Brake system having master cylinder driven by electric motor and low-pressure accumulator

Abstract

The invention relates to a brake system having an electric motor-driven master cylinder and a low-pressure accumulator. The brake system includes a motor-driven master cylinder for generating brake actuation pressures at first and second master cylinder outputs to hydraulically actuate pairs of wheel brakes. The secondary brake module is configured to selectively provide pressurized hydraulic fluid at the first and second power transfer unit outputs for actuating the first and second pairs of wheel brakes. A low pressure accumulator is hydraulically disposed between the first and second pairs of wheel brakes. The low pressure accumulator is in indirect fluid communication with the reservoir via the first and second master cylinder outputs and the master cylinder. The low pressure accumulator at least partially provides slip control to the wheel brakes in coordination with the secondary brake module when the brake system is in a normal non-fail braking mode.

Description

Technical Field

[0001] The present disclosure relates to an apparatus and method for using a brake system having a motor-driven master cylinder and a pump inlet attenuator, and more particularly to a method and apparatus for a brake system having a motor-driven master cylinder, a pump inlet attenuator, and a bypass valve. Background Art

[0002] The braking system may include an anti-lock control including a hydraulic brake pressure generator, a brake pressure regulator, a sensor and an electronic circuit, the brake pressure regulator being arranged in a pressure fluid conduit between the brake pressure generator and the wheel brakes and being used to change the brake pressure by changing the volume of a chamber containing the hydraulic fluid, the sensor being used to determine the wheel rotation behavior, the electronic circuit being used to process the sensor signal and being used to generate a brake pressure control signal. The braking system may also include an anti-lock control and a traction slip control, which may use the brake pressure regulator to control vehicle braking.

[0003] Descriptions of prior art braking systems are provided in U.S. Patent No. 10,730,501, issued to Blaise Ganzel on August 4, 2020, and entitled “Vehicle Braking System with Auxiliary Pressure Source,” U.S. Patent Application Publication No. 2020 / 0307538, published by Blaise Ganzel on October 1, 2020, and entitled “Braking System with Multiple Pressure Sources,” and U.S. Patent Application Publication No. 2023 / 0048447, published by Blaise Ganzel on February 16, 2023, and entitled “Apparatus and Method for Controlling a Hydraulic Braking System Including Manual Advancement,” all of which are incorporated herein by reference in their entirety for all purposes. Summary of the invention

[0004] In one aspect, alone or in combination with any other aspect, a braking system is described for actuating a plurality of wheel brakes including a first pair of wheel brakes and a second pair of wheel brakes. The braking system includes a reservoir and a motor-driven master cylinder, which can be operated to generate brake actuation pressure at a first master cylinder output and a second master cylinder output by actuation of a motor of the master cylinder during a normal non-fault braking mode, for hydraulically actuating the first pair of wheel brakes and the second pair of wheel brakes, respectively. The auxiliary brake module is configured to selectively provide pressurized hydraulic fluid at a first power transfer unit output and a second power transfer unit output, for actuating the first pair of wheel brakes and the second pair of wheel brakes in at least one of a normal non-fault braking mode and a backup braking mode. The auxiliary brake module includes a power transfer unit motor, which is configured to selectively pressurize the hydraulic fluid by transmitting rotational motion to at least two pump pistons. Each pump piston provides pressurized hydraulic fluid to a corresponding one of the first power transfer unit output and the second power transfer unit output. Each of the first power transfer unit output and the second power transfer unit output provides fluid to a corresponding pair of wheel brakes in the first pair of wheel brakes and the second pair of wheel brakes. A low-pressure accumulator is hydraulically disposed between the first pair of wheel brakes and the second pair of wheel brakes. The low-pressure accumulator is indirectly fluidically connected to the reservoir via the first master cylinder output and the second master cylinder output and the master cylinder. An electronic control unit is used to control at least one of the auxiliary brake module and the master cylinder in response to at least one brake pressure signal. When the brake system is in the normal non-fault braking mode, the low-pressure accumulator coordinates with the auxiliary brake module to at least partially provide slip control to the first pair of wheel brakes and the second pair of wheel brakes. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] For a better understanding, reference may be made to the accompanying drawings, in which:

[0006] Figure 1 is a schematic hydraulic diagram of an exemplary brake system according to one aspect of the present invention;

[0007] Figure 2 is a schematic hydraulic diagram of an exemplary brake system according to another aspect of the present invention;

[0008] Figure 3A is a schematic cross-sectional view of components of a brake system of any aspect of the present invention in a first configuration;

[0009] Figure 3B It is in the second configuration Figure 3A A schematic cross-sectional view of a component of;

[0010] Figure 4 is a schematic cross-sectional view of components of a brake system of any aspect of the invention in a first exemplary arrangement;

[0011] Figure 5 is a schematic cross-sectional view of components of a brake system of any aspect of the invention in a second exemplary arrangement;

[0012] Figure 6 is a schematic hydraulic diagram of an exemplary brake system according to another aspect of the present invention; and

[0013] Figure 7 is used for Figure 1 , Figure 2 and Figure 6 A schematic side view of an exemplary arrangement of components of any brake system. DETAILED DESCRIPTION

[0014] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0015] The present invention comprises, consists of, or consists essentially of any combination of the following features.

[0016] Figure 1 An exemplary braking system 100 for actuating a plurality of wheel brakes 102 is schematically shown. The braking system 100 is shown here as a hydraulic braking system in which fluid pressure is used to apply a braking force to the braking system 100. The braking system 100 may be suitably used on a ground vehicle, such as a motor vehicle having four wheels, wherein a wheel brake is associated with each wheel. In addition, the braking system 100 may be provided with other braking functions, such as anti-lock braking (ABS) and other skid control features to effectively brake the vehicle. The components of the braking system 100 may be housed in one or more blocks or housings. The blocks or housings may be made of a solid material (e.g., aluminum) that has been drilled, machined, or otherwise shaped to accommodate the various components. Fluid conduits may also be formed in the blocks or housings.

[0017] exist Figure 1In the illustrated embodiment of the braking system 100, there are four wheel brakes 102, each of which may have any suitable wheel brake structure that is electrically operated and / or operated by applying a pressurized brake fluid. Each wheel brake 102 may include, for example, a brake caliper mounted on the vehicle to engage a friction element (e.g., a brake disc) that rotates with the wheel to achieve braking of the associated wheel. The wheel brakes 102 may be associated with any combination of front wheels and rear wheels of the vehicle on which the corresponding braking system 100 is installed. For example, the braking systems 100 may each be configured as a vertically separated or diagonally separated system. Although a person of ordinary skill in the art can easily provide a suitable braking arrangement for a particular use environment, for the purposes of this specification, no distinction is made herein between the structures of the various wheel brakes 102. The wheel brakes 102 are described herein as including a first pair of wheel brakes 102 and a second pair of wheel brakes 102, wherein the first pair of wheel brakes 102 and the second pair of wheel brakes 102 are characterized by RF / LR and LF / RR, such as Figure 1 However, the brake system 100 may also or alternatively be assigned LF / LR and RF / RR or RF / LF and RR / LR pairs as desired.

[0018] Also for purposes of description, it is assumed that a deceleration signal transmitter (schematically shown at 104) is configured to provide a braking signal corresponding to a desired braking action of a vehicle operator in a wired or wireless manner. The deceleration signal transmitter 104 may include, but is not limited to, a brake pedal, an autonomous braking controller, and / or any other suitable scheme for generating a braking signal from which the braking system 100 can be actuated.

[0019] Braking system 100 also includes a fluid reservoir 106. Reservoir 106 stores and holds hydraulic fluid for use with braking system 100. The fluid within reservoir 106 is preferably maintained at or about atmospheric pressure, but the fluid may be stored at other pressures if desired. Figure 1 106 is schematically shown as having three tanks or sections to which fluid lines are connected. The sections may be separated by several inner walls within the reservoir 106 and provided to prevent complete discharge of the reservoir 106 in the event that one of the sections is exhausted due to a leak through one of the three lines connected to the reservoir 106. Alternatively, the reservoir 106 may include a plurality of separate housings. The reservoir 106 may include at least one fluid level sensor 108 for detecting the fluid level of one or more sections of the reservoir 106.

[0020] The motor-driven master cylinder ("MC" or "[master] power transfer unit") 110 (which may be a dual-chamber type master cylinder 110, also referred to as a tandem power transfer unit) of each braking system 100 is used as a pressure source to provide a desired pressure level to the hydraulically operated wheel brakes 102 during a typical or normal, non-fault braking application. An example of a suitable MC 110 arrangement is disclosed in co-pending U.S. Patent Application No. 17 / 708,070, filed on March 30, 2022, and entitled "Tandem Power Transfer Unit and Braking System Using the Same" (Attorney Docket No. 211835-US-NP), the entire contents of which are incorporated herein by reference for all purposes. The master cylinder 110 is operable to generate brake actuation pressures at a first MC output 114 and a second MC output 116 during a normal, non-fault braking mode by actuation of the motor 112 of the master cylinder 110 for hydraulically actuating the first pair of wheel brakes 102 and the second pair of wheel brakes 102, respectively.

[0021] After applying the brakes, fluid from the wheel brakes 102 may be returned to the master cylinder 110 and / or diverted to the reservoir 106. It is also contemplated that other configurations (not shown) of the brake system 100 may include hydraulic control of only a selected one or more wheel brakes (the other wheel brakes being electronically controlled / actuated). Following aspects of the present invention, one of ordinary skill in the art will be readily able to provide such an arrangement for the desired use environment.

[0022] An isolation / dump control valve device is associated with each wheel brake 102 of the plurality of wheel brakes 102. Each isolation / dump control valve device includes an isolation valve 118 and a dump valve 120 for providing a desired fluid route to the associated wheel brake 102. The reservoir 106 is hydraulically connected to the master cylinder 110 and is hydraulically connected to each isolation / dump control valve device, for example, via a return line 136. Each isolation / dump control valve device includes a corresponding isolation valve 118 and a dump valve 120 arranged in series. The normally open isolation valve 118 of each isolation / dump control valve device is hydraulically located between the corresponding wheel brake 102 and the master cylinder 110, and the normally closed dump valve 120 of each isolation / dump control valve device is hydraulically located between the corresponding wheel brake 102 and the reservoir 106 for the corresponding wheel brake 102.

[0023] The isolation / dump control valve arrangement may selectively provide slip control to at least one wheel brake 102 powered by a master cylinder 110 and / or a secondary brake module described below. More generally, the isolation / dump control valve arrangement and / or other valves of the braking system 100 (any of which may be solenoid operated and of any suitable configuration) may be used to help provide controlled braking operations such as, but not limited to, ABS, traction control, vehicle stability control, dynamic rear ratio adjustment, regenerative brake blending, and autonomous braking.

[0024] The first traction control isolation valve 122 is hydraulically interposed between the master cylinder 110 and the at least one isolation / dump control valve arrangement via the first MC output 114. The second traction control isolation valve 124 is hydraulically interposed between the master cylinder 110 and the at least one isolation / dump control valve arrangement via the second MC output 116. As shown, it is contemplated that the isolation / dump control valve arrangement may be associated with each wheel brake 102 in the first pair of wheel brakes and the second pair of wheel brakes. The first traction control isolation valve 122 is hydraulically interposed between the motor-driven master cylinder 110 and the isolation / dump control valve arrangement of the first pair of wheel brakes 102. Similarly, the second traction control isolation valve 124 is hydraulically interposed between the motor-driven master cylinder 110 and the isolation / dump control valve arrangement of the second pair of wheel brakes 102.

[0025] The pump piston 126 is associated with at least one wheel brake 102 of the plurality of wheel brakes 102. The pump piston 126 is driven by a power transfer unit (PTU) motor 128 (different from the motor 112 included in the master cylinder 110) that transmits rotational motion to each pump piston 126 to selectively provide pressurized hydraulic fluid to the isolation / dump control valve device of at least one wheel brake 102 associated with the pump piston 126. Figure 1One pump piston 126 is shown associated with two wheel brakes 102, for a total of two pump pistons 126 in the braking system 100. The pump piston 126 and the PTU motor 128 together can be considered to constitute a secondary brake module of the braking system 100. For example, the two pump pistons 126 shown in the figure can provide pressurized hydraulic fluid to the corresponding wheel brakes 102 via corresponding isolation / dump control valve devices (when present) at the first pump output 130 and the second pump output 132, respectively, to actuate the first pair of wheel brakes 102 and the second pair of wheel brakes 102 in at least one of a normal non-fault braking mode and a backup braking mode. Each of the first pump output 130 and the second pump output 132 can provide fluid to a corresponding pair of wheel brakes in the first pair of wheel brakes 102 and the second pair of wheel brakes 102. It is contemplated that in some configurations of the braking system 100, multiple pump pistons 126 can be associated with each of the first pump output 130 and the second pump output 132.

[0026] The slave brake modules (also referred to as "slave brake modules") of the brake system 100 serve as a pressure source to provide a desired pressure level to selected wheel brakes 102 in a backup or "failure" situation (when, for some reason, the master cylinder 110 is unable to provide fluid to those selected wheel brakes 102). Thus, each slave brake module is directly fluidly connected to the reservoir 106 for exchanging hydraulic fluid between these components without having to direct the fluid through the (potentially failed) motor-driven master cylinder 110 or another structure of the brake system 100.

[0027] The secondary brake module can be used to selectively provide hydraulic fluid to at least one wheel brake 102 not only in a backup braking mode but also in an enhanced braking mode, which can occur independently and / or simultaneously with the backup braking mode or the normal, non-fault braking mode. Examples of suitable enhanced braking mode functions that can be used for the braking system 100 include, but are not limited to, "overboost" (wherein a higher pressure is provided to a particular brake than is normally available from the master cylinder 110 alone) and "capacity increase" (wherein more fluid is provided to a particular brake than is normally available from the master cylinder 110). For example, in at least one of the normal, non-fault braking mode and the backup braking mode, the secondary brake module can then supply hydraulic fluid at a boost pressure (higher than the pressure available from the master cylinder 110) to at least one of the first pump output 130 and the second pump output 132.

[0028] It can be seen that each isolation / dump control valve device in the brake system 100 shown in the figure is directly or indirectly fluidly connected to a selected one of the first MC output port 114 and the second MC output port 116 and a selected one of the first pump output port 130 and the second pump output port 132 for selectively receiving pressurized fluid from these output ports, such as during different braking modes or as needed. A person of ordinary skill in the art will be able to easily configure the brake system 100 for any specific purpose application as needed.

[0029] Figure 1 The illustrated braking system 100 also includes at least one electronic control unit ("ECU") 134 for controlling at least one of the master cylinder 110 and the secondary brake module (via the PTU motor 128) in response to at least one brake pressure signal, wherein a first ECU 134A and a second ECU 134B are shown and described herein. The ECUs 134A, 134B may include a microprocessor and other circuits. The ECUs 134A, 134B receive various signals, process the signals, and control the operation of various electrical components of the corresponding braking system 100 in response to the received signals in a wired and / or wireless manner. The ECUs 134A, 134B may be connected to various sensors, such as a reservoir fluid level sensor 108, a pressure sensor, a travel sensor, a switch, a wheel speed sensor, and a steering angle sensor. The ECUs 134A, 134B may also be connected to an external module (not shown) for receiving information related to the vehicle's yaw rate, lateral acceleration, longitudinal acceleration, or other characteristics of vehicle operation for any reason, such as, but not limited to, controlling the brake system 100 during vehicle braking, stability operation, or other operating modes. Additionally, the ECUs 134A, 134B may be connected to an instrument cluster for collecting and providing information related to warning indicators, such as an ABS warning light, a brake fluid level warning light, and a traction control / vehicle stability control indicator light. It is contemplated that at least one of the ECUs 134A and 134B may be integrated, for example, with the master cylinder 110 or the PTU motor 128.

[0030] The first ECU 134A and the second ECU 134B may divide the control tasks for the brake system 100 in any desired manner and may be easily configured by a person of ordinary skill in the art for a particular use environment of the brake system, but it is contemplated that any control tasks performed by one or more of the ECUs 134 will be accomplished in response to at least one brake pressure signal and / or brake signal generated by the deceleration signal transmitter 104. For example, the first ECU 134A may be operable to control the motor 112 of the master cylinder 110. The second ECU 134B may be operable to control the PTU motor 128, at least one of the isolation / dump control valve devices, and at least one of the first traction control isolation valve 122 and the second traction control isolation valve 124.

[0031] A "brake pressure signal" is referred to above as at least one input that the ECU 134 may consider and responsively control one or more other components of the braking system 100 to achieve the desired braking result for a particular use environment. One potential source of a brake pressure signal is a brake pressure sensor. For example, as shown, the braking system 100 may include at least one (e.g., at least two) brake pressure sensors 138 (four are shown), wherein each brake pressure sensor 138 is optionally (and as shown) positioned directly hydraulically adjacent to a corresponding wheel brake 102 for sensing the hydraulic pressure at the corresponding wheel brake 102 and responsively generating a brake pressure signal. In other words, in Figure 1 In the illustrated brake system 100 , no other components are hydraulically interposed between the brake pressure sensors 138 and their corresponding wheel brakes 102 , such that the brake pressure signal generated by each brake pressure sensor 138 is correlated to the actual sensed brake pressure at the corresponding wheel brake 102 .

[0032] The first bypass isolation valve 140 is hydraulically disposed between the first traction control isolation valve 122 and the front brakes of the first pair of wheel brakes 102, and is connected in parallel with the isolation / dump control valve arrangement corresponding to the front brakes of the first pair of wheel brakes 102. The second bypass isolation valve 142 is hydraulically disposed between the second traction control isolation valve 124 and the front brakes of the second pair of wheel brakes 102, and is connected in parallel with the isolation / dump control valve arrangement corresponding to the front brakes of the second pair of wheel brakes 102. Figure 1 The illustrated first bypass isolation valve 140 and second bypass isolation valve 142 are shown as normally open isolation valves.

[0033] As shown, the first brake pressure sensor 138A may be hydraulically disposed between the first bypass isolation valve 140 and the corresponding front wheel brake in the first pair of wheel brakes 102, and the second brake pressure sensor 138B may be hydraulically disposed between the second bypass isolation valve 142 and the corresponding front wheel brake in the second pair of wheel brakes 102. One of ordinary skill in the art may readily provide the desired number / location / type of pressure sensors 138 for a particular brake system 100.

[0034] The first bypass isolation valve 140 and the second bypass isolation valve 142 are configured to close in response to a higher hydraulic fluid pressure on the upstream side (i.e., the side closer to the master cylinder 110) of the respective bypass isolation valves 140 and 142 so that the brake system 100 maintains the first bypass isolation valve 140 and the second bypass isolation valve 142 closed while the current draw on the system is relatively low. The first bypass isolation valve 140 and the second bypass isolation valve 142 also have a larger orifice size than the orifice size of the isolation valve 118 of the corresponding isolation / dump control valve device and are oriented in the opposite direction of fluid flow to the isolation valve 118 of the corresponding isolation / dump control valve device (i.e., are plumb in the opposite direction of the corresponding isolation valve 118). Therefore, the first bypass isolation valve 140 and the second bypass isolation valve 142 can therefore help to quickly pressurize the wheel brakes 102 during a "spike apply" condition. (It should be noted that the first bypass isolation valve 140 and the second bypass isolation valve 142 may also have larger orifice sizes than the orifice sizes of the corresponding first traction control isolation valve 122 and the second traction control isolation valve 124.) An example of the use of the first bypass isolation valve 140 and the second bypass isolation valve 142 is that once the isolation valve 118 is closed, an undesirably large pressure spike may occur due to the motor 112 of the master cylinder 110 having inertia and taking a predetermined amount of time to stop rotating and stop driving the piston in the chamber of the master cylinder 110. The presence of the first bypass isolation valve 140 and the second bypass isolation valve 142 in handling the "spike application" situation also allows the use of a smaller corresponding isolation valve 118 because the motor 112 does not need to rotate as quickly to achieve the desired amount of fluid pressure at the associated wheel brake 102 compared to the case where the isolation valve 118 is larger. FIG. 3A to FIG. 3B The structure of the first bypass isolation valve 140 and the second bypass isolation valve 142 are discussed in more detail.

[0035] A brake motor 144 may be associated with each rear wheel brake in the front and rear pair of wheel brakes 102. When present, the brake motor 144 may be operated in at least a backup braking mode and, when multiple ECUs 134 are present, may be controlled by the ECU 134 opposite the motor 112 of the master cylinder 110 (in response to the brake signal). For example, when the first ECU 134A controls the motor 112 of the master cylinder 110, the second ECU 134B may control the PTU motor 128 and the brake motor 144 for redundancy in the braking system 100 in the event that the first ECU 134A fails.

[0036] Figure 1 , Figure 2 and Figure 6 The braking system also includes a low-pressure accumulator 148 hydraulically disposed between the first pair of wheel brakes 102 and the second pair of wheel brakes 102. For example, the low-pressure accumulator 148 may be provided in direct fluid communication with the pump piston 126 of the secondary brake module and with the dump valve 120 of the isolation / dump control valve arrangement, as shown.

[0037] When present, the low pressure accumulator 148 is in indirect fluid communication with the reservoir 106 via the first MC output 114 and the second MC output 116 and the master cylinder 110. That is, the low pressure accumulator 148 is not directly connected to the reservoir 106. Figure 1 , Figure 2 and Figure 6 The reservoir 106 in the braking system 100 is provided with a low-pressure accumulator 148, and there is no return line for the low-pressure accumulator 148, because the low-pressure accumulator 148 stores fluid adjacent to the secondary brake module as needed. When the braking system 100 is in a normal non-fault braking mode, the low-pressure accumulator 148 can coordinate with the secondary brake module to at least partially provide slip control to the first pair of wheel brakes 102 and the second pair of wheel brakes 102.

[0038] Known brake systems use secondary brake modules to pull fluid from reservoir 106 along a high pressure brake pipe or along a low pressure hose ("return line"). Brake pipe solutions struggle with performance at low temperatures and / or high altitudes. By storing fluid in a low pressure accumulator 148, desired performance may be achieved while still omitting the low pressure hose from brake system 100. Low pressure accumulator 148 (also referred to as a "fluid storage accumulator") may assist in slip control.

[0039] A switch or sensor (e.g., a low pressure accumulator (LPA) switch 150) may be provided to detect the fluid level in the low pressure accumulator 148 and, in response, report the fluid level to the electronic control unit 134. For example, the LPA switch 150 may detect when the low pressure accumulator 148 is substantially empty and fluid has been removed from the fluid storage portion of the low pressure accumulator 148. Figure 4 and Figure 5 An exemplary low pressure accumulator 148 is described for use with any suitable braking system 100 .

[0040] Figure 2 A second embodiment of a brake system 100 is shown. Figure 2 The braking system is similar to Figure 1 The braking system is therefore different from the reference Figure 1 Describe the same or similar structure Figure 2 For the second embodiment, the description of common elements and operations similar to those in the aforementioned first embodiment will not be repeated, but should be considered to be appropriately incorporated by reference below.

[0041] exist Figure 2 In the brake system 100 of FIG. 1 , the low-pressure accumulator is a first low-pressure accumulator 148A, and the brake system 100 includes a second low-pressure accumulator 148B, which is hydraulically separated from the first low-pressure accumulator 148A by a secondary brake module, as shown. In other words, the first low-pressure accumulator 148A and the second low-pressure accumulator 148B are not directly connected to each other, but each exchanges hydraulic fluid with a different "side" of the brake system 100. Figure 2 As shown, each of the first low-pressure accumulator 148A and the second low-pressure accumulator 148B operates to selectively regulate the hydraulic fluid for the corresponding first pair of wheel brakes 102 or the second pair of wheel brakes 102. It should be noted that since a plurality of low-pressure accumulators 148 are provided Figure 2 In the braking system 100 of the embodiment of the present invention, (a) each low-pressure accumulator 148 can be smaller than in the case where only a single low-pressure accumulator 148 is provided, and / or (b) the fluid level switch 152 can be provided at the reservoir 106 instead of the fluid level sensor 108 of other embodiments of the braking system 100, which can result in a saving in cost and / or complexity of the system. Since the low-pressure accumulator 148 is not directly connected to the reservoir 106 (instead, the fluid must be transferred through the master cylinder 110), the low-pressure accumulator 148 should be configured to hold sufficient fluid to operate the wheel brakes 102 as needed, even if the fluid cannot be supplied through the master cylinder 110.

[0042] A person of ordinary skill in the art will be able to readily configure a brake system 100 according to any embodiment of the present invention that includes one or more low-pressure accumulators 148 for a particular use environment. For example, a fluid volume from the low-pressure accumulator 148 can be provided to the secondary brake module during conditions including, but not limited to, spike application, high system pressure (e.g., above about 180 bar), and / or a failed master cylinder 110. The low-pressure accumulator 148 can also be used to at least partially attenuate pressure spikes within the brake system 100 during slip control in a normal, non-fault braking mode.

[0043] For simplicity, the following FIG. 3A to FIG. 3B The description pertains to the first bypass isolation valve 140 , but in many use environments, the second bypass isolation valve 142 will be similarly configured. Figure 3A The bypass isolation valves 140, 142 are shown in an open state and Figure 3B The middle bypass isolation valves 140, 142 are energized to close. FIG. 3A to FIG. 3B , the first bypass isolation valve 140 and the second bypass isolation valve 142 may each include an MC channel 246 in fluid communication with the corresponding first MC output end 114 or the second MC output end 116, a brake-side channel 248 in fluid communication with the corresponding front wheel brake 102, and a longitudinally extending bypass valve sleeve 250. The MC channel 246 may be in indirect fluid communication with the corresponding first MC output end 114 or the second MC output end 116 via the corresponding first traction control isolation valve 122 or the second traction control isolation valve 124. The brake-side channel 248 may be in direct fluid communication with the corresponding front wheel brake 102. For a specific use environment, a person of ordinary skill in the art may easily configure the brake system 100 including one or more bypass isolation valves 140 and 142.

[0044] The bypass valve body 252 has a first body end 254 and a second body end 256 spaced longitudinally apart, with a bypass body lumen 258 extending between the first body end 254 and the second body end 256. The bypass valve body 252 spaces at least a portion of the bypass valve sleeve 250 that at least partially surrounds the first body end 254 from at least the brake side passage 248 located adjacent the second body end 256. A bypass armature 260 is located within the bypass valve sleeve 250 adjacent the first body end 254. A bypass tappet 262 is at least partially surrounded by the bypass armature 260 and the bypass valve sleeve 250. The bypass tappet 262 extends at least partially through the bypass body lumen 258. The bypass tappet 262 is selectively longitudinally moved within the bypass body lumen 258 toward the bypass valve body 252 by energizing the bypass armature 260. A bypass biasing spring 264 is mechanically interposed between the bypass lifter 262 and at least a portion of the bypass valve body 252 within the bypass body lumen 258. The bypass biasing spring 264 operates to bias the bypass lifter 262 toward the first body end 254. The bypass valve seat 266 is carried by a bypass seat body 268 positioned immediately adjacent the second body end 256.

[0045] Any desired number of bypass valve filters 270 may be provided, and the bypass valve filters 270 are shown here as a band filter 270A and a disc filter 270B associated with the MC channel 246 and the brake side channel 248, respectively. An air gap spacer 272 may be provided to help maintain tolerances, adjust the magnetic air gap, and / or transfer forces between components as desired. The bypass isolation valve 140, 142 may be carried by a housing block 274 of the brake system 100, and at least a portion of the MC channel 246 and the brake side channel 248 may be formed within the housing block 274. The bypass valve body 252 or any other desired component of the bypass isolation valve 140, 142 may be maintained within the valve bore 276 of the housing block 274 by riveting, crimping, welding, soldering, adhesives, fasteners, or any other desired maintenance solution.

[0046] The bypass valve fluid path F extends (in a bidirectional manner) through a selected one of the MC passage 246 and the brake-side passage 248, through the bypass valve seat 266, through at least one laterally extending side hole 278 in the bypass valve body 252, through at least a portion of the bypass body lumen 258, and through the other of the MC passage 246 and the brake-side passage 248 to place the two passages in fluid communication. Figure 3A Normally Open position shown.

[0047] exist Figure 3BIn the illustrated “energized closed” position, the bypass lifter 262 selectively engages the bypass valve seat 266 to substantially block the bypass valve fluid path F in response to energization of the bypass armature 260 to move the bypass lifter 262 toward the second body end 256 .

[0048] exist Figure 4 and Figure 5 The figure shows the Figure 1 , Figure 2 and Figure 6 Examples of two arrangements of suitable low pressure accumulators for any brake system 100 (or for use with any other brake system as desired).

[0049] See first Figure 4 , the low pressure accumulator 148 includes an LPA chamber 402 that includes at least one brake side channel (shown here as a first brake side channel 404 and a second brake side channel 406, respectively) adjacent a first end 408 of the LPA chamber 402. It is contemplated that, particularly for a brake system 100 having multiple low pressure accumulators 148, there may be only one brake side channel, but in Figure 4 and Figure 5 1 and 2 show a dual-channel version of the low-pressure accumulator 148 by way of example. In these figures, the first brake side channel 404 can be in fluid communication with the inlet of the pump piston 126, and the second brake side channel can be in fluid communication with the dump valve 120 of the isolation / dump control valve device, such as Figure 1 The use of the brake system 100 is shown. The LPA piston 410 is provided for reciprocating longitudinal movement within the LPA chamber 402 in response to a predetermined amount of hydraulic fluid flowing through a brake side passage (here, at least one of the first brake side passage 404 and the second brake side passage 406).

[0050] An LPA biasing spring 412 is provided for urging the LPA piston 410 toward the first end 408 of the LPA chamber 402. The hydraulic fluid flow will need to overcome the biasing force of the LPA biasing spring 412 to flow longitudinally downward (at Figure 4 The LPA piston 410 is pushed in the "wet side" of the low pressure accumulator 148 (i.e., the area above the LPA piston 410, marked "W"). The "dry side" of the low pressure accumulator 148 is Figure 4414. The LPA piston 410 is shown as the area below the LPA piston 410 in the orientation of FIG. 402 and is labeled "D". This "dry side" area is vented to atmosphere at any suitable location relative to the low pressure accumulator 148, for example, by a passage (not shown) including a Gore or other liquid-impermeable but gas-permeable membrane, and in some environments of use, the vent may be positioned to be in fluid communication with at least a portion of the electronic control unit 134. A retainer disk 416 may be positioned adjacent to the membrane 414 (when present) at the second end 418 of the LPA chamber 402, and the LPA biasing spring 412 may contact the retainer disk 416 as a "base" to apply an upward force (at the base) on the LPA piston 410 from the "base". Figure 4 orientation) bias pressure.

[0051] An LPA limiter (shown generally at 420) including an LPA rod 422 and an LPA cover 424 may be provided for selectively limiting the longitudinal travel of at least one of the LPA biasing spring 412 and the LPA piston 410. The LPA cover 424 may be pushed upwardly by the LPA biasing spring 412 to Figure 4 4. The LPA hood 424 is shown in the illustrated position, in which the retaining clip 426 prevents further upward travel of the LPA hood 424. (The LPA rod 422 may help guide and stabilize the travel of the LPA hood 424 within the LPA chamber 402.) Conversely, the LPA hood 424 may cooperate with the LPA bias spring 412 to block further downward travel of the LPA piston 410, and / or the lower skirt of the LPA piston 410 may contact the retainer plate 416 to prevent the face of the LPA piston 410 from traveling beyond a predetermined "bottom" position within the LPA chamber 402.

[0052] The LPA rod 422 may be connected to the LPA piston 410 and Figure 4 4. The LPA hood 424 is permitted to move longitudinally relative to a selected one of the second ends 418 of the LPA chamber 402 schematically shown in the figure. A spacer 428 may be provided to prevent the entire face of the LPA piston 410 from directly contacting the end face of the first end 408 of the LPA chamber 402. A person of ordinary skill in the art may readily provide a suitably configured low-pressure accumulator 148 for a particular use environment of the brake system 100. However, the low-pressure accumulator 148 is configured for a variable volume "wet" area (W) that may be used in a non-powered mechanical manner to hold different amounts of hydraulic fluid as required by a particular brake system 100.

[0053] Refer again Figure 4, the LPA piston 410 may include a circumferential LPA seal groove 430 around its head. A directional LPA seal 432 may be carried in the LPA seal groove 430 for longitudinal reciprocation relative to the inner wall of the LPA chamber 402 to prevent fluid from flowing longitudinally past the directional LPA seal 432. When present, the directional LPA seal 432 may provide a longitudinally movable demarcation line between the wet side and the dry side of the LPA chamber 402. If the LPA piston 410 should "float" upward (at a depth of 1.5 m) above the range of the restrained, shrouded LPA bias spring 412, the LPA piston 410 may be provided with a circumferential LPA seal groove 430 around its head. A directional LPA seal 432 may be carried in the LPA seal groove 430 for longitudinal reciprocation relative to the inner wall of the LPA chamber 402 to prevent fluid from flowing longitudinally past the directional LPA seal 432. When present, the directional LPA seal 432 may provide a longitudinally movable demarcation line between the wet side and the dry side of the LPA chamber 402. Figure 4 ), the directional LPA seal 432 can provide friction to resist the movement of the LPA piston 410 and thus prevent the LPA piston 410 from sliding freely within the LPA chamber 402. Figure 4 In the embodiment of the low pressure accumulator 148 , the LPA rod 422 remains in place relative to the LPA chamber 402 as the LPA piston 410 reciprocates longitudinally within the LPA chamber 402 .

[0054] on the contrary, Figure 5 The low pressure accumulator 148 (although some aspects are similar to Figure 4 The low pressure accumulator of FIG. 1 has an LPA chamber 402, which is included in the inner wall of the LPA chamber 402 and longitudinally (at the inner wall) between the first end 408 and the second end 418 of the LPA chamber 402. Figure 5 430. Figure 4 Compared with the embodiment of Figure 5 For the embodiment of the present invention, the LPA seal groove 430 located in the cavity requires more internal machining of the housing block 274, but this additional effort is taken to achieve the purpose of setting Figure 5 A multi-stage movement of the LPA piston 410 within the low pressure accumulator may be suitable. Figure 5 In the illustrated embodiment, a directional LPA seal 432 is positioned within the LPA seal groove 430 and similarly serves to prevent fluid from flowing longitudinally past the directional LPA seal 432 during reciprocation of the LPA piston 410 within the LPA chamber 402 , at least partially separating the “wet” and “dry” sides of the LPA chamber 402 .

[0055] for Figure 5 As shown in the low pressure accumulator 148, it can be seen that at least a portion of the LPA cover 424 is laterally disposed between the LPA piston 410 and the inner wall of the LPA chamber 402 for sliding movement relative to both, thereby facilitating Figure 5The LPA piston 410 includes a circumferential LPA seal groove 430' around its head and a non-directional second LPA seal 432', the non-directional second LPA seal 432' being arranged within the LPA seal groove 430' for longitudinal reciprocating sliding relative to the inner wall of the LPA cover 424 to prevent the fluid from longitudinally flowing through the non-directional second LPA seal 432'. The non-directional second LPA seal 432' may, for example, have a substantially circular or oval cross-sectional shape, which may help provide a desired direction and amount of friction on adjacent components of the low pressure accumulator.

[0056] like Figure 5 As shown, neither the LPA cover 424 nor the LPA rod 422 is fixed or retained at the second end 418 of the LPA chamber 402. Instead, the entire LPA limiter 420 (i.e., the LPA rod 422 and the LPA cover 424) is configured to reciprocate substantially together with the LPA piston 410 within the LPA chamber 402. That is, it should be noted that the LPA biasing spring 412 longitudinally urges both the LPA cover 424 and the LPA piston 410 to urge these structures apart, but the LPA cover 424 retains the bottom flange of the LPA rod 422 to prevent the longitudinal separation between the LPA cover 424 and the LPA piston 410 from exceeding a predetermined amount because the top end of the LPA rod 422 is retained by the LPA piston 410. (The predetermined amount of longitudinal separation is within 100 mm / s.) Figure 5 , wherein the low pressure accumulator 148 is shown in a static position. ) However, in Figure 5 In the arrangement of FIG. 4 , the LPA piston 410 is allowed to travel longitudinally downward against the force of the LPA bias spring 412 until the LPA rod 422 “bottoms out” against the retainer disk 416 and / or until the lower skirt of the LPA piston 410 contacts the inner bottom edge of the LPA cover 424. Either of these will prevent the LPA piston 410 from traveling further downward.

[0057] and Figure 5 In contrast to the low-pressure accumulator, Figure 5 The low pressure accumulator 148 may be desirable in certain use environments because Figure 5 The low pressure accumulator 148 includes a double seal arrangement shown in the figure. Figure 5 In the design shown, most of the LPA function is provided by the second LPA seal 432', and the first LPA seal 432 is rarely used as a dynamic seal. The second LPA seal 432' can be a high friction seal. Figure 4 In the design shown, all LPA dynamic sealing functions are performed by LPA seal 432 only, and Figure 4In the case of using very low friction seals in the low pressure accumulator 148, more leakage through the LPA seal 432 is possible. However, regardless of the specific configuration of the low pressure accumulator 148 used in the present brake system 100, a person skilled in the art will be able to easily provide a suitable arrangement for a particular use environment according to the present invention.

[0058] Figure 6 A third exemplary embodiment of a brake system 100 is shown. Figure 6 The braking system is similar to Figure 1 and Figure 2 The braking system is therefore different from the reference Figure 1 and Figure 2 Describe the same or similar structure Figure 6 The structures of the present invention have the same reference numerals. For the third embodiment, the description of common elements and operations similar to those in the first and second embodiments described previously will not be repeated, but should be considered to be appropriately incorporated by reference below.

[0059] exist Figure 6 In the brake system 100, each of the first bypass isolation valve 140' and the second bypass isolation valve 142' is the same isolation valve type as the isolation valve 118 of the corresponding isolation / dump control valve device (rather than Figure 1 and Figure 2 The first and second embodiments of the brake system 100 shown in FIG. Figure 3A and Figure 3B Bypass isolation valves 140, 142). That is, Figure 6 In the second embodiment of the brake system 100 shown, each of the first bypass isolation valve 140' and the second bypass isolation valve 142' includes a check valve mechanism 504 that selectively allows fluid to flow therethrough. Figure 1 In contrast to the arrangement of , each of the first bypass isolation valve 140 ′ and the second bypass isolation valve 142 ′ is configured to open in response to a higher hydraulic fluid pressure on the upstream side of the bypass valves 140 ′ and 142 ″ (ie, the side closer to the master cylinder 110 ). Figure 5 The brake system 100 shown may be Figure 1 The brake system is simpler in structure because Figure 5 The brake system includes at least one valve to be provided and configured. It is contemplated that any desired number of low-pressure accumulators 148 can be provided for the brake system 100 with any desired type of bypass isolation valve, and a person skilled in the art will be able to easily configure a suitable brake system for a particular use environment.

[0060] See now Figure 1 , Figure 2 and Figure 6, the reservoir 106 and the motor-driven master cylinder 110 may be co-located in a first housing (schematically indicated by a dashed line “1” in these figures), and the secondary brake module may be located in a second housing (schematically indicated by a dashed line “2” in these figures) spaced apart from the first housing. Figure 1 As shown, the isolation dump control valve arrangement, the first and second bypass isolation valves 140 and 142 , any desired low pressure accumulator 148 , and / or the first and second traction control isolation valves 122 and 124 may also be located in the second housing.

[0061] See now Figure 7 The components of the brake system 100 are housed in a common block housing 274, which has a common block housing having a longitudinal-lateral plane (i.e., parallel to Figure 7 The shell surface 280 extends in the plane of the page in FIG. Figure 7 In the diagram, the “longitudinal” direction is substantially vertical and is indicated by the arrow “Lo”; Figure 7 , the "lateral" direction is substantially horizontal and is indicated by arrow "La". Each of the first bypass isolation valve 140 and the second bypass isolation valve 142 is longitudinally located between the isolation valve 118 and the dump valve 120 of the corresponding isolation / dump valve arrangement. In the prior art brake system, this arrangement of the first bypass isolation valve 140 and the second bypass isolation valve 142 is where the supply valve is usually located.

[0062] The pressure sensor 138A is placed laterally between the first bypass isolation valve 140 and the second bypass isolation valve 142 directly above the pump drive bearing in the brake system 100. It should be noted that the prior art brake system only provides three pressure sensors (in Figure 7 138 in the description here. Figure 7 In the braking system 100 of FIG. 1 , it may be desirable to add a fourth pressure sensor 138A while maintaining a compact layout of the system; therefore, this arrangement is used for the pressure sensor 138A. Figure 7 As shown, the pressure sensors 138 on the centerline of the block housing 274 (one of which is on the motor bearing) are associated with the front brakes, while the other two (non-centerline positioned) pressure sensors 138 are associated with the rear brakes. However, it is contemplated that one of ordinary skill in the art can readily provide any desired number, type, arrangement or other configuration of pressure sensors for a particular use environment of the brake system 100.

[0063] The first housing and the second housing (and included / co-located components) of any braking system 100 can be provided and configured for a specific use application by a person of ordinary skill in the art based on factors including but not limited to achieving the desired results in at least one of design, manufacturing, maintenance, space utilization in the vehicle, cost, size, regulatory compliance, etc.

[0064] It is contemplated that a person of ordinary skill in the art may provide various other components, such as a service brake motor and / or a parking brake motor, in any brake system described herein to achieve a desired configuration for a particular use environment. For example, although a plurality of filters and pressure sensors or other sensors are shown in the accompanying drawings, their specific description is omitted here for the sake of brevity, because a person of ordinary skill in the art will readily understand how to provide the desired number, arrangement and / or operation of filters, sensors and any other components according to the needs of the particular use environment of the present invention.

[0065] As used herein, the singular forms "a", "an" and "the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include" and / or "comprise" used herein may specify the presence of the features, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components and / or combinations thereof.

[0066] As used herein, the term "and / or" may include any and all combinations of one or more of the associated listed items.

[0067] It should be understood that when an element is referred to as being "on another element," "attached to another element," "connected to another element," "coupled with another element," "in contact with another element," "adjacent to another element," etc., the element may be directly on, attached to, connected to, coupled with, in contact with, or adjacent to another element, or intervening elements may also be present. In contrast, when an element is referred to as being, for example, "directly on another element," "directly attached" to another element, "directly connected" to another element, "directly coupled with," "directly in contact with," or "directly adjacent to" another element, there are no intervening elements. One of ordinary skill in the art will also understand that references to structures or features that are disposed "directly adjacent to" another feature may have portions that overlap or underlie the adjacent features, whereas structures or features that are disposed "adjacent to" another feature may not have portions that overlap or underlie the adjacent features.

[0068] Spatially relative terms, such as "under," "beneath," "lower," "above," "upper," "proximal," "distal," and the like, may be used herein to facilitate describing the relationship of one element or feature to another element or feature as shown in the figures. It should be understood that spatially relative terms may include different orientations of the device in use or operation in addition to the orientation shown in the figures. For example, if the device in the figure is inverted, elements described as "under" or "beneath" other elements or features would be oriented "above" the other elements or features.

[0069] As used herein, the phrase "at least one of X and Y" may be interpreted to include: X; Y; or a combination of X and Y. For example, if an element is described as having at least one of X and Y, the element may include: X; Y; or a combination of X and Y at a particular time, the selection of which may change over time. Conversely, the phrase "at least one of X" may be interpreted to include one or more Xs.

[0070] It should be understood that although the terms "first", "second", etc. may be used herein to describe various elements, these elements are not limited by these terms. These terms are only used to distinguish one element from another element. Therefore, without departing from the teachings of the present disclosure, the "first" element discussed below may also be referred to as the "second" element. The order of operations (or steps) is not limited to the order given in the claims or drawings unless otherwise specifically noted.

[0071] Although aspects of the present disclosure have been specifically shown and described with reference to the above exemplary aspects, it will be understood by those skilled in the art that various additional aspects can be envisioned. For example, the specific methods of using the device described above are merely illustrative; a person skilled in the art can easily determine any number of tools, sequence of steps, or other ways / options for placing the above-mentioned device or its components in a position substantially similar to those shown and described herein. In order to maintain clarity in the drawings, certain repeated components are not specifically numbered, but a person skilled in the art will recognize the element numbers that should be associated with the unnumbered components based on the numbered components; the presence or absence of element numbers in the drawings does not intend or imply a distinction between similar components. Any of the described structures and components can be integrally formed as a single whole or monolithic piece, or composed of separate subcomponents, any of which includes any suitable raw materials or custom components and / or any suitable material or combination of materials. Any of the described structures and components can be disposable or reusable, depending on the needs of the specific use environment. Any component may have a user-perceivable mark to indicate the material, configuration, at least one dimension, etc. associated with the component, the user-perceivable mark potentially helping the user select a component from an array of similar components for a specific use environment. The "predetermined" state can be determined at any time before the structure being manipulated actually reaches the state, and the "predetermining" is performed shortly before the structure reaches the predetermined state. The term "substantially" is used herein to indicate a specified quality to a large extent (but not necessarily all)-the "substantially" quality allows for the possibility of some relatively small inclusion of non-quality items. Although certain components described herein are shown as having specific geometric shapes, all structures of the present disclosure may have any suitable shape, size, configuration, relative relationship, cross-sectional area or any other physical property desired for a particular application. Any structure or feature described with reference to one aspect or configuration may be provided to any other aspect or configuration alone or in combination with other structures or features, because it would be impractical to describe each aspect and configuration discussed herein as having all the options discussed with respect to all other aspects and configurations. Devices or methods that combine any of these features should be understood to fall within the scope of the present disclosure determined based on the following claims and any equivalents thereof.

[0072] Other aspects, objects and advantages can be obtained from a study of the drawings, the disclosure and the appended claims.

[0073] Related Applications

[0074] This application claims priority to U.S. Provisional Patent Application No. 63 / 580,042 (Agent File No. 301699-US-PSP), filed on September 1, 2023, and entitled “BRAKING SYSTEM WITH ELECTRIC MOTOR DRIVEN MASTER CYLINDER AND LOW-PRESSURE ACCUMULATOR,” the entire contents of which are incorporated herein by reference for all purposes.

[0075] This application relates to technology disclosed in one or more of the following: U.S. Provisional Patent Application No. 63 / 580,048 (Agent Docket No. 301647-US-PSP), filed on September 1, 2023 and entitled “Braking System with Motor-Driven Master Cylinder and Pump Inlet Attenuator”; U.S. Patent Application No. 18 / 474,657 (Agent Docket No. 301158-US-NP), filed on September 26, 2023 and entitled “Braking System with Motor-Driven Master Cylinder and Bypass Valve”; and U.S. Patent Application No. 18 / 474,714 (Agent Docket No. 301647-US-NP), filed on September 26, 2023 and entitled “Braking System with Motor-Driven Master Cylinder and Pump Inlet Attenuator”; the entire contents of all of these applications are incorporated herein by reference for all purposes.

Claims

1. A braking system for actuating a plurality of wheel brakes including a first pair of wheel brakes and a second pair of wheel brakes, the braking system comprising: Storage; a motor-driven master cylinder operable during a normal, non-fault braking mode by actuation of an electric motor of said master cylinder to generate brake actuation pressures at a first master cylinder output and a second master cylinder output for hydraulically actuating said first pair of wheel brakes and said second pair of wheel brakes, respectively; a secondary brake module configured to selectively provide pressurized hydraulic fluid at a first power transfer unit output and a second power transfer unit output for actuating the first pair of wheel brakes and the second pair of wheel brakes in at least one of a normal non-fault braking mode and a backup braking mode, the secondary brake module including a power transfer unit motor configured to selectively pressurize the hydraulic fluid by transmitting rotational motion to at least two pump pistons, each pump piston providing pressurized hydraulic fluid to a corresponding one of the first power transfer unit output and the second power transfer unit output, each of the first power transfer unit output and the second power transfer unit output providing fluid to a corresponding pair of wheel brakes of the first pair of wheel brakes and the second pair of wheel brakes; a low pressure accumulator hydraulically interposed between the first pair of wheel brakes and the second pair of wheel brakes, the low pressure accumulator being in indirect fluid communication with the reservoir via the first and second master cylinder outputs and the master cylinder; as well as an electronic control unit for controlling at least one of the secondary brake module and the master cylinder in response to at least one brake pressure signal; Wherein, when the brake system is in the normal non-fault braking mode, the low-pressure accumulator coordinates with the secondary brake module to at least partially provide slip control to the first pair of wheel brakes and the second pair of wheel brakes.

2. The brake system of claim 1, comprising an isolation / dump control valve device associated with each of the plurality of wheel brakes, each isolation / dump control valve device being controlled by the electronic control unit.

3. The braking system according to claim 2, wherein: Each isolation / dump control valve device is in fluid communication with a selected one of the first and second master cylinder outputs and a selected one of the first and second power transfer unit outputs for selectively receiving pressurized hydraulic fluid therefrom.

4. The braking system according to claim 1, wherein: A first brake pressure sensor is hydraulically interposed between the first master cylinder output and a corresponding first pair of wheel brakes, and a second brake pressure sensor is hydraulically interposed between the second master cylinder output and a corresponding second pair of wheel brakes.

5. The braking system according to claim 1, wherein: The secondary brake module includes a plurality of pump pistons associated with each of the first power transfer unit output and the second power transfer unit output.

6. The braking system according to claim 1, comprising: a first traction control isolation valve hydraulically interposed between the motor-driven master cylinder and the first pair of wheel brakes via the first master cylinder outlet; as well as A second traction control isolation valve is hydraulically interposed between the motor-driven master cylinder and the second pair of wheel brakes via the second master cylinder outlet.

7. The braking system of claim 6, comprising an isolation / dump control valve arrangement associated with each wheel brake of the first pair of wheel brakes and the second pair of wheel brakes, wherein: The first traction control isolation valve is hydraulically interposed between the motor-driven master cylinder and the isolation / dump control valve arrangement of the first pair of wheel brakes, and wherein the second traction control isolation valve is hydraulically interposed between the motor-driven master cylinder and the isolation / dump control valve arrangement of the second pair of wheel brakes.

8. The braking system of claim 7, comprising a first normally open bypass isolation valve hydraulically disposed between the first traction control isolation valve and the front brake of the first pair of wheel brakes, and comprising a second normally open bypass isolation valve hydraulically disposed between the second traction control isolation valve and the front brake of the second pair of wheel brakes, wherein The first bypass isolation valve and the second bypass isolation valve each have an orifice size that is larger than an orifice size of a corresponding isolation valve that isolates the dump control valve arrangement.

9. The braking system of claim 7, comprising a first bypass isolation valve hydraulically disposed between the first traction control isolation valve and the front brake of the first pair of wheel brakes, and comprising a second bypass isolation valve hydraulically disposed between the second traction control isolation valve and the front brake of the second pair of wheel brakes, wherein Each of the first bypass isolation valve and the second bypass isolation valve is a normally open isolation valve and is configured to close in response to a higher hydraulic fluid pressure on an upstream side of the bypass isolation valve, the upstream side being a side closer to the master cylinder.

10. The brake system according to claim 8, wherein: Each of the first bypass isolation valve and the second bypass isolation valve is configured to open in response to a higher hydraulic fluid pressure on an upstream side of the bypass isolation valve, the upstream side being a side closer to the master cylinder.

11. The brake system according to claim 10, wherein: Each of the first bypass isolation valve and the second bypass isolation valve includes a check valve mechanism that selectively allows fluid to flow therethrough.

12. The brake system of claim 7, comprising a first bypass isolation valve hydraulically disposed between the first traction control isolation valve and the front brake of the first pair of wheel brakes, and comprising a second bypass isolation valve hydraulically disposed between the second traction control isolation valve and the front brake of the second pair of wheel brakes, wherein: Each of the first bypass isolation valve and the second bypass isolation valve is the same type of isolation valve as the isolation valve of the isolation / dump control valve arrangement.

13. The braking system of claim 7, comprising a first bypass isolation valve hydraulically disposed between the first traction control isolation valve and the front brake of the first pair of wheel brakes, and comprising a second bypass isolation valve hydraulically disposed between the second traction control isolation valve and the front brake of the second pair of wheel brakes, wherein Each of the first bypass isolation valve and the second bypass isolation valve is oriented in an opposite direction of fluid flow from an isolation valve of the isolation / dump control valve arrangement.

14. The brake system according to claim 1, wherein: The low-pressure accumulator is a first low-pressure accumulator, and wherein the braking system includes a second low-pressure accumulator, which is hydraulically separated from the first low-pressure accumulator by the secondary brake module, and each of the first low-pressure accumulator and the second low-pressure accumulator is operated to selectively regulate hydraulic fluid for a corresponding first pair of wheel brakes or a second pair of wheel brakes.

15. The brake system according to claim 1, wherein: The first bypass isolation valve and the second bypass isolation valve each include: a master cylinder passage in fluid communication with a corresponding first master cylinder outlet or a second master cylinder outlet; a brake-side passage in fluid communication with a corresponding front wheel brake; a longitudinally extending bypass valve sleeve; a bypass valve body having first and second longitudinally spaced body ends, a bypass body lumen extending between the first and second body ends, the bypass valve body spacing at least a portion of the bypass valve sleeve at least partially surrounding the first body end from at least the brake-side passage located adjacent the second body end; a bypass armature disposed within the bypass valve sleeve adjacent the first body end; a bypass tappet at least partially surrounded by the bypass armature and the bypass valve sleeve, the bypass tappet extending at least partially through the bypass body lumen, the bypass tappet selectively movable longitudinally within the bypass body lumen toward the bypass valve body by energization of the bypass armature; and a bypass valve seat carried by the bypass seat body directly adjacent to the second body end; wherein a bypass valve fluid path extends through a selected one of the master cylinder passage and the brake side passage, through the bypass valve seat, through at least one laterally extending side hole in the bypass valve body, through at least a portion of the bypass body lumen, and through the other of the master cylinder passage and the brake side passage; and wherein, in response to energizing the bypass armature to move the bypass tappet toward the second body end, the bypass tappet selectively engages the bypass valve seat to substantially block the bypass valve fluid path.

16. The brake system according to claim 1, wherein: The low pressure accumulator, i.e., LPA, comprises: an LPA chamber including at least one brake-side passage adjacent a first end of the LPA chamber; an LPA piston for longitudinally reciprocating within the LPA chamber in response to a predetermined amount of hydraulic fluid flowing through the brake side passage; an LPA biasing spring for urging the LPA piston toward a first end of the LPA chamber; and an LPA limiter including an LPA rod and an LPA cover for selectively limiting longitudinal travel of at least one of the LPA biasing spring and the LPA piston; wherein the LPA rod is connected to a selected one of the LPA piston and a second end of the LPA chamber longitudinally spaced from the first end, and the LPA cover is allowed to move longitudinally relative to the selected one.

17. The braking system according to claim 16, wherein: The LPA piston includes a circumferential LPA seal groove around a head of the LPA piston and a directional LPA seal carried in the LPA seal groove for longitudinal reciprocation relative to an inner wall of the LPA cavity to prevent fluid from flowing longitudinally through the directional LPA seal.

18. The brake system according to claim 16, wherein: The LPA chamber includes a circumferential LPA seal groove in an inner wall of the LPA chamber and longitudinally spaced between a first end and a second end of the LPA chamber, a directional LPA seal located in the LPA seal groove and configured to prevent fluid from flowing longitudinally past the directional LPA seal during reciprocating motion of the LPA piston in the LPA chamber.

19. The braking system according to claim 16, wherein: At least a portion of the LPA cover is laterally disposed between the LPA piston and an inner wall of the LPA chamber for sliding movement relative thereto.

20. The braking system according to claim 19, wherein: The LPA piston includes a circumferential LPA seal groove around a head of the LPA piston and a non-directional second LPA seal in the LPA seal groove, wherein the LPA seal groove slides longitudinally reciprocatingly relative to an inner wall of the LPA cover to prevent fluid from flowing longitudinally through the LPA seal groove.

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