A wire brake system including a pressure-balanced PSU piston with a wet ball screw

Abstract

The present invention provides a wire-controlled braking system including a pressure-balanced PSU piston with a wet ball screw. The electro-hydraulic braking system includes a single-circuit master cylinder (MC) that is fluidly coupled to a first MC fluid passage and is configured to supply fluid into the first MC fluid passage in response to a pressing force on a brake pedal coupled to the single-circuit master cylinder. The electro-hydraulic braking system further includes a pressure supply unit (PSU) assembly that includes an electric motor coupled to a ball screw actuator, a PSU housing defining a piston bore having an end opposite to the electric motor, and a PSU piston that is disposed within the piston bore and is movable by the ball screw actuator through the piston bore and divides the piston bore into a first chamber and a second chamber each of which houses a hydraulic fluid. The ball screw actuator includes an actuator nut assembly having a plurality of ball bearings, each of the ball bearings being disposed within the piston bore and immersed in the hydraulic fluid.

Description

Technical Field

[0001] The present disclosure generally relates to a braking system for a vehicle such as an automobile. More specifically, the present disclosure relates to a brake-by-wire system having a pressure supply unit (PSU) with a pressure balancing piston. Background Art

[0002] As electric and hybrid vehicles continue to proliferate in the markets around the world, it is well known that a significant extension of battery life can be achieved by utilizing the motor-generator output capability of the device during braking. However, the input torque in the generator mode used to charge the battery does not match the driver input function of the pedal force / stroke for vehicle deceleration. To achieve this complex function, the hydraulic braking section of the vehicle must provide the difference between the generator braking torque and the braking torque required by the driver.

[0003] For many years, the engineering community has understood this requirement, commonly referred to as regenerative braking hybridization. The most effective way to achieve this is to use "brake-by-wire" technology. To achieve this, the brake pedal effectively becomes a joystick, so it must be connected to a stroke and / or force sensor to send a signal to the system ECU, which interprets this as the driver's intention for the vehicle to decelerate. In addition, the brake pedal "feel" must be simulated through an appropriate force-stroke relationship, and this brake pedal "feel" must also have the ability to be isolated from directly applying the master cylinder to the wheel brakes.

[0004] A brake-by-wire system generally includes a pressure supply unit (PSU) to provide a supply of pressurized fluid to actuate the wheel brakes. Summary of the Invention

[0005] The present invention provides an electro - hydraulic braking system. The electro - hydraulic braking system includes a single - circuit master cylinder (MC), the single - circuit MC is fluidly connected to a first MC fluid passageway, and is configured to supply fluid into the first MC fluid passageway in response to a pressing force on a brake pedal connected to the single - circuit master cylinder. The electro - hydraulic braking system further includes a pressure supply unit (PSU) assembly. The PSU assembly includes an electric motor connected to a ball - screw actuator, a PSU housing defining a piston bore having an end opposite to the electric motor, and a PSU piston. The PSU piston is disposed within the piston bore and is movable by the ball - screw actuator through the piston bore and divides the piston bore into a first chamber and a second chamber. Each of the first chamber and the second chamber contains a hydraulic fluid. The ball - screw actuator includes an actuator nut assembly having a plurality of ball bearings, and each of the plurality of ball bearings is disposed within the piston bore and immersed in the hydraulic fluid.

[0006] The present invention also provides a pressure supply unit (PSU) assembly for an electro - hydraulic braking system. The PSU assembly includes: an electric motor; a ball - screw actuator including a main shaft connected to the electric motor and configured to convert a rotational motion into a linear motion; a PSU housing connected to the electric motor and defining a piston bore having an end opposite to the electric motor; and a PSU piston disposed within the piston bore and translatable by the ball - screw actuator through the piston bore and dividing the piston bore into a first chamber and a second chamber. Each of the first chamber and the second chamber contains a hydraulic fluid. The ball - screw actuator includes an actuator nut assembly having a plurality of ball bearings, and each of the plurality of ball bearings is disposed within the second chamber of the piston bore and immersed in the hydraulic fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] More details, features, and advantages of the design of the present invention are derived from the following description of exemplary embodiments with reference to the associated drawings.

[0008] Figure 1 is a schematic block diagram of a brake - by - wire system in a vehicle;

[0009] Figure 2 shows a schematic diagram of the brake - by - wire system of the present disclosure;

[0010] Figure 3 shows a cross - sectional view of a pressure supply unit (PSU) according to an aspect of the present disclosure;

[0011] Figure 4A cross-sectional view of the PSU of the present disclosure with an alternative PSU for size reference is shown;

[0012] Figures 5A to 5C A cross-sectional view of three different PSUs according to aspects of the present disclosure is shown;

[0013] Figures 6A to 6C Perspective views of single-box by-wire braking devices are each shown, with each single-box by-wire braking device including Figures 5A to 5C a corresponding one of the three different PSUs shown in;

[0014] Figure 7 A cross-sectional view of a single-box by-wire braking device including the PSU of the present disclosure in a transverse motor configuration is shown;

[0015] Figure 8 A schematic diagram of a 10-valve by-wire control system with additional features according to aspects of the present disclosure is shown Figure 2 of;

[0016] Figure 9 A schematic diagram of an 11-valve by-wire control system according to aspects of the present disclosure is shown;

[0017] Figure 10 is a schematic diagram of a 12-valve by-wire control system according to aspects of the present disclosure;

[0018] Figure 11 A single-box by-wire braking device with an axial configuration is shown, where the PSU is axially aligned with the master cylinder;

[0019] Figure 12 A single-box by-wire braking device with a transverse motor configuration is shown;

[0020] Figure 13 A single-box by-wire braking device with a motor-up configuration is shown; and

[0021] Figure 14 A single-box by-wire braking device with a motor-down configuration is shown. DETAILED DESCRIPTION

[0022] The present invention will be described in detail in connection with the following embodiments with reference to the accompanying drawings.

[0023] Figure 1A schematic block diagram of a brake-by-wire (BbW) system 10 in a vehicle, such as an automobile, is shown, and the BbW system 10 includes a plurality of wheel brakes 22a, 22b, 22c, 22d, each having a corresponding actuator, such as a hydraulic cylinder. The basic brake-by-wire (BBW) architecture is now widely used in the automotive industry. The master cylinder 30 of the vehicle directly applies one or more of the wheel brakes 22a, 22b, 22c, 22d in a failed system fallback mode, or is isolated from the wheel brakes 22a, 22b, 22c, 22d and connected to a pedal feel emulator (PFE) 39 that replicates the force, travel, and damping of a conventional braking system. The brake pedal travel and / or force and / or brake pressure are used by the system 10 as input signals to a brake electronic control unit (ECU) 90. It in turn sends appropriate signals to a pressure supply unit (PSU) assembly 40. The PSU assembly 40 may include a high-efficiency brushless motor and a ball screw assembly that displaces one or more PSU pistons, which may be considered an electric master cylinder. The master cylinder 30 and / or the PSU assembly 40 may be coupled to the wheel brakes 22a, 22b, 22c, 22d via a series of control valves 15, which may include an apply valve and a release valve (not shown) for each of the wheel brakes 22a, 22b, 22c, 22d to provide functions such as anti-lock braking (ABS), electronic traction control, and the like.

[0024] The brake pedal input defines the driver's intent, which determines the speed and force with which the brakes are applied, with the aim of replicating the feel of a conventional vacuum-assisted braking system. The brake ECU 90 may also send signals to a drive control unit (DCU) 18, which may also be referred to as a powertrain control module (PCM) 18, to decelerate the vehicle using one or more electric motors in a regenerative mode.

[0025] Figure 2 A schematic view of a BbW system 20 for controlling the operation of a plurality of wheel brakes 22a, 22b, 22c, 22d in a vehicle is shown. Each of the wheel brakes 22a, 22b, 22c, 22d may include a corresponding one of the brake actuators 13. The wheel brakes 22a, 22b, 22c, 22d may also be referred to as base brakes to distinguish them from other braking systems, such as electric regenerative braking.

[0026] The BbW system 20 includes a fluid storage portion 24 that holds hydraulic fluid and supplies the hydraulic fluid to a single-circuit master cylinder 30 having a single-circuit configuration, and the single-circuit master cylinder 30 may be referred to as the master cylinder (MC) 30. A fluid level sensor 25 (such as a float switch) monitors the level of the hydraulic fluid in the fluid storage portion 24. The brake pedal 36 is coupled to press a brake linkage 38, which in turn actuates the master cylinder (MC) 30 to pump fluid from an inlet fluid passage 32 through the master cylinder (MC) 30 and pressurize the master cylinder (MC) fluid passage 34. A stroke sensor 37 monitors the position of the brake pedal 36. A first pressure sensor 33 monitors the pressure in the MC fluid passage 34.

[0027] The PFE 39 is fluidly coupled to the MC fluid passage 34 to selectively provide a natural feel of braking operation, particularly when the master cylinder 30 is separated from the operating wheel brakes 22a, 22b, 22c, 22d. The PFE 39 includes a PFE piston that divides the PFE 39 into an upper chamber and a lower chamber, and a spring that biases the PFE piston into the upper chamber. The upper chamber of the PFE 39 is fluidly coupled to the MC fluid passage 34.

[0028] The PSU assembly 40 includes an electric motor 42 and a PSU pump 44 to supply hydraulic fluid from the fluid storage portion 24 to a PSU fluid passage 50. The PSU assembly 40 can draw fluid from a return fluid passage 52 that is connected to the fluid storage portion 24 and maintained at or near ambient atmospheric pressure. A second pressure sensor 51 monitors the pressure in the PSU fluid passage 50. A rotor angle sensor 43 may be coupled to the electric motor 42 to determine the position of the rotor in the motor and thus the position of the PSU pump 44. The PSU pump 44 includes a PSU piston 45 that separates a first chamber 46 from a second chamber 48. The PSU pump 44 includes an electric motor 42 coupled to a ball screw actuator 118 that converts rotational motion into linear motion to move the PSU piston 45.

[0029] The first chamber 46 of the PSU assembly 40 is directly connected to the PSU fluid passage 50. In response to the PSU piston 45 moving away from the electric motor 42, fluid is forced out of the first chamber 46 and into the PSU fluid passage 50. The second chamber 48 of the PSU assembly 40 is directly connected to a supplementary fluid passage 54. A first check valve 56 allows fluid to flow from the return fluid passage 52 into the supplementary fluid passage 54 while preventing fluid from flowing in the opposite direction. A second check valve 58, also referred to as the PSU supplementary check valve (PRCV), allows fluid to flow from the supplementary fluid passage 54 into the PSU fluid passage 50 while preventing fluid from flowing in the opposite direction.

[0030] A PSU storage isolation valve (PRIV) 62, which can be a normally closed solenoid valve, selectively controls the fluid flow between the return fluid passage 52 and the intermediate fluid passage 64. A third check valve 66 is connected between the intermediate fluid passage 64 and the supplementary fluid passage 54 and is configured to allow fluid from the supplementary fluid passage 54 to flow into the intermediate fluid passage 64 while preventing fluid from flowing in the opposite direction.

[0031] A displacement fluid passage 68 is connected to the lower chamber of the PFE 39 for transmitting fluid from the lower chamber in response to movement of the PFE piston due to the application of the brake pedal 36. A fourth check valve 69 is connected between the displacement fluid passage 68 and the inlet fluid passage 32 and is configured to allow fluid to flow from the inlet fluid passage 32 into the displacement fluid passage 68 while preventing fluid from flowing in the opposite direction. A fifth check valve 70 is connected between the displacement fluid passage 68 and the intermediate fluid passage 64 and is configured to allow fluid from the displacement fluid passage 68 to flow into the intermediate fluid passage 64 while preventing fluid from flowing in the opposite direction.

[0032] A master cylinder isolation valve (MCIV) 72, which can be a normally open solenoid valve, selectively controls the fluid flow between the MC fluid passage 34 and the PSU fluid passage 50. The PSU fluid passage 50 divides the fluid supply into a first brake circuit 74 and a second brake circuit 76.

[0033] A control valve manifold 78 fluidly connects the two brake circuits 74, 76 to the corresponding wheel brakes 22a, 22b, 22c, 22d. The control valve manifold 78 includes an application valve 80a and a release valve 80b corresponding to each of the wheel brakes 22a, 22b, 22c, 22d to selectively control the fluid flow between a corresponding one of the wheel brakes 22a, 22b, 22c, 22d and one of the two brake circuits 74, 76 associated with the brake circuit. The application valve 80a and the release valve 68b can be collectively referred to as an anti-lock braking system (ABS) valve for use in such an ABS. However, the application valve 80a and the release valve 80b can be used for other functions, such as for traction control and / or for torque vector control.

[0034] In some embodiments, and as Figure 2As shown, a two-way check valve 82 is provided in each of the two brake circuits 74, 76 between the PSU fluid passage 50 and the control valve manifold 78. The two-way check valve 82 allows fluid to flow in either direction, but only when the pressure difference across the two-way check valve 82 is higher than a certain threshold. The two-way check valve 82 can limit the amount of fluid lost in the case of a system leak, such as a leak in the brake line supplying any one of the wheel brakes 22a, 22b, 22c, 22d.

[0035] When the driver applies the brake, the MCIV 72 closes and the PRIV 62 opens. Fluid from the master cylinder 30 is directed to the PFE 39 to simulate normal brake pedal force and travel. This same travel information can be sent to the electronic control unit (ECU) 90, which then applies an appropriate current to the PSU motor 42 to rotate the ball screw and mechanically displace the PSU piston 45. This causes fluid to travel through the double check valve 82, through the ABS application valve 80a, and ultimately to the wheel brakes 22a, 22b, 22c, 22d to apply pressure and decelerate the vehicle.

[0036] Figure 3 A cross-sectional view of the PSU assembly 40 of the present disclosure is shown. The PSU assembly 40 includes an electric motor 42 configured to operate a PSU pump 44 to discharge brake fluid into the PSU fluid passage 50.

[0037] The PSU assembly 40 includes a PSU housing 100 that defines a piston bore 102. The PSU housing 100 also defines a rear chamber 104 that houses the electric motor 42. A separator 106 separates the piston bore 102 from the rear chamber 104. The separator 106 allows the rear chamber 104 to remain dry while the piston bore 102 houses the brake fluid. The electric motor 42 includes a motor shaft 110 coupled to a rotor 112, and the rotor 112 is acted upon by a current in the stator 114. Shaft bearings 116 can support the motor shaft 110 on either side of the rotor 112.

[0038] The PSU pump 44 includes a PSU piston 45 that is pushed and / or pulled by a ball screw actuator 118, which converts rotational motion into linear motion to move the PSU piston 45. The ball screw actuator 118 includes a main shaft 122 and actuator nut assemblies 120, 124. The actuator nut assemblies 120, 124 include a nut 120 and a plurality of ball bearings 124 disposed between the main shaft 122 and the actuator nut 120. The actuator nut 120 is attached to the PSU piston 45. The electric motor 42 is configured to rotate the main shaft 122, which is threaded and configured to move the actuator nut 120 in a linear path, thereby causing the PSU piston 45 to translate in either direction towards or away from the electric motor 42 through the piston bore 102. Thus, the ball screw actuator causes the PSU piston 45 to linearly translate through the piston bore 102 in response to the electric motor 42 rotating the main shaft 122. The actuator nut 120 and the plurality of ball bearings 124 are each disposed within the piston bore 102 and submerged in hydraulic fluid.

[0039] In some embodiments, and as Figure 3 shown, the PSU piston 45 has a cup shape, and the actuator nut 120 and the plurality of ball bearings 124 are each disposed within the cup shape of the PSU piston.

[0040] In some embodiments, and as Figure 3 shown, the actuator nut 120 and the plurality of ball bearings 124 are each disposed within the second chamber 48. However, the PSU assembly 40 may have a different configuration, such as the actuator nut 120 and the plurality of ball bearings 124 being located within the first chamber 46.

[0041] In some embodiments, one or more ball bearings 124 may be disposed between the main shaft 122 and the actuator nut 120 to provide a ball-screw interface. A gear set 126, which may include one or more planetary reduction gears, mechanically couples the motor shaft 110 of the electric motor 42 to the main shaft 122, thereby reducing speed and increasing the torque applied to the main shaft 122. The gear set 126 is driven by the electric motor 42 and is configured to drive the main shaft 122 at a speed slower than the speed of the motor shaft 110 of the electric motor 42.

[0042] A ring seal 128 is disposed between the main shaft 122 and the separator 106 to provide a fluid seal between the piston bore 102 and the rear chamber 104 while allowing the main shaft 122 to rotate. The ring seal 128 may include a lip seal. However, many types of seals may be used. It should be noted that this enables fluid to be trapped at the rear side of the PSU piston 45, exposing the rear side of the piston seal 140 to the braking pressure from the supplementary fluid passage 54 and balancing the braking pressure from the PSU passage 50 that is exposed to the front side of the piston seal 140, thereby creating pressure balance.

[0043] The PSU piston 45 is disposed within the piston bore 102 and is configured to linearly move through the piston bore 102 in response to being pushed and / or pulled by the actuator nut 120. The piston bore 102 extends between the separator 106 and the end 130. The piston bore 102 defines a first chamber 46 that extends from the PSU piston 45 to the end 130. The piston bore 102 also defines a second chamber 48 that extends from the separator 106 to the PSU piston 45. The first PSU port 132 provides fluid communication between the first chamber 46 and the external fluid circuit. The first PSU port 132 may be fluidly coupled to the PSU fluid passage 50 for supplying fluid to the PSU fluid passage 50. The second PSU port 134 provides fluid communication between the second chamber 48 and the external fluid circuit. The second PSU port 134 may be fluidly coupled to the supplementary fluid passage 54 to convey fluid between the second chamber 48 and the supplementary fluid passage 54.

[0044] In some embodiments, and as Figure 3 shown, the PSU piston 45 includes a piston seal 140, such as a lip seal, that prevents fluid leakage through the PSU piston 45 between the first chamber 46 and the second chamber 48. In some embodiments, and also as Figure 3 shown, the PSU piston 45 includes a first anti-rotation structure 142, such as one or more protrusions that engage corresponding second anti-rotation structures 144 in the piston bore 102. For example, the second anti-rotation structure 144 may include one or more linear grooves or keyways configured to receive the corresponding first anti-rotation structure 142. The anti-rotation structures 142, 144 may together prevent the PSU piston 45 from rotating while allowing the PSU piston 45 to linearly translate through the piston bore 102.

[0045] According to one aspect of the present disclosure, the PSU assembly 40 includes a second chamber 48 for the spindle seal that uses a ball screw. This results in three significant design changes compared to other designs that use an actuator rod to move the PSU piston 45. The first is that the overall length of the PSU assembly 40 is significantly reduced to be nearly the same length as a standard drive system (i.e., a PSU 16 that has fluid on only one side of the piston). The second is that the ball screw is now immersed in the brake fluid. And the third is that any need for area balancing on the PSU piston 45 is eliminated because there is no actuator rod causing area imbalance. Figure 4 A cross-sectional view of the PSU assembly 40 of the present disclosure with an alternative PSU is shown, the alternative PSU including an actuator rod for moving the PSU piston 45, for dimensional reference.

[0046] Figures 5A to 5C Cross-sectional views of three different PSUs are shown. Figure 5A A first PSU assembly 150 with a double-acting configuration is shown, which includes a pressure-balanced design with fluid on both sides of the piston and has an actuator rod that couples a ball screw type linear actuator to the piston. Figure 5B A second PSU assembly 152 according to the present disclosure is shown. The second PSU assembly 152 may be similar or identical to the PSU assembly 40 of the present disclosure, but has a lip seal instead of the ring seal 128. Figure 5C A third PSU assembly 154 with a conventional design is shown, where there is fluid on only one side of the piston.

[0047] Figure 6A A first single-box line control brake device 160 including Figure 5A the first PSU assembly 150 is shown. The first single-box line control brake device 160 includes a first hydraulic control unit (HCU) body 170, the first HCU body 170 having a first top surface 171 opposite to the electric motor 42, where the first PSU assembly 150 extends along the side of the first HCU body 170 and substantially exceeds the first top surface 171 and is above the first top surface 171. Figure 6B A second single-box line control brake device 162 including Figure 5B the second PSU assembly 152 is shown. The second single-box line control brake device 162 includes a second hydraulic control unit (HCU) body 172, the second HCU body 172 having a second top surface 173 opposite to the electric motor 42, where the second PSU assembly 152 extends along the side of the second HCU body 172 and slightly protrudes beyond the second top surface 173 and is above the second top surface 173, but the extent of the extension is less than the extent to which the first PSU assembly 150 extends above the first top surface 171 of the first PSU assembly 150. Figure 6C A second single-box line control brake device 162 includingFigure 5C The third single - box line control brake device 164 of the third PSU assembly 154. The third single - box line control brake device 164 includes a third HCU body 174 having a third top surface 175 opposite to the electric motor 42, wherein the third PSU assembly 155 extends along the side of the third HCU body 174 and ends flush with the third top surface 175. Figure 5A and Figure 5B The differences between the PSUs shown illustrate examples of size and mass savings, which may be due to eliminating a separate actuator and filling the ball screw with brake fluid instead of being dry.

[0048] Figure 7 A cross - sectional view of the fourth single - box line control brake device 166 is shown. It still maintains the pressure - balanced PSU piston 45. The rear side of the piston seal 140 is exposed to the brake pressure from the supplementary fluid channel 54, while the front side of the piston seal 140 is exposed to the pressure from the PSU channel 50, thus achieving pressure balance. The fourth PSU assembly 156 is shown in a transverse motor configuration, where the motor 42 is oriented such that the motor shaft is horizontal and transverse to the master cylinder bore (not shown) in the fourth HCU body 176. The fourth PSU assembly 156 may have a configuration similar or identical to Figure 5B the second PSU assembly 152. The fourth single - box line control brake device 166 with a transverse motor configuration can save space and eliminate expensive motor - to - ECU connectors. This design may include a standard brushless motor driving a planetary gear train to minimize the total cost, maximize the motor efficiency, and minimize the motor current consumption. The reduced motor current consumption can provide additional cost savings in the electronics used to power the motor. This unique combination of designs: a pressure - balanced PSU piston with a rotary lip seal on the main shaft and a transverse motor layout with an integrated planetary gear set makes this a truly unique design combination.

[0049] Figure 8 A schematic diagram of a 10 - valve line control brake system having additional features in accordance with aspects of the present disclosure is shown. Figure 2 of Figure 8 Includes a single - box 10 - valve BbW device 220 as an integrated component. The 10 - valve system is so named because it includes ten actuating valves, including PRIV 62, MCIV 72 plus eight solenoid valves in the control valve manifold 78. Figure 8Also shown is a ten-valve BbW device 220 including an electronic control unit (ECU) 90 having electrical connections for monitoring various sensors and for controlling various actuators such as the electric motor 42 of the PSU assembly 40 and solenoid valves. The ECU 90 is also connected via a communication network such as a controller area network (CAN bus) to one or more external controllers 92 of the vehicle. The ECU 90 is further configured to control the actuation and / or other functions of one or more electric parking brake actuators EPB. The ECU 90 is also configured to receive a parking brake command from a parking brake switch 93 via the communication network. Alternatively or additionally, the parking brake switch 93 may be hardwired to the ECU 90.

[0050] Figure 8 The design of the ten valves shown in includes the PSU assembly 40 and the master cylinder 30. When in the by-wire braking mode and the driver depresses the brake pedal, the MCIV 72 closes and the PRIV 62 opens. Fluid is directed from the master cylinder 30 to the PFE 39 to simulate normal brake pedal force and travel. This same travel information is sent to the ECU 90, which then applies an appropriate current to the PSU motor to rotate the ball screw and mechanically displace the PSU piston 45. This causes fluid to travel through the double check valve 82, through the ABS application valve 80a, and ultimately to the wheel brakes to apply pressure and decelerate the vehicle.

[0051] Since this is an "open" system, meaning that fluid released from the wheel brakes in the ABS stopper is not captured but flows back to the reservoir at atmospheric pressure, it is necessary to replenish the PSU. This is achieved by first closing the PRIV 62 that captures the pressure behind the PSU piston 45. The ball screw and the PSU piston 45 retract. This forces the fluid behind the PSU piston 45 to flow to the front of the PSU piston 45 via the second check valve 58. The pressure on both sides of the PSU piston 45 is maintained during replenishment because both sides of the PSU piston 45 displace equal volumes as the PSU piston 45 travels.

[0052] Figure 9 A schematic diagram of an eleven-valve by-wire braking system according to aspects of the present disclosure is shown. The eleven-valve by-wire braking system may be similar or identical to the Figure 8 ten-valve system of , with some changes discussed herein. The eleven-valve by-wire braking system includes a PFE isolation valve (PFIV) 212, which may be a normally open solenoid valve that selectively couples an intermediate fluid passage 64 with a replacement fluid passage 68. The eleven-valve by-wire braking system also does not include several check valves present in the Figure 8 ten-valve system of , such as a third check valve 66, a fourth check valve 69, and a fifth check valve 70.

[0053] Figure 9 Includes the single - box 11 - valve BbW device 320 as an integrated component. The 11 - valve system is so named because it includes eleven actuation valves, which include the PRIV 62, MCIV 72, PFIV 212, plus eight solenoid valves in the control valve manifold 78.

[0054] Figure 9 The design of the 11 - valve shown includes the PSU assembly 40 and the master cylinder 30. When in the by - wire braking mode and the driver presses the brake pedal, the MCIV 72 closes and the PRIV 62 opens. Fluid from the master cylinder 30 is directed to the PFE 39 to simulate normal brake pedal force and travel. This same travel information is sent to the ECU 90, which then applies the appropriate current to the PSU motor 42 to rotate the ball screw and mechanically displace the PSU piston 45. This causes fluid to travel through the double check valve 82, through the ABS application valve 80a, and ultimately to the wheel brakes to apply pressure and decelerate the vehicle.

[0055] Since this is an "open" system, meaning that the fluid released from the wheel brakes in the ABS stopper is not captured but flows back to the reservoir at atmospheric pressure, it is necessary to replenish the PSU. This is achieved by first closing the PRIV 62 and PFIV 212, and the PFIV 212 captures the pressure behind the piston. (The PFIV 212 eliminates four check valves and facilitates servicing, bleeding the brakes). The ball screw and the PSU piston 45 retract. This forces the fluid behind the PSU piston 45 to flow to the front of the PSU piston 45 via the second check valve 58. The pressure on both sides of the PSU piston 45 is maintained during replenishment because both sides of the PSU piston 45 displace equal volumes as the PSU piston 45 travels.

[0056] Figure 10 Shows a schematic diagram of a 12 - valve by - wire braking system according to aspects of the present disclosure. The 12 - valve by - wire braking system can be similar or identical to Figure 9 the 11 - valve system discussed herein with some changes. The 12 - valve by - wire braking system includes a brake circuit isolation valve (BCIV) 312, which can be a normally - open solenoid valve that selectively couples the PSU fluid passage 50 and the second brake circuit 76.

[0057] Figure 10 Includes the single - box 12 - valve BbW device 420 as an integrated component. The 12 - valve system is so named because it includes twelve actuation valves, which include the PRIV 62, MCIV 72, PFIV 212, brake circuit isolation valve 312, plus eight solenoid valves in the control valve manifold 78.Figure 10 The single - cartridge 12 - valve BbW device 420 also includes a brake circuit balance orifice (BCBO) 314, which is configured to restrict fluid flow to only two of the wheel brakes 22a, 22b, 22c, 22d through the first brake circuit 74. The BCBO 314 is connected in series with the supply - side check valve of the dual check valve 82 to regulate the fluid flow from the PSU fluid passage 50 to the corresponding wheel brakes 22a, 22b, 22c, 22d.

[0058] Figure 10 The design of the 12 - valve shown includes a PSU assembly 40 and a master cylinder 30. When in the by - wire braking mode and the driver depresses the brake pedal, the MCIV 72 closes and the PRIV 62 opens. Fluid from the master cylinder 30 is directed to the PFE 39 to simulate normal brake pedal force and travel. This same travel information is sent to the ECU 90, which then applies an appropriate current to the PSU motor 42 to rotate the ball screw and mechanically displace the PSU piston. This causes fluid to travel through the BCIV 312, BCBO 314, dual check valve 82, through the ABS application valve 80a, and ultimately to the wheel brakes 22a, 22b, 22c, 22d to apply pressure and decelerate the vehicle. The BCBO 314 can equalize the flow between two diagonal circuits in a diagonal split system.

[0059] Since this is an “open” system, meaning that the fluid released from the wheel brakes 22a, 22b, 22c, 22d in the ABS stopper is not captured but flows back to the fluid reservoir 24 at atmospheric pressure, it is necessary to replenish the PSU assembly 40. This is achieved by first closing the PRIV 62 and the PFIV 212 that captures the pressure behind the PSU piston 45. (The PFIV 212 eliminates four check valves and facilitates servicing and bleeding of the brakes). The ball screw and the PSU piston 45 retract. This forces the fluid behind the PSU piston 45 to flow via the second check valve 58 to the front of the PSU piston 45. The pressure on both sides of the PSU piston 45 is maintained during replenishment because both sides of the PSU piston 45 displace equal volumes as the PSU piston 45 travels.

[0060] Figure 11 Shown is a fifth single - cartridge by - wire braking device 165 with an axial configuration, where the electric motor 42 and the piston bore 102 of the PSU assembly 40 are axially aligned with the master cylinder 30, and the fifth HCU 178 is located beside the axial arrangement of the PSU and the master cylinder 30. Figure 12 Shown in the assembled state of Figure 7The fourth single - box line - controlled braking device 166, where the fluid storage part 24 is attached to the top, and the ECU 90 is attached to the side of the fourth HCU body 176 opposite to the electric motor 42. Figure 13 The sixth single - box line - controlled braking device 168 with a motor - above configuration is shown. Figure 14 Shown is Figure 6C The third single - box line - controlled braking device 164 of, which has a motor - below configuration and is in an assembled state, where the fluid storage part 24 is attached to the top and the ECU 90 is attached to the side of the third HCU body 174 opposite to the electric motor 42.

[0061] As Figure 14 As shown, the third single - box line - controlled braking device 164 includes a fluid storage part 24 mounted on the top surface of the third HCU body 174, and the electric motor 42 of the PSU assembly 40 is mounted to the bottom surface of the third HCU body 174, opposite to the fluid storage part 24. Moreover, the third PSU assembly 154 including the PSU housing 100 that defines the piston hole 102 does not extend beyond the top surface of the third HCU body 174.

[0062] The single - box BbW devices 220, 320, 420 of the present disclosure can be packaged in any configuration. For example, any one of the single - box BbW devices 220, 320, 420 can have an axial configuration, where the PSU assembly 40 is axially aligned with the master cylinder 30, as Figure 11 shown. Additionally or alternatively, any one of the single - box BbW devices 220, 320, 420 can have a lateral motor configuration, where the electric motor 42 has a motor shaft that extends horizontally and laterally to the master cylinder 30, as Figure 12 shown. Additionally or alternatively, any one of the single - box BbW devices 220, 320, 420 can have a motor - above configuration, where the electric motor 42 is located above the master cylinder 30, as Figure 13 shown. Additionally or alternatively, any one of the single - box BbW devices 220, 320, 420 can have a motor - below configuration as Figure 14 shown.

[0063] According to one aspect of the present disclosure, a first braking system for a motor vehicle is provided. The first braking system can include the 10 - valve line - controlled braking system of the present disclosure. The first braking system can be actuated electrically by a vehicle driver in a normal line - controlled braking operation mode. The first braking system can also be operated by the same driver in at least one reverse operation mode, where in at least one reverse operation mode, one or more of the wheel brakes 22a, 22b, 22c, 22d can be directly operated in response to the application of the brake pedal 36 and without any power.

[0064] According to one aspect of the present disclosure, a first braking system may include: a brake pedal for actuating a master brake cylinder, the master brake cylinder having a housing and a single piston and defining a single pressure chamber, the single pressure chamber being subsequently connected to wheel brakes 22a, 22b, 22c, 22d, wherein when a vehicle driver actuates the braking system, the actuating force applied by the brake pedal is applied to the single piston, and when the brake pedal is not actuated, the piston is positioned in the starting position by a return spring;

[0065] According to one aspect of the present disclosure, the first braking system may further include: a pressure medium storage for the pressure medium, the pressure medium storage being exposed to atmospheric pressure and having a storage chamber associated with the pressure chamber.

[0066] According to one aspect of the present disclosure, the first braking system may further include: a stroke detection device that detects the actuation stroke of the brake pedal or at least the piston connected to the brake pedal; a pedal feel simulator that transmits a desired tactile brake pedal feel to the vehicle driver in an on-line control braking mode, the pedal feel simulator being directly hydraulically connected to the master cylinder pressure chamber.

[0067] According to one aspect of the present disclosure, the first braking system may further include: an electronically controlled pressure supply unit that delivers the braking system pressure and consists of a floating piston, the floating piston being sealed to a main housing bore and including at least one anti-rotation feature that is connected to at least one groove in the main housing bore, which prevents the piston from rotating but allows the piston to translate.

[0068] According to one aspect of the present disclosure, the first braking system may further include: the pressure supply unit piston is displaced at one end by a ball screw nut of an independent actuation of a ball screw assembly, while the ball screw spindle of the ball screw assembly is permanently attached to the inner ring of a ball bearing assembly, the outer ring of the ball bearing assembly is permanently attached to a stepped bore in the main housing, and the inner ring of the ball bearing assembly allows the ball screw spindle to rotate but prevents the ball screw spindle from translating.

[0069] According to one aspect of the present disclosure, the first braking system may further include: the ball screw assembly spindle is also sealed to the main housing in a corresponding bore containing a radial lip seal, thereby allowing brake fluid to enter the ball screw assembly nut and balls, but preventing brake fluid from entering the area containing the bearing inner ring.

[0070] According to one aspect of the present disclosure, the first braking system may further include: the inner ring of the ball bearing includes at least one pin, and the planetary gears of the planetary gear set assembly are rotatably attached to the at least one pin. The outer annular gear of the planetary gear set assembly is permanently attached to the stepped hole of the main hole, and the sun gear of the planetary gear set assembly is permanently attached to the output shaft of the electric motor. The motor may be a brushless motor.

[0071] According to one aspect of the present invention, the first braking system may further include: a normally open valve for isolating the master cylinder from the brake circuit located between the outlet port of the master cylinder and the wheel brake part.

[0072] According to one aspect of the present disclosure, the first braking system may further include: a normally closed valve for isolating the motor side of the electronically controlled pressure source from the storage part.

[0073] According to one aspect of the present disclosure, the first braking system may further include: a series of check valves that allow flow from the pedal feel simulator to the normally closed valve above but prevent flow in the opposite direction.

[0074] According to one aspect of the present disclosure, the first braking system may further include: a forward flow check valve and a reverse flow check valve, which are parallel to each other and located between the pressure supply unit and two of the wheel brake parts in the wheel brake part, wherein the second forward flow check valve and the second reverse flow check valve are parallel to each other and located between the pressure supply unit and the remaining pair of wheel brake parts.

[0075] According to one aspect of the present disclosure, the first braking system may further include: an inlet valve and an outlet valve for each wheel brake part for setting the individual wheel braking pressure derived from a signal generated by the electronic control unit. The inlet valve transfers fluid to the wheel brake part in the unactivated state and restricts or prevents the accumulation of wheel pressure in the activated state, and the outlet valve prevents the pressure medium from flowing out of the wheel brake part to the storage part in the unactivated state and allows and controls the outflow in the activated state. The inlet valve closes, thereby reducing the wheel braking pressure.

[0076] According to one aspect of the present disclosure, a second braking system for a motor vehicle is provided. The second braking system may include the 11-valve-by-wire control braking system of the present disclosure. The second braking system can be actuated by an electric actuation by a vehicle driver in a normal valve-by-wire braking operation mode. The second braking system can also be operated by the same driver in at least one reverse operation mode, wherein one or more of the wheel brake parts 22a, 22b, 22c, 22d can be directly operated in response to the application of the brake pedal 36 and without any power.

[0077] According to one aspect of the present disclosure, the second braking system may include: a brake pedal for actuating a master brake cylinder, the master brake cylinder having a housing and a single piston and defining a single pressure chamber, the single pressure chamber subsequently being connected to wheel brakes, wherein when a vehicle driver actuates the braking system, the actuating force applied by the brake pedal is applied to the single piston, and when the brake pedal is not actuated, the piston is positioned at a starting position by a return spring.

[0078] According to one aspect of the present disclosure, the second braking system may further include: a pressure medium storage for the pressure medium, the pressure medium storage being exposed to atmospheric pressure and having a storage chamber associated with the pressure chamber.

[0079] According to one aspect of the present disclosure, the second braking system may further include: a stroke detection device that detects the actuation stroke of the brake pedal or at least the piston connected to the brake pedal.

[0080] According to one aspect of the present disclosure, the second braking system may further include: a pedal feel simulator that transmits a desired tactile brake pedal feel to the vehicle driver in an on-line control braking mode, the pedal feel simulator being directly hydraulically connected to the master cylinder pressure chamber.

[0081] According to one aspect of the present disclosure, the second braking system may further include: an electronically controlled pressure supply unit that delivers braking system pressure and consists of a floating piston, the floating piston being sealed to a main housing bore and including at least one anti-rotation feature, the at least one anti-rotation feature being connected to at least one groove in the main housing bore, which prevents the piston from rotating but allows the piston to translate.

[0082] According to one aspect of the present disclosure, the second braking system may further include: the pressure supply unit piston is displaced at one end by a ball screw nut of an independent actuation of a ball screw assembly, while the ball screw spindle of the ball screw assembly is permanently attached to the inner ring of a ball bearing assembly, the outer ring of the ball bearing assembly is permanently attached to a stepped bore in the main housing, and the inner ring of the ball bearing assembly allows the ball screw spindle to rotate but prevents the ball screw spindle from translating.

[0083] According to one aspect of the present disclosure, the second braking system may further include: the ball screw assembly spindle is also sealed to the main housing in a corresponding bore containing a radial lip seal, thereby allowing brake fluid to enter the ball screw assembly nut and balls, but preventing brake fluid from entering the area containing the bearing inner ring.

[0084] According to one aspect of the present disclosure, the second braking system may further include: the inner ring of the ball bearing includes at least one pin, the planet gears of the planetary gear set assembly are rotatably attached to the at least one pin, the outer ring gear of the planetary gear set assembly is permanently attached to the stepped hole of the main hole, and the sun gear of the planetary gear set assembly is permanently attached to the output shaft of the electric motor. The motor may be a brushless motor.

[0085] According to one aspect of the present invention, the second braking system may further include: a normally open valve for isolating the master cylinder from the brake circuit located between the outlet port of the master cylinder and the wheel brake unit.

[0086] According to one aspect of the present disclosure, the second braking system may further include: a normally closed valve for isolating the motor side of the electronically controlled pressure source from the storage unit.

[0087] According to one aspect of the present disclosure, the second braking system may further include: a normally open valve for isolating the pedal feel simulator from the pressure supply unit during the regeneration cycle.

[0088] According to one aspect of the present disclosure, the second braking system may further include: a forward flow check valve and a reverse flow check valve, the forward flow check valve and the reverse flow check valve are parallel to each other and are located between two of the wheel brake units of the pressure supply unit and the wheel brake unit, wherein the second forward flow check valve and the second reverse flow check valve are parallel to each other and are located between the pressure supply unit and the remaining pair of wheel brake units.

[0089] According to one aspect of the present disclosure, the second braking system may further include: an inlet valve and an outlet valve for each wheel brake unit for setting the individual wheel braking pressure derived from the signal generated by the electronic control unit, wherein the inlet valve transfers fluid to the wheel brake unit in the unactivated state and restricts or prevents the accumulation of wheel pressure in the activated state, and the outlet valve prevents the pressure medium from flowing out of the wheel brake unit to the storage unit in the unactivated state and allows and controls the outflow in the activated state, and the inlet valve is closed so as to reduce the wheel braking pressure.

[0090] According to one aspect of the present disclosure, a third braking system for a motor vehicle is provided. The third braking system may include the 12-valve-by-wire braking system of the present disclosure. The third braking system may be actuated by electroactuation by a vehicle driver in a normal valve-by-wire braking operation mode. The third braking system may also be operated by the same driver in at least one fallback operation mode, in which the braking system can only be operated by the vehicle driver.

[0091] According to one aspect of the present disclosure, a third braking system may include: a brake pedal for actuating a master brake cylinder, the master brake cylinder having a housing and a single piston and defining a single pressure chamber, the single pressure chamber being subsequently connected to wheel brakes, wherein when a vehicle driver actuates the braking system, the actuating force applied by the brake pedal is applied to the single piston, and when the brake pedal is not actuated, the piston is positioned in the starting position by a return spring.

[0092] According to one aspect of the present disclosure, the third braking system may further include: a pressure medium reservoir for the pressure medium, the pressure medium reservoir being exposed to atmospheric pressure and having a reservoir chamber associated with the pressure chamber.

[0093] According to one aspect of the present disclosure, the third braking system may further include: a travel detection device that detects the actuation travel of the brake pedal or at least the piston connected to the brake pedal.

[0094] According to one aspect of the present disclosure, the third braking system may further include: a pedal feel simulator that conveys a desired tactile brake pedal feel to the vehicle driver in an on-line control braking mode, the pedal feel simulator being directly hydraulically connected to the master cylinder pressure chamber.

[0095] According to one aspect of the present disclosure, the third braking system may further include: an electronically controlled pressure supply unit that delivers braking system pressure and consists of a floating piston, the floating piston being sealed to a main housing bore and including at least one anti-rotation feature that is connected to at least one groove in the main housing bore, which prevents the piston from rotating but allows the piston to translate.

[0096] According to one aspect of the present disclosure, the third braking system may further include: the pressure supply unit piston is displaced at one end by a ball screw nut of an independently actuated ball screw assembly to supply braking system pressure, while the ball screw spindle of the ball screw assembly is permanently attached to the inner ring of a ball bearing assembly, the outer ring of the ball bearing assembly is permanently attached to a stepped bore in the main housing, and the inner ring of the ball bearing assembly allows the ball screw spindle to rotate but prevents the ball screw spindle from translating.

[0097] According to one aspect of the present disclosure, the third braking system may further include: the ball screw assembly spindle is also sealed to the main housing in a corresponding bore containing a radial lip seal, thereby allowing brake fluid to enter the ball screw assembly nut and balls, but preventing brake fluid from entering the area containing the bearing inner ring.

[0098] According to one aspect of the present disclosure, the third braking system may further include: the inner ring of the ball bearing includes at least one pin, the planetary gears of the planetary gear set assembly are rotatably attached to the at least one pin, the outer annular gear of the planetary gear set assembly is permanently attached to the stepped hole of the main hole, and the sun gear of the planetary gear set assembly is permanently attached to the output shaft of the electric motor. The motor may be a brushless motor.

[0099] According to one aspect of the present disclosure, the third braking system may further include: a normally open valve for isolating the master cylinder from the brake circuit located between the outlet port of the master cylinder and the wheel brake unit.

[0100] According to one aspect of the present disclosure, the third braking system may further include: a normally open valve for dividing the brake circuit into two equivalent parts.

[0101] According to one aspect of the present disclosure, the third braking system may further include: a filter orifice assembly to provide a balanced flow to one of the divided circuits for diagonal splitting of the circuit.

[0102] According to one aspect of the present disclosure, the third braking system may further include: a forward flow check valve and a reverse flow check valve, the forward flow check valve and the reverse flow check valve are parallel to each other and are located between the pressure supply unit and two of the wheel brake units, wherein the second forward flow check valve and the second reverse flow check valve are parallel to each other and are located between the pressure supply unit and the remaining pair of wheel brake units.

[0103] According to one aspect of the present disclosure, the third braking system may further include: an inlet valve and an outlet valve for each of the wheel brake units of the wheel brake unit to set the individual wheel braking pressure derived from the signal generated by the electronic control unit, wherein the inlet valve transfers fluid to the wheel brake unit in the unactivated state and restricts or prevents the accumulation of wheel pressure in the activated state, and the outlet valve prevents the pressure medium from flowing out of the wheel brake unit to the storage unit in the unactivated state and allows and controls the outflow in the activated state, and the inlet valve is closed, thereby reducing the wheel braking pressure.

[0104] The foregoing description is not intended to be exhaustive or to limit the present disclosure. The various elements or features of a particular embodiment are generally not limited to that particular embodiment, and where applicable, the various elements or features are interchangeable and can be used in selected embodiments even if not specifically shown or described. Similarly, the various elements or features of the embodiment can be changed in many ways. Such changes should not be regarded as departing from the present disclosure, and all such modifications are intended to be included within the scope of the present disclosure.

[0105] This patent application claims the benefit of U.S. Provisional Patent Application No. 63 / 257,097, filed on October 18, 2021, the entire content of which is incorporated herein by reference in its entirety.

Claims

1. An electro - hydraulic braking system, the electro - hydraulic braking system comprising: A single - circuit master cylinder fluidly coupled to a first master - cylinder fluid passage and configured to supply fluid into the first master - cylinder fluid passage in response to a pressing force on a brake pedal coupled to the single - circuit master cylinder; A pressure - supply unit assembly including an electric motor coupled to a ball - screw actuator, a pressure - supply unit housing defining a piston bore having an end opposite to the electric motor, and a pressure - supply unit piston disposed within the piston bore and movable by the ball - screw actuator through the piston bore and dividing the piston bore into a first chamber and a second chamber, each of the first chamber and the second chamber containing a hydraulic fluid; And wherein the ball - screw actuator includes an actuator nut assembly having a plurality of ball bearings, each of the plurality of ball bearings disposed within the piston bore and immersed in the hydraulic fluid, wherein the electro - hydraulic braking system further includes: A pedal - feel simulator including a pedal - feel simulator piston movable through a pedal - feel simulator bore and separating an upper chamber from a lower chamber; wherein the lower chamber of the pedal - feel simulator is fluidly coupled to the second chamber of the pressure - supply unit assembly to convey fluid from the lower chamber of the pedal - feel simulator to the second chamber of the pressure - supply unit assembly in response to compression of the pedal - feel simulator; and wherein the first master - cylinder fluid passage is fluidly coupled to the upper chamber of the pedal - feel simulator to provide a fluid path from the master cylinder to the upper chamber of the pedal - feel simulator.

2. The electro-hydraulic braking system according to claim 1, wherein, The pressure - supply unit piston has a cup shape, and wherein the actuator nut and the plurality of ball bearings are each disposed within the cup shape of the pressure - supply unit piston.

3. The electro-hydraulic braking system according to claim 1, wherein, The pressure - supply unit assembly further includes: a main shaft driven by the electric motor and extending through a ring seal to prevent fluid from leaking out of the piston bore.

4. The electro - hydraulic braking system according to claim 1, the electro - hydraulic braking system further including: A pressure - supply unit fluid passage providing fluid communication from the first chamber of the pressure - supply unit assembly to at least one wheel brake; A supplementary fluid passage fluidly coupled to the second chamber of the pressure - supply unit assembly; And A check valve configured to allow fluid to flow from the supplementary fluid passage to the pressure - supply unit fluid passage while preventing fluid from flowing in the opposite direction.

5. The electro - hydraulic braking system according to claim 1, the electro - hydraulic braking system further including: At least one brake circuit configured to transmit fluid from the pressure - supply unit assembly to at least one wheel brake; A control valve manifold including at least one of an application valve and a release valve to control fluid flow between the at least one brake circuit and the at least one wheel brake; wherein the pressure supply unit assembly includes at least one pressure supply unit port configured to discharge fluid from the at least one pressure supply unit port; and wherein the at least one pressure supply unit port is in fluid communication with the control valve manifold via the at least one brake circuit and without any actuation valve between the at least one pressure supply unit port and the control valve manifold.

6. The electro - hydraulic braking system according to claim 1, the electro - hydraulic braking system further comprising: A fluid reservoir that holds hydraulic fluid and supplies the hydraulic fluid to the master cylinder; A return fluid passage that is in direct fluid communication with the fluid reservoir; An intermediate fluid passage that is in fluid communication with each of the second chamber of the piston bore and the lower chamber of the pedal feel simulator; and A pressure supply unit reservoir isolation valve that selectively controls fluid communication between the return fluid passage and the intermediate fluid passage.

7. The electro - hydraulic braking system according to claim 6, the electro - hydraulic braking system further comprising a check valve disposed between the second chamber of the piston bore and the intermediate fluid passage and configured to allow fluid to flow from the second chamber of the piston bore to the intermediate fluid passage while preventing fluid from flowing in the opposite direction.

8. The electro - hydraulic braking system according to claim 6, the electro - hydraulic braking system further comprising: A check valve disposed between the lower chamber of the pedal feel simulator and the intermediate fluid passage and configured to allow fluid to flow from the lower chamber of the pedal feel simulator to the intermediate fluid passage while preventing fluid from flowing in the opposite direction.

9. The electro - hydraulic braking system according to claim 6, the electro - hydraulic braking system further comprising a pedal feel simulator isolation valve that selectively controls fluid communication between the lower chamber of the pedal feel simulator and the intermediate fluid passage.

10. The electro - hydraulic braking system according to claim 1, the electro - hydraulic braking system further comprising: A first brake circuit and a second brake circuit, each of the first brake circuit and the second brake circuit being configured to transfer fluid from the pressure supply unit assembly to at least one corresponding wheel brake; A pressure supply unit fluid passage that provides fluid communication from the pressure supply unit assembly to the first brake circuit; and A brake circuit isolation valve that selectively controls fluid communication between the pressure supply unit fluid passage and the second brake circuit.

11. The electro - hydraulic braking system according to claim 1, wherein the electro - hydraulic braking system further comprises: A pressure supply unit fluid passage configured to transfer fluid from the pressure supply unit assembly to at least one wheel brake. A control valve manifold including at least one of an application valve and a release valve for controlling fluid flow between the pressure supply unit fluid passage and the at least one wheel brake. And A check valve configured to allow fluid to flow in either of two opposite directions between the pressure supply unit fluid passage and the control valve manifold only when the pressure differential across the check valve is higher than a predetermined amount.

12. The electro - hydraulic braking system according to claim 1, wherein the electro - hydraulic braking system further comprises: A first brake circuit and a second brake circuit, each of the first brake circuit and the second brake circuit being configured to transfer fluid from the pressure supply unit assembly to at least one respective wheel brake. A pressure supply unit fluid passage providing fluid communication from the pressure supply unit assembly to the first brake circuit and the second brake circuit. And A brake circuit balancing orifice configured to restrict fluid flow only through the first brake circuit.

13. The electro - hydraulic braking system according to claim 1, wherein the electro - hydraulic braking system further comprises: A hydraulic control unit body defining a top surface and a bottom surface opposite the top surface, and including a pressure supply unit housing defining the piston bore. A fluid reservoir mounted on the top surface of the hydraulic control unit body. And Wherein the electric motor of the pressure supply unit assembly is mounted to the bottom surface of the hydraulic control unit body.

14. The electro-hydraulic braking system according to claim 13, wherein, The pressure supply unit assembly does not extend beyond the top surface of the hydraulic control unit body.

15. A pressure supply unit assembly for an electro - hydraulic braking system, the pressure supply unit assembly comprising: An electric motor; A ball screw actuator including a spindle coupled to the electric motor and configured to convert rotational motion into linear motion. A pressure supply unit housing coupled to the electric motor and defining a piston bore having an end opposite the electric motor. And A pressure supply unit piston disposed within the piston bore and translatable by the ball screw actuator through the piston bore and dividing the piston bore into a first chamber and a second chamber, each of the first chamber and the second chamber containing hydraulic fluid. Wherein, the ball screw actuator includes an actuator nut assembly having a plurality of ball bearings, each of the plurality of ball bearings being disposed within the second chamber of the piston bore and submerged in the hydraulic fluid, wherein the second chamber of the piston bore is fluidly connected to a lower chamber of a pedal feel simulator of the electro-hydraulic braking system to convey fluid from the lower chamber of the pedal feel simulator to the second chamber in response to compression of the pedal feel simulator, wherein the second chamber is further configured to be connected to a supplementary fluid passage of the electro-hydraulic braking system, and the first chamber is configured to be connected to a pressure supply unit fluid passage of the electro-hydraulic braking system, thereby achieving pressure balance of the pressure supply unit piston.

16. The pressure supply unit assembly according to claim 15, wherein, The pressure supply unit piston has a cup shape, and wherein the actuator nut and the plurality of ball bearings are each disposed within the cup shape of the pressure supply unit piston.

17. The pressure supply unit assembly according to claim 15, wherein, The main shaft extends through a ring seal to prevent fluid from leaking out of the piston bore.

18. The pressure supply unit assembly according to claim 17, wherein, The ring seal includes a lip seal.

19. The pressure supply unit assembly according to claim 15, the pressure supply unit assembly further comprising a gear set driven by the electric motor and configured to drive the main shaft at a slower speed than the speed of the electric motor.

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