JP2020063711A - Hybrid system, control device for hybrid system, and control method for hybrid system - Google Patents

Abstract

To operate an internal combustion engine regardless quantity of a remaining reductant when purifying exhaust air by means of a catalyst utilizing the reductant.SOLUTION: A hybrid system comprises: an internal combustion engine; an exhaust passage; a generator which generates electric power by utilizing motive force of the internal combustion engine; a power storage device which is charged with the electric power generated by the generator; a vehicle driving motor which is driven by discharged electric power of the power storage device and the electric power generated by the generator;a supply device which is disposed at an upstream side of the first catalyst in the exhaust passage and supplies the reductant; a first catalyst which is disposed in the exhaust passage and purifies a nitride oxide in exhaust air by utilizing the reductant; a second catalyst which is disposed in the exhaust passage, is activated at a higher temperature than an activation temperature of the first catalyst and purifies the nitride oxide in the exhaust air; and a control device which controls an operational state of the internal combustion engine. The second catalyst is heated by the exhaust air. In a case where quantity of a remaining reductant is less than predetermined quantity, the control device operates the internal combustion engine so as to provide, as a control object, an exhaust temperature at which the second catalyst is activated at all the time when operating the internal combustion engine (S122).SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a hybrid system, a hybrid system control device, and a hybrid system control method, and more particularly, to a hybrid system and a hybrid system including a catalyst that purifies nitrogen oxides contained in exhaust gas by using a reducing agent. The present invention relates to a control device and a hybrid system control method.

  Conventionally, there has been an exhaust emission control device for an internal combustion engine including a NOx trap catalyst and an SCR (Selective Catalytic Reduction) catalyst (see, for example, Patent Document 1). The SCR catalyst purifies NOx (nitrogen oxide) contained in the exhaust gas from the internal combustion engine by using ammonia as a reducing agent generated from urea water. The NOx trap catalyst purifies NOx contained in the exhaust gas without using the reducing agent. The exhaust emission control device of Patent Document 1 includes a switching unit that switches between a reduction mode that suppresses the supply amount of urea water from a supply unit that supplies urea water to the SCR catalyst and a normal mode that does not suppress it. As a result, even when the mode is switched to the reduction mode, NOx can be purified by the NOx trap catalyst, so that the consumption of urea water can be suppressed while maintaining the efficiency of NOx purification.

JP, 2017-115640, A

  However, since the catalyst temperature becomes high during high load running, it is possible to reduce the amount of urea water consumption in the SCR catalyst by relying on the NOx trap catalyst, but during further high load running or low load running, the NOx trap catalyst Since the purification rate decreases, the consumption of urea water in the SCR catalyst cannot be reduced. Therefore, if the urea water is exhausted, the exhaust gas cannot be purified, and the legal standard for the NOx emission amount cannot be satisfied. As a result, there is a problem that the internal combustion engine cannot be operated due to the regulation of the law.

  This disclosure has been made to solve the above-mentioned problems, and its purpose is to reduce the amount of reducing agent remaining when it is configured to purify exhaust gas of an internal combustion engine with a catalyst that utilizes a reducing agent. (EN) Provided are a hybrid system, a hybrid system control device, and a hybrid system control method capable of operating an internal combustion engine so as not to violate legal regulations.

  A hybrid system according to the present disclosure includes an internal combustion engine, an exhaust passage of the internal combustion engine, a generator that uses the power output from the internal combustion engine to generate power, a power storage device that charges the power generated by the power generator, and a power storage device. The electric motor for driving the vehicle, which is driven by using at least one of the electric power generated by the generator and the electric power generated by the generator, and the nitrogen oxide contained in the exhaust gas, which is arranged in the exhaust passage and uses the reducing agent. And a reducing agent supply device that is arranged on the upstream side of the first catalyst in the exhaust passage and supplies the reducing agent to the exhaust passage, and a temperature that is arranged in the exhaust passage and is higher than the activation temperature of the first catalyst. And a control device for controlling the operating state of the internal combustion engine. The second catalyst is warmed by the exhaust gas flowing through the exhaust passage. When the remaining amount of the reducing agent is less than a predetermined amount, the control device operates the internal combustion engine with a control target that the exhaust gas temperature of the internal combustion engine is always the exhaust gas temperature at which the second catalyst is activated when the internal combustion engine is operating. .

  Preferably, when the remaining amount of the reducing agent is less than a predetermined amount, the control device switches between operating the internal combustion engine according to the SOC of the power storage device and stopping the internal combustion engine to operate intermittently.

  More preferably, the control device operates the internal combustion engine when the SOC of the power storage device is less than the first predetermined value, and stops the internal combustion engine when the SOC of the power storage device reaches the second predetermined value. Operates the internal combustion engine intermittently.

  Preferably, the internal combustion engine is a diesel engine. The second catalyst is a three-way catalyst. When operating the internal combustion engine with the exhaust gas temperature of the internal combustion engine at the exhaust gas temperature at which the second catalyst is activated, the control device controls the internal combustion engine to have an air-fuel ratio lower than the theoretical air-fuel ratio. .

  Preferably, when the remaining amount of the reducing agent exceeds a predetermined amount, the control device reduces the exhaust gas temperature of the internal combustion engine when the internal combustion engine is operated with the exhaust gas temperature at which the first catalyst is activated as a control target. The reducing agent supply device is controlled to permit the supply of the reducing agent, and when the internal combustion engine is operated with the exhaust gas temperature of the internal combustion engine at the exhaust temperature at which the second catalyst is activated, the reducing agent is supplied. The reducing agent supply device is controlled to prohibit.

  More preferably, when operating the internal combustion engine with a control target that the exhaust gas temperature of the internal combustion engine becomes the exhaust gas temperature at which the second catalyst is activated, the control device sets the rotation speed to a predetermined speed and increases or decreases the output torque. Thus, when the internal combustion engine is operated with the output adjusted, and the exhaust gas temperature of the internal combustion engine reaches the exhaust gas temperature at which the first catalyst is activated, the output torque is set to a predetermined value and the rotational speed is increased or decreased. By adjusting the output.

  More preferably, when the remaining amount of the reducing agent is less than the predetermined amount, the control device reduces the supply of the reducing agent to the exhaust passage as compared with the case where the remaining amount of the reducing agent exceeds the predetermined amount. Control the agent supply device.

  More preferably, the first catalyst is an SCR catalyst and the reducing agent is aqueous urea. Even when the remaining amount of the reducing agent is less than a predetermined amount, the control device allows the reducing agent to be supplied when the vehicle speed of the vehicle equipped with the hybrid system becomes 0. To control.

  A control device for a hybrid system according to another aspect of the present disclosure includes an internal combustion engine, an exhaust passage of the internal combustion engine, a generator that generates power using power output from the internal combustion engine, and a generated electric power generated by the generator. A power storage device, a motor for driving the vehicle that is driven by at least one of the power discharged by the power storage device and the power generated by the generator, and included in the exhaust gas that is arranged in the exhaust passage and uses the reducing agent. A first catalyst for purifying nitrogen oxides, a reducing agent supply device arranged upstream of the first catalyst in the exhaust passage to supply a reducing agent to the exhaust passage, and an activation temperature of the first catalyst arranged in the exhaust passage. And a second catalyst which is activated at a temperature higher than that of the second catalyst for purifying nitrogen oxides contained in exhaust gas, and is a control device for controlling an operating state of an internal combustion engine of a hybrid system. When the remaining amount of the reducing agent is less than a predetermined amount, the control device operates the internal combustion engine with a control target that the exhaust gas temperature of the internal combustion engine is always the exhaust gas temperature at which the second catalyst is activated when the internal combustion engine is operating. .

  A hybrid system control method according to still another aspect of the present disclosure provides an internal combustion engine, an exhaust passage of the internal combustion engine, a generator that generates power using power output from the internal combustion engine, and power generated by the generator. A power storage device to be charged, a vehicle driving electric motor that is driven by using at least one of the discharge power of the power storage device and the power generated by the generator, and a reducing agent that is placed in the exhaust passage to generate exhaust gas. A first catalyst for purifying contained nitrogen oxides, a reducing agent supply device arranged upstream of the first catalyst in the exhaust passage to supply a reducing agent to the exhaust passage, and an activation of the first catalyst arranged in the exhaust passage. A control method by a control device for controlling an operating state of an internal combustion engine of a hybrid system including a second catalyst which is activated at a temperature higher than a temperature and purifies nitrogen oxides contained in exhaust gas. . In the control method, when the remaining amount of the reducing agent is less than a predetermined amount, the control device sets the internal combustion engine as a control target such that the exhaust gas temperature of the internal combustion engine is always the exhaust gas temperature at which the second catalyst is activated. Including the step of operating the engine.

  According to this disclosure, when the remaining amount of the reducing agent is less than the predetermined amount, the internal combustion engine is operated with a control target that the exhaust temperature is activated to activate the second catalyst that does not use the reducing agent. As a result, a hybrid system capable of operating the internal combustion engine regardless of the remaining amount of the reducing agent when the exhaust gas of the internal combustion engine is configured to be purified by the catalyst using the reducing agent, and a control device for the hybrid system , And a method of controlling the hybrid system can be provided.

It is a figure which shows schematic structure of the vehicle in this Embodiment. 6 is a flowchart showing a flow of engine control processing in this embodiment. It is a graph which shows the performance curve of the engine in this embodiment. It is a figure for demonstrating that the decrease in urea water can be suppressed by the control in this embodiment.

  Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, the same reference numerals are given to the same components. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  FIG. 1 is a diagram showing a schematic configuration of a vehicle 100 in this embodiment. Referring to FIG. 1, a vehicle 100 includes a battery 10, a power control unit (hereinafter, referred to as “PCU (Power Control Unit)”) 11, an engine 20, and a motor generator (hereinafter, “MG (Motor Generator)”). 31), MG 32, and drive wheel 40. The vehicle 100 further includes various electronic control units (ECUs) such as an HV-ECU 51 and an EG-ECU 52 described later. The battery 10 according to the present embodiment corresponds to an example of the “power storage device” according to the present disclosure.

  The engine 20 is an internal combustion engine that outputs power by converting combustion energy generated when fuel (gasoline, light oil, etc.) is burned into kinetic energy of a moving element such as a piston or a crankshaft. MG31 and MG32 are electric power devices that convert electric energy into mechanical energy or convert mechanical energy into electric energy. In the present embodiment, a diesel engine is adopted as engine 20, and a three-phase AC synchronous motor generator in which permanent magnets are embedded in rotors is adopted as MG31 and MG32. The engine 20 may include a turbocharger (for example, a variable nozzle turbo) in the intake / exhaust system.

  Vehicle 100 according to the present embodiment is a series hybrid vehicle. In vehicle 100, MG 31 (traveling motor) drives drive wheels 40 by operating as an electric motor, and MG 32 is driven by engine 20 to generate electric power. Power sources for driving MG 31 are electric power generated by MG 32 and electric power stored in battery 10. More specifically, the rotary shaft 21 of the engine 20 and the rotary shaft 22 of the MG 32 are mechanically connected to each other via a gear 23, and the rotary shaft 22 of the MG 32 also rotates with the rotation of the rotary shaft 21 of the engine 20. It rotates and the MG 32 generates electricity. On the other hand, rotary shaft 41 of MG 31 is not mechanically connected to rotary shafts 21 and 22, but mechanically connected to drive shaft 42 via power transmission gear 43. The torque (driving force) output to the rotating shaft 41 of the MG 31 is transmitted to the driving shaft 42 via the power transmission gear 43, and the driving force of the MG 31 causes the driving shaft 42 to rotate. Then, as the drive shaft 42 rotates, the drive wheels 40 provided at both ends of the drive shaft 42 rotate.

  MG 31 operates as an electric motor during acceleration of vehicle 100, and drives drive wheels 40 of vehicle 100. On the other hand, when the vehicle 100 is being braked or the acceleration on the down slope is being reduced, the MG 31 operates as a generator to perform regenerative power generation. The electric power generated by MG 31 is supplied to battery 10 via PCU 11.

  MG 32 is configured to generate power (engine power generation) by using power output from engine 20. The engine-generated electric power generated in MG 32 is supplied from MG 32 to MG 31, or is supplied from MG 32 to battery 10 via PCU 11.

  PCU 11 is configured to include two inverters provided corresponding to MG 31 and MG 32, and a boost converter that boosts the DC voltage supplied to each inverter to the voltage of battery 10 or higher (for example, 600V). PCU 11 executes electric power conversion between battery 10 and MG31 and MG32 in accordance with a control signal from HV-ECU 51. The PCU 11 is configured to be able to control the states of the MG 31 and the MG 32 separately.

  The battery 10 is a rechargeable DC power supply. The rated voltage of the battery 10 is, for example, 300V to 450V. The battery 10 is configured to include, for example, a secondary battery (rechargeable battery). As the secondary battery, for example, a lithium ion battery can be adopted. Battery 10 may include an assembled battery including a plurality of secondary batteries (for example, lithium ion batteries) connected in series and / or in parallel. The secondary battery forming the battery 10 is not limited to the lithium ion battery, and another secondary battery (for example, a nickel hydrogen battery) may be adopted. An electrolytic solution type secondary battery or an all solid state type secondary battery may be adopted. Further, as the battery 10, a large-capacity capacitor or the like can be adopted.

  A monitoring unit 61 that monitors the state of the battery 10 is provided for the battery 10. The monitoring unit 61 includes various sensors that detect the state of the battery 10 (temperature, current, voltage, etc.). The HV-ECU 51 is configured to detect the state (SOC or the like) of the battery 10 based on the output of the monitoring unit 61. SOC (State Of Charge) indicates the remaining charge amount, and represents, for example, the ratio of the current charge amount to the charge amount in the fully charged state, which is represented by 0 to 100%. As the SOC measuring method, various known methods such as a method by current value integration (Coulomb count) or a method by estimating open circuit voltage (OCV) can be adopted.

  A monitoring unit 62 that monitors the state of the engine 20 is provided for the engine 20. The monitoring unit 62 includes various sensors that detect the state of the engine 20 (cooling water temperature, intake air amount, rotational speed, etc.). The HV-ECU 51 and the EG-ECU 52 are configured to detect the state of the engine 20 based on the output of the monitoring unit 62.

  Further, monitoring units 63 and 64 for monitoring the states of MG31 and MG32 are provided for MG31 and MG32, respectively. Monitoring units 63 and 64 include various sensors that detect the states (temperature, rotation speed, etc.) of MG31 and MG32. HV-ECU 51 is configured to detect the states of MG31 and MG32 based on the outputs of monitoring units 63 and 64.

  Each of the ECUs (HV-ECU 51, EG-ECU 52) included in vehicle 100 includes a CPU (Central Processing Unit) as a computing device, a storage device, and an input / output port for inputting / outputting various signals (both are shown in FIG. (Not shown). The storage device includes a RAM (Random Access Memory) as a working memory and a storage for storage (ROM (Read Only Memory), rewritable nonvolatile memory, etc.). Each ECU receives signals from various devices (sensors and the like) connected to the input port and controls various devices connected to the output port based on the received signals. Various controls are executed by the CPU executing the programs stored in the storage device. However, the control performed by each ECU is not limited to the processing by software, and may be performed by dedicated hardware (electronic circuit). The HV-ECU 51 and the EG-ECU 52 according to the present embodiment function as the “control device” according to the present disclosure.

  HV-ECU 51 calculates an output request value for engine 20 and an output request value for MG 31 and MG 32 (for example, a torque request value). Then, HV-ECU 51 transmits the output request value for engine 20 to EG-ECU 52, and based on the output request values for MG 31 and MG 32, supplies power to MG 31 and MG 32 (and thus the output torque of MG 31 and MG 32). To control. The HV-ECU 51 can control the magnitude (amplitude) and frequency of the electric power supplied to the MG 31 and the MG 32 by controlling the PCU 11 and the like. Further, the HV-ECU 51 controls the charge and discharge of the battery 10 by controlling the PCU 11 and the like.

  The various devices connected to the input port of the HV-ECU 51 further include an accelerator opening sensor 65 and a vehicle speed sensor 66 in addition to the various sensors included in the monitoring units 61, 63, 64.

  The accelerator opening sensor 65 detects a depression amount of an accelerator pedal (not shown) of the vehicle 100 as an accelerator opening, and outputs the detection result (a signal indicating the accelerator opening) to the HV-ECU 51. The HV-ECU 51 increases the driving force of the MG 31 as the accelerator pedal depression amount increases.

  Further, vehicle speed sensor 66 detects the speed of vehicle 100 and outputs the detection result (a signal indicating the vehicle speed) to HV-ECU 51.

  The EG-ECU 52 receives an output request value for the engine 20 from the HV-ECU 51, and controls the operation of the engine 20 (fuel injection control, ignition control, so that kinetic energy corresponding to the output request value is generated in the engine 20). Intake air amount control etc.). Engine power generation is performed by driving the engine 20, and the engine 20 is stopped when the engine power generation is not performed. By driving engine 20, MG 32 generates engine-generated electric power. Further, the EG-ECU 52 receives the detection values of various sensors included in the monitoring unit 62 and transmits the detection values to the HV-ECU 51.

  The vehicle 100 travels when the MG 31 drives the drive wheels 40. The HV-ECU 51 starts charging the battery 10 with the engine-generated power when the SOC of the battery 10 becomes equal to or lower than the charge start SOC while the vehicle 100 is traveling, and the SOC of the battery 10 becomes equal to or higher than the charge completion SOC. If so, the charging is stopped.

  When the SOC of the battery 10 is equal to or lower than the charge start SOC and the battery 10 is charged by the engine-generated power, the HV-ECU 51 requests the EG-ECU 52 to drive the engine 20 under a predetermined condition suitable for power generation. By the EG-ECU 52 controlling the engine 20 in accordance with this request, the MG 32 generates engine generated electric power larger than the electric power consumed when the vehicle 100 travels. Further, the HV-ECU 51 controls the PCU 11 and the like to supply the generated engine generated electric power to the battery 10. As a result, the battery 10 is charged by the engine-generated power, and the SOC of the battery 10 increases.

  When the SOC of the battery 10 becomes equal to or higher than the charge completion SOC, the HV-ECU 51 instructs the EG-ECU 52 to stop the engine 20 and controls the PCU 11 and the like to stop the supply of electric power to the battery 10. Let

  As described above, while the vehicle 100 is traveling, the engine 20 is started each time the SOC of the battery 10 becomes equal to or lower than the charge start SOC, and the battery 10 is charged by the engine-generated power. As a result, the SOC of the battery 10 is generally maintained within the range from the charging start SOC to the charging completion SOC.

  Further, in the present embodiment, vehicle 100 includes a three-way catalyst 71, a DPF (Diesel Particulate Filter) 72, and an SCR catalyst 73 as a device that processes the exhaust gas of engine 20. Exhaust pipes are connected between the engine 20, the three-way catalyst 71, the DPF 72, and the SCR catalyst 73.

  The three-way catalyst 71 is a catalyst that purifies nitrogen oxides (NOx), carbon monoxide (CO), and unburned hydrocarbons (HC) contained in the exhaust flowing through the exhaust passage of the engine 20. The three-way catalyst 71 reduces NOx to nitrogen and oxygen in the presence of a reducing gas (H2, CO or hydrocarbon), oxidizes carbon monoxide to carbon dioxide in the presence of an oxidizing gas, and oxidizes the oxidizing gas. Oxidize unburned hydrocarbons (HC) to carbon dioxide and water in the presence of. In order for the three-way catalyst 71 to be efficiently oxidized or reduced, it is necessary for the engine 20 to completely burn fuel and to burn (stoichiometric combustion) at a stoichiometric stoichiometry with no oxygen remaining. If the oxygen is in a lean state, the three-way catalyst 71 is not preferable for NOx reduction. When the temperature of the catalyst is low, the efficiency of the three-way catalyst 71 decreases. The three-way catalyst 71 is activated in a temperature range higher than that of the SCR catalyst 73 and the processing efficiency is improved.

  An exhaust temperature sensor 81 and an A / F sensor 82 are provided in the exhaust pipe between the engine 20 and the three-way catalyst 71. The exhaust temperature sensor 81 detects the temperature of the exhaust gas from the engine 20, and outputs the detection result (a signal indicating the exhaust temperature) to the EG-ECU 52. The A / F sensor 82 analyzes the exhaust gas from the engine 20 to detect the air-fuel ratio, and outputs the detection result (a signal indicating the air-fuel ratio) to the EG-ECU 52.

  The DPF 72 is a filter that collects particulate matter (PM: Particulate Matter) contained in the exhaust flowing through the exhaust passage of the engine 20. The collected PM accumulates inside the DPF 72. Therefore, the DPF 72 is regenerated by periodically heating the inside of the DPF 72 to burn and remove PM.

  The SCR catalyst 73 is a catalyst that uses a reducing agent to selectively purify NOx contained in the exhaust flowing through the exhaust passage of the engine 20. As the reducing agent, urea water is used in the present embodiment. The urea water injection nozzle 74 is provided in the exhaust pipe between the DPF 72 and the SCR catalyst 73, and injects the urea water supplied from the urea water tank 75 into the exhaust pipe. A residual amount sensor 84 is provided in the urea water tank 75. The remaining amount sensor 84 detects the remaining amount of urea water in the urea water tank 75, and outputs the detection result (a signal indicating the remaining amount of urea water) to the EG-ECU 52. The urea water injected from the urea water injection nozzle 74 is hydrolyzed by exhaust heat to generate ammonia as a reducing agent. The produced ammonia is adsorbed on the surface of the SCR catalyst 73 and selectively reacts with NOx in the exhaust gas to purify NOx into nitrogen and water. The SCR catalyst 73 is activated in a temperature range lower than that of the three-way catalyst 71, and the processing efficiency is improved.

  An oxidation catalyst such as an ASC (Ammonia Slip Catalyst) that oxidizes ammonia that has passed through the SCR catalyst 73 and prevents the ammonia from being discharged into the atmosphere may be provided downstream of the SCR catalyst 73.

  A NOx sensor 83 is provided in the exhaust pipe downstream of the SCR catalyst 73. The NOx sensor 83 detects the amount of NOx contained in the exhaust gas emitted from the SCR catalyst 73, and outputs the detection result (a signal indicating the amount of NOx) to the EG-ECU 52.

  In the vehicle 100 including the SCR catalyst 73 as described above, if the urea water as the reducing agent is used up, the exhaust gas cannot be purified and the legal standard for the NOx emission amount cannot be satisfied. As a result, it becomes impossible to operate the internal combustion engine due to legal regulations.

  Therefore, in this embodiment, the HV-ECU 51 and the EG-ECU 52 operate the engine 20 so that the exhaust temperature is such that the three-way catalyst 71 is activated when the residual amount of urea water is less than a predetermined amount. To do so. As a result, when the remaining amount of urea water is less than the predetermined amount, the engine 20 is operated so as to reach the exhaust temperature at which the three-way catalyst 71 that does not use urea water is activated. As a result, when the SCR catalyst 73 that uses urea water is configured to purify the exhaust gas of the engine 20, it is possible to operate the engine 20 regardless of the remaining amount of urea water without violating legal regulations. it can.

  FIG. 2 is a flow chart showing the flow of engine control processing in this embodiment. The engine control process is called by the main process at predetermined control cycles and is executed by the EG-ECU 52. Referring to FIG. 2, EG-ECU 52 calculates the remaining amount of urea water using the detection result from remaining amount sensor 84 of urea water tank 75 (step (hereinafter referred to as “S”) 101).

  The EG-ECU 52 determines whether the remaining amount of urea water is equal to or less than a predetermined amount (S102). The predetermined amount is a predetermined amount recommended to replenish the urea water tank 75 with urea water, and is, for example, a fraction of the full amount of the urea water tank 75. When it is determined that the remaining amount is equal to or less than the predetermined amount (YES in S102), the EG-ECU 52 shifts the exhaust gas processing mode to the urea suppression mode (S103). When it is determined that the remaining amount is not less than or equal to the predetermined amount (NO in S102), the EG-ECU 52 shifts the exhaust gas processing mode to the urea non-suppression mode (S104).

  The EG-ECU 52 determines whether the mode for processing the exhaust gas is currently the urea suppression mode (S105). When it is determined that it is not the urea suppression mode (NO in S105), that is, the urea non-suppression mode, the EG-ECU 52 determines whether or not the power generation request is issued from the HV-ECU 51 (S111). The power generation request is issued by the HV-ECU 51 to the EG-ECU 52 when the SOC of the battery 10 becomes equal to or lower than the charge start SOC.

  When it is determined that there is no power generation request (NO in S111), the EG-ECU 52 controls to stop the engine 20 (S112). After that, the EG-ECU 52 returns the processing to be executed to the processing of the calling source.

  When it is determined that there is a power generation request (YES in S111), the EG-ECU 52 controls the engine 20 so that the load and the rotation speed are in accordance with the power generation request (S113).

  FIG. 3 is a graph showing a performance curve of the engine 20 in this embodiment. Referring to FIG. 3 (A), the maximum torque that can be output by engine 20 changes as the rotation speed changes, as indicated by torque curve L in FIG. 3 (A). The torque curve differs depending on the engine specifications. It is possible to control the torque generated by the engine 20 (= torque applied to the engine 20) and the rotation speed of the engine 20 within the range of the torque curve L. Since the thermal efficiency of the engine 20 is higher in the high load region, it is preferable to control the power generation request such that the load is mainly high.

  Returning to FIG. 2, the EG-ECU 52 determines whether the load on the engine 20 is equal to or higher than a predetermined load (S114). The higher the load on the engine 20, the higher the exhaust temperature. When the exhaust temperature is low, the SCR catalyst 73 is more active than the three-way catalyst 71, and when the exhaust temperature is higher, the three-way catalyst 71 is more active than the SCR catalyst 73. The predetermined load is determined as a load corresponding to the exhaust temperature at which the NOx purification efficiencies of the three-way catalyst 71 and the SCR catalyst 73 are about the same.

  When it is determined that the load on the engine 20 is equal to or greater than the predetermined load (YES in S114), the EG-ECU 52 prohibits the injection of the urea water and causes the three-way catalyst 71 to function properly. The engine 20 is controlled so that stoichiometric combustion is performed using the detection result (S115). It is preferable to be stoichiometric combustion with a stoichiometric air-fuel ratio, but it is sufficient if it is not combustion in a lean state with an air-fuel ratio higher than the theoretical air-fuel ratio, even if combustion is in a rich state with an air-fuel ratio lower than the theoretical air-fuel ratio Good. When the load on the engine 20 is equal to or higher than the predetermined load, the NOx purification efficiency of the three-way catalyst 71 is higher than the NOx purification efficiency of the SCR catalyst 73. When the load on the engine 20 is equal to or higher than the predetermined load, urea water is not injected.

  On the other hand, when it is determined that the load of the engine 20 is less than the predetermined load (NO in S114), the EG-ECU 52 permits the injection of the urea water, and urea according to the exhaust state (for example, the amount of NOx contained in the exhaust). The urea water injection nozzle 74 is controlled to inject water (S116). In the present embodiment, the injection amount of urea water is controlled using the detection result of the NOx sensor 83 provided downstream of the SCR catalyst 73. The amount of NOx contained in the exhaust gas flowing into the SCR catalyst 73 is calculated from the detection result of the NOx sensor 83 provided downstream of the SCR catalyst 73 and the injection amount of urea water from the urea water injection nozzle 74. A NOx sensor is also provided upstream of the SCR catalyst 73, and the amount of NOx contained in the exhaust gas flowing into the SCR catalyst 73, and the detection result of the NOx sensor 83 on the downstream side are used, and The injection amount of urea water may be calculated. When the load of the engine 20 is less than the predetermined load, the engine 20 is controlled so that the combustion is not the stoichiometric combustion but the lean combustion which is the combustion of the normal diesel engine. After S115 and S116, the EG-ECU 52 returns the process to be executed to the calling source of this process.

  Referring to FIG. 3 (A), in the urea non-suppression mode, when the load of engine 20 is equal to or higher than a predetermined load, that is, when engine 20 is operated so that the exhaust temperature activates three-way catalyst 71, As shown in FIG. 3 (A), the engine 20 is controlled in the three-way catalytic enable area. In the present embodiment, the target of the rotation speed is set to a constant speed, and the output torque is increased or decreased to adjust the output.

  In the urea non-suppression mode, when the engine 20 is operated so that the load of the engine 20 is less than the predetermined load, that is, the exhaust temperature activates the SCR catalyst 73, as shown in FIG. The engine 20 is controlled in the feasible region. In the present embodiment, the output is adjusted by setting the target of the output torque to a constant value and increasing or decreasing the rotation speed.

  Returning to FIG. 2, on the other hand, when it is determined that the mode for processing the exhaust gas is currently the urea suppression mode (YES in S105), the EG-ECU 52 determines whether the power generation request is issued from the HV-ECU 51. It is determined (S121). When it is determined that there is a power generation request (YES in S121), the EG-ECU 52 prohibits the injection of urea water and controls the engine 20 by stoichiometric combustion so that the load is higher than the predetermined load described above (S122). .

  Referring to FIG. 3 (B), in the urea suppression mode, as shown in FIG. 3 (B), engine 20 is controlled in the three-way catalyst available range. In the present embodiment, the output is adjusted by increasing and decreasing the output torque by setting the target of the rotation speed to a constant speed.

  Returning to FIG. 2, if it is determined that there is no power generation request (NO in S121), the EG-ECU 52 controls to stop the engine 20 (S123). After S122 and S123, the EG-ECU 52 returns the processing to be executed to the calling processing.

  FIG. 4 is a diagram for explaining that the decrease in the urea water can be suppressed by the control according to this embodiment. With reference to FIG. 4, as shown in FIG. 4 (A), a case where vehicle 100 is in steady operation at a constant vehicle speed will be described. In this case, it is assumed that the remaining amount of urea water has become equal to or less than the predetermined amount at time t1.

  Until time t1, as shown in FIGS. 4C and 4D, the engine 20 is controlled with a load and a rotation speed that can be covered in the SCR available region. As a result, the SOC of the battery 10 becomes substantially constant, as shown in FIG. Further, as shown in FIG. 4 (B), the residual amount of urea water decreases at a constant pace.

  After time t1, as shown in FIGS. 4C and 4D, the engine 20 is controlled in the three-way catalyst enabled area. As a result, as shown in FIG. 4 (E), at time t2, the SOC of battery 10 reaches the charge completion SOC, and engine 20 is stopped.

  The electric power of the battery 10 is used for driving the MG 31 and the like, and at time t3, the SOC of the battery 10 becomes equal to or lower than the SOC at which the charging is started, and the engine 20 is controlled in the three-way catalyst available range. As described above, when the residual amount of the urea water is equal to or less than the predetermined amount and the vehicle 100 is in the steady operation from low load to medium load, the engine 20 is intermittently operated according to the SOC of the battery 10. When vehicle 100 is operating under a high load, engine 20 may be continuously operated according to the SOC of the battery. As a result, the engine 20 is not controlled in the SCR usable area, but the engine 20 is controlled in the three-way catalyst enabled area. Therefore, NOx is treated by the three-way catalyst 71, and it is not necessary to use urea water.

[Modification]
(1) In the above-described embodiments, both MG31 and MG32 are motor generators. However, the MG 31 is not limited to this, and may be a generator. MG 32 may be an electric motor.

  (2) In the above-described embodiment, the catalyst that purifies NOx contained in the exhaust gas by using the reducing agent is the SCR catalyst 73 that uses urea water as the reducing agent. However, the catalyst is not limited to this as long as it is a catalyst that purifies NOx contained in exhaust gas by using a reducing agent, and may be, for example, an SCR catalyst that uses HC as a reducing agent.

  (3) In the above-described embodiment, as shown in FIG. 2, unlike the urea non-suppression mode, urea water is not used at all in the urea suppression mode. However, the urea suppression mode is not limited to this as long as the supply of the urea water to the SCR catalyst is suppressed as compared with the urea non-suppression mode. For example, when the engine 20 is started from the cold state, the processing efficiency of the three-way catalyst 71 is not good. Therefore, in order to suppress the emission of NOx in this case, when the vehicle speed becomes 0, the EG-ECU 52 Alternatively, the supply of urea water may be permitted, the engine 20 may be temporarily operated, and the urea water may be injected to cause the SCR catalyst 73 to adsorb ammonia.

  (4) The embodiment described above can be regarded as a disclosure of a hybrid system including the engine 20, the MG 31, the MG 32, the battery 10, the SCR catalyst 73, and the three-way catalyst 71. Further, it can be regarded as disclosure of such a hybrid system control device (HV-ECU 51, EG-ECU 52) or disclosure of a hybrid system control method. Further, it can be regarded as a disclosure of a vehicle 100 provided with such a hybrid system.

[effect]
(1) As shown in FIG. 1, the hybrid system charges the engine 20, the exhaust pipe of the engine 20, the MG 32 that generates electric power using the power output from the engine 20, and the electric power generated by the MG 32. Battery 10, MG 31 for driving a vehicle that is driven using at least one of the electric power discharged from battery 10 and the electric power generated by MG 32, and nitrogen contained in the exhaust gas that is arranged in the exhaust pipe and uses a reducing agent. The SCR catalyst 73 that purifies oxides, the urea water injection nozzle 74 and the urea water tank 75 that are arranged upstream of the SCR catalyst in the exhaust pipe and that supply the reducing agent to the exhaust pipe, and the SCR catalyst 73 that is arranged in the exhaust pipe A three-way catalyst 71 that is activated at a temperature higher than the activation temperature to purify nitrogen oxides contained in the exhaust gas and an operating state of the engine 20 are controlled. An EG-ECU 52 and an HV-ECU 51 are provided. As shown in S122 of FIG. 2, when the remaining amount of the reducing agent is less than the predetermined amount, the EG-ECU 52 and the HV-ECU 51 always activate the three-way catalyst 71 when the exhaust temperature of the engine 20 is in operation when the engine 20 is operating. The engine 20 is operated with the control target being that the exhaust gas temperature is reduced.

  As a result, when the remaining amount of the reducing agent is less than the predetermined amount, the engine 20 is operated with the control target of the exhaust temperature at which the three-way catalyst 71 that does not use the reducing agent is activated. As a result, when the SCR catalyst 73 using the reducing agent is configured to purify the exhaust gas of the engine 20, the engine 20 can be operated without violating the legal regulation regardless of the remaining amount of the reducing agent. it can.

  (2) As shown in FIGS. 4C and 4D, the EG-ECU 52 and the HV-ECU 51 operate the engine 20 according to the SOC of the battery 10 when the remaining amount of the reducing agent is less than the predetermined amount. The operation is intermittently switched by switching between the case and the case of stopping. As a result, the engine 20 can be operated under a high load that activates the three-way catalyst 71.

  (3) As shown in FIGS. 4C to 4E, the EG-ECU 52 and the HV-ECU 51 operate the engine 20 when the SOC of the battery 10 is less than the charge start SOC, and the When the SOC reaches the charge completion SOC, the engine 20 is stopped to intermittently operate the engine 20. As a result, the engine 20 can be operated under a high load that activates the three-way catalyst 71.

  (4) As shown in FIG. 1, the engine 20 is a diesel engine. As shown in S115 and S122 of FIG. 2, when the EG-ECU 52 and the HV-ECU 51 operate the engine 20 with a control target that the exhaust temperature of the engine 20 becomes the exhaust temperature at which the three-way catalyst 71 is activated. The engine 20 is controlled so that the air-fuel ratio is lower than the stoichiometric air-fuel ratio. This allows the three-way catalyst 71 to function efficiently.

  (5) As shown in S111 to S116 of FIG. 2, the EG-ECU 52 and the HV-ECU 51 have the exhaust gas temperature of the engine 20 that activates the SCR catalyst 73 when the remaining amount of the reducing agent exceeds a predetermined amount. When the engine 20 is operated with the temperature set as a control target, the urea water injection nozzle 74 is controlled so as to permit the supply of the reducing agent, and the exhaust temperature of the engine 20 becomes the exhaust temperature at which the three-way catalyst 71 is activated. When the engine 20 is operated with the control target set to "0" as the control target, the supply of the reducing agent is prohibited. Thereby, even when the remaining amount of the reducing agent exceeds the predetermined amount, the consumption of the reducing agent can be suppressed.

  (6) As shown in FIG. 3, when the EG-ECU 52 and the HV-ECU 51 operate the engine 20 with the control target that the exhaust temperature of the engine 20 becomes the exhaust temperature at which the three-way catalyst 71 is activated. When the engine 20 is operated with the control target that the exhaust temperature of the engine 20 becomes the exhaust temperature at which the SCR catalyst 73 is activated, the output is adjusted by setting the rotation speed to a predetermined speed and increasing or decreasing the output torque. , The output torque is set to a predetermined value, and the output is adjusted by increasing or decreasing the rotation speed. As a result, the engine 20 can be controlled so that the three-way catalyst 71 and the SCR catalyst 73 function efficiently.

  (7) As shown in FIG. 2, the EG-ECU 52 and the HV-ECU 51 exhaust the exhaust gas when the remaining amount of the reducing agent is less than the predetermined amount, compared to when the remaining amount of the reducing agent exceeds the predetermined amount. Control is performed so as to suppress the supply of the reducing agent to the tube. This makes it possible to suppress the consumption of the reducing agent when the amount of the reducing agent is small.

  (8) As shown in FIG. 1, the reducing agent is urea water. As shown in the modified example, the EG-ECU 52 and the HV-ECU 51 detect that the vehicle speed of the vehicle 100 equipped with the hybrid system becomes 0 even when the remaining amount of the reducing agent is less than the predetermined amount. To permit the supply of the reducing agent. As a result, even when the three-way catalyst 71 does not function efficiently when the engine 20 is started from the cold state, the NOx emission can be suppressed by the ammonia adsorbed on the SCR catalyst 73.

  The embodiments disclosed this time are also planned to be implemented in an appropriate combination. The embodiments disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present disclosure is shown not by the above description of the embodiments but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

  10 battery, 11 PCU, 20 engine, 21,22,41 rotary shaft, 23 gear, 31,32 MG, 40 drive wheel, 42 drive shaft, 43 power transmission gear, 51 HV-ECU, 52 EG-ECU, 61, 62, 63, 64 monitoring unit, 65 accelerator opening sensor, 66 vehicle speed sensor, 71 three-way catalyst, 73 SCR catalyst, 74 urea water injection nozzle, 75 urea water tank, 81 exhaust temperature sensor, 82 A / F sensor, 83 NOx sensor, 84 Remaining amount sensor, 100 Vehicle.

Claims (10)

An internal combustion engine,
An exhaust passage of the internal combustion engine,
A generator that generates power using the power output from the internal combustion engine;
A power storage device that charges the power generated by the generator,
An electric motor for driving a vehicle, which is driven by using at least one of electric power discharged from the power storage device and electric power generated by the generator,
A first catalyst disposed in the exhaust passage for purifying nitrogen oxides contained in the exhaust using a reducing agent;
A reducing agent supply device that is arranged upstream of the first catalyst in the exhaust passage and supplies the reducing agent to the exhaust passage;
A second catalyst that is disposed in the exhaust passage and that is activated at a temperature higher than the activation temperature of the first catalyst to purify nitrogen oxides contained in the exhaust;
A control device for controlling the operating state of the internal combustion engine,
The second catalyst is warmed by the exhaust gas flowing through the exhaust passage,
When the remaining amount of the reducing agent is less than a predetermined amount, the control device sets a control target that the exhaust gas temperature of the internal combustion engine is always the exhaust gas temperature at which the second catalyst is activated when the internal combustion engine is operating. A hybrid system for operating the internal combustion engine.   The control device performs intermittent operation by switching between a case where the internal combustion engine is operated and a case where the internal combustion engine is stopped according to the SOC of the power storage device, when the remaining amount of the reducing agent is less than the predetermined amount. The hybrid system described in.   The control device operates the internal combustion engine when the SOC of the power storage device is less than a first predetermined value, and stops the internal combustion engine when the SOC of the power storage device reaches a second predetermined value. The hybrid system according to claim 2, wherein the internal combustion engine is operated intermittently. The internal combustion engine is a diesel engine,
The second catalyst is a three-way catalyst,
When the internal combustion engine is operated with the exhaust gas temperature of the internal combustion engine being the exhaust gas temperature at which the second catalyst is activated as a control target, the control device sets the air-fuel ratio lower than the theoretical air-fuel ratio. The hybrid system according to claim 1, which controls an internal combustion engine. The control device, when the remaining amount of the reducing agent exceeds the predetermined amount,
When the internal combustion engine is operated with a control target that the exhaust gas temperature of the internal combustion engine becomes the exhaust gas temperature at which the first catalyst is activated, the reducing agent supply device is controlled to permit the supply of the reducing agent. ,
When the internal combustion engine is operated with a control target that the exhaust gas temperature of the internal combustion engine becomes the exhaust gas temperature at which the second catalyst is activated, the reducing agent supply device is controlled to prohibit the supply of the reducing agent. The hybrid system according to claim 1. The control device is
When the internal combustion engine is operated with a control target that the exhaust gas temperature of the internal combustion engine becomes the exhaust gas temperature at which the second catalyst is activated, the rotation speed is set to a predetermined speed and the output torque is increased or decreased to output the output. Adjust,
When the internal combustion engine is operated with a control target that the exhaust gas temperature of the internal combustion engine becomes the exhaust gas temperature at which the first catalyst is activated, the output torque is set to a predetermined value, and the rotation speed is increased or decreased to increase the output. The hybrid system of claim 5, wherein the hybrid system is tuned.   When the remaining amount of the reducing agent is less than the predetermined amount, the control device suppresses the supply of the reducing agent to the exhaust passage as compared with the case where the remaining amount of the reducing agent exceeds the predetermined amount. The hybrid system according to claim 5, wherein the reducing agent supply device is controlled to perform. The first catalyst is an SCR catalyst, the reducing agent is aqueous urea,
Even when the remaining amount of the reducing agent is less than the predetermined amount, the control device permits the supply of the reducing agent when the vehicle speed of the vehicle equipped with the hybrid system becomes zero. The hybrid system according to claim 5, which controls the reducing agent supply device. An internal combustion engine, an exhaust passage of the internal combustion engine, a generator that generates power using the power output from the internal combustion engine, a power storage device that charges the power generated by the power generator, and discharge power of the power storage device. And an electric motor for driving a vehicle that is driven by using at least one of the electric power generated by the generator, and a nitrogen oxide contained in the exhaust gas that is disposed in the exhaust passage and uses a reducing agent. 1 catalyst, a reducing agent supply device which is arranged on the upstream side of the first catalyst in the exhaust passage and supplies the reducing agent to the exhaust passage, and an activation temperature of the first catalyst which is arranged in the exhaust passage. A control device for controlling an operating state of the internal combustion engine of a hybrid system including a second catalyst which is activated at a high temperature and purifies nitrogen oxides contained in exhaust gas,
When the remaining amount of the reducing agent is less than a predetermined amount, the internal combustion engine is operated with a control target that the exhaust gas temperature of the internal combustion engine is always the exhaust gas temperature at which the second catalyst is activated when the internal combustion engine is operating. Control device for hybrid system. An internal combustion engine, an exhaust passage of the internal combustion engine, a generator that generates power using the power output from the internal combustion engine, a power storage device that charges the power generated by the power generator, and discharge power of the power storage device. And an electric motor for driving a vehicle that is driven by using at least one of the electric power generated by the generator, and a nitrogen oxide contained in the exhaust gas that is disposed in the exhaust passage and uses a reducing agent. 1 catalyst, a reducing agent supply device which is arranged on the upstream side of the first catalyst in the exhaust passage and supplies the reducing agent to the exhaust passage, and an activation temperature of the first catalyst which is arranged in the exhaust passage. A control method by a control device for controlling an operating state of the internal combustion engine of a hybrid system comprising a second catalyst which is activated at a high temperature and purifies nitrogen oxides contained in exhaust gas,
When the remaining amount of the reducing agent is less than a predetermined amount, the control device sets a control target that the exhaust gas temperature of the internal combustion engine is always the exhaust gas temperature at which the second catalyst is activated when the internal combustion engine is operating. A method of controlling a hybrid system, comprising: operating the internal combustion engine.

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