KR20230136809A - regenerative braking control method - Google Patents

Abstract

In the regenerative braking control method according to various embodiments of the present invention, the brake fluid flows into the wheel cylinder in a fade-out section in which the regenerative braking torque decreases and the hydraulic braking torque increases. The regenerative braking torque can be controlled using the liquid amount.

Description

Regenerative braking control method

The present invention relates to a regenerative braking control method.

Recently, as the market demand for eco-friendly vehicles increases, the popularity of electric or hybrid driven vehicles is increasing. These vehicles recover kinetic energy as electrical energy during braking and store it in the battery. , it will be equipped with a regenerative braking system that uses this to assist in driving the vehicle.

In addition to high-spec or high-performance vehicles, there is still consumer demand for economical compact cars or commercial vehicles, and compact cars or commercial vehicles are often equipped with mechanical braking systems that can reduce manufacturing costs and promote production efficiency.

The purpose of the present invention is to provide a regenerative braking control method for an economical mechanical braking device capable of controlling regenerative braking without a wheel pressure sensor.

In the regenerative braking control method according to various embodiments of the present invention, the brake fluid flows into the wheel cylinder in a fade-out section in which the regenerative braking torque decreases and the hydraulic braking torque increases. The regenerative braking torque can be controlled using the liquid amount.

Preferably, the duration of the fade-out section can be determined using the displacement amount of the brake pedal in the fade-out section, and the regenerative braking torque can be controlled to be reduced to 0 during the determined duration of the fade-out section. .

Preferably, the amount of displacement of the brake pedal in the fade-out section may be calculated using a preset brake pedal-braking torque map.

Preferably, in the initial regenerative braking section in which regenerative braking torque is provided by the driver applying pressure to the brake pedal, the target regenerative braking torque can be calculated by applying a preset weight to the driver's required braking torque according to the amount of displacement of the brake pedal. there is.

The regenerative braking control method according to various embodiments of the present invention can calculate regenerative braking torque without a sensor that detects the hydraulic pressure of brake fluid in a wheel cylinder, thereby reducing manufacturing costs.

1 is a hydraulic circuit diagram showing a mechanical braking device to which a regenerative braking control method is applied according to various embodiments of the present invention.
Figure 2 is a graph showing regenerative braking torque and hydraulic braking torque during braking in the regenerative braking control method according to various embodiments of the present invention.
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 according to various embodiments of the present invention.
4 is a preset brake pedal-braking torque map for driver requested braking torque.
Figure 5 is a diagram illustrating a method for calculating the duration time in a fade-out section in various embodiments of the present invention.

Hereinafter, for convenience of explanation, some embodiments of the present invention will be described through exemplary drawings. When assigning reference numerals to components in each drawing, identical components are indicated with the same reference numerals as much as possible, even if they are shown in different drawings.

The principle is that terms or words used in the specification and claims should not be limited to their common or dictionary meanings, and that the inventor may appropriately define the concept of the term in order to explain his or her invention in the best way. Based on this, it must be interpreted with meaning and concept consistent with the technical idea of the present invention. Additionally, when describing the components of an embodiment of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and the nature, sequence, or order of the component is not limited by the term. When a component is described as being 'connected' or 'coupled' to another component, that component may be directly connected or coupled to that other component, but there is another component between that component and that other component. It should be understood that elements may be 'connected' or 'combined'.

Therefore, the embodiments described in this specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent the entire technical idea of the present invention, and therefore, various equivalents that can replace them at the time of filing the present application may be used. It should be understood that there may be variations and examples. Additionally, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the gist of the present invention are omitted.

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 torque is generated at each wheel, which is called regenerative braking torque. In other words, the sum of the regenerative braking torque from the electric motor and the hydraulic braking torque from the mechanical braking device becomes the total braking torque applied to the wheel cylinder of the vehicle. Regenerative braking torque 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 only with hydraulic braking torque.

The mechanical braking device is designed to generate and provide hydraulic braking torque excluding the regenerative braking torque by the electric motor from the required braking torque based on the driver's brake pedal effort. The control unit (not shown) calculates the driver's required braking torque based on the amount of brake pedal effort or displacement of the mechanical braking system, and generates the braking torque excluding the regenerative braking torque from the electric motor as hydraulic braking torque using brake fluid. It can be supplied as a wheel cylinder.

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 brake fluid 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 that receive brake fluid 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), and a check valve is provided in the bypass passage, and the brake fluid from the master cylinder (MC) to each wheel cylinder is provided. It is designed to allow only the flow of brake fluid and block the flow of brake fluid in the opposite direction. As a result, even when the normally open type traction control valve (TC) is switched and maintained in the closed state when the vehicle is braking, the brake fluid discharged from the master cylinder (MC) will be delivered to each wheel cylinder through the bypass passage and check valve. You can.

The flow path connecting the normally open traction control valve (TC) and each wheel cylinder, that is, the flow path on the inlet side of each wheel cylinder, is provided with a normally open type inlet valve (NO), and the flow path on the outlet side of each wheel cylinder is a normally closed type valve. An outlet valve (NC) is provided for each.

At the rear of the plurality of normally closed outlet valves (NC), a pair of low pressure accumulators (LPA) may be provided to temporarily store the brake fluid discharged from each wheel cylinder or a portion of the brake fluid discharged from the master cylinder (MC). there is. The brake fluid stored in each low pressure accumulator (LPA) can be pressurized by a pair of hydraulic pumps (HP) and delivered to each wheel cylinder through each normally open inlet valve (NO), and a pair of hydraulic pumps A motor (M) that provides driving force to operate (HP) may 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 brake fluid flows from the master cylinder (MC) to the pair of hydraulic pumps (HP). ) can be supplied.

Here, a normally open type (NO: Normal Open) valve 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 a normally closed type (NC: Normal Close) valve is used before being energized. It refers to a valve that closes the valve passage but operates by opening the valve passage when energized.

The motor ( The operation of M) is controlled by an electronic control unit (ECU, not shown), and a pressure sensor may be placed to measure the hydraulic pressure of the master cylinder (MC). However, in the present invention, the pressure sensor that measures the hydraulic pressure applied to at least one wheel cylinder may be omitted.

In general, hydraulic braking torque can be generated using the sensed value of a pressure sensor of a wheel cylinder that senses the hydraulic pressure of multiple wheel cylinders. Since regenerative braking torque and hydraulic braking torque are applied together in the first to third sections described later, the regenerative braking torque and hydraulic braking torque are calculated using the pressure sensor value of the wheel cylinder, and the total braking torque is generated based on this. Controls regenerative braking. In general, regenerative braking torque can be calculated by subtracting the hydraulic braking torque calculated through the wheel pressure sensor from the driver's required braking torque.

The present invention proposes a method of controlling regenerative braking torque and/or hydraulic braking torque when the pressure sensor of the wheel cylinder is omitted to reduce costs.

Figure 2 is a graph showing regenerative braking torque and hydraulic braking torque during braking in the regenerative braking control method for a vehicle according to this embodiment, and Figure 3 is a graph showing a valve during braking in the regenerative braking control method for a vehicle according to this embodiment, This is a diagram showing the operating status of the hydraulic pump (HP) and low pressure accumulator (LPA).

Referring to Figures 2 and 3, the regenerative braking control method for a vehicle according to this embodiment can sequentially proceed through the first to fourth sections (①,②,③,④) according to the braking operation of the vehicle.

The first section (①) is when the vehicle starts braking, that is, the initial regenerative section at the beginning of braking, and the vehicle is braked with some hydraulic braking torque and some regenerative braking torque by the electric motor. The first section (①) can be entered if it is determined that the driver has the will to brake due to the pedal force or displacement of the brake pedal. Specifically, in the first section, the traction control valve (TC) is It is opened and brake fluid is supplied from the master cylinder (MC), and the inlet valve (NO) remains open, but the outlet valve (NC) switches to the open state. The brake fluid supplied from the master cylinder EJ (MC) is delivered to the low pressure accumulator (LPA) through the outlet valve (NC), and at the same time, some of it is delivered to the wheel cylinder. Therefore, some hydraulic braking torque and regenerative braking torque from the drive motor are applied together. At this time, the hydraulic pump and motor remain in a non-driving state. The second section (②) is a regenerative cooperation section in which not only regenerative braking torque by the electric motor but also hydraulic braking torque by brake fluid is provided, and both regenerative braking torque and hydraulic braking torque are provided to brake the vehicle. . In the second section (②), if the required braking torque corresponding to the driver's braking will is judged to be greater than the maximum regenerative braking torque by the electric motor, the second section (②) can be entered so that hydraulic braking torque can also be provided. You can.

Specifically, in the second section, the traction control valve (TC) and the inlet valve (NO) are maintained in the open state, and the outlet valve (NC) is switched to the closed state. The brake fluid discharged from the master cylinder (MC) is sequentially transmitted to each wheel cylinder through the check valve and inlet valve (NO), generating hydraulic braking torque and simultaneously braking the vehicle through regenerative braking torque from the electric motor. This can cause the vehicle to slow down. In the second section, the hydraulic pump (HP) and motor (M) maintain a non-driving state.

The third section (③), like the second section (②), brakes the vehicle by providing both regenerative braking torque and hydraulic braking torque. However, when the vehicle speed is sufficiently reduced and energy conversion efficiency is low, the regenerative braking torque It corresponds to a regenerative fade-out section that reduces and simultaneously increases hydraulic braking torque. The third section (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.

Specifically, the inlet valve (NO) is maintained in the open state, and the traction control valve (TC) is switched to the closed state. The outlet valve (NC) remains closed. As the traction control valve (TC) switches to the closed state, the brake fluid discharged from the master cylinder (MC) is no longer supplied to the wheel cylinder, and the brake fluid stored in the low pressure accumulator (LPA) through the hydraulic pump is supplied to the wheel cylinder. supplied to form additional hydraulic braking torque.

At this time, the regenerative braking torque by the electric motor must be controlled to decrease throughout the entire third section, and a specific method of controlling the reduction of the regenerative braking torque will be described later.

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

Specifically, in the fourth section (④), the traction control valve (TC) remains closed, the inlet valve (NO) remains open, and the outlet valve (NC) remains closed. Here, as in the third section, the traction control valve (TC) is closed, so the supply of brake fluid discharged from the master cylinder (MC) is blocked, and the brake fluid stored in the low pressure accumulator (LPA) through the hydraulic pump is supplied to the wheel cylinder. This forms the total hydraulic braking torque.

Hereinafter, the regenerative braking control method in the above-described first section and third section will be described in detail with reference to the attached drawings.

FIG. 4 is a preset brake pedal-braking torque map for driver requested braking torque, and FIG. 5 is a diagram illustrating a method for calculating the duration of a fade-out section in various embodiments of the present invention.

In the first section, the outlet valve (NC) is opened and part of the brake fluid discharged from the master cylinder (MC) flows into the wheel cylinder to generate hydraulic braking torque, and the rest is transferred to the low pressure accumulator through the open outlet valve (NC). (LPA) is filled in. In the first section, because the brake fluid discharged from the master cylinder (MC) is distributed and delivered, the hydraulic pressure of the wheel cylinder has a different value from the hydraulic pressure discharged from the master cylinder (MC).

Accordingly, the present invention proposes a method of estimating the target regenerative braking torque by applying an appropriate weight to the driver's requested braking torque. For example, if set to 30%, the initial braking torque may be insufficient, and if set to 80%, braking force may be excessive in a section where the braking torque is constant. Therefore, in an exemplary embodiment, the weight may be set to 60%. However, it is not limited to this, and the degree to which an appropriate overall braking torque is exerted compared to the braking torque required by the driver can be determined through a number of tests.

At the end of the first section, the larger of the target regenerative braking torque estimated through an appropriate weighting value for the driver's requested braking torque and the target regenerative braking torque calculated from the hydraulic pressure of the wheel cylinder estimated through the hydraulic pressure of the master cylinder (MC) The value can be set to the target regenerative braking torque.

This is because the outlet valve (NC) is closed again in the second section, so the hydraulic pressure of the wheel cylinder can be estimated through the hydraulic pressure of the master cylinder (MC). At the end of the first section, an appropriate weight is given to the driver's required braking torque. This is because there may be a section where the target regenerative braking torque estimated through the value is smaller than the target regenerative braking torque calculated from the hydraulic pressure of the wheel cylinder estimated through the hydraulic pressure of the master cylinder. Through this method, accuracy can be increased in estimating the target regenerative braking torque.

Meanwhile, in the third section, a method of controlling the regenerative braking torque is proposed using the amount of brake fluid flowing into the wheel cylinder. In the third section, the regenerative braking torque must be controlled to be sensitive until it becomes 0. To this end, a method for calculating the duration of the third section will be described.

The amount of brake fluid flowing into the wheel cylinder (amount of fluid required) is proportional to the amount of brake pedal displacement (PTS) caused by the driver. As explained previously, in the third section, since the traction control valve (TC) is closed, the brake fluid flowing into the wheel cylinder is the brake fluid stored in the low pressure accumulator (LPA) and is pumped into the wheel cylinder through the hydraulic pump (HP). It is supplied. Therefore, since the amount of brake fluid flowing into the wheel cylinder can be determined by the amount of fluid supplied from the hydraulic pump (HP), the amount of brake fluid flowing into the wheel cylinder (required amount) is determined by the flow rate of the hydraulic pump (HP) and the hydraulic pressure. It can be seen that it is proportional to the product of the operating time of the pump (HP).

The flow rate of the hydraulic pump (HP) is proportional to the RPM of the motor (M), which is the driving source, which is ultimately proportional to the driving voltage of the motor (M).

If so, the duration of the third section can be viewed as a factor linked to the driving time of the pump (HP), so it can be calculated through [Equation] below.

[Equation]

Fade out time=K*△PTS/motor driving voltage

Here, K is a correction coefficient to correct proportional factors and can vary depending on the specifications of the motor (M), △PTS is the brake pedal displacement amount, and the motor driving voltage can be determined by considering the flow rate of the pump (HP). It is a value.

ΔPTS can be calculated using a preset brake pedal-braking torque map for the driver's required braking torque curve O, as shown in FIG. 4. Referring to FIG. 5, the braking torque T2 formed by the hydraulic pressure of the master cylinder (MC) at the start of the third section is a value that can be confirmed in the second section, and the braking torque T2 at the start of the third section is a value that can be confirmed in the second section. The target friction torque (target hydraulic braking torque) (T1) is the sum of the braking torque (T2) formed by the hydraulic pressure of the master cylinder (MC) and the target regenerative braking torque (T3) at the start of the third target section. It is decided.

Looking again at FIG. 4, since the driver's required braking torque curve O is determined by the pedal force or displacement of the brake pedal, using the brake pedal-braking torque map of FIG. 4, at the start of the third section The displacement amount (△PTS) of the brake pedal in the fade-out section can be calculated through the braking torque (T2) formed by the hydraulic pressure of the master cylinder (MC) and the target friction torque (T1) at the start of the third section. It is possible.

In the present invention, the target regenerative braking torque can be controlled to be reduced to 0 at a constant slope from the start of the third section to the duration of the third section calculated according to the above [Equation].

As described above, the regenerative braking control method according to various embodiments of the present invention can calculate regenerative braking torque without a sensor that detects the hydraulic pressure of the brake fluid in the wheel cylinder in an economical mechanical braking device for cost reduction, thereby reducing costs and providing excellent performance. Control effect can be secured.

In the above, just because all the components constituting the embodiment of the present invention have been described as being combined or operated in combination, the present invention is not necessarily limited to this embodiment. That is, as long as it is within the scope of the purpose of the present invention, all of the components may be operated by selectively combining one or more of them. In addition, terms such as 'include', 'comprise', or 'have' described above mean that the corresponding component may be present, unless specifically stated to the contrary, and therefore do not exclude other components. Rather, it should be interpreted as being able to include other components. All terms, including technical or scientific terms, unless otherwise defined, have the same meaning as generally understood by a person of ordinary skill in the technical field to which the present invention pertains. Commonly used terms, such as terms defined in a dictionary, should be interpreted as consistent with the contextual meaning of the related technology, and should not be interpreted in an idealized or overly formal sense unless explicitly defined in the present invention.

The above description is merely an illustrative explanation of the technical idea of the present invention, and various modifications and variations will be possible to those skilled in the art without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but rather to explain it, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted in accordance with the claims below, and all technical ideas within the equivalent scope should be construed as being included in the scope of rights of the present invention.

MC: Master Cylinder
TC: Traction control valve
NO: Inlet valve
NC: outlet valve
LPA: low pressure accumulator
HP: Hydraulic pump
M: motor

Claims (5)

In the regenerative braking control method,
A regenerative braking control method for controlling the regenerative braking torque using the amount of brake fluid flowing into the wheel cylinder in a fade-out section where the regenerative braking torque decreases and the hydraulic braking torque increases.
According to paragraph 1,
A regenerative braking control method for determining the duration of the fade-out section using the displacement amount of the brake pedal in the fade-out section and controlling the regenerative braking torque to be reduced to 0 during the determined duration of the fade-out section.
According to paragraph 2,
A regenerative braking control method in which the displacement amount of the brake pedal in the fade-out section is calculated using a preset brake pedal-braking torque map.
According to paragraph 1,
A regenerative braking control method in which the target regenerative braking torque is calculated by applying a preset weight value to the driver's required braking torque according to the amount of displacement of the brake pedal in the initial regenerative section in which regenerative braking torque is provided by the driver applying pressure to the brake pedal.
According to paragraph 4,
The target regenerative braking torque before the outlet valve disposed on the outlet side of the wheel cylinder is converted to a closed state is determined by applying a preset weight to the driver's requested braking torque according to the displacement amount of the brake pedal, thereby dividing the target regenerative braking torque and the master cylinder. A regenerative braking control method that sets the larger value among the target regenerative braking torques calculated using the hydraulic pressure discharged from .