KR20200108812A - System and method for energy regeneration of mild hybrid electric vehicle - Google Patents

Abstract

The present invention relates to an energy regeneration device of a hybrid vehicle and a method thereof. The main object of the present invention is to provide the energy regeneration device of a hybrid vehicle and the method thereof, which control the speed of a hybrid starter-generator (HSG) to a speed range with high charging efficiency regardless of the speed of an engine in regenerative braking and coasting modes, thereby maximizing charging efficiency and fuel efficiency. To this end, the energy regeneration device of a hybrid vehicle includes: the hybrid starter-generator connected to the engine so as to transmit power; a transmission that shifts the power output from the engine and transmits the power to a drive shaft; an engine clutch for selectively connecting or disconnecting power between the engine and the transmission; a control unit that outputs a control signal for controlling the speed of the hybrid starter-generator that charges a battery by generating electricity during the regenerative braking mode and the coasting mode of the vehicle at a speed obtained from an efficiency map; and a variable speed control device for controlling the speed of the hybrid starter-generator by varying the speed of rotational force transmitted from the drive shaft to the hybrid starter-generator according to the control signal output from the control unit.

Description

TECHNICAL FIELD [System and method for energy regeneration of mild hybrid electric vehicle]

The present invention relates to an energy regeneration device and method for a hybrid vehicle, and more particularly, to control the speed of a hybrid starter-generator (HSG) in a regenerative braking and coasting mode to a speed range with high charging efficiency regardless of the speed of the engine. The present invention relates to an energy regeneration apparatus and method of a hybrid vehicle that can maximize charging efficiency and fuel economy improvement by allowing it to be performed.

The demand for eco-friendly vehicles is increasing in accordance with the constant demand for fuel efficiency improvement for automobiles and the strengthening of emission regulations in each country, and hybrid vehicles are being provided as a realistic alternative to this.

A typical hybrid vehicle is a vehicle that runs using an engine and a motor as a driving source, and it is an eco-friendly vehicle that can reduce exhaust gas and improve fuel efficiency because it uses both fossil fuel energy and electric energy for driving.

Hybrid vehicles can be classified into mild type and hard type according to the use ratio of the power source, and mild type hybrid vehicles (Mild HEV) use the engine as the basic driving source, while the motor assists torque. In the case of a hard type hybrid vehicle (Hard HEV), the engine assists torque while driving with a motor as a basic driving source.

Among them, the power train configuration of a typical mild hybrid vehicle (Mild HEV) is shown in FIG. 1.

As shown in FIG. 1, the power train configuration of a mild hybrid vehicle is an engine that serves as a driving source for driving a vehicle, and is connected to the engine to transmit power through a belt or the like to start the engine or receive power from the engine to generate power. A hybrid starter and generator (HSG) to perform, a transmission that shifts the power output through the engine and transmits it to the drive shaft, and an engine clutch that selectively connects or cuts power between the engine and the transmission. do.

In this configuration, the hybrid starter-generator (hereinafter referred to as'HSG') not only serves as a starter to start the engine, but also serves as a generator to charge the battery by generating rotational force transmitted from the engine during vehicle braking or driving. During vehicle acceleration, it is also used as a motor that assists engine output (torque) as an auxiliary drive source for driving the vehicle.

In such a mild hybrid vehicle, there is no EV (Electric Vehicle) mode that uses only the power of the motor during starting or driving, and regenerative braking that recovers the vehicle's energy to the battery through HSG while the engine clutch is attached when braking the vehicle. It has a Regenerative Braking mode and a Coasting mode in which the engine is turned off and the engine clutch is disconnected when driving in other lines.

In general, when the driver takes off the accelerator pedal (Accel Pedal Off) and presses the brake pedal (Brake Pedal On) for the purpose of decelerating the vehicle, the regenerative braking mode is executed, and in the regenerative braking mode, the engine is fuel cut. In addition to the state, the engine clutch continues to be engaged during the vehicle inertial driving, so that the rotational force of the drive wheels and the drive shaft is transmitted to the engine through the transmission.

At this time, while the frictional resistance of the engine acts, regenerative braking is performed in which HSG receives the rotational force of the engine through the belt and power generation is performed, and the generation operation and rotational resistance of the motor (HSG) together with the frictional resistance of the engine are performed. The electric braking force (regenerative braking force) is applied and the vehicle is decelerated, and the electric energy generated by the generation of HSG is stored in the battery.

Such a regenerative braking mode is for the purpose of braking the vehicle, and thus reduces the vehicle's moving distance by decelerating the vehicle, but recovers the vehicle's energy as electric energy, thereby improving fuel economy.

Of course, the portion of the braking force required by the driver that is insufficient only by the regenerative braking force is satisfied by using the frictional braking force (hydraulic braking force) of a brake device (eg, hydraulic brake) mounted on the wheel.

In addition, when the driver releases both the accelerator and brake pedals (Accel Pedal Off, Brake Pedal Off), the coasting mode is executed. In the coasting mode, the engine is turned off and the vehicle is inertial driving. Since the engine clutch is disconnected and the connection between the engine and the transmission remains disconnected, the frictional resistance of the engine is not transmitted to the vehicle.

As the frictional resistance of the engine that hinders the vehicle's driving is not transmitted in this way, the vehicle's travel distance may be extended, but the driving force that drives the HSG, that is, the rotational force transmitted through the belt from the engine, does not exist. It cannot be done.

Meanwhile, in a hybrid vehicle, the HSG is connected to the shaft of the engine by a belt, and the speed of the HSG (revolution) is determined according to the engine speed (revolution).

Therefore, in the conventional energy regeneration process, energy regeneration through HSG in coasting mode is not possible, and even in regenerative braking mode, the speed of HSG cannot be controlled to a high-efficiency speed range regardless of engine speed. It is impossible to maximize efficiency).

Accordingly, the present invention was created to solve the above problems, and in regenerative braking and coasting modes, the speed of HSG can be controlled to a speed range with high charging efficiency regardless of the speed of the engine, thereby reducing charging efficiency and fuel efficiency. An object of the present invention is to provide an energy regeneration apparatus and method for a hybrid vehicle that can maximize the improvement.

In addition, even in coasting mode while the vehicle is driving, a hybrid that can improve fuel efficiency of the vehicle by controlling the driving of HSG while minimizing the loss of the vehicle's travel distance and recovering energy while the battery can be charged. An object of the present invention is to provide an apparatus and method for regenerating energy in a vehicle.

In order to achieve the above object, according to an aspect of the present invention, a hybrid starter-generator connected to be capable of transmitting power to an engine; A transmission for transferring the power output from the engine to a drive shaft; An engine clutch for selectively connecting or disconnecting power between the engine and the transmission; A control unit for outputting a control signal for controlling the speed of the hybrid starter-generator for charging the battery by generating electricity during the regenerative braking mode and the coasting mode of the vehicle at a speed obtained from the efficiency map; And a variable speed control device for controlling the speed of the hybrid starter-generator by varying the speed of rotational force transmitted from the drive shaft to the hybrid starter-generator according to the control signal output from the control unit. to provide.

And, according to another aspect of the present invention for achieving the above object, when the control unit enters the regenerative braking mode or the coasting mode, the speed of the hybrid starter-generator that generates electricity and charges the battery is obtained from the efficiency map. Outputting a control signal for controlling by; And controlling the speed of the hybrid starter-generator by varying the speed of the rotational force transmitted from the drive shaft to the hybrid starter-generator by the variable speed control device according to the control signal output from the control unit. to provide.

Accordingly, according to the energy regeneration apparatus and method of a hybrid vehicle according to the present invention, the speed of the HSG is controlled to a speed region having high charging efficiency regardless of the speed of the engine in the regenerative braking mode, thereby maximizing the improvement of charging efficiency and fuel economy. do.

In addition, even in the coasting mode of a hybrid vehicle, it is possible to charge the battery (energy regeneration) by driving HSG in an area with high charging efficiency depending on the state of charge while minimizing the loss of travel distance, thus improving the fuel efficiency of the vehicle. do.

1 is a diagram showing the configuration of a power train of a general mild hybrid vehicle.
2 is a schematic diagram showing the configuration of a hybrid system including an energy regeneration device according to an embodiment of the present invention.
3 is a schematic diagram showing the configuration of a hybrid system including an energy regeneration device according to another embodiment of the present invention.
4 is a flow chart showing an energy regeneration method according to the present invention.
5 is a diagram illustrating an efficiency map showing charging efficiency according to a driving area in the energy regeneration method according to the present invention.
6 is a view for explaining the effect of the energy regeneration method according to the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention.

The present invention maximizes charging efficiency and fuel economy improvement by allowing the speed of a hybrid starter-generator (hereinafter referred to as'HSG') in regenerative braking and coasting modes to be controlled in a speed range with high charging efficiency regardless of the speed of the engine. It is intended to provide an energy regeneration device and method for a hybrid vehicle that can be.

2 is a schematic diagram showing the configuration of a mild hybrid system including an energy regeneration device according to an embodiment of the present invention, and FIG. 3 is a schematic view showing the configuration of a hybrid system including an energy regeneration device according to another embodiment of the present invention It is a schematic diagram.

As shown, the configuration of the mild hybrid system includes an engine 1 serving as a driving source for driving a vehicle, and the engine 1 is connected to the engine 1 to transmit power through a belt 3 or the like to start the engine or HSG (2) for generating power by receiving the transmission, a transmission (4) that shifts the power output through the engine (1) to transmit it to the drive shaft, and selectively selects power between the engine (1) and the transmission (4) It includes an engine clutch 5 that connects or disconnects.

In this configuration, the HSG 2 not only serves as a starter for starting the engine 1, but also serves as a generator for charging a battery (not shown) by generating power transmitted from the engine 1 when the vehicle is running, During vehicle acceleration, it is also used as a motor that assists engine output (torque) as an auxiliary drive source for driving.

In addition, in the regenerative braking mode and the coasting mode, the HSG 2 is powered by the rotational force transmitted from the drive shaft while the power is disconnected from the engine 1 to charge the battery.

In addition, by the configuration of the mild hybrid system described above, the engine alone mode in which the vehicle runs only by driving the engine 1, and the HSG 2 assists the engine output (torque) at the same time as the engine 1 is driven when the vehicle is running. The HEV mode can be implemented, and there is no difference in control of the engine alone mode and the HEV mode compared to a conventional hybrid vehicle.

On the other hand, in the present invention, the rotation shaft of the HSG 2 connected to the engine 1 through the belt 3, that is, the rotation shaft integrally connected to the rotor of the HSG 2 is the input shaft of the transmission 4 (Shaft through which engine driving force is input through engine clutch) and power transmission is possible.

In addition, a variable speed control device capable of controlling the speed of HSG by selectively transmitting the rotational force during vehicle inertia driving from the drive shaft of the vehicle to the HSG(2) and by varying the speed of the rotational force when transmitting the rotational force to the HSG. It is equipped with.

In the present invention, in order to increase the regenerated energy, a variable speed control device is used to move the speed of the HSG 2 to a region having high charging efficiency during energy regeneration.

In this case, the variable speed control device may be configured to change the speed of rotational force transmitted from the drive shaft of the vehicle to the HSG 2 or the rotational force transmitted from the drive shaft to the HSG 2 through the transmission 4 in a manner of varying the gear ratio. have.

In a preferred embodiment, as shown in Fig. 2, the variable speed control device is capable of transmitting power to the engine 1 through a rotating shaft integrally connected to the rotor of the HSG 2, that is, a belt 3 A continuously variable transmission (CVT:) that connects the rotating shaft of the connected HSG (2) to the input shaft of the transmission (4) so that power can be transmitted, but by varying the gear ratio between the HSG (2) and the transmission (4). It can be configured through Continuously Variable Transmission)(6).

At this time, the HSG (2) has a separate clutch means (not shown) between the pulley of the HSG to which the belt (3) is coupled and the rotating shaft of the HSG so that power can be selectively connected or cut off between the engine (1). Built-in, such a clutch means can be of a form similar to an electronic clutch, eg a magnetic clutch, as in an air conditioner compressor.

The adoption of such a magnetic clutch is a configuration that is already applied between the rotational shaft of the compressor and the pulley in the air conditioner compressor, and thus the drawing example or further detailed description will be omitted herein.

The magnetic clutch may be controlled by a transmission control unit (TCU) to be described later or a controller (HCU, ECU, MCU, etc.) mounted on a vehicle.

Or as another embodiment, as shown in Fig. 3, the variable speed control device applies the continuously variable transmission 4a as a transmission that shifts the power output through the engine 1 and transmits it to the drive shaft, and the HSG 2 It can be configured by connecting the rotary shaft of and the input shaft of the continuously variable transmission 4a with a separate clutch 7 interposed therebetween.

The clutch 7 is disengaged when transmitting the power of the engine 1 to the transmission 4 or when the HSG 2 assists the output of the engine 1, and only in the regenerative braking mode or the coasting mode. Is controlled to be done.

In the configuration of Fig. 2, the continuously variable transmission 6 is interposed between the HSG 2 and the transmission 4, and the clutch 7 and the continuously variable transmission 4a are interposed between the HSG 2 and the drive shaft in the configuration of Fig. 3 All can be configured such that the shift controller of the vehicle drives and controls.

At this time, as will be described later, a hybrid controller (HCU: Hybrid Control Unit), which is the highest controller that determines the driving mode of the vehicle, an engine controller (ECU: Engine Control Unit) that controls the engine 1, a shift controller (TCU), Under cooperative control between a battery controller (BMS: Battery Management System) that collects battery status information and a motor controller (MCU: Motor Control Unit) that controls the driving of the HSG (2), when the driving mode is determined, according to the determined driving mode. It is possible to make each component controllable.

Of course, one integrated control unit may be configured to control the operation of each component according to the driving mode.

Meanwhile, FIG. 4 is a flow chart showing an energy regeneration method according to the present invention, and FIG. 5 is a diagram illustrating an efficiency map showing charging efficiency according to a driving area in the energy regeneration method according to the present invention.

6 is a view for explaining the effect of the energy regeneration method according to the present invention.

Hereinafter, the energy regeneration method according to the present invention will be described.

First, when the driver steps on the brake pedal to satisfy the normal regenerative braking entry condition, the driver enters the regenerative braking mode to regenerate energy and charge the battery using the HSG(2). At this time, the speed of the HSG(2) generating power (Rotation speed) is controlled to a region with high charging efficiency during regenerative braking, and a variable speed control device is used to control the speed of the HSG (2).

At this time, the efficiency map as shown in FIG. 5 can be used, and during regenerative braking, the engine 1 is in a fuel cut state by the engine controller (control unit) while the engine clutch 5 is joined. In the second embodiment, the gear ratio of the continuously variable transmission 6 is in a state in which the transmission controller (control unit) separates the clutch means (magnetic clutch) built into the HSG 2 to cut off the power between the engine 1 and the HSG 2. Control to move the speed of HSG(2) to the area with high charging efficiency.

In the embodiment of Fig. 3, the transmission controller (control unit) bonds the clutch 7 between the HSG 2 and the continuously variable transmission 4a, and the continuously variable transmission 4a disposed between the engine 1 and the drive shaft. By controlling the gear ratio, the speed of HSG(2) is moved to the area with high charging efficiency.

In addition, when the driver is not depressing both the accelerator and brake pedals, the driver enters the coasting mode instead of the regenerative braking mode. In the coasting mode, the shift controller (control unit) releases the engine clutch 5 The engine controller (control unit) turns off the engine 1.

In addition, in this state, it is checked whether the battery can be charged from the battery charging state received from the battery controller, and if the battery is in the state of recharging, energy regeneration and battery charging are performed using HSG(2) as in regenerative braking. Control is performed.

That is, in the embodiment of FIG. 2, the speed change controller (control unit) separates the clutch means (magnetic clutch) built into the HSG 2 to cut off the power between the engine 1 and the HSG 2, and the continuously variable transmission 6 ) By controlling the gear ratio of HSG 2 to move the speed of the HSG 2 to the area with high charging efficiency, and in the embodiment of FIG. 3, the transmission controller (control unit) is the clutch 7 between the HSG 2 and the continuously variable transmission 4a. In addition to bonding, by controlling the gear ratio of the continuously variable transmission 4a disposed between the engine 1 and the drive shaft, the speed of the HSG 2 is moved to a region with high charging efficiency.

On the other hand, if the battery cannot be charged, energy regeneration using HSG(2) is not performed.

Of course, in the case of the embodiment of FIG. 2, in the case of the embodiment of FIG. 2, the engine clutch 5 is engaged and In the engaged state of the magnetic clutch built in the HSG 2 (power cut off from the continuously variable transmission 6), and in the case of the embodiment of Fig. 3, the engaged state of the engine clutch 5 and the HSG 2 and the continuously variable transmission 4a The engine 1 is driven or the engine 1 and the HSG 2 are driven together with the clutch 7 disconnected between ).

In addition, in the regenerative braking mode and the coasting mode, the regenerative torque (charging torque, power generation torque) control of the HSG 2 may be set to be in charge of the motor controller as in a normal case.

In this way, in the present invention, the speed of the HSG 2 in the regenerative braking mode is controlled to a speed region having a high charging efficiency regardless of the speed of the engine 1, thereby maximizing charging efficiency and fuel efficiency improvement.

In addition, even in the coasting mode of the hybrid vehicle, as shown in Fig. 6, the battery can be charged (energy regeneration) by driving the HSG 2 in a region with high charging efficiency according to the battery charging state while minimizing the loss of the travel distance. It is possible to improve the fuel efficiency of the vehicle.

As the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by the person skilled in the art using the basic concept of the present invention defined in the following claims The form is also included in the scope of the present invention.

1: engine 2: HSG
3: belt 4: transmission
4a: continuously variable transmission (CVT) 5: engine clutch
6: continuously variable transmission (CVT) 7: clutch

Claims (4)

A hybrid starter-generator connected to the engine to be powered;
A transmission for transferring the power output from the engine to a drive shaft;
An engine clutch for selectively connecting or disconnecting power between the engine and the transmission;
A control unit for outputting a control signal for controlling the speed of the hybrid starter-generator for charging the battery by generating electricity during the regenerative braking mode and the coasting mode of the vehicle at a speed obtained from the efficiency map; And
A variable speed control device for controlling a speed of a hybrid starter-generator by varying a speed of rotational force transmitted from a drive shaft to the hybrid starter-generator according to a control signal output from the control unit,
The variable speed control device,
The rotation shaft of the hybrid starter-generator is connected to the input shaft of the transmission so that power can be transmitted,
As the transmission, a continuously variable transmission is provided to change the speed of rotational force by varying the gear ratio,
The energy regeneration device of a mild hybrid vehicle, characterized in that the hybrid starter-generator is configured by interposing a clutch for connecting or blocking power between the rotation shaft of the generator and the input shaft of the continuously variable transmission.
The method according to claim 1,
The clutch of the variable speed control device is operated to connect power between the rotation shaft of the hybrid starter-generator and the input shaft of the continuously variable transmission by a control signal output from the control unit in the regenerative braking mode and the coasting mode of the vehicle. Hybrid vehicle energy regeneration device.
Outputting a control signal for controlling the speed of the hybrid starter-generator for charging the battery by power generation when the controller enters the regenerative braking mode or the coasting mode to a speed obtained from the efficiency map; And
Controlling the speed of the hybrid starter-generator by varying the speed of the rotational force transmitted from the drive shaft to the hybrid starter-generator by the variable speed control device according to the control signal output from the control unit,
The variable speed control device,
The rotation shaft of the hybrid starter-generator is connected to the input shaft of the transmission so that power can be transmitted,
As the transmission, a continuously variable transmission is provided to change the speed of rotational force by varying the gear ratio,
The energy regeneration method of a mild hybrid vehicle, characterized in that the hybrid starter-generator is configured by interposing a clutch for connecting or blocking power between the rotation shaft of the generator and the input shaft of the continuously variable transmission.
The method of claim 3,
The clutch of the variable speed control device is operated to connect power between the rotation shaft of the hybrid starter-generator and the input shaft of the continuously variable transmission by a control signal output from the control unit in the regenerative braking mode and the coasting mode of the vehicle. Hybrid vehicle energy regeneration method.

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