JP6194290B2 - Vehicle braking system - Google Patents

Description

  The present invention relates to a vehicle braking system.

  In the technique of Patent Document 1, in an electric vehicle provided with a regenerative braking unit and a mechanical braking unit using an electric motor, a deceleration calculation unit that calculates a deceleration required for the vehicle according to a throttle operation, a brake operation, and a running state of the vehicle. And a charge detection means for detecting the state of charge of the battery. When the throttle operation is stopped without a brake operation and the battery is fully charged at that time, instead of the operation of the electric braking means according to the deceleration obtained by the deceleration calculation means, the deceleration calculation means By operating the mechanical braking means according to the deceleration obtained in step (1), the necessary braking force accompanying the accelerator off is obtained.

JP-A-10-271605

  In an electric vehicle or the like, it is known that a regenerative braking force generates a braking force equivalent to an engine brake in a normal gasoline vehicle when an accelerator pedal is not operated. When the amount of charge of the battery for charging the electric power obtained by regeneration reaches a reference value, braking force equivalent to engine braking is generated by friction braking force instead of regenerative braking force.

However, when the friction braking force is activated instead of the regenerative braking force, an abnormality occurs in the control device that controls the regenerative braking force, or a system (CAN: Controller Area) that communicates between each part in the vehicle Network) may be abnormal. In that case, the controller that controls the friction braking force is required to generate a larger friction braking force than necessary, and a braking force equivalent to the engine brake may be generated, which gives the driver a sense of incongruity. There is a problem.
An object of the present invention is to prevent an excessive friction braking force from being generated due to the occurrence of an abnormality when shifting from a regenerative braking force to a friction braking force.

According to the present invention, a regenerative braking force generation unit that generates a regenerative braking force, a friction braking force generation unit that generates a friction braking force, and a battery that stores electric power generated by the generation of the regenerative braking force are in a predetermined state. A transition portion that shifts the braking force of the vehicle from the regenerative braking force to the friction braking force without depending on the driver's braking operation, and the transition braking portion reduces the shortage of the regenerative braking force to the friction braking force. In the vehicle braking system, the vehicle braking system includes an upper limit value setting unit that sets an upper limit value for the friction braking force.
According to the present invention, since the upper limit value is set for the friction braking force, it is possible to prevent an excessive friction braking force from being generated due to the occurrence of an abnormality when the regenerative braking force is shifted to the friction braking force. it can.

In this case, a switchback state determination unit that determines that the switchback is performed in the vehicle, and a wheel that determines that a slip has occurred in the wheel of the vehicle in order to stabilize the behavior of the vehicle A slip determination unit, wherein the upper limit value setting unit sets a first value as the upper limit value when the switchback is not performed and the slip does not occur, and the switchback Is set, the second value higher than the first value is set as the upper limit value, and the third value lower than the first value is set as the upper limit value when the slip occurs. You may make it do.
According to the present invention, it is possible to set an appropriate upper limit value of the friction braking force in order to perform switchback or prevent the occurrence of an operation that stabilizes the behavior of the vehicle.

  According to the present invention, when the regenerative braking force is shifted to the friction braking force, it is possible to prevent an excessive friction braking force from being generated due to the occurrence of an abnormality.

It is a principal part system diagram of the vehicle provided with the braking system for vehicles which is one Embodiment of this invention. It is a block diagram showing the outline | summary of the friction braking apparatus in the braking system for vehicles which is one Embodiment of this invention. It is a block diagram of the control system in the brake system for vehicles which is one embodiment of the present invention. It is a graph explaining control by the control system in the brake system for vehicles which is one embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a system diagram of a principal part of a vehicle 100 including a vehicle braking system according to the present embodiment. The vehicle 100 is, for example, an electric vehicle, and includes a pair of left and right front wheels 2aR and 2aL provided on the front side of the vehicle 100, and a pair of left and right rear wheels 2bR and 2bL provided on the rear side of the vehicle 100. . A motor generator 3 is connected to the front wheel axle 4 connected to the left and right front wheels 2aR, 2aL by a torque transmission mechanism. The vehicle 100 may be four-wheel drive or rear-wheel drive, or may be configured as a hybrid vehicle including the motor / generator 3. The differential mechanism provided on the front wheel axle 4 is not shown.

  The motor / generator 3 serves as both a vehicle driving motor and a regeneration generator. A battery 5 as a secondary battery supplies power to the motor / generator 3 by an inverter 6 as a power source of the motor / generator 3. Further, when the vehicle 100 is decelerated, the motor / generator 3 converts the deceleration energy into electric power, and the battery 5 stores the regenerated generated electric power. During this regeneration, the motor / generator 3 generates a regenerative braking force. That is, a regenerative braking force generator is realized by the motor / generator 3 or the like.

Further, the battery 5 is provided with a charge amount detection sensor 8 (voltage sensor and / or current sensor) for detecting a charge amount (SOC: State Of Charge) of the battery 5.
The control system 7 is a system including various control units that control each unit (details will be described later).

  The friction braking device 10 is a friction braking force generator. That is, each wheel 2aR, 2aL, 2aR, 2aL is connected to each wheel cylinder of the disc brake mechanism 30a-30d, and the wheel cylinder is driven by hydraulic pressure (hydraulic pressure), and the brake pad is pressed against the brake rotor for friction. A device for generating a braking force. As the friction braking device 10, various devices can be applied as long as they are brake devices for generating a friction braking force. In this example, a so-called by-wire brake system is used.

FIG. 2 is a configuration diagram illustrating an outline of the friction braking device 10.
The friction braking device 10 includes an input device 14 including a master cylinder 34 that converts a pedaling force input by a driver by operating the brake pedal 12 into a brake fluid pressure, etc., according to the brake fluid pressure generated in the master cylinder 34, or The motor cylinder device 16 that generates the brake fluid pressure regardless of the brake fluid pressure, the vehicle behavior stabilization device (VSA (registered trademark) device, etc.) 18, the disc brake mechanisms 30a to 30d, and the like are provided. The motor cylinder device 16 includes first and second slave pistons 77a and 77b that receive the driving force of the electric motor 72 and generate brake fluid pressure.
The pipes 22a to 22f are provided with brake fluid pressure sensors Pm, Pp, and Ph that detect the brake fluid pressure of each part. Further, the vehicle behavior stabilization device 18 includes a pump 73 for pressurizing brake fluid.

  The motor cylinder device 16 (via the vehicle behavior stabilization device 18) includes a wheel cylinder 32FR that generates friction braking force by hydraulic pressure with a disc brake mechanism 30a provided on a right front wheel of a vehicle (not shown), and a left rear wheel. A wheel cylinder 32RL that generates friction braking force by hydraulic pressure on the disc brake mechanism 30b provided on the wheel, a wheel cylinder 32RR that generates friction braking force by hydraulic pressure on the disc brake mechanism 30c provided on the right rear wheel, and a left side A wheel cylinder 32FL that generates a friction braking force by hydraulic pressure is connected to a disc brake mechanism 30d provided on the front wheel.

Next, the basic operation of the friction braking device 10 will be described.
In the friction braking device 10, when the driver steps on the brake pedal 12 during normal operation of the control system that controls the motor cylinder device 16 and the by-wire, a so-called by-wire brake system is activated. Specifically, in the friction braking device 10 during normal operation, when the driver steps on the brake pedal 12 (detected by a brake pedal stroke sensor 151 described later), the first cutoff valve 60a and the second cutoff valve 60b are the masters. Brake fluid pressure generated by the motor cylinder device 16 when the motor 72 is driven in a state where communication between the cylinder 34 and the disc brake mechanisms 30a to 30d (wheel cylinders 32FR, 32RL, 32RR, 32FL) for braking each wheel is cut off. Is used to actuate the disc brake mechanisms 30a to 30d to brake each wheel.

  During normal operation, the first shut-off valve 60a and the second shut-off valve 60b are shut off, while the third shut-off valve 62 is opened, and the brake fluid flows from the master cylinder 34 into the stroke simulator 64. Even when the first shut-off valve 60a and the second shut-off valve 60b are shut off, the brake fluid moves and a stroke is generated when the brake pedal 12 is operated, and a pedal reaction force is generated.

  On the other hand, in the friction braking device 10, when the driver steps on the brake pedal 12 in an abnormal state where the motor cylinder device 16 or the like is inoperative, the existing hydraulic brake system becomes active. Specifically, in the friction braking device 10 at the time of abnormality, when the driver steps on the brake pedal 12, the first cutoff valve 60a and the second cutoff valve 60b are opened, and the third cutoff valve 62 is As the valve is closed, the brake fluid pressure generated in the master cylinder 34 is transmitted to the disc brake mechanisms 30a to 30d (wheel cylinders 32FR, 32RL, 32RR, 32FL) and the disc brake mechanisms 30a to 30d (wheel cylinders 32FR, 32RL, 32RR, 32FL) is actuated to brake each wheel.

  The vehicle behavior stabilization device 18 can individually supply hydraulic pressure to the individual wheel cylinders 32FR, 32RL, 32RR, 32FL, thereby stabilizing the behavior of the vehicle 100. The anti-lock control of the wheel by ABS (Antilock Brake System) is also performed by the vehicle behavior stabilization device 18.

Next, the configuration and operation of the control system 7 will be described.
FIG. 3 is a block diagram of the control system 7. First, the regenerative braking force control unit 101 performs control to generate regenerative braking force by the motor / generator 3 and the like, and the regenerated electric power is stored in the battery 5.
The shift control unit 111 performs control related to a shift lever (select lever) (not shown) of the vehicle.

The motor control unit 121 controls the motor / generator 3 when the motor / generator 3 is driven as a motor.
The vehicle behavior stabilization control unit 131 performs control related to the vehicle behavior stabilization device 18. In particular, the vehicle behavior stabilization control unit 131 controls the operation of the ABS by the vehicle behavior stabilization device 18.

The friction braking force control unit 141 controls the by-wire brake by the friction braking device 10. The friction braking force control unit 141 includes a driver request hydraulic pressure calculation unit 142, a hydraulic pressure restriction processing unit 143, a switchback state determination unit 144, a wheel slip determination unit 145, a vehicle stop determination unit 146, and a hydraulic pressure limit. Unit 147 and a hydraulic pressure control unit 148.
The driver required hydraulic pressure calculation unit 142 calculates the hydraulic pressure (braking force) requested by the driver based on the detection result of the brake pedal stroke sensor 151 that detects the stroke amount and stroke speed of the brake pedal 12.

The regenerative braking force control unit 101 performs control to generate a braking force equivalent to an engine brake in a normal gasoline vehicle with the regenerative braking force without depending on a driver's braking operation when an accelerator pedal (not shown) is not operated. . At this time, when the battery 5 is in a predetermined state, such as when the amount of charge of the battery 5 reaches a value determined as the upper limit, the friction braking force is changed from the regenerative braking force by the regenerative braking force control unit 101. The braking force of the vehicle 100 is shifted to the friction braking force by the control unit 141. That is, in this case, the regenerative braking force control unit 101 is a request that is information indicating the hydraulic pressure (friction braking force) generated by the friction braking device 10 by the hydraulic pressure restriction processing unit 143 of the friction braking force control unit 141. Outputs hydraulic pressure. That is, the regenerative braking force control unit 101 and the hydraulic pressure restriction processing unit 143 realize a transition unit.
The hydraulic pressure restriction processing unit 143 basically instructs generation of a hydraulic pressure (friction braking force) corresponding to the required hydraulic pressure (the upper limit value of the hydraulic pressure will be described later). Then, the required hydraulic pressure instructed by the driver required hydraulic pressure calculation unit 142 and the required hydraulic pressure instructed by the hydraulic pressure restriction processing unit 143 are added by the adding unit 149 and output to the hydraulic pressure limiting unit 147.

  The vehicle behavior stabilization control unit 131 outputs wheel speed information indicating the wheel speed obtained from the wheel speed sensor 152 that measures the wheel speed of the vehicle 100 to the vehicle stop determination unit 146 of the friction braking force control unit 141. When the vehicle stop determination unit 146 determines that the vehicle 100 is stopped from the wheel speed information, the vehicle stop determination unit 146 places a predetermined restriction on the required hydraulic pressure added by the addition unit 149. The hydraulic pressure control unit 148 controls the motor 72 (FIG. 2) based on the required (or unrestricted) required hydraulic pressure after the restriction, and the friction braking device 10 generates a friction braking force.

  By the way, when the friction braking force is operated instead of the regenerative braking force as described above, an abnormality occurs in the regenerative braking force control unit 101 that controls the regenerative braking force, or communication is performed in the vehicle 100. An anomaly may occur in the system (CAN: Controller Area Network). In that case, the hydraulic pressure restriction processing unit 143 of the friction braking force control unit 141 is required to generate a friction braking force that is larger than necessary, and a braking force that is more than the engine brake may be generated. There is a risk of feeling uncomfortable.

Therefore, the hydraulic pressure limiting processing unit 143 sets an upper limit value for the required hydraulic pressure to be added to the adding unit 149 so that a hydraulic pressure (friction braking force) exceeding the upper limit value is not generated, and a frictional control larger than necessary is controlled. The generation of power is prevented. That is, the hydraulic pressure restriction processing unit 143 functions as an upper limit value setting unit.
In this case, normally, the hydraulic pressure restriction processing unit 143 sets “first value” as the upper limit value.

However, in the case of an electric vehicle or a plug-in hybrid vehicle, a state called switchback may occur. The switchback occurs when the vehicle 100 is moved in from the front in order to charge at the charging stand, and after the charging is completed, the shift lever (select lever) of the vehicle 100 is put in the reverse range (R). In other words, in this case, the vehicle 100 moves backward, but the driver wants to move the vehicle 100 forward as soon as possible. Therefore, the driver suddenly puts the shift lever (select lever) into the drive range (D) and tries to start immediately. To do. Thus, the case where the traveling direction of the vehicle (back movement) and the traveling direction of the vehicle indicated by the position of the shift lever (select lever) are reversed is referred to as switchback.
In the case of switchback, it is necessary to generate a relatively large braking force in order to quickly match the traveling direction of the vehicle with the position of the shift lever (select lever).

  Therefore, the switchback state determination unit 144 acquires shift information that is information regarding the position of the shift lever (select lever) from the shift control unit 111. The switchback state determination unit 144 also acquires vehicle traveling direction information, which is information on the rotation direction (vehicle traveling direction) of the motor / generator 3 during power running, from the motor control unit 121. Since the switchback state determination unit 144 can determine whether or not the switchback is performed from these pieces of information, the switchback state determination unit 144 transmits the information to the hydraulic pressure restriction processing unit 143 as hydraulic pressure restriction information. When the hydraulic pressure restriction processing unit 143 determines that the switchback has occurred based on the hydraulic pressure restriction information, the hydraulic pressure restriction processing unit 143 uses the first value as the upper limit value in order to generate a large braking force that temporarily stops the vehicle 100. A “second value” that is larger than the value is set.

Further, the ABS operates when slip occurs on the wheels of the vehicle 100. In this case, since the ABS operates even if the brake pedal 12 is not operated, there is a problem that the operation sound is annoying.
Therefore, in this case, it is necessary to generate a relatively small braking force in order to make the ABS difficult to operate.

Therefore, the wheel slip determination unit 145 acquires the wheel speed information from the vehicle behavior stabilization control unit 131 and determines whether or not the wheels of the vehicle 100 are slipping. Further, the wheel slip determination unit 145 acquires ABS operation information that is information indicating that the ABS is operating from the vehicle behavior stabilization control unit 131, and determines whether or not the ABS is operating. Then, the fact that the wheel is slipping or the ABS is already operating is transmitted to the hydraulic pressure restriction processing unit 143 as hydraulic pressure restriction information.
When the hydraulic pressure limit processing unit 143 determines that the wheel is slipping or the ABS is already operating according to the hydraulic pressure limit information, the hydraulic pressure limit processing unit 143 sets the first limit value as the upper limit value so as not to operate the ABS. A “third value” that is smaller than the value of 1 is set.

  FIG. 4 is a graph for explaining the operation of the control system 7. This graph shows a state of the vehicle 100 that is traveling in a state where neither the brake pedal 12 nor an accelerator pedal (not shown) is operated. Also shown are the time when the battery 5 is fully charged (charge value that is a predetermined reference value) and the time when the vehicle 100 creeps. “Regeneration restriction start” indicates a time point at which a gradual transition from the regenerative braking force to the friction braking force is started.

As shown in (a), when the state of charge of the battery 5 increases and becomes fully charged, the regenerative braking force shifts to the generation of the friction braking force, so that the charge value of the battery 5 does not become higher than the full charge.
Further, as shown in (b), a braking force equivalent to the engine brake of a normal gasoline vehicle is generated, so that the vehicle speed gradually decreases.
As shown in (c), a regenerative torque equivalent to engine braking is generated until the battery is fully charged (a negative value because it is in the deceleration direction), and no regenerative braking force is generated after the full charge. Thus, a positive regenerative torque is generated after creep. The limit torque is a torque limit determined from the state of charge.

As shown in (d), when the required torque of the friction braking force gradually increases from the start of regenerative restriction, reaches the maximum at the time of full charge, gradually decreases due to the increase of the regenerative torque (c) corresponding to engine brake, and creep occurs. 0.
(E) shows the required hydraulic pressure output by the hydraulic pressure restriction processing unit 143 corresponding to the required torque of the friction braking force in (d), and the actual hydraulic pressure generated by the friction braking device 10 using this as a target value. It shows. In addition, three types of upper limit values of the first value, the second value, and the third value are also shown. In this example, the first value is controlled as the upper limit value. That is, the required hydraulic pressure does not exceed the first value, and therefore the actual hydraulic pressure follows the required hydraulic pressure.

  According to the vehicle braking system of the present embodiment described above, since the upper limit value is set for the friction braking force, when the braking force equivalent to the engine brake is generated, when the regenerative braking force is shifted to the friction braking force, It is possible to prevent an excessive friction braking force from being generated due to the occurrence of an abnormality in the regenerative braking force control unit 101 or the like.

  Also, as the upper limit value, the second value and the third value are also used in addition to the first value, so that the ABS operation for switching back or stabilizing the behavior of the vehicle is performed. An appropriate upper limit value of the friction braking force can be set to prevent the occurrence.

  Needless to say, the present invention is not limited to the contents of the above-described embodiments, and various modifications are possible. For example, when the vehicle 100 is a hybrid vehicle, as the regenerative braking force, the engine may be idled by a motor / generator to generate a braking force, and the shortage may be compensated by the friction braking force.

3 Motor generator (regenerative braking force generator)
5 Battery 10 Friction braking device (friction braking force generator)
101 Regenerative braking force control unit (transition unit)
141 Friction braking force control unit (transition unit)
143 Hydraulic pressure restriction processing unit (upper limit setting unit)
144 Switchback state determination unit 145 Wheel slip determination unit

Claims (1)

A regenerative braking force generator that generates a regenerative braking force equivalent to engine braking without the driver's braking operation when the accelerator pedal is not operated ;
A friction braking force generator for generating friction braking force;
When the battery that stores the electric power generated by the generation of the regenerative braking force is in a predetermined state, the braking force of the vehicle is transferred from the regenerative braking force to the friction braking force without depending on the driver's braking operation. The transition department,
An upper limit setting unit configured to set an upper limit value for the friction braking force when the transition unit generates an insufficient amount of the regenerative braking force with the friction braking force ;
A switchback state determination unit for determining that switchback is being performed in the vehicle;
A wheel slip determination unit that determines that slip has occurred in the wheel of the vehicle in order to stabilize the behavior of the vehicle,
The upper limit setting unit sets a first value corresponding to the engine brake as the upper limit when the switchback is not performed and the slip does not occur, and the switchback When it is performed, a second value higher than the first value is set as the upper limit value, and when the slip occurs, a third value lower than the first value is set as the upper limit value. braking system for a vehicle, characterized in that.

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