KR102368608B1 - Hybrid vehicle and method of controliing mode transition - Google Patents

Abstract

The present invention relates to a hybrid vehicle and a mode change control method therefor, and more particularly, to a mode change control method capable of determining an optimal mode change condition by comparing driving efficiency for each mode, and a hybrid vehicle for performing the same. A method of switching a mode of a hybrid vehicle according to an embodiment of the present invention includes: determining a required power of a driver; setting a switching condition between the first driving mode using only the electric motor and the second driving mode using the engine together according to the driving history; transitioning from the first driving mode to the second driving mode when the required power is greater than the first power according to the set switching condition; transitioning to the first driving mode when the required power is less than the second power according to the set switching condition while driving in the second driving mode; determining efficiency in a second driving mode of a section driven from the second driving mode to the first driving mode; and updating the driving history according to a result of determining the efficiency of the second driving mode.

Description

Hybrid vehicle and mode switching control method thereof

The present invention relates to a hybrid vehicle and a mode change control method therefor, and more particularly, to a mode change control method capable of determining an optimal mode change condition by comparing driving efficiency for each mode, and a hybrid vehicle for performing the same.

A hybrid electric vehicle (HEV) generally refers to a vehicle that uses two power sources together, and the two power sources are mainly an engine and an electric motor. These hybrid vehicles have been developed in recent years because they have excellent fuel efficiency and excellent power performance as well as advantageous in reducing exhaust gas compared to vehicles having only an internal combustion engine.

Such a hybrid vehicle may operate in two driving modes depending on which power train is driven. One of them is an electric vehicle (EV) mode, which drives only with an electric motor, and the other is a hybrid electric vehicle (HEV) mode, in which an electric motor and an engine are operated together to obtain power. Hybrid vehicles perform switching between the two modes according to driving conditions.

In particular, in the case of a TMED (Transmission Mounted Electric Device) type hybrid vehicle, which is a kind of parallel hybrid type among hybrid vehicles, an engine clutch is disposed between the engine and the electric motor to connect or separate the rotation shaft of the engine and the rotation shaft of the electric motor. perform the role of For example, in the EV mode, the engine clutch is in an open state, and in the HEV mode, the engine clutch is in an engaged state.

In such a TMED-type hybrid vehicle, if the driver's demand for power increases while driving in the EV mode, the vehicle is converted to the HEV mode. In this case, an optimal mode conversion reference point is set in consideration of the efficiency of the engine, the motor, and the battery of the hybrid vehicle. However, when the mode transition reference point for transition from EV mode to HEV mode and the mode transition reference point for transition from HEV mode to EV mode are set identically, when the required power fluctuates around the mode transition reference point, frequent mode switching occurs There is a problem. In order to solve this problem, hysteresis may be applied to the reference point for mode switching according to the mode switching direction. However, when hysteresis is uniformly applied, hysteresis is applied not only when the driver's power demand fluctuates near the mode conversion reference point but also when the power demand rises or falls stably, resulting in an inefficient engine driving section. there is.

An object of the present invention is to provide a more efficient mode change control method in a hybrid vehicle and a vehicle for performing the same.

In particular, an object of the present invention is to provide a mode switching control method in which hysteresis in consideration of a driving situation can be determined and a vehicle performing the same.

The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those of ordinary skill in the art to which the present invention belongs from the description below. will be able

In order to solve the above technical problem, a mode switching method of a hybrid vehicle according to an embodiment of the present invention includes the steps of determining a driver's required power; setting a switching condition between the first driving mode using only the electric motor and the second driving mode using the engine together according to the driving history; transitioning from the first driving mode to the second driving mode when the required power is greater than the first power according to the set switching condition; transitioning to the first driving mode when the required power is less than the second power according to the set switching condition while driving in the second driving mode; determining the efficiency of a second driving mode of a section driven until the transition from the second driving mode to the first driving mode; and updating the driving history according to a result of determining the efficiency of the second driving mode.

In addition, a hybrid vehicle according to an embodiment of the present invention includes: a first controller for controlling an electric motor; a second controller for controlling the engine; and determining whether to switch modes between a first driving mode in which the driving mode is driven by the power of the electric motor and a second driving mode in which the driving mode is driven by using the power of the electric motor and the engine together, and according to the determination, the first controller and the A third controller for controlling the second controller may be included. Here, the third controller determines the required power of the driver, sets a switching condition between the first driving mode and the second driving mode according to the driving history, so that the required power is the second according to the set switching condition. When the power is greater than 1 power, the mode transitions from the first driving mode to the second driving mode, and when the required power is less than the second power according to the set switching condition while driving in the second driving mode, the first driving mode is switched to the first driving mode. can be transitioned In particular, the third controller determines the efficiency of the second driving mode of a section driven from the second driving mode to the first driving mode and updates the driving history according to the result of the determination of the efficiency of the second driving mode can do.

The hybrid vehicle according to at least one embodiment of the present invention configured as described above may perform mode change more efficiently.

In particular, by comparing the energy consumption when driving in the HEV mode and the energy consumption when driving in the EV mode, a mode switching reference point showing optimal efficiency in the actual driving situation may be set.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned may be clearly understood by those of ordinary skill in the art to which the present invention belongs from the following description. will be.

1 shows an example of a power train structure of a hybrid vehicle to which embodiments of the present invention can be applied.
2 is a block diagram showing an example of a control system of a hybrid vehicle to which embodiments of the present invention can be applied.
3 shows an example of a mode switching process according to an embodiment of the present invention.
4 illustrates an example of a hysteresis control type according to driving history feedback according to an embodiment of the present invention.
5 shows an example of a hysteresis setting form according to an embodiment of the present invention.
6 shows an example of a process for evaluating the efficiency of an HEV mode performed in a hybrid vehicle according to an embodiment of the present invention.

Hereinafter, a hybrid vehicle related to the present invention and an efficient control method therefor will be described in more detail with reference to the drawings. The suffixes "module" and "part" for components used in the following description are given or mixed in consideration of only the ease of writing the specification, and do not have distinct meanings or roles by themselves.

First, a structure of a hybrid vehicle to which embodiments of the present invention can be applied will be described with reference to FIG. 1 .

1 shows an example of a power train structure of a hybrid vehicle to which embodiments of the present invention can be applied.

1, a parallel type hybrid system in which an electric motor (or a driving motor, 140) and an engine clutch 130 are mounted between an internal combustion engine engine (ICE, 110) and a transmission 150 is employed The powertrain of a hybrid vehicle is shown.

In such a vehicle, in general, when the driver steps on the accelerator after starting, the motor 140 is first driven using the power of the battery while the engine clutch 130 is open, and the power of the motor is transferred to the transmission 150 and the final reducer. (FD: Final Drive, 160) and the wheel moves (ie, EV mode). When the vehicle is gradually accelerated and a larger driving force is required, the start-up generator motor (or HSG, 120) may operate to drive the engine 110 .

Accordingly, when the rotational speeds of the engine 110 and the motor 140 become the same, the engine clutch 130 is engaged and the engine 110 and the motor 140 drive the vehicle together (that is, the HEV mode transitions from the EV mode). ). When a preset engine-off condition is satisfied, such as when the vehicle is decelerated, the engine clutch 130 is opened and the engine 110 is stopped (ie, the EV mode transitions from the HEV mode). At this time, the vehicle uses the driving force of the wheel to charge the battery through the motor, which is called braking energy regeneration or regenerative braking. Accordingly, the HSG 120 performs a role of a start motor when the engine is started, and operates as a generator when the rotational energy of the engine is recovered after the engine is started or when the engine is turned off.

A correlation between controllers in a vehicle to which the above-described power train is applied is shown in FIG. 2 .

2 is a block diagram showing an example of a control system of a hybrid vehicle to which embodiments of the present invention can be applied.

Referring to FIG. 2 , in a hybrid vehicle to which embodiments of the present invention can be applied, the internal combustion engine 110 is controlled by the engine controller 210 , and the starting generator motor 120 and the motor 140 are motor controllers (MCU: Torque may be controlled by the Motor Control Unit 220 , and the engine clutch 130 may be controlled by the clutch controller 230 , respectively. Here, the engine controller 210 is also referred to as an engine control system (EMS). In addition, the transmission 150 is controlled by the transmission controller 250 . According to the embodiment, the starting power generation motor 120 and the motor 140 may be controlled by different separate motor controllers.

Each controller is connected to a controller (hereinafter, referred to as “hybrid controller” or “HCU: Hybrid Control Unit” 240 ) that performs overall control of the power train in the hybrid vehicle as its upper controller, and controls the hybrid controller 240 . Accordingly, information required for engine clutch control and/or engine stop control may be provided to the unit 240 for changing the driving mode, gear shifting, or an operation may be performed according to the control signal.

More specifically, the hybrid controller 240 determines whether to perform mode switching according to the driving state of the vehicle. For example, the hybrid controller determines when the engine clutches EC and 130 are released (open), and performs hydraulic (wet EC) control or torque capacity control (dry EC) when released. In addition, the hybrid controller 240 may determine the state of the EC (Lock-up, Slip, Open, etc.) and control the timing of stopping the fuel injection of the engine 110 . In addition, the hybrid controller may control the engine rotation energy recovery by controlling the torque of the starting power generation motor 120 for engine stop control.

Of course, it is apparent to those skilled in the art that the above-described connection relationship between the controllers and the function/classification of each controller are exemplary and are not limited by their names. For example, the hybrid controller 240 may be implemented such that a corresponding function is provided in any one of the other controllers, or the corresponding function may be distributed and provided in two or more of the other controllers.

Hereinafter, a mode switching control method according to the present embodiment will be described based on the above-described vehicle structure.

In order to solve the problem that occurs when the aforementioned uniform hysteresis is applied, a method of adjusting the hysteresis may be considered when the required power is stably increased or decreased, but this method also determines whether the required torque is high or low. In the case of judging by the holding time of , there is a problem in that it is difficult to accurately determine whether it is actually effective.

Accordingly, an embodiment of the present invention proposes to variably control the hysteresis according to the determination of driving efficiency in the HEV mode. Here, the driving efficiency of the HEV mode may be determined based on the HEV driving history. For example, the driving efficiency of the HEV mode may be determined by comparing the energy actually consumed when driving in the HEV mode with the energy estimated to be consumed when driving in the EV mode on a path traveled in the HEV mode.

First, a hysteresis setting process according to the driving history of the HEV mode will be described with reference to FIG. 3 .

3 shows an example of a mode switching process according to an embodiment of the present invention.

Referring to FIG. 3 , first, the required power of the driver may be calculated ( S310 ). The driver's demanded power may be calculated based on the value of the accelerator pedal sensor APS, but is not limited thereto, and the demanded power may be replaced with a requested torque.

Also, hysteresis adjustment according to the driving history may be performed ( S320 ). This step may be performed with reference to the driving history updated ( S370 ) according to the result of determining the efficiency of HEV mode driving ( S350 ), which will be described later. A specific form of hysteresis adjustment will be described later with reference to FIGS. 4 and 5 .

When the hysteresis is adjusted, it may be determined whether the current driver's requested power satisfies the HEV mode entry condition (ie, the required power > the first power) ( S330 ). Here, the first power may be variable according to a result of the hysteresis adjustment.

When the HEV mode entry condition is satisfied, the hybrid vehicle may transition to the HEV mode ( S340 ). As the HEV mode driving is performed, the efficiency may be determined ( S350 ). A detailed efficiency determination process will be described later with reference to FIG. 6 . In contrast, when the HEV mode entry condition is not satisfied, the EV mode driving may be maintained ( S380 ).

During HEV mode driving, it may be determined whether the driver's required power satisfies the EV mode entry condition (ie, the required power < the second power) ( S360 ). Here, the second power may also be variable according to the result of the hysteresis adjustment.

When the EV mode entry condition is satisfied, driving history information may be updated according to the determination result of step S350 (S370), and the vehicle enters the EV mode (S380).

Meanwhile, the determination of the efficiency of the HEV mode driving ( S350 ) may be performed after the HEV mode driving is finished, that is, after the conversion to the EV mode is determined.

Hereinafter, a form in which hysteresis adjustment is performed according to a driving history will be described with reference to FIGS. 4 and 5 .

4 shows an example of a hysteresis control form according to driving history feedback according to an embodiment of the present invention, and FIG. 5 shows an example of a hysteresis setting form according to an embodiment of the present invention.

Referring to FIG. 4 , the hysteresis given to the criterion for determining whether to enter/release the HEV mode is increased/decreased according to the driving history. The driving history is a factor determined based on the determination of efficiency/inefficiency of HEV driving, and may indicate how effective the currently set hysteresis is. Therefore, when the driving history indicates that the inefficient HEV driving frequency/ratio/inefficiency level is high, HEV driving may be suppressed by increasing the hysteresis, and in the opposite case, the hysteresis may be lowered so that the HEV driving is expanded.

For example, as shown in FIG. 4 , the hysteresis level may be increased or decreased according to the determination of whether the HEV mode is efficient during HEV driving while repeating the entry and exit of the HEV mode. The hysteresis level may be implemented by a plurality of preset torque lines as shown in FIG. 5 . Referring to the graph of FIG. 5 , it can be seen that the higher the level, the higher the required torque for the same RPM is, the more difficult it is to enter the HEV mode.

In FIG. 5 , the torque line is illustrated as being prepared in four levels including the base line, but the present invention is not limited to the number of hysteresis levels.

As this hysteresis level adjustment process is repeated while driving, a hysteresis optimized for the driving situation is found. In the present embodiment, the robustness and performance improvement of fuel economy performance can be obtained through this process. In addition, the effect of improving drivability due to frequent engine start suppression is obtained.

Hereinafter, an efficiency evaluation process of HEV mode driving will be described with reference to FIG. 6 . The efficiency evaluation process may correspond to step S350 of FIG. 3 .

6 shows an example of a process for evaluating the efficiency of an HEV mode performed in a hybrid vehicle according to an embodiment of the present invention.

Referring to FIG. 6 , the efficiency evaluation process includes calculating the energy used during HEV mode driving (S351), calculating the energy that would have been used if the section traveled in the HEV mode was driven in the EV mode (S353) , comparing the two energies previously calculated with each other (S355) and determining whether HEV mode driving was efficient (S357A) or inefficient (S357B) according to the comparison result. Hereinafter, each step will be described in detail, but since different energy sources (electrical energy and fuel) are used in the HEV mode, for comparison, electric energy is converted into fuel and the total energy used is compared with the amount of fuel.

First, a method of calculating the energy used during HEV mode driving ( S351 ) will be described.

When driving by transitioning from EV mode to HEV mode, the energy used is largely divided into the cranking section energy corresponding to the section from starting the engine until the engine power is used for driving, and the HEV mode driving section energy after the cranking section. and the sum of these two energies becomes the energy used during HEV mode driving.

Therefore, if the energy used during HEV mode driving is E, the cranking section energy is E1, and the driving section energy is E2, it can be expressed as E = E1 + E2.

Again, E1 is (E1 _{_Cranking} + E1 _{_ Dch} )*K _{_ Dch} + E1 _{_Injection} . Here, E1 _{_Cranking} is the electric energy used to raise the engine up to the engine speed (injection rpm) at which fuel injection is possible, E1 _{_ Dch} is the driving energy of the electric motor used during the cranking section, and E1 _{_Injection} is the cranking It means the amount of fuel consumed during the section. In addition, _{K_Dch} means an equivalent factor for converting electric energy used _during discharge into fuel.

Also, _E2 is _{E2_Chg} * K _{_ Chg} + E2 _{_ Dch} * It can be obtained as K _{_ Dch} + E2 _{_Injection} . _{where E2_Chg} is the charging energy of the motor in the driving section, E2 _{_ Dch} is the driving energy of the electric motor used during the driving section, and E2 _{_Injection} is the amount of fuel used during the driving section. _{where E2_Chg} Since is produced energy rather than consumed energy, it may have a negative sign. In addition, K _{_ Chg} is an equivalent factor that converts electric energy generated by charging into fuel.

Next, a method of calculating ( S353 ) energy predicted to be used during EV mode driving will be described.

Energy used in the EV mode (E _{_EV} ) can be largely divided into energy used to generate driving force in the electric motor and energy charged. E _{_EV} is E2 _{_ Chg} * K _{_ Chg} + E2 _{_ Dch} * It can be obtained like K _{_Dch} . Here, E2 _{_ Chg} is energy generated through charging in the EV mode, and may have a negative sign. In addition, _{E2_Dch} means energy used to generate a driving _force in the EV mode. Each energy is multiplied by an equivalence factor for conversion into a fuel unit, and the equivalence factor for charging (K _{_Chg} ) and the equivalence factor for discharging (K _{_Dch} ) may have different values. In addition, since there is a difference in efficiency between the electric motor and the engine according to the requested torque, and the efficiency of the electric motor may be different depending on the SOC of the battery even with the same requested torque, the equivalence factor may be variable depending on the situation of the vehicle.

In the comparison process ( S355 ), it is common to use more energy in the HEV mode due to the mode switching cost caused by the influence of the initial startup, such as cranking energy, at the initial stage of entering the HEV mode. However, as time elapses and the gain by using the optimal operating point of the engine increases according to the driving load, HEV driving may consume less energy in the corresponding section. The intersection of the energy used in the HEV mode driving and the energy used in the EV mode driving may be determined by the required power and the equivalence factor. For example, if the electric energy is evaluated as low by high SOC, the point at which the energy crossover occurs is delayed even in the same driving. Therefore, in the efficiency comparison process through the above-described method, since the equivalent factor reflecting the SOC is applied, more accurate efficiency determination is possible.

In addition, in the above description, each of the steps of FIGS. 3 and 6 may be performed by the hybrid controller, but this is exemplary and a controller responsible for determining at least one step may be separately provided, and the control system of FIG. At least one of the remaining controllers disclosed in , may perform some steps.

The present invention described above can be implemented as computer-readable codes on a medium in which a program is recorded. The computer-readable medium includes all types of recording devices in which data readable by a computer system is stored. Examples of computer-readable media include Hard Disk Drive (HDD), Solid State Disk (SSD), Silicon Disk Drive (SDD), ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, etc. There is this.

Accordingly, the above detailed description should not be construed as restrictive in all respects but as exemplary. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the present invention are included in the scope of the present invention.

Claims (19)

In the mode switching method of a hybrid vehicle,
determining the required power of the driver;
setting a switching condition between the first driving mode using only the electric motor and the second driving mode using the engine together according to the driving history;
transitioning from the first driving mode to the second driving mode when the required power is greater than the first power according to the set switching condition;
transitioning to the first driving mode when the required power is less than the second power according to the set switching condition while driving in the second driving mode;
determining the efficiency of a second driving mode of a section driven until the transition from the second driving mode to the first driving mode; and
The method of claim 1, further comprising: updating the driving history according to a result of determining the efficiency of the second driving mode. The method of claim 1,
The setting step is
and selecting a preset torque line corresponding to any one of a plurality of hysteresis levels according to the driving history. 3. The method of claim 2,
The selecting step is
lowering the hysteresis level when the driving history indicates that the efficiency of the second driving mode is high; or
and increasing the hysteresis level when the efficiency of the second driving mode is found to be low in the driving history. The method of claim 1,
The step of determining the efficiency of the second driving mode efficiency,
determining first energy used in the second driving mode during the section;
determining second energy expected to be used when driving in the first driving mode during the section;
comparing the first energy with the second energy;
determining that the second energy is effective when the second energy is large as a result of the comparison; and
and determining that it is inefficient when the first energy is large as a result of the comparison. 5. The method of claim 4,
The first energy is
The mode switching method of the hybrid vehicle, wherein the output of the engine includes 1-1 energy used in a cranking section not used for driving force and 1-2 energy used in a driving section other than the cranking section. 5. The method of claim 4,
Among the first energy and the second energy, energy charged or discharged in the electric motor is converted into fuel consumption by applying an equivalent factor. 7. The method of claim 6,
The equivalence factor is applied differently to each of the charged energy and the discharged energy. 7. The method of claim 6,
The equivalence factor is variably determined according to the required power and a state of charge (SOC) of a battery. The method of claim 1,
The first mode is an EV mode, and the second mode is an HEV mode. 10. A computer-readable recording medium recording a program for executing the mode switching method of a hybrid vehicle according to any one of claims 1 to 9. In a hybrid vehicle,
a first controller for controlling the electric motor;
a second controller for controlling the engine; and
It is determined whether to switch modes between a first driving mode in which the driving mode is driven by the power of the electric motor and a second driving mode in which the driving mode is driven by using the power of the electric motor and the engine together, and according to the determination, the first controller and the second driving mode 2 comprising a third controller for controlling the controller,
The third controller is
The driver's demand power is determined, and a switching condition between the first driving mode and the second driving mode is set according to the driving history, and when the required power is greater than the first power according to the set switching condition, the first Transitions from the driving mode to the second driving mode, and when the required power is less than the second power according to the set switching condition while driving in the second driving mode, transition to the first driving mode,
and determining the efficiency of a second driving mode of a section driven from the second driving mode to the transition to the first driving mode, and updating the driving history according to a result of the determination of the efficiency of the second driving mode. 12. The method of claim 11,
The third controller is
and setting the switching condition by selecting a preset torque line corresponding to any one of a plurality of hysteresis levels according to the driving history. 13. The method of claim 12,
The third controller is
and lowering the hysteresis level when the driving history indicates that the efficiency of the second driving mode is high, and increasing the hysteresis level when the driving history indicates that the efficiency of the second driving mode is low. 12. The method of claim 11,
The third controller is
determining the first energy used in the second driving mode during the section and a second energy expected to be used when driving in the first driving mode during the section, and comparing the first energy with the second energy; As a result of the comparison, it is determined that the second energy is high, and it is determined that the second energy is high, and when the first energy is large, the hybrid vehicle is determined as inefficient. 15. The method of claim 14,
The first energy is
The hybrid vehicle, wherein the output of the engine includes 1-1 energy used in a cranking section not used for driving force and 1-2 th energy used in the remaining driving sections excluding the cranking section. 15. The method of claim 14,
Among the first energy and the second energy, energy charged or discharged in the electric motor is converted into fuel consumption by applying an equivalent factor. 17. The method of claim 16,
The third controller is
The equivalence factor is applied differently to each of the charged energy and the discharged energy. 17. The method of claim 16,
The equivalence factor is variably determined according to the required power and a state of charge (SOC) of a battery. 12. The method of claim 11,
The first mode is an EV mode, and the second mode is an HEV mode.

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