KR20160007694A - Control method of hybrid vehicle - Google Patents

Abstract

An objective of the present invention is to provide a control method for a single starting of HSG of a hybrid vehicle to variably control an HSG output according to engine speeds and starting control sequences and to secure starting response performance. Another objecto of the present invention is to provide a control method in case of a single starting of HSG of a hybrid vehicle, which performs an optimized control of an engine operating point while driving in an HEV mode for recharging the electric energy used for starting the engine with a single HSG while driving in an EV mode to perform charging through a motor when the engine is operated at the highest efficiency and to maximize fuel efficiency.

Description

{CONTROL METHOD OF HYBRID VEHICLE}

[0001] The present invention relates to a control method for starting a hybrid vehicle with HSG alone, and more particularly, to a hybrid control system for controlling a hybrid vehicle in which only an HSG (Hybrid Shaft Generator) ≪ / RTI >

A hybrid vehicle is an environmentally friendly vehicle that uses two power sources consisting of an engine and a motor. In order to improve fuel economy, the hybrid vehicle is driven by properly combining the power of the engine and the motor according to the driver's will and battery condition. , And an EV operation mode in which only the motor is driven.

The TMED hybrid vehicle is a hybrid vehicle using a TMED (Transmission Mounted Electric Device) system. The hybrid system is composed of a motor connected to the transmission side.

In a typical TMED hybrid vehicle, an electric motor coupled between the engine and the transmission, an engine clutch connecting the engine and the electric motor, and a differential gear connected to the transmission form a power transmission structure, Power is connected or disconnected to drive in HEV mode and EV mode. An HSG (Hybrid Shaft Generator) is connected to the engine.

The HSG connected to the engine performs engine starting and battery charging. The operating conditions are classified into three types: ① EV mode → HEV mode transition ② HEV mode → EV mode transition ③ Idle charging .

① When transitioning from EV mode to HEV mode

1. HSG is controlled by a speed control method, and the engine is controlled by a part load method.

2. Engine cranking is performed using HSG, and HSG discharges battery SOC.

 3. After engine cranking, the engine speed is controlled and stabilized until the engine clutch is engaged, at which time the HSG charges the battery SOC.

② When transition from HEV mode to EV mode

1. HSG is controlled by a speed control system, and the engine is in a no-load state, that is, in a fuel cut state.

2. In the HEV mode, the engine is stopped by charging the battery through the HSG in the deceleration section after the engine fuel injection is turned off.

③ When charging (IDLE)

1. When the transmission gear is charged during stoppage in the state of being parked at the parking end (P) or the neutral end (N), or when the gear is in the running end (D) or rear end When the output of the HSG is limited (eg, at extremely low temperatures), the HSG is controlled by the torque control method and the engine is controlled by the speed control method. When there is no output restriction of the HSG, the HSG is controlled by the speed control method And the engine is controlled in a partial load manner.

2. When the transmission gear is charged during stoppage in a state where it is placed at the parking end (P) or the neutral end (N), control of charging the battery using the HSG as the engine output is performed.

3. When the transmission gear is charged while the series is running while the gear is in the running position, the battery is charged to the engine output using the HSG while the engine is running in the EV mode with the drive motor released.

On the other hand, the applicant of the present application has found that when the transmission gear is placed in the running end and the engine is shifted from the EV mode to the hybrid (HEV) mode during driving, the engine fuel injection is turned off until the engine clutch is engaged, And maximizes the output of HSG to increase the speed of the engine alone by increasing the speed linearity between the motor and the engine to secure the robustness of the speed synchronization control between the engine and the motor to minimize the impact on the engine clutch. (See FIG. 1).

Unlike the prior art in which the engine speed is controlled through the HSG output and the engine output in order to improve the fuel economy and the driving performance at the transition from the EV mode to the HEV mode as described above, , The following problems will occur.

① After the HSG output is maximized and the engine speed is controlled exclusively by the HSG from the engine start to the engagement of the engine clutch, the fuel injection is started at the same time as the engine clutch is engaged and soon the engine output is generated. At this time, Ripple occurs. The reason for the torque fluctuation is that the output of the explosion process during the four strokes (suction-compression-explosion-exhaust) of the piston in the engine shows a sudden change in output as compared with the other strokes. If this torque fluctuation can not be controlled, engine speed fluctuation or large impact may occur.

Therefore, in performing the engine startup with the HSG alone, a torque reserve capable of controlling the torque fluctuation must be considered. That is, 100% of the available output of HSG can not be used at engine start.

However, if the HSG output is used except for the torque reserve in all processes before start-up, the start-up responsiveness and the speed control linear tracking performance will be reduced. That is, in order to assure the same level of responsiveness as the conventional one ( the engine is started by controlling the engine speed through the HSG output and the engine output), the maximum output torque is set to a certain level (for example, 2000rpm), but the target performance can not be secured if the torque reserve is applied to the entire region before start-up with a deceleration rate of 10 to 15%.

② When engine starting is controlled by using HSG output and engine output, battery discharge and charging process through HSG are present from engine start to engine engage before engagement. That is, the engine is cranked through the HSG discharge (battery discharge through the HSG) until the initial engine speed (0-800 rpm), and then the engine is partially loaded until the engine clutch is engaged, To charge the battery.

However, during partial load operation, the engine torque corresponds to a transient section that moves from a low efficiency (30 Nm) to a high efficiency (70 Nm) region. Therefore, it can be said to be a loss in terms of engine efficiency as compared with the case where HSG charging is continuously performed in the engine high efficiency region.

Therefore, as described above, when the engine is started by HSG alone, it is possible to prevent the engine from operating in an inefficient region by fuel injection off and to improve fuel economy. However, from the viewpoint of electric energy, Since only HSG discharge is performed until just before, the electric energy used must be filled with engine power again.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a control method at the time of HSG single start of a hybrid vehicle in which a HSG output is variably controlled according to an engine speed and a startup control sequence, have.

Further, the present invention optimally controls the engine operating point in the HEV mode in order to recharge the electric energy used at the time of starting the engine by the HSG alone in the EV mode, and when the engine is operated at the maximum efficiency, The present invention also provides a method of controlling a hybrid vehicle in which HSG alone is started.

According to the present invention, there is provided a control method of a hybrid vehicle in which a drive motor is connected between an engine and a transmission, the engine and a drive motor are connected through an engine clutch, and a hybrid shot generator (HSG)

The HSG output torque is variably controlled from the engine cranking to the immediately before engaging of the engine clutch when the HSG alone controls the engine starting at the transition to the HEV mode in the EV mode, And the HSG output torque is determined as a torque value obtained by subtracting the HSG torque reserve from the HSG maximum output torque in the engine speed section, in addition to the control method of the HSG single start of the hybrid vehicle.

According to an embodiment of the present invention, the HSG torque reserve is variably controlled according to the speed difference between the engine and the motor, and is determined by a predetermined map by inputting the speed difference between the engine and the motor and outputting the HSG torque reserve.

The present invention also provides a control method of a hybrid vehicle in which a drive motor is connected between an engine and a transmission, the engine and a drive motor are connected via an engine clutch, and the HSG is connected to the engine,

The HSG alone controls the engine start and shifts to the HEV mode. When it is determined that the driver's requested torque change rate is less than the reference value during the HEV mode, the engine torque is increased and the battery is charged through the drive motor The HSG control method includes the steps of:

At this time, it is preferable that the engine torque is increased from the OOL (Optimize Operating Line) to the torque value of the highest efficiency engine operating point based on the current engine speed.

According to the control method at the time of starting the HSG alone of the hybrid vehicle according to the present invention, the engine starting is controlled solely by the HSG during the EV mode, and the HSG torque reserve is calculated on the basis of the fuel injection timing at which the engine torque fluctuation occurs significantly during the transition to the HEV mode The HSG engine can be started in the EV mode alone and the engine start can be controlled by changing the HEV mode to the HEV mode. Mode, it is possible to maximize the fuel efficiency by charging the battery through the driving motor when the engine is operated in the high efficiency region, and as a result, the HSG alone can improve the side effect that can be caused by starting the engine.

1 is a graph schematically showing a control process when the engine is started with HSG alone in a conventional TMED hybrid vehicle
Fig. 2 is a graph showing the results of a principle test for increasing the engine speed by HSG alone in a TMED hybrid vehicle
3 is a flowchart showing a control method for ensuring start-up response performance at the time of HSG single start of the hybrid vehicle according to the present invention
FIG. 4 is a graph showing the HSG discharge area and the HSG charged area until the engine clutch is engaged at startup using the HSG output and the engine output
5 is a flowchart showing a control method for maximizing the fuel efficiency after starting the HSG of the hybrid vehicle according to the present invention

Hereinafter, the present invention will be described with reference to the accompanying drawings.

The present invention relates to an improvement of a side effect which can be caused by controlling an engine start by an HSG attached to an engine in a conventional hybrid vehicle. In transitioning to a hybrid mode while driving in an EV mode, HSG alone is used as an HSG torque reserve To maximize the fuel efficiency by ensuring the start-up response performance by performing variable control of the engine, and also, when the engine is operated at the highest efficiency in the HEV mode, the electric energy used for starting the engine is recharged.

As is known, when transitioning from the EV mode to the HEV mode, the HSG torque reserve for controlling the engine torque fluctuation (Torque Ripple) during the HSG speed control for starting the engine is set at a certain rate of the HSG full torque , 10 to 15%) are required.

That is, when shifting to the HEV mode while driving in the EV mode, the HSG torque available at the start of the engine is limited to the extent that the HSG torque reserve is subtracted from the HSG full torque. If the HSG torque reserve The start response performance may be degraded.

Therefore, in the present invention, the HSG torque reserve is variably controlled by classifying the engine starting phase on the basis of the fuel injection timing at which the engine torque fluctuation largely occurs.

In other words, when transitioning from the EV mode to the HEV mode while driving, the HSG alone can variably control the HSG output according to the engine speed and the startup control sequence at engine startup.

The maximum engine speed (1500 ~ 2000rpm) at the time of transition from EV mode to HEV mode (at engine startup) was confirmed by testing using conventional HSG output and engine output, and the principle of increasing engine speed by HSG alone at engine startup As a result of the test, it was confirmed that the HSG maximum output torque can be used from 0 to 1700 rpm as shown in FIG.

Therefore, it can be seen that the HSG maximum torque can be maintained up to the maximum engine speed range (1500 rpm to 2000 rpm) at the time of starting the engine at the time of starting the engine by the HSG alone in the EV mode. Thus, by the variable control of the HSG torque reserve It can be seen that starting response performance can be secured at the same level as the response performance at the time of starting the engine using the conventional HSG output and the engine output.

The HSG output torque is preset to the HSG full torque, that is, the HSG maximum output torque at the set engine speed interval, and the speed The HSG output torque is controlled in consideration of the HSG torque reserve.

That is, the HSG output torque is determined by the torque value obtained by subtracting the HSG torque reserve from the maximum output torque of the HSG in the remaining speed sections except for the engine speed section in which the HSG maximum output torque is available.

3, the hybrid controller HCU determines whether the outside air temperature is equal to or higher than a reference temperature (for example, minus 10 ° C.) upon receipt of an engine ON request. If it is determined that the outside air temperature is below minus 10 Or more, that is, if the condition for limiting the HSG output is not satisfied, it is judged whether or not the transmission gear is in the traveling stage (positioning), and if it is judged that the transmission gear is running on the traveling stage, It is determined whether or not a transition is being made.

If it is judged that the transition from the EV mode to the HEV mode is in progress, the HSG torque reserve is variably controlled, and the HSG torque reserve is variably controlled according to the speed difference between the engine and the motor.

That is, the engine speed stabilization control section (engine fuel injection ON / operation section) corresponding to the region from the engine cranking to the immediately before engaging of the engine clutch is performed when the transmission gear is placed in the running end, ), The HSG torque reserve is variably controlled in accordance with the speed difference between the engine and the motor.

Here, the hybrid controller stores a map in which the speed difference between the engine and the motor is the input value and the HSG torque reserve is the output value, and when the variable control of the HSG torque reserve is performed, Obtain HSG torque reserve.

In the variable control of the HSG torque reserve, the HSG is controlled by the speed control system, the engine is controlled by the torque control system, and the HSG alone is used to control the engine start and is equivalent to the conventional (when starting the engine using the HSG output and engine output) It is possible to secure start-up responsiveness of the vehicle.

As a result of the above determination, when the vehicle is running without the transmission gear disposed on the traveling end, that is, when the transmission gear is placed in the neutral or rear end diagnosis, or when the transmission gear is stopped at the parking end or neutral end, The HSG torque reserve is limited to a fixed rate (for example, 15%). At this time, the HSG is controlled by the speed control method, the engine is controlled by the torque control method, and the engine start is controlled by using the HSG output and the engine output.

As a result of the determination, when the vehicle is not in transition from the EV mode to the HEV mode, that is, when the vehicle is traveling in series, the HSG torque reserve is controlled with a constant rate. At this time, the HSG is controlled by the speed control method, the engine is controlled by the torque control method, and the engine start is controlled by using the HSG output and the engine output.

As a result of the above determination, if the outside air temperature is below minus 10 ° C, the engine output is subject to engine speed control and the HSG output torque is maintained at a constant value because there is a restriction on the output of the HSG.

On the other hand, in order to maximize the fuel consumption after starting the engine by HSG alone, it is necessary to optimally control the engine operating point during the HEV mode.

In order to maximize the fuel efficiency after starting the engine, HSG alone is used as a driving motor when the battery is charged and the HEV mode is operated at the highest efficiency while the engine is running.

As is known, there exist both a battery discharge (HSG discharge) region through the HSG and a battery charge (HSG charge) region through the HSG until the engine clutch is engaged at the time of starting the engine using the HSG output and the engine output Reference).

For example, the HSG discharge region exists in the engine cranking range (0-800 rpm), and the HSG charged region exists in the section from after engine cranking to just before engaging the engine clutch.

When the total energy of charging and discharging is calculated considering about 40 times of starting the engine based on UDDS (Urban Dynamometer Driving Schedule) 4th stage (4bag) which measures the mileage upon one charging, discharge energy is 64 kJ (1.6 kJ / And the charge energy is 200 kJ (5.0 kJ / cycle).

Therefore, 200-64 = 136kJ, so that more energy is stored in the battery, and if the charge energy is used for driving the EV mode, a certain gain occurs in terms of fuel economy.

However, because the energy source for HSG charging is due to the engine power, it is important to consider the amount of fuel used to charge the battery, as well as the energy charged in the battery when considering fuel economy.

The engine output is in the range of 1500 to 2000 rpm in the HSG charging range and the engine torque is in the transient section operating at low efficiency (20 Nm) to high efficiency (70 Nm).

Therefore, it is a loss in terms of engine efficiency as compared to charging HSG continuously in the engine high efficiency range. That is, the amount of the fuel used for charging the HSG increases, and the final fuel consumption due to the engine startup using the HSG output and the engine output results in a certain loss (the amount of non-driving loss in which the supplied fuel can not be used for driving). In other words, it is like generating cheap electricity by using expensive fuel energy.

Therefore, it is necessary to use only the electric energy in the starting section by controlling the engine starting by HSG alone, and to prevent the engine from being used for charging in an inefficient section. Also, the energy used for HSG discharge (64kJ / UDDS cycle) needs to be controlled when the engine is operating in the high efficiency area (OOL) during HEV mode operation.

Since the discharge energy through the HSG corresponds to less than 1% of the total driving energy of the vehicle, it can be performed without a large change in the conventional engine control.

Referring to FIG. 5, a control process for maximizing the fuel efficiency after the engine startup control is performed by the HSG alone in the EV mode will be described. When the hybrid system receives the engine ON request, the hybrid system determines whether the hybrid vehicle is in the mode transition state transitioning from the EV mode to the HEV mode (For example, 10%) if the driver's requested torque change rate APS is running in the HEV mode. If the driver's requested torque change rate APS is in the HEV mode, If the driver's requested torque change rate is less than 10%, that is, if the driver's requested torque change rate is smaller than the predetermined value, the engine torque is increased and the battery is charged through the drive motor to increase the battery charge amount.

At this time, the engine torque is increased from the OOL (Optimize Operating Line) to the torque value of the highest efficiency engine operating point based on the current engine speed.

If the rate of change in the driver's requested torque is greater than or equal to 10% as a result of the above determination, that is, if the rate of change in the driver's requested torque is large, the engine torque is maintained and the HSG charged amount is maintained through the drive motor.

If it is determined that the vehicle is not running in the HEV mode, that is, while the vehicle is running in the EV mode, the HSG charging can not be performed.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments. Modifications are also included in the scope of the present invention.

Claims (7)

A control method of a hybrid vehicle, wherein a drive motor is connected between an engine and a transmission, the engine and a drive motor are connected through an engine clutch, and an HSG (Hybrid Shaft Generator)
The HSG output torque is variably controlled from the engine cranking to the immediately before engaging of the engine clutch when the HSG alone controls the engine starting at the transition to the HEV mode in the EV mode, And the HSG output torque is determined by the torque value obtained by subtracting the HSG torque reserve from the maximum output torque of the HSG in the engine speed section.
The method according to claim 1,
Wherein the HSG torque reserve variable control is performed between an engine and a motor in accordance with a speed difference.
The method according to claim 1,
Wherein the HSG torque reserve is variable according to a speed difference between an engine and a motor and is determined by a predetermined map by inputting a speed difference between an engine and a motor and outputting an HSG torque reserve as an output. Time control method.
The method according to claim 1,
The HSG alone controls the engine start and shifts to the HEV mode. When it is determined that the driver's requested torque change rate is less than the reference value during the HEV mode, the engine torque is increased and the battery is charged through the drive motor And a control unit for controlling the hybrid vehicle.
The method of claim 4,
Wherein the engine torque is increased from an OOL (Optimize Operating Line) to a torque value of the highest efficiency engine operating point based on the current engine speed.
A control method of a hybrid vehicle, wherein a drive motor is connected between an engine and a transmission, the engine and a drive motor are connected through an engine clutch, and an HSG (Hybrid Shaft Generator)
The HSG alone controls the engine start and shifts to the HEV mode. When it is determined that the driver's requested torque change rate is less than the reference value during the HEV mode, the engine torque is increased and the battery is charged through the drive motor And a control unit for controlling the hybrid vehicle.
The method of claim 6,
Wherein the engine torque is increased from an OOL (Optimize Operating Line) to a torque value of the highest efficiency engine operating point based on the current engine speed.

Images