JP5545490B2 - Brake control device - Google Patents

Description

  The present invention relates to a brake control device that controls the operation of a brake device of a vehicle.

  In a brake system of an automobile, a negative pressure actuator or an electric actuator is used to perform a boost control and a brake assist control to assist a driver's brake operation force, and using a pump, an accumulator, an electromagnetic switching valve, etc. Anti-lock brake control that prevents the wheels from locking during braking by adjusting the braking force for each wheel according to the road surface condition and running condition, etc., vehicle stability that suppresses understeer and oversteer and improves steering stability 2. Description of the Related Art A brake control device that performs various controls such as control is known.

  For example, Patent Document 1 discloses a brake fluid pressure boosted in a master cylinder by an input piston that is directly operated by a brake pedal and an assist member that is driven by an electric actuator that is operated according to an operation amount of the brake pedal. A brake control device that generates and supplies this hydraulic pressure to a wheel cylinder via a hydraulic circuit of an anti-lock brake device (hereinafter also referred to as ABS) is described. In this brake control device, during the operation of the ABS, the operation of the electric actuator is feedback-controlled based on the hydraulic pressure of the master cylinder detected by the hydraulic pressure sensor. The brake pedal operation feeling has been improved by suppressing fluctuations in the brake pedal force.

JP 2009-248673 A

  However, in the brake control device described in the above-mentioned Patent Document 1, when the hydraulic pressure information cannot be obtained due to the abnormality of the hydraulic pressure sensor or when the ABS operation information cannot be obtained due to the communication abnormality of the in-vehicle network, the master In situations where the feedback control of the electric actuator based on the hydraulic pressure of the cylinder is impossible, it is not possible to appropriately cope with the hydraulic pressure fluctuation of the master cylinder due to the operation of the ABS, and the deterioration of the brake pedal operation feeling can be avoided. Absent.

  Accordingly, an object of the present invention is to provide a brake control device that can improve the operational feeling by suppressing fluctuations in the depression force of the brake pedal even in a situation where sufficient control information cannot be obtained.

  In order to solve the above-described problems, a brake control device according to the present invention includes an input member that moves forward and backward by an operation of a brake pedal, an assist member that is movable relative to the input member, and the assist member. A master cylinder that generates brake fluid pressure by propulsion and supplies it to the brake device, an electric motor, and a rotation-linear motion conversion mechanism that propels the assist member by converting the rotational motion of the electric motor into a linear motion; In the brake control device comprising: a controller that controls the operation of the electric motor by supplying a current to the electric motor based on control information including operation information from the master cylinder side or the brake device side. When the operation information cannot be obtained from the master cylinder side or the brake device side, the electric motor is supplied. And limits the maximum value of the current to a predetermined limit current value.

  According to the brake control device according to the present invention, it is possible to improve the operation feeling by suppressing the depression force of the brake pedal even in a situation where sufficient control information cannot be obtained.

It is a figure showing a schematic structure of a brake control device concerning one embodiment of the present invention. It is a circuit diagram which shows schematic structure of the master pressure control apparatus of the brake control apparatus shown in FIG. It is a block diagram which shows the control by the master pressure control apparatus of FIG. It is explanatory drawing which shows the balance of force in the master pressure control mechanism of the brake control apparatus shown in FIG. It is a flowchart which shows relative displacement control in case it has a hysteresis by the displacement direction of a brake pedal. It is a graph which shows the relationship between the operation amount of the brake pedal in a relative displacement control means, and target relative displacement. It is a flowchart which shows hydraulic pressure control in case it has a hysteresis by the displacement direction of a brake pedal. It is a graph which shows the relationship between the operation amount of the brake pedal in a hydraulic-pressure control means, and target hydraulic pressure. 5 is a flowchart for executing switching between relative displacement control and hydraulic pressure control in normal brake control. It is a graph which shows the relationship between the electric current supplied to an electric motor, and a hydraulic pressure. 2 is a flowchart for executing control when sufficient control information cannot be obtained in the brake control device shown in FIG. 1. FIG. 2 is a graph showing a state of relative displacement control when sufficient control information cannot be obtained in the brake control device shown in FIG. 1.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a schematic configuration of a brake control device according to the present embodiment. As shown in FIG. 1, the brake control device 1 according to the present embodiment is applied to a braking device of an automobile, and the braking force of four wheels including a left front wheel Wa, a right rear wheel Wb, a right front wheel Wc, and a left rear wheel Wd. Is for controlling. The brake control device 1 includes a master cylinder 2, a master pressure control mechanism 3 integrated into the master cylinder 2, a master pressure control unit 4 that controls the operation of the master pressure control mechanism 3, and the wheels Wa, Wb, Controls the wheel pressure control mechanism 5 which is a hydraulic pressure control means for controlling the hydraulic pressure supplied to the wheel cylinders of the brake devices Ba, Bb, Bc and Bd mounted on the Wc and Wd, and the operation of the wheel pressure control mechanism 5. A wheel pressure control unit 6.

  The master cylinder 2 is a tandem master cylinder, and a primary piston 8 as an assist member is inserted into the opening side of the cylinder 7 filled with brake fluid, a secondary piston 9 is inserted into the bottom side, and the primary piston 8 A primary chamber 10 is formed between the secondary piston 9 and the secondary piston 9, and a secondary chamber 11 is formed between the secondary piston 9 and the bottom of the cylinder 7. As the primary piston 8 advances, the brake fluid in the primary chamber 10 is pressurized, and the secondary piston 9 is advanced to pressurize the brake fluid in the secondary chamber 11, so that the wheel pressure from the primary port 12 and the secondary port 13 is increased. Brake fluid is supplied to the wheel cylinders of the brake devices Ba, Bb, Bc, Bd via the control mechanism 5. The primary chamber 10 and the secondary chamber 11 are connected to the reservoir 14 via reservoir ports 14A and 14B provided on the side wall of the cylinder 7, respectively. The reservoir port 14 is opened when the primary piston 8 and the secondary piston 9 are in the retracted position, and the primary 10 chamber and the secondary chamber 11 are communicated with the reservoir 14 to replenish brake fluid as appropriate. When it moves forward, it closes, and the primary 10 chamber and the secondary chamber 11 can be pressurized. The primary piston 8 and the secondary piston 9 are biased backward by return springs 15 and 16.

  In this way, by supplying brake fluid from the primary port 12 and the secondary port 13 to the two hydraulic circuits by the two pistons of the primary piston 8 and the secondary piston 9, one hydraulic circuit should fail. Even in this case, the hydraulic pressure can be supplied by the other hydraulic pressure circuit, and the braking force can be secured.

  An input piston 17, which is an input member, is slidably and liquid-tightly penetrated through the center of the primary piston 8, and the tip of the input piston 17 is inserted into the primary chamber 10. An input rod 18 is connected to the rear end portion of the input piston 17, the input rod 18 extends outside through the master pressure control mechanism 3, and a brake pedal 19 is connected to the end portion. A pair of neutral springs 20 and 21 are interposed between the primary piston 8 and the input piston 17, and the primary piston 8 and the input piston 17 are elastically held in a neutral position by the spring force of the neutral springs 20 and 21. Thus, the spring force of the neutral springs 20 and 21 acts on the relative displacement in the axial direction.

  The master pressure control mechanism 3 includes an electric motor 22 that is an actuator that drives the primary piston 8, a ball screw mechanism 23 that is a rotation-linear motion conversion mechanism interposed between the primary piston 8 and the electric motor 22, and a speed reduction mechanism. A belt reduction mechanism 24. The electric motor 22 includes a rotation angle detection sensor 25 that detects the rotation position thereof, and is operated according to a command from the master pressure control device 4 to obtain a desired rotation position. The electric motor 22 can be, for example, a known DC motor, DC brushless motor, AC motor, or the like, but in this embodiment, a three-phase DC brushless motor is adopted from the viewpoint of controllability, quietness, durability, and the like. Yes.

  The ball screw mechanism 23 includes a hollow linear motion member 26 into which the input rod 18 is inserted, a cylindrical rotary member 27 into which the linear motion member 26 is inserted, and a plurality of screws loaded in a screw groove formed therebetween. And a ball 28 (steel ball) which is a rolling element of the above-mentioned, a front end portion of the linear motion member 26 abuts on a rear end portion of the primary piston 8, and a rotating member 27 is rotatably supported by the cylinder 7 by a bearing 29. Yes. Then, the rotating member 27 is rotated by the electric motor 22 via the belt speed reduction mechanism 24 so that the ball 28 rolls in the thread groove and the linear motion member 26 moves linearly to move the primary piston 8. It has become. The linear motion member 26 is biased toward the retracted position by the return spring 30.

  The rotation-linear motion conversion mechanism is another mechanism such as a rack and pinion mechanism as long as it converts the rotational motion of the electric motor 22 (that is, the belt reduction mechanism 24) into a linear motion and transmits it to the primary piston 8. However, in this embodiment, the ball screw mechanism 23 is employed from the viewpoint of less play, efficiency, durability, and the like. The ball screw mechanism 23 has back drivability and can rotate the rotating member 27 by the linear motion of the linear motion member 26. Further, the linear motion member 26 comes into contact with the primary piston 8 from the rear so that the primary piston 8 can move forward separately from the linear motion member 26. As a result, if the electric motor 22 becomes inoperable due to disconnection or the like, the linear motion member 26 is returned to the retracted position by the spring force of the return spring 30, and at this time, the primary piston 8 can move independently. The brake can be prevented from being dragged, and the hydraulic pressure can be generated by operating the input piston 17 by the brake pedal 19 and further operating the primary piston 8 via the input rod 18.

  The belt speed reduction mechanism 24 includes a drive pulley 31 attached to the output shaft of the electric motor 22, a driven pulley 32 attached around the rotating member 27 of the ball screw mechanism 23, and a belt 33 wound therebetween. The rotation of the output shaft of the electric motor 22 is reduced at a predetermined reduction ratio and transmitted to the ball screw mechanism 23. The belt reduction mechanism 24 may be combined with another reduction mechanism such as a gear reduction mechanism. A known gear speed reduction mechanism, chain speed reduction mechanism, differential speed reduction mechanism, or the like can be used in place of the belt speed reduction mechanism 24. However, when a sufficiently large torque can be obtained by the electric motor 22, the speed reduction mechanism is omitted. Then, the rotation / linear motion conversion mechanism may be directly driven by the electric motor 22.

  A brake operation amount detection device 34 is connected to the input rod 18. The brake operation amount detection device 34 can detect at least the position or displacement (stroke) of the input rod 18 (stroke detection means), and includes a plurality of position sensors including a displacement sensor of the input rod 18 and a brake by the driver. It may include a force sensor that detects the depression force of the pedal 19. The brake pedal 19 is provided with a brake switch 19A that detects the operation. The brake switch 19 </ b> A detects the operation of the brake pedal 19 regardless of whether the ignition switch is on or off, and supplies a brake operation signal to the master pressure control unit 4.

  The wheel pressure control mechanism 5 is a first hydraulic circuit 5A (wheel pressure in FIG. 1) for supplying the hydraulic pressure from the primary port 12 of the master cylinder 2 to the brake devices Ba and Bb of the left front wheel Wa and the right rear wheel Wb. The second hydraulic pressure circuit 5B (wheel of FIG. 1) for supplying hydraulic pressure from the secondary port 13 to the brake devices Bc and Bd of the right front wheel Wc and the left rear wheel Wd. 2 systems of hydraulic circuits comprising a pressure control mechanism 5 and a left part from the center of the pressure control mechanism 5 are provided. In the present embodiment, the brake devices Ba to Bd are hydraulic disc brakes that supply hydraulic pressure to the wheel cylinder to advance the piston and press the brake pad against the disc rotor that rotates together with the wheels to generate braking force. However, other hydraulic brakes such as a known drum brake may be used.

  The first hydraulic circuit 5A and the second hydraulic circuit 5B have the same configuration, and the hydraulic circuits connected to the brake devices Ba to Bd of the wheels Wa to Wd have the same configuration. In the following description, the subscripts A and B and a to d of the reference numerals indicate that they correspond to the first hydraulic circuit 5A, the second hydraulic circuit 5B, and the wheels Wa to Wd, respectively.

  The wheel pressure control mechanism 5 includes supply valves 35A and 35B that are electromagnetic on-off valves that control the supply of hydraulic pressure from the master cylinder 2 to the wheel cylinders of the brake devices Ba to Bd of the wheels Wa to Wd, and the brake device Ba. Pressure increase valves 36a to 36d that are electromagnetic on-off valves that control the supply of hydraulic pressure to Bd, reservoirs 37A and 37B for releasing hydraulic pressure from the brake devices Ba to Bd, and reservoir 37A from the brake devices Ba to Bd. , Pressure reducing valves 38a to 38d which are solenoid valve on / off valves for controlling the release of the hydraulic pressure to 37B, pumps 39A and 39B for supplying the hydraulic pressure to the brake devices Ba to Bd, and pumps for driving the pumps 39A and 39B Motor 40 and pressurizing valves 41A and 41B which are electromagnetic on-off valves for controlling the supply of hydraulic pressure from the master cylinder 2 to the suction side of the pumps 39A and 39B The check valves 42A, 42B, 43A, 43B, 44A, 44B for preventing the back flow from the downstream side to the upstream side of the pumps 39A, 39B, and the hydraulic pressures of the primary port 12 and the secondary port 13 of the master cylinder 2 Fluid pressure sensors 45A and 45B for detection are provided.

  The wheel pressure control unit 6 controls the operation of the supply valves 35A and 35B, the pressure increasing valves 36a to 36d, the pressure reducing valves 38a to 38d, the pressure increasing valves 41A and 41B, and the pump motor 40. At this time, the supply valves 35A and 35B and the pressure increasing valves 36a to 36d are opened, and the pressure reducing valves 38a to 38d and the pressure increasing valves 41A and 41B are closed, so that liquid is supplied from the master cylinder 2 to the brake devices Ba to Bd of the wheels Wa to Wd. Supply pressure. By opening the pressure reducing valves 38a to 38d and closing the supply valves 35A and 35B, the pressure increasing valves 36a to 36d and the pressure increasing valves 41A and 41B, the hydraulic pressures of the brake devices Ba to Bd are released to the reservoirs 37A and 37B to reduce the pressure. The hydraulic pressures of the brake devices Ba to Bd are maintained by closing the pressure increasing valves 36a to 36d and the pressure reducing valves 38a to 38d. By opening the pressure increasing valves 36a to 36d, closing the supply valves 35A and 35B, the pressure reducing valves 38a to 38d and the pressure increasing valves 41A and 41B, and operating the pump motor 40, the brake device regardless of the hydraulic pressure of the master cylinder 2 The liquid pressure of Ba to Bd is increased. Further, the pressurizing valves 41A and 41B and the pressure increasing valves 36a to 36d are opened, the pressure reducing valves 38a to 38d and the supply valves 35A and 35B are closed, and the pump motor 40 is operated, whereby the hydraulic pressure from the master cylinder 2 is pumped 42A. , 42B and further supplied to the brake devices Ba to Bd.

  Thereby, various brake control can be performed. For example, braking force distribution control that appropriately distributes the braking force to each wheel according to the ground load during braking, anti-lock brake control that automatically adjusts the braking force of each wheel during braking to prevent wheel locking, Vehicle stability control that suppresses understeer and oversteer and stabilizes the behavior of the vehicle by detecting the side slip of the running wheel and automatically automatically applying braking force to each wheel, especially on slopes (uphill) Slope start assist (HSA) control that assists starting while maintaining the braking state, traction control that prevents idling of the wheel at the start, vehicle follow-up control that maintains a certain distance from the preceding vehicle, travel lane The lane departure avoidance control to be held, the obstacle avoidance control to avoid the collision with the obstacle, and the like can be executed.

  As the pumps 39A and 39B, for example, known hydraulic pumps such as a plunger pump, a trochoid pump, and a gear pump can be used. However, considering the on-board performance, quietness, pump efficiency, etc., it is desirable to use a gear pump. As the pump motor 40, a known motor such as a DC motor, a DC brushless motor, an AC motor, or the like can be used. However, a DC brushless motor is desirable from the viewpoint of controllability, quietness, durability, in-vehicle performance, and the like.

  Further, the characteristics of the electromagnetic on-off valve of the wheel pressure control mechanism 5 can be appropriately set according to the use mode, but the supply valves 35A and 35B and the pressure increasing valves 36a to 36d are normally opened valves, and the pressure reducing valves 38a to 38d. Since the pressurizing valves 41A and 41B are normally closed valves, the hydraulic pressure can be supplied from the master cylinder 12 to the brake devices Ba to Bd when there is no control signal from the wheel pressure control unit 6. Such a configuration is desirable from the viewpoint of safety and control efficiency.

Next, the master pressure control unit 4 will be described. An example of the circuit configuration of the master pressure control unit 4 is shown in FIG.
As shown in FIG. 2, the master pressure control unit 4 includes a central processing unit (CPU) 46, a three-phase motor drive circuit 47 that outputs a drive current to the electric motor 22 (three-phase DC brushless motor), and a master pressure control. The rotation angle detection sensor 25 of the mechanism 3, the pedal operation amount detection device 34 including a displacement sensor, the temperature sensor 48 (shown only in FIG. 2), and the liquid for detecting the pressure in the primary chamber 10 and the secondary chamber 11 of the master cylinder 2. Rotation angle detection sensor interface 49, temperature sensor interface 50, displacement sensor interfaces 51 and 51 and hydraulic pressure sensor interface 52 for receiving various detection signals from pressure sensors 45A and 45B in central processing unit 46, wheel CAN communication interface for receiving a CAN signal from the vehicle-mounted device including the pressure control unit 6 A chair 53, a storage device 54 (EEPROM) storing various information for the central processing unit 46 (CPU) to execute processing, and first and second power supply circuits 55 for supplying stable power to the central processing unit 46, 56, a monitoring control circuit 57 for monitoring the abnormality of the central processing unit 46 and the first and second power supply units 55, 56, a fail safe relay 58, an ECU power supply relay 59, and a filter circuit 60.

  The central processing unit 46 includes various detection signals from the rotation angle detection sensor 25, the operation amount detection device 34, the temperature sensor 48 and the hydraulic pressure sensors 45 </ b> A and 45 </ b> B, and CAN signals from various in-vehicle devices including the wheel pressure control unit 6. Are processed according to a predetermined logic rule based on various information by the storage device 54 and information stored in the storage device 54 (EEPROM), and a command signal is output to the three-phase motor drive circuit 47 to control the operation of the electric motor 22. To do.

  Electric power is supplied from the in-vehicle power supply line 61 to the first and second power supply circuits 55 and 56 via the ECU power supply relay 59. At this time, the ECU power supply relay 59 detects either reception of a CAN signal by the CAN communication interface 53 or reception of a predetermined activation signal W / U from an ignition switch, a brake switch, a door switch, or the like. The first and second power supply circuits 55 and 56 are supplied with electric power. Further, power is supplied from the power supply line 61 to the three-phase motor drive circuit 47 via the filter circuit 60 and the fail safe relay 58. At this time, noise of power supplied to the three-phase motor drive circuit 47 by the filter circuit 60 is removed.

  Each phase of the three-phase output of the three-phase motor drive circuit 47 is monitored by a phase current monitor circuit 47A and a phase voltage monitor circuit 47B. The central processing unit 46 performs failure diagnosis of the master pressure control unit 4 based on these monitoring values and failure information stored in the storage device 54, and when it is determined that there is a failure, a failure signal is sent to the monitoring control circuit. To 57. The monitoring control circuit 57 operates the fail-safe relay 58 in the event of an abnormality based on various operation information such as a failure signal from the central processing unit 46 and the voltages of the first and second power supply circuits 55 and 56, thereby providing a three-phase motor. The supply of power to the drive circuit 47 is cut off.

A vehicle equipped with the brake control device 1 includes a regenerative braking system R. The regenerative braking system R collects kinetic energy as electric power by driving a generator (electric motor) by rotating a wheel during deceleration and braking. The regenerative braking system R is connected to the CAN signal line, and is connected to the master pressure control unit 4 via the CAN communication interface 53.
The communication signal is not limited to CAN, and may be an in-vehicle communication system of another standard.

Next, the control of the master pressure control mechanism 3 by the master pressure control unit 4 will be described.
Based on the operation amount (displacement amount, stepping force, etc.) of the brake pedal 19 detected by the operation amount detection device 34, the electric motor 22 is operated to control the position of the primary piston 8 to generate hydraulic pressure. At this time, the reaction force due to the hydraulic pressure acting on the input piston 17 is fed back to the brake pedal 19 via the input rod 18. The boost ratio, which is the ratio between the operation amount of the brake pedal 19 and the generated hydraulic pressure, can be adjusted by the pressure receiving area ratio and the relative displacement between the primary piston 8 and the input piston 17.

  For example, by making the primary piston 8 follow the displacement of the input piston 17 and controlling the relative displacement so that these relative displacements become zero, the constant is determined by the pressure receiving area ratio between the input piston 17 and the primary piston 8. Can be obtained. Further, the boost ratio can be changed by multiplying the displacement of the input piston 17 by a proportional gain to change the relative displacement between the input piston 17 and the primary piston 8.

  Thereby, the necessity of emergency braking is detected from the operation amount of the brake pedal 19, the operation speed (change rate of the operation amount), etc., and the necessary braking force (hydraulic pressure) is obtained quickly by increasing the boost ratio. So-called brake assist control can be executed. Further, based on the CAN signal from the regenerative braking system R, the boost ratio is adjusted so as to generate a hydraulic pressure obtained by subtracting the regenerative braking amount during regenerative braking, and the sum of the regenerative braking amount and the braking force due to the hydraulic pressure is obtained. Thus, it is possible to execute regenerative cooperative control so that a desired braking force can be obtained. Further, regardless of the operation amount of the brake pedal 19 (the displacement amount of the input piston 17), it is also possible to execute automatic brake control for generating a braking force by operating the electric motor 22 and moving the primary piston 8. It is. Thus, the master pressure control unit 4 is used by automatically adjusting the braking force based on the vehicle state detected by the various sensor means and appropriately combining with other vehicle controls such as engine control and steering control. It is also possible to execute vehicle driving control such as the vehicle following control, the lane departure avoidance control, and the obstacle avoidance control.

Next, control switching of the master pressure control unit 4 will be described.
A control configuration of the master pressure control mechanism 3 by the master pressure control unit 4 is shown in FIG. As shown in FIG. 3, the master pressure control unit 4 responds to a control input Sa with a relative displacement control means 46A for determining a target relative displacement ΔXT between the primary piston 8 and the input piston 17 and a control input Sb. The hydraulic pressure control means 46B for determining the target hydraulic pressure PT generated in the master cylinder 2 and the operation of the electric motor 22 of the master pressure control mechanism 3 are controlled based on either the target relative displacement ΔXT or the target hydraulic pressure PT. Control switching means 46C for determining whether or not to perform the control.

  The relative displacement control means 46A, for example, as the control input Sa, the displacement amount (stroke) of the input rod 18 (that is, the brake pedal 19) connected to the input piston 17 detected by the brake operation amount detection device 34, the brake pedal 19 Operating force (stepping force), the generated hydraulic pressure of the master cylinder 2, or an estimated pedaling force FC obtained by calculation from these detected values can be used. At this time, these values can be used alone or in combination. May be. The target relative displacement ΔXT may be set in advance with a table with respect to the control input Sa, or may be obtained by a predetermined calculation.

  The hydraulic pressure control means 46B can use the same information as the control input Sa described above as the control input Sb, and can be the same as or different from the control input Sa. The target hydraulic pressure PT may be set in advance with a table with respect to the control input Sb, or may be obtained by a predetermined calculation.

  The target relative displacement ΔXT and the target hydraulic pressure PT, which are target control amounts obtained from the relative displacement control means 46A and the hydraulic pressure control means 46B, are selected by the control switching means 46C according to a predetermined determination condition. At this time, the control switching unit 46C may perform processing such as limiting the target relative displacement ΔXT and the target hydraulic pressure PT according to the determination condition.

  Based on the target relative displacement ΔXT or the target hydraulic pressure PT selected by the control switching means 46C, a control drive signal is output by the three-phase motor control circuit 47 so that the target relative displacement ΔXT or the target hydraulic pressure PT is obtained. The operation of the electric motor 22 of the boost control device 3 is controlled. At this time, for example, the target position of the primary piston 8 corresponding to the target relative displacement ΔXT and the target hydraulic pressure PT is determined, and the operation of the electric motor 22 is controlled to move the primary piston 8 to the target position. The target relative displacement ΔXT or the target hydraulic pressure PT can be obtained.

The balance of pressure and force in the master cylinder 2 and the master pressure control mechanism 3 will be described with reference to FIG.
In FIG. 4, the following equation (1) holds.
F = −KΔX + Ai · P + N (1)
here,
F: Operating force (stepping force) of the brake pedal 19
K: composite spring constant ΔX of neutral springs 20 and 21: relative displacement between primary piston 8 and input piston 17 Ai: pressure receiving area of input piston 17 with respect to primary chamber 10 P: hydraulic pressure N of master cylinder 2 (primary chamber 10) A set load by the return springs 15 and 16 and the return spring 30.
From the equation (1), the operating force F (estimated treading force FC) of the brake pedal 19 can be obtained by calculation based on the relative displacement ΔX and the hydraulic pressure P. The estimated pedal effort FC thus obtained can be used as the control inputs Sa and Sb (in this case, the brake operation amount detection device 34 serves as a pedal effort estimating means).

Next, an example of relative displacement control by the relative displacement control means 46A will be described.
In this control, a certain amount of operation of the brake pedal 19 is returned (released) (return direction of the input rod 18) when the brake pedal 19 is depressed (advance direction of the input rod 18). Increase the target relative displacement ΔXT. As a result, when the brake pedal 19 starts to be returned, the target relative displacement ΔXT increases, and when the brake pedal 19 that has started to return is depressed again, the target relative displacement ΔXT decreases, so that the input rod 18 moves. On the other hand, a moderate delay occurs at the beginning of the return and advance of the primary piston 8, and the hydraulic pressure in the master cylinder 2 gradually decreases and increases, so that the operation feeling of the brake pedal 19 is improved.

  FIG. 5 shows a control flow for executing relative displacement control having hysteresis in the displacement direction of the brake pedal 19. Referring to FIG. 5, the target relative displacement ΔXT on the advance side of input rod 18 is calculated in step S1, the target relative displacement ΔXT on the return side of input rod 18 is calculated in step S2, and the input rod 18 of input rod 18 is calculated in step S3. It is determined whether the moving direction is the advance side or the return side. If it is determined to be the advance side, the advance side target relative displacement ΔXT is set as the target relative displacement ΔXT in step S4, and if it is determined to be the return side, the return side target relative displacement ΔXT is set as the target relative displacement ΔXT in step S5.

  At this time, as shown in FIG. 6, with respect to the displacement of the input rod 18, that is, the operation amount of the brake pedal 19 detected by the operation amount detector 34, the larger the operation amount, the larger the target relative displacement ΔXT, and the constant With respect to the manipulated variable, the return-side target relative displacement ΔXT (L3) is made larger than the advance-side target relative displacement ΔXT (L1) to set a counterclockwise hysteresis. Then, by setting the target relative displacement ΔXT so that the primary piston 8 does not move in the section L2 where the advance side target relative displacement ΔXT (L1) shifts to the return side target relative displacement ΔXT (L3), the primary piston 8 When excessive movement of the hydraulic pressure in the primary chamber 10 due to movement can be suppressed, vibration due to hydraulic pressure fluctuation transmitted to the brake pedal 19 via the input piston 17 is reduced, and the pedal force of the brake pedal 19 is released. The operation feeling is improved. In addition, since the movement frequency of the primary piston 8 is reduced, the operation frequency of the electric motor 22, the ball screw mechanism 23, and the belt speed reduction mechanism 24 is reduced to reduce the generation of noise and power consumption, and to improve the durability thereof. Can be increased.

  It should be noted that the section L2 in which the target relative displacement ΔXT (L1) on the advance side shifts to the target relative displacement ΔXT (L3) on the return side and the target relative displacement ΔXT (L1) on the advance side from the target relative displacement ΔXT (L3) on the return side. If the target relative displacement ΔXT is suddenly changed in the section L4 that shifts to, the direction of increase / decrease of the hydraulic pressure of the master cylinder 2 may not match the operation direction of the brake pedal 19, so that It is desirable to set the change of the target relative displacement ΔXT in these sections L2 and L4 gently so that the state does not occur.

  In the relative displacement control means 46A, as the control input Sa, the displacement of the brake pedal 19, that is, the input rod 18, detected by the operation amount detection device 34, the hydraulic pressure of the master cylinder 2, the primary piston 8 and the input piston 17 The estimated pedal effort FC of the brake pedal 19 obtained by calculation based on the above-described equation (1) from the relative displacement ΔX may be selectively switched and used.

Next, the hydraulic pressure control by the hydraulic pressure control means 46B will be described.
In this control, for a certain amount of operation, the return side when the brake pedal 19 is depressed (the advance direction of the input rod 18) with respect to the advance side target hydraulic pressure PT1 (when the input rod 18 returns). Increase the target hydraulic pressure PT2. As a result, when the brake pedal 19 starts to be returned, the target hydraulic pressure PT increases, and when the brake pedal 19 that has started to return is depressed again, the target hydraulic pressure PT decreases, so that the input rod 18 moves. On the other hand, a moderate delay occurs at the beginning of the return and advance of the primary piston 8, and the hydraulic pressure of the master cylinder 2 gradually decreases and rises, so that the operation feeling of the brake pedal 19 is improved. At this time, when the target hydraulic pressure PT is switched between the advance side and the return side, the target hydraulic pressure PT is smoothly changed, thereby suppressing a sudden change in the hydraulic pressure and preventing an unexpected sudden change in the braking force. it can.

  FIG. 7 shows a control flow for executing the hydraulic pressure control. Referring to FIG. 7, the target hydraulic pressure PT on the advance side of input rod 18 is calculated in step S11, the target hydraulic pressure PT on the return side of input rod 18 is calculated in step S12, and the input hydraulic pressure of input rod 18 is determined in step S13. It is determined whether the moving direction is the advance side or the return side. If it is determined to be the advance side, the advance side target hydraulic pressure PT1 is set as the target hydraulic pressure PT in step S14, and if it is determined to be the return side, the return side target hydraulic pressure PT2 is set as the target hydraulic pressure PT in step S15.

  At this time, as shown in FIG. 8, the target hydraulic pressure PT is increased as the operation amount increases with respect to the displacement of the input rod 18, that is, the operation amount detected by the operation amount detection device 34, and further, for a certain operation amount. Then, the return side target hydraulic pressure PT2 (section L3) is increased with respect to the advancing side target hydraulic pressure PT1 (section L1), and a counterclockwise hysteresis is set. Then, a section L2 that transitions from the advancing side target hydraulic pressure PT1 (section L1) to the return side target hydraulic pressure PT2 (section L3), and a leading side target hydraulic pressure PT1 (section) from the return side target hydraulic pressure PT2 (section L3). In the section L4 that shifts to L1), by making the target hydraulic pressure PT constant, the movement amount of the primary piston 8 can be minimized, and the primary chamber 10 is moved from the primary chamber 10 to the input rod 18 by the movement of the primary piston 8. The influence of reaction force can be reduced. This also reduces the frequency of movement of the primary piston 8, thereby reducing the frequency of operation of the electric motor 22, the ball screw mechanism 23, and the speed reduction mechanism 24, thereby reducing noise generation and power consumption, as well as their durability. Can increase the sex.

  In the control switching means 46C, the operation of the regenerative braking system, the normal braking force control, the hydraulic pressure control by the wheel pressure control device, the operation of the slope start assist (HSA) and whether or not the vehicle is stopped are determined, and the relative displacement control means The control using the target relative displacement ΔXT by 46A or the target hydraulic pressure PT by the hydraulic pressure control means 46B is appropriately switched.

  A switching control flow by the control switching means 46C in this case is shown in FIG. Referring to FIG. 9, in step S21, the relative displacement control means 46A determines the target relative displacement based on the operation amount of the brake pedal 19, and in step S22, the hydraulic pressure control means 46B determines the target hydraulic pressure PT. In step S23, it is determined whether or not the regenerative braking system R is executing regenerative braking. If regenerative braking is being executed, control using the target hydraulic pressure PT is performed in step S29. If regenerative braking is not being executed, the process proceeds to step S4.

  At the time of regenerative coordination, the hydraulic pressure to be generated in the master cylinder 2 is obtained by subtracting the hydraulic pressure corresponding to the regenerative braking from the hydraulic pressure required for braking only by the hydraulic brake in response to the driver's braking request. It becomes. Therefore, when the braking amount due to regenerative braking is given as a hydraulic pressure or an amount proportional to the hydraulic pressure, the operation of the electric motor 22 is controlled based on the target hydraulic pressure PT, so that the control based on the target relative displacement ΔXT is achieved. Thus, the calculation can be simplified and the control accuracy can be increased.

  In step S24, it is determined whether or not normal braking force control is being performed. If it is determined that normal braking force control is not being performed, control is performed using the target hydraulic pressure PT in step S29, and normal braking force is controlled. If it is determined that control is being performed, the process proceeds to step S25. Here, the normal braking force control refers to a case where the hydraulic pressure generated in the master cylinder 2 is directly transmitted to the wheel cylinder in response to the operation amount (braking force request) of the driver's brake pedal 19 (braking force distribution control). The wheel pressure control mechanism 6 is controlled by the wheel pressure control device 6 based on control inputs other than the operation amount of the brake pedal 19 such as ABS operation, traction control operation, vehicle stability control execution, etc. In the case of intervening, or in the case of executing slope start assistance (HSA) control or control during stopping, determination is performed by the following steps S25 to S27.

  In step S25, it is determined whether or not the wheel hydraulic pressure control device 6 is executing control of the wheel hydraulic pressure control mechanism 6. If it is determined that control is being executed, control is performed using the target hydraulic pressure PT in step S29. When the wheel hydraulic pressure control mechanism 5 is activated, the supply valves 35A and 35B and the pressurizing valves 41A and 41B are opened and closed, and the pumps 39A and 39B are activated and stopped, so that the hydraulic pressure of the hydraulic circuit downstream of the master cylinder 2 is reduced. When the rigidity is changed and the control is performed using the target relative displacement ΔXT, the position of the primary piston 8 becomes unstable due to the change in rigidity of the hydraulic circuit, and the generated hydraulic pressure of the master cylinder 2 is reduced. May become unstable. On the other hand, when the control is performed using the target hydraulic pressure PT, the hydraulic pressure of the master cylinder 2 is relatively unaffected by changes in the rigidity of the hydraulic pressure circuit, so that the generated hydraulic pressure of the master cylinder 2 is unstable. Hard to become.

  When it is determined in step S25 that the wheel hydraulic pressure control mechanism 5 is not executing control by the wheel hydraulic pressure control device 6, the process proceeds to step S26. In step S6, it is determined whether or not the slope start assistance (HSA) is in operation. If it is determined that the HSA is in operation, control using the target hydraulic pressure PT is performed in step S29. If it is determined that the HSA is not operating, the process proceeds to step S27. In step S27, it is determined whether or not the vehicle is stopped. If it is determined that the vehicle is stopped, control using the target hydraulic pressure PT is performed in step S29. If it is determined that the vehicle is not stopped, control using the target relative displacement ΔXT by the relative displacement control means 46A is performed in step S28. .

  In this way, switching between relative displacement control and hydraulic pressure control is performed. In the control flow shown in FIG. 9, steps S23 to S27 may change the order of determination as appropriate, and select and use only necessary determinations without using all the determinations. Also good.

  In the above embodiment, the case where the control using the target relative displacement ΔXT and the control using the target hydraulic pressure PT are switched according to a certain condition has been described. The conditions for switching these are the individual conditions of the system. What is necessary is just to set according to a characteristic, and it can set arbitrarily to which to switch.

  Next, the case where the above-described antilock brake control is executed will be described in more detail. When the anti-lock brake control is executed and the wheel pressure control mechanism 5 executes the depressurization mode, the pressurization mode, and the holding mode according to the locked state of the wheels Wa to Wd, the master cylinder 2 is operated by the operation of the pumps 39A and 39B. On the other hand, the brake fluid is frequently recirculated and sucked, and at the time of recirculation, the hydraulic pressure in the master cylinder 2 is considerably increased.

  At this time, when the relative position control is performed, the position of the primary piston 8 is held constant according to the position of the input piston 17 with respect to the fluctuation of the hydraulic pressure of the master cylinder 2. Increases rigidity. For this reason, the fluctuation of the hydraulic pressure of the master cylinder 2 is directly transmitted to the brake pedal 19 via the input piston 17, and the operation feeling of the brake pedal 19 is deteriorated. Moreover, there is a possibility that the piston seal of the primary piston 8 may be damaged due to an excessive increase in the hydraulic pressure of the master cylinder 2.

  In contrast, when the anti-lock brake control is executed, the control switching unit 46C switches from the relative displacement control by the normal relative displacement control unit 46A to the hydraulic pressure control by the hydraulic pressure control unit 46B. Then, based on the hydraulic pressure of the master cylinder 2 detected by the hydraulic pressure sensors 45A and 45B, the operation of the electric motor 22 is feedback-controlled to adjust the position of the primary piston 8, thereby increasing the hydraulic pressure of the master cylinder 2. On the other hand, the primary piston 8 moves backward to absorb the fluctuation of the hydraulic pressure, thereby preventing an excessive increase in the hydraulic pressure. As a result, fluctuations in the reaction force of the brake pedal 19 can be suppressed and the operation feeling of the brake pedal 19 can be improved. Moreover, the excessive increase of the hydraulic pressure of the master cylinder 2 can be suppressed, and damage to the piston seal of the primary piston 8 can be prevented.

  The master pressure control unit 4 monitors the abnormality of the hydraulic pressure sensors 45A and 45B and the abnormality of the CAN communication system, and the hydraulic pressure information of the master cylinder 2 from the hydraulic pressure sensors 45A and 45B cannot be obtained due to these abnormalities. Or, since the operation information of the hall pressure control mechanism 5 cannot be obtained from the wheel pressure control unit 6 via the CAN communication system, when switching to the hydraulic pressure control cannot be performed, a predetermined current limit control is executed. .

  Here, when switching to hydraulic pressure control is not possible, in addition to the above-described abnormalities of the hydraulic pressure sensors 45A and 45B and the CAN communication system, the brake system is activated with the brake pedal 19 depressed (for example, When the ignition switch is turned on when the brake pedal 19 is depressed, or when the brake system 19A is activated when the brake switch 19A detects that the brake pedal 19 is depressed), the hydraulic pressure sensors 45A and 45B, or the brake This includes a state in which the zero point learning of the operation amount detection device 34 (stroke detection device) and the rotation angle detection sensor 25 is not completed.

  In the current limit control, the above relative position control is executed, and the maximum value of the current supplied to the electric motor 22 is limited to a predetermined limit current value. By limiting the maximum value of the current supplied to the electric motor 22 in this way, the maximum output of the electric motor 22 (that is, the maximum thrust of the primary piston 8) is limited, so the hydraulic rigidity of the master cylinder 2 is low. Thus, the primary piston 8 can move and absorb the fluid pressure fluctuation of the master cylinder 2 in response to the recirculation and suction of the brake fluid by the wheel pressure control mechanism 5 during execution of the antilock control. As a result, the hydraulic pressure fluctuation of the master cylinder 2 can be suppressed and the operation feeling of the brake pedal 19 can be improved. Further, excessive increase in the hydraulic pressure of the master cylinder 2 can be prevented, and damage to the piston seal of the primary piston 8 can be prevented.

  Here, the relationship between the effective value of the current supplied to the electric motor 22 and the brake fluid pressure generated in the master cylinder 2 will be described with reference to FIG. The liquid in the master cylinder 2 with respect to the current supplied to the electric motor 22 due to a decrease in conversion efficiency during reverse operation of the ball screw mechanism 23 (during conversion from linear motion to rotation) and frictional resistance of each part of the belt speed reduction mechanism 24 and the like. The pressure has hysteresis as shown in FIG. That is, the current required to maintain the fluid pressure is smaller than the current required to generate a certain fluid pressure, and the difference is larger as the current is larger (the fluid pressure is higher). Referring to FIG. 10, for example, when current I1 is supplied to electric motor 22, when hydraulic pressure P1 is generated in master cylinder 2, this hydraulic pressure P1 is caused by current I2 (<I1) smaller than current I1. The hydraulic pressure P2 generated in the master cylinder 2 by supplying the current I2 can be held by a current I3 (<I2) smaller than the current I2.

  Therefore, in the current limit control, when setting the limit current value, it can be generated in the master cylinder 2 by supplying the maximum current I1 in the normal operation state and propelling the primary piston 8 by the electric motor 22. The current I2 necessary for maintaining the maximum hydraulic pressure P1 may be set as the limit current value. As a result, even when the master cylinder 2 is boosted due to the return of brake fluid from the wheel pressure control mechanism 5 during anti-lock brake control, the maximum fluid pressure that can be held by the limit current value I2 is the fluid pressure P1. Therefore, when the hydraulic pressure in the master cylinder 2 exceeds the hydraulic pressure P1, the primary piston 8 moves backward, so that the hydraulic pressure in the master cylinder 2 does not exceed the hydraulic pressure P1. As a result, an excessive increase in the hydraulic pressure of the master cylinder 2 can be reliably prevented, the brake pedal operation feeling can be improved, and damage to the piston seal of the primary piston 8 can be prevented.

Next, a control flow for executing the current limiting control will be described with reference to the flowchart of FIG.
Referring to FIG. 11, in step S <b> 31, it is determined whether switching to hydraulic pressure control for controlling the operation of electric motor 22 is possible based on the hydraulic pressure of master cylinder 2. Specifically, the following items (1) to (4) are determined, and it is determined whether or not all of (1) to (4) are affirmed.
(1) The hydraulic pressure sensors 45A and 45B are normal.
(2) Zero point learning of the hydraulic pressure sensors 45A and 45B is completed.
(3) Zero point learning of other sensors including the brake operation amount detection device 34 (stroke detection device) and the rotation angle detection sensor 25 is completed.
(4) The CAN communication system is normal, ABS operation information can be obtained, and hydraulic pressure control can be switched.
If all of (1) to (4) are affirmed, the process proceeds to step S32, and the normal brake control flow shown in FIG. 9 is executed. If any of (1) to (4) is negative, the process proceeds to step S33.

  In step S33, the maximum value of the current supplied to the electric motor 22 is limited to the limit current value, and the process proceeds to step S34. In step S34, the relative displacement of the input piston 17 with respect to the primary piston 8 is made constant by the control switching means 46C, and as shown in FIG. 12, the corresponding relative displacement amount is obtained when the primary piston 8 is at the standby position. The relative position control to be controlled is executed, and the process proceeds to Step S35.

In step S35, as in step S31, it is determined whether or not all of the above (1) to (4) are affirmed. When all of (1) to (4) are affirmed, the process proceeds to step S36, and when any of (1) to (4) is negated, the process returns to step S33. In step S36, it is determined whether or not the brake pedal 19 has been released. If released, the process returns to step S31. If not released, the process returns to step S33.
As a result, even when switching to the hydraulic pressure control becomes impossible during the anti-lock brake control, the current limit control is executed to suppress the deterioration of the brake pedal operation feeling and the piston seal. Damage can be prevented.

The operation information on the master cylinder side of the present invention refers to information on the upstream side of the wheel pressure control mechanism 5 such as the hydraulic pressure of the master cylinder, the operation amount of the brake pedal, etc., and is limited to the sensor directly attached to the master cylinder. It is not a thing.
Further, the operation information from the brake device side includes operation information of the wheel pressure control mechanism 5 and refers to information on the downstream side (wheel cylinder side).

  DESCRIPTION OF SYMBOLS 1 Brake control apparatus, 2 Master cylinder, 4 Master pressure control unit (controller), 8 Primary piston (assist member), 17 Input piston (input member), 19 Brake pedal, 22 Electric motor, 23 Ball screw mechanism (rotation-linear motion) Conversion mechanism)

Claims (5)

An input member that moves forward and backward by operating the brake pedal;
An assist member provided to be movable relative to the input member;
A master cylinder that generates brake fluid pressure by propulsion of the assist member and supplies the brake fluid to the brake device;
An electric motor;
A rotation-linear motion conversion mechanism for propelling the assist member by converting the rotational motion of the electric motor into a linear motion;
In a brake control device comprising a controller for supplying current to the electric motor and controlling the operation of the electric motor based on control information including operation information from the master cylinder side or the brake device side,
The controller limits a maximum value of a current supplied to the electric motor to a predetermined limit current value when operation information cannot be obtained from the master cylinder side or the brake device side. .   The hydraulic pressure detection means for detecting the brake hydraulic pressure of the master cylinder is provided, and the controller uses the brake hydraulic pressure detected by the hydraulic pressure detection means as operation information from the master cylinder side. The brake control device according to 1. A hydraulic pressure control means for controlling the brake hydraulic pressure supplied to the brake device is interposed between the brake device and the master cylinder, and the controller receives operation information from the hydraulic pressure control means from the brake device side. The brake control device according to claim 1, wherein: The controller sets, as the limit current value, a current value necessary for maintaining the maximum brake fluid pressure that can be generated in the master cylinder by propelling the assist member with the electric motor. The brake control device according to any one of claims 1 to 3. The controller controls the relative displacement amount of the assist member relative to the movement amount of the input member when the maximum value of the current supplied to the electric motor is limited to a predetermined limit current value. The brake control device according to any one of claims 1 to 4.

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