Electronic brake system and control method thereof

Disclosed are an electronic brake system and a control method thereof. The electronic brake system and the control method thereof include a reservoir in which oil is stored; a master cylinder connected to the reservoir and discharging oil according to a pedal effort of a brake pedal; a hydraulic pressure supply apparatus which is operated by an electrical signal corresponding to the pedal effort to generate a hydraulic pressure; a hydraulic control unit configured to be separated into a first hydraulic circuit and a second hydraulic circuit so as to transmit the hydraulic pressure discharged from the hydraulic pressure supply apparatus to wheel cylinders provided on two wheels, respectively; and a first hydraulic passage pressure sensor for sensing the hydraulic pressure of the first hydraulic circuit and a second hydraulic passage pressure sensor for sensing the hydraulic pressure of the second hydraulic circuit, the reservoir includes a first reservoir chamber connected to recover oil dumped from the first hydraulic circuit, a second reservoir chamber connected to supply oil to the hydraulic pressure supply apparatus, and a third reservoir chamber connected to recover oil dumped from the second hydraulic circuit, and the first reservoir chamber and the third reservoir chamber are separately provided.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2017-0063393, filed on May 23, 2017 in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to an electronic brake system and a control method thereof, and more particularly to an electronic brake system for generating a braking force in response to an electrical signal and detecting a leakage occurring in a hydraulic circuit and effectively braking the same.

2. Description of the Related Art

A vehicle is essentially equipped with a brake system for braking. Recently, various types of systems have been proposed for obtaining a more powerful and stable braking force.

Examples of the brake system include an anti-lock brake system (ABS) that prevents slippage of wheels during braking, a brake traction control system (BTCS) that prevents slippage of drive wheels during a sudden acceleration or a rapid acceleration, and an electronic stability control system (ESC) that stably maintains the running state of a vehicle by controlling the brake fluid pressure by combining the anti-lock brake system and the traction control.

The electronic brake system includes a hydraulic pressure supply apparatus that receives an electric signal of a driver's braking will from a pedal displacement sensor that senses displacement of a brake pedal when the driver depresses the brake pedal, and supplies pressure to wheel cylinders.

According to EP 2 520 473 A1 (Honda Motor Co., Ltd.), a hydraulic pressure supply apparatus is operated so that a motor operates according to a pedal effort of a brake pedal to generate braking pressure. At this time, the braking pressure is generated by converting the rotational force of the motor into linear motion and pressing a piston.

In addition, a conventional electronic brake system includes a reservoir in which brake oil is stored. The reservoir is located at an upper portion of a master cylinder and stores the oil circulated from the master cylinder, the hydraulic pressure supply apparatus, the wheel cylinders and the like.

The inner space of the reservoir used in the electronic brake system is partitioned into inner chambers so as to be connected to the two chambers of the master cylinder, respectively, in preparation for failure of the braking system operating with an electric signal. However, when the two inner chambers of the reservoir are each connected to the two chambers of the master cylinder, one of the chambers of the reservoir must be connected to the hydraulic pressure supply apparatus. Accordingly, when a failure occurs in the connection of the one of the chambers, problems may occur during normal braking as well as during emergency braking, and there is a possibility that the efficiency of the hydraulic pressure supply apparatus may decrease during ABS control.

SUMMARY

It is an aspect of the present disclosure to provide an electronic brake system and a control method thereof for detecting a leakage of a hydraulic circuit and effectively performing braking.

In accordance with one aspect of the present disclosure, there may be provided an electronic brake system comprising: a reservoir in which oil is stored; a master cylinder connected to the reservoir and discharging oil according to a pedal effort of a brake pedal; a hydraulic pressure supply apparatus which is operated by an electrical signal corresponding to the pedal effort to generate a hydraulic pressure; a hydraulic control unit configured to be separated into a first hydraulic circuit and a second hydraulic circuit so as to transmit the hydraulic pressure discharged from the hydraulic pressure supply apparatus to wheel cylinders provided on two wheels, respectively; and a first hydraulic passage pressure sensor for sensing the hydraulic pressure of the first hydraulic circuit and a second hydraulic passage pressure sensor for sensing the hydraulic pressure of the second hydraulic circuit, wherein the reservoir is configured such that a reservoir chamber connected to recover oil dumped from the first hydraulic circuit and a reservoir chamber connected to recover oil dumped from the second hydraulic circuit are separated from each other in the reservoir.

Further, the reservoir may comprise a first reservoir chamber connected to recover oil dumped from the first hydraulic circuit, a second reservoir chamber connected to supply oil to the hydraulic pressure supply apparatus, and a third reservoir chamber connected to recover oil dumped from the second hydraulic circuit, and the first reservoir chamber and the third reservoir chamber may be separately provided.

Further, the electronic brake system may further comprise a motor control sensor for sensing the drive of a motor provided in the hydraulic pressure supply apparatus, and an electronic control unit for sensing an oil leak generated in the first hydraulic circuit and the second hydraulic circuit with the first hydraulic passage pressure sensor and the second hydraulic passage pressure sensor upon sensing the drive of the motor.

Further, the electronic control unit may determine that the hydraulic pressure is leaked when the pressure received from the first hydraulic passage pressure sensor or the second hydraulic passage pressure sensor is lower than a minimum pressure preset in each of the first and second hydraulic pressure circuits.

Further, the hydraulic control unit may comprise inlet valves provided on flow passages connecting the hydraulic pressure supply apparatus and the wheel cylinders to transmit a hydraulic pressure discharged from the hydraulic pressure supply apparatus to the wheel cylinder provided on each wheel, and outlet valves provided on flow passages connecting between the wheel cylinders and the reservoir, and the electronic control unit may close the inlet valves in the leaked hydraulic circuit when a leak occurs in one of the first hydraulic circuit and the second hydraulic circuit, and may transmit the hydraulic pressure to the wheel cylinders with the other hydraulic circuit that is not leaked.

Further, the master cylinder may comprise first and second master chambers, and first and second pistons provided in the respective master chambers, wherein the first reservoir chamber may be connected to the first master chamber, and the second reservoir chamber may be connected to the second master chamber.

In accordance with another aspect of the present disclosure, there may be provided a method of controlling the above electronic brake system comprising: determining whether hydraulic pressure in the first hydraulic circuit and the second hydraulic circuit of the hydraulic control unit are in a normal state, and transmitting a braking pressure to the wheel cylinders corresponding to the other hydraulic circuit having the hydraulic pressure in a normal state if it is determined that the hydraulic pressure in one of the first hydraulic circuit and the second hydraulic circuit is in an abnormal state.

Further, the hydraulic control unit may comprise inlet valves provided on flow passages connecting the hydraulic pressure supply apparatus and the wheel cylinders to transmit a hydraulic pressure discharged from the hydraulic pressure supply apparatus to the wheel cylinder provided on each wheel, and outlet valves provided on flow passages connecting between the wheel cylinders and the reservoir, and the electronic control unit may close the inlet valves in the leaked hydraulic circuit when a leak occurs in one of the first hydraulic circuit and the second hydraulic circuit, and may transmit the hydraulic pressure to the wheel cylinders with the other hydraulic circuit that is not leaked.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following embodiments are provided to fully convey the spirit of the present disclosure to a person having ordinary skill in the art to which the present disclosure belongs. The present disclosure is not limited to the embodiments shown herein but may be embodied in other forms. The drawings are not intended to limit the scope of the present disclosure in any way, and the size of components may be exaggerated for clarity of illustration. Like reference numerals designate like elements throughout the specification.

FIG. 1is a hydraulic circuit diagram showing a non-braking state of an electronic brake system according to an embodiment of the present disclosure.

Referring toFIG. 1, an electronic brake system1typically includes a master cylinder20for generating a hydraulic pressure, a reservoir30coupled to an upper portion of the master cylinder20to store oil, an input rod12for pressing the master cylinder20in accordance with a pedal effort of the brake pedal10, wheel cylinders40that receive the hydraulic pressure and perform braking of each of wheels RR, RL, FR and FL, a pedal displacement sensor11for sensing the displacement of the brake pedal10, and a simulation apparatus50for providing a reaction force in accordance with the pedal effort of the brake pedal10.

The master cylinder20may be configured to include at least one chamber to generate hydraulic pressure. As an example, the master cylinder20may include a first master chamber20aand a second master chamber20b.

Next, the master cylinder20according to an embodiment of the present disclosure will be described with reference toFIG. 2.FIG. 2is an enlarged view showing the master cylinder20according to an embodiment of the present disclosure.

The first master chamber20ais provided with a first piston21aconnected to the input rod12and the second master chamber20bis provided with a second piston22a. The first master chamber20acommunicates with a first hydraulic pressure port24ato allow the oil to flow in and out and the second master chamber20bcommunicates with a second hydraulic pressure port24bto allow the oil to flow in and out. For example, the first hydraulic pressure port24amay be connected to a first backup passage251, and the second hydraulic pressure port24bmay be connected to a second backup passage252.

The master cylinder20has the two master chambers20aand20bto ensure safety in case of failure. For example, one master chamber20aof the two master chambers20aand20bmay be connected to the front right wheel FR and the rear left wheel RL of a vehicle through the first backup passage251, and the other master chamber20bmay be connected to the front left wheel FL and the rear right wheel RR through the second backup passage252. In this way, by independently configuring the two master chambers20aand20b, it is possible to brake the vehicle even if one of the master chambers fails.

Alternatively, unlike the drawing, one of the two master chambers may be connected to the two front wheels FR and FL, and the other master chamber may be connected to the two rear wheels RR and RL. In addition, one of the two master chambers may be connected to the front left wheel FL and the rear left wheel RL, and the other master chamber may be connected to the rear right wheel RR and the front right wheel FR. That is, the positions of the wheels connected to the master chambers of the master cylinder20can be variously configured.

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. That is, the first spring21bmay be accommodated in the first master chamber20a, and the second spring22bmay be accommodated in the second master chamber20b.

The first spring21band the second spring22bare compressed by the first piston21aand the second piston22awhich move as the displacement of the brake pedal10changes, so that the elastic force is stored. When the pushing force of the first piston21abecomes smaller than the elastic force, the first and second pistons21aand22amay be returned to the original state by using the restoring elastic force stored in the first spring21band the second spring22b.

The input rod12for pressing the first piston21aof the master cylinder20may be brought into close contact with the first piston21a. That is, a gap between the master cylinder20and the input rod12may not exist. Therefore, when the brake pedal10is depressed, the master cylinder20may be directly pressed without a pedal invalid stroke section.

The first master chamber20amay be connected to the reservoir30through a first reservoir passage61and the second master chamber20bmay be connected to the reservoir30through a second reservoir passage62.

The master cylinder20may include two sealing members25aand25bdisposed on the front and rear sides of the first reservoir passage61and two sealing members25cand25ddisposed on the front and rear sides of the second reservoir passage62. The sealing members25a,25b,25cand25dmay be in the form of a ring protruding from the inner wall of the master cylinder20or the outer peripheral surface of the first and second pistons21aand22a.

A check valve64, which allows the flow of oil flowing from the reservoir30to the first master chamber20awhile blocking the flow of oil flowing into the reservoir30from the first master chamber20a, may be provided on the first reservoir passage61. The check valve64may be provided to allow only one directional fluid flow.

The front and rear of the check valve64of the first reservoir passage61may be connected by a bypass passage63. An inspection valve60may be provided on the bypass flow passage63.

The inspection valve60may be provided as a bidirectional control valve for controlling the flow of oil between the reservoir30and the master cylinder20. The inspection valve60may be provided as a normally open type solenoid valve that is normally opened and operates to close the valve when receiving a close signal from an electronic control unit.

The specific function and operation of the inspection valve60will be described later.

FIG. 3is an enlarged view showing a connection relationship between the reservoir30and a hydraulic circuit according to an embodiment of the present disclosure. As shown inFIG. 3, the reservoir30according to the present embodiment may include three reservoir chambers31,32and33. As an example, the three reservoir chambers31,32and33may be arranged side by side in a row.

The adjacent reservoir chambers31,32and33may be partitioned by partition34and35. For example, the first reservoir chamber31and the second reservoir chamber32are partitioned into the first partition34, and the second reservoir chamber32and the third reservoir chamber33are partitioned into the second partition35.

The first partition34and the second partition35may be partially opened to allow the first to third reservoir chambers31,32and33to communicate with each other. Therefore, the pressures of the first to third reservoir chambers31,32and33may all be the same. As an example, the pressures of the first to third reservoir chambers31,32and33may be equal to atmospheric pressure.

The first reservoir chamber31may be connected to the first master chamber20aof the master cylinder20, the wheel cylinders40and the simulation apparatus50. The first reservoir chamber31may be connected to the first master chamber20athrough the first reservoir passage61. Further, the first reservoir chamber31may be connected to two wheel cylinders of the four wheel cylinders40, for example, to the wheel cylinders40of a first hydraulic circuit201provided on the front right wheel FR and the rear left wheel RL.

As shown inFIG. 1, the connection between the first reservoir chamber31and the first master chamber20amay be controlled by the check valve64and the inspection valve60, the connection between the first reservoir chamber31and the simulation apparatus50may be controlled by a simulator valve54and a simulator check valve55, and the connection between the first reservoir chamber31and the wheel cylinders40may be controlled by first and second outlet valves222aand222b.

The second reservoir chamber32may be connected to a hydraulic pressure supply apparatus100. Referring toFIG. 1, the second reservoir chamber32may be connected to a first pressure chamber112and a second pressure chamber113of a hydraulic pressure providing unit110. Specifically, the second reservoir chamber32may be connected to the first pressure chamber112through a first dump passage116and to the second pressure chamber113through a second dump passage117.

Alternatively, unlike the drawing, the second reservoir chamber32may be connected to various hydraulic pressure supply apparatuses. As an example, the second reservoir chamber32may be connected to a pump.

The third reservoir chamber33may be connected to the second master chamber20bof the master cylinder20and the wheel cylinders40. Referring toFIG. 1, the third reservoir chamber33may be connected to the second master chamber20bthrough the second reservoir passage62. In addition, the third reservoir chamber33may be connected to the wheel cylinders of a second hydraulic circuit202provided on the other two wheel cylinders of the four wheel cylinders40, for example, to the wheel cylinders40of the second hydraulic circuit202provided on the rear right wheel RR and the front left wheel FL.

The connection between the third reservoir chamber33and the wheel cylinders40may be controlled by third and fourth outlet valves222cand222d.

The reservoir30according to the present embodiment may be configured such that the second reservoir chamber32that is connected to the hydraulic pressure supply apparatus100and the first and third reservoir chambers31and33that are connected to the first and second master chambers20aand20bare separated from each other. If the reservoir chamber for supplying oil to the hydraulic pressure supply apparatus100and the reservoir chambers for supplying oil to the first and second master chambers20aand20bare provided in the same manner, the reservoir20may not properly supply oil to the first and second master chambers20aand20bif the reservoir20fails to properly supply oil to the hydraulic pressure supply apparatus100.

Accordingly, the reservoir30according to the present embodiment is provided such that the second reservoir chamber32and the first and third reservoir chambers31and33are separated from each other, and thus the reservoir30supplies oil normally to the first and second master chambers20aand20bso that emergency braking can be performed in an emergency when oil is not properly supplied to the hydraulic pressure supply apparatus100.

Similarly, the reservoir30according to an embodiment of the present disclosure may be provided such that the first reservoir chamber31connected to the first master chamber20aand the third reservoir chamber33connected to the second master chamber20bare separated from each other. This is because in a case where the reservoir chamber for supplying oil to the first master chamber20aand the reservoir chamber for supplying oil to the second master chamber20bare provided in the same manner, the reservoir20may not properly supply oil to the second master chamber20bif the reservoir20fails to properly supply oil to the first master chamber20a.

Accordingly, the reservoir30according to an embodiment of the present disclosure may be provided such that the first reservoir chamber31and the third reservoir chamber33are separated from each other, and thus the reservoir30normally supplies oil to the second master chamber20bso that a braking pressure can be formed in two wheel cylinders of the four wheel cylinders40in an emergency when oil is not properly supplied to the first master chamber20a.

Further, the reservoir30according to an embodiment of the present disclosure is provided such that an oil line connected to the reservoir30from the hydraulic pressure supply apparatus100and a dump line connected to the reservoir30from the wheel cylinders40are separated.

Therefore, it is possible to prevent bubbles, which may occur in the dump line at the time of the ABS braking, from flowing into the first and second pressure chambers112and113of the hydraulic pressure supply apparatus100, thereby preventing the ABS performance from being degraded.

Meanwhile, the simulation apparatus50may be connected to the first backup passage251, which will be described later, to provide a reaction force in accordance with the pedal effort of the brake pedal10. The reaction force is provided as much as compensating a driver's pedal effort so that the driver can finely regulate the braking force as intended.

Referring toFIG. 1, the simulation apparatus50includes a pedal simulator that has a simulation chamber51provided to store the oil flowing out from the first hydraulic pressure port24aof the master cylinder20, a reaction force piston52provided in the simulation chamber51and a reaction force spring53elastically supporting the reaction force piston52, and the simulator valve54connected to a front portion of the simulation chamber51.

The reaction force piston52and the reaction force spring53are installed so as to have a certain range of displacement in the simulation chamber51by the oil introduced into the simulation chamber51.

The reaction force spring53shown in the drawing is only one embodiment capable of providing an elastic force to the reaction force piston52and may include various embodiments capable of storing the elastic force by deforming the shape. For example, it includes various members capable of storing an elastic force by being made of a material such as rubber or having a coil or a plate shape.

The simulator valve54may connect the master cylinder20and the front portion of the simulation chamber51, and a rear portion of the simulation chamber51may be connected to the reservoir30. Therefore, even when the reaction force piston52is returned, the oil in the reservoir30inflows through the simulation valve51, so that the entire interior of the simulation chamber51may be filled with the oil.

The simulator valve54may be composed of a normally closed type solenoid valve that is normally kept closed. The simulator valve54may be opened when a driver presses the brake pedal10to deliver the oil in the simulation chamber51to the reservoir30.

The simulator valve54may be provided with the simulator check valve55in parallel. The simulator check valve55may ensure a quick return of the pedal simulator pressure when the brake pedal10is released.

The operation of the pedal simulation apparatus50is as follows. When a driver depresses the brake pedal10, the oil in the simulation chamber51is transmitted to the reservoir30as the reaction force piston52of the pedal simulator pushes the reaction force spring53, and the driver is provided with a sense of pedaling in this process. On the contrary, when the driver releases the pedal effort applied to the brake pedal10, the reaction force spring53pushes the reaction force piston52to be returned to the original state, and the oil in the reservoir30may flow into the simulation chamber51to fully fill the inside of the simulation chamber51.

As such, since the inside of the simulation chamber51is always filled with oil, the friction of the reaction force piston52is minimized during operation of the simulation apparatus50so that the durability of the simulation apparatus50is improved and the inflow of foreign matter from the outside is blocked.

The electronic brake system1according to an embodiment of the present disclosure may include the hydraulic pressure supply apparatus100which mechanically operates by receiving an electric signal of a driver's braking will from the pedal displacement sensor11which detects the displacement of the brake pedal10, a hydraulic control unit200composed of the first and second hydraulic circuits201and202for controlling the flow of hydraulic pressure transmitted to the wheel cylinders40provided on the two wheels FR and RL or FL and RR, a first cut valve261provided on the first backup passage251that connects the first hydraulic pressure port24aand the first hydraulic circuit201to control the flow of hydraulic pressure, a second cut valve262provided on the second backup passage252that connects the second hydraulic pressure port24band the second hydraulic circuit202to control the flow of hydraulic pressure, and an electronic control unit (ECU; not shown) for controlling the hydraulic pressure supply apparatus100and valves54,60,221a,221b,221c,221d,222a,222b,222c,222d,233,235,236and243based on hydraulic pressure information and pedal displacement information.

The hydraulic pressure supply apparatus100may include the hydraulic pressure providing unit110for providing oil pressure delivered to the wheel cylinders40, a motor120for generating a rotational force by an electrical signal of the pedal displacement sensor11, and a power converting unit130for converting the rotational motion of the motor120into a linear motion and transmitting the linear motion to the hydraulic pressure providing unit110. Alternatively, the hydraulic pressure providing unit110may be operated by the pressure supplied from a high pressure accumulator, not by the driving force supplied from the motor120.

Next, the hydraulic pressure providing unit110according to an embodiment of the present disclosure will be described with reference toFIG. 4.FIG. 4is an enlarged view showing the hydraulic pressure providing unit110according to an embodiment of the present disclosure.

The hydraulic pressure providing unit110includes a cylinder block111in which a pressure chamber for receiving and storing oil is formed, a hydraulic piston114accommodated in the cylinder block111, sealing members115(115a,115b) provided between the hydraulic piston114and the cylinder block111to seal pressure chambers, and a drive shaft133connected to the rear end of the hydraulic piston114to transmit the power output from the power converting unit130to the hydraulic piston114.

The pressure chambers may include the first pressure chamber112positioned forward (forward direction, leftward direction in the drawing) of the hydraulic piston114and the second pressure chamber113positioned rearward (rearward direction, rightward in the drawing) of the hydraulic piston114. That is, the first pressure chamber112is partitioned by the cylinder block111and the front end of the hydraulic piston114and is provided such that the volume thereof changes according to the movement of the hydraulic piston114, and the second pressure chamber113is partitioned by the cylinder block111and the rear end of the hydraulic piston114and is provided such that the volume thereof changes according to the movement of the hydraulic piston114.

The first pressure chamber112is connected to a first hydraulic passage211through a first communication hole111aformed at the rear side of the cylinder block111and is connected to a fourth hydraulic passage214through a second communication hole111bformed at the front side of the cylinder block111. The first hydraulic passage211connects the first pressure chamber112and the first and second hydraulic circuits201and202. In addition, the first hydraulic passage211is branched to a second hydraulic passage212communicating with the first hydraulic circuit201and a third hydraulic passage213communicating with the second hydraulic circuit202. The fourth hydraulic passage214connects the second pressure chamber113and the first and second hydraulic circuits201and202. In addition, the fourth hydraulic passage214is branched to a fifth hydraulic passage215communicating with the first hydraulic circuit201and a sixth hydraulic passage216communicating with the second hydraulic circuit202.

The sealing members115include a piston sealing member115aprovided between the hydraulic piston114and the cylinder block111to seal a gap between the first pressure chamber112and the second pressure chamber113, and a drive shaft sealing member115bprovided between the drive shaft133and the cylinder block111to seal a gap between the second pressure chamber113and the cylinder block111. That is, the hydraulic pressure or the negative pressure of the first pressure chamber112generated by the forward or backward movement of the hydraulic piston114may not be leaked to the second pressure chamber113by blocking by the piston sealing member115a, and may be transmitted to the first and fourth hydraulic passages211and214. In addition, the hydraulic pressure or the negative pressure of the second pressure chamber113generated by the forward or backward movement of the hydraulic piston114may not be leaked to the cylinder block111by blocking by the drive shaft sealing member115b.

The first and second pressure chambers112and113are connected to the reservoir30by the dump passages116and117, respectively, so that the first and second pressure chambers112and113may receive and store oil from the reservoir30, or the oil in the first pressure chamber112or the second pressure chamber113may be delivered to the reservoir30. For example, the dump passages116and117may include the first dump passage116branched from the first pressure chamber112and connected to the reservoir30, and the second dump passage117branched from the second pressure chamber113and connected to the reservoir30, respectively.

Further, the first pressure chamber112is connected to the first dump passage116through a third communication hole111cformed on the front side thereof, and the second pressure chamber113is connected to the second dump passage117through a fourth communication hole111dformed on the rear side thereof.

Flow passages211to217and valves231to236and241to243, which are connected to the first pressure chamber112and the second pressure chamber113, will be described below with reference toFIG. 1.

The second hydraulic passage212may communicate with the first hydraulic circuit201, and the third hydraulic passage213may communicate with the second hydraulic circuit202. Accordingly, the hydraulic pressure can be transmitted to the first hydraulic circuit201and the second hydraulic circuit202by advancing the hydraulic piston114.

Further, the electronic brake system1according to an embodiment of the present disclosure may include a first control valve231and a second control valve232provided on the second and third hydraulic passages212and213, respectively, to control the flow of oil.

The first and second control valves231and232may be provided as check valves that allow only the oil flow in the direction from the first pressure chamber112to the first or second hydraulic circuit201or202and block the oil flow in the opposite direction. That is, the first or second control valve231or232may allow the hydraulic pressure of the first pressure chamber112to be transmitted to the first or second hydraulic circuit201or202, but may prevent the hydraulic pressure of the first or second hydraulic circuit201or202from being leaked to the first pressure chamber112through the second or third hydraulic passage212or213.

The fourth hydraulic passage214may be branched into the fifth hydraulic passage215and the sixth hydraulic passage216to communicate with both the first hydraulic circuit201and the second hydraulic circuit202. For example, the fifth hydraulic passage215branched from the fourth hydraulic passage214may communicate with the first hydraulic circuit201, and the sixth hydraulic passage216branched from the fourth hydraulic passage214may communicate with the second hydraulic circuit202. Accordingly, the hydraulic pressure may be transmitted to both the first hydraulic circuit201and the second hydraulic circuit202by the backward movement of the hydraulic piston114.

Further, the electronic brake system1according to an embodiment of the present disclosure may include a third control valve233provided on the fifth hydraulic passage215to control the flow of oil, and a fourth control valve234provided on the sixth hydraulic passage216to control the flow of oil.

The third control valve233may be provided as a bidirectional control valve for controlling the oil flow between the second pressure chamber113and the first hydraulic circuit201. In addition, the third control valve233may be provided as a normally closed type solenoid valve which is normally closed and operates to be opened when receiving an open signal from the electronic control unit.

The fourth control valve234may be provided as a check valve that allows only the oil flow in the direction from the second pressure chamber113to the second hydraulic circuit202and blocks the oil flow in the opposite direction. That is, the fourth control valve234may prevent the hydraulic pressure in the second hydraulic circuit202from being leaked to the second pressure chamber113through the sixth hydraulic passage216and the fourth hydraulic passage214.

Further, the electronic brake system1according to an embodiment of the present disclosure may include a fifth control valve235provided on a seventh hydraulic passage217that connects the second hydraulic passage212and the third hydraulic passage213to control the flow of oil, and a sixth control valve236provided on an eighth hydraulic passage218that connects the second hydraulic passage212and the seventh hydraulic passage217to control the flow of oil. The fifth control valve235and the sixth control valve236may be provided as a normally closed type solenoid valve which is normally closed and operates to be opened when receiving an open signal from the electronic control unit.

The fifth control valve235and the sixth control valve236may operate to be opened when an abnormality occurs in the first control valve231or the second control valve232so that the hydraulic pressure in the first pressure chamber112is transmitted to both the first hydraulic circuit201and the second hydraulic circuit202.

Further, the fifth control valve235and the sixth control valve236may operate to be opened when the hydraulic pressure in the wheel cylinders40is exited and sent to the first pressure chamber112. This is because the first control valve231and the second control valve232provided on the second hydraulic passage212and the third hydraulic passage213are provided as check valves allowing only one directional oil flow.

Further, the electronic brake system1according to an embodiment of the present disclosure may further include a first dump valve241and a second dump valve242provided on the first dump passage116and the second dump passage117, respectively, to control the flow of oil. The first and second dump valves241and242may be provided as check valves that are opened only in the direction from the reservoir30to the first or second pressure chamber112or113and closed in the opposite direction. That is, the first dump valve241may be a check valve that allows the oil to flow from the reservoir30to the first pressure chamber112while blocking the flow of oil from the first pressure chamber112to the reservoir30, and the second dump valve242may be a check valve that allows the oil to flow from the reservoir30to the second pressure chamber113while blocking the flow of oil from the second pressure chamber113to the reservoir30.

The second dump passage117may include a bypass passage, and a third dump valve243for controlling the flow of oil between the second pressure chamber113and the reservoir30may be installed on the bypass passage.

The third dump valve243may be provided as a solenoid valve capable of controlling the bidirectional flow, and may also be provided as a normally open type solenoid valve that is opened in a normal state and operates to be closed when receiving a close signal from the electronic control unit.

The hydraulic pressure providing unit110of the electronic brake system1according to an embodiment of the present disclosure may operate in a double acting manner. That is, the hydraulic pressure generated in the first pressure chamber112as the hydraulic piston114advances is transmitted to the first hydraulic circuit201through the first hydraulic passage211and the second hydraulic passage212to operate the wheel cylinders40installed on the front right wheel FR and the rear left wheel RL, and is transmitted to the second hydraulic circuit202through the first hydraulic passage211and the third hydraulic passage213to operate the wheel cylinders40installed on the rear right wheel RR and the front left wheel FL.

Likewise, the hydraulic pressure generated in the second pressure chamber113as the hydraulic piston114moves backward is transmitted to the first hydraulic circuit201through the fourth hydraulic passage214and the fifth hydraulic passage215to operate the wheel cylinders40installed on the front light wheel FR and the rear left wheel RL, and is transmitted to the second hydraulic circuit202through the fourth hydraulic passage214and the sixth hydraulic passage216to operate the wheel cylinders40installed on the rear right wheel RR and the front left wheel FL.

Further, the negative pressure generated in the first pressure chamber112while the hydraulic piston114moves backward may suck oil in the wheel cylinders40installed on the front right wheel FR and the rear left wheel RL and transmit the oil to the first pressure chamber112through the first hydraulic circuit201, the second hydraulic passage212and the first hydraulic passage211, and may suck oil in the wheel cylinders40installed on the rear right wheel RR and the front left wheel FL and transmit the oil to the first pressure chamber112through the second hydraulic circuit202, the third hydraulic passage213and the first hydraulic passage211.

Next, the motor120and the power converting unit130of the hydraulic pressure supply apparatus100will be described.

The motor120which is a device for generating a rotational force by a signal output from an electronic control unit (ECU) (not shown) may generate a rotational force in a forward or reverse direction. The rotational angular velocity and rotation angle of the motor120may be precisely controlled. Since the motor120is a well-known technology, a detailed description thereof will be omitted.

The electronic control unit controls the valves54,60,221a,221b,221c,221d,222a,222b,222c,222d,233,235,236and243included in the electronic brake system1of the present disclosure, including the motor120, which will be described later. The operation in which a plurality of valves is controlled according to the displacement of the brake pedal10will be described later.

The driving force of the motor120causes the displacement of the hydraulic piston114through the power converting unit130, and the hydraulic pressure generated by the sliding movement of the hydraulic piston114in the pressure chambers is transmitted to the wheel cylinders40installed on the respective wheels RR, RL, FR and FL through the first and second hydraulic passages211and212. A brushless motor comprising a stator121and a rotor122may be used as the motor120.

The power converting unit130which is a device for converting a rotational force into a linear motion may include a worm shaft131, a worm wheel132, and the drive shaft133, for example.

The worm shaft131may be integrally formed with a rotation shaft of the motor120, and rotates the worm wheel132by forming a worm that engages with the worm wheel132on the outer circumferential surface thereof. The worm wheel132is coupled to be engaged with the drive shaft133to move the drive shaft133linearly, and the drive shaft133is connected to the hydraulic piston114to slide the hydraulic piston114in the cylinder block111.

The above operations may be described again as follows. A signal sensed by the pedal displacement sensor11as a displacement occurs in the brake pedal10is transmitted to the electronic control unit (ECU) (not shown), and the electronic control unit drives the motor120in one direction to rotate the worm shaft131in one direction. The rotational force of the worm shaft131is transmitted to the drive shaft133via the worm wheel132, and the hydraulic piston114connected to the drive shaft133moves forward to generate a hydraulic pressure to the first pressure chamber112.

On the contrary, when the pedal effort on the brake pedal10is released, the electronic control unit drives the motor120in the opposite direction to rotate the worm shaft131in the opposite direction. Accordingly, the worm wheel132also rotates in the opposite direction and the hydraulic piston114connected to the drive shaft133returns (moves backward), thereby generating a negative pressure in the first pressure chamber112.

On the other hand, the hydraulic pressure and the negative pressure may be generated in a direction opposite to the above. That is, a signal sensed by the pedal displacement sensor11as a displacement occurs in the brake pedal10is transmitted to the electronic control unit (ECU) (not shown), and the electronic control unit drives the motor120in the opposite direction to rotate the worm shaft131in the opposite direction. The rotational force of the worm shaft131is transmitted to the drive shaft133via the worm wheel132and the hydraulic piston114connected to the drive shaft133moves backward thereby generating a hydraulic pressure in the second pressure chamber113.

On the contrary, when the pedal effort on the brake pedal10is released, the electronic control unit drives the motor120in one direction so that the worm shaft131rotates in one direction. Accordingly, the worm wheel132also rotates in the opposite direction and the hydraulic piston114connected to the drive shaft133returns (advances), thereby generating a negative pressure in the second pressure chamber113.

As such, the hydraulic pressure supply apparatus100performs the function of transmitting the hydraulic pressure to the wheel cylinders40or sucking and transmitting the hydraulic pressure to the reservoir30in accordance with the rotational direction of the rotational force generated from the motor120.

When the motor120rotates in one direction, a hydraulic pressure may be generated in the first pressure chamber112or a negative pressure may be generated in the second pressure chamber113. In such a case, whether to brake by using the hydraulic pressure or to release the braking by using the negative pressure may be determined by controlling the valves54,60,221a,221b,221c,221d,222a,222b,222c,222d,233,235,236and243.

Although not shown in the drawings, the power converting unit130may be constituted by a ball screw nut assembly. The power converting unit130may include, for example, a screw integrally formed with the rotation shaft of the motor120or connected to rotate together with the rotation shaft of the motor120, and a ball nut that is screwed with the screw in a limited rotation state and linearly moves according to the rotation of the screw. The hydraulic piston114is connected to the ball nut of the power converting unit130and presses the pressure chambers by the linear movement of the ball nut. The structure of such a ball screw nut assembly is a known apparatus for converting a rotational motion into a linear motion, and thus a detailed description thereof will be omitted.

It should be understood that the power converting unit130according to an embodiment of the present disclosure may adopt any structure other than the structure of the ball screw nut assembly as long as the structure may convert a rotational motion into a linear motion.

Further, the electronic brake system1according to an embodiment of the present disclosure may further include the first and second backup passages251and252capable of directly supplying the oil discharged from the master cylinder20to the wheel cylinders40when operating abnormally.

The first cut valve261for controlling the flow of oil may be provided on the first backup passage251and the second cut valve262for controlling the flow of oil may be provided on the second backup passage252. Further, the first backup passage251may connect the first hydraulic pressure port24ato the first hydraulic circuit201, and the second backup passage252may connect the second hydraulic pressure port24band the second hydraulic circuit202.

The first and second cut valves261and262may be provided as normally open type solenoid valves that are opened in a normal state and operate to be closed when receiving a close signal from the electronic control unit.

Next, the hydraulic control unit200according to an embodiment of the present disclosure will be described.

The hydraulic control unit200may include the first hydraulic circuit201and the second hydraulic circuit202, each of which receives hydraulic pressure and controls two wheels, respectively. For 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. The wheel cylinders40are provided on the respective wheels FR, FL, RR, and RL to receive the hydraulic pressure and perform braking.

The first hydraulic circuit201is connected to the first hydraulic passage211and the second hydraulic passage212and is supplied with the hydraulic pressure from the hydraulic pressure supply apparatus100, and the second hydraulic passage212is branched into two flow passages connected to the front right wheel FR and the rear left wheel RL. Likewise, the second hydraulic circuit202is connected to the first hydraulic passage211and the third hydraulic passage213and is supplied with the hydraulic pressure from the hydraulic pressure supply apparatus100, and the third hydraulic passage213is branched into two flow passages connected to the front left wheel FL and the rear right wheel RR.

The first and second hydraulic circuits201and202may include a plurality of inlet valves221(221a,221b,221c, and221d) to control the flow of hydraulic pressure. For example, the first hydraulic circuit201may be provided with the two inlet valves221aand221bthat are connected to the first hydraulic passage211to control the hydraulic pressure transmitted to the two wheel cylinders40, respectively. Further, the second hydraulic circuit202may be provided with the two inlet valves221cand221dthat are connected to the second hydraulic passage212to control the hydraulic pressure transmitted to the two wheel cylinders40, respectively.

The inlet valves221may be provided as normally open type solenoid valves that are disposed on an upstream side of the wheel cylinders40and are opened in a normal state and operate to be closed when receiving a close signal from the electronic control unit.

The first and second hydraulic circuits201and202may include check valves223a,223b,223cand223dprovided on bypass passages that connect the front and the rear of each of the inlet valves221a,221b,221cand221d. The check valves223a,223b,223cand223dmay be provided to allow only the flow of oil in the direction to the hydraulic pressure providing unit110from the wheel cylinders40and to limit the flow of oil in the direction to the wheel cylinders40from the hydraulic pressure providing unit110. The check valves223a,223b,223cand223dmay quickly release the braking pressure of the wheel cylinders40, and may allow the hydraulic pressure of the wheel cylinders40to flow into the hydraulic pressure providing unit110when the inlet valves221a,221b,221cand221dare not operated normally.

The first and second hydraulic circuits201and202may further include a plurality of outlet valves222(222a,222b,222cand222d) connected to the reservoir30in order to improve the performance when releasing the brake. The outlet valves222are connected to the wheel cylinders40, respectively, to control the hydraulic pressure that escapes from each of the wheels RR, RL, FR and FL. That is, the outlet valves222may sense the braking pressure of each of the wheels RR, RL, FR and FL and may be selectively opened to control the pressure when the pressure reduction braking is required.

The outlet valves222may be provided as normally closed type solenoid valves that are closed in a normal state and operate to be opened when receiving an open signal from the electronic control unit.

The hydraulic control unit200may be connected to the first and second backup passages251and252. For example, the first hydraulic circuit201may be connected to the first backup passage251to be supplied with the hydraulic pressure from the master cylinder20, and the second hydraulic circuit202may be connected to the second backup passage252to be supplied with the hydraulic pressure from the master cylinder20.

At this time, the first backup passage251may join with the first hydraulic circuit201upstream (or downstream) of the first and second inlet valves221aand221b. Likewise, the second backup passage252may join with the second hydraulic circuit202upstream (or downstream) of the third and fourth inlet valves221cand221d. Accordingly, the hydraulic pressure provided from the hydraulic pressure supply apparatus100may be supplied to the wheel cylinders40through the first and second hydraulic circuits201and202when the first and second cut valves261and262are closed, and the hydraulic pressure provided from the master cylinder20may be supplied to the wheel cylinders40through the first and second backup passages251and252when the first and second cut valves261and262are opened. At this time, since the plurality of inlet valves221a,2211o,221cand221dis in an open state, there is no need to switch the operation state.

Reference numerals “PS1-1” and “PS1-2,” which are not described, are hydraulic passage pressure sensors that sense the hydraulic pressure of the first and second hydraulic circuits201and202, and Reference numeral “PS2” is a backup passage pressure sensor that measures the oil pressure of the master cylinder20. In addition, Reference numeral “MPS” is a motor control sensor that controls the rotation angle or current of the motor120.

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

The hydraulic pressure supply apparatus100may be used by separating a low pressure mode and a high pressure mode. The low pressure mode and the high pressure mode may be changed by changing the operation of the hydraulic control unit200. The hydraulic pressure supply apparatus100may generate a high hydraulic pressure without increasing the output of the motor120by using the high pressure mode. Accordingly, it is possible to secure stable braking power while lowering the price and weight of the brake system.

More specifically, the hydraulic piston114advances to generate the hydraulic pressure in the first pressure chamber112. The more the hydraulic piston114advances in an initial state, that is, the more the stroke of the hydraulic piston114increases, the more the braking pressure rises as the amount of oil transferred from the first pressure chamber112to the wheel cylinders40increases. However, since an effective stroke of the hydraulic piston114exists, a maximum pressure due to the advancement of the hydraulic piston114exists.

At this time, the maximum pressure in the low pressure mode is less than the maximum pressure in the high pressure mode. However, the high pressure mode has a small rate of pressure increase per stroke of the hydraulic piston114as compared with the low pressure mode. This is because not all of the oil pushed out of the first pressure chamber112flows into the wheel cylinders40but a part of the oil flows into the second pressure chamber113.

Accordingly, the low pressure mode with a large rate of pressure increase per stroke may be used in an early phase of braking where braking responsiveness is important, and the high pressure mode with high pressure may be used in a later phase of braking where the maximum braking force is important.

When the braking by a driver is started, a demanded braking amount of the driver may be sensed through information such as the pressure of the brake pedal10sensed by the pedal displacement sensor11. The electronic control unit (not shown) receives the electric signal output from the pedal displacement sensor11and drives the motor120.

Further, the electronic control unit may receive the magnitude of a regenerative braking amount through the backup passage pressure sensor PS2provided at an outlet side of the master cylinder20and the hydraulic passage pressure sensor PS1provided in the second hydraulic circuit202, and may calculate the magnitude of a friction braking amount in accordance with the difference between the demanded braking amount of the driver and the regenerative braking amount to thereby grasp the magnitude of a pressure increase or a pressure decrease of the wheel cylinders40.

When the driver depresses the brake pedal10at a beginning of braking, the motor120is operated to rotate in one direction and the rotational force of the motor120is transmitted to the hydraulic pressure providing unit110by the power converting unit130, and the hydraulic piston114of the hydraulic pressure providing unit110advances to generate the hydraulic pressure in the first pressure chamber112. The hydraulic pressure discharged from the hydraulic pressure providing unit110is transmitted to the wheel cylinders40provided on the four wheels through the first hydraulic circuit201and the second hydraulic circuit202to generate the braking force.

Specifically, the hydraulic pressure provided in the first pressure chamber112is directly transmitted to the wheel cylinders40provided on the two wheels FR and RL through the first hydraulic passage211and the second hydraulic passage212connected to the first communication hole111a. At this time, the first and second inlet valves221aand221b, which are respectively installed on two flow passages branched from the second hydraulic passage212, are provided in the open state. In addition, the first and second outlet valves222aand222b, which are respectively installed on two flow passages branched from the two flow passages branched from the second hydraulic passage212, are maintained in the closed state to prevent the hydraulic pressure from leaking to the reservoir30.

The hydraulic pressure provided in the first pressure chamber112is directly transmitted to the wheel cylinders40provided on the two wheels RR and FL through the first hydraulic passage211and the third hydraulic passage213connected to the first communication hole111a. At this time, the third and fourth inlet valves221cand221d, which are respectively installed on two flow passages branched from the third hydraulic passage213, are provided in the open state. In addition, the third and fourth outlet valves222cand222d, which are respectively installed on two flow passages branched from the two flow passages branched from the third hydraulic passage213, are maintained in the closed state to prevent the hydraulic pressure from leaking to the reservoir30.

Further, the fifth control valve235and the sixth control valve236may be switched to the open state to open the seventh hydraulic passage217and the eighth hydraulic passage218. As the seventh hydraulic passage217and the eighth hydraulic passage218are opened, the second hydraulic passage212and the third hydraulic passage213communicate with each other. However, at least one of the fifth control valve235and the sixth control valve236may be maintained in the closed state as necessary.

Further, the third control valve233may be maintained in the closed state to block the fifth hydraulic passage215. The hydraulic pressure generated in the first pressure chamber112is blocked from being transmitted to the second pressure chamber113through the fifth hydraulic passage215connected to the second hydraulic passage212, thereby increasing the rate of pressure increase per stroke. Therefore, a quick braking response may be expected at the beginning of braking.

Further, if the pressure transmitted to the wheel cylinders40is measured to be higher than a target pressure value in accordance with a pedal effort of the brake pedal10, the electronic control unit may open one or more of the first to fourth outlet valves222to control so as to follow the target pressure value.

Further, when the hydraulic pressure is generated in the hydraulic pressure supply apparatus100, the first and second cut valves261and262provided on the first and second backup passages251and252connected to the first and second hydraulic pressure ports24aand24bof the master cylinder20are closed so that the hydraulic pressure discharged from the master cylinder20is not transmitted to the wheel cylinders40.

Further, the pressure generated by the pressing of the master cylinder20according to the pedal effort of the brake pedal10is transmitted to the simulation apparatus50connected to the master cylinder20. At this time, the normally closed type simulator valve54disposed at the front end of the simulation chamber51is opened so that the oil filled in the simulation chamber51is delivered to the reservoir30through the simulator valve54. In addition, the reaction force piston52moves so that a pressure corresponding to the load of the reaction force spring53supporting the reaction force piston52is formed in the simulation chamber51, thereby providing a proper pedal feeling to the driver.

Further, the hydraulic passage pressure sensor PS1-2or PS1-1may detect the flow rate delivered to the wheel cylinder40installed on the front left wheel FL or the rear right wheel RR (hereinafter, simply referred to as the wheel cylinder40). Accordingly, the flow rate delivered to the wheel cylinder40may be controlled by controlling the hydraulic pressure supply apparatus100in accordance with the output of the hydraulic passage pressure sensor PS1-2. Specifically, the flow rate discharged from the wheel cylinder40and the discharge speed may be controlled by regulating the advancing distance and the advancing speed of the hydraulic piston114.

On the other hand, it is possible to switch from the low pressure mode to the high pressure mode before the hydraulic piston114advances to the maximum.

In the high pressure mode, the third control valve233may be switched to the open state to open the fifth hydraulic passage215. Accordingly, the hydraulic pressure generated in the first pressure chamber112is transmitted to the second pressure chamber113through the fifth hydraulic passage215connected to the second hydraulic passage212to be used to push out the hydraulic piston114.

In the high pressure mode, since a part of the oil pushed out of the first pressure chamber112flows into the second pressure chamber113, the rate of pressure increase per stroke decreases. However, since a part of the hydraulic pressure generated in the first pressure chamber112is used to push out the hydraulic piston114, the maximum pressure is increased. At this time, the reason why the maximum pressure is increased is that the volume per stroke of the hydraulic piston114in the second pressure chamber113is smaller than the volume per stroke of the hydraulic piston114in the first pressure chamber112.

Next, a case of releasing the braking force in the braking state in the normal operation of the electronic brake system1according to an embodiment of the present disclosure will be described.

When the pedal effort applied to the brake pedal10is released, the motor120generates a rotational force in a direction opposite to the braking direction and transmits the rotational force to the power converting unit130, and the worm shaft131, the worm wheel132and the drive shaft133of the power converting unit130are rotated in the opposite direction to the braking direction to move the hydraulic piston114back to its original position, so that the pressure in the first pressure chamber112is released or a negative pressure is generated in the first pressure chamber112. In addition, the hydraulic pressure providing unit110receives the hydraulic pressure discharged from the wheel cylinders40through the first and second hydraulic circuits201and202and transmits the hydraulic pressure to the first pressure chamber112.

Specifically, the negative pressure generated in the first pressure chamber112releases the pressure of the wheel cylinders40, which are provided on the two wheels FR and RL, through the first hydraulic passage211and the second hydraulic passage212connected to the first communication hole111a. At this time, the first and second inlet valves221aand221b, which are respectively installed on two flow passages branched from the second hydraulic passage212, are provided in the open state. In addition, the first and second outlet valves222aand222b, which are respectively installed on two flow passages branched from the two flow passages branched from the second hydraulic passage212, are maintained in the closed state to prevent oil in the reservoir30from being introduced.

Further, the negative pressure generated in the first pressure chamber112releases the pressure of the wheel cylinders40, which are provided on the two wheels FL and RR, through the first hydraulic passage211and the third hydraulic passage213connected to the first communication hole111a. At this time, the third and fourth inlet valves221cand221d, which are respectively installed on two flow passages branched from the third hydraulic passage213, are provided in the open state. In addition, the third and fourth outlet valves222cand222d, which are respectively installed on two flow passages branched from the third hydraulic passage213, are maintained in the closed state to prevent oil in the reservoir30from being introduced.

Further, the third control valve233is switched to the open state to open the fifth hydraulic passage215, the fifth control valve235is switched to the open state to open the seventh hydraulic passage217, and the sixth control valve236is switched to the open state to open the eighth hydraulic passage218. As the fifth hydraulic passage215, the seventh hydraulic passage217and the eighth hydraulic passage218communicate with each other, the first pressure chamber112and the second pressure chamber113communicate with each other.

In order for a negative pressure to be formed in the first pressure chamber112, the hydraulic piston114must move backward, but if oil is fully filled in the second pressure chamber113, a resistance is generated when the hydraulic piston114is reversed. At this time, when the third control valve233, the fifth control valve235and the sixth control valve236are opened so that the fourth hydraulic passage214and the fifth hydraulic passage215are communicated with the second hydraulic passage212, the oil in the second pressure chamber113is moved to the first pressure chamber112.

Further, the third dump valve243may be switched to the closed state. By closing the third dump valve243, the oil in the second pressure chamber113may be discharged only to the fourth hydraulic passage214. However, in some cases, the third dump valve243may be maintained in the open state so that the oil in the second pressure chamber113may flow into the reservoir30.

Further, in a case where the negative pressure transmitted to the first and second hydraulic circuits201and202is measured to be higher than a target pressure release value corresponding to the release amount of the brake pedal10, the electronic control unit may open one or more of the first to fourth outlet valves222to control so as to follow the target pressure value.

Further, when a hydraulic pressure is generated in the hydraulic pressure supply apparatus100, the first and second cut valves261and262provided on the first and second backup passages251and252connected to the first and second hydraulic pressure ports24aand24bof the master cylinder20are closed so that the negative pressure generated in the master cylinder20is not transmitted to the hydraulic control unit200.

In the high pressure mode, since the oil in the second pressure chamber113is moved to the first pressure chamber112together with the oil in the wheel cylinders40by the negative pressure in the first pressure chamber112generated as the hydraulic piston114moves backward, the pressure reduction rate of the wheel cylinders40is small. Therefore, it may be difficult to release the pressure quickly in the high pressure mode.

For this reason, the high pressure mode may only be used in high pressure situations and may be switched to the low pressure mode if the pressure falls below a certain level.

Next, a state in which the electronic brake system1according to an embodiment of the present disclosure is actuated by an ABS will be described. In this embodiment, for example, the wheel cylinders40disposed on the front left wheel FL and the front right wheel FR are operated by the ABS, but the present disclosure is not limited thereto.

When the motor120operates according to the pedal effort of the brake pedal10, a hydraulic pressure is generated as the rotational force of the motor120is transmitted to the hydraulic pressure providing unit110through the power converting unit130. At this time, the first and second cut valves261and262are closed so that the hydraulic pressure discharged from the master cylinder20is not transmitted to the wheel cylinders40.

The hydraulic piston114advances to generate the hydraulic pressure in the first pressure chamber112, the fourth inlet valve221dis provided in the open state and the hydraulic pressure transmitted through the first hydraulic passage211and the third hydraulic passage213actuates the wheel cylinder40disposed on the front left wheel FL, thereby generating a braking force.

At this time, the first to third inlet valves221a,221band221care switched to the closed state, and the first to fourth outlet valves222a,222b,222cand222dare maintained in the closed state. In addition, the third dump valve243is provided in the open state so that the oil is filled from the reservoir30to the second pressure chamber113.

The hydraulic pressure piston114moves backward to generate the hydraulic pressure in the second pressure chamber113, the first inlet valve221ais provided in the open state and the hydraulic pressure transmitted through the fourth hydraulic passage214and the second hydraulic passage212actuates the wheel cylinder40disposed in the front right wheel FR, thereby generating a braking force.

At this time, the second to fourth inlet valves221b,221cand221dare switched to the closed state, and the first to fourth outlet valves222a,222b,222cand222dare maintained in the closed state.

That is, the electronic brake system1according to an embodiment of the present disclosure can independently control the operation of the motor120and the respective valves54,60,221a,221b,221c,221d,222a,222b,222c,222d,233,235,236and243so that the hydraulic pressure may be selectively transmitted to or discharged from the wheel cylinders40of the wheels RL, RR, FL and FR according to the required pressure, and thus precise pressure control becomes possible.

Next, a case where the electronic brake system1as above does not operate normally (fallback mode) will be described.

In a case where the electronic brake system1is operated abnormally, the respective valves54,60,221a,221b,221c,221d,222a,222b,222c,222d,233,235,236and243are provided in an initial state of braking which is in a non-operating state.

When a driver presses the brake pedal10, the input rod12connected to the brake pedal10advances, at the same time the first piston21ain contact with the input rod12advances, and the second piston22aalso advances by the pressing or movement of the first piston21a. At this time, since there is no gap between the input rod12and the first piston21a, rapid braking may be performed.

Further, the hydraulic pressure discharged from the master cylinder20is transmitted to the wheel cylinders40through the first and second backup passages251and252connected for a backup brake, thereby performing the braking force.

At this time, the first and second cut valves261and262provided on the first and second backup passages251and252and the inlet valves221for opening and closing the flow passages of the first and second hydraulic circuits201and202are provided as normally open type solenoid valves, and the simulator valve54and the outlet valves222are provided as normally closed type solenoid valves, and thus the hydraulic pressure is immediately transmitted to the four wheel cylinders40. Therefore, since stable braking may be performed, the braking stability is improved.

The electronic brake system1according to an embodiment of the present disclosure may discharge only the braking pressure provided to the corresponding wheel cylinders40through the first to fourth outlet valves222ato222d.

In a case where the first to fourth inlet valves221ato221dare switched to the closed state, the first to third outlet valves222ato222care maintained in the closed state, and the fourth outlet valve222dis switched to the open state, the hydraulic pressure discharged from the wheel cylinder40provided on the front left wheel FL is discharged to the third reservoir chamber33through the fourth outlet valve222d.

The reason why the hydraulic pressure in the wheel cylinders40is discharged through the outlet valves222is because the pressure in the reservoir30is smaller than the pressure in the wheel cylinders40. The pressure in the reservoir30is usually provided at atmospheric pressure. Since the pressure in the wheel cylinders40is usually significantly higher than the atmospheric pressure, the hydraulic pressure in the wheel cylinders40is quickly discharged to the reservoir30when the outlet valves222are opened.

On the other hand, the fourth outlet valve222dis opened to discharge the hydraulic pressure of the corresponding wheel cylinder40, and at the same time the first to third inlet valves221ato221care maintained in the open state so that the hydraulic pressure may be supplied to the remaining three wheels FR, RL and RR.

The flow rate discharged from the wheel cylinders40increases as the difference between the pressure in the wheel cylinders40and the pressure in the first pressure chamber112increases. For example, the greater the volume of the first pressure chamber112as the hydraulic piston114moves backward, the larger the flow rate may be discharged from the wheel cylinders40.

As such, by independently controlling the respective valves221a,221b,221c,221d,222a,222b,222c,222d,233,235,236and243, the hydraulic pressure may be selectively transmitted to or discharged from the wheel cylinders40of the wheels RL, RR, FL and FR according to the required pressure, and thus precise pressure control becomes possible.

Although the hydraulic pressure generating operation when the hydraulic piston114advances is exemplified as an example in the above embodiment, the present disclosure is not limited thereto. For example, the operation may be controlled so that the hydraulic pressure and the negative pressure may be generated in the first pressure chamber112and the second pressure chamber113, respectively, even when the hydraulic piston114retracts.

Next, a state in which the electronic brake system1according to an embodiment of the present disclosure is operated in an inspection mode will be described.

In a case where the electronic brake system1operates abnormally, the respective valves54,60,221a,221b,221c,221d,222a,222b,222c,222d,233,235,236and243are provided in an initial state of braking which is in a non-operating state, and the first and second cut valves261and262provided on the first and second backup passages251and252and the inlet valves221provided on an upstream side of the wheel cylinders40provided on the respective wheels RR, RL, FR and FL are opened, so that the hydraulic pressure is immediately transmitted to the wheel cylinders40.

At this time, the simulator valve54is provided in the closed state so that the hydraulic pressure transmitted to the wheel cylinders40through the first backup passage251is prevented from leaking to the reservoir30through the simulation apparatus50. Therefore, when a driver depresses the brake pedal10, the hydraulic pressure discharged from the master cylinder20is transmitted to the wheel cylinders40without loss, thereby ensuring stable braking.

However, when a leak occurs in the simulator valve54, a part 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, but in this case, the hydraulic pressure discharged from the master cylinder20pushes the reaction force piston52of the simulation apparatus50, so that leakage may occur in the simulator valve54by the pressure formed at the rear end of the simulation chamber51.

In this way, in a case where leakage occurs in the simulator valve54, the driver does not obtain the intended braking force, thereby causing a problem in braking stability.

The inspection mode is a mode for generating a hydraulic pressure in the hydraulic pressure supply apparatus100to inspect whether there is a loss of pressure in order to inspect whether leakage occurs in the simulator valve54. If the hydraulic pressure discharged from the hydraulic pressure supply apparatus100flows into the reservoir30and pressure loss occurs, it is difficult to know whether or not leakage has occurred in the simulator valve54.

Therefore, in the inspection mode, the hydraulic circuit connected to the hydraulic pressure supply apparatus100may be constituted as a closed circuit by closing the inspection valve60. That is, by closing the inspection valve60, the simulator valve54and the outlet valves222, the flow passages connecting the hydraulic pressure supply apparatus100and the reservoir30may be blocked to constitute a closed circuit.

The electronic brake system1according to an embodiment of the present disclosure may provide hydraulic pressure only to the first backup passage251to which the simulation apparatus50is connected among the first and second backup passages251and252in the inspection mode. Accordingly, in order to prevent the hydraulic pressure discharged from the hydraulic pressure supply apparatus100from being transmitted to the master cylinder20along the second backup passage252, the second cut valve262may be switched to the closed state in the inspection mode. In addition, by maintaining the fifth control valve235which connects the first hydraulic circuit201and the second hydraulic circuit202in the closed state and closing the sixth control valve236which communicates with the fifth hydraulic passage215and the second hydraulic passage212, the hydraulic pressure in the second pressure chamber113may be prevented from leaking to the first pressure chamber112.

In the inspection mode, in the initial state of the valves54,60,221a,2210,221c,221d,222a,222b,222c,222d,233,235,236and243included in the electronic brake system1of the present disclosure, the first to fourth inlet valves221ato221dand the second cut valve262are switched to the closed state, and the first cut valve261and the third control valve233are maintained in the open state, so that the hydraulic pressure generated in the hydraulic pressure supply apparatus100may be transmitted to the master cylinder20.

The hydraulic pressure of the hydraulic pressure supply apparatus100may be prevented from being transmitted to the first and second hydraulic circuits201and202by closing the inlet valves221, the hydraulic pressure of the hydraulic pressure supply apparatus100may be prevented from circulating along the first backup passage251and the second backup passage252by switching the second cut valve262to the closed state, and the hydraulic pressure supplied to the master cylinder20may be prevented from leaking to the reservoir30by switching the inspection valve60to the closed state.

In the inspection mode, after generating the hydraulic pressure in the hydraulic pressure supply apparatus100, the electronic control unit may analyze a signal transmitted from the backup passage pressure sensor PS2that measures the oil pressure in the master cylinder20and sense a state in which leakage occurs in the simulator valve54. For example, as a result of the measurement of the backup passage pressure sensor PS2, it may be determined that the simulator valve54is not leaking when there is no loss, and it may be determined that there is a leak in the simulator valve54when a loss occurs.

The inspection mode may be executed in a preset condition through the electronic control unit during running or stopping.

According to an embodiment of the present disclosure, when a leak occurs in the first hydraulic circuit201or the second hydraulic circuit202of the hydraulic control unit200, the electronic brake system may lose the braking ability due to exhaustion of the brake oil in the reservoir30.

In the present embodiment, in order to prevent such a situation, the first hydraulic passage pressure sensor PS1-1for sensing the oil leak of the first hydraulic circuit201, the second hydraulic passage pressure sensor PS1-2for sensing the oil leak of the second hydraulic circuit202, the motor control sensor MPS for controlling the rotation angle or current of the motor120, and the electronic control unit for controlling the above elements are used.

Hereinafter, the braking operation of the electronic brake system according to the present embodiment when oil leakage occurs in the hydraulic circuits will be described with reference toFIGS. 5 and 6.

In order to perform the braking operation due to leakage, a first step S1of sensing which of the first hydraulic circuit201and the second hydraulic circuit202has leaked, and a second step S2of closing valves of the hydraulic circuit that is determined to be abnormal (leak occurred) when oil leakage occurs and supplying a braking pressure (hydraulic pressure) to the wheel cylinders40using valves of the hydraulic circuit that is determined to be normal (leak no occurred) are provided.

The first step S1may be performed using the first hydraulic passage pressure sensor PS1-1or the second hydraulic passage pressure sensor PS1-2.

For example, the electronic control unit receives pressure information required at braking through the first hydraulic passage pressure sensor PS1-1or the second hydraulic passage pressure sensor PS1-2. If the received pressure is lower than a preset minimum pressure in the hydraulic circuit, it is determined to be leaking. Herein, since the motor must be in a driven state for braking, that is, the stroke must be generated when the pressure information is received from the sensor, the motor control sensor (MPS) is assumed to be in the ON state. If it is determined that both the first hydraulic passage pressure sensor PS1-1and the second hydraulic passage pressure sensor PS1-2do not leak, the electronic control unit calculates the above-described frictional braking amount to perform a normal braking operation.

If it is determined that the leakage of the brake oil occurs in either the first hydraulic circuit201or the second hydraulic circuit202and the hydraulic circuit is in an abnormal state, the electronic control unit executes the second step S2.

That is, as shown inFIG. 5, when leakage occurs in the first hydraulic circuit201, the electronic control unit switches the first and second inlet valves221aand221bof the corresponding first hydraulic circuit201where the leakage has occurred to the closed state, and maintains the first to fourth outlet valves222a,222b,222cand222din the closed state.

Accordingly, the hydraulic pressure generated by the operation of the hydraulic piston114of the hydraulic pressure supply apparatus100is transmitted to the wheel cylinders40disposed on the front left wheel FL and the rear right wheel RR through the third and fourth inlet valves221cand221din the open state of the second hydraulic circuit202so that the wheel cylinders40may be normally operated to generate the braking force.

During ABS braking, the third to fourth inlet valves221cand221dare switched to the closed state and the third and fourth outlet valves222cand222dare switched to the open state. In this case, the hydraulic pressure discharged from the wheel cylinders40provided on the front left wheel FL and the rear right wheel RR is discharged to the reservoir30through the third and fourth outlet valves222cand222d.

The reason why the hydraulic pressure in the wheel cylinders40is discharged through the outlet valves222is because the pressure in the reservoir30is smaller than the pressure in the wheel cylinders40. The pressure in the reservoir30is usually provided at atmospheric pressure. Since the pressure in the wheel cylinders40is usually significantly higher than the atmospheric pressure, the hydraulic pressure in the wheel cylinders40is quickly discharged to the reservoir30when the outlet valves222are opened.

According to the present embodiment, the inside of the reservoir30is separated into the first to third reservoir chambers31,32, and33as described above. That is, the first hydraulic circuit201is connected to the first reservoir chamber31, and the second hydraulic circuit202is connected to the third reservoir chamber33. The second reservoir chamber32is connected to the hydraulic pressure supply apparatus100.

Accordingly, since the oil dumped from the wheel cylinders40provided on the rear right wheel RR and the front left wheel FL of the second hydraulic circuit202during ABS braking is discharged to the third reservoir chamber33through the opened third and fourth outlet valves222cand222d, even if the flow rate of the first reservoir chamber31is lost due to the leak, the second hydraulic circuit202secures a sufficient amount of brake oil so that normal braking may be performed. Further, since some oil overflowed out of the dumped brake oil of the third reservoir chamber33may move to the second reservoir chamber32, the hydraulic pressure supply apparatus100connected to the second reservoir chamber32may also perform a normal braking operation.

Herein, the above embodiment exemplifies the case where only the inlet valves221aand221bof the first hydraulic circuit201operating in an abnormal state when a leak occurs are closed, and only the normally operating second hydraulic circuit202performs a braking operation, but the present disclosure is not limited thereto. For example, in a case where the four wheel cylinders40are provided with a plurality of sensors for sensing leakage, the electronic control unit may control the inlet valves selectively so that only one inlet valve provided in the corresponding wheel cylinder is closed and the inlet valves provided in the other three wheel cylinders are kept open to allow a normal braking operation.

As is apparent from the above, the electronic brake system and the control method thereof according to the embodiments of the present disclosure are configured to separate the reservoir chambers connected to the first hydraulic circuit and the second hydraulic circuit for controlling two of the four wheel cylinders, respectively, so that the braking performance can be maintained by using the other hydraulic circuit even if a leak occurs in any one of the two hydraulic circuits.

Further, the electronic brake system and the control method thereof according to the embodiments of the present disclosure are configured to separate the reservoir chamber connected to the master cylinder and the reservoir chamber connected to the hydraulic pressure supply apparatus so that the braking efficiency of the hydraulic pressure supply apparatus can be kept constant during the electronic control.