The present disclosure relates in general to vehicle braking systems. Vehicles are commonly slowed and stopped with hydraulic brake systems.
These systems vary in complexity but a base brake system typically includes a brake pedal, a tandem master cylinder, fluid conduits arranged in two similar but separate brake circuits, and wheel brakes in each circuit. The driver of the vehicle operates a brake pedal which is connected to the master cylinder. When the brake pedal is depressed, the master cylinder generates hydraulic forces in both brake circuits by pressurizing brake fluid. The pressurized fluid travels through the fluid conduit in both circuits to actuate brake cylinders at the wheels to slow the vehicle.
Base brake systems typically use a brake booster which provides a force to the master cylinder which assists the pedal force created by the driver. The booster can be vacuum or hydraulically operated. A typical hydraulic booster generates pressurized fluid for assisting in pressurizing the wheel brakes, thereby increasing the pressures generated by the master cylinder. Hydraulic boosters are commonly located adjacent the master cylinder and use a boost valve to help control the pressurized fluid.
Braking a vehicle in a controlled manner under adverse conditions requires precise application of the brakes by the driver. Under these conditions, a driver can easily apply excessive braking pressure thus causing one or more wheels to lock, resulting in excessive slippage between the wheel and road surface. Such wheel lock-up conditions can lead to greater stopping distances and possible loss of directional control.
Advances in braking technology have led to the introduction of Anti-lock Braking Systems (ABS). An ABS system monitors wheel rotational behavior and selectively applies and relieves brake pressure in the corresponding wheel brakes in order to maintain the wheel speed within a selected slip range to achieve maximum braking force. While such systems are typically adapted to control the braking of each braked wheel of the vehicle, some systems have been developed for controlling the braking of only a portion of the plurality of braked wheels.
Electronically controlled ABS valves, comprising apply valves and dump valves, are located between the master cylinder and the wheel brakes. The ABS valves regulate the pressure between the master cylinder and the wheel brakes. Typically, when activated, these ABS valves operate in three pressure control modes: pressure apply, pressure dump and pressure hold. The apply valves allow pressurized brake fluid into respective ones of the wheel brakes to increase pressure during the apply mode, and the dump valves relieve brake fluid from their associated wheel brakes during the dump mode. Wheel brake pressure is held constant during the hold mode by closing both the apply valves and the dump valves.
To achieve maximum braking forces while maintaining vehicle stability, it is desirable to achieve optimum slip levels at the wheels of both the front and rear axles. During vehicle deceleration different braking forces are required at the front and rear axles to reach the desired slip levels. Therefore, the brake pressures should be proportioned between the front and rear brakes to achieve the highest braking forces at each axle. ABS systems with such ability, known as Dynamic Rear Proportioning (DRP) systems, use the ABS valves to separately control the braking pressures on the front and rear wheels to dynamically achieve optimum braking performance at the front and rear axles under the then current conditions.
A further development in braking technology has led to the introduction of Traction Control (TC) systems. Typically, valves have been added to existing ABS systems to provide a brake system which controls wheel speed during acceleration. Excessive wheel speed during vehicle acceleration leads to wheel slippage and a loss of traction. An electronic control system senses this condition and automatically applies braking pressure to the wheel cylinders of the slipping wheel to reduce the slippage and increase the traction available. In order to achieve optimal vehicle acceleration, pressurized brake fluid is made available to the wheel cylinders even if the master cylinder is not actuated by the driver.
During vehicle motion such as cornering, dynamic forces are generated which can reduce vehicle stability. A Vehicle Stability Control (VSC) brake system improves the stability of the vehicle by counteracting these forces through selective brake actuation. These forces and other vehicle parameters are detected by sensors which signal an electronic control unit. The electronic control unit automatically operates pressure control devices to regulate the amount of hydraulic pressure applied to specific individual wheel brakes. In order to achieve optimal vehicle stability, braking pressures greater than the master cylinder pressure must quickly be available at all times.
Brake systems may also be used for regenerative braking to recapture energy. An electromagnetic force of an electric motor/generator is used in regenerative braking for providing a portion of the braking torque to the vehicle to meet the braking needs of the vehicle. A control module in the brake system communicates with a powertrain control module to provide coordinated braking during regenerative braking as well as braking for wheel lock and skid conditions. For example, as the operator of the vehicle begins to brake during regenerative braking, electromagnet energy of the motor/generator will be used to apply braking torque (i.e., electromagnetic resistance for providing torque to the powertrain) to the vehicle. If it is determined that there is no longer a sufficient amount of storage means to store energy recovered from the regenerative braking or if the regenerative braking cannot meet the demands of the operator, hydraulic braking will be activated to complete all or part of the braking action demanded by the operator. Preferably, the hydraulic braking operates in a regenerative brake blending manner so that the blending is effectively and unnoticeably picked up where the electromagnetic braking left off. It is desired that the vehicle movement should have a smooth transitional change to the hydraulic braking such that the changeover goes unnoticed by the driver of the vehicle.
This disclosure relates to a brake system having a wheel brake and is operable under a non-failure normal braking mode and a manual push-through mode. The system includes a master cylinder operable by a brake pedal during a manual push-through mode to provide fluid flow at an output for actuating the wheel brake. A first source of pressurized fluid provides fluid pressure for actuating the wheel brake under a normal braking mode. A second source of pressurized fluid generates brake actuating pressure for actuating the wheel brake under the manual push-through mode.
Various aspects of this disclosure will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.
Referring now to the drawings, there is schematically illustrated in
The wheel brakes 12a, 12b, 12c, and 12d can be associated with any combination of front and rear wheels of the vehicle in which the brake system 10 is installed. A vertically split brake system is illustrated such that the wheel brake 12a is preferably associated with the left front wheel of the vehicle in which the brake system 10 is installed. A wheel brake 12b is preferably associated with the right front wheel. A wheel brake 12c is preferably associated with the left rear wheel. A wheel brake 12d is preferably associated with the right rear front wheel. Alternatively, the brake system 10 could be configured in a diagonally split system such that the wheel brake 12a is associated with the left rear wheel, the wheel brake 12b is associated with the right front wheel, the wheel brake 12c is associated with the left front wheel, and the wheel brake 12d is associated with the right rear wheel.
The brake system 10 includes a master cylinder, indicated generally at 14, a pedal simulator, indicated generally at 16, a plunger assembly, indicated generally at 18, and a reservoir 20. As will be discussed in detail below, the plunger assembly 18 of the brake system 10 functions as a source of pressure to provide a desired pressure level to the wheel brakes 12a, 12b, 12c, and 12d during a typical or normal brake apply. Fluid from the wheel brakes 12a, 12b, 12c, and 12d may be returned to the plunger assembly 18 and/or diverted to the reservoir 20. The master cylinder 14, the pedal simulator 16, and the plunger assembly 18 will be described in greater detail below.
The reservoir 20 stores and holds hydraulic fluid for the brake system 10. The fluid within the reservoir 20 is preferably held at or about atmospheric pressure but may store the fluid at other pressures if so desired. Ideally, the pressure within the reservoir is relatively low and is ideally less than 1 bar above atmospheric pressure. The fluid reservoir 20 is shown schematically having three sections with three conduit lines 24, 26, and 28 connected thereto. The sections can be separated by a couple of interior walls 20a and 20b within the reservoir 20 and are provided to prevent complete drainage of the reservoir 20 in case one of the sections is depleted due to a leakage in one of the three conduits 24, 26, and 28 connected to the reservoir 20. Alternatively, the reservoir 20 may include multiple separate housings.
The brake system 10 may include a fluid level sensor 20d for detecting the fluid level of the reservoir 20. The brake system 10 also includes a solenoid actuated normally open simulator test valve 29 in fluid communication with the conduit 28 and the master cylinder 14, the reason for which will be explained below.
The brake system 10 includes a main electronic control unit (ECU) 22. The main ECU 22 may include microprocessors. The main ECU 22 receives various signals, processes signals, and controls the operation of various electrical components of the brake system 10 in response to the received signals. The main ECU 22 can be connected to various sensors such as pressure sensors, travel sensors, switches, wheel speed sensors, and steering angle sensors. The main ECU 22 may also be connected to an external module (not shown) for receiving information related to yaw rate, lateral acceleration, longitudinal acceleration of the vehicle such as for controlling the brake system 10 during vehicle stability operation. Additionally, the main ECU 22 may be connected to the instrument cluster for collecting and supplying 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.
The brake system 10 further includes first and second isolation valves 30 and 32. The isolation valves 30 and 32 may be solenoid actuated three way valves. The isolation valves 30 and 32 are generally operable to two positions, as schematically shown in
In a preferred embodiment, the first and/or second isolation valves 30 and 32 may be mechanically designed such that flow is permitted to flow in the reverse direction (from conduit 34 to the conduits 36 and 38, respectively) when in their de-energized positions and can bypass the normally closed seat of the valves 30 and 32. Thus, although the 3-way valves 30 and 32 are not shown schematically to indicate this fluid flow position, it is noted that that the valve design may permit such fluid flow. This may be helpful in performing self-diagnostic tests of the brake system 10.
The system 10 further includes various solenoid actuated valves (slip control valve arrangement) for permitting controlled braking operations, such as ABS, traction control, vehicle stability control, and regenerative braking blending. A first set of valves includes a first apply valve 50 and a first dump valve 52 in fluid communication with the conduit 40 for cooperatively supplying fluid received from the first isolation valve 30 to the wheel brake 12a, and for cooperatively relieving pressurized fluid from the wheel brake 12a to the reservoir conduit 24 in fluid communication with the reservoir 20. A second set of valves includes a second apply valve 54 and a second dump valve 56 in fluid communication with the conduit 40 for cooperatively supplying fluid received from the first isolation valve 30 to the wheel brake 12b, and for cooperatively relieving pressurized fluid from the wheel brake 12b to the reservoir conduit 24. A third set of valves includes a third apply valve 58 and a third dump valve 60 in fluid communication with the conduit 42 for cooperatively supplying fluid received from the second isolation valve 32 to the wheel brake 12c, and for cooperatively relieving pressurized fluid from the wheel brake 12c to the reservoir conduit 24. A fourth set of valves includes a fourth apply valve 62 and a fourth dump valve 64 in fluid communication with the conduit 42 for cooperatively supplying fluid received from the second isolation valve 32 to the wheel brake 12d, and for cooperatively relieving pressurized fluid from the wheel brake 12d to the reservoir conduit 24. Note that in a normal braking event, fluid flows through the non-energized open apply valves 50, 54, 58, and 62. Additionally, the dump valves 52, 56, 60, and 64 are preferably in their non-energized closed positions to prevent the flow of fluid to the reservoir 20.
The master cylinder 14 is connected to a brake pedal 70 and is actuated by the driver of the vehicle as the driver presses on the brake pedal 70. A brake sensor or switch 72 may be connected to the main ECU 22 to provide a signal indicating a depression of the brake pedal 70. As will be discussed below, the master cylinder 14 may be used as a back-up source of pressurized fluid to essentially replace the normally supplied source of pressurized fluid from the plunger assembly 18 under certain failed conditions of the brake system 10. The master cylinder 14 can supply pressurized fluid in the conduits 36 and 38 (that are normally closed off at the first and second isolation valves 30 and 32 during a normal brake apply) to the wheel brake 12a, 12b, 12c, and 12d as required.
Referring now to the enlarged schematic representation of the master cylinder 14 as shown in
The input chamber 110 is in fluid communication with the pedal simulator 16 via a conduit 130. As is shown in
As shown in
The secondary chamber 114 is in fluid communication with the first isolation valve 30 via the conduit 36. The secondary piston 106 is slidably disposed in the bore 100 of the housing of the master cylinder 14. An outer wall 152 of the secondary piston 106 is engaged with a lip seal 154 and a seal 156 mounted in grooves formed in the housing. One or more lateral passageways 158 (compensation ports) are formed in the secondary piston 106. As shown in
If desired, the primary and secondary pistons 104 and 106 may be mechanically connected with limited movement therebetween. The mechanical connection of the primary and secondary pistons 104 and 106 prevents a large gap or distance between the primary and secondary pistons 104 and 106 and prevents having to advance the primary and secondary pistons 104 and 106 over a relatively large distance without any increase in pressure in the non-failed circuit. For example, as will be explained in detail below, the brake system 10 may be operated in a manual push through mode, in which the brake pedal 70 is depressed and the isolation valves 30 and 32 are in their deenergized state as shown in
The master cylinder 14 further includes a return spring 170 biasing the input piston 102 in the rightward direction as viewing
The master cylinder 14 further includes a primary spring 190 generally disposed between the secondary piston 106 and the primary piston 104. The primary spring 190 is disposed within the inner wall 135 and engages with a retainer 192 forming a caged spring assembly configuration with an axial stem 194 extending from bottom of the inner wall 135 of the primary piston 104. The retainer 192 is restrained by an enlarged head 196 formed on the end of the axial stem 194.
The master cylinder 14 further includes a secondary spring 200 generally disposed between the secondary piston 106 and the bottom wall 115 of the bore 100. The secondary spring 200 is disposed within a bore 204 formed in the left-hand end of the secondary piston 106 and engages with a retainer 208 forming a caged spring assembly configuration with an axial stem 210 extending from the bottom of the bore 204 of the secondary piston 106. The retainer 208 is restrained by an enlarged head 212 formed on the end of the axial stem 210.
In a preferred embodiment of the brake system 10, the master cylinder 14 includes a pair of travel sensors 214 and 215 for producing signals that are indicative of the length of travel of the input piston 102 and providing the signals to the main ECU 22. The travel sensors 214 and 215 may be similar in structure and may provide for redundancy. As will be explained below, the travel sensors 214 and 215 may also be used with an auxiliary brake module 400.
As shown in
As discussed above, the input chamber 110 of the master cylinder 14 is selectively in fluid communication with the reservoir 20 via the passageway 138 formed in the input piston 102 and via the conduits 137 and 28. The brake system 10 may include the optional simulator test valve 29 located within the conduit 137. The simulator test valve 29 may be electronically controlled between an open position, as shown in
As stated above, the brake system 10 includes a pedal simulator 16 and an associated solenoid actuated simulator valve 128. The pedal simulator 16, schematically shown in
With regards to operation of the pedal simulator 16, initial movement of the brake pedal 70 from its rest position causes movement of the input piston 102 in the leftward direction, as viewing
The brake system 10 may include an optional check valve 240 in parallel with a restricted orifice 242 positioned within the conduit 126. This configuration may help suppress rapid pressure increases during a spike apply in which the driver of the vehicle rapidly and forcefully depresses the brake pedal 70.
As shown schematically in
In the embodiment shown, the ball screw mechanism 312 includes a motor, indicated schematically and generally at 314, which is electrically connected to the main ECU 22 for actuation thereof. The motor 314 rotatably drives a screw shaft 316. The motor 314 generally includes a stator 315 and a rotor 317. In the schematic embodiment shown in
The piston 306 may include structures engaged with cooperating structures formed in the housing of the plunger assembly 18 to prevent rotation of the piston 306 as the screw shaft 316 rotates relative to the piston 306. For example, the piston 306 may include outwardly extending splines or tabs or splines 325 disposed within longitudinal grooves 324 formed in the housing. The splines 325 slide along within the grooves 324 as the piston 306 travels in the bore 300.
As will be discussed below, the plunger assembly 18 is preferably configured to provide pressure to the conduit 34 when the piston 306 is moved in both the forward and rearward directions. The plunger assembly 18 includes a seal 330 mounted on the enlarged end portion 308 of the piston 306. The seal 330 slidably engages with the inner cylindrical surface of the first portion 302 of the bore 300 as the piston 306 moves within the bore 300. A seal 334 and a seal 336 are mounted in grooves formed in the second portion 304 of the bore 300. The seals 334 and 336 slidably engage with the outer cylindrical surface of the central portion 310 of the piston 306. A first pressure chamber 340 is generally defined by the first portion 302 of the bore 300, the enlarged end portion 308 of the piston 306, and the seal 330. The first pressure chamber 340 is in fluid communication with a conduit 254 which is selectively in fluid communication with the output conduit 34, as will be explained below. An annular shaped second pressure chamber 342, located generally behind the enlarged end portion 308 of the piston 306, is generally defined by the first and second portions 302 and 304 of the bore 300, the seals 330 and 334, and the central portion 310 of the piston 306. The seals 330, 334, and 336 can have any suitable seal structure. The second pressure chamber 342 is in fluid communication with a conduit 243 which is in fluid communication with the output conduit 34.
Although the plunger assembly 18 may be configured to any suitable size and arrangement, in one embodiment, the effective hydraulic area of the first pressure chamber 340 is greater than the effective hydraulic area of the annular shaped second pressure chamber 342. The first pressure chamber 340 generally has an effective hydraulic area corresponding to the diameter of the central portion 310 of the piston 306 (the inner diameter of the seal 334) since fluid is diverted through the conduits 254, 34, and 243 as the piston 306 is advanced in the forward direction. The second pressure chamber 342 generally has an effective hydraulic area corresponding to the diameter of the first portion 302 of the bore 300 minus the diameter of the central portion 310 of the piston 306. If desired, the plunger assembly 18 could be configured to provide that on the back stroke in which the piston 306 is moving rearwardly, less torque (or power) is required by the motor 314 to maintain the same pressure as in its forward stroke. Besides using less power, the motor 314 may also generate less heat during the rearward stroke of piston 306. Under circumstances in which the driver presses on the pedal 70 for long durations, the plunger assembly 18 could be operated to apply a rearward stroke of the piston 306 to prevent overheating of the motor 314. Of course, it may also be desirable to configure the plunger assembly 18 such that the behavior of the rearward stroke is the same or similar to the forward stroke of the plunger assembly 18.
The plunger assembly 18 preferably includes a sensor, schematically shown as 318, for indirectly detecting the position of the piston 306 within the bore 300. The sensor 318 is in communication with the main ECU 22. In one embodiment, the sensor 318 detects the rotational position of the rotor 317 which may have metallic or magnetic elements embedded therein. Since the rotor 317 is schematically shown as being integrally formed with the shaft 316, the rotational position of the shaft 316 corresponds to the linear position of the piston 306. Thus, the position of the piston 306 can be determined by sensing the rotational position of the rotor 317 via the sensor 318. Note that due to ease of manufacturing, the rotor 317 may not be integrally formed with the shaft 316 but rather may be a separate part connected to the shaft 316.
As best shown in
Referring back to
Generally, the first and second plunger valves 280 and 282 are controlled to permit fluid flow at the outputs of the plunger assembly 18 and to permit venting to the reservoir 20 through the plunger assembly 18 when so desired. For example, the first plunger valve 280 is preferably energized to its open position during a normal braking event. Additionally, it is preferred that both the first and second plunger valves 280 and 282 remain open (which may reduce noise during operation). Preferably, the first plunger valve 280 is almost always energized during an ignition cycle when the engine is running. Of course, the first and second plunger valves 280 and 282 may be purposely operated to their closed positions such as during a pressure generating rearward stroke of the plunger assembly 18 or during a hill hold brake operation. The first and second plunger valves 280 and 282 are preferably in their open positions when the piston 306 of the plunger assembly 18 is operated in its forward stroke to maximize flow. When the driver releases the brake pedal 70, the first and second plunger valves 280 and 282 preferably remain in their open positions. However, under certain circumstances, such as during slip control and the driver is pushing hard on the brake pedal 70 during controlled low pressures and then the driver releases half way on the brake pedal 70, it may be desirable to operate the first and second plunger valves 280 and 282 to their closed positions. Note that fluid can flow through the check valve within the closed second plunger valve 282, as well as through the check valve 284 from the reservoir 20 depending on the travel direction of the piston 306 of the plunger assembly 18 and the state of the first and second plunger valves 280 and 282.
It may be desirable to configure the first plunger valve 280 with a relatively large orifice therethrough when in its open position. A relatively large orifice of the first plunger valve 280 helps to provide an easy flow path therethrough. The second plunger valve 282 may be provided with a much smaller orifice in its open position as compared to the first plunger valve 280. One reason for this is to help prevent the piston 306 of the plunger assembly 18 from rapidly being back driven upon a failed event due to the rushing of fluid through the first output conduit 254 into the first pressure chamber 340 of the plunger assembly 18, thereby preventing damage to the plunger assembly 18. As fluid is restricted in its flow through the relatively small orifice, dissipation will occur as some of the energy is transferred into heat. Thus, the orifice should be of a sufficiently small size so as to help prevent a sudden catastrophic back drive of the piston 306 of the plunger assembly 18 upon failure of the brake system 10, such as for example, when power is interrupted or lost to the motor 314 and the pressure within the output conduit 34 is relatively high.
The plunger assembly 18 may include an optional spring member (not shown), to assist in cushioning such a rapid rearward back drive of the piston 306. The spring washer may be located just behind the enlarged portion 308 of the piston 306. The spring washer may also assist in cushioning the piston 306 moving at any such speed as it approaches a rest position near its most retracted position within the bore 300. It is noted that although the isolation valves 30 and 32 could shuttle to their positions shown in
The first and second plunger valves 280 and 282 provide for an open parallel path between the pressure chambers 340 and 342 of the plunger assembly 18 during a normal braking operation (with the first plunger valve 280 energized). Although a single open path may be sufficient, the advantage of having both the first and second plunger valves 280 and 282 is that the first plunger valve 280 may provide for an easy flow path through the relatively large orifice thereof, while the second plunger valve 282 may provide for a restricted orifice path during certain failed conditions (when the first plunger valve 280 is de-energized to its closed position). It is noted that a single normally open valve with a relatively large orifice could be sufficient instead of the two plunger valves 280 and 282, however, the single valve may need a relatively large solenoid and during power losses the single valve could close causing possible locking of the isolation valves 30 and 32.
The brake system 10 further includes an auxiliary brake module, indicated generally at 400, as shown in
The auxiliary brake module 400 may further include a secondary ECU 401 (separate from the main ECU 22) for controlling the various valves and components of the auxiliary brake module 400. The secondary ECU 401 may also be in communication with the ECU 22. In a preferred embodiment, the secondary ECU 401 is also in communication with one or more of the travel sensors 214 and 215, the reason for which will be explained below.
The main ECU 22 and the secondary ECU 401 may both be connected to a vehicle CAN bus (Controller Area Network bus) for receiving various signals and controls. Both the main ECU 22 and the secondary ECU 401 may send out signals over the CAN bus indicating that they are operating properly. These signals may be received by the other of the ECU 22 and 401. For example, once the secondary ECU 401 does not receive the signal from the main ECU 22 over the CAN bus of proper operation of the main ECU 22, the secondary ECU 401 may begin operating the auxiliary brake module 400, as will be described below.
The secondary ECU 401 may even function as a fail-safe back up in case the main ECU 22 fails. It should be understood that the brake system 10 could be configured such that the main ECU 22 also controls the auxiliary brake module 400. Alternatively, the secondary ECU 401 may be eliminated such that the main ECU 22 controls the entire brake system 10 including the auxiliary brake module 400.
The auxiliary brake module 400 further includes a pump assembly, indicated generally at 404. In the embodiment shown, the pump assembly 404 includes a single electric motor 406 controlled by the secondary ECU 401. The pump assembly 404 includes first and second pumps 408 and 410 operated by the motor 406. Of course, the pump assembly 404 can have any suitable configuration other than what is schematically shown in
The outlet of the pump 408 is directed into a conduit 412 which is in fluid communication with a check valve 414. A conduit 416 extends between the check valve 418 and the wheel brake 12b. A solenoid actuated pump valve 420 is controllable by the secondary ECU 401 and is positioned in a conduit 422 extending between the outlet and inlet of the pump 408. The inlet of the pump 408 is in fluid communication with the reservoir 20 via a conduit 424 which in fluid communication with the conduit 26. If the auxiliary brake module 400 is located remotely from the remainder of the brake system 10, the conduit 424 is preferably a hose or pipe having a sufficiently large diameter to permit the easy flow of fluid therethrough. This relatively large diameter helps to assure that the pump 408 can quickly start pumping a sufficient amount of fluid when first turned on especially during extreme cold temperatures.
The outlet of the pump 410 is directed into a conduit 430 which is in fluid communication with a check valve 432. A conduit 434 extends between the check valve 432 and the wheel brake 12c. A solenoid actuated pump valve 436 is controllable by the secondary ECU 401 and is positioned in a conduit 438 extending between the outlet and inlet of the pump 410. The inlet of the pump 410 is in fluid communication with the reservoir 20 via a conduit 440 which in fluid communication with the conduit 28. As with the conduit 424, the conduit 440 is preferably a hose, pipe, or bored conduit having a sufficiently large diameter to permit the easy flow of fluid therethrough. Since the conduits 424 and 440 are connected to the reservoir 20, the pressure of the fluid supplied to the inlet of the pumps 408 and 410 is relatively low. Ideally, the fluid pressure of the reservoir 20 is at about atmospheric pressure and is preferably less than 1 bar above atmospheric pressure.
The operation of the brake system 10 will now be described. It is noted that the terms “normal braking” or “normal brake apply” generally refers to a braking event in which all of the components of the brake system 10 are functioning normally. Additionally, under a normal braking event, the brake system 10 is not experiencing any detrimental leakage that could hinder proper operation of the brake system 10.
During a normal brake apply braking operation, the flow of pressurized fluid from the master cylinder 14 generated by depression of the brake pedal 70 is diverted into the pedal simulator 16. The simulation valve 128 is actuated or energized to divert fluid through the simulation valve 128 from the input chamber 110 of the master cylinder 14 as the input piston 102 is moved via the brake pedal 70. Note that fluid flow from the input chamber 110 to the reservoir 20 is closed off once the passageway 138 in the input piston 102 moves past the lip seal 134. As the input piston 102 generates fluid pressure within the input chamber 110, the pressurized fluid is diverted into the pressure chamber 224 of the pedal simulator 16. The build-up of pressure within the pressure chamber 224 of the pedal simulator 16 moves the piston 222 against the bias of the spring assembly 220. Compression of the spring assembly 220 provides a force feedback to the driver of vehicle as the driver feels the resistance on the driver's foot via the brake pedal 70.
During this normal braking operation, the plunger assembly 18 is operated to provide pressure to the conduit 34 for actuation of the wheel brakes 12a, 12b, 12c, and 12d. Under certain driving conditions, the main ECU 22 communicates with a powertrain control module (not shown) and other additional braking controllers of the vehicle to provide coordinated braking during advanced braking control schemes (e.g., anti-lock braking (AB), traction control (TC), vehicle stability control (VSC), and regenerative brake blending).
During the duration of a normal braking event, the simulator valve 128 remains open, preferably. Also during the normal braking operation, the isolation valves 30 and 32 are energized to secondary positions to prevent the flow of fluid from the conduits 36 and 38 through the isolation valves 30 and 32, respectively. Note that the primary and secondary chambers 112 and 114 of the master cylinder 14 are not in fluid communication with the reservoir 20 due to the passageways 148 and 158 of the primary and secondary pistons 104 and 106, respectively, being positioned past the lip seals 144 and 154, respectively. Prevention of fluid flow through the isolation valves 30 and 32 hydraulically locks the primary and secondary chambers 112 and 114 of the master cylinder 14 preventing further movement of the primary and secondary pistons 104 and 106.
Preferably, the isolation valves 30 and 32 are energized throughout the duration of an ignition cycle such as when the engine is running instead of being energized on and off to help minimize noise. It is also generally desirable to maintain the isolation valves 30 and 32 energized during the normal braking mode to ensure venting of fluid to the reservoir 20 through the plunger assembly 18 such as during a release of the brake pedal 70 by the driver. As best shown in
As stated above, during normal braking operations, while the pedal simulator 16 is being actuated by depression of the brake pedal 70, the plunger assembly 18 can be actuated by the main ECU 22 to provide actuation of the wheel brakes 12a, 12b, 12c, and 12d. The plunger assembly 18 is operated to provide desired pressure levels to the wheel brakes 12a, 12b, 12c, and 12d instead of pressure being generated and delivered by the master cylinder 14 by the driver depressing the brake pedal 70. The main ECU 22 actuates the motor 314 of the plunger assembly 18 to rotate the screw shaft 316 in a first rotational direction. Rotation of the screw shaft 316 in the first rotational direction causes the piston 306 to advance in the forward direction (leftward as viewing
When the driver lifts off or releases the brake pedal 70, the main ECU 22 can operate the motor 314 of the plunger assembly 18 to rotate the screw shaft 316 in a second rotational direction, opposite the first rotational direction, causing the piston 306 to retract in the right-hand direction, as viewing
In some situations, the piston 306 of the plunger assembly 18 may reach its full stroke length within the bore 300 of the housing while additional boosted pressure is still desired to be delivered to the wheel brakes 12a, 12b, 12c, and 12d. Preferably, the plunger assembly 18 is a dual acting plunger assembly such that it is configured to also provide boosted pressure to the conduit 34 when the piston 306 is stroked rearwardly (rightward) or in a reverse direction. This has the advantage over a conventional plunger assembly that requires its piston to be brought backward before it can again advance the piston to create pressure within a single pressure chamber. If the piston 306 has reached its full stroke, for example, and additional boosted pressure is still desired, the second plunger valve 282 is energized to its closed check valve position. The first plunger valve 280 is de-energized to its normally closed position. The main ECU 22 actuates the motor 314 of the plunger assembly 18 in the second rotational direction to rotate the screw shaft 316 in the second rotational direction. Rotation of the screw shaft 316 in the second rotational direction causes the piston 306 to retract or move in the rearward direction (rightward as viewing
In a similar manner as during a forward stroke of the piston 306, the main ECU 22 can also selectively actuate the apply valves 50, 54, 58, and 62 and the dump valves 52, 56, 60, and 64 to provide a desired pressure level to the wheel brakes 12a, 12b, 12c, and 12d, respectively. When the driver lifts off or releases the brake pedal 70 during a pressurized rearward stroke of the plunger assembly 18, the first and second plunger valves 280 and 282 are preferably operated to their open positions, although having only one of the valves 280 and 282 open would generally still be sufficient. Note that when transitioning out of a slip control event, the ideal situation would be to have the position of the piston 306 and the displaced volume within the plunger assembly 18 correlate exactly with the given pressures and fluid volumes within the wheel brakes 12a, 12b, 12c, and 12d. However, when the correlation is not exact, such as for example, when there is excess fluid within the plunger assembly 18, fluid can escape via the passageway 344 to the reservoir 20. In situations where there is a deficiency of fluid, fluid can be drawn from the reservoir 20 via the check valve 284 into the chamber 340 of the plunger assembly 18.
During a braking event, the main ECU 22 can selectively actuate the apply valves 50, 54, 58, and 62 and the dump valves 52, 56, 60, and 64 to provide a desired pressure level to the wheel brakes, respectively. The main ECU 22 can also control the brake system 10 during ABS, DRP, TC, VSC, regenerative braking, and autonomous braking events by general operation of the plunger assembly 18 in conjunction with the apply valves and the dump valves. Even if the driver of the vehicle is not depressing the brake pedal 70, the main ECU 22 can operate the plunger assembly 18 to provide a source of pressurized fluid directed to the wheel brakes, such as during an autonomous vehicle braking event.
In the event of a loss of electrical power to portions of the brake system 10, the brake system 10 provides for manual push through or manual apply such that the master cylinder 14 can supply relatively high pressure fluid to the conduits 36 and 38. During an electrical failure, the motor 314 of the plunger assembly 18 might cease to operate, thereby failing to produce pressurized hydraulic brake fluid from the plunger assembly 18. The isolation valves 30 and 32 will shuttle (or remain) in their positions to permit fluid flow from the conduits 36 and 38 to the wheel brakes 12a, 12b, 12c, and 12d. The simulator valve 128 is shuttled to its normally closed position to prevent fluid from flowing out of the input chamber 110 of the master cylinder 14 to the pedal simulator 16. During the manual push-through apply, the input piston 102, the primary piston 104, and the secondary piston 106 will advance leftwardly such that the passageways 138, 148, 158 will move past the seals 134, 144, and 154, respectively, to prevent fluid flow from their respective fluid chambers 110, 112, and 114 to the reservoir 20, thereby pressurizing the chambers 110, 112, and 114. Fluid flows from the primary and secondary chambers 112 and 114 into the conduits 38 and 36, respectively, to actuate the wheel brakes 12a, 12b, 12c, and 12d.
The operation of the auxiliary brake module 400 will now be explained relative to the brake system 10 undergoing a manual push through event. The brake system 10 is ideally suited for vehicles, such as trucks, that have wheel brakes requiring a relatively high volume of fluid for full operation thereof. Thus, these vehicles may demand a brake system capable of providing a relatively large volume of fluid to the wheel brakes compared to brake systems designed for smaller passenger vehicles. This may be especially true in a failed condition when the brake system 10 is undergoing a manual push through operation. The brake system 10 can provide an increased volume of fluid for the front and rear circuits via the auxiliary brake module 400. For example, if an electrical failure occurred in the brake system 10, the auxiliary brake module 400 may be operated to provide an extra volume of fluid function to the front and rear wheel brakes. The auxiliary brake module 400 may be located remotely and/or electrically disconnected therefrom for such a reason.
The auxiliary brake module 400 may be operated when the brake system 10 undergoes a manual push through event. For example, in such a failed condition, the plunger assembly 18 may not be capable of providing the desired fluid pressure to the wheel brakes and electrical power may not be available to energize the valves of the brake system 10. If a failed condition occurred prior to the driver applying the brakes (pushing on the brake pedal 70), when the driver pushes on the brake pedal 70, fluid from the primary and secondary chambers 112 and 114 of the master cylinder 14 will be diverted through the deenergized isolation valves 30 and 32, respectively. The rear wheel brakes 12c and 12d will receive pressurized fluid in a rear fluid circuit from the primary chamber 112 of the master cylinder 14. Similarly, the front wheel brakes 12a and 12b will receive pressurized fluid in a front fluid circuit from the secondary chamber 114 of the master cylinder 14. For larger vehicles with wheel brakes having a relatively large volume of fluid, the driver would normally have to press the brake pedal 70 a relatively long distance during a manual push through event. To assist the driver in reducing the pedal travel length required, the auxiliary brake module 400 may be operated by the secondary ECU 401 (or possibly the main ECU 22) to add additional pressurized fluid (in addition to the fluid provided by the master cylinder 14) to the wheel brakes 12a, 12b, 12c, and 12d.
During operation of the auxiliary brake module 400, the secondary ECU 401 energizes the motor 406 to operate the pumps 408 and 410. Pressurized fluid from the outlet of the pump 408 is directed through the conduit 412 past the check valve 414 and into the conduit 416. This pressurized fluid is introduced into the right front wheel brake 12b in addition to the pressurized fluid from the master cylinder 14 via the conduit 36 and through the isolation valve 30 and the open apply valve 54. The fluid path from the pump 408 to the left front wheel brake 12a is greater (or more restricted) compared to the path to the right front wheel brake 12b just described. Pressurized fluid from the outlet of the pump 408 is directed through the conduit 412 past the check valve 414, into the conduit 416, through the open apply valve 54, and then through the open apply valve 50. Thus, the flow pressure path for the left front wheel brake 12a is more restricted than the path to the right front wheel brake 12b.
With regard to the rear wheel brakes, pressurized fluid from the outlet of the pump 410 is directed through the conduit 430 past the check valve 432 and into the conduit 434. This pressurized fluid is introduced into the left rear wheel brake 12c in addition to the pressurized fluid from the master cylinder 14 via the conduit 38 and through the isolation valve 32 and the open apply valve 58. The fluid path from the pump 410 to the right rear wheel brake 12d is greater (or more restricted) compared to the path to the left rear wheel brake 12c just described. Pressurized fluid from the outlet of the pump 410 is directed through the conduit 430 past the check valve 432, into the conduit 434, through the open apply valve 58, and then through the open apply valve 62. Thus, the flow pressure path for the right rear wheel brake 12d is more restricted than the path to the left rear wheel brake 12c.
As stated above, the flow pressure path to the left front wheel brake 12a and the right rear wheel brake 12d is more restricted than the other two wheel brakes. In this preferred embodiment the pressure to all wheel brakes will eventually equalize. However, under a relatively fast apply, the pressure in the right front wheel brake 12b and the left rear wheel brake 12c will be temporarily greater than the other two wheel brakes. Since the left front wheel brake 12a and the right rear wheel brake 12d are arranged in a diagonally split manner, unequal yaw forces acting on the vehicle are counteracted and are thus minimized or cancelled out. For example, if the restricted flow pressure paths instead corresponded to the same side of the vehicle, a fast apply could promote a bias across both axles of the vehicle which could cause instability of the vehicle during this braking event due to yaw forces acting on the vehicle.
To control the pressure exiting the conduits 416 and 434 from the auxiliary brake module 400, the solenoid actuated pump valves 420 and 436 are preferably controlled by the secondary ECU 401. The secondary ECU 401 is preferably included in the brake system 10 in case of a failure of the main ECU 22 which would not be able to control the auxiliary brake module 400. Thus, assisted braking can still be accomplished during a manual push through braking event with the secondary ECU 401 and the auxiliary brake module 400. As stated above, the solenoid actuated pump valves 420 and 436 are controlled by the secondary ECU 401 to obtain a desired fluid pressure exiting the conduits 416 and 434 from the auxiliary brake module 400. For example, a given electrical current is directed to the solenoid within the pump valve 420 to bias the pump valve 420 in a closed position preventing the flow of fluid therethrough. A pressure build up from the pump 408 in the conduit 412 will eventually exceed the force of the solenoid maintaining closure of the pump valve 420, thereby opening the pump valve 420. Once the pump valve 420 is open, fluid will be sent back to the inlet of the pump 408 via the conduit 422 until the pump valve 420 closes again. This cycle will repeat to maintain a relatively desired pressure relative to the current directed to the solenoid of the pump valve 420. The greater the electrical current sent to the pump valve 420, the greater the output pressure of the pump 408. The other pump valve 436 is controllable in the same manner with respect to controlling the pressure of the conduit 434.
The secondary ECU 401 controls the solenoid actuated pump valves 420 and 436 to a desired pressure based on the driver's demands. The driver's demands can be determined with the use of various sensors, such as for example the travel sensors 214 and 215 of the master cylinder 14. The secondary ECU 401 preferably receives signals from one or both of the travel sensors 214 and 215 of the master cylinder 14. Driver demand or intent can be determined by monitoring the travel sensors 214 and 215 as the input piston 102 moves in the housing of the master cylinder 14 caused by depression of the brake pedal 70 during a manual push through event. The auxiliary brake module 400 can be operated accordingly based on the travel sensor information since the driver's pedal travel demand is known. From previous knowledge from the main ECU 22 regarding the P-V (pressure-volume) characteristics of the wheel brakes and various components of the brake system 10, the secondary ECU 401 can control the auxiliary brake module 400 accordingly. For example, it may be known from previous data collection that for a given travel distance of the input piston 102, a certain pressure is generated in the circuit conduits 36 and 38. If it is known that the auxiliary brake module 400 should provide an added fluid volume by a predetermined ratio, for example ⅔ of the desired volume at a given pressure at the wheel brakes, the auxiliary brake module 400 can be operated to provide the necessary added volume increase. As stated above, this added volume of fluid from the auxiliary brake module 400 shortens the pedal travel length that the driver needs to initiate at the master cylinder 14 had the auxiliary brake module 400 not been included in the brake system 10.
The auxiliary brake module 400 may include separate conduits 424 and 440 in fluid communication with the reservoir 20 in case one of the circuits associated with one of the conduits 424 and 440 fails and starts leaking fluid. Under this situation, the pump 408 or 410 associated with the leaking circuit could run out of fluid at its intake such that the pump 408 or 410 injects air into the circuit and possibly the wheel brakes. Although that leaking circuit may not function properly, the pump 408 or 410 not associated with the leaking circuit would still function properly due to a separate connection with the reservoir 20, and thus braking of the vehicle can still be accomplished with just the one circuit (associated with the conduits 36 or 38). The leak may be detected by monitoring the correct operation of the motor 406.
Although use of the auxiliary brake module 400 was described above with respect to being used during a failure of one or more of the components of the brake system 10, such as during a manual push through event, the auxiliary brake module 400 could be triggered on during a non-failed braking event. For example, the auxiliary brake module 400 could be triggered during self-diagnostics.
If desired, the brake system 10 could be configured to operate even if the driver is not pressing on the brake pedal 70, and thus, no pressure can be generated from the master cylinder 14. For example, the auxiliary brake module 400 may be engaged due to a failed event of the brake system 10 during an autonomous driving/braking event. During a normal autonomous driving/braking event, the plunger assembly 18 can be operated to provide the desired braking control to the wheel brakes 12a, 12b, 12c, and 12d. However, if the main braking system 10 fails, such as an electrical power cut-off to the brake system 10 such that the plunger assembly 18 cannot be operated, the secondary ECU 401 can engage the auxiliary brake module 400 to provide pressure to the front and rear circuits via the conduits 416 and 434. To accomplish this, the brake system 10 would need to be configured to prevent fluid from flowing through the master cylinder 14 and into the reservoir 20. The auxiliary brake module 400 could be configured to operate the simulator test valve 29 to an energized closed position to prevent the flow of fluid through the now open compensation ports (passageways 138 and 148) of the master cylinder 14 to the reservoir 20. An additional valve (not shown) could be incorporated into the conduit 26 to prevent the flow of fluid through the passageway 158 and into the reservoir 20.
Although the brake system 10 functions sufficiently during a manual push through braking event, one disadvantage of the brake system 10 is that while the auxiliary brake module 400 can introduce a pressure increase (fluid added to the conduits 416 and 434), the auxiliary brake module 400 generally cannot remove fluid or relieve pressure at the wheel brakes 12a, 12b, 12c, and 12d. Fluid pressure is released when the master cylinder 14 is operated by the driver to its rest state such that pressure in the primary and secondary chambers 112 and 114 is vented to the reservoir 20. Assuming that the dump valves 52, 56, 60, and 64 are also inoperable during the manual push through braking event, such as due to a loss of electrical power or failure of the main ECU 22, fluid pressure cannot be released using these dump valves 52, 56, 60, and 64. However, there is illustrated in
Referring now to
The brake system 500 includes an auxiliary brake module, indicated generally at 510. The auxiliary brake module 510 functions as a second source of pressurized fluid, such as under certain failed conditions of the brake system 500. As a secondary source of pressurized fluid, the auxiliary brake module 510 provides an added volume of fluid to the brake system 500 during a manual push through braking event. Additionally, the auxiliary brake module 510 can relieve pressure within the wheel brakes during a manual push through braking event. The auxiliary brake module 510 may be housed in a different block or unit remotely located from the remainder of the brake system 500, or may be housed integrally therewith. The auxiliary brake module 510 may further include a secondary ECU 501 (separate from the main ECU 22) for controlling the various valves and components of the secondary brake module 510. The secondary ECU 501 may also be in communication with the ECU 22. In a preferred embodiment, the secondary ECU 501 is also in communication with the travel sensors 214 and 215, as discussed above with respect to the brake system 10. Similar to the brake system 10, the brake system 500 includes the pump assembly 404 having the motor 406 and first and second pumps 408 and 410. The brake system 500 also includes the pump valves 420 and 436, corresponding to the first and second pumps 408 and 410, respectively.
One of the differences between the brake systems 10 and 500 is that the brake system 500 includes first and second fluid separators 520 and 522 located within the conduits 416 and 434, respectively. It is noted that the brake system 500 does not include the check valves 414 and 432. The fluid separators 520 and 522 are essentially identical in structure in function. Thus, only the structure and function of the fluid separator 520 will be discussed in detail but it should be understood that the same description applies to the second fluid separator 522 as well. As shown in an enlarged schematic view in
During an actuation of the auxiliary brake module 510, a pressure increase in the first chamber 536 caused by an increase pressure in the conduit 412 from the outlet of the pump 408 expands the first chamber 536. Assuming that the pressure in the conduit 416 is lower than the pressure within the conduit 412, the expansion of the first chamber 536 causes the piston 530 to move leftwardly, as viewing
The fluid separators 520 and 522 isolate the fluid within the auxiliary brake module 510 from the front circuit (associated with the wheel brakes 12a and 12b, the conduits 416 and 36, etc.) and the rear circuit (associated with the wheel brakes 12c and 12d, the conduits 434 and 38, etc.). Since the auxiliary brake module 510 is now isolated, the brake system 500 needs only one conduit 546 leading to the reservoir 20 compared to the two conduits 424 and 440 of the brake system 10. If a leak occurs in the auxiliary brake module 510, such as in the conduit 546, the auxiliary brake module 510 may not function properly due to air being introduced into the pumps 408 and 410, however, this introduced air will not be sent into the main brake system 500 due to the barrier function of the fluid separators 520 and 522. It is also noted that the reservoir 20 of the brake system 500 includes an additional interior wall 20c to isolate this auxiliary brake module fluid circuit from the other circuits. This interior wall 20c helps to assure that a leakage in one of the circuits will not deplete the reservoir fluid for the auxiliary brake module 510.
Referring now to
One of the differences between the brake system 600 and the preceding brake systems is that the brake system 600 utilizes a two piston master cylinder, indicated generally at 602, instead of a three piston design such as the master cylinder 14. Referring now to the enlarged view of the master cylinder 602 in
As shown in
The master cylinder 602 may include a primary spring arrangement, indicated generally at 622, disposed between the primary piston 606 and the secondary piston 608. This positional relationship helps to define the volume of the primary chamber 610 in its at rest state or generally uncompressed condition. Additionally, the primary spring assembly 622 biases the primary and secondary pistons 606 and 608 away from each other when the primary spring assembly 622 is compressed. The primary spring arrangement 622 may have any suitable configuration, such as a caged spring assembly or a simple coil spring, as shown.
As shown in
The master cylinder 14 may include a secondary spring arrangement, indicated generally at 630, disposed between the secondary piston 608 and the end wall 614 of the housing of the master cylinder 602. The secondary spring arrangement 630 positions the secondary piston 608 at a desired placement relative to the end wall 614 when the master cylinder 602 is assembled. This positional relationship helps to define the volume of the secondary chamber 612 in its at rest state or generally uncompressed condition. Additionally, the secondary spring assembly 630 biases the secondary piston 608 in a rightward direction, as viewing
One advantage of the design of the two piston master cylinder 602 over the design of the three piston master cylinder 14 is the lower cost of the two piston design due to fewer components and simpler construction. Additionally, the two piston master cylinder design may be easier to package within the vehicle due to its smaller size compared to the three piston design. Another advantage of the master cylinder 602 is the possibility of a lower pedal force required due in part to the absence of a caged spring assembly design of the primary spring 622. However, during a manual push through event, a greater travel may be necessary due to the requirement of the compensation ports needing to be first closed. The three piston master cylinder design may also require additional seal friction to overcome due to the greater amount of seals compared to a two piston master cylinder design. However, the three piston design may have the advantage of having no or less fluid loss during a manual push through event since all of the volume of fluid in the primary chamber may be used in the three position design. Contrary, if the manual push through event is initiated after the driver has moved the primary piston in the two piston master cylinder design, fluid diverted into the pedal simulator is now not available. Of course, the design and size of the chambers of the master cylinders can be configured to avoid or minimize this issue.
Another difference of the brake system 600 is the configuration of a pedal simulator 650. Although the pedal simulator 650 performs the same function as the pedal simulator 16 of the brake system 10 to provide driver pedal feel feedback, in the brake system 600, the primary chamber 610 of the master cylinder 602 is in selective fluid communication with the pedal simulator 650 via a conduit 652 which is in fluid communication with the conduit 38. Leftward movement of the primary piston 606 caused by the driver depressing the brake pedal 70 will pressurize the primary chamber 610 causing fluid to flow into the pedal simulator 650 via the conduits 38 and 652.
The pedal simulator 650 can be any suitable structure which provides a feedback force to the driver's foot via the brake pedal 70 when depressed. The pedal simulator 650 may include movable components which mimic the feedback force from a conventional vacuum assist hydraulic brake system. For example, as fluid is diverted into the pedal simulator 650, a simulation pressure chamber 654 defined within the pedal simulator 650 will expand causing movement of a piston 656 within the pedal simulator 650. Note that in
The brake system 600 includes an auxiliary brake module, indicated generally at 670. Similar to the auxiliary brake module 400, the auxiliary brake module 670 functions as a second source of pressurized fluid, such as under certain failed conditions of the brake system 600. As a secondary source of pressurized fluid, the auxiliary brake module 670 provides an added volume of fluid to the brake system 600 during a manual push through braking event. Additionally, the auxiliary brake module 600 can relieve pressure within the wheel brakes during a manual push through braking event. The auxiliary brake module 670 may be housed in a different block or unit remotely located from the remainder of the brake system 600, or may be housed integrally therewith. The auxiliary brake module 670 may further include a secondary ECU 672 (separate from the main ECU 22) for controlling the various valves and components of the secondary brake module 670. The secondary ECU 672 may also be in communication with the main ECU 22. In a preferred embodiment, the secondary ECU 672 is also in communication with the travel sensors 214 and 215, as discussed above with respect to the brake system 10. Similar to the brake systems 10 and 500, the brake system 600 includes the pump assembly 404 having the motor 406 and first and second pumps 408 and 410. The first and second pumps 408 and 410 have output conduits 412 and 430, respectively, as well as input conduits 422 and 438, respectively. The auxiliary brake module 670 further includes the pump valves 420 and 436, corresponding to the first and second pumps 408 and 410, respectively. The inlet conduits 422 and 438 are in fluid communication with the single hose or conduit 546 in fluid communication with the reservoir 20.
It is noted that the brake system 600 is configured as a vertically split system such that the conduit 36 is associated with the front wheel brakes, and the conduit 38 is associated with the rear wheel brakes, as is the brake system 500. However, the wheel brake designation for the brake system 600, is slightly different from the brake system 10 as well as is the configuration of the auxiliary brake module 670, as will be explained below. For the brake system 600, the wheel brake 12a may be associated with the right front wheel of the vehicle in which the brake system 600 is installed. The wheel brake 12b may be associated with the left front wheel. The wheel brake 12c may be is associated with the right rear wheel. The wheel brake 12d may be associated with the left rear wheel.
Another difference between the brake systems 500 and 600 is that the brake system 600 includes differently configured first and second fluid separators 674 and 676. The fluid separators 674 and 676 have a dual seal design compared to the single seal design of the fluid separators 520 and 522. The fluid separators 674 and 676 essentially perform the same function as the fluid separators 520 and 522 in that they isolate the fluid within the auxiliary brake module 670. The fluid separators 674 and 676 are essentially identical in structure in function. Thus, only the structure and function of the fluid separator 674 will be discussed in detail with respect to
As shown in an enlarged schematic view in
A passageway(s) 696 is formed through the piston 680. The passageway 696 provides fluid communication between the second chamber 690 and a conduit 698 when the fluid separator 674 is in its rest position, as shown in
The fluid separator 674 may also include a fluid filter, as shown schematically at 699, for filtering out particulate matter and preventing this particulate matter from scratching, damaging, or preventing proper operation of the seal 684. Of course, the use of fluid filters (as shown schematically similar as the filter 699 in
As stated above, the second fluid separator 676 is similar in design as the first fluid separator 674. Thus, the first fluid chamber of the fluid separator 676 is in fluid communication with the conduit 430, the second fluid chamber is in fluid communication with a conduit 700 connected to the wheel brake 12b. In the rest position, the passageway of the piston of the second fluid separator 676 is in fluid communication with a conduit 702 in fluid communication with the conduit 40 through the apply valve 54. Thus, during normal braking, pressurized fluid from the conduit 40 is diverted to the wheel brake 12b via the conduit 702.
When the auxiliary brake module 670 is activated, such as during a failed condition of the brake system 10 in which the plunger assembly 18 is inoperative, the secondary ECU 672 actuates the motor 406 to engage the pumps 408 and 410 to provide pressurized fluid to the conduits 412 and 430, respectively. The pressure rise of the conduits 412 and 430 causes movement of the pistons within the fluid separators 674 and 676, thereby transferring the pressure therethrough causing a pressure rise within the conduits 692 and 700 to actuate the front wheel brakes 12a and 12b. Similar to the preceding auxiliary brake modules, the pump valves 420 and 436 of the auxiliary brake module 670 can be controlled to regulate the output pressure at the conduits 412 and 430. It is noted that unlike the brake system 500, the auxiliary brake module 670 of the brake system 600 does not provide pressure from the auxiliary brake module 670 to the rear wheel brakes 12c and 12d via a path. Instead, the pressure downstream from the fluid separators 674 and 676 is fed directly to the wheel brakes 12a and 12b, respectively, once the pistons of the fluid separators have moved a sufficient distance closing of the respective passageways (696) formed in the pistons (680).
It is also noted that the fluid separators 674 and 676 are preferably designed to permit a higher pressure fluid within the conduits 698 and 702 to be directed through the fluid separators 674 and 676 to the wheel brakes 12a and 12b should the pressure from the pumps 408 and 410 be less than the pressure from the conduits 698 and 702 such as by a manual push through brake apply. As shown in
The configuration of the brake system 600 permits the auxiliary brake module 670 to provide a higher pressure at the wheel brakes 12a and 12b than what the driver may want on all four brakes, as compared to the brake system 500 of
There is illustrated in
The fluid separator 710 is designed to permit a higher pressure fluid within the conduit 698 to be directed through the fluid separator 710 to the wheel brakes 12a, for example, as described above with respect to the schematic fluid separator 674. As shown in
There is also shown in
If desired, the pressure sensors may be connected to both the main ECU 22 and the secondary ECU 672. During normal braking, the pressure sensor 740 generally senses the pressure directed to the front wheel brakes 12a and 12b, and the pressure sensor 742 generally senses the pressure directed to the rear brakes 12c and 12d. The main ECU 22 may use the information from the pressure sensors 740 and 742 to control the plunger assembly 18 although the pressure readings are generally not used to determine the driver's intent.
Referring now to
One of the differences between the brake system 800 and the brake system 600 is that the brake system 800 is configured as a diagonally split brake system. As an example, the wheel brake 12a may be associated with the left rear wheel of the vehicle in which the brake system 800 is installed. The wheel brake 12b may be associated with the right front wheel. The wheel brake 12c may be associated with the left front wheel. The wheel brake 12d may be associated with the right rear wheel. As shown in
Another difference of the brake system 800 is the inclusion of electric motorized parking brakes 810 and 812. In the brake system 800 shown, the parking brake 810 is associated with the left rear wheel, while the parking brake 812 is associated with the right rear wheel. The parking brakes 810 and 812 can be any suitable mechanism for applying a braking force to a wheel. For example, the parking brakes 810 and 812 could include an electric motorized actuator connected to a brake pad for applying a frictional braking force to a rotor or drum connected to the wheel. The electrical motors of the parking brakes 810 and 812 are preferably controllable by one or both of the ECUs 22 and 672 for adding braking force to the associated wheel during a failed condition, such as for example, under a manual push through event. It should be understood that any of the brake systems described herein may include such parking brakes connected to the main or secondary ECUs, and any number of wheels may include such controllable parking brakes.
Referring now to
One of the differences between the brake system 850 and the brake system 800 is that the brake system 850 may be configured as an autonomous brake system. As such, the brake system 850 could be configured to eliminate the manually operated brake pedal, the master cylinder, and the pedal simulator. Thus, the brake system 850 may not receive any input from a driver for the vehicle but is controlled by the main ECU and/or the secondary ECU during normal braking as well as under failed conditions (such as by control of the auxiliary brake module 670). Alternatively, the brake system 850 could be configured as a “brake-by-wire” system such that the brake system 850 does receive input from a driver of the vehicle via a remote pedal simulator, indicated generally at 860. The pedal simulator 860 is not connected hydraulically to the brake system 850. Instead, the pedal simulator 860 provides a force feedback to the driver as the driver depresses a brake pedal 862 and is electrically connected to the main ECU 22 and/or the secondary ECU 672 for providing information of the driver's intentions. The pedal simulator 860 includes a spring assembly, indicated generally at 870, housed in an air-filled chamber 872. A piston 874, which is connected to the brake pedal 862, pushes against the spring assembly 870 during operation of the pedal simulator 860 as the driver depresses the brake pedal 862. The pedal simulator 860 may include a plurality of redundant travel sensors 876. Each of the travel sensors 876 produces a signal that is indicative of the length of travel of the piston 874 and provides the signal to one or both of the ECUs 22 and 672. The travel sensors 876 may detect the rate of travel of the piston 874 as well. In the illustrated embodiment shown in
Referring now to
The brake system 900 includes an auxiliary brake module, indicated generally at 902. The auxiliary brake module 902 functions as a second source of pressurized fluid, such as under certain failed conditions of the brake system 900. As a secondary source of pressurized fluid, the auxiliary brake module 902 provides an added volume of fluid to the brake system 900 during a manual push through braking event. Additionally, the auxiliary brake module 902 can relieve pressure within the wheel brakes during a manual push through braking event but generally cannot remove fluid other than what the auxiliary brake module contributes into the brake system 900. The auxiliary brake module 902 may be housed in a different block or unit remotely located from the remainder of the brake system 900, or may be housed integrally therewith. The auxiliary brake module 902 may further include a secondary ECU 904 (separate from the main ECU 22) for controlling the various valves and components of the secondary brake module 902. The secondary ECU 904 may also be in communication with the ECU 22. In a preferred embodiment, the secondary ECU 904 is also in communication with the travel sensors 214 and 215, as discussed above with respect to the brake system 10.
Similar to the auxiliary brake module 400 of the brake system 10, the auxiliary brake module 902 of the brake system 900 includes the pump assembly 404 having the motor 406 and first and second pumps 408 and 410. The auxiliary brake module 902 also includes the pump valves 420 and 436, corresponding to the first and second pumps 408 and 410, respectively. The outlet of the pump 408 is in fluid communication with the conduit 412, while the inlet of the pump 408 is in fluid communication with the conduit 422 and the pump valve 420. The outlet of the pump 410 is in fluid communication with the conduit 430, while the inlet of the pump 410 is in fluid communication with the conduit 438 and the pump valve 436.
One of the differences between the brake systems 500 and 900 is that the fluid separators 520 and 522 are replaced with volume intensifiers or flow intensifiers 910 and 912. The flow intensifiers 910 and 912 still perform the same function of isolating the fluid within the auxiliary brake module 902 from the front circuit (wheel brakes 12a and 12b) and the rear circuit (wheel brakes 12c and 12d). Similarly, only one fluid conduit 546 is necessary to connect the reservoir 20 to the inlet of the pumps 408 and 410 much the same as the brake system 500. However, the flow intensifiers 910 and 912 provide the additional advantage of increasing the volume of fluid exiting the flow intensifiers 910 and 912 towards the wheel brakes compared to the volume of fluid entering the flow intensifiers 910 and 912 from the outlets of the pumps 408 and 410.
The flow intensifiers 910 and 912 may be any suitable volume intensifier which increases the volume of fluid exiting the flow intensifier compared to the volume of fluid entering the flow intensifier. The flow intensifiers 910 and 912 are essentially identical in structure in function. Thus, only the structure and function of the flow intensifier 910 will be discussed in detail but it should be understood that the same description applies to the second flow intensifier 912 as well.
The flow intensifier 910 further includes a first seal 930 engaged with a larger diameter portion of the piston 920. The flow intensifier 910 includes a second seal 932 engaged with a smaller diameter portion of the piston 920. A cavity 934 is generally defined between the first and second seals 930 and 932, and the outer surface of the piston 920 and the bore 922 and is preferably vented to atmosphere, such as through a passageway 936. Thus, the cavity 934 does not include fluid therein.
Referring now to
The brake system 1000 includes an auxiliary brake module, indicated generally at 1002. The auxiliary brake module 1002 functions as a second source of pressurized fluid, such as under certain failed conditions of the brake system 1000. As a secondary source of pressurized fluid, the auxiliary brake module 1002 provides an added volume of fluid to the brake system 1000 during a manual push through braking event. The auxiliary brake module 1002 may be housed in a different block or unit remotely located from the remainder of the brake system 1000, or may be housed integrally therewith. The auxiliary brake module 1002 may further include a secondary ECU 1004 (separate from the main ECU 22) for controlling the various valves and components of the secondary brake module 1002. The secondary ECU 1004 may also be in communication with the main ECU 22. In a preferred embodiment, the secondary ECU 1004 is also in communication with the travel sensors 214 and 215, as discussed above with respect to the brake system 10.
Similar to the brake systems 10 and 500, the auxiliary brake module 1002 of the brake system 1000 includes the pump assembly 404 having the motor 406 and first and second pumps 408 and 410. The auxiliary brake module 1002 also includes the pump valves 420 and 436, corresponding to the first and second pumps 408 and 410, respectively. The outlet of the pump 408 is in fluid communication with the conduit 412, while the inlet of the pump 408 is in fluid communication with the conduit 422 and the pump valve 420. The outlet of the pump 410 is in fluid communication with the conduit 430, while the inlet of the pump 410 is in fluid communication with the conduit 438 and the pump valve 436. The auxiliary brake module 1002 also includes the fluid separators 520 and 522 similar to the brake system 500.
One of the differences between the brake systems 500 and 1000 is that the brake system 1000 uses a low pressure accumulator 1010 instead of utilizing the conduit 546 to obtain fluid from the reservoir 20. Depending on the length of the conduit 546, the hose or piping can be relatively expensive given that the conduit 546 needs to have the required internal diameter to supply a sudden intake of fluid to the pumps 408 and 410 especially during cold weather environments. The low pressure accumulator 1010 provides a source of fluid at a relatively low pressure, such as for example, less than 1 bar above atmospheric pressure. The low pressure accumulator 1010 can be configured to hold any desirable volume of fluid necessary for proper operation. If desired, the low pressure accumulator 1010 could be configured to contain enough brake fluid to assure that during operation of the auxiliary brake module 1002 the wheel brakes 12a, 12b, 12c, and 12d can be provided with enough fluid for maximum braking power (and fluid capacity) at the calipers of the wheel brakes. However, this is generally not necessary as the driver is also providing a source of pressurized fluid during a manual push-through event via the master cylinder 14. The low pressure accumulator 1010 can have any suitable structure.
Referring to the enlarged view of the low pressure accumulator 1010 in
To perform an initial fill of the auxiliary brake module 1002, the front and rear fluid circuits of the brake system 1000 have preferably not been filled yet and are still dry. One of the first steps is to pull a vacuum from the chamber 1020, the conduits 1022 and 1024, as well as the conduits 412, 422, 430 and 438. This can be accomplished with the assistance of a conduit 1032 connected to either the conduit 1022 or the conduit 1024, such as is shown in
There is illustrated in
Referring now to
The brake system 1100 is a diagonally split system such that the wheel brake 12a is associated with the left rear wheel of the vehicle in which the brake system 1100 is installed. The wheel brake 12b is associated with the right front wheel. The wheel brake 12c is associated with the left front wheel. The wheel brake 12d is associated with the right rear wheel.
The brake system 1100 includes an auxiliary brake module, indicated generally at 1110. The auxiliary brake module 1110 functions as a second source of pressurized fluid, such as under certain failed conditions of the brake system 1100. As a secondary source of pressurized fluid, the auxiliary brake module 1110 provides an added volume of fluid to the brake system 1100 during a manual push through braking event. Additionally, the brake system 1100 could be controlled to provide autonomous braking such that the auxiliary control module 1110 is operated even if the driver is not pressing on the brake pedal 70. The auxiliary brake module 1100 may be housed in a different block or unit remotely located from the remainder of the brake system 1100, or may be housed integrally therewith. The auxiliary brake module 1110 may further include a secondary ECU 1112 (separate from the main ECU 22) for controlling the various valves and components of the secondary brake module 1110. The secondary ECU 1112 may also be in communication with the main ECU 22.
Similar to the brake system 1050, the auxiliary brake module 1110 of the brake system 1000 includes the pump assembly 404 having the motor 406 and first and second pumps 408 and 410. The auxiliary brake module 1110 also includes the pump valves 420 and 436, corresponding to the first and second pumps 408 and 410, respectively. The outlet of the pump 408 is in fluid communication with the conduit 412, while the inlet of the pump 408 is in fluid communication with the conduit 422 and the pump valve 420. The outlet of the pump 410 is in fluid communication with the conduit 430, while the inlet of the pump 410 is in fluid communication with the conduit 438 and the pump valve 436.
One of the differences of the auxiliary brake module 1110 compared to the auxiliary brake module 1052 is the use of differently configured flow intensifiers 1120 and 1122 compared to the flow intensifiers 1060 and 1062. The flow intensifiers 1120 and 1122 have a three seal design. The flow intensifiers 1120 and 1122 essentially perform the same function as the flow intensifiers 1060 and 1062 in that they isolate the fluid within the auxiliary brake module 1110 as well as provide a larger volume of fluid to the wheel brakes 12b and 12c. The flow intensifiers 1120 and 1122 are essentially identical in structure in function. Thus, only the structure and function of the flow intensifier 1120 will be discussed in detail with respect to
As shown in an enlarged schematic view in
The flow intensifier 1120 further includes a lip seal 1140 engaged with a larger diameter portion of the piston 1130. The flow intensifier 1120 includes a seal 1142 also engaged with the larger diameter portion of the piston 1130. A lip seal 1144 is engaged with the smaller diameter portion of the piston 1130. A passageway(s) 1146 is formed through the piston 1130. The passageway 1146 provides fluid communication between the second chamber 1136 and a conduit 1150 when the flow intensifier 1120 is in its rest position, as shown in
As best shown in
As shown in
There is illustrated in
The flow intensifier 1200 further includes a seal 1220 engaged with a larger diameter portion of the piston 1204. The flow intensifier 1120 includes a seal 1222 also engaged with the larger diameter portion of the piston 1204. A seal 1224 is engaged with the smaller diameter portion of the piston 1204. A passageway(s) 1226 is formed through the piston 1204. The passageway 1226 provides fluid communication between the second chamber 1210 and a conduit 1230 when the flow intensifier 1200 is in its rest position, as shown in
Another difference between the brake systems 1050 and 1100 is that the brake system 1100 utilizes a pair of low pressure accumulators 1300 and 1302 one for each of the pumps 408 and 410 instead of a single low pressure accumulator 1010 as in the brake system 1050. The accumulator 1300 provides fluid to the inlet of the pump 408 via a conduit 1304. The accumulator 1302 provides fluid to the inlet of the pump 410 via a conduit 1306. The accumulators 1300 and 1302 function in the same manner as the single low pressure accumulator 1010 to provide a source of fluid at a relatively low pressure, such as for example, less than 1 bar above atmospheric pressure to the inlet of the pumps 408 and 410. The low pressure accumulators 1300 and 1302 can have any suitable structure to accomplish this maximum braking event. The low pressure accumulators 1300 and 1302 may have a similar structure as the low pressure accumulator 1010 although sized smaller.
Although the use of a single low pressure accumulator, such as the accumulator 1010, as in the brake system 1050, may be more cost effective and/or simplistic than a pair of accumulators, utilizations of a pair of smaller accumulators 1300 and 1302 may have other advantages over a single unit. One of the advantages of having a pair of low pressure accumulators 1300 and 1302 is that there may be a packaging advantage in that a pair of smaller components may be easier to mount in a block or housing rather than one large and/or long component. Also, having two separate low pressure accumulators 1300 and 1302 may be advantageous under certain failsafe conditions such that if one of the accumulators fails or leaks, the other accumulator will be able to provide fluid to at least the other pump. Additionally, it may be easier to design a pair of smaller springs versus a higher load spring for a single accumulator.
There is illustrated in
The low pressure accumulator 1320 may include optional features to assist in filling and/or bleeding the auxiliary brake module in which it is installed. For example, the low pressure accumulator 1320 may include a conduit 1360 which can be connected with a source of fluid during filling and/or bleeding of the system. Fluid from the conduit 1360 can flow past the seal 1328 during this process. An additional seal 1362 may be used to prevent this fluid from entering the cavity 1344.
Referring now to
The brake system 1400 is a vertically split system such that the wheel brake 12a is associated with the right front wheel of the vehicle in which the brake system 1400 is installed. The wheel brake 12b is associated with the left front wheel. The wheel brake 12c is associated with the right rear wheel. The wheel brake 12d is associated with the left rear wheel.
Referring now to
The brake system 1400 is a vertically split system such that the wheel brake 12a is associated with the right front wheel of the vehicle in which the brake system 1400 is installed. The wheel brake 12b is associated with the left front wheel. The wheel brake 12c is associated with the right rear wheel. The wheel brake 12d is associated with the left rear wheel.
Referring now to
The brake system 1500 is a diagonally split system such that the wheel brake 12a is associated with the left rear wheel of the vehicle in which the brake system 1500 is installed. The wheel brake 12b is associated with the right front wheel. The wheel brake 12c is associated with the left front wheel. The wheel brake 12d is associated with the right rear wheel.
There is illustrated in
As shown in
The rest of the structure of the fluid separator 1600 is similar as the structure of the fluid separator 520. The right-hand end of the piston 1630, the seal 1634, and the bore 1632 define a first chamber 1636 which is in fluid communication with the conduit 412 leading to the outlet of the pump 408. The left-hand end of the piston 1630, the seal 1634, and the bore 1632 define a second chamber 1638 which is in fluid communication with the conduit 416 leading to the wheel brakes 12a and 12b. The piston 1630 is biased by a spring 1640 in a rightward direction, as viewing
An advantage of the dual seal design of the fluid separator 1600 is that detection of proper sealing of the piston 1630 between the two chambers 1636 and 1638 within the fluid separator 1600 can be better detected than a single seal design. If one of the seals 1634 and 1635 is damaged and improperly seals with the piston 1630, this may be detectable as a system failure. Diagnostics could also be run to determine if a leakage occurs across the fluid separator 1600. For example, during a diagnostic mode, various valves within the main circuits could be closed to prevent fluid flow therein. The pumps 408 and 410 could then be run to determine if a pressure drop would occur indicating that one of the seals 1634 and/or 1635 is damaged and fluid is leaking past the damaged seal. In a single seal fluid separator, such a test would not cause a drop in pressure.
There is also shown in
With respect to the various valves of the brake system 10, the terms “operate” or “operating” (or “actuate”, “moving”, “positioning”) used herein (including the claims) may not necessarily refer to energizing the solenoid of the valve, but rather refers to placing or permitting the valve to be in a desired position or valve state. For example, a solenoid actuated normally open valve can be operated into an open position by simply permitting the valve to remain in its non-energized normally open state. Operating the normally open valve to a closed position may include energizing the solenoid to move internal structures of the valve to block or prevent the flow of fluid therethrough. Thus, the term “operating” should not be construed as meaning moving the valve to a different position nor should it mean to always energizing an associated solenoid of the valve.
The principle and mode of operation of the present disclosure has been explained and illustrated in its preferred embodiment. However, it must be understood that this disclosure may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.
This application is a national stage of International Application No. PCT/US19/025773, filed Apr. 4, 2019, the disclosure of which is incorporated herein by reference in its entirety, and which claimed priority to U.S. Patent Application No. 62/652,498, filed Apr. 4, 2018, the disclosure of which is incorporated herein by reference in its entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/US2019/025773 | 4/4/2019 | WO | 00 |
Number | Date | Country | |
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62652498 | Apr 2018 | US |