KR101500245B1 - Control method for mode change and shift of hybrid electric vehicle - Google Patents

Abstract

The present invention relates to a method to convert the mode of a hybrid vehicle and control the speed change of the hybrid vehicle. The controlling method is provided to minimize energy loss when converting a mode between a serial mode and a parallel mode, and changing a speed and maximizing a driving ability in a hybrid vehicle having two motors and a two-stage reduction gear. To achieve the aforementioned purpose, the method performs a serial-parallel mode conversion and controls the speed change of a hybrid vehicle having a power train composition wherein an engine and a first motor are directly connected to deliver power, and a transmission interposed between the engine and a second motor (MG2). The controlling method, disclosed by the present invention, controls engine torque by summing the torque of a transmission input request and the torque (negative torque) of a first motor and controls the torque of the first motor using negative minimum torque considering a battery charging condition when the minimum torque of the first motor considering the battery charging condition (SOC) is equal to or greater than ′-1× abs (((engine target rotation number - engine current rotation number) × engine inertia) + abs (engine driving torque - intervention request torque))′ for torque intervention which reduces transmission input torque when requesting a serial-parallel mode conversion or a speed change. In the present invention, the control of engine torque is desired to be performed by the control of an amount of air intake.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for a hybrid vehicle,

More particularly, the present invention relates to a hybrid vehicle having a hybrid vehicle having two motors and a two-stage deceleration mechanism, in which energy lost during switching between direct and parallel modes and during shifting is minimized And a control method capable of maximizing the driving performance.

The hybrid vehicle means to drive the vehicle by efficiently combining two or more kinds of driving sources, but most means a vehicle driven by an engine that obtains the rotational force by burning the fuel and a rotational force by the electric energy of the battery .

In hybrid vehicles, various power transmission structures can be constructed using engines and motors. Most hybrid vehicles adopt one of parallel and series power transmission structures.

In addition, the hybrid vehicle can generate an optimum output torque according to how the engine and the motor are operated in harmony in the course of running on two driving sources composed of an engine and a motor.

A typical type of powertrain of a hybrid vehicle is a type having an engine clutch between the engine and the motor, and includes an engine, a starter generator for engine starting and power generation, an engine clutch interposed between the engine and the motor, And the battery is connected to the motor and the starting generator through an inverter in a chargeable and dischargeable manner.

On the other hand, in a hybrid vehicle equipped with an automatic transmission, the shifting time is shortened through the optimal slip control of the clutch and the brake by using the fluid (transmission oil) during the shifting process, and the heterogeneity in shifting is minimized.

In addition, a torque intervention control is performed in which the transmission input torque is instantaneously reduced to reduce the impact generated when the clutch is engaged or disengaged during the shifting process.

In order to reduce the input torque of the transmission, the torque control target is an engine and a motor. In order to reduce the input torque of the transmission, the engine torque itself is reduced, or the engine operation torque is transmitted to the motor, Control is performed to reduce the transmission input torque during the operation (the engine output is absorbed through the battery charging).

More specifically, a motor that takes into account the maximum torque of the motor (the torque here is the torque absolute value and the torque during power generation is the actual negative torque) or the battery state of charge (SOC: state of charge) If the maximum torque (negative torque, maximum possible torque) is more than 'abs (engine target revolution - engine current revolution) x engine inertia) + abs (engine operation torque - intervention request torque) (&Quot; abs () " represents an absolute value).

At this time, the torque control is performed on the motor for generating power by the value of abs ((engine target rotation speed - engine current rotation speed) × engine inertia) + abs (engine operation torque - intervention required torque).

On the other hand, when the maximum torque of the motor in consideration of the maximum torque of the motor operating in the power generation or the state of charge (SOC) of the generator is' abs (engine target revolution speed - engine current revolution speed) Quot; required torque "), the intervention request torque control for reducing the output torque according to the intervention yoke value is performed through the ignition timing control for the engine, and at this time, the torque control is performed on the motor.

However, the above-described conventional shift control system reduces the engine torque by reducing the ignition timing while supplying and consuming the fuel in the engine torque control process for the torque intervention, which results in a problem of lowering the engine efficiency (fuel efficiency deteriorates) .

Recently, a hybrid vehicle having two motors has been developed. In this type of hybrid vehicle, torque intervention which minimizes energy loss and maximizes driving performance during series-parallel mode switching or parallel shift control, Control and drive source control strategies have not been proposed.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a hybrid vehicle having two motors and a two-stage speed reduction mechanism, And to provide a control method that can be used.

In order to achieve the above object, the present invention provides a hybrid vehicle having a power train configuration in which an engine and a first motor are directly connected to each other for power transmission and a transmission is interposed between an engine and a second motor (MG2) A control method in a switching and shifting mode, characterized in that, for the torque intervention to reduce the transmission input torque at the time of the direct-parallel mode switching or shift request, the negative minimum torque of the first motor in consideration of the battery charge state (SOC) If the engine torque is higher than or equal to 1 × abs (engine target speed - engine current speed) × engine inertia) + abs (engine operation torque - intervention request torque) And the torque of the first motor is controlled to a negative minimum torque in consideration of the state of charge of the battery.

Here, it is preferable that the engine torque control is performed by controlling the amount of intake air.

In addition, for the torque intervention in which the transmission input torque is reduced, the negative minimum torque of the first motor in consideration of the battery charge state (SOC) is -1x abs (engine target revolution speed - engine current revolution speed) ) + abs (engine operation torque - intervention required torque) ', the engine torque is controlled to the torque value set as the optimum operation point, and the torque of the first motor is controlled to be -1x abs Current engine speed) " x engine inertia) + abs (engine operation torque-intervention request torque) '.

The torque of the second motor is controlled by the torque corresponding to the difference between the transmission output demand torque and the transmission output torque.

Therefore, according to the mode switching and shifting control method of the present invention, appropriate torque control for each drive source is performed during torque intervention control, thereby minimizing energy loss during mode switching or shifting and maximizing operability. .

Particularly, when the mode is switched or the speed of the transmission is changed, the transmission rotation speed and the torque are controlled by using the first motor, and the optimal torque control of the engine is performed to reduce the excessive loss and reduce the slip loss using the fluid And the second motor can be utilized during the transient control time extended by the control of the rotation speed to compensate the heterogeneity of the driving force.

Further, by performing the engine torque control using the air amount when the output of the first motor for torque intervention is limited, it is possible to improve the efficiency of the engine due to the ignition timing control, Mode switching and shift control can be performed.

FIG. 1 is a flowchart showing a mode switching and shifting control method according to the present invention.
2 and 3 are conceptual diagrams of mode switching and shift control in a serial-parallel hybrid system having a two-stage speed reduction mechanism.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains.

It is an object of the present invention to provide a mode switching and a shift control method capable of minimizing energy lost during a direct-to-parallel mode switching operation or a shift operation and maximizing operability in a hybrid vehicle having two motors and a two- will be.

The hybrid vehicle to which the present invention is applied is a vehicle in which mode switching between direct and parallel using an engine and two motors MG1 and MG2 is performed. The hybrid vehicle is directly connected to the engine and the first motor MG1 so as to transmit power, And a two-stage reduction mechanism (transmission) is interposed between the first and second motors MG2.

As described above, in the hybrid system using the engine and the two motors, the engine and the first motor are disposed on the transmission input side, and the second motor is disposed on the transmission output side.

In the hybrid system described above, it is possible to implement a series mode in which only the power of the motor is used for driving the vehicle and a parallel mode in which the engine power is used, and in the serial mode and the parallel mode Can be selectively used.

In the series mode, the clutch of the transmission is disengaged so that the power of the front end of the transmission is not transmitted to the driving shaft of the vehicle. At this time, only the power of the second motor is transmitted to the driving shaft of the vehicle and used for driving the vehicle.

In this series mode, only the second motor is driven, or the engine is driven in a state where the power is disconnected by the transmission, so that the engine power is transmitted to the first motor, and at the same time, the first motor is driven by the power transmitted from the engine, Can be charged.

On the other hand, in the parallel mode, the clutch of the transmission is joined, and the power of the engine can be transmitted to the drive shaft of the vehicle through the transmission. It is possible to satisfy the driver's required torque by using the power of the engine and the second motor together.

In addition, since the transmission is implemented as a two-speed reduction gear mechanism, it is possible to perform shift control in one stage (UD: Underdrive) and two stages (OD: Overdrive) in the parallel mode.

In a hybrid system having two motors and a two-speed transmission (deceleration mechanism) as described above, torque intervention control for reducing the input torque of the transmission is required when switching between direct-parallel modes or parallel transmission is required. In the torque intervention control, Appropriate control strategies are needed.

Accordingly, the present invention proposes a mode switching and shift control method and a torque intervention control method that maximize fuel consumption and driving performance, and an optimal torque control method for each drive source when a mode is switched and a shift is requested.

In the present invention, the torque intervention is performed through the torque control of the engine and the first motor when the mode switching and the shift is requested (the torque intervention is the engine and the first motor), and when the torque intervention control of the engine and the first motor is performed, So that it is possible to improve the drivability and drivability.

More specifically, referring to FIG. 1, a torque intervention control for reducing a transmission input torque at the time of a mode change or a shift is required.

First, the minimum torque (negative torque) of the first motor in consideration of the battery charge state (SOC) is -1x abs ((engine target revolution speed - engine current revolution speed) x engine inertia) + abs - Intervention request torque) ', the reduction of the input torque of the transmission can be compensated only by the power generation operation of the first motor, so that the transmission input torque is reduced only by the power generation operation of the first motor without reducing the engine torque.

At this time, the engine torque is controlled to a torque value set as the optimum operating point, that is, the fuel efficiency optimum torque. In the case of the first motor, the torque at the time of power generation is controlled to be -1x abs (engine target revolution speed - engine current revolution speed) ) + abs (engine operation torque-intervention request torque) ", and for the second motor, the torque corresponding to the difference between the transmission output demand torque and the transmission output torque is controlled.

Here, 'abs ()' represents an absolute value.

In addition, during shift and mode switching, the rotational speed control is performed through slip control of a normal clutch and brake.

On the other hand, when the mode switching or the shift is requested, the minimum torque (negative torque) during power generation of the first motor in consideration of the battery charge state (SOC) is -1x abs Engine inertia) + abs (engine operation torque - intervention request torque) ', limit the torque at the time of power generation of the first motor within the allowable range while reducing the engine torque.

That is, the engine torque is controlled by the sum of the transmission input required torque and the torque of the first motor (negative torque). At this time, the engine torque control by the intake air amount control is performed instead of the torque control through the ignition timing control .

When the torque control is performed by using the intake air amount control to reduce the output torque of the engine as described above, unnecessary fuel consumption can be reduced compared to controlling the engine torque through the ignition timing control as in the prior art, have.

The torque of the first motor is controlled by the minimum torque of the first motor in consideration of the state of charge of the battery and the torque of the second motor is controlled by the torque corresponding to the difference between the transmission output demand torque and the transmission output torque.

In addition, during shift and mode switching, the rotational speed control is performed through slip control of a normal clutch and brake.

When the mode changeover or the shifting is completed, the normal torque control for the drive source, that is, the engine torque is the fuel efficiency optimum torque, the first motor is the torque corresponding to the difference between the transmission input required torque and the engine torque, And is controlled by the torque corresponding to the difference between the output demand torque and the transmission output torque.

In the present invention, when the mode switching and the shifting are performed, the torque required for the transmission input side and the torque required for controlling the engine speed are compared with the minimum torque of the first motor (negative torque and maximum torque when expressed in absolute value) So that it is possible to improve the driving performance by the detailed performance tuning through the control of the second motor mounted on the output side of the transmission.

FIG. 2 is a conceptual view of mode switching and shift control in a serial-parallel hybrid system having a two-stage speed reduction mechanism. FIG. 2 illustrates the speed and torque control state of the engine and the second motor when switching from the serial mode to the parallel mode is performed. (Based on engine and motor output shaft).

Referring to FIG. 2, in the engine speed control section of (2), the engine is controlled so as to maintain the torque in the series mode, wherein the speed of the first motor is controlled at the engine speed, and the second motor is controlled at the drive torque in the serial mode do.

Further, in the torque blending period of (3), the engine torque is controlled so as to follow the parallel mode torque, wherein the torque of the first motor is controlled to satisfy the required torque intervention through the battery charging operation (power generation operation) , The output of the second motor is controlled to be reduced.

3 is a diagram illustrating speed and torque control states of the engine and the second motor when shifting from the first stage (UD) to the second stage (OD) is performed (on the basis of the engine and the motor output shaft).

Referring to FIG. 3, in the torque blending period of (2), the engine is controlled so as to maintain the one-step torque at the speed change end, wherein the first motor is controlled to satisfy the required torque intervention through the battery charging operation The torque of the second motor is controlled so as to follow the wheel demand output.

Further, in the speed control period of (3), the engine is controlled so as to maintain the one-step torque at the speed change end, the first motor absorbs the engine output through charging (power generation), and the torque of the second motor is controlled to the wheel required output .

Further, in the torque blending period of (4), the engine is controlled so as to output the two-step torque at the speed change end, wherein the first motor is controlled to satisfy the torque intervention through charging (power generation operation), and the output of the second motor Respectively.

As described above, in the control method according to the present invention, the optimal torque control of the engine is performed to control the transmission input rotation speed and the torque at the time of mode switching or shifting using the first motor to reduce the excessive loss, The second motor is used during the transient control time increased by the rotation speed control while reducing the slip loss using the transmission oil.

Further, by performing the engine torque control using the air amount when the output of the first motor for torque intervention is limited, it is possible to improve the efficiency of the engine due to the ignition timing control, Mode switching and shift control can 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. Forms are also included within the scope of the present invention.

Claims (4)

A method of controlling a direct-to-parallel mode switching and a speed change of a hybrid vehicle having a power train configuration in which an engine and a first motor are directly connected to each other so as to be able to transmit power and a transmission is interposed between an engine and a second motor (MG2)
In the case of the direct-parallel mode switching or shift request,
For torque intervention to reduce the transmission input torque,
The minimum negative torque of the first motor in consideration of the battery charge state (SOC) is -1 x abs (engine target revolution speed - engine current revolution number) x engine inertia) abs (engine operation torque - intervention required torque) Or more,
The engine torque is controlled by the sum of the transmission input required torque and the torque of the first motor (negative torque), and the torque of the first motor is controlled to the negative minimum torque in consideration of the state of charge of the battery. And a control method for shifting.
The method according to claim 1,
Wherein the engine torque control is performed by controlling the amount of intake air.
The method according to claim 1,
For torque intervention to reduce the transmission input torque,
The minimum negative torque of the first motor in consideration of the battery charge state (SOC) is -1 x abs (engine target revolution speed - engine current revolution number) x engine inertia) abs (engine operation torque - intervention required torque) If less,
The engine torque is controlled to a torque value set as the optimum operating point, and the torque of the first motor is -1 x abs ((engine target revolution number - engine current revolution number) x engine inertia) + abs Torque ")".< / RTI >
The method according to any one of claims 1 to 3,
Wherein the torque of the second motor is controlled by a torque corresponding to the difference between the transmission output demand torque and the transmission output torque.

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