KR101198808B1 - Method for controling engine idle of hybrid electric vehicle - Google Patents

Abstract

PURPOSE: An engine idle control method for a hybrid vehicle is provided to improve fuel efficiency over 2% in an engine idle state as the feedback control of an engine speed is performed by a motor. CONSTITUTION: An engine idle control method for a hybrid vehicle comprises following steps. The charge amount of a battery(106) is determined according to the SOC(Stage Of Charge) of the battery. The target speed and engine torque according to charge amount of the battery are determined. The target speed and chare torque of a motor(300) corresponding to the target speed and torque of an engine(200) are determined. The speed control torque for the motor is determined by the deviation between the target speed and the current speed of the motor. The final motor torque is determined while the charge torque of the motor is added to the speed control torque. [Reference numerals] (101) Unit for extracting driving information; (106) Battery

Description

TECHNICAL FOR CONTROLING ENGINE IDLE OF HYBRID ELECTRIC VEHICLE}

The present invention relates to a method for controlling engine idle in a hybrid vehicle, and more particularly, to a method for controlling engine idle using a motor of a hybrid vehicle.

The demand for eco-friendly cars is increasing due to the continuous improvement of fuel efficiency for automobiles and the tightening of emission regulations of each country. As a realistic alternative, hybrid electric vehicles are provided.

A hybrid vehicle may be distinguished from a fuel cell vehicle and a pure electric vehicle in a narrow sense, but the meaning of the hybrid vehicle in this specification encompasses a pure electric vehicle and a fuel cell vehicle, and includes one or more batteries and stores energy stored in the battery. Refers to a vehicle used as a driving force of the vehicle.

Hybrid cars have engines and motors as their power sources, and the engines and motors can be used depending on driving conditions to provide fuel efficiency and reduced emissions.

Hybrid vehicles can improve fuel efficiency by how the engine and the motor are operated in harmony in the course of running on two power sources consisting of an engine and a motor.

The transmission of a commercial hybrid vehicle is typically applied to an ATM transmission (automatic manual transmission).

The ATM transmission is equipped with an automatic transmission unit in the manual transmission, and the clutch is also equipped with an automatic release unit.

The hybrid vehicle detects the displacement of the accelerator pedal and the brake pedal operated by the driver to determine the required torque input to the transmission, and then determines the engine torque through the engine torque map, and uses the input torque and engine torque map of the transmission. The difference in engine torque determined is determined as a motor torque and distributed to the engine and the motor to drive the vehicle.

The engine torque map is configured to follow the minimum fuel consumption in the region with the highest engine efficiency through simulation of a constant driving mode.

However, in the general driving mode, the input request torque of the transmission is a section that requires a lower torque than the engine operating point determined by the engine torque map.

Therefore, in this case, instead of driving the engine in a region of low efficiency in order to meet the input demand torque of the transmission, the input demand torque of the transmission is satisfied by driving the motor with negative torque.

Here, the negative torque driving of the motor means charging the battery, and the energy charged in the battery is used for driving the motor in a section in which the input request torque of the transmission requires low torque, such as a low speed section of the driving section.

At this time, since the engine efficiency is low in the section requiring low torque, the fuel economy is reduced, and thus driving is performed by driving only the motor without driving the engine.

As such, the hybrid vehicle can maximize the fuel efficiency by driving the engine driving point to the highest efficiency range and recovering the remaining energy to the battery and driving only by the motor (EV mode) in a section requiring low required torque.

Hybrid cars have P and N gears with the gearshift stages to stop fuel consumption and improve emissions, while the engine is turned off while the vehicle is stopped. In this situation, when the state of charge (SOC) of the battery falls below the reference value, the engine is turned on and the motor is driven with negative torque to charge the battery. In this way, the engine is turned on to charge the battery in the shift stages P and N stages.

Engine speed feedback control is performed by the engine itself in response to sudden changes in engine speed in engine idle situations. In order to control the engine speed feedback, a torque reservation control technique that basically reduces the ignition efficiency by arbitrarily perceiving the ignition angle is used. Torque retardation control technology has to increase the amount of torque reservation in order to respond quickly to load, which can adversely affect the ignition efficiency and fuel economy. In addition, the engine idle stability may be lowered with respect to a rapid load change due to the limitation of the torque recreation amount.

The technical problem to be solved by the present invention is to provide an engine idle control method that can perform the engine speed feedback control using a motor in the engine idle situation.

According to an embodiment of the present invention, a method of controlling engine idle using a motor of a hybrid vehicle includes determining a charge amount of a battery by a motor according to a stage of charge (SOC) of a battery, and the engine according to the charge amount of the battery. Determining a target speed and engine torque of the engine; determining a target speed and charging torque of the motor corresponding to the engine target speed of the engine and the engine torque; and determining a deviation between the target speed of the motor and the current motor speed. Determining a speed control torque of the motor by using the sum of the charging torque and the speed control torque of the motor to determine a final motor torque of the motor.

The determining of the target speed and engine torque of the engine may include determining a transmission input torque of the engine according to the target speed of the engine, and a trick fed back from the engine control unit (ECU) to the transmission input torque of the engine. And adding the shunt torque to determine the engine torque.

Calculating an engine torque deviation corresponding to the difference between the transmission input torque of the engine and the final torque of the motor, and calculating friction torque for each engine speed and engine coolant temperature using the engine torque deviation; It may include.

The method may further include determining engine idle speed stabilization by checking whether the deviation between the target speed of the engine and the current engine speed and the deviation between the target speed and the current motor speed of the motor are within a predetermined criterion.

When it is determined that the engine idling speed is stabilized, it is determined whether a deviation between the final motor torque of the first motor and the final motor torque of the second motor is within a predetermined criterion among the two motors connected to the engine through the planetary gear. It may further include determining the accuracy of the motor torque.

The engine idle fuel economy of the hybrid vehicle can be improved, and the stability of battery charging in the engine idle can be improved.

1 is a view schematically showing a shift control apparatus of a hybrid vehicle according to an embodiment of the present invention.
2 is a flowchart illustrating a method of controlling engine idle using a motor of a hybrid vehicle according to an exemplary embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In addition, in the various embodiments, components having the same configuration are represented by the same reference symbols in the first embodiment. In the other embodiments, only components different from those in the first embodiment will be described .

In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise.

1 is a view schematically showing a shift control apparatus of a hybrid vehicle according to an embodiment of the present invention.

Referring to FIG. 1, a shift control apparatus of a hybrid vehicle includes a driving information detector 101, an ECU (Engine Control Unit) 102, a HCU (Hybrid Control Unit: 103), a CCU (Clutch Control Unit: 104), and a PCU (Power). Control Unit: 105), Battery 106, BMS (Battery Management System: 107), Engine 200, HSG (Hybrid Starter and Generator: 210), Engine Clutch 250, Motor 300, Transmission 400 It includes.

The driving information detector 101 detects and provides the HCU 103 with information such as the displacement of the accelerator pedal, the displacement of the brake pedal, the selection of the automatic constant speed driving mode, and the like.

The ECU 102 interlocks with the HCU 103 connected to the network to control various operations of the engine 200 and provides operating status information of the engine 200 to the HCU 103. The ECU 102 feeds back the friction torque of the engine 200 itself to the HCU 103.

The HCU 103 is a top-level controller, and the battery 106 by the motor 300 according to the driving request provided from the driving information detector 101 and the state of charge (SOC) of the battery 106 provided from the BMS 107. ) To determine the amount of charge and to select the optimum operating point to control the output speed and torque of the engine 200 and the motor 300.

The CCU 104 controls an actuator included in the transmission 400 under the control of the HCU 103 connected to the network to control the engagement of the target speed change stage and controls the flow rate supplied to the engine clutch 250, By engaging and disengaging the clutch 250, the power transmission of the engine 200 is interrupted.

The PCU 105 includes a motor control unit (MCU), an inverter, and a protection circuit. The PCU 105 converts a DC voltage supplied from the battery 106 into a three-phase AC voltage according to a control signal applied from the HCU 103. Control the driving of 300).

The MCU included in the PCU 105 controls the HSG 210 to execute idle stop and restart of the engine 200. The MCU controls the output of the engine 200 in an engine idle situation. Engine idle means that the engine is turned on to charge the battery in shift stages P and N.

The power switching element included in the PCU 105 may be configured of any one of an Insulated Gate Bipolar Transistor (IGBT), a MOSFET, a transistor, and a relay.

The protection circuit included in the PCU 105 monitors the flow of driving power and distributes or cuts off the driving power when the overvoltage and overcurrent flow into the driving power due to various causes such as a collision, collision, or lightning strike of the vehicle. It protects various systems provided and stably protects occupants from high pressure.

The battery 106 supplies power to the motor 300 to assist the output of the engine 200 in the HEV mode, and charges the voltage generated by the motor 300 by regenerative braking control. The battery 106 supplies power to the motor 300 in the EV mode, and charges the generated voltage of the motor 300 operating as a generator during regenerative braking control.

The BMS 107 detects information on the voltage, current, and temperature of the battery 106, and manages the charge state. The BMS 107 controls the main relay for controlling the output of the battery 106 on or off under the control of the HCU 103, and controls the charge / discharge directing operation region determined in the automatic constant speed driving. It is applied to control the charging and discharging operation of the battery 106.

The engine 200 is driven and controlled to the optimum operating point under the control of the ECU 102. [

The HSG 210 executes idle stop and restart of the engine 200 according to the driving state of the vehicle.

The engine clutch 250 is disposed between the engine 200 and the motor 300 and is operated under the control of the CCU 104 to intercept power transmission between the engine 200 and the motor 300.

The motor 300 is driven by a three-phase AC voltage supplied through the PCU 105 to support the output torque of the engine 200, and is operated as a generator when there is excess torque at the output of the engine 200 or when braking. .

The transmission 400 adjusts the transmission ratio according to the control of the CCU 104, and distributes the output torques applied through the clutch 250 according to the driving mode to the transmission ratio to the driving wheels so that the vehicle can be driven. . The transmission 400 may be applied to an automatic transmission or a continuously variable transmission.

Now, a method of controlling engine idle using the motor 300 of the hybrid vehicle will be described.

2 is a flowchart illustrating a method of controlling engine idle using a motor of a hybrid vehicle according to an exemplary embodiment of the present invention.

1 and 2, the HCU 103 determines the amount of charge of the battery 106 by the motor 300 according to the SOC of the battery 106 provided by the BMS 107 (S101).

The HCU 103 determines the engine output according to the amount of charge of the battery 106, and determines the target speed of the engine 200 along the Brake mean Specific Fuel Consumption (BSFC) diagram from the engine output so that the engine 200 outputs the engine. Determine the transmission input torque to do. The HCU 103 determines the engine torque by adding the friction torque fed back from the ECU 102 to the transmission input torque (S102). The HCU 103 requests the ECU 102 for the engine torque to be output by the engine 200.

The HCU 103 determines the charging torque of the motor 300 through an electric variable transmission (EVT) structure to balance the determined engine torque (S103). That is, the HCU 103 determines the charging torque of the motor 300 corresponding to the determined engine torque.

The HCU 103 determines the target speed of the motor 300 by using the determined target speed of the engine 200 and the EVT structure (S104). Although one motor 300 is shown here, some of the hybrid vehicles connect the engine and the two motors through planetary gears to enable continuously variable speed. In a structure provided with two motors, the HCU 103 may determine a target speed of each of the first motor and the second motor.

The HCU 103 determines the speed control torque of the motor 300 through the PI control by using the deviation between the determined target speed of the motor 300 and the current motor speed (S105).

The HCU 103 determines the final motor torque of the motor 300 by adding the charging torque and the speed control torque of the motor 300 (S106). The HCU 103 requests the MCU the final motor torque for the motor 300 to output. The HCU 103 may determine the speed control torque of each of the first motor and the second motor, determine the final motor torque of each of the first motor and the second motor, and request the final motor torque from the MCU.

The HCU 103 checks whether the deviation between the target speed of the engine 200 and the current engine speed is within a certain criterion, and whether the deviation between the target speed of the motor 300 and the current motor speed is within a certain criterion. The speed stabilization is determined (S107). For example, when the HCU 103 lasts for 5 seconds or more in a state in which the deviation between the target speed of the engine 200 and the current engine speed, and the deviation between the target speed and the current motor speed of the motor 300 are 50 rpm or less, It can be determined that the idle speed is stabilized. If the speed of the engine idle is not stabilized, the HCU 103 may perform steps S102 to S106 again.

The HCU 103 transmits an engine idle speed stabilization signal to the ECU 102 when it is determined that the engine idle speed is stabilized.

The HCU 103 determines whether the deviation between the final motor torque of the first motor and the final motor torque of the second motor determined through the EVT structure is within a predetermined criterion to determine the accuracy of the motor torque (S108). For example, the HCU 103 may determine that the motor torque is correct when the deviation between the final motor torque of the first motor and the final motor torque of the second motor is 1 torque (Nm) or less. If the motor torque is not correct, the HCU 103 can perform steps S104 to S107 again.

The HCU 103 transmits a motor torque accuracy signal to the ECU 102 if it is determined that the motor torque is correct.

The HCU 103 calculates an engine torque deviation corresponding to the difference between the transmission input torque of the engine 200 determined in step S102 and the final motor torque of the motor 300 determined in step S106 (S109). HCU 103 communicates the engine torque deviation to ECU 102.

When the ECU 102 receives the engine idle speed stabilization signal and the motor torque accuracy signal from the HCU 103, the ECU 102 determines an engine torque learning time (S110).

When the engine torque learning time is determined, the ECU 102 calculates friction torque for each engine speed and engine coolant temperature using the engine torque deviation received from the HCU 103, and calculates the calculated friction torque from the HCU 103. (S111). The HCU 103 may record the friction torque for each engine speed and engine coolant temperature.

As described above, by controlling the engine idle using the motor of the hybrid vehicle, the engine idle fuel economy in the P and N stages can be improved by 2% or more, and the stability of battery charging in the engine idle can be improved.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are illustrative and explanatory only and are intended to be illustrative of the invention and are not to be construed as limiting the scope of the invention as defined by the appended claims. It is not. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

101: operation information detection unit 102: ECU
103: HCU 104: CCU
105: PCU 106: battery
107: BMS 200: Engine
210: HSG 250: Engine Clutch
300: motor 400: transmission

Claims (5)

In the method for controlling the engine idle using the motor of the hybrid vehicle,
Determining a charge amount of the battery by the motor according to a stage of charge (SOC) of the battery;
Determining a target speed and engine torque of the engine according to the amount of charge of the battery;
Determining a target speed and a charging torque of the motor corresponding to the engine target speed and the engine torque of the engine;
Determining a speed control torque of the motor using the deviation between the target speed of the motor and the current motor speed; And
And determining the final motor torque of the motor by adding the charging torque and the speed control torque of the motor. The method according to claim 1,
Determining a target speed and engine torque of the engine,
Determining a transmission input torque of the engine according to a target speed of the engine; And
And determining the engine torque by adding a friction torque fed back from an engine control unit (ECU) to a transmission input torque of the engine. The method of claim 2,
Calculating an engine torque deviation corresponding to the difference between the transmission input torque of the engine and the final torque of the motor; And
And calculating a friction torque for each engine speed and engine coolant temperature using the engine torque deviation. The method according to claim 1,
In the hybrid vehicle further comprising the step of determining the engine idle speed stabilization by checking whether the deviation between the target speed of the engine and the current engine speed, and whether the deviation between the target speed and the current motor speed of the motor is within a predetermined criterion. Engine idle control method. 5. The method of claim 4,
When it is determined that the engine idling speed is stabilized, it is determined whether a deviation between the final motor torque of the first motor and the final motor torque of the second motor is within a predetermined criterion among the two motors connected to the engine through the planetary gear. The engine idle control method of a hybrid vehicle further comprising determining the accuracy of the motor torque.

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