode. Figure 6 (B) indicates the control mapping used in NOx reduction mode.

[0130] In the control mapping of the EGR device 30E, the valve opening is set according to the engine speed and fuel injection quantity. It should be noted that... Figure 6 (A) and Figure 6 In (B), "large" and "small" indicate the valve opening size of the set EGR device 30E. Figure 6 (A) and Figure 6 In (B), the darker the color, the greater the valve opening.

[0131] Generally, when the temperature of combustion gases increases, the amount of NOx produced, an environmental pollutant, increases dramatically. The EGR device 30E reduces NOx production by recirculating exhaust gas into the intake manifold, lowering the oxygen concentration in the intake air and slowing the combustion rate. The valve opening of the EGR device 30E not only affects NOx production but also the engine 30's output torque, white smoke production, and fuel efficiency. Therefore, the control mapping of the EGR device 30E is pre-determined through experiments and other methods, specifying the optimal EGR valve opening for the engine's operating conditions (i.e., the optimal EGR intake).

[0132] In the abnormal control mapping, the valve opening is set larger in each operating state of the engine 30 compared to the normal control mapping. That is, in NOx reduction mode, the valve opening of the EGR device 30E is increased compared to normal mode (i.e., fuel efficiency priority mode), thereby increasing the EGR rate. This reduces the amount of NOx emitted by the engine 30.

[0133] It should be noted that in NOx reduction mode, controls such as reducing the boost pressure of the turbocharger (not shown) connected to engine 30 or delaying fuel injection timing can also be implemented. This can further reduce NOx emissions from engine 30.

[0134] In other words, when the vehicle 1 is driven in series hybrid mode, in fuel efficiency priority mode, the engine 30 is controlled to operate at a point close to its maximum efficiency operating point. In contrast, in NOx reduction mode, the engine 30 undergoes the control change described above and is controlled to operate at a point deviating from its maximum efficiency operating point. Therefore, in NOx reduction mode, the fuel efficiency is inherently lower than in fuel efficiency priority mode.

[0135] It should be noted that when the ECU100 is in NOx reduction mode, if the temperature of the SCR catalyst 73 is low, it is preferable to raise the temperature of the SCR catalyst 73 by using an electric heater (not shown) to heat the SCR catalyst 73. In NOx reduction mode, due to the decrease in exhaust temperature caused by increasing the valve opening of the EGR device 30E to reduce the combustion temperature of the engine 30, the SCR catalyst 73 may not be able to rise to a temperature sufficient for effective NOx purification. However, sometimes even if the combustion temperature decreases, the exhaust temperature may not decrease; therefore, it is preferable to control the on / off state of the electric heater based on the detected temperature of the SCR catalyst 73.

[0136] <Fuel-Rich Pulse Execution Control Unit 103>

[0137] The fuel-rich pulse execution control unit 103 causes the engine 30 to execute a fuel-rich pulse based on the NOx adsorption amount of the LNT catalyst 71.

[0138] The control of the rich pulse execution timing of the rich pulse execution control unit 103 is the same as the conventionally known method, and thus detailed description thereof is omitted herein. The rich pulse execution control unit 103, for example, calculates the amount of adsorbed NOx per unit time based on the sensor information of the flow rate sensor 80a and the first NOx sensor 80b, or based on the estimated NOx emission amount from the engine 30 and the model in the ECU 100, and estimates the amount of adsorbed NOx of the LNT catalyst 71 at each time point during driving by accumulating the amount of adsorbed NOx per unit time. Then, when the amount of adsorbed NOx of the LNT catalyst 71 exceeds a specified value (for example, 80%), the rich pulse execution control unit 103 causes the engine 30 to execute a rich pulse.

[0139] It should be noted that when an abnormality in the LNT system is detected, the rich pulse execution control unit 103 can stop executing the rich pulse.

[0140] <Operation flow of the ECU 100>

[0141] Figure 7 It is a flowchart showing an example of the operation of the LNT system abnormality detection function of the ECU 100.

[0142] In step S1, the ECU 100 determines whether an abnormality has occurred in the LNT system. Then, when an abnormality has occurred in the LNT system (S1: Yes), the ECU 100 advances the process to step S2. When no abnormality has occurred in the LNT system (S1: No), the ECU 100 ends without performing any processing. Figure 7 The processing of the flowchart to end.

[0143] In step S2, the ECU 100 restricts the driving mode of the vehicle 1 to series hybrid driving and prohibits engine direct connection driving. That is, when the vehicle 1 is in engine direct connection driving at the current time point, the ECU 100 switches to series hybrid driving.

[0144] In step S3, the ECU 100 sets the driving state of the engine 30 to steady-state operation in the NOx reduction mode. At this time, the ECU 100 causes the engine 30 to perform steady-state operation in such a manner that the output becomes an output above a specified value within the following output range, the output range being such that the NOx emission amount of the engine 30 does not exceed the NOx purifiable amount of the NOx purification system using the SCR catalyst 73.

[0145] It should be noted that at this time, the ECU100 calculates the NOx purification capacity of the SCR catalyst 73 based, for example, the temperature of the SCR catalyst 73 and the ammonia storage capacity of the SCR catalyst 73 at the current time. Then, the ECU100 calculates the output range of the engine 30 during steady-state operation (i.e., the NOx emissions of the engine 30 do not exceed the output range of the NOx purification capacity of the NOx purification system using the SCR catalyst 73) based on the calculated NOx purification capacity of the SCR catalyst 73 and the preset control mapping.

[0146] Furthermore, at this time, the ECU 100 sets the operating state of the engine 30 to NOx reduction mode. That is, it controls the opening of the valve of the EGR device 30E and reduces the boost pressure of the turbocharger connected to the engine 30 or delays the timing of fuel injection.

[0147] By performing the above processing, even in the event of an LNT system malfunction, ECU100 can suppress the amount of NOx emitted from vehicle1 to the outside while ensuring the necessary driving force for vehicle1 to drive.

[0148] [Effect]

[0149] As described above, the following is disclosed in this embodiment:

[0150] A control device for a hybrid vehicle, the hybrid vehicle having an engine and an electric motor as power sources, capable of using these power sources for series hybrid driving and engine direct drive, and having a NOx purification system using an SCR catalyst and an LNT catalyst in the exhaust passage of the engine, the control device comprising:

[0151] An anomaly detection unit detects anomalies in the NOx purification system related to the LNT catalyst; and

[0152] When the driving status control unit detects the abnormality, it restricts the vehicle's driving mode to the series hybrid driving mode and prohibits the engine from driving directly. It also enables the engine to operate in a steady state by making the output above a predetermined value within an output range, wherein the output range is the output range that ensures the NOx emissions of the engine do not exceed the NOx purifiable amount of the NOx purification system using the SCR catalyst.

[0153] According to the control device of this embodiment, even in the event of an malfunction in the LNT system, it is possible to suppress NOx emissions to the outside of the vehicle while ensuring the required vehicle driving force, thereby maintaining good driving performance.

[0154] The embodiments of the present invention have been described in detail above, but these are merely examples and do not limit the scope of protection of the present invention. The technology described in the present invention includes various modifications and variations to the embodiments of the above examples.

[0155] For example, the layout of the hybrid vehicle 1 to which the control device of the present invention is applicable, except... Figure 2 In addition to the arrangement shown, various variations can be considered. Specifically, the layout of the hybrid vehicle 1 can be such that the generator 40 and the axle are not on the same axle (a layout in which the generator 40 is driven by a transmission belt), or a layout in which an electric motor 20 is arranged between the engine 30 and the gear mechanism 60, etc.

[0156] Furthermore, various modifications can be considered for the various sensors 80 installed in the hybrid vehicle 1 to which the control device of the present invention is applicable. For example, the first NOx sensor 80b is not necessarily required. In this case, the ECU 100 can estimate the NOx emissions of the engine 30 based on, for example, the operating state of the engine 30 and the valve opening of the EGR device 30E.

[0157] Industrial applicability

[0158] The control device for hybrid vehicles according to the present invention can ensure good driving performance while suppressing NOx emissions to the outside of the vehicle, even in the event of an malfunction in the LNT system.

Claims

1. A control device for a hybrid vehicle, the hybrid vehicle having an engine and an electric motor as power sources, capable of using these power sources for series hybrid driving and engine direct drive, and having a NOx purification system using an SCR catalyst and an LNT catalyst in the exhaust passage of the engine, the control device comprising: An anomaly detection unit detects anomalies in the NOx purification system related to the LNT catalyst. as well as When the driving status control unit detects the abnormality, it restricts the vehicle's driving mode to the series hybrid driving mode and prohibits the engine from driving directly. It also enables the engine to operate in a steady state by making the output above a predetermined value within an output range, wherein the output range is the output range that ensures the NOx emissions of the engine do not exceed the NOx purifiable amount of the NOx purification system using the SCR catalyst.

2. The control device for a hybrid vehicle as claimed in claim 1, wherein, If the abnormality is detected, the driving state control unit causes the engine to switch from fuel efficiency priority mode to NOx reduction mode for steady-state operation.

3. The control device for a hybrid vehicle as described in claim 2, wherein, In the NOx reduction mode, the opening of the engine's EGR valve is increased to a level greater than that set in the fuel efficiency priority mode.

4. The control device for a hybrid vehicle as claimed in claim 1, wherein, The NOx purification capacity of the SCR catalyst is calculated based on the temperature of the SCR catalyst and the amount of ammonia stored at the time point when the anomaly was detected.

5. The control device for a hybrid vehicle as claimed in claim 1, wherein, If the abnormality is detected, the driving state control unit enables the engine to operate in a steady state with the maximum output within the output range or with a margin for the maximum output.

6. The control device for a hybrid vehicle as claimed in claim 1, wherein, In the event of the detected anomaly, the driving status control unit uses the engine output to generate electrical energy required for driving using the electric motor, and uses the electric motor output to meet the driving force required according to the driver's throttle operation.

7. The control device for a hybrid vehicle as claimed in claim 1, wherein, The anomaly refers to a failure mode that is determined to be unable to ensure the purification performance of the LNT catalyst.

8. The control device for a hybrid vehicle as claimed in claim 7, wherein, The anomalies include temperature anomalies of the LNT catalyst, as well as sensor value anomalies and malfunctions of the NOx sensor located upstream of the LNT catalyst.

9. A control method for a hybrid vehicle, the hybrid vehicle having an engine and an electric motor as power sources, capable of using these power sources for series hybrid driving and engine direct drive, and having a NOx purification system using an SCR catalyst and an LNT catalyst in the exhaust passage of the engine, the control method comprising: Handling of any abnormalities in the NOx purification system associated with the LNT catalyst; as well as In the event of the detected anomaly, the vehicle's driving mode is restricted to the series hybrid mode, and direct engine operation is prohibited. The engine is then operated in a steady state such that its output is above a specified value within a range where the NOx emissions from the engine do not exceed the NOx purifiable range of the NOx purification system using the SCR catalyst.

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