JP6500732B2 - Brake control device - Google Patents

Description

  The present invention relates to a brake control device.

  Conventionally, there is known a brake control device that operates a hydraulic brake device by boosting a brake hydraulic pressure by a brake actuator including a pump driven by an electric motor (for example, Patent Document 1 etc.).

  By using the pressure increase function of the brake actuator (pump), an automatic brake function for avoiding a collision, an ABS (Anti-lock Brake System) function, and the like can be realized.

JP 2005-59625 A

  By the way, when operating an automatic brake function, it is desirable from a viewpoint of improvement of safety performance to raise brake fluid pressure to target oil pressure by higher responsiveness. For that purpose, it is necessary to increase the output of the electric motor that drives the pump.

  However, adopting a high output electric motor increases the current consumption of the electric motor, which may affect the power supply system that supplies power to the electric motor. For example, a connector terminal for connecting to an in-vehicle wire harness is designed according to the current consumption, so if existing connector terminals are used, there is a possibility of abnormal heat generation or fuse melting due to continued high current consumption. . In addition, if a connector terminal corresponding to an increase in current consumption is adopted, the part size of the brake actuator including the electric motor may inevitably be increased.

  On the other hand, in order to suppress the continuation of high current consumption due to the high output electric motor, if the ON state of the electric motor is limited in a situation where high responsiveness is not required, the automatic brake function or ABS function etc. may be properly operated. It may not be possible. For example, if the electric motor is duty-controlled to keep the consumption current below the allowable current of the connector terminal, the target hydraulic pressure in the automatic braking function can not be maintained, or the high braking hydraulic pressure by sudden braking when the ABS function is activated. May be stalled.

  Therefore, in view of the above problems, it is an object of the present invention to provide a brake control device capable of appropriately operating the automatic brake function and the ABS function while suppressing the influence on the power supply system by increasing the output of the electric motor. .

In order to achieve the above object, in one embodiment, the brake control device
A brake control device that controls the operating state of a hydraulic brake device that generates a braking force on the wheels of a vehicle.
A power supply that supplies a predetermined voltage according to the state of charge;
A master cylinder that generates a first brake hydraulic pressure according to a brake operation, the upper limit being a predetermined first maximum value;
A brake actuator for generating a second brake hydraulic pressure for operating the brake device by holding, increasing or reducing the pressure of the first brake hydraulic pressure, wherein the hydraulic pump increases the first brake hydraulic pressure, and the predetermined voltage A brake actuator including: an electric motor that generates a torque necessary to saturate the second brake hydraulic pressure at a second maximum value that is equal to or greater than the first maximum value, and drives the hydraulic pump;
When it is determined that the vehicle may collide with an obstacle, the hydraulic brake is used to increase the first brake hydraulic pressure to automatically operate the brake device, controlling the operating state of the automatic brake function. Automatic brake control unit,
When it is determined that the wheel is in the locked state by the brake operation, the braking force is adjusted by the hydraulic pump, including the pressure increase of the first brake hydraulic pressure, and the locked state is canceled. ABS control unit to control,
The electric motor control unit controls the operating state of the electric motor, and when the automatic brake control unit operates the automatic brake function, the second brake hydraulic pressure is set to a predetermined target value lower than the second maximum value. It is necessary for the second brake hydraulic pressure to saturate at the target value when the second brake hydraulic pressure reaches the target value while continuously supplying the predetermined voltage from the power supply to the electric motor until reaching the target When the predetermined voltage is supplied from the power source to the electric motor at a duty ratio corresponding to a certain torque, and the ABS control unit operates the ABS function, the electric motor operates against the first brake hydraulic pressure And an electric motor control unit for supplying the predetermined voltage from the power supply to the electric motor at a duty ratio corresponding to a limit torque necessary to perform the operation.

  According to the present embodiment, it is possible to provide a brake control device capable of appropriately operating the automatic brake function and the ABS function while suppressing the influence on the power supply system due to the high output of the electric motor.

It is a block diagram which shows an example of a structure of a brake control apparatus. It is a flowchart which shows notionally an example of the control processing by a brake control device (electric motor control part). It is a figure explaining the control aspect of the brake control apparatus (electric motor control part) at the time of the action | operation of an automatic brake function.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing an example of the configuration of a brake control device 1 according to the present embodiment. The brake control device 1 is mounted on a vehicle and controls an operating state of a hydraulic brake device (drum brake) 10 that generates a braking force on each wheel of the vehicle.

  The brake device 10 includes a wheel cylinder 11 and a brake shoe 12 provided on each wheel, and operates with a brake hydraulic pressure (wheel cylinder pressure) supplied from a brake actuator 5 described later. That is, a piston (not shown) in the wheel cylinder 11 presses the brake shoe 12 against the inner surface of a drum (not shown) fixed to each wheel by the action of the wheel cylinder pressure supplied to the wheel cylinder 11. Thereby, braking force can be applied to each wheel.

  The drum brake as the brake device 10 is an example of a hydraulic brake device operated by the brake hydraulic pressure supplied from the brake actuator 5, and the brake device 10 may be, for example, a disk brake. For example, in the case of a disc brake, the piston in the wheel cylinder 11 presses the brake pad against the brake disc by the action of the wheel cylinder pressure supplied to the wheel cylinder 11. Thereby, braking force can be applied to each wheel.

  The brake control device 1 includes a master cylinder 4, a brake actuator 5, a brake device 10, a brake ECU 20, and a battery 30.

  Master cylinder 4 generates a brake hydraulic pressure (master cylinder pressure (MC pressure)) in response to a brake operation on brake pedal 45 by the driver of the vehicle. Specifically, the brake operating force on the brake pedal 45 is amplified by the brake booster 46, and the amplified brake operating force is taken out as the brake hydraulic pressure (MC pressure). The master cylinder 4 is connected to the brake actuator 5 in two systems (first system, second system), and the generated MC pressure is introduced to the brake actuator 5.

  The maximum value (maximum MC pressure) P1max of the MC pressure generated by the master cylinder 4 corresponds to the case of performing a full stroke brake operation on the brake pedal 45.

  The brake actuator 5 generates a wheel cylinder pressure that operates the brake device 10. The brake actuator 5 includes a first system for supplying wheel cylinder pressure to wheel cylinders 11 of two wheels (for example, right front wheel and left front wheel, right front wheel and left rear wheel, etc.) of the respective wheels, and For example, there is a second system for supplying the wheel cylinder pressure of the wheel cylinder 11 of the right rear wheel and the left rear wheel, the left front wheel and the right rear wheel, and the like. The second system has a configuration similar to that of the first system, and thus is omitted in the figure. The following describes the first system.

  The brake actuator 5 includes a control valve 51, a holding valve 52, a pressure reducing valve 53, a reservoir 54, a hydraulic pump 55, an electric motor 56, and the like.

  The MC pressure introduced from the master cylinder 47 is normally output to the wheel cylinder 11 of each wheel through the normally open adjusting valve 51 and the holding valve 52. Thus, the brake device 10 can apply a braking force corresponding to the driver's brake operation to the vehicle (wheels).

  Further, by opening the normally closed pressure reducing valve 53, a part of the MC pressure supplied through the adjusting valve 51 and the holding valve 52 is returned to the reservoir 54. Can be supplied.

  Further, the normally open adjustment valve 51 can adjust the degree of closure linearly, and by driving the hydraulic pump 55 by the electric motor 56 in a state where the adjustment valve 51 is closed (states other than full open), The wheel cylinder pressure in which the MC pressure is increased can be supplied to the wheel cylinder 11.

  In the present embodiment, the electric motor 56 for driving the hydraulic pump 55 has a relatively high output specification from the viewpoint of accelerating the rise of the braking force in the automatic brake function described later (in order to improve the wheel cylinder pressure response). The thing is adopted. The electric motor 56 can generate a torque necessary to saturate at the maximum wheel cylinder pressure P2max at which the wheel cylinder pressure P2 is equal to or higher than the maximum MC pressure P1max, by the predetermined voltage V1 supplied from the battery 30.

  Thus, the brake actuator 5 holds, increases or reduces the MC pressure to generate a wheel cylinder pressure that actuates the brake device 10.

  The adjusting valve 51, the holding valve 52, the pressure reducing valve 53, and the electric motor 56 operate in response to a control command from the brake ECU 20.

  The brake ECU 20 is an electronic control unit that controls the operating state of the brake device 10. The brake ECU 20 includes a microcomputer 21, a drive circuit 22, a power supply circuit 23, and the like.

  The microcomputer 21 includes a CPU, a RAM, a ROM, an input / output interface and the like, and can execute various control processes by executing various programs stored in the ROM on the CPU. The microcomputer 21 includes an automatic brake control unit 211, an ABS control unit 212, and an electric motor control unit 213 as functional units realized by executing one or more corresponding programs on the CPU.

  The automatic brake control unit 211 operates the function (automatic brake function) to automatically operate the brake device 10 regardless of the driver's brake operation when it is determined that the vehicle may collide with an obstacle ahead of the vehicle. Control the state. For example, the automatic brake control unit 211 calculates TTC (Time To Collision: collision time) from the distance D to the obstacle detected by a radar (not shown) mounted on the vehicle and the relative velocity Vr of the obstacle. Then, when the TTC becomes equal to or less than the predetermined threshold Tth, the automatic brake control unit 211 activates the automatic brake function.

  The automatic braking function can be realized by the pressure increasing function by the hydraulic pump 55. That is, the automatic brake control unit 211 closes the adjusting valve 51 and drives the electric motor 56 via the electric motor control unit 213 to increase the MC pressure and automatically make the brake device 10 It can be operated.

  The function of the automatic brake control unit 211 may be realized by an ECU other than the brake ECU (for example, a PCS-ECU or the like that executes control processing for collision avoidance of a vehicle). In such a case, the brake ECU 20 automatically operates the brake device 10 in response to the operation request from the PCS-ECU.

  When it is determined by the driver's brake operation that the wheel is in the locked state, the ABS control unit 212 adjusts the braking force acting on the wheel to control the operating state of the function (ABS function) for canceling the locked state. For example, when the wheel speed of each wheel detected by a wheel speed sensor (not shown) becomes equal to or more than a predetermined slip reference, the ABS control unit 212 determines that the wheel is in a locked state and performs ABS function Activate. The details of the control method of the ABS function are omitted because they are known, but the wheel lock is repeated by repeating the three steps of pressure reduction by the pressure reducing valve 53 of MC pressure, holding by the holding valve 52 and pressure increase by the hydraulic pump 55. Clear the condition.

  The electric motor control unit 213 controls the operating state of the electric motor 56. When operating the electric motor 56, the electric motor control unit 213 outputs a drive command to the drive circuit 22, and the predetermined voltage V1 (for example, 12 V to 15 V) according to the charge state supplied from the battery 30 is output to the electric motor Apply to 56. Details of control processing by the electric motor control unit 213 will be described later.

  The drive circuit 22 applies a predetermined voltage V1 supplied from the battery 30 to the electric motor 56 in accordance with a drive command from the electric motor control unit 213. For example, the drive circuit 22 includes a relay provided in a path for supplying power from the battery 30 to the electric motor 56.

  The power supply circuit 23 is an electronic circuit that converts the predetermined voltage V1 supplied from the battery 30 into a voltage for driving the microcomputer 21 and the like.

  The battery 30 is a power storage device mounted on a vehicle, and is, for example, a secondary battery such as a lead battery or a lithium ion battery. The battery 30 supplies a predetermined voltage V1 to the brake ECU 20, the electric motor 56, and the like.

  Next, with reference to FIG. 2, a characteristic operation by the brake control device 1 according to the present embodiment, that is, a control process by the electric motor control unit 213 will be described.

  FIG. 2 is a flow chart conceptually showing an example of control processing by the brake control device 1 (electric motor control unit 213). The process according to the present blow chart is repeatedly performed from ignition on (IG-ON) to ignition off (IG-OFF) of the vehicle.

  In step S102, the electric motor control unit 213 determines whether the automatic brake control unit 211 operates the automatic brake function. When the automatic brake control unit 211 operates the automatic brake function, the electric motor control unit 213 proceeds to step S104. When the automatic brake control unit 211 does not operate the automatic brake function, the electric motor control unit 213 proceeds to step S110.

  In step S104, the electric motor control unit 213 determines whether the wheel cylinder pressure P2 has reached the target hydraulic pressure Ptarget required in the automatic brake function. Such determination may be performed by monitoring the detection value of the wheel cylinder pressure sensor 90, or may be performed based on whether or not a predetermined time T1 (for example, 200 ms) based on the specification of the electric motor 56 has elapsed. . If the wheel cylinder pressure P2 does not reach the target hydraulic pressure Ptarget, the electric motor control unit 213 proceeds to step S106, and if the target hydraulic pressure Ptarget is reached, the electric motor control unit 213 proceeds to step S108.

  The target hydraulic pressure Ptarget is smaller than the maximum wheel cylinder pressure P2max which is the maximum value of the wheel cylinder pressure P2 that can be generated by the electric motor 56.

  In step S106, the electric motor control unit 213 keeps the electric motor 56 always in the ON state. That is, by constantly turning on the electric motor 56 until the wheel cylinder pressure P2 reaches the target hydraulic pressure Ptarget required by the automatic brake function, the rise of the wheel cylinder pressure P2 can be accelerated (response can be improved). .

  On the other hand, in step S108, the electric motor control unit 213 executes duty control of the electric motor 56 according to the target hydraulic pressure Ptarget (hereinafter, referred to as first duty control). The first duty control is duty control of the electric motor 56 for maintaining the wheel cylinder pressure P2 at the target hydraulic pressure Ptarget. Hereinafter, the first duty control will be described.

  The torque (necessary torque) T required to maintain the wheel cylinder pressure P2 at the target oil pressure Ptarget (the wheel cylinder pressure P2 saturates at the target oil pressure Ptarget) is expressed by the following equation (1).

T = TPmax · (Ptarget / P1max) (1)
TPmax is a torque (stall limit torque) required to prevent the electric motor 56 from stalling when the MC pressure P1 is the maximum MC pressure P1max. The stall limit torque TPmax is previously defined by the specifications of the electric motor 56 and the like.

  A required voltage (required voltage) V between the terminals of the electric motor 56 corresponding to the required torque T is expressed by the following equation (2).

V = Kt · Nstall + (r / Kt) · T (2)
Kt is a motor torque constant, Nstall is a stall rotational speed of the electric motor 56, r is a resistance of the electric motor 56, and is prescribed in advance by the specification of the electric motor 56 or the like.

  As described above, since the electric motor 56 can generate the predetermined value P2max larger than the target hydraulic pressure Ptarget by the predetermined voltage V1 supplied from the battery 30, the required voltage V represented by the equation (2) is predetermined Less than voltage V1. Therefore, the electric motor control unit 213 controls the battery via the drive circuit 22 at a duty ratio corresponding to the required voltage V, that is, a duty ratio corresponding to the torque T for saturating the wheel cylinder pressure P2 at the target hydraulic pressure Ptarget. A predetermined voltage V1 is supplied to the electric motor 56 from 30.

  Here, FIG. 3 is a diagram for explaining a control mode of the brake control device 1 (electric motor control unit 213) when the automatic brake function is activated.

  As shown in FIG. 3, the electric motor control unit 213 causes the processing from step S106 to set a predetermined value from the battery 30 to the electric motor 56 via the drive circuit 22 until the wheel cylinder pressure P2 reaches the target hydraulic pressure Ptarget. The voltage V1 is continuously supplied. As a result, the electric motor 56 can be driven with high responsiveness, and the wheel cylinder pressure P2 can be raised faster to the target hydraulic pressure Ptarget required in the automatic braking function.

  Further, when the wheel cylinder pressure P2 reaches the target hydraulic pressure Ptarget in the process of step S108, the electric motor control unit 213 performs electric drive at a duty ratio corresponding to the torque T for the wheel cylinder pressure P2 to saturate at the target hydraulic pressure Ptarget. The duty control of the motor 56 is performed. Thus, it is possible to maintain the wheel cylinder pressure P2 at the target hydraulic pressure Ptarget required by the automatic brake function while suppressing the current consumption of the electric motor 56.

  Referring back to FIG. 2, in step S110, the electric motor control unit 213 determines whether the ABS control unit 212 operates the ABS function. When the ABS control unit 212 operates the ABS function, the electric motor control unit 213 proceeds to step S112. When the ABS control unit 212 does not operate the ABS function, the electric motor control unit 213 ends the current process.

  In step S112, the electric motor control unit 213 executes duty control (hereinafter, referred to as second duty control) of the electric motor 56 in accordance with the driver's brake operation (MC pressure P1). The second duty control is duty control of the electric motor 56 for operating without stalling against the MC pressure P1. The second duty control will be described below.

  The torque (required torque) T of the electric motor 56 required to operate without stalling against the MC pressure P1 is expressed by the following equation (3).

T = TPmax (Puser / Pmax) (3)
Puser is an MC pressure P1 corresponding to the driver's brake operation detected by the master cylinder pressure sensor (MC pressure sensor) 80.

  The required voltage (required voltage) V between the terminals of the electric motor 56 corresponding to the required torque T is expressed by the equation (2) as described above.

  As described above, since the electric motor 56 can generate the predetermined value P2max larger than the maximum MC pressure P1max by the predetermined voltage V1 supplied from the battery 30, the required voltage V represented by the equation (2) is It is smaller than the predetermined voltage V1. Therefore, the electric motor control unit 213 controls the drive circuit 22 with a duty ratio corresponding to the required voltage V, that is, a duty ratio corresponding to the torque T necessary for the electric motor 56 to operate against the MC pressure P1. The predetermined voltage V1 is supplied from the battery 30 to the electric motor 56 through the same. Thereby, for example, when the high MC pressure P1 is generated by the brake operation while suppressing the current consumption of the electric motor 56 in the case where the predetermined voltage V1 from the battery 30 is constantly supplied to the electric motor 56. Even if there is, the electric motor 56 can be operated without stalling.

  As described above, in the present embodiment, it is possible to appropriately operate the automatic braking function and the ABS function while suppressing the current consumption of the electric motor 56. And, by suppressing the consumption current in the electric motor 56, as described above, even in the case of adopting the electric motor 56 of the high output specification, it is possible to suppress the influence on the power supply system. That is, in the present embodiment, the automatic braking function and the ABS function can be appropriately operated while suppressing the influence on the power supply system.

  As mentioned above, although the form for carrying out the present invention was explained in full detail, the present invention is not limited to such a specific embodiment, and within the range of the gist of the present invention described in the claim, It is possible to change and change

1 brake control device 4 master cylinder 5 brake actuator 10 brake device 11 wheel cylinder 12 brake shoe 20 brake ECU
21 microcomputer 22 drive circuit 23 power supply circuit 30 battery (power supply)
55 hydraulic pump 56 electric motor 80 master cylinder pressure sensor 90 wheel cylinder pressure sensor 211 automatic brake control unit 212 ABS control unit 213 electric motor control unit

Claims (1)

A brake control device that controls the operating state of a hydraulic brake device that generates a braking force on the wheels of a vehicle.
A power supply that supplies a predetermined voltage according to the state of charge;
A master cylinder that generates a first brake hydraulic pressure according to a brake operation, the upper limit being a predetermined first maximum value;
A brake actuator for generating a second brake hydraulic pressure for operating the brake device by holding, increasing or reducing the pressure of the first brake hydraulic pressure, wherein the hydraulic pump increases the first brake hydraulic pressure, and the predetermined voltage A brake actuator including: an electric motor that generates a torque necessary to saturate the second brake hydraulic pressure at a second maximum value that is equal to or greater than the first maximum value, and drives the hydraulic pump;
When it is determined that the vehicle may collide with an obstacle, the hydraulic brake is used to increase the first brake hydraulic pressure to automatically operate the brake device, controlling the operating state of the automatic brake function. Automatic brake control unit,
When it is determined that the wheel is in the locked state by the brake operation, the braking force is adjusted by the hydraulic pump, including the pressure increase of the first brake hydraulic pressure, and the locked state is canceled. ABS control unit to control,
The electric motor control unit controls the operating state of the electric motor, and when the automatic brake control unit operates the automatic brake function, the second brake hydraulic pressure is set to a predetermined target value lower than the second maximum value. It is necessary for the second brake hydraulic pressure to saturate at the target value when the second brake hydraulic pressure reaches the target value while continuously supplying the predetermined voltage from the power supply to the electric motor until reaching the target When the predetermined voltage is supplied from the power source to the electric motor at a duty ratio corresponding to a certain torque, and the ABS control unit operates the ABS function, the electric motor operates against the first brake hydraulic pressure An electric motor control unit for supplying the predetermined voltage from the power supply to the electric motor at a duty ratio corresponding to a limit torque required to
Brake control device.

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