Patent Publication Number: US-2018043865-A1

Title: Braking system for a vehicle with an adjustable brake pedal assembly

Description:
FIELD OF THE INVENTION 
     The subject invention relates to a vehicle braking system, and more particularly, to an adjustable brake pedal assembly of the braking system. 
     BACKGROUND 
     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. 
     SUMMARY OF THE INVENTION 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE 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: 
         FIG. 1  is a schematic plan view of a vehicle having a BBW system as one non-limiting example in accordance with the present disclosure; 
         FIG. 2  is a schematic of the BBW system; 
         FIG. 3  is a graph depicting driver applied brake pedal force as a function of brake pedal travel; 
         FIG. 4 . is a graph depicting a damping force exerted by a damping device of the BBW system as a function of brake pedal travel; 
         FIG. 5  is a schematic of a brake pedal assembly of the BBW system; and 
         FIG. 6  is a schematic of another embodiment of the brake pedal assembly. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     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,  FIG. 1  is a schematic of a vehicle  20  that may include a powertrain  22  (i.e., an engine, transmission and differential), a plurality of rotating wheels  24  (i.e., four illustrated), and a braking system  26  that may be a BBW system as one, non-limiting, example. The BBW system  26  may include a brake assembly  28  for each respective wheel  24 , a brake pedal assembly  30 , and a controller  32 . The powertrain  22  is adapted to drive at least one of the wheels  24  thereby propelling the vehicle  20  upon a surface (e.g., road). The BBW system  26  is configured to generally slow the speed and/or stop motion of the vehicle  20 . The vehicle  20  may be an automobile, truck, van, sport utility vehicle, or any other self-propelled or towed conveyance suitable for transporting a burden. 
     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  FIG. 2 , the brake pedal assembly  30  may include a brake pedal  42 , a linking member  58 , an adjustment mechanism  43 , and in the example where the braking system  26  may be a BBW system, a brake pedal emulator  44 . The brake pedal  42  may be supported by, and in moving relationship too, a fixed or stationary support structure  46 . Illustrated as one non-limiting example, the brake pedal  42  may be pivotally engaged to the fixed structure  46  about a first pivot axis  48 . The adjustment mechanism  43  generally adjusts the ‘firmness’ of the brake pedal ‘feel’ and is engaged to and carried by the brake pedal  42  (also see  FIG. 3 ). The linkage  58  is operatively connected to the brake assemblies  28  and one end may be pivotally engaged to the adjustment mechanism  43  at a second pivot axis  50 . 
     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  FIG. 3 , one example of a force profile of the force induction device  56  is generally illustrated as a function of brake pedal travel T, illustrated in the graph as driver applied brake pedal force F verse the brake pedal travel T. The solid arcuate or curved line  71  represents the targeted profile, and the dashed lines  73  represent the outer bounds (i.e., tolerance) of the targeted profile. The force induction device  56  may be designed to meet this targeted profile  71 . 
     Referring to  FIG. 4 , one example of a damping coefficient profile is generally illustrated as a function of brake pedal travel T, illustrated in the graph as the brake pedal travel T verse a damping coefficient D. The solid arcuate or curved line  75  represents the targeted profile, and the dashed lines  77  represent the outer bounds (i.e., tolerance) of the targeted profile. Similar to the force induction device  56 , the damping device  54  may be designed to meet this targeted profile. It is contemplated and understood that the data from the targeted force and damping profiles along with pre-established target tolerances (i.e., bounds) may be programmed into the controller  32  for various processing functions. It is further contemplated and understood that to various degrees, the damping device  54  may be adjustable with this adjustability being controlled by the controller  32  to, for example, meet the pre-programmed profiles of  FIGS. 3 and 4 . Yet further, the damping coefficient curve of  FIG. 4  may be one of a plurality of damping coefficient curves each associated with an aspect of vehicle modeling. It is further noted that the damping coefficient D is a function of pedal position, and the damping force is a function of pedal apply rate and pedal position. 
     Referring to  FIG. 2 , the brake pedal emulator  44  of the brake pedal assembly  30  may further include a displacement sensor  60  configured to measure displacement (e.g., linear, angular, and others) of at least one of the brake pedal  42  and the linking member  58 . The brake pedal emulator  44  may further include at least one pressure sensor  62  generally orientated at a reactive side of the devices  54 ,  56  (i.e., proximate to the third pivot axis  52 ) to measure applied pressure. It is contemplated and understood that the pressure sensor  62  may be a pressure transducer or other suitable pressure sensor configured or adapted to precisely detect, measure, or otherwise determine an applied pressure or force imparted to the brake pedal  42 . 
     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  FIG. 5 , the brake pedal emulator  44  of the brake pedal assembly  30  may further include a base member  70  pivotally connected directly to the fixed structure  46  about the pivot axis  52 . The damping device  54  and the force induction device  56  may generally be located between and operatively bear upon the base member  70  and the linking member  58 . In operation, as the brake pedal  42  is depressed by a driver, the linking member  58  is generally moved closer to the base member  70  and the devices  54 ,  56  are compressed there-between, creating (at least in-part) the desired brake pedal ‘feel.’ 
     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  FIG. 6 , one example of a brake pedal emulator  44  is illustrated having an ‘active variable force’ damping device  54 . In this embodiment, the force induction device  56  may be a coiled spring concentrically disposed about the damping device  54 . The damping device  54  may be a hydraulic cylinder that may utilize a magneto-rheological or electro-rheological fluid to actively alter the damping force based on, for example, pedal position. Both devices may be configured to compress along the centerline C when the brake pedal  42  is depressed. The force induction device  56  may also facilitate the return of the brake pedal  42  upon pedal release by the driver. In this embodiment, the base member  70  may include a rod or linkage  72  and a stop  74 . The linkage  72  may be pivotally engaged to the fixed structure  46  at one end, and is rigidly fixed to a bottom plate  76  of the damping device  54  at an opposite end. The stop  74  may be located axially between the pivot axis  52  and the bottom plate  76  of the damping device  54  with respect to centerline C, and may project radially outward from the linkage  72  for the seating of one end of the force induction device  56 . 
     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.