KR101013879B1 - Braking control method of hybrid electric vehicle - Google Patents

Abstract

The present invention relates to a braking control method of a hybrid vehicle, by reducing the reverse torque magnitude of the drive motor in advance even if the regenerative braking amount is lost during rapid deceleration braking, so that the friction braking device compensates the reverse torque reduction amount of the drive motor. The present invention relates to a braking control method of a hybrid vehicle that prevents a deterioration of braking performance and driving performance due to a reduction of vehicle deceleration force, and in particular, solves a problem that a vehicle is pushed during sudden deceleration braking.

Hybrid, Braking, Rapid Deceleration, Vehicle Controller, Motor Controller, Friction Braking System, Motor Reverse Torque, Friction Braking Force, Regenerative Braking, Motor Charge, Deceleration

Description

Braking control method of hybrid electric vehicle

The present invention relates to a braking control method for a hybrid vehicle, and more particularly, even if the regenerative braking amount is lost during rapid deceleration braking, the reverse torque reduction of the drive motor is reduced in advance, and the friction braking device reduces the reverse torque reduction amount of the drive motor. By compensating, the present invention relates to a braking control method of a hybrid vehicle that prevents a deterioration in braking performance and driving performance due to a reduction in vehicle deceleration force, and in particular, solves a problem that a vehicle is pushed during sudden deceleration braking.

A hybrid vehicle means an efficient combination of two or more different power sources to drive a vehicle, but in most cases, an engine that burns fuel (fossil fuel such as gasoline) to obtain torque and an electric motor that obtains torque by battery power Means a vehicle driven by.

This hybrid vehicle is a futuristic vehicle that adopts not only an engine but also an electric motor as an auxiliary power source to reduce emissions and improve fuel efficiency, and is actively researching in response to the request of the times to improve fuel efficiency and develop environmentally friendly products. It is becoming.

Hybrid vehicles are EV (Electric Vehicle) mode, which is a pure electric vehicle mode that uses only electric motor (drive motor) power, HEV (Hybrid Electric Vehicle) mode, which uses the rotational power of the engine as auxiliary power while the rotational power of the engine is the main power, When the vehicle is driven by braking or inertia, the vehicle travels in a driving mode such as regenerative braking (RB) mode in which braking and inertia energy is recovered through generation of the driving motor and charged in a battery.

As described above, in the hybrid vehicle, the mechanical energy of the engine and the electrical energy of the battery are used together, and the optimum operating area of the engine and the driving motor is used, and the energy is recovered by the driving motor during braking, thereby improving fuel efficiency and efficient energy use.

The hybrid vehicle is equipped with a hybrid control unit (HCU), and has a controller for each device constituting the system.

For example, an engine control unit (ECU) for controlling the overall operation of the engine, a motor control unit (MCU) (including an inverter) for controlling the overall operation of the driving motor, a transmission controller for controlling the transmission (CVT) (Transmission Control Unit (TCU)), a battery controller (Battery Management System (BMS)) that monitors and manages the battery status, and an air conditioner controller (Full Auto Temperature Controller, FATC) in charge of room temperature control.

Here, the HCU is a top-level controller in charge of driving control of each controller, hybrid driving mode setting, and overall vehicle control. Each of the controllers is connected to a high-speed CAN communication line centering on the HCU, which is the top-level controller. The upper controller is to transmit commands to the lower controller while exchanging information between them.

Next, the configuration of the hybrid vehicle will be described. As shown in FIG. 1, the engine 10, the electric motor (drive motor) 20, and the automatic transmission 30 have a layout arranged in a line.

In particular, the engine 10 and the drive motor 20 are connected to the power transmission in the state via the engine clutch 50, the drive motor 20 and the automatic transmission 30 are directly connected to each other. In addition, an integrated starter generator (ie, an integrated starter & generator) 40 that provides rotational force (ie, outputs a cranking torque) to the engine 10 at start-up, is connected to the engine 10.

In such a configuration, the driving force is obtained only by the driving motor 20 at the time of starting the vehicle or at low speed, and since the engine efficiency is lower than the motor efficiency at the initial starting, the driving motor 20 having better efficiency than the engine 10 is used. It is advantageous in terms of fuel economy of the vehicle to start the initial start of the vehicle (vehicle oscillation). After the vehicle starts, the ISG 40 starts the engine 10 so that the engine output and the motor output can be used simultaneously.

As described above, the hybrid vehicle uses the electric vehicle (EV) mode, which is a pure electric vehicle mode using only the rotational force of the driving motor 20, and the rotational force of the driving motor 20 while the rotational force of the engine 10 is the main driving force. The vehicle is driven in an operation mode such as a hybrid electric vehicle (HEV) mode used as an auxiliary power, and a mode change from the EV mode to the HEV mode is performed by starting the engine 10 by the ISG 40.

On the other hand, the hybrid vehicle enters the regenerative braking mode when braking while driving. At this time, the driving motor generates a reverse torque (reverse torque) in the rotational direction, thereby generating electrical energy. That is, the driving motor generates power by using the vehicle's regenerative energy and the like to charge the high voltage battery. In this case, the driving motor rotates with the reverse torque applied.

Deceleration force during braking while driving in a hybrid vehicle (represented as total deceleration torque in FIG. 2) is as shown in Equation (1) below.

Deceleration Force = Friction Braking Force + Motor Reverse Torque (1)

Here, the friction braking force means a braking force generated by pushing the friction type brake device configured in the wheel with friction as in a conventional vehicle, and the motor reverse torque means that the motor applies torque in a direction opposite to the traveling direction of the vehicle.

At this time, the electricity generated by the motor is as shown in Equation (2) below.

Motor power generation = motor speed × motor reverse torque (2)

In a hybrid vehicle, the amount of generated power of the motor is kept to the maximum as possible to improve fuel efficiency. For this purpose, the reverse torque of the driving motor is applied to the maximum value in the possible range.

However, in the hybrid vehicle as shown in FIG. 1, when the speed of the vehicle decreases due to braking, the shift is performed to restart starting performance or to charge at a more efficient motor driving point, in order to maximize regenerative braking during shifting. If the reverse torque applied is maintained as it is, shifting is not performed smoothly.

Therefore, when the vehicle decelerates as described above, the shift should be performed. In this case, the reverse torque of the drive motor should be reduced. If the reverse torque of the drive motor is too large, the life of the internal clutch of the transmission is also shortened, and the shift is smoothly performed. Not done. In extreme cases, the clutch inside the transmission slips, causing the drive motor to rotate in reverse.

That is, when the transmission performs the shift in the state in which reverse torque is applied, the transmission force of the clutch inside the transmission is lowered. At this time, when the reverse torque is stronger than the clutch transmission force in the transmission, the input shaft of the transmission rotates in the reverse direction. There is a case.

The reverse rotation of the transmission input shaft as described above is not generally considered in the design of the transmission. Such reverse rotation may cause problems in bearings and lubricants inside the transmission. Result in enemy damage.

In particular, when the transmission input RPM (revolution per minute) becomes negative (reverse rotation) in a transmission using a one-way clutch, there is no device for returning it to positive (reverse rotation) again. Serious transmission damage is caused.

In addition, even when the drive motor does not rotate in reverse, when the transmission is downshifted, when the reverse value of the motor torque is large and the transmission input RPM becomes low, durability is shortened due to an increase in the clutch slip amount inside the transmission. There is this.

For example, if the gearbox input RPM increases from 1000rpm to 2000rpm during the 4th to 3rd gearshifts, and if the transmission input RPM proceeds from 1000rpm to 500rpm during the shifting to 2000rpm due to the negative value of the drive motor torque, The clutch slip is increased from 500 rpm to 2000 rpm, not from 1000 rpm to 2000 rpm, which reduces the durability of the transmission.

For the same reason, in the initial stage of shift progress, a request is made to reduce the reverse torque of the drive motor. When the reverse torque of the drive motor is reduced, the deceleration force is reduced as in the above formula, and the reverse torque is reduced so that the deceleration force is not reduced. The frictional braking force should be increased by decreasing.

If the deceleration force is not compensated by the friction braking device of the vehicle as much as the reverse torque of the driving motor is reduced, the deceleration force of the vehicle is lowered, and a feeling of being pushed forward during braking occurs.

However, the rate of change of the deceleration force that can be increased by the friction braking device of the vehicle is limited. Accordingly, when the vehicle decelerates slowly, the shift braking time is sufficient to allow the friction braking device to sufficiently compensate for the reverse torque reduction of the driving motor. However, when the vehicle decelerates rapidly, the shift braking time is shortened. The reverse torque reduction amount of the drive motor cannot be compensated sufficiently.

As a result, a sudden deceleration may cause the vehicle to be pushed. In other words, if the reverse torque of the driving motor decreases faster than the friction braking force is increased, the reduction of the deceleration force of the vehicle occurs, and the feeling of the vehicle being pushed occurs.

2 is a view showing a state when the vehicle is slowly decelerating. When the vehicle is slowly decelerated, the shift time is sufficient, and the motor reverse torque is slowly decreased, and this shows that the friction braking force is sufficiently compensated.

In addition, Figure 3 is a diagram showing the state during rapid deceleration of the vehicle, if the vehicle decelerates rapidly, the shift time is insufficient, the friction braking force is not enough to compensate for the reduction of the motor reverse torque, thereby causing the vehicle during braking This feeling of thrust occurs.

Therefore, the present invention has been invented to solve the above problems, preventing the deterioration of braking performance and driving performance due to the reduction of the vehicle deceleration force during rapid deceleration braking, and in particular, the problem that the vehicle is pushed during sudden deceleration braking. It is an object of the present invention to provide a braking control method for a hybrid vehicle that can solve the problem.

In order to achieve the above object, the present invention includes the steps of calculating the deceleration by calculating the rate of change of the vehicle speed during vehicle braking during vehicle braking, and determining whether or not the sudden deceleration that the calculated deceleration is more than the reference value; When the sudden deceleration is determined, applying the motor reverse torque command value according to the calculated deceleration to the motor controller, and performing the motor braking by the motor controller to reduce the motor reverse torque in advance according to the command value; And simultaneously applying the friction braking force of the friction braking device to compensate for the braking amount by the amount of motor reverse torque reduced in advance at the driver's required total braking amount at the same time as the motor braking. Provide a control method.

In a preferred embodiment, the motor reverse torque command value for reducing the motor reverse torque in advance is set smaller as the deceleration is inversely proportional to the deceleration.

The performing of the friction braking may include: calculating, by the vehicle controller, the total amount of braking required by the vehicle controller; The vehicle controller calculates a friction braking force command so that the friction braking amount is 'driver's total braking amount-motor braking amount' and applies the command value to the friction braking device controller so that the friction braking device controller is reduced in advance. Controlling the friction braking device such that the friction braking force is applied in advance by an amount of torque; And then controlling, by the friction braking device, the friction braking device to increase the friction braking force so as to compensate for the motor reverse torque that is reduced as the motor reverse torque is reduced.

Accordingly, according to the braking control method of the hybrid vehicle according to the present invention, even if the regenerative braking amount is lost during rapid deceleration braking, the reverse torque of the drive motor is reduced in advance, and the friction braking device compensates the reverse torque reduction amount of the drive motor. By doing so, it is possible to prevent the deterioration of braking performance and deterioration of driving performance due to the reduction of the vehicle deceleration force, and in particular, it is possible to solve the problem that the feeling of pushing the vehicle during sudden deceleration braking occurs.

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

The present invention relates to a braking control method of a hybrid vehicle, and to a method for reducing a regenerative braking amount (motor generation amount (generation amount of a driving motor) or motor charging amount (battery charge amount by a driving motor)] according to a deceleration of the vehicle during braking. In the case of a rapid deceleration of a vehicle in a hybrid vehicle, the main point is that the friction braking device compensates the reverse torque reduction amount of the driving motor even in a short shifting time, and the deceleration of the vehicle is calculated to calculate the deceleration of the driving motor. By reducing the reverse torque in advance, it is intended to prevent the deterioration of braking performance and deterioration of driving performance due to the reduction of the deceleration force of the vehicle.

4 is a system configuration diagram for implementing the present invention, in which a vehicle controller (HCU) 1, a motor controller (MCU) 2, and a brake control unit (BCU) 3 are mutually connected. The cooperative control process of the present invention is implemented, and the friction braking device 60 in the figure becomes a friction type brake device configured on a wheel in a typical hybrid vehicle. In the following description, reverse torque of the drive motor means that the drive motor applies torque in a direction opposite to the traveling direction of the vehicle.

As shown in FIG. 4, the driving motor 20 receives power of a battery to provide power for driving a vehicle (battery discharge), and also recovers and stores energy through generation of power during battery braking (battery charging). .

In the present invention, as shown in Fig. 4, the vehicle controller 1 calculates the rate of change of the vehicle speed per hour to calculate the deceleration, and determines whether or not the sudden deceleration at which the calculated deceleration becomes equal to or greater than the reference value.

If the deceleration braking is less than the reference value (slow deceleration), do not limit the size of the motor reverse torque so as to obtain as much regenerative braking energy as possible (see Fig. 2), when the abrupt deceleration braking is more than the reference value ( In the case of sudden deceleration), even though the loss of the regenerative braking amount is taken, the control which focuses more on improving the braking performance by limiting the magnitude of the motor reverse torque is performed (see FIG. 5).

5 is a view illustrating a control state of the motor reverse torque and the friction braking force during rapid deceleration of the vehicle according to the present invention. In the present invention, the motor reverse torque is limited and reduced according to the deceleration.

The reason why the sudden deceleration control is performed is that the rate of increase of the friction braking force per hour is limited by the system. Therefore, during sudden deceleration braking, the motor reverse torque should be eliminated within a short time and braking only with the friction braking force (eg, Even if a shift occurs, it is impossible to increase the friction braking force by the motor reverse torque in the short time.

In such a rapid braking situation, it is highly likely that braking only with the friction braking force should be eliminated and the motor reverse torque should be eliminated within a short time. Therefore, it is not necessary to eliminate the motor reverse torque and braking only with the friction braking force. It is to improve the braking performance even if the regenerative braking amount is reduced by applying the friction braking force in advance to reduce and compensate the motor reverse torque.

6 is a flowchart illustrating a control process according to the present invention. In the present invention, the vehicle controller 1 determines whether the vehicle decelerates rapidly during braking, and calculates the deceleration rate by calculating an hourly rate of change of the vehicle speed. do. That is, after the vehicle controller 1 calculates the deceleration, it determines the sudden deceleration time when the deceleration becomes more than the reference value based on the calculated deceleration.

Of course, since the vehicle controller 1 already uses the vehicle speed signal and the brake pedal signal for various control processes of the vehicle, it is easily understood by those skilled in the art to calculate the deceleration rate by calculating the rate of change of the vehicle speed per hour at the time of braking. Of course, the deceleration is the rate of negative change in vehicle speed per hour.

In addition, the vehicle controller 1 calculates the deceleration and calculates the total braking amount required by the driver, and also calculates the motor reverse torque command value (that is, the negative torque command value) preset according to the deceleration. To the controller 2.

The motor controller 2 controls the driving motor 20 according to the motor reverse torque command value, and at this time, the motor braking which reduces the motor reverse torque (motor charging torque, regenerative braking motor torque) according to the vehicle deceleration during braking. Let this be done.

In addition, the vehicle controller 1 calculates a friction braking force command so that the friction braking force becomes 'the driver's required total braking amount-motor braking amount (a value corresponding to the motor reverse torque)' and applies it to the friction braking device controller 3. Therefore, the friction braking device controller 3 controls the friction braking device 60 to generate the friction braking force according to the command value.

As described above, in the present invention, the braking of the vehicle is performed by grabbing the difference of the braking amount using the motor charging from the total braking amount at the time of braking and deceleration of the hybrid vehicle, and the rate of change of the vehicle speed increases in the negative direction. As a result, the reduction in motor charge (regenerative braking) during braking is focused on improving braking performance.

In the case of rapid deceleration braking of the vehicle, the motor reverse torque is reduced in a predetermined ratio after the reduction as mentioned above, and the friction braking force is applied in advance to compensate for the amount by which the motor reverse torque is reduced in advance, and then the motor reverse torque is reduced. Gradually increase accordingly.

As described above, the motor reverse torque command value is set according to the deceleration of the vehicle. As the deceleration of the vehicle increases (it is a negative rate of change per hour), the motor reverse torque command value is set relatively small. If the amount of motor reverse torque is determined in inverse proportion to the deceleration of the vehicle, the amount of motor reverse torque has already been partially reduced at the time of sudden deceleration (the friction braking force for compensating as much as the motor reverse torque is reduced in advance). In the applied state), it is possible to reduce the motor reverse torque at a constant rate even in a short shift time, and the friction braking force is sufficiently compensated so that there is no variation in the total braking force of the vehicle.

1 is a schematic diagram showing the configuration of a hybrid vehicle;

2 is a view showing a motor reverse torque and a friction braking force control state during slowing and deceleration in a conventional hybrid vehicle;

3 is a view for explaining the problems of the prior art, showing a motor reverse torque and friction braking force control state during sudden deceleration in a conventional hybrid vehicle,

4 is a system configuration diagram for implementing the present invention;

5 is a view illustrating a motor reverse torque and a friction braking force control state during a rapid deceleration of a vehicle according to the present invention;

6 is a flowchart illustrating a control process according to the present invention.

<Explanation of symbols for the main parts of the drawings>

1: vehicle controller 2: motor controller

3: friction braking device controller 10: engine

20: drive motor 60: friction braking device

Claims (5)

delete Calculating, by the vehicle controller, the rate of change of the vehicle speed during braking to calculate the deceleration, and determining whether or not the sudden deceleration is greater than or equal to the reference value; When the sudden deceleration is determined, applying the motor reverse torque command value according to the calculated deceleration to the motor controller, and performing the motor braking by the motor controller to reduce the motor reverse torque in advance according to the command value; At the same time as the motor braking, performing a friction braking for applying the friction braking force of the friction braking device in advance so as to compensate for the braking amount by the amount of the motor reverse torque reduced in advance in the driver's required braking amount; Including; And the motor reverse torque command value for reducing the motor reverse torque in advance is set smaller as the deceleration is inversely proportional to the deceleration. delete Calculating, by the vehicle controller, the deceleration rate by calculating an hourly rate of change of vehicle speed during vehicle braking; Applying a motor reverse torque command value in inverse proportion to the calculated deceleration; The motor controller performing motor braking to reduce the motor reverse torque in advance according to a command value; At the same time as the motor braking, performing a friction braking for applying the friction braking force of the friction braking device in advance so as to compensate for the braking amount by the amount of the motor reverse torque reduced in advance in the driver's required braking amount; Braking control method of a hybrid vehicle comprising a. The method according to claim 4, The friction braking may include: Calculating, by the vehicle controller, the driver required total braking amount; The vehicle controller calculates a friction braking force command so that the friction braking amount is 'driver's total braking amount-motor braking amount' and applies the command value to the friction braking device controller so that the friction braking device controller is reduced in advance. Controlling the friction braking device such that the friction braking force is applied in advance by an amount of torque; Then the friction braking device controller controls the friction braking device to increase the friction braking force so as to compensate for the motor reverse torque reduced as the motor reverse torque is controlled to decrease; Braking control method of a hybrid vehicle, characterized in that comprises a.

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