WO2022181779A1 - Brake device for vehicle - Google Patents

Abstract

A brake device 40 comprises a hydraulic pressure generation device 41, a brake actuator 60, and a brake control unit 82. The brake control unit 82 executes an assistance process that, according to a master pressure in hydraulic pressure chambers 521, 522 of a master cylinder 43 in the hydraulic pressure generation device 41, or according to an operation-related force which is the operation force inputted to a brake operation member by a driver, controls an assisting hydraulic pressure which is the amount of increase in the wheel pressure due to movement of the brake actuator 60. The brake control unit 82 executes reduction control that reduces/corrects the assisting hydraulic pressure when pistons 511, 512 of the master cylinder 43 are located further in a retreating direction X2 than a second position during the assistance process.

Description

vehicle braking system

The present invention relates to a vehicle braking device that adjusts hydraulic pressure in wheel cylinders provided for wheels.

Patent Document 1 describes an example of a vehicle braking device that includes a hydraulic pressure generating device and a braking actuator. In the brake system, the hydraulic pressure generator includes a master cylinder and a reservoir tank in which brake fluid is stored. A hydraulic pressure chamber is defined within the master cylinder, and the hydraulic pressure chamber communicates with the inside of the reservoir tank via a port. The master cylinder has a piston that moves forward when the amount of braking operation by the driver is increased. The position of the piston when no braking operation is performed is defined as the first position. When the piston moves forward from the first position, the volume of the hydraulic chamber gradually decreases. Then, when the piston reaches the second position, the port is closed, and communication between the hydraulic pressure chamber and the inside of the reservoir tank via the port is cut off. Therefore, when the piston moves forward from this state, the master pressure, which is the hydraulic pressure in the hydraulic pressure chamber, increases. As a result, the wheel pressure, which is the hydraulic pressure in the wheel cylinder communicating with the hydraulic pressure chamber, increases. Note that the wheel pressure generated by the increase in the master pressure is called the base hydraulic pressure. Also, the amount of increase in the wheel pressure due to the actuation of the brake actuator is referred to as the control hydraulic pressure.

According to Patent Document 1, the port is provided with an orifice. Therefore, when the piston moves forward at a high speed due to the driver's braking operation, the orifice effect reduces the amount of brake fluid that flows from the hydraulic chamber to the reservoir tank as the volume of the hydraulic chamber changes. do. As a result, the master pressure starts increasing before the piston reaches the second position. That is, the base hydraulic pressure can be increased before the piston reaches the second position.

By the way, in the hydraulic pressure generating device as described above, a vacuum booster is adopted as a booster device that assists the driver's braking operation. In this case, if the driver performs a braking operation while the boost pressure, which is the negative pressure in the pressure chamber within the booster device, is not very high, the braking operation may not be sufficiently assisted. That is, compared to before the master pressure exceeds the hydraulic pressure corresponding to the boost pressure, after the master pressure exceeds the hydraulic pressure corresponding to the boost pressure, the assisting efficiency of the braking operation by the booster device suddenly decreases. . The master pressure at the timing at which the assisting efficiency suddenly changes is called an inflection point.

Therefore, in Patent Document 2, the brake actuator is operated before the master pressure reaches the inflection point to increase the wheel pressure and assist the driver's braking operation. When the amount of increase in wheel pressure for assisting the driver's braking operation due to the actuation of the brake actuator is defined as the assisting hydraulic pressure, the master pressure or a value corresponding to the operating force may be set as the assisting hydraulic pressure. In this case, the sum of the base hydraulic pressure and the boosting hydraulic pressure is the wheel pressure. The operating force referred to here is the force input from the driver to the brake pedal.

JP 2011-213242 A Japanese Patent No. 5217472

In the braking device described in Patent Document 1, as described in Patent Document 2, when the driver is performing a braking operation, the operation of the brake actuator increases the wheel pressure to assist the driver's braking operation. think of doing In the braking device disclosed in Patent Literature 1, when the moving speed of the piston in the forward direction due to the driver's braking operation is high, the master pressure starts to increase before the port is blocked by the piston. At this time, the operating force also increases as the master pressure increases. That is, even before the port is closed, the wheel pressure is increased by actuation of the brake actuator. Therefore, the wheel pressure may become too high for the amount of braking operation by the driver, and the brakes may become too effective.

A vehicle braking device for solving the above problems is a device that adjusts the wheel pressure, which is the hydraulic pressure in the wheel cylinders provided for the wheels. This braking device has a reservoir tank for storing brake fluid, and a master cylinder in which a fluid pressure chamber communicating with the inside of the reservoir tank via a port is provided. a hydraulic pressure generating device communicating with the inside of the wheel cylinder via a hydraulic pressure generating device for generating a base hydraulic pressure, which is the wheel pressure corresponding to the master pressure, which is the hydraulic pressure of the hydraulic pressure chamber, in the wheel cylinder; A brake actuator operable to regulate pressure and a controller for controlling the brake actuator are provided. When the brake operation member is operated to move the master cylinder in the forward direction, the master cylinder reduces the volume of the hydraulic pressure chamber. A piston is provided to increase the volume of the hydraulic chamber, and when the piston is positioned at the first position, the brake operating member is operated to move the piston in the forward direction, whereby the first hydraulic pressure chamber is moved forward. The port is closed when the piston reaches a second position located in the forward direction relative to the position, and the master pressure is increased when the piston moves in the forward direction with the port closed. is configured to The control device controls the amount of increase in the wheel pressure caused by the actuation of the brake actuator according to the master pressure or an operation-related force that is an operation force input to the brake operation member by the driver of the vehicle. An assisting process is executed to control a certain assisting hydraulic pressure. Further, in the assisting process, the control device performs reduction control for decreasing the assisting hydraulic pressure when the piston is positioned in the backward direction from the second position.

When the driver starts braking, the piston moves forward in the master cylinder. At this time, if the moving speed of the piston is high, the master pressure may start to increase even though the piston has not reached the second position and the hydraulic pressure chamber and the inside of the reservoir tank are communicated through the port. As a result, a base hydraulic pressure is generated in the wheel cylinder, increasing the wheel pressure.

In the above configuration, when the assisting process is executed while the braking operation is being performed, the assisting hydraulic pressure is controlled by operating the brake actuator based on the operation-related force. In this case, the wheel pressure is the sum of the base hydraulic pressure and the boosting hydraulic pressure.

When the piston is positioned in the backward direction from the second position, the fluid pressure chamber communicates with the inside of the reservoir tank via the port. In this case, in the above configuration, decrease control is performed to decrease and correct the assisting hydraulic pressure. When reduction control is performed in this manner, the assisting hydraulic pressure is less likely to increase. As a result, it is possible to prevent the wheel pressure from becoming too high when the master pressure is increased before the port is closed.

Therefore, according to the above configuration, it is possible to prevent the brake from becoming too effective with respect to the amount of braking operation by the driver.

1 is a configuration diagram showing an outline of a vehicle equipped with a braking device according to a first embodiment; FIG. The block diagram which shows the outline of the same braking device. FIG. 3 is an end view showing a part of the hydraulic pressure generator of the same braking device; 4 is a graph showing the relationship between the position of the piston and the master pressure in the hydraulic pressure generator. The figure explaining each process which the braking control part of the same braking device performs. (a) to (d) are timing charts for explaining a comparative example. (a) to (d) are timing charts when a driver performs a braking operation in the braking device of the first embodiment. FIG. 5 is a diagram showing the relationship between the operating force and the wheel pressure when the reference inflection point is the estimated inflection point; FIG. 4 is a diagram showing the relationship between the operating force and the wheel pressure when the value obtained by subtracting the correction value from the reference inflection point is set as the estimated inflection point. The figure explaining a part of each process which the braking control part in the braking device of 2nd Embodiment performs. FIG. 10 is a diagram showing changes in wheel pressure when the operating force input to the brake operating member is increased in the braking device of the second embodiment; The figure explaining a part of each process which the braking control part in the braking device of 3rd Embodiment performs.

(First embodiment)
A first embodiment of a vehicle braking device will be described below with reference to FIGS. 1 to 9. FIG.
<Overall composition>
FIG. 1 shows a vehicle 10 equipped with a braking device 40 of this embodiment. The vehicle 10 has a power unit 21 .

The power unit 21 has an engine 22 and a drive motor 23 as power sources for the vehicle 10 . That is, driving force output from at least one of the engine 22 and the drive motor 23 is input to the wheels 11 . Further, when the vehicle is braked, by transmitting the rotation of the wheels 11 to the drive motor 23, the drive motor 23 can generate electric power. In this case, the vehicle 10 generates regenerative braking force, which is braking force corresponding to the amount of power generated by the drive motor 23 .

A brake mechanism 30 is provided for each of the plurality of wheels 11 in the vehicle 10 . Each braking mechanism 30 has a rotating body 31 that rotates integrally with the corresponding wheel 11 , a friction material 32 , and a wheel cylinder 33 . As the wheel pressure, which is the hydraulic pressure in the wheel cylinder 33, increases, the pressing force, which is the force pressing the friction material 32 against the rotating body 31, increases. The greater the pressing force, the greater the frictional braking force on the wheels 11 due to the operation of the braking mechanism 30 .

The vehicle 10 includes a hydraulic pressure generator 41 and a brake actuator 60. The friction braking force for each wheel 11 is adjusted by the hydraulic pressure generator 41 and the braking actuator 60 . Note that the total frictional braking force for each wheel 11 corresponds to the frictional braking force for the vehicle 10 .

<Structure of liquid pressure generator 41>
As shown in FIG. 1 , the hydraulic pressure generator 41 has a booster device 42 , a master cylinder 43 and a reservoir tank 44 . A braking operation member 45 is connected to the booster device 42 . For example, a brake pedal can be used as the braking operation member 45 . The booster device 42 utilizes the boost pressure, which is the negative pressure generated by the operation of the engine 22, to boost the operation force input to the braking operation member 45 by the driver. Then, the operating force boosted by the booster device 42 is input to the master cylinder 43 .

As shown in FIG. 2, the master cylinder 43 has two pistons 511 and 512. Each of the pistons 511 and 512 moves in the forward direction X1 shown in FIG. 2 when an operation force is input. Assuming that the direction opposite to the forward direction X1 is the backward direction X2, of the two pistons 511 and 512, the piston 511 is located in the forward direction X1 and the piston 512 is located in the backward direction X2.

Two hydraulic chambers 521 and 522 are provided in the master cylinder 43 . That is, two pistons 511 and 512 define respective hydraulic chambers 521 and 522 . When the piston 511 moves in the forward direction X1, the volume of the hydraulic pressure chamber 521 decreases. When the piston 511 moves in the backward direction X2, the volume of the hydraulic pressure chamber 521 increases. Further, when the piston 512 moves relative to the piston 511 in the forward direction X1, the volume of the hydraulic pressure chamber 522 decreases. When the piston 512 moves relative to the piston 511 in the backward direction X2, the volume of the fluid pressure chamber 522 increases.

The master cylinder 43 has a spring 531 that biases the piston 511 in the backward direction X2 and a spring 532 that biases the piston 512 in the backward direction X2. Therefore, when the operating force input to the master cylinder 43 is reduced, the urging forces of the springs 531 and 532 move the pistons 511 and 512 in the backward direction X2.

The master cylinder 43 has a port 541 communicating between the fluid pressure chamber 521 and the inside of the reservoir tank 44 and a port 542 communicating between the fluid pressure chamber 522 and the inside of the reservoir tank 44 . As shown in FIG. 3, each port 541, 542 is provided with an orifice 54a.

The operation of the braking operation member 45 by the driver is defined as "braking operation", and the position of each piston 511, 512 when no braking operation is performed is defined as "first position". Let the hydraulic pressure in each of the hydraulic pressure chambers 521 and 522 be "master pressure". When each piston 511, 512 is located at the first position, each port 541, 542 is not blocked. That is, the hydraulic pressure chamber 521 communicates with the reservoir tank 44 via the port 541 , and the hydraulic pressure chamber 522 communicates with the reservoir tank 44 via the port 542 . A braking operation is started with the pistons 511 and 512 positioned at the first position, and the pistons 511 and 512 move in the forward direction X1. At this time, if the port 541 is not blocked, the master pressure in the hydraulic pressure chamber 521 is not increased. Similarly, if port 542 is not blocked, the master pressure in hydraulic chamber 522 will not increase. When each piston 511, 512 reaches a second position located in the forward direction X1 from the first position due to the movement of each piston 511, 512 in the forward direction X1, the port 541 is closed by the piston 511 and the port 542 is blocked by piston 512 . The second position is a position separated by a predetermined distance S in the forward direction X1 from the first position. Further movement of the pistons 511 and 512 in the forward direction X1 with the ports 541 and 542 closed increases the master pressure.

As indicated by broken lines in FIG. 4, when the pistons 511 and 512 are positioned in the backward direction X2 from the second position, the fluid pressure chambers 521 and 522 communicate with the inside of the reservoir tank 44, so that the master pressure is "0". That is, no master pressure is generated. However, when the pistons 511 and 512 move in the forward direction X1 from the state where the pistons 511 and 512 are positioned at the second position, communication between the fluid pressure chambers 521 and 522 and the inside of the reservoir tank 44 is cut off. The master pressure gradually increases. That is, master pressure is generated.

Orifices 54a are provided in the ports 541 and 542 as shown in FIG. Therefore, when the driver operates the brake operating member 45 at a high speed and the pistons 511 and 512 move at a high speed in the forward direction X1, the hydraulic pressures of the hydraulic pressure chambers 521 and 522 change as the volumes of the hydraulic pressure chambers 521 and 522 change. The orifice effect reduces the amount of brake fluid that flows out into the reservoir tank 44 from the chambers 521 and 522 through the ports 541 and 542 . As a result, as indicated by the solid line in FIG. 4, the master pressure in each of the hydraulic pressure chambers 521 and 522 starts increasing from the state where each of the pistons 511 and 512 is located in the backward direction X2 from the second position. That is, master pressure is generated in each of the hydraulic pressure chambers 521 and 522 .

　As shown in FIGS. 1 and 2, each of the hydraulic pressure chambers 521 and 522 communicates with the inside of the wheel cylinder 33. Therefore, when the master pressure is generated, that is, when the master pressure becomes higher than "0", the wheel pressure in each wheel cylinder 33 increases. A base hydraulic pressure is generated which is a wheel pressure corresponding to the master pressure. That is, the hydraulic pressure generator 41 is a device that generates the base hydraulic pressure in each wheel cylinder 33 .

In this embodiment, the second positions of the pistons 511 and 512 are both separated from the first positions by a predetermined distance S in the forward direction X1. Alternatively, each piston 511, 512 may have a different distance from the first position to the second position. In this case, when the distance from the first position to the second position in each piston 511, 512 reaches the greater distance, the master pressure in each hydraulic pressure chamber 521, 522 starts to increase.

<Configuration of Braking Actuator 60>
As shown in FIG. 2, the braking actuator 60 has two systems of hydraulic circuits 611 and 612 . Two wheel cylinders 33 out of the plurality of wheel cylinders 33 are connected to the first hydraulic circuit 611 . The remaining two wheel cylinders 33 are connected to the second hydraulic circuit 612 . The first hydraulic circuit 611 is connected to the hydraulic chamber 521 of the master cylinder 43 . The second hydraulic circuit 612 is connected to the hydraulic chamber 522 of the master cylinder 43 .

The first hydraulic circuit 611 includes a fluid path 62 connecting the fluid pressure chamber 521 and the wheel cylinder 33 and a differential pressure regulating valve 63 arranged in the fluid path 62 . The differential pressure regulating valve 63 is a normally open linear solenoid valve. The differential pressure adjusting valve 63 is driven to adjust the differential pressure between a portion closer to the master cylinder 43 than the differential pressure adjusting valve 63 and a portion closer to the wheel cylinder 33 than the differential pressure adjusting valve 63 . That is, by driving the differential pressure adjusting valve 63, the differential pressure between the hydraulic pressure chamber 521 and the inside of the wheel cylinder 33 can be adjusted.

The first hydraulic circuit 611 is provided with a holding valve 64 that is closed when restricting the increase in wheel pressure, and a pressure reducing valve 65 that is opened when decreasing the wheel pressure. The first hydraulic circuit 611 is provided with the same number of holding valves 64 and pressure reducing valves 65 as the wheel cylinders 33 connected to the first hydraulic circuit 611 . A reservoir 66 is also connected to the first hydraulic circuit 611 . The reservoir 66 temporarily stores the brake fluid that flows out from the wheel cylinder 33 when the pressure reducing valve 65 is opened.

The first hydraulic circuit 611 is connected to a pump 67 that supplies brake fluid to a supply fluid passage 62a that is a portion of the fluid passage 62 between the differential pressure regulating valve 63 and each wheel cylinder 33. Specifically, the pump 67 supplies brake fluid to the fluid passage between the differential pressure regulating valve 63 and the holding valve 64 . The pump 67 is a pump powered by a pump motor 68 . The pump 67 can pump up the brake fluid in the reservoir 66 and the brake fluid in the master cylinder 43 and supply them to the supply fluid passage 62a. A rod fixed to the reservoir piston pushes the ball of the check valve up when the reservoir 66 is depleted of brake fluid. As a result, the inside of the reservoir 66 and the inside of the master cylinder 43 are brought into communication. Therefore, the pump 67 pumps up the brake fluid inside the master cylinder 43 . On the other hand, when the reservoir 66 stores brake fluid, the reservoir piston is lowered, and the check valve blocks communication between the inside of the reservoir 66 and the inside of the master cylinder 43 . Therefore, the pump 67 pumps up the brake fluid within the reservoir 66 .

Since the structure of the second hydraulic circuit 612 is substantially the same as the structure of the first hydraulic circuit 611, the description of the structure of the second hydraulic circuit 612 is omitted in this specification.
In this embodiment, the brake actuator 60 can control the wheel pressure by adjusting the amount of brake fluid discharged from the pump 67 and the command value (current value) to the differential pressure control valve 63 . The amount of increase in wheel pressure due to actuation of the brake actuator 60 is referred to as "control hydraulic pressure."

<Regarding the control device 80>
As shown in FIG. 1 , vehicle 10 includes a control device 80 . The control device 80 has a drive control section 81 and a braking control section 82 . The drive control unit 81 and the braking control unit 82 can exchange information with each other. The drive control section 81 controls the power unit 21 . That is, the power unit 21 and the drive control section 81 correspond to the “drive device 20 ” that controls the driving force of the vehicle 10 .

The braking control section 82 controls the braking actuator 60 . That is, in this embodiment, the braking control section 82 corresponds to a “control device” that controls the braking actuator 60 . Also, the brake control unit 82, the hydraulic pressure generator 41, and the brake actuator 60 correspond to the "brake device 40" that adjusts the wheel pressure.

As shown in FIG. 2, the braking control unit 82 receives detection signals from various sensors. Examples of sensors include a stroke sensor 91 , a master pressure sensor 92 and a negative pressure sensor 93 . The stroke sensor 91 detects a stroke amount St, which is the amount of operation of the braking operation member 45 by the driver, and outputs a detection signal according to the detection result. The master pressure sensor 92 detects the master pressure Pmc of the hydraulic pressure chamber 521 and outputs a detection signal according to the detection result. The negative pressure sensor 93 detects the boost pressure BP generated within the booster device 42 and outputs a detection signal according to the detection result.

The braking control unit 82 is not limited to having a CPU and a memory for storing programs and executing software processing. In other words, the braking control section 82 may have any one of the following configurations (a) to (c).
(a) It has one or more processors that execute various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to perform processes. Memory, or computer-readable media, includes any available media that can be accessed by a general purpose or special purpose computer.
(b) contain one or more dedicated hardware circuits for performing various processes; Dedicated hardware circuits may include, for example, application specific integrated circuits, ie ASICs or FPGAs. ASIC is an abbreviation for "Application Specific Integrated Circuit", and FPGA is an abbreviation for "Field Programmable Gate Array".
(c) A processor that executes part of various processes according to a computer program, and a dedicated hardware circuit that executes the rest of the various processes.

The drive control unit 81 is not limited to having a CPU and a memory for storing programs and executing software processing. That is, the drive control section 81 may have any one of the configurations (a) to (c) described above.

<Processes Executed by Braking Control Unit 82 When Driver Performs Braking Operation>
As shown in FIG. 5, the braking control unit 82 acquires a stroke amount acquisition process M11 for acquiring the stroke amount St. The braking control unit 82 acquires the stroke amount St based on the detection signal of the stroke sensor 91 in the stroke amount acquisition process M11. In the present embodiment, the stroke amount St corresponds to the "braking operation amount", which is the amount of operation of the braking operation member 45 by the driver. ” corresponds to

The braking control unit 82 acquires a master pressure acquisition process M12 for acquiring the master pressure Pmc. The braking control unit 82 acquires the master pressure Pmc based on the detection signal of the master pressure sensor 92 in the master pressure acquisition process M12. In the present embodiment, the master pressure sensor value is obtained as the master pressure Pmc. Master pressure is the pressure generated in relation to the driver's braking operation. Therefore, it can be said that the master pressure is an operation-related force. Therefore, in the present embodiment, the master pressure acquisition process M12 can be said to be an "operation-related force acquisition process" for acquiring the master pressure Pmc as the operation-related force.

The braking control unit 82 executes a boost pressure acquisition process M13 for acquiring the boost pressure BP. The braking control unit 82 acquires the boost pressure BP based on the detection signal of the negative pressure sensor 93 in the boost pressure acquisition process M13.

The braking control unit 82 performs regenerative cooperative control M2. The cooperative regenerative control M2 derives the requested regenerative braking force RFTr, which is the regenerative braking force required for the drive motor 23, and the cooperative regenerative hydraulic pressure PwcA, which is the amount of increase in wheel pressure caused by the operation of the brake actuator 60.

The braking control unit 82 executes the requested deceleration acquisition process M21 in the cooperative regeneration control M2. The braking control unit 82 acquires a value corresponding to the stroke amount St as the required deceleration GRq in the required deceleration acquisition process M21. That is, when the stroke amount St is less than the play determination stroke amount StA1, the braking control unit 82 acquires "0" as the required deceleration GRq. When the stroke amount St is greater than or equal to the boundary stroke amount StA2, the braking control unit 82 acquires the prescribed value G1 as the requested deceleration GRq. The boundary stroke amount StA2 is larger than the determination stroke amount StA1. A value greater than "0" is set as the specified value G1. When the stroke amount St is greater than or equal to the play determination stroke amount StA1 and less than the boundary stroke amount StA2, the braking control unit 82 acquires a larger value as the required deceleration GRq as the stroke amount St increases.

For example, the design value of the stroke amount St when the pistons 511 and 512 reach the second position, or a value corresponding to the design value, may be set as the boundary stroke amount StA2. In this case, when the stroke amount St is equal to the boundary stroke amount StA2, it can be determined that each of the pistons 511 and 512 is positioned at the second position. When the stroke amount St is less than or equal to the boundary stroke amount StA2, it can be determined that the pistons 511 and 512 are positioned in the backward direction X2 relative to the second position. When the stroke amount St is larger than the boundary stroke amount StA2, it can be determined that the pistons 511 and 512 are positioned in the forward direction X1 relative to the second position. That is, in the present embodiment, the stroke amount acquisition process M11 for acquiring the stroke amount St corresponds to the “piston position acquisition process” for acquiring the positions of the pistons 511 and 512 . Then, in the required deceleration acquisition process M21, based on the positions of the pistons 511 and 512 acquired in the piston position acquisition process, it is determined whether or not the pistons 511 and 512 are positioned in the backward direction X2 relative to the second position. It can be said that there is Then, it can be said that the required deceleration GRq is set based on the determination result.

The braking control unit 82 executes a conversion process M22 for converting the requested deceleration GRq into the requested braking force FRq, which is the requested value of the braking force, in the regenerative cooperative control M2. For example, when the coefficient for converting deceleration into braking force is the first conversion coefficient, the braking control unit 82 calculates the product of the requested deceleration GRq and the first conversion coefficient as the requested braking force FRq in the conversion process M22. should be derived.

The braking control unit 82 executes a required regenerative braking force acquisition process M23 for acquiring the required regenerative braking force RFTr in the regenerative cooperative control M2. In the requested regenerative braking force acquisition process M23, the braking control unit 82 selects the smaller one of the requested braking force FRq and the regenerative braking force upper limit value RFLm as the requested regenerative braking force RFTr. The braking control unit 82 then outputs the requested regenerative braking force RFTr to the drive control unit 81 . As the regenerative braking force upper limit value RFLm, a value is set according to the performance of the drive motor 23 that applies the regenerative braking force to the vehicle 10, the amount of power stored in the storage battery that stores the power generated by the drive motor 23, and the like. be.

The braking control unit 82 executes a subtraction process M24 for deriving the required frictional braking force FFTr in the regenerative cooperative control M2. In a subtraction process M24, the braking control unit 82 derives a value obtained by subtracting the requested regenerative braking force RFTr from the requested braking force FRq as the requested frictional braking force FFTr.

The braking control unit 82 executes a regenerative cooperative hydraulic pressure derivation process M25 for deriving the regenerative cooperative hydraulic pressure PwcA in the regenerative cooperative control M2. The braking control unit 82 converts the requested friction braking force FFTr into the regenerative cooperative hydraulic pressure PwcA in the regenerative cooperative hydraulic pressure derivation process M25. For example, the braking control unit 82 may use a map showing the relationship between the frictional braking force and the wheel pressure to derive the wheel pressure corresponding to the requested frictional braking force FFTr as the regenerative cooperative hydraulic pressure PwcA.

The braking control unit 82 performs servo correction control M3. The servo correction control M3 is a process for deriving the servo assisting hydraulic pressure HPwc1, which is the assisting hydraulic pressure for assisting the driver's braking operation.

The braking control unit 82 executes an assisting gain acquisition process M31 for acquiring a value corresponding to the stroke amount St as an assisting gain α in the servo correction control M3. In the assisting gain acquisition process M31, the braking control unit 82 acquires "0" as the assisting gain α when the stroke amount St is less than the first stroke amount StB1. When the stroke amount St is greater than or equal to the second stroke amount StB2, the braking control unit 82 acquires "1" as the boosting gain α. A value larger than the first stroke amount StB1 is set as the second stroke amount StB2. When the stroke amount St is greater than or equal to the first stroke amount StB1 and less than the second stroke amount StB2, the braking control unit 82 acquires a larger value as the assist gain α as the stroke amount St increases. By gradually increasing the boosting gain α from "0" in this way, the braking feeling immediately after the start of the boosting control can be improved.

In the present embodiment, a value slightly smaller than the boundary stroke amount StA2 is set as the first stroke amount StB1. A value larger than the boundary stroke amount StA2 is set as the second stroke amount StB2.

In the servo correction control M3, the braking control unit 82 executes a basic value deriving process M32 for deriving the servo assisting hydraulic pressure basic value PmcB, which is the basic value of the servo assisting hydraulic pressure HPwc1. In a basic value deriving process M32, the braking control unit 82 derives a servo assist hydraulic pressure basic value PmcB based on the master pressure Pmc and the correction coefficient K1. For example, the braking control unit 82 can derive the servo boost hydraulic pressure base value PmcB using the following relational expression (Equation 1). As the correction coefficient K1, a value that corresponds to the design value of the servo ratio of the booster device 42 and is larger than "1" is set. The "servo ratio" referred to here is a value according to the design value of the boosting efficiency of the booster device 42. As shown in FIG.

PmcB=(K1−1)×Pmc (Formula 1)
In the servo correction control M3, the braking control unit 82 executes a servo assisting hydraulic pressure deriving process M33 for deriving the servo assisting hydraulic pressure HPwc1. The braking control unit 82 derives the product of the servo boosting hydraulic pressure base value PmcB and the boosting gain α as the servo boosting hydraulic pressure HPwc1 in the servo boosting hydraulic pressure deriving process M33.

The braking control unit 82 implements the low negative pressure assist control M4. The low negative pressure assisting control M4 is a process for acquiring the low negative pressure assisting hydraulic pressure HPwc2, which is the assisting hydraulic pressure for assisting the driver's braking operation when it can be estimated that the master pressure Pmc has exceeded the inflection point. is. The "inflection point" referred to here is the master pressure or the hydraulic pressure corresponding to the master pressure at the timing when the efficiency of assisting the braking operation by the booster device 42 suddenly changes.

The braking control unit 82 executes a reference inflection point acquisition process M41 for acquiring the reference inflection point Ppmc in the low negative pressure assist control M4. In the reference inflection point acquisition process M41, the braking control unit 82 acquires a value corresponding to the boost pressure BP as the reference inflection point Ppmc. A map showing the relationship between the boost pressure BP and the reference inflection point Ppmc shown in FIG. The braking control unit 82 acquires "0" as the reference inflection point Ppmc when the boost pressure BP is less than the first boost pressure BP1. The braking control unit 82 acquires the upper limit value PpmcL as the reference inflection point Ppmc when the boost pressure BP is equal to or higher than the second boost pressure BP2. The second boost pressure BP2 is higher than the first boost pressure BP1. When the boost pressure BP is greater than or equal to the first boost pressure BP1 and less than the second boost pressure BP2, the braking control unit 82 acquires a larger value as the reference inflection point Ppmc as the boost pressure BP increases.

The braking control unit 82 executes an estimated inflection point derivation unit M42 for deriving an estimated inflection point PpmcA in the low negative pressure assist control M4. Braking control unit 82 derives, in estimated inflection point derivation unit M42, a value obtained by subtracting a predetermined correction value β from reference inflection point Ppmc as estimated inflection point PpmcA. As the correction value β, a value is set that allows the estimated inflection point PpmcA to be equal to or less than the actual value of the inflection point.

The braking control unit 82 executes a post-correction hydraulic pressure derivation process M43 for deriving the post-correction hydraulic pressure PmcC in the low negative pressure assist control M4. In the corrected hydraulic pressure deriving process M43, the braking control unit 82 derives the corrected hydraulic pressure PmcC based on the value obtained by subtracting the estimated inflection point PpmcA from the master pressure Pmc. That is, the braking control unit 82 derives the larger value of the value obtained by subtracting the estimated inflection point PpmcA from the master pressure Pmc and "0" as the corrected hydraulic pressure PmcC.

In the low negative pressure assisting control M4, the braking control unit 82 executes a low negative pressure assisting hydraulic pressure derivation process M44 for deriving the low negative pressure assisting hydraulic pressure HPwc2. In the low negative assisting hydraulic pressure deriving process M44, the braking control unit 82 derives the low negative assisting hydraulic pressure HPwc2 based on the post-correction hydraulic pressure PmcC. For example, the braking control unit 82 can derive the low negative boosting hydraulic pressure HPwc2 using the following relational expression (Equation 2).

HPwc2=(K2-1)×PmcC (Formula 2)
The braking control unit 82 executes a command value acquisition process M5 for acquiring the total boosting hydraulic pressure HPwc as a command value for the boosting hydraulic pressure. In the command value acquisition process M5, the braking control unit 82 acquires the sum of the servo boosting hydraulic pressure HPwc1 and the low negative pressure boosting hydraulic pressure HPwc2 as the total boosting hydraulic pressure HPwc.

The braking control unit 82 executes a control wheel pressure acquisition process M6 for acquiring the control hydraulic pressure command value PwcTr. In the control wheel pressure acquisition process M6, the braking control unit 82 acquires the sum of the regenerative cooperation hydraulic pressure PwcA and the total boosting hydraulic pressure HPwc as the control hydraulic pressure command value PwcTr.

The braking control unit 82 executes an operation process M7 for operating the braking actuator 60 based on the control fluid pressure command value PwcTr. The braking control unit 82 operates the braking actuator 60 so that the differential pressure obtained by subtracting the master pressure Pmc from the wheel pressure becomes the control hydraulic pressure command value PwcTr.

In this embodiment, based on the servo assisting hydraulic pressure HPwc1 acquired by the servo correction control M3 and the low negative pressure assisting hydraulic pressure HPwc2 acquired by the low negative pressure assisting control M4, a A boost hydraulic pressure, which is the amount of increase in wheel pressure, is set. That is, the boosting hydraulic pressure is controlled according to the master pressure Pmc. Further, the boosting hydraulic pressure is controlled according to the stroke amount St in addition to the master pressure Pmc. Therefore, in this embodiment, the servo correction control M3, the low negative pressure assisting control M4, the command value obtaining process M5, the control wheel pressure obtaining process M6, and the operation process M7 correspond to the "assisting process".

Also, in the assisting gain acquisition process M31, a value corresponding to the stroke amount St is set as the assisting gain α. Then, in the servo-assisting hydraulic pressure deriving process M33, the smaller the assisting gain α, that is, the smaller the stroke amount St, the smaller the value derived as the servo-assisting hydraulic pressure HPwc1. Therefore, the total assisting hydraulic pressure HPwc decreases as the stroke amount St decreases. In other words, the assisting hydraulic pressure is corrected to decrease in accordance with the stroke amount St.

Here, the second stroke amount StB2, which is the criterion for determining whether the boosting gain α should be "1" or less than "1", is larger than the boundary stroke amount StA2. The boundary stroke amount StA2 is set to a design value of the stroke amount St when the pistons 511 and 512 are arranged at the second position, or a value according to the design value.

Therefore, in the assisting process, when the pistons 511 and 512 are positioned in the backward direction X2 from the second position, it can be said that "decrease control" is performed to decrease and correct the assisting hydraulic pressure. Specifically, the assist gain acquisition process M31 and the servo assist hydraulic pressure derivation process M33 correspond to "decrease control". Further, when the first stroke amount StB1 is set as the operation amount determination value, in the assisting control, when the stroke amount St is equal to or less than the operation amount determination value, the stroke amount St is larger than the operation amount determination value. It can be said that the decrease correction amount of the assisting hydraulic pressure is increased.

<Actions and effects in the first embodiment>
With reference to FIGS. 6 and 7, the action and effect when the driver operates the braking operation member 45 at a high speed and requests sudden braking will be described. Here, it is assumed that the boost pressure BP is high enough that the estimated inflection point PpmcA does not become smaller than the master pressure Pmc generated by the braking operation. It is also assumed that the regenerative braking force upper limit value RFLm is larger than the required braking force FRq and the regenerative coordination hydraulic pressure PwcA is "0".

First, a comparative example will be described with reference to FIG. Reduction control is not implemented in the comparative example. That is, regardless of the magnitude of the stroke amount St, "1" is set as the boosting gain α.

As shown in FIGS. 6(a), (b), (c), and (d), the driver's braking operation starts at timing t11, so the stroke amount St increases. In the comparative example shown in FIG. 6, the speed of increase of the stroke amount St is high, and the speed of movement of each of the pistons 511 and 512 in the forward direction X1 is high. Therefore, due to the orifice effect of the orifices 54 a of the ports 541 and 542 , the master pressure Pmc starts to increase before the ports 541 and 542 are closed by the pistons 511 and 512 . That is, the wheel pressure PW in each wheel cylinder 33, ie, the base hydraulic pressure, begins to increase.

Note that in the comparative example, as shown in FIG. 6(c), the stroke amount St does not become equal to or greater than the first stroke amount StB1 due to the driver's braking operation. Therefore, when the stroke amount St stops increasing, the master pressure Pmc decreases. This is because communication between the fluid pressure chambers 521 and 522 and the inside of the reservoir tank 44 via the ports 541 and 542 is maintained.

In the comparative example, the assisting gain α is fixed at "1". Therefore, when the stroke amount St increases and the master pressure Pmc becomes higher than "0", even if the stroke amount St is equal to or smaller than the first stroke amount StB1, a value larger than "0" is the servo assisting hydraulic pressure HPwc1. will be derived as As a result, compared to the case where "0" is derived as the servo boosting hydraulic pressure HPwc1, the total boosting hydraulic pressure HPwc increases. That is, the wheel pressure PW becomes higher than the master pressure Pmc.

As a result, the vehicle braking force FC, which is the sum of the frictional braking force FF and the regenerative braking force RF, may become too large immediately after the driver starts the braking operation. If the vehicle braking force FC becomes too large at the initial stage of braking in this manner, the driver who performs the braking operation may decrease the stroke amount St. When the stroke amount St is reduced, the regenerative braking force RF is reduced, and the regenerative efficiency of the vehicle 10 is lowered.

Next, with reference to FIG. 7, the operation and effects of this embodiment will be described.
As shown in FIGS. 7A, 7B, 7C, and 7D, the driver's braking operation starts at timing t21, so the stroke amount St increases. In the example shown in FIG. 7, similarly to the comparative example, the speed of increase of the stroke amount St is high, and the speed of movement of each of the pistons 511 and 512 in the forward direction X1 is high. Therefore, the orifice effect causes the master pressure Pmc to start increasing before the ports 541 and 542 are blocked by the pistons 511 and 512 . That is, the wheel pressure PW in each wheel cylinder 33, ie, the base hydraulic pressure, begins to increase.

In the period from timing t21 to timing t23, which will be described later, the stroke amount St is less than or equal to the first stroke amount StB1. Therefore, in this period, "0" is set as the boosting gain α. As a result, even if the master pressure Pmc becomes higher than "0", "0" is derived as the servo boosting hydraulic pressure HPwc1.

Furthermore, in the example shown in FIG. 7, the master pressure Pmc does not exceed the estimated inflection point PpmcA during the period from timing t21 to timing t23. As a result, "0" is derived as the low negative pressure assisting hydraulic pressure HPwc2.

Therefore, "0" is derived as the total boosting hydraulic pressure HPwc. As a result, when the master pressure Pmc is increased before the ports 541 and 542 are blocked by the pistons 511 and 512 because the pistons 511 and 512 move at a high speed in the forward direction X1, the wheel pressure PW increases. You can prevent it from becoming too much. Therefore, in the present embodiment, it is possible to prevent the brake from becoming too effective with respect to the stroke amount St.

If the vehicle braking force FC is prevented from becoming too large at the initial stage of braking in this way, the driver is less likely to reduce the stroke amount St. That is, it is possible to suppress a decrease in the regeneration efficiency of the vehicle 10 as well.

In the example shown in FIG. 7, the stroke amount St is restarted to be increased by the driver's braking operation from timing t22, which is after timing t21 and before timing t23. After timing t23, the stroke amount St becomes larger than the first stroke amount StB1. Thus, the boosting gain α gradually increases as the stroke amount St increases. Then, the servo boosting hydraulic pressure HPwc1 also gradually increases. As a result, the operation of the brake actuator 60 can increase the wheel pressure PW.

Incidentally, after timing t23, when the stroke amount St reaches the second stroke amount StB2, the assisting gain α becomes "1". After that, even if the stroke amount St continues to increase, the state where the boosting gain α is "1" is maintained.

In this embodiment, the following effects can be further obtained.
(1-1) In the present embodiment, when the stroke amount St is equal to or less than the first stroke amount StB1, a value smaller than when the stroke amount St is greater than the first stroke amount StB1 is set as the assisting gain α. derived. As a result, when the stroke amount St is equal to or less than the first stroke amount StB1, compared with the case where the stroke amount St is greater than the first stroke amount StB1, the reduction correction amount of the assisting hydraulic pressure during execution of the assisting process is reduced. growing. As a result, it is possible to prevent the assisting hydraulic pressure from becoming too high when the stroke amount St is relatively small.

(1-2) In the present embodiment, a value less than or equal to the actual value of the inflection point is derived as the estimated inflection point PpmcA. As a result, the low negative pressure assisting hydraulic pressure HPwc2 can be made greater than "0" from the time when the master pressure Pmc is equal to or less than the actual value of the inflection point. As a result, even if the master pressure Pmc becomes greater than the actual value of the inflection point, it is possible to suppress the occurrence of an event in which the assisting hydraulic pressure is not generated.

In the low negative pressure assisting control, the reference inflection point Ppmc is obtained based on a map showing the relationship between the boost pressure BP and the reference inflection point Ppmc created based on the specifications of the booster device 42 . The booster device 42 has variations in its characteristics. Also, the boost pressure BP has a detection error. Therefore, the reference inflection point Ppmc does not necessarily match the actual value PpmcR of the inflection point.

Here, FIG. 8 illustrates a case where the reference inflection point Ppmc is the estimated inflection point PpmcA. In FIG. 8, the solid line Z1 shows the transition of the wheel pressure with respect to the increase in the operating force OPbp when the reference point of inflection Ppmc is equal to the actual value PpmcR of the point of inflection. That is, the solid line Z1 indicates the ideal transition of the wheel pressure with respect to the increase in the operating force OPbp. A solid line Z2 shows the transition of the wheel pressure with respect to the increase in the operating force OPbp when the reference inflection point Ppmc is smaller than the actual value PpmcR of the inflection point. A solid line Z3 shows the transition of the wheel pressure with respect to the increase in the operating force OPbp when the reference inflection point Ppmc is greater than the actual value PpmcR of the inflection point. As shown in FIG. 8, when the reference inflection point Ppmc is greater than the actual value PpmcR of the inflection point, an event occurs in which the boosting hydraulic pressure is not generated even if the master pressure Pmc becomes greater than the actual value PpmcR of the inflection point. Occur. In FIG. 8, it is assumed that the regenerative braking force upper limit value RFLm is larger than the required braking force FRq and the regenerative cooperative hydraulic pressure PwcA is "0".

FIG. 9 shows a case where a value obtained by subtracting the correction value β from the reference inflection point Ppmc is set as the estimated inflection point PpmcA. In the present embodiment, the correction value β is set to a value that makes the estimated inflection point PpmcA equal to or less than the actual inflection point PpmcR. Therefore, a value greater than "0" can be set as the low negative pressure assisting hydraulic pressure HPwc2 from the time when the master pressure Pmc is equal to or lower than the actual value PpmcR of the inflection point. As a result, even if the master pressure Pmc becomes greater than the actual value PpmcR of the inflection point, it is possible to prevent the occurrence of a phenomenon in which the boosting hydraulic pressure is not generated.

(Second embodiment)
A second embodiment of a vehicle braking device will be described with reference to FIGS. 10 and 11. FIG. In the following description, the parts that are different from the first embodiment will be mainly described, and the same reference numerals will be given to members that are the same as or correspond to those of the first embodiment, and redundant description will be omitted. do.

<Regarding Servo Correction Control M3>
The servo correction control M3 executed by the braking control section 82 in this embodiment will be described with reference to FIG.

The braking control unit 82 executes an assisting gain acquisition process M31 in the servo correction control M3.
The braking control unit 82 executes a dead zone setting process M35 for setting a dead zone AR of the master pressure Pmc in the servo correction control M3. The braking control unit 82 sets a value corresponding to the master pressure Pmc as the dead band AR in the dead band setting process M35. That is, the braking control unit 82 sets "0" as the dead zone AR when the master pressure Pmc is higher than the first master pressure Pmc1. When the master pressure Pmc is equal to or lower than the first master pressure Pmc1, the braking control unit 82 sets a value greater than "0" as the dead band AR. For example, when the master pressure Pmc is equal to or lower than the second master pressure Pmc2, the braking control unit 82 sets the dead band maximum value ARmax as the dead band AR. A value lower than the first master pressure Pmc1 is set as the second master pressure Pmc2. A value greater than "0" is set as the maximum value ARmax. When the master pressure Pmc is higher than the second master pressure Pmc2 and equal to or lower than the first master pressure Pmc1, the braking control unit 82 sets the dead band AR to a smaller value as the master pressure Pmc increases.

For example, the maximum value of the master pressure Pmc that can be generated in the fluid pressure chambers 521 and 522 when the ports 541 and 542 are not blocked by the pistons 511 and 512, or a value corresponding to the maximum value, is the maximum value of the dead zone AR. It should be set as ARmax. The “maximum value of the master pressure Pmc” here means the maximum value of the moving speed of the pistons 511 and 512 in the forward direction X1 assumed in terms of design, and when the pistons 511 and 512 move in the forward direction X1, This is the generated master pressure Pmc. Also, it is preferable to set a value equal to or higher than the maximum value ARmax of the dead band AR as the second master pressure Pmc2.

The braking control unit 82 executes a subtraction process M36 in the servo correction control M3. In the subtraction process M36, the braking control unit 82 derives a value obtained by subtracting the dead band AR from the master pressure Pmc as the hydraulic pressure after subtraction PmcA. At this time, if the value obtained by subtracting the dead band AR from the master pressure Pmc is negative, the braking control unit 82 derives "0" as the post-subtraction hydraulic pressure PmcA.

The braking control unit 82 executes a basic value derivation process M32 in the servo correction control M3. In the base value deriving process M32, the braking control unit 82 derives the servo boosting hydraulic pressure base value PmcB based on the post-subtraction hydraulic pressure PmcA and the correction coefficient K1. For example, the braking control unit 82 can derive the servo boost hydraulic pressure base value PmcB using the following relational expression (Equation 3).

PmcB=(K1−1)×PmcA (Formula 3)
In the servo correction control M3, the braking control unit 82 executes a servo assisting hydraulic pressure deriving process M33 for deriving the servo assisting hydraulic pressure HPwc1.

In the present embodiment, in the dead zone setting process M35, a value corresponding to the master pressure Pmc is set as the dead zone AR. In the subtraction process M36, the larger the dead band AR, that is, the lower the master pressure Pmc, the smaller the value derived as the post-subtraction hydraulic pressure PmcA. Then, in the servo-assisting hydraulic pressure deriving process M33, a smaller value is derived as the servo-assisting hydraulic pressure HPwc1 as the post-subtraction hydraulic pressure PmcA is smaller. Therefore, the larger the dead band AR, that is, the lower the master pressure Pmc, the smaller the value derived as the servo boosting hydraulic pressure HPwc1. That is, when the master pressure Pmc is low, it can be said that the reduction correction amount of the boosting hydraulic pressure is larger than when the master pressure Pmc is high.

As described in the first embodiment, the master pressure Pmc is acquired as the operation-related force. Therefore, when the second master pressure Pmc2 is used as the force determination value, in the assisting control in the present embodiment, when the master pressure Pmc is equal to or less than the force determination value, it is compared with when the master pressure Pmc is greater than the force determination value. It can be said that the decrease correction amount of the assisting hydraulic pressure is increased.

<Actions and effects in the second embodiment>
With reference to FIG. 11, the transition of the wheel pressure PW, more specifically, the assisting hydraulic pressure when the servo correction control M3 is performed will be described. It is assumed that the regenerative braking force upper limit value RFLm is larger than the required braking force FRq and the regenerative cooperation hydraulic pressure PwcA is "0".

When the operating force input from the driver to the brake operating member 45 is increased, in the example shown in FIG. 11, when the operating force reaches the first operating force OPbp1, the master pressure Pmc begins to increase. At this time, if the master pressure Pmc is equal to or lower than the dead band AR, the post-subtraction hydraulic pressure PmcA becomes "0", so the servo assisting hydraulic pressure HPwc1 becomes "0". That is, when the master pressure Pmc is equal to or lower than the dead zone AR, the braking actuator 60 does not operate to generate the assisting hydraulic pressure. As a result, in the early stage of braking, it is possible to prevent the wheel pressure PW from becoming too high, and thus to prevent the brake from being excessively effective.

In the example shown in FIG. 11, when the operating force becomes greater than the second operating force OPbp2, the dead zone AR becomes smaller as the operating force increases. As a result, when the post-subtraction hydraulic pressure PmcA becomes greater than "0", the servo boosting hydraulic pressure HPwc1 becomes greater than "0". As a result, the total boosting hydraulic pressure HPwc also increases, so that the actuation of the braking actuator 60 assists the increase in the wheel pressure PW. That is, the boost hydraulic pressure is increased.

In FIG. 11, a dashed line indicates a first transition line L1, which is a line indicating the ideal relationship between the operating force and the wheel pressure PW in terms of design. A second transition line L2, which is a line indicating the relationship between the operating force and the assisting hydraulic pressure in this embodiment, is indicated by a solid line. After the operating force becomes greater than the second operating force OPbp2, the dead zone AR becomes smaller, so the second transition line L2 gradually approaches the first transition line L1. Then, when the operating force reaches the third operating force OPbp3, the dead zone AR becomes "0", so the second transition line L2 overlaps the first transition line L1. The master pressure corresponding to the second operating force OPbp2 is the second master pressure Pmc2, and the master pressure corresponding to the third operating force OPbp3 is the first master pressure Pmc1.

After that, when the operating force reaches the fourth operating force OPbp4 as the operating force increases, the master pressure Pmc reaches an inflection point. In the example shown in FIG. 11, the estimated inflection point PpmcA is equal to the actual value of the inflection point. Therefore, the low negative pressure assisting hydraulic pressure HPwc2 obtained by executing the low negative pressure assisting control M4 becomes greater than "0". Therefore, even after the master pressure Pmc exceeds the inflection point, the wheel pressure PW can be increased according to the increase in the operating force.

When the driver requests sudden braking, the operating force input from the driver to the brake operating member 45 may be large in the initial state of braking. In this case, naturally, the moving speed of each piston 511, 512 in the forward direction X1 within the master cylinder 43 is high. Therefore, in each of the hydraulic chambers 521 and 522, the master pressure Pmc is generated before the ports 541 and 542 are blocked by the pistons 511 and 512, respectively. Then, in the wheel cylinder 33, a base hydraulic pressure corresponding to the master pressure Pmc is generated.

In this embodiment, a dead band AR is set for the master pressure Pmc. When the master pressure Pmc is below the dead zone AR as shown in FIG. 11, the servo assisting hydraulic pressure HPwc1 becomes "0". That is, the boosting hydraulic pressure is corrected to decrease. As a result, it is possible to prevent the wheel pressure PW from becoming too high relative to the stroke amount St.

That is, in the present embodiment, in addition to setting the assisting gain α, the assisting hydraulic pressure is reduced and corrected through the setting of the dead zone AR. Therefore, the effect of suppressing the wheel pressure PW from becoming too high relative to the stroke amount St can be enhanced.

(Third Embodiment)
A third embodiment of a vehicle braking device will be described with reference to FIG. In the following description, the parts that are different from the above-described embodiments will be mainly described, and the same reference numerals will be given to members that are the same as or correspond to those of the above-described embodiments, and redundant description will be omitted. do.

As shown in FIG. 12, the braking control unit 82 executes an assisting gain acquisition process M31 in the servo correction control M3. In the present embodiment, in the assisting gain acquisition process M31, the braking control unit 82 acquires the gain lower limit value as the assisting gain α when the stroke amount St is less than the first stroke amount StB1. A value greater than "0" and less than "1" is set as the gain lower limit value. When the stroke amount St is greater than or equal to the second stroke amount StB2, the braking control unit 82 acquires "1" as the boosting gain α. When the stroke amount St is greater than or equal to the first stroke amount StB1 and less than the second stroke amount StB2, the braking control unit 82 acquires a larger value as the assist gain α as the stroke amount St increases.

The braking control unit 82 executes a gain correction process M37 in the servo correction control M3. In the gain correction process M37, the braking control unit 82 derives a value obtained by correcting the assist gain α based on the stroke change speed dSt, which is the change speed of the stroke amount St, as the corrected assist gain α1. For example, the braking control unit 82 derives the product of the correction coefficient corresponding to the stroke change speed dSt and the assisting gain α as the post-correction assisting gain α1. As a result, a smaller value can be derived as the post-correction assisting gain α1 as the stroke change speed dSt increases.

For example, a value obtained by differentiating the stroke amount St with respect to time may be used as the stroke change speed dSt. In this case, it is preferable to set a smaller value as the gain correction coefficient as the stroke change speed dSt increases.

In the servo-assisting hydraulic pressure deriving process M33, the braking control unit 82 derives the product of the servo-assisting hydraulic pressure base value PmcB and the post-correction assisting gain α1 as the servo-assisting hydraulic pressure HPwc1. As a result, a smaller value can be derived as the servo boosting hydraulic pressure HPwc1 as the stroke change speed dSt increases.

Note that the higher the stroke change speed dSt, the higher the moving speed of each of the pistons 511 and 512 in the forward direction X1. Therefore, in the servo-assisting hydraulic pressure deriving process M33, a smaller value is derived as the servo-assisting hydraulic pressure HPwc1 as the moving speed of the pistons 511 and 512 in the forward direction X1 increases.

In the present embodiment, a smaller value is derived as the post-correction boosting gain α1 as the moving speed of the pistons 511 and 512 in the forward direction X1 increases. Therefore, it can be said that the higher the moving speed of the pistons 511 and 512 in the forward direction X1, the larger the reduction correction amount of the boosting hydraulic pressure.

That is, the higher the moving speed of the pistons 511 and 512 in the forward direction X1, the greater the increase in the master pressure Pmc when the ports 541 and 542 are not blocked due to the orifice effect. In the present embodiment, the higher the moving speed of the pistons 511 and 512 in the forward direction X1 and the greater the amount of increase in the master pressure Pmc, the greater the reduction correction amount of the assisting hydraulic pressure. As a result, the effect of suppressing the wheel pressure PW from becoming excessively large relative to the stroke amount St in the initial stage of braking can be enhanced.

(Change example)
Each of the above embodiments can be implemented with the following modifications. Each of the above-described embodiments and the following modifications can be implemented in combination with each other within a technically consistent range.

- In each of the above embodiments, the master pressure is used as the operation-related force, but the operation force input to the brake operation member 45 by the driver may be used as the operation-related force. In this case, in the master pressure acquisition process M12, for example, the sensor value of the operating force may be acquired as the operating force based on the detection signal of the operating force sensor that detects the operating force. Then, in the master pressure acquisition process M12, an estimated master pressure may be derived by converting the operating force into a master pressure, and the estimated master pressure may be acquired as the master pressure Pmc. Even in this case, the same effects as those of the above embodiments can be obtained.

· In the first and second embodiments, the assisting gain α is set to "0" when the stroke amount St is less than or equal to the stroke amount StB1, but the present invention is not limited to this. For example, when the stroke amount St is equal to or less than the stroke amount StB1, a predetermined value greater than "0" and less than "1" may be set as the boosting gain α.

· In the second embodiment, if the dead zone AR is set by executing the dead zone setting process M35 as shown in FIG. 10, it is not necessary to vary the assisting gain α according to the stroke amount St. In this case, in the servo-assisting hydraulic pressure deriving process M33, the servo-assisting hydraulic pressure base value PmcB is derived as the servo-assisting hydraulic pressure HPwc1.

· In each of the above embodiments, a value equal to the boundary stroke amount StA2 may be set as the second stroke amount StB2. Alternatively, a value larger than the boundary stroke amount StA2 may be set as the second stroke amount StB2. Even in such a case, when the pistons 511 and 512 are located in the backward direction X2 from the second position in the assisting process, it is possible to carry out reduction control for decreasing the assisting hydraulic pressure.

· In the above-described first, second, and third embodiments, if it is possible to ensure that the master pressure Pmc does not exceed the inflection point, it is not necessary to perform the low negative pressure assist control M4. In this case, the servo boosting hydraulic pressure HPwc1 is derived as the total boosting hydraulic pressure HPwc.

· In the above-described first, second, and third embodiments, the reduction correction similar to the servo correction control M3 may be applied to the low negative pressure assist control M4. For example, the low negative pressure assisting hydraulic pressure HPwc2 may be derived from the product of the assisting gain α corresponding to the stroke amount St and the value obtained in the low negative pressure assisting hydraulic pressure deriving process M44. Further, for example, a dead band AR may be set for the master pressure Pmc in the low negative pressure assist control M4.

In each of the above embodiments, in the servo correction control M3, before the low negative pressure assisting hydraulic pressure HPwc2 begins to exceed "0", various processes are executed so that the reduction correction amount by the reduction control can be set to "0". do it.

- In each of the above-described embodiments, the brake actuator may have a configuration different from that of the brake actuator 60 as long as it can adjust the control hydraulic pressure.
The vehicle to which the braking device 40 is applied may be a vehicle that does not have the engine 22 as long as it has the drive motor 23 as the power source of the vehicle. In this case, a device having a vacuum pump may be adopted as the booster device 42 .

Claims (4)

1. A vehicle braking device that adjusts a wheel pressure, which is a hydraulic pressure in a wheel cylinder provided for a wheel,
   A reservoir tank for storing brake fluid and a master cylinder having therein a hydraulic chamber communicating with the inside of the reservoir tank via a port are provided, and the hydraulic chamber communicates with the wheel cylinder via a fluid passage. a hydraulic pressure generating device communicating with the inside of the wheel cylinder and generating a base hydraulic pressure, which is the wheel pressure corresponding to the master pressure, which is the hydraulic pressure of the hydraulic pressure chamber;
   a braking actuator operable to adjust the wheel pressure;
   a control device that controls the braking actuator;
   The master cylinder is
   When the brake operation member is operated to move forward, the volume of the hydraulic chamber is reduced. having a piston to increase the volume,
   With the piston positioned at the first position, operation of the braking operation member is started to move the piston in the forward direction, thereby moving the piston to the second position positioned further in the forward direction than the first position. When the piston reaches, it closes the port, and when the piston moves in the forward direction with the port closed, the master pressure is increased,
   The control device controls the amount of increase in the wheel pressure caused by the actuation of the brake actuator according to the master pressure or an operation-related force that is an operation force input to the brake operation member by the driver of the vehicle. It is designed to execute an assisting process that controls a certain assisting hydraulic pressure,
   The control device, in the assisting process, performs a decrease control for decreasing and correcting the assisting hydraulic pressure when the piston is positioned in the backward direction from the second position.
2. The control device is
   executing a piston position acquisition process for acquiring the position of the piston;
   2. The braking device for a vehicle according to claim 1, wherein it is determined based on the position of the piston acquired in the piston position acquisition process whether or not the piston is located in the backward direction relative to the second position.
3. 3. The braking device for a vehicle according to claim 1, wherein the control device performs the reduction control when the operation-related force is equal to or less than a force judgment value.
4. The control device according to any one of claims 1 to 3, wherein in the reduction control, the reduction correction amount of the boosting hydraulic pressure is increased as the movement speed of the piston in the forward direction increases. vehicle braking system.

Images