The present disclosure relates generally to brake systems for vehicles, such as automobiles. More specifically, the present disclosure relates to a brake-by-wire system with two integrated braking units to provide redundancy.
As electric and hybrid vehicles continue to proliferate in markets around the world, it is well understood that significant lengthening of battery life can be obtained by utilizing the motor-generator output capabilities of that device during braking. However, the input torque in the generator mode used to recharge batteries is not consistent with driver input function of pedal force/travel verses vehicle deceleration. In order to achieve that complex function, the hydraulic brakes of the vehicle must supply the difference between generator braking torque and driver requested braking torque.
The engineering world has understood this requirement for a number of years commonly known as regenerative brake blending. A most efficient way to achieve this is to use a “brake-by-wire” technique. To accomplish this, the brake pedal in effect becomes a joystick, so it must be connected to a travel and/or force sensor in order to send a signal to the system ECU that will interpret this as driver's intent of a desired vehicle deceleration. In addition, the brake pedal “feel” must be simulated by the appropriate force-travel relationship and must also have the ability to be isolated from directly applying the master cylinder to the wheel brakes. Brake-by-wire systems typically include a pressure supply unit (PSU) to provide a supply of pressurized fluid for actuating the wheel brakes.
As brake-by-wire systems are applied to vehicles desiring Level 3, 4 or 5 of the defined SAE autonomy scale, a redundant backup system may be required to allow the vehicle to operate in the event of the primary brake unit failing. In designing for systems for SAE Autonomy Level 3 or higher, one of the key factors involved is that of redundancy. As the influence of the driver diminishes, the ability of the brake system to have a fallback mode that allows full or nearly full performance is required.
The present disclosure provides a redundant brake unit for a motor vehicle. The redundant brake unit includes: an inlet port configured to receive fluid under pressure from an external source; an outlet port connected to a supply passage and configured for fluid connection to a wheel brake; a reservoir port connected to a return passage and configured for fluid connection to a fluid reservoir; a boost valve configured to selectively control fluid communication between the inlet port and the supply passage; and a pressure supply unit including a pump element configured to pump fluid between the return passage and the supply passage. The pump element has an inlet directly connected to the reservoir port with no actuated valves therebetween.
The present disclosure also provides a redundant brake unit for a motor vehicle. The redundant brake unit includes: an inlet port configured to receive fluid under pressure from an external source; an outlet port connected to a supply passage and configured for fluid connection to a wheel brake; a reservoir port connected to a return passage and configured for fluid connection to a fluid reservoir; a pressure supply unit including a pump element configured to pump fluid to the supply passage; and a normally-closed valve and a throttle valve in a series configuration between the supply passage and the return passage. The throttle valve is operable to vary fluid flow therethrough to control a fluid pressure in the supply passage.
The present disclosure also provides a brake system for a motor vehicle. The brake system includes: a wheel brake configured to apply a braking force in response to a fluid pressure; a primary brake unit including a first pressure supply unit (PSU) configured to generate the fluid pressure, and a fluid discharge port for providing the fluid pressure; and a redundant brake unit. The redundant brake unit includes: an inlet port fluidly coupled to the fluid discharge port of the primary brake unit, an outlet port connected to a supply passage and to the wheel brake, a boost valve configured to selectively control fluid communication between the inlet port and the supply passage, a reservoir port connected to a return passage and configured for fluid connection to a fluid reservoir, and a second PSU including a pump element configured to pump fluid between the return passage and the supply passage. The pump element has an inlet directly connected to the reservoir port with no actuated valves therebetween.
Further details, features and advantages of designs of the invention result from the following description of embodiment examples in reference to the associated drawings.
Referring to the drawings, the present invention will be described in detail in view of the following embodiments.
The present disclosure provides a two-box BbW system 20, which may include a redundant brake system (RBU), and which is capable of self-applying the brakes in case the driver is not alert (Level 3) or there is no driver (Levels 4 and 5). The two-box BbW system 20 of the present disclosure is unique, cost effective, and able to be constructed with existing brake controller components. The system of the present disclosure may be suitable for Level 3 or greater automation based on the “Levels of Driving Automation” standard by SAE International that defines six levels of driving automation, as specified in SAE standard J3016.
The brake pedal inputs define driver intent which determines how fast and how hard the brakes are applied with the goal to replicate the feel of a conventional vacuum booster brake system. The brake ECU 17 may also send a signal to a drive control unit (DCU) 18, which may also be called a powertrain control module (PCM), to slow the vehicle using one or more electric motors in a regenerative mode.
The vehicle's master cylinder either applies the brakes directly by the driver in a failed system fallback mode, or in normal mode, is totally isolated from the wheel brakes and connected to a pedal feel emulator that replicates force, travel, and damping of a traditional brake system. The brake pedal travel and/or force along with the measured hydraulic brake pressure is used by the system as an input signal to the electronic control unit. It in turn sends the appropriate signal to a pressure supply unit nowadays consisting of a high efficiency brushless motor and ballscrew assembly displacing one or two pistons. The applied pressure thus determines how fast and how hard the brakes are to be applied with the goal to replicate the driver's intended vehicle's instantaneous deceleration.
In some embodiments, an electronic HCU (EHUC) that is otherwise capable of controlling an entire brake system, such as a DBC 1280 EHCU from BWI, can be modified to meet such requirements. The DBC 1280 EHCU contains a power source (i.e. dual pump elements), hydraulic controls (i.e. solenoid valves), as well as electronic controls (ECU).
The primary brake unit 30 includes a fluid reservoir 24 holding a hydraulic fluid and supplying the hydraulic fluid to a master cylinder 38. In some embodiments, and as shown in
Still referring to
The first pressure supply unit (PSU) 50 includes the first electric motor 52 and a PSU pump 54 to supply the hydraulic fluid from the fluid reservoir 24 to a PSU fluid passageway 56. A second check valve allows fluid flow from the fluid reservoir 24 into the PSU fluid passageway 56 while blocking fluid flow in an opposite direction. A second pressure sensor 58 monitors the pressure in the PSU fluid passageway 56.
This hydraulic layout includes a set of valves 62 with an H-bridge circuit arrangement having four valves that control the switching between the MC fluid passageways 60, 61 of the master cylinder 38 and the first PSU 50 and to control fluid flow to the wheel brakes 22a, 22b, 22c, 22d via each of the first brake circuit 74 and the second brake circuit 76.
The primary brake unit 30 defines four fluid discharge ports 32a, 32b, 32c, 32d each fluidly coupled to a corresponding one of the wheel brakes 22a, 22b, 22c, 22d. A control valve manifold 78 fluidly connects the two brake circuits 74, 76 to the corresponding wheel brakes 22a, 22b, 22c, 22d via the four fluid discharge ports 32a, 32b, 32c, 32d. The control valve manifold 78 includes an apply valve 68a and a release valve 80b corresponding to each of the wheel brakes 22a, 22b, 22c, 22d to selectively control fluid flow between the corresponding one of the of the wheel brakes 22a, 22b, 22c, 22d and an associated one of the two brake circuits 74, 76. The apply valves 80a and the release valves 80b may collectively be called antilock brake system (ABS) valves for their use in such an ABS. However, the apply valves 80a and the release valves 80b may be used for other functions, such as for traction control and/or for torque vectoring. A return fluid passageway 82 provides fluid communication for flow from the control valve manifold 78 and back to the fluid reservoir 24.
Besides the eight standard ABS valves 80a, 80b, and the four H-bridge hydraulic control valves 62, conventional brake-by-wire systems include two more valves 64, 66, bringing the total to fourteen (14) valves. The PFE isolation valve 66 is a normally-closed valve and its sole purpose is to lock out the PFE 39 in the event of a failed pressure supply unit when master cylinder backup is required. The reservoir test valve 64 may be used to shut off the primary master cylinder return path to the fluid reservoir 24 so that the system may conduct a self-test to make sure the PFE isolation valve 66 and other valves are functioning properly.
The first ECU 34 may include one or more processors, microcontrollers, and/or electric circuits configured to control operation of one or more of the valves 62, 80a, 80b, 64, 66, to monitor one or more of the first pressure sensor 57 and the second pressure sensor 58 and/or to control operation of the first electric motor 52, and to thereby coordinate operation of the primary brake unit 30.
In some embodiments, a first set 32a, 32b of the four fluid discharge ports 32a, 32b, 32c, 32d is fluidly coupled to corresponding first wheel brakes 22a, 22b via the RBU 40, and a second set 32c, 32d of the four fluid discharge ports 32a, 32b, 32c, 32d are directly fluidly coupled to corresponding second wheel brakes 22c, 22d. For example, and as shown in
The RBU 40 provides fallback brake operation. The RBU 40 may operate independently on front wheels only. In a normal brake-by-wire mode, fluid may pass through the RBU 40 for the primary brake unit 30 to actuate the RF wheel brake 22a and the LF wheel brake 22b. In the fallback mode, the second PSU 70 of the RBU 40 may run continuously when brakes applied. Both of the two brake circuits 74, 76 in the primary brake unit 30 are input to the RBU 40.
The RBU 40 includes a first inlet port 94 and a second fluid input port 96, Each of the inlet ports 94, 96 are configured to receive fluid under pressure from an external source, such as the primary brake unit 30. As shown in
The RBU 40 also includes a RF outlet port 92a and a LF outlet port 92b. The RF outlet port 92a is directly fluidly connected to the RF wheel brake 22a for supplying fluid thereto, and the LF outlet port 92b is directly fluidly connected to the LF wheel brake 22b for supplying fluid thereto. The RBU 40 also includes a reservoir port 98 that is configured for fluid connection to the fluid reservoir 24. For example, and as shown in
The RBU 40 includes a second PSU 70 that includes the second electric motor 46 coupled to two pump elements 71, 171, with each of the two pump elements 71, 171 configured to pump fluid from a return passage 72 that is fluidly connected to the to the fluid reservoir 24 via the reservoir port 98. Each of the two pump elements 71, 171 includes an inlet for receiving the fluid and which is directly fluidly connected to the reservoir port 98, with no actuated valves therebetween. In some embodiments, and as shown in
A fifth fluid pressure sensor 120, which may also be called an inlet fluid pressure sensor, monitors pressure in a fluid passage of the RBU 40 that is connected to the first inlet port 94. The fifth fluid pressure sensor 120 is electrically connected to the second ECU 44 and provides an inlet pressure signal P-IN thereto representing the fluid pressure at the first inlet port 94. Another inlet fluid pressure sensor (Not shown in the FIGS.) may be included to measure a fluid pressure at the second inlet fluid port 96.
The RBU 40 also includes a first boost valve 100, which may include a normally-open solenoid valve, fluidly connected between the first inlet port 94 and the first supply passage 102 and configured to selectively control fluid communication therebetween. The first boost valve 100 may be energized, and thereby commanded to a closed position, in the fallback mode to prevent flow back to the primary brake unit 30. The RBU 40 also includes a first decrease valve 104 and a first throttle valve 106 connected in series therewith and together fluidly connected between the first supply passage 102 and the return passage 72. The first decrease valve 104 may include a normally-closed solenoid valve, and the first throttle valve 106 may include a normally-open modulating solenoid valve. The first decrease valve 104 may be de-energized, and thereby commanded to a closed position, in a normal braking mode to prevent a transfer of fluid from the first supply passage 102 to the reservoir 24. The first decrease valve 104 may be energized, and thereby commanded to an open position, in the fallback mode to permit flow from the first supply passage 102 to the first throttle valve 106. The first throttle valve 106 may be operated to regulate fluid pressure in the first supply passage 102, from an output of the first pump element 71, and for supply to the LF wheel brake 22b. The outlet pressure provided by the regulated pump flow, as measured by the third pressure sensor 108, is divided by an inlet pressure supplied by the driver, as measured by the fifth pressure sensor 120, to determine a boost ratio.
The RBU 40 also includes a second boost valve 110, which may include a normally-open solenoid valve, fluidly connected between the second inlet port 96 and the second supply passage 112 and configured to selectively control fluid communication therebetween. The second boost valve 110 may be energized, and thereby commanded to a closed position, in the fallback mode to prevent flow back to the primary brake unit 30. The RBU 40 also includes a second decrease valve 114 and a second throttle valve 116 connected in series therewith and together fluidly connected between the second supply passage 112 and the return passage 72. The second decrease valve 114 may include a normally-closed solenoid valve, and the second throttle valve 116 may include a normally-open modulating solenoid valve. The second decrease valve 104 may be de-energized, and thereby commanded to a closed position, in the normal braking mode to prevent a transfer of fluid from second supply passage 112 to reservoir 24. The second decrease valve 104 may be energized, and thereby commanded to an open position, in the fallback mode to permit flow from the first supply passage 112 to the first throttle valve 116. The second throttle valve 116 may be operated to regulate fluid pressure in the second supply passage 112, from an output of the second pump element 171, and for supply to the RF wheel brake 22a.
The second ECU 44 may include one or more processors, microcontrollers, and/or electric circuits configured to control operation of one or more of the valves 100, 104, 106, 110, 114, 116, to monitor one or more of the pressure sensors 108, 118, 120, and/or to control operation of the second electric motor 46, and to thereby coordinate operation of the RBU 40. For example, the second ECU 44 may receive a signal from the third pressure sensor 108 representing the pressure in the first supply passage 102 and provide control signals to either or both of the first boost valve 100 and/or the first throttle valve 106 for adjusting the pressure in the first supply passage 102. Additionally or alternatively, the second ECU 44 may receive a signal from the fourth pressure sensor 118 representing the pressure in the second supply passage 112 and provide control signals to either or both of the second boost valve 110 and/or the second throttle valve 116 for adjusting the pressure in the second supply passage 112.
One or more ECUs, such as the second ECU 44, may be configured to determine a pressure differential across the first boost valve 100 based on a difference between the fluid pressure in the first supply passage 102 and the fluid pressure at the first inlet port 94. The one or more ECUs may be further configured to determine a desired output pressure setting based on the difference between the fluid pressure in the first supply passage 102 and the fluid pressure at the first inlet port 94. The one or more ECUs may be further configured to generate a control signal for the first throttle valve 106 based on a difference between the desired output pressure setting and the fluid pressure in the first supply passage 102. The one or more ECUs may provide similar control functions for the second throttle valve 116. For example, the one or more ECUs may be configured to determine a pressure differential across the second boost valve 110 and to determine a second desired output pressure setting based on a difference between the fluid pressure in the second supply passage 112 and the fluid pressure at the first inlet port 94. The one or more ECU. As may be further configured to generate a control second signal for the second throttle valve 116 based on a difference between the second desired output pressure setting and the fluid pressure in the second supply passage 112.
In some embodiments, and in some modes, such as in the fallback mode shown in
The present disclosure provides a two-box BbW system 20 for a driverless motor vehicle which receives all braking commands from intelligent systems that are part of the vehicle's hardware and software and are known here as its autopilot and a high speed private CAN connection to assure instantaneous communications between the separate brake systems. The brake system includes: a primary brake unit 30 capable of providing independent pressure control to all four wheel brakes in a standard passenger vehicle or light truck; and a redundant brake unit (RBU) 40 consisting of two isolated pump elements 71, 171 driven by a second electric motor 46 and capable of providing pressure and flow to two independent left front and right front brake circuits. The RBU includes a left front (LF) inlet port 94 and a right front (RF) inlet port 96. Each of the inlet ports 94, 96 are fluidly connected to a corresponding one of the outlet ports 92a, 92b. The RBU 40 includes two boost valves 100, 110, with one located in each independent left front and right front circuit fluidly connected to their corresponding inlet ports 94, 96 and corresponding outlet ports 92a, 92b. The two boost valves 100, 110 may each include a normally-open linear valve, such as a modulating solenoid valve. The RBU 40 includes a pressure sensor 120 located between at least one of the inlet ports 94, 96 and at least one front boost valve. The RBU 40 includes two outlet pressures sensors 108, 118 with one located in each independent left front and right front circuit fluidly connected to outlets of their corresponding pump elements 71, 171 and corresponding outlet ports 92a, 92b. The RBU 40 includes two normally-closed decrease valves 104, 114 with one located in each left front and right front circuit fluidly connected to their corresponding outlet ports 92a, 92b and inlets of their corresponding pump elements 71, 171. The RBU 40 includes two throttle valves 106, 116 with one located in each left front and right front circuit fluidly connected between their corresponding decrease valves 104, 114 and inlets of their corresponding pump elements 71, 171. The two throttle valves 106, 116 may each include normally-open linear solenoid valves. The RBU 40 includes a reservoir port 98 fluidly connected to the inlet of the two pump elements 71, 171.
The present disclosure also provides a brake system 20 for a driverless motor vehicle which receives all braking commands from intelligent systems that are part of the vehicle's hardware and software and are known here as its autopilot and a high speed private CAN connection to assure instantaneous communications between the separate brake systems. The brake system includes: a primary brake unit capable of providing independent pressure control to all four wheel brakes in a standard passenger vehicle or light truck and an RBU capable of providing independent pressure control to each front wheel brake and linked together electronically by a high speed private CAN. The primary brake unit is configured to provide independent pressure control to all four wheel brakes in a standard passenger vehicle or light truck and an RBU capable of providing independent pressure control to each front wheel brake and linked together electronically by a high speed private CAN. The brake system further includes two wheel speed sensors at each wheel brake, one on each wheel is hard wired to the primary brake unit and the other on each wheel is wired to another vehicle ECU including a CAN transceiver such that wheel speed signals are available to the corresponding ECU even with the failure of the primary brake unit or the RBU.
The foregoing description is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
Number | Date | Country | Kind |
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202410963926.4 | Jul 2024 | CN | national |
This U.S. utility patent application claims the benefit of U.S. Provisional Patent Application No. 63/530,382, filed Aug. 2, 2023, and claims priority to Chinese Patent Application No. 202410963926.4 filed Jul. 17, 2024, which are incorporated herein by reference in their entirety.
Number | Date | Country | |
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63530382 | Aug 2023 | US |