Series hybrid vehicle control method and series hybrid vehicle

Abstract

A series hybrid vehicle control method is disclosed, which controls a series hybrid vehicle equipped with a power generation system that generates electricity by driving a generator with an internal combustion engine. In the case of a failure of the power generation system, the control unit limits the torque of the internal combustion engine, sets the engine speed within the limited torque range to maximize the power generation efficiency of the generator, and controls the internal combustion engine based on the engine speed.

Description

Technical Field

[0001] This invention relates to a control method for a series hybrid vehicle and a series hybrid vehicle. Background Technology

[0002] Japanese patent JP5086973B2 discloses a control method for so-called reverse driving in the event of an abnormality related to the internal combustion engine in a hybrid vehicle. Specifically, it discloses a method for driving via a second electric motor while the internal combustion engine is being electrically driven by a first electric motor in the event of an abnormality during engine operation. Switching from engine operation to electric drive is intended to prevent secondary malfunctions associated with rapid changes in engine speed at high vehicle speeds.

[0003] However, in series hybrid vehicles, if the internal combustion engine is switched to electric drive mode as described in the aforementioned literature for reverse driving control, then power generation based on the internal combustion engine cannot occur, and the driving distance depends on the battery's state of charge. Therefore, depending on the battery's state of charge and the distance to the reverse driving destination, it is possible to become out of power while driving. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a control method for a series hybrid vehicle that can avoid becoming power-depleted during reverse driving, and a series hybrid vehicle.

[0005] According to one aspect of the present invention, a hybrid vehicle control method is provided, which controls a series hybrid vehicle equipped with a power generation system that generates electricity by driving a generator with an internal combustion engine. In this control method, when a fault occurs in the power generation system, the control unit limits the torque of the internal combustion engine, sets an engine speed within the limited torque range that maximizes the power generation efficiency of the generator, and controls the internal combustion engine based on the engine speed.

[0006] According to another aspect of the present invention, a series hybrid vehicle is provided, comprising: a power generation system that generates electricity by driving a generator with an internal combustion engine, and a control unit for controlling the power generation system. In this vehicle, the control unit is programmed to perform the following processing: in the event of a failure in the power generation system, limiting the torque of the internal combustion engine, setting an engine speed within the limited torque range that maximizes the power generation efficiency of the generator, and controlling the internal combustion engine based on the engine speed. Attached Figure Description

[0007] Figure 1 This is a schematic structural diagram of a vehicle according to an embodiment of the present invention.

[0008] Figure 2 It is a schematic diagram of the engine system.

[0009] Figure 3 This is a flowchart of the control procedure for normal power generation control.

[0010] Figure 4 This is a block diagram used to illustrate the power generation control measures in the event of a fault.

[0011] Figure 5 This is a flowchart representing the control program executed by the fault determination unit, the torque limit determination unit, and the upper limit speed calculation unit.

[0012] Figure 6 This is an example of a speed-torque characteristic graph.

[0013] Figure 7 This is a timing diagram for situations where a fault occurs in the power generation system. Detailed Implementation

[0014] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0015] (Example of vehicle structure)

[0016] Figure 1 This is a schematic structural diagram of vehicle 1. Vehicle 1 is a series hybrid vehicle, and in this embodiment, the power generation control system of the series hybrid vehicle will be mainly described.

[0017] Vehicle 1 includes: an internal combustion engine (hereinafter referred to as "engine") 10, a generator 20, a battery 40, a drive motor 50, auxiliary equipment 60, gears 71, and drive wheels 72. Vehicle 1 generates electricity by driving the generator 20 with the engine 10, and uses the electricity generated by the generator 20 to drive the drive motor 50.

[0018] Engine 10 is, for example, a gasoline engine. Engine 10 is connected to generator 20 in a power-transmitting manner. Generator 20 is an electric generator that, in addition to generating electricity, can also electrically drive engine 10. Electric drive is achieved by generator 20 driving engine 10 when it is in a stopped state. Drive motor 50 is an electric generator that generates driving force for vehicle 1. The driving force generated by drive motor 50 is transmitted to drive wheel 72 via gear 71, which is a reduction gear. Drive motor 50 is driven by power from drive wheel 72, thereby regenerating energy. The energy regenerated by drive motor 50 as electricity can charge battery 40.

[0019] The battery 40 stores the electricity generated by the generator 20 and the electricity regenerated by the drive motor 50. For example, a lithium-ion secondary battery can be used as the battery 40. A discharge request SOC (State of Charge) is set for the battery 40. SOC is a parameter indicating the charging state of the battery 40, and the discharge request SOC is preset to specify the value for a full charge of the battery 40. In other words, a full charge of the battery 40 is specified by the discharge request SOC, for example, a full charge is defined as an SOC of 90% as the charge rate.

[0020] Furthermore, in the power generation control system shown in this embodiment, the drive wheel 72 and the engine 10 are independent, and the engine 10 is only connected to the generator 20. Additionally, the engine 10 and the generator 20 function as a power generation unit and constitute the power generation system.

[0021] Auxiliary equipment 60 is equipment installed on vehicle 1 that requires electricity. For example, auxiliary equipment 60 includes headlights and other lighting equipment, speakers, navigation systems, air conditioning units, etc.

[0022] Vehicle 1 also includes: an engine controller 11, a generator controller 21, a vehicle controller 30, a battery controller 41, and a drive motor controller 51. The engine controller 11, generator controller 21, vehicle controller 30, battery controller 41, and drive motor controller 51 are communicatively connected to form a control unit. The vehicle controller 30 consists of one or more microcomputers equipped with a central processing unit (CPU), read-only memory (ROM), random access memory (RAM), and input / output interfaces (I / O interfaces). The vehicle controller 30 can also be referred to as a VCM (Vehicle Control Module). In the vehicle controller 30, various controls are performed by executing programs stored in ROM or RAM via the CPU. The same applies to the engine controller 11, generator controller 21, battery controller 41, and drive motor controller 51.

[0023] Generator controller 21 controls generator 20. Generator controller 21 also includes a first inverter, which serves as an inverter for generator 20. The first inverter may also be a separate structure from generator controller 21. Generator controller 21 controls generator 20 by controlling the first inverter.

[0024] The drive motor controller 51 controls the drive motor 50. The drive motor controller 51 also includes a second inverter, which serves as the inverter for the drive motor 50. The second inverter can also be a separate structure from the drive motor controller 51. The drive motor controller 51 controls the drive motor 50 by controlling the second inverter.

[0025] The first inverter is connected to the generator 20 and the battery 40. The first inverter converts the alternating current supplied from the generator 20 into direct current and supplies it to the battery 40. Thus, the power generated by the generator 20 charges the battery 40. The first inverter also converts the direct current supplied from the battery 40 into alternating current and supplies it to the generator 20. Thus, the generator 20 is driven using the power from the battery 40. Current, voltage, and SOC signals are also input from the generator 20, drive motor 50, and battery 40 to the generator controller 21. The relationship between the second inverter, drive motor 50, and battery 40 is similar.

[0026] The engine controller 11 controls the engine 10. For example, the engine controller 11 controls the throttle valve, fuel injection valve, spark plugs, etc., and adjusts the intake air volume, injection volume, ignition timing, etc. to perform engine control. In addition, the engine control signal can also be further input to the vehicle controller 30 via the engine controller 11.

[0027] The vehicle controller 30 uniformly controls the engine 10, generator 20, battery 40, drive motor 50, etc. Signals from the accelerator opening sensor 91, which detects the accelerator opening APO, and the shift position sensor 92, which detects the shift position (gear) selected by the driver, are input to the vehicle controller 30.

[0028] (Example of engine system structure)

[0029] Figure 2 This is a schematic structural diagram of an engine system 100 including an engine 10 and an engine controller 11. The engine system 100 includes: an engine 10, an intake system 110, an exhaust system 120, a turbocharger 130, an exhaust gas recirculation device (hereinafter also referred to as an EGR device) 140, an exhaust bypass passage 170 and an exhaust gas bypass valve 171, and an engine controller 130.

[0030] The intake system 110 includes: an intake passage 111, an air flow meter 112, a differential pressure generating valve 115, a throttle valve 113, a collector 114, and a compressor 131. The intake passage 111 allows airflow into the engine 10. In the intake passage 111, the air flow meter 112, the differential pressure generating valve 115, the compressor 131, the throttle valve 113, and the collector 114 are arranged sequentially from the upstream side. The air flow meter 112 measures the intake air flow rate. The differential pressure generating valve 115 is an on / off valve used to generate a pressure difference between the portion of the intake passage 111 upstream of the compressor 131 and the portion between the upstream catalyst 122 and the downstream catalyst 123 of the exhaust passage 121. When the opening of the differential pressure generating valve 115 is reduced, the pressure in the portion of the intake passage 111 upstream of the compressor 13 decreases, and the aforementioned pressure difference increases. The throttle valve 113 regulates the amount of air entering the engine 10. Collector 114 is a volumetric chamber. Compressor 131 is the compressor of booster 130, which compresses the intake air.

[0031] The intake system 110 also includes a pressure sensor 117. The pressure sensor 117 is located in the intake passage 111 downstream of the throttle valve 113, specifically at the collector 114.

[0032] The exhaust system 120 includes: an exhaust passage 121, an upstream catalytic converter 122, a downstream catalytic converter 123, a muffler 124, and a turbine 132. The exhaust passage 121 allows exhaust gas from the engine 10 to flow. Within the exhaust passage 121, the turbine 132, upstream catalytic converter 122, downstream catalytic converter 123, and muffler 124 are sequentially arranged from the upstream side. The upstream catalytic converter 122 and downstream catalytic converter 123 purify the exhaust gas. The muffler 124 reduces exhaust noise. The turbine 132 is the turbine of the supercharger 130, recovering energy from the exhaust gas.

[0033] The supercharger 130 is a turbocharger, comprising a compressor 131, a turbine 132, and a shaft 133. The compressor 131 is disposed in the intake passage 111, and the turbine 132 is disposed in the exhaust passage 121. In the supercharger 130, the turbine 132 rotates due to the energy of the exhaust gas, thereby causing the compressor 131 to rotate via the shaft 133, compressing the intake air. The supercharger 130 thus compresses the intake air and supplies it to the engine 10.

[0034] EGR device 140 includes EGR passage 141, EGR cooler 142 and EGR valve 143. EGR device 140 recirculates exhaust gas from the downstream portion of the supercharger 130 in exhaust passage 121 to the upstream portion of the supercharger 130 in intake passage 111.

[0035] EGR passage 141 connects exhaust passage 121 and intake passage 111. A portion of the exhaust gas flowing through exhaust passage 121 is returned to intake passage 111 as EGR gas. EGR cooler 142 cools the EGR gas flowing through EGR passage 141. EGR valve 143 regulates the flow rate of EGR gas flowing through EGR passage 141.

[0036] EGR device 140, specifically EGR passage 141 connects the portion of exhaust passage 121 downstream of turbine 132 and the portion of intake passage 111 upstream of compressor 131. Thus, EGR passage 141 connecting intake passage 111 and exhaust passage 121 forms a so-called low-pressure loop EGR path.

[0037] EGR passage 141 is further specifically defined as the portion connecting the upstream catalyst 122 and the downstream catalyst 123 in exhaust passage 121, and the portion connecting the differential pressure generating valve 115 and the compressor 131 in intake passage 111.

[0038] An exhaust bypass passage 170 is provided in the exhaust passage 121. The exhaust bypass passage 170 connects the upstream and downstream portions of the exhaust passage 121 from the turbine 132. The exhaust bypass passage 170 allows exhaust gas to flow around the turbine 132.

[0039] An exhaust bypass valve 171 is installed in the exhaust bypass passage 170. The exhaust bypass valve 171 regulates the flow rate of exhaust gas flowing in the exhaust bypass passage 170. By regulating the exhaust flow rate, the exhaust bypass valve 171 adjusts the speed of the turbine 132 and the compressor 131, i.e., the speed of the turbocharger 130.

[0040] Signals from various sensors / switches, such as the air flow meter 112, pressure sensor 117, and crank angle sensor 193, are input to the engine controller 11.

[0041] The crank angle sensor 193 generates a crank angle signal for each specified crank angle. The crank angle signal is used as a signal representing the rotational speed of the engine 10.

[0042] (Normal power generation control)

[0043] In vehicle 1, electricity generated by generator 20 is supplied to battery 40, drive motor 50, or auxiliary equipment 60. Drive motor 50 is driven by electricity generated by generator 20, electricity supplied from battery 40, or both. For example, in situations requiring greater driving force, such as during acceleration, drive motor 50 is driven by both electricity generated by generator 20 and electricity supplied from battery 40. Additionally, when battery 40 needs charging, a portion of the electricity generated by generator 20 is supplied to battery 40. Furthermore, when battery 40 has a state of charge (SOC) margin, drive motor 50 may sometimes be driven solely by electricity supplied from battery 40.

[0044] Figure 3 This is a flowchart illustrating the control program for power generation control executed by the vehicle controller 30 when there are no abnormalities in the system of the vehicle 1, which includes the engine 10, generator 20, and battery 40 (hereinafter also referred to as normal operation). This control program is pre-programmed into the vehicle controller 30.

[0045] In step S100, the vehicle controller 30 receives information about the status of the engine 10, generator 20, and battery 40 from their respective controllers. Here, "status" refers to the results of fault diagnosis executed in parallel with this program, such as the temperature of the engine 10, generator 20, and battery 40, and the state of charge (SOC) of the battery 40.

[0046] In step S101, the vehicle controller 30 calculates the power output of the generator 20 based on the specifications of the generator 20 and the information received in step S100.

[0047] In step S102, the vehicle controller 30 calculates the output power of the battery 40 based on the specifications of the battery 40 and the information received in step S100.

[0048] In step S103, the vehicle controller 30 calculates the target driving force based on vehicle speed and accelerator pedal opening.

[0049] In step S104, the vehicle controller 30 performs a restriction based on the generated electricity and the battery output power, when it is necessary to limit the target driving force, and sets the restricted driving force as the target driving force. For example, if the state of charge (SOC) of the battery 40 is low, and even the sum of the generated electricity and the battery output power is insufficient to achieve the target driving force, the target driving force is restricted to a driving force that can be achieved by combining the generated electricity and the battery output power.

[0050] In step S105, the vehicle controller 30 calculates the amount of electricity generated (hereinafter also referred to as the required amount of electricity) needed to generate the target driving force set in step S104.

[0051] In step S106, the vehicle controller 30 generates a speed command value for the generator 20 based on the required power generation.

[0052] In step S107, the vehicle controller 30 generates the torque command value of the engine 10 based on the speed command value of the generator 20.

[0053] However, if a fault occurs in the power generation system, it will affect the calculation of the generateable power in step S101. For example, when a component associated with engine 10 malfunctions, the torque that engine 10 can generate decreases, and therefore the generateable power also decreases. In this case, the upper limit torque of engine 10 can be limited to the torque that can be generated under the faulty state, and power generation control can be performed. That is, if information indicating a fault is received in step S100, the generateable power under the faulty state can be calculated in step S101, and the processing after step S103 can be performed based on that generateable power.

[0054] However, limiting only the upper limit torque of engine 10 may lead to secondary malfunctions.

[0055] Here, as an example of a malfunction of a component associated with the engine 10, we will describe a situation where the differential pressure generating valve 115 is stuck in a partially open state, i.e., stuck when closed.

[0056] The opening of the differential pressure generating valve 115 is controlled according to the target value of the exhaust gas volume returned by the EGR device 140 (hereinafter also referred to as the target EGR amount). Furthermore, the target EGR amount is determined based on the operating conditions of the engine 10, namely, engine speed and torque. Therefore, when the engine 10 continues to operate with the differential pressure generating valve 115 closed and stuck at an opening smaller than the opening set according to the operating conditions of the engine 10, the negative pressure between the differential pressure generating valve 115 in the intake passage 111 and the compressor 131 increases. Moreover, when the negative pressure increases, oil may leak from the oil seal (not shown) used to prevent leakage of oil supplied to the shaft 133 for cooling and lubrication of the turbocharger 130 into the compressor housing. If oil leaks, the cooling and lubrication of the shaft 133 may become insufficient. Additionally, the leaked oil is supplied to the engine 10 along with the intake air and burned, so oil leakage from the oil seal also leads to deterioration of emission performance.

[0057] On the other hand, when the engine 10 is stopped, the driving range depends solely on the battery 40, and depending on the distance to the destination (e.g., a repair shop), it is possible to run out of power midway.

[0058] Therefore, in this embodiment, the torque of the engine 10 is limited so that the negative pressure in the portion between the differential pressure generating valve 115 of the intake passage 111 and the compressor 131 does not exceed the sealing limit of the oil seal. Furthermore, in order to obtain a driving range, the power generation system is controlled in a manner that maximizes power generation efficiency within the limited torque range. The power generation control in case of a malfunction will be described below.

[0059] (Power generation control during a fault)

[0060] Figure 4 This is a block diagram used to illustrate the power generation control measures in the event of a fault.

[0061] The engine controller 11 acquires the actual opening degree of the differential pressure generating valve 115. In the fault determination unit 11A, a fault determination of the differential pressure generating valve 115 is performed by comparing the actual opening degree with the opening command value of the differential pressure generating valve 115. The actual opening degree of the differential pressure generating valve 115 is acquired by reading the detection value from a position sensor (not shown) used to detect the opening degree of the differential pressure generating valve 115. The opening command value of the differential pressure generating valve 115 is a value set by the engine controller 11 itself, and this value is read. If the opening command value and the actual opening degree are inconsistent, a fault is determined to have occurred. However, considering factors such as the detection accuracy of the sensor, if the deviation between the opening command value and the actual opening degree is within a specified range, they can also be considered to be consistent.

[0062] The torque limit determination unit 11B determines the torque limit amount based on the fault determination result. Specifically, if the determination result is that no fault has occurred, it is determined that torque limit is not required. If the determination result is that a fault has occurred, a limit value for limiting the torque of the engine 10 is set according to the actual opening degree of the differential pressure generating valve 115. The limit value will be described later.

[0063] The determination result of the torque limit determination unit 11B is sent to the upper limit speed calculation unit 11C of the engine controller 11 and the power generation calculation unit 30A of the vehicle controller 30.

[0064] When torque limitation is not required, the upper limit speed calculation unit 11C sends the upper limit speed designed for the engine 10 to the power generation calculation unit 30A. If a limit value is set, it calculates the upper limit speed of the engine 10 corresponding to the limit value and sends the calculation result to the power generation calculation unit 30A. The upper limit speed will be described later.

[0065] The vehicle controller 30 calculates the amount of electricity that can be generated in the power generation calculation unit 30A based on the engine torque limit and the upper limit speed. Then, based on the amount of electricity that can be generated, the power generation torque command value is calculated by the power generation torque command value calculation unit 30B, and the speed command value of the generator 20 is calculated by the generator speed command value calculation unit 30C.

[0066] As described above, in this embodiment, when the differential pressure generating valve 115 is closed and stuck, not only is the engine torque limited, but also the upper limit speed of the engine 10 is limited if necessary, so as to maximize the power generation efficiency within the limited torque range.

[0067] Here, the limits on engine torque and the maximum speed are explained.

[0068] Figure 5 This indicates that the engine controller 11 is composed of Figure 4 The flowchart shows the control program executed by the fault determination unit 11A, torque limit determination unit 11B, and upper limit speed calculation unit 11C. This control program is pre-programmed into the engine controller 11.

[0069] In step S200, the fault determination unit 11A, as described above, determines whether a fault has occurred in the differential pressure generating valve 115. If a fault has occurred, the processing of step S201 is performed; if no fault has occurred, the processing of step S203 is performed.

[0070] In step S201, the fault determination unit 11A determines whether the actual opening degree is below a first threshold. If it is below the first threshold, the processing in step S202 is performed; if it is above the first threshold, the processing in step S203 is performed. The first threshold is a value larger than the second threshold described later, for example, set to an opening degree of about 60% to 70% when fully open.

[0071] In step S202, the fault determination unit 11A determines whether the actual opening degree is below the second threshold. If it is below the second threshold, the processing in step S204 is performed; if it is above the second threshold, the processing in step S206 is performed. The second threshold is, for example, set to an opening degree of about 30% to 40% when fully open.

[0072] In step S203, the torque limiting determination unit 11B determines that torque limiting is not required and proceeds to step S207. The determination that torque limiting is not required is because if the actual opening degree of the differential pressure generating valve 115 is greater than the first threshold, then even without torque limiting, the negative pressure in the intake passage 111 will not exceed the sealing limit of the turbocharger 130. Conversely, the first threshold is the lower limit of the opening degree at which the negative pressure in the intake passage 111 will not exceed the sealing limit of the turbocharger 130 even without torque limiting.

[0073] When the actual opening is below the second threshold, in step S204, the torque limit determination unit 11B sets the limit value for limiting the torque of the engine 10 to torque limit value 2, and in step S205, the upper limit speed calculation unit 11C sets the upper limit speed of the engine 10 based on torque limit value 2. On the other hand, when the actual opening is greater than the second threshold, in step S206, the torque limit determination unit 1B sets the limit value for limiting the torque of the engine 10 to torque limit value 1, which is larger than torque limit value 2, and in step S207, sets it so that engine speed limitation is not required. Engine speed limitation is not required because if engine torque is limited by torque limit value 1, the negative pressure of the intake passage 111 will not exceed the sealing limit of the turbocharger 130 even if the engine speed is not limited. Conversely, the second threshold is the lower limit value of the opening that requires torque limitation but does not require engine speed limitation, and torque limit value 1 is the value that the negative pressure of the intake passage 111 does not depend on the engine speed and does not exceed the sealing limit of the turbocharger 130 even when the differential pressure generating valve 115 is closed and stuck.

[0074] After the processing in step S205 or step S207 is completed, in step S208, the determination of whether a restriction is required and the restriction status, which was determined in the above processing, is sent from the torque restriction amount determination unit 11B and the upper limit speed calculation unit 11C to the power generation calculation unit 30A.

[0075] As described above, in this embodiment, when the differential pressure generating valve 115 is stuck in the closed state, two threshold values ​​are set for the actual opening degree in the stuck state. Based on the relationship with these threshold values, it is determined whether to perform torque limiting, limit with torque limiting value 1, or limit with torque limiting value 2. Furthermore, when limiting with torque limiting value 2, an upper limit speed of the engine speed is also set.

[0076] Next, the upper limit speed of engine 10 will be explained. Figure 6 This is an example of a speed-torque characteristic graph showing the relationship between engine speed and torque of engine 10. The horizontal axis of the graph is engine speed, and the vertical axis is engine torque.

[0077] In this embodiment, when limiting engine torque with torque limit value 2, setting an upper limit speed to limit engine speed is to ensure that the negative pressure in the intake passage 111 (more specifically, the negative pressure between the differential pressure generating valve 115 and the compressor 131) does not exceed the sealing limit of the turbocharger 131 when the differential pressure generating valve 115 is closed and stuck. The magnitude of this negative pressure is determined by the amount of air passing through the differential pressure generating valve 115, therefore it is necessary to limit the amount of air passing through the differential pressure generating valve 115. Thus, torque limit value 2 serves as an equal air volume line for the amount of air whose negative pressure does not exceed the upper limit of the sealing limit of the turbocharger 130.

[0078] Furthermore, in this embodiment, the objective is to enable the vehicle to autonomously travel to a repair location in the event of a malfunction in the differential pressure generating valve 115. For this purpose, it is necessary to maintain power generation capacity. Therefore, when power generation is performed with the differential pressure generating valve 115 closed and stuck, engine torque is limited to protect the engine system 100, and the engine 10 is operated at the point where power generation efficiency is maximized under this limitation—in other words, at the point where engine torque is maximized under this limitation. Figure 6 As can be seen, the torque limit value 2 decreases as the engine speed increases. Therefore, engine 10 operates at the engine speed N1, which provides the maximum torque. Furthermore, "maximum" here is not limited to the strict sense of maximum, but also includes a range considered to be the maximum.

[0079] Furthermore, engine speed N1 is the minimum speed at which engine 10 operates. However, if a function is installed to limit the engine speed to a lower speed for other purposes, that function can be used to operate at a speed lower than engine speed N1.

[0080] Figure 7 This is a timing diagram of the above-mentioned power generation control being executed when the differential pressure generating valve 115 is closed and stuck at an opening below the second threshold during the process of generating electricity while driving.

[0081] When the differential pressure generating valve 115 becomes stuck, the engine controller 11 determines that a fault has occurred in the differential pressure generating valve 115 (time T1). Then, the engine controller 11 establishes a fault occurrence flag and an upper speed limit flag, and notifies the vehicle controller 30 of them. Additionally, the engine controller 11 also notifies the vehicle controller 30 of the engine torque limit (here, torque limit value 2). Furthermore, by imposing a limit on the engine torque, the actual torque of the engine 10 decreases (time T1).

[0082] When the vehicle controller 30 receives a notification from the engine controller 11, it sends a reception completion notification to the engine controller 11, and as follows: Figure 4 Set the generator torque command value and generator speed command value (time T2) as described.

[0083] Then, when the engine torque drops to the torque limit value 2, the engine controller 11 reduces the engine speed to the upper limit speed.

[0084] The battery's SOC begins to decrease as the engine torque decreases (at time T1). This is because, due to the decrease in engine torque, the generator 20 is unable to generate the power required to maintain vehicle speed, and the power from the battery 40 is used to supplement the insufficient power. This situation, where the power from the battery 40 is used as driving power, is also called "electric assist".

[0085] The vehicle speed is maintained by implementing electric assist, but when the battery SOC drops to SOC2 at time T3, the power supply from battery 40 based on electric assist is limited. As a result, the vehicle speed begins to decrease. Then, when the battery SOC drops to SOC1 at time T4, electric assist is stopped. The limitation and cessation of electric assist, as described above, prioritizes suppressing the decrease in battery 40 SOC over maintaining vehicle speed. For example, SOC1 for stopping electric assist is set to 40%. SOC2 for limiting electric assist is set to, for example, 50%. Alternatively, electric assist can be unrestricted during the period when the battery 40 SOC decreases from SOC2 to SOC1, and then stopped when it reaches SOC1. In this way, by changing the power supply method to the drive motor 50 according to the battery 40 SOC, it is possible to prevent the battery 40 SOC from falling below SOC1.

[0086] Furthermore, in this embodiment, power generation control during a fault continues even after the vehicle stops at time T5. Since no driving power is needed while the vehicle is stationary, the battery 40 can be charged using the power generated by the generator 20. As a result, the State of Charge (SOC) increases, and after time T6, the SOC recovers to a level sufficient for electric assistance. Thus, by continuing power generation even when the vehicle is stationary, a state of power depletion can be prevented.

[0087] Furthermore, while this embodiment describes a situation where the differential pressure generating valve 115 is stuck shut, the failure of the power generation system is not limited to this. For example, in a multi-cylinder engine 10, malfunctions of some of the multiple fuel injectors and malfunctions of the fuel pump supplying fuel to the fuel injectors are also included in the failures of the power generation system. When these fuel system malfunctions occur, the desired fuel injection quantity cannot be obtained. Therefore, the engine torque is limited based on the injectable fuel injection quantity, and the engine speed that maximizes the power generation efficiency of the generator 20 is set within the limited engine torque range.

[0088] As described above, this embodiment provides a hybrid vehicle control method for controlling a series hybrid vehicle 1 equipped with a power generation system that generates electricity by driving a generator 20 via an engine 10. In this method, in the event of a fault in the power generation system, control units 11 and 30 limit the torque of the engine 10, set an engine speed within the limited torque range that maximizes the power generation efficiency of the generator 20, and control the engine 10 based on this engine speed. Thus, instead of completely stopping the power generation system when a fault occurs, by setting an upper limit speed for the engine 10 and generating electricity, the decrease in the state of charge (SOC) of the battery 40 can be suppressed, preventing a state of depletion. Furthermore, by avoiding a state of depletion, the vehicle can continue to operate even when the power generation system has failed.

[0089] In this embodiment, before the SOC (State of Charge) of the battery 40 falls below SOC1 (threshold), the control units 11 and 30 supply power from the battery 40 and the generator 20 to the drive motor 50 for operation. If the SOC falls below SOC1, the power supply from the battery 40 is stopped, and only the generator power is supplied to the drive motor 50 for operation. This prevents the SOC from exceeding SOC1 and further decreasing, thus avoiding a state of power depletion.

[0090] In this embodiment, when the State of Charge (SOC) is below SOC1 and the machine is stopped, the controllers 11 and 30 generate electricity based on the engine 10 and charge the battery 40 with the generated electricity. Therefore, even if the power generation system malfunctions, the SOC can be increased.

[0091] In this embodiment, when the State of Charge (SOC) recovers to above SOC1, the controllers 11 and 30 supply power from the battery 40 to the drive motor 50 when driving resumes. This suppresses the reduction in driving performance caused by a malfunction in the power generation system.

[0092] In this embodiment, a fault in the power generation system refers to a malfunction in a component associated with the engine 10. Therefore, by limiting the engine torque and engine speed as in this embodiment, secondary faults in the engine 10 can be avoided.

[0093] In this embodiment, a malfunction in a component associated with the engine 10 refers to, for example, a situation where the differential pressure generating valve 115, located in the intake passage 111 of the engine 10, becomes stuck and closed. If the engine continues to operate without limiting engine torque and speed while the differential pressure generating valve 115 is stuck and closed, the negative pressure in the intake passage 111 will increase, and oil may leak from the oil seal of the turbocharger 130. However, according to this embodiment, this situation can be avoided.

[0094] The embodiments of the present invention have been described above. However, the above embodiments are only a part of the application examples of the present invention and are not intended to limit the technical scope of the present invention to the specific structures of the above embodiments.

Claims

1. A control method for a series hybrid vehicle, comprising controlling a series hybrid vehicle having a power generation system that generates electricity by driving a generator through an internal combustion engine with a turbocharger, wherein, In the event of a fault where the differential pressure generating valve located in the intake passage of the internal combustion engine becomes stuck and closes, The control unit limits the torque of the internal combustion engine to a level where, even when the differential pressure generating valve is closed and stuck, the partial negative pressure between the differential pressure generating valve in the intake passage and the compressor of the turbocharger does not exceed the sealing limit of the oil seal of the turbocharger. Within a limited torque range, the engine speed that maximizes the power generation efficiency of the generator is set, and the internal combustion engine is controlled based on this engine speed.

2. The series hybrid vehicle control method as described in claim 1, wherein, The control unit performs the following processing: Before the battery's state of charge falls below a threshold, the power from the battery and the power generated by the generator are supplied to the drive motor for operation. If the charging state is below the threshold, the power supply from the battery is stopped, and the generated power is supplied only to the drive motor for driving.

3. The series hybrid vehicle control method as described in claim 2, wherein, When the charging state is below the threshold and the vehicle is parked, the control unit generates electricity based on the internal combustion engine and charges the battery with the generated electricity.

4. The series hybrid vehicle control method as described in claim 3, wherein, When the charging state returns to above the threshold, the control unit resumes the power supply from the battery to the drive motor for driving.

5. A series hybrid vehicle, comprising: A power generation system that generates electricity by a generator driven by an internal combustion engine with a turbocharger; The control unit controls the power generation system, wherein, The control unit is programmed to perform the following processes: In the event of a fault where the differential pressure generating valve located in the intake passage of the internal combustion engine becomes stuck and closes, The control unit limits the torque of the internal combustion engine to a level where, even when the differential pressure generating valve is closed and stuck, the partial negative pressure between the differential pressure generating valve in the intake passage and the compressor of the turbocharger does not exceed the sealing limit of the oil seal of the turbocharger. Within a limited torque range, the engine speed that maximizes the power generation efficiency of the generator is set, and the internal combustion engine is controlled based on this engine speed.

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