Series hybrid vehicle control method and series hybrid vehicle

Abstract

Provided is a series hybrid vehicle control method for controlling a series hybrid vehicle provided with an electric power generation system which generates electric power by using an internal combustion engine to drive an electric generator, wherein when a failure occurs to the electric power generation system, a control unit limits torque of the internal combustion engine, sets an engine rotation speed which achieves the maximum electric power generation efficiency of the electric generator within a range of the limited torque, and controls the internal combustion engine on the basis of this engine rotation speed.

Description

[Technical Field]

[0001] The present invention relates to a series hybrid vehicle control method and a series hybrid vehicle. [Background technology]

[0002] JP5086973B2 discloses a control for so-called evacuation running in the event of an abnormality related to the internal combustion engine in a hybrid vehicle. Specifically, it discloses that when an abnormality occurs while the internal combustion engine is operating, the vehicle runs using a second electric motor while the internal combustion engine is motored by a first electric motor. The reason for switching the internal combustion engine from an operating state to a motoring state is to suppress sudden fluctuations in rotation speed of the internal combustion engine at high vehicle speeds, thereby avoiding secondary failures associated with such fluctuations in rotation speed. Summary of the Invention

[0003] However, when the internal combustion engine of a series hybrid vehicle is switched to a motoring state as in the evacuation running control described in the above document, power generation by the internal combustion engine is no longer performed, and the distance that can be traveled depends on the state of charge of the battery. Therefore, depending on the state of charge of the battery and the distance to the destination of the evacuation running, there is a risk of the vehicle running out of power.

[0004] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for controlling a series hybrid vehicle that can prevent the vehicle from running out of power during evacuation travel, and the series hybrid vehicle.

[0005] According to one aspect of the present invention, there is provided a hybrid vehicle control method for controlling 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 failure occurs in the power generation system, a control unit limits the torque of the internal combustion engine, sets an engine rotation 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 rotation speed.

[0006] According to another aspect of the present invention, there is provided a series hybrid vehicle including a power generation system that generates electricity by driving a generator with an internal combustion engine, and a control unit that controls the power generation system, wherein the control unit is programmed to limit the torque of the internal combustion engine when a failure occurs in the power generation system, set an engine rotation speed within the limited torque range that maximizes the power generation efficiency of the generator, and control the internal combustion engine based on the engine rotation speed. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a vehicle according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram of the engine system. [Figure 3] FIG. 3 is a flowchart showing a control routine for normal power generation control. [Figure 4] FIG. 4 is a block diagram for explaining the contents of power generation control when a failure occurs. [Figure 5] FIG. 5 is a flowchart showing a control routine executed by the failure determination unit, the torque limit amount determination unit, and the upper limit rotation speed calculation unit. [Figure 6] FIG. 6 is an example of a rotational speed-torque characteristic diagram. [Figure 7] FIG. 7 is a timing chart showing a case where a failure occurs in the power generation system. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0009] [Vehicle configuration example] 1 is a diagram showing a schematic configuration of a vehicle 1. The vehicle 1 is a series hybrid vehicle, and in this embodiment, a power generation control system for a series hybrid vehicle will be mainly described.

[0010] The vehicle 1 includes an internal combustion engine (hereinafter simply referred to as "engine") 10, a generator 20, a battery 40, a drive motor 50, accessories 60, gears 71, and drive wheels 72. The vehicle 1 uses the engine 10 to drive the generator 20 to generate electricity, and the electric power generated by the generator 20 drives the drive motor 50.

[0011] The engine 10 is, for example, a gasoline engine. The engine 10 is connected to a generator 20 so that power can be transmitted. The generator 20 is a motor generator that can generate power as well as motor the engine 10. Motoring is achieved by driving the engine 10, which is stopped, with the generator 20. The drive motor 50 is a motor generator that generates driving force for the vehicle 1. The driving force generated by the drive motor 50 is transmitted to drive wheels 72 via gears 71, which are reduction gears. The drive motor 50 is driven by power from the drive wheels 72, and thus also regenerates energy. The energy regenerated as electric power by the drive motor 50 can be charged into the battery 40.

[0012] The battery 40 stores the electric power generated by the generator 20 and the electric power regenerated by the drive motor 50. For example, a lithium ion secondary battery can be used as the battery 40. A discharge required SOC (State Of Charge) is set for the battery 40. The SOC is a parameter that indicates the state of charge of the battery 40, and the discharge required SOC is set in advance as a value for determining whether the battery 40 is fully charged. In other words, whether the battery 40 is fully charged is determined by the discharge required SOC, and for example, a SOC of 90% as a charging rate is considered to be fully charged.

[0013] In the power generation control system shown in this embodiment, the drive wheels 72 and the engine 10 are independent, and the engine 10 is connected only to the generator 20. The engine 10 and the generator 20 function as a power generation unit and constitute a power generation system.

[0014] The auxiliary equipment 60 is equipment that requires electric power and is installed in the vehicle 1. For example, the auxiliary equipment 60 is lighting such as headlights, speakers, a navigation system, an air conditioner, etc.

[0015] The vehicle 1 further 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, the generator controller 21, the vehicle controller 30, the battery controller 41, and the drive motor controller 51 are interconnected to communicate with each other and form a control unit. The vehicle controller 30 is composed of one or more microcomputers equipped with a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). 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 the CPU executing programs stored in the ROM or RAM. The same applies to the engine controller 11, the generator controller 21, the battery controller 41, and the drive motor controller 51.

[0016] The generator controller 21 controls the generator 20. The generator controller 21 further includes a first inverter that is an inverter for the generator 20. The first inverter may be configured separately from the generator controller 21. The generator controller 21 controls the generator 20 by controlling the first inverter.

[0017] The drive motor controller 51 controls the drive motor 50. The drive motor controller 51 further includes a second inverter which is an inverter for the drive motor 50. The second inverter may be configured separately from the drive motor controller 51. The drive motor controller 51 controls the drive motor 50 by controlling the second inverter.

[0018] The first inverter is connected to the generator 20 and the battery 40. The first inverter converts AC current supplied from the generator 20 into DC current and supplies it to the battery 40. As a result, the battery 40 is charged with power generated by the generator 20. The first inverter further converts DC current supplied from the battery 40 into AC current and supplies it to the generator 20. As a result, the generator 20 is driven by power from the battery 40. Signals such as current, voltage, and SOC are also input to the generator controller 21 from the generator 20, the drive motor 50, and the battery 40. The same applies to the relationship between the second inverter, the drive motor 50, and the battery 40.

[0019] The engine controller 11 controls the engine 10. For example, the engine controller 11 controls a throttle valve, a fuel injection valve, a spark plug, etc., and adjusts the intake amount, injection amount, ignition timing, etc. to perform engine control. Note that the engine control signal can be further input to the vehicle controller 30 via the engine controller 11.

[0020] The vehicle controller 30 comprehensively controls the engine 10, the generator 20, the battery 40, the drive motor 50, etc. Signals are input to the vehicle controller 30 from an accelerator opening sensor 91 for detecting an accelerator opening APO and a shift position sensor 92 for detecting a shift position (range) selected by a driver operation.

[0021] [Engine system configuration example] 2 is a schematic configuration diagram of an engine system 100 including an engine 10 and an engine controller 11. The engine system 100 includes the 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, a wastegate valve 171, and the engine controller 11.

[0022] 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 intake air to flow through it to be introduced into the engine 10. The intake passage 111 is provided with the air flow meter 112, the differential pressure generating valve 115, the compressor 131, the throttle valve 113, and the collector 114, in this order from upstream to downstream. The air flow meter 112 measures the flow rate of the intake air. The differential pressure generating valve 115 is an on-off valve for generating a differential pressure between a portion of the intake passage 111 upstream of the compressor 13 and a portion of the exhaust passage 121 between the upstream catalyst 122 and the downstream catalyst 123. Reducing the opening of the differential pressure generating valve 115 reduces the pressure in the portion of the intake passage 111 upstream of the compressor 13, and the above-mentioned differential pressure develops. The throttle valve 113 adjusts the amount of intake air introduced into the engine 10. The collector 114 is a volume chamber. The compressor 131 is a compressor of the supercharger 130 and compresses the intake air.

[0023] The intake system 110 is further provided with a pressure sensor 117. The pressure sensor 117 is provided in a portion of the intake passage 111 downstream of the throttle valve 113, specifically in the collector 114.

[0024] The exhaust system 120 includes an exhaust passage 121, an upstream catalyst 122, a downstream catalyst 123, a silencer 124, and a turbine 132. The exhaust passage 121 allows exhaust gas emitted from the engine 10 to flow. The exhaust passage 121 is provided with the turbine 132, the upstream catalyst 122, the downstream catalyst 123, and the silencer 124, in this order from the upstream side. The upstream catalyst 122 and the downstream catalyst 123 purify the exhaust gas. The silencer 124 reduces exhaust noise. The turbine 132 is a turbine of the turbocharger 130, and recovers energy from the exhaust gas.

[0025] The supercharger 130 is a turbocharger and includes a compressor 131, a turbine 132, and a shaft 133. The compressor 131 is provided in the intake passage 111, and the turbine 132 is provided in the exhaust passage 121. In the supercharger 130, the turbine 132 is rotated by the energy of the exhaust gas, which rotates the compressor 131 via the shaft 133 and compresses the intake air. In this way, the supercharger 130 compresses the intake air and supplies it to the engine 10.

[0026] The EGR device 140 includes an EGR passage 141, an EGR cooler 142, and an EGR valve 143. The EGR device 140 recirculates exhaust gas from a portion of the exhaust passage 121 downstream of the turbocharger 130 to a portion of the intake passage 111 upstream of the turbocharger 130.

[0027] The EGR passage 141 connects the exhaust passage 121 and the intake passage 111. The EGR passage 141 recirculates a portion of the exhaust gas flowing through the exhaust passage 121 to the intake passage 111 as EGR gas. The EGR cooler 142 cools the EGR gas flowing through the EGR passage 141. The EGR valve 143 adjusts the flow rate of the EGR gas flowing through the EGR passage 141.

[0028] The EGR device 140, specifically the EGR passage 141, connects a portion of the exhaust passage 121 downstream of the turbine 132 with a portion of the intake passage 111 upstream of the compressor 131. The EGR passage 141, which connects the intake passage 111 and the exhaust passage 121 in this manner, forms a so-called low-pressure loop EGR path.

[0029] More specifically, the EGR passage 141 connects a portion of the exhaust passage 121 between the upstream catalyst 122 and the downstream catalyst 123 and a portion of the intake passage 111 between the differential pressure generation valve 115 and the compressor 131 .

[0030] The exhaust bypass passage 170 is provided in the exhaust passage 121. The exhaust bypass passage 170 connects portions of the exhaust passage 121 upstream and downstream of the turbine 132. The exhaust bypass passage 170 allows the exhaust gas to flow so as to bypass the turbine 132.

[0031] The wastegate valve 171 is provided in the exhaust bypass passage 170. The wastegate valve 171 adjusts the flow rate of exhaust gas flowing through the exhaust bypass passage 170. The wastegate valve 171 adjusts the rotation speed of the turbine 132 and the compressor 131, i.e., the rotation speed of the turbocharger 130, by adjusting the flow rate of exhaust gas.

[0032] The engine controller 11 receives signals from various sensors and switches such as an air flow meter 112, a pressure sensor 117, and a crank angle sensor 193.

[0033] The crank angle sensor 193 generates a crank angle signal at every predetermined crank angle. The crank angle signal is used as a signal representing the rotation speed of the engine 10.

[0034] [Normal power generation control] In the vehicle 1, the electric power generated by the generator 20 is supplied to the battery 40, the drive motor 50, or the accessories 60. The drive motor 50 is driven by the electric power generated by the generator 20, or the electric power supplied from the battery 40, or both. For example, when a large driving force is required, such as during acceleration, the drive motor 50 is driven by the electric power generated by the generator 20 and the electric power supplied from the battery 40. Furthermore, when the battery 40 needs to be charged, some of the electric power generated by the generator 20 is supplied to the battery 40. Furthermore, when the SOC of the battery 40 has a margin, the drive motor 50 may be driven only by the electric power supplied from the battery 40.

[0035] 3 is a flowchart showing a control routine for power generation control executed by the vehicle controller 30 when there is no abnormality in the system of the vehicle 1, including the engine 10, the generator 20, and the battery 40 (hereinafter also referred to as normal operation). This control routine is pre-programmed in the vehicle controller 30.

[0036] In step S100, the vehicle controller 30 receives information about the status of the engine 10, the generator 20, and the battery 40 from each of the respective controllers. The "status" here refers to the results of the fault diagnosis executed in parallel with this routine, the temperatures of the engine 10, the generator 20, and the battery 40, the SOC of the battery 40, etc.

[0037] In step S101, the vehicle controller 30 calculates the amount of power that can be generated by the generator 20 based on the specifications of the generator 20 and the information received in step S100.

[0038] In step S102, the vehicle controller 30 calculates the available power output of the battery 40 based on the specifications of the battery 40 and the information received in step S100.

[0039] In step S103, the vehicle controller 30 calculates a target driving force based on the vehicle speed, the accelerator pedal opening, and the like.

[0040] In step S104, vehicle controller 30 restricts the target driving force based on the power generation capacity and the battery output capacity if necessary, and sets the restricted driving force as the target driving force. For example, if the SOC of battery 40 is low and the sum of the power generation capacity and the battery output capacity is not enough to achieve the target driving force, the target driving force is restricted to a driving force that can be achieved with the sum of the power generation capacity and the battery output capacity.

[0041] In step S105, the vehicle controller 30 calculates the amount of power generation required to generate the target driving force set in step S104 (hereinafter also referred to as the required amount of power generation).

[0042] In step S106, the vehicle controller 30 generates a rotation speed command value for the generator 20 based on the required amount of power generation.

[0043] In step S107 , the vehicle controller 30 generates a torque command value for the engine 10 based on the rotation speed command value for the generator 20 .

[0044] Incidentally, if a fault occurs in the power generation system, this affects the calculation of the generateable power in step S101. For example, if a fault occurs in a component related to the engine 10, the torque that the engine 10 can generate decreases, and therefore the generateable power also decreases. In this case, power generation control can be performed by limiting the upper limit torque of the engine 10 to the torque that can be generated in the state in which the fault has occurred. In other words, if information indicating that a fault has occurred is received in step S100, the generateable power in the fault state can be calculated in step S101, and the processing from step S103 onwards can be performed based on this generateable power.

[0045] However, simply limiting the upper torque limit of the engine 10 may result in secondary failures.

[0046] Here, as an example of a case where a malfunction occurs in a part related to the engine 10, a case where the differential pressure generating valve 115 is stuck in a state where it is not fully open, that is, stuck closed, will be described.

[0047] The opening of the differential pressure generation valve 115 is controlled in accordance with a target value for the amount of exhaust gas recirculated by the EGR device 140 (hereinafter also referred to as a target EGR amount). The target EGR amount is determined in accordance with the operating state of the engine 10, i.e., the engine rotation speed and torque. Therefore, if the engine 10 continues to operate with the differential pressure generation valve 115 stuck closed at an opening smaller than the opening set based on the operating state of the engine 10, negative pressure will develop in the portion of the intake passage 111 between the differential pressure generation valve 115 and the compressor 131. If negative pressure develops, oil may leak from an oil seal (not shown) that prevents oil supplied to cool and lubricate the shaft 133 of the turbocharger 130 from leaking into the compressor housing. If oil leaks, the cooling and lubrication of the shaft 133 may become insufficient. Furthermore, the leaked oil is supplied to the engine 10 together with the intake air and is burned, so oil leakage from the oil seal can also lead to a deterioration in emissions performance.

[0048] On the other hand, if the engine 10 is stopped, the travelable distance will depend solely on the battery 40, and depending on the distance to the destination of the evacuation drive (for example, a repair shop), there is a risk of the battery running out of power along the way.

[0049] Therefore, in this embodiment, the torque of the engine 10 is limited so that the negative pressure in the portion of the intake passage 111 between the differential pressure generating valve 115 and the compressor 131 does not exceed the sealing limit of the oil seal. Then, in order to increase the driving distance, the power generation system is controlled so that power generation efficiency is maximized within the limited torque range. This power generation control in the event of a failure will be described below.

[0050] [Power generation control during failures] FIG. 4 is a block diagram for explaining the contents of power generation control when a failure occurs.

[0051] The engine controller 11 acquires the actual opening of the differential pressure generation valve 115, and performs a failure determination for the differential pressure generation valve 115 by comparing the actual opening with an opening command value of the differential pressure generation valve 115 in the failure determination unit 11A. The actual opening of the differential pressure generation valve 115 is acquired by reading the detection value of a position sensor (not shown) for detecting the opening of the differential pressure generation valve 115. The opening command value of the differential pressure generation valve 115 is a value set by the engine controller 11 itself, and is read in. If the opening command value and the actual opening do not match, it is determined that a failure has occurred. However, taking into consideration the detection accuracy of the sensor and the like, the opening command value and the actual opening may be considered to match if the difference between them is within a predetermined range.

[0052] The torque limit amount determination unit 11B determines the torque limit amount based on the result of the failure determination. Specifically, if the determination result indicates that there is no failure, it determines that torque limiting is unnecessary. If the determination result indicates that there is a failure, it sets a limit value that limits the torque of the engine 10 according to the actual opening of the differential pressure generation valve 115. The limit value will be described later.

[0053] The determination result of the torque limit amount determination unit 11B is sent to the upper limit rotation speed calculation unit 11C of the engine controller 11 and the potential power generation amount calculation unit 30A of the vehicle controller 30.

[0054] If torque limiting is not required, upper limit rotation speed calculation unit 11C transmits the designed upper limit rotation speed of engine 10 to potential power generation calculation unit 30A, and if a limit value is set, calculates the upper limit rotation speed of engine 10 according to the limit value and transmits the calculation result to potential power generation calculation unit 30A. The upper limit rotation speed will be described later.

[0055] The vehicle controller 30 calculates the amount of power that can be generated based on the engine torque limit and upper limit rotation speed in a power generation capacity calculation unit 30A. Then, based on the amount of power that can be generated, a power generation torque command value calculation unit 30B calculates a power generation torque command value, and a generator rotation speed command value calculation unit 30C calculates a rotation speed command value for the generator 20.

[0056] As described above, in this embodiment, when the differential pressure generating valve 115 is stuck closed, not only is the engine torque limited, but also, if necessary, the upper limit rotation speed of the engine 10 is limited so that the power generation efficiency is maximized within the limited torque range.

[0057] Here, the engine torque limit value and the upper limit rotation speed will be described.

[0058] 5 is a flowchart showing a control routine executed by the engine controller 11 in the failure determination unit 11A, the torque limit amount determination unit 11B, and the upper limit rotation speed calculation unit 11C shown in FIG. 4. The control routine is pre-programmed in the engine controller 11.

[0059] In step S200, the failure determination unit 11A determines whether or not a failure has occurred in the differential pressure generating valve 115 as described above, and if a failure has occurred, executes the processing of step S201, and if no failure has occurred, executes the processing of step S203.

[0060] In step S201, the failure determination unit 11A determines whether the actual opening is equal to or less than a first threshold value, and if it is equal to or less than the first threshold value, executes the process of step S202, and if it is greater than the first threshold value, executes the process of step S203. The first threshold value is a value greater than a second threshold value described later, and is set to, for example, about 60% to 70% of the fully open state.

[0061] In step S202, the failure determination unit 11A determines whether the actual opening is equal to or less than a second threshold value, and if it is equal to or less than the second threshold value, executes the process of step S204, and if it is greater than the second threshold value, executes the process of step S206. The second threshold value is, for example, about 30% to 40% of the opening when fully open.

[0062] In step S203, the torque limit amount determination unit 11B determines that torque limit is unnecessary, and the process proceeds to step S207. The reason why it is determined that torque limit is unnecessary is that if the actual opening of the differential pressure generation valve 115 is larger than the first threshold value, the negative pressure in the intake passage 111 will not exceed the sealing limit of the supercharger 130 and will not develop even without torque limit. In other words, the first threshold value is the lower limit of the opening at which the negative pressure in the intake passage 111 will not exceed the sealing limit of the supercharger 130 even without torque limit.

[0063] If the actual opening is equal to or smaller than the second threshold, in step S204 the torque limit amount 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 rotation speed calculation unit 11C sets the upper limit rotation speed of the engine 10 based on torque limit value 2. On the other hand, if the actual opening is greater than the second threshold, in step S206 the torque limit amount determination unit 11B sets the limit value for limiting the torque of the engine 10 to torque limit value 1 which is greater than torque limit value 2, and in step S207 it is determined that limiting the engine rotation speed is unnecessary. The reason why limiting the engine rotation speed is unnecessary is that if the engine torque is limited by torque limit value 1, the negative pressure in the intake passage 111 will not exceed the seal limit of the supercharger 130 and will not develop even if the engine rotation speed is not limited. In other words, the second threshold value is the lower limit of the opening degree at which torque limitation is necessary but engine speed limitation is not necessary, and the torque limit value 1 is a value at which the negative pressure in the intake passage 111 does not exceed the sealing limit of the turbocharger 130 regardless of the engine speed even when the differential pressure generation valve 115 is stuck closed.

[0064] After the processing of step S205 or step S207 is completed, the torque limit amount determination unit 11B and the upper limit rotational speed calculation unit 11C transmit the necessity of restriction and the restriction state determined in the above-described processing in step S208 to the potential power generation amount calculation unit 30A.

[0065] As described above, in this embodiment, when the differential pressure generating valve 115 is stuck closed, two threshold values ​​are set for the actual opening in the stuck closed state, and depending on the relationship with these threshold values, it is determined whether to not limit the torque, limit it by torque limit value 1, or limit it by torque limit value 2. When limiting by torque limit value 2, an upper limit rotation speed of the engine rotation speed is also set.

[0066] Next, we will explain the upper limit rotation speed of the engine 10. Figure 6 is an example of a rotation speed-torque characteristic diagram showing the relationship between the rotation speed and torque of the engine 10. The horizontal axis of the diagram is engine rotation speed, and the vertical axis is engine torque.

[0067] In this embodiment, when limiting the engine torque by the torque limit value 2, the engine rotation speed is limited by setting an upper limit rotation speed so that the negative pressure in the intake passage 111 (more specifically, the negative pressure in the portion between the differential pressure generation valve 115 and the compressor 131) does not exceed the sealing limit of the turbocharger 130 when the differential pressure generation valve 115 is stuck closed. Since the magnitude of the negative pressure is determined by the amount of air passing through the differential pressure generation valve 115, it is necessary to restrict the amount of air passing through the differential pressure generation valve 115. Therefore, the torque limit value 2 is set to an iso-air line of the upper limit of the air amount at which the negative pressure does not exceed the sealing limit of the turbocharger 130.

[0068] Furthermore, in this embodiment, an object is to enable the engine 10 to self-propel to a location where the differential pressure generation valve 115 can be repaired if the differential pressure generation valve 115 fails. To achieve this, it is necessary to maintain the power generation capacity. Therefore, when generating power with the differential pressure generation valve 115 stuck closed, the engine torque is limited to protect the engine system 100, and the engine 10 is operated at an operating point where the power generation efficiency is maximized under the limited engine torque, in other words, where the engine torque is maximized under the limited engine torque. In FIG. 6 , the torque limit value 2 decreases as the engine rotation speed increases. Therefore, the engine 10 is operated at an engine rotation speed N1 where the torque is greatest. Note that the term "maximum" here is not limited to a maximum in the strict sense, but also includes a range that can be considered to be maximum.

[0069] Furthermore, engine rotation speed N1 is the minimum rotation speed when operating engine 10. However, if a function for limiting the engine rotation speed to a lower speed is implemented for another purpose, that function may be used to operate engine 10 at a rotation speed lower than engine rotation speed N1.

[0070] FIG. 7 is a timing chart showing the case where the above-described power generation control is executed when the differential pressure generation valve 115 is stuck closed with an opening equal to or smaller than the second threshold value while the vehicle is running while generating power.

[0071] When the differential pressure generation valve 115 is stuck closed, the engine controller 11 determines that a failure has occurred in the differential pressure generation valve 115 (timing T1). Then, the engine controller 11 sets a failure occurrence flag and an upper limit rotational speed limit flag, and notifies the vehicle controller 30 of these. The engine controller 11 also notifies the vehicle controller 30 of the engine torque limit amount (torque limit value 2 in this case). Furthermore, as the engine torque is limited, the actual torque of the engine 10 decreases (timing T1).

[0072] When the vehicle controller 30 receives the notification sent from the engine controller 11, it sends a reception completion notification to the engine controller 11 and sets the power generation torque command value and the generator rotation speed command value as described in Figure 4 (timing T2).

[0073] Then, when the engine torque decreases to the torque limit value 2, the engine controller 11 decreases the engine rotation speed to the upper limit rotation speed.

[0074] The battery SOC starts to decrease as the engine torque decreases (at timing T1). This is because the decrease in engine torque makes it impossible for the generator 20 to generate the power necessary to maintain the vehicle speed, and the power of the battery 40 is used to make up for the power shortage. This supply of power from the battery 40 as driving power is also called "power assist."

[0075] By performing the power assist, the vehicle speed is maintained, but when the battery SOC drops to SOC2 at timing T3, the power supplied from the battery 40 by the power assist is limited. This causes the vehicle speed to begin to decrease. Then, when the battery SOC drops to SOC1 at timing T4, the power assist is stopped. The reason for limiting and stopping the power assist as described above is to prioritize preventing a decrease in the SOC of the battery 40 over maintaining the vehicle speed. The SOC1 at which the power assist is stopped is, for example, 40%. The SOC2 at which the power assist is limited is, for example, 50%. Note that the power assist may not be limited while the SOC of the battery 40 drops from SOC2 to SOC1, but may be stopped when the SOC of the battery 40 drops to SOC1. In this way, by changing the method of supplying power to the drive motor 50 depending on the SOC of the battery 40, it is possible to prevent the SOC of the battery 40 from dropping below SOC1.

[0076] Furthermore, in this embodiment, power generation control during a failure continues even after the vehicle stops at timing T5. Since no power is needed for driving while the vehicle is stopped, the battery 40 can be charged with the power generated by the generator 20. As a result, the SOC increases, and after timing T6, the SOC recovers to a level at which power assistance can be performed. By continuing to generate power even while the vehicle is stopped in this way, it is possible to prevent the battery from running out of power.

[0077] In this embodiment, the case where the differential pressure generating valve 115 is stuck closed has been described, but the power generation system failure is not limited to this. For example, a malfunction of some of the fuel injectors in the multi-cylinder engine 10 or a malfunction of the fuel pump that supplies fuel to the fuel injectors is also included in the power generation system failure. When such a malfunction in the fuel system occurs, the desired fuel injection amount cannot be obtained, so the engine torque is limited according to the injectable fuel injection amount, and the engine rotation speed at which the power generation efficiency of the generator 20 is maximized within the limited engine torque range is set.

[0078] 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 the generator 20 with the engine 10. In this method, when a failure occurs in the power generation system, the control units 11, 30 limit the torque of the engine 10, set an engine rotation speed within the torque limit range that maximizes the power generation efficiency of the generator 20, and control the engine 10 based on that engine rotation speed. In this way, rather than completely stopping the power generation system when the power generation system fails, by setting an upper limit rotation speed for the engine 10 and generating electricity, it is possible to suppress a decrease in the SOC of the battery 40 and avoid a state of power shortage. Furthermore, by avoiding a state of power shortage, it is possible to continue driving even when the power generation system fails.

[0079] In this embodiment, the control units 11, 30 supply the electric power of the battery 40 and the electric power generated by the generator 20 to the drive motor 50 until the SOC (state of charge) of the battery 40 falls below SOC1 (threshold value) to run the vehicle, and when the SOC falls below SOC1, stop the power supply from the battery 40 and supply only the generated electric power to the drive motor 50 to run the vehicle. This makes it possible to prevent the SOC from exceeding SOC1 and further decreasing, and as a result, to avoid a state of running out of power.

[0080] In this embodiment, when the SOC is below SOC1 and the vehicle is stopped, the controllers 11 and 30 cause the engine 10 to generate power and charge the generated power into the battery 40. This makes it possible to increase the SOC even when the power generation system has failed.

[0081] In this embodiment, when the SOC recovers to SOC1 or higher, the controllers 11, 30 resume the supply of power from the battery 40 to the drive motor 50 during driving. This makes it possible to suppress a decrease in driving performance due to a failure in the power generation system.

[0082] In this embodiment, a failure in the power generation system occurs when a malfunction occurs in a component related to the engine 10. Therefore, by limiting the engine torque and engine rotation speed as in this embodiment, secondary failure of the engine 10 can be avoided.

[0083] In this embodiment, a malfunction in a part related to the engine 10 occurs, for example, when the differential pressure generation valve 115 provided in the intake passage 111 of the engine 10 is stuck closed. If the engine continues to operate without limiting the engine torque and engine rotation speed while the differential pressure generation valve 115 is stuck closed, negative pressure may develop in the intake passage 111, causing oil to leak from the oil seal of the supercharger 130. However, this can be avoided according to this embodiment.

[0084] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

Claims

1. A method for controlling a series hybrid vehicle having a power generation system that generates electricity by driving a generator using an internal combustion engine equipped with a turbocharger, comprising: When a failure occurs in which a differential pressure generating valve provided in an intake passage of the internal combustion engine is stuck closed, the control unit limiting the torque of the internal combustion engine to a range in which a negative pressure in a portion of the intake passage between the differential pressure generation valve and the compressor of the turbocharger does not exceed a sealing limit of an oil seal of the turbocharger even in a state in which the differential pressure generation valve is stuck closed; A series hybrid vehicle control method comprising: setting an engine rotation speed at which the power generation efficiency of the generator is maximized within a limited torque range; and controlling the internal combustion engine based on the engine rotation speed.

2. 2. The method for controlling a series hybrid vehicle according to claim 1, The control unit The vehicle travels by supplying the electric power of the battery and the electric power generated by the generator to a drive motor until the state of charge of the battery falls below a threshold value; When the state of charge falls below the threshold, the power supply from the battery is stopped and only the generated power is supplied to the drive motor to run the series hybrid vehicle.

3. 3. The method for controlling a series hybrid vehicle according to claim 2, The control unit A series hybrid vehicle control method, wherein, when the state of charge is below the threshold and the vehicle is stopped, the internal combustion engine generates power and the generated power is charged into the battery.

4. 4. The method for controlling a series hybrid vehicle according to claim 3, The control unit When the state of charge is restored to or above the threshold, power supply from the battery to the drive motor during driving is resumed.

5. a power generation system that generates electricity by driving a generator using an internal combustion engine equipped with a turbocharger; a control unit that controls the power generation system; In a series hybrid vehicle having The control unit When a differential pressure generating valve provided in an intake passage of the internal combustion engine fails to close, limiting the torque of the internal combustion engine to a range in which a negative pressure in a portion of the intake passage between the differential pressure generation valve and the compressor of the turbocharger does not exceed a sealing limit of an oil seal of the turbocharger even in a state in which the differential pressure generation valve is stuck closed; A series hybrid vehicle programmed to set an engine rotation speed at which the power generation efficiency of the generator is maximized within a limited torque range, and to control the internal combustion engine based on the engine rotation speed.

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