KR102630989B1 - Method of controlling regenerative braking for vehicle - Google Patents

Abstract

A method for controlling regenerative braking of a vehicle is disclosed. The regenerative braking control method for a vehicle according to this embodiment includes a first mode in which only regenerative braking force is provided as the driver applies pressure to the brake pedal, a second mode in which both hydraulic braking force and regenerative braking force are provided, and the regenerative braking force is reduced. , a third mode in which the hydraulic braking force increases, and a fourth mode in which the provision of the regenerative braking force is stopped and only the hydraulic braking force is provided, between the master cylinder and the normally open type inlet valve provided on the inlet side of each wheel cylinder. The normally open type traction control valve provided can be switched to and maintained in a closed state throughout the first to fourth modes.

Description

{METHOD OF CONTROLLING REGENERATIVE BRAKING FOR VEHICLE}

The present invention relates to a regenerative braking control method for a vehicle, and more specifically, to a regenerative braking control method for a vehicle that can stably and effectively perform regenerative braking even in a mechanical braking device.

Vehicles are essentially equipped with a brake system to perform braking, and various types of brake systems are being proposed to ensure the safety of drivers and passengers.

In addition, recently, as the market demand for eco-friendly vehicles has increased, the popularity of electric or hybrid driven vehicles has increased. These vehicles recover kinetic energy as electrical energy during braking and store it in the battery. Afterwards, a regenerative braking system is installed to assist in driving the vehicle.

The existing regenerative braking system is designed to distribute the remaining braking force of the electric motor that performs regenerative braking from the driver's braking request, so that the electronic braking device distributes the remaining braking force, which controls the vehicle's braking force regardless of the amount of displacement of the brake pedal. It could only be implemented on the device.

Meanwhile, today, there is still consumer demand not only for high-spec or high-performance vehicles, but also for economical compact cars or commercial vehicles, and compact cars or commercial vehicles are sometimes equipped with mechanical braking systems that can reduce manufacturing costs and promote production efficiency. many.

This type of mechanical braking system has the problem of many technical difficulties in installing a general regenerative braking system because it is impossible to control the braking force electronically without the driver's intention to brake. Furthermore, even if a regenerative braking system is installed in a mechanical braking system, it is difficult to stably distribute the braking force applied to multiple wheels, which impedes the driving stability of the vehicle, and the driver's brake pedal operation feels strange due to a decrease in hydraulic braking force due to hydraulic pressure. There is a problem that arises.

Republic of Korea Patent Publication No. 10-2016-0123251 (October 25, 2016)

This embodiment seeks to provide a regenerative braking control method for a vehicle that can stably implement the regenerative braking function even in a mechanical braking device.

This embodiment seeks to provide a regenerative braking control method for a vehicle that can improve the driver's feel of operating the brake pedal.

This embodiment seeks to provide a regenerative braking control method for a vehicle that can effectively perform the regenerative braking function through a simple structure and operation.

This embodiment seeks to provide a regenerative braking control method for a vehicle with improved performance and operational reliability.

This embodiment is intended to provide a regenerative braking control method for a vehicle that can reduce the manufacturing cost of the braking device and improve productivity.

According to one aspect of the present invention, as the driver applies pedal force to the brake pedal, a first mode in which only regenerative braking force is provided, a second mode in which both hydraulic braking force and regenerative braking force are provided, the regenerative braking force decreases, and the hydraulic braking force decreases. It includes a third mode in which the provision of regenerative braking force is increased and a fourth mode in which only hydraulic braking force is provided, and a normally open type provided between the master cylinder and the normally open type inlet valve provided on the inlet side of each wheel cylinder. The traction control valve may be switched and maintained in a closed state throughout the first to fourth modes.

In the first to fourth modes, the pressurized medium discharged from the master cylinder may be delivered to the inlet valve through a check valve provided in a bypass passage connecting the front and rear ends of the traction control valve.

In the first mode, the normally closed outlet valve provided on the outlet side of each wheel cylinder is switched to an open state, and the pressurized medium discharged from the master cylinder at the beginning of braking is connected to the check valve, the inlet valve, and the It can be delivered to the low-pressure accumulator through the outlet valve sequentially.

The second mode may be switched from the first mode when the required braking force corresponding to the driver's intention to brake is greater than the maximum regenerative braking force.

In the second mode, the outlet valve is switched to a closed state, and the pressurized medium discharged from the master cylinder can be delivered to each wheel cylinder through the check valve and the inlet valve sequentially.

The third mode is switched from the second mode when the vehicle speed is lower than a preset speed, and the pressurized medium contained in the low pressure accumulator can be pressurized by a hydraulic pump and provided to each wheel cylinder.

The fourth mode is switched from the third mode when the provision of regenerative braking force is stopped, and the pressurized medium discharged from the master cylinder can be sequentially transmitted to each wheel cylinder through the check valve and the inlet valve. .

A master cylinder, a normally open type inlet valve provided on the inlet side of each wheel cylinder, a normally closed type outlet valve provided on the outlet side of each wheel cylinder, and a normally closed type outlet valve connected to the normally closed type outlet valve. A low-pressure accumulator that temporarily stores the pressurized medium supplied from the valve, a normally-open traction control valve provided between the master cylinder and the normally-open inlet valve, and a low-pressure accumulator that pressurizes the pressurized medium stored in the low-pressure accumulator toward each wheel cylinder. In the regenerative braking control method for a vehicle equipped with a hydraulic pump, a motor that operates the hydraulic pump, and an electric motor that converts the kinetic energy of the vehicle into electrical energy and brakes the vehicle through regenerative braking, the traction control valve can be switched and maintained in a closed state from the beginning of braking to the completion of braking.

It further includes a bypass passage connecting the front and rear ends of the traction control valve, and a check valve provided in the bypass passage, and the pressurized medium discharged from the master cylinder operates the check valve from the beginning of braking to the completion of braking. It can be transmitted to the inlet valve side.

It includes a first mode in which only regenerative braking force is provided at the beginning of braking, and in the first mode, the inlet valve and the outlet valve are opened, the pressurized medium discharged from the master cylinder is delivered to the low pressure accumulator, and the hydraulic pressure is increased. The pump can be disabled.

When the required braking force corresponding to the driver's braking will is greater than the maximum regenerative braking force, it further includes a second mode that is switched from the first mode to provide both pressure braking force and regenerative braking force, and in the second mode, the inlet valve is While maintaining the open state, the outlet valve is switched to a closed state, so that the pressurized medium discharged from the master cylinder is delivered to each wheel cylinder, and the hydraulic pump is not driven.

When the speed of the vehicle is lower than the preset speed, it further includes a third mode that is switched from the second mode, and in the third mode, the inlet valve is maintained in an open state and the outlet valve is maintained in a closed state. , the pressurized medium discharged from the master cylinder can be delivered to each wheel cylinder, and the hydraulic pump is driven to pressurize the pressurized medium contained in the low pressure accumulator and provide it to each wheel cylinder.

It further includes a fourth mode that is switched from the third mode when the provision of regenerative braking force is stopped, and in the fourth mode, the inlet valve is maintained in an open state and the outlet valve is maintained in a closed state, and the master The pressurized medium discharged from the cylinder is delivered to each wheel cylinder, and the hydraulic pump can be non-driven.

The vehicle regenerative braking control method according to this embodiment has the effect of stably implementing the regenerative braking function even in a mechanical braking device.

The vehicle regenerative braking control method according to this embodiment has the effect of improving the driver's feel of operating the brake pedal.

The vehicle regenerative braking control method according to this embodiment has the effect of effectively performing the regenerative braking function through a simple structure and operation.

The vehicle regenerative braking control method according to this embodiment has the effect of improving performance and operational reliability.

The vehicle regenerative braking control method according to this embodiment has the effect of reducing the manufacturing cost of the braking device and improving productivity.

1 is a hydraulic circuit diagram showing a mechanical braking device to which the vehicle regenerative braking control method according to this embodiment is applied.
Figure 2 is a graph showing regenerative braking force and hydraulic braking force during braking in the vehicle regenerative braking control method according to this embodiment.
Figure 3 is a diagram showing the operating states of the valve, hydraulic pump, and low pressure accumulator during braking in the regenerative braking control method for a vehicle according to this embodiment.
Figure 4 is a hydraulic circuit diagram showing the operating state of the first mode of the vehicle regenerative braking control method according to this embodiment.
Figure 5 is a hydraulic circuit diagram showing the operating state of the second mode of the vehicle regenerative braking control method according to this embodiment.
Figure 6 is a hydraulic circuit diagram showing the operating state of the third mode of the vehicle regenerative braking control method according to this embodiment.
Figure 7 is a hydraulic circuit diagram showing the operating state of the fourth mode of the vehicle regenerative braking control method according to this embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following examples are presented to sufficiently convey the idea of the present invention to those skilled in the art. The present invention is not limited to the embodiments presented herein and may be embodied in other forms. In order to clarify the present invention, the drawings may omit illustrations of parts unrelated to the description and may slightly exaggerate the sizes of components to aid understanding.

1 is a hydraulic circuit diagram showing a mechanical braking device to which the regenerative braking control method for a vehicle according to this embodiment is applied. Referring to FIG. 1, a vehicle to which the regenerative braking control method according to this embodiment is applied is an electrical system applied to each wheel cylinder. The motor is installed.

The electric motor can drive the vehicle by providing power to the wheels on which each wheel cylinder is mounted, and at the same time, when the vehicle decelerates due to braking, it functions as a generator or generator to convert the vehicle's kinetic energy into electrical energy to be used in the battery or It can be stored in a capacitor. When the vehicle's kinetic energy is converted into electrical energy by an electric motor, braking force is generated at each wheel, which is called regenerative braking force. In other words, the sum of the regenerative braking force from the electric motor and the hydraulic braking force from the mechanical braking device becomes the total braking force applied to the wheel cylinder of the vehicle. Regenerative braking power may vary depending on the speed of the vehicle. In particular, as the vehicle speed decreases and energy conversion efficiency decreases, braking of the vehicle is completed using only hydraulic braking power.

The mechanical braking device is designed to generate and provide hydraulic braking force excluding the regenerative braking force by the electric motor from the required braking force based on the driver's brake pedal effort. The control unit (not shown) calculates the driver's required braking force based on the amount of brake pedal pedal effort or displacement of the mechanical braking device, and generates the braking force, excluding the regenerative braking force by the electric motor, as hydraulic braking force by the pressurized medium and provides it to the wheel cylinder. You can.

Referring to FIG. 1, the mechanical braking device includes a master cylinder (MC) in which a booster operates by the operation of the brake pedal to generate hydraulic pressure of a pressurized medium such as brake fluid, and the master cylinder (MC) is connected through a plurality of flow paths. It may include a plurality of wheel cylinders (FL, FR, RR, RL, FR) that receive pressurized media from the master cylinder (MC).

The master cylinder (MC) has two pressure chambers inside, and one pressure chamber (MCP) of the master cylinder (MC) is connected to the wheel cylinders installed on the front left wheel (FL) and the rear right wheel (RR). The other pressure chamber (MCS) is connected to the wheel cylinders installed on the front right wheel (FR) and rear left wheel (RL). A normally open type traction control valve (TC) is provided in the outlet side passage of each pressure chamber. The normally open traction control valve (TC) is switched and maintained in a closed state from the beginning of the vehicle's braking until the end or completion of braking, and a detailed explanation of this will be provided later.

The check valve may be provided in parallel with the normally open traction control valve (TC). Specifically, a bypass passage is provided connecting the front and rear ends of the normally open type traction control valve (TC), a check valve is provided in the bypass passage, and each wheel cylinder (FL, FR, RR) is connected from the master cylinder (MC). , RL, FR), and is designed to block the flow of pressurized media in the opposite direction. Accordingly, even when the normally open type traction control valve (TC) is switched and maintained in the closed state when the vehicle is braking, the pressurized medium discharged from the master cylinder (MC) passes through the bypass passage and check valve to each wheel cylinder (FL, It can be transmitted to the FR, RR, RL, FR) side.

The flow path connecting the normally open type traction control valve (TC) and each wheel cylinder (FL, FR, RR, RL, FR), that is, the flow path on the inlet side of each wheel cylinder (FL, FR, RR, RL, FR), has a normal An open-type inlet valve (NO) is provided, and a normally-closed outlet valve (NC) is provided on the outlet side flow path of each wheel cylinder (FL, FR, RR, RL, FR).

At the rear end of the plurality of normally closed outlet valves (NC), a portion of the pressurized medium discharged from each wheel cylinder (FL, FR, RR, RL, FR) or the master cylinder (MC) is temporarily stored. A pair of low pressure accumulators (LPA) may be provided. The pressurized medium stored in each low pressure accumulator (LPA) is pressurized by a pair of hydraulic pumps (HP) and passes through each normally open inlet valve (NO) to each wheel cylinder (FL, FR, RR, RL, FR). It can be transmitted to, and a motor (M) that provides driving force to operate a pair of hydraulic pumps (HP) can be provided.

A normally closed electronic shuttle valve (ESV) is provided in the auxiliary passage connecting the suction side of a pair of hydraulic pumps (HP) and each pressure chamber of the master cylinder (MC). Accordingly, when the normally closed electronic shuttle valve (ESV) is opened, the auxiliary passage between the master cylinder (MC) and each hydraulic pump (HP) is opened, and the pressurized medium from the master cylinder (MC) is transferred to the pair of hydraulic pumps (HP). ) can be supplied.

A damper (H/Damper) and an orifice (L/Orifice) are sequentially provided in the discharge side passage of a pair of hydraulic pumps (HP) to reduce pulsation caused by the hydraulic pressure of the pressurized medium and to ensure a stable supply of the pressurized medium. You can.

Meanwhile, the normally open type (NO: Normal Open) valve described in this embodiment refers to a valve that operates in a way that opens the valve passage before being energized, but closes the valve passage when energized, and the Normal Close type (NC: Normal Close) valve. ) A valve refers to a valve that closes the valve passage before being energized, but opens the valve passage when energized.

The motor ( M) is controlled by an electronic control unit (ECU, not shown), and controls the hydraulic pressure of the master cylinder (MC) and the hydraulic pressure applied to at least one wheel cylinder ((FL, FR, RR, RL, FR). A plurality of measuring pressure sensors may be arranged.

Hereinafter, a method of controlling regenerative braking according to this embodiment of a vehicle equipped with a mechanical braking system will be described.

Figure 2 is a graph showing regenerative braking force and hydraulic braking force during braking in the vehicle regenerative braking control method according to this embodiment.

Referring to FIG. 2, the vehicle regenerative braking control method according to this embodiment may sequentially proceed through the first to fourth modes (①, ②, ③, ④) according to the vehicle's braking operation.

The first mode (①) is a regenerative initial mode when the vehicle starts braking, that is, at the beginning of braking, and the vehicle is braked using only the regenerative braking force from the electric motor without generating hydraulic braking force. The first mode (①) can be entered when it is determined that the driver has the will to brake due to the pedal force or displacement of the brake pedal.

The second mode (②) is a regenerative cooperation mode in which not only regenerative braking force by an electric motor but also hydraulic braking force by a pressurized medium is provided, and both regenerative braking force and hydraulic braking force are provided to brake the vehicle. If it is determined that the required braking force corresponding to the driver's braking will is greater than the maximum regenerative braking force by the electric motor, the second mode (②) can be entered so that hydraulic braking force can also be provided.

The third mode (③), like the second mode (②), provides both regenerative braking force and hydraulic braking force to brake the vehicle, but when the vehicle speed is low and energy conversion efficiency is low, it reduces the regenerative braking force and at the same time This corresponds to a regenerative fade-out mode that increases hydraulic braking force. The third mode (③) may be entered when the speed of the vehicle is lower than the preset speed or when the energy conversion efficiency is lower than the preset level.

The fourth mode (④) is a regenerative release mode, in which provision of regenerative braking force is stopped and the vehicle is braked by hydraulic braking force. The fourth mode (④) provides the required braking force corresponding to the driver's will to brake using only hydraulic braking force, and upon termination of the fourth mode (④), the braking of the vehicle is terminated or completed.

Hereinafter, each mode of the vehicle regenerative braking control method according to this embodiment will be described in detail.

FIG. 3 is a diagram showing the operating states of the valve, hydraulic pump, and low-pressure accumulator during braking in the regenerative braking control method for a vehicle according to this embodiment, and FIG. 4 is a first diagram of the regenerative braking control method for a vehicle according to this embodiment. This is a hydraulic circuit diagram showing the operating status of mode (①).

Referring to Figures 3 and 4, the first mode (①) proceeds in the initial regenerative mode at the beginning of braking, and the pressurized medium discharged from the master cylinder (MC) is delivered to the low pressure accumulator, and each wheel cylinder (FL, FR) , RR, RL, FR) brakes the vehicle using only regenerative braking power from the electric motor.

Specifically, when the vehicle is braking, the traction control valve (TC) is switched to the closed state, the inlet valve (NO) remains open, and the outlet valve (NC) is switched to the open state. Accordingly, the pressurized medium discharged from the master cylinder (MC) is delivered to the low pressure accumulator (LPA) through the check valve, inlet valve (NO), and outlet valve (NC) sequentially, and is transmitted to each wheel cylinder (FL, FR, RR, RL, FR) can slow down the vehicle by braking the vehicle using only the regenerative braking force from the electric motor. At this time, the hydraulic pump and motor remain in a non-driving state.

Figure 5 is a hydraulic circuit diagram showing the operating state of the second mode (②) of the regenerative braking control method for a vehicle according to this embodiment. Referring to Figures 3 and 5, the second mode (②) is operated by an electric motor. If the maximum regenerative braking force is less than the required braking force corresponding to the driver's will to brake, the regenerative cooperation mode is performed so that the hydraulic braking force and the regenerative braking force are transmitted together to each wheel cylinder (FL, FR, RR, RL, FR).

Specifically, in the second mode (②), the traction control valve (TC) is maintained in the closed state, the inlet valve (NO) is maintained in the open state, and the outlet valve (NC) is switched to the closed state. As a result, the pressurized medium discharged from the master cylinder (MC) is sequentially transmitted to each wheel cylinder (FL, FR, RR, RL, FR) through the check valve and inlet valve (NO), providing hydraulic braking force and electrical The vehicle can be decelerated by braking the vehicle using regenerative braking force from the motor. In the second mode (②), the hydraulic pump and motor remain in a non-driving state.

Figure 6 is a hydraulic circuit diagram showing the operating state of the third mode (③) of the vehicle regenerative braking control method according to this embodiment. Referring to Figures 3 and 6, the third mode (③) is the vehicle's speed If the speed is sufficiently decelerated and the efficiency of regenerative braking by electrical energy conversion is low, the vehicle proceeds to a regenerative fade-out mode that reduces the regenerative braking force but increases the hydraulic braking force.

Specifically, in the third mode (③), the traction control valve (TC) remains closed, the inlet valve (NO) remains open, and the outlet valve (NC) remains closed. As a result, the pressurized medium discharged from the master cylinder (MC) is sequentially transmitted to each wheel cylinder (FL, FR, RR, RL, FR) through the check valve and inlet valve (NO), providing hydraulic braking force and electrical The vehicle is braked using regenerative braking force from the motor to decelerate the vehicle. At this time, the regenerative braking force by the electric motor gradually decreases, and in order to increase the hydraulic braking force to maintain the required braking force corresponding to the driver's braking will, the motor is driven and the pressurized medium stored in the low-pressure accumulator is used by the hydraulic pump. It can be pressurized and provided together with the inlet valve (NO).

Figure 7 is a hydraulic circuit diagram showing the operating state of the fourth mode (④) of the vehicle regenerative braking control method according to this embodiment. Referring to Figures 3 and 7, the fourth mode (④) provides regenerative braking force. At the same time as this is stopped, it goes into a regenerative release mode that provides only hydraulic braking force.

Specifically, in the fourth mode (④), the traction control valve (TC) remains closed, the inlet valve (NO) remains open, and the outlet valve (NC) remains closed. As a result, the pressurized medium discharged from the master cylinder (MC) is sequentially transmitted to each wheel cylinder (FL, FR, RR, RL, FR) through the check valve and inlet valve (NO), providing only hydraulic braking force, thereby improving the vehicle's Braking can be completed and the vehicle stopped.

The method of controlling regenerative braking of a vehicle according to this embodiment switches and maintains the traction control valve (TC) in a closed state throughout the first to fourth modes (④) from the time the vehicle starts braking to a stop. Accordingly, the driver's pedal effort becomes constant, thereby improving the feel of pedal operation.

In particular, during the first mode (①) at the beginning of braking and the second mode (②) of the regenerative cooperation mode, regenerative braking force by the electric motor is provided to each wheel cylinder (FL, FR, RR, RL, FR). , the hydraulic braking force should be reduced correspondingly. At this time, when the traction control valve (TC) is in the open state, as the liquid volume or hydraulic pressure of the pressurized medium discharged from the master cylinder (MC) is reduced, the pedal force of the brake pedal is also reduced, making the operation of the brake pedal lighter and maintaining detailed braking. Not only is it difficult to control braking force, but there is also the problem of creating a sense of heterogeneity. Furthermore, when switching the opening and closing of the traction control valve (TC) according to the operating mode of regenerative braking, the amount of pressurized medium discharged from the master cylinder (MC) and delivered to the inlet valve (NO) varies from time to time, causing the driver's pedal There is a problem with the feeling being inconsistent.

However, the vehicle regenerative braking control method according to this embodiment switches and maintains the traction control valve (TC) in a closed state throughout the first to fourth modes (④), and the pressurized medium discharged from the master cylinder (MC) is By controlling the discharge to be constant through the bypass passage and check valve, the brake pedal's pedal effort is made constant throughout the entire braking period, and the driver's feel of the brake pedal can be improved by preventing the pedal feeling from becoming light. . In addition, it is possible to improve the operating feel of the brake pedal and achieve stable regenerative braking of the vehicle without adding additional devices or facilities, thereby reducing the manufacturing cost of the braking device and improving productivity.

MC: Master cylinder TC: Traction control valve
NO: Inlet valve NC: Outlet valve
LPA: Low pressure accumulator HP: Hydraulic pump
M: motor

Claims (13)

A first mode in which only regenerative braking force is provided as the driver applies pressure to the brake pedal;
a second mode in which hydraulic braking force and regenerative braking force are provided together;
a third mode in which the regenerative braking force decreases and the hydraulic braking force increases; and
Includes a fourth mode in which provision of regenerative braking force is stopped and only hydraulic braking force is provided,
The normally open type traction control valve is provided between the master cylinder and the normally open inlet valve provided on the inlet side of each wheel cylinder.
A regenerative braking control method for a vehicle that is switched to and maintained in a closed state throughout the first to fourth modes. According to paragraph 1,
The pressurized medium discharged from the master cylinder in the first to fourth modes is
A method of controlling regenerative braking of a vehicle in which the regenerative braking is transmitted to the inlet valve through a check valve provided in a bypass passage connecting the front and rear ends of the traction control valve. According to paragraph 1,
In the first mode
Switching the normally closed type outlet valve provided on the outlet side of each wheel cylinder to the open state,
The pressurized medium discharged from the master cylinder at the beginning of braking is sequentially delivered to the low pressure accumulator through a check valve provided in the bypass passage connecting the front and rear ends of the traction control valve, the inlet valve, and the outlet valve. How to control regenerative braking of a vehicle According to paragraph 1,
The second mode is
A regenerative braking control method for a vehicle that switches from the first mode when the required braking force corresponding to the driver's braking intention is greater than the maximum regenerative braking force. According to paragraph 4,
In the second mode
Switching the normally closed type outlet valve provided on the outlet side of each wheel cylinder to the closed state,
The pressurized medium discharged from the master cylinder is sequentially delivered to each wheel cylinder through a check valve provided in a bypass passage connecting the front and rear ends of the traction control valve and the inlet valve. A regenerative braking control method for a vehicle . According to paragraph 4,
The third mode is
When the speed of the vehicle is lower than the preset speed, the second mode is switched,
A regenerative braking control method for a vehicle in which the pressurized medium contained in the low-pressure accumulator is pressurized by a hydraulic pump and supplied to each wheel cylinder. According to clause 6,
The fourth mode is
When the provision of regenerative braking force is stopped, the third mode is switched,
The pressurized medium discharged from the master cylinder is sequentially delivered to each wheel cylinder through a check valve provided in a bypass passage connecting the front and rear ends of the traction control valve and the inlet valve. A regenerative braking control method for a vehicle .



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