Patent Application
20180001875
The subject invention relates to a vehicle brake-by-wire (BBW) system, and more particularly, to an adjustable brake pedal emulator assembly of the BBW 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 BBW systems that actuate the vehicle brakes via an electric signal typically generated by an on-board controller. A brake force or 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 BBW system of a vehicle includes a support structure, a brake pedal pivotally engaged to the support structure at a first pivot axis, and a brake pedal emulator assembly. The brake pedal emulator assembly extends between and is pivotally engaged to the brake pedal and the support structure at respective second and third pivot axis. The brake pedal emulator assembly includes a brake pedal emulator and an adjustment mechanism aligned along a centerline intersecting the second and third pivot axis. The brake pedal emulator is constructed and arranged to displace axially when the brake pedal is actuated, and the adjustment mechanism is constructed and arranged to adjust axial displacement.
In another exemplary embodiment of the invention, a BBW system for a vehicle includes a brake assembly, a support structure, a brake pedal pivotally engaged to the support structure at a first pivot axis, and a brake pedal emulator pivotally engaged to the brake pedal at a second pivot axis. An adjustment mechanism of the BBW system is operably coupled to the brake pedal emulator and is pivotally engaged to the support structure at a third pivot axis. The adjustment mechanism is configured to adjust an allowable displacement distance of the brake pedal emulator for adjusting brake pedal firmness.
In another exemplary embodiment of the invention, a method of operating a BBW system includes the detection of a condition by a computer-based controller. Once the condition is detected, an adjustment mechanism of a brake pedal emulator assembly is initiated to alter brake pedal firmness thereby alerting a driver of the condition.
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 actuators 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 may 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 assembly 41 may include an adjustment mechanism 43 and a brake pedal emulator 44 generally orientated along a centerline C that may intersect the second and third pivot axes 50, 52. The adjustment mechanism 43 is adapted to adjust the ‘firmness’ of the brake pedal ‘feel’, and may extend between the stationary structure 46 at the third pivot axis 52 and the brake pedal emulator 44. The brake pedal emulator 44 is configured to simulate the behavior and/or ‘feel’ of a more traditional hydraulic braking system, and may extend between the adjustment mechanism 43 and the brake pedal 42 at the second pivot axis 50.
Referring to
The housing 60 of the brake pedal emulator 44 may include a bottom plate 64, a stop or top plate 66, and a wall 68 engaged to and extending axially between the bottom plate 64 and stop 66. The bottom plate 62 of the brake pedal emulator 44 may axially oppose the enlarged end portion 62 of the linking member 58. The damping and force induction devices 54, 56 are disposed axially between the bottom plate 62 and the enlarged end portion 62 of the linking member 58 for axial compression as the brake pedal 42 is actuated by a driver. The enlarged end portion 62 is disposed axially between the stop 66 of the housing 60 and the devices 54, 56. When the devices 54, 56 are fully extended axially (i.e., the brake pedal 42 is in an un-actuated state), the enlarged head portion 62 may be biased against the stop 66 of the housing 60 by, for example, an axial force exerted by the force induction device 56. The wall 68 may be circumferentially continuous with respect to centerline C, thus wrapping about and encapsulating one or both of the devices 54, 56. Alternatively, the devices 54, 56 may include their own housings and the wall 68 may generally function to consistently axially space the bottom plate 64 from the opposing stop 66. The stop or top plate 66 may generally cover one or both of the devices 54, 56, and may contain opening 70 through which the linking member 58 extends (i.e., in a moving and sealable relationship with the top plate 66). It is contemplated and understood that the spring and the damping device may also be packaged in a coaxial fashion and in a single housing.
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 bottom plate 64 and stop 66 of the housing 60. 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, an active ball-screw device driven by a controller that also senses pedal position and speed (i.e., ball screw acts as a damping device), 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.
The adjustment mechanism 43 of the brake pedal emulator assembly 41 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 a base member 72, an electric motor 74, a threaded rod 76, and a carriage 78 that may include female threads. The base member 72 may be directly engaged pivotally to the support structure 46 at the third pivot axis 52. The electric motor 74 may be supported by and engaged to the base member 72. The threaded rod 76 is operably coupled to the electric motor 74 for rotation about a rotation axis (not shown) that may co-extend with the centerline C. The carriage 78 is threaded upon the threaded rod 76 for axial movement with reference to the rotation axis (i.e., centerline C) when the electric motor 74 rotates the threaded rod 76. The carriage 78 is mechanically coupled to the brake pedal emulator 44 to prevent or limit rotation about the rotation axis as the threaded rod 76 rotates. More specifically, the carriage 78 may be rigidly connected to a side of the bottom plate 64 of the housing 60 that is opposite a side of the bottom plate 64 upon which the devices 54, 56 are seated.
Referring to
In operation, the controller 32 is configured to receive a displacement signal (see arrow 84) and a pressure signal (see arrow 86) over pathway 38 and from the respective sensors 80, 82 as the brake pedal 42 is actuated by a driver. The controller 32 processes the displacement and pressure signals 84, 86 then sends appropriate command signal(s) 88 to the brake actuators 36 of the brake assemblies 28 over the pathway 40.
Referring to
Referring to
Referring to
In addition to providing an adjustable, desired, brake pedal feel for a driver, the adjustment mechanism 43 of the brake pedal emulator assembly 41 may be adapted to provide an automated brake pedal feel designed to alert the driver of any variety of vehicle conditions and/or simulate a brake system fault condition that one may typically expect to feel in more traditional, hydraulic, brake systems. Referring to
Per block 104, if a fault is not detected, the system 26 may monitor for a rotor thickness variation. Per block 106, if a rotor thickness variation is detected, the controller 32 may initiate the adjustment mechanism 43 to modulate the motor position at a frequency that may be based on deceleration oscillation frequency.
Per block 108, if a rotor thickness variation is not detected, the system 26 may monitor for boiling brake fluid (i.e., high temperature and degrading pressure-volume (PV) curve). Per block 110, if boiling brake fluid is detected, the controller 32 may initiate the adjustment mechanism 43 to reduce preload of the emulator 44 to a minimum value thus producing a soft pedal feel.
Per block 112, if boiling brake fluid is not detected, the system 26 may monitor for an active ABS. Per block 114, if an active ABS is detected, the controller 32 may initiate the adjustment mechanism to modulate the motor position (i.e. frequency based on ABS cycling frequency), thus modulating the brake pedal feel. Other examples that may modulate the motor position, may include a force based on instantaneous system volume (i.e., pressure) estimation, or, calibrated frequency for haptic pedal feedback.
Per block 116, if an active ABS is not detected, the system 26 may monitor for driver mode changes (e.g., preprogrammed brake feels for specific drivers, etc.). Per block 118, if a driver mode change is detected, the controller 32 may initiated the adjustment mechanism to adjust the preloading of the emulator 44 to, for example, pre-programmed values (e.g., sport/firm, tour/soft, etc.).
It is further contemplated and understood that the conditions may be pre-programmed into the controller 32, and the system 26 may monitor all the pre-programmed conditions described above in unison and/or in different order than provided. It is also understood that the system 26 may monitor conditions not directly related to the braking system and may, none-the-less, adjust the firmness of the brake pedal 42 for the purpose of alerting the driver of a detected condition.
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 the ability to alert a driver of a vehicle condition through an automated change in brake pedal feel. Yet further, the present disclosure enables a compact mechanical part envelope that simplifies design and physical integration of a pedal module, along with simplifying diagnosis and servicing of the module.
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.
