JPH1198608A - Apparatus and method for braking vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a braking force to be applied when a defect is generated in a mechanical braking system, in a vehicle provided with two mechanical brake systems and an electric brake system. SOLUTION: A unit 16 which discriminates whether or not a mechanical brake system 10 can produce an expected braking force is provided. When the mechanical brake system 10 is a friction brake which transmits the quantity of operation of a brake operating element through oil pressure, the discriminating unit 16 contains an oil pressure sensor which detects whether the oil pressure is a specified value or larger. When the discriminating unit 16 discriminates that a braking force by the mechanical brake system 10 is less than the expected value, a command issuing section 18 issues a command for an electric brake system 12 to increase the braking force. Consequently, at least a part of the braking force in the mechanical brake system 10 is recovered by the electric brake system 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking device and a braking method for a vehicle having both an electric braking system such as regenerative braking and a mechanical braking system such as friction braking, and more particularly to a braking force of two braking systems. The optimization of the distribution of

[0002]

2. Description of the Related Art A braking device performs mechanical braking that converts kinetic energy into thermal energy or kinetic energy of another member, or performs electrical braking that generates electric power by kinetic energy and converts it into electric energy. Etc. are known.
As mechanical braking, due to friction between relatively moving members,
Friction braking, which converts kinetic energy to heat energy, is well known. The electric braking includes a method in which generated electricity is consumed by a resistor, a method in which electric power is temporarily stored in a battery, and a so-called regenerative braking in which electric energy is supplied from the battery later.

Many vehicles equipped with an electric motor, such as electric vehicles, include a braking device for performing regenerative braking in addition to a braking device using friction in order to effectively use energy. Then, the distribution of the braking force by friction braking and the distribution of the braking force by regenerative braking are appropriately set, and control is performed so as to generate optimal braking force and regenerative power.

Japanese Patent Application Laid-Open No. Hei 4-221258 discloses a vehicle braking device provided with an electric braking system and a mechanical braking system. The electric braking system includes a regenerative braking device, and the mechanical braking system includes a friction braking device that transmits an operation amount of a brake operating member via hydraulic pressure and presses a friction member against a rotating member that rotates with a wheel. ing. A brake operation amount sensor for detecting an operation amount of a brake operation member is provided to detect a braking force desired by the driver. The distribution of the regenerative braking force and the friction braking force is determined based on the output of this sensor. When an abnormality of the brake operation amount sensor is detected, the braking force is controlled only by the friction braking force corresponding to the pressure of the liquid generated at that time.

[0005]

According to the apparatus disclosed in the above publication, when an abnormality occurs, the vehicle is braked only by the friction braking force corresponding to the pressure of the liquid for transmitting the operating force generated at that time. You. Therefore, a braking force higher than the braking force corresponding to the pressure of the liquid could not be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and even if it is determined that the operation of the mechanical braking system does not reach the expected operation amount, the operation amount is not achieved. The purpose is to obtain a braking force that is equal to or greater than the braking force according to.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a vehicle braking method according to the present invention is a method for braking a vehicle provided with a mechanical braking system and an electric braking system. When the operation of the braking system does not reach the expected operation amount, the operation amount of the electric braking system is increased from the expected operation amount.

Further, a braking device according to the present invention is a braking device for a vehicle provided with a mechanical braking system and an electric braking system, wherein the operation of the mechanical braking system does not achieve an intended operation amount. It has a determination means for determining, and a command means for issuing a command to increase the amount of operation of the electric braking system when the determination unit determines that the operation amount is not achieved. According to this,
At least a part of the shortage of the operation amount of the mechanical braking system is compensated by the electric braking system, and the braking force can be increased.

Further, the mechanical control system includes a friction braking system for transmitting an operation amount of a brake operating member via a fluid and generating a frictional force in accordance with the operation amount, and the determination means includes: Is determined not to reach the expected value.

Further, the friction braking system includes an assisting system for assisting the operation of the brake operator, and the assisting system includes a pump for pressurizing the fluid and an accumulator for storing the pressurized fluid. And the determining means includes:
It may be determined that the pressure of the accumulator has dropped.

[0011] Further, when the electric braking system is operating, suppressing means for suppressing the braking force of the mechanical braking system by a value corresponding to the braking force generated by the electric braking system;
When the determination unit determines that the intended operation amount is not achieved, the determination unit may include a suppression prohibition unit that prohibits suppression of a braking force of a mechanical braking system. .

[0012]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings. In the present embodiment, the present invention is applied to a so-called electric vehicle in which a vehicle is driven by an electric motor that is supplied with electric power from a vehicle-mounted battery.

FIG. 1 is a block diagram showing a configuration relating to control of a vehicle braking device according to the present invention.
The braking device according to the present embodiment has a mechanical control system 10 and an electric control system 12. The mechanical braking system 10 causes a brake pad or a brake shoe to abut on a brake disk or a brake drum rotating with the wheel by operating a brake operator such as a brake pedal,
This is a friction brake that generates a braking force by friction.
Transmission of the operation amount of the brake operator is performed via a fluid such as brake fluid. In addition, the electric braking system 12
Is a regenerative brake that uses a motor for driving the vehicle as a generator during braking and stores the generated power in a battery.

The control unit 14 controls the electric braking system 12 and the mechanical braking system 10 in an appropriate distribution according to the operation amount of the brake operator operated by the driver, the vehicle speed, the amount of charge of the battery at that time, and the like. Control each braking force. For example, if the battery is already fully charged and cannot be charged any more, the braking force is generated only by the mechanical braking system 10 without using the electric braking system 12. If the battery has a sufficient amount of charge, a braking force is generated by the electric braking system 12, and the braking force of the mechanical braking system 10 is reduced accordingly, so-called cooperative braking is performed. Electric braking system 1 during coordinated braking
If a sufficient braking force can be obtained by the mechanical braking system 10
Is controlled so as not to generate a braking force, and is controlled so as to compensate for the shortage if the braking force is insufficient. More specifically, as shown in FIG. 2, when the operation amount of the brake operator is small, most of the entire braking force of the vehicle is covered by the regenerative braking force. Power is added to obtain the total braking force. Normally, the upper limit value of the regenerative braking force is such that the acceleration of the vehicle is, for example, about-
1.96 m / s ² (−0.2G)
To obtain more braking force, friction braking force is added. In the case of the present embodiment, since the regenerative braking force acts only on the front wheels, the rear wheel braking force generates a slight braking force even when the brake operation amount is small in order to secure the braking force on the rear wheel. ing.

The control section 14 is provided with a determination section 16 for determining whether or not the operation of the mechanical control system 10 has attained an intended operation amount. The determination unit 16 monitors whether a physical quantity of the mechanical braking system 10, for example, a brake fluid pressure at a predetermined position on a fluid pressure circuit, has an intended value with respect to the operation amount of the brake operation element. For example,
When the brake fluid pressure is not the pressure that should be originally generated with respect to the operation amount of the brake operation element, it is determined that the intended operation amount is not achieved. When the determining unit 16 determines that the intended operation amount of the mechanical braking system 10 is not achieved, the command unit 18 instructs the electric braking system 12 to increase the braking force. Therefore, even in a situation where the above-mentioned -1.96 m / s ² is generated by regenerative braking in a normal state, control is performed so as to generate a greater braking force. Further, even when the battery is not normally regeneratively braked and the failure of the mechanical braking system 10 is determined, the braking force can be generated by the electric braking system 12.

FIG. 3 shows a mechanical braking system 10 according to this embodiment.
Is shown schematically. As described above, in the present embodiment, brake fluid is used as a fluid, and hereinafter, the fluid will be described simply as oil. A brake pedal 20, which is a brake operator for performing a brake operation by a driver, is connected to a master cylinder (M / C) 22. In the master cylinder 22, the brake pedal 10
A hydraulic pressure is generated according to the stroke amount of the stroke. The hydraulic pressure of the master cylinder 22 is controlled by the cooperative front pressure reducing system 24, the pressure increasing piston 26, and the antilock brake front control system 2.
The anti-lock brake is transmitted to the wheel cylinders (W / C) 30 and 32 of the left and right front wheels via the valve 8 (hereinafter, the anti-lock brake is referred to as ABS). Wheel cylinder 30,
With the stroke of 32, the brake pad comes into contact with the brake disk, and a friction braking force is generated.

The master cylinder 22 has a regulator 3
4 are attached. The regulator 34 is supplied with high-pressure oil from an accumulator 38 in which the oil increased in pressure by the hydraulic pump 36 is stored, and the pressure is reduced by the regulator 34 to the same level as the master cylinder 22.
In the present embodiment, the hydraulic pressure of the accumulator 38 assists the hydraulic pressure of the master cylinder 22. The hydraulic pressure of the regulator 34 is controlled by a cooperative rear pressure reducing system 40, an ABS rear control system 42, and a proportioning and bypass valve (hereinafter referred to as a P & B valve) 4.
Wheel cylinders (W / C) 4 for the left and right rear wheels via 4
6, 48. The hydraulic pressure is supplied from the master cylinder 22 to the P & B valve 44, and the P & B valve 4
4 controls the ratio of the braking force between the front wheels and the rear wheels.

The master cylinder 22 and the regulator 34
The communication system 50 communicates the pressure of the hydraulic system on the side.
The communication system 50 allows the regulator 3 to operate at the time of ABS operation.
The pressure on the fourth side is transmitted to the master cylinder 22 side. Oil is supplied from the reservoir 52 to the master cylinder 22, the regulator 34, and the hydraulic pump 36.

The cooperative front pressure reducing system 24 includes a master cylinder pressure sensor 5 for detecting the pressure in the master cylinder 22.
4. Front wheel cylinders 30, 32 when ABS is not operating
And a stroke sensor 58 for detecting the stroke of the brake pedal. Based on the outputs of these sensors 54, 46, 58, the braking device is controlled so that the braking force desired by the driver is achieved. Solenoid valve 60
Is controlled to the open state during non-cooperative braking, and transmits the pressure of the master cylinder 22 to the wheel cylinders 30 and 32 as it is. Therefore, during non-cooperative braking, the master cylinder 22
And the pressures of the wheel cylinders 30 and 32 have a substantially linear relationship as indicated by the broken line in FIG. Solenoid valve 60
Is controlled to the closed state during the cooperative braking, and the pressure reducing valve 6
2. Low pressure relief valve 64, high pressure relief valve 66
Further, the master cylinder 2 is operated by the solenoid valve 68.
2 is reduced to reduce the front wheel cylinders 30, 3
Transfer to 2. Therefore, at the time of cooperative braking, the pressures of the master cylinder 22 and the wheel cylinders 30 and 32 have a polygonal relationship as shown by the solid line in FIG. When the braking force desired by the driver is obtained by the regenerative braking force, the pressure reducing valve 6
2, the hydraulic pressure of the master cylinder 22 is reduced, and hydraulic pressure enough to eliminate brake play is transmitted to the wheel cylinders 30, 32 of the front wheels. When the desired braking force is equal to or higher than the braking force that can be generated by regenerative braking, the low-pressure relief valve 64 or the high-pressure relief valve 66 opens, and the hydraulic pressure for generating the insufficient braking force is increased by the wheel cylinders 30, 32. The two relief valves 64 and 66 have different opening pressures, and the low-pressure relief valve 64 is opened at a lower pressure. Selection of the two types of relief valves 64 and 66 is made by a solenoid valve 68. The two types of relief valves 64, 6
The reason why 6 is provided is that the upper limit value of the regenerative braking force is changed depending on the vehicle speed. That is, when the upper limit value of the regenerative braking force is lower than a certain threshold value, the low-pressure relief valve 64 starts the friction braking force from a low braking force. On the other hand, when the upper limit value of the regenerative braking force is higher than a certain threshold value, the solenoid valve 68 is closed, and the high-pressure relief valve 66 operates the friction braking from a higher braking force.

The cooperative rear pressure reducing system 40 includes a solenoid valve 70, a pressure reducing valve 72, and a relief valve 74. At the time of non-cooperative braking, the solenoid valve 70 is controlled to be in the open state, and the hydraulic pressure of the regulator 34 is supplied as it is downstream. At the time of cooperative braking, the solenoid valve 70 is closed, and the oil pressure of the regulator 34 is reduced by the pressure reducing valve 72 and the relief valve 74 and is supplied downstream. Therefore, the rear wheel also has substantially the same characteristics as those shown in FIG. When the braking force desired by the driver is obtained by the regenerative braking force, the oil pressure from the regulator 34 is reduced by the pressure reducing valve 72, and the oil pressure enough to eliminate the brake play is provided by the wheel cylinders 46, 48 of the rear wheels.
Is transmitted to When the desired braking force exceeds the braking force that can be generated by regenerative braking, the relief valve 74
Is opened, and hydraulic pressure for generating an insufficient braking force is transmitted to the wheel cylinders 46 and 48 of the rear wheels.

As described above, during the cooperative braking, as shown in FIG. 2, the total braking force is obtained by the regenerative braking force and the friction braking force of the front and rear wheels. Note that the upper limit of the regenerative braking force is such that the acceleration of the vehicle is, for example, about -1.96 m / s ² (−0.2
G).

The above is when the ABS is not operated. At the time of ABS operation, the solenoid valve 76 operates so that the regulator 34 communicates with the wheel cylinders 30 and 32 of the front wheels. The solenoid valves 70 and 60 are opened. When the ABS is activated, the pressure increasing valve 78 and the pressure reducing valve 8 are controlled so that the wheels are controlled to a state immediately before locking.
0 repeats opening and closing, and wheel cylinders 30, 32, 4
The hydraulic pressure of 6,48 is controlled. That is, when the rotation of the wheels is almost stopped, the pressure reducing valve 80 is opened, and the hydraulic pressure of the wheel cylinder is returned to the reservoir 52 to reduce the pressure. When the rotation of the wheels starts, the pressure increasing valve 78 is opened, the hydraulic pressure is supplied from the regulator 34, the hydraulic pressure of the wheel cylinder is increased again, and the braking force is increased. This repetition achieves the antilock operation. The pressure-increasing piston 26 increases the wheel cylinder pressure of the front wheels, which is reduced by using the regulator pressure, when the regenerative braking force is reduced, and is for separating two systems. By using the regulator pressure, the depth of the pedal can be avoided.

Further, in this embodiment, an accumulator pressure sensor 86 for detecting whether a predetermined oil pressure is accumulated in the accumulator 38 is provided. When the accumulator pressure sensor 86 detects that the pressure of the accumulator 38 has decreased, it is determined that the friction braking system is abnormal. Based on this determination, the solenoid valves 60 and 70 are controlled to open, and the wheel cylinders 30, 32, 46,
48. As a result, the maximum friction braking force that can be generated in that situation can be generated. Further, by adding the regenerative braking force, the decrease in the friction braking force due to the decrease in the accumulator pressure is compensated for.

In the present embodiment, if the hydraulic pressure of the accumulator 38 decreases, the hydraulic pressures of the wheel cylinders 46 and 48 of the rear wheels do not increase, and the desired braking force cannot be obtained. Further, since the hydraulic pressure of the accumulator 38 also acts as an assisting force of the hydraulic pressure of the master cylinder 22, the assisting force is lost due to the decrease in the hydraulic pressure. Therefore, the hydraulic pressure of master cylinder 22 does not increase, and the desired braking force cannot be obtained. With the above-described control, it is possible to prevent a reduction in the braking force due to a reduction in the accumulator pressure, or to reduce the reduction even if the reduction occurs.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of an embodiment of the present invention.

FIG. 2 is a diagram illustrating distribution of braking force during cooperative control according to the present embodiment.

FIG. 3 is a schematic configuration diagram of a hydraulic circuit of the present embodiment.

FIG. 4 is a diagram illustrating a relationship between a master cylinder pressure and a wheel cylinder pressure according to the present embodiment.

[Explanation of symbols]

Reference Signs List 10 mechanical braking system (friction brake), 12 electric braking system (regenerative braking), 14 control unit, 16 judgment unit (judgment unit), 18 command unit (command unit), 20 brake pedal (brake operator), 22 Master cylinder,
24 Front depressurization system during coordination (suppression means), 30, 3
2, 46, 48 Wheel cylinder, 34 regulator, 36 hydraulic pump, 38 accumulator, 40
Rear pressure reducing system during coordination (suppression means), 86 Accumulator pressure sensor (judgment means).

Continued on the front page (72) Inventor Naoyasu Enomoto 2-1-1 Asahi-cho, Kariya-shi, Aichi Pref. Aisin Seiki Co., Ltd.

Claims (5)

[Claims] 1. A method for braking a vehicle having a mechanical braking system and an electric braking system, wherein the mechanical braking system does not reach an intended operation amount.
A braking method for a vehicle, in which an operation amount of an electric braking system is increased more than intended. 2. A braking device for a vehicle having a mechanical braking system and an electric braking system, wherein: a determining unit configured to determine that an operation of the mechanical braking system does not achieve an expected operation amount; A braking device for a vehicle, comprising: a command unit configured to issue a command to increase an operation amount of an electric braking system when the operation unit does not achieve an operation amount. 3. The braking device for a vehicle according to claim 2, wherein the mechanical control system transmits an operation amount of the brake operation member via a fluid, and generates a frictional force according to the operation amount. A braking device for a vehicle, including a friction braking system, wherein the determining means determines that the pressure of the fluid does not reach an expected value. 4. The braking device for a vehicle according to claim 3, wherein the friction braking system includes an assisting system that assists the operation of the brake operator, and the assisting system pressurizes the fluid. A braking device for a vehicle, comprising: a pump; and an accumulator for storing the pressurized fluid, wherein the determination unit determines that the pressure of the accumulator has decreased. 5. The braking apparatus for a vehicle according to claim 2, wherein when the electric braking system is operating, the mechanical device is controlled by a value corresponding to a braking force generated by the electric braking system. A braking unit that suppresses the braking force of the mechanical braking system, when the determination unit determines that the intended operation amount is not achieved, the braking unit controls the braking force of the mechanical braking system. A braking device for a vehicle, comprising: a suppression prohibition unit that prohibits suppression.