Hybrid vehicle

Abstract

Hybrid vehicle (1) comprising an internal combustion engine (2) and an electric motor generator (4) as a power source which transmits power to a drive wheel (5) and which can drive in a state in which the operation of the internal combustion engine (2) is stopped, wherein the hybrid vehicle (1) comprises: a battery (33) that supplies an electric current to the electric motor generator (4); a battery residual capacity detection unit (16) that detects a state of charge of the battery (33); a vehicle speed detection unit (10) that detects a vehicle speed as the speed of the hybrid vehicle (1); and a control unit (11) configured to restart the internal combustion engine (2) in a case where a predefined restart condition is met, after a predefined restart delay time has elapsed, wherein the control unit (11) is configured to determine the predetermined delay time for restarting on the basis of the state of charge of the battery (33) and the vehicle speed, wherein the predetermined delay time for restarting in a case where the state of charge of the battery (33) is lower than a first threshold (Th1) is determined such that it is a longer time when the state of charge of the battery (33) or the vehicle speed is higher, and wherein the specified delay time for restarting in a case where the state of charge of the battery (33) is equal to or higher than the first threshold (Th1) is determined such that it is a shorter time when the vehicle speed is higher.

Description

[Technical field]

[0001] The present invention relates to a hybrid vehicle. [Previous state of the art]

[0002] JP 2004-156581 A discloses a hybrid vehicle. In this hybrid vehicle, a predetermined time Ts1, which is determined based on the completion of preheating of an internal combustion engine performed by a preheater, the completion of preparation of a sensor such as an air-fuel ratio sensor, and the completion of warming up of an exhaust gas purification device, is set as a delay time Tset in a normal state based on the temperature of the cooling water for the internal combustion engine and the state of an air-conditioning switch. In this hybrid vehicle, in a case where the hybrid vehicle can travel using an electric motor, the internal combustion engine is started after the elapse of the delay time Tset based on a requested torque, a requested power, and the remaining capacity (SOC) of a battery.

[0003] According to the hybrid vehicle disclosed in JP 2004 - 156 581 A, it is possible to efficiently perform the start of the internal combustion engine or an operation immediately after the start of the internal combustion engine and to simplify the process flow at the time of start more than in a case where an internal combustion engine is started based on the determination of completion of various kinds of preparation.

[0004] US 2014 / 0 288 744 A1 discloses a control device for a vehicle having an internal combustion engine and an electric motor as drive sources. The control device comprises a control unit that starts the internal combustion engine after a predetermined delay time has elapsed if a start condition is met based on a driver's operation. Furthermore, the control unit keeps the internal combustion engine stopped if the start condition is no longer met before the delay time expires after the start condition is met.

[0005] Document US 2013 / 0 124 026 A1 discloses a control device for a hybrid vehicle with an internal combustion engine, a motor generator, a clutch, and a mode transition control means. The clutch switches between an HEV (hybrid propulsion) mode and an EV (electric propulsion) mode. The mode transition control means implements a delay time from a time at which the engine is permitted to stop to a time at which a mode transition from the HEV mode to the EV mode is started in a high vehicle speed range, this delay time being longer than a delay time in another vehicle speed range.

[0006] JP 2017-74807 A discloses a control device for a hybrid vehicle with an internal combustion engine and an electric motor. The control device stops the internal combustion engine when a predetermined stop condition is met and starts the internal combustion engine when a predetermined start condition is met. Furthermore, a stop-prevention time is set that prevents the internal combustion engine from stopping according to the difference between the possible torque of the electric motor and the torque requested by the driver, and the internal combustion engine is stopped when the stop-prevention time has elapsed. [Summary of the invention][Problem to be solved by the invention]

[0007] Meanwhile, the hybrid vehicle can be decelerated by regenerating an electric motor generator in a state where the internal combustion engine is automatically stopped while the hybrid vehicle is driving. In a case where the SOC (remaining capacity) of a battery exceeds an upper limit threshold for battery protection at the time of such deceleration, the electric motor generator will not regenerate electric power.

[0008] Furthermore, when the hybrid vehicle is decelerated by the regeneration of the electric motor generator in a state where the internal combustion engine is automatically stopped while the hybrid vehicle is traveling at a high speed, a high regenerated energy of the electric motor generator is recovered.

[0009] For this reason, when the hybrid vehicle is decelerated by the aforementioned motor-generator regeneration in a state where the battery SOC is high while the hybrid vehicle is traveling at a high speed, there is a concern that the battery SOC may reach the upper limit threshold before engine braking is applied after the engine restart, in a case where a delay time for engine restart is a certain length. Since, in a case where the battery SOC reaches the upper limit threshold before engine braking is applied, as described above, a braking force obtained from the motor-generator regeneration is interrupted, drivability deteriorates.

[0010] This invention has been conceived in view of the above-mentioned circumstances, and an object of this invention is to provide a hybrid vehicle in which fuel efficiency can be improved and in which deterioration of drivability caused by interruption of a braking force obtained from regeneration of an electric motor generator can be prevented. [Means of solving the problem]

[0011] According to aspects of this invention, a hybrid vehicle is provided that includes an internal combustion engine and an electric motor generator as a drive source that transmits power to a drive wheel, and that can travel in a state where operation of the internal combustion engine is stopped. The hybrid vehicle includes: a battery that supplies electric power to the electric motor generator, a battery remaining capacity detection unit that detects a charge state of the battery, a vehicle speed detection unit that detects a vehicle speed as the speed of the hybrid vehicle, and a control unit that restarts the internal combustion engine after a lapse of a predetermined restart delay time in a case where a predetermined restart condition is met.The control unit determines the predetermined restart delay time based on the battery state of charge and the vehicle speed. The predetermined restart delay time is determined to be a longer time when the battery state of charge is lower than a first threshold, and a higher time when the battery state of charge or the vehicle speed is higher. The predetermined restart delay time is determined to be a shorter time when the battery state of charge is equal to or higher than the first threshold, and a higher time when the vehicle speed is higher. [Effect of the invention]

[0012] According to this invention, it is possible to provide a hybrid vehicle in which fuel efficiency can be improved and deterioration of drivability caused by interruption of a braking force obtained from regeneration of an electric motor generator can be prevented. [Brief description of the drawings] Fig. 1 is a diagram illustrating the configuration of a hybrid vehicle according to an embodiment of this invention; Fig. 2 is a diagram illustrating the flow of calculating a delay time for an automatic stop of a hybrid vehicle according to an embodiment of this invention; Fig. 3 is a diagram illustrating the flow of calculating a delay time for restarting the hybrid vehicle according to an embodiment of this invention; Fig. 4 is a flowchart illustrating the processing flow of automatic stop control performed in the hybrid vehicle according to an embodiment of this invention; Fig. 5 is a flowchart illustrating the processing flow of a restart control performed in the hybrid vehicle according to an embodiment of this invention. [Embodiment(s) of the invention]

[0013] A hybrid vehicle according to embodiments of this invention includes an internal combustion engine and an electric motor generator as a drive source that transmits power to a drive wheel, and can travel in a state where the operation of the internal combustion engine is stopped. The hybrid vehicle includes: a battery that supplies electric power to the electric motor generator, a battery remaining capacity detection unit that detects a charge state of the battery, a vehicle speed detection unit that detects a vehicle speed as the speed of the hybrid vehicle, and a control unit that restarts the internal combustion engine after a predetermined restart delay time has elapsed when a predetermined restart condition is met.The control unit determines the predetermined restart delay time based on the battery state of charge and the vehicle speed. The predetermined restart delay time is determined to be a longer time when the battery state of charge is lower than a first threshold, and a higher time when the battery state of charge or the vehicle speed is higher. The predetermined restart delay time is determined to be a shorter time when the battery state of charge is equal to or higher than the first threshold.Accordingly, in the hybrid vehicle according to embodiments of this invention, fuel efficiency can be improved and deterioration of drivability caused by interruption of a braking force obtained from regeneration of an electric motor generator can be prevented. [Embodiments]

[0014] Hereinafter, a hybrid vehicle according to an embodiment of this invention will be described with reference to the drawings.

[0015] As in Fig. As illustrated in Figure 1, a hybrid vehicle 1 includes an internal combustion engine 2 as an internal combustion engine, a transmission 3 as an automatic transmission, an electric motor generator 4, a drive wheel 5, a vehicle speed detection unit 10 in the form of a hybrid control unit (HCU) that comprehensively controls the hybrid vehicle 1, a control unit 11 in the form of an engine control module (ECM) that controls the internal combustion engine 2, a transmission control module (TCM) 12 that controls the transmission 3, an integrated starter generator control module (ISGCM) 13, an inverter control module (INVCM) 14, and a battery remaining capacity detection unit 16 in the form of a battery management system (BMS). The internal combustion engine 2 and the electric motor generator 4 constitute a drive source that transmits power to the drive wheel 5.

[0016] A plurality of cylinders are formed in the internal combustion engine 2. In this embodiment, the internal combustion engine 2 is designed such that a series of four strokes is performed for each cylinder, consisting of an intake stroke, a compression stroke, a power stroke, and an exhaust stroke.

[0017] An integrated starter generator (ISG) 20 and a starter 21 are connected to the internal combustion engine 2. The ISG 20 is connected to a crankshaft 18 of the internal combustion engine 2 by a belt 22 or the like. The ISG 20 functions as an electric motor driven by the supply of an electric current to cause the internal combustion engine 2 to rotate, and functions as a generator that converts the torque input from the crankshaft 18 into an electric current.

[0018] In this embodiment, the ISG 20 is configured to function as an electric motor, under the control of the ISGCM 13, to restart the engine 2 from a stop state (hereinafter referred to as an "automatic stop state") achieved by an automatic stop function. The ISG 20 can also assist the driving of the hybrid vehicle 1 in a case where the ISG 20 functions as an electric motor. The automatic stop function of the engine 2 includes, in addition to an idle stop function, a function in which the engine 2 is automatically stopped in a case where a predetermined automatic stop condition is met during driving of the hybrid vehicle 1.

[0019] The starter 21 includes an electric motor and a drive gear (not shown). The starter 21 is configured to drive the electric motor to rotate the crankshaft 18 and apply torque to the internal combustion engine 2 at the time of starting. The internal combustion engine 2 is started by the starter 21, as described above, and is restarted from the automatic stop state by the ISG 20.

[0020] The transmission 3 is designed to change the rotational speed output from the internal combustion engine 2 and transmit the rotation to the drive gear 5 through a drive shaft 23 to drive the drive gear 5. The transmission 3 includes a constant-tooth gear mechanism 25 consisting of a parallel-axis gear mechanism, a clutch 26 consisting of a normally closed dry clutch, a differential mechanism 27, and actuators 51 and 52.

[0021] The clutch 26 is provided on a power transmission path between the transmission mechanism 25 and the internal combustion engine 2 and interrupts or connects the power transmission path.

[0022] The transmission 3 is formed of a so-called automated manual transmission (AMT) and is configured such that the gear ratio of the transmission mechanism 25 is switched by means of the actuator 52 controlled by the TCM 12, and the clutch 26 is disengaged and engaged by means of the actuator 51. The differential mechanism 27 is configured such that a power output from the transmission mechanism 25 is transmitted to the drive shaft 23.

[0023] The electric motor generator 4 is connected to the differential mechanism 27 by a power transmission mechanism 28, such as a chain. The electric motor generator 4 functions as an electric motor.

[0024] As described above, the hybrid vehicle 1 constitutes a parallel hybrid system that can utilize power from both the engine 2 and the motor generator 4 to propel a vehicle, and is configured to travel using power output from at least one of the engine 2 and the motor generator 4. Accordingly, the hybrid vehicle 1 can travel even in a state where the operation of the engine 2 is stopped.

[0025] The electric motor generator 4 also functions as a generator and is designed to generate electricity through the driving of the hybrid vehicle 1. However, the electric motor generator 4 only needs to be connected to any portion of the power transmission path between the internal combustion engine 2 and the drive wheel 5 to transmit power, and does not necessarily need to be connected to the differential mechanism 27.

[0026] The hybrid vehicle 1 includes a first power storage device 30, a high-voltage power pack 34 including a second power storage device as a battery 33, a high-voltage cable 35, and a low-voltage cable 36.

[0027] Each of the first power storage device 30 and the battery 33 is formed of a rechargeable secondary battery. The first power storage device 30 is formed of a lead-acid battery. The first power storage device 30 is a low-voltage battery whose number of cells and the like is set to generate an output voltage of approximately 12 V. The first power storage device 30 is configured to supply electric power to at least the ISG 20 and a starter 21 as a starting device that starts or restarts the internal combustion engine 2.

[0028] The battery 33 is a high-voltage battery whose number of cells and the like is set to generate a voltage higher than that generated by the first power storage device 30, and generates an output voltage of, for example, 100 V. The state, such as a remaining capacity (hereinafter referred to as a "state of charge (SOC)") of the battery 33 is managed by the battery remaining capacity detection unit 16. In this embodiment, the battery 33 is formed of a lithium-ion battery.

[0029] In the hybrid vehicle 1, a general load 37 is provided as an electrical load. The general load 37 is an electrical load that is used temporarily. The general load 37 includes, for example, windshield wipers (not shown) and an electric cooling fan that supplies cooling air to the internal combustion engine 2.

[0030] The high-voltage power pack 34 includes, in addition to the battery 33, an inverter 45, the INVCM 14, and the battery remaining capacity detection unit 16. The high-voltage power pack 34 is connected to the electric motor generator 4 by the high-voltage cable 35, so that it is capable of supplying an electric current to the electric motor generator 4.

[0031] An alternating current applied to the high-voltage cable 35 and a direct current applied to the battery 33 are converted into each other by the control of the INVCM 14. For example, in a case where the electric motor generator 4 is driven in a reverse direction, the INVCM 14 converts a direct current taken from the battery 33 into an alternating current by means of the inverter 45 and supplies the alternating current to the electric motor generator 4.

[0032] In a case where the electric motor generator 4 is caused to regenerate electric power, the INVCM 14 causes the inverter 45 to convert the alternating current generated by the electric motor generator 4 into a direct current to charge the battery 33 with the direct current.

[0033] Each of the vehicle speed detection unit 10, the control unit 11, the TCM 12, the ISGCM 13, the INVCM 14, and the battery remaining capacity detection unit 16 is formed of a computer unit including a central processing unit (CPU), a random access memory (RAM), a read-only memory (ROM), a flash memory that saves backup data, and the like, an input terminal, and an output terminal.

[0034] Along with various constants, various maps, and the like, programs that enable the computer units to function as the vehicle speed detection unit 10, the control unit 11, the TCM 12, the ISGCM 13, the INVCM 14, and the battery remaining capacity detection unit 16 are stored in the ROMs of these computer units.

[0035] That is, in a case where the CPUs execute the programs stored in the ROMs while using the RAMs as work areas, these computer units function as the vehicle speed detection unit 10, the control unit 11, the TCM 12, the ISGCM 13, the INVCM 14, and the battery remaining capacity detection unit 16 of this embodiment, respectively.

[0036] In this embodiment, the control unit 11 may perform automatic stop control to automatically stop the engine 2 after the elapse of a predetermined automatic stop delay time or a predetermined torque range-dependent automatic stop delay time in a case where a predetermined automatic stop condition is met. Since unnecessary operation of the engine 2 is not performed by this automatic stop control, the fuel efficiency of the hybrid vehicle 1 is improved.

[0037] In this embodiment, a condition where the torque margin Tm of the electric motor generator 4 is equal to or greater than a predetermined automatic stop threshold is used as the predetermined automatic stop condition. The torque margin Tm is a value obtained when a requested torque, which is a driving force required for the hybrid vehicle 1, is subtracted from a motor torque that can be output by the electric motor generator 4, that is, a rated torque.

[0038] The requested torque is determined by the vehicle speed detection unit 10 by referring to a requested torque map based on, for example, the vehicle speed V of the hybrid vehicle 1 and an accelerator pedal position Acc. The requested torque map is a map obtained in a case where a relationship between the vehicle speed V, the accelerator pedal position Acc, and the requested torque is experimentally obtained in advance, and this map is stored in the ROM of the vehicle speed detection unit 10.

[0039] The control unit 11 is configured to calculate the predetermined automatic stop threshold by referring to an automatic stop threshold calculation map based on the vehicle speed V of the hybrid vehicle 1 and the SOC of the battery 33. The automatic stop threshold calculation map is a map obtained in a case where a relationship between the vehicle speed V, the SOC, and the automatic stop threshold is experimentally obtained in advance, and this map is stored in the ROM of the control unit 11.

[0040] In the automatic stop threshold calculation map, the automatic stop threshold is defined as a threshold at which it is easier to automatically stop the engine 2, that is, it is a smaller threshold as the SOC is higher, and the automatic stop threshold is defined as a threshold at which it is difficult to automatically stop the engine 2, that is, it is a higher threshold as the vehicle speed V is higher. Accordingly, since a high automatic stop threshold is calculated in a case where the vehicle speed V is high, the predetermined automatic stop condition is not satisfied unless the requested torque is reduced to a state close to a state where the driver does not step on the accelerator pedal, for example.

[0041] As described above, the control unit 11 automatically stops the internal combustion engine 2 after the elapse of the predetermined automatic stop delay time or the predetermined torque-range-dependent automatic stop delay time after the predetermined automatic stop condition is met. The predetermined automatic stop delay time and the predetermined torque-range-dependent automatic stop delay time are determined by the control unit 11 according to the following calculation method.

[0042] The control unit 11 is designed to calculate the predetermined delay time for an automatic stop with reference to a map 60 for calculating the delay time for an automatic stop (see Fig. 2) is calculated based on the SOC of the battery 33 and the vehicle speed V of the hybrid vehicle 1. The automatic stop delay time calculation map 60 is a map showing a relationship between the SOC, the vehicle speed V, and the predetermined automatic stop delay time, which is obtained experimentally in advance, and this map is stored in the ROM of the control unit 11.

[0043] The respective numerical values ​​“1”, “2”, and “3” of the automatic stop delay time calculation map 60 represent the measure of the length of the specified automatic stop delay time and are defined such that the specified automatic stop delay time is longer in the order “1” < “2” < “3”.

[0044] The control unit 11 is designed to calculate the predetermined torque range-dependent delay time for an automatic stop with reference to a torque range-dependent delay time calculation map 61 for an automatic stop (see Fig. 2) is calculated based on the vehicle speed V of the hybrid vehicle 1 and the torque margin Tm of the electric motor generator 4. The torque margin-dependent automatic stop delay time calculation map 61 is a map showing a relationship between the vehicle speed V, the torque margin Tm, and the torque margin-dependent automatic stop delay time, which is obtained experimentally in advance, and this map is stored in the ROM of the control unit 11.

[0045] The respective numerical values ​​“1”, “2”, and “3” of the map 61 for calculating the torque range-dependent delay time for an automatic stop represent the measure of the length of a torque range-dependent delay time for an automatic stop and are defined such that the torque range-dependent delay time for an automatic stop becomes longer in the order “1” < “2” < “3”.

[0046] The control unit 11 is configured to determine a longer one of the predetermined automatic stop delay time and the predetermined torque margin-dependent automatic stop delay time calculated as described above as a delay time with respect to the automatic stop of the internal combustion engine 2.

[0047] Accordingly, in a case where the predetermined automatic stop delay time is longer than the predetermined torque-range-dependent automatic stop delay time, the control unit 11 automatically stops the internal combustion engine 2 after the predetermined automatic stop delay time has elapsed. In a case where the predetermined torque-range-dependent automatic stop delay time is longer than the predetermined automatic stop delay time, the control unit 11 automatically stops the internal combustion engine 2 after the predetermined torque-range-dependent automatic stop delay time has elapsed.

[0048] As in Fig. 2, the automatic stop delay time calculation map 60 is defined such that, in a case where the SOC is lower than a second threshold Th2, a longer predetermined automatic stop delay time is determined as the SOC is lower or the vehicle speed V is lower.

[0049] The automatic stop delay time calculation map 60 is defined such that, in a case where the SOC is equal to or higher than the second threshold Th2, a longer predetermined automatic stop delay time is determined as the SOC or the vehicle speed V is higher. The second threshold Th2 is predetermined with a value obtained in a case where a fixed value is added to the lower limit of the SOC when the remaining capacity of the battery 33 is insufficient.

[0050] The map 61 for calculating the torque margin-dependent delay time for an automatic stop is defined such that a longer torque margin-dependent delay time for an automatic stop is determined when a torque margin Tm is lower or the vehicle speed V is higher.

[0051] In this embodiment, the control unit 11 may perform restart control to drive the ISG 20 through the ISGCM 13 to restart the engine 2 in a case where a predetermined restart condition is satisfied during the automatic stop of the engine 2, after the elapse of a predetermined restart delay time or a predetermined torque margin-dependent restart delay time.

[0052] In this embodiment, a condition that the torque margin Tm of the electric motor generator 4 is equal to or lower than a predetermined restart threshold is used as the predetermined restart condition. In a case where the torque margin Tm is equal to or lower than the predetermined restart threshold, the control unit 11 determines that the hybrid vehicle 1 does not have sufficient power to continue electric running and restarts the engine 2. Electric running means that the hybrid vehicle 1 runs using the power of the electric motor generator 4 in a state where the operation of the engine 2 is stopped.

[0053] The control unit 11 is configured to calculate the predetermined restart threshold by referring to a restart threshold calculation map based on the vehicle speed V of the hybrid vehicle 1 and the SOC of the battery 33. The restart threshold calculation map is a map obtained in a case where a relationship between the vehicle speed V, the SOC, and the restart threshold is experimentally obtained in advance, and this map is stored in the ROM of the control unit 11.

[0054] In the restart threshold calculation map, the restart threshold is defined as a threshold at which it is easier to restart the engine 2, that is, it is a higher threshold when the SOC is lower or the vehicle speed V is lower.

[0055] As described above, the control unit 11 restarts the engine 2 after the predetermined restart delay time or the predetermined torque-range-dependent restart delay time has elapsed after the predetermined restart condition is met. The predetermined restart delay time and the predetermined torque-range-dependent restart delay time are determined by the control unit 11 according to the following calculation method.

[0056] The control unit 11 is designed to calculate a predetermined restart delay time by referring to a restart delay time calculation map 70 (see Fig. 3) is determined based on the SOC of the battery 33 and the vehicle speed V of the hybrid vehicle 1. The restart delay time calculation map 70 is a map obtained in a case where a relationship between the SOC, the vehicle speed V, and the predetermined restart delay time is experimentally obtained in advance, and this map is stored in the ROM of the control unit 11.

[0057] The respective numerical values ​​"0", "1", "2", and "3" of the restart delay time calculation map 70 represent the length of the predetermined restart delay time and are defined so that the predetermined restart delay time becomes longer in the order of "0" < "1" < "2" < "3". A temporary restart delay time defined as "0" may include a case where a temporary restart delay time is equal to 0, that is, where a predetermined restart delay time does not occur.

[0058] The control unit 11 is designed to calculate the predetermined torque range-dependent delay time for a restart by referring to a map 71 for calculating the torque range-dependent delay time for a restart (see Fig. 3) is calculated based on the vehicle speed V of the hybrid vehicle 1 and the torque margin Tm of the electric motor generator 4. The torque margin-dependent restart delay time calculation map 71 is a map obtained in a case where a relationship between the vehicle speed V, the torque margin Tm, and the torque margin-dependent restart delay time is experimentally obtained in advance, and this map is stored in the ROM of the control unit 11.

[0059] The respective numerical values ​​"0", "1", "2", and "3" of the torque margin-dependent restart delay time calculation map 71 represent the measure of the length of a torque margin-dependent restart delay time, and are defined so that the torque margin-dependent restart delay time becomes longer in the order of "0" < "1" < "2" < "3". A torque margin-dependent restart delay time defined as "0" may include a case where a torque margin-dependent restart delay time is equal to 0, that is, where a torque margin-dependent restart delay time does not occur.

[0060] The control unit 11 is configured to determine a shorter one of the predetermined restart delay time and the predetermined torque margin-dependent restart delay time calculated as described above as a delay time with respect to restarting the internal combustion engine 2.

[0061] Accordingly, in a case where the predetermined restart delay time is shorter than the predetermined torque-range-dependent restart delay time, the control unit 11 restarts the internal combustion engine 2 after the predetermined restart delay time has elapsed. In a case where the predetermined torque-range-dependent restart delay time is shorter than the predetermined restart delay time, the control unit 11 restarts the internal combustion engine 2 after the predetermined torque-range-dependent restart delay time has elapsed.

[0062] As in Fig. 3, the restart delay time calculation map 70 is defined such that, in a case where the SOC is lower than a first threshold Th1, a longer predetermined restart delay time is determined as the SOC or the vehicle speed V is higher.

[0063] The restart delay time calculation map 70 is defined such that, in a case where the SOC is equal to or higher than the first threshold Th1, a shorter predetermined restart delay time is determined as the vehicle speed V is higher. The first threshold Th1 is predetermined with a value obtained in a case where a fixed value is subtracted from an upper limit threshold for protecting a battery.

[0064] The map 71 for calculating the torque margin-dependent delay time for a restart is defined such that a shorter torque margin-dependent delay time for a restart is determined when the torque margin Tm is lower or the vehicle speed V is lower.

[0065] As in Fig. 1, the hybrid vehicle 1 is provided with CAN communication lines 48 and 49 that form a local area network (LAN) in the vehicle that conforms to a standard such as a controller area network (CAN).

[0066] The vehicle speed detection unit 10 is connected to the INVCM 14 and the remaining battery capacity detection unit 16 through the CAN communication line 48. The vehicle speed detection unit 10, the INVCM 14, and the remaining battery capacity detection unit 16 transmit and receive signals, such as control signals, to and from each other through the CAN communication line 48.

[0067] The vehicle speed detection unit 10 is connected to the control unit 11, the TCM 12, and the ISGCM 13 through the CAN communication line 49. The vehicle speed detection unit 10, the control unit 11, the TCM 12, and the ISGCM 13 transmit and receive signals, such as control signals, to and from each other through the CAN communication line 49.

[0068] Connected to the vehicle speed detection unit 10 are a wheel speed sensor 10a that detects the rotational speed of each wheel including the drive wheel 5, an accelerator pedal position sensor 10b that detects the degree of depression of an accelerator pedal (not shown) as an accelerator pedal position Acc, a clutch stroke sensor 10c that detects the degree of engagement of the clutch 26, and a crank angle sensor 10d. The vehicle speed detection unit 10 calculates an engine speed, which is the rotational speed of the engine 2, based on the detection information output from the crank angle sensor 10d.

[0069] The wheel speed sensor 10a outputs a pulse signal that generates a pulse whenever the wheel is rotated by a predetermined angle, i.e., a vehicle speed pulse. The vehicle speed detection unit 10 calculates the vehicle speed of the hybrid vehicle 1 based on the vehicle speed pulse.

[0070] The remaining battery capacity detection unit 16 is configured to detect the SOC of the battery 33 based on the charging / discharging current of the battery 33. The remaining battery capacity detection unit 16 of this embodiment constitutes a remaining battery capacity detection unit.

[0071] Next, with reference to Fig. 4 describes the process flow of the control for an automatic stop, which is carried out by the control unit 11. The Fig. The automatic stop control process illustrated in Fig. 4 is repeatedly performed at predetermined time intervals during operation of the internal combustion engine 2.

[0072] As in Fig. 4, the control unit 11 determines whether an automatic stop delay timer is detecting time or not (step S1). The automatic stop delay timer is a timer provided in the control unit 11 that starts detecting time in response to the satisfaction of the predetermined automatic stop condition in step S3, which will be described later.

[0073] When the control unit 11 determines in step S1 that the automatic stop delay timer detects a time, the control unit 11 causes the process to advance to step S3 without performing the process of step S2.

[0074] When the control unit 11 determines in step S1 that the automatic stop delay timer detects no time, the control unit 11 determines one of the predetermined automatic stop delay time and the predetermined torque margin-dependent automatic stop delay time as a delay time with respect to the automatic stop of the internal combustion engine 2 (step S2).

[0075] In particular, the control unit 11 determines a longer delay time from the predetermined automatic stop delay time, which is calculated by referring to the automatic stop delay time calculation map 60 (see Fig. 2) is calculated based on the SOC of the battery 33 and the vehicle speed V, and the predetermined torque range-dependent delay time for an automatic stop, which is calculated with reference to the torque range-dependent delay time calculation map 61 for an automatic stop (see Fig. 2) is calculated based on the vehicle speed V and the torque margin Tm, as a delay time with respect to the automatic stop of the internal combustion engine 2.

[0076] Then, the control unit 11 determines whether the predetermined automatic stop condition is met (step S3). If the control unit 11 determines in step S3 that the predetermined automatic stop condition is not met, the control unit 11 terminates the process of this automatic stop control. In this case, if the automatic stop delay timer has already started to acquire time before the process of a previous automatic stop control, the control unit 11 clears the value of the automatic stop delay timer and terminates the process of this automatic stop control.

[0077] When the control unit 11 determines in step S3 that the predetermined automatic stop condition is satisfied, the control unit 11 determines, based on the automatic stop delay timer, whether the predetermined automatic stop delay time or the predetermined torque margin-dependent automatic stop delay time determined in step S2 as a delay time related to the automatic stop of the internal combustion engine 2 has elapsed or not (step S4). Further, when the control unit 11 determines in step S3 that the predetermined automatic stop condition is satisfied, the control unit 11 starts the automatic stop delay timer detection process.

[0078] When the control unit 11 determines in step S4 that the predetermined automatic stop delay time or the predetermined torque margin-dependent automatic stop delay time determined in step S2 as a delay time related to the automatic stop of the internal combustion engine 2 has not passed, the control unit 11 ends the process of this automatic stop control without performing the process of step S5.

[0079] When the control unit 11 determines in step S4 that the predetermined automatic stop delay time or the predetermined torque margin-dependent automatic stop delay time determined in step S2 as a delay time with respect to the automatic stop of the engine 2 has passed, the control unit 11 automatically stops the engine 2 (step S5) and ends the process of this automatic stop control.

[0080] Next, with reference to Fig. 5 describes the process flow of the control for a restart, which is carried out by the control unit 11. The Fig. The restart control process illustrated in Fig. 5 is repeatedly performed at predetermined time intervals during the automatic stop of the internal combustion engine 2.

[0081] As in Fig. 5, the control unit 11 determines whether a restart delay timer is acquiring time or not (step S11). The restart delay timer is a timer provided in the control unit 11 that starts acquiring time in response to the satisfaction of the predetermined restart condition in step S13, which will be described later.

[0082] When the control unit 11 determines in step S11 that the restart delay timer detects a time, the control unit 11 causes the process to advance to step S13 without performing the process of step S12.

[0083] When the control unit 11 determines in step S11 that the restart delay timer does not detect time, the control unit 11 determines one of the predetermined restart delay time and the predetermined torque margin-dependent restart delay time as a delay time with respect to the restart of the internal combustion engine 2 (step S12).

[0084] In particular, the control unit 11 determines a shorter restart delay time than the predetermined one, which is calculated with reference to the restart delay time calculation map 70 (see Fig. 3) is calculated based on the SOC of the battery 33 and the vehicle speed V, and the predetermined torque range-dependent delay time for restart, which is calculated with reference to the torque range-dependent delay time calculation map 71 (see Fig.3) is calculated based on the vehicle speed V and the torque margin Tm, as a delay time with respect to the restart of the internal combustion engine 2.

[0085] Then, the control unit 11 determines whether the predetermined restart condition is met (step S13). If the control unit 11 determines in step S13 that the predetermined restart condition is not met, the control unit 11 terminates the process of this restart control. In this case, if the restart delay timer has already started to acquire time before the process of a previous restart control, the control unit 11 clears the value of the restart delay timer and terminates the process of this restart control.

[0086] If the control unit 11 determines in step S13 that the predetermined restart condition is satisfied, the control unit 11 determines, based on the restart delay timer, whether the predetermined restart delay time or the predetermined torque margin-dependent restart delay time determined in step S12 as a delay time related to the restart of the engine 2 has elapsed or not (step S14). Further, if the control unit 11 determines in step S13 that the predetermined restart condition is satisfied, the control unit 11 starts the restart delay timer acquisition process.

[0087] When the control unit 11 determines in step S14 that the predetermined restart delay time or the predetermined torque margin-dependent restart delay time determined in step S12 as a delay time with respect to restarting the internal combustion engine 2 has not passed, the control unit 11 ends the process of this restart control without performing the process of step S15.

[0088] When the control unit 11 determines in step S14 that the predetermined restart delay time or the predetermined torque margin-dependent restart delay time determined in step S12 as a delay time with respect to restarting the engine 2 has passed, the control unit 11 restarts the engine 2 (step S15) and ends the process of this restart control.

[0089] As described above, the hybrid vehicle 1 according to this embodiment is configured such that, in a case where the SOC of the battery 33 is lower than the first threshold value Th1, a longer predetermined delay time for restarting is determined as the SOC or the vehicle speed V is higher.

[0090] In a case where the SOC is lower than the first threshold Th1, there is a margin in the electric current with which the battery 33 can be recharged, that is, the battery 33 can enable storage of the regenerated energy of the electric motor generator 4. Furthermore, the electric current to be obtained from the regenerated energy of the electric motor generator 4 is higher as the vehicle speed V is higher. For this reason, in the hybrid vehicle 1 according to this embodiment, by setting the predetermined delay time for restarting in a case where the SOC is lower than the first threshold Th1 to a longer time as the vehicle speed V is higher, the electric current to be obtained from the regenerated energy of the electric motor generator 4 can be increased. Accordingly, the fuel efficiency of the hybrid vehicle 1 is improved.

[0091] Furthermore, in the hybrid vehicle 1 according to this embodiment, the predetermined delay time for restarting in a case where the SOC is lower than the first threshold Th1 is set to a shorter time as the SOC is lower. There is a concern that the driving force of the electric motor generator 4 may be insufficient in a case where the SOC is low because the remaining capacity of the battery 33 is insufficient. For this reason, in the hybrid vehicle 1 according to this embodiment, by setting the predetermined delay time for restarting in a case where the SOC is lower than the first threshold Th1 to a shorter time as the SOC is lower, the driving force of the internal combustion engine 2 can be output early to prevent the hybrid vehicle 1 from being subjected to insufficient driving force.

[0092] Furthermore, the hybrid vehicle 1 according to this embodiment is configured such that, in a case where the SOC is equal to or higher than the first threshold value Th1, a shorter predetermined delay time for restarting is determined as the vehicle speed V is higher.

[0093] In a case where the SOC reaches an upper limit threshold for protecting a battery during regeneration of the electric motor generator 4, which is in operation, in a state where the engine 2 is automatically stopped, the regenerated torque must be set to 0 [Nm]. In such a case, there is a concern that drivability may deteriorate because a braking force obtained from the regeneration of the electric motor generator 4 is interrupted before engine braking acts. Such a situation is more likely to occur when the vehicle speed V is higher. This is because the SOC is more likely to reach an upper limit threshold for protecting a battery because a higher regenerated energy is recovered when the vehicle speed V is higher.

[0094] Accordingly, as described above, the hybrid vehicle 1 according to this embodiment is configured to restart the engine 2 early by setting the predetermined delay time for restarting in a case where the SOC is equal to or higher than the first threshold value Th1 to a shorter time as the vehicle speed V is higher.

[0095] For this reason, in the hybrid vehicle 1 according to this embodiment, since a braking operation can be switched from a braking operation using the regeneration of the electric motor generator 4 to an engine braking operation without interruption, it is possible to prevent the deterioration of drivability caused by the interruption of a braking force obtained from the regeneration of the electric motor generator 4.

[0096] Furthermore, in a case where the vehicle speed V is low, little regenerated energy is recovered even if the SOC is equal to or higher than the first threshold Th1. Accordingly, the SOC does not reach an upper limit threshold for battery protection in a short time compared to a case where the vehicle speed V is high.

[0097] Therefore, the hybrid vehicle 1 according to this embodiment is configured to delay the restart of the engine 2 by setting the predetermined delay time for restarting to a long time in a case where the vehicle speed V is low, even when the SOC is equal to or higher than the first threshold value Th1. Since the hybrid vehicle 1 according to this embodiment can keep the fuel consumption of the engine 2 low, the fuel efficiency of the hybrid vehicle 1 according to this embodiment can be improved accordingly.

[0098] Furthermore, the hybrid vehicle 1 according to this embodiment is configured such that, in a case where the SOC is lower than the second threshold Th2, a longer predetermined delay time for automatic stop is determined as the SOC is lower or the vehicle speed V is lower.

[0099] In a case where the SOC is lower than the second threshold Th2, there is a high tendency to restart the engine 2 to allow the engine 2 to output driving power before the electric motor generator 4 cannot output driving power, in order to prevent a situation in which the electric motor generator 4 cannot output driving power due to the insufficient remaining capacity of the battery 33. For this reason, there is a likelihood that the engine 2 is frequently restarted.

[0100] Furthermore, when the engine 2 is to be restarted in a state where the vehicle speed V is low, there is a likelihood that a vehicle occupant may feel a delay time until a driving force of the engine 2 is generated by the restart of the engine, that is, a time gap between the time of restarting and the time of generating the driving force, and there is a concern that drivability may deteriorate.

[0101] Accordingly, the hybrid vehicle 1 according to this embodiment is configured to delay the automatic stop of the engine 2 by setting the predetermined delay time for automatic stop in a case where the SOC is lower than the second threshold Th2 to a longer time as the SOC is lower or the vehicle speed V is lower. Accordingly, since the hybrid vehicle 1 according to this embodiment can reduce the frequency of restarting the engine 2, the deterioration of drivability can be prevented.

[0102] Furthermore, the hybrid vehicle 1 according to this embodiment is configured such that, in a case where the SOC is equal to or higher than the second threshold value Th2, a longer predetermined delay time for automatic stop is determined as the SOC or the vehicle speed V is higher.

[0103] For this reason, the automatic stop threshold used to determine the automatic stop condition is set to a high value in a region where the vehicle speed V is high (hereinafter referred to as a "vehicle high-speed region"). In a case where the automatic stop condition is met in the vehicle high-speed region, there is a likelihood of creating a state close to a state where a driver is not stepping on the accelerator pedal. In this case, there is a likelihood that the driver will reduce or release the accelerator pedal and expect a braking force to act on the hybrid vehicle.

[0104] In a case where the SOC is equal to or higher than the second threshold Th2, more regenerated energy is recovered as the vehicle speed V is higher, and the SOC is closer to an upper limit threshold for protecting a battery as the SOC is higher. Accordingly, since the SOC reaches an upper limit threshold for protecting a battery in a short time in a case where the engine 2 is automatically stopped and the electric motor generator 4 regenerates electric power, the regeneration must be interrupted.

[0105] For this reason, in a case where an automatic stop condition is satisfied in a vehicle high-speed region and a region where the SOC is high, there is a possibility that the engine 2 is restarted in a short time after the engine 2 is automatically stopped to cause a braking force generated by engine braking to act according to a driver's request, as described above.

[0106] In this case, the restart of the engine 2 is performed regardless of whether the aforementioned predetermined restart condition is met or not. Specifically, since the regenerated torque becomes 0 [Nm] in a case where the SOC approaches an upper limit threshold for battery protection during regenerative braking, and the regenerated torque cannot be caused to act, the engine 2 is restarted by the control unit 11 under a condition where the SOC reaches a predetermined threshold, which is obtained by subtracting a predetermined value from the upper limit threshold, to cause engine braking to act.

[0107] Accordingly, the hybrid vehicle 1 according to this embodiment is configured to delay the automatic stop of the engine 2 by setting the predetermined delay time for automatic stop in a case where the SOC is equal to or higher than the second threshold Th2 as described above to a longer time as the SOC or the vehicle speed V is higher. Therefore, the deterioration of drivability caused by the restart of the engine 2 being performed in a short time after the automatic stop of the engine 2 can be prevented in the hybrid vehicle 1 according to this embodiment.

[0108] Furthermore, the hybrid vehicle 1 according to this embodiment is configured to determine a shorter torque margin-dependent restart delay time as the torque margin Tm is lower or the vehicle speed V is lower. Furthermore, the hybrid vehicle 1 according to this embodiment is configured to restart the engine 2 after the elapse of the predetermined torque margin-dependent restart delay time when the predetermined torque margin-dependent restart delay time is shorter than the predetermined restart delay time.

[0109] Here, in a region where the vehicle speed V is low (hereinafter referred to as a “vehicle low-speed region”), a vehicle occupant is likely to feel a delay time until a driving force of the engine 2 is generated by the restart of the engine, that is, a time gap between the time of restart and the time of generation of the driving force, and there is a concern that drivability may deteriorate.

[0110] Accordingly, as described above, the hybrid vehicle 1 according to this embodiment is configured to restart the engine 2 early by setting the torque margin-dependent restart delay time to a shorter time as the torque margin Tm is lower or the vehicle speed V is lower. Therefore, the deterioration of drivability in the above-mentioned vehicle low-speed range can be prevented in the hybrid vehicle 1 according to this embodiment.

[0111] Furthermore, the hybrid vehicle 1 according to this embodiment is configured to determine a longer torque margin-dependent automatic stop delay time when the torque margin Tm is lower or the vehicle speed V is higher. Furthermore, the hybrid vehicle 1 according to this embodiment is configured to automatically stop the engine 2 after the elapse of the predetermined torque margin-dependent automatic stop delay time when the predetermined torque margin-dependent automatic stop delay time is longer than the predetermined automatic stop delay time.

[0112] Here, a change in the accelerator pedal position Acc associated with the driver's operation of an accelerator pedal is large in the vehicle high-speed range, and the amount of increase / decrease in the requested torque is larger than in the vehicle low-speed range. For this reason, even if the engine 2 has been automatically stopped in the vehicle high-speed range, there is a possibility that the engine 2 will be immediately restarted. As a result, since the automatic stop and restart of the engine 2 are repeated, there is a concern that drivability may deteriorate. The same applies to a case where the torque margin Tm is low.

[0113] Accordingly, the hybrid vehicle 1 according to this embodiment is configured to delay the automatic stop of the engine 2 by setting the torque margin-dependent delay time for automatic stop to a longer time when the torque margin Tm is lower or the vehicle speed V is higher, as described above. Accordingly, the deterioration of drivability caused by the repetition of the automatic stop and restart of the engine 2 can be prevented in the hybrid vehicle 1 according to this embodiment.

[0114] Meanwhile, in this embodiment, the vehicle speed V was used as a parameter when referring to the automatic stop delay time calculation map 60, the torque margin-dependent automatic stop delay time calculation map 61, the restart delay time calculation map 70, and the torque margin-dependent restart delay time calculation map 71. However, instead of the vehicle speed V, the change in the accelerator pedal position Acc or the rotational speed of a wheel may also be used.

[0115] Furthermore, in this embodiment, the torque margin Tm was used as a parameter when referring to the map 61 for calculating the torque margin-dependent delay time for automatic stop and the map 71 for calculating the torque margin-dependent delay time for restart. However, instead of a torque margin Tm, the requested torque requested for the hybrid vehicle 1 may also be used. (DESCRIPTION OF REFERENCE SYMBOLS)

[0116] 1 ... hybrid vehicle, 2 ... internal combustion engine, 3 ... transmission, 4 ... electric motor generator, 5 ... drive wheel, 10 ... vehicle speed detection unit, 10a ... wheel speed sensor, 10b ... accelerator pedal position sensor, 11 ... control unit, 16 ... battery remaining capacity detection unit, 20 ... ISG, 33 ... battery, 60 ... map for calculating the delay time for an automatic stop, 61 ... map for calculating the torque margin-dependent delay time for an automatic stop, 70 ... map for calculating the delay time for a restart, 71 ... map for calculating the torque margin-dependent delay time for a restart, Th1 ... first threshold, Th2 ... second threshold

Claims

[1] A hybrid vehicle (1) including an internal combustion engine (2) and an electric motor generator (4) as a drive source that transmits power to a drive wheel (5), and that can travel in a state where operation of the internal combustion engine (2) is stopped, the hybrid vehicle (1) comprising: a battery (33) which supplies an electric current to the electric motor generator (4); a battery remaining capacity detection unit (16) that detects a charge state of the battery (33); a vehicle speed detection unit (10) that detects a vehicle speed as the speed of the hybrid vehicle (1); and a control unit (11) configured to restart the internal combustion engine (2) in a case where a predetermined restart condition is met, after a predetermined restart delay time has elapsed, wherein the control unit (11) is configured to determine the predetermined delay time for the restart based on the state of charge of the battery (33) and the vehicle speed, wherein the predetermined delay time for restarting in a case where the state of charge of the battery (33) is lower than a first threshold value (Th1) is determined to be a longer time as the state of charge of the battery (33) or the vehicle speed is higher, and wherein the predetermined delay time for restarting in a case where the state of charge of the battery (33) is equal to or higher than the first threshold value (Th1) is determined to be a shorter time as the vehicle speed is higher. [2] Hybrid vehicle (1) according to claim 1, wherein the control unit (11) is configured to determine a predetermined delay time for an automatic stop based on the state of charge of the battery (33) and the vehicle speed and to automatically stop the internal combustion engine (2) after the predetermined delay time for the automatic stop has elapsed in a case where a predetermined condition for the automatic stop is met, and wherein the predetermined delay time for the automatic stop in a case where the state of charge of the battery (33) is lower than a second threshold value (Th2) which is smaller than the first threshold value (Th1) is determined to be a longer time as the state of charge of the battery (33) is lower or the vehicle speed is lower. [3] The hybrid vehicle (1) according to claim 2, wherein the predetermined delay time for the automatic stop in a case where the state of charge of the battery (33) is equal to or higher than the second threshold value (Th2) is determined to be a longer time as the state of charge of the battery (33) or the vehicle speed is higher. [4] Hybrid vehicle (1) according to one of claims 1 to 3, wherein the control unit (11) is configured to subtract a requested torque requested for the hybrid vehicle (1) from an electric motor torque that can be output by the electric motor generator (4) to calculate a torque margin, and to determine a predetermined torque margin-dependent delay time for the restart on a basis of the torque margin and the vehicle speed, wherein the predetermined torque margin-dependent delay time for restarting is determined to be a shorter time when the torque margin is lower or the vehicle speed is lower, and wherein the control unit (11) restarts the internal combustion engine (2) after a lapse of the predetermined torque range-dependent restart delay time in a case where the predetermined torque range-dependent restart delay time is shorter than the predetermined restart delay time. [5] Hybrid vehicle (1) according to claim 2 or 3, wherein the control unit (11) is configured to subtract a requested torque requested for the hybrid vehicle (1) from the electric motor torque that can be output by the electric motor generator (4) to calculate a torque margin, and to determine a predetermined torque margin-dependent delay time for the automatic stop on the basis of the torque margin and the vehicle speed, wherein the predetermined torque margin-dependent delay time for the automatic stop is determined to be a longer time when the torque margin is lower or the vehicle speed is higher, and wherein the control unit (11) is configured to automatically stop the internal combustion engine (2) after a lapse of the predetermined torque range-dependent automatic stop delay time in a case where the predetermined torque range-dependent automatic stop delay time is longer than the predetermined automatic stop delay time.

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