Control device for hybrid vehicles, and control method for hybrid vehicles

Abstract

To provide a control device for a hybrid vehicle that ensures good drivability while suppressing NOx emissions to the outside of the vehicle, even if a malfunction occurs in the SCR system. [Solution] A control device for a hybrid vehicle having an engine and an electric motor as power sources, enabling series hybrid driving and direct engine driving, and having a NOx purification system using an SCR catalyst and an LNT catalyst in the exhaust passage of the engine, comprising: an abnormality detection unit that detects abnormalities related to the NOx purification system using the SCR catalyst; and a driving state control unit that, when the abnormality is detected, prohibits direct engine driving as the driving mode of the vehicle and restricts it to series hybrid driving, and causes the engine to operate in a steady state so that the output from the engine is above a predetermined value within an output range that does not exceed the amount of NOx that can be purified by the NOx purification system using the LNT catalyst.

Description

Technical Field

[0001] The present disclosure relates to a control device for a hybrid vehicle and a control method for a hybrid vehicle.

Background Art

[0002] In recent years, due to demands for improving energy efficiency and demands for improving exhaust emissions (NOx), the configurations of hybrid vehicles have diversified.

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

[0004] Generally, a series hybrid vehicle runs by the driving force of an electric motor. The engine is only used for power generation, and the electric power generated by the generator using the driving force of the engine is either charged into the battery or supplied to the electric motor.

[0005] The driving modes of a series hybrid vehicle are two: "EV driving mode" and "series driving mode". In the EV driving mode, the hybrid vehicle runs by the driving force of the electric motor driven by power supply from the battery. At this time, the engine is not driven. Also, in the "series driving mode", the hybrid vehicle runs by the driving force of the electric motor driven by power supply from both the battery and the generator or power supply only from the generator. At this time, the engine is driven for power generation in the generator. The series driving mode is useful in that the engine can be operated steadily near the optimal fuel consumption point.

[0006] Parallel hybrid vehicles are driven by either an electric motor or an engine, or both. In particular, the mode in which a parallel hybrid vehicle is driven solely by the engine is called the "engine driving mode." The mode in which a parallel hybrid vehicle is driven by both the engine and the electric motor is called the "parallel driving mode." Both the engine driving mode and the parallel driving mode are useful in that they can suppress battery charging and discharging losses, as well as various resistance losses when operating the electric motor and / or generator.

[0007] Series / parallel hybrid vehicles employ a configuration that combines both of the above methods. Specifically, in this system, the power transmission system is switched between a series and a parallel configuration by disengaging or engaging (disengaging) a clutch depending on the driving conditions of the hybrid vehicle. Series / parallel hybrid vehicles are useful because they offer the advantages of both series and parallel hybrid vehicles.

[0008] Furthermore, 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 Documents 1 and 2). [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2020-050009 [Patent Document 2] Japanese Patent Publication No. 2019-166943 [Overview of the project] [Problems that the invention aims to solve]

[0010] Incidentally, conventionally, this type of vehicle is often equipped with a NOx purification system (hereinafter also referred to as the "SCR system") that uses an SCR catalyst (also called a NOx selective reduction catalyst) as an engine exhaust purification device.

[0011] Typically, in this type of vehicle, an ECU (Electric Control Unit) is installed that has a fault diagnosis function to sequentially check whether the SCR system is functioning correctly, such as checking for urea depletion in the urea water supply device that supplies urea water to the SCR catalyst, or malfunctions in the NOx sensors located before and after the SCR catalyst, from the perspective of preventing exhaust emissions (NOx).

[0012] Conventionally, when such an ECU determines that an abnormality has occurred in the SCR system, it is configured to limit the engine output (i.e., the amount of fuel injected) to suppress NOx emissions from the engine.

[0013] Figure 1 shows the conventional engine control method when the SCR system malfunctions.

[0014] As shown in Figure 1, limiting engine output makes it possible to suppress the amount of NOx emitted from the engine, even when NOx purification by the SCR catalyst is not functioning properly. However, when engine output is limited in this way, although the vehicle has enough power to drive to a repair center, when the vehicle is loaded or towed, or when more engine power is required for driving than when it is unloaded, the vehicle may have difficulty driving under its own power to keep up with the flow of traffic.

[0015] The present invention has been made in view of the above-mentioned problems, and aims to provide a control device and control method for a hybrid vehicle that can ensure good drivability while suppressing the emission of NOx to the outside of the vehicle, even when an abnormality occurs in the SCR system. [Means for solving the problem]

[0016] The main present invention that solves the aforementioned problems is: A control device for a hybrid vehicle having an engine and an electric motor as power sources, enabling series hybrid driving and direct engine-driven driving using these, and having a NOx purification system using an SCR catalyst and an LNT catalyst in the exhaust passage of the engine, An abnormality detection unit for detecting abnormalities in the NOx purification system using the aforementioned SCR catalyst, When the aforementioned abnormality is detected, the driving mode of the vehicle is restricted to the series hybrid mode, prohibiting the direct-drive mode, and the driving state control unit causes the engine to operate in a steady state so that the output from the engine is above a predetermined value within the output range, such that the NOx emissions from the engine do not exceed the NOx purification capacity of the NOx purification system using the LNT catalyst. This is a control device for hybrid vehicles equipped with [a specific feature / feature].

[0017] Also, in other situations, A control method for a hybrid vehicle having an engine and an electric motor as power sources, enabling series hybrid driving and direct engine-driven driving using these, and having a NOx purification system using an SCR catalyst and an LNT catalyst in the exhaust passage of the engine, A process for detecting abnormalities in the NOx purification system using the aforementioned SCR catalyst, If the aforementioned abnormality is detected, the vehicle's driving mode is restricted to series hybrid driving, prohibiting direct engine drive, and the engine is operated in a steady state so that the output is above a predetermined value within the output range, such that the NOx emissions from the engine do not exceed the NOx purification capacity of the NOx purification system using the LNT catalyst. This is a control method for a hybrid vehicle. [Effects of the Invention]

[0018] According to the control device for a hybrid vehicle according to the present invention, even when an abnormality occurs in the SCR system, it is possible to ensure good drivability while suppressing the emission of NOx to the outside of the vehicle.

Brief Description of the Drawings

[0019] [Figure 1] Figure showing the mode of engine control according to the prior art when an SCR system abnormality occurs [Figure 2] Figure schematically showing the overall configuration of a vehicle according to an embodiment of the present invention [Figure 3] Figure showing an example of the configuration of an exhaust gas purification device according to an embodiment of the present invention [Figure 4] Figure showing an example of the functional configuration of an ECU according to an embodiment of the present invention [Figure 5] Figure showing the mode of engine control by an ECU according to an embodiment of the present invention when an SCR system abnormality occurs [Figure 6] Figure showing an example of a control map for controlling the valve opening degree of an EGR device by an ECU according to an embodiment of the present invention [Figure 7] Flowchart showing an example of the operation related to the SCR system abnormality detection function of an ECU according to an embodiment of the present invention

Mode for Carrying Out the Invention

[0020] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same function are denoted by the same reference numerals, and redundant description is omitted.

[0021] <Overall Configuration of the Vehicle> Hereinafter, an example of the configuration of a hybrid vehicle (hereinafter referred to as "Vehicle 1") according to an embodiment of the present invention will be described. Vehicle 1 according to the present embodiment is a series / parallel hybrid vehicle that combines the series method and the parallel method.

[0022] Figure 2 is a schematic diagram showing the overall configuration of vehicle 1.

[0023] Vehicle 1 is equipped with a battery 10, an electric motor 20, an engine 30, a generator 40, a clutch 50, a gear mechanism 60, an exhaust gas purification device 70, various sensors 80, and an ECU 100.

[0024] Battery 10 is a lithium-ion battery that supplies a high voltage of, for example, 200-350V. Battery 10 is wired to the electric motor 20, and the power charged in battery 10 can be supplied to the electric motor 20. In addition, battery 10 is wired in parallel to the electric motor 20 to the generator 40, and can be charged with power generated by the generator 40.

[0025] The electric motor 20 generates power for the vehicle 1 to move using the power charged in the battery 10 and / or the power generated by the generator 40 (i.e., the power generated by the engine 30). The output torque generated by the electric motor 20 is transmitted to the drive wheels 1R of the vehicle 1 via the gear mechanism 60. The rotor of the electric motor 20 is directly connected to the gear mechanism 60. In addition, the electric motor 20 operates as a generator during regenerative braking, and the power generated by the electric motor 20 is used to charge the battery 10.

[0026] Furthermore, the electric motor 20 has an inverter (not shown) and uses DC power obtained from the battery 10 or DC power sent from the generator 40 (in this embodiment, the generator 40 converts the AC power it generates with its own power generation inverter into DC power and sends it to the electric motor 20 or battery 10) by converting it into AC voltage.

[0027] The engine 30 is directly connected to the rotor of the generator 40. When the clutch 50 is disengaged and the vehicle 1 is running in series, the engine 30 is used solely for generating electricity with the generator 40. However, when the clutch 50 is engaged, the output of the engine 30 is directly transmitted to the drive wheels 1R of the vehicle 1 via the generator 40, clutch 50, and gear mechanism 60 as mechanical energy for the vehicle 1 to move.

[0028] From the perspective of reducing NOx emissions, the engine 30 is equipped with an EGR (Exhaust Gas Recirculation) device 30E (see Figure 3). In addition, an exhaust gas purification device 70 is installed in the exhaust passage 30T of the engine 30.

[0029] The generator 40 generates electricity using the power of the engine 30. The electricity generated by the generator 40 is either used to charge the battery 10 or supplied directly to the electric motor 20. The generator 40 also has an inverter (not shown) that converts the AC voltage it generates into a DC voltage and sends it to the battery 10 or the electric motor 20.

[0030] The clutch 50 disconnects and reconnects the power transmission path from the engine 30 to the drive wheel 1R of the vehicle 1, based on instructions from the ECU 100.

[0031] 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 rotational speed and output torque at a predetermined gear ratio, and transmits it to the drive wheels 1R of the vehicle 1.

[0032] The various sensors 80 are sensors that detect the state of various parts of the vehicle 1 and the driver's driving operations. Examples of the various sensors 80 include a vehicle speed sensor that detects the vehicle's speed, an accelerator pedal position sensor that detects the driver's accelerator operation, a rotational speed sensor that detects the rotational speed of the engine 30, a rotational speed sensor that detects the rotational speed of the rotor of the generator 40, a rotational speed sensor that detects the rotational speed of the rotor of the electric motor 20, a voltage sensor that detects the charge level of the battery 10, and sensors that detect the state of various parts of the exhaust gas purification device 70 (see Figure 3, described later). The detection signals detected by the various sensors 80 are sent to the ECU 100.

[0033] The ECU 100 communicates with various parts of the vehicle 1 to comprehensively control the operation of each part of the vehicle 1. For example, the ECU 100 controls the switching of the power transmission system to the drive wheels 1R, the engagement and disengagement of the clutch 50, the operation of the engine 30, the operation of the generator 40, the operation of the electric motor 20, the charging and discharging of the battery 10, and the operation of the exhaust gas purification device 70.

[0034] Furthermore, the ECU 100 acquires sensor information from various sensors 80 installed in the vehicle 1 and detects the status of various parts of the vehicle 1.

[0035] The ECU100 is composed of components such as a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), input ports, and output ports. Each function of the ECU100 is realized, for example, by the CPU referencing control programs and various data stored in the ROM, RAM, etc. However, some or all of each function may be realized by processing by a DSP (Digital Signal Processor) or dedicated hardware circuitry (e.g., ASIC or FPGA) instead of, or in conjunction with, processing by the CPU.

[0036] Vehicle 1 has, for example, driving modes: (a) EV driving mode, (b) series driving mode, (c) engine driving mode, and (d) parallel driving mode.

[0037] In EV driving mode, the clutch 50 is disengaged and the engine 30 is stopped. Vehicle 1 is driven by the power of the electric motor 20, which is powered by the battery 10.

[0038] In series driving mode, the clutch 50 is disengaged, and the engine 30 is operated to supply power that the electric motor 20 can output to meet the required driving force based on the accelerator opening and vehicle speed. Vehicle 1 is driven by the driving force of the electric motor 20, which is powered by the generator 40. In addition, auxiliary power from the battery 10 may be supplied to the electric motor 20 at this time.

[0039] In engine-driven mode, the clutch 50 is engaged, and vehicle 1 is driven solely by the engine 30. When driving in engine-driven mode, the rotor of the electric motor 20 and the rotor of the generator 40 are driven along with the engine 30.

[0040] In parallel driving mode, the clutch 50 is engaged, and vehicle 1 is driven by the combined power of both the engine 30 and the electric motor 20. When driving in parallel driving mode, the rotor of the generator 40 is driven along with the engine 30.

[0041] The ECU100 switches between these driving modes, for example, to optimize fuel efficiency. Since this control is based on conventionally known technology, a detailed explanation is omitted here.

[0042] In the following, driving in engine-only mode and parallel driving mode will also be referred to as "direct engine drive." Driving in series driving mode will also be referred to as "series hybrid drive."

[0043] <Configuration of exhaust gas purification device 70> Figure 3 shows an example of the configuration of the exhaust gas purification device 70.

[0044] The exhaust gas 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. In this case, these catalysts 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 upstream to downstream.

[0045] The LNT catalyst 71 (also called a NOx storage catalyst) absorbs NOx from the exhaust gas when there is an excess of oxygen in the exhaust gas, and in a reducing atmosphere, it reacts the absorbed NOx with hydrocarbons in the exhaust gas to reduce it to harmless gases such as nitrogen and releases it. As an LNT catalyst 71, for example, one can be used in which a catalyst for reducing NOx, such as platinum or rhodium, and a NOx storage material such as calcium or barium are supported on a catalyst carrier such as alumina.

[0046] Furthermore, as the LNT catalyst 71 approaches saturation, its efficiency in absorbing NOx decreases. Therefore, the NOx absorption state of the LNT catalyst 71 is monitored by the ECU 100 (rich spike execution control unit 103). Specifically, when NOx absorption in the LNT catalyst 71 progresses and the NOx level approaches saturation, the ECU 100 (rich spike execution control unit 103) operates the engine 30 at a rich air-fuel ratio (hereinafter referred to as "rich spike"), thereby forcibly generating exhaust gas with a reducing atmosphere and purging NOx from the LNT catalyst 71 (details will be described later).

[0047] The PM filter 72 captures PM (Particulate Matter) contained in the exhaust gas. Porous ceramics such as cordierite or silicon carbide are used as the PM filter 72.

[0048] The SCR catalyst 73 adsorbs ammonia produced by hydrolysis of urea water supplied from the urea water supply device 75, and selectively reduces and purifies NOx from the exhaust gas using the adsorbed ammonia. As the SCR catalyst 73, for example, a NOx reduction catalyst such as Fe zeolite, Cu zeolite, or vanadium can be supported on the surface of a ceramic support.

[0049] The ASC catalyst 74 (also known as the ammonia slip suppression catalyst) prevents ammonia leaked from the SCR catalyst 73 from being released to the outside. The ASC catalyst 74 suppresses ammonia slip from the SCR catalyst 73 by oxidizing the ammonia that has passed through the SCR catalyst 73 and decomposing it into water and nitrogen.

[0050] The urea water supply device 75 injects urea water upstream of the SCR catalyst 73 in the exhaust passage 30T. The urea water supply device 75 is composed of, for example, a urea water addition valve, a urea water tank, and a supply pump. That is, in the urea water supply device 75, urea water pressurized by the supply pump from the urea water tank is injected into the exhaust passage 30T from the urea water addition valve.

[0051] The amount of urea solution injected from the urea solution supply device 75 into the exhaust passage 30T is controlled by adjusting the opening degree of the urea solution injection valve. The opening degree of the urea solution injection valve is controlled by a control signal output from the ECU 100.

[0052] The ECU 100 controls the injection of urea solution, which is the same as conventionally known methods, and therefore will not be explained here. However, the ECU 100 sets a target value for the amount of ammonia stored in the SCR catalyst 73 based on the catalyst temperature of the SCR catalyst 73 indicated by the temperature sensor 80e. The ECU 100 then sequentially calculates the amount of ammonia consumed in the SCR catalyst 73 based on the sensor values ​​indicated by the second NOx sensor 80c and the flow sensor 80a. The ECU 100 then controls the amount of urea solution injected by the urea solution supply device 75 so that the amount of ammonia stored in the SCR catalyst 73 is maintained at the target value.

[0053] Thus, in the exhaust gas purification device 70 according to this embodiment, both the SCR catalyst 73 and the LNT catalyst 71 are used in order to minimize exhaust gas emissions (NOx).

[0054] Generally, SCR catalysts 73 have high NOx purification performance, but they are inactive at low exhaust temperatures (for example, below 200°C). In this regard, by providing both SCR catalyst 73 and LNT catalyst 71 in the exhaust passage 30T, it becomes possible to purify NOx emitted from the engine 30 by the LNT catalyst 71 when the exhaust temperature is low and the SCR catalyst 73 is inactive, such as during engine startup.

[0055] In addition, this configuration makes it possible to perform NOx purification using the LNT catalyst 71 even if a malfunction occurs in the NOx purification system using the SCR catalyst 73.

[0056] Furthermore, the exhaust gas purification device 70 is equipped with various sensors 80, including a flow sensor 80a for detecting the flow rate of intake air flowing into the engine 30, a first NOx sensor 80b for detecting the amount of NOx discharged from 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 to the outside, a temperature sensor 80e for detecting the temperature of the SCR catalyst 73, and a urea water level sensor 80f for detecting the remaining amount in the urea water tank of the urea water supply device 75. These various sensors 80 sequentially transmit the sensor information obtained through detection to the ECU 100.

[0057] [Detailed configuration of ECU100] Figure 4 shows an example of the functional configuration of ECU100.

[0058] The ECU 100 has the functions of an abnormality detection unit 101, a driving state control unit 102, and a rich spike execution control unit 103.

[0059] <Anomaly detection unit 101> The abnormality detection unit 101 detects abnormalities related to the NOx purification system (hereinafter referred to as the SCR system) using the SCR catalyst 73 installed in the exhaust passage 30T of the engine 30.

[0060] Here, an abnormality related to the SCR system refers to an abnormality that leads to a state in which NOx in the exhaust gas cannot be sufficiently purified by the SCR catalyst 73 (i.e., a failure mode in which it is determined that the purification performance of the SCR catalyst 73 cannot be ensured).

[0061] Such abnormal situations include, for example, a shortage of urea solution in the urea solution supply device 75 that supplies urea solution to the SCR catalyst 73, as well as abnormal sensor values ​​and operational abnormalities of the second NOx sensor 80c, temperature sensor 80e, and third NOx sensor 80d located upstream of the urea solution supply device 75 in the exhaust passage 30T.

[0062] The abnormality detection unit 101 can detect the occurrence of a urea water shortage in the urea water supply device 75, for example, based on the sensor value indicated by the urea water level sensor 80f, which is located in the urea water tank of the urea water supply device 75. Furthermore, the abnormality detection unit 101 determines that an abnormality has occurred in the second NOx sensor 80c if, for example, the detection signal (i.e., sensor value) of the second NOx sensor 80c indicates an abnormal value or if the detection signal of the second NOx sensor 80c is interrupted. When the abnormality detection unit 101 detects such an abnormality related to the SCR system, it sets an abnormality occurrence flag in the memory unit (e.g., RAM) in order to switch the operating state of the vehicle 1.

[0063] Furthermore, the abnormality detection unit 101 may also set an abnormality flag in other cases, such as when an abnormality occurs in the flow sensor 80a or in the temperature sensor 80e that detects the temperature of the SCR catalyst 73. In such cases, the amount of ammonia stored in the SCR catalyst 73 becomes uncertain, making it impossible to accurately calculate the amount of urea water to be supplied to the SCR catalyst 73 from the urea water supply device 75.

[0064] <Driving State Control Unit 102> The driving state control unit 102 controls the driving mode of the vehicle 1.

[0065] As described above, 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 consumption) under normal conditions (meaning when the SCR system is functioning normally; the same applies hereinafter).

[0066] However, if the abnormality detection unit 101 detects an abnormality in the SCR system, the driving state control unit 102 prohibits direct engine drive as the driving mode of the vehicle 1 and restricts it to series hybrid drive. In this series hybrid drive, the driving state control unit 102 operates the engine 30 in a steady state such that the output from the engine 30 is above a predetermined value within the output range that does not exceed the amount of NOx that can be purified by the NOx purification system using the LNT catalyst 71.

[0067] The following will elaborate on this point.

[0068] Figure 5 shows the engine control behavior by ECU100 when the SCR system malfunctions.

[0069] As described above, in conventional engine control technology, when the SCR system malfunctions, the output (fuel injection amount) of the engine 30 is limited from the viewpoint of suppressing the amount of NOx emitted from the engine 30 to the outside. However, in this case, when the vehicle is loaded or towed, or when more engine output is required for driving compared to when the vehicle is unloaded, the vehicle 1 may have difficulty driving under its own power to keep up with the flow of traffic.

[0070] In this regard, the driving state control unit 102 according to this embodiment restricts the driving mode of the vehicle 1 to series hybrid driving and operates the engine 30 in a steady state such that the output from the engine 30 is at or above a predetermined value within the output range that does not exceed the amount of NOx that can be purified by the NOx purification system using the LNT catalyst 71.

[0071] Furthermore, while it is desirable for the engine output at this time to be near the maximum value within the above output range, it is even more desirable to set it to a value that secures a predetermined margin from the maximum value within the above output range, taking into consideration the change in the purification performance of the LNT catalyst 71 over time. Also, the engine output at this time does not have to be a perfectly constant value during steady-state operation, and may be gradually changed in accordance with the fluctuations in the required driving force at any given time.

[0072] This makes it possible to secure the necessary driving force for vehicle 1 without limiting output even in the event of an SCR system malfunction, thereby maintaining good drivability.

[0073] In this configuration, the output of the electric motor 20 is used to satisfy the required driving force necessary for the vehicle 1 to move, and the engine 30 performs power generation. The required driving force necessary for the vehicle 1 to move is set, for example, based on the vehicle's speed and the driver's accelerator operation (i.e., accelerator opening), and the electric motor 20 is controlled to output the required driving force. At this time, the power required to drive the electric motor 20 is supplied directly from the engine 30 (i.e., the generator 40), and any shortfall in the power generated by the engine 30 (i.e., the generator 40) is supplemented by the battery 10. In addition, any surplus power generated by the engine 30 (i.e., the generator 40) is used to charge the battery 10.

[0074] Generally, during direct engine-driven driving (i.e., engine-driven or parallel driving), the operating state of the engine 30 needs to be changed in response to the acceleration demands of the vehicle 1, which tends to increase instantaneous NOx emissions and the amount of NOx emitted outside the vehicle 1. In this respect, as described above, steady-state operation of the engine 30 using series hybrid driving reduces fluctuations in exhaust temperature, flow rate, and NOx emissions, thereby suppressing instantaneous NOx emissions caused by sudden acceleration, etc.

[0075] In addition, in the vehicle 1 according to this embodiment, in principle, all NOx emitted from the engine 30 is captured by the LNT catalyst 71. Therefore, even when the SCR catalyst 73 is not functioning completely, the amount of NOx emitted from the vehicle 1 to the outside can be suppressed to an extremely small amount.

[0076] Here, the "power output range of the engine 30 during steady-state operation" (i.e., the power output range in which the NOx emissions from the engine 30 do not exceed the NOx purification capacity of the NOx purification system using the LNT catalyst 71) may be set to a range determined in advance by experiments or simulations, taking into account the NOx purification performance of the LNT catalyst 71 under normal conditions. Alternatively, this power output range may be set to a more precise range, taking into account the current exhaust temperature, etc. By doing so, steady-state operation of the engine 30 can be performed with the engine output set to the highest possible value. Specifically, the current NOx purification capacity of the LNT catalyst 71 can be calculated, for example, based on the current exhaust temperature and exhaust flow rate. Then, using this NOx purification capacity, it is possible to accurately calculate the power output range of the engine 30 in which the NOx emissions from the engine 30 do not exceed this NOx purification capacity, using a pre-set control map (for example, a map in which the correspondence between the NOx purification capacity and the maximum engine output has been determined in advance by experiments or simulations).

[0077] Here, the driving condition control unit 102 prefers to operate the engine 30 in NOx reduction mode rather than fuel efficiency priority mode when the SCR system malfunctions. In other words, in fuel efficiency priority mode, the operating conditions of the engine 30 (for example, engine speed, output torque, fuel injection timing, EGR rate, and turbocharger boost pressure, etc.) are generally set from the viewpoint of improving fuel efficiency, but this fuel efficiency priority mode is not necessarily ideal from the viewpoint of reducing NOx emissions.

[0078] From this perspective, in NOx reduction mode, the driving state control unit 102, for example, increases the valve opening of the EGR device 30E compared to the opening set in fuel efficiency priority mode. This reduces NOx emissions from the engine 30.

[0079] Figure 6 shows an example of a control map for controlling the valve opening of the EGR device 30E. Figure 6A shows the control map used in fuel efficiency priority mode, and Figure 6B shows the control map used in NOx reduction mode.

[0080] The control map for the EGR device 30E has valve openings set for each engine speed and fuel injection amount. In Figures 6A and 6B, "Large" and "Small" represent the magnitude of the valve opening set for the EGR device 30E. In Figures 6A and 6B, darker areas indicate a larger valve opening.

[0081] Generally, when the combustion gas temperature rises, the amount of NOx, an environmental pollutant, generated increases sharply. The EGR device 30E reduces NOx generation by recirculating exhaust gas into the intake manifold, lowering the oxygen concentration in the intake air, and slowing the combustion speed, thereby lowering the combustion temperature. The valve opening of the EGR device 30E affects not only the amount of NOx generated, but also the output torque of the engine 30, the generation of white smoke, and fuel efficiency. Therefore, the control map of the EGR device 30E is pre-configured with the optimal EGR valve opening (i.e., the optimal amount of EGR introduced) according to the engine operating conditions, which has been derived through testing and other means.

[0082] In the abnormal operation control map, the valve opening is set larger for each operating state of the engine 30 compared to the normal operation control map. In other words, in NOx reduction mode, the valve opening of the EGR device 30E is increased compared to normal operation (i.e., fuel efficiency priority mode), thereby increasing the EGR rate. This reduces the amount of NOx emitted from the engine 30.

[0083] Furthermore, in NOx reduction mode, control may be applied to further reduce the boost pressure of the supercharger (not shown) connected to the engine 30, or to retard the fuel injection timing. This can further reduce NOx emissions from the engine 30.

[0084] In other words, when driving vehicle 1 in series hybrid mode, in fuel efficiency priority mode, engine 30 is controlled to operate at an operating point close to the point of maximum efficiency. In contrast, in NOx reduction mode, engine 30 is controlled to operate at an operating point outside the point of maximum efficiency, as described above. Therefore, in NOx reduction mode, fuel efficiency itself will be lower compared to fuel efficiency priority mode.

[0085] Furthermore, when the NOx reduction mode is activated, if the temperature of the LNT catalyst 71 is low, it is desirable for the ECU 100 to raise the temperature of the LNT catalyst 71 using an electric heater (not shown) to heat the LNT catalyst 71. This is because, in NOx reduction mode, the valve opening of the EGR device 30E is increased to lower the combustion temperature in the engine 30, which may cause the exhaust temperature to drop and prevent the LNT catalyst 71 from rising to a temperature at which it can efficiently absorb NOx. However, since there are cases where the exhaust temperature does not drop even if the combustion temperature drops, it is desirable to control the ON / OFF of the electric heater according to the detected temperature of the LNT catalyst 71.

[0086] <Rich Spike Execution Control Unit 103> The rich spike execution control unit 103 causes the engine 30 to execute a rich spike based on the NOx storage amount of the LNT catalyst 71.

[0087] The control of the rich spike execution timing by the rich spike execution control unit 103 is the same as conventionally known methods, so a detailed explanation is omitted here. The rich spike execution control unit 103 calculates the amount of NOx absorbed per unit time based on sensor information from the flow sensor 80a and the first NOx sensor 80b, or based on the estimated NOx emissions from the engine 30 and a model in the ECU 100, and estimates the amount of NOx absorbed by the LNT catalyst 71 at each point in time during driving by accumulating the amount of NOx absorbed per unit time. The rich spike execution control unit 103 then causes the engine 30 to execute a rich spike when the amount of NOx absorbed by the LNT catalyst 71 exceeds a predetermined value (for example, 80%).

[0088] When the rich spike is executed, the rich spike execution control unit 103 causes, for example, a fuel injection valve in the engine 30 to perform a short-time fuel injection (rich spike) as a post-injection, thereby operating the engine 30 at a rich air-fuel ratio and making the air-fuel ratio of the exhaust gas flowing into the LNT catalyst 71 spike to a rich air-fuel ratio.

[0089] By the way, generally in the ECU 100, a determination is made on the timing for implementing a rich spike in accordance with fluctuations in engine rotation and output so as not to cause a regeneration failure. Also, depending on the operating state of the engine 30, the NOx purge of the LNT catalyst 71 cannot be effectively performed. From this perspective as well, the determination of the timing for implementing a rich spike has become an inevitable process. However, because of this, during normal times, the rich spike is not executed until the storage amount of the LNT catalyst 71 increases beyond the reference amount, and there is a case where the NOx purification performance by the LNT catalyst 71 deteriorates.

[0090] In this regard, in the vehicle 1 according to the present embodiment, when an SCR system abnormality occurs, the vehicle 1 is made to perform series hybrid driving and the engine 30 is made to perform steady operation. Therefore, the rich spike execution control unit 103 can stably implement a rich spike without substantially being restricted by the implementation timing when an SCR system abnormality occurs. As a result, during this series hybrid driving, it is also possible to appropriately cause the engine 30 to execute a rich spike so that the NOx capture performance of the LNT catalyst 71 is maintained normally. In this regard as well, the engine control according to the present embodiment is useful.

[0091] <Operation flow of the ECU 100> FIG. 7 is a flowchart showing an example of an operation related to the SCR system abnormality detection function of the ECU 100.

[0092] In step S1, the ECU 100 determines whether or not an abnormality has occurred in the SCR system. If an abnormality has occurred in the SCR system (S1: YES), the ECU 100 proceeds to step S2. If no abnormality has occurred in the SCR system (S1: NO), the ECU 100 terminates the process shown in the flowchart of Figure 7 without performing any further processing.

[0093] In step S2, the ECU 100 prohibits direct-drive operation and restricts the driving mode of vehicle 1 to series hybrid operation. That is, if vehicle 1 is currently in direct-drive operation mode, the ECU 100 switches to series hybrid operation.

[0094] In step S3, the ECU 100 sets the engine 30's operating state to steady-state operation in NOx reduction mode. At this time, the ECU 100 operates the engine 30 in a steady state such that the output is near the maximum value within the output range where the NOx emissions from the engine 30 do not exceed the NOx purification capacity of the NOx purification system using the LNT catalyst 71. At this time, the ECU 100 also increases the valve opening of the EGR device 30E, reduces the boost pressure of the turbocharger connected to the engine 30, and retards the fuel injection timing.

[0095] By performing the above processing, the ECU 100 enables the vehicle 1 to run while suppressing the amount of NOx emitted from the vehicle 1 to the outside, and while ensuring the necessary driving force for the vehicle 1, even if an abnormality occurs in the SCR system.

[0096] [effect] As described above, in this embodiment, A control device for a hybrid vehicle having an engine and an electric motor as power sources, enabling series hybrid driving and direct engine-driven driving using these, and having a NOx purification system using SCR and LNT in the exhaust passage of the engine, An abnormality detection unit for detecting abnormalities in the NOx purification system using the aforementioned SCR catalyst, When the aforementioned abnormality is detected, the driving mode of the vehicle is restricted to the series hybrid mode, prohibiting the direct-drive mode, and the driving state control unit causes the engine to operate in a steady state so that the output from the engine is above a predetermined value within the output range, such that the NOx emissions from the engine do not exceed the NOx purification capacity of the NOx purification system using the LNT catalyst. A control device for a hybrid vehicle equipped with [the specified feature] was disclosed.

[0097] According to the control device of this embodiment, even if an abnormality occurs in the SCR system, it is possible to secure the necessary driving force of the vehicle while suppressing the emission of NOx to the outside of the vehicle, thereby maintaining good drivability.

[0098] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above.

[0099] For example, the layout of the hybrid vehicle 1 to which the control device of the present invention is applied can be varied in many ways other than the configuration shown in Figure 2. Specifically, the layout of the hybrid vehicle 1 may be such as a layout in which the generator 40 and the axle are not on the same axis (a layout in which the generator 40 is belt-driven), or a layout in which the electric motor 20 is positioned between the engine 30 and the gear mechanism 60.

[0100] Furthermore, various modifications are possible for the various sensors 80 provided in the hybrid vehicle 1 to which the control device of the present invention is applied. For example, the first NOx sensor 80b is not necessarily required. In this case, the ECU 100 may estimate the amount of NOx emissions from the engine 30 based on, for example, the operating state of the engine 30 and the valve opening of the EGR device 30E. [Industrial applicability]

[0101] According to the control device for hybrid vehicles of the present invention, even if an abnormality occurs in the SCR system, it is possible to ensure good drivability while suppressing the emission of NOx to the outside of the vehicle. [Explanation of Symbols]

[0102] 1 vehicle 1R drive wheel 10 batteries 20 Electric motor 30 Engine 30E EGR device 40 Generators 50 Clutch 60 gear mechanism 70 Exhaust purifying device 71 LNT catalyst 72 PM filter 73 SCR catalyst 74 ASC catalyst 75 Urea water supply equipment 80 Various Sensors 80a flow sensor 80b First NOx Sensor 80°C 2nd NOx Sensor 80d 3rd NOx sensor 80e Temperature Sensor 80f Urea solution level sensor 100 ECU 101 Anomaly detection unit 102 Driving State Control Unit 103 Rich Spike Execution Control Unit

Claims

1. A control device for a hybrid vehicle having an engine and an electric motor as power sources, enabling series hybrid driving and direct engine-driven driving using these, and having a NOx purification system using an SCR catalyst and an LNT catalyst in the exhaust passage of the engine, An abnormality detection unit for detecting abnormalities in the NOx purification system using the aforementioned SCR catalyst, When the aforementioned abnormality is detected, the driving mode of the vehicle is restricted to the series hybrid mode, prohibiting the direct-drive mode, and the driving state control unit causes the engine to operate in a steady state so that the output from the engine is above a predetermined value within the output range, such that the NOx emissions from the engine do not exceed the NOx purification capacity of the NOx purification system using the LNT catalyst. A control device for hybrid vehicles equipped with [a specific feature / feature].

2. If the aforementioned abnormality is detected, the driving state control unit will switch the engine from fuel efficiency priority mode to NOx reduction mode for steady operation. A control device for a hybrid vehicle according to claim 1.

3. In the NOx reduction mode, the opening of the EGR valve of the engine is increased compared to the opening set in the fuel efficiency priority mode. A control device for a hybrid vehicle according to claim 2.

4. When the aforementioned driving state control unit detects the abnormality, it causes the engine to operate at a steady state at the maximum output within the output range, or at an output that includes a margin over the maximum output. A control device for a hybrid vehicle according to claim 1.

5. The engine is further equipped with a rich spike execution control unit that, based on the NOx storage amount of the LNT catalyst, causes the engine to execute rich spikes at any given time. A control device for a hybrid vehicle according to claim 1.

6. When the aforementioned driving state control unit detects the abnormality, the engine output is used to generate the power necessary for driving with the electric motor, and the output of the electric motor is used to satisfy the required driving force corresponding to the driver's accelerator operation. A control device for a hybrid vehicle according to claim 1.

7. The aforementioned abnormality is a failure mode in which it is determined that the purification performance of the SCR catalyst cannot be ensured. A control device for a hybrid vehicle according to claim 1.

8. The aforementioned abnormalities include a shortage of urea solution in the urea solution supply device that supplies urea solution to the SCR catalyst, as well as abnormal sensor values ​​and operational abnormalities of the NOx sensor, temperature sensor, and NOx sensor located upstream and downstream of the SCR catalyst in the exhaust passage. A control device for a hybrid vehicle according to claim 7.

9. A control method for a hybrid vehicle having an engine and an electric motor as power sources, enabling series hybrid driving and direct engine-driven driving using these, and having a NOx purification system using an SCR catalyst and an LNT catalyst in the exhaust passage of the engine, A process for detecting abnormalities in the NOx purification system using the aforementioned SCR catalyst, If the aforementioned abnormality is detected, the vehicle's driving mode is restricted to prohibiting direct-drive operation and to series hybrid operation, and the engine is operated in a steady state so that the output from the engine is above a predetermined value within the output range that does not exceed the amount of NOx that can be purified by the NOx purification system using the LNT catalyst. Control method for a hybrid vehicle.

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