JP7548103B2 - Vehicle Brake Device - Google Patents

Description

The present invention relates to a vehicle braking system.

For example, Japanese Patent No. 5800437 discloses a braking device that includes an electric cylinder, a wheel cylinder, and a reservoir. In this braking device, when the piston position exceeds a predetermined position, the solenoid valve between the electric cylinder and the wheel cylinder is closed and the piston is driven toward the initial position, thereby performing suction control to suck in brake fluid from the reservoir.

Patent No. 5800437

In general, an electric cylinder comprises a cylinder, a piston, an electric motor, and a linear motion converter. The rotational motion of the electric motor is converted into linear motion of the piston by the linear motion converter. Inside the cylinder, a hydraulic chamber is defined by the inner circumferential surface of the cylinder and the piston. The driving force of the electric motor transmitted from the linear motion converter causes the piston to slide inside the cylinder to reduce the volume of the hydraulic chamber, causing the electric cylinder to discharge (supply) fluid to the hydraulic path.

The linear motion conversion unit includes, for example, a reducer and a ball screw mechanism. The linear motion conversion unit converts the rotational motion of the output shaft of the electric motor into linear motion of the piston via the reducer and ball screw mechanism. In the linear motion conversion unit, every time the piston is moved to a position where a braking force is generated and hydraulic pressure is maintained at that position, a load is applied to the same location (for example, part of the ball screw or part of the gear), making that part more susceptible to wear. In other words, there is room for improvement in terms of durability (extending life) of conventional electric cylinders.

The object of the present invention is to provide a vehicle braking device that can improve the durability of an electric cylinder.

The vehicle braking device of the present invention includes a fluid passage that connects a first electric cylinder, a second electric cylinder, and one or more wheel cylinders; a valve unit configured to open and close a first wheel connection that connects the first electric cylinder to the wheel cylinder and a second wheel connection that connects the second electric cylinder to the wheel cylinder through the fluid passage; and a control unit configured to execute fluid exchange control that causes the first electric cylinder to discharge fluid from the first electric cylinder into the fluid passage and causes the second electric cylinder to draw fluid from the fluid passage into the second electric cylinder when the inter-cylinder connection that connects the first electric cylinder to the second electric cylinder is opened and the first wheel connection and the second wheel connection are closed.

According to the present invention, when the first and second electric cylinders are disconnected from the wheel cylinder, a fluid exchange control is performed to supply fluid from one electric cylinder to the other electric cylinder. For example, when the second electric cylinder is in a high-pressure state, the fluid exchange control causes the first electric cylinder to discharge fluid and the second electric cylinder to suck fluid, thereby suppressing negative pressure in the second electric cylinder and changing the part of the second electric cylinder to which the load is applied. By performing this periodically, for example, a load can be applied to the entire linear conversion part of the second electric cylinder (for example, evenly), suppressing spot wear. In addition, the fluid exchange control can be expected to accurately supply grease to the entire linear conversion part. During the fluid exchange control, the hydraulic pressure of the wheel cylinder is maintained and fluctuations in the braking force are prevented. According to the present invention, the durability of the electric cylinder can be improved.

1 is a configuration diagram of a vehicle braking device according to a first embodiment; 4 is a flowchart for explaining an example of fluid exchange control in the first embodiment. FIG. 7 is a configuration diagram of a vehicle braking device according to a second embodiment. FIG. 11 is a configuration diagram of a modified example of the first embodiment.

The following describes an embodiment of the present invention with reference to the drawings. Note that in the following embodiments, parts that are identical or equivalent to each other are given the same reference numerals in the drawings. The descriptions of each embodiment can be mutually referred to. The drawings used in the description are conceptual diagrams.

First Embodiment
1, a vehicle braking device 1 of the first embodiment includes a first electric cylinder 2, a second electric cylinder 3, wheel cylinders 41, 42, a fluid passage 5, a valve unit 6, a control unit 7, and a master cylinder device 9. The first electric cylinder 2 and the second electric cylinder 3 are pressure regulating devices configured to be able to increase and decrease the pressure of the wheel cylinders 41, 42.

The first electric cylinder 2 has a first cylinder 21, a first piston 22, a first electric motor 23, and a first linear motion converter 24. The first cylinder 21 is a cylindrical cylinder member (part) with a bottom. The first piston 22 is slidably disposed within the first cylinder 21. Within the first cylinder 21, a first hydraulic chamber 21a is formed, which is partitioned by the inner circumferential surface of the first cylinder 21 and the first piston 22.

An output port 212 is formed in the first cylinder 21. The output port 212 is a port that connects the first hydraulic chamber 21a to the hydraulic passage 5. In the following description, the direction in which the first piston 22 moves to reduce the volume of the first hydraulic chamber 21a is referred to as "forward."

When the first piston 22 moves forward, the fluid in the first hydraulic chamber 21a is output to the hydraulic passage 5 via the output port 212. The initial position of the first piston 22 is the position where the volume of the first hydraulic chamber 21a is maximum. A biasing member 25 that biases the first piston 22 toward the initial position is disposed in the first hydraulic chamber 21a.

The first electric motor 23 has an output shaft 231 and is controlled by the control unit 7. The first linear motion conversion unit 24 is a mechanism that converts the rotational motion of the first electric motor 23 (output shaft 231) into the linear motion of the first piston 22. The first linear motion conversion unit 24 includes a reducer 241 that is linked to the output shaft 231, and a ball screw mechanism 242 that is linked to the reducer. The reducer 241 is composed of multiple gears. The ball screw mechanism 242 includes a bolt portion, a nut portion, and multiple balls arranged between the two, not shown. Details of the first linear motion conversion unit 24 are omitted as they are a known configuration.

In this way, the first electric cylinder 2 is a device that discharges fluid by sliding the first piston 22 so as to reduce the volume of the first hydraulic chamber 21a partitioned by the first cylinder 21 and the first piston 22. The first piston 22 slides so as to increase the volume of the first hydraulic chamber 21a, and fluid is drawn into the first hydraulic chamber 21a.

The second electric cylinder 3 has the same configuration as the first electric cylinder 2, and includes a second cylinder 31 equivalent to the first cylinder 21, a second piston 32 equivalent to the first piston 22, a second electric motor 33 equivalent to the first electric motor 23, and a second linear motion converter 34 equivalent to the first linear motion converter 24. The second electric motor 33 includes an output shaft 331.

A second hydraulic pressure chamber 31a corresponding to the first hydraulic pressure chamber 21a is formed in the second cylinder 31. The output port 312 is a port that connects the second hydraulic pressure chamber 31a to the hydraulic passage 5. In the following description, the direction in which the second piston 32 moves to reduce the volume of the second hydraulic pressure chamber 31a is referred to as "forward."

A biasing member 35 equivalent to the biasing member 25 is disposed in the second hydraulic chamber 31a. The second linear motion converter 34 includes a reducer 341 that is linked to the output shaft 331, and a ball screw mechanism 342 that is linked to the reducer 341.

The second electric cylinder 3 is a device that discharges fluid by sliding the second piston 32 so as to reduce the volume of the second hydraulic chamber 31a partitioned by the second cylinder 31 and the second piston 32. The second piston 32 slides so as to increase the volume of the second hydraulic chamber 31a, and fluid is drawn into the second hydraulic chamber 31a. A detailed explanation of the second electric cylinder 3 is omitted here, as the explanation of the first electric cylinder 2 can be referred to. The wheel cylinders 41, 42 are each provided on a different wheel, and apply a braking force to the wheel according to the hydraulic pressure.

The fluid path 5 is a fluid path that connects the first electric cylinder 2, the second electric cylinder 3, and the wheel cylinders 41, 42. In detail, the fluid path 5 is composed of a communication path 51, a first fluid path 52, and a second fluid path 53. The communication path 51 connects the first electric cylinder 2 (output port 212) and the second electric cylinder 3 (output port 312). The communication path 51 forms an inter-cylinder connection that connects the first electric cylinder 2 and the second electric cylinder 3 in the fluid path 5. The communication path 51 is connected to the master cylinder 91 via the master fluid path 90 and the master cut valve 95. The connection portion between the communication path 51 and the master fluid path 90 is called the connection portion 51a.

The first fluid path 52 connects the portion of the communication path 51 between the first electric cylinder 2 and the connection portion 51a to the wheel cylinder 41. In other words, the first fluid path 52 connects the first electric cylinder 2 and the wheel cylinder 41 through a portion of the communication path 51. The second fluid path 53 connects the portion of the communication path 51 between the second electric cylinder 3 and the connection portion 51a to the wheel cylinder 42. In other words, the second fluid path 53 connects the second electric cylinder 3 and the wheel cylinder 42 through a portion of the communication path 51.

The valve unit 6 is composed of multiple solenoid valves. The valve unit 6 is configured to be able to open and close the first wheel connection, which is the connection between the first electric cylinder 2 and the wheel cylinder 41 by the fluid path 5, and the second wheel connection, which is the connection between the second electric cylinder 3 and the wheel cylinder 42. The first wheel connection is formed by the communication path 51 and the first fluid path 52. The second wheel connection is formed by the communication path 51 and the second fluid path 53.

The valve unit 6 includes a first solenoid valve 61 that opens and closes (connects and cuts off) the first fluid path 52, and a second solenoid valve 62 that opens and closes (connects and cuts off) the second fluid path 53. The first solenoid valve 61 is a normally open solenoid valve provided in the first fluid path 52. The second solenoid valve 62 is a normally open solenoid valve provided in the second fluid path 53.

The control unit 7 is an electronic control unit (ECU) equipped with one or more processors, memories, etc. The control unit 7 is communicatively connected to a plurality of devices. Specifically, the control unit 7 mainly controls the first electric cylinder 2 (first electric motor 23), the second electric cylinder 3 (second electric motor 33), the valve unit 6, the master cut valve 95, and the simulator cut valve 82 described below. The control unit 7 receives detection information (e.g., the stroke of the brake pedal Z, the hydraulic pressure in the hydraulic chambers 21a, 31a, and the hydraulic pressure in the master chamber 91a, etc.) from stroke sensors and pressure sensors not shown. Various controls by the control unit 7 will be described later.

The master cylinder device 9 is a device that supplies fluid to the master fluid passage 90 in response to the operation of the brake pedal Z by the driver. The master cylinder device 9 includes a master cylinder 91, a master piston 92, a biasing member 93, and a reservoir 94. The master cylinder 91 is a cylindrical cylinder member with a bottom. The master piston 92 is disposed in the master cylinder 91 and slides within the master cylinder 91 in response to the operation of the brake pedal Z. A master chamber 91a is formed within the master cylinder 91, which is partitioned by the inner circumferential surface of the master cylinder 91 and the master piston 92. In the description, the direction in which the master piston 92 moves to reduce the volume of the master chamber 91a is referred to as "forward".

The biasing member 93 is a spring that biases the master piston 92 toward the initial position. The biasing member 93 is disposed in the master chamber 91a. The initial position is the position where the volume of the master chamber 91a is maximum. The master cylinder 91 is formed with an input port 911 and an output port 912. The input port 911 is a port that connects the master chamber 91a and the reservoir 94 via the fluid path 943. The output port 912 is a port that connects the master chamber 91a and the master fluid path 90.

When the master piston 92 advances a predetermined distance from the initial position due to braking, it closes the input port 911 to cut off the connection between the master chamber 91a and the reservoir 94. When the master piston 92 advances with the master chamber 91a and the reservoir 94 cut off, the fluid in the master chamber 91a is output to the master fluid path 90 via the output port 912. The master fluid path 90 is a fluid path that connects the master cylinder 91 and the fluid path 5 (communication path 51). The master fluid path 90 is provided with a master cut valve 95, which is a normally open solenoid valve.

The output port 912 is connected to a simulator cut valve 82 and a stroke simulator 83 via a fluid path 81 that branches off from the master fluid path 90. The branch point where the fluid path 81 branches off from the master fluid path 90 is located in a portion of the master fluid path 90 that is closer to the master cylinder 91 than the master cut valve 95. The simulator cut valve 82 is a normally closed type solenoid valve. The stroke simulator 83 is composed of a cylinder 831, a piston 832, and a biasing member 833, and applies a reaction force to the operation of the brake pedal Z by hydraulic pressure.

(Normal brake control)
When the control unit 7 detects a braking request (e.g., the amount of operation of the brake pedal Z or a request in other control), it executes normal brake control based on a braking request value (e.g., a requested deceleration or a target braking force). For example, in normal brake control in which both wheel cylinders 41, 42 are pressurized, the master cut valve 95 is closed, and the first solenoid valve 61, the second solenoid valve 62, and the simulator cut valve 82 are opened. This state can be said to be a by-wire state in which the master cylinder device 9 and the wheel cylinders 41, 42 are hydraulically separated. In the by-wire state, the control unit 7 operates at least one of the first electric cylinder 2 and the second electric cylinder 3 based on the braking request value.

(Fluid transfer control)
The control unit 7 is configured to be able to execute fluid exchange control. The fluid exchange control is a control in which, in a state where the inter-cylinder connection, which is a connection between the first electric cylinder 2 and the second electric cylinder 3, is opened and the first wheel connection and the second wheel connection are closed, the first electric cylinder 2 discharges the fluid in the first electric cylinder 2 to the fluid path 5, and the second electric cylinder 3 draws the fluid in the fluid path 5 into the second electric cylinder 3. More specifically, the fluid exchange control is a control in which, in a state where the inter-cylinder connection is opened, the first wheel connection and the second wheel connection are closed, and the volume of the second hydraulic chamber 31a is smaller than the maximum value, the first electric motor 23 slides the first piston 22 to discharge the fluid in the first hydraulic chamber 21a to the fluid path 5, and the second electric motor 33 slides the second piston 32 to draw the fluid in the fluid path 5 into the second hydraulic chamber 31a.

The control unit 7 executes fluid transfer control at a predetermined timing, for example, when there is no braking request or when there is no change in the braking request value. When there is no braking request, for example, when the vehicle is stopped by the parking brake or the like and the driver is not operating the brake pedal Z. When there is no change in the braking request value, for example, when there is no change in the stroke of the brake pedal Z (the brake pedal Z is not moving) and the hydraulic pressure in the wheel cylinders 41, 42 is maintained.

An example of fluid exchange control will be described with reference to FIG. 2. In this control example, the first electric cylinder 2 and the second electric cylinder 3 have the same specifications (the driving force of the electric motor and the volume of the hydraulic chamber are the same). The second electric cylinder 3 is set as the main pressure regulator. In other words, in normal brake control, the control unit 7 operates only the second electric cylinder 3 to pressurize and depressurize the wheel cylinders 41 and 42. The settings of the main pressure regulator are periodically changed by the control unit 7.

In the configuration of the first embodiment, the connection between the cylinders is always open (communicating). Therefore, when the control unit 7 starts fluid exchange control at a predetermined timing (S101), it closes the first solenoid valve 61, the second solenoid valve 62, and the master cut valve 95 (S102). In this state, the control unit 7 operates the second electric cylinder 3 to pressurize the communication passage 51 to a predetermined pressure (S103). The predetermined pressure is a hydraulic pressure according to the braking request value in normal brake control. The second piston 32 is stopped in a state where it has advanced a distance corresponding to the predetermined pressure. In other words, the volume of the second hydraulic pressure chamber 31a is smaller than the maximum value.

With each hydraulic pressure chamber 21a, 31a and the communication passage 51 pressurized, the control unit 7 operates the first electric motor 23 to advance the first piston 22 and the second electric motor 33 to move the second piston 32 backward (S104). At this time, the amount of operation of the first electric cylinder 2 is the same as the amount of operation of the second electric cylinder 3. In other words, the amount of decrease in the volume of the first hydraulic pressure chamber 21a is the same as the amount of increase in the volume of the second hydraulic pressure chamber 31a. In the fluid exchange control of this example, the brake unit 7 matches the amount of decrease in the volume of the first hydraulic pressure chamber 21a formed in the first electric cylinder 2 and connected to the hydraulic passage 5 with the amount of increase in the volume of the second hydraulic pressure chamber 31a formed in the second electric cylinder 3 and connected to the hydraulic passage 5.

(Effects of the First Embodiment)
According to the first embodiment, in a state where the first electric cylinder 2 and the second electric cylinder 3 are disconnected from the wheel cylinders 41 and 42, a fluid transfer control is executed to supply fluid from one electric cylinder 2 to the other electric cylinder 3. In a state where the second piston 32 is advanced to make the first hydraulic chamber 21a and the second hydraulic chamber 31a high pressure, the first piston 22 is advanced and the second piston 32 is advanced backward by the fluid transfer control, so that the part to which the load is applied in the second linear motion conversion unit 34 (for example, the ball screw mechanism 342) can be changed while suppressing the negative pressure of the second hydraulic pressure chamber 31a. By performing this periodically, for example, a load can be applied to the entire second linear motion conversion unit 34 (for example, evenly), and spot wear can be suppressed. In addition, the fluid transfer control can be expected to supply grease to the entire second linear motion conversion unit 34 with high accuracy. During the fluid transfer control, the hydraulic pressure of the wheel cylinders 41 and 42 is maintained, and fluctuations in the braking force are prevented. According to the first embodiment, it is possible to improve the durability of the linear motion conversion part (the second linear motion conversion part 34) of the main electric cylinder.

In addition, in the above control example, in the fluid exchange control, the amount of decrease in the volume of the first hydraulic pressure chamber 21a is the same as the amount of increase in the volume of the second hydraulic pressure chamber 31a, so the communication passage 51 and the hydraulic pressure chambers 21a and 31a are accurately prevented from becoming negative pressure. When negative pressure occurs, the air dissolved in the fluid turns into bubbles, which can have a detrimental effect on the hydraulic passage 5, etc. However, in this example, this is effectively prevented.

When fluid exchange control is executed, the hydraulic pressure (wheel pressure) of the wheel cylinders 41, 42 cannot be changed. Therefore, by executing fluid exchange control when there is no change in the target braking force (target wheel pressure), i.e., when there is no braking request or no change in the braking request value, it is possible to prevent a deviation between the target braking force and the actual braking force.

(Another example of fluid transfer control)
The fluid transfer control may be performed when one of the electric cylinders, the second electric cylinder 3 which is the main electric cylinder in this example, runs short of fluid. For example, when the brake pad (not shown) is worn down significantly due to rapid wear, the distance between the brake pad and the brake disc (not shown) becomes large, and even if the second electric cylinder 3 is operated to the maximum (until the second piston 32 bottoms out), the target braking force may not be reached. In such a case, the control unit 7 performs the fluid transfer control to move the fluid from the first electric cylinder 2 to the second electric cylinder 3.

In normal brake control (by-wire state), the control unit 7 operates the main second electric cylinder 3 according to the target braking force (required braking value). If the braking force does not reach the target braking force even when the second piston 32 is bottomed out due to uneven wear of the brake pads as described above, the control unit 7 starts fluid exchange control and closes the first solenoid valve 61 and the second solenoid valve 62. With the wheel pressure maintained, the control unit 7 advances the first piston 22 a predetermined amount and reverses the second piston 32 a predetermined amount.

When fluid flows into the second hydraulic chamber 31a and the volume of the second hydraulic chamber 31a increases, the fluid exchange control is completed and normal brake control is resumed. That is, the control unit 7 opens the first solenoid valve 61 and the second solenoid valve 62, and advances the second piston 32 to increase the wheel pressure. This achieves the target braking force. In this example, the pressurization control is temporarily stopped to execute the fluid exchange control, so that the volume of the second hydraulic chamber 31a is already smaller than the maximum value when the fluid exchange control starts, and S103 in FIG. 2 does not need to be executed.

In this way, the control unit 7 executes fluid exchange control when one of the electric cylinders (here, the second electric cylinder 3) runs short of fluid during pressure control that pressurizes the wheel cylinders 41, 42. This makes it possible to replenish fluid to one of the electric cylinders while suppressing the generation of negative pressure, thereby achieving the target braking force. This function works more effectively when one of the electric cylinders (here, the second electric cylinder 3) has a higher driving force than the other electric cylinder (here, the first electric cylinder 2).

For example, a case will be described in which the maximum driving force of the first electric motor 23 corresponds to a wheel pressure of 10 MPa, the maximum volume of the first hydraulic chamber 21a corresponds to a wheel pressure of 10 MPa, the maximum driving force of the second electric motor 33 corresponds to a wheel pressure of 20 MPa, and the maximum volume of the second hydraulic chamber 31a corresponds to a wheel pressure of 10 MPa.

In this case, if the target wheel pressure is 12 MPa, the control unit 7 first increases the wheel pressure to 10 MPa (i.e., until bottoming out) in the main second electric cylinder 3. The control unit 7 then executes fluid transfer control, moving at least 2 MPa of fluid from the first electric cylinder 2 to the second electric cylinder 3. The control unit 7 then completes the fluid transfer control, and increases the wheel pressure to 12 MPa through normal brake control.

Since the maximum driving force of the first electric motor 23 corresponds to a wheel pressure of 10 MPa, the first electric cylinder 2 can be operated even after bottoming out with the second electric cylinder 3. The maximum driving force of the first electric motor 23 is set so that the first piston 22 can be advanced even after bottoming out with the second electric cylinder 3. In this way, fluid exchange control is effective even in a vehicle braking device equipped with electric cylinders 2 and 3 with different specifications.

Another objective of the present disclosure is to provide a vehicle braking system that, when a fluid shortage occurs in one electric cylinder, can use the other electric cylinder to replenish fluid to one electric cylinder while preventing the hydraulic chamber and hydraulic passage from becoming negative pressure. This objective can also be achieved according to the present disclosure.

In addition, because the first piston 22 is advanced in addition to the second piston 32 being advanced backward, the load torque of the second electric motor 33 can be reduced compared to conventional refill control in which only the second piston 32 is advanced backward to replenish the fluid. In both control examples, the fluid exchange control of the first embodiment is performed with the second piston 32 advanced, i.e., with the hydraulic chambers 21a, 31a pressurized to a predetermined pressure.

Second Embodiment
3, the vehicle brake device 1A of the second embodiment further includes a communication control valve 63 in addition to the configuration of the first embodiment. The communication control valve 63 is a normally open type solenoid valve provided in the communication passage 51. The communication control valve 63 is provided in the communication passage 51 in a portion between the connection portion 51b between the communication passage 51 and the first fluid passage 52 and the connection portion 51c between the communication passage 51 and the second fluid passage 53 (excluding the connection portion 51a). In other words, the communication control valve 63 is provided in the communication passage 51 in a portion between the connection portion 51b and the connection portion 51a, or between the connection portion 51c and the connection portion 51a.

The valve section 6 is composed of a first solenoid valve 61, a second solenoid valve 62, and a communication control valve 63. The valve section 6 is configured to be able to open and close the inter-cylinder connection, which is the connection between the first electric cylinder 2 and the second electric cylinder 3, the first wheel connection, which is the connection between the first electric cylinder 2 and the wheel cylinder (corresponding to the "first wheel cylinder") 41, and the second wheel connection, which is the connection between the second electric cylinder 3 and the wheel cylinder (corresponding to the "second wheel cylinder") 42, by the fluid path 5.

In the fluid exchange control, the control unit 7 opens the communication control valve 63 to open the connection between the cylinders, and closes the first solenoid valve 61 and the second solenoid valve 62 to close the first wheel connection and the second wheel connection. The fluid exchange control is executed at a predetermined timing (for example, when there is no braking request, when there is no change in the braking request value, or when there is a shortage of fluid) as in the first embodiment.

According to the second embodiment, the same effect as the first embodiment is achieved by executing the fluid exchange control. Furthermore, according to the second embodiment, in normal brake control, the communication control valve 63 is closed to independently pressurize and depressurize each wheel cylinder 41, 42. In other words, by closing the communication control valve 63, the wheel cylinder 41 can be pressurized and depressurized by the first electric cylinder 2, and the wheel cylinder 42 can be pressurized and depressurized by the second electric cylinder 3. The control unit 7 can more effectively execute anti-skid control (ABS) and anti-skid control (ESC).

＜Other＞
The present invention is not limited to the above-described first and second embodiments. For example, the master cylinder device 9 may be omitted. For example, if the wheel cylinders 41, 42 are provided on the two rear wheels, the master cylinder device 9 need not be connected to the hydraulic passage 5, but only needs to be connected to the wheel cylinder of the front wheel. In this way, in the above-described embodiments, the vehicle braking system 1, 1A may not include the master cylinder device 9. A reservoir other than the reservoir 94 may be used as the electric cylinder reservoir.

In the first embodiment, the number of wheel cylinders may be one. As shown in FIG. 4, the vehicle braking device 1 may be configured such that two electric cylinders 2, 3 are provided for one wheel cylinder 4. In this case, the valve unit 6 may be a single solenoid valve. Even with this configuration, the same effects as in the first embodiment are achieved.

Furthermore, the fluid exchange control may be performed, for example, during an initial check, or at a timing other than the above. Furthermore, in the configuration of the electric cylinders 2, 3, the positions of the pistons 22, 32 can be controlled by the electric motors 23, 33, so the biasing members 25, 35 may not be required.

1, 1A...vehicle braking device, 2...first electric cylinder, 21...first cylinder, 21a...first hydraulic chamber, 22...first piston, 23...first electric motor, 24...first linear motion conversion unit, 3...second electric cylinder, 31...second cylinder, 31a...second hydraulic chamber, 32...second piston, 33...second electric motor, 34...second linear motion conversion unit, 41, 42...wheel cylinder, 5...fluid path, 51...communication path, 52...first hydraulic path, 53...second hydraulic path, 6...valve unit, 61...first solenoid valve, 62...second solenoid valve, 63...communication control valve, 7...control unit.

Claims (6)

a fluid passage connecting the first electric cylinder, the second electric cylinder, and one or more wheel cylinders;
a valve unit configured to open and close a first wheel connection, which is a connection between the first electric cylinder and the wheel cylinder, and a second wheel connection, which is a connection between the second electric cylinder and the wheel cylinder, by the fluid path;
a control unit configured to execute a fluid exchange control in which, in a state in which an inter-cylinder connection that is a connection between the first electric cylinder and the second electric cylinder is opened and the first wheel connection and the second wheel connection are closed, the first electric cylinder discharges fluid in the first electric cylinder into the fluid path and the second electric cylinder draws fluid in the fluid path into the second electric cylinder;
A vehicle braking device comprising: The wheel cylinder includes a first wheel cylinder and a second wheel cylinder,
the fluid path includes a communication path connecting the first electric cylinder and the second electric cylinder, a first fluid path connecting the first electric cylinder and the first wheel cylinder, and a second fluid path connecting the second electric cylinder and the second wheel cylinder,
the valve portion includes a communication control valve that opens and closes the communication passage, a first solenoid valve that opens and closes the first fluid passage, and a second solenoid valve that opens and closes the second fluid passage,
2. The vehicle brake device according to claim 1, wherein, in the fluid exchange control, the control unit opens the communication control valve to open the inter-cylinder connection and closes the first solenoid valve and the second solenoid valve to close the first wheel connection and the second wheel connection. The vehicle brake device according to claim 1 or 2, wherein the control unit, in the fluid exchange control, matches the amount of decrease in the volume of the first hydraulic pressure chamber formed in the first electric cylinder and connected to the hydraulic passage with the amount of increase in the volume of the second hydraulic pressure chamber formed in the second electric cylinder and connected to the hydraulic passage. The vehicle braking device according to any one of claims 1 to 3, wherein the control unit executes the fluid exchange control when there is no braking request. The vehicle braking device according to any one of claims 1 to 4, wherein the control unit executes the fluid exchange control when there is no change in the braking demand value. The vehicle braking device according to any one of claims 1 to 5, wherein the control unit executes the fluid exchange control when the fluid in the second electric cylinder is insufficient during pressure control for pressurizing the wheel cylinder.

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