KR100857658B1 - Torque control method of hybrid electric vehicle - Google Patents

Abstract

A torque decision method of a hybrid vehicle for improving fuel efficiency is provided to execute load leveling exactly by calculating efficiency in performing load leveling, in consideration of efficiency of a path where energy is stored in a battery and used again. A torque decision method of a hybrid vehicle having an engine and a motor for improving fuel efficiency comprises the steps of: calculating torque that a driver demands, from the present vehicle speed and an accelerator pedal value detected and input from a vehicle speed sensor and a pedal sensor in a controller of the vehicle; calculating output efficiency if load leveling is not executed, while outputting engine torque according to the demand torque without charging a battery and output efficiency if load leveling for using the rest engine torque except for the demanded torque, for charging the battery by the motor is executed; and comparing two efficiency values and determining engine torque as a torque value set as an optimal driving point and motor torque as a difference value between engine torque of an optimal driving point and the demanded torque of the driver, if output efficiency in case that load leveling is not executed is lower than output efficiency in case that load leveling is executed.

Description

Torque control method for improving fuel economy of hybrid vehicle {Torque control method of hybrid electric vehicle}

The present invention relates to a torque determination method for improving fuel efficiency of a hybrid vehicle, and more particularly, to calculate a driver's required torque based on a vehicle speed and an accelerator pedal value in a torque calculation process of an engine and an electric motor in a hybrid vehicle, and perform road leveling. After determining the respective efficiencies according to the efficiency equations in the case of the load leveling and the non-loading leveling, and comparing the efficiency of the two cases, it is determined whether to perform the load leveling. Is calculated in consideration of the efficiency of the route that has been stored in the battery and determines whether to perform the load leveling in consideration of the efficiency of the route, so that more accurate load leveling can be achieved than in the related art. How to determine torque to improve fuel economy One will.

In general, a hybrid vehicle in a broad sense means to drive a vehicle by efficiently combining two or more different power sources, but in most cases, an electric motor driven by the power of an engine and a battery that uses fuel to obtain driving power is used. It means a vehicle that obtains a driving force, it is called a hybrid electric vehicle (HEV).

In response to the recent demand for improving fuel economy and developing more environmentally friendly products, research on hybrid vehicles is being actively conducted.

Hybrid vehicles can form a variety of structures using engines and electric motors as power sources. Most of the vehicles studied so far employ either parallel or in series.

The tandem type is similar to a general electric vehicle. In the tandem hybrid vehicle, an engine is used to charge a battery, and the vehicle is driven by an electric motor (driving motor) that operates using the power of the battery.

That is, the driving force is all obtained from the electric motor, and the engine is only mounted for power generation to compensate for the shortcomings of the electric vehicle having a short traveling distance.

Compared with the parallel type, the series type has a simpler structure and a simpler control logic. However, since the mechanical energy from the engine must be stored in a battery and the vehicle must be driven by an electric motor, efficiency of energy conversion is required. There is a disadvantage in that.

In contrast, the parallel type allows the engine to charge the battery, but directly drives the vehicle with the electric motor, which has the disadvantage that the structure is relatively more complicated than the serial type and the control logic is more complicated. It can be used at the same time, because it can use the energy efficiently, the structure is widely adopted in passenger cars.

In particular, by using the optimum operating area of the engine and the electric motor, it improves the fuel efficiency of the entire drive system as well as recovers the energy with the electric motor during braking, thereby enabling efficient use of energy.

As described above, hybrid vehicles are attracting attention due to improved fuel efficiency compared to conventional gasoline or diesel vehicles, and technologies for improving fuel efficiency of hybrid vehicles can be classified as follows.

1) Stop the engine when the vehicle is stopped (idle stop)

2) regenerative braking

3) Electric vehicle driving using only electric motor rotational force and motor power assisted driving using engine rotational force as main power and electric motor rotational power as auxiliary power

4) Road leveling that uses charged and stored battery power while driving and assists in electric vehicle driving and motor power

Here, the load leveling of 4) is described as follows.

In terms of terms, it refers to leveling a vehicle's load.

In general cars, the engine outputs as much energy as the driver presses the accelerator pedal, that is, as much as the driver requires, and when the engine outputs less energy than the driver requires, the driver feels unsatisfactory in the power performance of the vehicle. On the contrary, if the engine outputs more energy than the driver requires, the vehicle's power performance is excessively felt.

In other words, as the driver presses the accelerator pedal, an appropriate level of engine power must be determined at 1: 1. Therefore, when the driver presses the pedal small, the engine power is reduced, and the engine operates in an area with poor efficiency. This can only be.

However, in the case of hybrid vehicles, an electric motor and a battery can be used to increase or decrease engine power.

In other words, if the driver presses the accelerator pedal small and the engine is operated in a low power area with low efficiency, the engine power is increased to a high efficiency area, and more engine power than necessary to move the vehicle is used to generate electric motors. Charge the battery with the generated energy.

Then, when the driver's accelerator pedal is greatly depressed, the engine output is maintained at the optimum efficiency when the engine output is required a lot, and the engine lacks the output by using the battery power to drive the motor to obtain the 'engine + motor' output. As a result, the engine can be operated in good condition while satisfying the power required by the driver.

This concept is road leveling, which is one of the fuel economy improvement means of hybrid vehicles.

However, such a load leveling technique is a technique that can significantly improve fuel economy and, on the contrary, worsen fuel economy according to use.

The load leveling technology applied to a conventional hybrid vehicle is mainly focused on the efficiency of the engine and operates under conditions where the engine efficiency is optimal.

However, this concept only considers the efficiency of the engine, and does not consider the efficiency when the mechanical energy of the engine for power generation is converted into electrical energy and stored in a battery and reused.

In other words, the mechanical energy of the engine must be taken into account through the paths of "generating efficiency of the motor and inverter, charging and discharging efficiency of the battery, driving efficiency of the motor and inverter", so that the accurate effect and gain of the load leveling can be predicted. Will be.

Therefore, it is necessary to improve the load leveling technology to optimize the efficiency of the engine and to consider the efficiency of the path in which the generated energy is stored and reused in the battery.

Accordingly, the present invention has been invented to solve the above problems, in the case of calculating the driver's required torque based on the vehicle speed and the accelerator pedal value in the torque calculation process of the engine and electric motor in a hybrid vehicle, the load leveling and the load After determining each efficiency according to the efficiency formula when not leveling, and comparing the efficiency of the two cases to determine whether to perform load leveling, the generated energy is stored in the battery when calculating the efficiency in the case of load leveling Calculation is made in consideration of the efficiency on the route to be reused, and the load leveling is determined in consideration of the efficiency on the route, so that the fuel efficiency of the hybrid vehicle can be more accurately implemented than in the related art. To provide a torque determination method. have.

Accordingly, in order to achieve the above object, the present invention provides a torque determining method for a hybrid vehicle having an engine and a motor as a power source, wherein the current vehicle speed and accelerator are detected and input from a vehicle speed sensor and a pedal sensor. Calculating driver demand torque from a pedal value; When the engine torque output is made according to the driver's required torque without charging the battery and the load leveling is not performed, the load leveling in which the engine torque surplus other than the driver's required torque in the engine torque is used to charge the battery by the motor is performed. Calculating efficiency in each case; Comparing the above two efficiencies, if the efficiency when no load leveling is performed is less than the efficiency when the load leveling is performed, the engine torque is set to the torque value set as the optimum operating point, and the motor torque is equal to the engine torque at the optimum operating point. And determining the difference value of the driver's required torque.

In this case, the efficiency when the load leveling is not performed, characterized in that it is calculated in consideration of the engine torque and the engine speed corresponding to the driver's requested torque with respect to the fuel amount and the heat generation amount of the fuel when driving without battery charging.

Preferably, the efficiency when the load leveling is not performed is characterized in that defined by the following formula (E1).

E1:

:엔진 토크,

:엔진 회전수,

:충전 없이 주행할 경우의 연료량, LHV : 연료의 발열량임.here,

Engine torque,

Engine speed,

: Fuel amount when driving without charge, LHV: Heat value of fuel.

In addition, the efficiency in the case where the load leveling is performed, the difference between the engine torque and the motor torque with respect to the fuel amount and the heat generation amount of the fuel when the battery charging and running at the same time, the engine speed, the motor speed, the power generated by the motor The electrical energy is stored in the battery, characterized in that it is calculated in consideration of the efficiency on the path to reuse the motor drive.

Preferably, the efficiency when the load leveling is performed is to take into account the efficiency on the path that the electrical energy generated by the motor is stored in the battery is reused to drive the motor, characterized in that defined by the following formula (E2) .

E2:

:엔진 토크,

:엔진 회전수,

:모터 토크,

:모터 회전수,

:충전과 주행을 병행할 경우의 연료량, LHV : 연료의 발열량,

:모터에 의해 발전된 전기에너지가 배터리에 저장되었다 모터 구동에 재사용되는 경로상의 효율,

:모터가 발전할 때의 효율,

:배터리의 충방전 효율,

:모터가 구동될 때의 효율임.here,

Engine torque

Engine speed,

Motor torque,

Motor speed,

: Fuel amount when charging and driving at the same time, LHV: Heating value of fuel,

The electrical energy generated by the motor is stored in the battery.

Efficiency when the motor develops,

: Charge and discharge efficiency of the battery,

: Efficiency when the motor is driven.

According to the torque determination method of the present invention having the above characteristics, it is determined whether or not to perform load leveling in consideration of the efficiency on the path that the generated energy is stored in the battery reuse, so that more accurate load leveling can be carried out than in the prior art do.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention relates to a torque determination method for improving fuel efficiency of a hybrid vehicle. The present invention relates to a parallel hybrid vehicle equipped with an electric motor (driving motor) between an engine and a transmission, and optimizes engine efficiency at the same time. It is a technology that finally determines the load leveling strategy in consideration of the efficiency on the path that the energy generated by the battery is stored (charged) and reused for driving the motor.

1 is a diagram illustrating an engine driving point of a hybrid vehicle, and illustrates an engine driving point movement when using road leveling.

As shown in FIG. 1, when the vehicle and the engine are operated in a region where the load of the engine is small, that is, the A region, the engine efficiency is very low, which is a disadvantage in terms of vehicle fuel efficiency.

Therefore, in this case, in order to move the operating point of the engine to the region of high efficiency of the engine, the engine torque is increased to generate power through the electric motor. In this case, the operating point of the engine is the region of high efficiency, that is, region B of FIG. Will move.

However, there is an essential consideration in moving the operation point of the engine. The loss in reuse of the energy generated by the engine torque, that is, the electrical energy generated by the torque corresponding to 'B-A' in the figure, It exists.

The efficiency on the path can be expressed by the following equation (1).

(1)

(One)

은 모터가 발전할 때의 효율이고,

는 배터리의 충방전 효율이며,

는 모터가 구동될 때의 효율이다.here,

Is the efficiency when the motor develops,

Is the charge and discharge efficiency of the battery,

Is the efficiency when the motor is driven.

In other words, in load leveling, there is a gain obtained by moving the engine operating point to an area of high efficiency, while there is a loss in path when the energy generated by the engine and reused in the battery is reused. The disadvantage is that you have to use less energy than energy.

Therefore, in controlling the torque of the hybrid vehicle, the effect of comparing the gains and losses described above is effective to determine whether to drive the vehicle in parallel with the battery charging or to drive the vehicle only with the engine without charging by introducing a load leveling concept. It is reasonable to carry out load leveling under certain conditions.

The present invention introduces the charging efficiency formula in performing the load leveling, and in each driving condition, when the vehicle is driven by the engine power without charging, and the vehicle is driven by the engine power and the battery is charged simultaneously. In comparison, it is based on operating in an advantageous case in terms of efficiency.

The efficiency equations in each of the above ①, ② are the same as the following equation (2) and equation (3), respectively.

① When driving the vehicle with engine power without charging (without road leveling)

(2)

(2)

② When driving the vehicle and charging the battery at the same time (load leveling)

(3)

(3)

The description of the variables used in Equations (2) and (3) is as follows.

: 변속기 입력 토크

Transmission input torque

: 변속기 입력 회전수

Transmission input speed

: 엔진 토크

Engine Torque

: 엔진 회전수

: Engine speed

: 모터 토크

: Motor torque

: 모터 회전수

: Motor speed

: 충전 없이 주행할 경우의 연료량

: Fuel amount when driving without charge

: 충전과 주행을 병행할 경우의 연료량

: Fuel amount when charging and running at the same time

LHV: calorific value of fuel

: 발전된 에너지가 거치는 경로상의 효율

: Efficiency in the path through which energy is generated

)는 엔진 토크(

)가 된다.In equation (2), all engine torque is input to the transmission without battery charging (no load leveling), so the transmission input torque (

) Is the engine torque (

)

)는 엔진 토크(

)와 모터 토크(

)의 차(

)가 된다.Further, in Equation (3), since the vehicle is driven by engine power and battery charging by the electric motor is performed in parallel, the transmission input torque for driving the vehicle (

) Is the engine torque (

) And motor torque (

) 'S car

)

)는 기본적으로 항상 엔진 회전수(

) 및 모터 회전수(

)와 같다(

).In addition, in equations (2) and (3), the engine, the motor, and the transmission rotate integrally regardless of whether the battery is charged or not.

) Always defaults to engine speed (

) And motor speed (

Is the same as

).

In a parallel hybrid vehicle, an electric motor is directly connected to the engine, and power is transmitted to the wheels through a continuously variable transmission (CVT). When the driver drives the accelerator pedal, the throttle valve is the engine's OOL (Optimal Operating Line). As a result, the motor is powered by battery power for the torque that is maximum open and low.

In such a parallel hybrid vehicle, when the torque required by the driver is determined from variables such as the current vehicle speed and the accelerator pedal value, the torque must be implemented by a combination of engine torque and motor torque.

At this time, whether the torque required by the driver is satisfied by the engine torque entirely or the torque greater than the torque required by the driver is output from the engine, and the excess torque is put into the motor generation to store electric energy in the battery. It is the content of the present invention to determine whether to reuse, and in two cases the criterion for selecting one becomes the two efficiency equations described above.

In carrying out the present invention, if the main input variable is the driver's required torque, the main output variable is the engine torque, the motor torque, and other environmental variables are the vehicle speed, the accelerator pedal value, the engine speed, and the like.

Hereinafter, the torque control process of the hybrid vehicle according to the present invention will be described with reference to FIG. 2.

First, the HCU (Hybrid Control Unit), the upper controller of the vehicle, calculates the driver's required torque (Tq_req) from the current vehicle speed and accelerator pedal values detected and input from the vehicle speed sensor and the pedal sensor, and then drives the vehicle with engine power without charging. For the case of performing the operation, that is, the case of not performing the load leveling, and the case of driving the vehicle and charging the battery at the same time, that is, the case of not performing the load leveling, respectively, the efficiency is calculated from the above equations (2) and (3). Obtain

)는 로드 레벨링을 하지 않는 경우의 엔진 토크이므로, 엔진 토크(

)가 곧 운전자 요구토크(

)가 된다(

).In equation (2), the engine torque (

) Is the engine torque when no load leveling, so the engine torque (

) Is coming soon

Becomes (

).

)는 최적 운전점에서의 엔진 토크(

)이고, 모터 토크(

)는 최적 운전점에서의 엔진 토크(

)와 운전자 요구토크(

)의 차가 된다(

). In addition, in equation (3), it is assumed that load leveling is performed.

) Is the engine torque (

) And the motor torque (

) Is the engine torque (

) And driver demand torque (

It becomes the difference of ()

).

이면 로드 레벨링 및 배터리 충전을 하지 않고 엔진 동력으로 차량 구동을 수행하며, 이때 엔진 토크는 하기 식(4)에서와 같이 운전자 요구토크에 해당하는 토크값으로 결정되는바, 운전자 요구토크만큼 토크를 출력하도록 엔진이 제어된다. 모터 토크는 0이 된다.Thereafter, an advantageous condition is selected by comparing the obtained two efficiencies, that is, the efficiency when the load leveling is not performed and the efficiency when the load leveling is performed.

The vehicle is driven by engine power without load leveling and battery charging, and the engine torque is determined by the torque value corresponding to the driver's required torque as shown in Equation (4) below. The engine is controlled. The motor torque is zero.

(4)

(4)

이면 로드 레벨링을 수행하는바, 이때 엔진은 최적 효율로 운전, 즉 최적 운전점의 토크를 출력하도록 운전되며, 최적 운전점의 엔진 토크에서 운전자 요구토크 이외의 엔진 토크 잉여분은 전기모터를 구동시키는데 사용되어 전기모터에 의해 발전된 전기에너지가 배터리에 저장되도록 한다.On the other hand,

In this case, the load leveling is performed. At this time, the engine is operated at the optimum efficiency, that is, outputs the torque of the optimum operating point, and an excess of the engine torque other than the required torque of the driver is used to drive the electric motor. The electrical energy generated by the electric motor is stored in the battery.

At this time, the engine torque and the motor torque are determined as shown in Equation (5), and the engine and the motor drive are controlled according to the determined torque. Is delivered to the motor to be charged.

(5)

(5)

In this way, in the present invention, after determining the respective efficiency according to the efficiency formula in the case of the load leveling and the non-load leveling, it is determined whether to perform the load leveling by comparing the efficiency of the two cases, The energy generated in the calculation of efficiency is stored in the battery and calculated in consideration of the efficiency on the path to be reused, and the load leveling is determined in consideration of the efficiency on the path, thereby making the load more accurate than before. The implementation of leveling can be made.

1 is a diagram showing an engine driving point of a hybrid vehicle,

2 is a view showing a torque control process of a hybrid vehicle according to the present invention.

Claims (5)

In the torque determination method of a hybrid vehicle having an engine and a motor as a power source, Calculating, by the controller of the vehicle, the driver's required torque from the current vehicle speed and the accelerator pedal value detected and inputted from the vehicle speed sensor and the pedal sensor; When the engine torque output is made according to the driver's required torque without charging the battery and the load leveling is not performed, the load leveling in which the engine torque surplus other than the driver's required torque in the engine torque is used to charge the battery by the motor is performed. Calculating efficiency in each case; Comparing the above two efficiencies, if the efficiency when no load leveling is performed is less than the efficiency when the load leveling is performed, the engine torque is set to the torque value set as the optimum operating point, and the motor torque is equal to the engine torque at the optimum operating point. Determining the difference value of the driver's required torque; Torque determination method for improving fuel economy of the hybrid vehicle comprising a. The method according to claim 1, The efficiency when the load leveling is not performed is calculated in consideration of the engine torque and the engine speed corresponding to the driver's required torque with respect to the fuel amount and the heat generation amount of the fuel when driving without the battery charge of the hybrid vehicle, characterized in that How to determine torque to improve fuel economy. The method according to claim 2, When the load leveling is not performed, the efficiency of the torque determination method for improving fuel efficiency of the hybrid vehicle, characterized in that defined as the following equation (E1). E1:

here,

Engine torque

Engine speed,

: Fuel amount when driving without charge, LHV: Heat value of fuel. The method according to claim 1, The efficiency in the case where the load leveling is performed is the difference between the engine torque and the motor torque with respect to the fuel amount and the heat generation amount of the fuel when the battery is charged and the driving, and the engine speed, the motor speed, and the power generated by the motor. The electric energy is stored in the battery. The torque determination method for improving fuel efficiency of the hybrid vehicle, characterized in that it is calculated in consideration of the efficiency on the path that is reused for driving the motor. The method according to claim 4, In the case where the load leveling is performed, the electric energy generated by the motor is stored in the battery. In consideration of the efficiency of the path reused for driving the motor, the fuel efficiency of the hybrid vehicle is defined as in the following formula (E2). How to determine torque for improvement. E2:

here,

Engine torque

Engine speed,

Motor torque,

Motor speed,

: Fuel amount when charging and driving at the same time, LHV: Heating value of fuel,

The electrical energy generated by the motor is stored in the battery.

Efficiency when the motor develops,

: Charge and discharge efficiency of the battery,

: Efficiency when the motor is driven.

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