Patent Publication Number: US-9840251-B2

Title: Hybrid electric vehicle, drive control method and device of the same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority and benefits of Chinese Patent Application No. 201510133521.9, filed with State Intellectual Property Office, P. R. C. on Mar. 25, 2015, the entire content of which application is incorporated herein by reference. 
     The present application is related to U.S. patent application Ser. No. 15/078,942 entitled “HYBRID ELECTRIC VEHICLE, DRIVE CONTROL METHOD AND DEVICE OF THE SAME” filed Mar. 23, 2016, U.S. patent application Ser. No. 15/078,947 entitled “HYBRID ELECTRIC VEHICLE, DRIVE CONTROL METHOD AND DEVICE OF THE SAME” filed Mar. 23, 2016, U.S. patent application Ser. No. 15/078,951 entitled “HYBRID ELECTRIC VEHICLE, DRIVE CONTROL METHOD AND DEVICE OF THE SAME” filed March 23, U.S. patent application Ser. No. 15/078,953 entitled “HYBRID ELECTRIC VEHICLE, DRIVE CONTROL METHOD AND DEVICE OF THE SAME” filed Mar. 23, 2016, and U.S. patent application Ser. No. 15/080,326 entitled “HYBRID ELECTRIC VEHICLE, DRIVE CONTROL METHOD AND DEVICE OF THE SAME” filed Mar. 24, 2016, all of which are incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to vehicle technology field, more particularly to a hybrid electric vehicle, a drive control method and a drive control device of the hybrid electric vehicle. 
     BACKGROUND 
     A traditional fuel vehicle is usually equipped with an additional automatic start-stop subsystem for realizing taxiing start-stop control on the vehicle, and thus fuel waste and air pollution caused by engine idling are reduced. There have been following forms of start-stop systems in vehicles. 
     1. Separating Starter/Generator Start-Stop System 
     In such a system, the starter and the generator are designed separately, in which the starter is used to provide power for starting an engine, and the generator is used to provide electric energy for the starter. This system includes a high enhanced starter, an enhanced battery (usually an AGM battery), a controllable generator, an engine ECU (Electronic Control Unit) with integrated start-stop coordination program, and a sensor, etc. In this system, the engine is started by the starter separately. 
     2. Integrated Starter/Generator Start-Stop System 
     The integrated start/generator is a synchronous machine actuated by a single teeth stator and a rotor in a permanent magnet, and a driving unit may be integrated into a hybrid power transmission system. With this system, the engine may be started by revise driving from the motor. 
     3. i-Start System 
     An electric control device is integrated in the generator. The engine stops when the vehicle stops at a red light, and automatically starts as soon as engaging a gear or releasing a brake pedal. 
     When the vehicle is driven on heavy-traffic roads, the engine will be started frequently, that is a huge test for both a spark plug and a battery. Although the start-stop systems described-above are intelligent enough, a service life of the engine will be shorten as an abrasion on the engine, and a vibration and a noise are inevitable as frequent start-stop, which severely reduces the comfort. In addition, the automatic start-stop system may work only in such conditions that a vehicle speed is 0, a rotating speed of the engine is lower than a prescribed target speed, the refrigerant is in a required range, the vacuum braking meets a required condition, an air conditioner is adjusted suitably, the braking pedal is depressed at a certain gear position (like N or P), and an electric charge level of the power battery meets a next start. Since the start-stop system is limited on many aspects, system units are required to have a high reliability and durability. Moreover, the special start-stop system increases the cost of the vehicle. 
     SUMMARY 
     Embodiments of the present disclosure seek to solve at least one of the problems existing in the related art to at least some extent. 
     According to embodiments of a first aspect of the present disclosure, a drive control method of a hybrid electric vehicle is provided. The method includes: obtaining a current gear position of the hybrid electric vehicle and a current electric charge level of a power battery; obtaining a slope of a road on which the hybrid electric vehicle is driving, if the current gear position of the hybrid electric vehicle and the current electric charge level of the power battery meet a preset requirement; and causing a working state of an engine and/or a motor of the hybrid electric vehicle according to the slope of the road on which the hybrid electric vehicle is driving. 
     With the drive control method of the hybrid electric vehicle according to embodiments of the present disclosure, when the current gear position of the hybrid electric vehicle and the current electric charge level of the power battery meet a preset requirement, the hybrid electric vehicle is configured to enter a small load stop mode or a small load stall mode according to the slope of the road on which the hybrid electric vehicle is driving. In this way, a driving distance for the vehicle may be increased, an economy performance may be improved, and fuel consumption and emission may be reduced, without increasing a working frequency of the starter, thus ensuring a working life of components. In addition, if the vehicle has an accelerator-releasing energy feedback function, wasted kinetic energy may be converted to electric energy by a motor through the energy feedback and stored in a power battery, thus increasing energy recovery. Moreover, for the hybrid electric vehicles, problems of bad ride comfort and bad power performance caused by frequent start-stop of the engine may be solved effectively. 
     According to embodiments of a second aspect of the present disclosure, a drive control device of a hybrid electric vehicle is provided. The device includes: a first obtaining module, configured to obtain a current gear position of the hybrid electric vehicle and a current electric charge level of a power battery; a second obtaining module, configured to obtain a slope of a road on which the hybrid electric vehicle is driving, if the current gear position of the hybrid electric vehicle and the current electric charge level of the power battery meet a preset requirement; and a first control module, configured to control a working state of an engine and/or a motor of the hybrid electric vehicle according to the slope of the road on which the hybrid electric vehicle is driving. 
     With the drive control device of the hybrid electric vehicle according to embodiments of the present disclosure, when the current gear position of the hybrid electric vehicle and the current electric charge level of the power battery meet a preset requirement, the hybrid electric vehicle is configured to enter a small load stop mode or a small load stall mode according to the slope of the road on which the hybrid electric vehicle is driving. In this way, a driving distance for the vehicle may be increased, an economy performance may be improved, and fuel consumption and emission may be reduced, without increasing a working frequency of the starter, thus ensuring a working life of components. In addition, if the vehicle has an accelerator-releasing energy feedback function, wasted kinetic energy may be converted to electric energy by a motor through the energy feedback and stored in a power battery, thus increasing energy recovery. Moreover, for the hybrid electric vehicles, problems of bad ride comfort and bad power performance caused by frequent start-stop of the engine may be solved effectively. 
     According to embodiments of a third aspect of the present disclosure, a hybrid electric vehicle is provided. The hybrid electric vehicle includes the drive control device mentioned in the above embodiments of the second aspect of the present disclosure. 
     With the hybrid electric vehicle according to embodiments of the present disclosure, when the current gear position of the hybrid electric vehicle and the current electric charge level of the power battery meet a preset requirement, the hybrid electric vehicle is configured to enter a small load stop mode or a small load stall mode according to the slope of the road on which the hybrid electric vehicle is driving. In this way, a driving distance for the vehicle may be increased, an economy performance may be improved, and fuel consumption and emission may be reduced, without increasing a working frequency of the starter, thus ensuring a working life of components. In addition, if the vehicle has an accelerator-releasing energy feedback function, wasted kinetic energy may be converted to electric energy by a motor through the energy feedback and stored in a power battery, thus increasing energy recovery. Moreover, for the hybrid electric vehicles, problems of bad ride comfort and bad power performance caused by frequent start-stop of the engine may be solved effectively. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects and advantages of embodiments of the present disclosure will become apparent and more readily appreciated from the following descriptions made with reference to the accompanying drawings, in which: 
         FIG. 1  is a flow chart of a drive control method of a hybrid electric vehicle according to an embodiment of the present disclosure; 
         FIG. 2  is a flow chart of determining whether a hybrid electric vehicle is within a taxiing start-stop interval or a speech start-stop interval according to an embodiment of the present disclosure; 
         FIG. 3  is a flow chart of causing a hybrid electric vehicle to enter a small load stop mode or a small load stall mode according to an embodiment of the present disclosure; 
         FIG. 4  is a schematic diagram of energy transfer in a drive control process of a hybrid electric vehicle according to an embodiment of the present disclosure; 
         FIG. 5  is a schematic diagram of control information interaction in a drive control process of a hybrid electric vehicle according to an embodiment of the present disclosure; 
         FIG. 6  is a flow chart of a drive control method of a hybrid electric vehicle according to an example embodiment of the present disclosure; 
         FIG. 7  is a block diagram of a drive control device of a hybrid electric vehicle according to an embodiment of the present disclosure; 
         FIG. 8  is a block diagram of a drive control device of a hybrid electric vehicle according to another embodiment of the present disclosure; and 
         FIG. 9  is a block diagram of a drive control device of a hybrid electric vehicle according to yet another example embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Example embodiments will be described in detail herein, and examples thereof are illustrated in accompanying drawings. Throughout figures referred by the following description, the same reference number in different figures indicates the same or similar elements unless otherwise stated. Implementations described in the following exemplary embodiments do not represent all the implementations consistent with the present disclosure. Instead, they are only examples of the device and method consistent with some aspects of the present disclosure. 
     A drive control method and device of a hybrid electric vehicle according to embodiments of the present disclosure will be described with reference to drawings. 
       FIG. 1  is a flow chart of a drive control method of a hybrid electric vehicle according to an embodiment of the present disclosure. 
     As shown in  FIG. 1 , the drive control method according to some embodiments of the present disclosure includes following steps. 
     In step S 101 , a current gear position of the hybrid electric vehicle and a current electric charge level of a power battery are obtained. 
     The current gear position may be obtained by a gearbox system of the hybrid electric vehicle through obtaining a gear signal. The current electric charge level of the power battery may be obtained by a BMS (Battery Management System) in the hybrid electric vehicle. 
     Specifically, the current gear position of the hybrid electric vehicle and the current electric charge level of the power battery may be obtained via communication between an internal communication network of the hybrid electric vehicle, e.g. CAN (Controller Area Network) and the gearbox system, the BMS. 
     In step S 102 , a slope of a road on which the hybrid electric vehicle is driving is obtained, if the current gear position of the hybrid electric vehicle and the current electric charge level of the power battery meet the preset requirement. 
     Specifically, if the current gear position of the hybrid electric vehicle and the current electric charge level of the power battery meet a requirement for entering a taxiing start-stop interval, it is determined that the current gear position and the current electric charge level meet the preset requirement. 
     In embodiments of the present disclosure, the drive control method may be performed only when the gear position of the vehicle is at D-position. 
     When the power battery of the hybrid electric vehicle could offer electric energy, a motor can work, and then the vehicle can have the taxiing start-stop function. Thus, the taxiing start-stop control is performed when the electric charge level of the power battery is sufficient. 
     Since a motor has a limited power output, it is difficult for the motor as an alone driving source to satisfy the power requirement of the vehicle, especially when the vehicle is climbing a sizable uphill slope. Thus, an engine is required to output power when the vehicle is climbing a slope. However, when the vehicle is driving downhill, the driving resistance may be completely overcome by gravity inertia, and thus the required torque is small. In this case, the engine may be configured to stop, a clutch may be released totally, and only the motor may be used to output power. On one hand, the fuel needed during the engine idling is saved, and on the other hand, if the hybrid electric vehicle has the accelerator-releasing energy feedback function, an energy feedback by the motor may be increased, since the clutch is completely released, and a drag force from the engine disappears. 
     Alternatively, a current operating mode of the hybrid electric vehicle and a discharge power of the power battery may also be obtained, and it may be determined whether the hybrid electric vehicle is within the taxiing start-stop interval according to the current gear position and the current operating mode of the hybrid electric vehicle, the current electric charge level and the discharge power of the power battery. 
     Specifically, the voltage and the current of the power battery may be obtained via data collectors in the BMS in real time, and then the current electric charge level and the allowable discharge power of the power battery may be computed. When the vehicle is at a low temperature or when the vehicle has a fault, the power battery has a risk of over discharge and over-low voltage. Thus, in order to protect the power battery from damage and prolong a use life of the power battery, the discharge power should be limited when the vehicle is at the low temperature or when the vehicle has a fault. At this time, the vehicle cannot output power normally. 
     A motor controller may determine a mode of the hybrid electric vehicle according to a mode switch signal, and then choose different driving strategies. Generally, the hybrid electric vehicle includes two working modes (electric mode and hybrid mode, namely EV mode and HEV mode) and two driving modes (Economy mode and Sport mode, namely ECO mode and Sport mode). Therefore, the hybrid electric vehicle may have four kinds of operating modes, such as EV-ECO mode, EV-Sport mode, HEV-ECO mode and HEV-Sport mode. In the EV mode, the vehicle is in a pure electric energy consumption mode and the motor outputs power separately; in the HEV mode, the vehicle is in a hybrid energy consumption mode, and a ratio of power output by the motor to power output by the engine is determined according to a preset strategy. In the ECO mode, the power output from the motor and the engine is limited since the economy is a primary control target; in the Sport mode, the power output from the motor and the engine is not limited since the power performance is the primary control target, especially, in the hybrid sport mode (HEV-Sport mode), the engine remains running. 
       FIG. 2  is a flow chart of determining whether a hybrid electric vehicle is within a taxiing start-stop interval or a speech start-stop interval according to an embodiment of the present disclosure. As shown in  FIG. 2 , following steps are performed. 
     In step S 201 , it is determined whether the current electric charge level of the power battery is greater than a first electric charge level threshold, and whether the discharge power of the power battery is greater than a first power threshold, if the current gear position is at D-position, and the current operating mode is the hybrid economy mode (HEV-ECO mode). 
     The first electric charge level threshold and the first power threshold may be determined according to a minimum electric charge level and a minimum discharge power at which the power battery may supply power normally. When the electric charge level of the power battery is less than or equal to the first electric charge level threshold or when the discharge power of the power battery is less than or equal to the first power threshold, the power battery may take the risk of over discharging and low voltage alarm. Therefore, in order to protect the power battery from damage and ensure the working life of the power battery, the first electric charge level threshold and the first power threshold should be set. 
     In step S 202 , if the current electric charge level of the power battery is greater than the first electric charge level threshold, and the discharge power of the power battery is greater than the first power threshold, it is further determined whether the current electric charge level is greater than or equal to a second electric charge level threshold, and whether a difference between the current electric charge level and a target electric charge level of the power battery is less than or equal to a preset value. 
     The target electric charge level is an electric charge level which the power battery finally has when charging or discharging under the HEV mode. 
     Therefore, if the difference between the current electric charge level and the target electric charge level of the power battery is less than or equal to the preset value, the current electric charge level of the power battery is relatively high and has a smaller difference with the target electric charge level, and the power battery is in a balance state. In this case, the power battery may not only meet a current driving requirement, but also is in a stable discharge state, and thus over discharging may be avoided effectively when the hybrid electric vehicle enters a small load control function, thereby protecting the power battery, prolonging the working life of the power battery, and keeping a better power performance and stability for the hybrid electric vehicle. 
     The small load control function refers to a drive control function used when the electric charge level of the power battery is large enough (e.g. the electric charge level is larger than a second electric threshold), the discharge power of the power battery is greater than the first power threshold, and the slope of the road satisfies following conditions: 
     the road is ascent and the slope of the road is less than a first slope threshold; or 
     the road is descent and the slope of the road is greater than or equal to a second slope threshold. 
     The second electric threshold is an electric charge level which may satisfy the requirement of driving in a pure electric mode at a low speed, such that part of the electric charge level are reserved for driving in a pure electric mode at a low speed when a taxiing start-stop control is performed, thus keeping the better power performance and stability for the hybrid electric vehicle. The first electric threshold and the second electric threshold may be set according to the driving habit of the user and the power consumption of the hybrid electric vehicle. 
     In step S 203 , if the current electric charge level is greater than or equal to the second electric charge level threshold, and the difference between the current electric charge level and the target electric charge level of the power battery is less than or equal to the preset value, it is determined that the hybrid electric vehicle is within the taxiing start-stop interval. 
     In some embodiments of the present disclosure, step S 204  is further included. 
     In step S 204 , if the current electric charge level is less than the second electric charge level threshold, or if the difference between the current electric charge level and the target electric charge level of the power battery is greater than the preset value, it is determined that the hybrid electric vehicle is within a speed start-stop interval. 
     In the taxiing start-stop interval, the engine is configured to start, stop or stall, while the accelerator pedal is released. In the speed start-stop interval, the engine is configured to start, stop or stall, while the accelerator pedal is depressed. The control strategy for the taxiing start-stop interval needs to consider factors like the speed, the working state of the engine, and the accelerator push depth, while the control strategy for the speed start-stop interval needs to consider factors like the speed and the slope of the road. In other words, in the speed start-stop interval, the engine is configured according to the speed and the slope of the road. 
     In some embodiments of the present disclosure, if the current gear position of the hybrid electric vehicle and the current electric charge level of the power battery meet the preset requirement, a slope of a road on which the hybrid electric vehicle is driving may be obtained via computing from a longitudinal acceleration of the vehicle, which is obtained by a longitudinal acceleration sensor in the hybrid electric vehicle. 
     Specifically, the slope of the road on which the hybrid electric vehicle is driving may be obtained via communication between an internal communication network of the hybrid electric vehicle, e.g. CAN (Controller Area Network) and the longitudinal acceleration sensor. 
     In step S 103 , a working state of an engine and/or a motor of the hybrid electric vehicle is configured according to the slope of the road on which the hybrid electric vehicle is driving. 
     Specifically, in some embodiments, it may be determined whether the slope of the road satisfies a preset condition. If the slope of the road on which the hybrid electric vehicle is driving meets the preset condition, the current speed of the hybrid electric vehicle may be obtained, and then the hybrid electric vehicle is configured to enter a small load stop mode or a small load stall mode according to the current speed. The current speed of the hybrid electric vehicle may be obtained from an ESC (Electrical Speed Controller) via the communication network in the hybrid electric vehicle. 
     Specifically, if the road is ascent and the slope of the road is less than the first slope threshold, it is determined that the slope of the road on which the hybrid electric vehicle is driving meets the preset condition; if the road is descent and the slope of the road is greater than the second slope threshold, it is determined that the slope of the road on which the hybrid electric vehicle is driving meets the preset condition. If it is determined that the slope of the road on which the hybrid electric vehicle is driving doesn&#39;t meet the preset condition, for example, if the road is ascent and the slope of the road is greater than or equal to the first slope threshold, then the engine may be released from start-stop control, or if the road is descent and the slope of the road is less than the second slope threshold, then the engine is configured to stop and the motor is configured to output power separately. 
     In some embodiments, as shown in  FIG. 3 , causing the hybrid electric vehicle to enter the small load stop mode or the small load stall mode includes following steps. 
     In step S 301 , the engine is configured to stop and the engine is configured to output power separately, if the current speed is less than a third speed threshold. 
     In step  302 , the hybrid electric vehicle is configured to enter the small load stop mode, if the current speed is greater than or equal to a third speed threshold and less than a fourth speed threshold. 
     Specifically, it is first determined whether the engine is in an operating state. 
     If the engine is not in the operating state, it is further determined whether an accelerator push depth is greater than or equal to a first accelerator threshold; if the accelerator push depth is greater than or equal to the first accelerator threshold, the engine is configured to start; and if the accelerator push depth is less than the first accelerator threshold, a state of the engine remains unchanged. 
     If the engine is in the operating state, it is further determined whether the accelerator push depth is less than a second accelerator threshold; if the accelerator push depth is less than the second accelerator threshold, the engine is configured to stop; if the accelerator push depth is greater than or equal to the second accelerator threshold, the state of the engine remains unchanged. 
     The first accelerator threshold and the second accelerator threshold may be set according to the driving habit of the user and the power consumption of the vehicle. The second accelerator threshold is less than the first accelerator threshold, thus avoiding a frequent engine start-stop caused by unclear accelerator thresholds. 
     In step S 303 , the hybrid electric vehicle is configured to enter the small load stall mode, if the current speed is greater than or equal to the fourth speed threshold and less than a fifth speed threshold. 
     Specifically, it is first determined whether the engine is in an operating state. 
     If the engine is not in the operating state, it is further determined whether an accelerator push depth is greater than or equal to a first accelerator threshold; if the accelerator push depth is greater than or equal to the first accelerator threshold, the engine is configured to start; and if the accelerator push depth is less than the first accelerator threshold, a state of the engine remains unchanged. 
     If the engine is in the operating state, it is further determined whether the accelerator push depth is less than a second accelerator threshold; if the accelerator push depth is less than the second accelerator threshold, the engine is configured to stall, a clutch is kept in a coupling state and fuel supply for the engine is cut off; if the accelerator push depth is greater than or equal to the second accelerator threshold, the state of the engine remains unchanged. 
     In step S 304 , the state of the engine remains unchanged if the current speed is greater than or equal to the fifth speed threshold. 
     In embodiments of the present disclosure, the fifth speed threshold is greater than the fourth speed threshold, and the fourth speed threshold is greater than the third speed threshold. And the third speed threshold, the fourth speed threshold and the fifth speed threshold may be set according to the driving habit of the user and the power consumption of the vehicle. 
     In embodiments of the present disclosure, the vehicle has the accelerator-releasing energy feedback function, and during the accelerator is released, the lost kinetic energy is converted to electric energy via the energy feedback of the motor and stored in the power battery. In this case, if the engine is stopped, the clutch is released totally and the drag force from the engine disappears, then the energy feedback by the motor is increased. 
     With the drive control method according to embodiments of the present disclosure, the hybrid electric vehicle is configured to enter the small load stall mode when the speed of the hybrid electric vehicle is relatively higher, since in this case, the vehicle motion inertia is large, and the drag force from the engine is relatively small, and thus has a little impact on the feedback charging of the power battery. Furthermore, the clutch keeps the coupling state, such that it does not require coupling the clutch again, thus reducing the friction loss of the clutch. Moreover, the hybrid electric vehicle is configured to enter the small load stop mode when the speed of the hybrid electric vehicle is relatively lower, when the vehicle speed is lower, the clutch is configured to open so as to avoid influence on charging the power battery, since in this case, the vehicle motion inertia is small, and the drag force from the engine is relatively large, which has a great impact on the feedback charging of the power battery. 
     When the hybrid electric vehicle enter the small load stop mode or the small load stall mode, after causing the engine (the engine is configured to start, stop or stall, or the state of the engine remains unchanged), a timing is started in order to determine whether to enter next drive control. Then, after the state of the engine is changed, the state of the engine may be changed again only after a preset time, thus to avoid frequent start-stop of the engine. 
     After determining that the hybrid electric vehicle is within the speed start-stop interval, the speed start-stop control may be performed according to the slope of the road and the current speed. Specifically, if the road is ascent and the slope of the road is greater than or equal to a third slope threshold, the engine is started; if the road is descent and the slope of the road is greater than or equal to a fourth slope threshold, the engine is configured to stop, i.e., the fuel supply for the engine is cut off and the clutch is configured to be open (at this time, the engine stops running), and the motor is configured to output power separately; if the road is ascent and the slope of the road is less than the third slope threshold, and the current speed is greater than a first speed threshold, the engine is started; if the road is descent and the slope less than the fourth slope threshold, and the current speed is greater than the first speed threshold, the engine is started. After starting the engine, the current speed of the hybrid electric vehicle is obtained, and when the current speed of the hybrid electric vehicle is less than a second speed threshold, the engine is configured to stop, and the motor is configured to output power separately, and if the current speed of the hybrid electric vehicle is greater than or equal to a second speed threshold, then step S 101  is executed. 
     In embodiments of the present disclosure, stopping the engine refers to a state in which fuel supply for the engine is cut off and the clutch is released, causing the engine to stall refers to a state in which fuel supply for the engine is cut off and the clutch is in a coupling state. 
     In the present disclosure, the first slope threshold, the second slope threshold, the third slope threshold and the fourth slope threshold may be set according to the driving habit of the user and the power consumption of the hybrid electric vehicle. 
     Specifically,  FIG. 4  is a schematic diagram of energy transfer in a drive control process of the hybrid electric vehicle according to an embodiment of the present disclosure. As shown in  FIG. 4 , when the mode of the hybrid electric vehicle is the hybrid economy mode, the current electric charge level of the power battery (an electric charge level of a high-voltage iron battery) is greater than the second electric charge level threshold, the discharge power is less than or equal to the first power threshold, and the slope of the road, the speed and the accelerator push depth meet a condition for low-speed, small-throttle and low-power driving, the hybrid electric vehicle is driven by the motor separately, and the energy transfer is shown as route {circle around (1)} in  FIG. 4 . If the discharge power of the hybrid electric vehicle is greater than the second power threshold (i.e. requiring a large power driving), the engine is started to output power, and at this time, the power is transferred to wheels via a DCT (Dual Clutch Transmission) gearbox and a reducer, which is shown as route {circle around (2)} in  FIG. 4 . Moreover, when the current electric charge level of the hybrid electric vehicle reduces to a certain electric charge level (less than or equal to the second electric charge level threshold), part of power of the engine is output to charge the high-voltage iron battery, the energy transfer of which is shown as route {circle around (7)} in  FIG. 4 . In addition, when the vehicle is taxiing, the braking pedal is depressed during the driving, or when the engine automatically stalls and stops running during idling, the motor converts the kinetic energy of the whole vehicle to the electric energy for storing in the power battery, the energy transfer of which is shown as route {circle around (7)} in  FIG. 4 . 
     In embodiments of the present disclosure, the hybrid electric vehicle may include the high-voltage iron battery used as the power battery and a low-voltage iron voltage used as the storage battery. 
     There are two ways for supplementing the electric charge level of the low-voltage iron battery. The first one is driving the generator to generate electricity when the engine start working, for charging the low-voltage iron battery, the energy transfer of which is shown as route {circle around (5)} in  FIG. 4 , and the other one is transferring a high voltage in the high-voltage iron battery to a low voltage by a DC-DC converter, for charging the low-voltage iron battery, the energy transfer of which is shown as route {circle around (6)} in  FIG. 4 . 
     It can be seen that, in embodiments of the present disclosure, there are two ways for starting the engine. The first one is starting the engine directly by the starter, the energy transfer of which is shown as route □ in  FIG. 4 , and the other one is starting the engine via inertia anti-drag force of the whole vehicle when the speed meets a requirement (i.e., the electric charge level of the power battery is large enough, such that the speed reaches the requirement of inertia anti-drag), the energy transfer of which is shown as route □ in  FIG. 4 . Thus, if the speed reaches the certain requirement, the starter does not need to work, such that a working frequency of the starter may not be increased, thus ensuring the working life of the components. 
       FIG. 5  is a schematic diagram of control information interaction in the drive control process of the hybrid electric vehicle according to an embodiment of the present disclosure. As shown in  FIG. 5 , a speed signal is sent from an electronic stability controller (shown as ESC in  FIG. 5 ) to a motor controller (shown as ECN in  FIG. 5 ); a gear controller (shown as SCU in  FIG. 5 ) is used to collect a gear signal and send the gear signal to the ECN; a battery management system (shown as BMS is  FIG. 5 ) is used to collect signals like current output power and current electric charge level and send collected signals to the ECN; the motor controller ECN is used to verify received signals like vehicle mode (such as EV/HEV/ECO/Sport mode) signal, accelerator signal or braking pedal signal, send signals like a target torque of the engine, the vehicle mode, and start-stop identification of the engine to an engine control module ECM, and send signals like the energy transfer state and the vehicle mode to a combination instrument; the BMS performs the battery monitoring and managing strategy; the ECM performs the start-stop control strategy; and the combination instrument performs the energy state and vehicle mode display strategy. 
       FIG. 6  is a flow chart of a drive control method of a hybrid electric vehicle according to an example embodiment of the present disclosure. As shown in  FIG. 6 , the drive control method of the hybrid electric vehicle includes following steps. 
     In step S 601 , it is determined whether the gear of the hybrid electric vehicle is at a preset position, if yes, step S 602  is performed, and if no, step S 605  is performed. 
     The preset position may be D gear position. 
     In step S 602 , it is determined whether the hybrid electric vehicle is in a preset operating mode, if yes, step S 603  is performed, and if no, step S 605  is performed. 
     The preset operating mode may be the hybrid economy mode. 
     In step S 603 , it is determined whether the current electric charge level of the power battery is greater than the first electric charge level threshold, and whether the discharge power of the power battery is greater than the first power threshold, if yes, step S 604  is performed, and if no, step S 605  is performed. 
     In step S 604 , it is determined whether the current electric charge level of the hybrid electric vehicle is greater than or equal to the second electric charge level threshold, and whether the difference between the current electric charge level and the target electric charge level of the power battery is less than or equal to the preset value, if yes, step S 607  is performed, and if no, step S 606  is performed. 
     In step S 605 , the hybrid electric vehicle quits from the engine start-stop control. 
     In step S 606 , the hybrid electric vehicle enters the speed start-stop control. 
     Specifically, if the road is ascent and the slope of the road is greater than or equal to a third slope threshold (p 3 ), the engine is started, and the engine is configured to output power for the vehicle; if the road is descent and the slope of the road is greater than or equal to a fourth slope threshold (p 4 ), the engine is configured to stop, and the motor is configured to output power separately; if the road is ascent and the slope of the road is less than the third slope threshold (p 3 ), and the current speed is greater than a first speed threshold, the engine is started; if the road is descent and the slope of the road is less than the fourth slope threshold (p 4 ), and the current speed is greater than the first speed threshold, the engine is started. After starting the engine, it may be further determined whether the current speed of the hybrid electric vehicle is less than a second speed threshold, if yes, the engine is configured to stop and the motor is configured to output power separately, and if no, step S 601  is returned to, for performing the engine start-stop control procedure again. 
     In step S 607 , the slope of the road on which the hybrid electric vehicle is driving obtained, and step S 608  and S 609  are performed. 
     In step S 608 , it is determined whether the road is ascent and the slope of the slope of the road is less than a first slope threshold (p 1 ), if yes, step S 610  is performed, and if no, step S 605  is performed. 
     In step S 609 , it is determined whether the road is descent and the slope of the road is less than a second slope threshold (p 2 ), if yes, step S 611  is performed, and if no, step S 610  is performed. 
     In step S 610 , the current speed of the hybrid electric vehicle is obtained. 
     In step S 611 , the engine is configured to stop, and the motor is configured to output power separately. 
     In step S 612 , if the current speed is less than a third speed threshold, the engine is configured to stop, and the motor is configured to output power separately. 
     In step S 613 , if the current speed is greater than or equal to a third speed threshold, and less than a fourth speed threshold, the hybrid electric vehicle is configured to enter the small load stop mode. 
     Specifically, it is first determined whether the engine is in an operating state. If the engine is not in the operating state, it is further determined whether an accelerator push depth (d) is greater than or equal to a first accelerator threshold (n). If the accelerator push depth is greater than or equal to the first accelerator threshold (n), the engine is started; and if the accelerator push depth is less than the first accelerator threshold (n), the state of the engine remains unchanged. 
     If the engine is in the operating state, it is further determined whether the accelerator push depth is less than a second accelerator threshold (m). If the accelerator push depth is less than the second accelerator threshold (m), the engine is configured to stop; and if the accelerator push depth is greater than or equal to the second accelerator threshold (m), the state of the engine remains unchanged. 
     The first accelerator threshold and the second accelerator threshold may be set according to a driving habit of a user and a performance of the hybrid electric vehicle. 
     In step S 614 , if the current speed is greater than or equal to the fourth speed threshold, and less than a fifth speed threshold, the hybrid electric vehicle is configured to enter the small load stall mode. 
     Specifically, it is first determined whether the engine is in an operating state. If the engine is not in the operating state, it is further determined whether an accelerator push depth (d) is greater than or equal to a first accelerator threshold (n). If the accelerator push depth is greater than or equal to the first accelerator threshold (n), the engine is started; and if the accelerator push depth is less than the first accelerator threshold (n), the state of the engine remains unchanged. 
     If the engine is in the operating state, it is further determined whether the accelerator push depth is less than a second accelerator threshold (m). If the accelerator push depth is less than the second accelerator threshold (m), the engine is configured to stall, the clutch remains in a coupling state, and fuel supply for the engine is cut off; and if the accelerator push depth is greater than or equal to the second accelerator threshold (m), the state of the engine remains unchanged. 
     The first accelerator threshold and the second accelerator threshold may be set according to a driving habit of a user and a performance of the hybrid electric vehicle. The second accelerator threshold is less than the first accelerator threshold, thus avoiding a frequent engine start-stop caused by unclear accelerator thresholds. 
     In step S 615 , if the current speed is greater than the fifth speed threshold, the state of the engine remains unchanged. 
     In the above-described process, when causing the engine, the motor is in the operating state, such that the motor may provide power for the vehicle separately or provide power for the vehicle along with the engine, according to different working states of the engine. 
     In some embodiments of the present disclosure, when the slope of the road meets the preset condition, the hybrid electric vehicle is configured to enter the small load stop mode or the small load stall mode according to the slope of the road. If the slope of the road doesn&#39;t satisfy the preset condition, for example, if the road is ascent and the slope of the road is greater than or equal to the first slope threshold, then it is executed to quit engine start-stop control, the hybrid electric vehicle is configured by the engine controller of the hybrid electric vehicle; and if the road is descent and the slope of the road is less than the second slope threshold, the engine is configured to stop, and the motor is configured to output power separately. 
     With the drive control method of the hybrid electric vehicle according to embodiments of the present disclosure, when the current gear position of the hybrid electric vehicle and the current electric charge level of the power battery meet a preset requirement, the hybrid electric vehicle is configured to enter a small load stop mode or a small load stall mode according to the slope of the road on which the hybrid electric vehicle is driving. In this way, a driving distance for the vehicle may be increased, an economy performance may be improved, and fuel consumption and emission may be reduced, without increasing a working frequency of the starter, thus ensuring a working life of components. In addition, if the vehicle has an accelerator-releasing energy feedback function, wasted kinetic energy may be converted to electric energy by a motor through the energy feedback and stored in a power battery, thus increasing energy recovery. Moreover, for the hybrid electric vehicles, problems of bad ride comfort and bad power performance caused by frequent start-stop of the engine may be solved effectively. 
     A drive control device of a hybrid electric vehicle is also provided in the present disclosure. 
       FIG. 7  is a block diagram of a drive control device of a hybrid electric vehicle according to an embodiment of the present disclosure. 
     As shown in  FIG. 7 , the drive control device according to an embodiment of the present disclosure includes a first obtaining module  10 , a second obtaining module  20  and a first control module  30 . 
     Specifically, the first obtaining module  10  is configured to obtain a current gear position of the hybrid electric vehicle and a current electric charge level of a power battery. 
     The second obtaining module  20  is configured to obtain a slope of a road on which the hybrid electric vehicle is driving, if the current gear position of the hybrid electric vehicle and the current electric charge level of the power battery meet a preset requirement. 
     The first control module  30  is configured to control a working state of an engine and/or a motor of the hybrid electric vehicle according to the slope of the road on which the hybrid electric vehicle is driving. 
     Specifically, in some embodiments according to the present disclosure, the first control module is configured to determine whether the slope of the road satisfies a preset condition, if the current gear position and the current electric charge level of a power battery meet the preset requirement. If the slope of the road satisfies the preset condition, the first control module is further configured to obtain a current speed of the hybrid electric vehicle and control the hybrid electric vehicle to enter a small load stop mode or a small load stall mode according to the current speed. The specific causing process may be shown in  FIG. 3 . 
     Specifically, if the road is ascent and the slope of the road is less than the first slope threshold, then it is determined that the slope of the road satisfies the preset condition, or if the road is descent and the slope of the road is greater than or equal to the second slope threshold, then it is determined that the slope of the road satisfies the preset condition. 
     When it is determined that the slope of the road doesn&#39;t satisfy the preset condition, the first control module is further configured to: 
     release the engine from start-stop control if the road is ascent and the slope of the road is greater than or equal to the first slope threshold, the hybrid electric vehicle may be configured by the engine controller; and 
     stop the engine and control a motor to output power separately if the road is descent and the slope of the road is less than the second slope threshold. 
     In some embodiments, as shown in  FIG. 8  the drive control device further includes a first determining module  40  and a third obtaining module  50 . 
     The third obtaining module  50  is configured to obtain a current operating mode of the hybrid electric vehicle and a discharge power of the power battery. 
     The first determining module  40  is configured to determine whether the hybrid electric vehicle is within a taxiing start-stop interval according to the current gear position and the current operating mode of the hybrid electric vehicle, the current electric charge level and the discharge power of the power battery. 
     Specifically, as shown in  FIG. 8 , the first determining module further includes: a first determining unit  41 , a second determining unit  42  and a third determining unit  43 . 
     The first determining unit  41  is configured to, if the current gear position is at D-position and the current operating mode is at a hybrid economy mode, determines whether the current electric charge level of the power battery is greater than a first electric charge level threshold, and whether the discharge power of the power battery is greater than a first power threshold. 
     The second determining unit  42  is configured to, if the current electric charge level of the power battery is greater than the first electric charge level threshold, and the discharge power of the power battery is greater than the first power threshold, determine whether the current electric charge level is greater than or equal to a second electric charge level threshold, and whether a difference between the current electric charge level and a target electric charge level of the power battery is less than or equal to a preset value. 
     The third determining unit  43  is configured to, if the current electric charge level is greater than or equal to the second electric charge level threshold, and the difference between the current electric charge level and the target electric charge level of the power battery is less than or equal to the preset value, determine that the hybrid electric vehicle is within the taxiing start-stop interval. 
     Alternatively, the first determining module may further include a fourth determining unit  44  configured to, if the current electric charge level of the power battery is less than the second electric charge level threshold, or the difference between the current electric charge level and the target electric charge level of the power battery is greater than the preset value, determine the hybrid electric vehicle is within the speed start-stop interval. 
     In some embodiments according to the present disclosure, as shown in  FIG. 9 , the drive control device further includes a second control module  60 . 
     The second control module is configured to, after it is determined that the hybrid electric vehicle is within a speed start-stop interval: start the engine if the road is ascent and the slope of the road is greater than or equal to a third slope threshold; stop the engine and control the motor to output power separately if the road is descent and the slope of the road is greater than or equal to a fourth slope threshold; and start the engine if the is ascent and the slope of the road is less than the third slope threshold and the current speed is greater than a first speed threshold, or if the road is descent and the slope of the road is greater than or equal to a fourth slope threshold and the current speed is greater than a first speed threshold. 
     After the engine is started, the second control module is further configured to obtain a current speed of the hybrid electric vehicle after the engine is started; determine whether the current speed is less than a second speed threshold; stop the engine and control the motor to output power separately if the current speed is less than a second speed threshold; and repeat obtaining a current speed of the hybrid electric vehicle if the current speed is great than or equal to a second speed threshold. 
     With respect to the devices in the above embodiments, the specific operation modes of individual modules therein have been described in detail in the embodiments regarding the drive control method of the hybrid electric vehicle, which will not be elaborated herein. 
     The energy transfer in a drive control process of a hybrid electric vehicle according to an embodiment of the present disclosure may be shown in  FIG. 4 , and the information interaction in a drive control process of a hybrid electric vehicle according to an embodiment of the present disclosure may be shown in  FIG. 5   
     With the drive control device of the hybrid electric vehicle according to embodiments of the present disclosure, when the current gear position of the hybrid electric vehicle and the current electric charge level of the power battery meet a preset requirement, the hybrid electric vehicle is configured to enter a small load stop mode or a small load stall mode according to the slope of the road on which the hybrid electric vehicle is driving. In this way, a driving distance for the vehicle may be increased, an economy performance may be improved, and fuel consumption and emission may be reduced, without increasing a working frequency of the starter, thus ensuring a working life of components. In addition, if the vehicle has an accelerator-releasing energy feedback function, wasted kinetic energy may be converted to electric energy by a motor through the energy feedback and stored in a power battery, thus increasing energy recovery. Moreover, for the hybrid electric vehicles, problems of bad ride comfort and bad power performance caused by frequent start-stop of the engine may be solved effectively. 
     In some embodiments, a hybrid electric vehicle is also provided in the present disclosure. The hybrid electric vehicle includes the drive control device described in any of above embodiments. 
     With the hybrid electric vehicle according to embodiments of the present disclosure, when the current gear position of the hybrid electric vehicle and the current electric charge level of the power battery meet a preset requirement, the hybrid electric vehicle is configured to enter a small load stop mode or a small load stall mode according to the slope of the road on which the hybrid electric vehicle is driving. In this way, a driving distance for the vehicle may be increased, an economy performance may be improved, and fuel consumption and emission may be reduced, without increasing a working frequency of the starter, thus ensuring a working life of components. In addition, if the vehicle has an accelerator-releasing energy feedback function, wasted kinetic energy may be converted to electric energy by a motor through the energy feedback and stored in a power battery, thus increasing energy recovery. Moreover, for the hybrid electric vehicles, problems of bad ride comfort and bad power performance caused by frequent start-stop of the engine may be solved effectively. 
     In the specification, it is to be understood that terms such as “central,” “longitudinal,” “lateral,” “length,” “width,” “thickness,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” and “counterclockwise” should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of description and do not require that the present invention be constructed or operated in a particular orientation. 
     In addition, terms such as “first” and “second” are used herein for purposes of description and are not intended to indicate or imply relative importance or significance or to imply the number of indicated technical features. Thus, the feature defined with “first” and “second” may comprise one or more of this feature. 
     In the present disclosure, unless specified or limited otherwise, the terms “mounted,” “connected,” “coupled,” “fixed” and the like are used broadly, and may be, for example, fixed connections, detachable connections, or integral connections; may also be mechanical or electrical connections; may also be direct connections or indirect connections via intervening structures; may also be inner communications of two elements, which can be understood by those skilled in the art according to specific situations. 
     In the present disclosure, unless specified or limited otherwise, a structure in which a first feature is “on” or “below” a second feature may include an embodiment in which the first feature is in direct contact with the second feature, and may also include an embodiment in which the first feature and the second feature are not in direct contact with each other, but are contacted via an additional feature formed therebetween. Furthermore, a first feature “on,” “above,” or “on top of” a second feature may include an embodiment in which the first feature is right or obliquely “on,” “above,” or “on top of” the second feature, or just means that the first feature is at a height higher than that of the second feature; while a first feature “below,” “under,” or “on bottom of” a second feature may include an embodiment in which the first feature is right or obliquely “below,” “under,” or “on bottom of” the second feature, or just means that the first feature is at a height lower than that of the second feature. 
     Reference throughout this specification to “an embodiment,” “some embodiments,” “one embodiment”, “another example,” “an example,” “a specific example,” or “some examples,” means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. Thus, the appearances of the phrases such as “in some embodiments,” “in one embodiment”, “in an embodiment”, “in another example,” “in an example,” “in a specific example,” or “in some examples,” in various places throughout this specification are not necessarily referring to the same embodiment or example of the present disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples. 
     Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that the above embodiments cannot be construed to limit the present disclosure, and changes, alternatives, and modifications can be made in the embodiments without departing from spirit, principles and scope of the present disclosure.