JP2021091249A - Control device for electric booster - Google Patents

Abstract

To provide a control device for an electric booster which can suppress generation of sound and vibration due to a negative pressure of a piston chamber during pressure holding control.SOLUTION: A control device (100) of an electric booster (10) includes a motor control part (110) for controlling a rotation speed of an electric motor (21), in which the motor control part (110) restricts the rotation speed of the electric motor (21) when it is estimated that a brake pedal (11) is returned and a master cylinder pressure becomes a negative pressure during establishment of an execution condition of pressure holding control of holding a wheel cylinder pressure by closing a liquid passage between a master cylinder (14) and a brake liquid pressure unit (20).SELECTED DRAWING: Figure 7

Description

The present invention relates to a control device for an electric booster.

In the brake device of an automobile such as a passenger car, an electric booster that generates a large output by boosting the input of the brake operation by the driver at a predetermined servo ratio is used. The electric booster receives an input of a brake operation by the driver on an input shaft, and boosts this input by the output of an electric motor to advance the push rod and press the piston of the master cylinder. As a result, the hydraulic oil in the master cylinder is supplied to the hydraulic pressure unit, and the wheel cylinder pressure rises.

Japanese Unexamined Patent Publication No. 2016-193645

Conventionally, in a vehicle braking device, control for holding the wheel cylinder pressure regardless of the braking operation (hereinafter, also referred to as “pressure holding control”) is known. In the pressure holding control, the control device of the hydraulic pressure unit controls the circuit control valve provided in the hydraulic pressure unit, and closes the hydraulic circuit that supplies hydraulic oil from the master cylinder to the hydraulic pressure unit to reduce the wheel cylinder pressure. Hold at a predetermined target pressure. As a result, for example, even when the driver releases the brake pedal, the braking force of the vehicle is maintained for a predetermined time, and the braking force of the vehicle can be maintained.

Here, the speed at which the brake pedal is returned is determined by the driver operation regardless of the execution state of the pressure holding control. During the execution of the pressure holding control, the hydraulic oil on the hydraulic unit side does not return to the master cylinder side. In this case, the hydraulic oil is supplied from the reservoir tank to the piston chamber in the master cylinder, but the hydraulic oil supply cannot catch up because the passage area of the hydraulic oil supplied from the reservoir tank to the piston chamber is narrow. , The piston chamber becomes negative pressure. When the negative pressure exceeds a predetermined level, the seal parts on the passage that supplies hydraulic oil from the reservoir tank to the piston chamber are deformed, and a large amount of hydraulic oil may flow into the piston chamber, causing noise and vibration. ..

The present invention has been made in view of the above problems, and provides a control device for an electric booster capable of suppressing the generation of noise and vibration caused by a negative pressure in the piston chamber during pressure holding control. ..

In order to solve the above problems, according to a certain viewpoint of the present invention, it is a control device of an electric booster that uses the output torque of the electric motor to boost the input of the brake operation, and the rotation of the electric motor. A motor control unit for controlling the speed is provided, and the motor control unit is a brake pedal when the execution condition of the pressure holding control for holding the wheel cylinder pressure by closing the liquid passage between the master cylinder and the brake hydraulic pressure control device is satisfied. Is returned to provide a control device for an electric booster that limits the rotational speed of the electric motor when it is estimated that the master cylinder pressure becomes negative.

As described above, according to the present invention, it is possible to suppress the generation of noise and vibration caused by the negative pressure in the piston chamber during pressure holding control.

It is explanatory drawing which shows the structural example of the brake device for a vehicle to which the control device of the electric booster which concerns on embodiment of this invention can apply. It is a schematic diagram which shows the whole structure example of the electric booster. It is sectional drawing which shows the structural example of a master cylinder. It is a block diagram which shows the structural example of the control device of the electric booster which concerns on this embodiment. It is explanatory drawing which shows the control map of the rotation speed of an electric motor. It is a flowchart which shows an example of the process of the control device of the electric booster which concerns on this embodiment. It is a timing chart which shows the specific operation example of the control device of the electric booster which concerns on this embodiment.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

As used herein, the term "front" means the direction in which the push rod moves toward the master cylinder. "Rear" means the direction in which the push rod moves toward the brake pedal.

<1. Overall configuration of vehicle braking system>
First, with reference to FIGS. 1 and 2, an overall configuration example of a vehicle brake device to which the control device of the electric booster according to the present embodiment can be applied will be described. FIG. 1 is a schematic view showing a configuration example of a vehicle brake device 1, and FIG. 2 is a cross-sectional view of a master cylinder 14 and an electric brake booster (hereinafter, also simply referred to as “booster”) 10. is there. In FIG. 2, side surfaces are shown for some members.

The vehicle braking device 1 shown in FIG. 1 is a braking device for a four-wheeled vehicle. The vehicle braking device 1 is applied to a so-called X-type piping type braking device which has two braking systems and brakes one front wheel and one rear wheel diagonally opposite to the front wheel as a set in each system. To. The vehicle braking device 1 may be applied to a so-called H-type piping type braking device in which one system brakes the left front and rear wheels and the other system brakes the right front and rear wheels. Further, the vehicle braking device 1 can be widely applied not only to a four-wheeled vehicle but also to a vehicle including a two-wheeled vehicle.

The vehicle brake device 1 includes a booster 10, a master cylinder 14, a hydraulic pressure unit 20, a hydraulic pressure control device 90 that controls the hydraulic pressure unit 20, and a motor control device 100 that controls the motor of the booster 10. The hydraulic pressure control device 90 and the motor control device 100 are all or partly composed of, for example, a microcomputer or a microprocessor unit. Alternatively, part or all of the hydraulic pressure control device 90 and the motor control device 100 may be composed of updatable firmware or the like, and a program module executed by a command from a CPU (Central Processing Unit) or the like. And so on.

The hydraulic pressure control device 90 and the motor control device 100 are configured to be able to communicate with each other via a communication bus such as CAN (Controller Area Network). In the present embodiment, the motor control device 100 has a function as a control device for the electric booster of the present invention.

In the vehicle brake device 1, the pedaling force applied to the brake pedal 11 is amplified by the booster 10 and transmitted to the master cylinder 14 as a hydraulic pressure generation source. In the master cylinder 14, two pressurizing chambers, a primary chamber 47 and a secondary chamber 48, defined by the primary piston 43 and the secondary piston 44 are formed (see FIG. 2). The primary piston 43 and the secondary piston 44 are pressed in response to the driver stepping on the brake pedal 11, and the brake fluid enters the hydraulic pressure unit 20 via a hydraulic pressure port (not shown) communicating with the primary chamber 47 and the secondary chamber 48, respectively. Move to.

The booster 10 is connected to the brake pedal 11 side via the input shaft 16, and the pedaling force amplified by the booster 10 is transmitted to the master cylinder 14 via the push rod 13 connected to the primary piston 43. .. In this embodiment, an electric booster is used as the booster 10.

From the hydraulic ports communicating with the primary chamber 47 and the secondary chamber 48 of the master cylinder 14, the first hydraulic circuits 28 and the first hydraulic circuits 28 and 38d toward the hydraulic brakes 38a to 38d of the wheels RF, LR, LF, and RR, respectively. The hydraulic circuit 30 of 2 is extended. The hydraulic circuit of the vehicle brake device 1 according to the present embodiment is an X-type piping system, and the wheel cylinder of the hydraulic brake 38a of the right front wheel RF and the wheel cylinder of the hydraulic brake 38b of the left rear wheel LR have the first wheel cylinder. The brake fluid is supplied through the hydraulic pressure circuit 28 of 1. Further, the brake fluid is supplied to the wheel cylinder of the hydraulic brake 38c of the left front wheel LF and the wheel cylinder of the hydraulic brake 38d of the right rear wheel RR via the second hydraulic circuit 30. As a result, each of the hydraulic brakes 38a to 38d can generate a braking force on each wheel RF, LR, LF, and RR by the hydraulic pressure.

The hydraulic unit 20 includes a first hydraulic circuit 28 and a second hydraulic circuit 30 having the same configuration. Brake fluid is supplied from the master cylinder 14 to the first hydraulic circuit 28 and the second hydraulic circuit 30. Hereinafter, the first hydraulic circuit 28 will be briefly described, and the description of the second hydraulic circuit 30 will be omitted.

As electromagnetic valves, the first hydraulic circuit 28 includes a normally open type circuit control valve 36a that can be linearly controlled, a normally closed type suction valve 34a that can be turned on and off, and a normally open type pressure boosting valve that can be linearly controlled. (Adjusting valve) 58aa, 58ba and pressure reducing valves 54aa, 54ba, which are normally closed and controlled on and off, are provided. The first hydraulic circuit 28 includes a pump 44a driven by a pump motor 96, a low-pressure accumulator 71a, and a damper 73a. The number of pumps 44a is not limited to one.

The first pressure boosting valve 58aa and the first pressure reducing valve 54aa provided adjacent to the hydraulic brake 38a of the right front wheel RF are used for ABS (Antilock Brake System) control or ESC (Electronic Stability Control) control of the right front wheel RF. Used. The second pressure boosting valve 58ba and the second pressure reducing valve 54ba provided adjacent to the hydraulic brake 38b of the left rear wheel LR are used for ABS control or ESC control of the left rear wheel LR.

The first pressure boosting valve 58aa of the right front wheel RF is provided between the circuit control valve 36a and the hydraulic brake 38a of the right front wheel RF. The linearly controllable first booster valve 58aa continuously adjusts the flow rate of the brake fluid from the circuit control valve 36a side to the wheel cylinder side of the hydraulic brake 38a of the right front wheel RF. The first pressure boosting valve 58aa includes a check valve that allows the brake fluid to flow from the hydraulic brake 38a side to the circuit control valve 36a side while the reverse flow is restricted when the first pressure boosting valve 58aa is closed. It is equipped with a bypass flow path.

The first pressure reducing valve 54aa of the right front wheel RF is a solenoid valve that can switch the valve only to the fully open or fully closed state, and is provided between the wheel cylinder of the hydraulic brake 38a of the right front wheel RF and the low pressure accumulator 71a. Has been done. The first pressure reducing valve 54aa decompresses the brake fluid supplied to the wheel cylinder of the hydraulic brake 38a of the right front wheel RF in the opened state. The first pressure reducing valve 54aa can adjust the flow rate of the brake fluid flowing from the wheel cylinder of the hydraulic brake 38a of the right front wheel RF to the low pressure accumulator 71a by intermittently repeating the opening and closing of the valve.

The second pressure boosting valve 58ba of the left rear wheel LR is provided between the circuit control valve 36a and the hydraulic brake 38b of the left rear wheel LR. The linearly controllable second booster valve 58ba continuously adjusts the flow rate of the brake fluid from the circuit control valve 36a side to the wheel cylinder side of the hydraulic brake 38b of the left rear wheel LR. The second pressure boosting valve 58ba includes a check valve that allows the brake fluid to flow from the hydraulic brake 38b side to the circuit control valve 36a side in a state where the second pressure boosting valve 58ba is closed, while limiting the flow in the opposite direction. It is equipped with a bypass flow path.

The second pressure reducing valve 54ba of the left rear wheel LR is a solenoid valve that can switch the valve only to the fully open or fully closed state, and is between the wheel cylinder of the hydraulic brake 38b of the left rear wheel LR and the low pressure accumulator 71a. It is provided in. The second pressure reducing valve 54ba depressurizes the brake fluid supplied to the wheel cylinder of the hydraulic brake 38b of the left rear wheel LR in the opened state. The second pressure reducing valve 54ba can adjust the flow rate of the brake fluid flowing from the wheel cylinder of the hydraulic brake 38b of the left rear wheel LR to the low pressure accumulator 71a by intermittently repeating the opening and closing of the valve.

The circuit control valve 36a is provided so as to communicate or shut off between the pressure boosting valves 58aa and 58ba and the master cylinder 14. The suction valve 34a is provided so as to communicate or shut off between the master cylinder 14 and the suction side of the pump 44a. A master cylinder hydraulic pressure sensor 24 is provided in the pipeline between the circuit control valve 36a and the suction valve 34a and the master cylinder 14. Since these are the same as the components of the hydraulic pressure unit 20, detailed description thereof will be omitted.

The second hydraulic circuit 30 controls the hydraulic brake 38c of the left front wheel LF and the hydraulic brake 38d of the right rear wheel RR. The second hydraulic circuit 30 replaces the wheel cylinder of the hydraulic brake 38a of the right front wheel RF in the description of the first hydraulic circuit 28 with the wheel cylinder of the hydraulic brake 38c of the left front wheel LF, and replaces the wheel cylinder of the left rear wheel LR. It is configured in the same manner as the first hydraulic circuit 28, except that the wheel cylinder of the hydraulic brake 38b is replaced with the wheel cylinder of the hydraulic brake 38d of the right rear wheel RR.

<2. Overall configuration of the electric booster>
Next, a configuration example of the booster 10 will be described with reference to FIG.

The booster 10 includes a housing 5, an input shaft 16, a push rod 13, a valve body 15, an electric motor 21, an assist mechanism 50, and a return spring 17. A push rod 13, an assist mechanism 50, and a return spring 17 are housed in the housing 5. A mounting plate 7 for mounting the booster 10 to the vehicle body is fixed to the rear of the housing 5. The tie rods 9a and 9b penetrate the mounting plate 7, and the booster 10 is fixed to the vehicle body by the tie rods 9a and 9b. The method of attaching the booster 10 to the vehicle body is not limited to the example of using the tie rods 9a and 9b.

The input shaft 16 is connected to a brake pedal (not shown) and moves in the axial direction in response to an input of pedal operation by the driver. The front end of the input shaft 16 is connected to the rear portion of the plunger 57 of the assist mechanism 50 via a ball joint.

The electric motor 21 may be, for example, a brushless DCDC motor including a stator as a fixed element and a rotor as a moving element. The electric motor 21 operates by receiving an electric power (current) supply controlled by the motor control device 100. The electric motor 21 is a motor capable of forward rotation for moving the push rod 13 forward and reverse rotation for moving the push rod 13 backward by switching the direction of the electric current.

The assist mechanism 50 receives the output of the electric motor 21 and moves the valve body 15 and the push rod 13 toward the master cylinder 14. The assist mechanism 50 includes a reduction mechanism 23, a spindle nut 51, a spindle 53, and a plunger 57. The speed reduction mechanism 23 is configured by using, for example, a gear type speed reduction mechanism, and reduces the rotation of the electric motor 21 at a predetermined reduction ratio and transmits it to the spindle nut 51.

A screw groove 51a is formed in the inner peripheral hole of the spindle nut 51. A spindle 53 is arranged in the inner peripheral hole of the spindle nut 51. A screw thread 53a is formed on the outer peripheral surface of the spindle 53. The thread groove 51a of the spindle nut 51 and the thread 53a of the spindle 53 mesh with each other, and the rotation of the spindle nut 51 makes the spindle 53 movable relative to the spindle nut 51 in the axial direction.

In the configuration in which the spindle 53 is moved in the axial direction by the rotation of the spindle nut 51, screw grooves are formed in the inner peripheral hole of the spindle nut 51 and the outer peripheral surface of the spindle 53, respectively, and a plurality of rolling elements are formed in the facing screw grooves. It may be a ball screw mechanism in which the balls of the above are arranged.

The spindle 53 is formed in a hollow shape having axial holes opened at both ends in the axial direction. A plunger 57 is slidably arranged in the axial hole of the spindle 53 in the axial direction. The plunger 57 can be displaced relative to the spindle 53 by receiving an operation input of the brake pedal by the driver via the input shaft 16.

The valve body 15 is supported by a support member 31. The support member 31 is supported so as to be slidable in the axial direction with respect to the tie rods 9a and 9b. As a result, the valve body 15 can move in the axial direction. The valve body 15 moves in the forward direction as the spindle 53 advances. An input receiving member 71 is fitted in the inner peripheral hole of the valve body 15 so as to be movable relative to the valve body 15 in the axial direction. The front end of the plunger 57 is connected to the input receiving member 71 so as to be relatively movable in the axial direction. The rear end of the push rod 13 is fitted in the inner peripheral hole on the front surface of the valve body 15 so as to be relatively movable in the axial direction. The push rod 13 is held by a retainer 73 attached to the valve body 15. The push rod 13 advances by the operation of the electric motor 21 and presses the primary piston 43 of the master cylinder 14.

A reaction disc 75 made of an elastic member such as rubber is arranged between the rear end of the push rod 13 and the front surface of the valve body 15. The front surface of the input receiving member 71 faces the rear surface of the reaction disk 75 via a minute gap. A key member 87 is arranged between the rear surface of the valve body 15 and the front surface of the spindle nut 51 of the assist mechanism 50. The key member 87 is fixed to the plunger 57 and moves in the axial direction integrally with the plunger 57. The key member 87 defines the range of movement of the plunger 57 and the input receiving member 71 with respect to the valve body 15.

A return spring 17 is arranged in a compressed state between the housing 5 and the valve body 15. The return spring 17 always urges the valve body 15 in the backward direction. When the valve body 15 retracts, both the push rod 13 and the reaction disc 75 retract. A return spring 19 is arranged between the spindle 53 and the input shaft 16 in a compressed state. The return spring 19 always urges the input shaft 16 with respect to the spindle 53 in the backward direction. The non-operating position of the valve body 15 and the push rod 13 is defined by the support member 31 supporting the valve body 15 coming into contact with the front surface of the spindle nut 51.

A tandem type master cylinder 14 is connected to the front side of the housing 5. A reservoir tank 60 that supplies brake fluid to the master cylinder 14 is attached to the upper portion of the master cylinder 14. The master cylinder 14 includes a primary piston 43 and a secondary piston 44 which are arranged so as to be movable in the axial direction in a bottomed cylinder bore 41. The primary piston 43 is arranged on the side closer to the push rod 13, and the secondary piston 44 is arranged on the side farther from the push rod 13.

The primary piston 43 and the secondary piston 44 are each formed in a cylindrical shape. The entire secondary piston 44 is arranged in the cylinder bore 41, and a part of the primary piston 43 is arranged in the cylinder bore 41. A primary chamber 47 is formed between the primary piston 43 and the secondary piston 44, and a secondary chamber 48 is formed between the secondary piston 44 and the bottom of the cylinder bore 41. A first spring 45 is arranged in the primary chamber 47 between the primary piston 43 and the secondary piston 44. A second spring 46 is arranged in the secondary chamber 48 between the secondary piston 44 and the bottom of the cylinder bore 41.

One end of the push rod 13 that advances by the output of the electric motor 21 and presses the primary piston 43 comes into contact with the primary piston 43. The axial movement of the primary piston 43 also causes the secondary piston 44 to move axially. A first reservoir port 61 and a second reservoir port 63 communicating with the reservoir tank 60 are formed in the primary chamber 47 and the secondary chamber 48, respectively, and brake fluid is supplied from the reservoir tank 60 to the primary chamber 47 and the secondary chamber 48, respectively. To.

Further, the booster 10 includes a stroke sensor 80. The stroke sensor 80 has a magnetic sensor 85 such as a Hall element integrally provided on the valve body 15, and a magnet 81 integrally provided on the key member 87. The magnetic sensor 85 detects the relative displacement of the key member 87, that is, the plunger 57 and the input receiving member 71 with respect to the valve body 15, and outputs a sensor signal to the motor control device 100. Specifically, the magnet 81 provided on the key member 87 moves relative to the magnetic sensor 85 due to the relative displacement of the plunger 57 and the input receiving member 71 with respect to the valve body 15, so that the magnetic sensor 85 moves from the magnet 81. A current corresponding to the fluctuation of the magnetic field is output to the motor control device 100.

The motor control device 100 determines the relative displacement of the plunger 57 and the input receiving member 71 with respect to the valve body 15 based on the magnitude of the current input from the magnetic sensor 85. In the non-operating state of the booster 10, the relative displacement of the plunger 57 and the input receiving member 71 with respect to the valve body 15 is defined as zero.

In the motor control device 100, the current of the magnetic sensor 85 generated by the magnetic field of the magnet 81 in the non-operating state of the booster 10 is set to zero as a reference value. At this time, the motor control device 100 does not supply electric power (current) to the stator of the electric motor 21. On the other hand, when the driver depresses the brake pedal, the return spring 19 bends and the input shaft 16 advances. Along with this, the input receiving member 71 advances, and the plunger 57 and the input receiving member 71 are displaced relative to the valve body 15. As a result, the magnetic field of the magnet 81 with respect to the magnetic sensor 85 fluctuates, and the magnetic sensor 85 generates a current and outputs it to the motor control device 100. The motor control device 100 supplies electric power (current) to the stator of the electric motor 21.

<3. Master cylinder hydraulic circuit>
Next, the liquid passages connected to the primary chamber 47 and the secondary chamber 48 of the master cylinder 14 will be described. FIG. 3 is an enlarged view of a cross section of the master cylinder 14 shown in FIG.

The master cylinder 14 includes a first hydraulic port 62 that connects the primary chamber 47 and the first hydraulic circuit 28 of the hydraulic unit 20. Further, the master cylinder 14 includes a second hydraulic port 64 that connects the secondary chamber 48 and the second hydraulic circuit 30 of the hydraulic unit 20.

The master cylinder 14 has a first reservoir port 61 that opens at a position facing the outer peripheral surface of the primary piston 43. A first gallery chamber 65 is formed on the inner peripheral surface of the cylinder bore 41 corresponding to the position where the first reservoir port 61 is formed over the entire circumference. Two sealing members 68a and 68b are arranged between the outer peripheral surface of the primary piston 43 and the inner peripheral surface of the cylinder bore 41 so as to sandwich the first gallery chamber 65 in the axial direction. Of these, a narrow liquid passage (not shown) is formed in the seal member 68a located on the primary chamber 47 side (front side).

Further, the master cylinder 14 has a second reservoir port 63 that opens at a position facing the outer peripheral surface of the secondary piston 44. A second gallery chamber 67 is formed on the inner peripheral surface of the cylinder bore 41 corresponding to the position where the second reservoir port 63 is formed over the entire circumference. Two sealing members 69a and 69b are arranged between the outer peripheral surface of the secondary piston 44 and the inner peripheral surface of the cylinder bore 41 so as to sandwich the second gallery chamber 67 in the axial direction. Of these, a narrow liquid passage (not shown) is formed in the seal member 69a located on the secondary chamber 48 side (front side).

The liquid passage between the secondary chamber 48 and the second hydraulic circuit 30 and the liquid passage between the secondary chamber 48 and the reservoir tank 60 are between the primary chamber 47 and the first hydraulic circuit 28. It is configured in the same manner as the liquid passage and the liquid passage between the primary chamber 47 and the reservoir tank 60. Hereinafter, the liquid passage on the side of the primary chamber 47 will be described.

The brake fluid is supplied from the primary chamber 47 to the first hydraulic pressure circuit 28 via the first hydraulic pressure port 62, and is returned from the first hydraulic pressure circuit 28 to the primary chamber 47. Further, the brake fluid is supplied from the reservoir tank 60 to the primary chamber 47 via the first reservoir port 61, and also flows back from the primary chamber 47 to the reservoir tank 60.

The liquid passage between the primary chamber 47 and the first hydraulic circuit 28 is not provided with a portion where the passage area is sharply narrowed, and the brake fluid is not subjected to a large resistance between the primary chamber 47 and the first hydraulic circuit 28. It goes back and forth with the hydraulic circuit 28 of 1. Therefore, as the driver operates the brake, the brake fluid is supplied to the first hydraulic pressure circuit 28 or recirculated from the first hydraulic pressure circuit 28. As a result, the wheel cylinder pressures of the hydraulic brakes 38a to 38d of the respective wheels RF, LR, LF, and RR are adjusted.

On the other hand, the liquid passage between the primary chamber 47 and the reservoir tank 60 is provided with a portion where the passage area is sharply narrowed. Specifically, the liquid passage between the primary chamber 47 and the reservoir tank 60 includes a narrow liquid passage (not shown) formed in the seal member 68a. This makes it difficult for the brake fluid to return to the reservoir tank 60 side when the driver depresses the brake pedal so that the brake fluid is supplied to the first hydraulic circuit 28 side, and the driver returns the brake pedal. This is to ensure that the brake fluid is replenished from the reservoir tank 60 to the primary chamber 47 when the amount of brake fluid in the hydraulic pressure circuit drops.

In the master cylinder configured in this way, when the brake pedal is suddenly returned and the primary piston 43 and the secondary piston 44 are suddenly retracted, and the inside of the primary chamber 47 becomes negative pressure, the seal member 68a is deformed. A large amount of brake fluid may flow from the reservoir tank 60 into the primary chamber 47. The same applies to the secondary room 48. On the other hand, the motor control device 100 according to the present embodiment controls to limit the rotation speed of the electric motor 21 so that the degree of negative pressure in the primary chamber 47 and the secondary chamber 48 does not increase (hereinafter, such control). Is also called "rotation speed limiting process").

<4. Motor control device>
Next, a functional configuration and an operation example of the motor control device 100 according to the present embodiment will be described.

FIG. 4 is a block diagram showing a configuration example of the motor control unit 110. As shown in FIG. 4, the motor control device 100 is configured to be able to communicate with the hydraulic pressure control device 90 via a communication means (not shown). Further, the motor control device 100 is configured to be able to acquire the sensor signals of the stroke sensor 80, the master cylinder hydraulic pressure sensor 24, and the vehicle speed sensor 101. The motor control device 100 may acquire sensor signals directly from various sensors, or may acquire sensor signal information via other control devices.

The motor control device 100 according to the present embodiment includes a motor control unit 110, a motor drive circuit 112, and a storage unit 114. In addition, the motor control device 100 is configured to include electronic components such as an interface for communication.

The storage unit 114 includes storage elements such as a RAM (Random Access Memory) and a ROM (Read Only Memory). The storage unit 114 may include a storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive). The storage unit 114 stores the software program executed by the motor control unit 110 and various parameters used for executing the software program. In addition, the storage unit 114 stores calculation results obtained by executing a software program, detection data based on acquired sensor signals of various sensors, and the like.

The motor drive circuit 112 is composed of various electronic components such as a switching element and a capacitor, receives a drive command signal from the motor control unit 110, and outputs a drive signal to the electric motor 21 of the booster 10.

The motor control unit 110 includes a processor such as a CPU, and controls the rotation speed of the electric motor 21 by executing a software program. In the motor control device 100 according to the present embodiment, it is estimated that the pressure in the primary chamber 47 and the secondary chamber 48 becomes negative pressure in the motor control unit 110 when the execution condition of the pressure holding control by the hydraulic pressure control device 90 is satisfied. In this case, the rotation speed limiting process for limiting the rotation speed of the electric motor 21 is executed.

The pressure holding control is a control executed by the hydraulic pressure control device 90 when the brake pedal 11 is returned. When the brake pedal 11 is returned from the state where the brake pedal 11 is depressed by a predetermined amount or more, the hydraulic pressure control device 90 closes the liquid passage between the master cylinder 14 and the hydraulic pressure unit 20, and the hydraulic pressure unit 20 to the master cylinder 14 Shut off the return of brake fluid to. Specifically, the hydraulic pressure control device 90 is mastered from the hydraulic pressure unit 20 by driving the circuit control valves 36a and 36b provided in the first hydraulic pressure circuit 28 and the second hydraulic pressure circuit 30, respectively. The return of the brake fluid to the cylinder 14 is blocked.

As a result, the wheel cylinder pressures of the hydraulic brakes 38a to 38d of the respective wheels LF, RF, LR, and RR are maintained, and the braking force of the vehicle can be maintained. For example, by executing the pressure holding control when the vehicle does not move in a traffic jam or the like, the vehicle can be stopped even when the brake pedal is released. Further, for example, when the vehicle starts to move from a state of being stopped on a slope, the pressure holding control is executed for a short time, so that the vehicle can be started without sliding forward or backward.

When the pressure holding control illustrated above is executed, if the return speed (opening speed) of the brake pedal 11 by the driver is high, the supply of the brake fluid from the reservoir tank 60 to the primary chamber 47 and the secondary chamber 48 cannot catch up. , There is a possibility that the inside of the primary chamber 47 and the secondary chamber 48 becomes negative pressure. In such a case, as described above, the seal members 68a and 69a forming a part of the liquid passage from the reservoir tank 60 to the primary chamber 47 or the secondary chamber 48 are deformed, and a large amount of brake fluid is discharged to the primary chamber 47 or the secondary. There is a risk of flowing into the room 48.

Therefore, the motor control unit 110 limits the rotation speed of the electric motor 21 when the preset operating conditions for the rotation speed control process are satisfied. By limiting the rotation speed of the electric motor 21 when the brake pedal 11 is returned, the speed at which the primary piston 43 and the secondary piston 44 retract becomes less than a predetermined speed, and the inside of the primary chamber 47 and the secondary chamber 48 Can reduce the risk of negative pressure.

In the present embodiment, the motor control unit 110 switches the control map of the rotation speed of the electric motor 21 depending on whether the rotation speed limiting process is executed or released. FIG. 5 is an explanatory diagram showing an example of switching the control map of the rotation speed of the electric motor 21. The horizontal axis represents the stroke amount (mm) of the push rod 13, and the vertical axis represents the rotation speed (rad./sec) of the electric motor 21. The rotation speed of the electric motor 21 is indicated by a positive value in the rotation direction in which the push rod 13 is advanced and a negative value in the rotation direction in which the push rod 13 is retracted. That is, the rotational speed of the electric motor 21 when the push rod 13 is retracted changes from right to left along the solid line or broken line shown in FIG.

In the example shown in FIG. 5, in the range of the stroke amount (st_PR ≦ st_X) where the pressure in the primary chamber 47 and the secondary chamber 48 can be negative, the set value of the rotation speed of the electric motor 21 is a broken line from the value shown by the solid line. It can be switched to the value indicated by. As a result, the rotational speed of the electric motor 21 decreases, and the speed at which the push rod 13, the primary piston 43, and the secondary piston 44 retreat decreases. Therefore, in order for the brake fluid to be appropriately supplied from the reservoir tank 60, it is possible to suppress the negative pressure in the primary chamber 47 and the secondary chamber 48. As a result, deformation of the sealing members 68a and 69a is suppressed.

The method of limiting the rotation speed of the electric motor 21 is not limited to the method of switching the control map. For example, the rotation speed of the electric motor 21 may be controlled based on the pressure value detected by the master cylinder hydraulic pressure sensor 24. However, by switching the control map and limiting the rotation speed of the electric motor 21, the certainty of reducing the rotation speed of the electric motor 21 before the pressure inside the primary chamber 47 and the secondary chamber 48 actually becomes negative is increased. be able to.

FIG. 6 is a flowchart showing a control process executed by the motor control unit 110 when the brake pedal 11 is returned.
First, the motor control unit 110 determines whether or not the operating condition establishment flag for the rotation speed limiting process is set (step S11). When the operating condition establishment flag is set (S11 / Yes), the motor control unit 110 sets the vehicle speed threshold value to a predetermined first vehicle speed threshold value (step S13). The first vehicle speed threshold value is a vehicle speed threshold value used for determining the end of the rotation speed limiting process during operation, and is set to, for example, a value of 0.25 m / sec or more and less than 0.30 m / sec.

On the other hand, when the operating condition establishment flag is not set (S11 / No), the motor control unit 110 sets the vehicle speed threshold value to a predetermined second vehicle speed threshold value (step S15). The second vehicle speed threshold value is a vehicle speed threshold value used for determining the start of the rotation speed limiting process, and is set to, for example, a value of 0.20 m / sec or more and less than 0.25 m / sec. That is, in the present embodiment, the rotation speed limiting process starts from the state of the vehicle speed smaller than the second vehicle speed threshold value, and ends when the vehicle speed reaches the first vehicle speed threshold value larger than the second vehicle speed threshold value. It is configured as follows.

Next, the motor control unit 110 determines whether or not the master cylinder pressure is equal to or lower than a predetermined pressure threshold value (step S17). This pressure threshold value is a threshold value for determining whether or not the master cylinder pressure is in a pressure state in which there is a risk of becoming a negative pressure. The pressure threshold value is set to an appropriate value according to the configuration of the master cylinder 14 or the vehicle braking device 1, and is set to, for example, 2.0 MPa.

When the master cylinder pressure is equal to or lower than the pressure threshold value (S17 / Yes), the motor control unit 110 sets a flag indicating that the master cylinder pressure is in a pressure state where the pressure may become negative (step S19). On the other hand, when the master cylinder pressure is not equal to or lower than the pressure threshold value (S17 / No), the motor control unit 110 lowers the flag indicating that the master cylinder pressure is in a pressure state where the pressure may become negative (step S21). ).

Following step S13, step S19 or step S21, the motor control unit 110 determines whether or not the operating conditions for the rotation speed limiting process are satisfied (step S23). The operating conditions for the rotation speed limiting process are at least that the pressure holding control by the hydraulic pressure control device 90 is being executed (first condition), and that the automatic brake control such as ABS (Antilock Brake System) or ESC is not operating. (Second condition), the master cylinder pressure is in a pressure state where there is a possibility of becoming negative pressure (third condition), and the return speed of the brake pedal 11 is equal to or higher than a predetermined speed threshold (fourth condition). including.

The first condition is included in the operating conditions because the fact that the master cylinder pressure becomes a negative pressure occurs when the pressure holding control is executed. Whether or not the pressure holding control is being executed can be determined based on the message transmitted from the hydraulic pressure control device 90.

The second condition is that when the automatic brake control is in operation, the circuit control valves 36a and 36b may be opened to supply the brake fluid from the master cylinder 14 to the hydraulic unit 20. Included in the conditions. Whether or not the automatic brake control is operating can be determined based on the message transmitted from the hydraulic pressure control device 90.

The third condition is included in the operating conditions because it is not necessary to execute the rotation speed limiting process when the master cylinder pressure does not become a negative pressure. Whether or not the master cylinder pressure may become negative can be determined by whether or not the flag is set. As described above, in this embodiment, this flag is set when the master cylinder pressure is 2.0 MPa or less.

The fourth condition is that the master cylinder pressure becomes negative because the supply of brake fluid from the reservoir tank 60 cannot catch up when the return speed of the brake pedal 11 is equal to or higher than a predetermined value, and thus is included in the operating conditions. It has been. Whether or not the return speed of the brake pedal 11 is equal to or higher than a predetermined speed threshold value can be determined based on the sensor signal of the stroke sensor 80. The speed threshold value is appropriately set according to the configuration of the master cylinder 14 or the vehicle braking device 1, but can be, for example, 5 mm / sec.

In addition, the stroke amount of the push rod 13 is within a predetermined range (fifth condition), the vehicle speed is below the set threshold value (sixth condition), or the driver has no intention of driving (seventh condition). Conditions) may include at least one of the conditions.

The fifth condition is preferably included in the operating conditions because the fact that the master cylinder pressure becomes a negative pressure depends on the relationship between the stroke amount of the push rod 13 and the pressure state in the master cylinder. Whether or not the stroke amount of the push rod 13 is within the predetermined range can be determined based on the sensor signal of the stroke sensor 80. The range of the stroke amount is appropriately set according to the configuration of the master cylinder 14 or the vehicle braking device 1.

The sixth condition is that when the vehicle speed is equal to or higher than a predetermined value, even if the master cylinder pressure becomes negative and a large amount of brake fluid flows into the primary chamber 47 and the secondary chamber 48 from the reservoir tank 60 side. , It is preferable to include it in the operating conditions because it is difficult for the occupant to feel the sound and vibration generated. Whether or not the vehicle speed is equal to or higher than a predetermined value can be determined based on the sensor signal of the vehicle speed sensor 101.

The seventh condition is that if the driver intends to drive, the pressure holding control by the hydraulic pressure control device 90 is released, the circuit control valves 36a and 36b are opened, and the master is from the hydraulic pressure unit 20 side. It is included in the operating conditions because the brake fluid returns to the cylinder 14 and it is no longer necessary to limit the rotational speed of the electric motor 21. The driver's driving intention can be determined, for example, by acquiring information indicating that the accelerator pedal is depressed.

Further, the operating conditions of the rotation speed limiting process may include that all the in-vehicle devices or systems related to the operation of the rotation speed limiting process are operating normally. This is to enable judgment on the premise that the system is operating normally.

In step S23, when the operating condition of the rotation speed limiting process is not satisfied (S23 / No), the motor control unit 110 is set to a state in which a flag indicating the establishment of the operating condition of the rotation speed control process is set, and the rotation speed is controlled. The process is not executed (step S27). That is, when the execution of the pressure holding control by the hydraulic pressure control device 90 is canceled, the stroke amount of the push rod 13 deviates from the predetermined range, or the vehicle speed exceeds the predetermined vehicle speed threshold value, the driver has an intention to drive. At some point, or when the brake pedal 11 is depressed again, the execution of the rotation speed limiting process is canceled.

On the other hand, when the operating condition of the rotation speed limiting process is satisfied (S23 / Yes), the motor control unit 110 sets a flag indicating that the operating condition of the rotation speed control process is satisfied and limits the rotation speed of the electric motor 21. (Step S25). The motor control unit 110 of the present embodiment limits the rotation speed by switching the control map of the rotation speed of the electric motor 21 (see FIG. 5). As a result, the speed at which the primary piston 43 and the secondary piston 44 retreat is limited, and negative pressure in the primary chamber 47 and the secondary chamber 48 is suppressed. As a result, the deformation of the seal members 68a and 69a is suppressed, and the generation of vibration and sound due to the large amount of brake fluid being supplied from the reservoir tank 60 side can be prevented.

FIG. 7 is a timing chart showing a specific example of the change in the master cylinder pressure depending on whether or not the rotation speed limiting process is executed when the pressure holding control is executed. In FIG. 7, the rotation speed rad_MT_cur of the electric motor 21 when the rotation speed limiting process is not executed, the stroke amount st_PR_cur of the push rod 13 and the master cylinder pressure pMC_cur are shown by solid lines, and the electric motor when the rotation speed limiting process is executed. The rotation speed rad_MT_rev of 21, the stroke amount st_PR_rev of the push rod 13, and the master cylinder pressure pMC_rev are indicated by broken lines.

When the rotation speed limiting process is not executed, the master cylinder pressure pMC_cur becomes zero when the rotation speed of the electric motor 21 is controlled without limitation in accordance with the decrease in the stroke amount st_PR_cur of the push rod 13 (retraction of the push rod 13). It becomes a negative pressure below pMC = 0). In this case, a large amount of brake fluid flows from the reservoir tank 60 to the master cylinder 14 due to the deformation of the seal members 68a and 69a, and noise and vibration are generated by the impact in the primary chamber 47 and the secondary chamber 48 (in the figure). The period surrounded by the alternate long and short dash line).

On the other hand, when the rotation speed control process is executed, the control map of the rotation speed of the electric motor 21 is switched at the time Ti1 when the operating condition is satisfied, and the rotation speed rad_MT_rev of the electric motor 21 is fixed to the target value. As a result, the subsequent decrease in the stroke amount st_PR_rev of the push rod 13 becomes gradual and constant, and the master cylinder pressure pMC_rev is suppressed from becoming a negative pressure. Therefore, it is possible to prevent a large amount of brake fluid from flowing from the reservoir tank 60 into the master cylinder 14. After that, the control map of the rotation speed of the electric motor 21 is restored at the time Ti2 when the stroke amount st_PR_rev of the push rod 13 becomes equal to or less than a predetermined range.

As described above, in the motor control device 100 according to the present embodiment, it is estimated that the brake pedal 11 is returned and the master cylinder pressure becomes a negative pressure when the execution condition of the pressure holding control by the hydraulic pressure control device 90 is satisfied. In some cases, the rotation speed of the electric motor 21 is limited. Therefore, it is possible to suppress the pressure in the primary chamber 47 and the secondary chamber 48 from becoming a negative pressure, and it is possible to suppress the inflow of a large amount of brake fluid from the reservoir tank 60 due to the deformation of the seal members 68a and 69a. Therefore, it is possible to suppress the generation of noise and vibration caused by the inflow of the brake fluid.

Further, the motor control device 100 according to the present embodiment fixes the rotation speed to a predetermined target value when limiting the rotation speed of the electric motor 21. Therefore, the control becomes easy, and the retreat speeds of the push rod 13, the primary piston 43, and the secondary piston 44 become constant, and the pressure in the primary chamber 47 and the secondary chamber 48 can be stabilized.

Further, the motor control device 100 according to the present embodiment limits the rotation speed of the electric motor 21 only when the operating conditions that can cause negative pressure in the primary chamber 47 and the secondary chamber 48 are satisfied, and any of the operating conditions If the above is not satisfied, the restriction on the rotation speed is released. Therefore, it is possible to prevent the vehicle from interfering with the running and brake control.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical idea described in the claims. It is naturally understood that these also belong to the technical scope of the present invention.

10 ... Electric booster, 11 ... Brake pedal, 13 ... Push rod, 14 ... Master cylinder, 20 ... Brake hydraulic unit, 21 ... Electric motor, 43 ... Primary piston, 44 ... Secondary piston, 47 ... Primary chamber, 48 ... secondary chamber, 60 ... reservoir tank, 68a, 69a ... seal member, 100 ... motor control device, 110 ... motor control unit,

Claims (4)

In the control device (100) of the electric booster (10) that boosts the input of the brake operation by using the output torque of the electric motor (21).
A motor control unit (110) for controlling the rotation speed of the electric motor (21) is provided.
When the execution condition of the pressure holding control for holding the wheel cylinder pressure is satisfied, the motor control unit (110) closes the liquid passage between the master cylinder (14) and the brake hydraulic pressure unit (20). When it is estimated that the master cylinder pressure becomes negative when 11) is returned, the rotation speed of the electric motor (21) is limited.
A control device for an electric booster. The motor control unit (110)
The execution condition of the pressure holding control is satisfied.
The master cylinder pressure is equal to or less than a predetermined pressure threshold value.
The stroke amount of the push rod (13) of the electric booster (10) is within a predetermined range.
The vehicle speed is below the specified vehicle speed threshold and
When the brake pedal (11) is returned faster than the predetermined speed,
Limiting the rotational speed of the electric motor (21),
The control device for the electric booster according to claim 1. The motor control unit (110) controls the electric motor (21) at a rotation speed set according to the stroke amount of the push rod (13) of the electric booster (10).
When limiting the rotation speed, the rotation speed is fixed at a predetermined target value.
The control device for the electric booster according to claim 1 or 2. The motor control unit (110)
When the execution of the pressure holding control is released,
When the stroke amount of the push rod (13) of the electric booster (10) deviates from the predetermined range.
When the vehicle speed exceeds the predetermined vehicle speed threshold value
When it is determined that the driver of the vehicle equipped with the electric booster (10) has a driving intention, and
When the brake pedal (11) is stepped on,
When at least one of the conditions is satisfied, the restriction on the rotation speed of the electric motor (21) is released.
The control device for the electric booster according to claim 2.

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