KR20080054998A - 2nd shock reducing method at hybrid engine starting - Google Patents

Abstract

A secondary shock reducing method in starting a hybrid engine is provided to reduce shock during first explosion by minimizing target torque during first explosion in an engine and to control secondary shock changed according to an OPD(Operating Point Determination), at uniform level by keeping target torque uniform. A secondary shock reducing method in starting a hybrid engine comprises a follow-up control step for executing engine demand torque fixed at a constant value, by adding predetermined torque to friction torque if an engine start bit and a fuel injection bit are input at the same time(S302,S304); a maintenance and control step for keeping engine demand torque uniform by delaying engine demand torque for the predetermined time to a hybrid mode range while predetermined torque is added to friction torque(S306,S308); and a follow-up control step for determining target torque with reference to maximum torque at the present speed and engine maximum torque at the normal state by executing engine demand torque according to an OPD, if an engine start bit and a fuel injection bit are not input at the same time or after a maintenance and control step is executed, and then passing only target torque of a low-frequency band by restraining the inclination of target torque(S310,S312,S314,S316,S318).

Description

2nd Shock Reducing Method at Hybrid Engine Starting}

1A and 1B are a logic block diagram and a flow chart of a conventional hybrid engine startup,

Figure 2 is a graph showing the engine secondary shock according to Figure 1,

3A and 3B are a logic block diagram and a flowchart of a hybrid engine startup according to the present invention;

4A and 4B are torque diagrams during engine start before and after applying the present invention.

The present invention relates to a secondary impact reduction method when starting a hybrid engine, and more particularly, to reduce the impact of fuel injection ignition at the time of switching to the hybrid mode of driving the engine and the motor at the same time in the electric vehicle mode (EV mode). It is about how to.

Hybrid electric vehicles (HEVs), for example, have two power sources, an engine and a motor, each of which is used most efficiently according to the purpose to achieve energy savings and low pollution.

Hard type HEV is controlled to operate with optimum efficiency according to each driving situation by combining engine, motor, and generator.In contrast to conventional fossil fuel vehicles, it has EV (Electric Vehicle) mode at initial start-up. The engine does not turn on immediately, but when the engine RPM rises by applying torque to the generator to start the engine, the ignition starts.

In the case of such a hard type hybrid vehicle, frequent engine on / off occurs, and the impact caused therefrom leaves a big problem of reducing ride comfort.

1A and 1B are a logic block diagram and a flowchart of a conventional hybrid engine startup, which is a conventional engine startup logic of a hybrid control unit (HCU).

In FIG. 1A, the dotted line logic is a part of calculating the operating point of the engine determined by the operating point determination (OPD) block as an actual command, and the torque command of the engine is the maximum at the current speed input from the engine controller (ECU). Torque and steady state engine maximum torque map block 12 are limited.

In the EV mode (S102), at the time of switching to the hybrid mode for driving the engine and the motor at the same time, the switch 1 block SW1 switches to the upper part when the fuel injection (CF_Inj_FuelOnoff) is started (S104). The MIN MAX limit map block 14 is connected to the engine demand torque VT_SoOpd_EngTa_Nm according to the operating point determined in the block (S106), and the MIN MAX limit map block 14 is the maximum torque and the steady state at the current speed. The target torque according to the engine demand torque VT_SoOpd_EngTa_Nm is determined with reference to the maximum torque at the current speed and the steady state engine maximum torque determined in the engine maximum torque map block 12 (S108).

In order to reduce the sudden rise or fall of the target torque, the slope (change rate) of the target torque is limited (Rate_Limit_Tq) in the torque change rate limiting block 16 (S110), and LPF to prevent the target torque in the high frequency band from being input. In block 18, the target torque of the high frequency band is blocked and only the target torque of the low frequency band is passed (S112), and finally, the target engine torque VT_SoTrc_EngTq-Nm is output (S114).

As a result, conventionally, the output of the engine torque has been set to follow the target torque of the engine as it is without any control by the fuel injection request.

As described above, in the case of a conventional engine start, the HCU controls the ECU to generate a required torque equal to the target torque in order to reach a driving point required by the driver, and the ECU sharply increases the torque of the engine according to the ultra-low driving point. The resulting impact is a significant part of the engine start secondary shock.

That is, the engine torque rapidly increased due to the amount of air during the engine explosion and the ignition timing is transmitted to the drive shaft to generate an engine cranking shock (engine starting secondary shock) as shown in FIG. 2.

As a result, the ride feeling and driving ability which the driver feels are deteriorated, and since the required torque is changed because the output required by the driver is changed, there is a problem that the shock at the time of addition is not constant and the discomfort felt by the driver is added.

The present invention has been made to solve the above-mentioned problems, hybrid engine start that can improve the operability and ride comfort of the hard type HEV through a method that can reduce the impact of the explosion defined as secondary impact The purpose is to provide a secondary impact reduction method.

In the hybrid engine startup method according to the present invention for achieving the above-described secondary impact reduction method, the mode of the hybrid electric vehicle (HEV) is switched to the hybrid mode for driving the engine and motor at the same time in the electric vehicle mode (EV Mode) A method of starting a hybrid engine at a point in time;

When the engine start bit and the fuel injection bit are input at the same time, a follow-up control step of performing a fixed engine demand torque by adding a fixed amount of torque to the friction torque, and a constant amount of torque is applied to the friction torque. A maintenance control step of maintaining a constant engine demand torque by delaying the required torque to the hybrid mode section for a predetermined time, and after the engine start bit and the fuel injection bit are not simultaneously input or the maintenance control step is performed, The target torque is determined by referring to the maximum torque at the current speed and the steady state engine maximum torque by performing the required torque according to the engine, and the tracking control step of restricting the slope of the target torque and passing only the target torque in the low frequency band is performed. It features.

Hereinafter, the configuration and operation of the present invention will be described with reference to the accompanying drawings.

3A and 3B are a logic block diagram and a flow chart of a hybrid engine startup in accordance with the present invention.

In the EV mode (S300), when switching to the hybrid mode for driving the engine and the motor at the same time, the AND gate block 100 when the engine start bit (F_Eng_Start) and the fuel injection bit (CF_Inj_FuelOnoff) is input at the same time (S302) That is, when the engine start bit is 1 and fuel injection is started, the signal is output to the switch 3 block SW3, whereby the switch 3 block SW3 is switched upward and fixed to a constant value. The loop of the torque variable (C_SoTrc_ConstEngTq_Nm) variable side is performed (S304).

The engine start bit = 1 is applied when the engine reaches 800 rpm.

The engine demand torque (C_SoTrc_ConstEngTq_Nm) variable fixed to the constant value is added to a friction torque (V_Eng_FrictionTq_Nm) as a calibration variable and a certain amount of torque (for example, 5 Nm, preferably 3 to 10 Nm).

The first step following control is performed by performing the above steps.

Next, the required torque of the engine is delayed in a state in which a predetermined amount of torque is applied to the friction torque (S306), but delayed for a time constant (C, for example, 10 msec) (S308), and the engine required torque (Demand_Engine_Torque) until the HEV mode section. Keep it constant

The second step maintenance control is performed by performing the above steps.

When the second stage maintenance control is completed, the switch 3 block SW3 is switched downward to be connected to the engine request torque VT_SoOpd_EngTa_Nm according to the operating point determined in the OPD block.

Meanwhile, the AND gate block 100 does not output a signal when only one of the fuel injection bits is input or not all of the fuel injection bits, and the switch 3 block SW3 is lower when the signal is not input. Is connected to the engine demand torque VT_SoOpd_EngTa_Nm according to the operating point determined in the OPD block.

When the fuel injection CF_Inj_FuelOnoff is started, the switch 2 block SW2 after the switch 3 block SW3 is switched upward and connected to the engine demand torque VT_SoOpd_EngTa_Nm according to the operating point (S310). The MIN MAX limit map block 104 is input to the limit map block 104, and the maximum torque at the current speed and the maximum torque at the current speed determined in the steady state engine maximum torque map block 102 and the steady state engine max. The target torque according to the engine demand torque VT_SoOpd_EngTa_Nm is determined with reference to the torque (S312).

In order to reduce the sudden rise or fall of the target torque, the slope (change rate) of the target torque is limited (Rate_Limit_Tq) in the torque change rate limiting block 106 (S314), so that the target torque in the high frequency band is not inputted. In block 108, the target torque of the high frequency band is blocked and only the target torque of the low frequency band is passed (S316) to finally output the target engine torque (VT_SoTrc_EngTq-Nm) (S318).

The third step estimation control is performed by performing the above steps.

As described above, the present invention is largely composed of the following step of the following control, the second step of the maintaining control, and the third step of the following control.

Figures 4a and 4b is a torque diagram when the engine is started before and after the application of the present invention, a significant portion of the secondary impact through the first, second and third stage control described above at the time of switching from the EV mode to the HEV mode in FIG. It can be seen that it is possible to improve a sudden change in the engine demand torque Demand_Engine_Torque occupying.

As described above, according to the present invention, it is possible to minimize the target torque during the engine explosion and to reduce the magnitude of the impact shock, and to maintain the target torque at the constant value at a constant value. By controlling it constantly, it is possible to improve the operability and ride comfort of the hard type HEV.

Claims (1)

A method of starting a hybrid engine at a time of switching a mode of a hybrid electric vehicle (HEV) to a hybrid mode for simultaneously driving an engine and a motor in an electric vehicle mode (EV mode); A follow-up control step of performing a fixed engine demand torque by adding a predetermined amount of torque to the friction torque when the engine start bit and the fuel injection bit are simultaneously input; A maintenance control step of maintaining a constant engine demand torque by delaying a required torque of the engine for a predetermined time to a hybrid mode section in a state where a predetermined amount of torque is applied to the friction torque; After the engine start bit and the fuel injection bit are not input at the same time or after performing the maintenance control step, the target torque is determined by referring to the maximum torque at the current speed and the steady state engine maximum torque by performing the required engine torque according to the driving point. Determining, limiting the slope of the target torque and the following control step of passing only the target torque of the low frequency band, characterized in that the secondary shock reduction method when starting the hybrid engine.

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