Electric brake system

An electric brake system is disclosed. The electric brake system includes a hydraulic pressure supply device configured to generate hydraulic pressure using a piston which is operated by means of an electrical signal that is output corresponding to displacement of a brake pedal, and including a first pressure chamber provided at one side of the piston movably accommodated inside a cylinder block and connected to one or more wheel cylinders, and a second pressure chamber provided at the other side of the piston and connected to the one or more wheel cylinders, a first hydraulic flow path configured to communicate with the first pressure chamber, a second hydraulic flow path configured to branch from the first hydraulic flow path, a third hydraulic flow path configured to branch from the first hydraulic flow path, a fourth hydraulic flow path configured to communicate with the second pressure chamber and connected to the third hydraulic flow path, a fifth hydraulic flow path configured to communicate the second hydraulic flow path with the third hydraulic flow path, a first hydraulic circuit including first and second branching flow paths which branch from the second hydraulic flow path and are connected to two wheel cylinders, respectively, and a second hydraulic circuit including third and fourth branching flow paths which branch from the third hydraulic flow path and are connected to two wheel cylinders, respectively.

This application claims the benefit of Korean Patent Application No. 2015-0162415, filed on Nov. 19, 2015 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

Embodiments of the present disclosure relate to an electric brake system, and more particularly, to an electric brake system generating a braking force using an electrical signal corresponding to a displacement of a brake pedal.

2. Description of the Related Art

A brake system for braking is necessarily mounted on a vehicle, and a variety of systems for providing stronger and more stable braking have been proposed recently.

For example, there are brake systems including an anti-lock brake system (ABS) for preventing a wheel from sliding while braking, a brake traction control system (BTCS) for preventing a driving wheel from slipping when a vehicle is unintentionally or intentionally accelerated, an electronic stability control (ESC) system for stably maintaining a driving state of a vehicle by combining an ABS with traction control to control hydraulic pressure of a brake, and the like.

Generally, an electric brake system includes a hydraulic pressure supply device which receives a braking intent of a driver in the form of an electrical signal from a pedal displacement sensor which senses displacement of a brake pedal when the driver steps on the brake pedal and then supplies hydraulic pressure to a wheel cylinder.

An electric brake system provided with such a hydraulic pressure supply device is disclosed in European Registered Patent No. EP 2 520 473. According to the disclosure in that document, the hydraulic pressure supply device is configured such that a motor is activated according to a pedal effort of a brake pedal to generate braking pressure. At this point, the braking pressure is generated by converting a rotational force of the motor into rectilinear movement to pressurize a piston.

PRIOR ART DOCUMENT

SUMMARY

Therefore, it is an aspect of the present disclosure to provide an electric brake system including a hydraulic pressure supply device that is operated with double action.

In accordance with one aspect of the present invention, there may be provided an electric brake system, which comprises a hydraulic pressure supply device configured to generate hydraulic pressure using a piston which is operated by means of an electrical signal that is output corresponding to displacement of a brake pedal, and including a first pressure chamber provided at one side of the piston movably accommodated inside a cylinder block and connected to one or more wheel cylinders, and a second pressure chamber provided at the other side of the piston and connected to the one or more wheel cylinders, a first hydraulic flow path configured to communicate with the first pressure chamber, a second hydraulic flow path configured to branch from the first hydraulic flow path, a third hydraulic flow path configured to branch from the first hydraulic flow path, a fourth hydraulic flow path configured to communicate with the second pressure chamber and connected to the third hydraulic flow path, a fifth hydraulic flow path configured to communicate the second hydraulic flow path with the third hydraulic flow path, a first hydraulic circuit including first and second branching flow paths which branch from the second hydraulic flow path and are connected to two wheel cylinders, respectively, and a second hydraulic circuit including third and fourth branching flow paths which branch from the third hydraulic flow path and are connected to two wheel cylinders, respectively.

Also, the electric brake system may further include a first control valve provided at the second hydraulic flow path and configured to control an oil flow, a second control valve provided at the third hydraulic flow path and configured to control an oil flow, a third control valve provided at the fourth hydraulic flow path and configured to control an oil flow, and a circuit balance valve provided at the fifth hydraulic flow path and configured to control an oil flow.

Also, the first control valve may be configured with a check valve configured to allow an oil flow in a direction from the hydraulic pressure supply device toward the one or more wheel cylinders and block an oil flow in a reverse direction, and the second and third control valves and the circuit balance valve may be configured with a solenoid valve configured to control an oil flow between the hydraulic pressure supply device and the one or more wheel cylinders bidirectionally.

Also, the first and third control valves may be configured with a check valve configured to allow an oil flow in a direction from the hydraulic pressure supply device toward the one or more wheel cylinders and block an oil flow in a reverse direction, and the second control valve and the circuit balance valve may be configured with a solenoid valve configured to control an oil flow between the hydraulic pressure supply device and the one or more wheel cylinders bidirectionally.

Also, the second and third control valves may be normally closed type valves that are usually closed and are open when an opening signal is received.

Also, the circuit balance valve may be a normally closed type valve that is usually closed and is open when an opening signal is received.

Also, the electric brake system may further include a sixth hydraulic flow path configured to communicate the second hydraulic flow path with the fourth hydraulic flow path, and a fourth control valve provided at the sixth hydraulic flow path and configured to control an oil flow.

Also, the fourth control valve may be provided with a check valve configured to allow an oil flow in a direction from the hydraulic pressure supply device toward the one or more wheel cylinders and block an oil flow in a reverse direction.

Also, the electric brake system may further include a seventh hydraulic flow path configured to communicate the second hydraulic flow path with the fifth hydraulic flow path, and a fifth control valve provided at the seventh hydraulic flow path and configured to control an oil flow.

Also, the fifth control valve may be provided with a solenoid valve configured to control an oil flow between the hydraulic pressure supply device and the one or more wheel cylinders bidirectionally.

Also, the fifth control valve may be a normally closed type valve that is usually closed and is open when an opening signal is received.

Also, the circuit balance valve may be installed at the fifth hydraulic flow path between a position at which the fifth hydraulic flow path is connected to the second hydraulic flow path and a position at which the fifth hydraulic flow path and the seventh hydraulic flow path are connected to each other, and between a position at which the fifth hydraulic flow path is connected to the third hydraulic flow path and the position at which the fifth hydraulic flow path and the seventh hydraulic flow path are connected to each other, based on a position at which the seventh hydraulic flow path is connected to the fifth hydraulic flow path.

Also, the electric brake system may further include a first dump flow path configured to communicate with the first pressure chamber and connected to a reservoir, a second dump flow path configured to communicate with the second pressure chamber and connected to the reservoir, a first dump valve provided at the first dump flow path, configured to control an oil flow, and configured with a check valve configured to allow an oil flow in a direction from the reservoir toward the first pressure chamber and block an oil flow in a reverse direction, a second dump valve provided at the second dump flow path, configured to control an oil flow, and configured with a check valve configured to allow an oil flow in a direction from the reservoir toward the second pressure chamber and block an oil flow in a reverse direction, and a third dump valve provided at a bypass flow path connecting an upstream side of the second dump valve to a downstream side thereof at the second dump flow path, configured to control an oil flow, and configured with a solenoid valve configured to control an oil flow between the reservoir and the second pressure chamber bidirectionally.

Also, the third dump valve may be a normally opened type valve that is usually opened and is closed when a closing signal is received.

Also, the hydraulic pressure supply device may further include the cylinder block, the piston movably accommodated inside the cylinder block and configured to perform reciprocal movement by means of a rotational force of a motor, a first communicating hole formed at the cylinder block forming the first pressure chamber and configured to communicate with the first hydraulic flow path, and a second communicating hole formed at the cylinder block forming the second pressure chamber and configured to communicate with the fourth hydraulic flow path.

In accordance with another aspect of the present invention, there is provided an electric brake system, which comprises a master cylinder at which first and second hydraulic ports are formed, connected to a reservoir storing oil therein, configured with one or more pistons, and configured to discharge oil according to a pedal effort of a brake pedal, a pedal displacement sensor configured to sense displacement of the brake pedal, a hydraulic pressure supply device configured to generate hydraulic pressure using a piston which is operated by means of an electrical signal that is output from the pedal displacement sensor, and including a first pressure chamber provided at one side of the piston movably accommodated inside a cylinder block and connected to one or more wheel cylinders, and a second pressure chamber provided at the other side of the piston and connected to one or more wheel cylinders, a first hydraulic flow path configured to communicate with the first pressure chamber, a second hydraulic flow path configured to branch from the first hydraulic flow path, a third hydraulic flow path configured to branch from the first hydraulic flow path, a fourth hydraulic flow path configured to communicate with the second pressure chamber and connected to the third hydraulic flow path, a fifth hydraulic flow path configured to communicate the second hydraulic flow path with the third hydraulic flow path, a first hydraulic circuit including first and second branching flow paths which branch from the second hydraulic flow path and are connected to two wheel cylinders, respectively, and first and second inlet valves configured to control the first and second branching flow paths, respectively, a second hydraulic circuit including third and fourth branching flow paths which branch from the third hydraulic flow path and are connected to two wheel cylinders, respectively, a first backup flow path configured to connect the first hydraulic port to the second hydraulic flow path, a second backup flow path configured to connect the second hydraulic port to the third hydraulic flow path, a first cut valve provided at the first backup flow path and configured to control an oil flow, a second cut valve provided at the second backup flow path and configured to control an oil flow, and a simulation device provided at a flow path branching from the first backup flow path, configured with a simulator valve provided at a flow path connecting a simulation chamber storing oil therein to the reservoir, and configured to provide a reaction force according to a pedal effort of the brake pedal.

Also, the electric brake system may further include a first control valve provided at the second hydraulic flow path and configured to control an oil flow, a second control valve provided at the third hydraulic flow path and configured to control an oil flow, a third control valve provided at the fourth hydraulic flow path and configured to control an oil flow, and a circuit balance valve provided at the fifth hydraulic flow path and configured to control an oil flow.

Also, the first backup flow path may be connected to a downstream side of the first control valve at the second hydraulic flow path, and the second backup flow path is connected to a downstream side of the second control valve at the third hydraulic flow path.

Also, the electric brake system may include an electronic control unit (ECU) configured to control an operation of the motor, and opening and closing of the second and third control valves, the circuit balance valve, and first to fourth inlet valves on the basis of hydraulic pressure information and displacement information of the brake pedal.

Also, when an imbalance in pressure between the first pressure chamber and the second pressure chamber occurs, the ECU may open the second control valve and the third control valve to accomplish a balance in pressure between the first pressure chamber and the second pressure chamber.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The embodiments to be described below are provided to fully convey the spirit of the present disclosure to a person skilled in the art. The present disclosure is not limited to the embodiments disclosed herein and may be implemented in other forms. In the drawings, some portions not related to the description will be omitted and will not be shown in order to clearly describe the present disclosure, and also sizes of components may be somewhat exaggerated to help understanding.

FIG. 1is a hydraulic circuit diagram illustrating a non-braking state of an electric brake system1according to a first embodiment of the present disclosure.

Referring toFIG. 1, the electric brake system1generally includes a master cylinder20for generating hydraulic pressure, a reservoir30coupled to an upper part of the master cylinder20to store oil, an input rod12for pressurizing the master cylinder20according to a pedal effort of a brake pedal10, a wheel cylinder40for receiving the hydraulic pressure to perform braking of each of wheels RR, RL, FR, and FL, a pedal displacement sensor11for sensing displacement of the brake pedal10, and a simulation device50for providing a reaction force according to the pedal effort of the brake pedal10.

The master cylinder20may be configured to include at least one chamber to generate hydraulic pressure. As one example, the master cylinder20may be configured to include two chambers, a first piston21aand a second piston22amay be provided at the two chambers, respectively, and the first piston21amay be connected to the input rod12. Further, the master cylinder20may include first and second hydraulic ports24aand24bwhich are formed thereon and through which hydraulic pressure is delivered from each of the two chambers.

Meanwhile, the master cylinder20may include two chambers to secure safety when one chamber fails. For example, one of the two chambers may be connected to a front right wheel FR and a rear left wheel RL of a vehicle, and the remaining chamber may be connected to a front left wheel FL and a rear right wheel RR thereof. As described above, the two chambers may be independently configured so that braking of the vehicle may be possible even when one of the two chambers fails.

Alternatively, unlike the drawing, one of the two chambers may be connected to the two front wheels FR and FL and the remaining chamber may be connected to the two rear wheels RR and RL. In addition to the described above, one of the two chambers may be connected to the front left wheel FL and the rear left wheel RL, and the remaining chamber may be connected to the rear right wheel RR and the front right wheel FR. In other words, a variety of connected configurations may be established between the chambers of the master cylinder20and the wheels.

Further, a first spring21bmay be provided between the first piston21aand the second piston22aof the master cylinder20, and a second spring22bmay be provided between the second piston22aand an end of the master cylinder20.

The first spring21band the second spring22bare provided at the two chambers, respectively, to store an elastic force when the first piston21aand the second piston22aare compressed according to a variance of displacement of the brake pedal10. Further, when a force pushing the first piston21ais less than the elastic force, the first spring21band the second spring22bmay use the stored elastic force to push the first and second pistons21aand22aand return the first and second pistons21aand22ato their original positions, respectively.

Meanwhile, the input rod12pressurizing the first piston21aof the master cylinder20may come into close contact with the first piston21a. In other words, there may be no gap between the master cylinder20and the input rod12. Consequently, when the brake pedal10is stepped on, the master cylinder20may be directly pressurized without a pedal dead stroke section.

The simulation device50may be connected to a first backup flow path251, which will be described below, to provide a reaction force according to a pedal effort of the brake pedal10. The reaction force may be provided to compensate for a pedal effort provided from a driver such that a braking force may be finely controlled as intended by the driver.

The simulation device50includes a simulation chamber51provided to store oil flowing from the first hydraulic port24aof the master cylinder20, a reaction force piston52provided inside the simulation chamber51, a pedal simulator provided with a reaction force spring53elastically supporting the reaction force piston52, and a simulator valve54connected to a rear end part of the simulation chamber51.

The reaction force piston52and the reaction force spring53are respectively installed to have a predetermined range of displacement within the simulation chamber51by means of oil flowing therein.

Meanwhile, the reaction force spring53shown in the drawing is merely one embodiment capable of providing an elastic force to the reaction force piston52, and thus it may include numerous embodiments capable of storing the elastic force through shape deformation. As one example, the reaction force spring53includes a variety of members which are configured with a material including rubber and the like and have a coil or plate shape, thereby being able to store an elastic force.

The simulator valve54may be provided at a flow path connecting a rear end of the simulation chamber51to the reservoir30. A front end of the simulation chamber51may be connected to the master cylinder20, and the rear end of the simulation chamber51may be connected to the reservoir30through the simulator valve54. Therefore, even when the reaction force piston52returns, oil inside the reservoir30may flow through the simulator valve54so that an inside of the simulation chamber51is entirely filled with the oil.

Meanwhile, a plurality of reservoirs30are shown in the drawing, and the same reference number is assigned to each of the plurality of reservoirs30. These reservoirs may be configured with the same components, and may alternatively be configured with different components. As one example, the reservoir30connected to the simulation device50may be the same as the reservoir30connected to the master cylinder20, or may be a storage part capable of storing oil in separation from the reservoir30connected to the master cylinder20.

Meanwhile, the simulator valve54may be configured with a normally closed type solenoid valve usually maintaining a closed state. When the driver applies a pedal effort to the brake pedal10, the simulator valve54may be opened to deliver oil inside the simulation chamber51to the reservoir30.

Also, a simulator check valve55may be installed to be connected in parallel with the simulator valve54between the pedal simulator and the reservoir30. The simulator check valve55may allow the oil inside the reservoir30to flow toward the simulation chamber51and may block the oil inside the simulation chamber51from flowing toward the reservoir30through a flow path at which the simulator check valve55is installed. When the pedal effort of the brake pedal10is released, the oil may be provided inside the simulation chamber51through the simulator check valve55to ensure a rapid return of pressure of the pedal simulator.

To describe an operating process of the simulation device50, when the driver applies a pedal effort to the brake pedal10, the oil inside the simulation chamber51, which is pushed by the reaction force piston52of the pedal simulator while the reaction force piston52compresses the reaction force spring53and is delivered to the reservoir30through the simulator valve54, and then a pedal feeling is provided to the driver through such an operation. Further, when the driver releases the pedal effort from the brake pedal10, the reaction force spring53may push the reaction force piston52to return the reaction force piston52to its original state, and the oil inside the reservoir30may flow into the simulation chamber51through the flow path at which the simulator valve54is installed and the flow path at which the simulator check valve55is installed, thereby completely filling the inside of the simulation chamber51with the oil.

As described above, because the inside of the simulation chamber51is in a state in which the oil is filled therein at all times, friction of the reaction force piston52is minimized when the simulation device50is operated, and thus durability of the simulation device50may be improved and also introduction of foreign materials from the outside may be blocked.

The electric brake system1according to the first embodiment of the present disclosure may include a hydraulic pressure supply device100which is mechanically operated by receiving a braking intent of the driver in the form of an electrical signal from the pedal displacement sensor11measuring displacement of the brake pedal10, a hydraulic control unit200configured with first and second hydraulic circuits201and202, each of which is provided at two wheels, and controlling a hydraulic pressure flow delivered to the wheel cylinder40that is provided at each of the wheels RR, RL, FR, and FL, a first cut valve261provided at the first backup flow path251connecting the first hydraulic port24ato the first hydraulic circuit201to control a hydraulic pressure flow, a second cut valve262provided at a second backup flow path252connecting the second hydraulic port24bto the second hydraulic circuit202to control a hydraulic pressure flow, and an electronic control unit (ECU) (not shown) controlling the hydraulic pressure supply device100and valves54,60,221a,221b,221c,221d,222a,222b,222c,222d,232,233,243, and250on the basis of hydraulic pressure information and pedal displacement information.

The hydraulic pressure supply device100may include a hydraulic pressure supply unit110for providing oil pressure delivered to the wheel cylinder40, a motor120for generating a rotational force in response to an electrical signal of the pedal displacement sensor11, and a power conversion unit130for converting rotational movement of the motor120into rectilinear movement and transmitting the rectilinear movement to the hydraulic pressure supply unit110. Alternatively, the hydraulic pressure supply unit110may be operated by means of pressure provided from a high pressure accumulator instead of a driving force supplied from the motor120.

Next, the hydraulic pressure supply unit110according to the embodiment of the present disclosure will be described with reference toFIG. 2.FIG. 2is an enlarged diagram illustrating the hydraulic pressure supply unit110according to the embodiment of the present disclosure.

The hydraulic pressure supply unit110includes a cylinder block111in which a pressure chamber for receiving and storing oil therein is formed, a hydraulic piston114accommodated in the cylinder block111, a sealing member115(that is,115aand115b) provided between the hydraulic piston114and the cylinder block111to seal the pressure chamber, and a drive shaft133connected to a rear end of the hydraulic piston114to deliver power output from the power conversion unit130to the hydraulic piston114.

The pressure chamber may include a first pressure chamber112located at a front side (in a forward movement direction, that is, a leftward direction of the drawing) of the hydraulic piston114, and a second pressure chamber113located at a rear side (in a backward movement direction, that is, a rightward direction of the drawing) of the hydraulic piston114. In other words, the first pressure chamber112is comparted by means of the cylinder block111and a front end of the hydraulic piston114and is provided to have a volume that varies according to movement of the hydraulic piston114, and the second pressure chamber113is comparted by means of the cylinder block111and the rear end of the hydraulic piston114and is provided to have a volume that varies according to the movement of the hydraulic piston114.

The first pressure chamber112is connected to a first hydraulic flow path211through a first communicating hole111aformed at a front side of the cylinder block111.

The first hydraulic flow path211branches into a second hydraulic flow path212and a third hydraulic flow path213and connects the first pressure chamber112to the first and second hydraulic circuits201and202.

Further, the second pressure chamber113is connected to a fourth hydraulic flow path214through a second communicating hole111bformed at a rear side of the cylinder block111. The fourth hydraulic flow path214branches into the second hydraulic flow path212and the third hydraulic flow path213and connects the hydraulic pressure supply unit110to the first hydraulic circuit201and the second hydraulic circuit202.

The sealing member115includes a piston sealing member115aprovided between the hydraulic piston114and the cylinder block111to seal between the first pressure chamber112and the second pressure chamber113, and a drive shaft sealing member115bprovided between the drive shaft133and the cylinder block111to seal openings of the second pressure chamber113and the cylinder block111. In other words, hydraulic pressure or negative pressure of the first pressure chamber112, which is generated while the hydraulic piston114is moved forward or backward, may be blocked by the piston sealing member115aand may be delivered to the first and fourth hydraulic flow paths211and214without leaking into the second pressure chamber113. Further, hydraulic pressure or negative pressure of the second pressure chamber113, which is generated while the hydraulic piston114is moved forward or backward, may be blocked by the drive shaft sealing member115band may not leak into the cylinder block111.

The first and second pressure chambers112and113may be respectively connected to the reservoir30by means of dump flow paths116and117, and receive and store oil supplied from the reservoir30or deliver oil inside the first or second pressure chamber112or113to the reservoir30. As one example, the dump flow paths116and117may include a first dump flow path116branching from the first pressure chamber112and connected to the reservoir30, and a second dump flow path117branching from the second pressure chamber113and connected to the reservoir30.

Also, the first pressure chamber112may be connected to the first dump flow path116through a third communicating hole111cformed at a front side, and the second pressure chamber113may be connected to the second dump flow path117through a fourth communicating hole111dformed at a rear side.

Referring back toFIG. 1, flow paths211,212,213,214,215,216, and217, and valves231,232,233,234,235,236,237,241,242, and243, which are connected to the first pressure chamber112and the second pressure chamber113, will be described.

The first communicating hole111acommunicating with the first hydraulic flow path211and the third communicating hole111ccommunicating with the first dump flow path116may be formed at the front side of the first pressure chamber112. Further, the second communicating hole111bcommunicating with the fourth hydraulic flow path214and the fourth communicating hole111dcommunicating with the second dump flow path117may be formed at the second pressure chamber113.

The first hydraulic flow path211branches into the second hydraulic flow path212communicating with the first hydraulic circuit201and the third hydraulic flow path213communicating with the second hydraulic circuit202. Therefore, hydraulic pressure may be delivered to both the first hydraulic circuit201and the second hydraulic circuit202while the hydraulic piston114is moved forward.

Also, the electric brake system1according to the first embodiment of the present disclosure may include a first control valve231and a second control valve232which are provided at the second and third hydraulic flow paths212and213, respectively, to control an oil flow.

Further, the first control valve231may be configured with a check valve that allows only an oil flow in a direction from the first pressure chamber112toward the first hydraulic circuit201and blocks an oil flow in a reverse direction. That is, the first control valve231may allow the hydraulic pressure of the first pressure chamber112to be delivered to the first hydraulic circuit201, and prevent the hydraulic pressure of the first hydraulic circuit201from leaking into the first pressure chamber112through the second hydraulic flow path212.

Further, the second control valve232may be configured with a solenoid valve capable of bidirectionally controlling an oil flow of the third hydraulic flow path213. That is, the second control valve232may allow the hydraulic pressure of the first pressure chamber112to be delivered to the second hydraulic circuit202when braking is performed, whereas it may allow hydraulic pressure of the second hydraulic circuit202to be delivered to the first pressure chamber112through the third hydraulic flow path213when braking is released.

Also, the second control valve232may be configured with a normally closed type solenoid valve that is usually closed and is open when an opening signal is received from the ECU.

In addition, the fourth hydraulic flow path214may be provided to communicate the second pressure chamber113with the third hydraulic flow path213.

Moreover, the electric brake system1according to the first embodiment of the present disclosure may be provided with a fifth hydraulic flow path215communicating the first hydraulic circuit201and the second hydraulic circuit202. As one example, the fifth hydraulic flow path215may be provided to communicate the second hydraulic flow path212with the third hydraulic flow path213, and in particular, one side of the fifth hydraulic flow path215may be connected to a downstream side of the first control valve231and the other side thereof may be connected to a downstream side of the second control valve232.

Also, the electric brake system1according to the first embodiment of the present disclosure may include a circuit balance valve250which is provided at the fifth hydraulic flow path215communicating the first pressure chamber112with the second pressure chamber113to control an oil flow. As one example, the circuit balance valve250may be installed at the fifth hydraulic flow path215communicating the second hydraulic flow path212with the third hydraulic flow path213.

Further, the circuit balance valve250may be configured with a solenoid valve capable of bidirectionally controlling an oil flow of the fifth hydraulic flow path215. That is, the circuit balance valve250may allow hydraulic pressure of the second hydraulic flow path212to be delivered to the third hydraulic flow path213and also hydraulic pressure of the third hydraulic flow path213to be delivered to the second hydraulic flow path212.

Also, the circuit balance valve250may be configured with a normally closed type solenoid valve that is usually closed and is open when an opening signal is received from the ECU.

Further, the second pressure chamber113may communicate with both the first hydraulic circuit201and the second hydraulic circuit202. That is, the fourth hydraulic flow path214may be connected to the third hydraulic flow path213to communicate with the second hydraulic circuit202, and may communicate with the first hydraulic circuit201through the fifth hydraulic flow path215that branches from the third hydraulic flow path213and is connected to the second hydraulic flow path212. Consequently, hydraulic pressure may be delivered to both the first hydraulic circuit201and the second hydraulic circuit202while the hydraulic piston114is moved backward.

While the hydraulic piston114is moved backward, two operations may be performed. First, using the negative pressure generated in the first pressure chamber112, the oil in the first and second hydraulic circuits201and202may be returned to the first pressure chamber112to release a braking force. Second, using the hydraulic pressure generated in the second pressure chamber113, the oil in the second pressure chamber113may be delivered to the first and second hydraulic circuits201and202to apply a braking force.

The second control valve232and the third control valve233may control oil flows of the third hydraulic flow path213and the fourth hydraulic flow path214, respectively, to enable a selection of the above described two operations. In other words, when the second control valve232opens the third hydraulic flow path213and the third control valve233blocks the fourth hydraulic flow path214, the oil in the first and second hydraulic circuits201and202may be returned to the first pressure chamber112to release a braking force. On the other hand, when the second control valve232blocks the third hydraulic flow path213and the third control valve233opens the fourth hydraulic flow path214, the oil in the second pressure chamber113may be delivered to the first and second hydraulic circuits201and202to apply a braking force.

Also, the electric brake system1according to the first embodiment of the present disclosure may further include a first dump valve241and a second dump valve242which are provided at the first and second dump flow paths116and117, respectively, and control an oil flow. The dump valves241and242may be a check valve that opens in a direction from the reservoir30to the first and second pressure chambers112and113, and blocks in a reverse direction. That is, the first dump valve241may be a check valve that allows oil to flow from the reservoir30to the first pressure chamber112, and blocks the oil from flowing from the first pressure chamber112to the reservoir30, and the second dump valve242may be a check valve that allows oil to flow from the reservoir30to the second pressure chamber113, and blocks the oil from flowing from the second pressure chamber113to the reservoir30.

Also, the second dump flow path117may include a bypass flow path, and a third dump valve243may be installed at the bypass flow path to control an oil flow between the second pressure chamber113and the reservoir30.

The third dump valve243may be configured with a solenoid valve capable of bidirectionally controlling an oil flow, and with a normally open type solenoid valve that is usually open and is closed when a closing signal is received from the ECU.

The hydraulic pressure supply unit110of the electric brake system1according to the first embodiment of the present disclosure may operate in double action. In other words, hydraulic pressure, which is generated in the first pressure chamber112while the hydraulic piston114is moved forward, may be delivered to the first hydraulic circuit201through the first hydraulic flow path211and the second hydraulic flow path212to operate the wheel cylinders40installed at the front right wheel FR and the rear left wheel RL, and to the second hydraulic circuit202through the first hydraulic flow path211and the third hydraulic flow path213to operate the wheel cylinders40installed at the rear right wheel RR and the front left wheel FL.

Similarly, hydraulic pressure, which is generated in the second pressure chamber113while the hydraulic piston114is moved backward, may be delivered to the first hydraulic circuit201through the fourth hydraulic flow path214and the second hydraulic flow path212to operate the wheel cylinders40installed at the front right wheel FR and the rear left wheel RL, and to the second hydraulic circuit202through the fourth hydraulic flow path214and the third hydraulic flow path213to operate the wheel cylinders40installed at the rear right wheel RR and the front left wheel FL.

Also, negative pressure, which is generated in the first pressure chamber112while the hydraulic piston114is moved backward, may cause the oil of the wheel cylinders40installed at the front right wheel FR and the rear left wheel RL to be suctioned and delivered to the first pressure chamber112through the first hydraulic circuit201and the second hydraulic flow path212, and may cause the oil of the wheel cylinders40installed at the rear right wheel RR and the front left wheel FL to be suctioned and delivered to the first pressure chamber112through the second hydraulic circuit202and the third hydraulic flow path213.

Meanwhile, the hydraulic pressure supply unit110operating with a double action may discriminately use a low compression section and a high compression section. Also, a low decompression section and a high decompression section may be discriminately used. Hereinafter, a compression situation in which the hydraulic pressure is delivered to the wheel cylinders40will be described. However, the same principle is applicable to a decompression situation in which the hydraulic pressure is discharged from the wheel cylinder40.

While the hydraulic piston114is moved forward, the hydraulic pressure is generated in the first pressure chamber112. Further, the more the hydraulic piston114is moved forward in an initial stage, the more an amount of oil delivered from the first pressure chamber112to the wheel cylinders40to increase braking pressure. However, because there is an active stroke of the hydraulic piston114, an increase of braking pressure due to the forward movement of the hydraulic piston114is limited.

The hydraulic pressure supply unit110according to the first embodiment of the present disclosure may continuously increase the braking pressure using the hydraulic piston114that is provided to be operable with a double action even after the low compression section. That is, while the hydraulic piston114is again moved backward in a state in which the hydraulic piston114is maximally moved forward, the hydraulic pressure is generated in the second pressure chamber113and then it is additionally provided to the wheel cylinders40, thereby increasing the braking pressure.

At this point, because negative pressure is generated in the first pressure chamber112while the hydraulic piston114is moved backward, the hydraulic pressure of the wheel cylinders40should be prevented from being discharged due to such a negative pressure. For this purpose, the second control valve232, which is operated to be open when the hydraulic pressure is discharged from the wheel cylinders40, is maintained in a closed state such that the hydraulic pressure of the wheel cylinders40may be prevented from being discharged through the third hydraulic flow path213. Meanwhile, because the first control valve231is configured with a check valve that allows only an oil flow in a direction from the first pressure chamber112to the second hydraulic circuit202, discharging of the hydraulic pressure of the wheel cylinders40through the second hydraulic flow path212is not allowed.

Meanwhile, an increase rate of pressure in a section in which the hydraulic piston114is moved forward to generate the hydraulic pressure in the first pressure chamber112may be different from that in a section in which the hydraulic piston114is moved backward to generate the hydraulic pressure in the second pressure chamber113. The reason for that is that a cross section of the hydraulic piston114in the second pressure chamber113is less than that of the hydraulic piston114in the first pressure chamber112by a cross section of the drive shaft133. As a cross section of the hydraulic piston114is small, an increase and decrease rate of volume according to a stroke of the hydraulic piston114is reduced. Therefore, a volume per stroke distance of the oil, which is pushed while the hydraulic piston114is moved backward, in the second pressure chamber113is less than that of the oil, which is pushed while the hydraulic piston114is moved forward, in the first pressure chamber112.

Next, the motor120and the power conversion unit130of the hydraulic pressure supply device100will be described.

The motor120is a device for generating a rotational force according to a signal output from the ECU (not shown) and may generate the rotational force in a forward or backward direction. An angular velocity and a rotational angle of the motor120may be precisely controlled. Because such a motor120is generally known in the art, a detailed description thereof will be omitted.

Meanwhile, the ECU controls not only the motor120but also valves54,60,221a,221b,221c,221d,222a,222b,222c,222d,232,233,243, and250provided at the electric brake system1of the present disclosure, which will be described below. An operation of controlling a plurality of valves according to displacement of the brake pedal10will be described below.

A driving force of the motor120generates displacement of the hydraulic piston114through the power conversion unit130, and hydraulic pressure, which is generated while the hydraulic piston114slides inside the pressure chamber, is delivered to the wheel cylinder40installed at each of the wheels RR, RL, FR, and FL through the first and second hydraulic flow paths211and212.

The power conversion unit130is a device for converting a rotational force into rectilinear movement, and, as one example, may be configured with a worm shaft131, a worm wheel132, and the drive shaft133.

The worm shaft131may be integrally formed with a rotational shaft of the motor120, and rotates the worm wheel132engaged therewith and coupled thereto through a worm that is formed on an outer circumferential surface of the worm shaft131. The worm wheel132linearly moves the drive shaft133engaged therewith and coupled thereto, and the drive shaft133is connected to the hydraulic piston114to slide the hydraulic piston114inside the cylinder block111.

To describe such operations again, a signal, which is sensed by the pedal displacement sensor11when displacement occurs at the brake pedal10, is transmitted to the ECU (not shown), and then the ECU drives the motor120in one direction to rotate the worm shaft131in the one direction. A rotational force of the worm shaft131is transmitted to the drive shaft133via the worm wheel132, and then the hydraulic piston114connected to the drive shaft133is moved forward to generate hydraulic pressure in the first pressure chamber112.

On the other hand, when the pedal effort is released from the brake pedal10, the ECU drives the motor120in a reverse direction, and thus the worm shaft131is reversely rotated. Consequently, the worm wheel132is also reversely rotated, and thus negative pressure is generated in the first pressure chamber112while the hydraulic piston114connected to the drive shaft133is returned to its original position, that is, moved backward.

Meanwhile, it is possible for the generation of hydraulic pressure and negative pressure to be opposite to that which is described above. That is, the signal, which is sensed by the pedal displacement sensor11when the displacement occurs at the brake pedal10, is transmitted to the ECU (not shown), and then the ECU drives the motor120in the reverse direction to reversely rotate the worm shaft131. The rotational force of the worm shaft131is transmitted to the drive shaft133via the worm wheel132, and then the hydraulic piston114connected to the drive shaft133is moved backward to generate hydraulic pressure in the second pressure chamber113.

On the other hand, when the pedal effort is released from the brake pedal10, the ECU drives the motor120in the one direction, and thus the worm shaft131is rotated in the one direction. Consequently, the worm wheel132is also reversely rotated, and thus negative pressure is generated in the second pressure chamber113while the hydraulic piston114connected to the drive shaft133is returned to its original position, that is, is moved forward.

As described above, the hydraulic pressure supply device100serves to deliver the hydraulic pressure to the wheel cylinders40or to cause the hydraulic pressure to be discharged therefrom and delivered to the reservoir30according to a rotational direction of the rotational force generated from the motor120.

Meanwhile, when the motor120is rotated in the one direction, the hydraulic pressure may be generated in the first pressure chamber112or the negative pressure may be generated in the second pressure chamber113, and whether the hydraulic pressure is used for braking or the negative pressure is used for releasing braking may be determined through the control of the valves54,60,221a,221b,221c,221d,222a,222b,222c,222d,232,233,243, and250. This will be described in detail below.

Although not shown in the drawing, the power conversion unit130may be configured with a ball screw nut assembly. For example, the power conversion unit130may be configured with a screw which is integrally formed with the rotational shaft of the motor120or is connected to and rotated with the rotational shaft thereof, and a ball nut which is screw-coupled to the screw in a state in which rotation of the ball nut is restricted to perform rectilinear movement according to rotation of the screw. The hydraulic piston114is connected to the ball nut of the power conversion unit130to pressurize the pressure chamber by means of the rectilinear movement of the ball nut. Such a ball screw nut assembly is a device for converting rotational movement into rectilinear movement, and a structure thereof is generally known in the art so that a detailed description thereof will be omitted.

Further, it should be understood that the power conversion unit130according to one embodiment of the present disclosure may employ any structure capable of converting a rotational movement into a rectilinear movement in addition to the structure of the ball screw nut assembly.

Also, the electric brake system1according to the first embodiment of the present disclosure may further include the first and second backup flow paths251and252capable of directly supplying oil discharged from the master cylinder20to the wheel cylinders40when the hydraulic pressure supply device100operates abnormally.

The first cut valve261for controlling an oil flow may be provided at the first backup flow path251, and the second cut valve262for controlling an oil flow may be provided at the second backup flow path252. Also, the first backup flow path251may connect the first hydraulic port24ato the first hydraulic circuit201, and the second backup flow path252may connect the second hydraulic port24bto the second hydraulic circuit202.

Further, the first and second cut valves261and262may be configured with a normally opened type solenoid valve that is usually open and is closed when a closing signal is received from the ECU.

Next, the hydraulic control unit200according to the first embodiment of the present disclosure will be described with reference toFIG. 1.

The hydraulic control unit200may be configured with the first hydraulic circuit201and the second hydraulic circuit202, each of which receives hydraulic pressure to control two wheels. As one example, the first hydraulic circuit201may control the front right wheel FR and the rear left wheel RL, and the second hydraulic circuit202may control the front left wheel FL and the rear right wheel RR. Further, the wheel cylinder40is installed at each of the wheels FR, FL, RR, and RL to perform braking by receiving the hydraulic pressure.

The first hydraulic circuit201is connected to the first hydraulic flow path211to receive the hydraulic pressure provided from the hydraulic pressure supply device100, and the first hydraulic flow path211branches into two flow paths that are connected to the front right wheel FR and the rear left wheel RL, respectively. Similarly, the second hydraulic circuit202is connected to the second hydraulic flow path212to receive the hydraulic pressure provided from the hydraulic pressure supply device100, and the second hydraulic flow path212branches into two flow paths that are connected to the front left wheel FL and the rear right wheel RR, respectively.

The hydraulic circuits201and202may be provided with a plurality of inlet valves221(that is,221a,221b,221c, and221d) to control a hydraulic pressure flow. As one example, two inlet valves221aand221bmay be provided at the first hydraulic circuit201and connected to the first hydraulic flow path211to independently control the hydraulic pressure delivered to two of the wheel cylinders40. Also, two inlet valves221cand221dmay be provided at the second hydraulic circuit202and connected to the second hydraulic flow path212to independently control the hydraulic pressure delivered to two of the wheel cylinders40.

Further, the plurality of inlet valves221may be disposed at an upstream side of each of the wheel cylinders40and may be configured with a normally opened type solenoid valve that is usually open and is closed when a closing signal is received from the ECU.

Also, the hydraulic circuits201and202may include check valves223a,223b,223c, and223d, each of which is provided at a bypass flow path connecting a front side to a rear side of each of the inlet valves221a,221b,221c, and221d. Each of the check valves223a,223b,223c, and223dmay be provided to allow only an oil flow in a direction from the wheel cylinder40to the hydraulic pressure supply unit110and block an oil flow in a direction from the hydraulic pressure supply unit110to the wheel cylinder40. Each of the check valves223a,223b,223c, and223dmay be operated to rapidly discharge braking pressure from the wheel cylinder40, and to allow the hydraulic pressure of the wheel cylinder40to be delivered to hydraulic pressure supply unit110when the inlet valves221a,221b,221c, and221dare operated abnormally.

Also, the hydraulic circuits201and202may be further provided with a plurality of outlet valves222(that is,222a,222b,222c, and222d) connected to the reservoirs30to improve brake release performance when the brake is released. Each of the outlet valves222is connected to the wheel cylinder40to control discharging of the hydraulic pressure from each of the wheels RR, RL, FR, and FL. That is, when braking pressure of each of the wheels RR, RL, FR, and FL is measured and decompression of the brake is determined to be required, the outlet valves222may be selectively opened to control the braking pressure.

Further, the outlet valves222may be configured with normally closed type solenoid valves that are usually closed and are open when an opening signal is received from the ECU.

In addition, the hydraulic control unit200may be connected to the backup flow paths251and252. As one example, the first hydraulic circuit201may be connected to the first backup flow path251to receive the hydraulic pressure provided from the master cylinder20, and the second hydraulic circuit202may be connected to the second backup flow path252to receive the hydraulic pressure provided from the master cylinder20. As one example, the first backup flow path251may be connected to the second hydraulic flow path212, and the second backup flow path252may be connected to the third hydraulic flow path213.

At this point, the first backup flow path251may be connected to the first hydraulic circuit201at an upstream side of each of the first and second inlet valves221aand221b. Similarly, the second backup flow path252may be connected to the second hydraulic circuit202at an upstream side of each of the third and fourth inlet valves221cand221d. Consequently, when the first and second cut valves261and262are closed, the hydraulic pressure provided from the hydraulic pressure supply device100may be supplied to the wheel cylinders40through the first and second hydraulic circuits201and202. Also, when the first and second cut valves261and262are opened, the hydraulic pressure provided from the master cylinder20may be supplied to the wheel cylinders40through the first and second backup flow paths251and252. At this point, because the plurality of inlet valves221a,221b,221c, and221dare in an opened state, there is no need to switch their operation states.

Meanwhile, an undescribed reference number “PS1” is a hydraulic flow path pressure sensor which senses hydraulic pressure of each of the first and second hydraulic circuits201and202, and an undescribed reference number “PS2” is a backup flow path pressure sensor which senses oil pressure of the master cylinder20. Further, an undescribed reference number “MPS” is a motor control sensor which controls a rotational angle or a current of the motor120.

Hereinafter, an operation of the electric brake system1according to the first embodiment of the present disclosure will be described in detail.

FIGS. 3 and 4show a state in which the electric brake system1according to the first embodiment of the present disclosure performs a braking operation normally,FIG. 3is a hydraulic circuit diagram illustrating a situation in which braking pressure is provided while the hydraulic piston114is moved forward, andFIG. 4is a hydraulic circuit diagram illustrating a situation in which braking pressure is provided while the hydraulic piston114is moved backward.

When a driver begins braking, an amount of braking requested by the driver may be sensed through the pedal displacement sensor11on the basis of information including pressure put on the brake pedal10by the driver, and the like. The ECU (not shown) receives an electrical signal output from the pedal displacement sensor11to drive the motor120.

Also, the ECU may receive an amount of regenerative braking through the backup flow path pressure sensor PS2provided at an outlet side of the master cylinder20and the hydraulic flow path pressure sensor PS1provided at the second hydraulic circuit202, and may calculate an amount of braking friction based on a difference between the amount of braking requested by the driver and the amount of regenerative braking, thereby determining the magnitude of an increase or reduction of pressure at the wheel cylinder40.

Referring toFIG. 3, when the driver steps on the brake pedal10at an initial stage of braking, the motor120is operated to rotate in one direction, and a rotational force of the motor120is delivered to the hydraulic pressure supply unit110by means of the power conversion unit130, and thus the hydraulic pressure is generated in the first pressure chamber112while the hydraulic piston114of the hydraulic pressure supply unit110is moved forward. The hydraulic pressure discharged from the hydraulic pressure supply unit110is delivered to the wheel cylinder40provided at each of the four wheels through the first hydraulic circuit201and the second hydraulic circuit202to generate a braking force.

In particular, the hydraulic pressure provided from the first pressure chamber112is directly delivered to the wheel cylinders40provided at the two wheels FR and RL through the first hydraulic flow path211connected to the first communicating hole111a. At this point, the first and second inlet valves221aand221b, which are respectively installed at two flow paths branching from the first hydraulic flow path211, are provided in an opened state. Also, the first and second outlet valves222aand222b, which are respectively installed at flow paths which respectively branch from the two flow paths branching from the first hydraulic flow path211, are maintained in a closed state to prevent the hydraulic pressure from leaking into the reservoirs30.

Further, the hydraulic pressure provided from the first pressure chamber112is directly delivered to the wheel cylinders40provided at the two wheels RR and FL through the first hydraulic flow path211and the third hydraulic flow path213connected to the first communicating hole111a. At this point, the third and fourth inlet valves221cand221d, which are respectively installed at two flow paths branching from the third hydraulic flow path213, are provided in an opened state. Also, the third and fourth outlet valves222cand222d, which are respectively installed at flow paths which respectively branch from the two flow paths branching from the third hydraulic flow path213, are maintained in the closed state to prevent the hydraulic pressure from leaking into the reservoirs30.

Also, the circuit balance valve250is switched to an opened state to open the fifth hydraulic flow path215so that the first hydraulic circuit201and the second hydraulic circuit202may communicate with each other. Therefore, even when an abnormality occurs at the first control valve231and the second control valve232, the hydraulic pressure may be delivered to the first and second hydraulic circuits201and202to ensure stable braking.

In addition, when the pressure delivered to the wheel cylinders40is measured as being higher than a target pressure value according to the pedal effort of the brake pedal10, one or more among the first to fourth outlet valves222may be opened to control the pressure to converge on the target pressure value.

Further, when the hydraulic pressure is generated in the hydraulic pressure supply device100, the first and second cut valves261and262installed at the first and second backup flow paths251and252, which are connected to the first and second hydraulic ports24aand24bof the master cylinder20, are closed, and thus the hydraulic pressure discharged from the master cylinder20is not delivered to the wheel cylinders40.

Moreover, the pressure generated by means of pressurization of the master cylinder20according to the pedal effort of the brake pedal10is delivered to the simulation device50connected to the master cylinder20. At this point, the normally closed type simulator valve54arranged at the rear end of the simulation chamber51is opened so that the oil filled in the simulation chamber51is delivered to the reservoir30through the simulator valve54. Also, the reaction force piston52is moved, and pressure corresponding to a reaction force of the reaction force spring53supporting the reaction force piston52is generated inside the simulation chamber51to provide an appropriate pedal feeling to the driver.

Also, the hydraulic flow path pressure sensor PS1installed at the second hydraulic flow path212may detect a flow rate delivered to the wheel cylinder40installed at the front left wheel FL or the rear right wheel RR (hereinafter, simply referred to as the wheel cylinder40). Therefore, the hydraulic pressure supply device100may be controlled according to an output of the hydraulic flow path pressure sensor PS1to control a flow rate delivered to the wheel cylinder40. In particular, a distance and a speed of the forward movement of the hydraulic piston114may be adjusted so that a flow rate discharged from the wheel cylinder40and a discharge speed thereof may be controlled.

UnlikeFIG. 3, even when the hydraulic piston114is moved in a reverse direction, that is, moved backward, a braking force may be generated at the wheel cylinders40.

Referring toFIG. 4, when the driver steps on the brake pedal10at an initial stage of braking, the motor120is operated to rotate in the reverse direction, and a rotational force of the motor120is delivered to the hydraulic pressure supply unit110by means of the power conversion unit130, and thus the hydraulic pressure is generated in the second pressure chamber113while the hydraulic piston114of the hydraulic pressure supply unit110is moved backward. The hydraulic pressure discharged from the hydraulic pressure supply unit110is delivered to the wheel cylinder40provided at each of the four wheels through the first hydraulic circuit201and the second hydraulic circuit202to generate a braking force.

At this point, because the fourth hydraulic flow path214communicating with the second pressure chamber113is connected to the third hydraulic flow path213, the third hydraulic flow path213connected to the second hydraulic circuit202and the second hydraulic flow path212should be connected to each other to deliver the hydraulic pressure to the second hydraulic circuit202. As one example, the circuit balance valve250may be switched to an opened state, and thus the third hydraulic flow path213may communicate with the second hydraulic flow path212.

In particular, the hydraulic pressure provided from the second pressure chamber113is directly delivered to the wheel cylinders40provided at the two wheels FR and RL through the fourth hydraulic flow path214, the third hydraulic flow path213, the fifth hydraulic flow path215, and the second hydraulic flow path212which are connected to the second communicating hole111b, and to the wheel cylinders40provided at the two wheels RR and FL through the fourth hydraulic flow path214and the third hydraulic flow path213.

Alternatively, when the second control valve232is switched to an opened state, the hydraulic pressure supplied from the second pressure chamber113may be directly delivered to the wheel cylinders40, which are provided at the two wheels FR and RL, connected from the second hydraulic flow path212to the third hydraulic flow path213through the second control valve232

Next, a case of releasing the braking force in the braking state established when the electric brake system1according to the first embodiment of the present disclosure operates normally will be described.

FIG. 5shows a state in which the braking force is released when the electric brake system1according to the first embodiment of the present disclosure operates normally, and it is a hydraulic circuit diagram illustrating a situation in which braking pressure is released while the hydraulic piston114is moved backward

Referring toFIG. 5, when a pedal effort applied to the brake pedal10is released, the motor120generates a rotational force in a reverse direction compared to that when the braking operation is performed to deliver the generated rotational force to the power conversion unit130, and the worm shaft131of the power conversion unit130, the worm wheel132thereof, and the drive shaft133thereof are rotated in a reverse direction compared to that when the braking operation is performed to move backward and return the hydraulic piston114to its original position, thereby releasing the pressure of the first pressure chamber112or generating negative pressure therein. Further, the hydraulic pressure supply unit110receives the hydraulic pressure discharged from the wheel cylinders40through the first and second hydraulic circuits201and202to deliver the received hydraulic pressure to the first pressure chamber112.

In particular, the negative pressure generated in the first pressure chamber112releases the pressure of the wheel cylinders40provided at the two wheels FR and RL through the first hydraulic flow path211and the second hydraulic flow path212connected to the first communicating hole111a. At this point, the first and second inlet valves221aand221b, which are respectively installed at the two flow paths branching from the second hydraulic flow path212, are provided in the opened state. Also, the first and the second outlet valves222aand222b, which are respectively installed at flow paths that respectively branch from the two flow paths branching from the second hydraulic flow path212, are maintained in the closed state to prevent the oil of the reservoirs30from flowing into the second hydraulic flow path212.

Meanwhile, the first control valve231installed at the second hydraulic flow path212is a check valve that blocks an oil flow flowing into the first pressure chamber112through the second hydraulic flow path212. Consequently, the oil flowing from the first hydraulic circuit201should bypass the first control valve231to move to the first pressure chamber112.

For this purpose, the second control valve232and the circuit balance valve250are switched to an opened state. As a result, the oil discharged from the wheel cylinders40, which are provided at the two wheels FR and RL of the first hydraulic circuit201, flows into the first pressure chamber112through the fifth hydraulic flow path215, the third hydraulic flow path213, and the first hydraulic flow path211.

Further, the negative pressure generated in the first pressure chamber112releases the pressure of the wheel cylinders40provided at the two wheels FL and RR through the first hydraulic flow path211and the third hydraulic flow path213connected to the first communicating hole111a. At this point, the third and fourth inlet valves221cand221d, which are respectively installed at the two flow paths branching from the third hydraulic flow path213, are provided in an opened state. Also, the third and fourth outlet valves222cand222d, which are respectively installed at flow paths that respectively branch from the two flow paths branching from the second hydraulic flow path212, are maintained in the closed state to prevent the oil of the reservoirs30from flowing into the second hydraulic flow path212.

Also, when the negative pressure delivered to the first and second hydraulic circuits201and202is measured as being higher than a target pressure releasing value according to an amount of release of the brake pedal10, one or more among the first to fourth outlet valves222may be opened to control the negative pressure to converge on the target pressure releasing value.

In addition, when the hydraulic pressure is generated in the hydraulic pressure supply device100, the first and second cut valves261and262installed at the first and second backup flow paths251and252, which are connected to the first and second hydraulic ports24aand24bof the master cylinder20, are closed so that the negative pressure generated in the master cylinder20is not delivered to the wheel cylinders40.

Moreover, the hydraulic flow path pressure sensor PS1installed at the second hydraulic flow path212may detect a flow rate discharged from the wheel cylinder40installed at the front left wheel FL or the rear right wheel RR. Therefore, the hydraulic pressure supply device100may be controlled according to an output of the hydraulic flow path pressure sensor PS1so that a flow rate discharged from the wheel cylinder40may be controlled. In particular, a distance and a speed of the forward movement of the hydraulic piston114may be adjusted so that a flow rate discharged from the wheel cylinder40and a discharge speed thereof may be controlled.

Meanwhile, even when the hydraulic piston114is moved in a reverse direction, that is, moved forward, a braking force may be generated at the wheel cylinder40.

Referring toFIG. 6, when a pedal effort applied to the brake pedal10is released, the motor120generates a rotational force in a reverse direction compared to that when performing the braking operation to deliver the generated rotational force to the power conversion unit130, and the worm shaft131of the power conversion unit130, the worm wheel132thereof, and the drive shaft133thereof are rotated in a reverse direction compared to that when performing the braking operation to move forward and return the hydraulic piston114to its original position, thereby releasing the pressure of the second pressure chamber113or generating negative pressure therein. Further, the hydraulic pressure supply unit110receives the hydraulic pressure discharged from the wheel cylinders40through the first and second hydraulic circuits201and202to deliver the received hydraulic pressure to the second pressure chamber113.

The second hydraulic flow path212, which is connected to the first hydraulic circuit201, is connected to the fourth hydraulic flow path214through the fifth hydraulic flow path215and the third hydraulic flow path213, and the first and second inlet valves221aand221b, which are respectively installed at the two flow paths branching from the second hydraulic flow path212, are provided in an opened state. Also, the first and second outlet valves222aand222b, which are respectively installed at flow paths that branch from the second hydraulic flow path212, are maintained in the closed state to prevent the oil of the reservoirs30from flowing into the second hydraulic flow path212.

In particular, the negative pressure generated in the second pressure chamber113releases the pressure of the wheel cylinders40provided at the two wheels FR and RL through the fourth hydraulic flow path214connected to the second communicating hole111b. At this point, because the first control valve231is configured with a check valve that blocks an oil flow flowing into the first pressure chamber112through the second hydraulic flow path212, the oil flowing from the first hydraulic circuit201should bypass the first control valve231.

For this purpose, the circuit balance valve250is switched to an opened state. Therefore, the oil discharged from the wheel cylinders40, which are provided at the two wheels FR and RL of the first hydraulic circuit201, flows into the second pressure chamber113through the fifth hydraulic flow path215and the fourth hydraulic flow path214.

Further, the negative pressure generated in the second pressure chamber113releases the pressure of the wheel cylinders40provided at the two wheels FL and RR through the fourth hydraulic flow path214and the third hydraulic flow path213which are connected to the second communicating hole111b. At this point, the third and fourth inlet valves221cand221d, which are respectively installed at the two flow paths branching from the third hydraulic flow path213, are provided in an opened state. Also, the third and fourth outlet valves222cand222d, which are respectively installed at flow paths that branch from the second hydraulic flow path212, are maintained in the closed state to prevent the oil of the reservoirs30from flowing into the second hydraulic flow path212.

FIGS. 7 and 8show a state in which an anti-lock brake system (ABS) is operated through the electric brake system1according to the first embodiment of the present disclosure,FIG. 7is a hydraulic circuit diagram illustrating a situation in which the hydraulic piston114is moved forward and selective braking is performed, andFIG. 8is a hydraulic circuit diagram illustrating a situation in which the hydraulic piston114is moved backward and selective braking is performed.

When the motor120is operated according to a pedal effort of the brake pedal10, a rotational force of the motor120is transmitted to the hydraulic pressure supply unit110through the power conversion unit130, thereby generating hydraulic pressure. At this point, the first and second cut valves261and262are closed and thus the hydraulic pressure discharged from the master cylinder20is not delivered to the wheel cylinders40.

Referring toFIG. 7, because hydraulic pressure is generated in the first pressure chamber112while the hydraulic piston114is moved forward and the fourth inlet valve221dis provided in the opened state, the hydraulic pressure delivered through the third hydraulic flow path213operates the wheel cylinder40located at the front left wheel FL to generate a braking force.

At this point, the second control valve232is switched to an opened state. Further, the first to third inlet valves221a,221b, and221care switched to a closed state, and the first to fourth outlet valves222a,222b,222c, and222dare maintained in the closed state. Moreover, the third dump valve243is provided in an opened state, and thus the second pressure chamber113is filled with the oil flowing from the reservoir30.

Referring toFIG. 8, because hydraulic pressure is generated in the second pressure chamber113while the hydraulic piston114is moved backward and the first inlet valve221ais provided in the opened state, the hydraulic pressure delivered through the fourth hydraulic flow path214and the fifth hydraulic flow path215operates the wheel cylinder40located at the front right wheel FR to generate a braking force.

At this point, the third control valve233and the circuit balance valve250are switched to an opened state. Further, the second to fourth inlet valves221b,221c, and221dare switched to the closed state, and the first to fourth outlet valves222a,222b,222c, and222dare maintained in the closed state.

That is, the electric brake system1according to the first embodiment of the present disclosure may independently control operations of the motor120and each of the valves54,60,221a,221b,221c,221d,222a,222b,222c,222d,232,233,243, and250to selectively deliver or discharge the hydraulic pressure to or from the wheel cylinder40of each of the wheels RL, RR, FL, and FR according to a required pressure such that a precise control of the hydraulic pressure may be possible.

Next, a case in which such an electric brake system1operates abnormally will be described.FIG. 9is a hydraulic circuit diagram illustrating a situation in which the electric brake system1according to the first embodiment of the present disclosure operates abnormally.

Referring toFIG. 9, when the electric brake system1operates abnormally, each of the valves54,60,221a,221b,221c,221d,222a,222b,222c,222d,232,233,243, and250is provided in an initial state of braking, that is, a non-operating state.

When a driver pressurizes the brake pedal10, the input rod12connected to the brake pedal10is moved forward, and the first piston21a, which is in contact with the input rod12, is moved forward and at the same time the second piston22ais moved forward by means of the pressurization or movement of the first piston21a. At this point, because there is no gap between the input rod12and the first piston21a, the braking may be rapidly performed.

Further, the hydraulic pressure discharged from the master cylinder20is delivered to the wheel cylinders40through the first and second backup flow paths251and252that are connected for the purpose of backup braking to realize a braking force.

At this point, the first and second cut valves261and262respectively installed at the first and second backup flow paths251and252, and the inlet valves221opening and closing the flow paths of the first hydraulic circuit201and the second hydraulic circuit202are configured with normally opened type solenoid valves, and the simulator valve54and the outlet valves222are configured with normally closed type solenoid valves so that the hydraulic pressure is directly delivered to the four wheel cylinders40. Therefore, braking is stably realized to improve braking safety.

FIG. 10is a hydraulic circuit diagram illustrating a state in which the electric brake system1according to the first embodiment of the present disclosure operates in a dump mode.

The electric brake system1according to the first embodiment of the present disclosure may discharge only braking pressure provided to corresponding wheel cylinders40through the first to fourth outlet valves222a,222b,222c, and222d.

Referring toFIG. 10, when the first to fourth inlet valves221a,221b,221c, and221dare switched to the closed state, the first to third outlet valves222a,222b, and222care maintained in the closed state, and the fourth outlet valve222dis switched to the opened state, the hydraulic pressure discharged from the wheel cylinder40installed at the front left wheel FL is discharged to the reservoir30through the fourth outlet valve222d.

The reason for that the hydraulic pressure in the wheel cylinders40is discharged through the outlet valves222is that pressure in the reservoir30is less than that in the wheel cylinder40. Generally, the pressure in the reservoir30is provided as atmospheric pressure. Because the pressure in the wheel cylinder40is generally and considerably higher than atmospheric pressure, the hydraulic pressure of the wheel cylinders40may be rapidly discharged to the reservoirs30when the outlet valves222are opened.

Meanwhile, although not shown in the drawing, the fourth outlet valve222dis opened to discharge the hydraulic pressure of the corresponding wheel cylinder40and at the same time the first to third inlet valves221a,221b, and221care maintained in the opened state so that the hydraulic pressure may be supplied to the three remaining wheels FR, RL, and RR.

Further, a flow rate discharged from the wheel cylinder40is increased when a difference in pressure between the wheel cylinder40and the first pressure chamber112is large. As one example, as a volume of the first pressure chamber112is increased while the hydraulic piston114is moved backward, a larger amount of flow rate may be discharged from the wheel cylinder40.

As described above, each of the valves221a,221b,221c,221d,222a,222b,222c,222d,232,233,243, and250of the hydraulic control unit200may be independently controlled to selectively deliver or discharge the hydraulic pressure to or from the wheel cylinder40of each of the wheels RL, RR, FL, and FR according to a required pressure such that a precise control of the hydraulic pressure may be possible.

FIG. 11is a hydraulic circuit diagram illustrating a state in which the electric brake system1according to the first embodiment of the present disclosure operates in a balance mode.

Generally, a balance in pressure between the first pressure chamber112and the second pressure chamber113is maintained. As one example, under a braking situation in which the hydraulic piston114is moved forward to apply a braking force, only hydraulic pressure of the first pressure chamber112of the two pressure chambers is delivered to the wheel cylinders40. However, in such a situation, because the oil in the reservoir30is delivered to the second pressure chamber113through the second dump flow path117, a balance in pressure between the two pressure chambers is still maintained. On the other hand, under a braking situation in which the hydraulic piston114is moved backward to apply a braking force, only hydraulic pressure of the second pressure chamber113of the two pressure chambers is delivered to the wheel cylinders40. However, even in such a situation, because the oil in the reservoir30is delivered to the first pressure chamber112through the first dump flow path116, a balance in pressure between the two pressure chambers is still maintained.

However, when a leak occurs due to a repetitive operation of the hydraulic pressure supply device100or an ABS operation is abruptly performed, an imbalance in pressure between the first pressure chamber112and the second pressure chamber113may be caused. That is, the hydraulic piston114may not be located at a calculated position to cause an incorrect operation.

In such a situation, the first hydraulic flow path211and the fourth hydraulic flow path214are connected to each other such that the first pressure chamber112and the second pressure chamber113communicate with each other. Therefore, a balance in pressure between the first pressure chamber112and the second pressure chamber113is caused. At this point, to promote the balancing process, the motor120may be operated to move the hydraulic piston114forward or backward.

The balance mode is performed when an imbalance in pressure between the first pressure chamber112and the second pressure chamber113occurs. As one example, the ECU may sense an imbalance state in pressure by detecting the hydraulic pressure of the first hydraulic circuit201and the hydraulic pressure of the second hydraulic circuit202from the hydraulic flow path pressure sensor PS1.

In the balance mode, the first pressure chamber112and the second pressure chamber113communicate with each other. As one example, the second control valve232and the third control valve233are switched to an opened state, and thus the first hydraulic flow path211, the third hydraulic flow path213, and the fourth hydraulic flow path214may be connected to each other. Thus, with only communication of the first hydraulic flow path211and the fourth hydraulic flow path214, a balance in pressure between the first pressure chamber112and the second pressure chamber113may be accomplished. To promote a balancing process, however, the hydraulic pressure supply device100may operate.

Hereinafter, an example when pressure in the first pressure chamber112is greater than that in the second pressure chamber113will be described. When the motor120is operated, the hydraulic piston114is moved forward, the hydraulic pressure in the first pressure chamber112is delivered from the first hydraulic flow path211to the fourth hydraulic flow path214through the second control valve232and the third control valve233which are in the opened state, and during this process, a balance in pressure between the first pressure chamber112and the second pressure chamber113is accomplished.

When the pressure in the second pressure chamber113is greater than that in the first pressure chamber112, the hydraulic pressure in the second pressure chamber113is delivered to the first pressure chamber112to balance pressure.

FIG. 12is a hydraulic circuit diagram illustrating a state in which the electric brake system1according to the first embodiment of the present disclosure operates in an inspection mode.

As shown inFIG. 12, when the electric brake system1operates abnormally, the valves54,60,221a,221b,221c,221d,222a,222b,222c,222d,232,233,243, and250are provided in an initial state of braking, that is, a non-operating state, and the first and second cut valves261and262respectively installed at the first and second backup flow paths251and252and each of the inlet valves221provided at the upstream of the wheel cylinder40that is provided at each of the wheels RR, RL, FR, and FL are opened so that the hydraulic pressure is directly delivered to the wheel cylinders40.

At this point, the simulator valve54is provided in the closed state so that the hydraulic pressure delivered to the wheel cylinders40through the first backup flow path251is prevented from leaking into the reservoir30through the simulation device50. Therefore, the driver steps on the brake pedal10so that the hydraulic pressure discharged from the master cylinder20is delivered to the wheel cylinders40without a loss to ensure stable braking.

However, when a leak occurs at the simulator valve54, a portion of the hydraulic pressure discharged from the master cylinder20may be lost to the reservoir30through the simulator valve54. The simulator valve54is provided to be closed in an abnormal mode, and the hydraulic pressure discharged from the master cylinder20pushes the reaction force piston52of the simulation device50so that a leak may occur at the simulator valve54by means of pressure formed at the rear end of the simulation chamber51.

Therefore, when the leak occurs at the simulator valve54, a braking force may not be obtained as intended by the driver. Consequently, there is a problem in safety of braking.

The inspection mode is a mode in which it is inspected whether there is a loss of pressure by generating hydraulic pressure at the hydraulic pressure supply device100to inspect whether a leak occurs in the simulator valve54. When the hydraulic pressure discharged from the hydraulic pressure supply device100is delivered to the reservoir30and causes a loss of pressure, it is difficult to verify whether a leak occurs at the simulator valve54.

Therefore, in the inspection mode, an inspection valve60may be closed and thus a hydraulic circuit connected to the hydraulic pressure supply device100may be configured as a closed circuit. That is, the inspection valve60, the simulator valve54, and the outlet valves222are closed and thus the flow paths connecting the hydraulic pressure supply device100to the reservoirs30are closed so that the closed circuit may be configured.

In the inspection mode, the electric brake system1according to the first embodiment of the present disclosure may provide the hydraulic pressure to only the first backup flow path251, which is connected to the simulation device50, of the first and second backup flow paths251and252. Therefore, to prevent the hydraulic pressure discharged from the hydraulic pressure supply device100from being delivered to the master cylinder20through the second backup flow path252, the second cut valve262may be switched to a closed state and the circuit balance valve250may be maintained in the closed state in the inspection mode.

Referring toFIG. 12, in the inspection mode, at an initial state of each of the valves54,60,221a,221b,221c,221d,222a,222b,222c,222d,232,233,243, and250provided at the electric brake system1of the present disclosure, the first to fourth inlet valves221a,221b,221c, and221dand the second cut valve262may be switched to the closed state, and the first cut valve261is maintained in the opened state so that the hydraulic pressure generated at the hydraulic pressure supply device100may be delivered to the master cylinder20. The inlet valves221are closed so that the hydraulic pressure of the hydraulic pressure supply device100may be prevented from being delivered to the first and second hydraulic circuits201and202, the second cut valve262is switched to the closed state so that the hydraulic pressure of the hydraulic pressure supply device100may be prevented from circulating along the first backup flow path251and the second backup flow path252, and the inspection valve60is switched to a closed state so that the hydraulic pressure supplied to the master cylinder20may be prevented from leaking into the reservoir30.

Also, even when the second control valve232and the circuit balance valve250are not switched to an opened state, the inspection mode may be performed. The reason for that is that the hydraulic pressure generated in the first pressure chamber112may flow into the first backup flow path251through the first control valve231provided at the second hydraulic flow path212. Further, because the second control valve232and the circuit balance valve250are maintained in the closed state, a case in which a leak occurs at the second control valve232and the circuit balance valve250may be detected.

In the inspection mode, after generating the hydraulic pressure at the hydraulic pressure supply device100, the ECU may analyze a signal transmitted from the backup flow path pressure sensor PS2measuring oil pressure of the master cylinder20to sense whether a leak occurs at the simulator valve54. As one example, when there is no loss on the basis of the measurement result of the backup flow path pressure sensor PS2, the simulator valve54may be determined to have no leak, and when the loss occurs, the simulator valve54may be determined to have a leak.

FIG. 13is a hydraulic circuit diagram illustrating a non-braking state of an electric brake system2according to a second embodiment of the present disclosure.

ComparingFIG. 1withFIG. 13, a third control valve233-1of the electric brake system2according to the second embodiment of the present disclosure may be configured with a check valve that allows only an oil flow in a direction from the second pressure chamber113to the hydraulic control unit200and blocks an oil flow in a reverse direction. That is, the third control valve233-1may allow the hydraulic pressure of the second pressure chamber113to be delivered to the hydraulic control unit200and also prevent the hydraulic pressure of the hydraulic control unit200from leaking into the second pressure chamber113through the fourth hydraulic flow path214.

FIG. 14is a hydraulic circuit diagram illustrating a non-braking state of an electric brake system3according to a third embodiment of the present disclosure.

ComparingFIG. 13withFIG. 14, the electric brake system3according to the third embodiment of the present disclosure may further include a sixth hydraulic flow path216that directly communicates the second hydraulic flow path212with the fourth hydraulic flow path214.

In the electric brake system2according to the second embodiment of the present disclosure shown inFIG. 13, a connection of the second hydraulic flow path212and the fourth hydraulic flow path214should pass the third hydraulic flow path213at which the second control valve232is installed, or the fifth hydraulic flow path215at which the circuit balance valve250is provided.

However, in the electric brake system3according to the third embodiment of the present disclosure shown inFIG. 14, the second hydraulic flow path212and the fourth hydraulic flow path214may be directly connected to each other through the sixth hydraulic flow path216.

Further, a fourth control valve234may be installed at the sixth hydraulic flow path216. The fourth control valve234may be configured with a check valve that allows only an oil flow in a direction from the first pressure chamber112to the hydraulic control unit200and blocks an oil flow in a reverse direction. That is, the fourth control valve234may allow the hydraulic pressure of the first pressure chamber112to be delivered to the hydraulic control unit200and also prevent the hydraulic pressure of the hydraulic control unit200from leaking into the first pressure chamber112through the sixth hydraulic flow path216.

FIG. 15is a hydraulic circuit diagram illustrating a non-braking state of an electric brake system4according to a fourth embodiment of the present disclosure.

ComparingFIG. 1withFIG. 15, the electric brake system4according to the fourth embodiment of the present disclosure may further include a seventh hydraulic flow path217communicating the second hydraulic flow path212with the fifth hydraulic flow path215(that is,215-1and215-2). Further, the fourth hydraulic flow path214may communicate with the seventh hydraulic flow path217.

Also, a second control valve232-1may be configured with a check valve that allows only an oil flow in a direction from the first pressure chamber112to the hydraulic control unit200and blocks an oil flow in a reverse direction. That is, the second control valve232-1may allow the hydraulic pressure of the first pressure chamber112to be delivered to the hydraulic control unit200and also prevent the hydraulic pressure of the hydraulic control unit200from leaking into the first pressure chamber112through the third hydraulic flow path213.

Further, a third control valve233-1may be configured with a check valve that allows only an oil flow in a direction from the second pressure chamber113to the hydraulic control unit200and blocks an oil flow in a reverse direction. That is, the third control valve233-1may allow the hydraulic pressure of the second pressure chamber113to be delivered to the hydraulic control unit200and also prevent the hydraulic pressure of the hydraulic control unit200from leaking into the second pressure chamber113through the fourth hydraulic flow path214.

Further, a fifth control valve235may be installed at the seventh hydraulic flow path217. The fifth control valve235may be configured with a solenoid valve capable of bidirectionally controlling an oil flow of the seventh hydraulic flow path217. That is, the fifth control valve235may allow the hydraulic pressure of the first pressure chamber112to be delivered to the hydraulic control unit200when a braking operation is performed, whereas it may allow the hydraulic pressure of the hydraulic control unit200to be delivered to the first pressure chamber112through the seventh hydraulic flow path217.

Also, the fifth control valve235may be configured with a normally closed type solenoid valve that is usually closed and is open when an opening signal is received from the ECU.

Also, the fifth hydraulic flow path215-1, which is located at a right side in the drawing based on a point at which the fifth hydraulic flow path215and the seventh hydraulic flow path217are connected to each other, may be connected to the second hydraulic flow path212, and a first circuit balance valve250-1may be installed between the point and a position at which the fifth hydraulic flow path215-1is connected to the second hydraulic flow path212.

The fifth hydraulic flow path215-2, which is located at a left side in the drawing, is connected to the third hydraulic flow path213, and a second circuit balance valve250-2may be installed between the point and a position at which the fifth hydraulic flow path215-2is connected to the third hydraulic flow path213.

Further, the first and second circuit balance valves250-1and250-2may be configured with solenoid valves capable of bidirectionally controlling oil flows of the fifth hydraulic flow paths215-1and215-2, respectively. That is, the first circuit balance valve250-1may allow the hydraulic pressure of the second hydraulic flow path212to be delivered to the seventh hydraulic flow path217, and also the hydraulic pressure of the seventh hydraulic flow path217to be delivered to the second hydraulic flow path212. Further, the second circuit balance valve250-2may allow the hydraulic pressure of the third hydraulic flow path213to be delivered to the seventh hydraulic flow path217, and also the hydraulic pressure of the seventh hydraulic flow path217to be delivered to the third hydraulic flow path213.

Also, first and second circuit balance valves250-1and250-2may be configured with normally closed type solenoid valves that are usually closed and are open when an opening signal is received from the ECU.

As is apparent from the above description, the electric brake system according to the embodiments of the present disclosure is capable of more rapidly providing hydraulic pressure and more precisely controlling an increase of pressure by providing a plurality of pistons of a hydraulic pressure supply device to configure a double action structure.

Also, hydraulic pressure or negative pressure may be provided by dividing a section into a low pressure section and a high pressure section so that a braking force may be adaptively provided or released according to a braking situation.

In addition, using the high pressure section, a braking force may be provided with a pressure greater than a maximum pressure in the low pressure section.

[Description of Reference Numerals]10: Brake Pedal11: Pedal Displacement Sensor20: Master Cylinder30: Reservoir40: Wheel Cylinder50: Simulation Device54: Simulator Valve60: Inspection Valve100: Hydraulic Pressure Supply110: Hydraulic Pressure SupplyDeviceUnit120: Motor130: Power Conversion Unit200: Hydraulic Control Unit201: First Hydraulic Circuit202: Second Hydraulic Circuit211: First Hydraulic Flow Path212: Second Hydraulic Flow Path213: Third Hydraulic Flow Path214: Fourth Hydraulic Flow Path215: Fifth Hydraulic Flow Path221: Inlet Valves222: Outlet Valves223: Check Valve231: First Control Valve232: Second Control Valve233: Third Control Valve250: Circuit Balance Valve241: First Dump Valve242: Second Dump Valve251: First Backup Flow Path252: Second Backup Flow Path261: First Cut Valve262: Second Cut Valve