Patent Application
20180043865
The subject invention relates to a vehicle braking system, and more particularly, to an adjustable brake pedal assembly of the braking system.
Traditional service braking systems of a vehicle are typically hydraulic fluid based systems actuated by a driver depressing a brake pedal that generally actuates a master cylinder. In-turn, the master cylinder pressurizes hydraulic fluid in a series of hydraulic fluid lines routed to respective actuators at brakes located adjacent to each wheel of the vehicle. Such hydraulic braking may be supplemented by a hydraulic modulator assembly that facilitates anti-lock braking, traction control, and vehicle stability augmentation features. The wheel brakes may be primarily operated by the manually actuated master cylinder with supplemental actuation pressure gradients supplied by the hydraulic modulator assembly during anti-lock, traction control, and stability enhancement modes of operation.
When a plunger of the master cylinder is depressed by the brake pedal to actuate the wheel brakes, pedal resistance is encountered by the driver. This resistance may be due to a combination of actual braking forces at the wheels, hydraulic fluid pressure, mechanical resistance within the booster/master cylinder, the force of a return spring acting on the brake pedal, and other factors. Consequently, a driver is accustomed to and expects to feel this resistance as a normal occurrence during operation of the vehicle. Unfortunately, the ‘feel’ of conventional brake pedals are not adjustable to meet the desires of a driver.
More recent advancements in braking systems include brake-by-wire (BBW) systems that actuate the vehicle brakes via an electric signal typically generated by an on-board controller. Brake torque may be applied to the wheel brakes without a direct hydraulic link to the brake pedal. The BBW system may be an add-on, (i.e., and/or replace a portion of the more conventional hydraulic brake systems), or may completely replace the hydraulic brake system (i.e., a pure BBW system). In either type of BBW system, the brake pedal ‘feel’, which a driver is accustomed to, must be emulated.
Accordingly, it is desirable to provide a brake pedal emulator that may simulate the brake pedal ‘feel’ of more conventional brake systems, and may further be compatible with a means of adjusting brake pedal ‘feel’ by a driver.
In one exemplary embodiment of the invention, a brake pedal assembly of a braking system for a vehicle includes a brake pedal pivotally engaged to a support structure at a first pivot axis. A linkage of the brake pedal assembly is pivotally engaged to the brake pedal at a second pivot axis spaced from the first pivot access by a distance. An adjustment mechanism of the assembly is carried by the brake pedal and is constructed and arranged to alter the distance.
In another exemplary embodiment of the invention, a braking system for a vehicle includes a brake pedal pivotally engage to a support structure at a first pivot axis. A linkage of the braking system is pivotally engage to the brake pedal at a second pivot axis and is adjustably spaced from the first pivot access by a distance. The linkage is operatively connected to a brake assembly of the braking system. An adjustment mechanism is carried by the brake pedal, and is constructed and arranged to alter the distance. A controller of the braking system is configured to operate the adjustment mechanism thereby altering the distance associated with brake pedal firmness.
The above features and advantages and other features and advantages of the invention are readily apparent from the following detailed description of the invention when taken in connection with the accompanying drawings.
Other features, advantages and details appear, by way of example only, in the following detailed description of embodiments, the detailed description referring to the drawings in which:
The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. As used herein, the terms module and controller refer to processing circuitry that may include an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
In accordance with an exemplary embodiment of the invention,
Each brake assembly 28 of the BBW system 26 may include a brake 34 and an actuator 36 configured to operate the brake. The brake 34 may include a caliper and may be any type of brake including disc brakes, drum brakes, and others. As non-limiting examples, the actuator 36 may be an electro-hydraulic brake actuator (EHBA) or other actuator capable of actuating the brake 34 based on an electrical input signal that may be received from the controller 32. More specifically, the actuator 36 may be or include any type of motor capable of acting upon a received electric signal and as a consequence converting energy into motion that controls movement of the brake 34. Thus, the actuator 36 may be a direct current motor configured to generate electro-hydraulic pressure delivered to, for example, the calipers of the brake 34.
The controller 32 may include a computer-based processor (e.g., microprocessor) and a computer readable and writeable storage medium. In operation, the controller 32 may receive one or more electrical signals from the brake pedal assembly 30 over a pathway (see arrow 38) indicative of driver braking intent. In-turn, the controller 32 may process such signals, and based at least in-part on those signals, output an electrical command signal to the actuators 36 over a pathway (see arrow 40). Based on any variety of vehicle conditions, the command signals directed to each wheel 24 may be the same or may be distinct signals for each wheel 24. The pathways 38, 40 may be wired pathways, wireless pathways, or a combination of both.
Non-limiting examples of the controller 32 may include an arithmetic logic unit that performs arithmetic and logical operations; an electronic control unit that extracts, decodes, and executes instructions from a memory; and, an array unit that utilizes multiple parallel computing elements. Other examples of the controller 32 may include an engine control module, and an application specific integrated circuit. It is further contemplated and understood that the controller 32 may include redundant controllers, and/or the system may include other redundancies, to improve reliability of the BBW system 26.
Referring to
The brake pedal emulator 44 may be supported by and extends between an opposite end of the linking member 58 and the support structure 46. More specifically, the emulator 44 may be pivotally engaged to the adjustment mechanism 43, via the linking member 58, at the second pivot axis 50, and may be pivotally engaged to the fixed structure 46 at a third pivot axis 52. The second and third pivot axis 50, 52 may be spaced from the first pivot axis 48, and all three pivot axis 48, 50, 52 may be substantially parallel to one another.
The emulator 44 of the brake pedal assembly 30 is configured to simulate the behavior and/or ‘feel’ of a more traditional hydraulic braking system. The emulator 44 may include a damping device 54 and a force induction device 56 to at least simulate a desired or expected ‘feel’ of the brake pedal 42 during operation by the driver. The damping device 54 is constructed and arranged to generally produce a damping force that is a function of the speed upon which a driver depresses the brake pedal 42. The force induction device 56 produces an induced force (e.g., spring force) that is a function of brake pedal displacement.
Referring to
Referring to
Referring to
To optimize system reliability, the brake pedal emulator 44 may include more than one displacement sensor located at different locations of the brake pedal assembly 30. Similarly, the brake pedal emulator 44 may include more than one pressure sensor (i.e., force) configured to, for example, output redundant signals to more than one controller to facilitate fault tolerance for sensor faults. In operation, the controller 32 is configured to receive a displacement signal (see arrow 64) and a pressure signal (see arrow 66) over pathway 38 and from the respective sensors 60, 62 as the brake pedal 42 is actuated by a driver. The controller 32 processes the displacement and pressure signals 64, 66 then sends appropriate command signal(s) 68 to the brake actuators 36 of the brake assemblies 28 over the pathway 40.
Referring to
One example of the force induction device 56 may be a resiliently compressible, coiled, spring (as illustrated) having opposite ends that bear upon the opposing members 58, 70. Other non-limiting examples of a force induction device 56 include an elastomeric foam, a wave spring, and any other device capable of producing a variable force generally as a function of brake pedal displacement. One example of the damping device 54 may include a hydraulic cylinder having at least one internal orifice for the flow and exchange of hydraulic fluid between chambers. Such a damping device (and others) may be designed to exert a constant force when a constant speed is applied to the brake pedal throughout the brake pedal throw. One example of such a ‘constant force’ damping device 54 may be a hydraulic cylinder with a single orifice. Another non-limiting example of a damping device 54 may include a device designed to increase a force with increasing pedal displacement and when the brake pedal 42 is depressed at a constant speed. Such ‘variable force’ damping devices may be passive and dependent solely upon the brake pedal position and/or displacement, or may be active and controllable by the controller 32. One example of a ‘passive variable force’ damping device may include a hydraulic cylinder with multiple orifices individually exposed depending upon the brake pedal position. Other non-limiting examples of a damping device 54 may include a friction damper, and any other device capable of producing a variable force generally as a function of pedal actuation speed. Although illustrated in a parallel (i.e., side-by-side) relationship to one-another, it is further contemplated and understood that the orientation of the devices 54, 56 with respect to one-another may take any variety of forms. For example, the devices 54, 56 may be concentric to one-another about a common centerline C that may intersect pivot axis 50 and pivot axis 52.
Referring to
The linking member 58 of the brake pedal assembly 30 may include a rod or linkage 78 and a stop 80 that is axially spaced from and opposes the stop 74 of the base member 70. A first end of the linkage 78 may be pivotally engaged to and projects axially outward from the adjustment mechanism 43 at the pivot axis 50 and along the centerline C. The linkage 78 may project from the first end, sealably through a top plate 82 of the damping device 54, and to a distal, opposite, second end. The stop 80 may be located axially between the pivot axis 50 and the top plate 82 of the damping device 54 with respect to centerline C, and may project radially outward from the linkage 78 for engagement and/or seating of an opposite end of the force induction device 56 (e.g., coiled spring).
As previously stated, the damping device 54 may be a hydraulic cylinder that utilizes a magneto-rheological or electro-rheological fluid to actively alter the damping force based on, for example, pedal position. The damping device 54 may include a circumferentially continuous wall 84 that may be cylindrical, the bottom plate 76, the top plate 82, a hydraulic or piston head 86, and an electrical element 88 that may be a coil. The wall 84 may be located radially inwardly from the force induction device or coiled spring 56, and extends axially between the bottom and top plates 76, 82. The wall 84 combined with the bottom and top plates 76, 82 generally define the boundaries of a hydraulic chamber 90 filled with the hydraulic fluid. The head 86 is located in the chamber 90 and may be engaged to a distal end of the linkage 78 of the linking member 58. The wall 84 carries a circumferentially continuous surface that faces radially inward and is in sealed, sliding, contact with the head 86.
In operation, as the brake pedal 42 is actuated, the head 86 (via the linkage 78) reciprocates within the chamber 90. The chamber 90 is generally divided into two separate cavities by the piston head 86 that change in volume as the head reciprocates. The damping device 54 further includes an orifice 92 in fluid communication between the cavities. In one example, the orifice 92 may be defined by and communicates through the head 86. As the head 86 moves within the chamber 90, one cavity becomes larger as the other cavity becomes smaller. With the changing volumes between the cavities, the hydraulic fluid flows through the orifice 92 and into the cavity that is enlarging. The resistance to fluid flow through the orifice 92 generally produces the damping force of the damping device 54.
The resistance to fluid flow through the orifice 92 is dependent, at least in-part, upon the viscosity of the hydraulic fluid. The lower the viscosity, the lower is the damping coefficient, or damping force at a constant flow rate. In the present embodiment, the fluid viscosity may be altered, during any given moment in time, to vary the damping force. To facilitate this active damping force control, the electrical element 88 of the damping device 54 may be electrically energized via a command/control signal from the controller 32. When energized, the electrical element 88 may produce a magnetic field that alters molecules of the hydraulic fluid thereby increasing viscosity. In one example, the electrical element 88 may be mounted to the head 86 in close proximity to the orifice 92. The element 88 may be energized via a hard wired conductive path to, for example, a battery and/or the controller 32, or may be energized via a wireless power transfer arrangement (i.e., induction).
The adjustment mechanism 43 of the brake pedal assembly 30 is configured to adjust the firmness of the brake pedal ‘feel’ to the desire of the driver. The firmness adjustment may be considered an indirect means of adjusting the effects of the force induction device 56. The adjustment mechanism 43 may be a ball-screw device, and may include an electric motor 94, a threaded rod 96, and a threaded carriage 98. The threaded rod 96 may be configured to rotate about rotation axis R and may be mounted at opposite end portions to the brake pedal 42. The electric motor 94 may be fixed to the brake pedal 42 and is configured to rotate the threaded rod 96 upon an initiation signal from, for example, the controller 32. The threaded carriage 98 is threaded onto the rod 96 and thus configured to move axially along the rod as the rod rotates. The rotation axis R may generally intersect pivot axis 48 and pivot axis 50. An adjustable distance (see arrow 100) may be measured along rotation axis R and between pivot axis 48 and pivot axis 50.
Operation of the adjustment mechanism 43 may be initiated by a driver utilizing a human-machine interface (HMI) 102. The HMI 102 may be configured to provide a driver with the option of a softer or firmer brake pedal feel, and may be any variety of interfaces including switches and interactive touch screens. In operation, if a driver desires a firmer brake pedal feel, the driver may interact with the HMI 102 and the HMI 102 may accordingly output a command signal (see arrow 104) to the controller 32. In response, the controller 32 may output an initiation signal (see arrow 106) to the motor 94 causing the motor to rotate in a first direction that moves the carriage 98 away from pivot axis 48 thereby increasing the distance 100. By increasing the distance 100, the firmness of the brake pedal feel is increased, and the brake pedal travel may decrease. Similarly, if the driver desires a softer brake pedal feel, the driver may interact with the HMI 102 and the HMI 102 may accordingly output a command signal 108 to the controller 32. In response, the controller 32 may output an initiation signal (see arrow 110) to the motor 94 causing the motor to rotate in an opposite second direction that moves the carriage 98 toward the pivot axis 48 thereby decreasing the distance 100. By decreasing the distance 100, the firmness of the brake pedal feel is decreased, and the brake pedal travel may increase.
Advantages and benefits of the present disclosure include the ability of a driver to select brake pedal firmness and aggressiveness. Other advantages include the ability to correlate such selected brake pedal firmness with a brake pedal emulator of a BBW system which includes the ability to simulate brake pedal damping and other forces similar to more traditional brake systems. Other advantages may include a simulated brake pedal stiffness, damping and hysteresis similar to that of a vacuum boosted system.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the application.
